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Sample records for nanoparticles hnps stabilized

  1. Physical stability, biocompatibility and potential use of hybrid iron oxide-gold nanoparticles as drug carriers

    Barnett, Christopher M. [School of Pharmacy, Keele University (United Kingdom); Gueorguieva, Mariana [Institute of Medical Science and Technology, University of Dundee (United Kingdom); Lees, Martin R. [University of Warwick, Physics Department (United Kingdom); McGarvey, David J. [School of Physical and Geographical Sciences, Keele University, Lennard-Jones Laboratories (United Kingdom); Hoskins, Clare, E-mail: c.hoskins@keele.ac.uk [Institute for Science and Technology in Medicine, Keele University (United Kingdom)

    2013-06-15

    Hybrid nanoparticles (HNPs) such as iron oxide-gold nanoparticles are currently being exploited for their potential application in image-guided therapies. However, little investigation has been carried out into their physical or chemical stability and potential cytotoxicity in biological systems. Here, we determine the HNPs physical stability over 6 months and chemical stability in physiological conditions, and estimate the biological activity of uncoated and poly(ethylene glycol) coated nanoparticles on human pancreatic adenocarcinoma (BxPC-3) and differentiated human monocyte cells (U937). The potential of these HNPs to act as drug carrier vehicles was determined using the model drug 6-Thioguanine (6-TG). The data showed that the HNPs maintained their structural integrity both physically and chemically throughout the duration of the studies. In addition, negligible cytotoxicity or free radical production was observed in the cell lines tested. The 6-TG was successfully conjugated; with a ratio of 3:1:10 Fe:Au:6-TG (wt:wt:wt). After incubation with BxPC-3 cells, enhanced cellular uptake was reported with the 6-TG-conjugated HNPs compared with free drug along with a 10-fold decrease in IC{sub 50}. This exciting data highlights the potential of HNPs for use in image-guided drug delivery.

  2. Hybrid Lipid/Polymer Nanoparticles for Pulmonary Delivery of siRNA: Development and Fate Upon In Vitro Deposition on the Human Epithelial Airway Barrier.

    d'Angelo, Ivana; Costabile, Gabriella; Durantie, Estelle; Brocca, Paola; Rondelli, Valeria; Russo, Annapina; Russo, Giulia; Miro, Agnese; Quaglia, Fabiana; Petri-Fink, Alke; Rothen-Rutishauser, Barbara; Ungaro, Francesca

    2017-10-16

    Nowadays, the downregulation of genes involved in the pathogenesis of severe lung diseases through local siRNA delivery appears an interesting therapeutic approach. In this study, we propose novel hybrid lipid-polymer nanoparticles (hNPs) consisting of poly(lactic-co-glycolic) acid (PLGA) and dipalmitoyl phosphatidylcholine (DPPC) as siRNA inhalation system. A panel of DPPC/PLGA hNPs was prepared by emulsion/solvent diffusion and fully characterized. A combination of model siRNAs against the sodium transepithelial channel (ENaC) was entrapped in optimized hNPs comprising or not poly(ethylenimine) (PEI) as third component. siRNA-loaded hNPs were characterized for encapsulation efficiency, release kinetics, aerodynamic properties, and stability in artificial mucus (AM). The fate and cytotoxicity of hNPs upon aerosolization on a triple cell co-culture model (TCCC) mimicking human epithelial airway barrier were assessed. Finally, the effect of siRNA-loaded hNPs on ENaC protein expression at 72 hours was evaluated in A549 cells. Optimized muco-inert hNPs encapsulating model siRNA with high efficiency were produced. The developed hNPs displayed a hydrodynamic diameter of ∼150 nm, a low polydispersity index, a negative ζ potential close to -25 mV, and a peculiar triphasic siRNA release lasting for 5 days, which slowed down in the presence of PEI. siRNA formulations showed optimal in vitro aerosol performance after delivery with a vibrating mesh nebulizer. Furthermore, small-angle X-ray scattering analyses highlighted an excellent stability upon incubation with AM, confirming the potential of hNPs for direct aerosolization on mucus-lined airways. Studies in TCCC confirmed that fluorescent hNPs are internalized inside airway epithelial cells and do not exert any cytotoxic or acute proinflammatory effect. Finally, a prolonged inhibition of ENaC protein expression was observed in A549 cells upon treatment with siRNA-loaded hNPs. Results demonstrate the great potential

  3. Gold nanoparticles stabilized by chitosan

    Geraldes, Adriana N.; Oliveira, Maria Jose A.; Silva, Andressa A. da; Leal, Jessica; Batista, Jorge G.S.; Lugao, Ademar B.

    2015-01-01

    In our laboratory has been growing the interest in studying gold nanoparticles and for this reason, the aim of this work is report the first results of the effect of chitosan as stabilizer in gold nanoparticle formulation. AuNPs were synthesized by reducing hydrogen tetrachloroaurate (HAuCl 4 ) using NaBH 4 or gamma irradiation (25kGy) as reduction agent. The chitosan (3 mol L -1 ) was added at 0.5; 1.0 and 1.5 mL. The gold nanoparticles were characterized by UV-Vis absorption spectroscopy, X-ray diffraction (XRD) and Transmission electron microscopy (TEM). Their physical stability was determined using a UV-Vis spectrophotometer over one week during storage at room temperature. Absorption measurements indicated that the plasmon resonance wavelength appears at a wavelength around 530 nm. Has been observed that Chitosan in such quantities were not effective in stabilizing the AuNPs. (author)

  4. Nitride stabilized core/shell nanoparticles

    Kuttiyiel, Kurian Abraham; Sasaki, Kotaro; Adzic, Radoslav R.

    2018-01-30

    Nitride stabilized metal nanoparticles and methods for their manufacture are disclosed. In one embodiment the metal nanoparticles have a continuous and nonporous noble metal shell with a nitride-stabilized non-noble metal core. The nitride-stabilized core provides a stabilizing effect under high oxidizing conditions suppressing the noble metal dissolution during potential cycling. The nitride stabilized nanoparticles may be fabricated by a process in which a core is coated with a shell layer that encapsulates the entire core. Introduction of nitrogen into the core by annealing produces metal nitride(s) that are less susceptible to dissolution during potential cycling under high oxidizing conditions.

  5. ATMP-stabilized iron nanoparticles: chelator-controlled nanoparticle synthesis

    Greenlee, Lauren F.; Rentz, Nikki S.

    2014-11-01

    In this study, we characterize iron nanoparticles synthesized in water in the presence of a phosphonate chelator, amino tris(methylene phosphonic acid) (ATMP) for a range of molar ratios of ATMP to iron. An increase in the molar ratio from 0.05 to 0.8 decreases nanoparticle size from approximately 150 nm to less than 10 nm. Zeta potential measurements were used to evaluate colloidal stability. Zeta potential values varied as a function of pH, and zeta potential values decreased with increasing pH. At lower molar ratios of ATMP to iron, the zeta potential varied between 15 and -40 mV, passing through an isoelectric point at pH 7.5. At higher ratios, the zeta potential was negative across the measured pH range of 2-12 and varied from -2 to -55 mV. Diffraction analysis indicates that ATMP-stabilized iron nanoparticles may have a nano-crystalline structure, potentially with regions of amorphous iron. Characterization results of ATMP-stabilized iron nanoparticles are compared to results obtained for carboxymethyl cellulose (CMC)-stabilized iron nanoparticles. CMC stabilization caused similar peak broadening in diffraction spectra as for ATMP, suggesting similar nano-crystalline/amorphous structure; however, an increase in the molar ratio of CMC to iron did not cause the same reduction in nanoparticle size as was observed for ATMP-stabilized iron nanoparticles.

  6. Paclitaxel Albumin-stabilized Nanoparticle Formulation

    This page contains brief information about paclitaxel albumin-stabilized nanoparticle formulation and a collection of links to more information about the use of this drug, research results, and ongoing clinical trials.

  7. Molten-droplet synthesis of composite CdSe hollow nanoparticles

    Gullapalli, Sravani; Grider, Jason M.; Bagaria, Hitesh G.; Lee, Kyusung; Cho, Minjung; Colvin, Vicki L.; Jabbour, Ghassan E.; Wong, Michael

    2012-01-01

    Many colloidal synthesis routes are not scalable to high production rates, especially for nanoparticles of complex shape or composition, due to precursor expense and hazards, low yields, and the large number of processing steps. The present work describes a strategy to synthesize hollow nanoparticles (HNPs) out of metal chalcogenides, based on the slow heating of a low-melting-point metal salt, an elemental chalcogen, and an alkylammonium surfactant in octadecene solvent. The synthesis and characterization of CdSe HNPs with an outer diameter of 15.6 ± 3.5 nm and a shell thickness of 5.4 ± 0.9 nm are specifically detailed here. The HNP synthesis is proposed to proceed with the formation of alkylammonium-stabilized nano-sized droplets of molten cadmium salt, which then come into contact with dissolved selenium species to form a CdSe shell at the droplet surface. In a reaction-diffusion mechanism similar to the nanoscale Kirkendall effect it is speculated that the cadmium migrates outwardly through this shell to react with more selenium, causing the CdSe shell to thicken. The proposed CdSe HNP structure comprises a polycrystalline CdSe shell coated with a thin layer of amorphous selenium. Photovoltaic device characterization indicates that HNPs have improved electron transport characteristics compared to standard CdSe quantum dots, possibly due to this selenium layer. The HNPs are colloidally stable in organic solvents even though carboxylate, phosphine, and amine ligands are absent; stability is attributed to octadecene-selenide species bound to the particle surface. This scalable synthesis method presents opportunities to generate hollow nanoparticles with increased structural and compositional variety. © 2012 IOP Publishing Ltd.

  8. Molten-droplet synthesis of composite CdSe hollow nanoparticles

    Gullapalli, Sravani

    2012-11-16

    Many colloidal synthesis routes are not scalable to high production rates, especially for nanoparticles of complex shape or composition, due to precursor expense and hazards, low yields, and the large number of processing steps. The present work describes a strategy to synthesize hollow nanoparticles (HNPs) out of metal chalcogenides, based on the slow heating of a low-melting-point metal salt, an elemental chalcogen, and an alkylammonium surfactant in octadecene solvent. The synthesis and characterization of CdSe HNPs with an outer diameter of 15.6 ± 3.5 nm and a shell thickness of 5.4 ± 0.9 nm are specifically detailed here. The HNP synthesis is proposed to proceed with the formation of alkylammonium-stabilized nano-sized droplets of molten cadmium salt, which then come into contact with dissolved selenium species to form a CdSe shell at the droplet surface. In a reaction-diffusion mechanism similar to the nanoscale Kirkendall effect it is speculated that the cadmium migrates outwardly through this shell to react with more selenium, causing the CdSe shell to thicken. The proposed CdSe HNP structure comprises a polycrystalline CdSe shell coated with a thin layer of amorphous selenium. Photovoltaic device characterization indicates that HNPs have improved electron transport characteristics compared to standard CdSe quantum dots, possibly due to this selenium layer. The HNPs are colloidally stable in organic solvents even though carboxylate, phosphine, and amine ligands are absent; stability is attributed to octadecene-selenide species bound to the particle surface. This scalable synthesis method presents opportunities to generate hollow nanoparticles with increased structural and compositional variety. © 2012 IOP Publishing Ltd.

  9. Sustainable steric stabilization of colloidal titania nanoparticles

    Elbasuney, Sherif, E-mail: sherif_basuney2000@yahoo.com

    2017-07-01

    Graphical abstract: Controlled surface properties of titania nanoparticles via surface modification, flocculation from aqueous phase (a), stabilization in aqueous phase (b), extraction to organic phase (c). - Highlights: • Complete change in surface properties of titania nanoparticles from hydrophilic to hydrophobic. • Harvesting the formulated nanoparticles from the aqueous phase to the organic phase. • Exclusive surface modification in the reactor during nanoparticle synthesis. • Sustainable stabilization of titania nanoparticles in aqueous media with polar polymeric dispersant. - Abstract: A route to produce a stable colloidal suspension is essential if mono-dispersed particles are to be successfully synthesized, isolated, and used in subsequent nanocomposite manufacture. Dispersing nanoparticles in fluids was found to be an important approach for avoiding poor dispersion characteristics. However, there is still a great tendency for colloidal nanoparticles to flocculate over time. Steric stabilization can prevent coagulation by introducing a thick adsorbed organic layer which constitutes a significant steric barrier that can prevent the particle surfaces from coming into direct contact. One of the main features of hydrothermal synthesis technique is that it offers novel approaches for sustainable nanoparticle surface modification. This manuscript reports on the sustainable steric stabilization of titanium dioxide nanoparticles. Nanoparticle surface modification was performed via two main approaches including post-synthesis and in situ surface modification. The tuneable hydrothermal conditions (i.e. temperature, pressure, flow rates, and surfactant addition) were optimized to enable controlled steric stabilization in a continuous fashion. Effective post synthesis surface modification with organic ligand (dodecenyl succinic anhydride (DDSA)) was achieved; the optimum surface coating temperature was reported to be 180–240 °C to ensure DDSA ring opening

  10. Sustainable steric stabilization of colloidal titania nanoparticles

    Elbasuney, Sherif

    2017-07-01

    A route to produce a stable colloidal suspension is essential if mono-dispersed particles are to be successfully synthesized, isolated, and used in subsequent nanocomposite manufacture. Dispersing nanoparticles in fluids was found to be an important approach for avoiding poor dispersion characteristics. However, there is still a great tendency for colloidal nanoparticles to flocculate over time. Steric stabilization can prevent coagulation by introducing a thick adsorbed organic layer which constitutes a significant steric barrier that can prevent the particle surfaces from coming into direct contact. One of the main features of hydrothermal synthesis technique is that it offers novel approaches for sustainable nanoparticle surface modification. This manuscript reports on the sustainable steric stabilization of titanium dioxide nanoparticles. Nanoparticle surface modification was performed via two main approaches including post-synthesis and in situ surface modification. The tuneable hydrothermal conditions (i.e. temperature, pressure, flow rates, and surfactant addition) were optimized to enable controlled steric stabilization in a continuous fashion. Effective post synthesis surface modification with organic ligand (dodecenyl succinic anhydride (DDSA)) was achieved; the optimum surface coating temperature was reported to be 180-240 °C to ensure DDSA ring opening and binding to titania nanoparticles. Organic-modified titania demonstrated complete change in surface properties from hydrophilic to hydrophobic and exhibited phase transfer from the aqueous phase to the organic phase. Exclusive surface modification in the reactor was found to be an effective approach; it demonstrated surfactant loading level 2.2 times that of post synthesis surface modification. Titania was also stabilized in aqueous media using poly acrylic acid (PAA) as polar polymeric dispersant. PAA-titania nanoparticles demonstrated a durable amorphous polymeric layer of 2 nm thickness. This

  11. Silica nanoparticle stability in biological media revisited.

    Yang, Seon-Ah; Choi, Sungmoon; Jeon, Seon Mi; Yu, Junhua

    2018-01-09

    The stability of silica nanostructure in the core-silica shell nanomaterials is critical to understanding the activity of these nanomaterials since the exposure of core materials due to the poor stability of silica may cause misinterpretation of experiments, but unfortunately reports on the stability of silica have been inconsistent. Here, we show that luminescent silver nanodots (AgNDs) can be used to monitor the stability of silica nanostructures. Though relatively stable in water and phosphate buffered saline, silica nanoparticles are eroded by biological media, leading to the exposure of AgNDs from AgND@SiO 2 nanoparticles and the quenching of nanodot luminescence. Our results reveal that a synergistic effect of organic compounds, particularly the amino groups, accelerates the erosion. Our work indicates that silica nanostructures are vulnerable to cellular medium and it may be possible to tune the release of drug molecules from silica-based drug delivery vehicles through controlled erosion.

  12. Optical properties of stabilized copper nanoparticles

    Mohindroo, Jeevan Jyoti, E-mail: jjmdav@gmail.com [Punjab Technical University, Kapurthala Punjab (India); Department of Chemistry, DAV College, Amritsar, Punjab India (India); Garg, Umesh Kumar, E-mail: Umeshkgarg@gmail.com [Punjab Technical University, Kapurthala Punjab (India); Guru Teg Bahadur Khalsa College of IT, Malout, Punjab (India); Sharma, Anshul Kumar [Department of Physics, Guru Nanak Dev University, Amritsar 143005 (India)

    2016-05-06

    Optical studies involving calculation of Band Gap of the synthesized copper nanoparticles were carried out in the wavelength range of 500 to 650 nm at room temperature, the particles showed high absorption at 550 nm indicating their good absorptive properties. In this method water is used as the medium for reduction of copper ions in to copper Nanoparticles the stabilization of copper Nanoparticles was studied with starch both as a reductant and stabilizer,. The reaction mixture was heated using a kitchen microwave for about 5 minutes to attain the required temp for the reaction. The pH of the solution was adjusted to alkaline using 5% solution of NaOH. Formation of Copper Nanoparticles was indicated by change in color of the solution from blue to yellowish black which is supported by the UV absorption at 570 nm.the synthesized particles were washed with water and alcohol. The optical properties depend upon absorption of radiations which in turn depends upon ratio of electrons and holes present in the material and also on the shape of the nanoparticles. In the present investigation it was observed that optical absorption increases with increase in particle size. The optical band gap for the Nanoparticles was obtained from plots between hv vs. (αhv){sup 2} and hv vs. (αhv){sup 1/2}. The value of Band gap came out to be around 1.98–2.02 eV which is in close agreement with the earlier reported values.

  13. Dispersion and stabilization of cochleate nanoparticles.

    Bozó, Tamás; Wacha, András; Mihály, Judith; Bóta, Attila; Kellermayer, Miklós S Z

    2017-08-01

    Cochleates, calcium-stabilized membrane rolls of nanoscale diameter, promise a unique and efficient way of delivering lipid-soluble drugs, proteins or nucleic acids into biological systems because they protect the encapsulated material against enzymatic or chemical degradation. Self-aggregation, which typically arises during production and storage is a major obstacle that has so far precluded the development of an efficient cochleate-based drug-delivery system. Here we show that citric acid, added transiently in a narrow concentration range, effectively disperses cochleate aggregates, stabilizes the disperse state for long-term storage and preserves the canonical ultrastructure and topological characteristics of cochleate nanoparticles. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Investigation of carrier oil stabilized iron oxide nanoparticles and its ...

    Iron oxide nanoparticles were synthesized by co-precipitation method. The polyunsaturated carrier oil (flaxseed oil) is used as a stabilizing agent for iron oxide nanoparticles. Kirby Bauer method was used to investigate the antibiotic sensitivity of carrier oil stabilized and uncoated SPIONs at 10 and 20 μg/L on Gram-positive ...

  15. Foams Stabilized with Nanoparticles for Gas Well Deliquification

    Knapik Ewa; Stopa Jerzy; Marzec Anna

    2014-01-01

    This study examined the interaction of solid nanoparticles and anionic and non-ionic surfactant at an air–water interface. Aqueous foams stabilized by silica nanoparticles in water with different levels of salinity were studied in detail. The stability of solid/surfactant dispersion was evaluated visually. Nanoparticles content impact and concentration of surfactant on the foamability, deliquification of foams and structure of wet foams were studied. It was found that the foamability of dispe...

  16. Nanoparticle-stabilized CO₂ foam for CO₂ EOR application

    Liu, Ning [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Lee, Robert [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Yu, Jianjia [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Li, Liangxiong [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Bustamante, Elizabeth [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Khalil, Munawar [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Mo, Di [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Jia, Bao [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Wang, Sai [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); San, Jingshan [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); An, Cheng [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States)

    2015-01-31

    The purpose of this project was to develop nanoparticle-stabilized CO₂ foam for CO₂ -EOR application, in which nanoparticles instead of surfactants are used for stabilizing CO₂ foam to improve the CO₂ sweep efficiency and increase oil recovery. The studies included: (1) investigation of CO₂ foam generation nanoparticles, such as silica nanoparticles, and the effects of particle concentration and surface properties, CO₂/brine ratio, brine salinity, pressure, and temperature on foam generation and foam stability; (2) coreflooding tests to understand the nanoparticle-stabilized CO₂ foam for waterflooded residual oil recovery, which include: oil-free coreflooding experiments with nanoparticle-stabilized CO₂ foam to understand the transportation of nanoparticles through the core; measurements of foam stability and CO₂ sweep efficiency under reservoir conditions to investigate temperature and pressure effects on the foam performance and oil recovery as well as the sweep efficiency in different core samples with different rock properties; and (3) long-term coreflooding experiments with the nanoparticle- stabilized CO₂ foam for residual oil recovery. Finally, the technical and economical feasibility of this technology was evaluated.

  17. Nanoparticle Stabilized Liposomes for Acne Therapy

    Fu, Victoria

    Acne vulgaris is a common skin disease that affects over 40 million people in the United States alone. The main cause of acne vulgaris is Propionibacterium acnes (P. acnes), resides deep in the pores and follicles of the skin in order to feed on oil produced by the sebaceous glands. The liposome is a lipid based nanoparticle with numerous advantages over free drug molecules as an acne treatment alternative. Bare liposomes loaded with lauric acid (LipoLA) were found to show strong antimicrobial activity against P. acnes while generating minimal toxicity. However, the platform is limited by the spontaneous tendency of liposomes to fuse with each other. Attaching nanoparticles to the surface of liposomes can overcome this challenge by providing steric repulsion and reduce surface tension. Thus, carboxyl-functionalized gold nanoparticles (AuC) were attached to the surface of liposomes (AuC-liposomes) loaded with doxycycline, a general tetracycline antibiotic. These particles were found to have a diameter of 120 nm and a zeta potential of 20.0 mV. Both fluorescent and antimicrobial studies demonstrated that based on electrostatic interaction, negatively charged AuC attached to the liposome's positively charged surface and stabilized liposomes in a neutral pH environment (pH = 7.4). Upon entering the skin's acidic environment (pH = 4), AuC detached from the liposome's surface and liposomes could fuse with P. acnes residing in the pores. Furthermore, toxicity studies showed that AuC-liposomes did not induce any significant toxicity, while two of the leading over-the-counter therapies, benzoyl peroxide and salicylic acid, generated substantial skin irritation.

  18. Glycine functionalized alumina nanoparticles stabilize collagen in ...

    Al2O3 nanoparticles thereby suggesting ... 1. Introduction. Collagen is a naturally occurring skin protein in animal tis- ... easily adsorb on the surface of the nanoparticles and amino .... [19,23], agglomeration is prevented by the electrostatic.

  19. Exploiting the high-affinity phosphonate-hydroxyapatite nanoparticle interaction for delivery of radiation and drugs

    Ong, Hooi Tin; Loo, Joachim S. C.; Boey, Freddy Y. C.; Russell, Stephen J.; Ma Jan; Peng, Kah-Whye

    2008-01-01

    Hydroxyapatite is biocompatible and used in various biomedical applications. Here, we generated hydroxyapatite nanoparticles (HNPs) of various sizes (40-200 nm) and demonstrated that they can be stably loaded with drugs or radioisotopes by exploiting the high-affinity HA-(poly)phosphonate interaction. Clinically available phosphonates, clodronate, and Tc-99m-methylene-diphosphonate (Tc-99m-MDP), were efficiently loaded onto HNPs within 15 min. Biodistribution of radiolabeled HNP-MDP-Tc99m in mice was monitored non-invasively using microSPECT-CT. Imaging and dosimetry studies indicated that the HNPs, regardless of size, were quickly taken up by Kupffer cells in the liver after systemic administration into mice. Clodronate loaded onto HNPs remained biologically active and were able to result in selective depletion of Kupffer cells. This method of drug or isotope loading on HA is fast and easy as it eliminates the need for additional surface modifications of the nanoparticles

  20. Synthesis of Various Silica Nanoparticles for Foam Stability

    Yoon, Suk Bon; Yoon, Inho; Jung, Chonghun; Kim, Chorong; Choi, Wangkyu; Moon, Jeikwon

    2013-01-01

    The synthesis of the non-porous silica nanoparticles with uniform sizes has been reported through the Sto ber method, the synthesis of meso porous silica nanoparticles with a specific morphology such as core-shell, rod-like, and hexagonal shapes is not so common. As a synthetic strategy for controlling the particle size, shape, and porosity, the synthesis of core-shell silicas with meso porous shells formed on silica particle cores through the self-assembly of silica precursor and organic templates or spherical meso porous silicas using modified Sto ber method was also reported. Recently, in an effort to reduce the amount of radioactive waste and enhance the decontamination efficiency during the decontamination process of nuclear facilities contaminated with radionuclides, a few research for the preparation of the decontamination foam containing solid nanoparticles has been reported. In this work, the silica nanoparticles with various sizes, shapes, and structures were synthesized based on the previous literatures. The resulting silica nanoparticles were used to investigate the effect of the nanoparticles on the foam stability. In a study on the foam stability using various silica nanoparticles, the results showed that the foam volume and liquid volume in foam was enhanced when using a smaller size and lower density of the silica nanoparticles. Silica nanoparticles with various sizes, shapes, and structures such as a non-porous, meso porous core-shell, and meso porous silica were synthesized to investigate the effect of the foam stability. The sizes and structural properties of the silica nanoparticles were easily controlled by varying the amount of silica precursor, surfactant, and ammonia solution as a basic catalyst. The foam prepared using various silica nanoparticles showed that foam the volume and liquid volume in the foam were enhanced when using a smaller size and lower density of the silica nanoparticles

  1. Reversible, reagentless solubility changes in phosphatidylcholine-stabilized gold nanoparticles

    Mackiewicz, Marilyn R; Ayres, Benjamin R; Reed, Scott M

    2008-01-01

    Phosphatidylcholine (PC) is a versatile ligand for synthesizing gold nanoparticles that are soluble in either organic or aqueous media. Here we report a novel route to organic-soluble, PC-stabilized gold nanoparticles that can be re-suspended in water after removal of the organic solvent. Similarly, we show that PC-stabilized gold nanoparticles synthesized in water can be re-suspended in organic solvents after complete removal of water. Without complete removal of the solvent, the nanoparticles retain their original solubility and do not phase transfer. This change in solvent preference from organic to aqueous and vice versa without the use of an additional phase transfer reagent is novel, visually striking, and of utility for synthetic modification of nanoparticles. This approach allows chemical reactions to be performed on nanoparticles in organic solvents followed by conversion of the products to water-soluble materials. A narrow distribution of PC-stabilized gold nanoparticles was obtained after phase transfer to water as characterized by UV-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM), demonstrating that the narrow distribution obtained from the organic synthesis is retained after transfer to water. This method produces water-soluble nanoparticles with a narrower dispersity than is possible with direct aqueous synthesis

  2. Photocatalytic Hybrid Semiconductor-Metal Nanoparticles; from Synergistic Properties to Emerging Applications.

    Waiskopf, Nir; Ben-Shahar, Yuval; Banin, Uri

    2018-04-14

    Hybrid semiconductor-metal nanoparticles (HNPs) manifest unique combined and often synergetic properties stemming from the materials combination. These structures exhibit spatial charge separation across the semiconductor-metal junction upon light absorption, enabling their use as photocatalysts. So far, the main impetus of photocatalysis research in HNPs addresses their functionality in solar fuel generation. Recently, it was discovered that HNPs are functional in efficient photocatalytic generation of reactive oxygen species (ROS). This has opened the path for their implementation in diverse biomedical and industrial applications where high spatially temporally resolved ROS formation is essential. Here, the latest studies on the synergistic characteristics of HNPs are summarized, including their optical, electrical, and chemical properties and their photocatalytic function in the field of solar fuel generation is briefly discussed. Recent studies are then focused concerning photocatalytic ROS formation with HNPs under aerobic conditions. The emergent applications of this capacity are then highlighted, including light-induced modulation of enzymatic activity, photodynamic therapy, antifouling, wound healing, and as novel photoinitiators for 3D-printing. The superb photophysical and photocatalytic properties of HNPs offer already clear advantages for their utility in scenarios requiring on-demand light-induced radical formation and the full potential of HNPs in this context is yet to be revealed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Standardization of Nanoparticle Characterization: Methods for Testing Properties, Stability, and Functionality of Edible Nanoparticles.

    McClements, Jake; McClements, David Julian

    2016-06-10

    There has been a rapid increase in the fabrication of various kinds of edible nanoparticles for oral delivery of bioactive agents, such as those constructed from proteins, carbohydrates, lipids, and/or minerals. It is currently difficult to compare the relative advantages and disadvantages of different kinds of nanoparticle-based delivery systems because researchers use different analytical instruments and protocols to characterize them. In this paper, we briefly review the various analytical methods available for characterizing the properties of edible nanoparticles, such as composition, morphology, size, charge, physical state, and stability. This information is then used to propose a number of standardized protocols for characterizing nanoparticle properties, for evaluating their stability to environmental stresses, and for predicting their biological fate. Implementation of these protocols would facilitate comparison of the performance of nanoparticles under standardized conditions, which would facilitate the rational selection of nanoparticle-based delivery systems for different applications in the food, health care, and pharmaceutical industries.

  4. Preparation and bactericide activity of gallic acid stabilized gold nanoparticles

    Moreno-Alvarez, S. A.; Martinez-Castanon, G. A.; Nino-Martinez, N.; Reyes-Macias, J. F.; Patino-Marin, N.; Loyola-Rodriguez, J. P.; Ruiz, Facundo

    2010-01-01

    In this work, gold nanoparticles with three different sizes (13.7, 39.4, and 76.7 nm) were prepared using a simple aqueous method with gallic acid as the reducing and stabilizing agent, the different sizes were obtained varying some experimental parameters as the pH of the reaction and the amount of the gallic acid. The prepared nanoparticles were characterized using X-ray diffraction, transmission electron microscopy, dynamic light scattering, and UV-Vis spectroscopy. Samples were identified as elemental gold and present spherical morphology, a narrow size distribution and good stabilization according to TEM and DLS results. The antibacterial activity of this gallic acid stabilized gold nanoparticles against S. mutans (the etiologic agent of dental caries) was assessed using a microdilution method obtaining a minimum inhibitory concentration of 12.31, 12.31, and 49.25 μg/mL for 13.7, 39.4, and 76.7 nm gold nanoparticles, respectively. The antibacterial assay showed that gold nanoparticles prepared in this work present a bactericide activity by a synergistic action with gallic acid. The MIC found for this nanoparticles are much lower than those reported for mixtures of gold nanoparticles and antibiotics.

  5. Preparation and bactericide activity of gallic acid stabilized gold nanoparticles

    Moreno-Alvarez, S. A. [UASLP, Doctorado Institucional en Ingenieria y Ciencia de Materiales (Mexico); Martinez-Castanon, G. A., E-mail: mtzcastanon@fciencias.uaslp.m [UASLP, Maestria en Ciencias Odontologicas, Facultad de Estomatologia (Mexico); Nino-Martinez, N. [UASLP, Facultad de Ciencias (Mexico); Reyes-Macias, J. F.; Patino-Marin, N.; Loyola-Rodriguez, J. P. [UASLP, Maestria en Ciencias Odontologicas, Facultad de Estomatologia (Mexico); Ruiz, Facundo [UASLP, Facultad de Ciencias (Mexico)

    2010-10-15

    In this work, gold nanoparticles with three different sizes (13.7, 39.4, and 76.7 nm) were prepared using a simple aqueous method with gallic acid as the reducing and stabilizing agent, the different sizes were obtained varying some experimental parameters as the pH of the reaction and the amount of the gallic acid. The prepared nanoparticles were characterized using X-ray diffraction, transmission electron microscopy, dynamic light scattering, and UV-Vis spectroscopy. Samples were identified as elemental gold and present spherical morphology, a narrow size distribution and good stabilization according to TEM and DLS results. The antibacterial activity of this gallic acid stabilized gold nanoparticles against S. mutans (the etiologic agent of dental caries) was assessed using a microdilution method obtaining a minimum inhibitory concentration of 12.31, 12.31, and 49.25 {mu}g/mL for 13.7, 39.4, and 76.7 nm gold nanoparticles, respectively. The antibacterial assay showed that gold nanoparticles prepared in this work present a bactericide activity by a synergistic action with gallic acid. The MIC found for this nanoparticles are much lower than those reported for mixtures of gold nanoparticles and antibiotics.

  6. Iron oxide nanoparticles stabilized inside highly ordered ...

    CdS nanoparticles prepared in reverse micellar system was incorporated into ... The molar ratio of various constituents of the hydrothermal gel was ... other synthesis techniques for the preparation of iron oxide nanocomposites using.

  7. Pattern transfer with stabilized nanoparticle etch masks

    Hogg, Charles R; Majetich, Sara A; Picard, Yoosuf N; Narasimhan, Amrit; Bain, James A

    2013-01-01

    Self-assembled nanoparticle monolayer arrays are used as an etch mask for pattern transfer into Si and SiO x substrates. Crack formation within the array is prevented by electron beam curing to fix the nanoparticles to the substrate, followed by a brief oxygen plasma to remove excess carbon. This leaves a dot array of nanoparticle cores with a minimum gap of 2 nm. Deposition and liftoff can transform the dot array mask into an antidot mask, where the gap is determined by the nanoparticle core diameter. Reactive ion etching is used to transfer the dot and antidot patterns into the substrate. The effect of the gap size on the etching rate is modeled and compared with the experimental results. (paper)

  8. Synthesis of Stabilized Myrrh-Capped Hydrocolloidal Magnetite Nanoparticles

    Ayman M. Atta

    2014-07-01

    Full Text Available Herein we report a new method for synthesizing stabilized magnetic nanoparticle (MNP colloids. A new class of monodisperse water-soluble magnetite nano-particles was prepared by a simple and inexpensive co-precipitation method. Iron ions and iodine were prepared by the reaction between ferric chloride and potassium iodide. The ferrous and ferric ions were hydrolyzed at low temperature at pH 9 in the presence of iodine to produce iron oxide nanoparticles. The natural product myrrh gum was used as capping agent to produce highly dispersed coated magnetite nanoparticles. The structure and morphology of the magnetic nanogel was characterized by Fourier transform infrared spectroscopy (FTIR and transmission electron microscopy (TEM, and X-ray diffraction (XRD was used to examine the crystal structure of the produced magnetite nanoparticles.

  9. Passivation and Stabilization of Aluminum Nanoparticles for Energetic Materials

    Matthew Flannery

    2015-01-01

    Full Text Available In aircraft applications, fuel is used not only as a propellant but also as a coolant and improving both the thermal conductivity and combustion enthalpy of the fuel is beneficial in these applications. These properties can be enhanced by dispersing aluminum nanoparticles into the fuel; however, the nanoparticles require stabilization from agglomeration and passivation from oxidation in order for these benefits to be realized in aircraft applications. To provide this passivation and stabilization, aluminum nanoparticles were encapsulated with a coating by the plasma enhanced chemical vapor deposition (PE-CVD method from toluene precursors. The thermal conductivity, combustion and ignition properties, and stability of the nanoparticles dispersed in RP-2 fuel were subsequently evaluated. In addition, the effect of dispersing aluminum nanoparticles in RP-2 fuel on the erosion rate of fuel nozzles was evaluated. The dispersion of PE-CVD coated aluminum nanoparticles at a concentration of 3.0% by volume exhibited a 17.7% and 0.9% increase in thermal conductivity and volumetric enthalpy of combustion, respectively, compared to the baseline RP-2 fuel. Additionally, particle size analysis (PSA of the PE-CVD coated aluminum nanofuel exhibited retention of particle size over a five-month storage period and erosion testing of a 1 mm stainless steel nozzle exhibited a negligible 1% change in discharge coefficient after 100 hours of testing.

  10. Microbial exopolysaccharide-mediated synthesis and stabilization of metal nanoparticles.

    Sathiyanarayanan, Ganesan; Dineshkumar, Krishnamoorthy; Yang, Yung-Hun

    2017-11-01

    Exopolysaccharides (EPSs) are structurally and functionally valuable biopolymer secreted by different prokaryotic and eukaryotic microorganisms in response to biotic/abiotic stresses and to survive in extreme environments. Microbial EPSs are fascinating in various industrial sectors due to their excellent material properties and less toxic, highly biodegradable, and biocompatible nature. Recently, microbial EPSs have been used as a potential template for the rapid synthesis of metallic nanoparticles and EPS-mediated metal reduction processes are emerging as simple, harmless, and environmentally benign green chemistry approaches. EPS-mediated synthesis of metal nanoparticles is a distinctive metabolism-independent bio-reduction process due to the formation of interfaces between metal cations and the polyanionic functional groups (i.e. hydroxyl, carboxyl and amino groups) of the EPS. In addition, the range of physicochemical features which facilitates the EPS as an efficient stabilizing or capping agents to protect the primary structure of the metal nanoparticles with an encapsulation film in order to separate the nanoparticle core from the mixture of composites. The EPS-capping also enables the further modification of metal nanoparticles with expected material properties for multifarious applications. The present review discusses the microbial EPS-mediated green synthesis/stabilization of metal nanoparticles, possible mechanisms involved in EPS-mediated metal reduction, and application prospects of EPS-based metal nanoparticles.

  11. Stabilized amorphous glibenclamide nanoparticles by high-gravity technique

    Yu Lei; Li Caixia; Le Yuan; Chen Jianfeng; Zou Haikui

    2011-01-01

    Highlights: · Amorphous glibenclamide nanoparticles of 220 nm are obtained using the high-gravity technique. · The dissolution rate of these nanoparticles achieves 85% in 5 min, while those of the raw glibenclamide and the commercial glibenclamide tablet only reach 35% and 55% respectively during the same period. · The morphology, particle size, crystalline form and dissolution rate of these nanoparticles almost remain constant after keeping more than 70 days. - Abstract: The stable amorphous glibenclamide nanoparticles was obtained via anti-solvent precipitation using the high-gravity technique in this study. The effects of operating variables on the particle size were investigated. The properties of glibenclamide nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC) and dissolution test. The prepared glibenclamide nanoparticles had a mean size of 220 nm within a narrow distribution. The dissolution rate of glibenclamide nanoparticles was obviously faster than that of the raw glibenclamide or the commercial glibenclamide tablet. It achieved 85% in 5 min, while those of the raw glibenclamide and the commercial glibenclamide tablet achieved 35% and 55% respectively during the same period. The physical stability of the nanoparticles was tested after storing for more than 70 days at room conditions. Their morphology, particle size, crystalline form and dissolution rate almost remained constant during storage.

  12. Stability of polyvinyl alcohol-coated biochar nanoparticles in brine

    Griffith, Christopher, E-mail: cgriffith@utexas.edu; Daigle, Hugh [University of Texas at Austin, Department of Petroleum and Geosystems Engineering (United States)

    2017-01-15

    This paper reports on the dispersion stability of 150 nm polyvinyl alcohol coated biochar nanoparticles in brine water. Biochar is a renewable, carbon based material that is of significant interest for enhanced oil recovery operations primarily due to its wide ranging surface properties, low cost of synthesis, and low environmental toxicity. Nanoparticles used as stabilizing agents for foams (and emulsions) or in nanofluids have emerged as potential alternatives to surfactants for subsurface applications due to their improved stability at reservoir conditions. If, however, the particles are not properly designed, they are susceptible to aggregation because of the high salinity brines typical of oil and gas reservoirs. Attachment of polymers to the nanoparticle surface, through covalent bonds, provides steric stabilization, and is a necessary step. Our results show that as the graft density of polyvinyl alcohol increases, so too does the stability of nanoparticles in brine solutions. A maximum of 34 wt% of 50,000 Da polyvinyl alcohol was grafted to the particle surface, and the size of the particles was reduced from ~3500 nm (no coating) to 350 nm in brine. After 24 h, the particles had a size of ~500 nm, and after 48 h completely aggregated. 100,000 Da PVA coated at 24 wt% on the biochar particles were stable in brine for over 1 month with no change in mean particle size of ~330 nm.

  13. Polymeric nanoparticles stabilized by surfactants: kinetic studies

    Pánek, Jiří; Filippov, Sergey K.; Koňák, Čestmír; Steinhart, Miloš; Štěpánek, Petr

    2011-01-01

    Roč. 32, č. 8 (2011), s. 1105-1110 ISSN 0193-2691 R&D Projects: GA ČR GAP208/10/1600 Institutional research plan: CEZ:AV0Z40500505 Keywords : nanoparticles * solvent shifting * time-resolved SAXS Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.560, year: 2011

  14. Structure and stability of charged colloid-nanoparticle mixtures

    Weight, Braden M.; Denton, Alan R.

    2018-03-01

    Physical properties of colloidal materials can be modified by addition of nanoparticles. Within a model of like-charged mixtures of particles governed by effective electrostatic interactions, we explore the influence of charged nanoparticles on the structure and thermodynamic phase stability of charge-stabilized colloidal suspensions. Focusing on salt-free mixtures of particles of high size and charge asymmetry, interacting via repulsive Yukawa effective pair potentials, we perform molecular dynamics simulations and compute radial distribution functions and static structure factors. Analysis of these structural properties indicates that increasing the charge and concentration of nanoparticles progressively weakens correlations between charged colloids. We show that addition of charged nanoparticles to a suspension of like-charged colloids can induce a colloidal crystal to melt and can facilitate aggregation of a fluid suspension due to attractive van der Waals interactions. We attribute the destabilizing influence of charged nanoparticles to enhanced screening of electrostatic interactions, which weakens repulsion between charged colloids. This interpretation is consistent with recent predictions of an effective interaction theory of charged colloid-nanoparticle mixtures.

  15. Synthesis and electrochemical characterization of stabilized nickel nanoparticles

    Dominguez-Crespo, M.A.; Ramirez-Meneses, E.; Torres Huerta, A.M. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, CICATA-IPN Unidad Altamira, Carretera Tampico-Puerto Industrial, C.P. 89600 Altamira, Tamaulipas (Mexico); Montiel-Palma, V. [Centro de Investigaciones Quimicas, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, Colonia Chamilpa, C.P.62201 Cuernavaca, Morelos (Mexico); Dorantes Rosales, H. [Departamento de Metalurgia, Escuela Superior de Ingenieria Quimica e Industrias Extractivas - IPN, C.P. 07300, D.F. (Mexico)

    2009-02-15

    Nickel stabilized nanoparticles produced by an organometallic approach (Chaudret's method) starting from the complex Ni(1,5-COD){sub 2} were used as electrode materials for hydrogen evolution in NaOH at two temperatures (298 and 323 K). The synthesis of the nickel nanoparticles was performed in the presence of two different stabilizers, 1,3-diaminopropane (DAP) and anthranilic acid (AA), by varying the molar ratios (1:1, 1:2 and 1:5 metal:ligand) in order to evaluate their influence on the shape, dispersion, size and electrocatalytic activity of the metallic particles. The presence of an appropriate amount of stabilizer is an effective alternative to the synthesis of small monodispersed metal nanoparticles with diameters around 5 and 8 nm for DAP and AA, respectively. The results are discussed in terms of morphology and the surface state of the nanoparticles. The importance of developing a well-controlled synthetic method which results in higher performances of the resulting nanoparticles is highlighted. Herein we found that the performance with respect to the HER of the Ni electrodes dispersed on a carbon black Vulcan substrate is active and comparable to that reported in the literature for the state-of-the-art electrocatalysts. Appreciable cathodic current densities of {proportional_to}240 mA cm{sup -2} were measured with highly dispersed nickel particles (Ni-5{sub DAP}). This work demonstrates that the aforementioned method can be extended to the preparation of highly active stabilized metal particles without inhibiting the electron transfer for the HER reaction, and it could also be applied to the synthesis of bimetallic nanoparticles. (author)

  16. Hairy nanoparticle assemblies as one-component functional polymer nanocomposites: opportunities and challenges

    Fernandes, Nikhil J.

    2013-03-01

    Over the past three decades, the combination of inorganic-nanoparticles and organic-polymers has led to a wide variety of advanced materials, including polymer nanocomposites (PNCs). Recently, synthetic innovations for attaching polymers to nanoparticles to create hairy nanoparticles (HNPs) has expanded opportunities in this field. In addition to nanoparticle compatibilization for traditional particle-matrix blending, neat-HNPs afford one-component hybrids, both in composition and properties, which avoids issues of mixing that plague traditional PNCs. Continuous improvements in purity, scalability, and theoretical foundations of structure-performance relationships are critical to achieving design control of neat-HNPs necessary for future applications, ranging from optical, energy, and sensor devices to lubricants, green-bodies, and structures. © 2013 Materials Research Society.

  17. Hairy nanoparticle assemblies as one-component functional polymer nanocomposites: opportunities and challenges

    Fernandes, Nikhil J.; Koerner, Hilmar; Giannelis, Emmanuel P.; Vaia, Richard A.

    2013-01-01

    Over the past three decades, the combination of inorganic-nanoparticles and organic-polymers has led to a wide variety of advanced materials, including polymer nanocomposites (PNCs). Recently, synthetic innovations for attaching polymers to nanoparticles to create hairy nanoparticles (HNPs) has expanded opportunities in this field. In addition to nanoparticle compatibilization for traditional particle-matrix blending, neat-HNPs afford one-component hybrids, both in composition and properties, which avoids issues of mixing that plague traditional PNCs. Continuous improvements in purity, scalability, and theoretical foundations of structure-performance relationships are critical to achieving design control of neat-HNPs necessary for future applications, ranging from optical, energy, and sensor devices to lubricants, green-bodies, and structures. © 2013 Materials Research Society.

  18. Effect of Chemical Stabilizers in Silver Nanoparticle Suspensions on Nanotoxicity

    Bae, Eun Joo; Park, Hee Jin; Park, Jun Su; Yoon, Je Yong; Yi, Jong Heop; Kim, Young Hun; Choi, Kyung Hee

    2011-01-01

    Colloidal silver nanoparticles (AgNPs) have been commercialized as the typically stabilized form via the addition of a variety of surfactants or polymers. Herein, to examine the effects of stabilizing AgNPs in suspension, we modified the surface of bare AgNPs with four type of surfactants (NaDDBS, SDS, TW80, CTAB) and polymers (PVP, PAA, PAH, CMC). The modified AgNPs was applied to compare suspension stability and nanotoxicity test using Escherichia coli (E. coli) as a model organism. Modification of AgNPs surface using chemical stabilizer may be not related with molecular weight, but chemical structure such as ionic state and functional group of stabilizer. In this study, it is noteworthy that AgNPs modified with a cationic stabilizer (CTAB, PAH) were importantly toxic to E. coli, rather than anionic stabilizers (NaDDBS, SDS). Comparing similar anionic stabilizer, i.e., NaDDBS and SDS, the result showed that lipophilicity of chemical structure can affect on E. coli, because NaDDBS, which contains a lipophilic benzene ring, accelerated the cytotoxicity of AgNPs. Interestingly, none of the stabilizers tested, including biocompatible nonionic stabilizers (i.e., TW80 and cellulose) caused a reduction in AgNP toxicity. This showed that toxicity of AgNPs cannot be reduced using stabilizers

  19. Effect of Chemical Stabilizers in Silver Nanoparticle Suspensions on Nanotoxicity

    Bae, Eun Joo; Park, Hee Jin; Park, Jun Su; Yoon, Je Yong; Yi, Jong Heop [Seoul National University, Seoul (Korea, Republic of); Kim, Young Hun [Kwangwoon University, Seoul (Korea, Republic of); Choi, Kyung Hee [National Institute of Environmental Research, Incheon (Korea, Republic of)

    2011-02-15

    Colloidal silver nanoparticles (AgNPs) have been commercialized as the typically stabilized form via the addition of a variety of surfactants or polymers. Herein, to examine the effects of stabilizing AgNPs in suspension, we modified the surface of bare AgNPs with four type of surfactants (NaDDBS, SDS, TW80, CTAB) and polymers (PVP, PAA, PAH, CMC). The modified AgNPs was applied to compare suspension stability and nanotoxicity test using Escherichia coli (E. coli) as a model organism. Modification of AgNPs surface using chemical stabilizer may be not related with molecular weight, but chemical structure such as ionic state and functional group of stabilizer. In this study, it is noteworthy that AgNPs modified with a cationic stabilizer (CTAB, PAH) were importantly toxic to E. coli, rather than anionic stabilizers (NaDDBS, SDS). Comparing similar anionic stabilizer, i.e., NaDDBS and SDS, the result showed that lipophilicity of chemical structure can affect on E. coli, because NaDDBS, which contains a lipophilic benzene ring, accelerated the cytotoxicity of AgNPs. Interestingly, none of the stabilizers tested, including biocompatible nonionic stabilizers (i.e., TW80 and cellulose) caused a reduction in AgNP toxicity. This showed that toxicity of AgNPs cannot be reduced using stabilizers.

  20. Porous silicon nanoparticle as a stabilizing support for chondroitinase.

    Daneshjou, Sara; Dabirmanesh, Bahareh; Rahimi, Fereshteh; Khajeh, Khosro

    2017-01-01

    Chondroitinase ABCI (cABCI) from Proteus vulgaris is a drug enzyme that can be used to treat spinal cord injuries. One of the main problems of chondroitinase ABC1 is its low thermal stability. The objective of the current study was to stabilize the enzyme through entrapment within porous silicon (pSi) nanoparticles. pSi was prepared by an electrochemical etch of p-type silicon using hydrofluoric acid/ethanol. The size of nanoparticles were determined 180nm by dynamic light scattering and the mean pore diameter was in the range of 40-60nm obtained by scanning electron microscopy. Enzymes were immobilized on porouse silicon nanoparticles by entrapment. The capacity of matrix was 35μg enzyme per 1mg of silicon. The immobilized enzyme displayed lower V max values compared to the free enzyme, but Km values were the same for both enzymes. Immobilization significantly increased the enzyme stability at various temperatures (-20, 4, 25 and 37°C). For example, at 4°C, the free enzyme (in 10mM imidazole) retained 20% of its activity after 100min, while the immobilized one retained 50% of its initial activity. Nanoparticles loading capacity and the enzyme release rate showed that the selected particles could be a pharmaceutically acceptable carrier for chondroitinase. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Direct measurements of protein-stabilized gold nanoparticle interactions.

    Eichmann, Shannon L; Bevan, Michael A

    2010-09-21

    We report integrated video and total internal reflection microscopy measurements of protein stabilized 110 nm Au nanoparticles confined in 280 nm gaps in physiological media. Measured potential energy profiles display quantitative agreement with Brownian dynamic simulations that include hydrodynamic interactions and camera exposure time and noise effects. Our results demonstrate agreement between measured nonspecific van der Waals and adsorbed protein interactions with theoretical potentials. Confined, lateral nanoparticle diffusivity measurements also display excellent agreement with predictions. These findings provide a basis to interrogate specific biomacromolecular interactions in similar experimental configurations and to design future improved measurement methods.

  2. Stability and precipitation of diverse nanoparticles

    Desai, Chintal

    Nanotechnology is a rapidly growing industry that is exploiting the novel characteristics of materials manufactured at the nanoscale. Carbon based nanomaterials such as Carbon Nanotubes (CNTs) and Detonation Nanodiamond (DND) possess unique properties and find a wide range of industrial applications. With the advent of mass production of such materials, there is a possibility of contamination of water resources. Depending on the surface properties and structures, they might aggregate and settle down, or be dispersed and transported by the water. Therefore, there is a need to develop an understanding of the fate of such materials in aqueous media. The understanding and effect of solution chemistry is a key to predicting their deposition, transport, reactivity, and bioavailability in aquatic environments. The colloidal behavior of organic dispersed CNTs and water dispersed DNDs is investigated. The aggregation behavior of these two colloidal systems is quite different from that of hydrophilic, water soluble functionalized CNTs (F-CNTs). The values of the Fuchs stability ratio or the critical coagulant concentration are determined experimentally using time-resolved dynamic light scattering and are used to predict the stability of such systems. It is found that the aggregation behavior of the organic dispersed, antisolvent precipitated system does not follow the conventional Derjaguin--Landau--Verwey-- Overbeek (DLVO) theory. But they stabilize in the long term, which is attributed to the supersaturation generated by different solubility of a solute in the solvent/antisolvent. Based on particle size distribution, zeta potential as well as the aggregation kinetics, the water dispersed DNDs are found to be relatively stable in aqueous solutions, but aggregate rapidly in presence of mono and divalent salts. Also, the formation of carboxylic groups on the DND surface does not alter colloidal behavior as dramatically as it does for other nanocarbons especially carbon

  3. Temperature stability of AgCu nanoparticles

    Sopoušek, Jiří, E-mail: sopousek@mail.muni.cz; Zobač, Ondřej; Vykoukal, Vít [Masaryk University, Department of Chemistry, Faculty of Science (Czech Republic); Buršík, Jiří; Roupcová, Pavla [Institute of Physics of Materials ASCR (Czech Republic); Brož, Pavel; Pinkas, Jiří [Masaryk University, Department of Chemistry, Faculty of Science (Czech Republic); Vřešťál, Jan [Masaryk University, Central European Institute of Technology, CEITEC (Czech Republic)

    2015-12-15

    The colloidal solutions of the Ag–Cu nanoparticles (NPs, 10–32 nm) were prepared by solvothermal reactions. The samples of dried AgCu NPs and the resulting microstructures after heat treatment in air were investigated by various methods including electron microscopy (TEM, SEM) and high-temperature X-ray powder diffraction (HTXRD). The AgCu randomly mixed, Cu-rich, and Ag-rich face centred cubic crystal lattices were detected during the experiments. The temperature induced sintering was observed experimentally by HTXRD at 250 °C. The phase transformations at high temperatures were monitored by differential scanning calorimetry. The formation of the Ag-rich grains during heating in air and evolution of copper oxide microstructure were detected.Graphical abstract.

  4. PEG-Stabilized Core–Shell Surface-Imprinted Nanoparticles

    Moczko, Ewa; Guerreiro, Antonio; Piletska, Elena; Piletsky, Sergey

    2013-01-01

    Here we present a simple technique to produce target-specific molecularly imprinted polymeric nanoparticles (MIP NPs) and their surface modification in order to prevent the aggregation process that is ever-present in most nanomaterial suspensions/dispersions. Specifically, we studied the influence of surface modification of MIP NPs with polymerizable poly(ethylene glycol) on their degree of stability in water, in phosphate buffer, and in the presence of serum proteins. Grafting a polymer shel...

  5. Colloidal stability of silver nanoparticles in biologically relevant conditions

    MacCuspie, Robert I.

    2011-01-01

    Understanding the colloidal stability of nanoparticles (NPs) plays a key role in phenomenological interpretation of toxicological experiments, particularly if single NPs or their aggregates or agglomerates determine the dominant experimental result. This report examines a variety of instrumental techniques for surveying the colloidal stability of aqueous suspensions of silver nanoparticles (AgNPs), including atomic force microscopy, dynamic light scattering, and colorimetry. It was found that colorimetry can adequately determine the concentration of single AgNPs that remained in solution if morphological information about agglomerates is not required. The colloidal stability of AgNPs with various surface capping agents and in various solvents ranging from cell culture media to different electrolytes of several concentrations, and in different pH conditions was determined. It was found that biocompatible bulky capping agents, such as bovine serum albumin or starch, that provided steric colloidal stabilization, as opposed to purely electrostatic stabilization such as with citrate AgNPs, provided better retention of single AgNPs in solution over a variety of conditions for up to 64 h of observation.

  6. In situ hybridization of superparamagnetic iron-biomolecule nanoparticles.

    Moghimi, Nafiseh; Donkor, Apraku David; Mohapatra, Mamata; Thomas, Joseph Palathinkal; Su, Zhengding; Tang, Xiaowu Shirley; Leung, Kam Tong

    2014-07-23

    The increase in interest in the integration of organic-inorganic nanostructures in recent years has promoted the use of hybrid nanoparticles (HNPs) in medicine, energy conversion, and other applications. Conventional hybridization methods are, however, often long, complicated, and multistepped, and they involve biomolecules and discrete nanostructures as separate entities, all of which hinder the practical use of the resulting HNPs. Here, we present a novel, in situ approach to synthesizing size-specific HNPs using Fe-biomolecule complexes as the building blocks. We choose an anticancer peptide (p53p, MW 1.8 kDa) and an enzyme (GOx, MW 160 kDa) as model molecules to demonstrate the versatility of the method toward different types of molecules over a large size range. We show that electrostatic interaction for complex formation of metal hydroxide ion with the partially charged side of biomolecule in the solution is the key to hybridization of metal-biomolecule materials. Electrochemical deposition is then used to produce hybrid NPs from these complexes. These HNPs with controllable sizes ranging from 30 nm to 3.5 μm are found to exhibit superparamagnetic behavior, which is a big challenge for particles in this size regime. As an example of greatly improved properties and functionality of the new hybrid material, in vitro toxicity assessment of Fe-GOx HNPs shows no adverse effect, and the Fe-p53p HNPs are found to selectively bind to cancer cells. The superparamagnetic nature of these HNPs (superparamagnetic even above the size regime of 15-20 nm!), their biocompatibility, and the direct integration approach are fundamentally important to biomineralization and general synthesis strategy for bioinspired functional materials.

  7. Electrochemical characterization of platinum nanoparticles stabilized by amines

    Ramirez-Meneses, E.; Dominguez-Crespo, M.A.; Montiel-Palma, V.; Chavez-Herrera, V.H.; Gomez, E.; Hernandez-Tapia, G.

    2009-01-01

    In this work we present the synthesis by Chaudret approach of Pt nanoparticles stabilized by primary amine (-NH 2 ) compounds. Their electrochemical performance as cathodes in low temperature polymer electrolite fuel cells on the oxygen reduction reaction (ORR) is also presented. Transmission electron microscopy (TEM) images of the samples show Pt nanostructures with particle size varying from 10 to 100 nm depending on the kind of the stabilizer used during the catalyst preparation. In some cases well-dispersed isolated platinum nanoparticles were observed. The activity of the dispersed catalysts (Pt/C) with respect to the ORR was investigated using steady state polarization measurements. The kinetic parameters showed that although no significant differences between the Tafel slopes of the Pt catalysts exist, transfer coefficients and exchange current densities show higher activities when the Pt nanoparticles were stabilized by tert-butylamine (TBA). The performance with respect to the ORR of the Pt/C catalyst on vulcan carbon substrate is active and comparable to that reported in the literature for state-of-art electrocatalysts.

  8. PEG-stabilized core-shell surface-imprinted nanoparticles.

    Moczko, Ewa; Guerreiro, Antonio; Piletska, Elena; Piletsky, Sergey

    2013-08-06

    Here we present a simple technique to produce target-specific molecularly imprinted polymeric nanoparticles (MIP NPs) and their surface modification in order to prevent the aggregation process that is ever-present in most nanomaterial suspensions/dispersions. Specifically, we studied the influence of surface modification of MIP NPs with polymerizable poly(ethylene glycol) on their degree of stability in water, in phosphate buffer, and in the presence of serum proteins. Grafting a polymer shell on the surface of nanoparticles decreases the surface energy, enhances the polarity, and as a result improves the dispersibility, storage, and colloidal stability as compared to those of core (unmodified) particles. Because of the unique solid-phase approach used for synthesis, the binding sites of MIP NPs are protected during grafting, and the recognition properties of nanoparticles are not affected. These results are significant for developing nanomaterials with selective molecular recognition, increased biocompatibility, and stability in solution. Materials synthesized this way have the potential to be used in a variety of technological fields, including in vivo applications such as drug delivery and imaging.

  9. PEG-Stabilized Core–Shell Surface-Imprinted Nanoparticles

    Moczko, Ewa; Guerreiro, Antonio; Piletska, Elena; Piletsky, Sergey

    2016-01-01

    Here we present a simple technique to produce target-specific molecularly imprinted polymeric nanoparticles (MIP NPs) and their surface modification in order to prevent the aggregation process that is ever-present in most nanomaterial suspensions/dispersions. Specifically, we studied the influence of surface modification of MIP NPs with polymerizable poly(ethylene glycol) on their degree of stability in water, in phosphate buffer, and in the presence of serum proteins. Grafting a polymer shell on the surface of nanoparticles decreases the surface energy, enhances the polarity, and as a result improves the dispersibility, storage, and colloidal stability as compared to those of core (unmodified) particles. Because of the unique solid-phase approach used for synthesis, the binding sites of MIP NPs are protected during grafting, and the recognition properties of nanoparticles are not affected. These results are significant for developing nanomaterials with selective molecular recognition, increased biocompatibility, and stability in solution. Materials synthesized this way have the potential to be used in a variety of technological fields, including in vivo applications such as drug delivery and imaging. PMID:23855734

  10. Polyvinylpyrrolidone Matrix as an Effective Reducing Agent and Stabilizer during Reception of Silver Nanoparticles in Composites

    Semenyuk, Nataliya; Kostiv, Ulyana; Dudok, Galyna; Nechay, Jaroslav; Skorokhoda, Volodymyr

    2013-01-01

    The use of polyvinylpyrrolidone matrix as an effective reducing agent and stabilizer during reception of silver nanoparticles in composites is substantiated. The influence of various factors on patterns of obtaining silver nanoparticles and their size.

  11. A potential non-invasive glioblastoma treatment: Nose-to-brain delivery of farnesylthiosalicylic acid incorporated hybrid nanoparticles.

    Sekerdag, Emine; Lüle, Sevda; Bozdağ Pehlivan, Sibel; Öztürk, Naile; Kara, Aslı; Kaffashi, Abbas; Vural, Imran; Işıkay, Ilkay; Yavuz, Burҫin; Oguz, Kader Karlı; Söylemezoğlu, Figen; Gürsoy-Özdemir, Yasemin; Mut, Melike

    2017-09-10

    New drug delivery systems are highly needed in research and clinical area to effectively treat gliomas by reaching a high antineoplastic drug concentration at the target site without damaging healthy tissues. Intranasal (IN) administration, an alternative route for non-invasive drug delivery to the brain, bypasses the blood-brain-barrier (BBB) and eliminates systemic side effects. This study evaluated the antitumor efficacy of farnesylthiosalicylic acid (FTA) loaded (lipid-cationic) lipid-PEG-PLGA hybrid nanoparticles (HNPs) after IN application in rats. FTA loaded HNPs were prepared, characterized and evaluated for cytotoxicity. Rat glioma 2 (RG2) cells were implanted unilaterally into the right striatum of female Wistar rats. 10days later, glioma bearing rats received either no treatment, or 5 repeated doses of 500μM freshly prepared FTA loaded HNPs via IN or intravenous (IV) application. Pre-treatment and post-treatment tumor sizes were determined with MRI. After a treatment period of 5days, IN applied FTA loaded HNPs achieved a significant decrease of 55.7% in tumor area, equal to IV applied FTA loaded HNPs. Herewith, we showed the potential utility of IN application of FTA loaded HNPs as a non-invasive approach in glioblastoma treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Thermal stability of carbon nanotubes probed by anchored tungsten nanoparticles

    Xianlong Wei, Ming-Sheng Wang, Yoshio Bando and Dmitri Golberg

    2011-01-01

    Full Text Available The thermal stability of multiwalled carbon nanotubes (CNTs was studied in high vacuum using tungsten nanoparticles as miniaturized thermal probes. The particles were placed on CNTs inside a high-resolution transmission electron microscope equipped with a scanning tunneling microscope unit. The setup allowed manipulating individual nanoparticles and heating individual CNTs by applying current to them. CNTs were found to withstand high temperatures, up to the melting point of 60-nm-diameter W particles (~3400 K. The dynamics of W particles on a hot CNT, including particle crystallization, quasimelting, melting, sublimation and intradiffusion, were observed in real time and recorded as a video. Graphite layers reel off CNTs when melted or premelted W particles revolve along the tube axis.

  13. Selective Electrocatalytic Activity of Ligand Stabilized Copper Oxide Nanoparticles

    Kauffman, Douglas R; Ohodnicki, Paul R; Kail, Brian W; Matranga, Christopher

    2011-01-01

    Ligand stabilization can influence the surface chemistry of Cu oxide nanoparticles (NPs) and provide unique product distributions for electrocatalytic methanol (MeOH) oxidation and CO{sub 2} reduction reactions. Oleic acid (OA) stabilized Cu{sub 2}O and CuO NPs promote the MeOH oxidation reaction with 88% and 99.97% selective HCOH formation, respectively. Alternatively, CO{sub 2} is the only reaction product detected for bulk Cu oxides and Cu oxide NPs with no ligands or weakly interacting ligands. We also demonstrate that OA stabilized Cu oxide NPs can reduce CO{sub 2} into CO with a {approx}1.7-fold increase in CO/H{sub 2} production ratios compared to bulk Cu oxides. The OA stabilized Cu oxide NPs also show 7.6 and 9.1-fold increases in CO/H{sub 2} production ratios compared to weakly stabilized and non-stabilized Cu oxide NPs, respectively. Our data illustrates that the presence and type of surface ligand can substantially influence the catalytic product selectivity of Cu oxide NPs.

  14. Improvement of the oxidation stability of cobalt nanoparticles

    Celin Dobbrow

    2012-01-01

    Full Text Available In order to enhance the resistance of cobalt nanoparticles to oxidation in air, the impact of different stabilization strategies on the isothermal oxidation of particle dispersions and powders was kinetically investigated and compared to as-prepared particle preparations. A post-synthesis treatment with different alcohols was employed, and we also investigate the influence of two different polymer shells on the oxidation process. We found a parabolic decrease of the magnetization for all particle charges, indicating that the process is dominated by a diffusion of oxygen to the cobalt core and a radial growth of the oxide layer from the particle surface to the core. A significant deceleration of the oxidation process was observed for all alcohol-passivated particle preparations, and this resulted finally in a stagnation effect. The stabilizing effect increases in the sequence Co@OA/MeOH < Co@OA/EtOH < Co@OA/iPrOH. For polymer-coated particle preparations Co@PCL and Co@PS, the deceleration was even more pronounced. The results demonstrate that cobalt nanoparticles can effectively be protected against oxidation in order to improve their mid- to longterm stability.

  15. The effect of nanoparticle aggregation on surfactant foam stability.

    AlYousef, Zuhair A; Almobarky, Mohammed A; Schechter, David S

    2018-02-01

    The combination of nanoparticles (NPs) and surfactant may offer a novel technique of generating stronger foams for gas mobility control. This study evaluates the potential of silica NPs to enhance the foam stability of three nonionic surfactants. Results showed that the concentration of surfactant and NPs is a crucial parameter for foam stability and that there is certain concentrations for strong foam generation. A balance in concentration between the nonionic surfactants and the NPs can enhance the foam stability as a result of forming flocs in solutions. At fixed surfactant concentration, the addition of NPs at low to intermediate concentrations can produce a more stable foam compared to the surfactant. The production of small population of flocs as a result of mixing the surfactant and NPs can enhance the foam stability by providing a barrier between the gas bubbles and delaying the coalescence of bubbles. Moreover, these flocs can increase the solution viscosity and, therefore, slow the drainage rate of thin aqueous film (lamellae). The measurements of foam half-life, bubble size, and mobility tests confirmed this conclusion. However, the addition of more solid particles or surfactant might have a negative impact on foam stability and reduce the maximum capillary pressure of coalescence as a result of forming extensive aggregates. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Glycol stabilized magnetic nanoparticles for photocatalytic degradation of xylenol orange

    Ullah, Ikram; Ali, Farman; Ali, Zarshad; Humayun, Muhammad; wahab, Zain Ul

    2018-05-01

    In this work, we have successfully prepared ZnFe2O4 magnetic nanoparticles as photocatalysts via co-precipitation method using triethylene glycol as a stabilizing agent. The resultant nanoparticles were annealed at 400 °C and then acid etched and surface functionalized with 3-(triethoxysilyl) propyl amine (APTES). Fourier transform infrared (FTIR) spectroscopy and x-ray diffraction (XRD) analysis were used to characterize these magnetic photocatalysts. XRD patterns revealed that the size of annealed and functionalized ZnFe2O4 nanoparticles falls in the range of 23.3 and 13.9 nm, respectively. The optical band gaps of the magnetic photocatalysts were calculated from UV–Visible absorption spectra using Tauc plots. The band gap of the ZnFe2O4 photocatalyst in acidic and basic medium was 2.47 and 2.7 eV, respectively. The performance of the magnetic photocatalysts was evaluated for xylenol orange (XO) degradation. The degradation rates of XO dye for the blank, annealed and functionalized photocatalysts at pH = 4 were 76%, 85%, and 90%, respectively. In addition, the influence of important parameters such as contact time, pH, catalyst, and dye dose were also investigated for all the three photocatalysts. The applied kinetics models demonstrated that the degradation followed pseudo 1st order.

  17. Stability of colloidal silver nanoparticles trapped in lipid bilayer: effect of lecithin concentration and applied temperature

    Barani, H.; Montazer, M.; Braun, H.G.; Dutschk, Victoria

    2014-01-01

    The use of silver nanoparticle on various substrates has been widespread because of its good antibacterial properties that directly depend on the stability of the silver nanoparticles in a colloidal suspension. In this study, the colloidal solutions of the silver nanoparticles were synthesised by a

  18. Progesterone PLGA/mPEG-PLGA Hybrid Nanoparticle Sustained-Release System by Intramuscular Injection.

    Xie, Bin; Liu, Yang; Guo, Yuting; Zhang, Enbo; Pu, Chenguang; He, Haibing; Yin, Tian; Tang, Xing

    2018-02-14

    To prepare sustained-release PLGA/mPEG-PLGA hybrid nanoparticles of progesterone (PRG), and evaluate the descending required administration dosage in vivo. PRG hybrid nanoparticles (PRG H-NPs) based on PLGA/mPEG-PLGA were compared with PRG nanoparticles (PRG-NPs) of pure PLGA as the matrix and PRG-oil solutions. Nanoparticles (NPs) were formed by the method of nanoemulsion, and the pharmacokinetics of the sustained-release PRG H-NPs in male Sprague dawley (SD) rats were investigated. The rats were randomly divided into four groups, each group received: single dose of PRG H-NPs (14.58 mg/kg, i.m.) and PRG-NPs (14.58 mg/kg, i.m.), repeated dosing for 7 days of PRG-oil (2.08 mg/kg, i.m.) solution (Oil-L) and a higher dosage of PRG-oil (6.24 mg/kg, i.m.) solution (Oil-H), respectively. In the pharmacokinetic test, the PRG H-NPs exhibited a comparatively good sustained-release effect against the PRG-NPs without mPEG-PLGA and PRG-oil solution. The pharmacokinetic parameters of the PRG H-NPs, PRG-NPs, Oil-L and Oil-H were AUC 0-t (ng·h·mL -1 ) 8762.1, 1546.1, 1914.5, and 12,138.9, t 1/2 (h)52.7, 44.1, 8.4 and 44.6 respectively. Owing to the modification of PEG, PRG H-NPs can act as safe delivery platforms for sustained-release of drugs with a lower dosage required.

  19. Facile synthesis of chondroitin sulfate-stabilized gold nanoparticles

    Li Wei, E-mail: weilixj8510@163.com [School of Science, Henan Agricultural University, No. 95 Wenhua Road, Zhengzhou, Henan 450002 (China); Li Xin; Su Hui; Zhao Shiju; Li Yanyun; Hu Jiandong [School of Science, Henan Agricultural University, No. 95 Wenhua Road, Zhengzhou, Henan 450002 (China)

    2011-02-15

    A facile and simple method for the synthesis of biocompatible gold nanoparticles (AuNPs) at room temperature has been developed by using sodium borohydride as the reducing agent and employing an inexpensive water-soluble chondroitin sulfate (CS) biopolymer as the stabilizing agent. The as-prepared AuNPs were characterized with ultraviolet-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM). Additionally, the stability of AuNPs in aqueous solution was investigated as a function of the electrolyte sodium chloride concentration. The experimental results showed that even high sodium chloride concentration (1 M) also did not destabilize the colloidal gold solution. So it could be speculated that the high stability of AuNPs should be attributed to the electrostatic repulsion and steric hindrance between the AuNPs stabilized by CS molecules, which wrapped around the surface of as-prepared AuNPs and prevented their agglomeration, and simultaneously improve biocompatibility of AuNPs as well.

  20. Facile synthesis of chondroitin sulfate-stabilized gold nanoparticles

    Li Wei; Li Xin; Su Hui; Zhao Shiju; Li Yanyun; Hu Jiandong

    2011-01-01

    A facile and simple method for the synthesis of biocompatible gold nanoparticles (AuNPs) at room temperature has been developed by using sodium borohydride as the reducing agent and employing an inexpensive water-soluble chondroitin sulfate (CS) biopolymer as the stabilizing agent. The as-prepared AuNPs were characterized with ultraviolet-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM). Additionally, the stability of AuNPs in aqueous solution was investigated as a function of the electrolyte sodium chloride concentration. The experimental results showed that even high sodium chloride concentration (1 M) also did not destabilize the colloidal gold solution. So it could be speculated that the high stability of AuNPs should be attributed to the electrostatic repulsion and steric hindrance between the AuNPs stabilized by CS molecules, which wrapped around the surface of as-prepared AuNPs and prevented their agglomeration, and simultaneously improve biocompatibility of AuNPs as well.

  1. Stabilization and functionalization of iron oxide nanoparticles for biomedical applications

    Amstad, Esther; Textor, Marcus; Reimhult, Erik

    2011-07-01

    Superparamagnetic iron oxide nanoparticles (NPs) are used in a rapidly expanding number of research and practical applications in the biomedical field, including magnetic cell labeling separation and tracking, for therapeutic purposes in hyperthermia and drug delivery, and for diagnostic purposes, e.g., as contrast agents for magnetic resonance imaging. These applications require good NP stability at physiological conditions, close control over NP size and controlled surface presentation of functionalities. This review is focused on different aspects of the stability of superparamagnetic iron oxide NPs, from its practical definition to its implementation by molecular design of the dispersant shell around the iron oxide core and further on to its influence on the magnetic properties of the superparamagnetic iron oxide NPs. Special attention is given to the selection of molecular anchors for the dispersant shell, because of their importance to ensure colloidal and functional stability of sterically stabilized superparamagnetic iron oxide NPs. We further detail how dispersants have been optimized to gain close control over iron oxide NP stability, size and functionalities by independently considering the influences of anchors and the attached sterically repulsive polymer brushes. A critical evaluation of different strategies to stabilize and functionalize core-shell superparamagnetic iron oxide NPs as well as a brief introduction to characterization methods to compare those strategies is given.Superparamagnetic iron oxide nanoparticles (NPs) are used in a rapidly expanding number of research and practical applications in the biomedical field, including magnetic cell labeling separation and tracking, for therapeutic purposes in hyperthermia and drug delivery, and for diagnostic purposes, e.g., as contrast agents for magnetic resonance imaging. These applications require good NP stability at physiological conditions, close control over NP size and controlled surface

  2. Stabilizing liquid drops of arbitrary shape by the interfacial jamming of nanoparticles

    Russell, Thomas P.; Cui, Mengmeng; Emrick, Todd

    2018-01-30

    A stabilized assembly including a first liquid phase of non-spherical droplets in a second liquid phase, wherein the second liquid phase is immiscible with the first phase, and nanoparticle surfactants assembled at an interface of the non-spherical droplets and the second phase is disclosed. The nanoparticle surfactants include nanoparticles and end-functionalized polymers that can interact through ligand type interactions, and the first phase is stabilized by a disordered, jammed layer of nanoparticle surfactants. A method of preparing a stabilized assembly is also disclosed.

  3. Comparative study of gum arabic and PVP as stabilizing agents for synthesis of gold nanoparticles

    Silva, Andressa A.; Leal, Jessica; Geraldes, Adriana N.; Lugao, Ademar B.

    2015-01-01

    Use Colloidal metallic nanoparticles such as gold nanoparticles have received a great attention, due in part to their specific properties and potential applications. Control of size and uniformity of nanoparticles is important to prevent aggregation. High-molecular-weight polymers were used as stabilizer agents. Natural polymers, such as gum Arabic, are used as stabilizer because of capping nanoparticles behavior and present advantages such as solubility, non- toxicity and its compatibility for pharmaceutical and biomedical applications. Previous studies showed that the hydrophilic group of Poly(vinyl pyrrolidone) (PVP) caused repulsion on gold nanoparticles surface because steric interactions with polymer, for this reason this kind of polymers could be used as stabilizer agent. The aim of this work is to study the synthesis and stabilization of gold nanoparticles with PVP and gum Arabic using gamma radiation. The results obtained by samples analysis using UV-Visible showed that the gamma irradiation doses influenced the nanoparticles formation by PVP but that is not the case with the GA, because for smaller quantity of Arabic gum in different doses produced and stabilized nanoparticles. The samples were observed for 20 days and showed stability. We have obtained preliminary results showed that the use of radiation is applicable to the formation of gold nanoparticles. (author)

  4. Comparative study of gum arabic and PVP as stabilizing agents for synthesis of gold nanoparticles

    Silva, Andressa A.; Leal, Jessica; Geraldes, Adriana N.; Lugao, Ademar B., E-mail: andressa_alvess@yahoo.com.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    Use Colloidal metallic nanoparticles such as gold nanoparticles have received a great attention, due in part to their specific properties and potential applications. Control of size and uniformity of nanoparticles is important to prevent aggregation. High-molecular-weight polymers were used as stabilizer agents. Natural polymers, such as gum Arabic, are used as stabilizer because of capping nanoparticles behavior and present advantages such as solubility, non- toxicity and its compatibility for pharmaceutical and biomedical applications. Previous studies showed that the hydrophilic group of Poly(vinyl pyrrolidone) (PVP) caused repulsion on gold nanoparticles surface because steric interactions with polymer, for this reason this kind of polymers could be used as stabilizer agent. The aim of this work is to study the synthesis and stabilization of gold nanoparticles with PVP and gum Arabic using gamma radiation. The results obtained by samples analysis using UV-Visible showed that the gamma irradiation doses influenced the nanoparticles formation by PVP but that is not the case with the GA, because for smaller quantity of Arabic gum in different doses produced and stabilized nanoparticles. The samples were observed for 20 days and showed stability. We have obtained preliminary results showed that the use of radiation is applicable to the formation of gold nanoparticles. (author)

  5. Synthesis and Stability of Iron Nanoparticles for Lunar Environment Studies

    Hung, Ching-cheh; McNatt, Jeremiah

    2009-01-01

    Simulant of lunar dust is needed when researching the lunar environment. However, unlike the true lunar dust, today s simulants do not contain nanophase iron. Two different processes have been developed to fabricate nanophase iron to be used as part of the lunar dust simulant: (1) Sequentially treating a mixture of ferric chloride, fluorinated carbon, and soda lime glass beads at about 300 C in nitrogen, at room temperature in air, and then at 1050 C in nitrogen. The product includes glass beads that are grey in color, can be attracted by a magnet, and contain alpha-iron nanoparticles (which seem to slowly lose their lattice structure in ambient air during a period of 12 months). This product may have some similarity to the lunar glassy regolith that contains Fe(sup 0). (2) Heating a mixture of carbon black and a lunar simulant (a mixed metal oxide that includes iron oxide) at 1050 C in nitrogen. This process simulates lunar dust reaction to the carbon in a micrometeorite at the time of impact. The product contains a chemically modified simulant that can be attracted by a magnet and has a surface layer whose iron concentration increased during the reaction. The iron was found to be alpha-iron and Fe3O4 nanoparticles, which appear to grow after the fabrication process, but stabilizes after 6 months of ambient air storage.

  6. Synthesis, Structure, Stability and Redispersion of Gold-based Nanoparticles

    Tiruvalam, Ram Chandra

    ' particles with Pd-shell/Au-core and Au-shell/Pd-core morphologies, have been prepared and immobilized on both activated carbon and TiO2 supports. These have subsequently been compared as catalysts for the direct production of H2O2 and for benzyl alcohol oxidation in an attempt to elucidate the optimum particle morphology/support combination for both these reactions. Aberration corrected analytical electron microscopy has been used extensively to characterize these sol-immobilized materials. In particular, the STEM -HAADF technique has provided invaluable new (and often unexpected) information on the atomic structure, elemental distribution within particles, and compositional variations between particles for these controlled catalyst preparations. In addition, we have been able to compare their differing thermal stability and sintering behaviors, and to demonstrate that they have quite varying wetting interactions with activated carbon and TiO2 supports. Over the course of their lifetime, many supported metal catalysts exposed to elevated temperatures tend to de-activate by nanoparticle sintering, which decreases the overall exposed metal surface area and the number of active sites available for catalysis. It is sometimes desirable to devise chemical re-dispersion treatments whereby the mean size of the particles is reduced and the catalytic activity regenerated. In this work, the possibility of re-dispersing gold nanoparticles by a simple low temperature methyl iodide (CH3 I) treatment has been investigated. A variety of characterization techniques, including EXAFS, XRD, XPS, UV-DRS and STEM-HAADF imaging has been applied to samples before and after CH3 I treatment, in an attempt to determine the efficacy of the re-dispersion method. It is shown that re-dispersion of Au nanoparticles on activated carbon, graphite, Al2 O3 and TiO2 substrates is possible to varying degrees. A complete re-dispersion of `bulk' gold nanoparticles down to the atomic scale has been achieved on

  7. Advances of Researches on Improving the Stability of Foams by Nanoparticles

    Wang, G.; Wang, K. L.; Lu, C. J.

    2017-09-01

    Recently, nano-tech made a change of traditional oil-gas exploration. Considering that foam fluid had a poor stability, investigators proposed to add nanoparticles to stabilize the foam fluid system. This paper described the mechanism of particles to improve the stability of the foam fluid in detail; and emphasized the synergistic effect between nanoparticles and surfactants and its effect on the foaming and foam stability of dispersions; and reviewed the latest applications of foam fluid that was stabilized by nanoparticle in enhancing oil-gas recovery, in which there are analysis that showed that the nanoparticles not only greatly increase the stability of the foam fluid, but also improve the efficiency of foam fluid; and lastly, forecasted the development of nanotechnology in petroleum areas.

  8. In vitro cytotoxicity of iron oxide nanoparticles: effects of chitosan and polyvinyl alcohol as stabilizing agents

    Tran, Phong A.; Nguyen, Hiep T.; Fox, Kate; Tran, Nhiem

    2018-03-01

    Iron oxide magnetic nanoparticles have significant potential in biomedical applications such as in diagnosis, imaging and therapeutic agent delivery. The choice of stabilizers and surface functionalization is important as it is known to strongly influence the cytotoxicity of the nanoparticles. The present study aimed at investigating the effects of surface charges on the cytotoxicity of iron oxide nanoparticles. We used a co-precipitation method to synthesize iron oxide nanoparticles which were then stabilized with either chitosan (CS) or polyvinyl alcohol (PVA) which have net positive charge and zero charge at physiological pH, respectively. The nanoparticles were characterized in terms of size, charges and chemical oxidation state. Cytotoxicity of the nanoparticles was assessed using mouse fibroblast cells and was correlated with surface charges of the nanoparticles and their aggregation.

  9. Biopolymer-stabilized Pt nanoparticles colloid: a highly active and recyclable catalyst for biphasic catalysis

    Wang, Yujia; Shen, Yueyue; Qiu, Yunfei; Zhang, Ting; Liao, Yang; Zhao, Shilin; Ma, Jun; Mao, Hui

    2016-01-01

    Noble metal nanoparticles are promising candidates to replace conventional bulk counterparts owing to their high activity and selectivity. To enable catalyst recovery, noble metal nanoparticles are often supported onto solid matrices to prepare heterogeneous catalyst. Although recycle of noble metal nanoparticles is realized by heterogenization, a loss of activity is usually encountered. In the present investigation, Pt nanoparticles with tunable particle size (1.85–2.80 nm) were facilely prepared by using polyphenols as amphiphilic stabilizers. The as-prepared Pt nanoparticles colloid solution could be used as highly active catalyst in aqueous–organic biphasic catalysis. The phenolic hydroxyls of polyphenols could constrain Pt nanoparticles in aqueous phase, and simultaneously, the aromatic scaffold of polyphenols ensured effective interactions between substrates and Pt nanoparticles. As a consequence, the obtained polyphenols-stabilized Pt nanoparticles exhibited high activity and cycling stability in biphasic hydrogenation of a series of unsaturated compounds. Compared with conventional heterogeneous Pt-C and Pt-Al 2 O 3 catalysts, polyphenols-stabilized Pt nanoparticles showed obvious advantage both in activity and cycling stability.

  10. Biopolymer-stabilized Pt nanoparticles colloid: a highly active and recyclable catalyst for biphasic catalysis

    Wang, Yujia; Shen, Yueyue; Qiu, Yunfei; Zhang, Ting; Liao, Yang; Zhao, Shilin; Ma, Jun, E-mail: 1044208419@qq.com; Mao, Hui, E-mail: rejoice222@163.com [Sichuan Normal University, College of Chemistry and Materials Science (China)

    2016-10-15

    Noble metal nanoparticles are promising candidates to replace conventional bulk counterparts owing to their high activity and selectivity. To enable catalyst recovery, noble metal nanoparticles are often supported onto solid matrices to prepare heterogeneous catalyst. Although recycle of noble metal nanoparticles is realized by heterogenization, a loss of activity is usually encountered. In the present investigation, Pt nanoparticles with tunable particle size (1.85–2.80 nm) were facilely prepared by using polyphenols as amphiphilic stabilizers. The as-prepared Pt nanoparticles colloid solution could be used as highly active catalyst in aqueous–organic biphasic catalysis. The phenolic hydroxyls of polyphenols could constrain Pt nanoparticles in aqueous phase, and simultaneously, the aromatic scaffold of polyphenols ensured effective interactions between substrates and Pt nanoparticles. As a consequence, the obtained polyphenols-stabilized Pt nanoparticles exhibited high activity and cycling stability in biphasic hydrogenation of a series of unsaturated compounds. Compared with conventional heterogeneous Pt-C and Pt-Al{sub 2}O{sub 3} catalysts, polyphenols-stabilized Pt nanoparticles showed obvious advantage both in activity and cycling stability.

  11. Gold nanoparticles synthesized by gamma radiation and stabilized by bovine serum albumin

    Leal, Jessica; Silva, Andressa A.; Geraldes, Adriana N.; Lugao, Ademar B.; Grasselli, Mariano

    2015-01-01

    Gold nanoparticles (AuNPs) are a new option for pharmaceutical and cosmetic industries due to their interesting chemical, electrical and catalytic properties. Research for cancer treatments have been developed using this promising radiotherapy agent. The challenge of gold nanoparticles is to keep them stable, due to metallic behavior. It is know that surface plasma resonance promotes agglomeration of metallic nanoparticles, but they are not stable. Stabilizers have been used to reduce agglomeration. The aim of this work is reduction of HAuCl 4 salt to AuNPs performed by gamma radiation 60 Co source and the stabilization of gold nanoparticles using bovine serum albumin (BSA) fraction V as stabilizer agent. AuNPs were characterized by UV-visible to verify the nanoparticles formation. Samples containing BSA and samples obtained by the conventional method (without stabilizer) were monitored for two weeks and analyzed. Results were compared. (author)

  12. Gold nanoparticles synthesized by gamma radiation and stabilized by bovine serum albumin

    Leal, Jessica; Silva, Andressa A.; Geraldes, Adriana N.; Lugao, Ademar B., E-mail: jessicaleal@usp.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Grasselli, Mariano, E-mail: mariano.grasselli@gmail.com [Departamento de Ciencia y Tecnologia, Universidad Nacional de Quilmes, Bernal (Argentina)

    2015-07-01

    Gold nanoparticles (AuNPs) are a new option for pharmaceutical and cosmetic industries due to their interesting chemical, electrical and catalytic properties. Research for cancer treatments have been developed using this promising radiotherapy agent. The challenge of gold nanoparticles is to keep them stable, due to metallic behavior. It is know that surface plasma resonance promotes agglomeration of metallic nanoparticles, but they are not stable. Stabilizers have been used to reduce agglomeration. The aim of this work is reduction of HAuCl{sub 4} salt to AuNPs performed by gamma radiation {sup 60}Co source and the stabilization of gold nanoparticles using bovine serum albumin (BSA) fraction V as stabilizer agent. AuNPs were characterized by UV-visible to verify the nanoparticles formation. Samples containing BSA and samples obtained by the conventional method (without stabilizer) were monitored for two weeks and analyzed. Results were compared. (author)

  13. Cu-Ag core–shell nanoparticles with enhanced oxidation stability for printed electronics

    Lee, Changsoo; Kim, Na Rae; Koo, Jahyun; Lee, Yung Jong; Lee, Hyuck Mo

    2015-01-01

    In this work, we synthesized uniform Cu–Ag core–shell nanoparticles using a facile two-step process that consists of thermal decomposition and galvanic displacement methods. The core–shell structure of these nanoparticles was confirmed through characterization using transmission electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. Furthermore, we investigated the oxidation stability of the Cu–Ag core–shell nanoparticles in detail. Both qualitative and quantitative x-ray photoelectron spectroscopy analyses confirm that the Cu–Ag core–shell nanoparticles have considerably higher oxidation stability than Cu nanoparticles. Finally, we formulated a conductive ink using the synthesized nanoparticles and coated it onto glass substrates. Following the sintering process, we compared the resistivity of the Cu–Ag core–shell nanoparticles with that of the Cu nanoparticles. The results of this study clearly show that the Cu–Ag core–shell nanoparticles can potentially be used as an alternative to Ag nanoparticles because of their superior oxidation stability and electrical properties. (paper)

  14. Synthesis of netlike gold nanoparticles using ampicillin as a stabilizing reagent and its application

    Song, Y.Z.; Zhou, J.F.; Song, Y.; Cheng, Z.P.; Xu, J.

    2012-01-01

    Graphical abstract: Electrochemical deposition of netlike gold nanoparticles (GNPs) on the surface of glassy carbon electrode and preparation of netlike GNPs in aqueous solution using ampicillin as a stabilizing reagent were proposed. The catalytic properties of netlike gold nanoparticles on the glassy carbon electrode for dopamine were demonstrated. The results indicate that the netlike gold nanoparticle modified electrode has an excellent repeatability and reproducibility. Display Omitted Highlights: ► Synthesis of netlike gold nanoparticles using ampicillin as a stabilizing reagent. ► Excellent repeatability and reproducibility of netlike gold nanoparticle modified glassy carbon electrode. ► The catalytic properties of netlike gold nanoparticle for dopamine. -- Abstract: Electrochemical deposition of netlike gold nanoparticles on the surface of glassy carbon electrode and preparation of netlike GNPs in aqueous solution using ampicillin as a stabilizing reagent were proposed. The netlike gold nanoparticles were characterized by scanning electron microscope, transmission electron microscope, infrared spectrometer, UV spectrophotometer, powder X-ray diffractometer and electrochemical analyzer. The catalysis of the netlike gold nanoparticles on the glassy carbon electrode for dopamine was demonstrated. The results indicate that the gold nanoparticle modified electrode has an excellent repeatability and reproducibility.

  15. Influence of functionalized nanoparticles on conformational stability of type I collagen for possible biomedical applications.

    Kandamchira, Aswathy; Selvam, Sangeetha; Marimuthu, Nidhin; Janardhanan, Sreeram Kalarical; Fathima, Nishter Nishad

    2013-12-01

    Collagen-nanoparticle interactions are vital for many biomedical applications including drug delivery and tissue engineering applications. Iron oxide nanoparticles synthesized using starch template according to our earlier reported procedures were functionalized by treating them with Gum Arabic (GA), a biocompatible polysaccharide, so as to enhance the interaction between nanoparticle surfaces and collagen. Viscosity, circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) techniques have been used to study the collagen-nanoparticle interactions. The relative viscosity for collagen-nanoparticle conjugate was found to increase with increase in concentration of the nanoparticle within the concentration range investigated, which is due to the aggregation of protein onto the surface of nanoparticle. The CD spectra for the collagen-nanoparticle at different concentration ratios do not have much variation in the Rpn values (ratio of positive peak intensity over negative peak intensity) after functionalization with GA. The variation of molar ellipticity values for collagen-nanoparticle is due to the glycoprotein present in GA. The collagen triple helical structure is maintained after interaction with nanoparticles. The FTIR spectra of native collagen, Coll-Fs (nanoparticle without functionalization) and Coll-FsG (nanoparticle functionalized with GA) show clearly the amide I, II, III bands, with respect to collagen. The ability of polysaccharide stabilized/functionalized nanoparticles to maintain the collagen properties would help in its biomedical applications. © 2013.

  16. Rheology and stability kinetics of bare silicon nanoparticle inks for low-cost direct printing

    More, Priyesh V.; Jeong, Sunho; Seo, Yeong-Hui; Ryu, Beyong-Hwan; Choi, Youngmin; Kim, Seong Jip; Nahm, Sahn

    2013-01-01

    Highly dispersed and stable silicon nanoparticles ink is formulated for its application in direct printing or printable electronics. These dispersions are prepared from free-standing silicon nanoparticles which are not capped with any organic ligand, making it suitable for electronic applications. Silicon nanoparticles dispersions are prepared by suspending the nanoparticles in benzonitrile or ethanol by using polypropylene glycol (PPG) as a binder. All the samples show typical shear thinning behavior while the dispersion samples show low viscosities signifying good quality dispersion. Such thinning behavior favors in fabrication of dense films with spin-coating or patterns with drop casting. The dispersion stability is monitored by turbiscan measurements showing good stability for one week. A low-cost direct printing method for dispersion samples is also demonstrated to obtain micro-sized patterns. Low electrical resistivity of resulting patterns, adjustable viscosity and good stability makes these silicon nanoparticles dispersions highly applicable for direct printing process

  17. Rheology and stability kinetics of bare silicon nanoparticle inks for low-cost direct printing

    More, Priyesh V.; Jeong, Sunho; Seo, Yeong-Hui; Ryu, Beyong-Hwan; Choi, Youngmin [Advanced Materials Division, Korea Research Institute of Chemical Technology 141 Gajeong-ro, Yuseong-gu, Daejeon 305-600 (Korea, Republic of); Kim, Seong Jip [Advanced Materials Division, Korea Research Institute of Chemical Technology 141 Gajeong-ro, Yuseong-gu, Daejeon 305-600 Korea and Department of Materials Science and Engineering, Korea University 5-1 Anam-Dong, Seongbuk-gu, Seoul 136-701 (Korea, Republic of); Nahm, Sahn [Department of Materials Science and Engineering, Korea University 5-1 Anam-Dong, Seongbuk-gu, Seoul 136-701 (Korea, Republic of)

    2013-12-16

    Highly dispersed and stable silicon nanoparticles ink is formulated for its application in direct printing or printable electronics. These dispersions are prepared from free-standing silicon nanoparticles which are not capped with any organic ligand, making it suitable for electronic applications. Silicon nanoparticles dispersions are prepared by suspending the nanoparticles in benzonitrile or ethanol by using polypropylene glycol (PPG) as a binder. All the samples show typical shear thinning behavior while the dispersion samples show low viscosities signifying good quality dispersion. Such thinning behavior favors in fabrication of dense films with spin-coating or patterns with drop casting. The dispersion stability is monitored by turbiscan measurements showing good stability for one week. A low-cost direct printing method for dispersion samples is also demonstrated to obtain micro-sized patterns. Low electrical resistivity of resulting patterns, adjustable viscosity and good stability makes these silicon nanoparticles dispersions highly applicable for direct printing process.

  18. Aqueous starch as a stabilizer in zinc oxide nanoparticle synthesis via laser ablation

    Zamiri, Reza; Zakaria, Azmi; Ahangar, Hossein Abbastabar; Darroudi, Majid; Zak, Ali Khorsand; Drummen, Gregor P.C.

    2012-01-01

    Highlights: ► Zinc oxide nanoparticles were synthesized via LASiS in aqueous starch solution. ► Nanoparticles of ±15 nm are produced with a narrow size distribution. ► Starch can be used as a template to control nanoparticle size. ► Starch stabilizes zinc oxide nanoparticles in solution through steric hindrance. - Abstract: Zinc oxide is a semiconductor with exceptional thermal, luminescent and electrical properties, even compared with other semiconducting nanoparticles. Its potential for advanced applications in lasers and light emitting diodes, as bio-imaging agent, in biosensors and as drug delivery vehicles, in ointments, coatings and pigments has pulled zinc oxide into the focus of various scientific and engineering research fields. Recently we started investigating if nanoparticle synthesis via laser ablation in the presence of natural stabilizers allows control over size and shape and constitutes a useful, uncomplicated alternative over conventional synthesis methods. In the current paper, we determined the ability of natural starch to act as a size controller and stabilizer in the preparation of zinc oxide nanoparticles via ablation of a ZnO plate in a starch solution with a nanosecond Q-Switched Nd:YAG pulsed laser at its original wavelength (λ = 1064 nm). Our results show that the particle diameter decreases with increasing laser irradiation time to a mean nanoparticle size of approximately 15 nm with a narrow size distribution. Furthermore, the obtained particle size in starch solution is considerably smaller compared with analogous ZnO nanoparticle synthesis in distilled water. The synthesized and capped nanoparticles retained their photoluminescent properties, but showed blue emission rather than the often reported green luminescence. Evaluation of old preparations compared with freshly made samples showed no agglomeration or flocculation, which was reflected in no significant change in the ZnO nanoparticle size and size distribution. Overall

  19. Stabilization of Pt nanoparticles by single stranded DNA and the binary assembly of Au and Pt nanoparticles without hybridization

    Yang, J.; Lee, Jim Yang; Too, Heng-Phon; Chow, Gan-Moog; Gan, Leong M.

    2006-01-01

    The non-specific interaction between single stranded DNA (ssDNA) and 12 nm Pt nanoparticles is investigated in this work. The data show a strong and non-specific interaction between the two which can be exploited for the stabilization of Pt nanoparticles in aqueous solutions. Based on the experimental findings, a non-hybridization based protocol to assemble 17 nm Au and Pt nanoparticles (12 nm cubic and 3.6 nm spherical) by single-stranded DNA was developed. Transmission electron microscopy (TEM) and UV-visible spectroscopy confirmed that Au and Pt nanoparticles could be assembled by the non-specific interaction in an orderly manner. The experimental results also caution against the potential pitfalls in using DNA melting point analysis to infer metal nanoparticle assembly by DNA hybridization

  20. Humid Heat Autoclaving of Hybrid Nanoparticles Achieved by Decreased Nanoparticle Concentration and Improved Nanoparticle Stability Using Medium Chain Triglycerides as a Modifier.

    Gou, Jingxin; Chao, Yanhui; Liang, Yuheng; Zhang, Ning; He, Haibing; Yin, Tian; Zhang, Yu; Xu, Hui; Tang, Xing

    2016-09-01

    Humid heat autoclaving is a facile technique widely used in the sterilization of injections, but the high temperature employed would destroy nanoparticles composed of biodegradable polymers. The aim of this study was to investigate whether incorporation of medium chain triglycerides (MCT) could stabilize nanoparticles composed of poly (ethylene glycol)-b-polycaprolactone (PEG-b-PCL) during autoclaving (121°C, 10 min). Polymeric nanoparticles with different MCT contents were prepared by dialysis. Block copolymer degradation was studied by GPC. The critical aggregation concentrations of nanoparticles at different temperatures were determined using pyrene fluorescence. The size, morphology and weight averaged molecular weight of pristine/autoclaved nanoparticles were studied using DLS, TEM and SLS, respectively. Drug loading content and release profile were determined using RP-HPLC. The protecting effect of MCT on nanoparticles was dependent on the amount of MCT incorporated. Nanoparticles with high MCT contents, which assumed an emulsion-like morphology, showed reduced block copolymer degradation and particle disassociation after incubation at 100°C for 24 h. Nanoparticles with high MCT content showed the lowest critical aggregation concentration (CAC) under either room temperature or 60°C and the lowest particle concentration among all samples. And the particle size, drug loading content, physical stability and release profile of nanoparticles with high MCT contents remained nearly unchanged after autoclaving. Incorporation of high amount of MCT changed the morphology of PEG-b-PCL based nanoparticles to an emulsion-like structure and the nanoparticles prepared could withstand autoclaving due to improved particle stability and decreased particle concentration caused by MCT incorporation.

  1. Synthesis of silver nanoparticles using a biosurfactant produced in low-cost medium as stabilizing agent

    Charles B.B. Farias

    2014-05-01

    Conclusions: This process provided a simpler route for nanoparticle synthesis compared to existing systems using whole organisms or partially purified biological extracts, showing that the low-cost biosurfactant can be used for nanoparticle synthesis as a non-toxic and biodegradable stabilizing agent.

  2. Increase of electrodeposited catalyst stability via plasma grown vertically oriented graphene nanoparticle movement restriction.

    Vanrenterghem, Bart; Hodnik, Nejc; Bele, Marjan; Šala, Martin; Amelinckx, Giovanni; Neukermans, Sander; Zaplotnik, Rok; Primc, Gregor; Mozetič, Miran; Breugelmans, Tom

    2017-08-17

    Beside activity, electrocatalyst stability is gaining in importance. The most common degradation mechanism is the loss of the active surface area due to nanoparticle growth via coalescence/agglomeration. We propose a particle confinement strategy via vertically oriented graphene deposition to overcome degradation of the nanoparticles.

  3. Stability of colloidal silver nanoparticles trapped in lipid bilayer: effect of lecithin concentration and applied temperature.

    Barani, Hossein; Montazer, Majid; Braun, Hans-Georg; Dutschk, Victoria

    2014-12-01

    The use of silver nanoparticle on various substrates has been widespread because of its good antibacterial properties that directly depend on the stability of the silver nanoparticles in a colloidal suspension. In this study, the colloidal solutions of the silver nanoparticles were synthesised by a simple and safe method by using lecithin as a stabilising agent and their stability was examined at various temperatures. The effect of the lecithin concentrations on the stability of the synthesised silver nanoparticles was examined from 25 to 80°C at 5°C intervals, by recording the changes in the UV-vis absorption spectra, the hydrodynamic diameter and the light scattering intensity of the silver nanoparticles. In addition, the morphology of the synthesised silver nanoparticles was investigated with the low-voltage scanning electron microscopy and transmission electron microscopy. The results indicated that increasing temperature caused different changes in the size of the stabilised and the unstabilised silver nanoparticles. The size of the stabilised silver nanoparticles reduced from 38 to 36 nm during increasing temperature, which confirmed good stability.

  4. Comparison of the Efficiencies of Zero-Valent Iron Nanoparticles and Stabilized Iron Nanoparticles for Nitrate Reduction from Polluted Waters

    Fatemeh Nooralivand

    2015-12-01

    Full Text Available The present study was conducted to evaluate the feasibility of zero-valent iron nanoparticles (ZVIN for the removal of nitrate from aqueous solutions. For this purpose, bare zero-valent iron nanoparticles (bare-ZVIN and CMC-ZVIN were synthesized using the borohydride reduction method and their morphological characteristics were examined via scanning electron microscopy (SEM, X-ray diffraction (XRD, and Fourier Transmission Infrared Spectroscopy (FTIR. The effects of pH of the aqueous solution, initial nitrate concentration, ZVIN concentration, and contact time on nitrate reduction were investigated as operational parameters and the kinetics of nitrate reduction was studied in batch experiments. The results showed that 93.65% of nitrate was removed by stabilized nanoparticles at pH=6 while non-stabilized nanoparticles at pH=2 were able to remove 85.55% of the nitrate.Furthermore, nitrate reduction was enhanced by increasing ZVIN concentration and contact time while it was decreased as a result of increasing initial nitrate concentration. The major product of nitrate reduction at an acidic pH was found to be ammonium; at an alkaline pH, however, nitrate was converted to nitrogen and nitrite production dropped to less than 2%. Kinetic analysis demonstrated that denitrification of nitrate by the nanoparticles fitted well with first-order and second-order reaction models. The results also demonstrated that the stabilized ZVI nanoparticles were more effective than bare-ZVIN for nitrate reduction in aqueous solutions.

  5. Carboxymethyl Hyaluronan-Stabilized Nanoparticles for Anticancer Drug Delivery.

    Woodman, Jessica L; Suh, Min Sung; Zhang, Jianxing; Kondaveeti, Yuvabharath; Burgess, Diane J; White, Bruce A; Prestwich, Glenn D; Kuhn, Liisa T

    2015-01-01

    Carboxymethyl hyaluronic acid (CMHA) is a semisynthetic derivative of HA that is recognized by HA binding proteins but contains an additional carboxylic acid on some of the 6-hydroxyl groups of the N-acetyl glucosamine sugar units. These studies tested the ability of CMHA to stabilize the formation of calcium phosphate nanoparticles and evaluated their potential to target therapy resistant, CD44(+)/CD24(-/low) human breast cancer cells (BT-474EMT). CMHA stabilized particles (nCaP(CMHA)) were loaded with the chemotherapy drug cis-diamminedichloroplatinum(II) (CDDP) to form nCaP(CMHA)CDDP. nCaP(CMHA)CDDP was determined to be poorly crystalline hydroxyapatite, 200 nm in diameter with a -43 mV zeta potential. nCaP(CMHA)CDDP exhibited a two-day burst release of CDDP that tapered resulting in 86% release by 7 days. Surface plasmon resonance showed that nCaP(CMHA)CDDP binds to CD44, but less effectively than CMHA or hyaluronan. nCaP(CMHA-AF488) was taken up by CD44(+)/CD24(-) BT-474EMT breast cancer cells within 18 hours. nCaP(CMHA)CDDP was as cytotoxic as free CDDP against the BT-474EMT cells. Subcutaneous BT-474EMT tumors were more reproducibly inhibited by a near tumor dose of 2.8 mg/kg CDDP than a 7 mg/kg dose nCaP(CMHA)CDDP. This was likely due to a lack of distribution of nCaP(CMHA)CDDP throughout the dense tumor tissue that limited drug diffusion.

  6. Phase stability and dynamics of entangled polymer-nanoparticle composites.

    Mangal, Rahul

    2015-06-05

    Nanoparticle-polymer composites, or polymer-nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.

  7. Phase stability and dynamics of entangled polymer-nanoparticle composites.

    Mangal, Rahul; Srivastava, Samanvaya; Archer, Lynden A

    2015-01-01

    Nanoparticle-polymer composites, or polymer-nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.

  8. Synthesis and Catalytic Activity of Pluronic Stabilized Silver-Gold Bimetallic Nanoparticles

    Holden, Megan S.; Nick, Kevin E.; Hall, Mia; Milligan, Jamie R.; Chen, Qiao; Perry, Christopher C.

    2014-01-01

    In this report, we demonstrate a rapid, simple, and green method for synthesizing silver-gold (Ag-Au) bimetallic nanoparticles (BNPs). We used a novel modification to the galvanic replacement reaction by suspending maltose coated silver nanoparticles (NPs) in ≈ 2% aqueous solution of EO100PO65EO100 (Pluronic F127) prior to HAuCl4 addition. The Pluronic F127 stabilizes the BNPs, imparts biocompatibility, and mitigates the toxicity issues associated with other surfactant stabilizers. BNPs with ...

  9. Fabrication, characterization and antimicrobial activities of thymol-loaded zein nanoparticles stabilized by sodium caseinate-chitosan hydrochloride double layers.

    Zhang, Yaqiong; Niu, Yuge; Luo, Yangchao; Ge, Mei; Yang, Tian; Yu, Liangli Lucy; Wang, Qin

    2014-01-01

    Thymol-loaded zein nanoparticles stabilized with sodium caseinate (SC) and chitosan hydrochloride (CHC) were prepared and characterized. The SC stabilized nanoparticles had well-defined size range and negatively charged surface. Due to the presence of SC, the stabilized zein nanoparticles showed a shift of isoelectric point from 6.18 to 5.05, and had a desirable redispersibility in water at neutral pH after lyophilization. Coating with CHC onto the SC stabilized zein nanoparticles resulted in increased particle size, reversal of zeta potential value from negative to positive, and improved encapsulation efficiency. Both thymol-loaded zein nanoparticles and SC stabilized zein nanoparticles had a spherical shape and smooth surface, while the surfaces of CHC-SC stabilized zein nanoparticles seemed rough and had some clumps. Encapsulated thymol was more effective in suppressing gram-positive bacterium than un-encapsulated thymol for a longer time period. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. Tailorable thiolated trimethyl chitosans for covalently stabilized nanoparticles.

    Verheul, Rolf J; van der Wal, Steffen; Hennink, Wim E

    2010-08-09

    A novel four-step method is presented to synthesize partially thiolated trimethylated chitosan (TMC) with a tailorable degree of quaternization and thiolation. First, chitosan was partially N-carboxylated with glyoxylic acid and sodium borohydride. Next, the remaining amines were quantitatively dimethylated with formaldehyde and sodium borohydride and then quaternized with iodomethane in NMP. Subsequently, these partially carboxylated TMCs dissolved in water were reacted with cystamine at pH 5.5 using EDC as coupling agent. After addition of DTT and dialysis, thiolated TMCs were obtained, varying in degree of quaternization (25-54%) and degree of thiolation (5-7%), as determined with (1)H NMR and Ellman's assay. Gel permeation chromatography with light scattering detection indicated limited intermolecular cross-linking. All thiolated TMCs showed rapid oxidation to yield disulfide cross-linked TMC at pH 7.4, while the thiolated polymers were rather stable at pH 4.0. When Calu-3 cells were used, XTT and LDH cell viability tests showed a slight reduction in cytotoxicity for thiolated TMCs as compared to the nonthiolated polymers with similar DQs. Positively charged nanoparticles loaded with fluorescently labeled ovalbumin were made from thiolated TMCs and thiolated hyaluronic acid. The stability of these particles was confirmed in 0.8 M NaCl, in contrast to particles made from nonthiolated polymers that dissociated under these conditions, demonstrating that the particles were held together by intermolecular disulfide bonds.

  11. Hydrolase stabilization via entanglement in poly(propylene sulfide) nanoparticles: stability towards reactive oxygen species

    Allen, Brett L; Johnson, Jermaine D; Walker, Jeremy P

    2012-01-01

    In the advancement of green syntheses and sustainable reactions, enzymatic biocatalysis offers extremely high reaction rates and selectivity that goes far beyond the reach of chemical catalysts; however, these enzymes suffer from typical environmental constraints, e.g. operational temperature, pH and tolerance to oxidative environments. A common hydrolase enzyme, diisopropylfluorophosphatase (DFPase, EC 3.1.8.2), has demonstrated a pronounced efficacy for the hydrolysis of a variety of substrates for potential toxin remediation, but suffers from the aforementioned limitations. As a means to enhance DFPase’s stability in oxidative environments, enzymatic covalent immobilization within the polymeric matrix of poly(propylene sulfide) (PPS) nanoparticles was performed. By modifying the enzyme’s exposed lysine residues via thiolation, DFPase is utilized as a comonomer/crosslinker in a mild emulsion polymerization. The resultant polymeric polysulfide shell acts as a ‘sacrificial barrier’ by first oxidizing to polysulfoxides and polysulfones, rendering DFPase in an active state. DFPase–PPS nanoparticles thus retain activity upon exposure to as high as 50 parts per million (ppm) of hypochlorous acid (HOCl), while native DFPase is observed as inactive at 500 parts per billion (ppb). This trend is also confirmed by enzyme-generated (chloroperoxidase (CPO), EC 1.11.1.10) reactive oxygen species (ROS) including both HOCl (3 ppm) and ClO 2 (100 ppm). (paper)

  12. Gold Nanoparticles: Synthesis, Stability Test, and Application for the Rice Growth

    Wang, Aiwu; Ng, Hoi Pong; Xu, Yi; Li, Yuyu; Zheng, Yuhong; Yu, Jingping; Han, Fugui; Peng, Feng; Fu, Li

    2014-01-01

    In today’s science, with the use of nanotechnology, nanomaterials, which behave very differently from the bulk solid, can be made. One of the capable uses of nanomaterials is bioapplications which make good use of the specific properties of nanoparticles. However, since the nanoparticles will be used both in-vivo and in-vitro, their stability is an important issue to the scientists, concern. In this dissertation, we are going to test the stability of gold nanoparticles in a number of media in...

  13. Preparation of gold nanoparticles by γ-ray irradiation method using polyvinyl pyrrolidone (PVP) as stabilizer

    Nguyen Tan Man; Le Hai; Le Huu Tu; Tran Thu Hong; Tran Thi Tam; Pham Thi Le Ha; Pham Thi Sam

    2011-01-01

    Gold nanoparticles were prepared from (Au 3+ ) aqueous solution by the method of γ-ray irradiation using polyvinylpyrrolidone (PVP) as stabilizer. The saturated conversion dose (Au 3+ --> Au o ) determined by UV-Vis spectroscopy was found to be about 5 kGy. The UV-Vis spectrum showed that an absorption peak at λ max =524 nm due to surface plasmon resonance. The image of transmission electron microscopy (TEM) showed that the gold nanoparticles are mostly spherical in shape and have an average diameter of ≅20 nm. The prepared colloidal gold nanoparticles solution is good stability for 6 months of storage. (author)

  14. Stability of silver nanoparticles (nAg) in aqueous solution: the role of particle size and water ionic strength

    Radebe, N

    2014-01-01

    Full Text Available biota which can arise from the particulates, dissolved species or both forms. However, there is limited and contradicting information on how the nanoparticle and aqueous solution characteristics influence nanoparticle stability and toxicity. This study...

  15. A Study On Dispersion Stability Of Nickel Nanoparticles Synthesized By Wire Explosion In Liquid Media

    Kim C.K.

    2015-06-01

    Full Text Available In this study, nickel nanoparticles were synthesized in ethanol using portable pulsed wire evaporation, which is a one-step physical method. From transmission electron microscopy images, it was found that the Ni nanoparticles exhibited a spherical shape with an average diameter of 7.3 nm. To prevent aggregation of the nickel nanoparticles, a polymer surfactant was added into the ethanol before the synthesis of nickel nanoparticles, and adsorbed on the freshly synthesized nickel nanoparticles during the wire explosion. The dispersion stability of the prepared nickel nanofluids was investigated by zeta-potential analyzer and Turbiscan optical analyzer. As a result, the optimum concentration of polymer surfactant to be added was suggested for the maximized dispersion stability of the nickel nanofluids.

  16. The study of the antimicrobial activity of colloidal solutions of silver nanoparticles prepared using food stabilizers.

    Balandin, G V; Suvorov, O A; Shaburova, L N; Podkopaev, D O; Frolova, Yu V; Ermolaeva, G A

    2015-06-01

    The bactericidal effect of colloidal solutions of silver nanoparticles based on food stabilizers, gum arabic and chitosan, against bacterial cultures of microorganisms in food production is described. The antibacterial activity of nanotechnology products containing different amounts of stabilizing additives when applied to solid pH-neutral substrates is studied. For its evaluation a method making it possible to take into account the capability of nanoparticles to diffuse in solid media was applied. Minimal inhibitory concentrations of nanoparticles used against Erwinia herbicola, Pseudomonas fluorescens, Bacillus subtilis, Sarcina flava were found. A suggestion was made concerning the influence of the spatial structure of bacteria on the antibacterial activity of colloidal solutions of silver nanoparticles. The data concerning the antibacterial activity and minimal inhibiting concentrations of nanoparticles may be used for development of products suppressing activity of microorganisms hazardous for food production.

  17. Shape-controlled synthesis of NIR absorbing branched gold nanoparticles and morphology stabilization with alkanethiols

    Van de Broek, B; Frederix, F; Bonroy, K; Jans, H; Jans, K; Borghs, G; Maes, G

    2011-01-01

    Gold nanoparticles are ideal candidates for clinical applications if their plasmon absorption band is situated in the near infrared region (NIR) of the electromagnetic spectrum. Various parameters, including the nanoparticle shape, strongly influence the position of this absorption band. The aim of this study is to produce stabilized NIR absorbing branched gold nanoparticles with potential for biomedical applications. Hereto, the synthesis procedure for branched gold nanoparticles is optimized varying the different synthesis parameters. By subsequent electroless gold plating the plasmon absorption band is shifted to 747.2 nm. The intrinsic unstable nature of the nanoparticles' morphology can be clearly observed by a spectral shift and limits their use in real applications. However, in this article we show how the stabilization of the branched structure can be successfully achieved by exchanging the initial capping agent for different alkanethiols and disulfides. Furthermore, when using alkanethiols/disulfides with poly(ethylene oxide) units incorporated, an increased stability of the gold nanoparticles is achieved in high salt concentrations up to 1 M and in a cell culture medium. These achievements open a plethora of opportunities for these stabilized branched gold nanoparticles in nanomedicine.

  18. Thermodynamic stability and kinetic inertness of a Gd-DTPA bisamide complex grafted onto gold nanoparticles.

    Mogilireddy, Vijetha; Déchamps-Olivier, Isabelle; Alric, Christophe; Laurent, Gautier; Laurent, Sophie; Vander Elst, Luce; Muller, Robert; Bazzi, Rana; Roux, Stéphane; Tillement, Olivier; Chuburu, Françoise

    2015-01-01

    Gold nanoparticles coated by gadolinium (III) chelates (Au@DTDTPA) where DTDTPA is a dithiolated bisamide derivative of diethylenetriamine-N,N,N',N'',N''-pentaacetic acid (DTPA), constituted contrast agents for both X-ray computed tomography and magnetic resonance imaging. In an MRI context, highly stable Gd(3+) complexes are needed for in vivo applications. Thus, knowledge of the thermodynamic stability and kinetic inertness of these chelates, when grafted onto gold nanoparticles, is crucial since bisamide DTPA chelates are usually less suited for Gd(3+) coordination than DTPA. Therefore, these parameters were evaluated by means of potentiometric titrations and relaxivity measurements. The results showed that, when the chelates were grafted onto the nanoparticle, not only their thermodynamic stability but also their kinetic inertness were improved. These positive effects were correlated to the chelate packing at the nanoparticle surface that stabilized the corresponding Gd(3+) complexes and greatly enhanced their kinetic inertness. Copyright © 2014 John Wiley & Sons, Ltd.

  19. Ultrasonic Studies of Emulsion Stability in the Presence of Magnetic Nanoparticles

    A. Józefczak

    2015-01-01

    Full Text Available Pickering emulsions are made of solid particle-stabilized droplets suspended in an immiscible continuous liquid phase. A magnetic emulsion can be obtained using magnetic particles. Solid magnetic nanoparticles are adsorbed strongly at the oil-water interface and are able to stabilize emulsions of oil and water. In this work emulsions stabilized by magnetite nanoparticles were obtained using high-energy ultrasound waves and a cavitation mechanism and, next, their stability in time was tested by means of acoustic waves with a low energy, without affecting the structure. An acoustic study showed high stability in time of magnetic emulsions stabilized by magnetite particles. The study also showed a strong influence of an external magnetic field, which can lead to changes of the emulsion properties. It is possible to control Pickering emulsion stability with the help of an external stimulus—a magnetic field.

  20. Characterizing the Role of Nanoparticle Design on Tumor Transport and Stability in the Extracellular Environment

    Albanese, Alexandre

    Nanotechnology has emerged as an exciting strategy for the delivery of diagnostic and therapeutic agents into established tumors. Advancements in nanomaterial synthesis have generated an extensive number of nanoparticle designs made from different materials. Unfortunately, it remains impossible to predict a design's effectiveness for in vivo tumor accumulation. Little is known about how a nanoparticle's morphology and surface chemistry affect its interactions with cells and proteins inside the tumor tissue. This thesis focuses on the development of in vitro experimental tools to evaluate how nanoparticle design affects transport in a three-dimensional tumor tissue and stability in the tumor microenvironment. Nanoparticle transport was evaluated using a novel 'tumor-on-a-chip' system where multicellular tumor spheroids were immobilized in a microfluidic channel. This setup created a three-dimensional tumor environment displaying physiological cell density, extracellular matrix organization, and interstitial flow rates. The tumor-on-a-chip demonstrated that accumulation of nanoparticles was limited to diameters below 110 nm and was improved by receptor targeting. Nanoparticle stability in the tumor microenvironment was evaluated using media isolated from different tumor cell lines. Nanoparticle diameter and surface chemistry were important determinants of stability in cancer cell-conditioned media. Small nanoparticles with unstable surface chemistries adsorbed cellular proteins on their surface and were prone to aggregation. Nanoparticle aggregation altered cellular interactions leading to changes in cell uptake. Using a novel technique to generate different aggregate sizes possessing a uniform surface composition, it was determined that aggregation can change receptor affinity, cell internalization mechanisms and sub-cellular sequestration patterns. Data from this thesis characterize the behavior of nanoparticles within modeled tumor environments and provide some

  1. Cobalt ferrite nanoparticles with improved aqueous colloidal stability and electrophoretic mobility

    Munjal, Sandeep; Khare, Neeraj

    2016-01-01

    We have synthesized CoFe 2 O 4 (CFO) nanoparticles of size ∼ 12.2 nm by hydrothermal synthesis method. To control the size of these CFO nanoparticles, oleic acid was used as a surfactant. The inverse spinel phase of the synthesized nanoparticles was confirmed by X-ray diffraction method. As synthesized oleic acid coated CFO (OA@CFO) nanoparticles has very less electrophoretic mobility in the water and are not water dispersible. These OA@CFO nanoparticles were successfully turned into water soluble phase with a better colloidal aqueous stability, through a chemical treatment using citric acid. The modified citric acid coated CFO (CA@CFO) nanoparticles were dispersible in water and form a stable aqueous solution with high electrophoretic mobility.

  2. Effect of nanoparticles generation method on ionic conductivity in Yttria stabilized zirconia

    Khare, J.; Joshi, M.P.; Kukreja, L.M.; Satapathy, S.

    2013-01-01

    Yttria stabilized zirconia nanoparticles were generated in pulsed and CW mode of laser operation using CO 2 laser based laser vaporization method. Impedance spectroscopic measurements were carried out in frequency range of 100 Hz - 1 MHz at various temperatures ranging from room temperature to 500 C. The deconvolution of grain and grain boundary contribution were obtained from impedance spectra by an equivalent circuit analysis. Grain and grain boundary ionic conductivity of pellet made from nanoparticles generated in pulsed mode was two orders of magnitude large in comparison to pellets made from nanoparticles generated in CW mode of laser operation. The difference in ionic conductivities of pellets made from nanoparticles generated in pulsed mode and CW mode were explained on the basis of defect associations in nanoparticles produced during nanoparticles generation. (author)

  3. Superparamagnetic iron oxide nanoparticles incorporated into silica nanoparticles by inelastic collision via ultrasonic field: Role of colloidal stability

    Sodipo, Bashiru Kayode; Azlan, Abdul Aziz [Nano-Optoelectronics Research and Technology (NOR) Lab, School of Physics, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia Nano-Biotechnology Research (Malaysia); Innovation (NanoBRI), Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, 11800, Pulau Pinang (Malaysia)

    2015-04-24

    Superparamagnetic iron oxide nanoparticles (SPION)/Silica composite nanoparticles were prepared by ultrasonically irradiating colloidal suspension of silica and SPION mixture. Both silica and SPION were synthesized independently via co-precipitation and sol-gel method, respectively. Their mixtures were sonicated at different pH between 3 and 5. Electrophoresis measurement and other physicochemical analyses of the products demonstrate that at lower pH SPION was found incorporated into the silica. However, at pH greater than 4, SPION was unstable and unable to withstand the turbulence flow and shock wave from the ultrasonic field. Results suggest that the formation of the SPION/silica composite nanoparticles is strongly related to the inelastic collision induced by ultrasonic irradiation. More so, the formation the composite nanoparticles via the ultrasonic field are dependent on the zeta potential and colloidal stability of the particles.

  4. Stability and enzyme inhibition activities of au nanoparticles using an aqueous extract of clove as a reducing and stabilizing agent

    Hameed, A.; Khan, I.; Naz, S.S.; Islam, N.U.

    2014-01-01

    Gold nanoparticles (AuNPs) were synthesized in one pot using aqueous extract of clove buds (CB) to reduce HAuCl/sub 4/ and stabilize gold in its atomic form at room temperature. To determine the potential of gold nanoparticles with clove buds (AuCB) for in vivo applications, the stability of the nanoparticles was explored as a function of temperature, pH and salt concentration. The suspensions were found to be stable for salt concentrations up to 1 mol/L, temperatures of up to 100 degree C and a pH range of 2-13. Our results indicate that CB exhibited comparable activities to standards of urease and carbonic anhydrase, but its conjugation to Au knocks out the enzyme inhibition activity by about two times. In case of xanthine oxidase activity, CB and its gold Au bio-conjugates (AuCB) are found to be absolutely inactive. (author)

  5. Fouling behavior during microfiltration of silica nanoparticles and polymeric stabilizers

    Trzaskus, Krzystof; Zdeb, Aneta; de Vos, Wiebe Matthijs; Kemperman, Antonius J.B.; Nijmeijer, Dorothea C.

    2016-01-01

    Nanotechnology applications give rise to new forms of water pollution, resulting in a need for reliable technologies that can remove nanoparticles from water. Membrane filtration is an obvious candidate. The tendency of nanoparticles to become instable in suspension and form aggregates strongly

  6. Factors affecting drug encapsulation and stability of lipid-polymer hybrid nanoparticles.

    Cheow, Wean Sin; Hadinoto, Kunn

    2011-07-01

    Lipid-polymer hybrid nanoparticles are polymeric nanoparticles enveloped by lipid layers that combine the highly biocompatible nature of lipids with the structural integrity afforded by polymeric nanoparticles. Recognizing them as attractive drug delivery vehicles, antibiotics are encapsulated in the present work into hybrid nanoparticles intended for lung biofilm infection therapy. Modified emulsification-solvent-evaporation methods using lipid as surfactant are employed to prepare the hybrid nanoparticles. Biodegradable poly (lactic-co-glycolic acid) and phosphatidylcholine are used as the polymer and lipid models, respectively. Three fluoroquinolone antibiotics (i.e. levofloxacin, ciprofloxacin, and ofloxacin), which vary in their ionicity, lipophilicity, and aqueous solubility, are used. The hybrid nanoparticles are examined in terms of their drug encapsulation efficiency, drug loading, stability, and in vitro drug release profile. Compared to polymeric nanoparticles prepared using non-lipid surfactants, hybrid nanoparticles in general are larger and exhibit higher drug loading, except for the ciprofloxacin-encapsulated nanoparticles. Hybrid nanoparticles, however, are unstable in salt solutions, but the stability can be conferred by adding TPGS into the formulation. Drug-lipid ionic interactions and drug lipophilicity play important roles in the hybrid nanoparticle preparation. First, interactions between oppositely charged lipid and antibiotic (i.e. ciprofloxacin) during preparation cause failed nanoparticle formation. Charge reversal of the lipid facilitated by adding counterionic surfactants (e.g. stearylamine) must be performed before drug encapsulation can take place. Second, drug loading and the release profile are strongly influenced by drug lipophilicity, where more lipophilic drug (i.e. levofloxacin) exhibit a higher drug loading and a sustained release profile attributed to the interaction with the lipid coat. Copyright © 2011 Elsevier B.V. All

  7. Synthesis of an ultradense forest of vertically aligned triple-walled carbon nanotubes of uniform diameter and length using hollow catalytic nanoparticles.

    Baliyan, Ankur; Nakajima, Yoshikata; Fukuda, Takahiro; Uchida, Takashi; Hanajiri, Tatsuro; Maekawa, Toru

    2014-01-22

    It still remains a crucial challenge to actively control carbon nanotube (CNT) structure such as the alignment, area density, diameter, length, chirality, and number of walls. Here, we synthesize an ultradense forest of CNTs of a uniform internal diameter by the plasma-enhanced chemical vapor deposition (PECVD) method using hollow nanoparticles (HNPs) modified with ligand as a catalyst. The diameters of the HNPs and internal cavities in the HNPs are uniform. A monolayer of densely packed HNPs is self-assembled on a silicon substrate by spin coating. HNPs shrink via the collapse of the internal cavities and phase transition from iron oxide to metallic iron in hydrogen plasma during the PECVD process. Agglomeration of catalytic NPs is avoided on account of the shrinkage of the NPs and ligand attached to the NPs. Diffusion of NPs into the substrate, which would inactivate the growth of CNTs, is also avoided on account of the ligand. As a result, an ultradense forest of triple-walled CNTs of a uniform internal diameter is successfully synthesized. The area density of the grown CNTs is as high as 0.6 × 10(12) cm(-2). Finally, the activity of the catalytic NPs and the NP/carbon interactions during the growth process of CNTs are investigated and discussed. We believe that the present approach may make a great contribution to the development of an innovative synthetic method for CNTs with selective properties.

  8. Radiation-assisted synthesis of Prussian blue nanoparticles using sugar as stabilizer

    Ling Chang; Shuquan Chang; Wei Han; Zheng Li; Zheng Zhang; Yaodong Dai; Haiqian Zhang

    2017-01-01

    Prussian blue (PB) nanoparticles were successfully synthesized via a γ radiation route in aqueous solutions using sugar as stabilizer at room temperature and ambient pressure. The particle size and shape can be affected by stabilizer and radiation conditions. When the stabilizer was sucrose and the radiation dose was 30 kGy, well-dispersed and uniform PB nanoparticles were obtained, which are 100-200 nm in diameter. They exhibit good ions exchange properties and have maximal Cs + adsorption capacity of 125.8 mg g -1 , which may be applied in radioactive wastewater treatments, ion battery etc. (author)

  9. Application of magnetic iron oxide nanoparticles in stabilization process of biological molecules

    Mohammad Hossien Salmani

    2017-07-01

    Conclusion: Co-precipitation method is an easy way to prepare magnetic nanoparticles of iron with a large surface and small particle size, which increases the ability of these particles to act as a suitable carrier for enzyme stabilization. Adequate modification of the surface of these nanoparticles enhances their ability to bind to biological molecules. The immobilized protein or enzyme on magnetic nanoparticles are more stable against structural changes, temperature and pH in comparison with un-stabilized structures, and it is widely used in various sciences, including protein isolation and purification, pharmaceutical science, and food analysis. Stabilization based on the covalent bonds and physical absorption is nonspecific, which greatly limits their functionality. The process of stabilization through bio-mediums provide a new method to overcome the selectivity problem.

  10. Green synthesis of Au nanoparticles using potato extract: stability and growth mechanism

    Castillo-López, D. N.; Pal, U.

    2014-08-01

    We report on the synthesis of spherical, well-dispersed colloidal gold nanoparticles of 17.5-23.5 nm average sizes in water using potato extract (PE) both as reducing and stabilizing agent. The effects of PE content and the pH value of the reaction mixture have been studied. Formation and growth dynamics of the Au nanoparticles in the colloids were studied using transmission electron microscopy and UV-Vis optical absorption spectroscopy techniques. While the reductor content and, hence, the nucleation and growth rates of the nanoparticles could be controlled by controlling the PE content in the reaction solution, the stability of the nanoparticles depended strongly on the pH of the reaction mixture. The mechanisms of Au ion reduction and stabilization of Au nanoparticles by potato starch have been discussed. The use of common natural solvent like water and biological reductor like PE in our synthesis process opens up the possibility of synthesizing Au nanoparticles in fully green (environmental friendly) way, and the Au nanoparticles produced in such way should have good biocompatibility.

  11. Biosurfactants as green stabilizers for the biological synthesis of nanoparticles.

    Kiran, G Seghal; Selvin, Joseph; Manilal, Aseer; Sujith, S

    2011-12-01

    Taking into consideration the needs of greener bioprocesses and novel enhancers for synthesis using microbial processes, biosurfactants, and/or biosurfactant producing microbes are emerging as an alternate source for the rapid synthesis of nanoparticles. A microemulsion technique using an oil-water-surfactant mixture was shown to be a promising approach for nanoparticle synthesis. Biosurfactants are natural surfactants derived from microbial origin composed mostly of sugar and fatty acid moieties, they have higher biodegradability, lower toxicity, and excellent biological activities. The biosurfactant mediated process and microbial synthesis of nanoparticles are now emerging as clean, nontoxic, and environmentally acceptable "green chemistry" procedures. The biosurfactant-mediated synthesis is superior to the methods of bacterial- or fungal-mediated nanoparticle synthesis, since biosurfactants reduce the formation of aggregates due to the electrostatic forces of attraction and facilitate a uniform morphology of the nanoparticles. In this review, we highlight the biosurfactant mediated synthesis of nanoparticles with relevant details including a greener bioprocess, sources of biosurfactants, and biological synthesized nanoparticles based on the available literature and laboratory findings.

  12. Interaction of bilirubin with Ag and Au ions: green synthesis of bilirubin-stabilized nanoparticles

    Shukla, Shashi P. [Bhabha Atomic Research Centre, Radiation and Photochemistry Division (India); Roy, Mainak [Bhabha Atomic Research Centre, Chemistry Division (India); Mukherjee, Poulomi [Bhabha Atomic Research Centre, Nuclear Agriculture and Biotechnology Division (India); Tyagi, A. K. [Bhabha Atomic Research Centre, Chemistry Division (India); Mukherjee, Tulsi [Bhabha Atomic Research Centre, Chemistry Group (India); Adhikari, Soumyakanti, E-mail: asoumya@barc.gov.in [Bhabha Atomic Research Centre, Radiation and Photochemistry Division (India)

    2012-07-15

    We report a simple green chemistry to synthesize and stabilize monodispersed silver and gold nanoparticles sols by reducing aqueous solution of the respective metal salts in the presence of bilirubin (BR). No additional capping agent was used in the process of stabilization of the nanoparticles. As a completely new finding, we have observed that BR known to be toxic at higher concentration in one hand and conversely an antioxidant at physiological concentration reduces these metal ions to form the respective metal nanoparticles. Moreover, BR and its oxidized products also serve as capping agents to the nanoparticles. The particles were characterized by transmission electron microscopy. BR and its oxidized products capped nanoparticles are stable for months. The UV-Vis absorption spectra of the silver sol show the plasmon peak of symmetric spherical particles which was further reflected in the TEM images. The sizes of the silver particles were about 5 nm. These silver particles showed reasonably high antibacterial activity in Gram negative wild type E. coli. In the case of interaction of BR with gold ions, we could obtain cubic gold nanoparticles of average sizes 20-25 nm. Possible modes of anchorage of BR and/its oxidized products to silver nanoparticles were demonstrated by surface-enhanced resonance Raman spectroscopy (SERS) that in turn demonstrated the feasibility of using these nanoparticles as SERS substrates.

  13. Interaction of bilirubin with Ag and Au ions: green synthesis of bilirubin-stabilized nanoparticles

    Shukla, Shashi P.; Roy, Mainak; Mukherjee, Poulomi; Tyagi, A. K.; Mukherjee, Tulsi; Adhikari, Soumyakanti

    2012-07-01

    We report a simple green chemistry to synthesize and stabilize monodispersed silver and gold nanoparticles sols by reducing aqueous solution of the respective metal salts in the presence of bilirubin (BR). No additional capping agent was used in the process of stabilization of the nanoparticles. As a completely new finding, we have observed that BR known to be toxic at higher concentration in one hand and conversely an antioxidant at physiological concentration reduces these metal ions to form the respective metal nanoparticles. Moreover, BR and its oxidized products also serve as capping agents to the nanoparticles. The particles were characterized by transmission electron microscopy. BR and its oxidized products capped nanoparticles are stable for months. The UV-Vis absorption spectra of the silver sol show the plasmon peak of symmetric spherical particles which was further reflected in the TEM images. The sizes of the silver particles were about 5 nm. These silver particles showed reasonably high antibacterial activity in Gram negative wild type E. coli. In the case of interaction of BR with gold ions, we could obtain cubic gold nanoparticles of average sizes 20-25 nm. Possible modes of anchorage of BR and/its oxidized products to silver nanoparticles were demonstrated by surface-enhanced resonance Raman spectroscopy (SERS) that in turn demonstrated the feasibility of using these nanoparticles as SERS substrates.

  14. Synthesis and characterization of thiolated pectin stabilized gold coated magnetic nanoparticles

    Arora, Varun, E-mail: varun.arora3986@gmail.com [University School of Basic and Applied Sciences, Guru Gobind Singh Indraprastha University, Sector 16-C, Dwarka, New Delhi 110078 (India); Sood, Ankur, E-mail: ankursood02@gmail.com [University School of Basic and Applied Sciences, Guru Gobind Singh Indraprastha University, Sector 16-C, Dwarka, New Delhi 110078 (India); Shah, Jyoti, E-mail: shah.jyoti1@gmail.com [National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012 (India); Kotnala, R.K., E-mail: rkkotnala@nplindia.org [National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012 (India); Jain, Tapan K., E-mail: tapankjain@gmail.com [University School of Basic and Applied Sciences, Guru Gobind Singh Indraprastha University, Sector 16-C, Dwarka, New Delhi 110078 (India)

    2016-04-15

    Core–shell nanoparticles, magnetic core and gold shell, were synthesized by reduction of gold chloride on the surface of magnetic nanoparticles; using tyrosine as a reducing agent. The formation of gold shell on magnetic nanoparticles was confirmed by X-ray diffraction (XRD) and UV-Visible spectroscopy. The core–shell nanoparticles (CSn) were conjugated with thiolated pectin to form a stable aqueous dispersion. The hydrodynamic size of thiolated pectin stabilized core–shell nanoparticles (TP-CSn) measured by Dynamic light scattering (DLS) was 160.5 nm with a poly dispersity index (PDI) of 0.302, whereas the mean particle size of TP-CSn calculated by high resolution transmission electron microscopy (HRTEM) was 10.8 ± 2.7 nm. The value of zeta potential for TP-CSn was −13.6 mV. There was a decrease in the value of saturation magnetization upon formation of the gold shell on magnetic nanoparticles. The amount of thiolated pectin bound to the surface of core–shell nanoparticles, calculated using Thermogravimetric analysis (TGA), was 6% of sample weight. - Highlights: • Use of side group of tyrosine (phenol) as a pH dependent reducing agent to synthesize gold coated magnetic nanoparticles. • Successful coating of gold shell on magnetic nanoparticles core. • Synthesis of thiolated pectin and stabilization of aqueous dispersion of core–shell nanoparticles with thiolated pectin. • The superparamagnetic behaviour of magnetic nanoparticles is retained after shell formation.

  15. Impact of the organic coating on nanoparticles stability and reactivity

    Gelabert, A.; Sivry, Y.; Ould Boualy, L.; Roselyne, F.; Juillot, F.; Menguy, N.; Benedetti, M. F.

    2010-12-01

    The strong increase in the use of engineered nanoparticles (NPs) during the last decade may ultimately result in their release in environmental settings, as predicted for different types of NPs by Gottshalk et al.. Most of these NPs incorporate functionalized coatings to gain industrial benefits, which in turn may play a critical rule for the whole NPs reactivity. Thus, along with stability studies focusing on the fate of NPs in natural systems, an accurate understanding of the coating impacts on the NPs behaviour and reactivity is highly required. This study aims to estimate the impact of three different coatings on the NPs dissolution rates in natural water (Seine river water), and their sorption properties onto a model mineral substrate. In this work, ZnO NPs have been coated, either with triethoxycaprylylsilane (hydrophobic), methacryloxypropyltrimethoxysilane (hydrophilic), or aminopropyltriethoxusilane (cationic). The dissolution rates were determined using two protocols: the Donnan Membrane Technique to measure the remaining free metal concentration in solution, and a 1 kDa ultrafiltration procedure to access both the free metal and small organic complexes part. For all three coating types, a fast dissolution step is reached in less than one day, followed by a slow precipitation of new mineral phases to finally reach a steady state. No major differences in the dissolution rates and profiles have been observed. Sorption studies on synthetic microsized goethite have been conducted at pH 7.5. The sorption ratio has been estimated as a function of initial NPs concentrations (from 10-7 M to 10-3 M), and follows a Langmuir shape for the hydrophobic and hydrophilic coatings at concentrations lower than 2.10-4 M. Interestingly, those two NPs exhibit high sorption capacities (10 times higher) compared to free Zn2+ sorption. On the other hand, at those concentrations, the cationic coating only induces a weak sorption without any defined trend. Moreover, for the

  16. PVA stabilized gold nanoparticles by use of unexplored albeit conventional reducing agent

    Khanna, P K [Nanomaterials Laboratory, Centre for Materials for Electronics Technology (C-MET), Panchwati, Off Pashan Road, Pune 411008 (India); Gokhale, R [Nanomaterials Laboratory, Centre for Materials for Electronics Technology (C-MET), Panchwati, Off Pashan Road, Pune 411008 (India); Subbarao, V V.V.S. [Nanomaterials Laboratory, Centre for Materials for Electronics Technology (C-MET), Panchwati, Off Pashan Road, Pune 411008 (India); Vishwanath, A Kasi [Nanomaterials Laboratory, Centre for Materials for Electronics Technology (C-MET), Panchwati, Off Pashan Road, Pune 411008 (India); Das, B K [Nanomaterials Laboratory, Centre for Materials for Electronics Technology (C-MET), Panchwati, Off Pashan Road, Pune 411008 (India); Satyanarayana, C V.V. [National Chemical Laboratory, Pashan Road, Pune 41108 (India)

    2005-07-15

    Poly(vinyl alcohol) (PVA) stabilized gold nanoparticles have been prepared in aqueous medium using two different reducing viz.; hydrazine hydrate, a stronger reducing agent and sodium formaldehydesulfoxylate (SFS), a slightly weaker reducing agent. SFS is used for first ever time for reduction of gold metal salt. The PVA stabilized gold nanoparticles solutions are wine red to blood red coloured and are stable over a long period of time with no indication of aggregation. The solution shows strong visible light absorptions in the range of 520-540 nm, characteristics of gold nanoparticles. Powder X-ray diffraction patterns of freshly prepared films containing gold nanoparticles indicated particles size to be about 15 nm. Transmission electron microscopy (TEM) of a more than two-week-old sample revealed well-defined non-agglomerated spherical particles of about 50 nm diameter in solutions.

  17. Antibacterial surfaces by adsorptive binding of polyvinyl-sulphonate-stabilized silver nanoparticles

    Vasilev, Krasimir; Sah, Vasu R; Goreham, Renee V; Short, Robert D [Mawson Institute, University of South Australia, Mawson Lakes Campus, Mawson Lakes, Adelaide, SA 5095 (Australia); Ndi, Chi; Griesser, Hans J, E-mail: Krasimir.vasilev@unisa.edu.au [Ian Wark Research Institute, University of South Australia, Mawson Lakes, Adelaide, SA 5095 (Australia)

    2010-05-28

    This paper presents a novel and facile method for the generation of efficient antibacterial coatings which can be applied to practically any type of substrate. Silver nanoparticles were stabilized with an adsorbed surface layer of polyvinyl sulphonate (PVS). This steric layer provided excellent colloidal stability, preventing aggregation over periods of months. PVS-coated silver nanoparticles were bound onto amine-containing surfaces, here produced by deposition of an allylamine plasma polymer thin film onto various substrates. SEM imaging showed no aggregation upon surface binding of the nanoparticles; they were well dispersed on amine surfaces. Such nanoparticle-coated surfaces were found to be effective in preventing attachment of Staphylococcus epidermidis bacteria and also in preventing biofilm formation. Combined with the ability of plasma polymerization to apply the thin polymeric binding layer onto a wide range of materials, this method appears promising for the fabrication of a wide range of infection-resistant biomedical devices.

  18. PVA stabilized gold nanoparticles by use of unexplored albeit conventional reducing agent

    Khanna, P.K.; Gokhale, R.; Subbarao, V.V.V.S.; Vishwanath, A. Kasi; Das, B.K.; Satyanarayana, C.V.V.

    2005-01-01

    Poly(vinyl alcohol) (PVA) stabilized gold nanoparticles have been prepared in aqueous medium using two different reducing viz.; hydrazine hydrate, a stronger reducing agent and sodium formaldehydesulfoxylate (SFS), a slightly weaker reducing agent. SFS is used for first ever time for reduction of gold metal salt. The PVA stabilized gold nanoparticles solutions are wine red to blood red coloured and are stable over a long period of time with no indication of aggregation. The solution shows strong visible light absorptions in the range of 520-540 nm, characteristics of gold nanoparticles. Powder X-ray diffraction patterns of freshly prepared films containing gold nanoparticles indicated particles size to be about 15 nm. Transmission electron microscopy (TEM) of a more than two-week-old sample revealed well-defined non-agglomerated spherical particles of about 50 nm diameter in solutions

  19. UV Treatment of the Stabilizing Shell for Improving the Photostability of Silver Nanoparticles

    Silvia Rinaldi

    2016-01-01

    Full Text Available Silver nanoparticles or nanoclusters are quite sensitive to light exposure. In particular, irradiation in the localized surface plasmon resonance (LSPR region brings about a drastic modification of their optical properties due to growth and reshaping of the nanoparticles. In order to obtain luminescent colloids, small silver colloidal nanoparticles were prepared in chloroform using vinylpyrrolidone oligomers as capping agent and their luminescence properties were used to control their stability upon prolonged exposure to visible light. The polymeric shell around the metal clusters was hardened through photo-cross-linking by UV light. This process did not alter the morphology and the optical properties of the nanoparticles but greatly improved the particle photostability as confirmed also by confocal laser scanning microscopy measurements. The data clearly show that UV curing of the stabilizing layer could be a simple postsynthetic procedure to obtain materials with stable properties.

  20. Understanding the Thermal Stability of Silver Nanoparticles Embedded in a-Si

    Gould, Anna L.; Kadkhodazadeh, Shima; Wagner, Jakob Birkedal

    2015-01-01

    properties of the amorphous-Si environment are important as well as incomplete packing of the Ag nanoparticle surfaces. These factors affect the melting temperature, causing some parts of the Ag nanoparticles to dissolve preferentially and other areas to remain stable at high temperatures.......The inclusion of silver plasmonic nanoparticles in silicon is highly relevant for photovoltaics as it may enhance optical absorption. We report an investigation of the stability of such pristine silver nanoparticles embedded in a-Si upon heat treatment. We have investigated the morphological...... changes via in situ and ex situ high-resolution and high-angle annular dark-field scanning transmission electron microscopy (HRTEM and HAADF STEM). The melting of Ag particles and subsequent interdiffusion of Ag and Si atoms are strongly related to the size of the Ag nanoparticles, as well as the presence...

  1. Investigations of suspension stability of iron oxide nanoparticles using time-resolved UV–visible spectroscopy

    Vikram, S.; Vasanthakumari, R. [B. S. Abdur Rahman University, Polymer Nanotechnology Centre (India); Tsuzuki, Takuya [Australian National University, Research School of Engineering, College of Engineering and Computer Science (Australia); Rangarajan, Murali, E-mail: r-murali@cb.amrita.edu [Amrita University, Center of Excellence in Advanced Materials and Green Technologies, Amrita School of Engineering Coimbatore (India)

    2016-09-15

    This study examines the suspension stability of iron oxide nanoparticles of different sizes, magnetic susceptibility, and saturation magnetization over long time scales in dilute systems using time-resolved UV–visible spectroscopy. The effects of citric acid as a chelating agent and applied external magnetic field are also studied. UV–visible spectra are obtained at different times for citric-acid-stabilized nanoparticles dispersed in water, and the peak absorbance is tracked with time, in the presence and absence of external magnetic fields. It is seen that the nanoparticles sediment slowly even in the absence of chain formation, with the phenomenon occurring in two-to-three regimes for the systems studied. Sedimentation exhibits either exponential or power-law behavior of maximum absorbance with time. In the dilute dispersions studied, thermal dispersion is about two orders of magnitude stronger than van der Waals interactions, and chain formation is not easy. Yet, it is likely that local anisotropic structures of the nanoparticles form, through which the attractive interactions result in sedimentation. Citric acid gradually stabilizes the aggregating particles; after an initial faster sedimentation, electrostatic repulsion causes the particles to segregate, as observed by a linear increase in the concentration of the nanoparticles at long times. In the presence of magnetic field, stabilization effects are significantly reduced. It is seen that though the attractive force between the nanoparticles and the external field is smaller than Brownian forces, together with van der Waals interactions, these attractive forces likely act as directing agents facilitating sedimentation. This study demonstrates that aggregation-induced sedimentation of magnetic nanoparticles is likely to play a significant role in magnetic drug targeting even when the particles are stabilized with chelating agents.Graphical abstract.

  2. Investigations of suspension stability of iron oxide nanoparticles using time-resolved UV–visible spectroscopy

    Vikram, S.; Vasanthakumari, R.; Tsuzuki, Takuya; Rangarajan, Murali

    2016-01-01

    This study examines the suspension stability of iron oxide nanoparticles of different sizes, magnetic susceptibility, and saturation magnetization over long time scales in dilute systems using time-resolved UV–visible spectroscopy. The effects of citric acid as a chelating agent and applied external magnetic field are also studied. UV–visible spectra are obtained at different times for citric-acid-stabilized nanoparticles dispersed in water, and the peak absorbance is tracked with time, in the presence and absence of external magnetic fields. It is seen that the nanoparticles sediment slowly even in the absence of chain formation, with the phenomenon occurring in two-to-three regimes for the systems studied. Sedimentation exhibits either exponential or power-law behavior of maximum absorbance with time. In the dilute dispersions studied, thermal dispersion is about two orders of magnitude stronger than van der Waals interactions, and chain formation is not easy. Yet, it is likely that local anisotropic structures of the nanoparticles form, through which the attractive interactions result in sedimentation. Citric acid gradually stabilizes the aggregating particles; after an initial faster sedimentation, electrostatic repulsion causes the particles to segregate, as observed by a linear increase in the concentration of the nanoparticles at long times. In the presence of magnetic field, stabilization effects are significantly reduced. It is seen that though the attractive force between the nanoparticles and the external field is smaller than Brownian forces, together with van der Waals interactions, these attractive forces likely act as directing agents facilitating sedimentation. This study demonstrates that aggregation-induced sedimentation of magnetic nanoparticles is likely to play a significant role in magnetic drug targeting even when the particles are stabilized with chelating agents.Graphical abstract

  3. Size-dependent properties of silica nanoparticles for Pickering stabilization of emulsions and foams

    Kim, Ijung, E-mail: ijungkim@utexas.edu [The University of Texas at Austin, Department of Petroleum and Geosystems Engineering (United States); Worthen, Andrew J.; Johnston, Keith P. [The University of Texas at Austin, McKetta Department of Chemical Engineering (United States); DiCarlo, David A.; Huh, Chun [The University of Texas at Austin, Department of Petroleum and Geosystems Engineering (United States)

    2016-04-15

    Nanoparticles are a promising alternative to surfactants to stabilize emulsions or foams in enhanced oil recovery (EOR) processes due to their effectiveness in very harsh environments found in many of the oilfields around the world. While the size-dependent properties of nanoparticles have been extensively studied in the area of optics or cellular uptake, little is known on the effects of nanoparticle size on emulsion/foam generation, especially for EOR applications. In this study, silica nanoparticles with four different sizes (5, 12, 25, and 80 nm nominal diameter) but with the same surface treatment were employed to test their emulsion or foam generation behavior in high-salinity conditions. The decane-in-brine emulsion generated by sonication or flowing through sandpack showed smaller droplet size and higher apparent viscosity as the nanoparticle size decreased. Similarly, the CO{sub 2}-in-brine foam generation in sandstone or sandpacks was also significantly affected by the nanoparticle size, exhibiting higher apparent foam viscosity as the nanoparticle size decreased. In case of foam generation in sandstone cores with 5 nm nanoparticles, a noticeable hysteresis occurred when the flow velocity was initially increased and then decreased, implying a strong foam generation initially; and then the trapping of the generated foam in the rock pores, as the flow velocity decreased. On the other hand, weak foams stabilized with larger nanoparticles indicated a rapid coalescence of bubbles which prevented foam generation. Overall, stable emulsions/foams were achievable by the smaller particles as a result of greater diffusivity and/or higher number concentration, thus allowing more nanoparticles with higher surface area to volume ratio to be adsorbed at the fluid/fluid interfaces of the emulsion/foam dispersion.Graphical abstract.

  4. Aqueous starch as a stabilizer in zinc oxide nanoparticle synthesis via laser ablation

    Zamiri, Reza; Zakaria, Azmi [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor (Malaysia); Ahangar, Hossein Abbastabar [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor (Malaysia); Darroudi, Majid [Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor (Malaysia); Zak, Ali Khorsand [Low Dimensional Material Research Center, Department of Physics, University of Malaya, Kuala Lumpur 50603 (Malaysia); Drummen, Gregor P.C., E-mail: gpcdrummen@bionano-solutions.de [Bionanoscience and Bio-Imaging Program, Cellular Stress and Ageing Program, Bio and Nano-Solutions, D-40472 Duesseldorf (Germany)

    2012-03-05

    Highlights: Black-Right-Pointing-Pointer Zinc oxide nanoparticles were synthesized via LASiS in aqueous starch solution. Black-Right-Pointing-Pointer Nanoparticles of {+-}15 nm are produced with a narrow size distribution. Black-Right-Pointing-Pointer Starch can be used as a template to control nanoparticle size. Black-Right-Pointing-Pointer Starch stabilizes zinc oxide nanoparticles in solution through steric hindrance. - Abstract: Zinc oxide is a semiconductor with exceptional thermal, luminescent and electrical properties, even compared with other semiconducting nanoparticles. Its potential for advanced applications in lasers and light emitting diodes, as bio-imaging agent, in biosensors and as drug delivery vehicles, in ointments, coatings and pigments has pulled zinc oxide into the focus of various scientific and engineering research fields. Recently we started investigating if nanoparticle synthesis via laser ablation in the presence of natural stabilizers allows control over size and shape and constitutes a useful, uncomplicated alternative over conventional synthesis methods. In the current paper, we determined the ability of natural starch to act as a size controller and stabilizer in the preparation of zinc oxide nanoparticles via ablation of a ZnO plate in a starch solution with a nanosecond Q-Switched Nd:YAG pulsed laser at its original wavelength ({lambda} = 1064 nm). Our results show that the particle diameter decreases with increasing laser irradiation time to a mean nanoparticle size of approximately 15 nm with a narrow size distribution. Furthermore, the obtained particle size in starch solution is considerably smaller compared with analogous ZnO nanoparticle synthesis in distilled water. The synthesized and capped nanoparticles retained their photoluminescent properties, but showed blue emission rather than the often reported green luminescence. Evaluation of old preparations compared with freshly made samples showed no agglomeration or

  5. Dispersion of Pt Nanoparticle-Doped Reduced Graphene Oxide Using Aniline as a Stabilizer

    Hyoung-Joon Jin

    2012-12-01

    Full Text Available In this study, a simple one-step method was developed to load small-sized Pt nanoparticles (3.1 ± 0.3 nm in large quantities (50 wt % on aniline-functionalized and reduced graphene oxide (r-fGO. In the process, an ethylene glycol solution and aniline-functionalized moiety play the roles of reducing agent and stabilizer for the Pt nanoparticles, respectively, without damaging the graphite structures of the r-fGO. The Pt nanoparticles loading on the surface of r-fGO with uniform dispersion have a great effect on the electrical conductivity.

  6. On the formation and stability of Y-Ti-O nanoparticles in ODS alloys

    Sundar, C.S.

    2012-01-01

    The thermal and radiation stability of Y-Ti-O nanoparticles in oxide dispersion strengthened steels is a topic of interest, given that these nanoparticles bestow the crucial high temperature creep strength, and these ferritic alloys are candidate materials for cladding and structural materials for fast and fusion reactors. In addition, there is also interest in obtaining a basic understanding of the various issues, such as the role of alloying element Ti, on the formation of uniform sized and small nanoparticles in these alloys that are formed using the powder metallurgy route of ball milling followed by consolidation using hot extrusion

  7. [Effect of stability and dissolution of realgar nano-particles using solid dispersion technology].

    Guo, Teng; Shi, Feng; Yang, Gang; Feng, Nian-Ping

    2013-09-01

    To improve the stability and dissolution of realgar nano-particles by solid dispersion. Using polyethylene glycol 6000 and poloxamer-188 as carriers, the solid dispersions were prepare by melting method. XRD, microscopic inspection were used to determine the status of realgar nano-particles in solid dispersions. The content and stability test of As(2)0(3) were determined by DDC-Ag method. Hydride generation atomic absorption spectrometry was used to determine the content of Arsenic and investigated the in vitro dissolution behavior of solid dispersions. The results of XRD and microscopic inspection showed that realgar nano-particles in solid dispersions were amorphous. The dissolution amount and rate of Arsenic from realgar nano-particles of all solid dispersions were increased significantly, the reunion of realgar nano-particles and content of As(2)0(3) were reduced for the formation of solid dispersions. The solid dispersion of realgar nano-particles with poloxamer-188 as carriers could obviously improve stability, dissolution and solubility.

  8. Solvent-free formation of hydroxyapatite coated biodegradable particles via nanoparticle-stabilized emulsion route

    Okada, Masahiro; Fujii, Syuji; Nishimura, Taiki; Nakamura, Yoshinobu; Takeda, Shoji; Furuzono, Tsutomu

    2012-01-01

    Highlights: ► Hydroxyapatite (HAp) nanoparticles stabilized polymer melt-in-water emulsions without any molecular surfactants. ► Interaction between polymer and HAp played a crucial role. ► HAp-coated polymer particles were obtained from the emulsions without any organic solvents. - Abstract: Hydroxyapatite (HAp) nanoparticle-coated biodegradable polymer particles were fabricated from a nanoparticle-stabilized emulsion in the absence of any molecular surfactants or organic solvents. First, a polymer melt-in-water emulsion was prepared by mixing a water phase containing nanosized HAp particles as a particulate emulsifier and an oil phase consisting of poly(ε-caprolactone) (PCL) or poly(L-lactide-co-ε-caprolactone) (P(LLA-CL)) above its melting point. It was clarified that the interaction between ester/carboxyl groups of the polymers and the HAp nanoparticles at the polymer–water interface played a crucial role to prepare the nanoparticle-stabilized emulsion. The HAp nanoparticle-coated biodegradable polymer particle (a polymer solid-in-water emulsion) was fabricated by cooling the emulsion. The particle morphology and particle size were evaluated using scanning electron microscope.

  9. Biocompatible transferrin-conjugated sodium hexametaphosphate-stabilized gold nanoparticles: synthesis, characterization, cytotoxicity and cellular uptake

    Parab, Harshala J; Huang, Jing-Hong; Liu, Ru-Shi; Lai, Tsung-Ching; Jan, Yi-Hua; Wang, Jui-Ling; Hsiao, Michael; Chen, Chung-Hsuan; Hwu, Yeu-Kuang; Tsai, Din Ping; Chuang, Shih-Yi; Pang, Jong-Hwei S

    2011-01-01

    The feasibility of using gold nanoparticles (AuNPs) for biomedical applications has led to considerable interest in the development of novel synthetic protocols and surface modification strategies for AuNPs to produce biocompatible molecular probes. This investigation is, to our knowledge, the first to elucidate the synthesis and characterization of sodium hexametaphosphate (HMP)-stabilized gold nanoparticles (Au-HMP) in an aqueous medium. The role of HMP, a food additive, as a polymeric stabilizing and protecting agent for AuNPs is elucidated. The surface modification of Au-HMP nanoparticles was carried out using polyethylene glycol and transferrin to produce molecular probes for possible clinical applications. In vitro cell viability studies performed using as-synthesized Au-HMP nanoparticles and their surface-modified counterparts reveal the biocompatibility of the nanoparticles. The transferrin-conjugated nanoparticles have significantly higher cellular uptake in J5 cells (liver cancer cells) than control cells (oral mucosa fibroblast cells), as determined by inductively coupled plasma mass spectrometry. This study demonstrates the possibility of using an inexpensive and non-toxic food additive, HMP, as a stabilizer in the large-scale generation of biocompatible and monodispersed AuNPs, which may have future diagnostic and therapeutic applications.

  10. Stabilization of 2D assemblies of silver nanoparticles by spin-coating polymers

    Hu, Longyu; Pfirman, Aubrie; Chumanov, George, E-mail: gchumak@clemson.edu

    2015-12-01

    Graphical abstract: - Highlights: • Spin-coating of polymers onto 2D assemblies of Ag NPs was used to stabilize the assemblies against aggregation. • The polymer filled the space between the particles leaving the metal surface uncoated and accessible to various chemical reactions. • Etching nanoparticles produced crater-like structures. - Abstract: Silver nanoparticles self-assembled on poly(4-vinylpyridine) modified surfaces were spin-coated with poly(methyl methacrylate), poly(butyl methacrylate) and polystyrene from anisole and toluene solutions. The polymers filled the space between the particles thereby providing stabilization of the assemblies against particle aggregation when dried or chemically modified. The polymers did not coat the top surface of the nanoparticles offering the chemical accessibility to the metal surface. This was confirmed by converting the stabilized nanoparticles into silver sulfide and gold clusters. Etching the nanoparticles resulted in crater-like polymeric structures with the cavities extending down to the underlying substrate. Electrochemical reduction of silver inside the craters was performed. The approach can be extended to other nanoparticle assemblies and polymers.

  11. Biocompatible transferrin-conjugated sodium hexametaphosphate-stabilized gold nanoparticles: synthesis, characterization, cytotoxicity and cellular uptake

    Parab, Harshala J; Huang, Jing-Hong; Liu, Ru-Shi [Department of Chemistry, National Taiwan University, Taipei 106, Taiwan (China); Lai, Tsung-Ching; Jan, Yi-Hua; Wang, Jui-Ling; Hsiao, Michael; Chen, Chung-Hsuan [Genomics Research Center, Academia Sinica, Taipei 115, Taiwan (China); Hwu, Yeu-Kuang [Institute of Physics, Academia Sinica, Taipei 115, Taiwan (China); Tsai, Din Ping [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Chuang, Shih-Yi; Pang, Jong-Hwei S, E-mail: rsliu@ntu.edu.tw, E-mail: mhsiao@gate.sinica.edu.tw [Graduate Institute of Clinical Medical Sciences, Chang Gung University, Tao-Yuan, Taiwan (China)

    2011-09-30

    The feasibility of using gold nanoparticles (AuNPs) for biomedical applications has led to considerable interest in the development of novel synthetic protocols and surface modification strategies for AuNPs to produce biocompatible molecular probes. This investigation is, to our knowledge, the first to elucidate the synthesis and characterization of sodium hexametaphosphate (HMP)-stabilized gold nanoparticles (Au-HMP) in an aqueous medium. The role of HMP, a food additive, as a polymeric stabilizing and protecting agent for AuNPs is elucidated. The surface modification of Au-HMP nanoparticles was carried out using polyethylene glycol and transferrin to produce molecular probes for possible clinical applications. In vitro cell viability studies performed using as-synthesized Au-HMP nanoparticles and their surface-modified counterparts reveal the biocompatibility of the nanoparticles. The transferrin-conjugated nanoparticles have significantly higher cellular uptake in J5 cells (liver cancer cells) than control cells (oral mucosa fibroblast cells), as determined by inductively coupled plasma mass spectrometry. This study demonstrates the possibility of using an inexpensive and non-toxic food additive, HMP, as a stabilizer in the large-scale generation of biocompatible and monodispersed AuNPs, which may have future diagnostic and therapeutic applications.

  12. Dissecting the structure of surface stabilizer on the dispersion of inorganic nanoparticles in aqueous medium

    Ding, Yong; Yu, Zongzhi; Zheng, Junping, E-mail: jpzheng@tju.edu.cn [Tianjin University, Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering (China)

    2017-03-15

    Dispersing inorganic nanoparticles in aqueous solutions is a key requirement for a great variety of products and processes, including carriers in drug delivery or fillers in polymers. To be highly functional in the final product, inorganic particles are required to be finely dispersed in nanoscale. In this study, silica was selected as a representative inorganic particle. Surface stabilizers with different chain length and charged group were designed to reveal the influence of electrostatic and van der Waals forces between silica and stabilizer on the dispersion of silica particles in aqueous medium. Results showed surface stabilizer with longer alkyl chain and charged group exerted best ability to deaggregate silica, leading to a hydrodynamic size of 51.1 nm. Surface stabilizer designing with rational structure is a promising solution for deagglomerating and reducing process time and energy. Giving the designability and adaptability of surface stabilizer, this method is of potential for dispersion of other inorganic nanoparticles.

  13. Dissecting the structure of surface stabilizer on the dispersion of inorganic nanoparticles in aqueous medium

    Ding, Yong; Yu, Zongzhi; Zheng, Junping

    2017-03-01

    Dispersing inorganic nanoparticles in aqueous solutions is a key requirement for a great variety of products and processes, including carriers in drug delivery or fillers in polymers. To be highly functional in the final product, inorganic particles are required to be finely dispersed in nanoscale. In this study, silica was selected as a representative inorganic particle. Surface stabilizers with different chain length and charged group were designed to reveal the influence of electrostatic and van der Waals forces between silica and stabilizer on the dispersion of silica particles in aqueous medium. Results showed surface stabilizer with longer alkyl chain and charged group exerted best ability to deaggregate silica, leading to a hydrodynamic size of 51.1 nm. Surface stabilizer designing with rational structure is a promising solution for deagglomerating and reducing process time and energy. Giving the designability and adaptability of surface stabilizer, this method is of potential for dispersion of other inorganic nanoparticles.

  14. High temperature stability of surfactant capped CoFe2O4 nanoparticles

    Ayyappan, S.; Panneerselvam, G.; Antony, M.P.; Philip, John

    2011-01-01

    Highlights: → Self-assembled molecular layers of surfactant on nanoparticles are often used to modify surface properties. → We demonstrate that a surfactant nanolayer on CoFe 2 O 4 nanoparticles can act as a strong reducing agent under high temperature vacuum annealing. → We propose a possible reduction mechanism of CoFe 2 O 4 nanoparticles under air and vacuum annealing. → Our results are important in the understanding of the stability of nanoparticles at high temperatures. - Abstract: We investigate the effect of adsorbed surfactant on the structural stability of CoFe 2 O 4 nanoparticles during vacuum thermal annealing. In-situ high temperature X-ray diffraction studies show a reduction of oleic acid coated CoFe 2 O 4 nanoparticles into α-Fe and CoO under annealing at 800 deg. C. On the contrary, the uncoated CoFe 2 O 4 nanoparticles remains stable, with its cubic phase intact, even at 1000 deg. C. Thermo-gravimetric analysis coupled mass spectra reveals that the evolved carbon from the surfactant aids the removal of oxygen atom from CoFe 2 O 4 lattice thereby reducing it to α-Fe and CoO phases. These results are important in tailoring stable CoFe 2 O 4 nanostructures for various applications.

  15. Studies on electronic structure of interfaces between Ag and gelatin for stabilization of Ag nanoparticles

    Tani, Tadaaki; Uchida, Takayuki

    2015-01-01

    Extremely high stability of Ag nanoparticles in photographic materials has forced us to study the electronic structures of the interfaces between thin layers of Ag, Au, and Pt and their surface membranes in ambient atmosphere by photoelectron yield spectroscopy in air and Kelvin probe method. Owing to the Fermi level equalization between a metal layer and a membrane coming from air, the electron transfer took place from the membrane to Pt and Au layers and from an Ag layer to the membrane, giving the reason for poor stability of Ag nanoparticles in air. The control of the Fermi level of an Ag layer with respect to that of a gelatin membrane in air could be widely made according to Nernst's equation by changing the pH and pAg values of an aqueous gelatin solution used to form the membrane, and thus available to stabilize Ag nanoparticles in a gelatin matrix. (author)

  16. Protein capped nanosilver free radical oxidation: role of biomolecule capping on nanoparticle colloidal stability and protein oxidation.

    Ahumada, Manuel; Bohne, Cornelia; Oake, Jessy; Alarcon, Emilio I

    2018-05-03

    We studied the effect of human serum albumin protein capped spherical nanosilver on the nanoparticle stability upon peroxyl radical oxidation. The nanoparticle-protein composite is less prone to oxidation compared to the individual components. However, higher concentrations of hydrogen peroxide were formed in the nanoparticle-protein system.

  17. A versatile synthesis of highly bactericidal Myramistin (registered) stabilized silver nanoparticles

    Vertelov, G K; Krutyakov, Yu A; Olenin, A Yu; Lisichkin, G V; Efremenkova, O V

    2008-01-01

    Silver nanoparticles stabilized by a well-known antibacterial surfactant benzyldimethyl[3-(myristoylamino)propyl]ammonium chloride (Myramistin) were produced for the first time by borohydride reduction of silver chloride sol in water. Stable aqueous dispersions of silver nanoparticles without evident precipitation for several months could be obtained. In vitro bactericidal tests showed that Myramistin capped silver NPs exhibited notable activity against six different microorganisms-gram-positive and gram-negative bacteria, yeasts and fungi. The activity was up to 20 times higher (against E. coli) compared to Myramistin at the same concentrations and on average 2 times higher if compared with citrate-stabilized NPs

  18. A versatile synthesis of highly bactericidal Myramistin® stabilized silver nanoparticles

    Vertelov, G. K.; Krutyakov, Yu A.; Efremenkova, O. V.; Olenin, A. Yu; Lisichkin, G. V.

    2008-09-01

    Silver nanoparticles stabilized by a well-known antibacterial surfactant benzyldimethyl[3-(myristoylamino)propyl]ammonium chloride (Myramistin®) were produced for the first time by borohydride reduction of silver chloride sol in water. Stable aqueous dispersions of silver nanoparticles without evident precipitation for several months could be obtained. In vitro bactericidal tests showed that Myramistin® capped silver NPs exhibited notable activity against six different microorganisms—gram-positive and gram-negative bacteria, yeasts and fungi. The activity was up to 20 times higher (against E. coli) compared to Myramistin® at the same concentrations and on average 2 times higher if compared with citrate-stabilized NPs.

  19. Ultrasound-induced inertial cavitation from gas-stabilizing nanoparticles.

    Kwan, J J; Graham, S; Myers, R; Carlisle, R; Stride, E; Coussios, C C

    2015-08-01

    The understanding of cavitation from nanoparticles has been hindered by the inability to control nanobubble size. We present a method to manufacture nanoparticles with a tunable single hemispherical depression (nanocups) of mean diameter 90, 260, or 650 nm entrapping a nanobubble. A modified Rayleigh-Plesset crevice model predicts the inertial cavitation threshold as a function of cavity size and frequency, and is verified experimentally. The ability to tune cavitation nanonuclei and predict their behavior will be useful for applications ranging from cancer therapy to ultrasonic cleaning.

  20. Green synthesis of gold nanoparticles using Stevia rebaudiana leaf extracts: Characterization and their stability.

    Sadeghi, Babak; Mohammadzadeh, M; Babakhani, B

    2015-07-01

    Various methods invented and developed for the synthesis of gold nanoparticles that increases daily consumed. According to this method, including potential environmental pollution problems and the complexity of the synthesis, in this study, the feasibility of using the leaves extract of Stevia rebaudiana (SR) for the reduction of gold ions to nanoparticles form have been studied. Stevia leaves were used to prepare the aqueous extract for this study. Gold nanoparticles were characterized with different techniques such as UV-vis spectroscopy, FT-IR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Transmission electron microscopy experiments showed that these nanoparticles are spherical and uniformly distributed and its size is from 5 to 20 nm. FT-IR spectroscopy revealed that gold nanoparticles were functionalized with biomolecules that have primary amine group (NH2), carbonyl group, OH groups and other stabilizing functional groups. X-ray diffraction pattern showed high purity and face centered cubic structure of gold nanoparticles with size of 17 nm. The scanning electron microscopy (SEM) implies the right of forming gold nanoparticles. The results, confirm that gold nanoparticles have synthesized by the leaves extract of S. rebaudiana (SR). Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Stabilization of sputtered gold and silver nanoparticles in PEG colloid solutions

    Slepička, P.; Elashnikov, R.; Ulbrich, P.; Staszek, M.; Kolská, Z.; Švorčík, V.

    2015-01-01

    In this study, a simple technique for preparation of colloid solution of metal nanoparticles in polyethylene glycol (PEG)/H 2 O is described. By this technique, stable colloidal metal solutions can be prepared ready for use without application of chemical reactions, stabilizers, or reducing agents. The nanoparticles are created by direct sputtering of metal into PEG. The influence of sputter conditions and the concentration of PEG/H 2 O on the properties of nanoparticles was studied. The nanoparticles were characterized by transmission electron microscopy, atomic absorption spectrometry, dynamic light scattering, and UV–Vis spectroscopy. UV–Vis spectra of gold nanoparticle solution exhibit localized surface plasmon resonance characteristic peaks located in the region 513–560 nm (PEG/H 2 O—1/1), 509–535 nm (PEG/H 2 O—1/9), and for silver nanoparticles in the region from 401 to 421 nm. Silver nanoparticles have a broader size distribution compared with gold ones. An appropriate choice of concentration, mixing, and deposition conditions allows preparing the stable solution of gold or silver nanoparticles

  2. Stabilization of sputtered gold and silver nanoparticles in PEG colloid solutions

    Slepička, P., E-mail: petr.slepicka@vscht.cz; Elashnikov, R. [University of Chemistry and Technology Prague, Department of Solid State Engineering (Czech Republic); Ulbrich, P. [University of Chemistry and Technology Prague, Department of Biochemistry and Microbiology (Czech Republic); Staszek, M. [University of Chemistry and Technology Prague, Department of Solid State Engineering (Czech Republic); Kolská, Z. [University of J. E. Purkyně, Faculty of Science (Czech Republic); Švorčík, V. [University of Chemistry and Technology Prague, Department of Solid State Engineering (Czech Republic)

    2015-01-15

    In this study, a simple technique for preparation of colloid solution of metal nanoparticles in polyethylene glycol (PEG)/H{sub 2}O is described. By this technique, stable colloidal metal solutions can be prepared ready for use without application of chemical reactions, stabilizers, or reducing agents. The nanoparticles are created by direct sputtering of metal into PEG. The influence of sputter conditions and the concentration of PEG/H{sub 2}O on the properties of nanoparticles was studied. The nanoparticles were characterized by transmission electron microscopy, atomic absorption spectrometry, dynamic light scattering, and UV–Vis spectroscopy. UV–Vis spectra of gold nanoparticle solution exhibit localized surface plasmon resonance characteristic peaks located in the region 513–560 nm (PEG/H{sub 2}O—1/1), 509–535 nm (PEG/H{sub 2}O—1/9), and for silver nanoparticles in the region from 401 to 421 nm. Silver nanoparticles have a broader size distribution compared with gold ones. An appropriate choice of concentration, mixing, and deposition conditions allows preparing the stable solution of gold or silver nanoparticles.

  3. Solid-stabilized emulsion formation using stearoyl lactylate coated iron oxide nanoparticles

    Vengsarkar, Pranav S.; Roberts, Christopher B.

    2014-10-01

    Iron oxide nanoparticles can exhibit highly tunable physicochemical properties that are extremely important in applications such as catalysis, biomedicine and environmental remediation. The small size of iron oxide nanoparticles can be used to stabilize oil-in-water Pickering emulsions due to their high energy of adsorption at the interface of oil droplets in water. The objective of this work is to investigate the effect of the primary particle characteristics and stabilizing agent chemistry on the stability of oil-in-water Pickering emulsions. Iron oxide nanoparticles were synthesized by the co-precipitation method using stoichiometric amounts of Fe2+ and Fe3+ salts. Sodium stearoyl lactylate (SSL), a Food and Drug Administration approved food additive, was used to functionalize the iron oxide nanoparticles. SSL is useful in the generation of fat-in-water emulsions due to its high hydrophilic-lipophilic balance and its bilayer-forming capacity. Generation of a monolayer or a bilayer coating on the nanoparticles was controlled through systematic changes in reagent concentrations. The coated particles were then characterized using various analytical techniques to determine their size, their crystal structure and surface functionalization. The capacity of these bilayer coated nanoparticles to stabilize oil-in-water emulsions under various salt concentrations and pH values was also systematically determined using various characterization techniques. This study successfully demonstrated the ability to synthesize iron oxide nanoparticles (20-40 nm) coated with SSL in order to generate stable Pickering emulsions that were pH-responsive and resistant to significant destabilization in a saline environment, thereby lending themselves to applications in advanced oil spill recovery and remediation.

  4. Dissolution, agglomerate morphology, and stability limits of protein-coated silver nanoparticles.

    Martin, Matthew N; Allen, Andrew J; MacCuspie, Robert I; Hackley, Vincent A

    2014-09-30

    Little is understood regarding the impact that molecular coatings have on nanoparticle dissolution kinetics and agglomerate formation in a dilute nanoparticle dispersion. Dissolution and agglomeration processes compete in removing isolated nanoparticles from the dispersion, making quantitative time-dependent measurements of the mechanisms of nanoparticle loss particularly challenging. In this article, we present in situ ultra-small-angle X-ray scattering (USAXS) results, simultaneously quantifying dissolution, agglomeration, and stability limits of silver nanoparticles (AgNPs) coated with bovine serum albumin (BSA) protein. When the BSA corona is disrupted, we find that the loss of silver from the nanoparticle core is well matched by a second-order kinetic rate reaction, arising from the oxidative dissolution of silver. Dissolution and agglomeration are quantified, and morphological transitions throughout the process are qualified. By probing the BSA-AgNP suspension around its stability limits, we provide insight into the destabilization mechanism by which individual particles rapidly dissolve as a whole rather than undergo slow dissolution from the aqueous interface inward, once the BSA layer is breached. Because USAXS rapidly measures over the entire nanometer to micrometer size range during the dissolution process, many insights are also gained into the stabilization of NPs by protein and its ability to protect the labile metal core from the solution environment by prohibiting the diffusion of reactive species. This approach can be extended to a wide variety of coating molecules and reactive metal nanoparticle systems to carefully survey their stability limits, revealing the likely mechanisms of coating breakdown and ensuing reactions.

  5. Nanoparticle-stabilized liposomes for pH-responsive gastric drug delivery.

    Thamphiwatana, Soracha; Fu, Victoria; Zhu, Jingying; Lu, Diannan; Gao, Weiwei; Zhang, Liangfang

    2013-10-01

    We report a novel pH-responsive gold nanoparticle-stabilized liposome system for gastric antimicrobial delivery. By adsorbing small chitosan-modified gold nanoparticles (diameter ~10 nm) onto the outer surface of negatively charged phospholipid liposomes (diameter ~75 nm), we show that at gastric pH the liposomes have excellent stability with limited fusion ability and negligible cargo releases. However, when the stabilized liposomes are present in an environment with neutral pH, the gold stabilizers detach from the liposomes, resulting in free liposomes that can actively fuse with bacterial membranes. Using Helicobacter pylori as a model bacterium and doxycycline as a model antibiotic, we demonstrate such pH-responsive fusion activity and drug release profile of the nanoparticle-stabilized liposomes. Particularly, at neutral pH the gold nanoparticles detach, and thus the doxycycline-loaded liposomes rapidly fuse with bacteria and cause superior bactericidal efficacy as compared to the free doxycycline counterpart. Our results suggest that the reported liposome system holds a substantial potential for gastric drug delivery; it remains inactive (stable) in the stomach lumen but actively interacts with bacteria once it reaches the mucus layer of the stomach where the bacteria may reside.

  6. Surface functionalization of microwave plasma-synthesized silica nanoparticles for enhancing the stability of dispersions

    Sehlleier, Yee Hwa; Abdali, Ali; Schnurre, Sophie Marie; Wiggers, Hartmut; Schulz, Christof

    2014-08-01

    Gas phase-synthesized silica nanoparticles were functionalized with three different silane coupling agents (SCAs) including amine, amine/phosphonate and octyltriethoxy functional groups and the stability of dispersions in polar and non-polar dispersing media such as water, ethanol, methanol, chloroform, benzene, and toluene was studied. Fourier transform infrared spectroscopy showed that all three SCAs are chemically attached to the surface of silica nanoparticles. Amine-functionalized particles using steric dispersion stabilization alone showed limited stability. Thus, an additional SCA with sufficiently long hydrocarbon chains and strong positively charged phosphonate groups was introduced in order to achieve electrosteric stabilization. Steric stabilization was successful with hydrophobic octyltriethoxy-functionalized silica nanoparticles in non-polar solvents. The results from dynamic light scattering measurements showed that in dispersions of amine/phosphonate- and octyltriethoxy-functionalized silica particles are dispersed on a primary particle level. Stable dispersions were successfully prepared from initially agglomerated nanoparticles synthesized in a microwave plasma reactor by designing the surface functionalization.

  7. Effects of Humic and Fulvic Acids on Silver Nanoparticle Stability, Dissolution, and Toxicity

    Gunsolus, Ian L.; Mousavi, Maral P. S.; Hussein, Kadir; Bühlmann, Philippe; Haynes, Christy L.

    2015-01-01

    The colloidal stability of silver nanoparticles (AgNPs) in natural aquatic environments influences their transport and environmental persistence, while their dissolution to Ag+ influences their toxicity to organisms. Here, we characterize the colloidal stability, dissolution behavior, and toxicity of two industrially relevant classes of AgNPs (i.e., AgNPs stabilized by citrate or polyvinylpyrrolidone) after exposure to natural organic matter (NOM, i.e., Suwannee River Humic and Fulvic Acid Standards and Pony Lake Fulvic Acid Reference). We show that NOM interaction with the nanoparticle surface depends on (i) the NOM’s chemical composition, where sulfur- and nitrogen-rich NOM more significantly increases colloidal stability, and (ii) the affinity of the capping agent for the AgNP surface, where nanoparticles with loosely bound capping agents are more effectively stabilized by NOM. Adsorption of NOM is shown to have little effect on AgNP dissolution under most experimental conditions, the exception being when the NOM is rich in sulfur and nitrogen. Similarly, the toxicity of AgNPs to a bacterial model (Shewanella oneidensis MR-1) decreases most significantly in the presence of sulfur- and nitrogen-rich NOM. Our data suggest that the rate of AgNP aggregation and dissolution in aquatic environments containing NOM will depend on the chemical composition of the NOM, and that the toxicity of AgNPs to aquatic microorganisms is controlled primarily by the extent of nanoparticle dissolution. PMID:26047330

  8. Cyclodextrin-grafted barium titanate nanoparticles for improved dispersion and stabilization in water-based systems

    Serra-Gómez, R. [Universidad de Navarra, Departamento de Química y Edafología (Spain); Martinez-Tarifa, J. M. [Universidad Carlos III de Madrid, Departamento de Ingeniería Eléctrica (Spain); González-Benito, J. [Universidad Carlos III de Madrid, Departamento de Ciencia e Ingeniería de Materiales e Ingeniería Química, IQMAAB (Spain); González-Gaitano, G., E-mail: gaitano@unav.es [Universidad de Navarra, Departamento de Química y Edafología (Spain)

    2016-01-15

    Ceramic nanoparticles with piezoelectric properties, such as BaTiO{sub 3} (BT), constitute a promising approach in the fields of nanocomposite materials and biomaterials. In the latter case, to be successful in their preparation, the drawback of their fast aggregation and practically null stability in water has to be overcome. The objective of this investigation has been the surface functionalization of BaTiO{sub 3} nanoparticles with cyclodextrins (CDs) as a way to break the aggregation and improve the stability of the nanoparticles in water solution, preventing and minimizing their fast precipitation. As a secondary goal, we have achieved extra-functionality of the nanoparticles, bestowed from the hydrophobic cavity of the macrocycle, which is able to lodge guest molecules that can form inclusion complexes with the oligosaccharide. The nanoparticle functionalization has been fully tracked and characterized, and the cytotoxicity of the modified nanoparticles with fibroblasts and pre-osteoblasts cell lines has been assessed with excellent results in a wide range of concentrations. The modified nanoparticles were found to be suitable for the easy preparation of nanocomposite hydrogels, via dispersion in hydrophilic polymers of typical use in biomedical applications (PEG, Pluronics, and PEO), and further processed in the form of films via water casting, showing very good results in terms of homogeneity in the dispersion of the filler. Likewise, as examples of application and with the aim of exploring a different range of nanocomposites, rhodamine B was included in the macrocycles as a model molecule, and films prepared from a thermoplastic matrix (EVA) via high-energy ball milling have been tested by impedance spectroscopy to discuss their dielectric properties, which indicated that even small modifications in the surface of the nanoparticles generate a different kind of interaction with the polymeric matrix. The CD-modified nanoparticles are thus suitable for easy

  9. Ionic liquid stabilized Rh Nanoparticles for Citral Cyclodehydration

    Quek, X.Y.; Guan, Y.; Santen, van R.A.; Hensen, E.J.M.

    2010-01-01

    Smells nice, too: The cyclodehydration of citral is achieved by using rhodium nanoparticles dispersed in an imidazolium-based ionic liquid. p-Cymene, p--dimethylstyrene, and limonene are obtained with selectivity greater than 75¿%. The interaction between the imidazolium cations and the metal

  10. Water-Soluble N-Heterocyclic Carbene-Protected Gold Nanoparticles: Size-Controlled Synthesis, Stability, and Optical Properties

    Salorinne, Kirsi; Man, Renee W.Y.; Li, Chien-Hung; Taki, Masayasu; Nambo, Masakazu; Crudden, Cathleen M.

    2017-01-01

    NHC-Au(I) complexes were used to prepare stable, water-soluble, NHC-protected gold nanoparticles. The water-soluble, charged nature of the nanoparticles permitted analysis by polyacrylamide gel electrophoresis (PAGE), which showed that the nanoparticles were highly monodisperse, with tunable core diameters between 2.0 and 3.3 nm depending on the synthesis conditions. Temporal, thermal, and chemical stability of the nanoparticles were determined to be high. Treatment with thiols caused etching...

  11. Magnetic nanoparticles coated with polyaniline to stabilize immobilized trypsin

    Maciel, J. C., E-mail: jackeline-maciel@hotmail.com [Universidade Federal de Roraima (Brazil); Mercês, A. A. D.; Cabrera, M. [Universidade Federal de Pernambuco, Laboratório de Imunopatologia Keizo Asami (Brazil); Shigeyosi, W. T. [Universidade Federal de São Carlos, Departamento de Física (Brazil); Souza, S. D. de; Olzon-Dionysio, M.; Fabris, J. D. [Universidade Federal dos Vales de Jequitinhonha e Mucuri (Brazil); Cardoso, C. A. [Universidade Federal de São Carlos, Departamento de Física (Brazil); Neri, D. F. M. [Universidade Federal do Vale do São Francisco (Brazil); Silva, M. P. C.; Carvalho, L. B. [Universidade Federal de Pernambuco, Laboratório de Imunopatologia Keizo Asami (Brazil)

    2016-12-15

    It is reported the synthesis of magnetic nanoparticles via the chemical co-precipitation of Fe {sup 3+} ions and their preparation by coating them with polyaniline. The electronic micrograph analysis showed that the mean diameter for the nanoparticles is ∼15 nm. FTIR, powder X-ray diffraction and Mössbauer spectroscopy were used to understand the chemical, crystallographic and {sup 57}Fe hyperfine structures for the two samples. The nanoparticles, which exhibited magnetic behavior with relatively high spontaneous magnetization at room temperature, were identified as being mainly formed by maghemite (γFe{sub 2}O{sub 3}). The coated magnetic nanoparticles (sample labeled “mPANI”) presented a real ability to bind biological molecules such as trypsin, forming the magnetic enzyme derivative (sample “mPANIG-Trypsin”). The amount of protein and specific activity of the immobilized trypsin were found to be 13±5 μg of protein/mg of mPANI (49.3 % of immobilized protein) and 24.1±0.7 U/mg of immobilized protein, respectively. After 48 days of storage at 4 {sup ∘}C, the activity of the immobilized trypsin was found to be 89 % of its initial activity. This simple, fast and low-cost procedure was revealed to be a promising way to prepare mPANI nanoparticles if technological applications addressed to covalently link biomolecules are envisaged. This route yields chemically stable derivatives, which can be easily recovered from the reaction mixture with a magnetic field and recyclable reused.

  12. Stability of polyelectrolyte-coated iron nanoparticles for T2-weighted magnetic resonance imaging

    McGrath, Andrew J.; Dolan, Ciaran; Cheong, Soshan; Herman, David A. J.; Naysmith, Briar; Zong, Fangrong; Galvosas, Petrik; Farrand, Kathryn J.; Hermans, Ian F.; Brimble, Margaret; Williams, David E.; Jin, Jianyong; Tilley, Richard D.

    2017-10-01

    Iron nanoparticles are highly-effective magnetic nanoparticles for T2 magnetic resonance imaging (MRI). However, the stability of their magnetic properties is dependent on good protection of the iron core from oxidation in aqueous media. Here we report the synthesis of custom-synthesized phosphonate-grafted polyelectrolytes (PolyM3) of various chain lengths, for efficient coating of iron nanoparticles with a native iron oxide shell. The size of the nanoparticle-polyelectrolyte assemblies was investigated by transmission electron microscopy and dynamic light scattering, while surface attachment was confirmed by Fourier transform infrared spectroscopy. Low cytotoxicity was observed for each of the nanoparticle-polyelectrolyte ("Fe-PolyM3") assemblies, with good cell viability (>80%) remaining up to 100 μg mL-1 Fe in HeLa cells. When applied in T2-weighted MRI, corresponding T2 relaxivities (r2) of the Fe-PolyM3 assemblies were found to be dependent on the chain length of the polyelectrolyte. A significant increase in contrast was observed when polyelectrolyte chain length was increased from 6 to 65 repeating units, implying a critical chain length required for stabilization of the α-Fe nanoparticle core.

  13. Effect of Maillard Conjugates on the Physical Stability of Zein Nanoparticles Prepared by Liquid Antisolvent Coprecipitation.

    Davidov-Pardo, Gabriel; Joye, Iris J; Espinal-Ruiz, Mauricio; McClements, David Julian

    2015-09-30

    Protein nanoparticles are often not very stable in a complex food matrix because they are primarily stabilized by electrostatic repulsion. In this study, we envisaged the stabilization of zein nanoparticles through Maillard conjugation reactions with polysaccharides of different molecular mass. Zein nanoparticles (0.5% w/v) containing resveratrol (0.025% w/v grape skin extract) were produced by liquid antisolvent precipitation and coated with Maillard conjugates (MC) of sodium caseinate and different molecular mass carbohydrates during particle production. Zein nanoparticles coated with conjugated polysaccharides of 2.8, 37, and 150 kDa had diameters of 198 ± 5, 176 ± 6, and 180 ± 3 nm, respectively. The encapsulation efficiency (∼83%) was not affected by conjugation, but the conjugates significantly improved particle stability against changes in pH (2.0-9.0), CaCl2 addition (up to 100 mM), and heat treatment (30-90 °C, 30 min). Zein nanoparticles coated by MC may therefore be suitable delivery systems for hydrophobic bioactive molecules in a wide range of commercial products.

  14. Synthesis, Antibacterial and Thermal Studies of Cellulose Nanocrystal Stabilized ZnO-Ag Heterostructure Nanoparticles

    Mohd Zobir Hussein

    2013-05-01

    Full Text Available Synthesis of ZnO-Ag heterostructure nanoparticles was carried out by a precipitation method with cellulose nanocrystals (CNCs as a stabilizer for antimicrobial and thermal studies. ZnO-Ag nanoparticles were obtained from various weight percentages of added AgNO3 relative to Zn precursors for evaluating the best composition with enhanced functional properties. The ZnO-Ag/CNCs samples were characterized systematically by TEM, XRD, UV, TGA and DTG. From the TEM studies we observed that ZnO-Ag heterostructure nanoparticles have spherical shapes with size diameters in a 9–35 nm range. The antibacterial activities of samples were assessed against the bacterial species Salmonella choleraesuis and Staphylococcus aureus. The CNC-stabilized ZnO-Ag exhibited greater bactericidal activity compared to cellulose-free ZnO-Ag heterostructure nanoparticles of the same particle size. The incorporation of ZnO-Ag hetreostructure nanoparticles significantly increased the thermal stability of cellulose nanocrystals.

  15. Dispersion stability of nanoparticles in ecotoxicological investigations: the need for adequate measurement tools

    Tantra, Ratna, E-mail: ratna.tantra@npl.co.uk; Jing Shingheng; Pichaimuthu, Sivaraman K. [National Physical Laboratory (United Kingdom); Walker, Nicholas [University of Exeter, School of Biosciences (United Kingdom); Noble, James [National Physical Laboratory (United Kingdom); Hackley, Vincent A. [National Institute of Standards and Technology (United States)

    2011-09-15

    One of the main challenges in nanoecotoxicological investigations is in the selection of the most suitable measurement methods and protocols for nanoparticle characterisation. Several parameters have been identified as being important as they govern nanotoxicological activity, with some parameters being better defined than others. For example, as a parameter, there is some ambiguity as to how to measure dispersion stability in the context of ecotoxicological investigations; indeed, there is disagreement over which are the best methods to measure nanoparticle dispersion stability. The purpose of this article is to use various commercially available tools to measure dispersion stability and to understand the information given by each tool. In this study, CeO{sub 2} was dispersed in two different types of media: de-ionised water and electrolyte-containing fish medium. The DLS mean particle size of freshly dispersed sample in DI water was {approx}200 nm in diameter. A visual sedimentation experiment showed that nanoparticle dispersion made in the fish medium was less stable compared to corresponding dispersion in de-ionised water. Stability of these dispersions was monitored using various techniques, for a period of 3 days. Our findings have shown that dispersion stability can be suitably assessed by monitoring: (a) surface charge, (b) sedimentation events and (c) presence of agglomerates, through time. The majority of techniques employed here (zeta potential, particle size via DLS, fluorescence and UV-Vis spectroscopy and SEM) were shown to provide useful, complementary information on dispersion stability. Nanoparticle Tracking Analysis (NTA) provides useful, quantitative information on the concentration of nanoparticles in suspension, but is limited by its inability to accurately track the motion of large agglomerates found in the fish medium.

  16. Dispersion stability of nanoparticles in ecotoxicological investigations: the need for adequate measurement tools

    Tantra, Ratna; Jing Shingheng; Pichaimuthu, Sivaraman K.; Walker, Nicholas; Noble, James; Hackley, Vincent A.

    2011-01-01

    One of the main challenges in nanoecotoxicological investigations is in the selection of the most suitable measurement methods and protocols for nanoparticle characterisation. Several parameters have been identified as being important as they govern nanotoxicological activity, with some parameters being better defined than others. For example, as a parameter, there is some ambiguity as to how to measure dispersion stability in the context of ecotoxicological investigations; indeed, there is disagreement over which are the best methods to measure nanoparticle dispersion stability. The purpose of this article is to use various commercially available tools to measure dispersion stability and to understand the information given by each tool. In this study, CeO 2 was dispersed in two different types of media: de-ionised water and electrolyte-containing fish medium. The DLS mean particle size of freshly dispersed sample in DI water was ∼200 nm in diameter. A visual sedimentation experiment showed that nanoparticle dispersion made in the fish medium was less stable compared to corresponding dispersion in de-ionised water. Stability of these dispersions was monitored using various techniques, for a period of 3 days. Our findings have shown that dispersion stability can be suitably assessed by monitoring: (a) surface charge, (b) sedimentation events and (c) presence of agglomerates, through time. The majority of techniques employed here (zeta potential, particle size via DLS, fluorescence and UV–Vis spectroscopy and SEM) were shown to provide useful, complementary information on dispersion stability. Nanoparticle Tracking Analysis (NTA) provides useful, quantitative information on the concentration of nanoparticles in suspension, but is limited by its inability to accurately track the motion of large agglomerates found in the fish medium.

  17. Nanoparticle Stabilized Foam in Carbonate and Sandstone Reservoirs

    Roebroeks, J.; Eftekhari, A.A.; Farajzadeh, R.; Vincent-Bonnieu, S.

    2015-01-01

    Foam flooding as a mechanism to enhance oil recovery has been intensively studied and is the subject of multiple research groups. However, limited stability of surfactant-generated foam in presence of oil and low chemical stability of surfactants in the high temperature and high salinity of an oil

  18. Preparation of poly(N-vinylpyrrolidone-stabilized ZnO colloid nanoparticles

    Tatyana Gutul

    2014-04-01

    Full Text Available We propose a method for the synthesis of a colloidal ZnO solution with poly(N-vinylpyrrolidone (PVP as stabilizer. Stable colloidal solutions with good luminescence properties are obtained by using PVP as stabilizer in the synthesis of ZnO nanoparticles by a sol–gel method assisted by ultrasound. Nanoparticles with sizes of 30–40 nm in a PVP matrix are produced as a solid product. The colloidal ZnO/PVP/methanol solution, apart from the most intense PL band at 356 nm coming from the PVP, exhibits a strong PL band at 376 nm (3.30 eV which corresponds to the emission of the free exciton recombination in ZnO nanoparticles.

  19. Stabilization of 200-atom platinum nanoparticles by organosilane fragments

    Pelzer, Katrin

    2011-04-19

    Three\\'s a charm: Platinum nanoparticles of 2 nm diameter and containing approximately 200 atoms covered with n-octylsilyl groups (see picture, right; Pt blue, Si red, C gray, H turquoise) form when [Pt(dba)2] (dba=dibenzylideneacetone) decomposes in the presence of n-octylsilane. The particles adopt a cuboctahedral structure with an edge length of three atoms. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Stabilization of 200-atom platinum nanoparticles by organosilane fragments

    Pelzer, Katrin; Hä vecker, Michael; Boualleg, Malika; Candy, Jean Pierre; Basset, Jean-Marie

    2011-01-01

    Three's a charm: Platinum nanoparticles of 2 nm diameter and containing approximately 200 atoms covered with n-octylsilyl groups (see picture, right; Pt blue, Si red, C gray, H turquoise) form when [Pt(dba)2] (dba=dibenzylideneacetone) decomposes in the presence of n-octylsilane. The particles adopt a cuboctahedral structure with an edge length of three atoms. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Highly stabilized and photoluminescence enhancement of ZnS:Mn2+ nanoparticles in biotin matrix

    Keshari, Ashish K.; Pandey, Avinash C.

    2009-01-01

    We synthesized the ZnS:Mn 2+ nanoparticles passivated by biocompatible layer, namely, biotin by chemical precipitation route and studied their temporal evolution for size, structure, optical, and photoluminescence stability. To monitor the structural and optoelectronic properties of the nanoparticles with time, we have characterized the grown product by x-ray diffraction, small angle x-ray scattering, UV visible, and photoluminescence spectroscopic techniques at a regular interval for a period of three months. Results showed that the properties of nanophosphors capped with biotin are remaining the same even after 3 months. Energy dispersive x-ray analysis of 3 month aged sample shows long time compatibility between ZnS:Mn 2+ nanoparticles and the biotin. This is also confirmed by electron microscopy that the growth of the nanoparticles is strongly arrested by the biotin. X-ray photoelectron spectra were also recorded to show the chemical state of the elements. Enhanced ratio of Zn 2p to Mn 2p peaks in the x-ray photoelectron spectra of ZnS:Mn 2+ nanoparticles shows that the Mn 2+ ions are incorporated within ZnS host matrix. We found that biotin capping will enhance the luminescence from ZnS:Mn 2+ nanoparticles as compared to without capped particles. Absence of biotin will gradually degrade the luminescence upon aging while drastic degradation in luminescence intensity was observed after annealing. Properties show that biotin also protected the nanoparticles from any environmental attack

  2. Green Fabrication of Silver Nanoparticles by Gum Tragacanth (Astragalus gummifer: A Dual Functional Reductant and Stabilizer

    Aruna Jyothi Kora

    2012-01-01

    Full Text Available A simple and ecofriendly procedure have been devised for the green synthesis of silver nanoparticles using the aqueous extract of gum tragacanth (Astragalus gummifer, a renewable, nontoxic natural phyto-exudate. The water soluble components in the gum act as reductants and stabilizers. The generated nanoparticles were analyzed using UV-visible spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy, and Raman spectroscopy. The role of gum concentration and reaction time on the synthesis of nanoparticles was studied. By regulating the reaction conditions, spherical nanoparticles of 13.1±1.0 nm size were produced. Also, the possible functional groups involved in reduction and capping of nanoparticles has been elucidated. The antibacterial activity of the fabricated nanoparticles was tested on model Gram-negative and Gram-positive bacterial strains with well-diffusion method. These nanoparticles exhibited considerable antibacterial activity on both the Gram classes of bacteria, implying their potential biomedical applications.

  3. Effect of gold nanoparticle on stability of the DNA molecule: A study of molecular dynamics simulation.

    Izanloo, Cobra

    2017-09-02

    An understanding of the mechanism of DNA interactions with gold nanoparticles is useful in today medicine applications. We have performed a molecular dynamics simulation on a B-DNA duplex (CCTCAGGCCTCC) in the vicinity of a gold nanoparticle with a truncated octahedron structure composed of 201 gold atoms (diameter ∼1.8 nm) to investigate gold nanoparticle (GNP) effects on the stability of DNA. During simulation, the nanoparticle is closed to DNA and phosphate groups direct the particles into the major grooves of the DNA molecule. Because of peeling and untwisting states that are occur at end of DNA, the nucleotide base lies flat on the surface of GNP. The configuration entropy is estimated using the covariance matrix of atom-positional fluctuations for different bases. The results show that when a gold nanoparticle has interaction with DNA, entropy increases. The results of conformational energy and the hydrogen bond numbers for DNA indicated that DNA becomes unstable in the vicinity of a gold nanoparticle. The radial distribution function was calculated for water hydrogen-phosphate oxygen pairs. Almost for all nucleotide, the presence of a nanoparticle around DNA caused water molecules to be released from the DNA duplex and cations were close to the DNA.

  4. TPGS-Stabilized Curcumin Nanoparticles Exhibit Superior Effect on Carrageenan-Induced Inflammation in Wistar Rat

    Heni Rachmawati

    2016-08-01

    Full Text Available Curcumin, a hydrophobic polyphenol compound derived from the rhizome of the Curcuma genus, has a wide spectrum of biological and pharmacological applications. Previously, curcumin nanoparticles with different stabilizers had been produced successfully in order to enhance solubility and per oral absorption. In the present study, we tested the anti-inflammatory effect of d-α-Tocopheryl polyethylene glycol 1000 succinate (TPGS-stabilized curcumin nanoparticles in vivo. Lambda-carrageenan (λ-carrageenan was used to induce inflammation in rats; it was given by an intraplantar route and intrapelurally through surgery in the pleurisy test. In the λ-carrageenan-induced edema model, TPGS-stabilized curcumin nanoparticles were given orally one hour before induction and at 0.5, 4.5, and 8.5 h after induction with two different doses (1.8 and 0.9 mg/kg body weight (BW. Sodium diclofenac with a dose of 4.5 mg/kg BW was used as a standard drug. A physical mixture of curcumin-TPGS was also used as a comparison with a higher dose of 60 mg/kg BW. The anti-inflammatory effect was assessed on the edema in the carrageenan-induced paw edema model and by the volume of exudate as well as the number of leukocytes reduced in the pleurisy test. TPGS-stabilized curcumin nanoparticles with lower doses showed better anti-inflammatory effects, indicating the greater absorption capability through the gastrointestinal tract.

  5. Pickering emulsions stabilized by whey protein nanoparticles prepared by thermal cross-linking

    Wu, Jiande; Shi, Mengxuan; Li, Wei; Zhao, Luhai; Wang, Ze; Yan, Xinzhong; Norde, Willem; Li, Yuan

    2015-01-01

    A Pickering (o/w) emulsion was formed and stabilized by whey protein isolate nanoparticles (WPI NPs). Those WPI NPs were prepared by thermal cross-linking of denatured WPI proteins within w/o emulsion droplets at 80. °C for 15. min. During heating of w/o emulsions containing 10% (w/v) WPI

  6. Improved thermal stability of gas-phase Mg nanoparticles for hydrogen storage

    Krishnan, Gopi; Palasantzas, G.; Kooi, B. J.

    2010-01-01

    This work focuses on improving the thermal stability of Mg nanoparticles (NPs) for use in hydrogen storage. Three ways are investigated that can achieve this goal. (i) Addition of Cu prevents void formation during NP production and reduces the fast evaporation/voiding of Mg during annealing. (ii)

  7. Influence of energy and duration of laser pulses on stability of dielectric nanoparticles in optical trap

    Ho Quang Quy; Mai Van Luu; Hoang Dinh Hai

    2010-01-01

    In this article the gradient force of optical trap using two counter- propagating pulsed Gaussian beam and the Brownian motion in optical force field are investigated. The influence of the energy and duration time of optical pulsed Gaussian beams on stability of nano-particle in trap is simulated and discussed. (author)

  8. Comparison of the colloidal stability, bioaccessibility and antioxidant activity of corn protein hydrolysate and sodium caseinate stabilized curcumin nanoparticles.

    Wang, Yong-Hui; Yuan, Yang; Yang, Xiao-Quan; Wang, Jin-Mei; Guo, Jian; Lin, Yuan

    2016-07-01

    The aims of this work were to construct corn protein hydrolysate (CPH)-based curcumin nanoparticles (Cur NPs) and to compare the colloidal stability, bioaccessibility and antioxidant activity of the Cur NPs stabilized CPH and sodium caseinate (NaCas) respectively. The results indicated that Cur solubility could be considerably improved after the Cur NPs fabrication. The spectroscopy results demonstrated that the solubilization of Cur should be attributed to its complexation with CPH or NaCas. The Cur NPs exhibited good colloidal stability after 1 week's storage but showed smaller (40 nm) size in CPH than in NaCas (100 nm). After lyophilization, the Cur NPs powders showed good rehydration properties and chemical stability, and compared with NaCas, the size of Cur NPs stabilized by CPH was still smaller. Additionally, the Cur NPs exhibited higher chemical stability against the temperature compared with free Cur, and the CPH could protect Cur from degradation more efficiently. Comparing with NaCas, the Cur NPs stabilized by CPH exhibited better bioaccessibility and antioxidant activity. This study demonstrated that CPH may be better than NaCas in Cur NPs fabrication and it opens up the possibility of using hydrophobic protein hydrolysate to construct the NPs delivery system.

  9. New Perspective in the Formulation and Characterization of Didodecyldimethylammonium Bromide (DMAB Stabilized Poly(Lactic-co-Glycolic Acid (PLGA Nanoparticles.

    Rebecca Gossmann

    Full Text Available Over the last few decades the establishment of nanoparticles as suitable drug carriers with the transport of drugs across biological barriers such as the gastrointestinal barrier moved into the focus of many research groups. Besides drug transport such carrier systems are well suited for the protection of drugs against enzymatic and chemical degradation. The preparation of biocompatible and biodegradable nanoparticles based on poly(lactic-co-glycolic acid (PLGA is intensively described in literature, while especially nanoparticles with cationic properties show a promising increased cellular uptake. This is due to the electrostatic interaction between the cationic surface and the negatively charged lipid membrane of the cells. Even though several studies achieved the successful preparation of nanoparticles stabilized with the cationic surfactants such as didodecyldimethylammonium bromide (DMAB, in most cases insufficient attention was paid to a precise analytical characterization of the nanoparticle system. The aim of the present work was to overcome this deficit by presenting a new perspective in the formulation and characterization of DMAB-stabilized PLGA nanoparticles. Therefore these nanoparticles were carefully examined with regard to particle diameter, zeta potential, the effect of variation in stabilizer concentration, residual DMAB content, and electrolyte stability. Without any steric stabilization, the DMAB-modified nanoparticles were sensitive to typical electrolyte concentrations of biological environments due to compression of the electrical double layer in conjunction with a decrease in zeta potential. To handle this problem, the present study proposed two modifications to enable electrolyte stability. Both polyvinyl alcohol (PVA and polyethylene glycol (PEG modified DMAB-PLGA-nanoparticles were stable during electrolyte addition. Furthermore, in contrast to unmodified DMAB-PLGA-nanoparticles and free DMAB, such modifications led to

  10. Stability and phase transfer of catalytically active platinum nanoparticle suspensions

    Sriram, Indira; Curtin, Alexandra E.; Chiaramonti, Ann N.; Cuchiaro, J. Hunter; Weidner, Andrew R.; Tingley, Tegan M.; Greenlee, Lauren F.; Jeerage, Kavita M.

    2015-01-01

    In this work, we present a robust synthesis protocol for platinum nanoparticles that yields a monomodal dispersion of particles that are approximately 100 nm in diameter. We determine that these particles are actually agglomerates of much smaller particles, creating a “raspberry” morphology. We demonstrate that these agglomerates are stable at room temperature for at least 8 weeks by dynamic light scattering. Furthermore, we demonstrate consistent electrocatalytic activity for methanol oxidation. Finally, we quantitatively explore the relationship between dispersion solvent and particle agglomeration; specifically, particles are found to agglomerate abruptly as solvent polarity decreases

  11. Stability and phase transfer of catalytically active platinum nanoparticle suspensions

    Sriram, Indira; Curtin, Alexandra E.; Chiaramonti, Ann N.; Cuchiaro, J. Hunter; Weidner, Andrew R.; Tingley, Tegan M.; Greenlee, Lauren F.; Jeerage, Kavita M., E-mail: jeerage@boulder.nist.gov [National Instrument of Standards and Technology, Applied Chemicals and Materials Division (United States)

    2015-05-15

    In this work, we present a robust synthesis protocol for platinum nanoparticles that yields a monomodal dispersion of particles that are approximately 100 nm in diameter. We determine that these particles are actually agglomerates of much smaller particles, creating a “raspberry” morphology. We demonstrate that these agglomerates are stable at room temperature for at least 8 weeks by dynamic light scattering. Furthermore, we demonstrate consistent electrocatalytic activity for methanol oxidation. Finally, we quantitatively explore the relationship between dispersion solvent and particle agglomeration; specifically, particles are found to agglomerate abruptly as solvent polarity decreases.

  12. Iron oxide nanoparticles stabilized with a bilayer of oleic acid for magnetic hyperthermia and MRI applications

    Soares, Paula I.P. [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Laia, César A.T. [Laboratório Associado para a Química Verde (LAQV), REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Carvalho, Alexandra [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Pereira, Laura C.J.; Coutinho, Joana T. [C2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, ao km 139,7, 2695-066 Bobadela LRS (Portugal); Ferreira, Isabel M.M., E-mail: imf@fct.unl.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Novo, Carlos M.M. [Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, IHMT/UNL, 1349-008 Lisboa (Portugal); Borges, João Paulo, E-mail: jpb@fct.unl.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal)

    2016-10-15

    Highlights: • Superparamagnetic iron oxide nanoparticles were stabilized with oleic acid. • Maximum stabilization was achieved at neutral pH. • Magnetic resonance imaging and magnetic hyperthermia applications were tested. • The produced nanoparticles are viable for both biomedical applications. - Abstract: Iron oxide nanoparticles (Fe{sub 3}O{sub 4}, IONPs) are promising candidates for several biomedical applications such as magnetic hyperthermia and as contrast agents for magnetic resonance imaging (MRI). However, their colloidal stability in physiological conditions hinders their application requiring the use of biocompatible surfactant agents. The present investigation focuses on obtaining highly stable IONPs, stabilized by the presence of an oleic acid bilayer. Critical aspects such as oleic acid concentration and pH were optimized to ensure maximum stability. NPs composed of an iron oxide core with an average diameter of 9 nm measured using transmission electron microscopy (TEM) form agglomerates with an hydrodynamic diameter of around 170 nm when dispersed in water in the presence of an oleic acid bilayer, remaining stable (zeta potential of −120 mV). Magnetic hyperthermia and the relaxivities measurements show high efficiency at neutral pH which enables their use for both magnetic hyperthermia and MRI.

  13. Iron oxide nanoparticles stabilized with a bilayer of oleic acid for magnetic hyperthermia and MRI applications

    Soares, Paula I.P.; Laia, César A.T.; Carvalho, Alexandra; Pereira, Laura C.J.; Coutinho, Joana T.; Ferreira, Isabel M.M.; Novo, Carlos M.M.; Borges, João Paulo

    2016-01-01

    Highlights: • Superparamagnetic iron oxide nanoparticles were stabilized with oleic acid. • Maximum stabilization was achieved at neutral pH. • Magnetic resonance imaging and magnetic hyperthermia applications were tested. • The produced nanoparticles are viable for both biomedical applications. - Abstract: Iron oxide nanoparticles (Fe_3O_4, IONPs) are promising candidates for several biomedical applications such as magnetic hyperthermia and as contrast agents for magnetic resonance imaging (MRI). However, their colloidal stability in physiological conditions hinders their application requiring the use of biocompatible surfactant agents. The present investigation focuses on obtaining highly stable IONPs, stabilized by the presence of an oleic acid bilayer. Critical aspects such as oleic acid concentration and pH were optimized to ensure maximum stability. NPs composed of an iron oxide core with an average diameter of 9 nm measured using transmission electron microscopy (TEM) form agglomerates with an hydrodynamic diameter of around 170 nm when dispersed in water in the presence of an oleic acid bilayer, remaining stable (zeta potential of −120 mV). Magnetic hyperthermia and the relaxivities measurements show high efficiency at neutral pH which enables their use for both magnetic hyperthermia and MRI.

  14. Langmuir-Blodgett films of alkane chalcogenice (S, Se, Te) stabilized gold nanoparticles

    Brust, M.; Stuhr-Hansen, N.; Norgaard, K.

    2001-01-01

    Gold nanoparticles stabilized by alkanethiolates, alkaneselenides, and alkanetellurides have been prepared by analogous methods. Chloroform solutions of thiolate and selenide stabilized particles were spread and evaporated on the water/air interface where the particles formed well-defined Langmuir...... films. The films were transferred to solid supports of freshly cleaved mica and were studied by atomic force microscopy (AFM). The particles were found to have an average core diameter of 2 nm. The stability of the particles under ambient conditions increased in the order Te

  15. Dispersion and Stabilization of Photocatalytic TiO2 Nanoparticles in Aqueous Suspension for Coatings Applications

    Siti Hajar Othman

    2012-01-01

    Full Text Available To produce titanium dioxide (TiO2 nanoparticle coatings, it is desirable that the nanoparticles are dispersed into a liquid solution and remain stable for a certain period of time. Controlling the dispersion and aggregation of the nanoparticles is crucial to exploit the advantages of the nanometer-sized TiO2 particles. In this work, TiO2 nanoparticles were dispersed and stabilized in aqueous suspensions using two common dispersants which were polyacrylic acid (PAA and ammonium polymethacrylate (Darvan C. The effect of parameters such as ultrasonication amplitude and type and amount of dispersants on the dispersibility and stability of the TiO2 aqueous suspensions were examined. Rupture followed by erosion was determined to be the main break up mechanisms when ultrasonication was employed. The addition of dispersant was found to produce more dispersed and more stabilized aqueous suspension. 3 wt.% of PAA with average molecular weight (Mw of 2000 g/mol (PAA 2000 was determined to produce the best and most stable dispersion. The suspensions were then coated on quartz glass, whereby the photocatalytic activity of the coatings was studied via the degradation of formaldehyde gas under UV light. The coatings were demonstrated to be photocatalytically active.

  16. Hydraulic Properties of Porous Media Saturated with Nanoparticle-Stabilized Air-Water Foam

    Xianglei Zheng

    2016-12-01

    Full Text Available The foam generated by the mixture of air and water has a much higher viscosity and lower mobility than those of pure water or gas that constitutes the air-water foam. The possibility of using the air-water foam as a flow barrier for the purpose of groundwater and soil remediation is explored in this paper. A nanoparticle-stabilized air-water foam was fabricated by vigorously stirring the nano-fluid in pressurized condition. The foam bubble size distribution was analyzed with a microscope. The viscosities of foams generated with the solutions with several nanoparticle concentrations were measured as a function of time. The breakthrough pressure of foam-saturated microfluidic chips and sand columns were obtained. The hydraulic conductivity of a foam-filled sand column was measured after foam breakthrough. The results show that: (1 bubble coalescence and the Ostwald ripening are believed to be the reason of bubble size distribution change; (2 the viscosity of nanoparticle-stabilized foam and the breakthrough pressures decreased with time once the foam was generated; (3 the hydraulic conductivity of the foam-filled sand column was almost two orders of magnitude lower than that of a water-saturated sand column even after the foam-breakthrough. Based on the results in this study, the nanoparticle-stabilized air-water foam could be injected into contaminated soils to generate vertical barriers for temporary hydraulic conductivity reduction.

  17. COLOR STABILITY FOR WOOD PRODUCTS DURING USE: EFFECTS OF INORGANIC NANOPARTICLES

    Vincent Blanchard

    2011-04-01

    Full Text Available Despite significant progress having been achieved in recent years to improve wood’s durability, additional developments are still necessary to increase its color stability. ZnO and CeO2 nanoparticles were compared to UV absorbers (Tinuvin 477 DW, 292 and 5151 commonly used to stabilize the wood products color. Nanoparticles, with concentrations in the range 1 to 2 wt%, and UV absorbers, using concentrations advised by the manufacturer, were dispersed in a waterborne UV curable polyurethane/polyacrylate resin. Dispersions were carried out with a high speed mixer at 2,500 RPM with micro glass beads or not, depending on the form of the nanoparticles. Nanocomposite coatings were aged with a weather-o-meter (CI 3000+ - Atlas according ASTM G155. Color variations were measured with a colorimeter (BYK Gardner – Color Guide 45/0 working with the CIE L*a*b* system. The aim of the present study was to assess the effects of inorganic UV absorbers on the stabilization of color under indoor conditions. Results showed that nanoparticles (ZnO, CeO2 absorbed UV light frequencies in a manner similar to common organic molecules. Their efficiency was better at medium durations of light exposure, for which they could achieve the action of organic absorbers. Finally, the simultaneous use of both absorbers seems to create a protective synergy when degradation is due to UV energy alone.

  18. Ultrastructural and some functional changes in tumor cells treated with stabilized iron oxide nanoparticles.

    Yurchenko, O V; Todor, I N; Khayetsky, I K; Tregubova, N A; Lukianova, N Yu; Chekhun, V F

    2010-12-01

    To study the ultrastructure and some functional indexes of tumor cells treated with stabilized iron nanoparticles in vitro. 3-[4,5dimethylthiazol-2-1]-2,5-diphenyltetrazolium bromide (MTT)-test, electron microscopy, polarography with applying of closed Clark's electrode. It was shown that cultivation of cells with stabilized Fe(3)O(4) leads to intracellular accumulation of ferromagnetic nanoparticles. The most active ferromagnetic uptake by cells has been observed after 24 and 48 h of incubation. The presence of ferromagnetic in cells led to altered mitochondrial structure that caused the decrease of oxygen uptake rate in the cells of all studied lines. Ferromagnetic released from the majority of cells via exocytosis or clasmacytosis after a certain period of time. The number of dead cells or cells with severe damage was moderate, so cytotoxic action of stabilized iron oxide nanoparticles was minimal toward the studied cell lines. the presence of ferromagnetic nanoparticles in culture medium led to alterations in mitochondria ultrastructural organization and decrease of oxygen uptake by mitochondria in sensitive and anticancer-drugs resistant cells.

  19. Behavior and chronic toxicity of two differently stabilized silver nanoparticles to Daphnia magna

    Sakka, Yvonne; Skjolding, Lars Michael; Mackevica, Aiga

    2016-01-01

    While differences in silver nanoparticle (AgNP) colloidal stability, surface potential, or acute aquatic toxicity for differently stabilized AgNP have often been reported, these have rarely been studied in long-term ecotoxicity tests. In the current study, we investigated the chronic toxicity of Ag...... types of AgNP during a typical media exchange period in the D. magna test for chronic toxicity. As expected, the sterically stabilized AgNP were more stable in the test medium, also in the presence of food; however, a higher uptake of silver after 24 h exposure of the charge stabilized AgNP was found...... compared to the detergent-stabilized AgNP (0.046 ± 0.006 μg Ag μg DW−1 and 0.023 ± 0.005 μg Ag μg DW−1, respectively). In accordance with this, the higher reproductive effects and mortality were found for the charge-stabilized than for the sterically-stabilized silver nanoparticles in 21-d tests...

  20. Shape-and size-controlled Ag nanoparticles stabilized by in situ generated secondary amines

    Ramírez-Meneses, E., E-mail: esther.ramirez@ibero.mx [Departamento de Ingeniería y Ciencias Químicas, Universidad Iberoamericana, Prolongación Paseo de la Reforma 880, Lomas de Santa Fe, Distrito Federal C.P. 01219 (Mexico); Montiel-Palma, V. [Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001 Col. Chamilpa, Cuernavaca, Morelos C.P. 62209 (Mexico); Domínguez-Crespo, M.A.; Izaguirre-López, M.G. [Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada-IPN, Unidad Altamira. Km 14.5 Carretera Tampico-Puerto Industrial, 89600 Altamira, Tamaulipas (Mexico); Palacios-Gonzalez, E. [Laboratorio de Microscopia de Ultra alta Resolución, Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas No. 152, C.P. 07730 México D.F. (Mexico); Dorantes-Rosales, H. [Departamento de Metalurgia, E.S.I.Q.I.E.-I.P.N., Unidad Profesional Adolfo López Mateos, Zacatenco, Delegación. Gustavo A. Madero, C.P. 07738 México D.F. (Mexico)

    2015-09-15

    Highlights: • Ag nanoparticles were generated from Ag amido complexes AgN{sup i}Pr{sub 2} and AgN(SiMe{sub 3}){sub 2}. • Ag nanoparticles were stabilized by in situ generated HN{sup i}Pr{sub 2} or HN(SiMe{sub 3}){sub 2}. • 1 or 5 equiv. of ethylenediamine as additional capping agent decreases the average size of the particles. • Ethylenediamine favor the formation of spherical particles. - Abstract: Silver amides such as AgN{sup i}Pr{sub 2} and AgN(SiMe{sub 3}){sub 2} have been employed successfully as precursors for the yield synthesis of silver nanoparticles under mild conditions of dihydrogen gas reduction (2 atm) in organic media. Transmission electron microscopy (TEM) showed the formation of silver nanoparticles with FCC structure, variously sized from 26 to 35 nm for AgN{sup i}Pr{sub 2} and from 14 to 86 nm for AgN(SiMe{sub 3}){sub 2}, the synthesis could take place in absence of added stabilizers due to the in situ formation of secondary amines from the reaction of dihydrogen gas with the amide ligands of the silver precursor. Indeed, the presence of HNR{sub 2} (R = iPr{sub 2}, N(SiMe{sub 3}){sub 2}) on the surface of the nanoparticle was confirmed by spectroscopic means. Finally, the addition of ethylenediamine as additional capping agent allowed not only the control of the structural characteristics of the resulting Ag nanoparticles (well-dispersed with spherical shape), but that regarding the nanoparticle size as it inhibited overgrowth, limiting it to ca. 25 nm.

  1. Limitations and possibilities of green synthesis and long-term stability of colloidal Ag nanoparticles

    Velgosová, Oksana; Mražíková, Anna

    2017-12-01

    In this paper the influence of algae life cycle and the solutions pH on the green synthesis of colloidal Ag nanoparticles (AgNPs) as well as effect of different storage conditions on AgNPs long-term stability was investigated. Silver nanoparticles were biologically synthesized using extracts of Parachlorella kessleri algae cultivated 1, 2, 3 and 4 weeks. The formation of AgNPs was monitored using a UV-vis spectrophotometer and verified by TEM observation. The results confirmed formation of polyhedron and/or near polyhedron AgNPs, ranging between 5 and 60 nm in diameter. The age of algae influenced the synthesis rate and an amount of AgNPs in solution. The best results were obtained using tree weeks old algae. UV-vis analysis and TEM observation also revealed that the size and the stability of AgNPs depend on the pH of solution. AgNPs formed in solutions of higher pH (8 and 10) are polyhedron, fine, with narrow size interval and stabile. Nanoparticles formed in solutions of low pH (2, 4 and 6) started to lose their stability on 10th day of experiment, and the particle size interval was wide. The long-term stability of AgNPs can be influenced by light and temperature conditions. The most significant stability loss was observed at day light and room temperature (21°C). After 200-days significant amount of agglomerated particles settled on the bottom of the Erlenmeyer flask. AgNPs stored at dark and room temperature showed better long-term stability, weak particles agglomeration was observed. AgNPs stored at dark and at temperature 5°C showed the best long-term stability. Such AgNPs remained spherical, fine (5-20 nm), with narrow size interval and stable (no agglomeration) even after more than six months.

  2. Immobilization of mercury in field soil and sediment using carboxymethyl cellulose stabilized iron sulfide nanoparticles

    Gong, Yanyan; Liu, Yuanyuan; Xiong, Zhong; Kaback, Dawn; Zhao, Dongye

    2012-07-01

    Mercury (Hg) is one of the most pervasive and bio-accumulative metals in the environment. Yet, effective in situ remediation technologies have been lacking. This study investigated the effectiveness of a class of soil-deliverable FeS nanoparticles for in situ immobilization of Hg in two field-contaminated soils from a New Jersey site and one sediment from an Alabama site. The nanoparticles were prepared using sodium carboxymethyl cellulose (CMC) as a stabilizer. Transmission electron microscopy measurements revealed a particle size of 34.3 ± 8.3 nm (standard deviation), whereas dynamic light scattering gave a hydrodynamic diameter of 222.5 ± 3.2 nm. Batch tests showed that at an FeS-to-Hg molar ratio of 28:1-118:1, the nanoparticles reduced water-leachable Hg by 79%-96% and the TCLP (toxicity characteristic leaching procedure) based leachability by 26%-96%. Column breakthrough tests indicated that the nanoparticles were deliverable in the sediment/soil columns under moderate injection pressure. However, once the external pressure was removed, the delivered nanoparticles remained virtually mobile under typical groundwater flow conditions. When the Hg-contaminated soil and sediment were treated with 52-95 pore volumes of a 500 mg l-1 FeS nanoparticle suspension, water-leachable Hg was reduced by 90%-93% and TCLP-leachable Hg was reduced by 65%-91%. The results warrant further field demonstration of this promising in situ remediation technology.

  3. Catalase-only nanoparticles prepared by shear alone: Characteristics, activity and stability evaluation.

    Huang, Xiao-Nan; Du, Xin-Ying; Xing, Jin-Feng; Ge, Zhi-Qiang

    2016-09-01

    Catalase is a promising therapeutic enzyme; however, it carries risks of inactivation and rapid degradation when it is used in practical bioprocess, such as delivery in vivo. To overcome the issue, we made catalase-only nanoparticles using shear stress alone at a moderate shear rate of 217s(-1) in a coaxial cylinder flow cell. Properties of nanoparticles, including particle size, polydispersity index and zeta potential, were characterized. The conformational changes of pre- and post-sheared catalase were determined using spectroscopy techniques. The results indicated that the conformational changes of catalase and reduction in α-helical content caused by shear alone were less significant than that by desolvation method. Catalase-only nanoparticles prepared by single shear retained over 90% of its initial activity when compared with the native catalase. Catalase nanoparticles lost only 20% of the activity when stored in phosphate buffer solution for 72h at 4°C, whereas native catalase lost 53% under the same condition. Especially, the activity of nanogranulated catalase was decreased only slightly in the simulated intestinal fluid containing α-chymotrypsin during 4h incubation at 37°C, implying that the catalase nanoparticle was more resistant to the degradation of proteases than native catalase molecules. Overall, catalase-only nanoparticles offered a great potential to stabilize enzymes for various pharmaceutical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Electrochemical extraction of gold from wastes as nanoparticles stabilized by phospholipids.

    Moriwaki, Hiroshi; Yamada, Kotaro; Usami, Hisanao

    2017-02-01

    A simple one-step method for the extraction of gold from wastes as nanoparticles stabilized by phospholipids is demonstrated. This is achieved by applying an AC voltage for 5s to the gold-containing wastes, which act as the electrodes in a buffer solution containing a dispersed phospholipid (1,2-dioleoyl-sn-glycero-3-phosphocholine, DOPC). This is an environmentally friendly and rapid method for recovering gold from wastes. The extracted gold nanoparticles have significant potential as a catalyst or biomedical material. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Growth kinetics and long-term stability of CdS nanoparticles in aqueous solution under ambient conditions

    Mullaugh, Katherine M.; Luther, George W.

    2011-01-01

    The ubiquity of naturally occurring nanoparticles in the aquatic environment is now widely accepted, but a better understanding of the conditions that promote their formation and persistence is needed. Using cadmium sulfide (CdS) as a model metal sulfide species, thiolate-capped CdS nanoparticles were prepared in the laboratory to evaluate how aquatic conditions influence metal sulfide nanoparticle growth and stability. This work examines CdS nanoparticle growth directly in aqueous solution at room temperature by utilizing the size-dependent spectroscopic properties of semiconductors detectable by UV/vis. CdS nanoparticle growth was governed by oriented attachment, a non-classical mechanism of crystallization in which small precursor nanoparticles coalesce to form larger nanoparticle products. Nanoparticle growth was slowed with increasing capping agent and decreasing ionic strength. In addition to examining the short-term (hours) growth of the nanoparticles, a long-term study was conducted in which cysteine-capped CdS nanoparticles were monitored over 3 weeks in solutions of various ionic strengths. The long-term study revealed an apparent shift from small nanoparticles to nanoparticles twice their original size, suggesting nanoparticle growth may continue through oriented attachment over longer time scales. High-ionic strength solutions resulted in salt-induced aggregation and eventual settling of nanoparticles within days, whereas low-ionic strength solutions were stable against settling over the course of the experiment. Sulfide recovery from cysteine-capped CdS nanoparticles as acid volatile sulfide was nearly quantitative after 2 weeks in fully oxygenated water, demonstrating significantly slowed oxidation of sulfide when complexed to Cd(II) within CdS nanoparticles. The nanoparticles were also shown to be resistant to oxidation by Fe(III) (hydr)oxide. This study illustrates that aggregation, rather than chemical oxidation, is likely more important to the

  6. Stabilization of silica nanoparticles dispersions by surface modification with silicon derivative of thiacalix[4]arene

    Gorbachuk, Vladimir V.; Ziatdinova, Ramilia V. [Kazan Federal University, A.M. Butlerov’ Chemical Institute (Russian Federation); Evtugyn, Vladimir G. [Kazan Federal University, Interdisciplinary Centre for Analytical Microscopy (Russian Federation); Stoikov, Ivan I., E-mail: ivan.stoikov@mail.ru [Kazan Federal University, A.M. Butlerov’ Chemical Institute (Russian Federation)

    2015-03-15

    For the first time, silica nanopowder functionalized with thiacalixarene derivatives was synthesized by ultrasonication of nanoparticles (diameter 23.7 ± 2.4 nm) with organosilicon derivative of thiacalixarene in glacial acetic acid. The protocol resulted in the formation of colloidal solution of low-disperse (polydispersity index of 0.11) submicron-sized (diameter 192.5 nm) clusters of nanoparticles according to the dynamic light scattering data. As defined by scanning electron microscopy (SEM), mean diameter of thiacalixarene-functionalized nanoparticles is equal to 25.5 ± 2.5 nm and the shape is close to spherical. SEM images confirm low aggregation of thiacalixarene-modified nanoparticle compared to initial silica nanopowder (mean diameter of aggregates 330 and 429 nm, correspondingly). According to the thermogravimetry/differential scanning calorimetry and elemental analysis of the nanoparticles obtained, 5 % of the powder mass was related to thiacalixarene units. The effect of thiacalixarene functionalization of silica nanoparticles on linear polydimethylsiloxane (PDMS)—silica dispersions was modeled to achieve high resistance toward liquid media required for similar sol–gel prepared PDMS-based materials applied for solid-phase microextraction. In such a manner, the influence of thiacalixarene-modified nanofiller on thermal stability and resistance against polar organic solvents was estimated. Similarity of decomposition temperature of both thiacalixarene-functionalized nanoparticles and non-functionalized silica nanoparticles was found. Swelling/solubility behavior observed was related to partial dissolution of PDMS/silica (10 % mixture) in alcohols. Thiacalixarene-functionalized silica particles exerted significantly higher resistance of PDMS/silica composites toward alcohol solvents.

  7. Stabilization of silica nanoparticles dispersions by surface modification with silicon derivative of thiacalix[4]arene

    Gorbachuk, Vladimir V.; Ziatdinova, Ramilia V.; Evtugyn, Vladimir G.; Stoikov, Ivan I.

    2015-01-01

    For the first time, silica nanopowder functionalized with thiacalixarene derivatives was synthesized by ultrasonication of nanoparticles (diameter 23.7 ± 2.4 nm) with organosilicon derivative of thiacalixarene in glacial acetic acid. The protocol resulted in the formation of colloidal solution of low-disperse (polydispersity index of 0.11) submicron-sized (diameter 192.5 nm) clusters of nanoparticles according to the dynamic light scattering data. As defined by scanning electron microscopy (SEM), mean diameter of thiacalixarene-functionalized nanoparticles is equal to 25.5 ± 2.5 nm and the shape is close to spherical. SEM images confirm low aggregation of thiacalixarene-modified nanoparticle compared to initial silica nanopowder (mean diameter of aggregates 330 and 429 nm, correspondingly). According to the thermogravimetry/differential scanning calorimetry and elemental analysis of the nanoparticles obtained, 5 % of the powder mass was related to thiacalixarene units. The effect of thiacalixarene functionalization of silica nanoparticles on linear polydimethylsiloxane (PDMS)—silica dispersions was modeled to achieve high resistance toward liquid media required for similar sol–gel prepared PDMS-based materials applied for solid-phase microextraction. In such a manner, the influence of thiacalixarene-modified nanofiller on thermal stability and resistance against polar organic solvents was estimated. Similarity of decomposition temperature of both thiacalixarene-functionalized nanoparticles and non-functionalized silica nanoparticles was found. Swelling/solubility behavior observed was related to partial dissolution of PDMS/silica (10 % mixture) in alcohols. Thiacalixarene-functionalized silica particles exerted significantly higher resistance of PDMS/silica composites toward alcohol solvents

  8. Lignosulfonate-stabilized selenium nanoparticles and their deposition on spherical silica.

    Modrzejewska-Sikorska, Anna; Konował, Emilia; Klapiszewski, Łukasz; Nowaczyk, Grzegorz; Jurga, Stefan; Jesionowski, Teofil; Milczarek, Grzegorz

    2017-10-01

    We report a novel room-temperature synthesis of selenium nanoparticles, which for the first time uses lignosulfonate as a stabilizer. Various lignosulfonates obtained both from hardwood and softwood were tested. Selenium oxide was used as the precursor of zero-valent selenium. Three different reducers were tested - sodium borohydride, hydrazine and ascorbic acid - and the latter proved most effective in terms of the particle size and stability of the final colloid. The lignosulfonate-stabilized selenium nanoparticles had a negative zeta potential, dependent on pH, which for some lignosulfonates reached -50mV, indicating the excellent stability of the colloid. When spherical silica particles were introduced to the synthesis mixture, selenium nanoparticles were deposited on their surface. Additionally, star-like structures consisting of sharp selenium needles with silica cores were observed. After drying, the selenium-functionalized silica had a grey metallic hue. The method reported here is simple and cost-effective, and can be used for the preparation of large quantities of selenium colloids or the surface modification of other materials with selenium. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Rapid and controlled transformation of nitrate in water and brine by stabilized iron nanoparticles

    Xiong Zhong; Zhao Dongye; Pan Gang

    2009-01-01

    Highly reactive zero-valent iron (ZVI) nanoparticles stabilized with carboxymethyl cellulose (CMC) were tested for reduction of nitrate in fresh water and brine. Batch kinetic tests showed that the pseudo first-order rate constant (k obs ) with the stabilized nanoparticles was five times greater than that for non-stabilized counterparts. The stabilizer not only increased the specific surface area of the nanoparticles, but also increased the reactive particle surface. The allocation between the two reduction products, NH 4 + and N 2 , can be manipulated by varying the ZVI-to-nitrate molar ratio and/or applying a Cu-Pd bimetallic catalyst. Greater CMC-to-ZVI ratios lead to faster nitrate reduction. Application of a 0.05 M HEPES buffer increased the k obs value by 15 times compared to that without pH control. Although the presence of 6% NaCl decreased k obs by 30%, 100% nitrate was transformed within 2 h in the saline water. The technology provides a powerful alternative for treating water with concentrated nitrate such as ion exchange brine.

  10. Stability and toxicity of ZnO quantum dots: Interplay between nanoparticles and bacteria

    Bellanger, Xavier, E-mail: xavier.bellanger@univ-lorraine.fr [Université de Lorraine and CNRS, Laboratoire de Chimie Physique et Microbiologie pour l’Environnement (LCPME), UMR 7564, 15 Avenue du Charmois, 54500 Vandoeuvre-lès-Nancy (France); Billard, Patrick, E-mail: patrick.billard@univ-lorraine.fr [Université de Lorraine and CNRS, Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC), UMR 7360, Boulevard des Aiguillettes, Faculté des Sciences et Techniques, BP 70239, 54506 Vandoeuvre-lès-Nancy (France); Schneider, Raphaël, E-mail: raphael.schneider@univ-lorraine.fr [Université de Lorraine and CNRS, Laboratoire Réactions et Génie des Procédés (LRGP), UMR 7274, 1 rue Grandville, BP 20451, 54001 Nancy Cedex (France); Balan, Lavinia, E-mail: lavinia.balan@uha.fr [Institut de Science des Matériaux de Mulhouse (IS2M), UMR 7361, CNRS, 15 rue Jean Starcky, 68093 Mulhouse (France); Merlin, Christophe, E-mail: christophe.merlin@univ-lorraine.fr [Université de Lorraine and CNRS, Laboratoire de Chimie Physique et Microbiologie pour l’Environnement (LCPME), UMR 7564, 15 Avenue du Charmois, 54500 Vandoeuvre-lès-Nancy (France)

    2015-02-11

    Graphical abstract: - Highlights: • Dilution of aminosilane-capped ZnO QDs dramatically increases their dissolution. • Bacteria limit Zn{sup 2+} leakage from ZnO QDs in a physiological-dependent process. • Implementation of biosensors for assessing free metal promotes QDs instability. • Dialysis combined to ICP allows studying QDs stability without prior dilution. - Abstract: The toxicity of quantum dots (QDs) has been commonly attributed to the release of metal ions from the core as well as to the production of reactive oxygen species. However, the information related to the stability of the nanoparticles are relatively scarce although this parameter may strongly influence their toxicity. The stability of aminosilane-capped ZnO QDs, here used as model nanoparticles, was investigated by inductively coupled plasma-optical emission spectrometer (ICP-OES) and whole cell biosensors using a dialysis setup to separate the QDs from the leaked Zn{sup 2+} ions. The integrity of the ZnO QDs appeared strongly affected by their dilution in aqueous medium, whereas the nanoparticles were slightly stabilized by bacteria. Our results demonstrate some inadequacy between the implementation and use of whole cell biosensors, and the monitoring of metal release from QDs.

  11. "Precipitation on Nanoparticles": Attractive Intermolecular Interactions Stabilize Specific Ligand Ratios on the Surfaces of Nanoparticles.

    Chu, Zonglin; Han, Yanxiao; Kral, Petr; Klajn, Rafal

    2018-04-19

    Confining organic molecules to the surfaces of inorganic nanoparticles can induce intermolecular interactions between them, which can affect the composition of the mixed self-assembled monolayers obtained by co-adsorption from solution of two different molecules. Here, we study co-adsorption of two thiolated ligands-a dialkylviologen and a zwitterionic sulfobetaine-that can interact with each other electrostatically, onto gold nanoparticles. Consequently, the nanoparticles favor a narrow range of ratios of these two molecules that is largely independent of the molar ratio in solution. We show that changing the solution molar ratio of two ligands by a factor of ~5,000 affects the on-nanoparticle ratio of these ligands by only 3 times. This behavior is reminiscent of the formation of insoluble inorganic salts (e.g., AgCl), which similarly compensate positive and negative charges upon crystallizing. Our results pave the way towards developing well-defined hybrid organic-inorganic nanostructures. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Electron beam assisted synthesis of silver nanoparticle in chitosan stabilizer: Preparation, stability and inhibition of building fungi studies

    Jannoo, Kanokwan; Teerapatsakul, Churapa; Punyanut, Adisak; Pasanphan, Wanvimol

    2015-07-01

    Silver nanoparticles (AgNPs) in chitosan (CS) stabilizer were successfully synthesized using electron beam irradiation. The effects of irradiation dose, molecular weight (MW) of CS stabilizer, concentration of AgNO3 precursor and addition of tert-butanol on AgNPs production were studied. The stability of the AgNPs under different temperatures and storage times were also investigated. The AgNPs formation in CS was observed using UV-vis, FT-IR and XRD. The characteristic surface plasmon resonance (SPR) of the obtained AgNPs was around 418 nm. The CS stabilizer and its MW, AgNO3 precursor and irradiation doses are important parameters for the synthesis of AgNPs. The optimum addition of 20% v/v tert-butanol could assist the formation of AgNPs. The AgNPs in CS stabilizer were stable over a period of one year when the samples were kept at 5 °C. The AgNPs observed from TEM images were spherical with an average particle size in the range of 5-20 nm depending on the irradiation doses. The AgNPs in CS solution effectively inhibited the growth of several fungi, i.e., Curvularia lunata, Trichoderma sp., Penicillium sp. and Aspergillus niger, which commonly found on the building surface.

  13. Streptavidin-coated gold nanoparticles: critical role of oligonucleotides on stability and fractal aggregation

    Roberta D'Agata

    2017-01-01

    Full Text Available Gold nanoparticles (AuNPs exhibit unique properties that can be modulated through a tailored surface functionalization, enabling their targeted use in biochemical sensing and medical diagnostics. In particular, streptavidin-modified AuNPs are increasingly used for biosensing purposes. We report here a study of AuNPs surface-functionalized with streptavidin-biotinylated oligonucleotide, focussing on the role played by the oligonucleotide probes in the stabilization/destabilization of the functionalized nanoparticle dispersion. The behaviour of the modified AuNP dispersion as a consequence of the competitive displacement of the biotinylated oligonucleotide has been investigated and the critical role of displaced oligonucletides in triggering the quasi one-dimensional aggregation of nanoparticles is demonstrated for the first time. The thorough understanding of the fundamental properties of bioconjugated AuNPs is of great importance for the design of highly sensitive and reliable functionalized AuNP-based assays.

  14. Robust gold nanoparticles stabilized by trithiol for application in chemiresistive sensors

    Garg, Niti; Mohanty, Ashok; Jin, Rongchao [Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Lazarus, Nathan; Santhanam, Suresh; Fedder, Gary K [Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Schultz, Lawrence; Weiss, Lee [Robotics Institute, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Rozzi, Tony R; Snyder, Jay L, E-mail: zpx5@cdc.gov, E-mail: fedder@ece.cmu.edu, E-mail: rongchao@andrew.cmu.edu [National Institute for Occupational Safety and Health (NIOSH), Pittsburgh, PA 15236 (United States)

    2010-10-08

    The use of gold nanoparticles coated with an organic monolayer of thiol for application in chemiresistive sensors was initiated in the late 1990s; since then, such types of sensors have been widely pursued due to their high sensitivities and reversible responses to volatile organic compounds (VOCs). However, a major issue for chemical sensors based on thiol-capped gold nanoparticles is their poor long-term stability as a result of slow degradation of the monothiol-to-gold bonds. We have devised a strategy to overcome this limitation by synthesizing a more robust system using Au nanoparticles capped by trithiol ligands. Compared to its monothiol counterpart, the new system is significantly more stable and also shows improved sensitivity towards different types of polar or non-polar VOCs. Thus, the trithiol-Au nanosensor shows great promise for use in real world applications.

  15. Robust gold nanoparticles stabilized by trithiol for application in chemiresistive sensors

    Garg, Niti; Mohanty, Ashok; Jin, Rongchao; Lazarus, Nathan; Santhanam, Suresh; Fedder, Gary K; Schultz, Lawrence; Weiss, Lee; Rozzi, Tony R; Snyder, Jay L

    2010-01-01

    The use of gold nanoparticles coated with an organic monolayer of thiol for application in chemiresistive sensors was initiated in the late 1990s; since then, such types of sensors have been widely pursued due to their high sensitivities and reversible responses to volatile organic compounds (VOCs). However, a major issue for chemical sensors based on thiol-capped gold nanoparticles is their poor long-term stability as a result of slow degradation of the monothiol-to-gold bonds. We have devised a strategy to overcome this limitation by synthesizing a more robust system using Au nanoparticles capped by trithiol ligands. Compared to its monothiol counterpart, the new system is significantly more stable and also shows improved sensitivity towards different types of polar or non-polar VOCs. Thus, the trithiol-Au nanosensor shows great promise for use in real world applications.

  16. Extracellular facile biosynthesis, characterization and stability of gold nanoparticles by Bacillus licheniformis.

    Singh, Sneha; Vidyarthi, Ambarish Sharan; Nigam, Vinod Kumar; Dev, Abhimanyu

    2014-02-01

    The development of a reliable, eco-friendly process for synthesis of gold nanoparticles (AuNPs) has gained impetus in recent years to counter the drawbacks of chemical and physical methods. This study illustrates simple, green synthesis of AuNPs in vitro using cell lysate supernatant (CLS) of non-pathogenic bacteria and to investigate its potential antimicrobial activity. Gold nanoparticles were synthesized by the reduction of precursor AuCl4- ions using the CLS of Bacillus licheniformis at 37°C upon 24 h of incubation. The nanoparticles were characterized for their morphology, particle size, optical absorption, zeta potential, and stability. Further the antimicrobial activity was assayed using cup-plate method. The process of biosynthesis was extracellular and the gold ions were reduced to stable nanogold of average size 38 nm. However, upon storage of AuNPs for longer duration at room temperature stability was influenced in terms of increase in particle size and decrease in zeta potential with respect to as synthesized nanoparticles. SEM micrographs revealed the spherical shape of AuNPs and EDX analysis confirmed the presence of gold in the sample. Also clear zone of inhibition was observed against Bacilllus subtilis MTCC 8364, Pseudomonas aeruginosa MTCC 7925, and Escherichia coli MTCC 1698 confirming the antimicrobial activity of AuNPs. The bioprocess under study was simple and less time consuming as compared to other methods as the need for harvesting AuNPs from within the microbial cells via downstream process will be eliminated. Nanoparticles exhibited good stability even in absence of external stabilizing agents. AuNPs showed good antimicrobial activity against several Gram-negative and Gram-positive pathogenic bacteria. The extracellular biosynthesis from CLS may serve as a suitable alternative for large scale synthesis of gold nanoparticles in vitro. The synthesis from lysed bacterial cell strongly suggests that exposure of microbial whole cells to the

  17. Radiation induced synthesis of colloidal silver nanoparticles stabilized by PVP/chitosan

    Dang Van Phu; Nguyen Trieu; Vo Thi Kim Lang; Nguyen Quoc Hien; Bui Duy Du

    2008-01-01

    Colloidal silver nanoparticle solution (10 mmol) was prepared by gamma 60 Co irradiation using polyvinyl pyrrolidone (PVP), water soluble chitosan (WSC) and mixture of PVP/WSC as stabilizers. Saturated conversion doses (Ag + → Ag 0 ) and maximum absorption wavelengths (λ max ) were determined by UV-vis spectra to be of 28 kGy (405.5 nm), 20 kGy (418.5 nm), 24 kGy (415.0 nm) and 24 kGy (407.0 nm) for PVP 1% (C1), WSC 0.5% (C2), PVP 1%/WSC 0.5% (C3) and PVP 1%/ethanol 1 M (C4), respectively. Results of the conversion doses indicated that WSC and ethanol plays a role in scavenging the OH* and H* arising from radiolysis of water, which reduced the conversion dose from 28 kGy (C1) to 20 kGy (C2). The average size of silver nanoparticles was characterized by Transmission Electron Microscopy (TEM) as 15.96 ± 0.51, 5.55 ± 0.25, 2.92 ± 0.05, and 11.44 ±2.07 nm for C1, C2, C3 and C4, respectively. The obtained result of silver nanoparticle sizes showed that WSC exhibited the effect of reducing silver nanoparticle size in colloids, especially the mixture of PVP/WSC that reduced the size of silver nanoparticle from ∼16 nm (C1) to about 3 nm (C3). The effect of NaNO 3 on stability of colloidal silver nanoparticles has been also investigated. (author)

  18. Performance of dielectric nanocomposites: matrix-free, hairy nanoparticle assemblies and amorphous polymer-nanoparticle blends.

    Grabowski, Christopher A; Koerner, Hilmar; Meth, Jeffrey S; Dang, Alei; Hui, Chin Ming; Matyjaszewski, Krzysztof; Bockstaller, Michael R; Durstock, Michael F; Vaia, Richard A

    2014-12-10

    Demands to increase the stored energy density of electrostatic capacitors have spurred the development of materials with enhanced dielectric breakdown, improved permittivity, and reduced dielectric loss. Polymer nanocomposites (PNCs), consisting of a blend of amorphous polymer and dielectric nanofillers, have been studied intensely to satisfy these goals; however, nanoparticle aggregates, field localization due to dielectric mismatch between particle and matrix, and the poorly understood role of interface compatibilization have challenged progress. To expand the understanding of the inter-relation between these factors and, thus, enable rational optimization of low and high contrast PNC dielectrics, we compare the dielectric performance of matrix-free hairy nanoparticle assemblies (aHNPs) to blended PNCs in the regime of low dielectric contrast to establish how morphology and interface impact energy storage and breakdown across different polymer matrices (polystyrene, PS, and poly(methyl methacrylate), PMMA) and nanoparticle loadings (0-50% (v/v) silica). The findings indicate that the route (aHNP versus blending) to well-dispersed morphology has, at most, a minor impact on breakdown strength trends with nanoparticle volume fraction; the only exception being at intermediate loadings of silica in PMMA (15% (v/v)). Conversely, aHNPs show substantial improvements in reducing dielectric loss and maintaining charge/discharge efficiency. For example, low-frequency dielectric loss (1 Hz-1 kHz) of PS and PMMA aHNP films was essentially unchanged up to a silica content of 50% (v/v), whereas traditional blends showed a monotonically increasing loss with silica loading. Similar benefits are seen via high-field polarization loop measurements where energy storage for ∼15% (v/v) silica loaded PMMA and PS aHNPs were 50% and 200% greater than respective comparable PNC blends. Overall, these findings on low dielectric contrast PNCs clearly point to the performance benefits of

  19. A Novel Photosynthesis of Carboxymethyl Starch-Stabilized Silver Nanoparticles

    El-Sheikh, M. A.

    2014-01-01

    The water soluble photoinitiator (PI) 4-(trimethyl ammonium methyl) benzophenone chloride is used for the first time in the synthesis of silver nanoparticles (AgNPs). A new green synthesis method involves using PI/UV system, carboxymethyl starch (CMS), silver nitrate, and water. A mechanism of the reduction of silver ions to AgNPs by PI/UV system as well as by the newly born aldehydic groups was proposed. The synthesis process was assessed by UV-vis spectra and TEM of AgNPs colloidal solution. The highest absorbance was obtained using CMS, PI and AgNO3 concentrations of 10 g/L, 1 g/L, and 1 g/L, respectively; 40°C; 60 min; pH 7; and a material : liquor ratio 1 : 20. AgNPs so-obtained were stable in aqueous solution over a period of three weeks at room temperature (~25°C) and have round shape morphology. The sizes of synthesized AgNPs were in the range of 1–21 nm and the highest counts % of these particles were for particles of 6–10 and 1–3 nm, respectively. PMID:24672325

  20. A Novel Photosynthesis of Carboxymethyl Starch-Stabilized Silver Nanoparticles

    M. A. El-Sheikh

    2014-01-01

    Full Text Available The water soluble photoinitiator (PI 4-(trimethyl ammonium methyl benzophenone chloride is used for the first time in the synthesis of silver nanoparticles (AgNPs. A new green synthesis method involves using PI/UV system, carboxymethyl starch (CMS, silver nitrate, and water. A mechanism of the reduction of silver ions to AgNPs by PI/UV system as well as by the newly born aldehydic groups was proposed. The synthesis process was assessed by UV-vis spectra and TEM of AgNPs colloidal solution. The highest absorbance was obtained using CMS, PI and AgNO3 concentrations of 10 g/L, 1 g/L, and 1 g/L, respectively; 40°C; 60 min; pH 7; and a material : liquor ratio 1 : 20. AgNPs so-obtained were stable in aqueous solution over a period of three weeks at room temperature (~25°C and have round shape morphology. The sizes of synthesized AgNPs were in the range of 1–21 nm and the highest counts % of these particles were for particles of 6–10 and 1–3 nm, respectively.

  1. Determination of pyrophosphate and sulfate using polyhexamethylene guanidine hydrochloride-stabilized silver nanoparticles.

    Terenteva, E A; Apyari, V V; Dmitrienko, S G; Garshev, A V; Volkov, P A; Zolotov, Yu A

    2018-04-01

    Positively charged polyhexamethylene guanidine hydrochloride-stabilized silver nanoparticles (PHMG-AgNPs) were prepared and applied as a colorimetric probe for single-step determination of pyrophosphate and sulfate. The approach is based on the nanoparticles aggregation leading to change in their absorption spectra and color of the solution. Due to both electrostatic and steric stabilization these nanoparticles show decreased sensitivity relatively to many common anions, which allows for simple and rapid direct single-step determination of pyrophosphate and sulfate. Effects of different factors (time of interaction, pH, concentrations of anions and the nanoparticles) on aggregation of PHMG-AgNPs and analytical performance of the procedure were investigated. The method allows for the determination of pyrophosphate and sulfate in the range of 0.16-2μgmL -1 and 20-80μgmL -1 with RSD of 2-5%, respectively. The analysis can be performed using either spectrophotometry or naked-eye detection. Practical application of the method was shown by the example of pyrophosphate determination in baking powder sample. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Toxicity, toxicokinetics and biodistribution of dextran stabilized Iron oxide Nanoparticles for biomedical applications.

    Remya, N S; Syama, S; Sabareeswaran, A; Mohanan, P V

    2016-09-10

    Advancement in the field of nanoscience and technology has alarmingly raised the call for comprehending the potential health effects caused by deliberate or unintentional exposure to nanoparticles. Iron oxide magnetic nanoparticles have an increasing number of biomedical applications and hence a complete toxicological profile of the nanomaterial is therefore a mandatory requirement prior to its intended usage to ensure safety and to minimize potential health hazards upon its exposure. The present study elucidates the toxicity of in house synthesized Dextran stabilized iron oxide nanoparticles (DINP) in a regulatory perspective through various routes of exposure, its associated molecular, immune, genotoxic, carcinogenic effects and bio distribution profile. Synthesized ferrite nanomaterials were successfully coated with dextran (dextran helps in improvising particle stability in biological environments. The nanoparticles do not seem to induce oxidative stress mediated toxicological effects, nor altered physiological process or behavior changes or visible pathological lesions. Furthermore no anticipated health hazards are likely to be associated with the use of DINP and could be concluded that the synthesized DINP is nontoxic/safe to be used for biomedical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. A green synthesis of copper nanoparticles using native cyclodextrins as stabilizing agents

    Javier Suárez-Cerda

    2017-03-01

    Full Text Available In this work, a comparative study of the effect of the NCD size as a stabilizing agent, on the synthesis of copper nanoparticles (Cu-NPs by an easy green method was reported. The nanoparticles were synthesized through the chemical reduction of aqueous solutions of copper (II sulfate with ascorbic acid, using different native cyclodextrins (NCDs (α-, β-, or γ-NCD as stabilizing agents. Cu-NPs were characterized by scanning electron microscopy–energy dispersive spectroscopy (SEM–EDX, powder X-ray diffraction (XRD and transmission electron microscopy (TEM. The pattern showed in the typical selected area electron diffraction (SAED and lattice fringes, evidence that the crystalline structure of Cu-NPs is face-centered cubic (FCC with a (111, (200 and (220 lattice planes of Cu. The analysis of the TEM images show that the size of the Cu-NPs depends on the type of native cyclodextrin (NCD, also it was observed that the nanoparticles are spherical and with a size between ∼2 and 33 nm. The smaller Cu-NPs were obtained with α-NCD (mode 4 nm, while the nanoparticles obtained with β-NCD show the narrow size distribution (mode 6.5 nm. The average particle size and particle size distribution of Cu-NPs depend upon the type of CDs.

  4. Highly stabilized gadolinium chelates functionalized on metal nanoparticles as magnetic resonance imaging contrast agent

    Siddiqui, Talha S.

    Magnetic resonance imaging (MRI) is a non-invasive method for imaging and diagnosing tissue damage, organ function and the vascular system. Magnevist(TM) a complex of diethylenetriaminepentaacetic acid (DTPA) and Gd3+ is a clinically approved contrast agent for MRI. A derivative of DTPA was formed by the addition of two cysteine groups (DTPA-L-Cys) through amide linkage. The Gd complex of this ligand bonds with the silver surfaces through the cysteine thiols. GdDTPA-L-Cys was bound to ˜10nm diameter Ag nanoparticles for use as a multifunctional MRI contrast agent. The ligand and complex were characterized by 1H and 13C NMR, ESI-MS and IR spectroscopy. The silver construct was characterized by TEM, TGA and UV-Vis absorption spectra. The per metal complex r1 relaxivity of GdDTPA-L-Cys{Ag} greater than that of Magnavist(TM) with the same molarity for both compounds. The synthesis of a DTPA derivative is described that allows it to bind to silver or gold nanoparticles through a single thiol linkage (DTPASH). The resulting Gd complex, GdDTPASH, was bound to Ag nanoparticles to create a single monolayer on the surface. The construct was further stabilized in buffered solution with the addition of a thiolated PEG chain. The highly stabilized nanoparticle construct delivers a high payload of Gd compelex and is an effective T1 brightening agent. The production of this type of construct opens the way for engineered multimodal MRI contrast agents.

  5. Influence of nanoparticles on color stability, microhardness, and flexural strength of acrylic resins specific for ocular prosthesis.

    Andreotti, Agda Marobo; Goiato, Marcelo Coelho; Moreno, Amália; Nobrega, Adhara Smith; Pesqueira, Aldiéris Alves; dos Santos, Daniela Micheline

    2014-01-01

    The aim of this study was to assess the effect of adding nanoparticles to N1 acrylic resin intended for artificial sclera, in terms of the color stability, microhardness, and flexural strength of the resin. Three hundred samples of N1 acrylic resin were used: 100 samples for color stability and microhardness tests (each test was performed on the opposite side of each sample), and 200 samples for flexural strength testing (100 samples before and after 1,008 hours of accelerated aging). Samples for each test were separated into ten groups (n=10), ie, without nanoparticles (control group) or with nanoparticles of zinc oxide, titanium dioxide (TiO₂), and barium sulfate at weight concentrations of 1%, 2%, and 2.5% (nanoparticle groups). Data were subjected to statistical analysis with nested analysis of variance and Tukey's test (P<0.05 significance level). Among the nanoparticle groups, the TiO₂ groups showed better color stability at all concentrations. Microhardness values increased after artificial aging, except for the control and zinc oxide groups. After aging, the 1%-2% TiO₂ groups had significantly higher microhardness values compared with the other nanoparticle groups. Before aging, there was a significant difference in flexural strength between the control and nanoparticle groups. After aging, the control and TiO₂ groups, regardless of concentration, showed the lowest flexural strength values. Incorporation of nanoparticles directly influenced the acrylic resin properties, with TiO₂ being the most influential nanoparticle in terms of the evaluated properties.

  6. Suzuki coupling reactions catalyzed by poly(N-ethyl-4-vinylpyridinium bromide stabilized palladium nanoparticles in aqueous solution

    2008-04-01

    Full Text Available InIn this work, it was investigated to use of poly(N-ethyl-4-vinylpyridinium bromide stabilized palladium nanoparticles in the Suzuki reaction between phenylboronic acid and aryl halides in aqueous solution. The nanoparticles were isolated and re-used several times with low loss of activity.

  7. Selective and reactive hydration of nitriles to amides in water using silver nanoparticles stabilized by organic ligands

    Kawai, Koji; Kawakami, Hayato; Narushima, Takashi; Yonezawa, Tetsu

    2015-01-01

    Water-dispersible silver nanoparticles stabilized by silver–carbon covalent bonds were prepared. They exhibited high catalytic activities for the selective hydration of nitriles to amides in water. The activation of a nitrile group by the functional groups of the substrates and the hydrophobic layer on the nanoparticles influenced the catalyzed reaction were confirmed. Alkyl nitriles could also be selectively hydrated

  8. Chemical and thermal stability of core-shelled magnetite nanoparticles and solid silica

    Cendrowski, Krzysztof; Sikora, Pawel; Zielinska, Beata; Horszczaruk, Elzbieta; Mijowska, Ewa

    2017-06-01

    Pristine nanoparticles of magnetite were coated by solid silica shell forming core/shell structure. 20 nm thick silica coating significantly enhanced the chemical and thermal stability of the iron oxide. Chemical and thermal stability of this structure has been compared to the magnetite coated by mesoporous shell and pristine magnetite nanoparticles. It is assumed that six-membered silica rings in a solid silica shell limit the rate of oxygen diffusion during thermal treatment in air and prevent the access of HCl molecules to the core during chemical etching. Therefore, the core/shell structure with a solid shell requires a longer time to induce the oxidation of iron oxide to a higher oxidation state and, basically, even strong concentrated acid such as HCl is not able to dissolve it totally in one month. This leads to the desired performance of the material in potential applications such as catalysis and environmental protection.

  9. Extremely efficient catalysis of carbon-carbon bond formation using "click" dendrimer-stabilized palladium nanoparticles.

    Astruc, Didier; Ornelas, Cátia; Diallo, Abdou K; Ruiz, Jaime

    2010-07-20

    This article is an account of the work carried out in the authors' laboratory illustrating the usefulness of dendrimer design for nanoparticle palladium catalysis. The "click" synthesis of dendrimers constructed generation by generation by 1-->3 C connectivity, introduces 1,2,3-triazolyl ligands insides the dendrimers at each generation. Complexation of the ligands by Pd(II) followed by reduction to Pd(0) forms dendrimer-stabilized Pd nanoparticles (PdNPs) that are extremely reactive in the catalysis of olefin hydrogenation and C-C bond coupling reactions. The stabilization can be outer-dendritic for the small zeroth-generation dendrimer or intra-dendritic for the larger first- and second-generation dendrimers. The example of the Miyaura-Suzuki reaction that can be catalyzed by down to 1 ppm of PdNPs with a "homeopathic" mechanism (the less, the better) is illustrated here, including catalysis in aqueous solvents.

  10. Co-encapsulation of lyoprotectants improves the stability of protein-loaded PLGA nanoparticles upon lyophilization

    Fonte, Pedro; Araújo, Francisca; Seabra, Vítor

    2015-01-01

    The purpose of this work was to evaluate the influence of the co-encapsulation of lyoprotectants with insulin into PLGA nanoparticles, on the stability of the protein and nanoparticles upon lyophilization. Different lyoprotectants were used, namely trehalose, glucose, sucrose, fructose and sorbitol...... formulations with externally added lyoprotectants, except trehalose, showed crystallinity. FTIR assessment showed that co-encapsulating lyoprotectants better preserved insulin structure upon lyophilization with a spectral area overlap of 82-87%, compared to only 72% in lyoprotectant absence. These results were...... confirmed by circular dichroism spectroscopy. Surprisingly, the simultaneous co-encapsulation and addition of lyoprotectants was detrimental to protein stabilization. The insulin in vitro release studies demonstrated that formulations with co-encapsulated trehalose, glucose, sucrose, fructose and sorbitol...

  11. Zein nanoparticles and the strategies to improve the colloidal stability: a mini review

    Pascoli, Mônica; de Lima, Renata; Fraceto, Leonardo F.

    2018-01-01

    Zein, a protein extracted from maize, can be employed to easily produce nanoscale particles suitable for use as carrier systems. This review investigates the main methods for obtaining zein nanoparticles, as well as the problems and options available in the development of stable colloidal suspensions. Considerable gaps were identified in the literature concerning this topic, with studies being unclear about the factors that affect the stability of zein particles. In the vast majority of cases, no data are presented in relation to the stability of the formulations over time. It could be concluded that in order to produce a high quality system, detailed evaluation is required, considering factors including the zein concentration, pH, ionic strength, thermal treatment of the protein prior to preparation of the nanoparticles, strategies employing other materials as coatings, and the storage conditions. It is extremely important that these aspects should be considered during product development, prior to commercial-scale manufacture.

  12. The Effect of pH and Time on The Stability of Superparamagnetic Maghemite Nanoparticle Suspensions

    Nurdin Irwan

    2016-01-01

    Full Text Available Maghemite (γ-Fe2O3 nanoparticles have been synthesized using a chemical co-precipitation method. The morphology and particle size is characterized using Transmission Electron Microscopy (TEM, and magnetic characterization using Alternating Gradient Magnetometry (AGM. The stability of the maghemite nanoparticles suspension were studied at different pH and time of storage. Dynamic Light Scattering (DLS and Zeta Potential were conducted to determine the stability of the suspensions. TEM observation showed that the particles size is 9.6 nm and have spherical morphology. The particles showed superparamagnetic behavior with saturation magnetization 25.5 emu/g. The suspensions are stable in the acidic condition at pH 4 and alkaline condition at pH 10. The suspensions remain stable after 4 weeks of storage.

  13. Stabilization of gold nanoparticles by 6-mercaptopurine monolayers. Effects of the solvent properties.

    Viudez, Alfonso J; Madueño, Rafael; Pineda, Teresa; Blázquez, Manuel

    2006-09-14

    6-Mercaptopurine-coated gold nanoparticles (6MP-AuNPs) have been prepared by modification of the nanoparticle surface with 6MP upon displacement of the protective layer of citrate anions. The modification has been studied by UV-vis and FTIR spectroscopies. A study of the stability of these 6MP-AuNPs in aqueous solutions as a function of ionic strength and pH has shown the importance of the charges on the stabilization. The protonation of N9 of the 6MP molecules brings about a sudden flocculation phenomenon. However, the flocculation is reversible upon changing the pH to values where the molecules become newly charged. Evidence of the competence between the interaction of capping solvent molecules and the attractive forces between particles is also shown in this paper.

  14. SERS studies on the interaction between UO22+ and PVP-stabilized silver nanoparticles

    Roy, M.; Tyagi, A.K.; Kumar, Rakesh; Pandey, A.K.; Goswami, A.

    2010-01-01

    Interaction between uranyl (UO 2 2+ ) ions and silver nanoparticles (Ag-nps) stabilized by suitable polymeric capping agents has been studied in aqueous phase using surface enhanced resonance Raman spectroscopy technique (SERS). Polyvinylpyrrolidone (PVP) stabilized Ag-nps were synthesized by dissolving in water appropriate amount of PVP and AgNO 3 along with a suitable reducing agent in the form of either formamide or sodium borohydride. The solution was vigorously stirred for 5h and finally nanoparticle sols were obtained. A series of analyte samples was prepared by adding an appropriate amount of silver sol to different volumes of uranyl stock solution prepared at pH=3. The solutions were then drop cast on glass slides and dried in air. Preliminary results on drop-cast samples are presented here

  15. Colloidal stability of superparamagnetic iron oxide nanoparticles in the central nervous system: a review.

    Champagne, Pierre-Olivier; Westwick, Harrison; Bouthillier, Alain; Sawan, Mohamad

    2018-06-01

    Superparamagnetic iron oxide nanoparticles (SPIONs) consist of nanosized metallic-based particles with unique magnetic properties. Their potential in both diagnostic and therapeutic applications in the CNS is at the source of an expanding body of the literature in recent years. Colloidal stability of nanoparticles represents their ability to resist aggregation and is a central aspect for the use of SPION in biological environment such as the CNS. This review gives a comprehensive update of the recent developments and knowledge on the determinants of colloidal stability of SPIONs in the CNS. Factors leading to aggregate formation and the repercussions of colloidal instability of SPION are reviewed in detail pertaining to their use in the CNS.

  16. Precipitation, stabilization and molecular modeling of ZnS nanoparticles in the presence of cetyltrimethylammonium bromide.

    Praus, Petr; Dvorský, Richard; Horínková, Petra; Pospíšil, Miroslav; Kovář, Petr

    2012-07-01

    ZnS nanoparticles were precipitated in aqueous dispersions of cationic surfactant cetyltrimethylammonium bromide (CTAB). The sphere radii of ZnS nanoparticles calculated by using band-gap energies steeply decreased from 4.5 nm to 2.2 nm within CTAB concentrations of 0.4-1.5 mmol L(-1). Above the concentration of 1.5 mmol L(-1), the radii were stabilized at R=2.0 nm and increased up to R=2.5 nm after 24 h. The hydrodynamic diameters of CTAB-ZnS structures observed by the dynamic light scattering (DLS) method ranged from 130 nm to 23 nm depending on CTAB concentrations of 0.5-1.5 mmol L(-1). The complex structures were observed by transmission electron microscopy (TEM). At the higher CTAB concentrations, ZnS nanoparticles were surrounded by CTA(+) bilayers forming positively charged micelles with the diameter of 10nm. The positive zeta-potentials of the micelles and their agglomerates were from 16 mV to 33 mV. Wurtzite and sphalerite nanoparticles with R=2.0 nm and 2.5 nm covered by CTA(+) were modeled with and without water. Calculated sublimation energies confirmed that a bilayer arrangement of CTA(+) on the ZnS nanoparticles was preferred to a monolayer. Copyright © 2012 Elsevier Inc. All rights reserved.

  17. Red tea leaves infusion as a reducing and stabilizing agent in silver nanoparticles synthesis

    Pluta, K.; Tryba, A. M.; Malina, D.; Sobczak-Kupiec, A.

    2017-12-01

    Due to the unique properties of silver nanoparticles there is growing interest in their applications. Current trends in nanotechnology are focused on developing a new technique to synthesize nanoparticles using biological methods associated with the use of plant extracts, fungi, bacteria or essential oils. These methods are a promising alternative to conventional approaches which can minimize the use of hazardous substances. The silver nanoparticles synthesis using red tea infusion as a reducing and stabilizing agent and their characteristics have been described. Total antioxidant capacity using DPPH radical and total content of phenolic compounds by Folin-Ciocalteau method were measured in tea infusion. Synthesis of silver nanoparticles was carried out using chemical reduction at various temperatures. Furthermore, the effect of tea infusion volume added to reaction mixture on nanoparticles’ properties was investigated. Finally, nanosilver suspensions were characterized by UV-vis spectrophotometer, dynamic light scattering (DLS) scanning electron microscope (SEM) and transmission electron microscope (TEM). Moreover, phytotoxicity of silver nanoparticles was determined using Phytotestkit microbiotest.

  18. Gold nanoparticles stabilized by chitosan; Sintese de nanoparticulas de ouro estabilizadas por quitosana

    Geraldes, Adriana N.; Oliveira, Maria Jose A.; Silva, Andressa A. da; Leal, Jessica; Batista, Jorge G.S.; Lugao, Ademar B., E-mail: drinager@ig.com.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    In our laboratory has been growing the interest in studying gold nanoparticles and for this reason, the aim of this work is report the first results of the effect of chitosan as stabilizer in gold nanoparticle formulation. AuNPs were synthesized by reducing hydrogen tetrachloroaurate (HAuCl{sub 4}) using NaBH{sub 4} or gamma irradiation (25kGy) as reduction agent. The chitosan (3 mol L{sup -1}) was added at 0.5; 1.0 and 1.5 mL. The gold nanoparticles were characterized by UV-Vis absorption spectroscopy, X-ray diffraction (XRD) and Transmission electron microscopy (TEM). Their physical stability was determined using a UV-Vis spectrophotometer over one week during storage at room temperature. Absorption measurements indicated that the plasmon resonance wavelength appears at a wavelength around 530 nm. Has been observed that Chitosan in such quantities were not effective in stabilizing the AuNPs. (author)

  19. Synthesis and stabilization of gold nanoparticles for biotechnological and cosmetics uses

    Silva, Andressa Alves da

    2016-01-01

    This study focuses on the synthesis and characterization of gold nanoparticles (AuNPs) with reducing agents and stabilizing sodium citrate and gum arabic. The synthesis was carried out by heating and use of gamma radiation source 60 Co in doses 1, 7.5 and 15 kGy. In this context, we studied the properties and stability of AuNPs formed through characterization techniques such as UV- Vis absorption, checking the characteristics of AuNPs bands as well as the physical stability thereof. The samples synthesized with sodium citrate (AuCit) showed wavelengths ranging from 520 to 525 nm and the samples synthesized with gum arabic (AuGA) showed wavelengths between 530 and 540 nm. The dynamic light scattering analysis (DLS) was used to determine the hydrodynamic diameter of nanoparticles formed during a period of three months, demonstrating that AuCit samples showed mean hydrodynamic sizes ranging from 20 to 50 nm while AuGA samples synthesized by heating and the use of gamma radiation had mean hydrodynamic sizes ranging 50 - 115 nm. Analysis of scanning electron microscope with field emission (SEM - FEG) and transmission electron microscopy (TEM) were used to determine the actual size distribution of nanoparticles and their geometric shape. The characterization of the AuGA showed smaller diameters in comparison to the one resulted from the DLS analysis, thus suggesting possible encapsulation of AuNPs. (author)

  20. Silver nanoparticle colloids with γ-cyclodextrin: enhanced stability and Gibbs–Marangoni flow

    Amiri, Setareh; Duroux, Laurent; Larsen, Kim Lambertsen, E-mail: kll@bio.aau.dk [Aalborg University, Department of Chemistry and Bioscience (Denmark)

    2015-01-15

    Although cyclodextrins (CD) are effective stabilizers for metal nanoparticle colloids, differences between α-, β- and γ-CD in stabilizing such colloids have not been previously reported. In this study, silver nanoparticles (AgNP) were synthesized using NaBH{sub 4} as reducing agent and cyclodextrins as stabilizers. Long-term stability of AgNP colloids in equilibrium conditions showed no marked differences between CD types. Transmission electron microscopy and quantitative image analysis revealed only marginal differences in particle sizes for CD-AgNP, although statistically significant. CD-AgNP colloids showed dispersed particles with average diameters of 7.3 ± 2.2, 6.3 ± 2.9 and 4.9 ± 1.9 nm for α-, β- and γ-CD, respectively, and with similar ζ-potentials about −25 to −30 mV. AgNP without CD showed bigger and aggregated particles of 15.0 ± 2.0 nm with lower ζ-potentials of about −40 mV. When subjected to centrifugal forces, i.e. non-equilibrium conditions, γ-CD was markedly more efficient than α- and β-CD in stabilizing the colloids. Drying patterns of colloid droplets showed a typical self-pinned coffee ring for all but the colloid stabilized by γ-CD, which showed a pattern resulting from a dominant Gibbs–Marangoni flow inside the drying droplet. Calculations using the Derjaguin, Landau, Verwey and Overbeek (DLVO) theory supported the stabilizing effect of CD in equilibrium conditions; it however did not provide clues for the superior stabilization by γ-CD in conditions of hydrodynamic stress.

  1. Air, aqueous and thermal stabilities of Ce3+ ions in cerium oxide nanoparticle layers with substrates

    Naganuma, Tamaki

    2014-01-01

    Abundant oxygen vacancies coexisting with Ce3+ ions in fluorite cerium oxide nanoparticles (CNPs) have the potential to enhance catalytic ability, but the ratio of unstable Ce3+ ions in CNPs is typically low. Our recent work, however, demonstrated that the abundant Ce3+ ions created in cerium oxide nanoparticle layers (CNPLs) by Ar ion irradiation were stable in air at room temperature. Ce valence states in CNPs correlate with the catalytic ability that involves redox reactions between Ce3+ and Ce4+ ions in given application environments (e.g. high temperature in carbon monoxide gas conversion and immersion conditions in biomedical applications). To better understand the mechanism by which Ce3+ ions achieve stability in CNPLs, we examined (i) extra-long air-stability, (ii) thermal stability up to 500 °C, and (iii) aqueous stability of Ce 3+ ions in water, buffer solution and cell culture medium. It is noteworthy that air-stability of Ce3+ ions in CNPLs persisted for more than 1 year. Thermal stability results showed that oxidation of Ce 3+ to Ce4+ occurred at 350 °C in air. Highly concentrated Ce3+ ions in ultra-thin CNPLs slowly oxidized in water within 1 day, but stability was improved in the cell culture medium. Ce 3+ stability of CNPLs immersed in the medium was associated with phosphorus adsorption on the Ce3+ sites. This study also illuminates the potential interaction mechanisms of stable Ce3+ ions in CNPLs. These findings could be utilized to understand catalytic mechanisms of CNPs with abundant oxygen vacancies in their application environments. © The Royal Society of Chemistry 2014.

  2. Silver nanoparticle colloids with γ-cyclodextrin: enhanced stability and Gibbs–Marangoni flow

    Amiri, Setareh; Duroux, Laurent; Larsen, Kim Lambertsen

    2015-01-01

    Although cyclodextrins (CD) are effective stabilizers for metal nanoparticle colloids, differences between α-, β- and γ-CD in stabilizing such colloids have not been previously reported. In this study, silver nanoparticles (AgNP) were synthesized using NaBH 4 as reducing agent and cyclodextrins as stabilizers. Long-term stability of AgNP colloids in equilibrium conditions showed no marked differences between CD types. Transmission electron microscopy and quantitative image analysis revealed only marginal differences in particle sizes for CD-AgNP, although statistically significant. CD-AgNP colloids showed dispersed particles with average diameters of 7.3 ± 2.2, 6.3 ± 2.9 and 4.9 ± 1.9 nm for α-, β- and γ-CD, respectively, and with similar ζ-potentials about −25 to −30 mV. AgNP without CD showed bigger and aggregated particles of 15.0 ± 2.0 nm with lower ζ-potentials of about −40 mV. When subjected to centrifugal forces, i.e. non-equilibrium conditions, γ-CD was markedly more efficient than α- and β-CD in stabilizing the colloids. Drying patterns of colloid droplets showed a typical self-pinned coffee ring for all but the colloid stabilized by γ-CD, which showed a pattern resulting from a dominant Gibbs–Marangoni flow inside the drying droplet. Calculations using the Derjaguin, Landau, Verwey and Overbeek (DLVO) theory supported the stabilizing effect of CD in equilibrium conditions; it however did not provide clues for the superior stabilization by γ-CD in conditions of hydrodynamic stress

  3. STABILITY OF SYNTHESIZED SILVER NANOPARTICLES IN CITRATE AND MIXED GELATIN/CITRATE SOLUTION

    Jana Kavuličová

    2018-04-01

    Full Text Available The study focuses on an investigation of the influence of both citrate and mixed gelatin/citrate as a reductant and stabilizer on the colloidal stability of silver nanoparticles (AgNPssynthesized by a chemical reduction of Ag+ ions after a short - (7th day - and long - (118th day - term storage. Formed AgNPs were characterized by a UV–vis Spectroscopy, Transmission Electron Microscope (TEM, Dynamic light scattering (DLS and Zeta-potential (ZP. The obtained results revealed that a short-term stability of the synthesized AgNPs was greatly influenced by a citrate stabilizer with the absence of gelatin. Smaller-sized AgNPs (average particle diameter of 3 nm, roughly spherical in a shape, were obtained with a narrow size distribution. The very negative value of the Zeta-potential confirmed a strong stability of the citrate capped AgNPs. However, a surface coating of the AgNPs by a gelatin/citrate stabilizer was found to be a dominant contributor in improving a long-term stability of the AgNPs (average particle diameter of 26 nm. The use of gelatin in mixed stabilizer solution provided the AgNPs with higher monodispersity and a controllable size after both the short and long-term storage.

  4. Dechlorination of 2,4-dichlorophenoxyacetic acid by sodium carboxymethyl cellulose-stabilized Pd/Fe nanoparticles

    Zhou, Hongyi; Han, Jian; Baig, Shams Ali; Xu, Xinhua

    2011-01-01

    Highlights: ► CMC-stabilized Pd/Fe nanoparticles were synthesized and used for 2,4-D removal. ► Particle stability, ζ-potential and IEP of non- and stabilized Pd/Fe were compared. ► Dechlorination of 2,4-D by different Pd/Fe systems was investigated. ► The reaction mechanism has been discussed and presented in the article. ► Effects of CMC/Fe mass ratio and pH were also investigated. - Abstract: This paper describes the synthesis of sodium carboxymethyl cellulose (CMC)-stabilized Pd/Fe nanoparticles and their applications to the dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) under controlled laboratorial conditions. For this purpose batch mode experiments were conducted to understand the effects of CMC on the surface characteristics of Pd/Fe nanoparticles, optimum removal of 2,4-D and other surface interactions mechanism. Our experimental results demonstrated considerable enhancements in particle stability and chemical reactivity with the addition of CMC to Pd/Fe nanoparticles. Transmission electron microscopy (TEM) analysis indicated that CMC-stabilized Pd/Fe nanoparticles were well dispersed, and nanoparticles remained in suspension for days compared to non-stabilized Pd/Fe nanoparticles precipitated within minutes. The isoelectric point (IEP) of the nanoparticles shifted from pH 6.5 to 2.5, suggesting that CMC-stabilized Pd/Fe nanoparticles were negatively charged over a wider pH range. Our batch experiments demonstrated that CMC-stabilized Pd/Fe nanoparticles (0.6 g Fe L −1 ) were able to remove much higher levels of 2,4-D with only one intermediate 2-chlorophenoxyacetic acid (2-CPA) and the final organic product phenoxyacetic acid (PA), than non-stabilized Pd/Fe nanoparticles or microsized Pd/Fe particles. The removal percentage of 2,4-D increased from 10% to nearly 100% as the reaction pH decreased from 11.5 to 2.5. The optimal CMC/Fe mass ratio for the dechlorination of 2,4-D was determined to be 5/1, and the removal of 2,4-D was

  5. Dechlorination of 2,4-dichlorophenoxyacetic acid by sodium carboxymethyl cellulose-stabilized Pd/Fe nanoparticles

    Zhou, Hongyi, E-mail: zhouhy@zjut.edu.cn [College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032 (China); Han, Jian [College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032 (China); Baig, Shams Ali; Xu, Xinhua [Department of Environmental Engineering, Zhejiang University, Hangzhou 310027 (China)

    2011-12-30

    Highlights: Black-Right-Pointing-Pointer CMC-stabilized Pd/Fe nanoparticles were synthesized and used for 2,4-D removal. Black-Right-Pointing-Pointer Particle stability, {zeta}-potential and IEP of non- and stabilized Pd/Fe were compared. Black-Right-Pointing-Pointer Dechlorination of 2,4-D by different Pd/Fe systems was investigated. Black-Right-Pointing-Pointer The reaction mechanism has been discussed and presented in the article. Black-Right-Pointing-Pointer Effects of CMC/Fe mass ratio and pH were also investigated. - Abstract: This paper describes the synthesis of sodium carboxymethyl cellulose (CMC)-stabilized Pd/Fe nanoparticles and their applications to the dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) under controlled laboratorial conditions. For this purpose batch mode experiments were conducted to understand the effects of CMC on the surface characteristics of Pd/Fe nanoparticles, optimum removal of 2,4-D and other surface interactions mechanism. Our experimental results demonstrated considerable enhancements in particle stability and chemical reactivity with the addition of CMC to Pd/Fe nanoparticles. Transmission electron microscopy (TEM) analysis indicated that CMC-stabilized Pd/Fe nanoparticles were well dispersed, and nanoparticles remained in suspension for days compared to non-stabilized Pd/Fe nanoparticles precipitated within minutes. The isoelectric point (IEP) of the nanoparticles shifted from pH 6.5 to 2.5, suggesting that CMC-stabilized Pd/Fe nanoparticles were negatively charged over a wider pH range. Our batch experiments demonstrated that CMC-stabilized Pd/Fe nanoparticles (0.6 g Fe L{sup -1}) were able to remove much higher levels of 2,4-D with only one intermediate 2-chlorophenoxyacetic acid (2-CPA) and the final organic product phenoxyacetic acid (PA), than non-stabilized Pd/Fe nanoparticles or microsized Pd/Fe particles. The removal percentage of 2,4-D increased from 10% to nearly 100% as the reaction pH decreased from 11

  6. Tunable release of clavam from clavam stabilized gold nanoparticles — Design, characterization and antimicrobial study

    Manju, V. [Electrodics and Electrocatalysis Division, CSIR-Central Electrochemical Research Institute, Karaikudi, Tamilnadu 630006 (India); Dhandapani, P. [Corrosion Materials and Protection Division, CSIR-Central Electrochemical Research Institute, Karaikudi, Tamilnadu, 630006 (India); Gurusamy Neelavannan, M. [Characterization and Measurement lab, CSIR-Central Electrochemical Research Institute, Karaikudi, Tamilnadu 630006 (India); Maruthamuthu, S. [Corrosion Materials and Protection Division, CSIR-Central Electrochemical Research Institute, Karaikudi, Tamilnadu, 630006 (India); Berchmans, S. [Electrodics and Electrocatalysis Division, CSIR-Central Electrochemical Research Institute, Karaikudi, Tamilnadu 630006 (India); Palaniappan, A., E-mail: palani112@gmail.com [Electrodics and Electrocatalysis Division, CSIR-Central Electrochemical Research Institute, Karaikudi, Tamilnadu 630006 (India)

    2015-04-01

    A facile one-step approach is developed to synthesize highly stable (up to 6 months) gold nanoparticles (GNPs) using Clavam, pharmaceutical form of amoxicillin which contains a mixture of amoxicillin and potassium salt of clavulanic acid, at room temperature (25–30 °C). The clavam stabilized GNPs are characterized using various techniques including UV–Visible, FT-IR spectrophotometry and transmission electron microscopy (TEM). Tunable release of clavam from clavam stabilized GNPs is demonstrated using intracellular concentrations of glutathione (GSH). The process is monitored using an UV–Vis spectroscopy and the amount of clavam released in terms of amoxicillin concentration is quantitatively estimated using reverse phase high performance liquid chromatographic (RP-HPLC) technique. In vitro study reveals that the clavam released from GNPs' surface was found to show a significant enhancement in antibacterial activity against Escherichia coli and the cause of enhancement is addressed. - Graphical abstract: Stable and nearly monodisperse gold nanoparticles (GNPs) are prepared at room temperature (~ 25–30 °C) using clavam; commercial form of amoxicillin antibiotic. Tunable release of clavam from clavam stabilized GNPs is demonstrated by the addition of varying concentrations of glutathione. Interactions between clavam and gold core are investigated in detail. The mechanism of enhanced antimicrobial activity of clavam released from clavam stabilized GNPs is probed. - Highlights: • Gold nanoparticles (GNPs) are prepared without reducing agent using antibiotic clavam{sup TR}. • Our work shed lights on the nature of interaction between the clavam and GNPs. • Sustained release of clavam from clavam stabilized GNPs is demonstrated using glutathione. • Antimicrobial activity of the released clavam is confirmed using various techniques. • Our study suggests that the clavam released from GNPs shows better inhibition of E. coli.

  7. Effect of Stabilized Zero-Valent Iron Nanoparticles on Nitrate Removal from Sandy Soil

    F. Nooralivand

    2016-02-01

    Full Text Available Introduction: During the recent decades, the use of N fertilizers has undeniable development regardless of their effects on the soil and environment. Increasing nitrate ion concentration in soil solution and then, leaching it into groundwater causes increase nitrate concentration in the water and raise the risk suffering from the people to some diseases. World health organization recommended maximum concentration level for nitrate and nitrite in the drinking water 50 and 3 mg/l, respectively. There are different technologies for the removal of nitrate ions from aqueous solution. The conventional methods are ion exchange, biological denitrification, reverse osmosis and chemical reduction. Using nanoscale Fe0 particles compared to other methods of nitrate omission was preferred because of; its high surface area, more reactive, lower cost and higher efficiency. More studies on the reduction of nitrate by zero-valent iron nanoparticles have been in aqueous solutions or in the soil in batch scale. Nanoparticles surface modified with poly-electrolytes, surfactants and polymers cause colloidal stability of the particles against the forces of attraction between particles and increases nanoparticle transport in porous media. The objectives of this study were to synthesize carboxymethyl cellulose stabilized zero-valent iron nanoparticles and consideration of their application for nitrate removal from sandy soil. Materials and Methods: The nanoparticles were synthesized in a lab using borohydride reduction method and their morphological characteristics were examined via scanning electron microscopy (SEM, X-ray diffraction (XRD and Fourier Transmission Infrared Spectroscopy (FTIR. Experiments were conducted on packed sand column (40 cm length and 2.5 cm inner diameter under conditions of different nanoparticle concentration (1, 2, and 3 g1-1and high initial NO3- concentration (150, 250, and 350 mgl-1. Homogeneous soil column was filled with the wet packed

  8. Sub-10 ohm resistance gold films prepared by removal of ligands from thiol-stabilized 6 nm gold nanoparticles.

    Sugden, Mark W; Richardson, Tim H; Leggett, Graham

    2010-03-16

    The optical and electrical properties of dodecanethiol-stabilized nanoparticles (6 nm diameter gold core) have been investigated over a range of film thicknesses and temperatures. The surface plasmon resonance absorbance is found to be dependent on temperature. Heating of the nanoparticle film causes desorption of the thiol from the surface of the gold nanoparticle, resulting in irreversible changes to the absorption spectra of the nanoparticle film. Atomic force microscopy images of the samples before and after heating for different film thicknesses reveal structural changes and increased domain connectivity for thicker films leading to sub-10 ohm resistances measured for the 15-layer film.

  9. Synthesis of Monodispersed Gold Nanoparticles with Exceptional Colloidal Stability with Grafted Polyethylene Glycol-g-polyvinyl Alcohol

    Alaaldin M. Alkilany

    2015-01-01

    Full Text Available Herein, we report the synthesis of spherical gold nanoparticles with tunable core size (23–79 nm in the presence of polyethylene glycol-g-polyvinyl alcohol (PEG-g-PVA grafted copolymer as a reducing, capping, and stabilizing agent in a one-step protocol. The resulted PEG-g-PVA-capped gold nanoparticles are monodispersed with an exceptional colloidal stability against salt addition, repeated centrifugation, and extensive dialysis. The effect of various synthesis parameters and the kinetic/mechanism of the nanoparticle formation are discussed.

  10. Nanoparticle Stability in Axial InAs-InP Nanowire Heterostructures with Atomically Sharp Interfaces.

    Zannier, Valentina; Rossi, Francesca; Dubrovskii, Vladimir G; Ercolani, Daniele; Battiato, Sergio; Sorba, Lucia

    2018-01-10

    The possibility to expand the range of material combinations in defect-free heterostructures is one of the main motivations for the great interest in semiconductor nanowires. However, most axial nanowire heterostructures suffer from interface compositional gradients and kink formation, as a consequence of nanoparticle-nanowire interactions during the metal-assisted growth. Understanding such interactions and how they affect the growth mode is fundamental to achieve a full control over the morphology and the properties of nanowire heterostructures for device applications. Here we demonstrate that the sole parameter affecting the growth mode (straight or kinked) of InP segments on InAs nanowire stems by the Au-assisted method is the nanoparticle composition. Indeed, straight InAs-InP nanowire heterostructures are obtained only when the In/Au ratio in the nanoparticles is low, typically smaller than 1.5. For higher In content, the InP segments tend to kink. Tailoring the In/Au ratio by the precursor fluxes at a fixed growth temperature enables us to obtain straight and radius-uniform InAs-InP nanowire heterostructures (single and double) with atomically sharp interfaces. We present a model that is capable of describing all the experimentally observed phenomena: straight growth versus kinking, the stationary nanoparticle compositions in pure InAs and InAs-InP nanowires, the crystal phase trends, and the interfacial abruptness. By taking into account different nanowire/nanoparticle interfacial configurations (forming wetting or nonwetting monolayers in vertical or tapered geometry), our generalized model provides the conditions of nanoparticle stability and abrupt heterointerfaces for a rich variety of growth scenarios. Therefore, our results provide a powerful tool for obtaining high quality InAs-InP nanowire heterostructures with well-controlled properties and can be extended to other material combinations based on the group V interchange.

  11. Enhancement of temozolomide stability by loading in chitosan-carboxylated polylactide-based nanoparticles

    Di Martino, Antonio; Kucharczyk, Pavel; Capakova, Zdenka; Humpolicek, Petr; Sedlarik, Vladimir, E-mail: sedlarik@ft.utb.cz [Tomas Bata University in Zlín, Centre of Polymer Systems, University Institute (Czech Republic)

    2017-02-15

    In the presented work, amphiphilic nanoparticles based on chitosan and carboxy-enriched polylactic acid have been prepared to improve the stability of the pro-drug temozolomide in physiological media by encapsulation. The carrier, with a diameter in the range of 150–180 nm, was able to accommodate up to 800 μg of temozolomide per mg of polymer. The obtained formulation showed good stability in physiological condition and preparation media up to 1 month. Temozolomide loaded inside the carrier exhibited greater stability than the free drug, in particular in simulated physiological solution at pH 7.4 where the hydrolysis in the inactive metabolite was clearly delayed. CS-SPLA nanoparticles demonstrated a pH-dependent TMZ release kinetics with the opportunity to increase or decrease the rate. Mass spectroscopy, UV-Vis analysis, and in vitro cell tests confirmed the improvement in temozolomide stability and effectiveness when loaded into the polymeric carrier, in comparison with the free drug.

  12. Improvement of the stability and activity of immobilized glucose oxidase on modified iron oxide magnetic nanoparticles

    Abbasi, Mahboube, E-mail: mahbubeabbasi@yahoo.com; Amiri, Razieh, E-mail: razieh.amiri@gmail.com; Bordbar, Abdol-Kalegh, E-mail: bordbar@chem.ui.ac.ir; Ranjbakhsh, Elnaz, E-mail: e.ranjbakhsh@yahoo.com; Khosropour, Ahmad-Reza, E-mail: khosropour@chem.ui.ac.ir

    2016-02-28

    Graphical abstract: - Highlights: • Modified iron oxide magnetic nanoparticles were synthesized by co-precipitation method and characterized by TEM and XRD. • Covalent attachment of GOX to MIMNs was confirmed by FT-IR technique. • Optimization of the reaction time and initial amount of the GOX were carried out. • Improvement of activity and stability of immobilized GOX have been increased in comparison of free GOX. - Abstract: Immobilized proteins and enzymes are widely investigated in the medical field as well as the food and environmental fields. In this study, glucose oxidase (GOX) was covalently immobilized on the surface of modified iron oxide magnetic nanoparticles (MIMNs) to produce a bioconjugate complex. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to the size, shape and structure characterization of the MIMNs. Binding of GOX to these MIMNs was confirmed by using FT-IR spectroscopy. The stability of the immobilized and free enzyme at different temperature and pH values was investigated by measuring the enzymatic activity. These studies reveal that the enzyme's stability is enhanced by immobilization. Further experiments showed that the storage stability of the enzyme is improved upon binding to the MIMNs. The results of kinetic measurements suggest that the effect of the immobilization process on substrate and product diffusion is small. Such bioconjugates can be considered as a catalytic nanodevice for accelerating the glucose oxidation reaction for biotechnological purposes.

  13. Experimental investigation on the use of highly charged nanoparticles to improve the stability of weakly charged colloidal system.

    Zubir, Mohd Nashrul Mohd; Badarudin, A; Kazi, S N; Misran, Misni; Amiri, Ahmad; Sadri, Rad; Khalid, Solangi

    2015-09-15

    The present work highlighted on the implementation of a unique concept for stabilizing colloids at their incipiently low charge potential. A highly charged nanoparticle was introduced within a coagulated prone colloidal system, serving as stabilizer to resist otherwise rapid flocculation and sedimentation process. A low size asymmetry of nanoparticle/colloid serves as the new topic of investigation in addition to the well-established large size ratio nanoparticle/microparticle study. Highly charged Al2O3 nanoparticles were used within the present research context to stabilize TiO2 and Fe3O4 based colloids via the formation of composite structures. It was believed, based on the experimental evidence, that Al2O3 nanoparticle interact with the weakly charged TiO2 and Fe3O4 colloids within the binary system via absorption and/or haloing modes to increase the overall charge potential of the respective colloids, thus preventing further surface contact via van der Waal's attraction. Series of experimental results strongly suggest the presence of weakly charged colloids in the studied bimodal system where, in the absence of highly charged nanoparticle, experience rapid instability. Absorbance measurement indicated that the colloidal stability drops in accordance to the highly charged nanoparticle sedimentation rate, suggesting the dominant influence of nanoparticles to attain a well-dispersed binary system. Further, it was found that the level of colloidal stability was enhanced with increasing nanoparticle fraction within the mixture. Rheological observation revealed that each hybrid complexes demonstrated behavior reminiscence to water with negligible increase in viscosity which serves as highly favorable condition particularly in thermal transport applications. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Freeze-drying of HI-6-loaded recombinant human serum albumin nanoparticles for improved storage stability.

    Dadparvar, Miriam; Wagner, Sylvia; Wien, Sascha; Worek, Franz; von Briesen, Hagen; Kreuter, Jörg

    2014-10-01

    Severe intoxications with organophosphates require the immediate administration of atropine in combination with acetyl cholinesterase (AChE) reactivators such as HI-6. Although this therapy regimen enables the treatment of peripheral symptoms, the blood-brain barrier (BBB) restricts the access of the hydrophilic antidotes to the central nervous system which could lead to a fatal respiratory arrest. Therefore, HI-6-loaded albumin nanoparticles were previously developed to enhance the transport across this barrier and were able to reactivate organophosphate-(OP)-inhibited AChE in an in vitro BBB model. Since HI-6 is known to be moisture-sensitive, the feasibility of freeze-drying of the HI-6-loaded nanoparticles was investigated in the present study using different cryo- and lyoprotectants at different concentrations. Trehalose and sucrose (3%, w/v)-containing formulations were superior to mannitol concerning the physicochemical parameters of the nanoparticles whereas trehalose-containing samples were subject of a prolonged storage stability study at temperatures between -20°C and +40°C for predetermined time intervals. Shelf-life computations of the freeze-dried HI-6 nanoparticle formulations revealed a shelf-life time of 18 months when stored at -20°C. The formulations' efficacy was proven in vitro by reactivation of OP-inhibited AChE after transport over a porcine brain capillary endothelial cell layer model. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Amorphous iron–chromium oxide nanoparticles with long-term stability

    Iacob, Mihail [“Petru Poni” Institute of Macromolecular Chemistry, Iasi 700487 (Romania); Institute of Chemistry of ASM, Academiei str. 3, Chisinau 2028, Republic of Moldova (Moldova, Republic of); Cazacu, Maria, E-mail: mcazacu@icmpp.ro [“Petru Poni” Institute of Macromolecular Chemistry, Iasi 700487 (Romania); Turta, Constantin [Institute of Chemistry of ASM, Academiei str. 3, Chisinau 2028, Republic of Moldova (Moldova, Republic of); Doroftei, Florica [“Petru Poni” Institute of Macromolecular Chemistry, Iasi 700487 (Romania); Botko, Martin; Čižmár, Erik; Zeleňáková, Adriana; Feher, Alexander [Institute of Physics, Faculty of Science, P.J. Šafárik University, Park Angelinum 9, SK-04154 Košice (Slovakia)

    2015-05-15

    Highlights: • Fe–Cr oxide nanoparticles with pre-established metals ratio were obtained. • The amorphous state and its long-term stability were highlighted by X-ray diffraction. • The average diameter of dried nanoparticles was 3.5 nm, as was estimated by TEM, AFM. • In hexane dispersion, nanoparticles with diameter in the range 2.33–4.85 nm were found. • Superparamagnetic state of NPs co-exists with diamagnetism of the organic layer. - Abstract: Iron–chromium nanoparticles (NPs) were obtained through the thermal decomposition of μ{sub 3}-oxo heterotrinuclear (FeCr{sub 2}O) acetate in the presence of sunflower oil and dodecylamine (DA) as surfactants. The average diameter of the NPs was 3.5 nm, as estimated on the basis of transmission electron microscopy and atomic force microscopy images. Both techniques revealed the formation of roughly approximated spheres with some irregularities and agglomerations in larger spherical assemblies of 50–100 nm. In hexane, NPs with diameters in the 2.33–4.85 nm range are individually dispersed, as emphasized by dynamic light scattering measurements. The amorphous nature of the product was emphasized by X-ray powder diffraction. The study of the magnetic properties shows the presence of superparamagnetic state of iron–chromium oxide NPs and the diamagnetic contribution from DA layer forming a shell of NPs.

  16. Synthesis of Yttria-stabilized zirconia nanoparticles by decomposition of metal nitrates coated on carbon powder

    Jiang, S.; Stangle, G.C.; Amarakoon, V.R.; Schulze, W.A.

    1996-01-01

    Weakly agglomerated nanoparticles of yttria-stabilized zirconia (YSZ) were synthesized by a novel process which involved the decomposition of metal nitrates that had been coated on ultrafine carbon black powder, after which the carbon black was gasified. The use of ultrafine, high-surface-area carbon black powder apparently allowed the nanocrystalline oxide particles to form and remain separate from each other, after which the carbon black was gasified at a somewhat higher temperature. As a result, the degree of agglomeration was shown to be relatively low. The average crystallite size and the specific surface area of the as-synthesized YSZ nanoparticles were 5∼6 nm and 130 m 2 /g, respectively, for powder synthesized at 650 degree C. The as-synthesized YSZ nanoparticles had a light brown color and were translucent, which differs distinctly from conventional YSZ particles which are typically white and opaque. The mechanism of the synthesis process was investigated, and indicated that the gasification temperature had a direct effect on the crystallite size of the as-synthesized YSZ nanoparticles. High-density and ultrafine-grained YSZ ceramic articles were prepared by fast-firing, using a dwell temperature of 1250 degree C and a dwell time of two minutes or less. copyright 1996 Materials Research Society

  17. Thermal stability and electrochemical properties of PVP-protected Ru nanoparticles synthesized at room temperature

    Kumar, Manish; Devi, Pooja; Shivling, V. D.

    2017-08-01

    Stable ruthenium nanoparticles (RuNPs) have been synthesized by the chemical reduction of ruthenium trichloride trihydrate (RuCl3 · 3H2O) using sodium borohydride (NaBH4) as a reductant and polyvinylpyrrolidone (PVP) as a protecting agent in the aqueous medium at room temperature. The nanoparticles thus prepared were characterized by their morphology and structural analysis from transmission electron microscopy (TEM), X-ray powder diffraction (XRD), UV-vis spectroscopy, Fourier transformation infrared and thermogravimetric analysis (TGA) techniques. The TEM image suggested a homogeneous distribution of PVP-protected RuNPs having a small average diameter of 2-4 nm with a chain-like network structure. The XRD pattern also confirmed that a crystallite size is around 2 nm of PVP-protected RuNPs having a single broad peak. The thermal stability studied using TGA, indicated good stability and the electrochemical properties of these nanoparticles revealed that saturation current increases for PVP-protected RuNPs/GC.

  18. A magnetic nanoparticle stabilized gas containing emulsion for multimodal imaging and triggered drug release.

    Guo, Wei; Li, Diancheng; Zhu, Jia-an; Wei, Xiaohui; Men, Weiwei; Yin, Dazhi; Fan, Mingxia; Xu, Yuhong

    2014-06-01

    To develop a multimodal imaging guided and triggered drug delivery system based on a novel emulsion formulation composed of iron oxide nanoparticles, nanoscopic bubbles, and oil containing drugs. Iron oxide paramagnetic nanoparticles were synthesized and modified with surface conjugation of polyethylenimide (PEI) or Bovine Serum Albumin (BSA). Both particles were used to disperse and stabilize oil in water emulsions containing coumarin-6 as the model drug. Sulfur hexafluoride was introduced into the oil phase to form nanoscopic bubbles inside the emulsions. The resulted gas containing emulsions were evaluated for their magnetic resonance (MR) and ultrasound (US) imaging properties. The drug release profile triggered by ultrasound was also examined. We have successfully prepared the highly integrated multi-component emulsion system using the surface modified iron oxide nanoparticles to stabilize the interfaces. The resulted structure had distinctive MR and US imaging properties. Upon application of ultrasound waves, the gas containing emulsion would burst and encapsulated drug could be released. The integrated emulsion formulation was multifunctional with paramagnetic, sono-responsive and drug-carrying characteristics, which may have potential applications for disease diagnosis and imaging guided drug release.

  19. Stabilization of antimicrobial silver nanoparticles by a polyhydroxyalkanoate obtained from mixed bacterial culture.

    Castro-Mayorga, J L; Martínez-Abad, A; Fabra, M J; Olivera, Catarina; Reis, M; Lagarón, J M

    2014-11-01

    The incorporation of antimicrobials into polymer matrices is a promising technology in the food packaging and biomedical areas. Among the most widely used antimicrobials, silver nanoparticles (AgNPs) have emerged as one of the most researched technologies to prevent microbial outbreaks. However, it is known that AgNPs are rather unstable and present patterns of agglomeration that might limit their application. In this work, AgNPs were produced by chemical reduction in suspensions of an unpurified poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) which was previously obtained from a mixed culture fermentation using a synthetic medium mimicking fermented cheese whey. The synthesis of AgNPs was carried out within the unpurified PHBV suspension (in situ) and by physical mixing (mix). The stability of crystalline and spherical nanoparticles (7±3nm) obtained in situ was found to be stable during at least 40 days. The results suggest that the unpurified PHBV appears to be a very efficient capping agent, preventing agglomeration and, thereby, stabilizing successfully the silver nanoparticles. The in situ obtained AgNP-PHBV materials were also found to exhibit a strong antibacterial activity against Salmonella enterica at low concentration (0.1-1ppm). Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Effect of Nitric Acid Concentrations on Synthesis and Stability of Maghemite Nanoparticles Suspension

    Irwan Nurdin

    2014-01-01

    Full Text Available Maghemite (γ-Fe2O3 nanoparticles have been synthesized using a chemical coprecipitation method at different nitric acid concentrations as an oxidizing agent. Characterization of all samples performed by several techniques including X-ray diffraction (XRD, transmission electron microscopy (TEM, alternating gradient magnetometry (AGM, thermogravimetric analysis (TGA, dynamic light scattering (DLS, and zeta potential. The XRD patterns confirmed that the particles were maghemite. The crystallite size of all samples decreases with the increasing concentration of nitric acid. TEM observation showed that the particles have spherical morphology with narrow particle size distribution. The particles showed superparamagnetic behavior with decreased magnetization values at the increasing concentration of nitric acid. TGA measurement showed that the stability temperature decreases with the increasing concentration of nitric acid. DLS measurement showed that the hydrodynamic particle sizes decrease with the increasing concentration of nitric acid. Zeta potential values show a decrease with the increasing concentration of nitric acid. The increasing concentration of nitric acid in synthesis of maghemite nanoparticles produced smaller size particles, lower magnetization, better thermal stability, and more stable maghemite nanoparticles suspension.

  1. Radiation synthesis of chitosan stabilized gold nanoparticles comparison between e− beam and γ irradiation

    Vo, Khoa Dang Nguyen; Kowandy, Christelle; Dupont, Laurent; Coqueret, Xavier; Hien, Nguyen Quoc

    2014-01-01

    Gold nanoparticles were synthesized via radiolytic reduction of Au(III) salts induced by e − beam or γ-irradiation, using chitosan as a stabilizer. The effect of irradiation dose, chitosan concentration and the conditioning of HAuCl 4 –chitosan solutions were studied. UV–visible absorption measurements reveal that the size of Au clusters formed immediately after irradiation is correlated with the extent of chitosan scission chain of chitosan and fall with the increase of dose absorbed. This effect is more pronounced with solution conditioned under Argon (Ar). Au clusters coalesce to form stable nanoparticles after two weeks. - Highlights: • This paper underlines the potential of ionizing radiations in the synthesis of AuNps. • The size of the nanoparticles, and their stability are controlled by the ratio [GLA]/[Au(III)] • This paper compares results obtained with e − beam and γ irradiation for the AuNps synthesis. • This paper points the influence of dose rate on the size of preformed Au clusters

  2. Gold nanoparticles stabilized by starch polymer and their use as catalyst in homocoupling of phenylboronic acid

    Kittiyaporn Wongmanee

    2017-10-01

    Full Text Available In this study, gold nanoparticles (Au NPs stabilized by a starch polymer have been successfully prepared and characterized via a number of techniques including X-ray photoelectron spectroscopy (XPS, X-ray diffraction (XRD, UV-visible spectroscopy (UV-vis, transmission electron microscopy (TEM, and dynamic light scattering (DLS measurements. The catalytic activity of starch-stabilized Au NPs was also examined toward the homocoupling of phenylboronic acid in water using oxygen in air as oxidant at an ambient temperature (25 ± 1 °C. Several parameters including the catalyst loading, base equivalent (eq., base type, and reaction time were studied. This study offers a simple, inexpensive and environmentally friendly procedure for the stabilization of colloidal gold catalysts using a hydroxyl-rich structure of starch polymer with a great promise through potential applications in related fields.

  3. Improving the oxidation resistance and stability of Ag nanoparticles by coating with multilayered reduced graphene oxide

    Li, Yahui; Zhang, Huayu; Wu, Bowen; Guo, Zhuo

    2017-12-01

    A kind of coating nanostructure, Ag nanoparticles coated with multilayered reduced graphene oxide (RGO), is fabricated by employing a three-step reduction method in an orderly manner, which is significantly different from the conventional structures that are simply depositing or doping with Ag nanoparticles on RGO via chemical reduction. The as-prepared nanostructure is investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected-area electronic diffraction (SEAD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results show that the obtained Ag/RGO nanostructure is observed to be a perfect coating structure with well dispersed Ag particles, which is responsible for the remarkable oxidation resistance. The results of XPS spectra indicate the content of metallic Ag is far greater than that of Ag oxides despite of prolonged exposure to the air, which fully demonstrate the excellent stability of thus coating nanostructure.

  4. PVP-Stabilized Palladium Nanoparticles in Silica as Effective Catalysts for Hydrogenation Reactions

    Caroline Pires Ruas

    2013-01-01

    Full Text Available Palladium nanoparticles stabilized by poly (N-vinyl-2-pyrrolidone (PVP can be synthesized by corresponding Pd(acac2 (acac = acetylacetonate as precursor in methanol at 80°C for 2 h followed by reduction with NaBH4 and immobilized onto SiO2 prepared by sol-gel process under acidic conditions (HF or HCl. The PVP/Pd molar ratio is set to 6. The effect of the sol-gel catalyst on the silica morphology and texture and on Pd(0 content was investigated. The catalysts prepared (ca. 2% Pd(0/SiO2/HF and ca. 0,3% Pd(0/SiO2/HCl were characterized by TEM, FAAS, and SEM-EDS. Palladium nanoparticles supported in silica with a size 6.6 ± 1.4 nm were obtained. The catalytic activity was tested in hydrogenation of alkenes.

  5. Synthesis of dextrin-stabilized colloidal silver nanoparticles and their application as modifiers of cement mortar.

    Konował, Emilia; Sybis, Marta; Modrzejewska-Sikorska, Anna; Milczarek, Grzegorz

    2017-11-01

    Various commercial dextrins were used as reducing and stabilizing agents for a novel one-step synthesis of silver nanoparticles from ammonia complexes of silver ions. As a result, stable colloids of silver were formed during the reaction with the particle size being the function of the dextrin type. The obtained colloids were characterized by UV-vis spectrophotometry, size distribution (using Non-Invasive Backscatter optics) and transmission electron microscopy (TEM). The achieved results clearly indicate the possibility of low-cost production of large quantities of colloidal silver nanoparticles using materials derived from renewable sources. The resulting silver colloids can be used for different purposes, e.g. as bactericidal agents. Combination of the aforementioned properties of nanosilver particles with plasticizing properties of dextrin enables to obtain cement mortars with increased workability and enhanced compressive strength. Moreover, the obtained material is also characterized by increased immunity to adverse impact of microorganisms. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Agglomeration, colloidal stability, and magnetic separation of magnetic nanoparticles: collective influences on environmental engineering applications

    Yeap, Swee Pin; Lim, JitKang; Ooi, Boon Seng; Ahmad, Abdul Latif

    2017-11-01

    Magnetic nanoparticles (MNPs) which exhibit magnetic and catalytic bifunctionalities have been widely accepted as one of the most promising nanoagents used in water purification processes. However, due to the magnetic dipole-dipole interaction, MNPs can easily lose their colloidal stability and tend to agglomerate. Thus, it is necessary to enhance their colloidal stability in order to maintain the desired high specific surface area. Meanwhile, in order to successfully utilize MNPs for environmental engineering applications, an effective magnetic separation technology has to be developed. This step is to ensure the MNPs that have been used for pollutant removal can be fully reharvested back. Unfortunately, it was recently highlighted that there exists a conflicting role between colloidal stability and magnetic separability of the MNPs, whereby the more colloidally stable the particle is, the harder for it to be magnetically separated. In other words, attaining a win-win scenario in which the MNPs possess both good colloidal stability and fast magnetic separation rate becomes challenging. Such phenomenon has to be thoroughly understood as the colloidal stability and the magnetic separability of MNPs play a pivotal role on affecting their effective implementation in water purification processes. Accordingly, it is the aim of this paper to provide reviews on (i) the colloidal stability and (ii) the magnetic separation of MNPs, as well as to provide insights on (iii) their conflicting relationship based on recent research findings. [Figure not available: see fulltext.

  7. nanoparticles

    Andreu-Cabedo, Patricia; Mondragon, Rosa; Hernandez, Leonor; Martinez-Cuenca, Raul; Cabedo, Luis; Julia, J. Enrique

    2014-10-01

    Thermal energy storage (TES) is extremely important in concentrated solar power (CSP) plants since it represents the main difference and advantage of CSP plants with respect to other renewable energy sources such as wind, photovoltaic, etc. CSP represents a low-carbon emission renewable source of energy, and TES allows CSP plants to have energy availability and dispatchability using available industrial technologies. Molten salts are used in CSP plants as a TES material because of their high operational temperature and stability of up to 500°C. Their main drawbacks are their relative poor thermal properties and energy storage density. A simple cost-effective way to improve thermal properties of fluids is to dope them with nanoparticles, thus obtaining the so-called salt-based nanofluids. In this work, solar salt used in CSP plants (60% NaNO3 + 40% KNO3) was doped with silica nanoparticles at different solid mass concentrations (from 0.5% to 2%). Specific heat was measured by means of differential scanning calorimetry (DSC). A maximum increase of 25.03% was found at an optimal concentration of 1 wt.% of nanoparticles. The size distribution of nanoparticle clusters present in the salt at each concentration was evaluated by means of scanning electron microscopy (SEM) and image processing, as well as by means of dynamic light scattering (DLS). The cluster size and the specific surface available depended on the solid content, and a relationship between the specific heat increment and the available particle surface area was obtained. It was proved that the mechanism involved in the specific heat increment is based on a surface phenomenon. Stability of samples was tested for several thermal cycles and thermogravimetric analysis at high temperature was carried out, the samples being stable.

  8. Stability and antimicrobial effect of amikacin-loaded solid lipid nanoparticles

    Solmaz Ghaffari

    2010-12-01

    Full Text Available Solmaz Ghaffari1, Jaleh Varshosaz1, Afrooz Saadat2, Fatemeh Atyabi21Department of Pharmaceutics, Faculty of Pharmacy and Isfahan Pharmaceutical Sciences Research Center, Isfahan University of Medical Sciences, Isfahan, Iran; 2Department of Pharmaceutics, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, IranAbstract: Solid lipid nanoparticles (SLNs of amikacin were designed in this study for pulmonary delivery to reduce the dose or its administration intervals leading to reduction of its toxicities especially in long term treatment. Nanoparticles of amikacin were prepared from cholesterol by solvent diffusion technique and homogenization. The size, zeta potential, loading efficiency, and release profile of the nanoparticles were studied. The conventional broth macrodilution tube method was used to determine the minimum inhibitory concentration (MIC and minimum bacteriostatic concentration (MBC of amikacin SLNs with respect to Pseudomonas aeruginosa in vitro. To guarantee the stability of desired SLNs, they were lyophilized using cryoprotectants. Results showed that considering the release profile of amikacin from the studied nanocarrier, MIC and MBC of amikacin could be about two times less in SLNs of amikacin compared to the free drug. Therefore, fewer doses of amikacin in SLNs can clear the infection with less adverse effects and more safety. Particle size enlargement after lyophilization of desired SLNs after two months storage was limited in comparison with non-lyophilized particles, 996 and 194 nm, respectively. Zeta potential of lyophilized particles was increased to +17 mV from +4 mV before lyophilization. Storage of particles in higher temperature caused accelerated drug release.Keywords: amikacin, antimicrobial effects, Pseudomonas aeruginosa, solid lipid nanoparticles, stability

  9. Influence of nanoparticles on color stability, microhardness, and flexural strength of acrylic resins specific for ocular prosthesis

    Andreotti AM

    2014-12-01

    Full Text Available Agda Marobo Andreotti, Marcelo Coelho Goiato, Amália Moreno, Adhara Smith Nobrega, Aldiéris Alves Pesqueira, Daniela Micheline dos Santos Araçatuba Dental School, São Paulo State University, Araçatuba, São Paulo, Brazil Abstract: The aim of this study was to assess the effect of adding nanoparticles to N1 acrylic resin intended for artificial sclera, in terms of the color stability, microhardness, and flexural strength of the resin. Three hundred samples of N1 acrylic resin were used: 100 samples for color stability and microhardness tests (each test was performed on the opposite side of each sample, and 200 samples for flexural strength testing (100 samples before and after 1,008 hours of accelerated aging. Samples for each test were separated into ten groups (n=10, ie, without nanoparticles (control group or with nanoparticles of zinc oxide, titanium dioxide (TiO2, and barium sulfate at weight concentrations of 1%, 2%, and 2.5% (nanoparticle groups. Data were subjected to statistical analysis with nested analysis of variance and Tukey’s test (P<0.05 significance level. Among the nanoparticle groups, the TiO2 groups showed better color stability at all concentrations. Microhardness values increased after artificial aging, except for the control and zinc oxide groups. After aging, the 1%–2% TiO2 groups had significantly higher microhardness values compared with the other nanoparticle groups. Before aging, there was a significant difference in flexural strength between the control and nanoparticle groups. After aging, the control and TiO2 groups, regardless of concentration, showed the lowest flexural strength values. Incorporation of nanoparticles directly influenced the acrylic resin properties, with TiO2 being the most influential nanoparticle in terms of the evaluated properties. Keywords: acrylic resins, eye, artificial, color, hardness, nanoparticles

  10. Improvement of thermal stability of UV curable pressure sensitive adhesive by surface modified silica nanoparticles

    Pang, Beili; Ryu, Chong-Min; Kim, Hyung-Il, E-mail: hikim@cnu.ac.kr

    2013-11-01

    Highlights: • Silica nanoparticles were modified to carry the vinyl groups for photo-crosslinking. • Acrylic copolymer was modified to have the vinyl groups for photo-crosslinking. • Strong and extensive interfacial bondings were formed between polymer and silica. • Thermal stability of PSA was improved by forming nanocomposite with modified silica. -- Abstract: Pressure sensitive adhesives (PSAs) with higher thermal stability were successfully prepared by forming composite with the silica nanoparticles modified via reaction with 3-methacryloxypropyltrimethoxysilane. The acrylic copolymer was synthesized as a base resin for PSAs by solution polymerization of 2-EHA, EA, and AA with AIBN as an initiator. The acrylic copolymer was further modified with GMA to have the vinyl groups available for UV curing. The peel strength decreased with the increase of gel content which was dependent on both silica content and UV dose. Thermal stability of the composite PSAs was improved noticeably with increasing silica content and UV dose mainly due to the strong and extensive interfacial bonding between the organic polymer matrix and silica.

  11. Development of Nanoparticle-Stabilized Foams to Improve Performance of Water-less Hydraulic Fracturing

    Prodanovic, Masa [The University of Texas at Austin; Johnston, Keith P. [The University of Texas at Austin

    2017-12-29

    We have successfully created ultra dry carbon-dioxide-in-water and nitrogen-in-water foams (with water content down to 2-5% range), that are remarkably stable at high temperatures (up to 120 deg, C) and pressures (up to 3000psi) and viscous enough (100-200 cP tunable range) to carry proppant. Two generations of these ultra-dry foams have been developed; they are stabilized either with a synergy of surfactants and nanoparticle, or just with viscoelastic surfactants that viscosify the aqueous phase. Not only does this reduce water utilization and disposal, but it minimizes fluid blocking of hydrocarbon production. Further, the most recent development shows successful use of environmentally friendly surfactants at high temperature and pressure. We pay special attention to the role of nanoparticles in stabilization of the foams, specifically for high salinity brines. The preliminary numerical simulation for which shows they open wider fractures with shorter half-length and require less clean-up due to minimal water use. We also tested the stability and sand carrying properties of these foams at high pressure, room temperature conditions in sapphire cell. We performed on a preliminary numerical investigation of applicability for improved oil recovery applications. The applicability was evaluated by running multiphase flow injection simulations in a case-study oil reservoir. The results of this research thus expand the options available to operators for hydraulic fracturing and can simplify the design and field implementation of foamed fracturing fluids.

  12. Efficient chemotherapy of rat glioblastoma using doxorubicin-loaded PLGA nanoparticles with different stabilizers.

    Stefanie Wohlfart

    Full Text Available BACKGROUND: Chemotherapy of glioblastoma is largely ineffective as the blood-brain barrier (BBB prevents entry of most anticancer agents into the brain. For an efficient treatment of glioblastomas it is necessary to deliver anti-cancer drugs across the intact BBB. Poly(lactic-co-glycolic acid (PLGA nanoparticles coated with poloxamer 188 hold great promise as drug carriers for brain delivery after their intravenous injection. In the present study the anti-tumour efficacy of the surfactant-coated doxorubicin-loaded PLGA nanoparticles against rat glioblastoma 101/8 was investigated using histological and immunohistochemical methods. METHODOLOGY: The particles were prepared by a high-pressure solvent evaporation technique using 1% polyvinylalcohol (PLGA/PVA or human serum albumin (PLGA/HSA as stabilizers. Additionally, lecithin-containing PLGA/HSA particles (Dox-Lecithin-PLGA/HSA were prepared. For evaluation of the antitumour efficacy the glioblastoma-bearing rats were treated intravenously with the doxorubicin-loaded nanoparticles coated with poloxamer 188 using the following treatment regimen: 3 × 2.5 mg/kg on day 2, 5 and 8 after tumour implantation; doxorubicin and poloxamer 188 solutions were used as controls. On day 18, the rats were sacrificed and the antitumour effect was determined by measurement of tumour size, necrotic areas, proliferation index, and expression of GFAP and VEGF as well as Isolectin B4, a marker for the vessel density. CONCLUSION: The results reveal a considerable anti-tumour effect of the doxorubicin-loaded nanoparticles. The overall best results were observed for Dox-Lecithin-PLGA/HSA. These data demonstrate that the poloxamer 188-coated PLGA nanoparticles enable delivery of doxorubicin across the blood-brain barrier in the therapeutically effective concentrations.

  13. Antibacterial activity of silver nanoparticles stabilized on tannin-grafted collagen fiber

    He Li [National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065 (China); Gao Siying; Wu Hao [Department of Biomass Chemistry and Engineering, Sichuan University, Chengdu 610065 (China); Liao Xuepin, E-mail: xpliao@scu.edu.cn [Department of Biomass Chemistry and Engineering, Sichuan University, Chengdu 610065 (China); He Qiang [National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065 (China); Shi Bi, E-mail: sibitannin@vip.163.com [National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065 (China) and Department of Biomass Chemistry and Engineering, Sichuan University, Chengdu 610065 (China)

    2012-07-01

    Bayberry tannin (BT), a typical plant polyphenol, was grafted on collagen fiber (CF) in different mass ratios. Subsequently, the BT-grafted CF (BT-CF) was used as carrier and stabilizer to prepare BT-CF stabilized silver nanoparticles (BT-CF-AgNPs). Scanning Electron Microscopy image of BT-CF-AgNPs showed that the BT-CF-AgNPs was in ordered fibrous state. X-ray Diffraction patterns and Transmission Electron Microscopy images offered evidence that the Ag nanoparticles were well dispersed on BT-CF. Fourier Transform-Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) investigations revealed that the Ag NPs were stabilized by the phenolic hydroxyls and quinones of BT on CF through electron donation/acception interaction. Antibacterial experiments demonstrated that BT-CF-AgNPs exhibited high antibacterial activity. When cell suspensions of Escherichia coli and Staphylococcus aureus (10{sup 4}-10{sup 5} cfu/mL) were contacted with BT{sub 0.19}-CF-AgNPs (mass ratio of BT to CF = 0.19, conc. of Ag = 8 {mu}g/mL) at 310 K under constant shaking, the number of cells went down to zero within 2 h. In addition, the minimal inhibitory concentration of BT{sub 0.19}-CF-AgNPs against Escherichia coli, Staphylococcus aureus, Penicillium glaucum and Saccharomyces cerevisiae was 2 {mu}g/mL, 4 {mu}g/mL, 6 {mu}g/mL and 12 {mu}g/mL Ag, respectively. During recycling use, the antibacterial activity of BT{sub 0.19}-CF-AgNPs against Escherichia coli can last for 5 cycles. These facts suggest that BT-CF-AgNPs can be used as a new and effective antibacterial agent. - Highlights: Black-Right-Pointing-Pointer Bayberry tannin-grafted collagen fiber can be acted as carrier and stabilizer for the preparation of nano-silver (AgNPs) with different particle size. Black-Right-Pointing-Pointer Bayberry tannin-grafted collagen fiber stabilized silver nanoparticles (BT-CF-AgNPs) were characterized by SEM, XRD, TEM, FTIR and XPS. Black-Right-Pointing-Pointer BT-CF-AgNPs has the

  14. Interfacial bonding stabilizes rhodium and rhodium oxide nanoparticles on layered Nb oxide and Ta oxide supports.

    Strayer, Megan E; Binz, Jason M; Tanase, Mihaela; Shahri, Seyed Mehdi Kamali; Sharma, Renu; Rioux, Robert M; Mallouk, Thomas E

    2014-04-16

    Metal nanoparticles are commonly supported on metal oxides, but their utility as catalysts is limited by coarsening at high temperatures. Rhodium oxide and rhodium metal nanoparticles on niobate and tantalate supports are anomalously stable. To understand this, the nanoparticle-support interaction was studied by isothermal titration calorimetry (ITC), environmental transmission electron microscopy (ETEM), and synchrotron X-ray absorption and scattering techniques. Nanosheets derived from the layered oxides KCa2Nb3O10, K4Nb6O17, and RbTaO3 were compared as supports to nanosheets of Na-TSM, a synthetic fluoromica (Na0.66Mg2.68(Si3.98Al0.02)O10.02F1.96), and α-Zr(HPO4)2·H2O. High surface area SiO2 and γ-Al2O3 supports were also used for comparison in the ITC experiments. A Born-Haber cycle analysis of ITC data revealed an exothermic interaction between Rh(OH)3 nanoparticles and the layered niobate and tantalate supports, with ΔH values in the range -32 kJ·mol(-1) Rh to -37 kJ·mol(-1) Rh. In contrast, the interaction enthalpy was positive with SiO2 and γ-Al2O3 supports. The strong interfacial bonding in the former case led to "reverse" ripening of micrometer-size Rh(OH)3, which dispersed as 0.5 to 2 nm particles on the niobate and tantalate supports. In contrast, particles grown on Na-TSM and α-Zr(HPO4)2·H2O nanosheets were larger and had a broad size distribution. ETEM, X-ray absorption spectroscopy, and pair distribution function analyses were used to study the growth of supported nanoparticles under oxidizing and reducing conditions, as well as the transformation from Rh(OH)3 to Rh nanoparticles. Interfacial covalent bonding, possibly strengthened by d-electron acid/base interactions, appear to stabilize Rh(OH)3, Rh2O3, and Rh nanoparticles on niobate and tantalate supports.

  15. Thermal stability of carbon-encapsulated Fe-Nd-B nanoparticles

    Bystrzejewski, M.; Cudzilo, S.; Huczko, A.; Lange, H.

    2006-01-01

    Thermal stability of various magnetic nanomaterials is very essential, due to their prospective future applications. In this paper, thermal behaviour of the carbon-encapsulated Fe-Nd-B nanoparticles is studied. These nanostructures were produced by direct current arcing of carbon anodes filled with Nd 2 Fe 14 B material. The thermogravimetry and differential thermal analysis curves were recorded in an oxygen atmosphere. The thermal processes were monitored by X-ray diffraction to follow the changes in the phase composition. The investigated samples have been thermally stable up to 600 K

  16. Effects of the silica nanoparticles (NPSiO2 on the stabilization and transport of hazardous nanoparticle suspensions into landfill soil columns

    Elizabeth Mendes de Oliveira

    Full Text Available Abstract This study evaluates the stability and transport behaviors of hazardous nanoparticles into soil landfills using experimental procedures to simulate the effects of natural silica nanoparticle suspensions during their percolation into the soil layers of municipal waste landfills. For this, we prepared stabilized suspensions of nanoparticle oxides containing silicon (NPSiO2, titanium (NPTiO2, copper (NPCuO and zinc (NPZnO, which are recognized as hazardous to the environment, and we conducted leaching experiments within the soil column by simulating landfills layers and simulating the capture and attenuation of nanomaterials into municipal waste landfills. The results demonstrated that the presence of NPSiO2 in suspensions increases the stable concentrations of copper, zinc and titanium oxides and strongly decreases soil layer effectiveness. In contrast, NPZnO improves effectiveness due to its ability to promote agglomeration and setting conditions, allowing further complexation.

  17. Biocompatible and colloidally stabilized mPEG-PE/calcium phosphate hybrid nanoparticles loaded with siRNAs targeting tumors.

    Gao, Pei; Zhang, Xiangyu; Wang, Hongzhi; Zhang, Qinghong; Li, He; Li, Yaogang; Duan, Yourong

    2016-01-19

    Calcium phosphate nanoparticles are safe and effective delivery vehicles for small interfering RNA (siRNA), as a result of their excellent biocompatibility. In this work, mPEG-PE (polyethylene glycol-L-α-phosphatidylethanolamine) was synthesized and used to prepare nanoparticles composed of mPEG-PE and calcium phosphate for siRNA delivery. Calcium phosphate and mPEG-PE formed the stable hybrid nanoparticles through self-assembly resulting from electrostatic interaction in water. The average size of the hybrid nanoparticles was approximately 53.2 nm with a negative charge of approximately -16.7 mV, which was confirmed by dynamic light scattering (DLS) measurements. The nanoparticles exhibited excellent stability in serum and could protect siRNA from ribonuclease (RNase) degradation. The cellular internalization of siRNA-loaded nanoparticles was evaluated in SMMC-7721 cells using a laser scanning confocal microscope (CLSM) and flow cytometry. The hybrid nanoparticles could efficiently deliver siRNA to cells compared with free siRNA. Moreover, the in vivo distribution of Cy5-siRNA-loaded hybrid nanoparticles was observed after being injected into tumor-bearing nude mice. The nanoparticles concentrated in the tumor regions through an enhanced permeability and retention (EPR) effect based on the fluorescence intensities of tissue distribution. A safety evaluation of the nanoparticles was performed both in vitro and in vivo demonstrating that the hybrid nanoparticle delivery system had almost no toxicity. These results indicated that the mPEG-PE/CaP hybrid nanoparticles could be a stable, safe and promising siRNA nanocarrier for anticancer therapy.

  18. Ultra-fast electron capture by electrosterically-stabilized gold nanoparticles.

    Ghandi, Khashayar; Findlater, Alexander D; Mahimwalla, Zahid; MacNeil, Connor S; Awoonor-Williams, Ernest; Zahariev, Federico; Gordon, Mark S

    2015-07-21

    Ultra-fast pre-solvated electron capture has been observed for aqueous solutions of room-temperature ionic liquid (RTIL) surface-stabilized gold nanoparticles (AuNPs; ∼9 nm). The extraordinarily large inverse temperature dependent rate constants (k(e)∼ 5 × 10(14) M(-1) s(-1)) measured for the capture of electrons in solution suggest electron capture by the AuNP surface that is on the timescale of, and therefore in competition with, electron solvation and electron-cation recombination reactions. The observed electron transfer rates challenge the conventional notion that radiation induced biological damage would be enhanced in the presence of AuNPs. On the contrary, AuNPs stabilized by non-covalently bonded ligands demonstrate the potential to quench radiation-induced electrons, indicating potential applications in fields ranging from radiation therapy to heterogeneous catalysis.

  19. Carboxymethylated chitosan-stabilized copper nanoparticles: a promise to contribute a potent antifungal and antibacterial agent

    Tantubay, Sangeeta, E-mail: sang.chem2@gmail.com [Indian Institute of Technology Kharagpur, Department of Chemistry (India); Mukhopadhyay, Sourav K. [Indian Institute of Technology Kharagpur, Department of Biotechnology (India); Kalita, Himani; Konar, Suraj [Indian Institute of Technology Kharagpur, Department of Chemistry (India); Dey, Satyahari [Indian Institute of Technology Kharagpur, Department of Biotechnology (India); Pathak, Amita, E-mail: ami@chem.iitkgp.ernet.in; Pramanik, Panchanan, E-mail: ppramanik1946@yahoo.in, E-mail: pramanik1946@gmail.com [Indian Institute of Technology Kharagpur, Department of Chemistry (India)

    2015-06-15

    Carboxymethylated chitosan (CMC)-stabilized copper nanoparticles (Cu-NPs) have been synthesized via chemical reduction of copper(II)–CMC complex in aqueous medium by hydrazine under microwave irradiation in ambient atmosphere. Structural morphology, phase, and chemical compositions of CMC-stabilized Cu-NPs (CMC–Cu-NPs) have been analyzed through high-resolution transmission electron microscopy, field emission scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Antifungal and antibacterial activities of CMC–Cu-NPs have been evaluated against Candida tropicalis and Escherichia coli through agar well diffusion method, broth microdilution assay, live–dead assay, and microscopic observation. Antimicrobial activity of spherical CMC–Cu-NPs (∼4–15 nm of diameters) has been observed to be significant for both C. tropicalis and E. coli. The cytotoxicity study indicates that CMC–Cu-NPs have no significant toxic effect against normal cell line, L929.

  20. Study on gamma radiation-induced synthesis of gold nanoparticles stabilized by hyaluronan

    Dang Van Phu; Nguyen Ngoc Duy; Nguyen Tue Anh; Nguyen Quoc Hien

    2011-01-01

    Gold nanoparticles (AuNPs) with diameter from 4 to 10 nm were synthesized in hyaluronan (HA) solution without usage of any reductant and *OH radical scavenger by gamma irradiation reduction. The size and size distribution of AuNPs were determined by TEM images. The λ max (517 - 525 nm) of colloidal AuNPs solutions as prepared were measured by UV-Vis spectroscopy. The influence factors on the size of AuNPs particularly the concentration of Au 3+ , HA and dose rate were investigated. The stability of AuNPs/HA as synthesized was more than 6 months in storage under atmospheric condition. AuNPs with the size less than 10 nm and narrow size distribution stabilized by HA which is biocompatible natural polysaccharide so that AuNPs/HA can potentially be applied in biomedicine and cosmetic. (author)

  1. Stability of titania nanoparticles in soil suspensions and transport in saturated homogeneous soil columns

    Fang Jing [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085 (China); Shan Xiaoquan [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085 (China)], E-mail: xiaoquan@rcees.ac.cn; Wen Bei [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085 (China)], E-mail: bwen@rcees.ac.cn; Lin Jinming [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085 (China); Owens, Gary [Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SA 5095 (Australia)

    2009-04-15

    The stability of TiO{sub 2} nanoparticles in soil suspensions and their transport behavior through saturated homogeneous soil columns were studied. The results showed that TiO{sub 2} could remain suspended in soil suspensions even after settling for 10 days. The suspended TiO{sub 2} contents in soil suspensions after 24 h were positively correlated with the dissolved organic carbon and clay content of the soils, but were negatively correlated with ionic strength, pH and zeta potential. In soils containing soil particles of relatively large diameters and lower solution ionic strengths, a significant portion of the TiO{sub 2} (18.8-83.0%) readily passed through the soils columns, while TiO{sub 2} was significantly retained by soils with higher clay contents and salinity. TiO{sub 2} aggregate sizes in the column outflow significantly increased after passing through the soil columns. The estimated transport distances of TiO{sub 2} in some soils ranged from 41.3 to 370 cm, indicating potential environmental risk of TiO{sub 2} nanoparticles to deep soil layers. - TiO{sub 2} nanoparticles could efficiently suspend in soil suspensions and potentially transport to deeper soil layers.

  2. Stability of titania nanoparticles in soil suspensions and transport in saturated homogeneous soil columns

    Fang Jing; Shan Xiaoquan; Wen Bei; Lin Jinming; Owens, Gary

    2009-01-01

    The stability of TiO 2 nanoparticles in soil suspensions and their transport behavior through saturated homogeneous soil columns were studied. The results showed that TiO 2 could remain suspended in soil suspensions even after settling for 10 days. The suspended TiO 2 contents in soil suspensions after 24 h were positively correlated with the dissolved organic carbon and clay content of the soils, but were negatively correlated with ionic strength, pH and zeta potential. In soils containing soil particles of relatively large diameters and lower solution ionic strengths, a significant portion of the TiO 2 (18.8-83.0%) readily passed through the soils columns, while TiO 2 was significantly retained by soils with higher clay contents and salinity. TiO 2 aggregate sizes in the column outflow significantly increased after passing through the soil columns. The estimated transport distances of TiO 2 in some soils ranged from 41.3 to 370 cm, indicating potential environmental risk of TiO 2 nanoparticles to deep soil layers. - TiO 2 nanoparticles could efficiently suspend in soil suspensions and potentially transport to deeper soil layers

  3. Structural characterization, formation mechanism and stability of curcumin in zein-lecithin composite nanoparticles fabricated by antisolvent co-precipitation.

    Dai, Lei; Sun, Cuixia; Li, Ruirui; Mao, Like; Liu, Fuguo; Gao, Yanxiang

    2017-12-15

    Curcumin (Cur) exhibits a range of bioactive properties, but its application is restrained due to its poor water solubility and sensitivity to environmental stresses. In this study, zein-lecithin composite nanoparticles were fabricated by antisolvent co-precipitation technique for delivery of Cur. The result showed that the encapsulation efficiency of Cur was significantly enhanced from 42.03% in zein nanoparticles to 99.83% in zein-lecithin composite nanoparticles. The Cur entrapped in the nanoparticles was in an amorphous state confirmed by differential scanning calorimetry and X-ray diffraction. Fourier transform infrared analysis revealed that hydrogen bonding, electrostatic interaction and hydrophobic attraction were the main interactions among zein, lecithin, and Cur. Compared with single zein and lecithin nanoparticles, zein-lecithin composite nanoparticles significantly improved the stability of Cur against thermal treatment, UV irradiation and high ionic strength. Therefore, zein-lecithin composite nanoparticles could be a potential delivery system for water-insoluble bioactive compounds with enhanced encapsulation efficiency and chemical stability. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Bio-prospective of Polyscias fruticosa leaf extract as redactor and stabilizer of gold nanoparticles formation

    Yulizar, Y.; Ayun, Q.

    2017-03-01

    Metal nanoparticle is a great interest to researches due to its applications toward catalysis, sensors, and drug delivery. Biosynthesis of gold nanoparticles (AuNPs) using aqueous leaf extract of Polycias fruticosa (PFE) is reported in this article. PFE plays a role as reductor and stabilizer of AuNPs. The formation of PFE-AuNPs under radiation of natrium lamp for 15 min was monitored by UV - Vis spectrophotometer. The growth process and stability of PFE-AuNPs was observed from the colour and absorbance change in the wavelength range of 529-533 nm. The optimum synthesis condition of PFE-AuNPs was obtained at 0.06% (w/v) of PFE concentration. Size and its distribution of PFE-AuNPs were identified by particle size analyzer (PSA) as 35.02 nm and stable up until 21 days. The stable PFE-AuNPs was further characterized by Fourier transform infrared (FT-IR) spectroscopy to identify the functional group in phenolic compound of PFE interact with AuNps.

  5. One pot light assisted green synthesis, storage and antimicrobial activity of dextran stabilized silver nanoparticles.

    Hussain, Muhammad Ajaz; Shah, Abdullah; Jantan, Ibrahim; Tahir, Muhammad Nawaz; Shah, Muhammad Raza; Ahmed, Riaz; Bukhari, Syed Nasir Abbas

    2014-12-03

    Green synthesis of nanomaterials finds the edge over chemical methods due to its environmental compatibility. Herein, we report green synthesis of silver nanoparticles (Ag NPs) mediated with dextran. Dextran was used as a stabilizer and capping agent to synthesize Ag NPs using silver nitrate (AgNO3) under diffused sunlight conditions. UV-vis spectra of as synthesized Ag nanoparticles showed characteristic surface plasmon band in the range from ~405-452 nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies showed spherical Ag NPs in the size regime of ~50-70 nm. Face centered cubic lattice of Ag NPs was confirmed by powder X-ray diffraction (PXRD). FT-IR spectroscopy confirmed that dextran not only acts as reducing agent but also functionalizes the surfaces of Ag NPs to make very stable dispersions. Moreover, on drying, the solution of dextran stabilized Ag NPs resulted in the formation of thin films which were found stable over months with no change in the plasmon band of pristine Ag NPs. The antimicrobial assay of the as synthesized Ag NPs showed remarkable activity. Being significantly active against microbes, the Ag NPs can be explored for antimicrobial medical devices.

  6. Gum tragacanth stabilized green gold nanoparticles as cargos for Naringin loading: A morphological investigation through AFM.

    Rao, Komal; Imran, Muhammad; Jabri, Tooba; Ali, Imdad; Perveen, Samina; Shafiullah; Ahmed, Shakil; Shah, Muhammad Raza

    2017-10-15

    Gold nanoparticles (AuNPs) have attracted greater scientific interests for the construction of drugs loading cargos due to their biocompatibility, safety and facile surface modifications. This study deals with the fabrication of gum tragacanth (GT) green AuNPs as carrier for Naringin, a less water soluble therapeutic molecule. The optimized AuNPs were characterized through UV-vis spectroscopy, FT-IR and atomic force microscope (AFM). Naringin loaded nanoparticles were investigated for their bactericidal potentials using Tetrazolium Microplate assay. Morphological studies conducted via AFM revealed spherical shape for AuNPs with nano-range size and stabilized by GT multi-functional groups. The AuNPs acted as carrier for increased amount of Naringin. Upon loading in AuNPs, Naringin An increased in the bactericidal potentials of Naringin was observed after loading on AuNPs against various tested bacterial strains. This was further authenticated by the surface morphological analysis, showing enhanced membrane destabilizing effects of loaded Naringin. The results suggest that GT stabilized green AuNPs can act as effective delivery vehicles for enhancing bactericidal potentials of Naringin. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Gd_2O_3 nanoparticles stabilized by hydrothermally modified dextrose for positive contrast magnetic resonance imaging

    Babić-Stojić, Branka; Jokanović, Vukoman; Milivojević, Dušan; Požek, Miroslav; Jagličić, Zvonko; Makovec, Darko; Arsikin, Katarina; Paunović, Verica

    2016-01-01

    Gd_2O_3 nanoparticles of a few nm in size and their agglomerates dispersed in dextrose derived polymer template were synthesized by hydrothermal treatment. The produced nanosized material was investigated by TEM, FTIR spectroscopy, SQUID measurements and NMR relaxometry. Biological evaluation of this material was done by crystal violet and MTT assays to determine the cell viability. Longitudinal and transverse NMR relaxivities of water diluted Gd_2O_3 nanoparticle dispersions measured at the magnetic field of 1.5 T, estimated to be r_1(Gd_2O_3)=9.6 s"−"1 mM"−"1 in the Gd concentration range 0.1–30 mM and r_2(Gd_2O_3)=17.7 s"−"1 mM"−"1 in the lower concentration range 0.1–0.8 mM, are significantly higher than the corresponding relaxivities measured for the standard contrast agent r_1(Gd-DTPA)=4.1 s"−"1 mM"−"1 and r_2(Gd-DTPA)=5.1 s"−"1 mM"−"1. The ratio of the two relaxivities for Gd_2O_3 nanoparticles r_2/r_1=1.8 is suitable for T_1-weighted imaging. Good MRI signal intensities of the water diluted Gd_2O_3 nanoparticle dispersions were recorded at lower Gd concentrations 0.2–0.8 mM. The Gd_2O_3 samples did not exert any significant cytotoxic effects at Gd concentrations of 0.2 mM and below. These properties of the produced Gd_2O_3 nanoparticles in hydrothermally modified dextrose make them promising for potential application in MRI for the design of a positive MRI contrast agent. - Highlights: • Gd_2O_3 nanoparticles (NPs) were stabilized by hydrothermally modified dextrose. • Magnetic moment per Gd"3"+ ion in the Gd_2O_3 NPs is much lower than that in the bulk. • The ratio r_2/r_1=1.8 for Gd_2O_3 NPs dispersions is favorable for T_1-weighted MRI. • Gd_2O_3 NPs dispersions had good MRI signal intensity just at lower Gd concentrations. • Gd concentrations of 0.2 mM and below in the Gd_2O_3 NPs dispersions were not toxic.

  8. Green Adeptness in the Synthesis and Stabilization of Copper Nanoparticles: Catalytic, Antibacterial, Cytotoxicity, and Antioxidant Activities

    Din, Muhammad Imran; Arshad, Farhan; Hussain, Zaib; Mukhtar, Maria

    2017-12-01

    Copper nanoparticles (CuNPs) are of great interest due to their extraordinary properties such as high surface-to-volume ratio, high yield strength, ductility, hardness, flexibility, and rigidity. CuNPs show catalytic, antibacterial, antioxidant, and antifungal activities along with cytotoxicity and anticancer properties in many different applications. Many physical and chemical methods have been used to synthesize nanoparticles including laser ablation, microwave-assisted process, sol-gel, co-precipitation, pulsed wire discharge, vacuum vapor deposition, high-energy irradiation, lithography, mechanical milling, photochemical reduction, electrochemistry, electrospray synthesis, hydrothermal reaction, microemulsion, and chemical reduction. Phytosynthesis of nanoparticles has been suggested as a valuable alternative to physical and chemical methods due to low cytotoxicity, economic prospects, environment-friendly, enhanced biocompatibility, and high antioxidant and antimicrobial activities. The review explains characterization techniques, their main role, limitations, and sensitivity used in the preparation of CuNPs. An overview of techniques used in the synthesis of CuNPs, synthesis procedure, reaction parameters which affect the properties of synthesized CuNPs, and a screening analysis which is used to identify phytochemicals in different plants is presented from the recent published literature which has been reviewed and summarized. Hypothetical mechanisms of reduction of the copper ion by quercetin, stabilization of copper nanoparticles by santin, antimicrobial activity, and reduction of 4-nitrophenol with diagrammatic illustrations are given. The main purpose of this review was to summarize the data of plants used for the synthesis of CuNPs and open a new pathway for researchers to investigate those plants which have not been used in the past.

  9. Lysozyme-loaded lipid-polymer hybrid nanoparticles: preparation, characterization and colloidal stability evaluation.

    Devrim, Burcu; Kara, Aslı; Vural, İmran; Bozkır, Asuman

    2016-11-01

    Lipid-polymer hybrid nanoparticles (LPNPs) are polymeric nanoparticles enveloped by lipid layers, which have emerged as a potent therapeutic nanocarrier alternative to liposomes and polymeric nanoparticles. The aim of this work was to develop, characterize and evaluate LPNPs to deliver a model protein, lysozyme. Lysozyme-loaded LPNPs were prepared by using the modified w/o/w double-emulsion-solvent-evaporation method. Poly-ɛ-caprolactone (PCL) was used as polymeric core material and tripalmitin:lechitin mixture was used to form a lipid shell around the LPNPs. LPNPs were evaluated for particle size distribution, zeta potential, morphology, encapsulation efficiency, in vitro drug release, stability and cytotoxicity. The DLS measurement results showed that the particle size of LPNPs ranged from 58.04 ± 1.95 nm to 2009.00 ± 0.52 nm. The AFM and TEM images of LPNPs demonstrate that LPNPs are spherical in shape. The protein-loading capacity of LPNPs ranged from 5.81% to 60.32%, depending on the formulation parameters. LPNPs displayed a biphasic drug release pattern with a burst release within 1 h, followed by sustained release afterward. Colloidal stability results of LPNPs in different media showed that particle size and zeta potential values of particles did not change significantly in all media except of FBS 100% for 120 h. Finally, the results of a cellular uptake study showed that LPNPs were significantly taken up by 83.3% in L929 cells. We concluded that the LPNPs prepared with PCL as polymeric core material and tripalmitin:lechitin mixture as lipid shell should be a promising choice for protein delivery.

  10. Stabilization of temperature during magnetic hyperthermia by Ce substituted magnetite nanoparticles

    Shaw, S.K.; Alla, S.K. [Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Meena, S.S. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Mandal, R.K. [Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Prasad, N.K., E-mail: nandkp.met@iitbhu.ac.in [Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

    2017-07-15

    Highlights: • Ce{sub x}Fe{sub 3−x}O{sub 4} (0.01 ≤ x ≤ 0.5) nanoparticles below 15 nm were synthesized by microwave refluxing method. • The saturation magnetization decreased with increased Ce concentration. • The sample displayed stabilization of temperature near 42 °C during magnetic hyperthermia. - Abstract: We report here magnetic hyperthermia using nanoparticles of Ce{sub x}Fe{sub 3−x}O{sub 4} (x = 0.01, 0.05, 0.1, 0.3 and 0.5) during which temperature was found to be stabilizing near 42 °C. This happens despite of their high saturation magnetization (M{sub S}) and Curie temperature (T{sub C}) values. It was observed that by selecting an appropriate magnetic field the temperature can be rose exactly near the therapeutic temperature and thus it will help to selectively kill the cancerous cells leaving normal cells unaffected. These nanoparticles (size around 8–15 nm) were produced by single step microwave refluxing technique. X-ray diffraction (XRD) analysis demonstrates that samples were essentially single phase except for x = 0.5 sample. The X-ray photoelectron spectroscopy (XPS) study for the samples demonstrated that Ce was present in both Ce{sup 3+} and Ce{sup 4+} states. The saturation magnetization value of the samples decreased sharply from 62 Am{sup 2}/kg for x = 0.01 to 19 Am{sup 2}/kg for x = 0.1. This value further decreased with increased Ce doping.

  11. Structure, electrical characteristics, and high-temperature stability of aerosol jet printed silver nanoparticle films

    Rahman, Md Taibur; McCloy, John; Panat, Rahul, E-mail: rahul.panat@wsu.edu, E-mail: rvchintalapalle@utep.edu [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99163 (United States); Ramana, C. V., E-mail: rahul.panat@wsu.edu, E-mail: rvchintalapalle@utep.edu [Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States)

    2016-08-21

    Printed electronics has emerged as a versatile eco-friendly fabrication technique to create sintered nanoparticle (NP) films on arbitrary surfaces with an excellent control over the film microstructure. While applicability of such films for high-temperature applications is not explored previously, herein we report the high-temperature electrical stability of silver (Ag) metal NP films fabricated using an Aerosol Jet based printing technique and demonstrate that this behavior is dictated by changes in the film microstructure. In-situ high temperature (24–500 °C) impedance spectroscopy measurements show that the real part of the impedance increases with increasing temperature up to 150 °C, at which point a decreasing trend prevails until 300 °C, followed again by an increase in impedance. The electrical behavior is correlated with the in-situ grain growth of the Ag NP films, as observed afterwards by scanning electron microscopy and X-ray diffraction (XRD), and could be tailored by controlling the initial microstructure through sintering conditions. Using combined diffraction and spectroscopic analytical methods, it is demonstrated the Aerosol Jet printed Ag NP films exhibit enhanced thermal stability and oxidation resistance. In addition to establishing the conditions for stability of Ag NP films, the results provide a fundamental understanding of the effect of grain growth and reduction in grain boundary area on the electrical stability of sintered NP films.

  12. Metal Hydride Nanoparticles with Ultrahigh Structural Stability and Hydrogen Storage Activity Derived from Microencapsulated Nanoconfinement.

    Zhang, Jiguang; Zhu, Yunfeng; Lin, Huaijun; Liu, Yana; Zhang, Yao; Li, Shenyang; Ma, Zhongliang; Li, Liquan

    2017-06-01

    Metal hydrides (MHs) have recently been designed for hydrogen sensors, switchable mirrors, rechargeable batteries, and other energy-storage and conversion-related applications. The demands of MHs, particular fast hydrogen absorption/desorption kinetics, have brought their sizes to nanoscale. However, the nanostructured MHs generally suffer from surface passivation and low aggregation-resisting structural stability upon absorption/desorption. This study reports a novel strategy named microencapsulated nanoconfinement to realize local synthesis of nano-MHs, which possess ultrahigh structural stability and superior desorption kinetics. Monodispersed Mg 2 NiH 4 single crystal nanoparticles (NPs) are in situ encapsulated on the surface of graphene sheets (GS) through facile gas-solid reactions. This well-defined MgO coating layer with a thickness of ≈3 nm efficiently separates the NPs from each other to prevent aggregation during hydrogen absorption/desorption cycles, leading to excellent thermal and mechanical stability. More interestingly, the MgO layer shows superior gas-selective permeability to prevent further oxidation of Mg 2 NiH 4 meanwhile accessible for hydrogen absorption/desorption. As a result, an extremely low activation energy (31.2 kJ mol -1 ) for the dehydrogenation reaction is achieved. This study provides alternative insights into designing nanosized MHs with both excellent hydrogen storage activity and thermal/mechanical stability exempting surface modification by agents. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Myricetin solid lipid nanoparticles: Stability assurance from system preparation to site of action.

    Gaber, Dina M; Nafee, Noha; Abdallah, Osama Y

    2017-11-15

    Myricetin - a natural flavonoid - has attracted a great interest due to its antioxidant and free-radical scavenging potential. However, its physicochemical instability critically impairs its dosage form design, evaluation and administration. In an attempt to protect from degradation, MYR was encapsulated into Gelucire-based solid lipid nanoparticles (SLNs). The impact of medium pH, processing temperature and different additives on the drug degradation either in free or nanoencapsulated form was assessed. MYR stability was further monitored in essential biorelevant fluids. Investigations have led to the recommendation that the presence of fat-soluble antioxidant is necessary during SLN preparation to protect the drug at high temperature. Meanwhile, physiological buffers as well as simulated fluids should be supplemented with stabilizers as tween 80 and Poloxamer 407, in addition to water-soluble antioxidant such as sodium sulfite. Interestingly, mucin-containing fluids are suggested to provide better protection to MYR, in contrast, cell culture media do not guarantee MYR stability. The degradation kinetics changed from 1st to 2nd order mechanism after MYR nanoencapsulation. In presence of the aforementioned additives, MYR-SLNs significantly reduced the drug degradation rate constant up to 300-folds and prolonged the half-life time up to 4500-folds compared to free MYR in physiological buffers (One-way ANOVA, p8h with no signs of degradation. The study emphasizes virtuous guidance regarding appropriate nanoencapsulation conditions and evaluation attributes ensuing MYR physicochemical stability. Copyright © 2017. Published by Elsevier B.V.

  14. Influence of different stabilizers on the encapsulation of desmopressin acetate into PLGA nanoparticles.

    Primavessy, Daniel; Günday Türeli, Nazende; Schneider, Marc

    2017-09-01

    To address targeting and bioavailability issues of peptidic drugs like desmopressin, the encapsulation into nanoparticles (NP) has become standard in pharmaceutics. This study investigated the encapsulation of desmopressin into PLGA NP by the use of pharmaceutically common stabilizers as a precursor to future, optional targeting and bioavailability experiments. Polymer dry weights were measured by freeze drying and thermo gravimetric analysis (TGA). Particle sizes (ranging between 105 and 130nm, PDIDoppler-Anemometry (LDA) respectively. Highest loading efficiencies, quantified by RP-HPLC, were achieved with Pluronic F-68 as stabilizer of the inner aqueous phase (1.16±0.07μg desmopressin/mg PLGA) and were significantly higher than coating approaches and approaches without stabilizer (0.74±0.01μg/mg). Optimized nanoformulations are thus in competition with the concentration of commercial non-nanoparticulate desmopressin products. Stability of desmopressin after the process was evaluated by HPLC peak purity analysis (diode array detector) and by mass spectrometry. Desmopressin was shown to remain intact during the whole process; however, despite these very good results the encapsulation efficiency turned out to be a bottle neck and makes the system a challenge for potential applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Structure, electrical characteristics, and high-temperature stability of aerosol jet printed silver nanoparticle films

    Rahman, Md Taibur; McCloy, John; Panat, Rahul; Ramana, C. V.

    2016-01-01

    Printed electronics has emerged as a versatile eco-friendly fabrication technique to create sintered nanoparticle (NP) films on arbitrary surfaces with an excellent control over the film microstructure. While applicability of such films for high-temperature applications is not explored previously, herein we report the high-temperature electrical stability of silver (Ag) metal NP films fabricated using an Aerosol Jet based printing technique and demonstrate that this behavior is dictated by changes in the film microstructure. In-situ high temperature (24–500 °C) impedance spectroscopy measurements show that the real part of the impedance increases with increasing temperature up to 150 °C, at which point a decreasing trend prevails until 300 °C, followed again by an increase in impedance. The electrical behavior is correlated with the in-situ grain growth of the Ag NP films, as observed afterwards by scanning electron microscopy and X-ray diffraction (XRD), and could be tailored by controlling the initial microstructure through sintering conditions. Using combined diffraction and spectroscopic analytical methods, it is demonstrated the Aerosol Jet printed Ag NP films exhibit enhanced thermal stability and oxidation resistance. In addition to establishing the conditions for stability of Ag NP films, the results provide a fundamental understanding of the effect of grain growth and reduction in grain boundary area on the electrical stability of sintered NP films.

  16. Structure, electrical characteristics, and high-temperature stability of aerosol jet printed silver nanoparticle films

    Rahman, Md Taibur; McCloy, John; Ramana, C. V.; Panat, Rahul

    2016-08-01

    Printed electronics has emerged as a versatile eco-friendly fabrication technique to create sintered nanoparticle (NP) films on arbitrary surfaces with an excellent control over the film microstructure. While applicability of such films for high-temperature applications is not explored previously, herein we report the high-temperature electrical stability of silver (Ag) metal NP films fabricated using an Aerosol Jet based printing technique and demonstrate that this behavior is dictated by changes in the film microstructure. In-situ high temperature (24-500 °C) impedance spectroscopy measurements show that the real part of the impedance increases with increasing temperature up to 150 °C, at which point a decreasing trend prevails until 300 °C, followed again by an increase in impedance. The electrical behavior is correlated with the in-situ grain growth of the Ag NP films, as observed afterwards by scanning electron microscopy and X-ray diffraction (XRD), and could be tailored by controlling the initial microstructure through sintering conditions. Using combined diffraction and spectroscopic analytical methods, it is demonstrated the Aerosol Jet printed Ag NP films exhibit enhanced thermal stability and oxidation resistance. In addition to establishing the conditions for stability of Ag NP films, the results provide a fundamental understanding of the effect of grain growth and reduction in grain boundary area on the electrical stability of sintered NP films.

  17. Curcuma mangga-Mediated Synthesis of Gold Nanoparticles: Characterization, Stability, Cytotoxicity, and Blood Compatibility

    Yiing Yee Foo

    2017-05-01

    Full Text Available The utilization of toxic chemicals as reducing and stabilizing agents in the preparation of gold nanoparticles (AuNPs has increased in vivo toxicity and thus limited its application in clinical settings. Herein, we propose an alternative method of preparing highly stable AuNPs, where non-toxic Curcuma mangga (CM extract was used as a single reducing and stabilizing agent to overcome the aforementioned constraints. The morphological images enunciated that the homogeneously dispersed AuNPs exhibited spherical morphology with an average particle diameter of 15.6 nm. Fourier Transform infrared (FTIR and cyclic voltammetry analysis demonstrated that carbonyl groups of terpenoids in CM extract played an important role in the formation and stabilization of AuNPs. Green-synthesized AuNPs were found to have good stability in physiological media after 24 h of dispersion. The AuNPs were also cytocompatible with human colon fibroblast cell (CCD-18Co and human lung fibroblast cell (MRC-5. Hemocompatibility tests revealed that the AuNPs were blood-compatible, with less than 10% of hemolysis without any aggregation of erythrocytes. The current study suggests potential in employing a CM-extract-based method in the preparation of AuNPs for anticancer diagnosis and therapy.

  18. Influence of Temperature on the Colloidal Stability of Polymer-Coated Gold Nanoparticles in Cell Culture Media.

    Zyuzin, Mikhail V; Honold, Tobias; Carregal-Romero, Susana; Kantner, Karsten; Karg, Matthias; Parak, Wolfgang J

    2016-04-06

    The temperature-dependence of the hydrodynamic diameter and colloidal stability of gold-polymer core-shell particles with temperature-sensitive (poly(N-isopropylacrylamide)) and temperature-insensitive shells (polyallylaminine hydrochloride/polystyrensulfonate, poly(isobutylene-alt-maleic anhydride)-graft-dodecyl) are investigated in various aqueous media. The data demonstrate that for all nanoparticle agglomeration, i.e., increase in effective nanoparticle size, the presence of salts or proteins in the dispersion media has to be taken into account. Poly(N-isopropylacrylamide) coated nanoparticles show a reversible temperature-dependent increase in size above the volume phase transition of the polymer shell when they are dispersed in phosphate buffered saline or in media containing protein. In contrast, the nanoparticles coated with temperature-insensitive polymers show a time-dependent increase in size in phosphate buffered saline or in medium containing protein. This is due to time-dependent agglomeration, which is particularly strong in phosphate buffered saline, and induces a time-dependent, irreversible increase in the hydrodynamic diameter of the nanoparticles. This demonstrates that one has to distinguish between temperature- and time-induced agglomerations. Since the size of nanoparticles regulates their uptake by cells, temperature-dependent uptake of thermosensitive and non-thermosensitive nanoparticles by cells lines is compared. No temperature-specific difference between both types of nanoparticles could be observed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Viscosity of the oil-in-water Pickering emulsion stabilized by surfactant-polymer and nanoparticle-surfactant-polymer system

    Sharma, Tushar; Kumar, G. Suresh; Chon, Bo Hyun; Sangwai, Jitendra S.

    2014-11-01

    Information on the viscosity of Pickering emulsion is required for their successful application in upstream oil and gas industry to understand their stability at extreme environment. In this work, a novel formulation of oil-in-water (o/w) Pickering emulsion stabilized using nanoparticle-surfactant-polymer (polyacrylamide) system as formulated in our earlier work (Sharma et al., Journal of Industrial and Engineering Chemistry, 2014) is investigated for rheological stability at high pressure and high temperature (HPHT) conditions using a controlled-strain rheometer. The nanoparticle (SiO2 and clay) concentration is varied from 1.0 to 5.0 wt%. The results are compared with the rheological behavior of simple o/w emulsion stabilized by surfactant-polymer system. Both the emulsions exhibit non-Newtonian shear thinning behavior. A positive shift in this behavior is observed for surfactant-polymer stabilized emulsion at high pressure conditions. Yield stress is observed to increase with pressure for surfactant-polymer emulsion. In addition, increase in temperature has an adverse effect on the viscosity of emulsion stabilized by surfactant-polymer system. In case of nanoparticle-surfactant-polymer stabilized o/w emulsion system, the viscosity and yield stress are predominantly constant for varying pressure and temperature conditions. The viscosity data for both o/w emulsion systems are fitted by the Herschel-Bulkley model and found to be satisfactory. In general, the study indicates that the Pickering emulsion stabilized by nanoparticle-surfactant-polymer system shows improved and stable rheological properties as compared to conventional emulsion stabilized by surfactant-polymer system indicating their successful application for HPHT environment in upstream oil and gas industry.

  20. The cellular responses and antibacterial activities of silver nanoparticles stabilized by different polymers

    Lin, Jiang-Jen; Lin, Wen-Chun; Dong, Rui-Xuan; Hsu, Shan-hui

    2012-02-01

    Silver nanoparticles (AgNPs) are known for their excellent antibacterial activities. The possible toxicity, however, is a major concern for their applications. Three types of AgNPs were prepared in this study by chemical processes. Each was stabilized by a polymer surfactant, which was expected to reduce the exposure of cells to AgNPs and therefore their cytotoxicity. The polymer stabilizers included poly(oxyethylene)-segmented imide (POEM), poly(styrene-co-maleic anhydride)-grafting poly(oxyalkylene) (SMA) and poly(vinyl alcohol) (PVA). The cytotoxicity of these chemically produced AgNPs to mouse skin fibroblasts (L929), human hepatocarcinoma cells (HepG2), and mouse monocyte macrophages (J774A1) was compared to that of physically produced AgNPs and gold nanoparticles (AuNPs) as well as the standard reference material RM8011 AuNPs. Results showed that SMA-AgNPs were the least cytotoxic among all materials, but cytotoxicity was still observed at higher silver concentrations (>30 ppm). Macrophages demonstrated the inflammatory response with cell size increase and viability decrease upon exposure to 10 ppm of the chemically produced AgNPs. SMA-AgNPs did not induce hemolysis at a silver concentration below 1.5 ppm. Regarding the antibacterial activity, POEM-AgNPs and SMA-AgNPs at 1 ppm silver content showed 99.9% and 99.3% growth inhibition against E. coli, while PVA-AgNPs at the same silver concentration displayed 79.1% inhibition. Overall, SMA-AgNPs demonstrated better safety in vitro and greater antibacterial effects than POEM-AgNPs and PVA-AgNPs. This study suggested that polymer stabilizers may play an important role in determining the toxicity of AgNPs.

  1. Improvement of the stability and activity of immobilized glucose oxidase on modified iron oxide magnetic nanoparticles

    Abbasi, Mahboube; Amiri, Razieh; Bordbar, Abdol-Kalegh; Ranjbakhsh, Elnaz; Khosropour, Ahmad-Reza

    2016-02-01

    Immobilized proteins and enzymes are widely investigated in the medical field as well as the food and environmental fields. In this study, glucose oxidase (GOX) was covalently immobilized on the surface of modified iron oxide magnetic nanoparticles (MIMNs) to produce a bioconjugate complex. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to the size, shape and structure characterization of the MIMNs. Binding of GOX to these MIMNs was confirmed by using FT-IR spectroscopy. The stability of the immobilized and free enzyme at different temperature and pH values was investigated by measuring the enzymatic activity. These studies reveal that the enzyme's stability is enhanced by immobilization. Further experiments showed that the storage stability of the enzyme is improved upon binding to the MIMNs. The results of kinetic measurements suggest that the effect of the immobilization process on substrate and product diffusion is small. Such bioconjugates can be considered as a catalytic nanodevice for accelerating the glucose oxidation reaction for biotechnological purposes.

  2. Effect of laundry surfactants on surface charge and colloidal stability of silver nanoparticles.

    Skoglund, Sara; Lowe, Troy A; Hedberg, Jonas; Blomberg, Eva; Wallinder, Inger Odnevall; Wold, Susanna; Lundin, Maria

    2013-07-16

    The stability of silver nanoparticles (Ag NPs) potentially released from clothing during a laundry cycle and their interactions with laundry-relevant surfactants [anionic (LAS), cationic (DTAC), and nonionic (Berol)] have been investigated. Surface interactions between Ag NPs and surfactants influence their speciation and stability. In the absence of surfactants as well as in the presence of LAS, the negatively charged Ag NPs were stable in solution for more than 1 day. At low DTAC concentrations (≤1 mM), DTAC-Ag NP interactions resulted in charge neutralization and formation of agglomerates. The surface charge of the particles became positive at higher concentrations due to a bilayer type formation of DTAC that prevents from agglomeration due to repulsive electrostatic forces between the positively charged colloids. The adsorption of Berol was enhanced when above its critical micelle concentration (cmc). This resulted in a surface charge close to zero and subsequent agglomeration. Extended DLVO theory calculations were in compliance with observed findings. The stability of the Ag NPs was shown to depend on the charge and concentration of the adsorbed surfactants. Such knowledge is important as it may influence the subsequent transport of Ag NPs through different chemical transients and thus their potential bioavailability and toxicity.

  3. Effect of nanoparticle metal composition: mono- and bimetallic gold/copper dendrimer stabilized nanoparticles as solvent-free styrene oxidation catalysts

    Blanckenberg, A.; Kotze, G.; Swarts, A. J.; Malgas-Enus, R.

    2018-02-01

    A range of mono- and bimetallic AumCun nanoparticles (NPs), with varying metal compositions, was prepared by using a third-generation diaminobutane poly(propylene imine) (G3 DAB-PPI) dendrimer, modified with alkyl chains, as a stabilizer. It was found that the length of the peripheral alkyl chain, ( M1 (C15), M2 (C11), and M3 (C5)), had a direct influence on the average nanoparticle size obtained, confirming the importance of the nanoparticle stabilizer during synthesis. The Au NPs showed the highest degree of agglomeration and polydispersity, whereas the Cu NPs were the smallest and most monodisperse of the NPs. The bimetallic NPs sizes were found to vary between those of the monometallic NPs, depending on the metal composition. Interestingly, the bimetallic NPs were found to be the most stable, showing very little variation in size over time, even up to 9 months. The DSNs were evaluated in the catalytic oxidation of styrene, using either H2O2 or TBHP as oxidant. Here, we show that the bimetallic DSNs are indeed the superior catalysts when compared to their monometallic analogues, under the same reaction conditions, since a good compromise between stability and activity can be achieved where the Au provides catalytic activity and the Cu serves as a stabilizer. These AumCun bimetallic DSNs present a less expensive and more stable catalyst with negligible loss of activity, opening the door to green catalysis.

  4. Immobilization of non-point phosphorus using stabilized magnetite nanoparticles with enhanced transportability and reactivity in soils

    Pan Gang; Li Lei; Zhao Dongye; Chen Hao

    2010-01-01

    Laboratory batch and column experiments were conducted to investigate the immobilization of phosphorus (P) in soils using synthetic magnetite nanoparticles stabilized with sodium carboxymethyl cellulose (CMC-NP). Although CMC-stabilized magnetite particles were at the nanoscale, phosphorus removal by the nanoparticles was less than that of microparticles (MP) without the stabilizer due to the reduced P reactivity caused by the coating. The P reactivity of CMC-NP was effectively recovered when cellulase was added to degrade the coating. For subsurface non-point P pollution control for a water pond, it is possible to inject CMC-NP to form an enclosed protection wall in the surrounding soils. Non-stabilized 'nanomagnetite' could not pass through the soil column under gravity because it quickly agglomerated into microparticles. The immobilized P was 30% in the control soil column, 33% when treated by non-stabilized MP, 45% when treated by CMC-NP, and 73% when treated by both CMC-NP and cellulase. - CMC-stabilized magnetite nanoparticles can effectively penetrate soil columns and immobilize phosphate in situ.

  5. Thermal stability and fracture toughness of epoxy resins modified with epoxidized castor oil and Al2O3 nanoparticles

    Zhu, Lin; Jin, Fanlong; Park, Soojin

    2012-01-01

    This study examined the effects of the epoxidized castor oil (ECO) and Al 2 O 3 content on the thermal stability and fracture toughness of the diglycidylether of bisphenol-A (DGEBA)/ECO/Al 2 O 3 ternary composites using a range of techniques. The thermal stability of the composites was decreased by the addition of ECO and Al 2 O 3 nanoparticles. The fracture toughness of the composites was improved significantly by the addition of ECO and Al 2 O 3 nanoparticles. The composite containing 3 wt % Al 2 O 3 nanoparticles showed the maximum flexural strength. Scanning electron microscopy (SEM) revealed tortuous cracks in the DGEBA/ECO/Al 2 O 3 composites, which prevented deformation and crack propagation

  6. A fast method for the determination of lead in honey samples using stabilizer-free silver nanoparticles

    Bittar, Dayana Borges; Catelani, Tiago Augusto; Pezza, Leonardo; Pezza, Helena Redigolo

    2018-01-01

    A sensitive, rapid and robust method based on the use of stabilizer-free silver nanoparticles was developed for lead detection in honey. Silver nanoparticles were synthesized without the presence of any stabilizers using silver nitrate and sodium borohydride as precursors where the latter was applied as reducing agent. The optimization of the experimental variables (AgNO3 and NaBH4) for the formation of the nanoparticles was carried out using varying volumes of these solutions. Spectrophotometric measurements at 393 nm showed a linear working range between 0.0500 and 0.167 mg L- 1 lead (R = 0.994), with limits of detection (LOD) and quantification (LOQ) of 0.0135 and 0.0451 mg L- 1, respectively. The proposed method proved to be a significantly sensitive mechanism for lead detection in honey samples.

  7. Moderating effect of ammonia on particle growth and stability of quasi-monodisperse silver nanoparticles synthesized by the Turkevich method.

    Gorup, Luiz F; Longo, Elson; Leite, Edson R; Camargo, Emerson R

    2011-08-15

    A new method to stabilize silver nanoparticles by the addition of ammonia is proposed. Colloidal dispersions of silver nanoparticles were synthesized by the Turkevich method using sodium citrate to reduce silver nitrate at high pH and at 90 °C. After approximately 12 min, a diluted ammonia solution was added to the reaction flask to form soluble diamine silver (I) complexes that played an important growth moderating role, making it possible to stabilize metallic silver nanoparticles with sizes as small as 1.6 nm after 17 min of reaction. Colloidal dispersions were characterized by UV-visible absorption spectroscopy, X-ray diffraction, and transmission electronic microscopy. Copyright © 2011 Elsevier Inc. All rights reserved.

  8. High impact of in situ dextran coating on biocompatibility, stability and magnetic properties of iron oxide nanoparticles.

    Shaterabadi, Zhila; Nabiyouni, Gholamreza; Soleymani, Meysam

    2017-06-01

    Biocompatible ferrofluids based on dextran coated iron oxide nanoparticles were fabricated by conventional co-precipitation method. The experimental results show that the presence of dextran in reaction medium not only causes to the appearance of superparamagnetic behavior but also results in significant suppression in saturation magnetization of dextran coated samples. These results can be attributed to size reduction originated from the role of dextran as a surfactant. Moreover, weight ratio of dextran to magnetic nanoparticles has a remarkable influence on size and magnetic properties of nanoparticles, so that the sample prepared with a higher weight ratio of dextran to nanoparticles has the smaller size and saturation magnetization compare with the other samples. In addition, the ferrofluids containing such nanoparticles have an excellent stability at physiological pH for several months. Furthermore, the biocompatibility studies reveal that surface modification of nanoparticles by dextran dramatically decreases the cytotoxicity of bare nanoparticles and consequently improves their potential application for diagnostic and therapeutic purposes. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Stability of silver nanoparticle monolayers determined by in situ streaming potential measurements

    Morga, Maria; Adamczyk, Zbigniew; Oćwieja, Magdalena

    2013-01-01

    A silver particle suspension obtained by a chemical reduction was used in this work. Monolayers of these particles (average size 28 nm) on mica modified by poly(allylamine hydrochloride) were produced under diffusion-controlled transport. Monolayer coverages, quantitatively determined by atomic force microscopy (AFM) and SEM, was regulated by adjusting the nanoparticle deposition time and the suspension concentration. The zeta potential of the monolayers was determined by streaming potential measurements carried out under in situ (wet) conditions. These measurements performed for various ionic strengths and pH were interpreted in terms of the three-dimensional (3D) electrokinetic model. The stability of silver monolayers was also investigated using streaming potential and the AFM methods. The decrease in the surface coverage of particles as a function of time and ionic strength varied between 10 −1 and 10 −4  M was investigated. This allowed one to determine the equilibrium adsorption constant K a and the binding energy of silver particles (energy minima depth). Energy minima depth were calculated that varied between −18 kT for I = 10 −1  M and −19 kT for I = 10 −4 for pH 5.5 and T = 298 K. Our investigations suggest that the interactions between surface and nanoparticles are controlled by the electrostatic interactions among ion pairs. It was also shown that the in situ electrokinetic measurements are in accordance with those obtained by more tedious ex situ AFM measurements. This confirmed the utility of the streaming potential method for direct kinetic studies of nanoparticle deposition/release processes.Graphical Abstract

  10. Cellular uptake of beta-carotene from protein stabilized solid lipid nano-particles prepared by homogenization-evaporation method

    Using a homogenization-evaporation method, beta-carotene (BC) loaded nano-particles were prepared with different ratios of food-grade sodium caseinate (SC), whey protein isolate (WPI), or soy protein isolate (SPI) to BC and evaluated for their physiochemical stability, in vitro cytotoxicity, and cel...

  11. Transport and retention of surfactant- and polymer-stabilized engineered silver nanoparticles in silicate-dominated aquifer material

    Packed column experiments were conducted to investigate the transport and blocking behavior of surfactant- and polymer-stabilized engineered silver nanoparticles (Ag-ENPs) in saturated natural aquifer material with varying silt and clay content, background solution chemistry, and flow velocity. Brea...

  12. Effect of the Freezing Step in the Stability and Bioactivity of Protein-Loaded PLGA Nanoparticles Upon Lyophilization

    Fonte, Pedro; Andrade, Fernanda; Azevedo, Cláudia

    2016-01-01

    , sucrose and sorbitol as cryoprotectants was evaluated. METHODS: Cryoprotectants were co-encapsulated with insulin into PLGA nanoparticles and lyophilized using an optimized cycle with freezing at -80°C, in liquid nitrogen, or ramped cooling at -40°C. Upon lyophilization, the stability of protein structure...

  13. Exploring the Stability of Gold Nanoparticles by Experimenting with Adsorption Interactions of Nanomaterials in an Undergraduate Lab

    Lee, Chi-Feng; You, Pei-Yun; Lin, Ying-Chiao; Hsu, Tsai-Ling; Cheng, Pi-Yun; Wu, Yu-Xuan; Tseng, Chi-Shun; Chen, Sheng-Wen; Chang, Huey-Por; Lin, Yang-Wei

    2015-01-01

    The proposed experiment can help students to understand the factors involved in the stability of gold nanoparticles (Au NPs) by exploring the adsorption interaction between Au NPs and various substances. The students in this study found that the surface plasmon resonance band of Au NP solutions underwent a red shift (i.e., from 520 to 650 nm)…

  14. Effects of different combinations of nanocrystallization technologies on avanafil nanoparticles: in vitro, in vivo and stability evaluation.

    Soliman, Kareem AbuBakr; Ibrahim, Howida Kamal; Ghorab, Mahmoud Mohammed

    2017-01-30

    The study investigated the effects of different combined top-down and bottom-up nanocrystallization technologies on particle size and solid state of avanafil nanoparticles. Combined antisolvent precipitation-ultrasonication (sonoprecipitation) technique was adopted to prepare 18 formulas according to 3 2 .2 1 factorial design using 3 stabilizers; Tween 80, polyvinyl alcohol (PVA) and Pluronic F68 at different concentrations with different cryoprotectants. Particle size analysis of the lyophilized formulas showed that Tween 80 was an effective nanoparticles stabilizer in contrast to Pluronic F68 and PVA which failed to prevent nanoparticles flocculation when they were used at high concentration. The combined effects of nanonization and amorphism contributed to the improvement in solubility. Further processing of the sonoprecipitated formulas by high pressure homogenization (HPH) (modified NANOEDGE™ technology) resulted in further size reduction of PVA-stabilized particles, while it stimulated flocculation of Tween-stabilized nanoparticles. Nevertheless, all of the homogenized formulas partially retrieved their crystallinity which reduced their solubility. Non-homogenized formula 2E composed of 1:2 (avanafil: Tween) with glucose as cryoprotectant, exhibited 13.68- and 2.59-fold improvement in solubility and in vitro dissolution, respectively. This formula had oral bioavailability of 137.02% relative to Spedra ® tablets and it maintained its nanosize, amorphism and dissolution behavior over 6 months of storage under stress conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Mesquite Gum as a Novel Reducing and Stabilizing Agent for Modified Tollens Synthesis of Highly Concentrated Ag Nanoparticles

    Maira Berenice Moreno‐Trejo

    2016-10-01

    Full Text Available The synthesis that is described in this study is for the preparation of silver nanoparticles of sizes ranging from 10 nm to 30 nm with a defined shape (globular, confirmed by UV-vis, SEM, STEM and DLS analysis. This simple and favorable one-step modified Tollens reaction does not require any special equipment or other stabilizing or reducing agent except for a solution of purified mesquite gum, and it produces aqueous colloidal dispersions of silver nanoparticles with a stability thatexceeds three months, a relatively narrow size distribution, a low tendency to aggregate and a yield of at least 95% for all cases. Reaction times are between 15 min and 60 min to obtain silver nanoparticles in concentrations ranging from 0.1 g to 3 g of Ag per 100 g of reaction mixture. The proposed synthetic method presents a high potential for scale-up, since its production capacity is rather high and the methodology is simple.The synthesis that is described in this study is for the preparation of silver nanoparticles of sizes ranging from 10 nm to 30 nm with a defined shape (globular, confirmed by UV-vis, SEM, STEM and DLS analysis. This simple and favorable one-step modified Tollens reaction does not require any special equipment or other stabilizing or reducing agent except for a solution of purified mesquite gum, and it produces aqueous colloidal dispersions of silver nanoparticles with a stability thatexceeds three months, a relatively narrow size distribution, a low tendency to aggregate and a yield of at least 95% for all cases. Reaction times are between 15 min and 60 min to obtain silver nanoparticles in concentrations ranging from 0.1 g to 3 g of Ag per 100 g of reaction mixture. The proposed synthetic method presents a high potential for scale-up, since its production capacity is rather high and the methodology is simple.

  16. Titania nanotube stabilized BiOCl nanoparticles in visible-light photocatalysis

    Buchholcz, B.

    2017-03-14

    Photocatalysis is a green approach in environmental organic pollutant decomposition. Lately, considerable improvement in the activity of photocatalysts has been achieved with the realization of p–n heterostructures due to the lifetime extension of the photogenerated charge carriers. Herein, we report a facile synthesis approach for decorating n-type titanate nanotubes with p-type V–VI–VII compound semiconductor BiOCl nanoparticles. It is well-known that BiOX (X = Cl, Br, I) materials form nanometer-thick platelets, which can eventually assemble into micrometer size flower-like 3D structures. Here, we demonstrate that the tubular titanate support can stabilize BiOCl on its surface in the form of nanoparticles measuring a few nanometers in diameter, instead of forming the well-known bismuth-oxyhalide nanoflowers. Subsequent calcination at 400 °C transforms the pristine titanate structures into one-dimensional anatase nanotubes, along with the formation of a heterojunction at the interface of the emerging Bi2Ti2O7 and anatase phases. The resulting nanocomposite shows activity in visible-light photocatalytic test reactions.

  17. The structure and binding mode of citrate in the stabilization of gold nanoparticles

    Al-Johani, Hind

    2017-03-27

    Elucidating the binding mode of carboxylate-containing ligands to gold nanoparticles (AuNPs) is crucial to understand their stabilizing role. A detailed picture of the three-dimensional structure and coordination modes of citrate, acetate, succinate and glutarate to AuNPs is obtained by 13C and 23Na solid-state NMR in combination with computational modelling and electron microscopy. The binding between the carboxylates and the AuNP surface is found to occur in three different modes. These three modes are simultaneously present at low citrate to gold ratios, while a monocarboxylate monodentate (1κO1) mode is favoured at high citrate:gold ratios. The surface AuNP atoms are found to be predominantly in the zero oxidation state after citrate coordination, although trace amounts of Auδ+ are observed. 23Na NMR experiments show that Na+ ions are present near the gold surface, indicating that carboxylate binding occurs as a 2e− L-type interaction for each oxygen atom involved. This approach has broad potential to probe the binding of a variety of ligands to metal nanoparticles.

  18. Impacts of select organic ligands on the colloidal stability, dissolution dynamics, and toxicity of silver nanoparticles.

    Pokhrel, Lok R; Dubey, Brajesh; Scheuerman, Phillip R

    2013-11-19

    Key understanding of potential transformations that may occur on silver nanoparticle (AgNP) surface upon interaction with naturally ubiquitous organic ligands (e.g., -SH (thoil), humic acid, or -COO (carboxylate)) is limited. Herein we investigated how dissolved organic carbon (DOC), -SH (in cysteine, a well-known Ag(+) chelating agent), and -COO (in trolox, a well-known antioxidant) could alter the colloidal stability, dissolution rate, and toxicity of citrate-functionalized AgNPs (citrate-AgNPs) against a keystone crustacean Daphnia magna. Cysteine, DOC, or trolox amendment of citrate-AgNPs differentially modified particle size, surface properties (charge, plasmonic spectra), and ion release dynamics, thereby attenuating (with cysteine or trolox) or promoting (with DOC) AgNP toxicity. Except with DOC amendment, the combined toxicity of AgNPs and released Ag under cysteine or trolox amendment was lower than of AgNO3 alone. The results of this study show that citrate-AgNP toxicity can be associated with oxidative stress, ion release, and the organism biology. Our evidence suggests that specific organic ligands available in the receiving waters can differentially surface modify AgNPs and alter their environmental persistence (changing dissolution dynamics) and subsequently the toxicity; hence, we caveat to generalize that surface modified nanoparticles upon environmental release may not be toxic to receptor organisms.

  19. Colloidal stability of carbonate-coated silver nanoparticles in synthetic and natural freshwater.

    Piccapietra, Flavio; Sigg, Laura; Behra, Renata

    2012-01-17

    To gain important information on fate, mobility, and bioavailability of silver nanoparticles (AgNP) in aquatic systems, the influence of pH, ionic strength, and humic substances on the stability of carbonate-coated AgNP (average diameter 29 nm) was systematically investigated in 10 mM carbonate and 10 mM MOPS buffer, and in filtered natural freshwater. Changes in the physicochemical properties of AgNP were measured using nanoparticle tracking analysis, dynamic light scattering, and ultraviolet-visible spectroscopy. According to the pH-dependent carbonate speciation, below pH 4 the negatively charged surface of AgNP became positive and increased agglomeration was observed. Electrolyte concentrations above 2 mM Ca(2+) and 100 mM Na(+) enhanced AgNP agglomeration in the synthetic media. In the considered concentration range of humic substances, no relevant changes in the AgNP agglomeration state were measured. Agglomeration of AgNP exposed in filtered natural freshwater was observed to be primarily controlled by the electrolyte type and concentration. Moreover, agglomerated AgNP were still detected after 7 days of exposure. Consequently, slow sedimentation and high mobility of agglomerated AgNP could be expected under the considered natural conditions. A critical evaluation of the different methods used is presented as well.

  20. The structure and binding mode of citrate in the stabilization of gold nanoparticles

    Al-Johani, Hind; Abou-Hamad, Edy; Jedidi, Abdesslem; Widdifield, Cory M.; Viger-Gravel, Jasmine; Sangaru, Shiv; Gajan, David; Anjum, Dalaver H.; Ould-Chikh, Samy; Hedhili, Mohamed N.; Gurinov, Andrei; Kelly, Michael J.; El Eter, Mohamad; Cavallo, Luigi; Basset, Jean-Marie; Basset, Jean-Marie

    2017-01-01

    Elucidating the binding mode of carboxylate-containing ligands to gold nanoparticles (AuNPs) is crucial to understand their stabilizing role. A detailed picture of the three-dimensional structure and coordination modes of citrate, acetate, succinate and glutarate to AuNPs is obtained by 13C and 23Na solid-state NMR in combination with computational modelling and electron microscopy. The binding between the carboxylates and the AuNP surface is found to occur in three different modes. These three modes are simultaneously present at low citrate to gold ratios, while a monocarboxylate monodentate (1κO1) mode is favoured at high citrate:gold ratios. The surface AuNP atoms are found to be predominantly in the zero oxidation state after citrate coordination, although trace amounts of Auδ+ are observed. 23Na NMR experiments show that Na+ ions are present near the gold surface, indicating that carboxylate binding occurs as a 2e− L-type interaction for each oxygen atom involved. This approach has broad potential to probe the binding of a variety of ligands to metal nanoparticles.

  1. Obtaining Highly Crystalline Barium Sulphate Nanoparticles via Chemical Precipitation and Quenching in Absence of Polymer Stabilizers

    Ángela B. Sifontes

    2015-01-01

    Full Text Available Here we report the synthesis of barium sulphate (BaSO4 nanoparticles from Ba(OH2/BaCl2 solutions by a combined method of precipitation and quenching in absence of polymer stabilizers. Transmission electron microscopy (HRTEM, Fourier transforms infrared spectroscopy (FTIR, and X-ray diffraction (XRD were employed to characterize the particles. The Scherrer formula was applied to estimate the particle size using the width of the diffraction peaks. The obtained results indicate that the synthesized material is mainly composed of nanocrystalline barite, with nearly spherical morphology, and diameters ranging from 4 to 92 nm. The lattice images of nanoparticles were clearly observed by HRTEM, indicating a high degree of crystallinity and phase purity. In addition, agglomerates with diameters between 20 and 300 nm were observed in both lattice images and dynamic light scattering measurements. The latter allowed obtaining the particle size distribution, the evolution of the aggregate size in time of BaSO4 in aqueous solutions, and the sedimentation rate of these solutions from turbidimetry measurements. A short discussion on the possible medical applications is presented.

  2. Analysis of the Evolution of Tannic Acid Stabilized Gold Nanoparticles Using Mie Theory

    Assia Rachida Senoudi

    2014-01-01

    Full Text Available Spherical gold nanoparticles (GNPs have been synthesized in aqueous solutions using sodium citrate (SC and tannic acid (TA as reducing and stabilizing agents. Upon addition of TA and compared to the GNP TA-free aqueous solutions, a reduction of the GNPs size and consequently a dramatic change of their optical properties have been observed and quantitatively analyzed using Mie theory. An increase in the concentration of TA reveals a modification of the colloidal solution refractive index that is evidenced by the shift in the peak position of the localized surface plasmon resonance (LSPR band. The variations of the peak absorbance with the TA concentration are examined in the low and high concentration regimes.

  3. Time-dependent preparation of gelatin-stabilized silver nanoparticles by pulsed Nd:YAG laser

    Darroudi, Majid; Ahmad, M. B.; Zamiri, Reza; Abdullah, A. H.; Ibrahim, N. A.; Sadrolhosseini, A. R.

    2011-03-01

    Colloidal silver nanoparticles (Ag-NPs) were successfully prepared using a nanosecond pulsed Nd:YAG laser, λ = 1064 nm, with laser fluence of approximately about 360 mJ/pulse, in an aqueous gelatin solution. In this work, gelatin was used as a stabilizer, and the size and optical absorption properties of samples were studied as a function of the laser ablation times. The results from the UV-vis spectroscopy demonstrated that the mean diameter of Ag-NPs decrease as the laser ablation time increases. The Ag-NPs have mean diameters ranging from approximately 10 nm to 16 nm. Compared with other preparation methods, this work is clean, rapid, and simple to use.

  4. Study on gamma radiation-induced synthesis of gold nanoparticles stabilized by hyaluronan

    Dang Van Phu; Bui Duy Du

    2013-01-01

    Gold nanoparticles (AuNPs) with diameter from 4 to 10 nm were synthesized by γ-irradiation in hyaluronan (HA) solution without usage of any OH radical scavenger. The size distribution of AuNPs were determined by TEM images. The λ max (517-525 nm) of colloidal AuNPs solutions as prepared was measured by UV-Vis spectroscopy. The influence factor on the size of AuNPs particularly the concentration of Au 3+ , HA and dose rate were investigated. The colloidal solution of AuNPs/HA as synthesized was stable more than 6 months stored under ambient condition. AuNPs with the size less than 10 nm narrow size distribution stabilized by HA which is biocompatible polysaccharide can potentially be applied in biomedicine and cosmetic. (author)

  5. Stability of silver nanoparticles: agglomeration and oxidation in biological relevant conditions

    Valenti, Laura E.; Giacomelli, Carla E.

    2017-05-01

    Silver nanoparticles (Ag-NP) are the most used nanomaterial in consumer products due to the intrinsic antimicrobial capacity of silver. However, Ag-NP may be also harmful to algae, aquatic species, mammalian cells, and higher plants because both Ag+ and nanoparticles are responsible of cell damages. The oxidative dissolution of Ag-NP would proceed to completion under oxic conditions, but the rate and extent of the dissolution depend on several factors. This work correlates the effect of the capping agent (albumin and citrate) with the stability of Ag-NP towards agglomeration in simulated body fluid (SBF) and oxidation in the presence of ROS species (H2O2). Capping provides colloidal stability only through electrostatic means, whereas albumin acts as bulky ligands giving steric and electrostatic repulsion, inhibiting the agglomeration in SBF. However, citrate capping protects Ag-NP from dissolution to a major extent than albumin does because of its reducing power. Moreover, citrate in solution minimizes the oxidation of albumin-coated Ag-NP even after long incubation times. H2O2-induced dissolution proceeds to completion with Ag-NP incubated in SBF, while incubation in citrate leads to an incomplete oxidation. In short, albumin is an excellent capping agent to minimize Ag-NP agglomeration whereas citrate provides a mild-reductive medium that prevents dissolution in biological relevant media as well as in the presence of ROS species. These results provide insight into how the surface properties and media composition affect the release of Ag+ from Ag-NP, related to the cell toxicity and relevant to the storage and lifetime of silver-containing nanomaterials.

  6. Stability Studies of Certain Chemotherapeutic Agents Following Gamma Irradiation and Silver Nanoparticles Conjugation

    El-Sayyad, Gh.E.S.M.

    2014-01-01

    The Chemical stability of drug is of great importance since it becomes less effective as it undergoes degradation in case of applied of gamma irradiation process. The application of gamma irradiation for different chemotherapeutic agents Such as (ofloxacin, sodium ampicillin, sodium cefotaxime, gentamycin and amoxicillin) and studying the effect of applied doses on chemical structure and biological activity of the irradiated antibiotics compared to unirradiated ones was studied by ultraviolet-Visible spectrophotometer (UV-Visible), Fourier transform infrared spectroscopy measurements (FTIR spectra) and high performance liquid chromatography (HPLC) in addition to microbiological assay were run before and after irradiation to probe any change after irradiation. The results showed that all of the irradiated compounds remain stable and radio resistant; retaining their structure and activity unchanged up to 25 KGy. The radiation-induced AgNPs synthesis is a simple, clean which involves radiolysis of aqueous solution that provides an efficient method to reduce metal ions. Also, in this study, Bacillus megaterium was found to be an effective biological tool for the extracellular biosynthesis of stable AgNPs which are highly stable and this method has advantages over other methods as the organism used here is safe. This study would therefore lead to an easy procedure for producing silver nanoparticles with the added advantage of bio safety. The Synthesized AgNPs exhibit remarkable antimicrobial activity against both Gram-positive and Gram negative bacterial strains regardless of their drug-resistant mechanisms. The bactericidal activity have proved that AgNPs kill bacteria at such low concentrations (units of ppm), which Stability Studies of Certain Chemotherapeutic Agents Following Gamma Irradiation and Silver Nanoparticles Conjugation. do not reveal acute toxic effects on human cell, in addition to overcoming resistance, and lowering cost when compared to conventional

  7. Stability of silver nanoparticles: agglomeration and oxidation in biological relevant conditions

    Valenti, Laura E.; Giacomelli, Carla E., E-mail: giacomel@fcq.unc.edu.ar [Universidad Nacional de Córdoba, Ciudad Universitaria, Instituto de Investigaciones en Físico Química de Córdoba (INFIQC) CONICET-UNC, Departamento de Fisicoquímica, Facultad de Ciencias Químicas (Argentina)

    2017-05-15

    Silver nanoparticles (Ag-NP) are the most used nanomaterial in consumer products due to the intrinsic antimicrobial capacity of silver. However, Ag-NP may be also harmful to algae, aquatic species, mammalian cells, and higher plants because both Ag{sup +} and nanoparticles are responsible of cell damages. The oxidative dissolution of Ag-NP would proceed to completion under oxic conditions, but the rate and extent of the dissolution depend on several factors. This work correlates the effect of the capping agent (albumin and citrate) with the stability of Ag-NP towards agglomeration in simulated body fluid (SBF) and oxidation in the presence of ROS species (H{sub 2}O{sub 2}). Capping provides colloidal stability only through electrostatic means, whereas albumin acts as bulky ligands giving steric and electrostatic repulsion, inhibiting the agglomeration in SBF. However, citrate capping protects Ag-NP from dissolution to a major extent than albumin does because of its reducing power. Moreover, citrate in solution minimizes the oxidation of albumin-coated Ag-NP even after long incubation times. H{sub 2}O{sub 2}-induced dissolution proceeds to completion with Ag-NP incubated in SBF, while incubation in citrate leads to an incomplete oxidation. In short, albumin is an excellent capping agent to minimize Ag-NP agglomeration whereas citrate provides a mild-reductive medium that prevents dissolution in biological relevant media as well as in the presence of ROS species. These results provide insight into how the surface properties and media composition affect the release of Ag{sup +} from Ag-NP, related to the cell toxicity and relevant to the storage and lifetime of silver-containing nanomaterials.

  8. Brightly luminescent colloidal Ag–In–S nanoparticles stabilized in aqueous solutions by branched polyethyleneimine

    Raevskaya, Alexandra E.; Ivanchenko, Maria V.; Skoryk, Mykola A.; Stroyuk, Oleksandr L., E-mail: alstroyuk@ukr.net

    2016-10-15

    Silver indium sulfide nanoparticles (NPs) stabilized in water by branched polyethyleneimine (PEI) were produced by a mild and direct synthesis. The Ag–In–S NPs exhibit relatively bright photoluminescence (PL) in the visible spectral range. The key parameters influencing color and intensity of PL are the Ag:In and Ag:S molar ratios and duration of the post-synthesis thermal treatment at ~100 °C. A maximal PL quantum yield, 20%, was observed for the Ag–In–S–PEI NPs produced at a molar Ag:In:S ratio of 1:5:5 and a thermal treatment at ~100 °C for 2 h. Such NPs are characterized by an average hydrodynamic size of around 100 nm. According to SEM each 100-nm globule comprises many smaller Ag–In–S NPs. Reasonably high PL quantum yield, variability of the emission color and self-aggregation of Ag–In–S–PEI NPs into polymer globules that do not scatter light makes such NPs promising for the luminescent bio-labeling applications. The PL band maximum energy of the Ag–In–S–PEI NPs produced in optimal conditions is very close to the band gap derived from the absorption spectra of colloidal solutions indicating that PL originates from the radiative recombination of delocalized or shallowly trapped charge carriers. - Highlights: • Ag–In–S nanoparticles (NPs) stabilized by polyethyleneimine in water were synthesized. • Ag–In–S NPs emit bright visible photoluminescence varying in color from green to red. • Maximal quantum yield of emission, ~20%, is observed at a Ag:In:S ratio of 1:5:5. • Separate Ag–In–S NPs are assembled into ~100-nm polyethyleneimine globules.

  9. Enhanced stability and dissolution of CuO nanoparticles by extracellular polymeric substances in aqueous environment

    Miao, Lingzhan; Wang, Chao; Hou, Jun; Wang, Peifang; Ao, Yanhui; Li, Yi; Lv, Bowen; Yang, Yangyang; You, Guoxiang; Xu, Yi

    2015-01-01

    Stability of engineered nanoparticles in aquatic environment is an essential parameter to evaluate their fate, bioavailability, and potential toxic effects toward living organisms. As CuO NPs enter the wastewater systems, they will encounter extracellular polymeric substances (EPS) from microbial community before directly interacting with bacterial cells. EPS may play an important role in affecting the stability and the toxicity of CuO NPs in aquatic environment. In this study, the influences of flocculent sludge-derived EPS, as well as model protein (BSA) and natural polysaccharides (alginate) on the dissolution kinetics and colloidal stability of CuO NPs were investigated. Results showed that the presence of NOMs strongly suppressed CuO NPs aggregation, confirmed by DLS, zeta potentials, and TEM analysis. The enhanced stability of CuO NPs in the presence of EPS and alginate were attributed to the electrostatic combined with steric repulsion, while the steric-hindrance effect may be the predominant mechanism retarding nano-CuO aggregation for BSA. Higher degrees of copper release were achieved with the increasing concentrations of NOMs. EPS are more effective than alginate and BSA in releasing copper, probably due to the abundant functional groups and the excellent metal-binding capacity. The ratio of free-Cu 2+ /total dissolved Cu significantly decreased in the presence of EPS, indicating that EPS may affect the speciation and Cu bioavailability in aqueous environment. These results may be important for assessing the fate and transport behaviors of CuO NPs in the environment as well as for setting up usage regulation and treatment strategy.

  10. Enhanced stability and dissolution of CuO nanoparticles by extracellular polymeric substances in aqueous environment

    Miao, Lingzhan; Wang, Chao; Hou, Jun, E-mail: hhuhjyhj@126.com; Wang, Peifang; Ao, Yanhui; Li, Yi; Lv, Bowen; Yang, Yangyang; You, Guoxiang; Xu, Yi [Hohai University, Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education (China)

    2015-10-15

    Stability of engineered nanoparticles in aquatic environment is an essential parameter to evaluate their fate, bioavailability, and potential toxic effects toward living organisms. As CuO NPs enter the wastewater systems, they will encounter extracellular polymeric substances (EPS) from microbial community before directly interacting with bacterial cells. EPS may play an important role in affecting the stability and the toxicity of CuO NPs in aquatic environment. In this study, the influences of flocculent sludge-derived EPS, as well as model protein (BSA) and natural polysaccharides (alginate) on the dissolution kinetics and colloidal stability of CuO NPs were investigated. Results showed that the presence of NOMs strongly suppressed CuO NPs aggregation, confirmed by DLS, zeta potentials, and TEM analysis. The enhanced stability of CuO NPs in the presence of EPS and alginate were attributed to the electrostatic combined with steric repulsion, while the steric-hindrance effect may be the predominant mechanism retarding nano-CuO aggregation for BSA. Higher degrees of copper release were achieved with the increasing concentrations of NOMs. EPS are more effective than alginate and BSA in releasing copper, probably due to the abundant functional groups and the excellent metal-binding capacity. The ratio of free-Cu{sup 2+}/total dissolved Cu significantly decreased in the presence of EPS, indicating that EPS may affect the speciation and Cu bioavailability in aqueous environment. These results may be important for assessing the fate and transport behaviors of CuO NPs in the environment as well as for setting up usage regulation and treatment strategy.

  11. Interaction of Freshwater Diatom with Gold Nanoparticles: Adsorption, Assimilation, and Stabilization by Cell Exometabolites

    Aridane G. González

    2018-03-01

    Full Text Available The rising concern about the potential toxicity of synthetic gold nanoparticles (AuNPs in aquatic environments requires a rigorous estimation of physico-chemical parameters of reactions between AuNPs and major freshwater microorganisms. This study addresses the interaction of 10-nm size, positively charged AuNPs with periphytic freshwater diatoms (Eolimna minima. The adsorption experiments on viable cells were performed in 10 mM NaCl and 5 mM NaCl + 5 mM NaHCO3 solution at a variable pH (3–10, at an AuNPs concentration from 1 µg/L to 10,000 µg/L, and an exposure time from a few minutes to 55 days. Three types of experiments, adsorption as a function of time (kinetics, pH-dependent adsorption edge, and constant-pH “Langmuirian” type isotherms, were conducted. In addition, long-term interactions (days to weeks of live diatoms (under light and in the darkness were performed. The adsorption was maximal at a pH from 3 to 6 and sizably decreased at a pH of 6 to 10. Results of adsorption experiments were modeled using a second order kinetic model, a Linear Programming Model, Freundlich isotherm, and a ligand binding equation for one site competition. The adsorption of AuNPs(+ most likely occurred on negatively-charged surface sites of diatom cell walls such as carboxylates or phosphorylates, similar to previously studied metal cations. Under light exposure, the AuNPs were stabilized in aqueous solution in the presence of live cells, probably due to the production of exometabolites by diatoms. The adsorbed amount of AuNPs decreased after several days of reaction, suggesting some AuNPs desorption. In the darkness, the adsorption and assimilation were stronger than under light. Overall, the behavior of positively charged AuNPs at the diatom–aqueous solution interface is similar to that of metal cations, but the affinity of aqueous AuNPs to cell exometabolites is higher, which leads to the stabilization of nanoparticles in solution in the

  12. A Study On Dispersion Stability Of Nickel Nanoparticles Synthesized By Wire Explosion In Liquid Media

    Kim C.K.; Lee G.-J.; Lee M.K.; Rhee C.K.

    2015-01-01

    In this study, nickel nanoparticles were synthesized in ethanol using portable pulsed wire evaporation, which is a one-step physical method. From transmission electron microscopy images, it was found that the Ni nanoparticles exhibited a spherical shape with an average diameter of 7.3 nm. To prevent aggregation of the nickel nanoparticles, a polymer surfactant was added into the ethanol before the synthesis of nickel nanoparticles, and adsorbed on the freshly synthesized nickel nanoparticles ...

  13. Enhanced photocatalysis, colloidal stability and cytotoxicity of synchrotron X-ray synthesized Au/TiO2 nanoparticles

    Liu, Chi-Jen; Yang, Tsung-Yeh; Wang, Chang-Hai; Chien, Chia-Chi; Chen, Shin-Tai; Wang, Cheng-Liang; Leng, Wei-Hua; Hwu, Y.; Lin, Hong-Ming; Lee, Yao-Chang; Cheng, Chia-Liang; Je, J.H.; Margaritondo, G.

    2009-01-01

    Au/TiO 2 nanocomposite particles were synthesized by a method based on intense X-ray irradiation without adding any reducing agent or stabilizer. The nanocomposite exhibits promising photocatalytic and biological properties at physiologically relevant concentration ([Au] = 0.028 mM, [TiO 2 ] = 0.5 mM). The structure and photocatalysis were examined by X-ray diffraction, electron microscopy and ultraviolet-visible spectroscopy demonstrating that gold nanoparticles of 2-5 nm size were successfully deposited on TiO 2 nanoparticle surfaces. The nanocomposite exhibited good colloidal stability within a typical cellular environment and was nontoxic to cancer cell according to evaluations under controlled conditions. The Au/TiO 2 nanoparticles were also found to enhance the photocatalytic efficiency of UV radiation and even more that of X-ray radiation. In vitro studies indicated that the cell-killing effect under X-ray irradiation is more pronounced with the addition of Au/TiO 2 nanoparticles than of bare TiO 2 nanoparticles.

  14. Enhanced photocatalysis, colloidal stability and cytotoxicity of synchrotron X-ray synthesized Au/TiO{sub 2} nanoparticles

    Liu, Chi-Jen; Yang, Tsung-Yeh; Wang, Chang-Hai [Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan (China); Chien, Chia-Chi [Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan (China); Department of Engineering Science and System, National Tsing Hua University, Hsinchu 300, Taiwan (China); Chen, Shin-Tai; Wang, Cheng-Liang; Leng, Wei-Hua [Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan (China); Hwu, Y., E-mail: phhwu@sinica.edu.tw [Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan (China); Department of Engineering Science and System, National Tsing Hua University, Hsinchu 300, Taiwan (China); Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung 202, Taiwan (China); National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan (China); Lin, Hong-Ming [Department of Materials Engineering, Tatung University, Taipei 10461, Taiwan (China); Lee, Yao-Chang [National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan (China); Cheng, Chia-Liang [Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan (China); Je, J.H. [X-ray Imaging Center, Pohang University of Science and Technology, Pohang (Korea, Republic of); Margaritondo, G. [Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2009-09-15

    Au/TiO{sub 2} nanocomposite particles were synthesized by a method based on intense X-ray irradiation without adding any reducing agent or stabilizer. The nanocomposite exhibits promising photocatalytic and biological properties at physiologically relevant concentration ([Au] = 0.028 mM, [TiO{sub 2}] = 0.5 mM). The structure and photocatalysis were examined by X-ray diffraction, electron microscopy and ultraviolet-visible spectroscopy demonstrating that gold nanoparticles of 2-5 nm size were successfully deposited on TiO{sub 2} nanoparticle surfaces. The nanocomposite exhibited good colloidal stability within a typical cellular environment and was nontoxic to cancer cell according to evaluations under controlled conditions. The Au/TiO{sub 2} nanoparticles were also found to enhance the photocatalytic efficiency of UV radiation and even more that of X-ray radiation. In vitro studies indicated that the cell-killing effect under X-ray irradiation is more pronounced with the addition of Au/TiO{sub 2} nanoparticles than of bare TiO{sub 2} nanoparticles.

  15. Stability and dewetting of metal nanoparticle filled thin polymer films: control of instability length scale and dynamics.

    Mukherjee, Rabibrata; Das, Soma; Das, Anindya; Sharma, Satinder K; Raychaudhuri, Arup K; Sharma, Ashutosh

    2010-07-27

    We investigate the influence of gold nanoparticle addition on the stability, dewetting, and pattern formation in ultrathin polymer-nanoparticle (NP) composite films by examining the length and time scales of instability, morphology, and dynamics of dewetting. For these 10-50 nm thick (h) polystyrene (PS) thin films containing uncapped gold nanoparticles (diameter approximately 3-4 nm), transitions from complete dewetting to arrested dewetting to absolute stability were observed depending on the concentration of the particles. Experiments show the existence of three distinct stability regimes: regime 1, complete dewetting leading to droplet formation for nanoparticle concentration of 2% (w/w) or below; regime 2, partial dewetting leading to formation of arrested holes for NP concentrations in the range of 3-6%; and regime 3, complete inhibition of dewetting for NP concentrations of 7% and above. Major results are (a) length scale of instability, where lambdaH approximately hn remains unchanged with NP concentration in regime 1 (n approximately 2) but increases in regime 2 with a change in the scaling relation (n approximately 3-3.5); (b) dynamics of instability and dewetting becomes progressively sluggish with an increase in the NP concentration; (c) there are distinct regimes of dewetting velocity at low NP concentrations; (d) force modulation AFM, as well as micro-Raman analysis, shows phase separation and aggregation of the gold nanoparticles within each dewetted polymer droplet leading to the formation of a metal core-polymer shell morphology. The polymer shell could be removed by washing in a selective solvent, thus exposing an array of bare gold nanoparticle aggregates.

  16. Facile synthesis of octahedral Pt-Pd nanoparticles stabilized by silsesquioxane for the electrooxidation of formic acid

    Li, Yusong; Hao, Furui; Wang, Yihong; Zhang, Yihong; Ge, Cunwang; Lu, Tianhong

    2014-01-01

    Graphical abstract: The octahedral Pt-Pd alloy nanoparticles (octahedral Pt-Pd NPs) with dominant {111} facets were successfully synthesized through a facile route in the presence of octa(3-aminopropyl) silsesquioxane as the capping agent and complexing agent, methanol as the reductant and solvent. The octahedral Pt-Pd NPs display the significantly enhanced electrocatalytic activity, increased CO tolerance and favourable stability for the electrooxidation of formic acid. - Highlights: • Octa Pt-Pd nanoparticles were synthesized with silsesquioxane as capping agent. • Octa Pt-Pd nanoparticles display uniform morphology and favorable dispersibility. • Octa Pt-Pd nanoparticles have high catalytic activity for formic acid by direct process. - Abstract: The octahedral Pt-Pd alloy nanoparticles (octahedral Pt-Pd NPs) with dominant {111} facets were successfully synthesized through a facile route in the presence of octa(3-aminopropyl) silsesquioxane as the capping agent and complexing agent, methanol as the reductant and solvent. Their morphology, composition and structure were charactered by transmission electron microscopy (TEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD). The electrocatalytic activity, CO tolerance and stability of the octahedral Pt-Pd NPs for the electrooxidation of formic acid were investigated by cyclic voltammetry, CO stripping voltammetry and chronoamperometry, respectively. Compared with the Pt nanoparticles and commercial Pt black, the octahedral Pt-Pd NPs display a significantly enhanced electrocatalytic activity, increased CO tolerance and favourable stability for the electrooxidation of formic acid. Therefore, the octahedral Pt-Pd NPs might be an alternative candidate for the anode catalyst for the electrooxidation of formic acid in future

  17. Color stability of maxillofacial silicone with nanoparticle pigment and opacifier submitted to disinfection and artificial aging.

    Filié Haddad, Marcela; Coelho Goiato, Marcelo; Micheline Dos Santos, Daniela; Moreno, Amália; Filipe D'almeida, Nuno; Alves Pesqueira, Aldiéris

    2011-09-01

    The purpose of this study was to evaluate the color stability of a maxillofacial elastomer with the addition of a nanoparticle pigment and∕or an opacifier submitted to chemical disinfection and artificial aging. Specimens were divided into four groups (n = 30): group I: silicone without pigment or opacifier, group II: ceramic powder pigment, group III: Barium sulfate (BaSO(4)) opacifier, and group IV: ceramic powder and BaSO(4) opacifier. Specimens of each group (n = 10) were disinfected with effervescent tablets, neutral soap, or 4% chlorhexidine gluconate. Disinfection was done three times a week during two months. Afterward, specimens were submitted to different periods of artificial aging. Color evaluation was initially done, after 60 days (disinfection period) and after 252, 504, and 1008 h of artificial aging with aid of a reflection spectrophotometer. Data were analyzed by three-way ANOVA and Tukey test (α = 0.05). The isolated factor disinfection did not statistically influence the values of color stability among groups. The association between pigment and BaSO(4) opacifier (GIV) was more stable in relationship to color change (△E). All values of △E obtained, independent of the disinfectant and the period of artificial aging, were considered acceptable in agreement with the norms presented in literature.

  18. Nanoparticle and gelation stabilized functional composites of an ionic salt in a hydrophobic polymer matrix.

    Selin Kanyas

    Full Text Available Polymer composites consisted of small hydrophilic pockets homogeneously dispersed in a hydrophobic polymer matrix are important in many applications where controlled release of the functional agent from the hydrophilic phase is needed. As an example, a release of biomolecules or drugs from therapeutic formulations or release of salt in anti-icing application can be mentioned. Here, we report a method for preparation of such a composite material consisted of small KCOOH salt pockets distributed in the styrene-butadiene-styrene (SBS polymer matrix and demonstrate its effectiveness in anti-icing coatings. The mixtures of the aqueous KCOOH and SBS-cyclohexane solutions were firstly stabilized by adding silica nanoparticles to the emulsions and, even more, by gelation of the aqueous phase by agarose. The emulsions were observed in optical microscope to check its stability in time and characterized by rheological measurements. The dry composite materials were obtained via casting the emulsions onto the glass substrates and evaporations of the organic solvent. Composite polymer films were characterized by water contact angle (WCA measurements. The release of KCOOH salt into water and the freezing delay experiments of water droplets on dry composite films demonstrated their anti-icing properties. It has been concluded that hydrophobic and thermoplastic SBS polymer allows incorporation of the hydrophilic pockets/phases through our technique that opens the possibility for controlled delivering of anti-icing agents from the composite.

  19. Unique coexistence of dispersion stability and nanoparticle chemisorption in alkylamine/alkylacid encapsulated silver nanocolloids.

    Aoshima, Keisuke; Hirakawa, Yuya; Togashi, Takanari; Kurihara, Masato; Arai, Shunto; Hasegawa, Tatsuo

    2018-04-17

    Surface encapsulation of metal nanoparticles (NPs) is fundamental to achieve sufficient dispersion stability of metal nanocolloids, or metal nanoink. However, the feature is incompatible with surface reactive nature of the metal NPs, although these features are both essential to realizing the functional applications into printed electronics technologies. Here we show that two different kinds of encapsulation for silver NPs (AgNPs) by alkylamine and alkylacid together are the key to achieve unique compatibility between the high dispersion stability as dense nanoclolloids and the AgNP chemisorption printing on activated patterned polymer surfaces. Advanced confocal dynamic light scattering study reveals that an additive trace amount of oleic acid is the critical parameter for controlling the dispersion and coagulative (or surface-reactive) characteristics of the silver nanocolloids. The composition of the disperse media is also important for obtaining highly concentrated but low-viscosity silver nanocolloids that show very stable dispersion. The results demonstrate that the high-resolution AgNP chemisorption printing is possible only by using unique silver nanocolloids composed of an exceptional balance of ligand formulation and dispersant composition.

  20. Effect of sonication on the colloidal stability of iron oxide nanoparticles

    Sodipo, Bashiru Kayode [Nano-Optoelectronics Research and Technology (NOR) Lab, School of Physics, Universiti Sains Malaysia, 11800 Pulau Pinang (Malaysia); Aziz, Azlan Abdul [Nano-Biotechnology Research and Innovation (NanoBRI), Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, 11800, Pulau Pinang (Malaysia)

    2015-04-24

    Colloidal stability of superparamagnetic iron oxide nanoparticles’ (SPION) suspensions, ultrasonically irradiated at various pH was studied. Electrophoresis measurement of the sonicated SPION showed that the shock waves and other unique conditions generated from the acoustic cavitation process (formation, growth and collapse of bubbles) affect the zeta potential value of the suspension. In this work, stabled colloidal suspensions of SPION were prepared and their pH is varied between 3 and 5. Prior to ultrasonic irradiation of the suspensions, their initial zeta potential values were determined. After ultrasonic irradiation of the suspensions, we observed that the sonication process interacts with colloidal stability of the nanoparticles. The results demonstrated that only suspensions with pH less 4 were found stable and able to retain more than 90% of its initial zeta potential value. However, at pH greater than 4, the suspensions were found unstable. The result implies that good zeta potential value of SPION can be sustained in sonochemical process as long as the pH of the mixture is kept below 4.

  1. Synthesis, characterization and antimicrobial activity of dextran sulphate stabilized silver nanoparticles

    Cakić, Milorad; Glišić, Slobodan; Nikolić, Goran; Nikolić, Goran M.; Cakić, Katarina; Cvetinov, Miroslav

    2016-04-01

    Dextran sulphate stabilized silver nanoparticles (AgNPs - DS) were synthesized from aqueous solution of silver nitrate (AgNO3) and dextran sulphate sodium salt (DS). The characterization of AgNPs - DS was performed by ultraviolet-visible spectroscopy (UV-VIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and antimicrobial activity. The formation of AgNPs - DS was monitored by colour changes of the reaction mixture from yellowish to brown and by measuring the surface plasmon resonance absorption peak in UV-VIS spectra at 420 nm. The SEM analysis was used for size and shape determination of AgNPs - DS. The presence of elemental silver and its crystalline structure in AgNPs - DS were confirmed by EDX and XRD analyses. The possible functional groups of DS responsible for the reduction and stabilization of AgNPs were determinated by FTIR spectroscopy. The AgNPs - DS showed strong antibacterial activity against Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 11778, Bacillus luteus in haus strain, Bacillus subtilis ATTC 6633, Listeria monocytogenes ATCC 15313, Escherichia coli ATTC 25922, Pseudomonas aeruginosa ATTC 27853, Klebsiella pneumoniae ATTC 700603, Proteus vulgaris ATTC 8427, and antifungal activity against Candida albicans ATTC 2091.

  2. Silver colloidal nanoparticle stability: influence on Candida biofilms formed on denture acrylic.

    Monteiro, Douglas Roberto; Takamiya, Aline Satie; Feresin, Leonardo Perina; Gorup, Luiz Fernando; de Camargo, Emerson Rodrigues; Delbem, Alberto Carlos Botazzo; Henriques, Mariana; Barbosa, Debora Barros

    2014-08-01

    Our aim in this study was to evaluate how the chemical stability of silver nanoparticles (SNs) influences their efficacy against Candida albicans and C. glabrata biofilms. Several parameters of SN stability were tested, namely, temperature (50ºC, 70ºC, and 100ºC), pH (5.0 and 9.0), and time of contact (5 h and 24 h) with biofilms. The control was defined as SNs without temperature treatment, pH 7, and 24 h of contact. These colloidal suspensions at 54 mg/L were used to treat mature Candida biofilms (48 h) formed on acrylic. Their efficacy was determined by total biomass and colony-forming unit quantification. Data were analyzed using analysis of variance and the Bonferroni post hoc test (α = 0.05). The temperature and pH variations of SNs did not affect their efficacy against the viable cells of Candida biofilms (P > 0.05). Moreover, the treatment periods were not decisive in terms of the susceptibility of Candida biofilms to SNs. These findings provide an important advantage of SNs that may be useful in the treatment of Candida-associated denture stomatitis. © The Author 2014. Published by Oxford University Press on behalf of The International Society for Human and Animal Mycology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  3. Facile Synthesis Polyethylene Glycol Coated Magnetite Nanoparticles for High Colloidal Stability

    Mun Foong Tai

    2016-01-01

    Full Text Available Polyethylene glycol (PEG is one of the most frequently used synthetic polymers for surface modifications of magnetite nanoparticles (MNPs to provide a new opportunity for constructing high colloidal stability. Herein, a facile in situ coprecipitation technique is described for the synthesis of PEG coated MNPs using ammonium hydroxide as the precipitating agent. The structure and morphology of the prepared PEG coated MNPs samples were characterized by Fourier transform infrared (FTIR spectroscopy, X-ray spectroscopy, thermogravimetric analysis (TGA, and the high resolution transmission electron microscopy (HRTEM. In this study, all samples demonstrated hydrodynamic size in the range of 32 to 43 nm with narrow size distribution. In addition, the magnetic properties of resultant samples were investigated using a vibrating sample magnetometer (VSM to reveal the superparamagnetic behaviour with saturation magnetization. The saturation magnetization of PEG coated MNPs samples was in the range of 63 to 66 emu/g at 300 K. Interestingly, it was found that 1.0 g of PEG coated MNPs exhibited high colloidal stability in a basic solution (pH = 10 and nitrile (NBR latex up to 21 days as compared to the unmodified MNPs during the sedimentation test.

  4. The Effect of PEI and PVP-Stabilized Gold Nanoparticles on Equine Platelets Activation: Potential Application in Equine Regenerative Medicine

    Mateusz Hecold

    2017-01-01

    Full Text Available The aim of this work was to assess the effect of different stabilizing agents, for example, polyethylenimine (PEI and polyvinylpyrrolidone (PVP, on gold nanoparticles (AuNPs and their influence on equine platelet activation and release of particular growth factors. The gold nanoparticles were produced by chemical reduction of chloroauric acid. UV-Vis spectroscopy confirmed the presence of gold nanoparticles in investigated solutions. The AuNPs were incubated with whole blood at various concentrations. The morphology of platelets in PRP prepared from the blood incubated with AuNPs was characterized by scanning transmission electron microscopy, whereas the concentrations of growth factors and cytokines were evaluated by ELISA assays. The most promising results were obtained with equine platelets incubated with 5% AuNPs stabilized by PEI, which lead to secretion of bone morphogenetic protein 2 (BMP-2, vascular endothelial growth factor (VEGF, and fibroblast growth factor 1 (FGF-1 and simultaneously cause decrease in concentration of interleukin-1 alpha (IL-1α. The qRT-PCR confirmed ELISA test results. The incubation with 5% AuNPs stabilized by PEI leads to upregulation of BMP-2 and VEGF transcripts of mRNA level and to downregulating expression of interleukin-6 (IL-6. Obtained data shed a promising light on gold nanoparticle application for future regenerative medicine application.

  5. The impact of aminated surface ligands and silica shells on the stability, uptake, and toxicity of engineered silver nanoparticles

    Bonventre, Josephine A.; Pryor, Joseph B.; Harper, Bryan J.; Harper, Stacey L., E-mail: stacey.harper@oregonstate.edu [Oregon State University, Department of Environmental and Molecular Toxicology (United States)

    2014-12-15

    Inherent nanomaterial characteristics, composition, surface chemistry, and primary particle size, are known to impact particle stability, uptake, and toxicity. Nanocomposites challenge our ability to predict nanoparticle reactivity in biological systems if they are composed of materials with contrasting relative toxicities. We hypothesized that toxicity would be dominated by the nanoparticle surface (shell vs core), and that modulating the surface ligands would have a direct impact on uptake. We exposed developing zebrafish (Danio rerio) to a series of ∼70 nm amine-terminated silver nanoparticles with silica shells (AgSi NPs) to investigate the relative influence of surface amination, composition, and size on toxicity. Like-sized aminated AgSi and Si NPs were more toxic than paired hydroxyl-terminated nanoparticles; however, both AgSi NPs were more toxic than the Si NPs, indicating a significant contribution of the silver core to the toxicity. Incremental increases in surface amination did not linearly increase uptake and toxicity, but did have a marked impact on dispersion stability. Mass-based exposure metrics initially supported the hypothesis that smaller nanoparticles (20 nm) would be more toxic than larger particles (70 nm). However, surface area-based metrics revealed that toxicity was independent of size. Our studies suggest that nanoparticle surfaces play a critical role in the uptake and toxicity of AgSi NPs, while the impact of size may be a function of the exposure metric used. Overall, uptake and toxicity can be dramatically altered by small changes in surface functionalization or exposure media. Only after understanding the magnitude of these changes, can we begin to understand the biologically available dose following nanoparticle exposure.

  6. Stability of single dispersed silver nanoparticles in natural and synthetic freshwaters: Effects of dissolved oxygen.

    Zou, Xiaoyan; Li, Penghui; Lou, Jie; Fu, Xiaoyan; Zhang, Hongwu

    2017-11-01

    Silver nanoparticles (AgNPs) are increasingly used in various commercial products. This increased use raises ecological concerns because of the large release of AgNPs into the environment. Once released, the local water chemistry has the potential to influence the environmental fates and behaviors of AgNPs. The impacts of dissolved oxygen and natural organic matter (NOM) on the dissolution and stability of AgNPs were investigated in synthetic and natural freshwaters for 7 days. In synthetic freshwater, the aggregation of AgNPs occurred due to the compression of the electric double layer, accompanied by the dissolution of AgNPs. However, once oxygen was removed, the highest dissolved Ag (Ag dis ) concentration decreased from 356.5 μg/L to 272.1 μg/L, the pH of the AgNP suspensions increased from less than 7.6 to more than 8.4, and AgNPs were regenerated by the reduction of released Ag + by citrate. The addition of NOM mitigated aggregation, inhibited oxidative dissolution and induced the transformation of AgNPs into Ag 2 S due to the formation of NOM-adsorbed layers, the reduction of Ag + by NOM, and the high affinity of sulfur-enriched species in NOM for Ag. Likewise, in oxygen-depleted natural freshwaters, the inhibition of oxidative dissolution was obtained in comparison with oxygenated freshwaters, showing a decrease in the maximum Ag dis concentration from 137.6 and 57.0 μg/L to 83.3 and 42.4 μg/L from two natural freshwater sites. Our results suggested that aggregation and dissolution of AgNPs in aquatic environments depend on the chemical composition, where oxygen-depleted freshwaters more significantly increase the colloidal stability. In comparison with oxic conditions, anoxic conditions were more favorable to the regeneration of AgNPs by reducing species (e.g., citrate and NOM) and enhanced the stability of nanoparticles. This indicates that some AgNPs will be more stable for long periods in oxygen-deprived freshwaters, and pose more serious

  7. Stabilization of gold nanoparticles by thiol functionalized poly(ε-Caprolactone) for the labeling of PCL biocarrier

    Aryal, Santosh; Remant Bahadur, K.C.; Bhattarai, Narayan; Lee, Byoung Min; Kim, Hak Yong

    2006-01-01

    Polymer terminated by 2-(2,4-dinitrophenylsulfanyl) ethanol was synthesized by ring opening bulk polymerization of ε-Caprolactone initiated by the reaction product of aluminum isopropoxide and 2-(2,4-dinitrophenylsulfenyl) ethanol. The corresponding thiolyated poly(ε-Caprolactone) (PCL) was obtained after removal of protecting group under slightly basic condition. Both of PCL end capped by protected thiol and thiolyated PCL (PCLS-H) were characterized by 1 H NMR and the molecular weights were determined by gel permeation chromatography (GPC). Decrease in polydispersity after deprotection was observed. The PCLS-H can be grafted to the gold nanoparticles either by direct incorporation or ligand exchange with the existing undecanethiol on the gold nanoparticles. The resulting nanoparticles were characterized by Raman spectroscopy and transmission electron microscope (TEM). Mixed ligands stabilized gold nanoparticles were further used for the labeling of PCL biocarrier by nanoprecipitation. The sizes of these nanoparticles-labeled biocarrier were determined by TEM. This is an easy and convenient way to label biocarrier by the gold nanoparticles based contrasting agent in order to study its consequences in vivo

  8. Synthesis and characterization of CdxMn1-xS nanoparticles stabilized with poly(vinyl alcohol)

    Schatkoski, Vanessa M.; Mansur, Alexandra A.P.; Mansur, Herman S.; Gonzalez, Juan C.

    2011-01-01

    Colloidal luminescent semiconductor nanocrystals, also known as quantum dots, have attracted considerable attention due to their significant potential application. The doping of nanocrystalline semiconductors with divalent manganese ions results in new optical properties of these semimagnetic semiconductor quantum dots. In this work we report the synthesis and characterization Cd x Mn 1-x S nanoparticles using poly(vinyl alcohol) as stabilizing agent. Different fractions of Cd 2+ /Mn 2+ ions were investigated aiming the production of stable nanoparticles with different photoluminescence properties. (author)

  9. Exchange coupling mechanism for magnetization reversal and thermal stability of Co nanoparticles embedded in a CoO matrix

    Givord, Dominique; Skumryev, Vassil; Nogues, Josep

    2005-01-01

    A model providing a semi-quantitative account of the magnetic behavior of Co nanoparticles embedded in a CoO matrix is presented. The results confirm that exchange coupling at the interface between ferromagnetic (FM) and antiferromagnetic (AFM) nanostructures could provide an extra source of magnetic anisotropy, leading to thermal stability of the FM nanoparticles. It is shown that perpendicular coupling between the AFM and FM moments may result in large coercivities. The energy barrier, which works against reversal is due to the AFM susceptibility anisotropy. The experimentally observed exchange bias is tentatively ascribed to pre-existing intrinsic canting of the AFM moments at the interface

  10. Newly Synthesized Water Soluble Cholinium-Purpurin Photosensitizers and Their Stabilized Gold Nanoparticles as Promising Anticancer Agents

    Young Key Shim

    2008-05-01

    Full Text Available For possible future use in Photodynamic Therapy (PDT and/or Photothermal Therapy (PTT of cancer and screening of cancer cells a new type of ionic liquid photosensitizer –Cholinium-Purpurin-18 (Chol-Pu-18 – was synthesized and small gold (Au nanoparticles, stabilized by this photosensitizer were prepared without adding any particular reducing agents and CTAB. UV-Vis spectroscopy and Transmission Electron Microscopy (TEM were used for characterization of the nanoparticles and FAB-MS and NMR of the ionic liquid choline hydroxide, purpurin carboxylate and their ionic liquid type of photosensitizer were obtained.

  11. Preparation of chitosan-stabilized Fe{sup 0} nanoparticles for removal of hexavalent chromium in water

    Geng, Bing [Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, College of Environmental Science and Engineering, Nankai University, Tianjin 300071 (China); Jin, Zhaohui, E-mail: jinzh@nankai.edu.cn [Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, College of Environmental Science and Engineering, Nankai University, Tianjin 300071 (China); Li, Tielong; Qi, Xinhua [Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, College of Environmental Science and Engineering, Nankai University, Tianjin 300071 (China)

    2009-09-01

    Chitosan-stabilized Fe{sup 0} nanoparticles (CTO-Fe{sup 0}) and Fe{sup 0} nanoparticles synthesized in ethanol-water mixed system (EW-Fe{sup 0}) were tested for reduction of Cr(VI) in water. Fourier transform infrared (FTIR) study suggested that nitrogen and oxygen atoms are the binding sites for chitosan on iron which was accountable for the stability of Fe{sup 0} nanoparticles. While the EW-Fe{sup 0} ignites spontaneously when exposed to air, the CTO-Fe{sup 0} was still in zero valence state after exposure to air over 2-month period as shown by X-ray powder diffraction patterns. Batch experiments demonstrated that the maximum Cr(VI) reduction rates for CTO-Fe{sup 0} was about 3 times higher than EW-Fe{sup 0}. Characterizations with high-resolution X-ray photoelectron spectroscopy (HR-XPS) revealed that Cr(VI) was reduced to Cr(III) and Fe(III) was the only component present on the Fe{sup 0} nanoparticles surface. Additionally, chitosan can inhibited the formation of Fe(III)-Cr(III) precipitation due to its high ability to chelate Fe(III) which resulted in k{sub obs} for CTO-Fe{sup 0} was about 1-3 times higher than EW-Fe{sup 0}. Due to the fast reaction kinetics and good stability against oxidation in air, the chitosan-stabilized Fe{sup 0} nanoparticles have the potential to become an effective agent for in situ subsurface environment remediation.

  12. MMB4 DMS nanoparticle suspension formulation with enhanced stability for the treatment of nerve agent intoxication.

    Dixon, Hong; Clark, Andrew P-Z; Cabell, Larry A; McDonough, Joe A

    2013-01-01

    Various oximes are currently fielded or under investigation in the United States and other countries as a component of autoinjector emergency treatment systems for organophosphate nerve agent chemical weapons. Bis-pyridinium oximes in general have greater efficacy against a broad spectrum of nerve agents, but they have poor stability due to hydrolytic degradation at elevated temperatures. 1,1'-Methylenebis-4-[(hydroxyimino)methyl]pyridinium dimethanesulfonate (MMB4 DMS) is a leading candidate for next-generation nerve agent treatment systems, because it is more stable than other bis-pyridinium oximes, but it still degrades quickly at temperatures often encountered during storage and field use. The primary goal is to increase the stability and shelf life of MMB4 while maintaining the desirable pharmacokinetic (PK) properties of the aqueous formulation. We have developed a formulation to be used in a phase 1 clinical trial consisting of MMB4 micro/nanoparticles suspended in cottonseed oil, a biocompatible vegetable oil. Through various milling techniques, the average particle size can be controlled from approximately 200 to 6000 nm to produce non-Newtonian formulations that are viscous enough to resist rapid particle sedimentation while remaining injectable at a range of concentrations from 5 to 400 mg/mL. The preliminary accelerated stability test shows that MMB4 in these formulations is stable for at least 2 years at temperatures up to 80°C. Preliminary preclinical in vivo studies have demonstrated that all concentrations and particle sizes have desirable PK properties, including high bioavailability and rapid absorption, which is critical to combat potent and fast-acting nerve agents.

  13. Characterizing the collagen stabilizing effect of crosslinked chitosan nanoparticles against collagenase degradation.

    Kishen, Anil; Shrestha, Suja; Shrestha, Annie; Cheng, Calvin; Goh, Cynthia

    2016-08-01

    Antibacterial and chelating properties of chitosan has been widely studied for various dental applications. To characterize the interaction between chitosan-nanoparticles (CSnp) and collagen, and understand their stabilizing effect against collagenase degradation for dentin matrix stabilization. Phase-1: a single Type I collagen-fibril model was used to study the interaction with CSnp along with carbodiimides crosslinking treatment. Degradation of the crosslinked fibrils was studied with bacterial collagenase enzyme and monitored using Fourier Transform Infrared (FTIR) spectroscopy, turbidity measurement (400nm), ninhydrin assay and Atomic Force Microscopy (AFM). Interaction of CSnp with collagenase and Type I collagen, were evaluated using SDS-PAGE, and proteolytic cleavage potential of a synthetic peptide. Phase-2: degradation of dentin collagen crosslinked with/without CSnp was evaluated using FTIR, ninhydrin assay and Scanning Electron Microscopy (SEM). Glutaraldehyde crosslinking was used as a positive control. Both native collagen-fibrils and dentin collagen after crosslinking showed higher resistance to collagenase degradation, as observed in turbidity measurements and FTIR spectra. AFM images showed the interaction of CSnp with single collagen-fibril and crosslinked collagen resisted collagenase degradation up to 54h. The collagen and collagenase both formed complexes with CSnp resulting in thickening of bands and reduction in collagen degradation. CSnp treated collagenase showed significantly reduced cleavage of the fluorescent peptides. Dentin collagen was coated with CSnp following crosslinking with significant increase in resistance to collagenase degradation. Crosslinked CSnp on collagen stabilized and enhanced the resistance of dentin matrix against bacterial collagenase degradation due to non-specific interaction with both collagen and collagenase. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  14. Protein-silver nanoparticle interactions to colloidal stability in acidic environments.

    Tai, Jui-Ting; Lai, Chao-Shun; Ho, Hsin-Chia; Yeh, Yu-Shan; Wang, Hsiao-Fang; Ho, Rong-Ming; Tsai, De-Hao

    2014-11-04

    We report a kinetic study of Ag nanoparticles (AgNPs) under acidic environments (i.e., pH 2.3 to pH ≈7) and systematically investigate the impact of protein interactions [i.e., bovine serum albumin (BSA) as representative] to the colloidal stability of AgNPs. Electrospray-differential mobility analysis (ES-DMA) was used to characterize the particle size distributions and the number concentrations of AgNPs. Transmission electron microscopy was employed orthogonally to provide visualization of AgNPs. For unconjugated AgNPs, the extent of aggregation, or the average particle size, was shown to be increased significantly with an increase of acidity, where a partial coalescence was found between the primary particles of unconjugated AgNP clusters. Aggregation rate constant, kD, was also shown to be proportional to acidity, following a correlation of log(kD) = -1.627(pH)-9.3715. Using ES-DMA, we observe BSA had a strong binding affinity (equilibrium binding constant, ≈ 1.1 × 10(6) L/mol) to the surface of AgNPs, with an estimated maximum molecular surface density of ≈0.012 nm(-2). BSA-functionalized AgNPs exhibited highly-improved colloidal stability compared to the unconjugated AgNPs under acidic environments, where both the acid-induced interfacial dissolution and the particle aggregation became negligible. Results confirm a complex mechanism of colloidal stability of AgNPs: the aggregation process was shown to be dominant, and the formation of BSA corona on AgNPs suppressed both particle aggregation and interfacial dissolution of AgNP samples under acidic environments.

  15. Cadmium Immobilization in Soil using Sodium Dodecyl Sulfate Stabilized Magnetite Nanoparticles

    Ahmad Farrokhian Firouzi

    2017-06-01

    Full Text Available Introduction Some methods of contaminated soils remediation reduces the mobile fraction of trace elements, which could contaminate groundwater or be taken up by soil organisms. Cadmium (Cd as a heavy metal has received much attention in the past few decades due to its potential toxic impact on soil organism activity and compositions. Cadmium is a soil pollutant of no known essential biological functions, and may pose threats to soil-dwelling organisms and human health. Soil contamination with Cd usually originates from mining and smelting activities, atmospheric deposition from metallurgical industries, incineration of plastics and batteries, land application of sewage sludge, and burning of fossil fuels. Heavy metal immobilization using amendments is a simple and rapid method for the reduction of heavy metal pollution. One way of the assessment of contaminated soils is sequential extraction procedure. Sequential extraction of heavy metals in soils is an appropriate way to determine soil metal forms including soluble, exchangeable, carbonate, oxides of iron and manganese, and the residual. Its results are valuable in prediction of bioavailability, leaching rate and elements transformation in contaminated agricultural soils. Materials and Methods The objective of this study was to synthesize magnetite nanoparticles (Fe3O4 stabilized with sodium dodecyl sulfate (SDS and to investigate the effect of its different percentages (0, 1, 2.5, 5, and 10% on the different fractions of cadmium in soil by sequential extraction method. The nanoparticles were synthesized following the protocol described by Si et al. (19. The investigations were carried out with a loamy sand topsoil. Before use, the soil was air-dried, homogenized and sieved (

  16. Studies on the antimicrobial properties of colloidal silver nanoparticles stabilized by bovine serum albumin.

    Mathew, Thomas V; Kuriakose, Sunny

    2013-01-01

    Colloidal silver nanoparticles were synthesised using sol-gel method and these nanoparticles were stabilised by encapsulated into the scaffolds of bovine serum albumin. Silver nanoparticles and encapsulated products were characterised by FTIR, NMR, XRD, TG, SEM and TEM analyses. Silver nanoparticle encapsulated bovine serum albumin showed highly potent antibacterial activity towards the bacterial strains such as Staphylococcus aureus, Serratia marcescens, Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Engineering the lipid layer of lipid-PLGA hybrid nanoparticles for enhanced in vitro cellular uptake and improved stability.

    Hu, Yun; Hoerle, Reece; Ehrich, Marion; Zhang, Chenming

    2015-12-01

    Lipid-polymer hybrid nanoparticles (NPs), consisting of a polymeric core and a lipid shell, have been intensively examined as delivery systems for cancer drugs, imaging agents, and vaccines. For applications in vaccine particularly, the hybrid NPs need to be able to protect the enclosed antigens during circulation, easily be up-taken by dendritic cells, and possess good stability for prolonged storage. However, the influence of lipid composition on the performance of hybrid NPs has not been well studied. In this study, we demonstrate that higher concentrations of cholesterol in the lipid layer enable slower and more controlled antigen release from lipid-poly(lactide-co-glycolide) acid (lipid-PLGA) NPs in human serum and phosphate buffered saline (PBS). Higher concentrations of cholesterol also promoted in vitro cellular uptake of hybrid NPs, improved the stability of the lipid layer, and protected the integrity of the hybrid structure during long-term storage. However, stabilized hybrid structures of high cholesterol content tended to fuse with each other during storage, resulting in significant size increase and lowered cellular uptake. Additional experiments demonstrated that PEGylation of NPs could effectively minimize fusion-caused size increase after long term storage, leading to improved cellular uptake, although excessive PEGylation will not be beneficial and led to reduced improvement. This paper reports the engineering of the lipid layer that encloses a polymeric nanoparticle, which can be used as a carrier for drug and vaccine molecules for targeted delivery. We demonstrated that the concentration of cholesterol is critical for the stability and uptake of the hybrid nanoparticles by dendritic cells, a targeted cell for the delivery of immune effector molecules. However, we found that hybrid nanoparticles with high cholesterol concentration tend to fuse during storage resulting in larger particles with decreased cellular uptake. This problem is

  18. Effect of cobalt doping on crystallinity, stability, magnetic and optical properties of magnetic iron oxide nano-particles

    Anjum, Safia; Tufail, Rabia; Rashid, Khalid; Zia, Rehana; Riaz, S.

    2017-01-01

    Highlights: • The stability of Co x Fe (2-x) O 3 nanoparticles enhances. • Energy losses increases. • Anisotropy of NP is high. - Abstract: This paper is dedicated to investigate the effect of Co 2+ ions in magnetite Fe 3 O 4 nano-particles with stoichiometric formula Co x Fe 3-x O 4 where (x = 0, 0.05, 0.1 and 0.15) prepared by co-precipitation method. The structural, thermal, morphological, magnetic and optical properties of magnetite and Co 2+ doped magnetite nanoparticles have been carried out using X-ray Diffractometer, Fourier Transform Infrared Spectroscopy, Themogravimetric Analysis, Scanning Electron Microscopy, Vibrating Sample Magnetometer (VSM) and UV–Vis Spectrometer (UV–Vis) respectively. Structural analysis verified the formation of single phase inverse spinel cubic structure with decrease in lattice parameters due to increase in cobalt content. FTIR analysis confirms the single phase of Co x Fe 3-x O 4 nanoparticles with the major band at 887 cm −1 , which might be due to the stretching vibrations of metal-oxide bond. The DSC results corroborate the finding of an increase in the maghemite to hematite phase transition temperature with increase in Co 2+ content. The decrease in enthalpy with increase in Co 2+ concentration attributed to the fact that the degree of conversion from maghemite to hematite decrease which shows that the stability increases with increasing Co 2+ content in B-site of Fe 3 O 4 structure. SEM analysis demonstrated the formation of spherical shaped nanoparticles with least agglomeration. The magnetic measurements enlighten that the coercivity and anisotropy of Co x Fe 3-x O 4 nanoparticles are significantly increased. From UV–Vis analysis it is revealed that band gap energy increases with decreasing particle size. This result has a great interest for magnetic fluid hyperthermia application (MPH).

  19. Xanthan gum stabilized PEGylated gold nanoparticles for improved delivery of curcumin in cancer

    Swami Muddineti, Omkara; Kumari, Preeti; Ajjarapu, Srinivas; Manish Lakhani, Prit; Bahl, Rishabh; Ghosh, Balaram; Biswas, Swati

    2016-08-01

    In recent years, gold nanoparticles (AuNPs) have received immense interest in various biomedical applications including drug delivery, photothermal ablation of cancer and imaging agent for cancer diagnosis. However, the synthesis of AuNPs poses challenges due to the poor reproducibility and stability of the colloidal system. In the present work, we developed a one step, facile procedure for the synthesis of AuNPs from hydrogen tetrachloroaurate (III) hydrate (HAuCl4. 3H2O) by using ascorbic acid and xanthan gum (XG) as reducing agent and stabilizer, respectively. The effect of concentrations of HAuCl4, 3H2O, ascorbic acid and methoxy polyethylene glycol-thiol (mPEG800-SH) were optimized and it was observed that stable AuNPs were formed at concentrations of 0.25 mM, 50 μM and 1 mM for HAuCl4.3H2O, ascorbic acid, and mPEG800-SH, respectively. The XG stabilized, deep red wine colored AuNPs (XG-AuNPs) were obtained by drop-wise addition of aqueous solution of ascorbic acid (50 mM) and XG (1.5 mg ml-1). Synthesized XG-AuNPs showed λmax at 540 nm and a mean hydrodynamic diameter of 80 ± 3 nm. PEGylation was performed with mPEG800-SH to obtain PEGylated XG-AuNPs (PX-AuNPs) and confirmed by Ellman’s assay. No significant shift observed in λmax and hydrodynamic diameter between XG-AuNPs and PX-AuNPs. Colloidal stability of PX-AuNPs was studied in normal saline, buffers within a pH range of 1.2-7.4, DMEM complete medium and in normal storage condition at 4 ˚C. Further, water soluble curcumin was prepared using PVP-K30 as solid dispersion and loaded on to PX-AuNPs (CPX-AuNPs), and evaluated for cellular uptake and cytotoxicity in Murine melanoma (B16F10) cells. Time and concentration dependent studies using CPX-AuNPs showed efficient uptake and decreased cell viability compared to free curcumin.

  20. Synthesis of Silver Nanoparticles in Cotton Fabric by Polyvinyl-2-pyrrolidone as a Reducing and Stabilizing Agent

    Farbod Alimohammadi

    2012-12-01

    Full Text Available Silver nanoparticles have been extensively applied in various fields suchas polymers and textile fibers considering their well known antimicrobialproperties. In conventional methods nano silver is synthesized through chemical reduction however, in this paper a novel synthesis method based on aqueous solution of ammonia/silver complex with cationic stabilizer along with UV-C irradiation is introduced. On this basis, silver nitrate was oxidized with sodium hydroxide and then transformed into [Ag(NH32]+ aqueous solution with ammonia followed by adding PVP as a reducing and stabilizing agent and irradiated by UV-C. The formation of silver nanoparticles was confirmed from the appearance of surface plasmon absorption and the X-ray diffraction (XRD demonstrated that the colloidal nanoparticles were pure silver and Zeta sizer showed particle size distribution. Cotton fabric finishing was accomplished in pad process with various concentrations of nano-sized colloidal silver. Some characteristics of the fabric such as antimicrobial against different microorganisms including gram positive bacteria (Staphylococcous aureus, one gram negative bacteria (Escherichia coli, UV–vis spectrophotometry, color space a*, b* and L*, scanning electron microscopy, EDAX were investigated. Very good antibacterial efficacy against S. aureus and E. coli (higher than 97% appeared even by applying a low nanosilver content (200 ppm for twenty cycles of home laundering. Polyvinyl pyrrolidone resulted in a remarkable control in the release of silver nanoparticle from the coating and can improve the long-term microbiological activity, especially against home laundering.

  1. Synthesis of gold nanoparticles on the surface of pyrolytic graphite using penicillin as a stabilizing reagent and the catalytic oxidation of α-naphthylamine

    Song, Y. Z.; Song, Y.; Cheng, Z. P.; Zhou, J. F.; Wei, C.

    2013-01-01

    Electrochemical synthesis of gold nanoparticles on the surface of pyrolytic graphite using penicillin as a stabilizing reagent was proposed. The gold nanoparticles were characterized by scanning electron microscopy, cyclic voltammetry, IR spectra, UV spectra, and powder X-ray diffraction spectra. The electro-chemical catalysis of penicillin for α-naphthylamine was demonstrated.

  2. Stability of anti-reflection coatings via the self-assembly encapsulation of silica nanoparticles by diazo-resins

    Metzman, Jonathan S.; Ridley, Jason I.; Khalifa, Moataz B.; Heflin, James R.

    2015-12-01

    A modified silica nanoparticle (MSNP) solution was formed by the encapsulation of negatively charged silica nanoparticles by the UV-crosslinkable polycation oligomer diazo-resin (DAR). Appropriate DAR encapsulation concentrations were determined by use of zeta-potential and dynamic light scattering measurements. The MSNPs were used in conjunction with poly(styrene sulfonate) (PSS) to grow homogenous ionic self-assembled multilayer anti-reflection coatings. Stability was induced within the films by the exposure of UV-irradiation that allowed for crosslinking of the DAR and PSS. The films were characterized by UV/vis/IR spectroscopy and field emission scanning electron microscopy. The transmission and reflection levels were >98.5% and <0.05%, respectively. The refractive indices resided in the 1.25-1.26 range. The solvent stability was tested by sonication of the films in a ternary solvent (H2O/DMF/ZnCl2 3:5:2 w/w/w).

  3. Co-Immobilization of Enzymes and Magnetic Nanoparticles by Metal-Nucleotide Hydrogelnanofibers for Improving Stability and Recycling

    Chunfang Li

    2017-01-01

    Full Text Available In this paper we report a facile method for preparing co-immobilized enzyme and magnetic nanoparticles (MNPs using metal coordinated hydrogel nanofibers. Candida rugosa lipase (CRL was selected as guest protein. For good aqueous dispersity, low price and other unique properties, citric acid-modified magnetic iron oxide nanoparticles (CA-Fe3O4 NPs have been widely used for immobilizing enzymes. As a result, the relative activity of CA-Fe3O4@Zn/AMP nanofiber-immobilized CRL increased by 8-fold at pH 10.0 and nearly 1-fold in a 50 °C water bath after 30 min, compared to free CRL. Moreover, the immobilized CRL had excellent long-term storage stability (nearly 80% releative activity after storage for 13 days. This work indicated that metal-nucleotide nanofibers could efficiently co-immobilize enzymes and MNPs simultaneously, and improve the stability of biocatalysts.

  4. Silver nanoparticles in complex biological media: assessment of colloidal stability and protein corona formation

    Argentiere, Simona, E-mail: simona.argentiere@fondazionefilarete.com; Cella, Claudia, E-mail: claudia.cella@unimi.it [Fondazione Filarete (Italy); Cesaria, Maura, E-mail: maura.cesaria@le.infn.it [Università del Salento, Dipartimento di Matematica e Fisica “Ennio De Giorgi” (Italy); Milani, Paolo, E-mail: paolo.milani@mi.infn.it; Lenardi, Cristina, E-mail: cristina.lenardi@mi.infn.it [Università degli Studi di Milano, CIMAINA and Dipartimento di Fisica (Italy)

    2016-08-15

    Engineered silver nanoparticles (AgNPs) are among the most used nanomaterials in consumer products, therefore concerns are raised about their potential for adverse effects in humans and environment. Although an increasing number of studies in vitro and in vivo are being reported on the toxicity of AgNPs, most of them suffer from incomplete characterization of AgNPs in the tested biological media. As a consequence, the comparison of toxicological data is troublesome and the toxicity evaluation still remains an open critical issue. The development of a reliable protocol to evaluate interactions of AgNPs with surrounding proteins as well as to assess their colloidal stability is therefore required. In this regard, it is of importance not only to use multiple, easy-to-access and simple techniques but also to understand limitations of each characterization methods. In this work, the morphological and structural behaviour of AgNPs has been studied in two relevant biological media, namely 10 % FBS and MP. Three different techniques (Dynamic Light Scattering, Transmission Electron Microscopy, UV–Vis spectroscopy) were tested for their suitability in detecting AgNPs of three different sizes (10, 40 and 100 nm) coated with either citrate or polyvinylpyrrolidone. Results showed that UV–Vis spectroscopy is the most versatile and informative technique to gain information about interaction between AgNPs and surrounding proteins and to determine their colloidal stability in the tested biological media. These findings are expected to provide useful insights in characterizing AgNPs before performing any further in vitro/in vivo experiment.

  5. Dendrimer-stabilized bismuth sulfide nanoparticles: synthesis, characterization, and potential computed tomography imaging applications.

    Fang, Yi; Peng, Chen; Guo, Rui; Zheng, Linfeng; Qin, Jinbao; Zhou, Benqing; Shen, Mingwu; Lu, Xinwu; Zhang, Guixiang; Shi, Xiangyang

    2013-06-07

    We report here a general approach to synthesizing dendrimer-stabilized bismuth sulfide nanoparticles (Bi2S3 DSNPs) for potential computed tomography (CT) imaging applications. In this study, ethylenediamine core glycidol hydroxyl-terminated generation 4 poly(amidoamine) dendrimers (G4.NGlyOH) were used as stabilizers to first complex the Bi(III) ions, followed by reaction with hydrogen sulfide to generate Bi2S3 DSNPs. By varying the molar ratio of Bi atom to dendrimer, stable Bi2S3 DSNPs with an average size range of 5.2-5.7 nm were formed. The formed Bi2S3 DSNPs were characterized via different techniques. X-ray absorption coefficient measurements show that the attenuation of Bi2S3 DSNPs is much higher than that of iodine-based CT contrast agent at the same molar concentration of the active element (Bi versus iodine). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay and hemolysis assay reveal that the formed Bi2S3 DSNPs are noncytotoxic and have a negligible hemolysis effect in the studied concentration range. Furthermore, we show that cells incubated with the Bi2S3 DSNPs are able to be imaged using CT, a prominent enhancement at the point of rabbit injected subcutaneously with the Bi2S3 DSNPs is able to be visualized via CT scanning, and the mouse's pulmonary vein can be visualized via CT after intravenous injection of the Bi2S3 DSNPs. With the good biocompatibility, enhanced X-ray attenuation property, and tunable dendrimer chemistry, the designed Bi2S3 DSNPs should be able to be further functionalized, allowing them to be used as a highly efficient contrast agent for CT imaging of different biological systems.

  6. Synergistically enhanced stability of laccase immobilized on synthesized silver nanoparticles with water-soluble polymers.

    Cunha, M N M; Felgueiras, H P; Gouveia, I; Zille, A

    2017-06-01

    Silver nanoparticles (AgNPs) were synthesized by citrate reduction method in the presence of polymers, poly(ethylene glycol) (PEG), poly(vinyl alcohol) (PVA) and chitosan, used as stabilizing agents, and an oxidoreductase enzyme, laccase (Lac), with the goal of expanding the NPs antimicrobial action. AgNPs were characterized by UV-vis spectrometry, dynamic light scattering and transmission electron microscopy. As protecting agents, PEG and PVA promoted the formation of spherical uniformly-shaped, small-sized, monodispersed AgNPs (≈20nm). High Mw polymers were established as most effective in producing small-sized NPs. Chitosan's viscosity led to the formation of aggregates. Despite the decrease in Lac activity registered for the hybrid formulation, AgNPs-polymer-Lac, a significant augment in stability over time (up to 13days, at 50°C) was observed. This novel formulation displays improved synergistic performance over AgNPs-Lac or polymer-Lac conjugates, since in the former the Lac activity becomes residual at the end of 3days. By enabling many ionic interactions, chitosan restricted the mass transfer between Lac and substrate and, thus, inhibited the enzymatic activity. These hybrid nanocomposites made up of inorganic NPs, organic polymers and immobilized antimicrobial oxidoreductive enzymes represent a new class of materials with improved synergistic performance. Moreover, the Lac and the AgNPs different antimicrobial action, both in time and mechanism, may also constitute a new alternative to reduce the probability of developing resistance-associated mutations. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Cyanide Removal Efficiency of Photocatalytic Nanoparticles Stabilized on Glass Microbeads Under Sun Irradiation

    Neda Masoudipour

    2017-01-01

    Full Text Available This paper investigates cyanide photodestruction (at pH 9 using the S, N-TiO2 photocatalyst synthesized by the sol-gel method and stabilized on glass microbeads. The main raw materials were thiourea, as a source of N and S, and tetra butyl ortho titanate. The effects of S and N doses, visible light (a 400W light, sunlight, irradiation time, and different initial cyanide concentrations (50, 100, 200, and 300 ppm were studied on cyanide photodestruction. Cyanide concentration was measured by the titration method and the photocatalyst film was characterized by X-ray diffraction (XRD, UV-Vis diffuse reflection spectroscopy (DRS, Scanning Electron Microscopy (SEM, and Energy dispersive X-ray (EDX analysis. XRD patterns and SEM images were used to determine the nanoparticle size of the photocatalyst on glass microbeads. EDX and DRS analyses confirmed the presence of S and N as well as the activity of the photocatalyst in the visible region, respectively. The S, N-TiO2 film with 0.25 g Thiuourea proved to be the best cyanide photodestruction agent in the visible light. Based on the results obtained, S, N-TiO2/ glass microbead was capable of destroying cyanide (50 ppm by up to 94% in the visible light and by approximately 100% in the sunlight. The results also indicated that S, N-Tio2/scoria stone was capable of destroying cyanide by 85% in the visible light and by 94% in the sunlight within 4 h.  The reaction kinetic for all cyanide concentrations and two photocatalyst substrates were described by a first order equation. Finally, it was concluded that the S, N-TiO2 stabilized on glass microbeads could be effectively used as a new method for treating wastewater containing free cyanide under the sunlight.

  8. Magneto-optical detection of the relaxation dynamics of alloy nanoparticles with a high-stability magnetic circular dichroism setup

    Cavigli, L.; Julian Fernandez, C. de; Gatteschi, D.; Gurioli, M.; Sangregorio, C.; Mattei, G.; Mazzoldi, P.; Bogani, L.

    2007-01-01

    We present a versatile high-stability and high-sensitivity magneto-optical setup that allows transmission and reflection measurements at high fields and low temperatures. We apply the technique to measure the decay in time of the magnetization of highly monodisperse 3.3nm Co 33 Ni 67 alloy nanoparticles embedded in a silica host. We demonstrate the possibility of observing the dynamics of the magnetization over a macroscopic timescale in dilute samples, where other techniques are unavailable

  9. Magneto-optical detection of the relaxation dynamics of alloy nanoparticles with a high-stability magnetic circular dichroism setup

    Cavigli, L.; de Julián Fernández, C.; Gatteschi, D.; Gurioli, M.; Sangregorio, C.; Mattei, G.; Mazzoldi, P.; Bogani, L.

    2007-09-01

    We present a versatile high-stability and high-sensitivity magneto-optical setup that allows transmission and reflection measurements at high fields and low temperatures. We apply the technique to measure the decay in time of the magnetization of highly monodisperse 3.3 nm Co33Ni67 alloy nanoparticles embedded in a silica host. We demonstrate the possibility of observing the dynamics of the magnetization over a macroscopic timescale in dilute samples, where other techniques are unavailable.

  10. Segregation and stability at Pt3Ni(1 1 1) surfaces and Pt75Ni25 nanoparticles

    Fowler, Ben; Lucas, Christopher A.; Omer, Ahmed; Wang, Guofeng; Stamenkovic, Vojislav R.; Markovic, Nenad M.

    2008-01-01

    Using in situ surface X-ray diffraction we have determined the atomic structure and stability of a Pt 3 Ni(1 1 1) surface in the electrochemical environment. Surface segregation leads to a pure Pt(1 1 1) skin with enrichment of Ni in the sub-surface atomic layer that determines the surface electronic structure. The Pt-skin surface exhibits inward relaxation upon the adsorption of oxygenated species and this explains the surface stability compared to pure Pt(1 1 1). Using Monte Carlo calculations it is shown that nanoparticles with the same surface composition and stochiometry are energetically stable

  11. Chitosan-stabilized Silver Nanoparticles for Colorimetric Assay of Mercury (II) Ions in aqueous system

    Zarlaida, Fitri; Adlim, M.; Syukri Surbakti, M.; Fairuz Omar, Ahmad

    2018-05-01

    Mercury is considered as dangerous pollutant. Among the many form of mercury, the most stable and soluble in water is mercury (II) ions which it cause threat to human health and surroundings. Silver nanoparticles (AgNPs) used in this method were prepared by chitosan (chi) which act as stabilizing agent. The Chi-AgNPs has good dispersity with size ranging from 2.50 to 6.00 nm as shown by transmission electron microscopy (TEM) analysis and it is stable for 3 months. Color of Chi-AgNPs fades from brownish-yellow to colorless only with Hg2+ ions, but it shows no significant changes upon addition of other metal ions such as Al3+, Ba2+, Ca2+, Cd2+, Cr3+, Co2+, Cu2+, Fe2+, K+, Mg2+, Mn2+, Na+, Ni2+, Pb2+, and Zn2+. The detection limit for Hg2+ ions by bare-eye is estimated to be ∼1µM. This method can be used for sensing mercury(II) ions in numerous water samples.

  12. Gold nanoparticles stabilized by poly(4-vinylpyridine) grafted cellulose nanocrystals as efficient and recyclable catalysts.

    Zhang, Zhen; Sèbe, Gilles; Wang, Xiaosong; Tam, Kam C

    2018-02-15

    pH-responsive poly(4-vinylpyridine) (P4VP) grafted cellulose nanocrystals (P4VP-g-CNC) were prepared by Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) and subsequently used to stabilize gold nanoparticles (Au NPs) as efficient and recyclable nanocatalysts for the reduction of 4-nitrophenol (4NP). The presence of P4VP brushes on the CNC surface controlled the growth of Au NPs yielding smaller averaged diameter compared to Au NPs deposited directly on pristine CNC. The catalytic performances of pristine Au NPs, Au@CNC and Au@P4VP-g-CNC were compared by measuring the turnover frequency (TOF) for the catalytic reduction of 4NP. Compared to pristine Au NPs, the catalytic activity of Au@CNC and Au@P4VP-g-CNC were 10 and 24 times better. Moreover, the Au@P4VP-g-CNC material could be recovered via flocculation at pH>5, and the recycled nanocatalyst remained highly active. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Copper Metal-Organic Framework Nanoparticles Stabilized with Folic Acid Improve Wound Healing in Diabetes.

    Xiao, Jisheng; Zhu, Yunxiao; Huddleston, Samantha; Li, Peng; Xiao, Baixue; Farha, Omar K; Ameer, Guillermo A

    2018-02-27

    The successful treatment of chronic nonhealing wounds requires strategies that promote angiogenesis, collagen deposition, and re-epithelialization of the wound. Copper ions have been reported to stimulate angiogenesis; however, several applications of copper salts or oxides to the wound bed are required, leading to variable outcomes and raising toxicity concerns. We hypothesized that copper-based metal-organic framework nanoparticles (Cu-MOF NPs), referred to as HKUST-1, which are rapidly degraded in protein solutions, can be modified to slowly release Cu 2+ , resulting in reduced toxicity and improved wound healing rates. Folic acid was added during HKUST-1 synthesis to generate folic-acid-modified HKUST-1 (F-HKUST-1). The effect of folic acid incorporation on NP stability, size, hydrophobicity, surface area, and copper ion release profile was measured. In addition, cytotoxicity and in vitro cell migration processes due to F-HKUST-1 and HKUST-1 were evaluated. Wound closure rates were assessed using the splinted excisional dermal wound model in diabetic mice. The incorporation of folic acid into HKUST-1 enabled the slow release of copper ions, which reduced cytotoxicity and enhanced cell migration in vitro. In vivo, F-HKUST-1 induced angiogenesis, promoted collagen deposition and re-epithelialization, and increased wound closure rates. These results demonstrate that folic acid incorporation into HKUST-1 NPs is a simple, safe, and promising approach to control Cu 2+ release, thus enabling the direct application of Cu-MOF NPs to wounds.

  14. Stabilized chitosan/Fe(0)-nanoparticle beads to remove heavy metals from polluted sediments.

    Liu, T; Sun, Y; Wang, Z L

    2016-01-01

    Sediment contamination by heavy metals has become a widespread problem that can affect the normal behaviors of rivers and lakes. After chitosan/Fe(0)-nanoparticles (CS-NZVI) beads were cross-linked with glutaraldehyde (GLA), their mechanical strength, stability and separation efficiency from the sediment were obviously improved. Moreover, the average aperture size of GLA-CS-NZVI beads was 20.6 μm and NZVI particles were nearly spherical in shape with a mean diameter of 40.2 nm. In addition, the pH showed an insignificant effect on the removal rates from the sediment. Due to the dissolution of metals species into aqueous solutions as an introduction of the salt, the removal rates of all heavy metals from the sediment were increased with an increase of the salinity. The competitive adsorption of heavy metals between the sediment particles and GLA-CS-NZVI beads became stronger as the sediment particles became smaller, leading to decreased removal rates. Therefore, the removal efficiency could be enhanced by optimizing experimental conditions and choosing appropriate materials for the target contaminants.

  15. DNA-linked NanoParticle Lattices with Diamond Symmetry: Stability, Shape and Optical Properties

    Emamy, Hamed; Tkachenko, Alexei; Gang, Oleg; Starr, Francis

    The linking of nanoparticles (NP) by DNA has been proven to be an effective means to create NP lattices with specific order. Lattices with diamond symmetry are predicted to offer novel photonic properties, but self-assembly of such lattices has proven to be challenging due to the low packing fraction, sensitivity to bond orientation, and local heterogeneity. Recently, we reported an approach to create diamond NP lattices based on the association between anisotropic particles with well-defined tetravalent DNA binding topology and isotropically functionalized NP. Here, we use molecular dynamics simulations to evaluate the Gibbs free energy of these lattices, and thereby determine the stability of these lattices as a function of NP size and DNA stiffness. We also predict the equilibrium shape for the cubic diamond crystallite using the Wulff construction method. Specifically, we predict the equilibrium shape using the surface energy for different crystallographic planes. We evaluate surface energy directly form molecular dynamics simulation, which we correlate with theoretical estimates from the expected number of broken DNA bonds along a facet. Furthermore we study the optical properties of this structure, e.g optical bandgap.

  16. Stability of magnetite nanoparticles with different coatings in a simulated blood plasma

    Favela-Camacho, Sarai E.; Pérez-Robles, J. Francisco [Center for Research and Advanced Studies of National Polytechnic Institute, CINVESTAV-Querétaro Unit (Mexico); García-Casillas, Perla E. [Autonomous University of Juarez, Department of Materials Science, Institute of Engineering and Technology (Mexico); Godinez-Garcia, Andrés, E-mail: andgodinez@xanum.uam.mx [Universidad Autónoma Metropolitana, Departamento de Ingeniería de Procesos e Hidráulica (Mexico)

    2016-07-15

    Magnetite nanoparticles (MNPs) have demonstrated to be a potential platform for simultaneous anticancer drug delivery and magnetic resonance imaging (MRI). However, magnetite is unstable at the blood plasma conditions. Therefore, to study their stability in a broad range of particle size, the MNPs were synthesized using two methods, the fast injection co-precipitation method (FIC) and the reflux co-precipitation method (RC). The MNPs obtained by the RC and the FIC methods have an average size of agglomerates of 200 and 45 nm respectively. They were dispersed using sodium citrate as surfactant and were coated with silica and chitosan. A total of four kind of coated MNPs were synthesized: magnetite/sodium citrate, magnetite/silica, magnetite/sodium citrate/silica and magnetite/sodium citrate/silica/chitosan. Different samples of the coated MNPs were immersed in a simulated blood plasma solution (Phosphate-Buffered Saline, PBS, Gibco{sup ®}), for periods of 24, 48 and 72 h. Inductively coupled plasma (ICP) technique was used to analyze the composition of the simulated plasma after those periods of time. The obtained results suggest that the uncoated samples showed an appreciable weight loss, and the iron composition in the simulated plasma increased. This last means that the used coatings avoid iron dissolution from the MNPs.Graphical abstract.

  17. Scale up, optimization and stability analysis of Curcumin C3 complex-loaded nanoparticles for cancer therapy

    2012-01-01

    Background Nanoparticle based delivery of anticancer drugs have been widely investigated. However, a very important process for Research & Development in any pharmaceutical industry is scaling nanoparticle formulation techniques so as to produce large batches for preclinical and clinical trials. This process is not only critical but also difficult as it involves various formulation parameters to be modulated all in the same process. Methods In our present study, we formulated curcumin loaded poly (lactic acid-co-glycolic acid) nanoparticles (PLGA-CURC). This improved the bioavailability of curcumin, a potent natural anticancer drug, making it suitable for cancer therapy. Post formulation, we optimized our process by Reponse Surface Methodology (RSM) using Central Composite Design (CCD) and scaled up the formulation process in four stages with final scale-up process yielding 5 g of curcumin loaded nanoparticles within the laboratory setup. The nanoparticles formed after scale-up process were characterized for particle size, drug loading and encapsulation efficiency, surface morphology, in vitro release kinetics and pharmacokinetics. Stability analysis and gamma sterilization were also carried out. Results Results revealed that that process scale-up is being mastered for elaboration to 5 g level. The mean nanoparticle size of the scaled up batch was found to be 158.5 ± 9.8 nm and the drug loading was determined to be 10.32 ± 1.4%. The in vitro release study illustrated a slow sustained release corresponding to 75% drug over a period of 10 days. The pharmacokinetic profile of PLGA-CURC in rats following i.v. administration showed two compartmental model with the area under the curve (AUC0-∞) being 6.139 mg/L h. Gamma sterilization showed no significant change in the particle size or drug loading of the nanoparticles. Stability analysis revealed long term physiochemical stability of the PLGA-CURC formulation. Conclusions A successful effort towards

  18. Implications of the stability behavior of zinc oxide nanoparticles for toxicological studies

    Meißner, Tobias; Oelschlägel, Kathrin; Potthoff, Annegret

    2014-08-01

    The increasing use of zinc oxide (ZnO) nanoparticles in sunscreens and other cosmetic products demands a risk assessment that has to be done in toxicological studies. Such investigations require profound knowledge of the behavior of ZnO in cell culture media. The current study was performed to get well-dispersed suspensions of a hydrophilic (ZnO-hydro) and a lipophilic coated (ZnO-lipo) ZnO nanomaterial for use in in vitro tests. Therefore, systematic tests were carried out with common dispersants (phosphate, lecithin, proteins) to elucidate chemical and physical changes of ZnO nanoparticles in water and physiological solutions (PBS, DMEM). Non-physiological stock suspensions were prepared using ultrasonication. Time-dependent changes of pH, conductivity, zeta potential, particle size and dissolution were recorded. Secondly, the stock suspensions were added to physiological media with or without albumin (BSA) or serum (FBS), to examine characteristics such as agglomeration and dissolution. Stable stock suspensions were obtained using phosphate as natural and physiological electrostatic stabilizing agent. Lecithin proved to be an effective wetting agent for ZnO-lipo. Although the particle size remained constant, the suspension changed over time. The pH increased as a result of ZnO dissolution and formation of zinc phosphate complexes. The behavior of ZnO in physiological media was found to depend strongly on the additives used. Applying only phosphate as additive, ZnO-hydro agglomerated within minutes. In the presence of lecithin or BSA/serum, agglomeration was inhibited. ZnO dissolution was higher under physiological conditions than in the stock suspension. Serum especially promoted this process. Using body-related dispersants (phosphate, lecithin) non-agglomerating stock suspensions of hydrophilic and lipophilic ZnO were prepared as a prerequisite to perform meaningful toxicological investigation. Both nanomaterials showed a non-negligible dissolution behavior

  19. Quantum chemical evaluation for the stability of liquid sodium containing titanium nanoparticles

    Suzuki, Ai; Inaba, Kenji; Ishizawa, Yukie; Miura, Ryuji; Hatakeyama, Nozomu; Miyamoto, Akira; Saito, Jun-ichi; Ara, Kuniaki

    2015-01-01

    Recently, liquid sodium containing titanium nanoparticles (LSnanop) have attracted considerable attention. In this study, suspension state of Ti nanoparticle in liquid sodium was quantum chemically evaluated. The atomic interaction between Ti nanoparticles and sodium atoms in the liquid sodium medium was investigated. There were some literatures which gained quantum chemical insight into a nanoparticle with the surrounding sodium atom. However, liquid sodium medium itself together with a Ti nanoparticle under the realistic temperature has not yet been investigated theoretically. To overcome the problem of conventional theoretical method, we applied computationally low-load Tight Binding Quantum Chemical Molecular Dynamics (TB-QCMD) calculation method to investigate the suspension state of the Ti nanoparticle in liquid sodium metal. (author)

  20. On the role of the colloidal stability of mesoporous silica nanoparticles as gene delivery vectors

    Cebrian, Virginia [Hospital Universitario La Paz-IdiPAZ (Spain); Yaguee, Clara; Arruebo, Manuel, E-mail: arruebom@unizar.es [University of Zaragoza, Aragon Nanoscience Institute (INA), C/Mariano Esquillor, Edif. I-D (Spain); Martin-Saavedra, Francisco M. [Hospital Universitario La Paz-IdiPAZ (Spain); Santamaria, Jesus [CIBER de Bioingenieria, Biomateriales y Nanomedicina, CIBER-BBN (Spain); Vilaboa, Nuria [Hospital Universitario La Paz-IdiPAZ (Spain)

    2011-09-15

    Mesoporous silica nanoparticles have been synthesized and functionalized with four different types of molecules containing amino groups, i.e., with primary amines only, with quaternary amines, with quaternized cyclic amines, or with polyethylenimine (PEI), which is formed by primary, secondary, and tertiary amines. These nanoparticles were then incubated with reporter plasmids and the ability of the resulting complexes to transfect human cells was studied. Only nanoparticles functionalized with PEI were efficient for transfection. The agglomeration behavior and the electrokinetic potential of the nanoparticle-plasmid complexes have been studied, as well as their cell internalization behavior using a fluorescent-labeled plasmid that allows its monitorization by confocal microscopy. The results indicate that the efficiency of PEI-functionalized nanoparticles for transfection resides to some extent in the different characteristics imparted to the nanoparticles regarding agglomeration and surface charge behavior.

  1. Preparation of silica doped titania nanoparticles with thermal stability and photocatalytic properties and their application for leather surface functionalization

    Carmen Gaidau

    2017-11-01

    Full Text Available Doped nanoparticles based on titanium dioxide are of interest for their multifunctional properties and enlarged photocatalytic activity in visible domain. Silica doped titanium dioxide nanoparticles were prepared by hydrothermal method and their structural characteristics and photocatalytic activity were determined, in order to be used for leather coating as alternative to halogen based flame retardants and dry cleaning solvents. A range of concentrations from 2% to 20% silica doped titanium dioxide nanoparticles (% denotes the theoretical weight percent of Si was synthesized and characterized by ICP-OES, FT-IR, UV-vis spectroscopy, XRD, HRTEM and DLS. Titanium dioxide network penetration was supported by Si-O-Ti and OH identification in FT-IR spectra mainly on surface of 10% and 20% silica doped titanium dioxide nanoparticles. The increase of Si-O-Ti bonds with Si dopant concentration acts as efficient barriers against sinterization and growth of TiO2 particles and explains the low particle size identified in HRTEM analyses as compared to undoped TiO2NPs. UV-vis diffuse reflectance spectra of doped titanium dioxide nanoparticles showed the shifting of absorption band to visible domain for 10% silica doped titanium dioxide nanoparticles. The crystallite sizes were calculated from XRD spectra, ranging between 16.2 and 18.1 nm. HRTEM measurement of hydrothermally synthesized titanium dioxide nanoparticles showed anatase crystallites in the range of 8.8–27 nm, while in the 20% silica doped titanium dioxide nanoparticle sample smaller crystallite with sizes between 2.7 nm and 3.5 nm was identified due to the constraints of the SiO2-based amorphous matrix. Nano sizes of 64 nm and 72 nm were found in water dispersions of 10% and 20% silica doped titanium dioxide nanoparticles and the Zeta potentials were of −53.6 mV and −52.9 mV, which indicate very good stabilities. The leather surface treated with composites of film forming polymers

  2. Optical and structural properties of radiolytically in situ synthesized silver nanoparticles stabilized by chitosan/poly(vinyl alcohol) blends

    Krstić, Jelena; Spasojević, Jelena; Radosavljević, Aleksandra; Šiljegovć, Milorad; Kačarević-Popović, Zorica

    2014-01-01

    In this study, the potential of chitosan/poly(vinyl alcohol) (CS/PVA) blends as capping agent for stabilization of Ag-nanoparticles (Ag NPs) during their in situ gamma irradiation induced synthesis was investigated. The UV–vis absorption spectra show the surface plasmon absorption band around 410 nm, which confirms the formation of Ag-nanoparticles. It was found that the composition of CS/PVA blend affected the size of the obtained Ag-nanoparticles, as well as the parameters such as density, molar concentration and effective surface area, calculated from the experimentally obtained UV–vis absorption spectra and spectra obtained by simulation according to the Mie theory. SEM micrograph and XRD measurement indicated a spherical morphology and face centered cubic crystal structure of Ag-nanoparticles, with diameter around 12 nm. The values of optical band gap energy between valence and conduction bands (E g ), calculated from the UV–vis absorption spectra, also show dependence on the blend composition for Ag–CS/PVA colloids as well as for Ag–CS/PVA nanocomposites. - Highlights: • Ag NPs were synthesized by γ-irradiation and stabilized by CS/PVA blends. • Composition of CS/PVA blends has influence on the size of spherical Ag NPs. • simulation based on Mie theory was used to calculate the parameters of Ag NPs. • Ag NPs are stabilized through interactions with -OH and -NH 2 groups of polymers. • Optical band gap energy was calculated from UV–vis spectra by Tauc's expression

  3. Biofunctionalized Hybrid Magnetic Gold Nanoparticles as Catalysts for Photothermal Ablation of Colorectal Liver Metastases.

    White, Sarah B; Kim, Dong-Hyun; Guo, Yang; Li, Weiguo; Yang, Yihe; Chen, Jeane; Gogineni, Venkateswara R; Larson, Andrew C

    2017-12-01

    Purpose To demonstrate that anti-MG1 conjugated hybrid magnetic gold nanoparticles (HNPs) act as a catalyst during photothermal ablation (PTA) of colorectal liver metastases, and thus increase ablation zones. Materials and Methods All experiments were performed with approval of the institutional animal care and use committee. Therapeutic and diagnostic multifunctional HNPs conjugated with anti-MG1 monoclonal antibodies were synthesized, and the coupling efficiency was determined. Livers of 19 Wistar rats were implanted with 5 × 10 6 rat colorectal liver metastasis cell line cells. The rats were divided into three groups according to injection: anti-MG1-coupled HNPs (n = 6), HNPs only (n = 6), and cells only (control group, n = 7). Voxel-wise R2 and R2* magnetic resonance (MR) imaging measurements were obtained before, immediately after, and 24 hours after injection. PTA was then performed with a fiber-coupled near-infrared (808 nm) diode laser with laser power of 0.56 W/cm 2 for 3 minutes, while temperature changes were measured. Tumors were assessed for necrosis with hematoxylin-eosin staining. Organs were analyzed with inductively coupled plasma mass spectrometry to assess biodistribution. Therapeutic efficacy and tumor necrosis area were compared by using a one-way analysis of variance with post hoc analysis for statistically significant differences. Results The coupling efficiency was 22 μg/mg (55%). Significant differences were found between preinfusion and 24-hour postinfusion measurements of both T2 (repeated measures analysis of variance, P = .025) and T2* (P the anti-MG1 HNP and HNP-only groups (P = .034). Mean temperature ± standard deviation with PTA in the anti-MG1-coated HNP, HNP, and control groups was 50.2°C ± 7.8, 51°C ± 4.4, and 39.5°C ± 2.0, respectively. Inductively coupled plasma mass spectrometry revealed significant tumor targeting and splenic sequestration. Mean percentages of tumor necrosis in the anti-MG1-coated HNP, HNP, and

  4. Impact of alginate concentration on the stability of agglomerates made of TiO{sub 2} engineered nanoparticles: Water hardness and pH effects

    Loosli, Frédéric, E-mail: frederic.loosli@unige.ch [University of Geneva, Section des Sciences de la Terre et de l’Environnement, Group of Environmental Physical Chemistry, F.-A. Forel Institute (Switzerland); Coustumer, Philippe Le, E-mail: philippe.le-coustumer@u-bordeaux1.fr [Université Bordeaux 3, EA 4592 Géoressources & Environnement, ENSEGID (France); Stoll, Serge, E-mail: serge.stoll@unige.ch [University of Geneva, Section des Sciences de la Terre et de l’Environnement, Group of Environmental Physical Chemistry, F.-A. Forel Institute (Switzerland)

    2015-01-15

    The stability of engineered nanoparticles in natural aquatic systems is of high interest for environmental risk assessment since an already important quantity of these reactive species is entering aquatic systems. In the present study, an important issue is addressed by investigating (i) the influence of divalent cations and water hardness (Mg{sup 2+} and Ca{sup 2+}) in agglomerate formation and (ii) alginate concentration effect on the stability TiO{sub 2} agglomerates formed in environmental freshwater conditions (pH and total hardness) representative of Lake Geneva, France/Switzerland. Our results indicate that the presence of alginate at typical natural organic matter concentration strongly modifies the stability of TiO{sub 2} nanoparticle agglomerates by inducing their partial disagglomeration. Significant TiO{sub 2} nanoparticles redispersion and formation of small fragments are expected to be induced by alginate adsorbed layer formed at the nanoparticle surfaces within the agglomerates.Graphical Abstract.

  5. Efficient MRI labeling of endothelial progenitor cells: design of thiolated surface stabilized superparamagnetic iron oxide nanoparticles.

    Shahnaz, Gul; Kremser, Christian; Reinisch, Andreas; Vetter, Anja; Laffleur, Flavia; Rahmat, Deni; Iqbal, Javed; Dünnhaupt, Sarah; Salvenmoser, Willi; Tessadri, Richard; Griesser, Ulrich; Bernkop-Schnürch, Andreas

    2013-11-01

    The aim of this study was to design thiolated surface stabilized superparamagnetic iron oxide nanoparticles (TSS-SPIONs) for efficient internalization with high MRI sensitivity. TSS-SPIONs were developed by chelation between thiolated chitosan-thioglycolic acid (chitosan-TGA) hydrogel and iron ions (Fe(2+)/Fe(3+)). Likely, unmodified chitosan hydrogel SPIONs (UC-SPIONs) and uncoated SPIONs were used as control. Moreover, TSS-SPIONs were investigated regarding to their iron core size, hydrodynamic diameter, zeta potential, iron contents, molar relaxivities (r1 and r2), and cellular internalization. TSS-SPIONs demonstrated an iron oxide core diameter (crystallite size by XRD) of 3.1 ± 0.02 nm, a hydrodynamic diameter of 94 ± 20 nm, a zeta potential of +21 ± 5 mV, and an iron content of 3.6 ± 0.9 mg/mL. In addition, internalization of TSS-SPIONs into human endothelial progenitor cells (EPC) from umbilical cord blood was more than threefold and 17-fold higher in contrast to UC-SPIONs and SPIONs, respectively. With twofold lower incubation iron concentration of TSS-SPIONs, more than threefold higher internalization was achieved as compared to Resovist®. Also, cell viability of more than 90% was observed in the presence of TSS-SPIONs after 24h. The molar MR relaxivities (r2) value at 1.5 T was threefold higher than that of Resovist® and demonstrated that TSS-SPIONs have the potential as very effective T2 contrast-enhancement agent. According to these findings, TSS-SPIONs with efficient internalization, lower cytotoxicity, and high MRI sensitivity seem to be promising for cell tracking. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Effects of intermolecular interactions on the stability of carbon nanotube–gold nanoparticle conjugates in solution

    Konczak L

    2016-11-01

    Full Text Available Lukasz Konczak,1 Jolanta Narkiewicz-Michalek,2 Giorgia Pastorin,3 Tomasz Panczyk1 1Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Cracow, 2Department of Chemistry, Maria Curie-Sklodowska University, Lublin, Poland; 3Department of Pharmacy, National University of Singapore, Singapore Abstract: This work deals with the role of intermolecular interactions in the stability of a carbon nanotube (CNT capped by functionalized gold nanoparticles (AuNPs. The importance of such a system is due to its potential application as a pH-controlled drug carrier. Our preliminary experimental studies showed that fabrication of such a nanobottle/nanocontainer is feasible and it is possible to encapsulate the anticancer drug cisplatin inside the inner space of a CNT and seal its ends by functionalized AuNPs. The expected behavior, that is, detachment of AuNPs at acidic pH and the release of cisplatin, was, however, not observed. On the other hand, our theoretical studies of chemically identical system led to the conclusion that the release of cisplatin at acidic pH should be observed. Therefore, in this work, a deeper theoretical analysis of various factors that could be responsible for the disagreement between experimental and theoretical results were performed. The study found that the major factor is a large dispersion interaction component acting between CNT and AuNP in solution in the case of the experimental system. This factor can be controlled to some extent by tuning the system size or the ratio between AuNP diameter and CNT diameter. Thus, such kind of a pH-sensitive drug carrier is still of great interest, but its structural parameters need to be properly adjusted. Keywords: hydrazone bond, drug delivery, dispersion interactions, cisplatin, acidic pH

  7. The Stability of Silver Nanoparticles in a Model of Pulmonary Surfactant

    Fen, Leo Bey; Chen, Shu; Kyo, Yoshihiko; Herpoldt, Karla-Luise; Terrill, Nicholas J.; Dunlop, Iain E.; McPhail, David S.; Shaffer, Milo S.; Schwander, Stephan; Gow, Andrew; Zhang, Junfeng (Jim); Chung, Kian Fan; Tetley, Teresa D.; Porter, Alexandra E.; Ryan, Mary P.

    2013-01-01

    The growing use of silver nanoparticles (AgNPs) in consumer products has raised concerns about their potential impact on the environment and human health. Whether AgNPs dissolve and release Ag+ ions, or coarsen to form large aggregates, is critical in determining their potential toxicity. In this work, the stability of AgNPs in dipalmitoylphosphatidylcholine (DPPC), the major component of pulmonary surfactant, was investigated as a function of pH. Spherical, citrate-capped AgNPs with average diameters of 14 ± 1.6 nm (n=200) were prepared by a chemical bath reduction. The kinetics of Ag+ ion release was strongly pH-dependent. After 14 days of incubation in sodium perchlorate (NaClO4) or perchloric acid (HClO4) solutions, the total fraction of AgNPs dissolved varied from ~10 % at pH 3, to ~2 % at pH 5, with negligible dissolution at pH 7. A decrease in pH from 7 to 3 also promoted particle aggregation and coarsening. DPPC (100 mg.L−1) delayed the release of Ag+ ions, but did not significantly alter the total amount of Ag+ released after two weeks. In addition, DPPC improved the dispersion of the AgNPs and inhibited aggregation and coarsening. TEM images revealed that the AgNPs were coated with a DPPC layer serving as a semi-permeable layer. Hence, lung lining fluid, particularly DPPC, can modify the aggregation state and kinetics of Ag+ ion release of inhaled AgNPs in the lung. These observations have important implications for predicting the potential reactivity of AgNPs in the lung and the environment. PMID:23988335

  8. Assessing the physical-chemical properties and stability of dapivirine-loaded polymeric nanoparticles.

    das Neves, José; Amiji, Mansoor; Bahia, Maria Fernanda; Sarmento, Bruno

    2013-11-18

    Nanocarriers may provide interesting delivery platforms for microbicide drugs and their characterization should be addressed early in development. Differently surface-engineered dapivirine-loaded, poly(epsilon-caprolactone) (PCL)-based nanoparticles (NPs) were obtained by nanoprecipitation using polyethylene oxide (PEO), sodium lauryl sulfate (SLS), or cetyltrimethylammonium bromide (CTAB) as surface modifiers. Physical-chemical properties of NP aqueous dispersions were evaluated upon storage at -20-40 °C for one year. NPs presented 170-200 nm in diameter, roundish-shape, low polydispersity index (≤0.18), and high drug association efficiency (≥97%) and loading (≥12.7%). NPs differed in zeta potential, depending on surface modifier (PEO: -27.9 mV; SLS: -54.7 mV; CTAB: +42.4 mV). No interactions among formulation components were detected by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), except for SLS-PCL NPs. Colloidal properties of NPs were lost at -20 °C storage. Negatively charged NPs were stable up to one year at 5-40°C; as for CTAB-PCL NPs, particle aggregation was observed from 30 to 90 days of storage depending on temperature. Colloidal instability affected the in vitro drug release of CTAB-PCL NPs after 360 days. In any case, no degradation of dapivirine was apparent. Overall, PEO-PCL and SLS-PCL NPs presented suitable properties as nanocarriers for dapivirine. Conversely, CTAB-PCL NPs require additional strategies in order to increase stability. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Preliminary protein corona formation stabilizes gold nanoparticles and improves deposition efficiency

    Luby, Alexandra O.; Breitner, Emily K.; Comfort, Kristen K.

    2016-08-01

    Due to their advantageous characteristics, gold nanoparticles (AuNPs) are being increasingly utilized in a vast array of biomedical applications. However, the efficacy of these procedures are highly dependent upon strong interactions between AuNPs and the surrounding environment. While the field of nanotechnology has grown exponentially, there is still much to be discovered with regards to the complex interactions between NPs and biological systems. One area of particular interest is the generation of a protein corona, which instantaneously forms when NPs encounter a protein-rich environment. Currently, the corona is viewed as an obstacle and has been identified as the cause for loss of application efficiency in physiological systems. To date, however, no study has explored if the protein corona could be designed and advantageously utilized to improve both NP behavior and application efficacy. Therefore, we sought to identify if the formation of a preliminary protein corona could modify both AuNP characteristics and association with the HaCaT cell model. In this study, a corona comprised solely of epidermal growth factor (EGF) was successfully formed around 10-nm AuNPs. These EGF-AuNPs demonstrated augmented particle stability, a modified corona composition, and increased deposition over stock AuNPs, while remaining biocompatible. Analysis of AuNP dosimetry was repeated under dynamic conditions, with lateral flow significantly disrupting deposition and the nano-cellular interface. Taken together, this study demonstrated the plausibility and potential of utilizing the protein corona as a means to influence NP behavior; however, fluid dynamics remains a major challenge to progressing NP dosimetry.

  10. Improvement of kinetics, yield, and colloidal stability of biogenic gold nanoparticles using living cells of Euglena gracilis microalga

    Dahoumane, Si Amar; Yéprémian, Claude; Djédiat, Chakib; Couté, Alain; Fiévet, Fernand; Coradin, Thibaud; Brayner, Roberta

    2016-03-01

    Recent years have witnessed a boom in the biosynthesis of a large variety of nanomaterials using different biological resources among which algae-based entities have been gaining much more attention within the community of material scientists worldwide. In our previously published findings, we explored some factors that governed the biofabrication of gold nanoparticles using living cultures of microalgae, such as the utilized microalgal genera, the phylum they belong to, and the impact of tetrachloroauric acid concentrations on the ability of these strains to perform the biosynthesis of gold nanoparticles once in contact with these cations. As a follow-up, we present in this paper an improvement of the features of bioproduced gold colloids using living cells of Euglena gracilis microalga when this species is grown under either mixotrophic or autotrophic conditions, i.e., exposed to light and grown in an organic carbon-enriched culture medium versus under autotrophic conditions. As an outcome to this alteration, the growth rate of this photosynthetic microorganism is multiplied 7-8 times when grown under mixotrophic conditions compared to autotrophic ones. Therefore, the yield, the kinetics, and the colloidal stability of the biosynthesized gold nanoparticles are dramatically enhanced. Moreover, the shape and the size of the as-produced nano-objects via this biological method are affected. In addition to round-shaped gold nanoparticles, particular shapes, such as triangles and hexagons, appear. These findings add up to the amassed knowledge toward the design of photobioreactors for the scalable and sustainable production of interesting nanomaterials.

  11. Improvement of kinetics, yield, and colloidal stability of biogenic gold nanoparticles using living cells of Euglena gracilis microalga

    Dahoumane, Si Amar, E-mail: sa.dahoumane@gmail.com [Paris-Diderot University, Sorbonne Paris Cité, Interfaces, Traitements, Organisation et Dynamique des Systèmes (ITODYS), UMR 7086, CNRS (France); Yéprémian, Claude; Djédiat, Chakib; Couté, Alain [Muséum National d’Histoire Naturelle, Département RDDM, UMR 7245, Unité MCAM (France); Fiévet, Fernand [Paris-Diderot University, Sorbonne Paris Cité, Interfaces, Traitements, Organisation et Dynamique des Systèmes (ITODYS), UMR 7086, CNRS (France); Coradin, Thibaud, E-mail: thibaud.coradin@upmc.fr [UPMC—Paris 06, CNRS, Chimie de la Matière Condensée de Paris, Collège de France (France); Brayner, Roberta, E-mail: roberta.brayner@univ-paris-diderot.fr [Paris-Diderot University, Sorbonne Paris Cité, Interfaces, Traitements, Organisation et Dynamique des Systèmes (ITODYS), UMR 7086, CNRS (France)

    2016-03-15

    Recent years have witnessed a boom in the biosynthesis of a large variety of nanomaterials using different biological resources among which algae-based entities have been gaining much more attention within the community of material scientists worldwide. In our previously published findings, we explored some factors that governed the biofabrication of gold nanoparticles using living cultures of microalgae, such as the utilized microalgal genera, the phylum they belong to, and the impact of tetrachloroauric acid concentrations on the ability of these strains to perform the biosynthesis of gold nanoparticles once in contact with these cations. As a follow-up, we present in this paper an improvement of the features of bioproduced gold colloids using living cells of Euglena gracilis microalga when this species is grown under either mixotrophic or autotrophic conditions, i.e., exposed to light and grown in an organic carbon-enriched culture medium versus under autotrophic conditions. As an outcome to this alteration, the growth rate of this photosynthetic microorganism is multiplied 7–8 times when grown under mixotrophic conditions compared to autotrophic ones. Therefore, the yield, the kinetics, and the colloidal stability of the biosynthesized gold nanoparticles are dramatically enhanced. Moreover, the shape and the size of the as-produced nano-objects via this biological method are affected. In addition to round-shaped gold nanoparticles, particular shapes, such as triangles and hexagons, appear. These findings add up to the amassed knowledge toward the design of photobioreactors for the scalable and sustainable production of interesting nanomaterials.

  12. Novel microwave-synthesis of Cu nanoparticles in the absence of any stabilizing agent and their antibacterial and antistatic applications

    Raspolli Galletti, Anna Maria, E-mail: roxy@dcci.unipi.it [Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa (Italy); Antonetti, Claudia, E-mail: claudia.antonetti@ns.dcci.unipi.it [Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa (Italy); Marracci, Mirko, E-mail: mirko.marracci@ing.unipi.it [Dipartimento di Ingegneria dell’Energia, dei Sistemi, del Territorio e delle, Costruzioni, Università di Pisa, via Diotisalvi 2, 56125 Pisa (Italy); Piccinelli, Fabio, E-mail: fabio.piccinelli@univr.it [Laboratorio di Chimica dello Stato Solido, DB, Università di Verona, and INSTM, UdR Verona, Strada le Grazie 15, 37134 Verona (Italy); Tellini, Bernardo, E-mail: bernardo.tellini@ing.unipi.it [Dipartimento di Ingegneria dell’Energia, dei Sistemi, del Territorio e delle, Costruzioni, Università di Pisa, via Diotisalvi 2, 56125 Pisa (Italy)

    2013-09-01

    For the first time, copper nanoparticles were synthesized under microwave (MW) irradiation in the absence of any stabilizing agent. A 2-step synthetic approach was adopted working in basic ethanol solution and then ascorbic acid was added as a reducing reagent in the second step. The obtained copper nanoparticles were characterized by UV–vis spectroscopy, XRPD and TEM analysis. UV–vis spectra show an absorption peak at about 580–590 nm, typical of the plasma resonance of copper nanoparticles and XRPD analysis reveals that the complete reduction to metallic copper was reached at the end of the second step. Average sizes in the range 7–15 nm were ascertained through TEM microscopy. These copper nanoparticles are suitable for antibacterial and antistatic applications. The bactericidal effect was investigated in relation to the diameter of inhibition zone in disk diffusion tests on calf crust leather sample and an interesting antibacterial activity was verified against both Gram positive and Gram negative bacteria (Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Candida albicans). Moreover, this treated leather showed encouraging antistatic behavior: in particular, equivalent circuital parameters were estimated via an impedance spectroscopy technique to have a first evaluation of the charge dissipation activity by volume conduction.

  13. Structural, optical and magnetic properties of Cr doped SnO2 nanoparticles stabilized with polyethylene glycol

    Subramanyam, K.; Sreelekha, N.; Murali, G.; Reddy, D. Amaranatha; Vijayalakshmi, R.P.

    2014-01-01

    Pure and Cr (1, 3, 5 and 7 at%) doped SnO 2 nanoparticles were synthesized in aqueous solution by a simple chemical co-precipitation method using polyethylene glycol (PEG) as a stabilizing agent. The effect of Cr doping on the structural, optical and magnetic properties of SnO 2 nanoparticles was investigated. EDAX spectra confirmed the presence of Sn, O and Cr in near stoichiometry. XRD patterns revealed that particles of all samples were crystallized in single phase rutile type tetragonal crystal structure (P4 2 /mnm) of SnO 2 . The peak positions with Cr concentration shifted to higher 2θ values. Lattice parameters were also decreased with increasing Cr concentration. TEM studies indicated that the particle size is in the range of 8–10 nm. The optical absorption studies indicated that the absorption edge shifted towards lower wavelengths with inclusion of Cr content. FTIR spectrum displays various bands that are due to fundamental overtones of PEG and O–Sn–O entities. Further it revealed that the undoped and as well as Cr doped SnO 2 nanoparticles were capped by PEG. Magnetization measurements at room temperature revealed that all the doped samples were ferromagnetic in nature. Well defined strong room temperature ferromagnetic hysteresis loop was observed for 1% Cr doped SnO 2 nanoparticles

  14. Structural, optical and magnetic properties of Cr doped SnO{sub 2} nanoparticles stabilized with polyethylene glycol

    Subramanyam, K.; Sreelekha, N. [Department of Physics, Sri Venkateswara University, Tirupati 517502 (India); Murali, G. [Department of BIN Fusion Technology and Department of Polymer-Nano Science and Technology, Chonbuk National University, Jeonju, Jeonbuk (Korea, Republic of); Reddy, D. Amaranatha [Department of Chemistry and Chemical Institute for Functional Materials, Pusan National University, Busan 609-735 (Korea, Republic of); Vijayalakshmi, R.P., E-mail: vijayaraguru@gmail.com [Department of Physics, Sri Venkateswara University, Tirupati 517502 (India)

    2014-12-01

    Pure and Cr (1, 3, 5 and 7 at%) doped SnO{sub 2} nanoparticles were synthesized in aqueous solution by a simple chemical co-precipitation method using polyethylene glycol (PEG) as a stabilizing agent. The effect of Cr doping on the structural, optical and magnetic properties of SnO{sub 2} nanoparticles was investigated. EDAX spectra confirmed the presence of Sn, O and Cr in near stoichiometry. XRD patterns revealed that particles of all samples were crystallized in single phase rutile type tetragonal crystal structure (P4{sub 2}/mnm) of SnO{sub 2}. The peak positions with Cr concentration shifted to higher 2θ values. Lattice parameters were also decreased with increasing Cr concentration. TEM studies indicated that the particle size is in the range of 8–10 nm. The optical absorption studies indicated that the absorption edge shifted towards lower wavelengths with inclusion of Cr content. FTIR spectrum displays various bands that are due to fundamental overtones of PEG and O–Sn–O entities. Further it revealed that the undoped and as well as Cr doped SnO{sub 2} nanoparticles were capped by PEG. Magnetization measurements at room temperature revealed that all the doped samples were ferromagnetic in nature. Well defined strong room temperature ferromagnetic hysteresis loop was observed for 1% Cr doped SnO{sub 2} nanoparticles.

  15. Synergistic antifungal effect of chitosan-stabilized selenium nanoparticles synthesized by pulsed laser ablation in liquids against Candida albicans biofilms.

    Lara, Humberto H; Guisbiers, Gregory; Mendoza, Jonathan; Mimun, Lawrence C; Vincent, Brandy A; Lopez-Ribot, Jose L; Nash, Kelly L

    2018-01-01

    Candida albicans is a major opportunistic fungal pathogen. One of the most important virulence factors that contribute to the pathogenesis of candidiasis is its ability to form biofilms. A key characteristic of Candida biofilms is their resistance to antifungal agents. Due to significant morbidity and mortality rates related to biofilm-associated drug resistance, there is an urgency to develop novel nanotechnology-based approaches preventing biofilm-related infections. In this study, we report, for the first time, the synthesis of selenium nanoparticles by irradiating selenium pellets by nanosecond pulsed laser ablation in liquid chitosan as a capping agent. Synergy of the fungicidal effect of selenium nanoparticles and chitosan was quantified by the combination index theorem of Chou-Talalay. This drug combination resulted in a potent fungicidal effect against a preformed C. albicans biofilm in a dose-response manner. By advanced electron microscopy techniques, we documented the adhesive and permeabilizing properties of chitosan, therefore allowing selenium nanoparticles to enter as the cell wall of the yeast became disrupted and distorted. Most importantly, we demonstrated a potent quantitative synergistic effect when compounds such as selenium and chitosan are combined. These chitosan-stabilized selenium nanoparticles could be used for ex vivo applications such as sterilizers for surfaces and biomedical devices.

  16. Improved thermal stability of methylsilicone resins by compositing with N-doped graphene oxide/Co3O4 nanoparticles

    Jiang, Bo; Zhao, Liwei; Guo, Jiang; Yan, Xingru; Ding, Daowei; Zhu, Changcheng; Huang, Yudong; Guo, Zhanhu

    2016-01-01

    Nanoparticles play important roles in enhancing the thermal-resistance of hosting polymer resins. Despite tremendous efforts, developing thermally stable methylsilicone resin at high temperatures is still a challenge. Herein, we report a strategy to increase the activation energy to slow down the decomposition/degradation of methylsilicone resin using synergistic effects between the Co 3 O 4 nanoparticles and the nitrogen doped graphene oxide. The N-doped graphene oxides composited with Co 3 O 4 nanoparticles were prepared by hydrolysis of cobalt nitrate hexahydrate in the presence of graphene oxide and were incorporated into the methylsilicone resin. Two-stage decompositions were observed, i.e., 200–300 and 400–500 °C. The activation energy for the low temperature region was enhanced by 47.117 kJ/mol (vs. 57.76 kJ/mol for pure resin). The enhanced thermal stability was due to the fact that the nanofillers prevented the silicone hydroxyl chain ends ‘‘biting’’ to delay the degradation. The activation energy for high-temperature region was enhanced by 11.585 kJ/mol (vs. 171.95 kJ/mol for pure resin). The nanofillers formed a protective layer to isolate oxygen from the hosting resin. The mechanism for the enhanced thermal stability through prohibited degradation with synergism of these nitrogen-doped graphene oxide nanocomposites was proposed as well.Graphical Abstract

  17. Synthesis and characterization of Zn-doped MgAl-layered double hydroxide nanoparticles as PVC heat stabilizer

    Wang, Gongling; Yang, Mei; Li, Zhiwen; Lin, Kaifeng; Jin, Quan; Xing, Chaojian; Hu, Zhudong; Wang, Dan

    2013-01-01

    Zn-doped MgAl-layered double hydroxides (LDHs) with M 2+ /M 3+ = 2 and different molar ratios of Mg/Zn have been synthesized by modified homogeneous co-precipitation method and characterized by powder X-ray diffraction, Transmission electron microscopy, Fourier transform infrared spectrum and thermogravimetry, and differential thermal analysis techniques. The thermal stabilizing effects of different LDHs on PVC were studied by Congo red test and thermal aging test. All of the nanoparticles show plate-like morphology and the average diameter of particles is around 90 nm. Results show that the introduction of Zn increased the average bond length and area of the layers of LDHs, therefore enhanced the adsorption ability on HCl gas which was generated during degradation of PVC to improve the thermal stability of PVC. LDHs with molar ratio of Mg/Zn = 1.0 shows the best thermal stabilizing effect on PVC

  18. Synthesis and characterization of Zn-doped MgAl-layered double hydroxide nanoparticles as PVC heat stabilizer

    Wang, Gongling; Yang, Mei [Chinese Academy of Sciences, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering (China); Li, Zhiwen; Lin, Kaifeng [Harbin Institute of Technology, Academy of Fundamental Interdisciplinary Sciences (China); Jin, Quan; Xing, Chaojian; Hu, Zhudong [Chinese Academy of Sciences, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering (China); Wang, Dan, E-mail: danwang@mail.ipe.ac.cn [Harbin Institute of Technology, Academy of Fundamental Interdisciplinary Sciences (China)

    2013-09-15

    Zn-doped MgAl-layered double hydroxides (LDHs) with M{sup 2+}/M{sup 3+} = 2 and different molar ratios of Mg/Zn have been synthesized by modified homogeneous co-precipitation method and characterized by powder X-ray diffraction, Transmission electron microscopy, Fourier transform infrared spectrum and thermogravimetry, and differential thermal analysis techniques. The thermal stabilizing effects of different LDHs on PVC were studied by Congo red test and thermal aging test. All of the nanoparticles show plate-like morphology and the average diameter of particles is around 90 nm. Results show that the introduction of Zn increased the average bond length and area of the layers of LDHs, therefore enhanced the adsorption ability on HCl gas which was generated during degradation of PVC to improve the thermal stability of PVC. LDHs with molar ratio of Mg/Zn = 1.0 shows the best thermal stabilizing effect on PVC.

  19. Synthesis, characterization and antimicrobial activity of dextran stabilized silver nanoparticles in aqueous medium.

    Bankura, K P; Maity, D; Mollick, M M R; Mondal, D; Bhowmick, B; Bain, M K; Chakraborty, A; Sarkar, J; Acharya, K; Chattopadhyay, D

    2012-08-01

    A simple one-step rapid synthetic route is described for the preparation of silver nanoparticles by reduction of silver nitrate (AgNO3) using aqueous dextran solution which acts as both reducing and capping agent. The formation of silver nanoparticles is assured by characterization with UV-vis spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The absorbance of the silver nanoparticles is observed at 423 nm. The AFM image clearly shows the surface morphology of the well-dispersed silver nanoparticles with size range of 10-60 nm. TEM images show that the nanoparticles are spherical in shape with ∼5-10 nm dimensions. The crystallinity of Ag nanoparticles is assured by XRD analysis. The antimicrobial activity of as synthesized silver nanoparticles is tested against the bacteria, Bacillus subtilis, Bacillus cereus, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The bacterial growth is inhibited by gradual reduction of the concentration of the silver nanoparticles. Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. Nanoembedded Microparticles for Stabilization and Delivery of Drug-Loaded Nanoparticles

    Bohr, Adam; Water, Jorrit; Beck-Broichsitter, Moritz

    2015-01-01

    Nanoparticle-based pharmaceutical products are currently finding their way onto the market as a popular strategy to improve the therapeutic efficacy of numerous drugs, hereunder medications for a targeted treatment of severe diseases (e.g., cancer). Drug-loaded polymer and lipid nanoparticles...

  1. On the role of the colloidal stability of mesoporous silica nanoparticles as gene delivery vectors

    Cebrián, Virginia; Yagüe, Clara; Arruebo, Manuel; Martín-Saavedra, Francisco M.; Santamaría, Jesus; Vilaboa, Nuria

    2011-01-01

    Mesoporous silica nanoparticles have been synthesized and functionalized with four different types of molecules containing amino groups, i.e., with primary amines only, with quaternary amines, with quaternized cyclic amines, or with polyethylenimine (PEI), which is formed by primary, secondary, and tertiary amines. These nanoparticles were then incubated with reporter plasmids and the ability of the resulting complexes to transfect human cells was studied. Only nanoparticles functionalized with PEI were efficient for transfection. The agglomeration behavior and the electrokinetic potential of the nanoparticle–plasmid complexes have been studied, as well as their cell internalization behavior using a fluorescent-labeled plasmid that allows its monitorization by confocal microscopy. The results indicate that the efficiency of PEI-functionalized nanoparticles for transfection resides to some extent in the different characteristics imparted to the nanoparticles regarding agglomeration and surface charge behavior.

  2. Polyhydroxy surfactants for the formulation of lipid nanoparticles (SLN and NLC): effects on size, physical stability and particle matrix structure.

    Kovacevic, A; Savic, S; Vuleta, G; Müller, R H; Keck, C M

    2011-03-15

    The two polyhydroxy surfactants polyglycerol 6-distearate (Plurol(®)Stearique WL1009 - (PS)) and caprylyl/capryl glucoside (Plantacare(®) 810 - (PL)) are a class of PEG-free stabilizers, made from renewable resources. They were investigated for stabilization of aqueous solid lipid nanoparticle (SLN) and nanostructured lipid carrier (NLC) dispersions. Production was performed by high pressure homogenization, analysis by photon correlation spectroscopy (PCS), laser diffraction (LD), zeta potential measurements and differential scanning calorimetry (DSC). Particles were made from Cutina CP as solid lipid only (SLN) and its blends with Miglyol 812 (NLC, the blends containing increasing amounts of oil from 20% to 60%). The obtained particle sizes were identical for both surfactants, about 200 nm with polydispersity indices below 0.20 (PCS), and unimodal size distribution (LD). All dispersions with both surfactants were physically stable for 3 months at room temperature, but Plantacare (PL) showing a superior stability. The melting behaviour and crystallinity of bulk lipids/lipid blends were compared to the nanoparticles. Both were lower for the nanoparticles. The crystallinity of dispersions stabilized with PS was higher, the zeta potential decreased with storage time associated with this higher crystallinity, and leading to a few, but negligible larger particles. The lower crystallinity particles stabilized with PL remained unchanged in zeta potential (about -50 mV) and in size. These data show that surfactants have a distinct influence on the particle matrix structure (and related stability and drug loading), to which too little attention was given by now. Despite being from the same surfactant class, the differences on the structure are pronounced. They are attributed to the hydrophobic-lipophilic tail structure with one-point anchoring in the interface (PL), and the loop conformation of PS with two hydrophobic anchor points, i.e. their molecular structure and its

  3. Parallel array of nanochannels grafted with polymer-brushes-stabilized Au nanoparticles for flow-through catalysis.

    Liu, Jianxi; Ma, Shuanhong; Wei, Qiangbing; Jia, Lei; Yu, Bo; Wang, Daoai; Zhou, Feng

    2013-12-07

    Smart systems on the nanometer scale for continuous flow-through reaction present fascinating advantages in heterogeneous catalysis, in which a parallel array of straight nanochannels offers a platform with high surface area for assembling and stabilizing metallic nanoparticles working as catalysts. Herein we demonstrate a method for finely modifying the nanoporous anodic aluminum oxide (AAO), and further integration of nanoreactors. By using atomic transfer radical polymerization (ATRP), polymer brushes were successfully grafted on the inner wall of the nanochannels of the AAO membrane, followed by exchanging counter ions with a precursor for nanoparticles (NPs), and used as the template for deposition of well-defined Au NPs. The membrane was used as a functional nanochannel for novel flow-through catalysis. High catalytic performance and instantaneous separation of products from the reaction system was achieved in reduction of 4-nitrophenol.

  4. Parallel array of nanochannels grafted with polymer-brushes-stabilized Au nanoparticles for flow-through catalysis

    Liu, Jianxi; Ma, Shuanhong; Wei, Qiangbing; Jia, Lei; Yu, Bo; Wang, Daoai; Zhou, Feng

    2013-11-01

    Smart systems on the nanometer scale for continuous flow-through reaction present fascinating advantages in heterogeneous catalysis, in which a parallel array of straight nanochannels offers a platform with high surface area for assembling and stabilizing metallic nanoparticles working as catalysts. Herein we demonstrate a method for finely modifying the nanoporous anodic aluminum oxide (AAO), and further integration of nanoreactors. By using atomic transfer radical polymerization (ATRP), polymer brushes were successfully grafted on the inner wall of the nanochannels of the AAO membrane, followed by exchanging counter ions with a precursor for nanoparticles (NPs), and used as the template for deposition of well-defined Au NPs. The membrane was used as a functional nanochannel for novel flow-through catalysis. High catalytic performance and instantaneous separation of products from the reaction system was achieved in reduction of 4-nitrophenol.

  5. Selective retardation of perfume oil evaporation from oil-in-water emulsions stabilized by either surfactant or nanoparticles.

    Binks, Bernard P; Fletcher, Paul D I; Holt, Benjamin L; Beaussoubre, Pascal; Wong, Kenneth

    2010-12-07

    We have used dynamic headspace analysis to investigate the evaporation rates of perfume oils from stirred oil-in-water emulsions into a flowing gas stream. We compare the behavior of an oil of low water solubility (limonene) and one of high water solubility (benzyl acetate). It is shown how the evaporation of an oil of low water solubility is selectively retarded and how the retardation effect depends on the oil volume fraction in the emulsion. We compare how the evaporation retardation depends on the nature of the adsorbed film stabilizing the emulsion. Surfactant films are less effective than adsorbed films of nanoparticles, and the retardation can be further enhanced by compression of the adsorbed nanoparticle films by preshrinking the emulsion drops.

  6. Stability and electronic structure of iron nanoparticle anchored on defective hexagonal boron nitrogen nanosheet: A first-principle study

    Lin, Sen; Huang, Jing; Ye, Xinxin

    2014-01-01

    Highlights: • Fe 13 nanoparticle strongly interacts with the monovacancy of h-BN nanosheet. • Significant charges are transferred from Fe 13 to the defective h-BN nanosheet. • The upshift of d-band center makes the surface Fe atoms of supported Fe 13 with higher reactivity. - Abstract: By first-principle methods, we investigate the stability and electronic structures of Fe 13 nanoparticles anchored on hexagonal boron nitrogen nanosheets (h-BNNSs) with monovacancy defect sites. It is found that the defect sites such as boron and nitrogen vacancy significantly increase the adsorption energies of Fe 13 , suggesting that the supported Fe 13 nanoparticles should be very stable against sintering at high temperatures. From the calculated density of states, we testify that the strong interaction is attributed to the coupling between the 3d orbitals of Fe atoms with the sp 2 dangling bonds at the defect sites. The Bader charge and differential charge density analyses reveal that there is significant charge redistribution at the interface between Fe 13 and the substrates, leading to positive charges located on most of the Fe atoms. Additionally, our results show that the strong binding of the nanoparticle results in the upshift of d-band center of Fe 13 toward the Fermi level, thus making the surface Fe atoms with higher reactivity. This work gives a detailed understanding the interaction between Fe 13 nanoparticle and defective h-BNNS and will provide helpful instructions in the design and synthesis of supported Fe-based catalysts in heterogeneous catalysis

  7. Effect of cobalt doping on crystallinity, stability, magnetic and optical properties of magnetic iron oxide nano-particles

    Anjum, Safia, E-mail: safia_anjum@hotmail.com [Department of Physics, Lahore College for Women University, Lahore (Pakistan); Tufail, Rabia [Department of Physics, Lahore College for Women University, Lahore (Pakistan); Rashid, Khalid [PCSIR Laboratories Lahore (Pakistan); Zia, Rehana [Department of Physics, Lahore College for Women University, Lahore (Pakistan); Riaz, S. [Centre for Solid State Physics, University of the Punjab, Lahore (Pakistan)

    2017-06-15

    Highlights: • The stability of Co{sub x}Fe{sub (2-x)}O{sub 3} nanoparticles enhances. • Energy losses increases. • Anisotropy of NP is high. - Abstract: This paper is dedicated to investigate the effect of Co{sup 2+} ions in magnetite Fe{sub 3}O{sub 4} nano-particles with stoichiometric formula Co{sub x}Fe{sub 3-x}O{sub 4} where (x = 0, 0.05, 0.1 and 0.15) prepared by co-precipitation method. The structural, thermal, morphological, magnetic and optical properties of magnetite and Co{sup 2+} doped magnetite nanoparticles have been carried out using X-ray Diffractometer, Fourier Transform Infrared Spectroscopy, Themogravimetric Analysis, Scanning Electron Microscopy, Vibrating Sample Magnetometer (VSM) and UV–Vis Spectrometer (UV–Vis) respectively. Structural analysis verified the formation of single phase inverse spinel cubic structure with decrease in lattice parameters due to increase in cobalt content. FTIR analysis confirms the single phase of Co{sub x}Fe{sub 3-x}O{sub 4} nanoparticles with the major band at 887 cm{sup −1}, which might be due to the stretching vibrations of metal-oxide bond. The DSC results corroborate the finding of an increase in the maghemite to hematite phase transition temperature with increase in Co{sup 2+} content. The decrease in enthalpy with increase in Co{sup 2+} concentration attributed to the fact that the degree of conversion from maghemite to hematite decrease which shows that the stability increases with increasing Co{sup 2+} content in B-site of Fe{sub 3}O{sub 4} structure. SEM analysis demonstrated the formation of spherical shaped nanoparticles with least agglomeration. The magnetic measurements enlighten that the coercivity and anisotropy of Co{sub x}Fe{sub 3-x}O{sub 4} nanoparticles are significantly increased. From UV–Vis analysis it is revealed that band gap energy increases with decreasing particle size. This result has a great interest for magnetic fluid hyperthermia application (MPH).

  8. Stability of Porous Platinum Nanoparticles: Combined In Situ TEM and Theoretical Study

    Chang, Shery L. Y.; Barnard, Amanda S.; Dwyer, Christian

    2012-01-01

    Porous platinum nanoparticles provide a route for the development of catalysts that use less platinum without sacrificing catalytic performance. Here, we examine porous platinum nanoparticles using a combination of in situ transmission electron microscopy and calculations based on a first-principles......-parametrized thermodynamic model. Our experimental observations show that the initially irregular morphologies of the as-sythesized porous nanoparticles undergo changes at high temperatures to morphologies having faceted external surfaces with voids present in the interior of the particles. The increasing size of stable...

  9. Functional PEG–PAMAM-Tetraphosphonate Capped NaLnF4 Nanoparticles and their Colloidal Stability in Phosphate Buffer

    2015-01-01

    Developing surface coatings for NaLnF4 nanoparticles (NPs) that provide long-term stability in solutions containing competitive ions such as phosphate remains challenging. An amine-functional polyamidoamine tetraphosphonate (NH2-PAMAM-4P) as a multidentate ligand for these NPs has been synthesized and characterized as a ligand for the surface of NaGdF4 and NaTbF4 nanoparticles. A two-step ligand exchange protocol was developed for introduction of the NH2-PAMAM-4P ligand on oleate-capped NaLnF4 NPs. The NPs were first treated with methoxy-poly(ethylene glycol)-monophosphoric acid (Mn = 750) in tetrahydrofuran. The mPEG750-OPO3-capped NPs were stable colloidal solutions in water, where they could be ligand-exchanged with NH2-PAMAM-4P. The surface amine groups on the NPs were available for derivatization to attach methoxy-PEG (Mn = 2000) and biotin-terminated PEG (Mn = 2000) chains. The surface coverage of ligands on the NPs was examined by thermal gravimetric analysis, and by a HABA analysis for biotin-containing NPs. Colloidal stability of the NPs was examined by dynamic light scattering. NaGdF4 and NaTbF4 NPs capped with mPEG2000–PAMAM-4P showed colloidal stability in DI water and in phosphate buffer (10 mM, pH 7.4). A direct comparison with NaTbF4 NPs capped with a mPEG2000-lysine-based tetradentate ligand that we reported previously (Langmuir2012, 28, 12861−1287022906305) showed that both ligands provided long-term stability in phosphate buffer, but that the lysine-based ligand provided better stability in phosphate-buffered saline. PMID:24898128

  10. Functional PEG-PAMAM-tetraphosphonate capped NaLnF₄ nanoparticles and their colloidal stability in phosphate buffer.

    Zhao, Guangyao; Tong, Lemuel; Cao, Pengpeng; Nitz, Mark; Winnik, Mitchell A

    2014-06-17

    Developing surface coatings for NaLnF4 nanoparticles (NPs) that provide long-term stability in solutions containing competitive ions such as phosphate remains challenging. An amine-functional polyamidoamine tetraphosphonate (NH2-PAMAM-4P) as a multidentate ligand for these NPs has been synthesized and characterized as a ligand for the surface of NaGdF4 and NaTbF4 nanoparticles. A two-step ligand exchange protocol was developed for introduction of the NH2-PAMAM-4P ligand on oleate-capped NaLnF4 NPs. The NPs were first treated with methoxy-poly(ethylene glycol)-monophosphoric acid (M(n) = 750) in tetrahydrofuran. The mPEG750-OPO3-capped NPs were stable colloidal solutions in water, where they could be ligand-exchanged with NH2-PAMAM-4P. The surface amine groups on the NPs were available for derivatization to attach methoxy-PEG (M(n) = 2000) and biotin-terminated PEG (M(n) = 2000) chains. The surface coverage of ligands on the NPs was examined by thermal gravimetric analysis, and by a HABA analysis for biotin-containing NPs. Colloidal stability of the NPs was examined by dynamic light scattering. NaGdF4 and NaTbF4 NPs capped with mPEG2000-PAMAM-4P showed colloidal stability in DI water and in phosphate buffer (10 mM, pH 7.4). A direct comparison with NaTbF4 NPs capped with a mPEG2000-lysine-based tetradentate ligand that we reported previously (Langmuir 2012, 28, 12861-12870) showed that both ligands provided long-term stability in phosphate buffer, but that the lysine-based ligand provided better stability in phosphate-buffered saline.

  11. Effect of electrolyte valency, alginate concentration and pH on engineered TiO₂ nanoparticle stability in aqueous solution.

    Loosli, Frédéric; Le Coustumer, Philippe; Stoll, Serge

    2015-12-01

    Agglomeration and disagglomeration processes are expected to play a key role on the fate of engineered nanoparticles in natural aquatic systems. These processes are investigated here in detail by studying first the stability of TiO2 nanoparticles in the presence of monovalent and divalent electrolytes at different pHs (below and above the point of zero charge of TiO2) and discussing the importance of specific divalent cation adsorption with the help of the DLVO theory as well as the importance of the nature of the counterions. Then the impact of one polysaccharide (alginate) on the stability of agglomerates formed under pH and water hardness representative of Lake Geneva environmental conditions is investigated. In these conditions the large TiO2 agglomerates (diameter>1μm) are positively charged due to Ca(2+) and Mg(2+) specific adsorption and alginate, which is negatively charged, adsorbs onto the agglomerate surface. Our results indicate that the presence of alginate at typical natural organic matter concentration (1-10 mg L(-1)) strongly modifies the TiO2 agglomerate (50 mg L(-1)) stability by inducing their partial and rapid disagglomeration. The importance of disagglomeration is found dependent on the alginate concentration with maximum of disagglomeration obtained for alginate concentration ≥8 mg L(-1) and leading to 400 nm fragments. From an environmental point of view partial restabilization of TiO2 agglomerates in the presence of alginate constitutes an important outcome. Disagglomeration will enhance their transport and residence time in aquatic systems which is an important step in the current knowledge on risk assessment associated to engineered nanoparticles. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Magneto-optical detection of the relaxation dynamics of alloy nanoparticles with a high-stability magnetic circular dichroism setup

    Cavigli, L. [L.E.N.S. University of Florence, via N. Carrara 1, I-50019 Sesto F.no (Italy); INSTM Department of Chemistry, University of Florence, via della Lastruccia 5, I-50019 Sesto F.no (Italy); Julian Fernandez, C. de [Department of Physics, University of Padua, via Marzolo 8, I-35131 Padova (Italy); Gatteschi, D. [INSTM Department of Chemistry, University of Florence, via della Lastruccia 5, I-50019 Sesto F.no (Italy); Gurioli, M. [L.E.N.S. University of Florence, via N. Carrara 1, I-50019 Sesto F.no (Italy); Sangregorio, C. [INSTM Department of Chemistry, University of Florence, via della Lastruccia 5, I-50019 Sesto F.no (Italy)]. E-mail: claudio.sangregorio@unifi.it; Mattei, G. [Department of Physics, University of Padua, via Marzolo 8, I-35131 Padova (Italy); Mazzoldi, P. [Department of Physics, University of Padua, via Marzolo 8, I-35131 Padova (Italy); Bogani, L. [L.E.N.S. University of Florence, via N. Carrara 1, I-50019 Sesto F.no (Italy); INSTM Department of Chemistry, University of Florence, via della Lastruccia 5, I-50019 Sesto F.no (Italy)

    2007-09-15

    We present a versatile high-stability and high-sensitivity magneto-optical setup that allows transmission and reflection measurements at high fields and low temperatures. We apply the technique to measure the decay in time of the magnetization of highly monodisperse 3.3nm Co{sub 33}Ni{sub 67} alloy nanoparticles embedded in a silica host. We demonstrate the possibility of observing the dynamics of the magnetization over a macroscopic timescale in dilute samples, where other techniques are unavailable.

  13. Nanoparticle core stability and surface functionalization drive the mTOR signaling pathway in hepatocellular cell lines

    Lunova, Mariia; Prokhorov, Andriy; Jirsa, M.; Hof, Martin; Olžyńska, Agnieszka; Jurkiewicz, Piotr; Kubinová, Šárka; Lunov, Oleg; Dejneka, Alexandr

    2017-01-01

    Roč. 7, Nov (2017), s. 1-16, č. článku 16049. ISSN 2045-2322 R&D Projects: GA MŠk LO1409; GA MŠk LM2015088 Grant - others:AV ČR(CZ) Fellowship J. E. Purkyně Institutional support: RVO:68378271 ; RVO:61388955 Keywords : nanoparticle core stability * surface functionalization drive * mTOR signaling pathway * hepatocellular cell lines Subject RIV: BO - Biophysics; CF - Physical ; Theoretical Chemistry (UFCH-W) OBOR OECD: Biophysics; Physical chemistry (UFCH-W) Impact factor: 4.259, year: 2016

  14. Bactericidal effect of starch-stabilized zero-valent iron nanoparticles on Escherichia coli

    Mohammad Mosaferi

    2016-01-01

    Conclusion: The present study showed that nonstabilized Fe 0 nanoparticles have higher bactericidal efficiency than that of S-NZVI. This investigation also suggests that NZVI can be used as an effective and strong agent for antimicrobial applications.

  15. Green synthesis of metal nanoparticles: biodegradable polymers and enzymes in stabilization and surface functionalization

    Current breakthroughs in green nanotechnology are capable to transform many of the existing processes and products that enhance environmental quality, reduce pollution, and conserve natural and non-renewable resources. Noteworthy, successful use of metal nanoparticles and 10 nano...

  16. Synthesis of polymer-stabilized monometallic Cu and bimetallic Cu/Ag nanoparticles and their surface-enhanced Raman scattering properties

    Zhang, Danhui; Liu, Xiaoheng

    2013-03-01

    The present study demonstrates a facile process for the production of spherical-shaped Cu and Ag nanoparticles synthesized and stabilized by hydrazine and gelatin, respectively. Advantages of the synthetic method include its production of water dispersible copper and copper/silver nanoparticles at room temperature under no inert atmosphere. The resulting nanoparticles (copper or copper/silver) are investigated by X-ray diffraction (XRD), UV-vis spectroscopy, and transmission electron microscopy (TEM). The nanometallic dispersions were characterized by surface plasmon absorbance measuring at 420 and 572 nm for Ag and Cu nanoparticles, respectively. Transmission electron microscopy showed the formation of nanoparticles in the range of ˜10 nm (silver), and ˜30 nm (copper). The results also demonstrate that the reducing order of Cu2+/Ag+ is important for the formation of the bimetallic nanoparticles. The surface-enhanced Raman scattering effects of copper and copper/silver nanoparticles were also displayed. It was found that the enhancement ability of copper/silver nanoparticles was little higher than the copper nanoparticles.

  17. Highly Stabilized Curcumin Nanoparticles Tested in an In Vitro Blood–Brain Barrier Model and in Alzheimer’s Disease Tg2576 Mice

    Cheng, Kwok Kin; Yeung, Chin Fung; Ho, Shuk Wai; Chow, Shing Fung; Chow, Albert H. L.; Baum, Larry

    2012-01-01

    The therapeutic effects of curcumin in treating Alzheimer’s disease (AD) depend on the ability to penetrate the blood–brain barrier. The latest nanoparticle technology can help to improve the bioavailability of curcumin, which is affected by the final particle size and stability. We developed a stable curcumin nanoparticle formulation to test in vitro and in AD model Tg2576 mice. Flash nanoprecipitation of curcumin, polyethylene glycol-polylactic acid co-block polymer, and polyvinylpyrrolidon...

  18. Localized surface plasmon behavior of Ag-Cu alloy nanoparticles stabilized by rice-starch and gelatin

    Singh, Manish Kumar; Mandal, R. K., E-mail: rkmandal.met@itbhu.ac.in [Department of Metallurgical Engineering, IIT (BHU), Varanasi and DST Unit on Nanoscience and Technology, BHU, Varanasi-221 005 (India); Manda, Premkumar; Singh, A. K. [DefenceMetallurgical Research Laboratory, KanchanBagh, Hyderabad-500058 (India)

    2015-10-15

    The purpose of this communication was to understand localized surface plasmon behavior of a series of Ag-Cu alloy nanoparticles capped by rice-starch and gelatin. The structures of dried powders were investigated with the help of X-ray diffraction. The analysis revealed Ag-rich and Cu-rich phases with maximum solid solubility of Cu ∼9 atom per cent; 8 atom per cent and Ag ∼ 16 atom per cent; 14 atom per cent in rice-starch and gelatin capped samples respectively. Transmission electron microscope was used for knowing the particle size as well as to supplement FCC phase formations of Ag-rich and Cu-rich solid phases arrived at based on X-ray diffraction studies. The UV-Vis spectra of sols were examined for the formation and stability of alloy nanoparticles. The temporal evolution of LSPR curves gave us to assert that the sol is stable for more than two months. Small angle X-ray scattering in the sol state was extensively utilized to understand nature of suspensions in terms of fractals. Such a study is important for having a correlation between LSPR behaviors with those of nanoparticle dispersion in aqueous media. It is believed that this work will be a contribution to the emerging field of plasmonics that include applications in the area of photophysical processes and photochemical reactions.

  19. Evaluation of Colloidal Stability and Ecotoxicity of Metal-based Nanoparticles in the Aquatic and Terrestrial Systems

    Pokhrel, Lok Raj

    Intrinsic to the many nano-enabled products are atomic-size multifunctional engineered nanomaterials, which upon release contaminate the environments, raising considerable health and safety concerns. This Ph.D. dissertation is designed to investigate (i) whether metals or oxide nanoparticles are more toxic than ions, and if MetPLATE(TM) bioassay is applicable as a rapid nanotoxicity screening tool; (ii) how variable water chemistry (dissolved organic carbon (DOC), pH, and hardness) and organic compounds (cysteine, humic acid, and trolox) modulate colloidal stability, ion release, and aquatic toxicity of silver nanoparticles (AgNP); and (iii) the developmental responses of crop plants exposed to Ag- or ZnO- (zinc oxide) nanoparticles. Results suggest that the MetPLATE can be considered a high-throughput screening tool for rapid nanotoxicity evaluation. Detectable changes in the colloidal diameter, surface charge, and plasmonic resonance revealed modulating effects of variable water chemistry and organic ligands on the particle stability, dissolution, and toxicity of AgNPs against Escherichia coli or Daphnia magna. Silver dissolution increased as a function of DOC concentrations but decreased with increasing hardness, pH, cysteine, or trolox levels. Notably, the dissociated Ag+ was inadequate to explain AgNP toxicity, and that the combined effect of AgNPs and dissolved Ag+ under each ligand treatment was lower than of AgNO 3. Significant attenuation by trolox signifies an oxidative stress-mediated AgNP toxicity; its inability to attenuate AgNO3 toxicity, however, negates oxidative stress as Ag+ toxicity mechanism, and that cysteine could effectively quench free Ag+ to alleviate AgNO 3 toxicity in D. magna. Surprisingly, DOC-AgNPs complex that apparently formed at higher DOC levels might have led daphnids filter-feed on aggregates, potentially elevating internal dose, and thus higher mortality. Maize root anatomy showed differential alterations upon exposure to Ag

  20. Stability of templated and nanoparticles dye-sensitized solar cells: photovoltaic and electrochemical investigation of degradation mechanisms at the photoelectrode interface

    Dewalque, Jennifer; Nguyen, Ngoc Duy; Colson, Pierre; Krins, Natacha; Cloots, Rudi; Henrist, Catherine

    2014-01-01

    Graphical abstract: Highly porous templated TiO 2 films are promising alternative to nanoparticle layers for dye-sensitized solar cell applications. However, the increase of the electron transfer surface could promote detrimental side reactions and accelerate cell degradation upon ageing. Therefore, stability of templated cells under UV exposure, visible light soaking and thermal stress was studied in comparison to nanoparticle cells. -- Highlights: •Stability of templated and nanoparticle dye-sensitized solar cells is compared. •Templated cells are more sensitive to UV degradation than nanoparticle cells. •Templated cells are as stable as nanoparticle cells under light soaking. •Templated cells are more stable than nanoparticle cells under thermal stress. •Templated cells present better overall performances than nanoparticle cells. -- Abstract: A key issue in the commercialization of dye-sensitized solar cells is to maintain high efficiency and long lifetime. As reported in the literature, dye-sensitized solar cells are stable under visible light soaking but thermal stress and UV exposure lead to efficiency degradation. However, all the stability studies published so far have been performed on cells whose TiO 2 electrodes were prepared by tape casting or screen printing of nanoparticle pastes/inks. The present study concerns cells based on highly porous templated TiO 2 electrodes, whose larger surface area could enhance the negative effects of thermal stress, light soaking and UV exposure. The long-term stability of these cells is compared with a classical nanoparticle-based cell using current-voltage measurements (I-V curves) and electrochemical impedance spectroscopy. Due to their higher active interface, templated cells are more sensitive than nanoparticle cells to UV illumination, although this can be easily solved in both cases by the use of a UV filter. The templated cells are as stable as the nanoparticle cells under visible light soaking (UV

  1. Tunable thermodynamic stability of Au-CuPt core-shell trimetallic nanoparticles by controlling the alloy composition: insights from atomistic simulations.

    Huang, Rao; Shao, Gui-Fang; Wen, Yu-Hua; Sun, Shi-Gang

    2014-11-07

    A microscopic understanding of the thermal stability of metallic core-shell nanoparticles is of importance for their synthesis and ultimately application in catalysis. In this article, molecular dynamics simulations have been employed to investigate the thermodynamic evolution of Au-CuPt core-shell trimetallic nanoparticles with various Cu/Pt ratios during heating processes. Our results show that the thermodynamic stability of these nanoparticles is remarkably enhanced upon rising Pt compositions in the CuPt shell. The melting of all the nanoparticles initiates at surface and gradually spreads into the core. Due to the lattice mismatch among Au, Cu and Pt, stacking faults have been observed in the shell and their numbers are associated with the Cu/Pt ratios. With the increasing temperature, they have reduced continuously for the Cu-dominated shell while more stacking faults have been produced for the Pt-dominated shell because of the significantly different thermal expansion coefficients of the three metals. Beyond the overall melting, all nanoparticles transform into a trimetallic mixing alloy coated by an Au-dominated surface. This work provides a fundamental perspective on the thermodynamic behaviors of trimetallic, even multimetallic, nanoparticles at the atomistic level, indicating that controlling the alloy composition is an effective strategy to realize tunable thermal stability of metallic nanocatalysts.

  2. Synthesis and controllable oxidation of monodisperse cobalt-doped wüstite nanoparticles and their core-shell stability and exchange-bias stabilization.

    Chen, Chih-Jung; Chiang, Ray-Kuang; Kamali, Saeed; Wang, Sue-Lein

    2015-09-14

    Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ∼4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (H(E)), an enhanced coercivity field (H(C)), and a pronounced vertical shift, thus indicating the presence of a strong exchange bias coupling effect. More importantly, the onset temperature of H(E) was found to be higher than 200 K, which suggests that cobalt doping increases the Néel temperature (T(N)) of the CWT core. In general, the results show that the homogeneous dispersion of Co in iron precursors improves the stability of the final CWT nanoparticles. Moreover, the CoFe2O4 shells formed following oxidation increase the oxidation resistance of the CWT cores and enhance their anisotropy energy.

  3. Thiol-PEG-carboxyl-stabilized Fe2O3/Au nanoparticles targeted to CD105: Synthesis, characterization and application in MR imaging of tumor angiogenesis

    Zhang, Song; Gong, Mingfu; Zhang, Dong; Yang, Hua; Gao, Fabao; Zou, Liguang

    2014-01-01

    Objective: To detect tumor angiogenesis in tumor-bearing mice using thiol-PEG-carboxyl-stabilized Fe 2 O 3 /Au nanoparticles targeted to CD105 on magnetic resonance imaging (MRI). Methods: Fe 2 O 3 /Au nanoparticles (hybrids) were prepared by reducing Au 3+ on the surface of Fe 2 O 3 nanoparticles. Hybrids were stabilized with thiol-PEG-carboxyl via the Au–S covalent bond, and further conjugated with anti-CD105 antibodies through amide linkages. Characteristics of the hybrid-PEG-CD105 nanoparticles were evaluated. Using these nanoparticles, the labeling specificity of human umbilical vein endothelial cells (HUVECs) was evaluated in vitro. MRI T2*-weighted images were obtained at different time points after intravenous administration of the hybrid-PEG-CD105 nanoparticles in the tumor-bearing mice. After MR imaging, the breast cancer xenografts were immediately resected for immunohistochemistry staining and Prussian blue staining to measure the tumor microvessel density (MVD) and evaluate the labeling of blood microvessels by the hybrid-PEG-CD105 nanoparticles in vivo. Results: The mean diameter of the hybrid-PEG-CD105 nanoparticles was 56.6 ± 8.0 nm, as measured by transmission electron microscopy (TEM). Immune activity of the hybrid-PEG-CD105 nanoparticles was 53% of that of the anti-CD105 antibody, as detected by enzyme-linked immunosorbent assay (ELISA). The specific binding of HUVECs with the hybrid-PEG-CD105 nanoparticles was proved by immunostaining and Prussian blue staining in vitro. For breast cancer xenografts, the combination of the hybrid-PEG-CD105 nanoparticles with blood microvessels was detectable by MRI after 60 min administration of the contrast agent. The T2* relative signal intensity (SI R ) was positively correlated with the tumor MVD (R 2 = 0.8972). Conclusion: Anti-CD105 antibody-coupled, thiol-PEG-carboxyl-stabilized core–shell Fe 2 O 3 /Au nanoparticles can efficiently target CD105 expressed by HUVECs. Furthermore, the hybrid-PEG-CD105

  4. Sonochemical synthesis of stibnite nanoparticles and their use as radiolytic stabilizer in polynomial chloride matrix

    Albuquerque, Marilia Cordeiro C. de; Lima, Thaysa Araujo de; Aquino, Katia Aparecida da Silva; Araujo, Elmo S.

    2011-01-01

    Stibnite (Sb 2 S 3 ) was synthesized by sonochemical method. Amorphous powder of Sb 2 S 3 was obtained and exhibit nanospheres structure with an average size in the range of 300-500 nm. Commercial Polyvinyl Chloride (PVC) containing Sb 2 S 3 nanoparticles (PVC/Sb) at concentrations of 0.10; 0.30 and 0.50 wt% were investigated. The samples were irradiated with gamma radiation ( 60 Co) at room temperature and air atmosphere. The viscosity-average molar mass (M v ) was measured for PVC systems without nanoparticles and with nanoparticles. Decreases in molar mass observed when the systems were gamma irradiated reflect the random scission effects that take place in the main chain. Degradation index (DI) value was also obtained by viscosity analysis. DI results showed that the addition of Sb 2 S 3 nanoparticles at 0.3 wt% into PVC matrix irradiated at dose of 25 kGy decreased the number of main chain scissions and was calculated a protection index of 66,5% in PVC matrix. Results about the free radical scavenger action of the Sb 2 S 3 were obtained by use of 2,2-diphenyl-1-(2,4,6-trinitrophenyl)-hydrazyl radical (DPPH) and are discussed in this study. Changes in the infrared spectra of PVC systems indicated that polymer molecules interact with Sb 2 S 3 nanoparticles. (author)

  5. Nanoparticles Stabilize Thin Polymer Films: A Fundamental Study to Understand the Phenomenon

    Michael E. Mackay

    2009-03-04

    A new understanding of thermodynamics at the nanoscale resulted in a recently discovered first order phase transition that nanoparticles in a polymer film will all segregate to the supporting substrate. This is an unusual phase transition that was predicted using a modeling technique developed at Sandia National Laboratories and required the equivalent of many computational years on one computer. This project is a collaboration between Prof. Michael Mackay's group and Dr. Amalie Frischknecht (Sandia National Laboratories) where experimental observation and theoretical rationalization and prediction are brought together. Other discoveries were that this phase transition could be avoided by changing the nanoparticle properties yielding control of the assembly process at the nanoscale. In fact, the nanoparticles could be made to assemble to the supporting substrate, to the air interface or not assemble at all within a thin polymer film of order 100 nm in thickness. However, when the assembly process is present it is so robust that it is possible to make rough liquid films at the nanoscale due to nanoparticles assembling around three-dimensional objects. From this knowledge we are able to design and manufacture new coatings with particular emphasis on polymer-based solar cells. Careful control of the morphology at the nanoscale is expected to provide more efficient devices since the physics of these systems is dictated at this length scale and assembly of nanoparticles to various interfaces is critical to operation.

  6. Human serum albumin as protecting agent of silver nanoparticles: role of the protein conformation and amine groups in the nanoparticle stabilization

    Alarcon, Emilio I.; Bueno-Alejo, Carlos J.; Noel, Christopher W.; Stamplecoskie, Kevin G. [Centre for Catalysis Research and Innovation, University of Ottawa, Department of Chemistry (Canada); Pacioni, Natalia L. [Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, INFIQC, Departamento de Quimica Organica (Argentina); Poblete, Horacio [Center for Bioinformatics and Molecular Simulations, Universidad de Talca (Chile); Scaiano, J. C., E-mail: tito@photo.chem.uottawa.ca [Centre for Catalysis Research and Innovation, University of Ottawa, Department of Chemistry (Canada)

    2013-01-15

    Thermally denatured human serum albumin interacts with {approx}3.0 nm spherical AgNP enhancing the fluorescence of Trp-214 at large protein/nanoparticle ratios. However, using native HSA, no changes in the emission were observed. The observation is likely due to differences between native and denatured protein packing resulting from protein corona formation. We have also found that NH{sub 2} blocking of the protein strongly affects the ability of the protein to protect AgNP from different salts/ions such as NaCl, PBS, Hank's buffer, Tris-HCl, MES, and DMEM. Additionally, AgNP can be readily prepared in aqueous solutions by a photochemical approach employing HSA as an in situ protecting agent. The role of the protein in this case is beyond that of protecting agent; thus, Ag{sup +} ions and I-2959 complexation within the protein structure also affects the efficiency of AgNP formation. Blocking NH{sub 2} in HSA modified the AgNP growth profile, surface plasmon band shape, and long-term stability suggesting that amine groups are directly involved in the formation and post-stabilization of AgNP. In particular, AgNP size and shape are extensively influenced by NH{sub 2} blocking, leading primarily to cubes and plates with sizes around 5-15 nm; in contrast, spherical monodisperse 4.0 nm AgNP are observed for native HSA. The nanoparticles prepared by this protocol are non-toxic in primary cells and have remarkable antibacterial properties. Finally, surface plasmon excitation of native HSA-AgNP promoted loss of protein conformation in just 5 min, suggesting that plasmon heating causes protein denaturation using continuous light sources such as commercial LED.

  7. Human serum albumin as protecting agent of silver nanoparticles: role of the protein conformation and amine groups in the nanoparticle stabilization

    Alarcon, Emilio I.; Bueno-Alejo, Carlos J.; Noel, Christopher W.; Stamplecoskie, Kevin G.; Pacioni, Natalia L.; Poblete, Horacio; Scaiano, J. C.

    2013-01-01

    Thermally denatured human serum albumin interacts with ∼3.0 nm spherical AgNP enhancing the fluorescence of Trp-214 at large protein/nanoparticle ratios. However, using native HSA, no changes in the emission were observed. The observation is likely due to differences between native and denatured protein packing resulting from protein corona formation. We have also found that NH 2 blocking of the protein strongly affects the ability of the protein to protect AgNP from different salts/ions such as NaCl, PBS, Hank’s buffer, Tris–HCl, MES, and DMEM. Additionally, AgNP can be readily prepared in aqueous solutions by a photochemical approach employing HSA as an in situ protecting agent. The role of the protein in this case is beyond that of protecting agent; thus, Ag + ions and I-2959 complexation within the protein structure also affects the efficiency of AgNP formation. Blocking NH 2 in HSA modified the AgNP growth profile, surface plasmon band shape, and long-term stability suggesting that amine groups are directly involved in the formation and post-stabilization of AgNP. In particular, AgNP size and shape are extensively influenced by NH 2 blocking, leading primarily to cubes and plates with sizes around 5–15 nm; in contrast, spherical monodisperse 4.0 nm AgNP are observed for native HSA. The nanoparticles prepared by this protocol are non-toxic in primary cells and have remarkable antibacterial properties. Finally, surface plasmon excitation of native HSA-AgNP promoted loss of protein conformation in just 5 min, suggesting that plasmon heating causes protein denaturation using continuous light sources such as commercial LED.

  8. Pickering emulsion stabilized by cashew gum- poly-l-lactide copolymer nanoparticles: Synthesis, characterization and amphotericin B encapsulation.

    Richter, A R; Feitosa, J P A; Paula, H C B; Goycoolea, F M; de Paula, R C M

    2018-04-01

    In this work, we provide proof-of-concept of formation, physical characteristics and potential use as a drug delivery formulation of Pickering emulsions (PE) obtained by a novel method that combines nanoprecipitation with subsequent spontaneous emulsification process. To this end, pre-formed ultra-small (d.∼10 nm) nanoprecipitated nanoparticles of hydrophobic derivatives of cashew tree gum grafted with polylactide (CGPLAP), were conceived to stabilize Pickering emulsions obtained by spontaneous emulsification. These were also loaded with Amphotericin B (AmB), a drug of low oral bioavailability used in the therapy of neglected diseases such as leishmaniasis. The graft reaction was performed in two CG/PLA molar ratio conditions (1:1 and 1:10). Emulsions were prepared by adding the organic phase (Miglyol 812 ® ) in the aqueous phase (nanoprecipitated CGPLAP), resulting the immediate emulsion formation. The isolation by centrifugation does not destabilize or separate the nanoparticles from oil droplets of the PE emulsion. Emulsions with CGPLAP 1:1 presented unimodal distributions at different CGPLA concentration, lower values in size and PDI and the best stability over time. The AmB was incorporated in the emulsions with a process efficiency of 21-47%, as determined by UV-vis. AmB in CGPLAP emulsions is in less aggregated state than observed in commercial AmB formulation. Copyright © 2018 Elsevier B.V. All rights reserved.

  9. Study of the synthesis of copper nanoparticles: the role of capping and kinetic towards control of particle size and stability

    Granata, Giuseppe, E-mail: giuseppe.granata@aoni.waseda.jp; Yamaoka, Taishi [Waseda University, School of Creative Science and Engineering (Japan); Pagnanelli, Francesca [Sapienza University of Rome, Department of Chemistry (Italy); Fuwa, Akio [Waseda University, School of Creative Science and Engineering (Japan)

    2016-05-15

    The synthesis of copper nanoparticles (CuNPs) by surfactant-assisted chemical reduction method was studied aiming to identify and quantify the role of kinetic and capping on particle size distribution. The use of a strong and a mild reducing agent (hydrazine, d-glucose) has been investigated as well as the use of three different capping agents: cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP). Experimental tests were arranged according to factorial designs. CuNPs were characterized by XRD, FE-SEM and UV–Vis spectrophotometry. Particle size distribution was determined by image analysis and significance of investigated factors was statistically assessed by analysis of variance. Under the investigated conditions, CTAB was found capable of preventing oxidation but it had a significant positive effect on nanoparticle size (about 40 and 30 nm); SDS determined a good size control but no stabilization, whilst PVP could provide both size control (significant negative effect of about 15 and 25 nm) and stability. Average size of CuNPs can be significantly reduced of about 50 nm by replacing d-glucose with hydrazine.Graphical Abstract.

  10. Dihydrogen Phosphate Stabilized Ruthenium(0 Nanoparticles: Efficient Nanocatalyst for The Hydrolysis of Ammonia-Borane at Room Temperature

    Feyyaz Durap

    2015-07-01

    Full Text Available Intensive efforts have been devoted to the development of new materials for safe and efficient hydrogen storage. Among them, ammonia-borane appears to be a promising candidate due to its high gravimetric hydrogen storage capacity. Ammonia-borane can release hydrogen on hydrolysis in aqueous solution under mild conditions in the presence of a suitable catalyst. Herein, we report the synthesis of ruthenium(0 nanoparticles stabilized by dihydrogenphosphate anions with an average particle size of 2.9 ± 0.9 nm acting as a water-dispersible nanocatalyst in the hydrolysis of ammonia-borane. They provide an initial turnover frequency (TOF value of 80 min−1 in hydrogen generation from the hydrolysis of ammonia-borane at room temperature. Moreover, the high stability of these ruthenium(0 nanoparticles makes them long-lived and reusable nanocatalysts for the hydrolysis of ammonia-borane. They provide 56,800 total turnovers and retain ~80% of their initial activity even at the fifth catalytic run in the hydrolysis of ammonia-borane at room temperature.

  11. Functionalized gold nanoparticles for the binding, stabilization, and delivery of therapeutic DNA, RNA, and other biological macromolecules

    Robert K DeLong

    2010-09-01

    Full Text Available Robert K DeLong1, Christopher M Reynolds1, Yaneika Malcolm1, Ashley Schaeffer1, Tiffany Severs2, Adam Wanekaya21Department of Biomedical Science (Cell and Molecular Biology Program, 2Department of Chemistry, Missouri State University, Springfield, MO, USAAbstract: Nanotechnology has virtually exploded in the last few years with seemingly limitless opportunity across all segments of our society. If gene and RNA therapy are to ever realize their full potential, there is a great need for nanomaterials that can bind, stabilize, and deliver these macromolecular nucleic acids into human cells and tissues. Many researchers have turned to gold nanomaterials, as gold is thought to be relatively well tolerated in humans and provides an inert material upon which nucleic acids can attach. Here, we review the various strategies for associating macromolecular nucleic acids to the surface of gold nanoparticles (GNPs, the characterization chemistries involved, and the potential advantages of GNPs in terms of stabilization and delivery.Keywords: gold, nanoparticles, nanomaterials, RNA, nucleic acid

  12. Microwave assisted polymer stabilized synthesis of silver nanoparticles and its application in the degradation of environmental pollutants

    Rastogi, Pankaj Kumar; Ganesan, Vellaichamy; Krishnamoorthi, S.

    2012-01-01

    Highlights: ► Graft copolymers of polyacrylamide and dextran are synthesized by grafting PAM chains onto a Dx backbone. ► Silver nanoparticles dispersed copolymer nano-composite (Ag-HDx-g-PAM) is synthesized by microwave heating. ► The environmentally benign and biodegradable copolymer, HDx-g-PAM acts as stabilizing and reducing agent. ► Ag-HDx-g-PAM nano-composite shows efficient catalytic activity for the reduction of environmental pollutants. - Abstract: Graft copolymers of polyacrylamide (PAM) and dextran (Dx) are synthesized by grafting PAM chains onto a Dx backbone (Dx-g-PAM) with ceric ion induced solution polymerization technique. Partial hydrolysis of Dx-g-PAM is carried out with sodium hydroxide solution to obtain HDx-g-PAM. To synthesize silver nanoparticles dispersed copolymer nano-composite (Ag-HDx-g-PAM), reduction of silver ions with HDx-g-PAM is carried out using microwave heating. The environmentally benign and biodegradable copolymer, HDx-g-PAM acts as both stabilizer and reducing agent. The copolymer nano-composite, Ag-HDx-g-PAM is characterized by FT-IR, transmission electron microscopy, scanning electron microscopy and optical spectroscopy. Further, the catalytic activity of Ag-HDx-g-PAM nano-composite towards the reduction of environmental pollutants like phenosafranine dye and aromatic nitro compounds are studied.

  13. Microwave assisted polymer stabilized synthesis of silver nanoparticles and its application in the degradation of environmental pollutants

    Rastogi, Pankaj Kumar [Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221 005, UP (India); Ganesan, Vellaichamy, E-mail: velganesh@yahoo.com [Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221 005, UP (India); Krishnamoorthi, S., E-mail: dr.skmoorthi@gmail.com [Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221 005, UP (India)

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Graft copolymers of polyacrylamide and dextran are synthesized by grafting PAM chains onto a Dx backbone. Black-Right-Pointing-Pointer Silver nanoparticles dispersed copolymer nano-composite (Ag-HDx-g-PAM) is synthesized by microwave heating. Black-Right-Pointing-Pointer The environmentally benign and biodegradable copolymer, HDx-g-PAM acts as stabilizing and reducing agent. Black-Right-Pointing-Pointer Ag-HDx-g-PAM nano-composite shows efficient catalytic activity for the reduction of environmental pollutants. - Abstract: Graft copolymers of polyacrylamide (PAM) and dextran (Dx) are synthesized by grafting PAM chains onto a Dx backbone (Dx-g-PAM) with ceric ion induced solution polymerization technique. Partial hydrolysis of Dx-g-PAM is carried out with sodium hydroxide solution to obtain HDx-g-PAM. To synthesize silver nanoparticles dispersed copolymer nano-composite (Ag-HDx-g-PAM), reduction of silver ions with HDx-g-PAM is carried out using microwave heating. The environmentally benign and biodegradable copolymer, HDx-g-PAM acts as both stabilizer and reducing agent. The copolymer nano-composite, Ag-HDx-g-PAM is characterized by FT-IR, transmission electron microscopy, scanning electron microscopy and optical spectroscopy. Further, the catalytic activity of Ag-HDx-g-PAM nano-composite towards the reduction of environmental pollutants like phenosafranine dye and aromatic nitro compounds are studied.

  14. Dihydrogen Phosphate Stabilized Ruthenium(0) Nanoparticles: Efficient Nanocatalyst for The Hydrolysis of Ammonia-Borane at Room Temperature

    Durap, Feyyaz; Caliskan, Salim; Özkar, Saim; Karakas, Kadir; Zahmakiran, Mehmet

    2015-01-01

    Intensive efforts have been devoted to the development of new materials for safe and efficient hydrogen storage. Among them, ammonia-borane appears to be a promising candidate due to its high gravimetric hydrogen storage capacity. Ammonia-borane can release hydrogen on hydrolysis in aqueous solution under mild conditions in the presence of a suitable catalyst. Herein, we report the synthesis of ruthenium(0) nanoparticles stabilized by dihydrogenphosphate anions with an average particle size of 2.9 ± 0.9 nm acting as a water-dispersible nanocatalyst in the hydrolysis of ammonia-borane. They provide an initial turnover frequency (TOF) value of 80 min−1 in hydrogen generation from the hydrolysis of ammonia-borane at room temperature. Moreover, the high stability of these ruthenium(0) nanoparticles makes them long-lived and reusable nanocatalysts for the hydrolysis of ammonia-borane. They provide 56,800 total turnovers and retain ~80% of their initial activity even at the fifth catalytic run in the hydrolysis of ammonia-borane at room temperature. PMID:28793435

  15. Non-Aqueous Sol-Gel Synthesis of FePt Nanoparticles in the Absence of In Situ Stabilizers

    Tobias Preller

    2018-05-01

    Full Text Available The synthesis of FePt nanocrystals is typically performed in an organic solvent at rather high temperatures, demanding the addition of the in situ stabilizers oleic acid and oleylamine to produce monomodal particles with well-defined morphologies. Replacing frequently-used solvents with organic media bearing functional moieties, the use of the stabilizers can be completely circumvented. In addition, various morphologies and sizes of the nanocrystals can be achieved by the choice of organic solvent. The kinetics of particle growth and the change in the magnetic behavior of the superparamagnetic FePt nanocrystals during the synthesis with a set of different solvents, as well as the resulting morphologies and stoichiometries of the nanoparticles were determined by powder X-ray diffraction (PXRD, small-angle X-ray scattering (SAXS, transmission electron microscopy (TEM, inductively coupled plasma optical emission spectroscopy (ICP-OES/mass spectrometry (ICP-MS, and superconducting quantum interference device (SQUID measurements. Furthermore, annealing of the as-prepared FePt nanoparticles led to the ordered L10 phase and, thus, to hard magnetic materials with varying saturation magnetizations and magnetic coercivities.

  16. Degradation of soil-sorbed trichloroethylene by stabilized zero valent iron nanoparticles: Effects of sorption, surfactants, and natural organic matter

    Zhang, Man [Auburn University, Auburn, Alabama; He, Feng [ORNL; Zhao, Dongye [Auburn University, Auburn, Alabama; Hao, Xiaodi [Beijing University of Civil Engineering and Architecture

    2011-01-01

    Zero valent iron (ZVI) nanoparticles have been studied extensively for degradation of chlorinated solvents in the aqueous phase, and have been tested for in-situ remediation of contaminated soil and groundwater. However, little is known about its effectiveness for degrading soil-sorbed contaminants. This work studied reductive dechlorination of trichloroethylene (TCE) sorbed in two model soils (a potting soil and Smith Farm soil) using carboxymethyl cellulose (CMC) stabilized Fe-Pd bimetallic nanoparticles. Effects of sorption, surfactants and dissolved organic matter (DOC) were determined through batch kinetic experiments. While the nanoparticles can effectively degrade soil-sorbed TCE, the TCE degradation rate was strongly limited by desorption kinetics, especially for the potting soil which has a higher organic matter content of 8.2%. Under otherwise identical conditions, {approx}44% of TCE sorbed in the potting soil was degraded in 30 h, compared to {approx}82% for Smith Farm soil (organic matter content = 0.7%). DOC from the potting soil was found to inhibit TCE degradation. The presence of the extracted SOM at 40 ppm and 350 ppm as TOC reduced the degradation rate by 34% and 67%, respectively. Four prototype surfactants were tested for their effects on TCE desorption and degradation rates, including two anionic surfactants known as SDS (sodium dodecyl sulfate) and SDBS (sodium dodecyl benzene sulfonate), a cationic surfactant hexadecyltrimethylammonium (HDTMA) bromide, and a non-ionic surfactant Tween 80. All four surfactants were observed to enhance TCE desorption at concentrations below or above the critical micelle concentration (cmc), with the anionic surfactant SDS being most effective. Based on the pseudo-first-order reaction rate law, the presence of 1 x cmc SDS increased the reaction rate by a factor of 2.5 when the nanoparticles were used for degrading TCE in a water solution. SDS was effective for enhancing degradation of TCE sorbed in Smith Farm

  17. Encapsulation-Stabilized, Europium Containing Nanoparticle as a Probe for Time-Resolved luminescence Detection of Cardiac Troponin I

    Ka Ram Kim

    2017-10-01

    Full Text Available The use of a robust optical signaling probe with a high signal-to-noise ratio is important in the development of immunoassays. Lanthanide chelates are a promising material for this purpose, which provide time-resolved luminescence (TRL due to their large Stokes shift and long luminescence lifetime. From this, they have attracted considerable interest in the in vitro diagnostics field. However, the direct use of lanthanide chelates is limited because their luminescent signal can be easily affected by various quenchers. To overcome this drawback, strategies that rely on the entrapment of lanthanide chelates inside nanoparticles, thereby enabling the protection of the lanthanide chelate from water, have been reported. However, the poor stability of the lanthanide-entrapped nanoparticles results in a significant fluctuation in TRL signal intensity, and this still remains a challenging issue. To address this, we have developed a Lanthanide chelate-Encapsulated Silica Nano Particle (LESNP as a new immunosensing probe. In this approach, the lanthanide chelate is covalently crosslinked within the silane monomer during the silica nanoparticle formation. The resulting LESNP is physically stable and retains TRL properties of the parent lanthanide chelate. Using the probe, a highly sensitive, sandwich-based TRL immunoassay for the cardiac troponin I was conducted, exhibiting a limit of detection of 48 pg/mL. On the basis of the features of the LESNP such as TRL signaling capability, stability, and the ease of biofunctionalization, we expect that the LESNP can be widely applied in the development of TRL-based immunosensing.

  18. Ion beam synthesis of Fe nanoparticles in MgO and yttria-stabilized zirconia

    Potzger, K.; Reuther, H.; Zhou, Shengqiang; Mücklich, A.; Grötzschel, R.; Eichhorn, F.; Liedke, M. O.; Fassbender, J.; Lichte, H.; Lenk, A.

    2006-04-01

    To form embedded Fe nanoparticles, MgO(001) and YSZ(001) single crystals have been implanted at elevated temperatures with Fe ions at energies of 100 keV and 110 keV, respectively. The ion fluence was fixed at 6×1016 cm-2. As a result, γ- and α-phase Fe nanoparticles were synthesized inside MgO and YSZ, respectively. A synthesis efficiency of 100% has been achieved for implantation at 1273 K into YSZ. The ferromagnetic behavior of the α-Fe nanoparticles is reflected by a magnetic hyperfine field of 330 kOe and a hysteretic magnetization reversal. Electron holography showed a fringing magnetic field around some, but not all of the particles.

  19. Ion beam synthesis of Fe nanoparticles in MgO and yttria-stabilized zirconia

    Potzger, K.; Reuther, H.; Zhou, Shengqiang; Muecklich, A.; Groetzschel, R.; Eichhorn, F.; Liedke, M. O.; Fassbender, J.; Lichte, H.; Lenk, A.

    2006-01-01

    To form embedded Fe nanoparticles, MgO(001) and YSZ(001) single crystals have been implanted at elevated temperatures with Fe ions at energies of 100 keV and 110 keV, respectively. The ion fluence was fixed at 6x10 16 cm -2 . As a result, γ- and α-phase Fe nanoparticles were synthesized inside MgO and YSZ, respectively. A synthesis efficiency of 100% has been achieved for implantation at 1273 K into YSZ. The ferromagnetic behavior of the α-Fe nanoparticles is reflected by a magnetic hyperfine field of 330 kOe and a hysteretic magnetization reversal. Electron holography showed a fringing magnetic field around some, but not all of the particles

  20. Stabilizing ability of surfactant on physicochemical properties of drug nanoparticles generated from solid dispersions.

    Thongnopkoon, Thanu; Puttipipatkhachorn, Satit

    2017-07-01

    This study was aimed to examine the nanoparticle formation from redispersion of binary and ternary solid dispersions. Binary systems are composed of various ratios of glibenclamide (GBM) and polyvinylpyrrolidone K30 (PVP-K30), whereas a constant amount at 2.5%w/w of a surfactant, sodium lauryl sulfate (SLS) or Gelucire44/14 (GLC), was added to create ternary systems. GBM nanoparticles were collected after the systems were dispersed in water for 15 min. The obtained nanoparticles were characterized for size distribution, crystallinity, thermal behavior, molecular structure, and dissolution properties. The results indicated that GBM nanoparticles could be formed when the drug content of the systems was lower than 30%w/w in binary systems and ternary systems containing SLS. The particle size ranged from 200 to 500 nm in diameter with narrow size distribution. The particle size was increased with increasing drug content in the systems. The obtained nanoparticles were spherical and showed the amorphous state. Furthermore, because of being amorphous form and reduced particle size, the dissolution of the generated nanoparticles was markedly improved compared with the GBM powder. In contrast, all the ternary solid dispersions prepared with GLC anomalously provided the crystalline particles with the size ranging over 5 µm and irregular shape. Interestingly, this was irrelevant to the drug content in the systems. These results indicated the ability of GLC to destabilize the polymer network surrounding the particles during particle precipitation. Therefore, this study suggested that drug content, quantity, and type of surfactant incorporated in solid dispersions drastically affected the physicochemical properties of the precipitated particles.

  1. Size and shape dependent Gibbs free energy and phase stability of titanium and zirconium nanoparticles

    Xiong Shiyun; Qi Weihong; Huang Baiyun; Wang Mingpu; Li Yejun

    2010-01-01

    The Debye model of Helmholtz free energy for bulk material is generalized to Gibbs free energy (GFE) model for nanomaterial, while a shape factor is introduced to characterize the shape effect on GFE. The structural transitions of Ti and Zr nanoparticles are predicted based on GFE. It is further found that GFE decreases with the shape factor and increases with decreasing of the particle size. The critical size of structural transformation for nanoparticles goes up as temperature increases in the absence of change in shape factor. For specified temperature, the critical size climbs up with the increase of shape factor. The present predictions agree well with experiment values.

  2. Effect of starting pH and stabilizer/metal ion ratio on the photocatalytic activity of ZnS nanoparticles

    Devi, L. Meerabai; Negi, Devendra P.S., E-mail: dpsnegi@nehu.ac.in

    2013-09-16

    ZnS nanoparticles have been synthesized using the amino acid histidine as a stabilizing agent. The syntheses were carried out by varying the starting pH and histidine/Zn{sup 2+} ratio. The as-prepared ZnS nanoparticles were characterized by various analytical techniques. The photocatalytic activity of the ZnS nanoparticles was determined by studying the degradation of methyl orange. The ZnS nanoparticles synthesized with 1:1 histidine/Zn{sup 2+} ratio and starting pH of 10.3 were found to exhibit the highest photocatalytic activity. Nearly 95% of methyl orange was degraded in 30 min of irradiation using the photocatalyst. Particle size was not the main factor in determining the photocatalytic activity of the ZnS nanoparticles. Fluorescence lifetime measurements indicated that photocatalytic activity of the ZnS nanoparticles was enhanced with increase in their fluorescence lifetime. - Graphical abstract: Display Omitted - Highlights: • Photocatalytic activity of ZnS nanoparticles dependent on synthesis parameters. • About 95% of methyl orange degraded in 30 min of irradiation using optimal ZnS nanoparticles. • Particle size is not the main factor in determining the photocatalytic activity of ZnS. • Photocatalytic activity of ZnS was enhanced with increase in fluorescence lifetime.

  3. Stability and transport of graphene oxide nanoparticles in groundwater and surface water

    A transport study investigating the effects of natural organic matter (NOM) in the presence of monovalent (KCl) and divalent (CaCl2) salts was performed in a packed bed column. The electrophoretic mobility (EPM) and effective diameter of the graphene oxide nanoparticles (GONPs) were measured as a fu...

  4. Ni3Si(Al)/a-SiOx core shell nanoparticles: characterization, shell formation, and stability

    Pigozzi, G.; Mukherji, D.; Gilles, R.; Barbier, B.; Kostorz, G.

    2006-08-01

    We have used an electrochemical selective phase dissolution method to extract nanoprecipitates of the Ni3Si-type intermetallic phase from two-phase Ni-Si and Ni-Si-Al alloys by dissolving the matrix phase. The extracted nanoparticles are characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray powder diffraction, and electron powder diffraction. It is found that the Ni3Si-type nanoparticles have a core-shell structure. The core maintains the size, the shape, and the crystal structure of the precipitates that existed in the bulk alloys, while the shell is an amorphous phase, containing only Si and O (SiOx). The shell forms around the precipitates during the extraction process. After annealing the nanoparticles in nitrogen at 700 °C, the tridymite phase recrystallizes within the shell, which remains partially amorphous. In contrast, on annealing in air at 1000 °C, no changes in the composition or the structure of the nanoparticles occur. It is suggested that the shell forms after dealloying of the matrix phase, where Si atoms, the main constituents of the shell, migrate to the surface of the precipitates.

  5. Preparation and characterization of natural polymers as stabilizer for magnetic nanoparticles by gamma irradiation

    Eid, M.

    2012-01-01

    A Highly stable and uniformly distributed magnetic nanoparticles have been obtained onto hydroxyethyl methacrylate (HEMA)-Agar- Fe 3 O 4 (HAF), and HEMA-Gelatin- Fe 3 O 4 (HGF) networks via gamma irradiation and loading technique. The swelling property of the prepared hydrogels in bidistilled water and different ph's was studied and the results showed that, the swelling percent of the plain hydrogel was found to be higher for all different compositions. The morphology and structure of the prepared hydrogels and dispersion of the magnetite nanoparticles in the hydrogel network were examined by Scanning electron microscopy (SEM) and Infrared spectroscopy (FT-IR). The particle size of the formed magnetite nanoparticles has been confirmed by Dynamic light scattering (DLS) and Transmission electron microscope (TEM), and it was found to be smaller in loading technique than irradiation technique. The HEMA-Gelatin-Fe 3 O 4 has higher particle size than HEMA-Agar-Fe 3 O 4 (HAF). Finally, the drug loading capacities of the magnetite nanoparticles and their releasing dependence on different ph were investigated with doxorubicin hydrochloride (DOX) as an anticancer drug model.

  6. Formation, stability, and solubility of metal oxide nanoparticles: surface entropy, and free energy of ferrihydrite

    Hiemstra, T.

    2015-01-01

    Ferrihydrite (Fh) is an excellent model for understanding nanoparticle behavior in general. Moreover, Fh is one of the most important Fe (hydr) oxides in nature. Fh particles can be extremely small leading to a very high reactive surface area that changes its chemical potential, strongly affecting

  7. Viscoelastic gels of guar and xanthan gum mixtures provide long-term stabilization of iron micro- and nanoparticles

    Xue Dingqi [Politecnico di Torino, Dipartimento Scienza Applicata e Tecnologia-DISAT and Dipartimento di Ingegneria dell' Ambiente, del Territorio e delle Infrastrutture-DIATI (Italy); Sethi, Rajandrea, E-mail: rajandrea.sethi@polito.it [Politecnico di Torino, Dipartimento di Ingegneria dell' Ambiente, del Territorio e delle Infrastrutture-DIATI (Italy)

    2012-11-15

    Iron micro- and nanoparticles used for groundwater remediation and medical applications are prone to fast aggregation and sedimentation. Diluted single biopolymer water solutions of guar gum (GG) or xanthan gum (XG) can stabilize these particles for few hours providing steric repulsion and by increasing the viscosity of the suspension. The goal of the study is to demonstrate that amending GG solutions with small amounts of XG (XG/GG weight ratio 1:19; 3 g/L of total biopolymer concentration) can significantly improve the capability of the biopolymer to stabilize highly concentrated iron micro- and nanoparticle suspensions. The synergistic effect between GG and XG generates a viscoelastic gel that can maintain 20 g/L iron particles suspended for over 24 h. This is attributed to (i) an increase in the static viscosity, (ii) a combined polymer structure the yield stress of which contrasts the downward stress exerted by the iron particles, and (iii) the adsorption of the polymers to the iron surface having an anchoring effect on the particles. The XG/GG viscoelastic gel is characterized by a marked shear thinning behavior. This property, coupled with the low biopolymer concentration, determines small viscosity values at high shear rates, facilitating the injection in porous media. Furthermore, the thermosensitivity of the soft elastic polymeric network promotes higher stability and longer storage times at low temperatures and rapid decrease of viscosity at higher temperatures. This feature can be exploited in order to improve the flowability and the delivery of the suspensions to the target as well as to effectively tune and control the release of the iron particles.

  8. Viscoelastic gels of guar and xanthan gum mixtures provide long-term stabilization of iron micro- and nanoparticles

    Xue Dingqi; Sethi, Rajandrea

    2012-01-01

    Iron micro- and nanoparticles used for groundwater remediation and medical applications are prone to fast aggregation and sedimentation. Diluted single biopolymer water solutions of guar gum (GG) or xanthan gum (XG) can stabilize these particles for few hours providing steric repulsion and by increasing the viscosity of the suspension. The goal of the study is to demonstrate that amending GG solutions with small amounts of XG (XG/GG weight ratio 1:19; 3 g/L of total biopolymer concentration) can significantly improve the capability of the biopolymer to stabilize highly concentrated iron micro- and nanoparticle suspensions. The synergistic effect between GG and XG generates a viscoelastic gel that can maintain 20 g/L iron particles suspended for over 24 h. This is attributed to (i) an increase in the static viscosity, (ii) a combined polymer structure the yield stress of which contrasts the downward stress exerted by the iron particles, and (iii) the adsorption of the polymers to the iron surface having an anchoring effect on the particles. The XG/GG viscoelastic gel is characterized by a marked shear thinning behavior. This property, coupled with the low biopolymer concentration, determines small viscosity values at high shear rates, facilitating the injection in porous media. Furthermore, the thermosensitivity of the soft elastic polymeric network promotes higher stability and longer storage times at low temperatures and rapid decrease of viscosity at higher temperatures. This feature can be exploited in order to improve the flowability and the delivery of the suspensions to the target as well as to effectively tune and control the release of the iron particles.

  9. Synthesis of Gold Nanoparticles Stabilized in Dextran Solution by Gamma Co-60 Ray Irradiation and Preparation of Gold Nanoparticles/Dextran Powder

    Phan Ha Nu Diem

    2017-01-01

    Full Text Available Gold nanoparticles (AuNPs in spherical shape with diameter of 6–35 nm stabilized by dextran were synthesized by γ-irradiation method. The AuNPs were characterized by UV-Vis spectroscopy and transmission electron microscopy. The influence of pH, Au3+ concentration, and dextran concentration on the size of AuNPs was investigated. Results indicated that the smallest AuNPs size (6 nm and the largest AuNPs size (35 nm were obtained for pH of 1 mM Au3+/1% dextran solution of 5.5 and 7.5, respectively. The smaller Au3+ concentration favored smaller size and conversely the smaller dextran concentration favored bigger size of AuNPs. AuNPs powders were prepared by spay drying, coagulation, and centrifugation and their sizes were also evaluated. The purity of prepared AuNPs powders was also examined by energy dispersive X-ray (EDX analysis. Thus, the as-prepared AuNPs stabilized by biocompatible dextran in solution and/or in powder form can be potentially applied in biomedicine and pharmaceutics.

  10. Solvent and stabilizer free growth of Ag and Pd nanoparticles using metallic salts/cyclotriphosphazenes mixtures

    Díaz Valenzuela, C. [Departamento de Química, Facultad de Química, Universidad de Chile, La Palmeras 3425, Nuñoa, Casilla 653, Santiago de Chile (Chile); Valenzuela, M.L., E-mail: mlvalenzuela@unab.cl [Universidad Andres Bello, Departamento de Ciencias Química, Facultad de Ciencias Exactas, Av. Republica 275, Santiago (Chile); Caceres, S.; Diaz, R. [Departamento de Química, Facultad de Química, Universidad de Chile, La Palmeras 3425, Nuñoa, Casilla 653, Santiago de Chile (Chile); O' Dwyer, C. [Applied Nanoscience Group, Department of Chemistry, University College Cork, Cork (Ireland); Micro and Nanoelectronics Centre, Tyndall National Institute, Lee Maltings, Cork (Ireland)

    2013-12-16

    Cyclotriphosphazene is used as a sacrificial solid-state template to synthesize a range of Ag and Pd nanoparticles with diverse geometries by thermal treatment using MLn/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} mixtures. The Pd and Ag nanoparticles are synthesized by solid-state pyrolysis of AgPPh{sub 3}[CF{sub 3}SO{sub 3}]/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} and PdCl{sub 2}/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} mixtures with molar relationships of 1:1, 1:5 and 1:10 respectively, in air and at 800 °C. The morphology of the as-prepared nanoparticles is found to depend on the molar ratio of the precursor mixture, the preparation method and of the nature of the metal. Ag and Pd, microcrystals were thermally grown on Si from the respective 1:1 precursors while that metal foams were grown from 1:5 ratios precursors on SiO{sub 2} wafers. High resolution transmission electron microscopy investigations reveal in most cases small crystals of Pd. HRSTEM measurements indicate that the formation of the Pd and Ag nanoparticles occurs through a phase demixing and dewetting mechanism. This approach has potential to be a useful and facile method to prepare metallic nanoparticles without requiring solutions or surfactants for application in electronic, catalytic and sensor materials and devices. - Highlights: • Pyrolysis MLn/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} mixtures under air, give Pd and Ag nanoparticles. • AgPPh{sub 3}[CF{sub 3}SO{sub 3}] and PdCl{sub 2} in molar ratios 1:1 and 1:5 were used. • Metal foams were obtained from 1:5 ratios when deposited on SiO{sub 2.} • Using crucible supporting in 1:1 metal/trimer <2 nm Pd nanoparticles were obtained. • The probable mechanism involves a dewetting, nucleation and ripening crystallization.

  11. Gd2O3 nanoparticles stabilized by hydrothermally modified dextrose for positive contrast magnetic resonance imaging

    Babić-Stojić, Branka; Jokanović, Vukoman; Milivojević, Dušan; Požek, Miroslav; Jagličić, Zvonko; Makovec, Darko; Arsikin, Katarina; Paunović, Verica

    2016-04-01

    Gd2O3 nanoparticles of a few nm in size and their agglomerates dispersed in dextrose derived polymer template were synthesized by hydrothermal treatment. The produced nanosized material was investigated by TEM, FTIR spectroscopy, SQUID measurements and NMR relaxometry. Biological evaluation of this material was done by crystal violet and MTT assays to determine the cell viability. Longitudinal and transverse NMR relaxivities of water diluted Gd2O3 nanoparticle dispersions measured at the magnetic field of 1.5 T, estimated to be r1(Gd2O3)=9.6 s-1 mM-1 in the Gd concentration range 0.1-30 mM and r2(Gd2O3)=17.7 s-1 mM-1 in the lower concentration range 0.1-0.8 mM, are significantly higher than the corresponding relaxivities measured for the standard contrast agent r1(Gd-DTPA)=4.1 s-1 mM-1 and r2(Gd-DTPA)=5.1 s-1 mM-1. The ratio of the two relaxivities for Gd2O3 nanoparticles r2/r1=1.8 is suitable for T1-weighted imaging. Good MRI signal intensities of the water diluted Gd2O3 nanoparticle dispersions were recorded at lower Gd concentrations 0.2-0.8 mM. The Gd2O3 samples did not exert any significant cytotoxic effects at Gd concentrations of 0.2 mM and below. These properties of the produced Gd2O3 nanoparticles in hydrothermally modified dextrose make them promising for potential application in MRI for the design of a positive MRI contrast agent.

  12. Sonochemical synthesis of stibnite nanoparticles and their use as radiolytic stabilizer in polynomial chloride matrix

    Albuquerque, Marilia Cordeiro C. de; Lima, Thaysa Araujo de; Aquino, Katia Aparecida da Silva; Araujo, Elmo S., E-mail: aquino@ufpe.b [Universidade Federal de Pernambuco (DEN/UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear

    2011-07-01

    Stibnite (Sb{sub 2}S{sub 3}) was synthesized by sonochemical method. Amorphous powder of Sb{sub 2}S{sub 3} was obtained and exhibit nanospheres structure with an average size in the range of 300-500 nm. Commercial Polyvinyl Chloride (PVC) containing Sb{sub 2}S{sub 3} nanoparticles (PVC/Sb) at concentrations of 0.10; 0.30 and 0.50 wt% were investigated. The samples were irradiated with gamma radiation ({sup 60}Co) at room temperature and air atmosphere. The viscosity-average molar mass (M{sub v}) was measured for PVC systems without nanoparticles and with nanoparticles. Decreases in molar mass observed when the systems were gamma irradiated reflect the random scission effects that take place in the main chain. Degradation index (DI) value was also obtained by viscosity analysis. DI results showed that the addition of Sb{sub 2}S{sub 3} nanoparticles at 0.3 wt% into PVC matrix irradiated at dose of 25 kGy decreased the number of main chain scissions and was calculated a protection index of 66,5% in PVC matrix. Results about the free radical scavenger action of the Sb{sub 2}S{sub 3} were obtained by use of 2,2-diphenyl-1-(2,4,6-trinitrophenyl)-hydrazyl radical (DPPH) and are discussed in this study. Changes in the infrared spectra of PVC systems indicated that polymer molecules interact with Sb{sub 2}S{sub 3} nanoparticles. (author)

  13. Reactivity enhancement of iron sulfide nanoparticles stabilized by sodium alginate: Taking Cr (VI) removal as an example

    Wu, Jun; Wang, Xian-Bin; Zeng, Raymond J., E-mail: rzeng@ustc.edu.cn

    2017-07-05

    Highlights: • Sodium alginate can be used to stabilize FeS nanoparticles. • FeS-SA enhances Cr(VI) removal efficiency from 65% to 100% compared to naked FeS. • Reduction and adsorption respectively account for 82% and 18% of Cr removal by FeS-SA. • Analysis of reaction products reveals the co-existence of α-FeOOH, S{sub 8}, and Cr(OH){sub 3.} - Abstract: The widespread distribution of chromium(VI) in the environment leads to groundwater contamination. The use of iron sulfide (FeS) to remove Cr(VI) has therefore been proposed. However, aggregation is one of the main problems associated with the use of FeS nanoparticles prepared by traditional methods In this study, we used sodium alginate (SA) to stabilize FeS nanoparticles (FeS-SA). SA could prevent aggregation of FeS by the concurrent electrostatic repulsion and steric hindrance. Homogeneously dispersed FeS-SA nanoparticles 100 nm in diameter were observed. FeS-SA showed high efficiency in Cr(VI) removal, corresponding to an enhancement of efficiency from 65% (7.50 mmol Cr(VI) per g FeS) to 100% (11.54 mmol Cr per g FeS) relative to that achieved with naked FeS. Analysis of reaction products by X-ray diffraction and X-ray photoelectron spectroscopy revealed the co-existence of α-FeOOH, S{sub 8}, and Cr(OH){sub 3} that apparently were introduced by Fe(II), S(−II), and Cr(VI), respectively. In-depth analysis of the removal mechanism revealed that reduction and adsorption respectively account for 82% and 18% of the Cr removal. In addition, higher pH and CaCl{sub 2} concentration resulted in lower removal efficiency. This study provides a promising application of SA in enhancing FeS reactivity for the remediation of groundwater pollution.

  14. A Platinum Monolayer Core-Shell Catalyst with a Ternary Alloy Nanoparticle Core and Enhanced Stability for the Oxygen Reduction Reaction

    Haoxiong Nan

    2015-01-01

    Full Text Available We synthesize a platinum monolayer core-shell catalyst with a ternary alloy nanoparticle core of Pd, Ir, and Ni. A Pt monolayer is deposited on carbon-supported PdIrNi nanoparticles using an underpotential deposition method, in which a copper monolayer is applied to the ternary nanoparticles; this is followed by the galvanic displacement of Cu with Pt to generate a Pt monolayer on the surface of the core. The core-shell Pd1Ir1Ni2@Pt/C catalyst exhibits excellent oxygen reduction reaction activity, yielding a mass activity significantly higher than that of Pt monolayer catalysts containing PdIr or PdNi nanoparticles as cores and four times higher than that of a commercial Pt/C electrocatalyst. In 0.1 M HClO4, the half-wave potential reaches 0.91 V, about 30 mV higher than that of Pt/C. We verify the structure and composition of the carbon-supported PdIrNi nanoparticles using X-ray powder diffraction, X-ray photoelectron spectroscopy, thermogravimetry, transmission electron microscopy, and energy dispersive X-ray spectrometry, and we perform a stability test that confirms the excellent stability of our core-shell catalyst. We suggest that the porous structure resulting from the dissolution of Ni in the alloy nanoparticles may be the main reason for the catalyst’s enhanced performance.

  15. UV-Visible intensity ratio (aggregates/single particles) as a measure to obtain stability of gold nanoparticles conjugated with protein A

    Rios-Corripio, M. A. [Instituto Politecnico Nacional, CIBA-Tlaxcala (Mexico); Garcia-Perez, B. E. [Instituto Politecnico Nacional, Departamento de Inmunologia, ENCB (Mexico); Jaramillo-Flores, M. E. [Instituto Politecnico Nacional, Departamento de Ingenieria Bioquimica, ENCB (Mexico); Gayou, V. L.; Rojas-Lopez, M., E-mail: marlonrl@yahoo.com.mx [Instituto Politecnico Nacional, CIBA-Tlaxcala (Mexico)

    2013-05-15

    We have analyzed the titration process of gold nanoparticles with several amounts of protein A (0.3, 0.5, 1, 3, 6, and 9 {mu}g/ml) in the presence of NaCl, which induces aggregation if the surface of particles is not fully covered with protein A. The colloidal solutions with different particle size (16, 18, 20, 33 nm) were synthesized by citrate reduction to be conjugated with protein A. UV-Visible spectroscopy was used to measure the absorption of the surface plasmon resonance of gold nanoparticles as a function of the concentration of protein A. Such dependence shows an aggregation region (0 < x<6 {mu}g/ml), where the amount of protein A was insufficient to cover the surface of particles, obtaining aggregation caused by NaCl. The next part is the stability region (x {>=} 6 {mu}g/ml), where the amount of protein used covers the surface of particles and protects it from the aggregation. In addition to that the ratio between the intensities of both: the aggregates and of the gold nanoparticle bands was plotted as a function of the concentration of protein A. It was determined that 6 {mu}g/ml is a sufficient value of protein A to stabilize the gold nanoparticle-protein A system. This method provides a simple way to stabilize gold nanoparticles obtained by citrate reduction, with protein A.

  16. Optimizing Glassy Polymer Network Morphology for Nano-particle Dispersion, Stabilization and Performance

    2016-10-03

    viscosity and stabilization of MWCNTs within rheological regimes which inhibit re-agglomeration to aid in post processing stabilization of dispersion state...polypropylene- clay nanocomposites subjected to laser pulse heating Bartolucci, Stephen, Supan, Karen, Wiggins, Jeffrey, LaBeaud, Lawrence, Warrender...addition, concurrent chain extension reactions advance prepolymer molecular weights to desired viscosities in less than 2 minutes of mean residence

  17. Evaluation of local anesthetic effects of Lidocaine-Ibuprofen ionic liquid stabilized silver nanoparticles in Male Swiss mice.

    Jiang, Qiliang; Yu, Shashuang; Li, Xingwang; Ma, Chuangen; Li, Aixiang

    2018-01-01

    A simple approach for the synthesis of Lidocaine-Ibuprofen ionic liquid stabilized silver nanoparticles (IL-AgNPs) was reported in this work. The shape, size and surface morphology of the Lidocaine-Ibuprofen ionic liquid stabilized AgNPs were characterized by using spectroscopic and microscopic techniques such as Ultraviolet-visible spectroscopy (UV-Visible), X-ray diffraction (XRD) analysis, Selected area electron diffraction (SAED), Transmission electron microscopy (TEM). TEM analysis showed the formation of 20-30nm size of IL-AgNPs with very clear lattice fringes. SAED pattern confirmed the highly crystalline nature of fabricated IL stabilized AgNPs. EDS results confirmed the formation of nanosilver. The fabricated IL-AgNPs were studied for their local anesthetic effect in rats. The results of local anesthetic effect showed that the time for onset of action by IL-AgNPs is 10min, which is significantly higher than that for EMLA. Further, tactile test results confirmed the stronger and faster local anesthetic effect of IL-AgNPs when compared to that of EMLA. Copyright © 2017. Published by Elsevier B.V.

  18. Platinum-nanoparticle-supported core-shell polymer nanospheres with unexpected water stability and facile further modification

    Yuan, Conghui; Xu, Yiting; Luo, Weiang; Zeng, Birong; Qiu, Wuhui; Liu, Jie; Huang, Huiling; Dai, Lizong

    2012-05-01

    Core-shell nanospheres (CSNSs) with hydrophobic cores and hydrophilic shells were fabricated via a simple mini-emulsion polymerization for the stabilization of platinum nanoparticles (Pt-NPs). The CSNSs showed extremely high loading capacity of Pt-NPs (the largest loading amount of the Pt-NPs was about 49.2 wt%). Importantly, the Pt-NPs/CSNSs nanocomposites had unexpected stability in aqueous solution. DLS results revealed that the CSNSs loaded with Pt-NPs exhibited almost no aggregation after standing for a long time . However, the Pt-NPs immobilized on the CSNSs were not straitlaced: they could transport and redistribute between CSNSs freely when the environmental temperature was higher than the melting point of the CSNS shell. Owing to their excellent stability in aqueous solution, the surface of the Pt-NPs/CSNSs nanocomposites could be further decorated easily. For example, polyaniline (PANI)-coated Pt-NPs/CSNSs, nickel (Ni)-coated Pt-NPs/CSNSs and PANI/Pt-NPs dual-layer hollow nanospheres were facilely fabricated from the Pt-NPs/CSNS nanocomposites.

  19. Stability optimisation of molecular electronic devices based on  nanoelectrode–nanoparticle bridge platform in air and different storage liquids

    Jafri, S. H. M.; Blom, T.; Wallner, A.; Ottosson, H.; Leifer, K.

    2014-01-01

    The long-term stability of metal nanoparticle–molecule junctions in molecular electronic devices based on nanoelectrodes (NEL) is a major challenge in the effort to bring related molecular electronic devices to application. To optimize the reproducibility of molecular electronic nanodevices, the time-dependent modification of such junctions as exposed to different media needs to be known. Here, we have studied (1) the stability of Au-NEL and (2) the electrical stability of molecule–Au nanoparticle (AuNP) junctions themselves with the molecule being  1,8-octanedithiol (ODT). Both the NELs only and the junctions were exposed to air and liquids such as deionized water, tetrahydrofuran, toluene and tetramethylethylenediamine (TMEDA) over a period of 1 month. The nanogaps remained stable in width when stored in either deionized water or toluene, whereas the current through 1,8-octanedithiol–NP junctions remained most stable when stored in TMEDA as compared to other solvents. Although it is difficult to follow the chemical processes in such devices in the 10-nm range with analytical methods, the behavior can be interpreted from known interactions of solvent molecules with electrodes and ODT

  20. Enhanced electrochemical stability of carbon-coated antimony nanoparticles with sodium alginate binder for sodium-ion batteries

    Jianmin Feng

    2018-04-01

    Full Text Available The poor cycling stability of antimony during a repeated sodium ion insertion and desertion process is the key issue, which leads to an unsatisfactory application as an anode material in a sodium-ion battery. Addressed at this, we report a facile two-step method to coat antimony nanoparticles with an ultrathin carbon layer of few nanometers (denoted Sb@C NPs for sodium-ion battery anode application. This carbon layer could buffer the volume change of antimony in the charge-discharge process and improve the battery cycle performance. Meanwhile, this carbon coating could also enhance the interfacial stability by firmly connecting the sodium alginate binders through its oxygen-rich surface. Benefitted from these advantages, an improved initial discharge capacity (788.5 mA h g−1 and cycling stability capacity (553 mA h g−1 after 50 times cycle have been obtained in a battery using Sb@C NPs as anode materials at 50 mA g−1. Keywords: Sodium-ion battery, Antimony, Sodium alginate, Liquid-phase reduction, Carbon coating

  1. Platinum-nanoparticle-supported core–shell polymer nanospheres with unexpected water stability and facile further modification

    Yuan Conghui; Xu Yiting; Luo Weiang; Zeng Birong; Qiu Wuhui; Liu Jie; Dai Lizong; Huang Huiling

    2012-01-01

    Core–shell nanospheres (CSNSs) with hydrophobic cores and hydrophilic shells were fabricated via a simple mini-emulsion polymerization for the stabilization of platinum nanoparticles (Pt-NPs). The CSNSs showed extremely high loading capacity of Pt-NPs (the largest loading amount of the Pt-NPs was about 49.2 wt%). Importantly, the Pt-NPs/CSNSs nanocomposites had unexpected stability in aqueous solution. DLS results revealed that the CSNSs loaded with Pt-NPs exhibited almost no aggregation after standing for a long time . However, the Pt-NPs immobilized on the CSNSs were not straitlaced: they could transport and redistribute between CSNSs freely when the environmental temperature was higher than the melting point of the CSNS shell. Owing to their excellent stability in aqueous solution, the surface of the Pt-NPs/CSNSs nanocomposites could be further decorated easily. For example, polyaniline (PANI)-coated Pt-NPs/CSNSs, nickel (Ni)-coated Pt-NPs/CSNSs and PANI/Pt-NPs dual-layer hollow nanospheres were facilely fabricated from the Pt-NPs/CSNS nanocomposites. (paper)

  2. Shape-Selection of Thermodynamically Stabilized Colloidal Pd and Pt Nanoparticles Controlled via Support Effects

    Ahmadi, M.; Behafarid, F.; Holse, Christian

    2015-01-01

    Colloidal chemistry, in combination with nanoparticle (NP)/support epitaxial interactions is used here to synthesize shape-selected and thermodynamically stable metallic NPs over a broad range of NP sizes. The morphology of three-dimensional palladium and platinum NPs supported on TiO2(110) was i......Colloidal chemistry, in combination with nanoparticle (NP)/support epitaxial interactions is used here to synthesize shape-selected and thermodynamically stable metallic NPs over a broad range of NP sizes. The morphology of three-dimensional palladium and platinum NPs supported on TiO2...... rows and was found to be responsible for the shape control. The ability of synthesizing thermally stable shape-selected metal NPs demonstrated here is expected to be of relevance for applications in the field of catalysis, since the activity and selectivity of NP catalysts has been shown to strongly...

  3. Stability and Antimicrobial Activity of Nisin-Loaded Mesoporous Silica Nanoparticles: A Game-Changer in the War against Maleficent Microbes.

    Behzadi, Faezeh; Darouie, Sheyda; Alavi, S Mehdi; Shariati, Parvin; Singh, Gurvinder; Dolatshahi-Pirouz, Alireza; Arpanaei, Ayyoob

    2018-04-25

    Antimicrobial agents, such as nisin, are used extensively in the food industry. Here, we investigated various approaches to load nisin onto mesoporous silica nanoparticles (MSNs, 92 ± 10 nm in diameter), to enhance its stability and sustained release. The morphology, size, and surface charge of the as-prepared nanoparticles were analyzed using scanning transmission electron microscopy, dynamic light scattering, and ζ potential measurement. Nisin was either physically adsorbed or covalently attached to the variously functionalized MSNs, with high loading capacities (>600 mg of nisin g -1 of nanoparticles). The results of antibacterial activity analysis of nisin against Staphylococcus aureus showed that, despite the very low antibacterial activity of nisin covalently conjugated onto MSNs, the physical adsorption of nisin onto the unfunctionalized nanoparticles enhances its antimicrobial activities under various conditions, with no significant cytotoxicity effects on mouse fibroblast L929 cells. In conclusion, MSNs can be recommended as suitable carriers for nisin under various conditions.

  4. Effect of pH variation on the stability and structural properties of In(OH){sub 3} nanoparticles synthesized by co-precipitation method

    Goh, Kian Wei; Wong, Yew Hoong [University of Malaya, Department of Mechanical Engineering, Faculty of Engineering, Kuala Lumpur (Malaysia); Johan, Mohd Rafie [University of Malaya, Department of Mechanical Engineering, Faculty of Engineering, Kuala Lumpur (Malaysia); University of Malaya, Nanotechnology and Catalysis Research Centre, Kuala Lumpur (Malaysia)

    2016-10-15

    Indium hydroxide (In(OH){sub 3}) nanoparticles were synthesized at various pH values (8-11) by co-precipitation method. Its properties were characterized by X-ray diffractometer, Fourier transform infrared spectroscopy, Raman spectroscopy and transmission electron microscope. The electrostatic stability of nanoparticles is carried out through zeta potential measurement. The crystallite size of nanoparticles calculated by Scherrer equation has similar trend with the values obtained from William-Hall plot. TEM images show that the particles size is within the range of 11.76-20.76 nm. The maximum zeta potential is 3.68 mV associated with the smallest particle size distribution of 92.6 nm occurred at pH 10. Our work clearly confirms the crystallite size, stability and the morphology of In(OH){sub 3} NPs are strongly depending on the pH of precursor solution. (orig.)

  5. Gold Nanoparticles Assembly on Silicon and Gold Surfaces: Mechanism, Stability and Efficiency in Diclofenac Biosensing

    Ben Haddada , Maroua; Hübner , Maria; Casale , Sandra; Knopp , Dietmar; Niessner , Reinhard; Salmain , Michele; Boujday , Souhir

    2016-01-01

    International audience; We investigated the assembly of Gold nanoparticles (AuNPs) on Gold and Silicon sensors with two final objectives: (i) understanding the factors governing the interaction and (ii) building up a nanostructured piezoelectric immunosensor for diclofenac, a small-sized pharmaceutical pollutant. Different surface chemistries were devised to achieve AuNPs assembly on planar substrates. These surface chemistries included amines to immobilize AuNPs via electrostatic interaction...

  6. New chiral ligands in asymmetric catalysis. Application in stabilization of metal nanoparticles

    Axet Martí, M. Rosa

    2006-01-01

    Thesis M. Rosa AxetThis thesis deals with the development and application of diphosphite ligands derived from carbohydrates to rhodium-catalysed asymmetric hydroformylation and hydrogenation reactions. The use of various carbohydrate derivative ligands as stabilisers of metal nanoparticles is also studied. The synthesis and the characterisation of the series of diphosphite ligands are described in Chapter 2. The results of the asymmetric hydroformylation of styrene and related vinyl arenes ar...

  7. Stability and Antimicrobial Activity of Nisin-Loaded Mesoporous Silica Nanoparticles: A Game-Changer in the War against Maleficent Microbes

    Behzadi, Faezeh; Darouie, Sheyda; Alavi, S. Mehdi

    2018-01-01

    Antimicrobial agents, such as nisin, are used extensively in the food industry. Here, we investigated various approaches to load nisin onto mesoporous silica nanoparticles (MSNs, 92 ± 10 nm in diameter), to enhance its stability and sustained release. The morphology, size, and surface charge...

  8. Intercorrelated Ag3PO4 nanoparticles decorated with graphic carbon nitride: Enhanced stability and photocatalytic activities for water treatment

    Ren, Jia; Chai, Yuanyuan; Liu, Qianqian; Zhang, Lu; Dai, Wei-Lin

    2017-05-01

    The method of decorating Ag3PO4 nanoparticles with carbon nitride material (g-C3N4) is demonstrated as an efficient pathway to remarkably improve the stability and photocatalytic performance of Ag3PO4 nanoparticles which have been widely used in photocatalysis, but limited by the instability. The improved material herein results in the largely enhanced photocatalytic performance for water purification under visible light irradiation, which was nearly 7 times as high as that of pure Ag3PO4. Meanwhile, the as-obtained materials show the unique stable property, mainly contributed by the protection effect of decorated g-C3N4 sheet. Additionally, the radical trapping experiments revealed that the introduction of g-C3N4 transformed the photocatalytic mechanism to some degree, where rad O2- played a more important role. The tremendous enhancement in catalytic performance may be attributed to the larger surface area, controllable particle size and the synergistic effect between Ag3PO4 and g-C3N4, promoting the separation efficiency of the photogenerated electron-hole pairs. The decorating system can in principle be broadly put into use for unstable photocatalysts.

  9. Green chemistry approach for the synthesis and stabilization of biocompatible gold nanoparticles and their potential applications in cancer therapy

    Mukherjee, Sudip; Sushma, V; Patra, Sujata; Barui, Ayan Kumar; Bhadra, Manika Pal; Patra, Chitta Ranjan; Sreedhar, Bojja

    2012-01-01

    The biological approach to synthesis of AuNPs is eco-friendly and an ideal method to develop environmentally sustainable nanoparticles alternative to existing methods. We have developed a simple, fast, clean, efficient, low-cost and eco-friendly single-step green chemistry approach for the synthesis of biocompatible gold nanoparticles (AuNPs) from chloroauric acid (HAuCl 4 ) using a water extract of Eclipta Alba leaves at room temperature. The AuNPs using Eclipta extract have been formed in very short time, even in less than 10 min. The as-synthesized AuNPs were thoroughly characterized by several physico-chemical techniques. The in vitro stability of as-synthesized AuNPs was studied in different buffer solutions. A plausible mechanism for the synthesis of AuNPs by Eclipta extract has been discussed. The biocompatibility of AuNPs was observed by in vitro cell culture assays. Finally, we have designed and developed a AuNPs-based drug delivery system (DDS) (Au-DOX) containing doxorubicin (DOX), a FDA approved anticancer drug. Administration of this DDS to breast cancer cells (MCF-7 and MDA-MB-231) shows significant inhibition of breast cancer cell proliferation compared to pristine doxorubicin. Therefore we strongly believe that the use of Eclipta Alba offers large-scale production of biocompatible AuNPs that can be used as a delivery vehicle for the treatment of cancer diseases. (paper)

  10. Green chemistry approach for the synthesis and stabilization of biocompatible gold nanoparticles and their potential applications in cancer therapy

    Mukherjee, Sudip; Sushma, V.; Patra, Sujata; Barui, Ayan Kumar; Pal Bhadra, Manika; Sreedhar, Bojja; Ranjan Patra, Chitta

    2012-11-01

    The biological approach to synthesis of AuNPs is eco-friendly and an ideal method to develop environmentally sustainable nanoparticles alternative to existing methods. We have developed a simple, fast, clean, efficient, low-cost and eco-friendly single-step green chemistry approach for the synthesis of biocompatible gold nanoparticles (AuNPs) from chloroauric acid (HAuCl4) using a water extract of Eclipta Alba leaves at room temperature. The AuNPs using Eclipta extract have been formed in very short time, even in less than 10 min. The as-synthesized AuNPs were thoroughly characterized by several physico-chemical techniques. The in vitro stability of as-synthesized AuNPs was studied in different buffer solutions. A plausible mechanism for the synthesis of AuNPs by Eclipta extract has been discussed. The biocompatibility of AuNPs was observed by in vitro cell culture assays. Finally, we have designed and developed a AuNPs-based drug delivery system (DDS) (Au-DOX) containing doxorubicin (DOX), a FDA approved anticancer drug. Administration of this DDS to breast cancer cells (MCF-7 and MDA-MB-231) shows significant inhibition of breast cancer cell proliferation compared to pristine doxorubicin. Therefore we strongly believe that the use of Eclipta Alba offers large-scale production of biocompatible AuNPs that can be used as a delivery vehicle for the treatment of cancer diseases.

  11. The identification of goat peroxiredoxin-5 and the evaluation and enhancement of its stability by nanoparticle formation

    Feng, Xiaozhou; Liu, Juanjuan; Fan, Shuai; Liu, Fan; Li, Yadong; Jin, Yuanyuan; Bai, Liping; Yang, Zhaoyong

    2016-04-01

    An anticancer bioactive peptide (ACBP), goat peroxiredoxin-5 (gPRDX5), was identified from goat-spleen extract after immunizing the goat with gastric cancer-cell lysate. Its amino acid sequence was determined by employing 2D nano-LC-ESI-LTQ-Orbitrap MS/MS combined with Mascot database search in the goat subset of the Uniprot database. The recombinant gPRDX5 protein was acquired by heterogeneous expression in Escherichia coli. Subsequently, the anti-cancer bioactivity of the peptide was measured by several kinds of tumor cells. The results indicated that the gPRDX5 was a good anti-cancer candidate, especially for killing B16 cells. However, the peptide was found to be unstable without modification with pharmaceutical excipients, which would be a hurdle for future medicinal application. In order to overcome this problem and find an effective way to evaluate the gPRDX5, nanoparticle formation, which has been widely used in drug delivery because of its steadiness in application, less side-effects and enhancement of drug accumulation in target issues, was used here to address the issues. In this work, the gPRDX5 was dispersed into nanoparticles before delivered to B16 cells. By the nanotechnological method, the gPRDX5 was stabilized by a fast and accurate procedure, which suggests a promising way for screening the peptide for further possible medicinal applications.

  12. Diblock-copolymer-mediated self-assembly of protein-stabilized iron oxide nanoparticle clusters for magnetic resonance imaging.

    Tähkä, Sari; Laiho, Ari; Kostiainen, Mauri A

    2014-03-03

    Superparamagnetic iron oxide nanoparticles (SPIONs) can be used as efficient transverse relaxivity (T2 ) contrast agents in magnetic resonance imaging (MRI). Organizing small (Doxide) diblock copolymer (P2QVP-b-PEO) to mediate the self-assembly of protein-cage-encapsulated iron oxide (γ-Fe2 O3 ) nanoparticles (magnetoferritin) into stable PEO-coated clusters. This approach relies on electrostatic interactions between the cationic N-methyl-2-vinylpyridinium iodide block and magnetoferritin protein cage surface (pI≈4.5) to form a dense core, whereas the neutral ethylene oxide block provides a stabilizing biocompatible shell. Formation of the complexes was studied in aqueous solvent medium with dynamic light scattering (DLS) and cryogenic transmission electron microcopy (cryo-TEM). DLS results indicated that the hydrodynamic diameter (Dh ) of the clusters is approximately 200 nm, and cryo-TEM showed that the clusters have an anisotropic stringlike morphology. MRI studies showed that in the clusters the longitudinal relaxivity (r1 ) is decreased and the transverse relaxivity (r2 ) is increased relative to free magnetoferritin (MF), thus indicating that clusters can provide considerable contrast enhancement. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Spectrophotometric determination of L-cysteine by using polyvinylpyrrolidone-stabilized silver nanoparticles in the presence of barium ions

    Bamdad, Farzad; Khorram, Fateme; Samet, Maryam; Bamdad, Kourosh; Sangi, Mohammad Reza; Allahbakhshi, Fateme

    2016-05-01

    In this article a simple and selective colorimetric probe for cysteine determination using silver nano particles (AgNPS) is described. The determination process was based upon the surface plasmon resonance properties of polyvinylpyrrolidone-stabilized AgNPS. Interaction of AgNPS with cysteine molecules in the presence of barium ions induced a red shift in the surface plasmon resonance (SPR) maximum of AgNPs, as a result of nanoparticle aggregation. Consequently, yellow color of AgNP solution was changed to pink. The linear range for the determination of cysteine was 3.2-8.2 μM (R = 0.9965) with a limit of detection equal to 2.8 μM (3σ). The proposed method was successfully applied to the determination of cysteine in human plasma samples. Acceptable recovery results of the spiked samples confirmed the validity of the proposed method.

  14. 1-Hexadecylamine as both reducing agent and stabilizer to synthesize Au and Ag nanoparticles and their SERS application

    Hou Xiaomiao; Zhan, Xiaoling; Fang Yan; Chen Shutang; Li Na; Zhou Qi

    2011-01-01

    1-Hexadecylamine (HDA)-capped Au and Ag nanoparticles (NPs) have been successfully prepared by a one-pot solution growth method. The HDA is used as both reducing agent and stabilizer in the synthetic process is favorable for investigating the capping mechanism of Au and Ag NPs’ surface. The growth process and characterization of Au and Ag NPs are determined by Ultraviolet–visible (UV–vis) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Experimental results demonstrate that the HDA-capped Au and Ag NPs are highly crystalline and have good optical properties. Furthermore, surface-enhanced Raman scattering (SERS) spectra of 2-thionaphthol are obtained on the Au and Ag NPs modified glass surface, respectively, indicating that the as-synthesized noble metal NPs have potentially high sensitive optical detection application.

  15. 1-Hexadecylamine as both reducing agent and stabilizer to synthesize Au and Ag nanoparticles and their SERS application

    Hou Xiaomiao; Zhan, Xiaoling, E-mail: zhangxl@bit.edu.cn [Beijing Institute of Technology, Department of Chemistry, School of Science (China); Fang Yan, E-mail: fangyan@mail.cnu.edu.cn [Capital Normal University, Beijing Key Lab for Nano-Photonics and Nano-Structure (NPNS), Department of Physics (China); Chen Shutang; Li Na; Zhou Qi [Beijing Institute of Technology, Department of Chemistry, School of Science (China)

    2011-05-15

    1-Hexadecylamine (HDA)-capped Au and Ag nanoparticles (NPs) have been successfully prepared by a one-pot solution growth method. The HDA is used as both reducing agent and stabilizer in the synthetic process is favorable for investigating the capping mechanism of Au and Ag NPs' surface. The growth process and characterization of Au and Ag NPs are determined by Ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Experimental results demonstrate that the HDA-capped Au and Ag NPs are highly crystalline and have good optical properties. Furthermore, surface-enhanced Raman scattering (SERS) spectra of 2-thionaphthol are obtained on the Au and Ag NPs modified glass surface, respectively, indicating that the as-synthesized noble metal NPs have potentially high sensitive optical detection application.

  16. Effect of ordering of PtCu₃ nanoparticle structure on the activity and stability for the oxygen reduction reaction.

    Hodnik, Nejc; Jeyabharathi, Chinnaiah; Meier, Josef C; Kostka, Alexander; Phani, Kanala L; Rečnik, Aleksander; Bele, Marjan; Hočevar, Stanko; Gaberšček, Miran; Mayrhofer, Karl J J

    2014-07-21

    In this study the performance enhancement effect of structural ordering for the oxygen reduction reaction (ORR) is systematically studied. Two samples of PtCu3 nanoparticles embedded on a graphitic carbon support are carefully prepared with identical initial composition, particle dispersion and size distribution, yet with different degrees of structural ordering. Thus we can eliminate all coinciding effects and unambiguously relate the improved activity of the ORR and more importantly the enhanced stability to the ordered nanostructure. Interestingly, the electrochemically induced morphological changes are common to both ordered and disordered samples. The observed effect could have a groundbreaking impact on the future directions in the rational design of active and stable platinum alloyed ORR catalysts.

  17. Spectrophotometric determination of L-cysteine by using polyvinylpyrrolidone-stabilized silver nanoparticles in the presence of barium ions.

    Bamdad, Farzad; Khorram, Fateme; Samet, Maryam; Bamdad, Kourosh; Sangi, Mohammad Reza; Allahbakhshi, Fateme

    2016-05-15

    In this article a simple and selective colorimetric probe for cysteine determination using silver nano particles (AgNPS) is described. The determination process was based upon the surface plasmon resonance properties of polyvinylpyrrolidone-stabilized AgNPS. Interaction of AgNPS with cysteine molecules in the presence of barium ions induced a red shift in the surface plasmon resonance (SPR) maximum of AgNPs, as a result of nanoparticle aggregation. Consequently, yellow color of AgNP solution was changed to pink. The linear range for the determination of cysteine was 3.2-8.2 μM (R=0.9965) with a limit of detection equal to 2.8 μM (3σ). The proposed method was successfully applied to the determination of cysteine in human plasma samples. Acceptable recovery results of the spiked samples confirmed the validity of the proposed method. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Facile formation of dendrimer-stabilized gold nanoparticles modified with diatrizoic acid for enhanced computed tomography imaging applications.

    Peng, Chen; Li, Kangan; Cao, Xueyan; Xiao, Tingting; Hou, Wenxiu; Zheng, Linfeng; Guo, Rui; Shen, Mingwu; Zhang, Guixiang; Shi, Xiangyang

    2012-11-07

    We report a facile approach to forming dendrimer-stabilized gold nanoparticles (Au DSNPs) through the use of amine-terminated fifth-generation poly(amidoamine) (PAMAM) dendrimers modified by diatrizoic acid (G5.NH(2)-DTA) as stabilizers for enhanced computed tomography (CT) imaging applications. In this study, by simply mixing G5.NH(2)-DTA dendrimers with gold salt in aqueous solution at room temperature, dendrimer-entrapped gold nanoparticles (Au DENPs) with a mean core size of 2.5 nm were able to be spontaneously formed. Followed by an acetylation reaction to neutralize the dendrimer remaining terminal amines, Au DSNPs with a mean size of 6 nm were formed. The formed DTA-containing [(Au(0))(50)-G5.NHAc-DTA] DSNPs were characterized via different techniques. We show that the Au DSNPs are colloid stable in aqueous solution under different pH and temperature conditions. In vitro hemolytic assay, cytotoxicity assay, flow cytometry analysis, and cell morphology observation reveal that the formed Au DSNPs have good hemocompatibility and are non-cytotoxic at a concentration up to 3.0 μM. X-ray absorption coefficient measurements show that the DTA-containing Au DSNPs have enhanced attenuation intensity, much higher than that of [(Au(0))(50)-G5.NHAc] DENPs without DTA or Omnipaque at the same molar concentration of the active element (Au or iodine). The formed DTA-containing Au DSNPs can be used for CT imaging of cancer cells in vitro as well as for blood pool CT imaging of mice in vivo with significantly improved signal enhancement. With the two radiodense elements of Au and iodine incorporated within one particle, the formed DTA-containing Au DSNPs may be applicable for CT imaging of various biological systems with enhanced X-ray attenuation property and detection sensitivity.

  19. Entrapment of curcumin into monoolein-based liquid crystalline nanoparticle dispersion for enhancement of stability and anticancer activity

    Baskaran R

    2014-06-01

    Full Text Available Rengarajan Baskaran,1 Thiagarajan Madheswaran,2 Pasupathi Sundaramoorthy,1 Hwan Mook Kim,1 Bong Kyu Yoo1 1College of Pharmacy, Gachon University, Incheon, South Korea; 2College of Pharmacy Yeungnam University, Gyeongsan, South Korea Abstract: Despite the promising anticancer potential of curcumin, its therapeutic application has been limited, owing to its poor solubility, bioavailability, and chemical fragility. Therefore, various formulation approaches have been attempted to address these problems. In this study, we entrapped curcumin into monoolein (MO-based liquid crystalline nanoparticles (LCNs and evaluated the physicochemical properties and anticancer activity of the LCN dispersion. The results revealed that particles in the curcumin-loaded LCN dispersion were discrete and monodispersed, and that the entrapment efficiency was almost 100%. The stability of curcumin in the dispersion was surprisingly enhanced (about 75% of the curcumin survived after 45 days of storage at 40°C, and the in vitro release of curcumin was sustained (10% or less over 15 days. Fluorescence-activated cell sorting (FACS analysis using a human colon cancer cell line (HCT116 exhibited 99.1% fluorescence gating for 5 µM curcumin-loaded LCN dispersion compared to 1.36% for the same concentration of the drug in dimethyl sulfoxide (DMSO, indicating markedly enhanced cellular uptake. Consistent with the enhanced cellular uptake of curcumin-loaded LCNs, anticancer activity and cell cycle studies demonstrated apoptosis induction when the cells were treated with the LCN dispersion; however, there was neither noticeable cell death nor significant changes in the cell cycle for the same concentration of the drug in DMSO. In conclusion, entrapping curcumin into MO-based LCNs may provide, in the future, a strategy for overcoming the hurdles associated with both the stability and cellular uptake issues of the drug in the treatment of various cancers. Keywords: liquid

  20. The precipitation, growth and stability of mercury sulfide nanoparticles formed in the presence of marine dissolved organic matter.

    Mazrui, Nashaat M; Seelen, Emily; King'ondu, Cecil K; Thota, Sravan; Awino, Joseph; Rouge, Jessica; Zhao, Jing; Mason, Robert P

    2018-04-25

    The methylation of mercury is known to depend on the chemical forms of mercury (Hg) present in the environment and the methylating bacterial activity. In sulfidic sediments, under conditions of supersaturation with respect to metacinnabar, recent research has shown that mercury precipitates as β-HgS(s) nanoparticles (β-HgS(s)nano). Few studies have examined the precipitation of β-HgS(s)nano in the presence of marine dissolved organic matter (DOM). In this work, we used dynamic light scattering (DLS) coupled with UV-Vis spectroscopy and transmission electron microscopy (TEM) to investigate the formation and fate of β-HgS(s)nano formed in association with marine DOM extracted from the east and west of Long Island Sound, and at the shelf break of the North Atlantic Ocean, as well as with low molecular weight thiols. We found that while the β-HgS(s)nano formed in the presence of oceanic DOM doubled in size after 5 weeks, those forming in solutions with coastal DOM did not grow over time. In addition, when the HgII : DOM ratio was varied, β-HgS(s)nano only rapidly aggregated at high ratios (>41 μmol HgII per mg C) where the concentration of thiol groups was determined to be substantially low relative to HgII. This suggests that functional groups other than thiols could be involved in the stabilization of β-HgS(s)nano. Furthermore, we showed that β-HgS(s)nano forming under anoxic conditions remained stable and could therefore persist in the environment sufficiently to impact the methylation potential. Exposure of β-HgS(s)nano to sunlit and oxic environments, however, caused rapid aggregation and sedimentation of the nanoparticles, suggesting that photo-induced changes or oxidation of organic matter adsorbed on the surface of β-HgS(s)nano affected their stability in surface waters.

  1. Green synthesis of stabilized spherical shaped gold nanoparticles using novel aqueous Elaeis guineensis (oil palm) leaves extract

    Ahmad, Tausif; Bustam, Mohamad Azmi; Irfan, Muhammad; Moniruzzaman, Muhammad; Anwaar Asghar, Hafiz Muhammad; Bhattacharjee, Sekhar

    2018-05-01

    In the last decade, development of bioinspired protocols to synthesize gold nanoparticles (AuNPs) using plants and their extracts have been dealt by researchers due to their low cost, renewability and non-toxic features. A simple, cheap and ecofriendly method is reported to synthesize stabilized AuNPs of size 35-75 nm at room temperature using aqueous Elaeis guineensis (oil palm) leaves extract without addition of any external agent. Oil palm leaves mediated AuNPs were characterized using FTIR, UV-vis spectrophotometer, EDAX, XPS, FESEM, TEM, DLS and TGA. FTIR spectra results revealed contribution of phenolic, carboxylic, amines and amides in reduction of trivalent gold ions and stabilization of formed gold atoms. Reaction solution color change and UV-vis spectra confirmed reduction of gold ions to generate gold atoms. Reaction mechanism explained the role of phenolic compounds in reduction reaction using FTIR and UV-vis spectra results. EDAX and XPS results further validated the formation of metallic gold particles through bioreduction of gold ions. Crystal structure of metallic gold particles was confirmed through XRD peaks indexing to (111), (200), (220) and (311) planes. TEM and FESEM particles size measurements exhibited the formation of nanostructured AuNPs. Synthesis of well scattered and spherical shaped AuNPs was revealed through FESEM and TEM images. The excellent stability of AuNPs was shown through high negative zeta potential value (-14.7 ± 4.68 mV) and uniform dispersion in aqueous media. Our results disclosed the excellent potential of Elaeis guineensis (oil palm) leaves as reducing and stabilizing agents in green synthesis of well scattered spherical shaped AuNPs, which can be employed as strong candidates in medical drug delivery and industrial applications.

  2. Chemical modifications and stability of diamond nanoparticles resolved by infrared spectroscopy and Kelvin force microscopy

    Kozak, Halyna; Remeš, Zdeněk; Houdková, Jana; Stehlík, Štěpán; Kromka, Alexander; Rezek, Bohuslav

    2013-01-01

    Roč. 15, č. 4 (2013), "1568-1"-"1568-9" ISSN 1388-0764 R&D Projects: GA ČR GAP108/12/0910; GA ČR GPP205/12/P331; GA MŠk LH12186 Institutional support: RVO:68378271 Keywords : diamond nanoparticles * chemical modification * GAR-FTIR * AFM * KFM * XPS Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.278, year: 2013 http://link.springer.com/article/10.1007%2Fs11051-013-1568-7

  3. Enhancing the stability of colloidal silver nanoparticles using polyhydroxyalkanoates (PHA) from Bacillus circulans (MTCC 8167) isolated from crude oil contaminated soil.

    Phukon, Pinkee; Saikia, Jyoti Prasad; Konwar, Bolin Kumar

    2011-09-01

    Polyhydroxyalkanoate (PHA) was produced by growing Bacillus circulans (MTCC 8167) in the specific detection medium. The identification of the polymer as PHA was confirmed by fluorescence microscopy. The PHA was purified and characterized using FT-IR. The silver nanoparticles (SNP) were synthesized from AgNO3 in the dispersed colloids of PHA (0.085%) using NaBH4 (sodium borohydrate as reducing agent). The stability was tested using wave length scanning with a UV-Vis spectrophotometer and finally with transmission electron microscopy. The PHA stabilized solution was found to be stable for 30 days as against the low stability of silver nanoparticles (SNP) solution alone. Copyright © 2011 Elsevier B.V. All rights reserved.

  4. Aminolysis of polyethylene terephthalate surface along with in situ synthesis and stabilizing ZnO nanoparticles using triethanolamine optimized with response surface methodology

    Poortavasoly, Hajar; Montazer, Majid, E-mail: tex5mm@aut.ac.ir; Harifi, Tina

    2016-01-01

    This research concerned the simultaneous polyester surface modification and synthesis of zinc oxide nano-reactors to develop durable photo-bio-active fabric with variable hydrophobicity/hydrophilicity under sunlight. For this purpose, triethanolamine (TEA) was applied as a stabilizer and pH adjusting chemical for the aminolysis of polyester surface and enhancing the surface reactivity along with synthesis and deposition of ZnO nanoparticles on the fabric. Therefore, TEA played a crucial role in providing the alkaline condition for the preparation of zinc oxide nanoparticles and acting as stabilizer controlling the size of the prepared nanoparticles. The stain–photodegradability regarded as self-cleaning efficiency, wettability and weight change under the process was optimized based on zinc acetate and TEA concentrations, using central composite design (CCD). Findings also suggested the potential of the prepared fabric in inhibiting Staphylococcus aureus and Escherichia coli bacteria growth with greater than 99.99% antibacterial efficiency. Besides, the proposed treatment had no detrimental effect on tensile strength and hand feeling of the polyester fabric. - Highlights: • Durable photo-bio-active polyester with variable hydrophobicity/hydrophilicity • Simultaneous polyester surface aminolysis and ZnO ball-like nanoparticle production • Multi-role of TEA for polyester aminolysis and nanoparticle formation • Optimization of photoactivity and wettability by central composite design.

  5. Gd{sub 2}O{sub 3} nanoparticles stabilized by hydrothermally modified dextrose for positive contrast magnetic resonance imaging

    Babić-Stojić, Branka, E-mail: babic@vinca.rs [Vinča Institute of Nuclear Sciences, University of Belgrade, PO Box 522, 11001 Belgrade (Serbia); Jokanović, Vukoman; Milivojević, Dušan [Vinča Institute of Nuclear Sciences, University of Belgrade, PO Box 522, 11001 Belgrade (Serbia); Požek, Miroslav [Department of Physics, Faculty of Science, University of Zagreb, 10000 Zagreb (Croatia); Jagličić, Zvonko [Institute of Mathematics, Physics and Mechanics, Jadranska 19, 1000 Ljubljana (Slovenia); Makovec, Darko [Department for Materials Synthesis, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Arsikin, Katarina; Paunović, Verica [Institute of Microbiology and Immunology, School of Medicine, University of Belgrade, 11000 Belgrade (Serbia)

    2016-04-01

    Gd{sub 2}O{sub 3} nanoparticles of a few nm in size and their agglomerates dispersed in dextrose derived polymer template were synthesized by hydrothermal treatment. The produced nanosized material was investigated by TEM, FTIR spectroscopy, SQUID measurements and NMR relaxometry. Biological evaluation of this material was done by crystal violet and MTT assays to determine the cell viability. Longitudinal and transverse NMR relaxivities of water diluted Gd{sub 2}O{sub 3} nanoparticle dispersions measured at the magnetic field of 1.5 T, estimated to be r{sub 1}(Gd{sub 2}O{sub 3})=9.6 s{sup −1} mM{sup −1} in the Gd concentration range 0.1–30 mM and r{sub 2}(Gd{sub 2}O{sub 3})=17.7 s{sup −1} mM{sup −1} in the lower concentration range 0.1–0.8 mM, are significantly higher than the corresponding relaxivities measured for the standard contrast agent r{sub 1}(Gd-DTPA)=4.1 s{sup −1} mM{sup −1} and r{sub 2}(Gd-DTPA)=5.1 s{sup −1} mM{sup −1}. The ratio of the two relaxivities for Gd{sub 2}O{sub 3} nanoparticles r{sub 2}/r{sub 1}=1.8 is suitable for T{sub 1}-weighted imaging. Good MRI signal intensities of the water diluted Gd{sub 2}O{sub 3} nanoparticle dispersions were recorded at lower Gd concentrations 0.2–0.8 mM. The Gd{sub 2}O{sub 3} samples did not exert any significant cytotoxic effects at Gd concentrations of 0.2 mM and below. These properties of the produced Gd{sub 2}O{sub 3} nanoparticles in hydrothermally modified dextrose make them promising for potential application in MRI for the design of a positive MRI contrast agent. - Highlights: • Gd{sub 2}O{sub 3} nanoparticles (NPs) were stabilized by hydrothermally modified dextrose. • Magnetic moment per Gd{sup 3+} ion in the Gd{sub 2}O{sub 3} NPs is much lower than that in the bulk. • The ratio r{sub 2}/r{sub 1}=1.8 for Gd{sub 2}O{sub 3} NPs dispersions is favorable for T{sub 1}-weighted MRI. • Gd{sub 2}O{sub 3} NPs dispersions had good MRI signal intensity just at lower Gd concentrations

  6. Impedimetric Aptasensor for Ochratoxin A Determination Based on Au Nanoparticles Stabilized with Hyper-Branched Polymer

    Gennady Evtugyn

    2013-11-01

    Full Text Available An impedimetric aptasensor for ochratoxin A (OTA detection has been developed on the base of a gold electrode covered with a new modifier consisting of electropolymerized Neutral Red and a mixture of Au nanoparticles suspended in the dendrimeric polymer Botlorn H30®. Thiolated aptamer specific to OTA was covalently attached to Au nanoparticles via Au-S bonding. The interaction of the aptamer with OTA induced the conformational switch of the aptamer from linear to guanine quadruplex form followed by consolidation of the surface layer and an increase of the charge transfer resistance. The aptasensor makes it possible to detect from 0.1 to 100 nM of OTA (limit of detection: 0.02 nM in the presence of at least 50 fold excess of ochratoxin B. The applicability of the aptasensor for real sample assay was confirmed by testing spiked beer samples. The recovery of 2 nM OTA was found to be 70% for light beer and 78% for dark beer.

  7. Use of lead (II) sulfide nanoparticles as stabilizer for PMMA exposed to gamma irradiation

    Garcia, Olga Pinheiro; Albuquerque, Marilia Cordeiro Carneiro de; Aquino, Katia Aparecida da Silva; Araujo, Elmo Silvano de, E-mail: aquino@ufpe.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear; Araujo, Patricia Lopes Barros de [Universidade Federal Rural de Pernambuco (UFRPE), Recife, PE (Brazil)

    2015-03-15

    Lead (II) sulfide (PbS) were synthesized by sonochemical method and crystals with cubic structure exhibit aggregated nanoparticles with size in the range of 50-100 nm. Commercial Poly(methyl methacrylate) (PMMA) containing the PbS nanoparticles (PbS-NP) exposed to gamma irradiation were investigated and both the viscosity-average molar mass (Mv ) and degradation index (DI) values were measured. Ours results showed decreases in molar mass when the systems were gamma irradiated, i. e., random scission effects that take place in the main chain. On the other hand, DI results showed that the addition of PbS-NP at 0.3 wt% into the PMMA matrix decreased 100% the number of main chain scissions. Results about the free radical scavenger action of the PbS-NP were obtained by use of 2,2-diphenyl-1-(2,4,6-trinitrophenyl)-hydrazyl radical (DPPH) and are discussed in this study. Analysis of infrared spectra, refraction index, mechanical, and thermal properties showed influence of the PbS-NP in the physical behavior of PMMA. (author)

  8. Temperature effects on the stability of gold nanoparticles in the presence of a cationic thermoresponsive copolymer

    Pamies, Ramón [Technical University of Cartagena, Department of Material Engineering and Manufacturing (Spain); Zhu, Kaizheng [University of Oslo, Department of Chemistry (Norway); Kjøniksen, Anna-Lena, E-mail: anna.l.kjoniksen@hiof.no [Østfold University College, Faculty of Engineering (Norway); Nyström, Bo [University of Oslo, Department of Chemistry (Norway)

    2016-11-15

    New hybrid complexes composed by a thermoresponsive copolymer and gold nanoparticles (R{sub h} = 22 nm) have been characterized by dynamic light scattering (DLS) and UV-visible spectroscopy. A cationic thermoresponsive triblock copolymer, methoxy-poly(ethylene glycol)-block-poly(N-isopropylacrylamide)-block-poly((3-acrylamidopropyl) trimethyl ammonium chloride), abbreviated as MPEG-b-PNIPAAM-b-PN(+), has been synthesized by atom transfer radical polymerization (ATRP). We have evaluated the thermal response at low concentrations of this triblock copolymer in bulk solution and the effect of concentration on the interaction between this thermosensitive copolymer and the gold nanoparticles (AuNPs) to form new hybrid complexes (60–1000 nm) at different temperatures. The thermosensitive nature of the copolymer causes both aggregation and contraction of the aggregates at elevated temperatures. The AuNPs were found to be separately embedded in the hybrid complexes. Interestingly, the AuNPs prevent macroscopic phase separation of the system at high temperatures.

  9. Role of phosphate on stability and catalase mimetic activity of cerium oxide nanoparticles.

    Singh, Ragini; Singh, Sanjay

    2015-08-01

    Cerium oxide nanoparticles (CeNPs) have been recently shown to scavenge reactive oxygen and nitrogen species (ROS and RNS) in different experimental model systems. CeNPs (3+) and CeNPs (4+) have been shown to exhibit superoxide dismutase (SOD) and catalase mimetic activity, respectively. Due to their nanoscale dimension, CeNPs are expected to interact with the components of biologically relevant buffers and medium, which could alter their catalytic properties. We have demonstrated earlier that CeNPs (3+) interact with phosphate and lose the SOD activity. However, very little is known about the interaction of CeNPs (4+) with the phosphate and other anions, predominantly present in biological buffers and their effects on the catalase mimetic-activity of these nanoparticles. In this study, we report that catalase mimetic-activity of CeNPs (4+) is resistant to the phosphate anions, pH changes and composition of cell culture media. Given the abundance of phosphate anions in the biological system, it is likely that internalized CeNPs would be influenced by cytoplasmic and nucleoplasmic concentration of phosphate. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Stabilization of the nitric oxide (NO) prodrugs and anticancer leads, PABA/NO and Double JS-K, through incorporation into PEG-protected nanoparticles.

    Kumar, Varun; Hong, Sam Y; Maciag, Anna E; Saavedra, Joseph E; Adamson, Douglas H; Prud'homme, Robert K; Keefer, Larry K; Chakrapani, Harinath

    2010-02-01

    We report the stabilization of the nitric oxide (NO) prodrugs and anticancer lead compounds, PABA/NO (O(2)-{2,4-dinitro-5-[4-(N-methylamino)benzoyloxy]phenyl} 1-(N,N-dimethylamino)diazen-1-ium-1,2-diolate) and "Double JS-K" 1,5-bis-{1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diol-2-ato}-2,4-dinitrobenzene, through their incorporation into polymer-protected nanoparticles. The prodrugs were formulated in block copolymer-stabilized nanoparticles with sizes from 220 to 450 nm by a novel rapid precipitation process. The block copolymers, with polyethylene glycol (PEG) soluble blocks, provide a steric barrier against NO prodrug activation by glutathione. Too rapid activation and NO release has been a major barrier to effective administration of this class of compounds. The nanoparticle stabilized PABA/NO are protected from attack by glutathione as evidenced by a significant increase in time taken for 50% decomposition from 15 min (unformulated) to 5 h (formulated); in the case of Double JS-K, the 50% decomposition time was extended from 4.5 min (unformulated) to 40 min (formulated). The more hydrophobic PABA/NO produced more stable nanoparticles and correspondingly more extended release times in comparison with Double JS-K. The hydrophobic blocks of the polymer were either polystyrene or polylactide. Both blocks produced nanoparticles of approximately the same size and release kinetics. This combination of PEG-protected nanoparticles with sizes appropriate for cancer targeting by enhanced permeation and retention (EPR) and delayed release of NO may afford enhanced therapeutic benefit.

  11. Understanding the growth mechanism of stabilizer-free Ag nanoparticles on reduced graphene oxide: the role of CO

    Gao Weiyin; Ran Chenxin; Wang Minqiang; Yao Xi; He Delong; Bai Jinbo

    2013-01-01

    In this study, one-step approach to prepare stabilizer-free Ag–graphene nanocomposites using DMAc-assisted thermal reduction method with uniform distribution of “near spherical” Ag nanoparticles (Ag NPs) in the range of 16–20 nm is reported. Interestingly, from the change of absorption spectrum as a function of reaction time, we observed that the characteristic absorption peak of Ag NPs shows no peak position shift in a quite long time without extra stabilizer while red-shift and broaden after continuous reaction. To explain this phenomenon, we further proposed a growth mechanism that CO, which is generated from reduction of functional groups on GO, adsorbed on the surface of Ag NPs and leaded to growth cease of Ag NPs into a narrow size distribution during the reduction of GO. Meanwhile, Ag NPs can catalyze the oxidation of adsorbed-CO to CO 2 in the presence of O 2 which can easily desorb from Ag surfaces. Hence, after fully removal of functional groups on GO, continuous supply of CO was cutoff while the desorption of adsorbed-CO was still happening continually, so Ag NPs start to gradually grow and resulting in aggregation. Moreover, the dosage of less DMAc or more AgNO 3 would cause the anisotropic growth and form multiply twinned structure of Ag NPs. Our study presents a useful understanding on the growth of Ag NPs on graphene.

  12. Dispersion stability of 1-octanethiol coated Cu nanoparticles in a 1-octanol solvent for the application of nanoink

    Cho, Danee [Department of Materials Engineering, Hanyang University, Ansan 426-791 (Korea, Republic of); Baik, Jong-Hwan [Lean on Tech., Guri 471-854 (Korea, Republic of); Choi, Da-hyun [Department of Materials Engineering, Hanyang University, Ansan 426-791 (Korea, Republic of); Lee, Caroline Sunyong, E-mail: sunyonglee@hanyang.ac.kr [Department of Materials Engineering, Hanyang University, Ansan 426-791 (Korea, Republic of)

    2014-08-01

    Conductive ink with Copper nanoparticles (Cu NPs) has various advantages compared with conventional ink, such as good electrical conductivity and low cost. However, it suffers through easily oxidization problem, leading to an unstable electrical conductivity, which decreases over time. Therefore, it is important to prevent (or least minimize) oxidation of the Cu NPs. In this study, Cu NPs with diameter of 50 nm were coated with 1-octanethiol (CH₃(CH₂)₇SH) in a high-vacuum condition (5.33 × 10⁻⁴ Pa). The coating conditions were systematically varied to investigate the effect on the coating thicknesses. Coated Cu NPs were dispersed in 1-octanol to form the conductive ink, and the dispersion behavior was studied as a function of the thickness of the 1-octanethiol coating. The thickness of the coating layer was characterized using transmission electron microscopy and X-ray spectroscopy analysis, and was found to be 3 nm, 6 nm, and 10 nm. The dispersion stability of the inks was characterized by Turbiscan dispersion stability and viscosity measurements, and it was found that the copper nanoink formed using Cu NPs with a 6-nm-thick coating exhibited the most stable dispersion properties.

  13. Dispersion stability of 1-octanethiol coated Cu nanoparticles in a 1-octanol solvent for the application of nanoink

    Cho, Danee; Baik, Jong-Hwan; Choi, Da-hyun; Lee, Caroline Sunyong

    2014-01-01

    Conductive ink with Copper nanoparticles (Cu NPs) has various advantages compared with conventional ink, such as good electrical conductivity and low cost. However, it suffers through easily oxidization problem, leading to an unstable electrical conductivity, which decreases over time. Therefore, it is important to prevent (or least minimize) oxidation of the Cu NPs. In this study, Cu NPs with diameter of 50 nm were coated with 1-octanethiol (CH 3 (CH 2 ) 7 SH) in a high-vacuum condition (5.33 × 10 −4 Pa). The coating conditions were systematically varied to investigate the effect on the coating thicknesses. Coated Cu NPs were dispersed in 1-octanol to form the conductive ink, and the dispersion behavior was studied as a function of the thickness of the 1-octanethiol coating. The thickness of the coating layer was characterized using transmission electron microscopy and X-ray spectroscopy analysis, and was found to be 3 nm, 6 nm, and 10 nm. The dispersion stability of the inks was characterized by Turbiscan dispersion stability and viscosity measurements, and it was found that the copper nanoink formed using Cu NPs with a 6-nm-thick coating exhibited the most stable dispersion properties.

  14. As-grown graphene/copper nanoparticles hybrid nanostructures for enhanced intensity and stability of surface plasmon resonance

    Li, Yun-Fei; Dong, Feng-Xi; Chen, Yang; Zhang, Xu-Lin; Wang, Lei; Bi, Yan-Gang; Tian, Zhen-Nan; Liu, Yue-Feng; Feng, Jing; Sun, Hong-Bo

    2016-11-01

    The transfer-free fabrication of the high quality graphene on the metallic nanostructures, which is highly desirable for device applications, remains a challenge. Here, we develop the transfer-free method by direct chemical vapor deposition of the graphene layers on copper (Cu) nanoparticles (NPs) to realize the hybrid nanostructures. The graphene as-grown on the Cu NPs permits full electric contact and strong interactions, which results in a strong localization of the field at the graphene/copper interface. An enhanced intensity of the localized surface plasmon resonances (LSPRs) supported by the hybrid nanostructures can be obtained, which induces a much enhanced fluorescent intensity from the dye coated hybrid nanostructures. Moreover, the graphene sheets covering completely and uniformly on the Cu NPs act as a passivation layer to protect the underlying metal surface from air oxidation. As a result, the stability of the LSPRs for the hybrid nanostructures is much enhanced compared to that of the bare Cu NPs. The transfer-free hybrid nanostructures with enhanced intensity and stability of the LSPRs will enable their much broader applications in photonics and optoelectronics.

  15. Enhanced Colloidal Stability of CeO2 Nanoparticles by Ferrous Ions: Adsorption, Redox Reaction, and Surface Precipitation.

    Liu, Xuyang; Ray, Jessica R; Neil, Chelsea W; Li, Qingyun; Jun, Young-Shin

    2015-05-05

    Due to the toxicity of cerium oxide (CeO2) nanoparticles (NPs), a better understanding of the redox reaction-induced surface property c