Three-dimensional cross-linking composite of graphene, carbon nanotubes and Si nanoparticles for lithium ion battery anode

Science.gov (United States)

Tian, Suyun; Zhu, Guannan; Tang, Yanping; Xie, Xiaohua; Wang, Qian; Ma, Yufei; Ding, Guqiao; Xie, Xiaoming

2018-03-01

Various graphene-based Si nanocomposites have been reported to improve the performance of active materials in Li-ion batteries. However, these candidates still yield severe capacity fading due to the electrical disconnection and fractures caused by the huge volume changes over extended cycles. Therefore, we have designed a novel three-dimensional cross-linked graphene and single-wall carbon nanotube structure to encapsulate the Si nanoparticles. The synthesized three-dimensional structure is attributed to the excellent self-assembly of carbon nanotubes with graphene oxide as well as a thermal treatment process at 900 °C. This special structure provides sufficient void spaces for the volume expansion of Si nanoparticles and channels for the diffusion of ions and electrons. In addition, the cross-linking of the graphene and single-wall carbon nanotubes also strengthens the stability of the structure. As a result, the volume expansion of the Si nanoparticles is restrained. The specific capacity remains at 1450 mAh g-1 after 100 cycles at 200 mA g-1. This well-defined three-dimensional structure facilitates superior capacity and cycling stability in comparison with bare Si and a mechanically mixed composite electrode of graphene, single-wall carbon nanotubes and silicon nanoparticles.

Temperature-controlled cross-linking of silver nanoparticles with diels-alder reaction and its application on antibacterial property

Science.gov (United States)

Liu, Lian; Yang, Pengfei; Li, Junying; Zhang, Zhiliang; Yu, Xi; Lu, Ling

2017-05-01

Sliver nanoparticles (AgNPs) were synthesized and functionalized with furan group on their surface, followed by the reverse Diels-Alder (DA) reaction with bismaleimide to vary the particle size, so as to give different antibacterial activities. These nanoparticles were characterized using Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Ultraviolet-Visible (UV-vis), Nanoparticle Size Analyzer and X-Ray Photoelectron Spectroscopy (XPS). It was found that the cross-linking reaction with bismaleimide had a great effect on the size of AgNPs. The size of the AgNPs could be controlled by the temperature of DA/r-DA equilibrium. The antibacterial activity was assessed using the inhibition zone diameter by introducing the particles into a media containing Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus, respectively. It was found that these particles were effective bactericides. Furthermore, the antibacterial activity of the nanoparticles decreased orderly as the particle size enlarged.

Microscopic Electron Dynamics in Metal Nanoparticles for Photovoltaic Systems

Directory of Open Access Journals (Sweden)

Katarzyna Kluczyk

2018-06-01

Full Text Available Nanoparticles—regularly patterned or randomly dispersed—are a key ingredient for emerging technologies in photonics. Of particular interest are scattering and field enhancement effects of metal nanoparticles for energy harvesting and converting systems. An often neglected aspect in the modeling of nanoparticles are light interaction effects at the ultimate nanoscale beyond classical electrodynamics. Those arise from microscopic electron dynamics in confined systems, the accelerated motion in the plasmon oscillation and the quantum nature of the free electron gas in metals, such as Coulomb repulsion and electron diffusion. We give a detailed account on free electron phenomena in metal nanoparticles and discuss analytic expressions stemming from microscopic (Random Phase Approximation—RPA and semi-classical (hydrodynamic theories. These can be incorporated into standard computational schemes to produce more reliable results on the optical properties of metal nanoparticles. We combine these solutions into a single framework and study systematically their joint impact on isolated Au, Ag, and Al nanoparticles as well as dimer structures. The spectral position of the plasmon resonance and its broadening as well as local field enhancement show an intriguing dependence on the particle size due to the relevance of additional damping channels.

Encapsulation of cobalt nanoparticles in cross-linked-polymer cages

Energy Technology Data Exchange (ETDEWEB)

Hatamie, Shadie [Department of Electronic-Science, Fergusson College, Pune 411 004 (India); Dhole, S.D. [Department of Physics, University of Pune, Pune 411 007 (India); Ding, J. [Department of Materials Science and Engineering, National University of Singapore, 7, Engineering Drive 1, Singapore 117574 (Singapore); Kale, S.N. [Department of Electronic-Science, Fergusson College, Pune 411 004 (India)], E-mail: sangeetakale2004@gmail.com

2009-07-15

Nanoparticles embedded in polymeric cages give rise to interesting applications ranging from nanocatalysis to drug-delivery systems. In this context, we report on synthesis of cobalt (Co) nanoparticles trapped in polyvinyl alcohol (PVA) matrix to yield self-supporting magnetic films in PVA slime. A 20 nm, Co formed in FCC geometry encapsulated with a weak citrate coat when caged in PVA matrix exhibited persistence of magnetism and good radio-frequency response. Cross-linking of PVA chains to form cage-like structures to arrest Co nanoparticles therein, is believed to be the reason for oxide-free nature of Co, promising applications in biomedicine as well as in radio-frequency shielding.

Selective Magnetic Removal of Pb(II from Aqueous Solution by Porphyrin Linked-Magnetic Nanoparticles

Directory of Open Access Journals (Sweden)

H. Ghanbarnejad

2012-12-01

Full Text Available The discharge of lead containing effluents into the environment and water bodies is harmful for the human, animals, aquatic flora and fauna. Herein, a novel surface engineered magnetic nanoparticle for removing Pb2+  ions was studied. After surface modification of the magnetite by 3-amino-propyltriethoxysilane (APTES magnetic nanoparticles with covalently linked porphyrins were synthesized. Two atropisomers of  meso-tetrakis(2-carboxy-4-nonylphenyl porphyrin (TCNP were tested to analyze the atropisomeric effect on lead uptake. For characterize the synthesized nanosorbents methods like: Transform Infrared Spectroscopy, X-ray diffraction, Transmission Electron Microscopy and Thermo-Gravimetric Analysis were used. The effects of pH, contact time, sorbent dosage and some co-existing cations were investigated. Regeneration of lead adsorbed material could be possible and the modified magnetic nanoparticles exhibited good reusability. The use of such a system can provide fast and efficient removal of the lead ion by using an external magnetic field. The competitive adsorption tests showed good adsorption selectivity for lead ion.

Cross-linked gelatin/nanoparticles composite coating on micro-arc oxidation film for corrosion and drug release

Energy Technology Data Exchange (ETDEWEB)

Xu Xinhua, E-mail: xhxu_tju@eyou.com [Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Lu Ping; Guo Meiqing; Fang Mingzhong [Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China)

2010-02-01

A composite coating which could control drug release and biocorrosion of magnesium alloy stent materials WE42 was prepared. This composite coating was fabricated on the surface of the micro-arc oxidation (MAO) film of the magnesium alloy, WE42, by mixing different degrees of cross-linked gelatin with well-dispersed poly(DL-lactide-co-glycolide) (PLGA) nanoparticles. The PLGA nanoparticles were prepared by emulsion solvent evaporation/extraction technique. Nano ZS laser diffraction particle size analyzer detected that the size of the nanoparticles to be 150-300 nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) was used to analyze the morphology of the nanoparticles and the composite coating. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion behavior of the composite coating. Drug release was determined by ultraviolet-visible (UV-vis) spectrophotometer. The corrosion resistance of the composite coating was improved by preventing the corrosive ions from diffusing to the MAO films. The drug release rate of paclitaxel (PTX) exhibited a nearly linear sustained-release profile with no significant burst releases.

Cross-linked gelatin/nanoparticles composite coating on micro-arc oxidation film for corrosion and drug release

International Nuclear Information System (INIS)

Xu Xinhua; Lu Ping; Guo Meiqing; Fang Mingzhong

2010-01-01

A composite coating which could control drug release and biocorrosion of magnesium alloy stent materials WE42 was prepared. This composite coating was fabricated on the surface of the micro-arc oxidation (MAO) film of the magnesium alloy, WE42, by mixing different degrees of cross-linked gelatin with well-dispersed poly(DL-lactide-co-glycolide) (PLGA) nanoparticles. The PLGA nanoparticles were prepared by emulsion solvent evaporation/extraction technique. Nano ZS laser diffraction particle size analyzer detected that the size of the nanoparticles to be 150-300 nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) was used to analyze the morphology of the nanoparticles and the composite coating. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion behavior of the composite coating. Drug release was determined by ultraviolet-visible (UV-vis) spectrophotometer. The corrosion resistance of the composite coating was improved by preventing the corrosive ions from diffusing to the MAO films. The drug release rate of paclitaxel (PTX) exhibited a nearly linear sustained-release profile with no significant burst releases.

Cross-linked gelatin/nanoparticles composite coating on micro-arc oxidation film for corrosion and drug release

Science.gov (United States)

Xu, Xinhua; Lu, Ping; Guo, Meiqing; Fang, Mingzhong

2010-02-01

A composite coating which could control drug release and biocorrosion of magnesium alloy stent materials WE42 was prepared. This composite coating was fabricated on the surface of the micro-arc oxidation (MAO) film of the magnesium alloy, WE42, by mixing different degrees of cross-linked gelatin with well-dispersed poly( DL-lactide-co-glycolide) (PLGA) nanoparticles. The PLGA nanoparticles were prepared by emulsion solvent evaporation/extraction technique. Nano ZS laser diffraction particle size analyzer detected that the size of the nanoparticles to be 150-300 nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) was used to analyze the morphology of the nanoparticles and the composite coating. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion behavior of the composite coating. Drug release was determined by ultraviolet-visible (UV-vis) spectrophotometer. The corrosion resistance of the composite coating was improved by preventing the corrosive ions from diffusing to the MAO films. The drug release rate of paclitaxel (PTX) exhibited a nearly linear sustained-release profile with no significant burst releases.

Electronic and magnetic properties of MnAu nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Safi 46000 (Morocco); LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Mounkachi, O; El moussaoui, H. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

2014-03-15

Self-consistent ab initio calculations, based on DFT (Density Functional Theory) approach and using FLAPW (Full potential Linear Augmented Plane Wave) method, are performed to investigate both electronic and magnetic properties of the MnAu nanoparticles. Polarized spin is included in calculations within the framework of the antiferromagnetic. The Mn magnetic moments where considered to be along c axes. Obtained data from ab initio calculations are used as input for the high temperature series expansions (HTSEs) calculations to compute other magnetic parameters. The zero-field high temperature static susceptibility series of the magnetic moment (m) and nearest-neighbour Heisenberg and XY models on a MnAu nanoparticles is thoroughly analyzed by means of a power series coherent anomaly method (CAM) for different nanoparticles. The exchanges interactions between the magnetic atoms are obtained for MnAu nanoparticles. - Highlights: • The electronic properties of the MnAu nanoparticles are studied using the DFT and FLAPW. • Magnetic moment is computed. • The ab initio calculations are used as input for HTSEs to compute other magnetic parameters. • The exchanges interactions and blocking temperature are obtained for MnAu nanoparticles.

Electronic and magnetic properties of MnAu nanoparticles

International Nuclear Information System (INIS)

Masrour, R.; Hlil, E.K.; Hamedoun, M.; Benyoussef, A.; Mounkachi, O; El moussaoui, H.

2014-01-01

Self-consistent ab initio calculations, based on DFT (Density Functional Theory) approach and using FLAPW (Full potential Linear Augmented Plane Wave) method, are performed to investigate both electronic and magnetic properties of the MnAu nanoparticles. Polarized spin is included in calculations within the framework of the antiferromagnetic. The Mn magnetic moments where considered to be along c axes. Obtained data from ab initio calculations are used as input for the high temperature series expansions (HTSEs) calculations to compute other magnetic parameters. The zero-field high temperature static susceptibility series of the magnetic moment (m) and nearest-neighbour Heisenberg and XY models on a MnAu nanoparticles is thoroughly analyzed by means of a power series coherent anomaly method (CAM) for different nanoparticles. The exchanges interactions between the magnetic atoms are obtained for MnAu nanoparticles. - Highlights: • The electronic properties of the MnAu nanoparticles are studied using the DFT and FLAPW. • Magnetic moment is computed. • The ab initio calculations are used as input for HTSEs to compute other magnetic parameters. • The exchanges interactions and blocking temperature are obtained for MnAu nanoparticles

Size Control Technology of Silver Nanoparticles Using Electron Beam Irradiation

International Nuclear Information System (INIS)

Kang, Hyun Suk; Kim, Byungnam; Kim, Hye Won; Koo, Yong Hwan; Lee, Byung Cheol; Park, Ji Hyun; Bae, Hyung Bin; Park, Changmoon

2013-01-01

The manufacturing of silver nanoparticles using an electron beam is easy, fast, and highly productive, and it is possible at room temperature with no chemical residuals. Its various advantages therefore make this an important method for manufacturing nanoparticles such as silver, copper, and platinum. In particular, despite the use of electron beam irradiation, the results show that this method makes it possible to produce silver nanoparticles at low cost since low beam energy and low doses are used. This means that middle and high-energy electron beam accelerators are very expensive, but a low-energy electron beam accelerator has a relatively low cost of around 4-5 times, and mass production for a flow reaction without the need for extra radiation shielding is possible. Silver nanoparticles are of great interest to many researchers owing to their ability to be used in many applications such as catalysis, nanoelectronics, optical filters, electromagnetic interference shielding, surface Raman scattering, medical supplies, fabrics, cosmetics, hygiene and kitchen supplies, and electric home appliances

Size Control Technology of Silver Nanoparticles Using Electron Beam Irradiation

Energy Technology Data Exchange (ETDEWEB)

Kang, Hyun Suk; Kim, Byungnam; Kim, Hye Won; Koo, Yong Hwan; Lee, Byung Cheol [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Park, Ji Hyun [Univ. of Science and Technology, Daejeon (Korea, Republic of); Bae, Hyung Bin [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Park, Changmoon [Chungnam National Univ., Daejeon (Korea, Republic of)

2013-12-15

The manufacturing of silver nanoparticles using an electron beam is easy, fast, and highly productive, and it is possible at room temperature with no chemical residuals. Its various advantages therefore make this an important method for manufacturing nanoparticles such as silver, copper, and platinum. In particular, despite the use of electron beam irradiation, the results show that this method makes it possible to produce silver nanoparticles at low cost since low beam energy and low doses are used. This means that middle and high-energy electron beam accelerators are very expensive, but a low-energy electron beam accelerator has a relatively low cost of around 4-5 times, and mass production for a flow reaction without the need for extra radiation shielding is possible. Silver nanoparticles are of great interest to many researchers owing to their ability to be used in many applications such as catalysis, nanoelectronics, optical filters, electromagnetic interference shielding, surface Raman scattering, medical supplies, fabrics, cosmetics, hygiene and kitchen supplies, and electric home appliances.

Design and Preparation of Cross-Linked Polystyrene Nanoparticles for Elastomer Reinforcement

Directory of Open Access Journals (Sweden)

Ming Lu

2010-01-01

Full Text Available Cross-linked polystyrene (PS particles in a latex form were synthesized by free radical emulsion polymerization. The nano-PS-filled elastomer composites were prepared by the energy-saving latex compounding method. Results showed that the PS particles took a spherical shape in the size of 40–60 nm with a narrow size distribution, and the glass-transition temperature of the PS nanoparticles increased with the cross-linking density. The outcomes from the mechanical properties demonstrated that when filled into styrene-butadiene rubber (SBR, nitrile-butadiene rubber (NBR, and natural rubber (NR, the cross-linked PS nano-particles exhibited excellent reinforcing capabilities in all the three matrices, and the best in the SBR matrix. In comparison with that of the carbon black filled composites, another distinguished advantage of the cross-linked PS particles filled elastomer composites was found to be light weight in density, which could help to save tremendous amount of energy when put into end products.

Low-energy electron irradiation assisted diffusion of gold nanoparticles in polymer matrix

International Nuclear Information System (INIS)

Deore, Avinash V.; Bhoraskar, V.N.; Dhole, S.D.

2014-01-01

A simple and controllable method to synthesize nanoparticles in the surface region of polymers was used by low energy electron irradiation. Using this method, gold nanoparticles have been synthesized by irradiating gold coated PVA (Polyvinyl Alcohol) sheets. This method was easy in operation and even period of few minutes was sufficient to obtain the nanoparticles. The coatings (∼10 μm) made from a mixture of ethanol and HAuCl 4 on PVA sheets (∼150 μm) by simple drop cast method were irradiated with 30 keV electrons, at room temperature and 10 −6 mbar vacuum level. The electron fluence was varied from coating to coating in the range of 0 to 24×10 15 e/cm 2 . The irradiated samples were characterized by the UV–Vis, XRD, SEM and RBS techniques. The plasmon absorption peak at ∼539 nm in UV–Vis spectra was an evidence for the initiation of the growth of gold nanoparticles. The X-ray diffraction results and the blue shift in the plasmon absorption peak reveal that the size of nanoparticles could be tailored in the range from 58 to 40 nm by varying the electron fluence. The diffusion of gold in the PVA was confirmed by the Rutherford backscattering spectroscopy and scanning electron microscopy techniques. This method of synthesis of metal nanoparticles by low energy electron beam irradiation has the key importance in the development of new fabrication techniques for nanomaterials. - Highlights: • The results indicate that low energy electrons can effectively be used for the synthesis of nanoparticles of different sizes. • This study leads to a definite conclusion that gold nanoparticles have been synthesized in surface region of the PVA sheet. • The size of nanoparticles decreases with increasing electron fluence. • The depth of diffusion of Au atoms at maximum fluence was found to be ∼1.5 μm

Electron and photon emissions from gold nanoparticles irradiated by X-ray photons

Energy Technology Data Exchange (ETDEWEB)

Casta, R., E-mail: castaromain@gmail.com, E-mail: romain.casta@irsamc.ups-tlse.fr; Champeaux, J.-P.; Moretto-Capelle, P.; Sence, M.; Cafarelli, P. [Université de Toulouse, UPS, Laboratoire Collisions Agrégats Réactivité, IRSAMC, CNRS, UMR 5589 (France)

2015-01-15

In this paper, we develop a totally new probabilistic model for the electron and photon emission of gold nanoparticles irradiated by X-ray photons. This model allows direct applications to recent researches about the radiotherapy enhancement by gold nanoparticles in the context of cancer treatment. Our model uses, in a complete original way, simulated Auger cascade and stopping power to compute electron emission spectra, photon emission spectra and released energy inside the material of gold nanoparticles. It allows us to present new results about the electron and photon emission of gold nanoparticle irradiated by hard X-rays.

Fabrication of carbon layer coated FE-nanoparticles using an electron beam irradiation

Science.gov (United States)

Kim, Hyun Bin; Jeun, Joon Pyo; Kang, Phil Hyun; Oh, Seung-Hwan

2016-01-01

A novel synthesis of carbon encapsulated Fe nanoparticles was developed in this study. Fe chloride (III) and polyacrylonitrile (PAN) were used as precursors. The crosslinking of PAN molecules and the nucleation of Fe nanoparticles were controlled by the electron beam irradiation dose. Stabilization and carbonization processes were carried out using a vacuum furnace at 275 °C and 1000 °C, respectively. Micro structures were evaluated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fe nanoparticles were formed with diameters of 100 nm, and the Fe nanoparticles were encapsulated by carbon layers. As the electron beam irradiation dose increased, it was observed that the particle sizes decreased.

In situ investigation of bismuth nanoparticles formation by transmission electron microscope.

Science.gov (United States)

Liu, Liming; Wang, Honghang; Yi, Zichuan; Deng, Quanrong; Lin, Zhidong; Zhang, Xiaowen

2018-02-01

Bismuth (Bi) nanoparticles are prepared by using NaBi(MoO 4 ) 2 nanosheets in the beam of electrons emitted by transmission electron microscope. The formation and growth of Bi nanoparticles are investigated in situ. The sizes of Bi nanoparticles are confined within the range of 6-10nm by controlling irradiation time. It is also observed that once the diameter of nanoparticles is larger than 10nm, the Bi particles are stable as a result of the immobility of large nanoparticles. In addition, some nanoparticles on the edges form nanorods, which are explained as the result of a coalescence process, if the irradiation period is longer than 10min. The in situ research on Bi nanoparticles facilitates in-depth investigations of the physicochemical behavior and provides more potential applications in various fields such as sensors, catalysts and optical devices. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of Some Synthetic Parameters on Size and Polydispersity Index of Gelatin Nanoparticles Cross-Linked by CDI/NHS System

Directory of Open Access Journals (Sweden)

S. Zinatloo-Ajabshir

2015-04-01

Full Text Available In our previous work, the effect of use of a water soluble CDI/NHS system as nontoxic cross-linking agent on fabrication of gelatin nanoparticles was investigated. In this research, the effect of variation in some synthetic parameters of gelatin nanoparticles cross-linked by CDI/NHS system such as type of gelatin and formulation of cross- linking agent on their size and distribution was examined. The conventional two step desolvation method was used for preparation of gelatin nanoparticles. The morphology, mean size and size distribution of the formed nanoparticles were evaluated and compared with each other. In addition, intrinsic viscosities of all the nanoparticles were measured and compared under different conditions. The results showed that the presence of more NHS and absence of NHS catalyst in CDI/NHS system lead to the large particle size and broad size distribution of nanoparticles that were attributed to the fast and slow cross-linking rate, respectively.

Antigen-decorated shell cross-linked nanoparticles: synthesis, characterization, and antibody interactions.

Science.gov (United States)

Joralemon, Maisie J; Smith, Norah L; Holowka, David; Baird, Barbara; Wooley, Karen L

2005-01-01

Antigen-decorated shell cross-linked knedel-like nanoparticles (SCKs) were synthesized and studied as multivalent nanoscale surfaces from which antibody-binding units were presented in a manner that was designed to approach virus particle surfaces. The SCK nanostructures were fabricated with control over the number of antigenic groups, from mixed micellization of amphiphilic diblock copolymer building blocks that contained either an antigen (2,4-dinitrophenyl) or an ethylpropionate group at the hydrophilic alpha-chain terminus. Amphiphilic diblock copolymers were synthesized by atom transfer radical polymerization of tert-butyl acrylate and methyl acrylate sequentially from either a 2,4-dinitrophenyl-functionalized initiator or ethyl 2-bromopropionate, followed by selective removal of the tert-butyl groups to afford 2,4-dinitrophenyl-poly(acrylic acid)60-b-poly(methyl acrylate)60 (DNP-PAA(60)-b-PMA60) and poly(acrylic acid)70-b-poly(methyl acrylate) (PAA70-b-PMA70). Micelles were assembled via addition of water to THF solutions of the polymers in 0:1, 1:1, and 1:0 molar ratios of DNP-PAA60-b-PMA60 to PAA70-b-PMA70, followed by dialysis against water. The acrylic acid groups of the micelle coronas were partially cross-linked (nominally 50%) with 2,2'-(ethylenedioxy)bis(ethylamine), in the presence of 1-(3'-dimethylaminopropyl)-3-ethylcarbodiimide methiodide. Following extensive dialysis against water, the 0%, 50%, and 100% dinitrophenylated shell cross-linked nanoparticles (DNP-SCKs) were characterized with dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), infrared and UV-vis spectroscopies, and analytical ultracentrifugation (AU). The surface accessibility and bioavailability of the DNP units upon the DNP-SCKs were investigated by performing quenching titrations of fluorescein-labeled IgE antibody in solution and degranulation of Ig

Harvesting multiple electron-hole pairs generated through plasmonic excitation of Au nanoparticles.

Science.gov (United States)

Kim, Youngsoo; Smith, Jeremy G; Jain, Prashant K

2018-05-07

Multi-electron redox reactions, although central to artificial photosynthesis, are kinetically sluggish. Amidst the search for synthetic catalysts for such processes, plasmonic nanoparticles have been found to catalyse multi-electron reduction of CO 2 under visible light. This example motivates the need for a general, insight-driven framework for plasmonic catalysis of such multi-electron chemistry. Here, we elucidate the principles underlying the extraction of multiple redox equivalents from a plasmonic photocatalyst. We measure the kinetics of electron harvesting from a gold nanoparticle photocatalyst as a function of photon flux. Our measurements, supported by theoretical modelling, reveal a regime where two-electron transfer from the excited gold nanoparticle becomes prevalent. Multiple electron harvesting becomes possible under continuous-wave, visible-light excitation of moderate intensity due to strong interband transitions in gold and electron-hole separation accomplished using a hole scavenger. These insights will help expand the utility of plasmonic photocatalysis beyond CO 2 reduction to other challenging multi-electron, multi-proton transformations such as N 2 fixation.

Electron energy loss spectroscopy of gold nanoparticles on graphene

International Nuclear Information System (INIS)

DeJarnette, Drew; Roper, D. Keith

2014-01-01

Plasmon excitation decay by absorption, scattering, and hot electron transfer has been distinguished from effects induced by incident photons for gold nanoparticles on graphene monolayer using electron energy loss spectroscopy (EELS). Gold nano-ellipses were evaporated onto lithographed graphene, which was transferred onto a silicon nitride transmission electron microscopy grid. Plasmon decay from lithographed nanoparticles measured with EELS was compared in the absence and presence of the graphene monolayer. Measured decay values compared favorably with estimated radiative and non-radiative contributions to decay in the absence of graphene. Graphene significantly enhanced low-energy plasmon decay, increasing mode width 38%, but did not affect higher energy plasmon or dark mode decay. This decay beyond expected radiative and non-radiative mechanisms was attributed to hot electron transfer, and had quantum efficiency of 20%, consistent with previous reports

A correlative optical microscopy and scanning electron microscopy approach to locating nanoparticles in brain tumors.

Science.gov (United States)

Kempen, Paul J; Kircher, Moritz F; de la Zerda, Adam; Zavaleta, Cristina L; Jokerst, Jesse V; Mellinghoff, Ingo K; Gambhir, Sanjiv S; Sinclair, Robert

2015-01-01

The growing use of nanoparticles in biomedical applications, including cancer diagnosis and treatment, demands the capability to exactly locate them within complex biological systems. In this work a correlative optical and scanning electron microscopy technique was developed to locate and observe multi-modal gold core nanoparticle accumulation in brain tumor models. Entire brain sections from mice containing orthotopic brain tumors injected intravenously with nanoparticles were imaged using both optical microscopy to identify the brain tumor, and scanning electron microscopy to identify the individual nanoparticles. Gold-based nanoparticles were readily identified in the scanning electron microscope using backscattered electron imaging as bright spots against a darker background. This information was then correlated to determine the exact location of the nanoparticles within the brain tissue. The nanoparticles were located only in areas that contained tumor cells, and not in the surrounding healthy brain tissue. This correlative technique provides a powerful method to relate the macro- and micro-scale features visible in light microscopy with the nanoscale features resolvable in scanning electron microscopy. Copyright © 2014 Elsevier Ltd. All rights reserved.

Electron beam patterning for writing of positively charged gold colloidal nanoparticles

Science.gov (United States)

Zafri, Hadar; Azougi, Jonathan; Girshevitz, Olga; Zalevsky, Zeev; Zitoun, David

2018-02-01

Synthesis at the nanoscale has progressed at a very fast pace during the last decades. The main challenge today lies in precise localization to achieve efficient nanofabrication of devices. In the present work, we report on a novel method for the patterning of gold metallic nanoparticles into nanostructures on a silicon-on-insulator (SOI) wafer. The fabrication makes use of relatively accessible equipment, a scanning electron microscope (SEM), and wet chemical synthesis. The electron beam implants electrons into the insulating material, which further anchors the positively charged Au nanoparticles by electrostatic attraction. The novel fabrication method was applied to several substrates useful in microelectronics to add plasmonic particles. The resolution and surface density of the deposition were tuned, respectively, by the electron energy (acceleration voltage) and the dose of electronic irradiation. We easily achieved the smallest written feature of 68 ± 18 nm on SOI, and the technique can be extended to any positively charged nanoparticles, while the resolution is in principle limited by the particle size distribution and the scattering of the electrons in the substrate. [Figure not available: see fulltext.

Reconstruction and visualization of nanoparticle composites by transmission electron tomography

Energy Technology Data Exchange (ETDEWEB)

Wang, X.Y. [National Institute for Nanotechnology, 11421 Saskatchewan Drive, Edmonton, Canada T6H 2M9 (Canada); Department of Physics, University of Alberta, Edmonton, Canada T6G 2G7 (Canada); Lockwood, R. [National Institute for Nanotechnology, 11421 Saskatchewan Drive, Edmonton, Canada T6H 2M9 (Canada); Malac, M., E-mail: marek.malac@nrc-cnrc.gc.ca [National Institute for Nanotechnology, 11421 Saskatchewan Drive, Edmonton, Canada T6H 2M9 (Canada); Department of Physics, University of Alberta, Edmonton, Canada T6G 2G7 (Canada); Furukawa, H. [SYSTEM IN FRONTIER INC., 2-8-3, Shinsuzuharu bldg. 4F, Akebono-cho, Tachikawa-shi, Tokyo 190-0012 (Japan); Li, P.; Meldrum, A. [National Institute for Nanotechnology, 11421 Saskatchewan Drive, Edmonton, Canada T6H 2M9 (Canada)

2012-02-15

This paper examines the limits of transmission electron tomography reconstruction methods for a nanocomposite object composed of many closely packed nanoparticles. Two commonly used reconstruction methods in TEM tomography were examined and compared, and the sources of various artefacts were explored. Common visualization methods were investigated, and the resulting 'interpretation artefacts' ( i.e., deviations from 'actual' particle sizes and shapes arising from the visualization) were determined. Setting a known or estimated nanoparticle volume fraction as a criterion for thresholding does not in fact give a good visualization. Unexpected effects associated with common built-in image filtering methods were also found. Ultimately, this work set out to establish the common problems and pitfalls associated with electron beam tomographic reconstruction and visualization of samples consisting of closely spaced nanoparticles. -- Highlights: Black-Right-Pointing-Pointer Electron tomography limits were explored by both experiment and simulation. Black-Right-Pointing-Pointer Reliable quantitative volumetry using electron tomography is not presently feasible. Black-Right-Pointing-Pointer Volume rendering appears to be better choice for visualization of composite samples.

Ferrite nanoparticles: Synthesis, characterisation and applications in electronic device

Energy Technology Data Exchange (ETDEWEB)

Kefeni, Kebede K., E-mail: kkefeni@gmail.com; Msagati, Titus A.M.; Mamba, Bhekie B.

2017-01-15

Highlights: • Available synthesis methods of ferrite nanoparticles (FNPs) are briefly reviewed. • Summary of the advantage and limitation of FNPs synthesis techniques are presented. • The existing most common FNPs characterisation techniques are briefly reviewed. • Major application areas of FNPs in electronic materials are reviewed. - Abstract: Ferrite nanoparticles (FNPs) have attracted a great interest due to their wide applications in several areas such as biomedical, wastewater treatment, catalyst and electronic device. This review focuses on the synthesis, characterisation and application of FNPs in electronic device with more emphasis on the recently published works. The most commonly used synthesis techniques along with their advantages and limitations are discussed. The available characterisation techniques and their application in electronic materials such as sensors and biosensors, energy storage, microwave device, electromagnetic interference shielding and high-density recording media are briefly reviewed.

Cross-linked lysozyme crystal templated synthesis of Au nanoparticles as high-performance recyclable catalysts

International Nuclear Information System (INIS)

Liang Miao; Liu Xia; Qi Wei; Su Rongxin; Huang Renliang; Yu Yanjun; He Zhimin; Wang Libing

2013-01-01

Bio-nanomaterials fabricated using a bioinspired templating technique represent a novel class of composite materials with diverse applications in biomedical, electronic devices, drug delivery, and catalysis. In this study, Au nanoparticles (NPs) are synthesized within the solvent channels of cross-linked lysozyme crystals (CLLCs) in situ without the introduction of extra chemical reagents or physical treatments. The as-prepared AuNPs-in-protein crystal hybrid materials are characterized by light microscopy, transmission electron microscopy, x-ray diffraction, and Fourier-transform infrared spectroscopy analyses. Small AuNPs with narrow size distribution reveal the restriction effects of the porous structure in the lysozyme crystals. These composite materials are proven to be active heterogeneous catalysts for the reduction of 4-nitrophenol to 4-aminophenol. These catalysts can be easily recovered and reused at least 20 times because of the physical stability and macro-dimension of CLLCs. This work is the first to use CLLCs as a solid biotemplate for the preparation of recyclable high-performance catalysts. (paper)

Manufacture of polyethylene foam by electron beam cross-linking

International Nuclear Information System (INIS)

Tamai, Isamu

1976-01-01

The manufacturing process of polyethylene foam, comparison between electron beam cross-linking process and chemical cross-linking process, the electron beam irradiation technique for continuous sheets, the characteristics and uses of polyethylene foam are reviewed. The pore diameter can be controlled by selecting the dose rate, because there is strong relationship between the pore diameter and the dose rate. As the dose if higher, the foam becomes finer. The electron accelerators having large capacity show the lowest cost as the radiation source, and are applicable industrially. If the production capacity exceeds about 200 tons per month, the costs of electron beam irradiation process may be more advantageous than that of chemical process according to the circumstances. It is difficult to obtain the uniform distribution of absorption dose in the direction of thickness. General characteristics of cross-linked polyethylene foam are listed. The special feature of electron beam process is that the degree of cross-linking can be controlled arbitrarily before foaming. The products obtained by the electron beam cross-linking process have finer foams and smoother surfaces than those obtained by the chemical process, because the separation of the decomposition of foaming agents from that of cross-linking agents in the chemical cross-linking is difficult. (Iwakiri, K.)

Electron scattering in graphene with adsorbed NaCl nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Drabińska, Aneta, E-mail: Aneta.Drabinska@fuw.edu.pl; Kaźmierczak, Piotr; Bożek, Rafał; Karpierz, Ewelina; Wysmołek, Andrzej; Kamińska, Maria [Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw (Poland); Wołoś, Agnieszka [Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw (Poland); Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Pasternak, Iwona; Strupiński, Włodek [Institute of Electronic Materials Technology, Wólczyńska 133, 01-919 Warsaw (Poland); Krajewska, Aleksandra [Institute of Electronic Materials Technology, Wólczyńska 133, 01-919 Warsaw (Poland); Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland)

2015-01-07

In this work, the results of contactless magnetoconductance and Raman spectroscopy measurements performed for a graphene sample after its immersion in NaCl solution were presented. The properties of the immersed sample were compared with those of a non-immersed reference sample. Atomic force microscopy and electron spin resonance experiments confirmed the deposition of NaCl nanoparticles on the graphene surface. A weak localization signal observed using contactless magnetoconductance showed the reduction of the coherence length after NaCl treatment of graphene. Temperature dependence of the coherence length indicated a change from ballistic to diffusive regime in electron transport after NaCl treatment. The main inelastic scattering process was of the electron-electron type but the major reason for the reduction of the coherence length at low temperatures was additional, temperature independent, inelastic scattering. We associate it with spin flip scattering, caused by NaCl nanoparticles present on the graphene surface. Raman spectroscopy showed an increase in the D and D′ bands intensities for graphene after its immersion in NaCl solution. An analysis of the D, D′, and G bands intensities proved that this additional scattering is related to the decoration of vacancies and grain boundaries with NaCl nanoparticles, as well as generation of new on-site defects as a result of the decoration of the graphene surface with NaCl nanoparticles. The observed energy shifts of 2D and G bands indicated that NaCl deposition on the graphene surface did not change carrier concentration, but reduced compressive biaxial strain in the graphene layer.

Electron scattering in graphene with adsorbed NaCl nanoparticles

International Nuclear Information System (INIS)

Drabińska, Aneta; Kaźmierczak, Piotr; Bożek, Rafał; Karpierz, Ewelina; Wysmołek, Andrzej; Kamińska, Maria; Wołoś, Agnieszka; Pasternak, Iwona; Strupiński, Włodek; Krajewska, Aleksandra

2015-01-01

In this work, the results of contactless magnetoconductance and Raman spectroscopy measurements performed for a graphene sample after its immersion in NaCl solution were presented. The properties of the immersed sample were compared with those of a non-immersed reference sample. Atomic force microscopy and electron spin resonance experiments confirmed the deposition of NaCl nanoparticles on the graphene surface. A weak localization signal observed using contactless magnetoconductance showed the reduction of the coherence length after NaCl treatment of graphene. Temperature dependence of the coherence length indicated a change from ballistic to diffusive regime in electron transport after NaCl treatment. The main inelastic scattering process was of the electron-electron type but the major reason for the reduction of the coherence length at low temperatures was additional, temperature independent, inelastic scattering. We associate it with spin flip scattering, caused by NaCl nanoparticles present on the graphene surface. Raman spectroscopy showed an increase in the D and D′ bands intensities for graphene after its immersion in NaCl solution. An analysis of the D, D′, and G bands intensities proved that this additional scattering is related to the decoration of vacancies and grain boundaries with NaCl nanoparticles, as well as generation of new on-site defects as a result of the decoration of the graphene surface with NaCl nanoparticles. The observed energy shifts of 2D and G bands indicated that NaCl deposition on the graphene surface did not change carrier concentration, but reduced compressive biaxial strain in the graphene layer

Electron tomography of porous materials and magnetic nanoparticles

International Nuclear Information System (INIS)

Uusimäki, T.

2015-01-01

Electron tomography, as carried out in a transmission electron microscope is a method to reveal the three dimensional structure of the sample at the nanometer scale. It is based on tilting the sample and recording subsequent images at different projections angles. Using specific reconstruction algorithms the density distribution of the sample can then be reproduced. In this thesis, electron tomography has been implemented for material science specimens and more rigorously to porous media infiltrated with magnetic nanoparticles. The volume and spatial distribution along with the knowledge of the demagnetizing factors were then used within a magnetic Monte Carlo simulation to predict the magnetic response of the nanoparticle assembly. The local curvature of nanoparticles within the template, known to be a critical geometrical parameter influencing material properties, was extracted with two distinctive methods. Furthermore, new capabilities needed for image analysis and processing of the tilt series had to be implemented for improved alignments and segmentation. A new method to align the tilt series without depending on markers was written for obtaining high quality reconstructions. Also a comparison was made between different scanning TEM acquisition modes such as incoherent bright field and high angle annular dark field imaging modes with respect to resolution and contrast changes. (author) [de

Electron transport in gold colloidal nanoparticle-based strain gauges

Science.gov (United States)

Moreira, Helena; Grisolia, Jérémie; Sangeetha, Neralagatta M.; Decorde, Nicolas; Farcau, Cosmin; Viallet, Benoit; Chen, Ke; Viau, Guillaume; Ressier, Laurence

2013-03-01

A systematic approach for understanding the electron transport mechanisms in resistive strain gauges based on assemblies of gold colloidal nanoparticles (NPs) protected by organic ligands is described. The strain gauges were fabricated from parallel micrometer wide wires made of 14 nm gold (Au) colloidal NPs on polyethylene terephthalate substrates, elaborated by convective self-assembly. Electron transport in such devices occurs by inter-particle electron tunneling through the tunnel barrier imposed by the organic ligands protecting the NPs. This tunnel barrier was varied by changing the nature of organic ligands coating the nanoparticles: citrate (CIT), phosphines (BSPP, TDSP) and thiols (MPA, MUDA). Electro-mechanical tests indicate that only the gold NPs protected by phosphine and thiol ligands yield high gauge sensitivity. Temperature-dependent resistance measurements are explained using the ‘regular island array model’ that extracts transport parameters, i.e., the tunneling decay constant β and the Coulomb charging energy EC. This reveals that the Au@CIT nanoparticle assemblies exhibit a behavior characteristic of a strong-coupling regime, whereas those of Au@BSPP, Au@TDSP, Au@MPA and Au@MUDA nanoparticles manifest a weak-coupling regime. A comparison of the parameters extracted from the two methods indicates that the most sensitive gauges in the weak-coupling regime feature the highest β. Moreover, the EC values of these 14 nm NPs cannot be neglected in determining the β values.

High-resolution electron-beam patternable nanocomposite containing metal nanoparticles for plasmonics

International Nuclear Information System (INIS)

Abargues, R; Marques-Hueso, J; Canet-Ferrer, J; Pedrueza, E; Valdes, J L; Jimenez, E; MartInez-Pastor, J P

2008-01-01

Polymer nanocomposites containing noble metal nanoparticles are promising materials for plasmonic applications. In this paper, we report on a high-resolution negative-tone nanocomposite resist based on poly(vinyl alcohol) where silver nanoparticles and nanopatterns are simultaneously generated by electron-beam lithography. Our results indicate nanostructures with a relatively high concentration of nanoparticles and, consequently, an electromagnetic coupling among the nanoparticles. Therefore, the patternable nanocomposite described in this work may be a suitable material for future plasmonic circuitry

Scanning electron microscopy of individual nanoparticle bio-markers in liquid

Energy Technology Data Exchange (ETDEWEB)

Liv, Nalan, E-mail: n.liv@tudelft.nl; Lazić, Ivan; Kruit, Pieter; Hoogenboom, Jacob P.

2014-08-01

We investigated SEM imaging of nanoparticle biomarkers suspended below a thin membrane, with the ultimate goal of integrating functional fluorescence and structural SEM measurements of samples kept at ambient or hydrated conditions. In particular, we investigated how resolving power in liquid SEM is affected by the interaction of the electron beam with the membrane. Simulations with the Geant4-based Monte Carlo scheme developed by Kieft and Bosch (2008) [1] are compared to experimental results with suspended nanoparticles. For 20 nm and 50 nm thin membranes, we found a beam broadening of 1.5 nm and 3 nm, respectively, with an excellent agreement between simulations and experiments. 15 nm Au nanoparticles and bio-functionalized core-shell quantum dots can be individually resolved in denser clusters. We demonstrated the imaging of single EGF-conjugated quantum dots docked at filopodia during cellular uptake with both fluorescence microscopy and SEM simultaneously. These results open novel opportunities for correlating live fluorescence microscopy with structural electron microscopy. - Highlights: • We investigate the achievable resolution in liquid scanning electron microscopy (SEM). • We demonstrate liquid SEM imaging of individual fluorescent nanoparticle bio-markers • We show imaging of cellular QDot uptake with simultaneous fluorescence microscopy and SEM. • The positions of individual QDots can be resolved with details on cellular structure.

Scanning electron microscopy of individual nanoparticle bio-markers in liquid

International Nuclear Information System (INIS)

Liv, Nalan; Lazić, Ivan; Kruit, Pieter; Hoogenboom, Jacob P.

2014-01-01

We investigated SEM imaging of nanoparticle biomarkers suspended below a thin membrane, with the ultimate goal of integrating functional fluorescence and structural SEM measurements of samples kept at ambient or hydrated conditions. In particular, we investigated how resolving power in liquid SEM is affected by the interaction of the electron beam with the membrane. Simulations with the Geant4-based Monte Carlo scheme developed by Kieft and Bosch (2008) [1] are compared to experimental results with suspended nanoparticles. For 20 nm and 50 nm thin membranes, we found a beam broadening of 1.5 nm and 3 nm, respectively, with an excellent agreement between simulations and experiments. 15 nm Au nanoparticles and bio-functionalized core-shell quantum dots can be individually resolved in denser clusters. We demonstrated the imaging of single EGF-conjugated quantum dots docked at filopodia during cellular uptake with both fluorescence microscopy and SEM simultaneously. These results open novel opportunities for correlating live fluorescence microscopy with structural electron microscopy. - Highlights: • We investigate the achievable resolution in liquid scanning electron microscopy (SEM). • We demonstrate liquid SEM imaging of individual fluorescent nanoparticle bio-markers • We show imaging of cellular QDot uptake with simultaneous fluorescence microscopy and SEM. • The positions of individual QDots can be resolved with details on cellular structure

Mapping the electrostatic potential of Au nanoparticles using hybrid electron holography

Energy Technology Data Exchange (ETDEWEB)

Ozsoy-Keskinbora, Cigdem, E-mail: c.ozsoy@fkf.mpg.de [Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Boothroyd, Chris B.; Dunin-Borkowski, Rafal E. [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich (Germany); Aken, Peter A. van [Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Koch, Christoph T. [Structure Research & Electron Microscopy group, Department of Physics, Humboldt University of Berlin, Newtonstraße 15, 12489 Berlin (Germany)

2016-06-15

Electron holography is a powerful technique for characterizing electrostatic potentials, charge distributions, electric and magnetic fields, strain distributions and semiconductor dopant distributions with sub-nm spatial resolution. Mapping internal electrostatic and magnetic fields within nanoparticles and other low-dimensional materials by TEM requires both high spatial resolution and high phase sensitivity. Carrying out such an analysis fully quantitatively is even more challenging, since artefacts such as dynamical electron scattering may strongly affect the measurement. In-line electron holography, one of the variants of electron holography, features high phase sensitivity at high spatial frequencies, but suffers from inefficient phase recovery at low spatial frequencies. Off-axis electron holography, in contrast, can recover low spatial frequency phase information much more reliably, but is less effective in retrieving phase information at high spatial frequencies when compared to in-line holography. We investigate gold nanoparticles using hybrid electron holography at both atomic-resolution and intermediate magnification. Hybrid electron holography is a novel technique that synergistically combines off-axis and in-line electron holography, allowing the measurement of the complex wave function describing the scattered electrons with excellent signal-to-noise properties at both high and low spatial frequencies. The effect of dynamical electron scattering is minimized by beam tilt averaging. - Highlights: • Hybrid electron holography approach applied to Au nanoparticles. • Proof of principle of atomic resolution hybrid electron holography experiment demonstrated. • Dynamical scattering artifacts decrease by varying the illumination direction. • The effect of the number of iterations and noise on the low spatial frequencies in the phase are discussed.

Mapping the electrostatic potential of Au nanoparticles using hybrid electron holography

International Nuclear Information System (INIS)

Ozsoy-Keskinbora, Cigdem; Boothroyd, Chris B.; Dunin-Borkowski, Rafal E.; Aken, Peter A. van; Koch, Christoph T.

2016-01-01

Electron holography is a powerful technique for characterizing electrostatic potentials, charge distributions, electric and magnetic fields, strain distributions and semiconductor dopant distributions with sub-nm spatial resolution. Mapping internal electrostatic and magnetic fields within nanoparticles and other low-dimensional materials by TEM requires both high spatial resolution and high phase sensitivity. Carrying out such an analysis fully quantitatively is even more challenging, since artefacts such as dynamical electron scattering may strongly affect the measurement. In-line electron holography, one of the variants of electron holography, features high phase sensitivity at high spatial frequencies, but suffers from inefficient phase recovery at low spatial frequencies. Off-axis electron holography, in contrast, can recover low spatial frequency phase information much more reliably, but is less effective in retrieving phase information at high spatial frequencies when compared to in-line holography. We investigate gold nanoparticles using hybrid electron holography at both atomic-resolution and intermediate magnification. Hybrid electron holography is a novel technique that synergistically combines off-axis and in-line electron holography, allowing the measurement of the complex wave function describing the scattered electrons with excellent signal-to-noise properties at both high and low spatial frequencies. The effect of dynamical electron scattering is minimized by beam tilt averaging. - Highlights: • Hybrid electron holography approach applied to Au nanoparticles. • Proof of principle of atomic resolution hybrid electron holography experiment demonstrated. • Dynamical scattering artifacts decrease by varying the illumination direction. • The effect of the number of iterations and noise on the low spatial frequencies in the phase are discussed.

In-situ transmission electron microscopy growth of nanoparticles under extreme conditions

International Nuclear Information System (INIS)

Luce, F. P.; Azevedo, G. de M.; Baptista, D. L.; Zawislak, F. C.; Oliviero, E.; Fichtner, P. F. P.

2016-01-01

The formation and time resolved behavior of individual Pb nanoparticles embedded in silica have been studied by in-situ transmission electron microscopy observations at high temperatures (400–1100 °C) and under 200 keV electron irradiation. It is shown that under such extreme conditions, nanoparticles can migrate at long distances presenting a Brownian-like behavior and eventually coalesce. The particle migration phenomenon is discussed considering the influence of the thermal energy and the electron irradiation effects on the atomic diffusion process which is shown to control particle migration. These results and comparison with ex-situ experiments tackle the stability and the microstructure evolution of nanoparticles systems under extreme conditions. It elucidates on the effects of energetic particle irradiation-annealing treatments either as a tool or as a detrimental issue that could hamper their long-term applications in radiation-harsh environments such as in space or nuclear sectors

Field emission studies of silver nanoparticles synthesized by electron cyclotron resonance plasma

International Nuclear Information System (INIS)

Purohit, Vishwas; Mazumder, Baishakhi; Bhise, A.B.; Poddar, Pankaj; Joag, D.S.; Bhoraskar, S.V.

2011-01-01

Field emission has been studied for silver nanoparticles (25-200 nm), deposited within a cylindrical silver target in an electron cyclotron resonance (ECR) plasma. Particle size distribution was controlled by optimum biasing voltages between the chamber and the target. Presence of non-oxidized silver was confirmed from the X-Ray diffraction analysis; however, thin protective layer of oxide was identified from the selective area electron diffraction pattern obtained with transmission electron microscopy. The silver nanoparticles were seen to exhibit hilly pointed like structures when viewed under the atomic force microscopy (AFM). The emissive properties of these particles were investigated by field emission microscopy. It is found that this technique of deposition is ideal for formation of nanoparticles films on different substrate geometries with size controllability as well as its application to emission devices.

Preparation of PbSe nanoparticles by electron beam irradiation

Indian Academy of Sciences (India)

A novel method has been developed by electron beam irradiation to prepare PbSe nanoparticles. 2 MeV 10mA GJ-2-II electronic accelerator was used as radiation source. Nanocrystalline PbSe was prepared rapidly at room temperature under atmospheric pressure without any kind of toxic reagents. The structure and ...

Comparing electron tomography and HRTEM slicing methods as tools to measure the thickness of nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Alloyeau, D., E-mail: alloyeau.damien@gmail.com [Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7/CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris (France); Laboratoire d' Etude des Microstructures - ONERA/CNRS, UMR 104, B.P. 72, 92322 Chatillon (France); Ricolleau, C. [Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7/CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris (France); Oikawa, T. [Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7/CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris (France); JEOL (Europe) SAS, Espace Claude Monet, 1 Allee de Giverny, 78290 Croissy-sur-Seine (France); Langlois, C. [Laboratoire Materiaux et Phenomenes Quantiques, Universite Paris 7/CNRS, UMR 7162, 2 Place Jussieu, 75251 Paris (France); Le Bouar, Y.; Loiseau, A. [Laboratoire d' Etude des Microstructures - ONERA/CNRS, UMR 104, B.P. 72, 92322 Chatillon (France)

2009-06-15

Nanoparticles' morphology is a key parameter in the understanding of their thermodynamical, optical, magnetic and catalytic properties. In general, nanoparticles, observed in transmission electron microscopy (TEM), are viewed in projection so that the determination of their thickness (along the projection direction) with respect to their projected lateral size is highly questionable. To date, the widely used methods to measure nanoparticles thickness in a transmission electron microscope are to use cross-section images or focal series in high-resolution transmission electron microscopy imaging (HRTEM 'slicing'). In this paper, we compare the focal series method with the electron tomography method to show that both techniques yield similar particle thickness in a range of size from 1 to 5 nm, but the electron tomography method provides better statistics since more particles can be analyzed at one time. For this purpose, we have compared, on the same samples, the nanoparticles thickness measurements obtained from focal series with the ones determined from cross-section profiles of tomograms (tomogram slicing) perpendicular to the plane of the substrate supporting the nanoparticles. The methodology is finally applied to the comparison of CoPt nanoparticles annealed ex situ at two different temperatures to illustrate the accuracy of the techniques in detecting small particle thickness changes.

Determination of the threshold of nanoparticle behavior: Structural and electronic properties study of nano-sized copper

International Nuclear Information System (INIS)

Torres-Vega, Juan J.; Medrano, L.R.; Landauro, C.V.; Rojas-Tapia, J.

2014-01-01

In the present work we determine the threshold of the nanoparticle behavior of copper nanoparticles by studying their structural and electronic properties. The studied nanoparticles contain from 13 to 8217 atoms and were obtained by molecular dynamics simulations using the Johnson potential for copper based on the embedded atom method. The results indicate that for small copper nanoparticles ( 2000atoms, ∼3.5 nm), with spherical-like external shape and large percentage of fcc-like local structure, this effect is negligible and their electronic character are similar to such expected in solid copper. Finally, it has also been shown that copper nanoparticles change their electronic character, from metallic to insulating, after increasing the strength of the chemical disorder

Synthesis of AuPd alloyed nanoparticles via room-temperature electron reduction with argon glow discharge as electron source.

Science.gov (United States)

Yang, Manman; Wang, Zongyuan; Wang, Wei; Liu, Chang-Jun

2014-01-01

Argon glow discharge has been employed as a cheap, environmentally friendly, and convenient electron source for simultaneous reduction of HAuCl4 and PdCl2 on the anodic aluminum oxide (AAO) substrate. The thermal imaging confirms that the synthesis is operated at room temperature. The reduction is conducted with a short time (30 min) under the pressure of approximately 100 Pa. This room-temperature electron reduction operates in a dry way and requires neither hydrogen nor extra heating nor chemical reducing agent. The analyses using X-ray photoelectron spectroscopy (XPS) confirm all the metallic ions have been reduced. The characterization with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) shows that AuPd alloyed nanoparticles are formed. There also exist some highly dispersed Au and Pd monometallic particles that cannot be detected by XRD and transmission electron microscopy (TEM) because of their small particle sizes. The observed AuPd alloyed nanoparticles are spherical with an average size of 14 nm. No core-shell structure can be observed. The room-temperature electron reduction can be operated in a larger scale. It is an easy way for the synthesis of AuPd alloyed nanoparticles.

Novel Schiff base (DBDDP) selective detection of Fe (III): Dispersed in aqueous solution and encapsulated in silica cross-linked micellar nanoparticles in living cell.

Science.gov (United States)

Gai, Fangyuan; Yin, Li; Fan, Mengmeng; Li, Ling; Grahn, Johnny; Ao, Yuhui; Yang, Xudong; Wu, Xuming; Liu, Yunling; Huo, Qisheng

2018-03-15

This work demonstrated the synthesis of (4E)-4-(4-(diphenylamino)benzylideneamino)-1,2-dihydro-1,5- dimethyl-2-phenylpyrazol-3-one (DBDDP) for Fe (III) detection in aqueous media and in the core of silica cross-linked micellar nanoparticles in living cells. The free DBDDP performed fluorescence enhancement due to Fe (III)-promoted hydrolysis in a mixed aqueous solution, while the DBDDP-doped silica cross-linked micellar nanoparticles (DBDDP-SCMNPs) performed an electron-transfer based fluorescence quenching of Fe (III) in living cells. The quenching fluorescence of DBDDP-SCMNPs and the concentration of Fe (III) exhibited a linear correlation, which was in accordance with the Stern-Volmer equation. Moreover, DBDDP-SCMNPs showed a low limit of detection (LOD) of 0.1 ppm and an excellent selectivity against other metal ions. Due to the good solubility and biocompatibility, DBDDP-SCMNPs could be applied as fluorescence quenching nanosensors in living cells. Copyright © 2017 Elsevier Inc. All rights reserved.

Cryo-transmission electron microscopy of Ag nanoparticles grown on an ionic liquid substrate

KAUST Repository

Anjum, Dalaver H.

2010-07-01

We report a novel method of growing silver nanostructures by cathodic sputtering onto an ionic liquid (IL) and our visualization by transmission cryo-electron microscopy to avoid beam-induced motion of the nanoparticles. By freezing the IL suspension and controlling electron dose, we can assess properties of particle size, morphology, crystallinity, and aggregation in situ and at high detail. We observed round silver nanoparticles with a well-defined diameter of 7.0 ± 1.5 nm that are faceted with crystalline cubic structures and ∼80% of the particles have multiply twinned faults. We also applied cryo-electron tomography to investigate the structure of the nanoparticles and to directly visualize the IL wetting around them. In addition to particles, we observed nanorods that appear to have assembled from individual nanoparticles. Reexamination of the samples after 4-5 days from initial preparation showed significant changes in morphology, and potential mechanisms for this are discussed. © 2010 Materials Research Society.

The use of transmission electron microscopy in the quantification of nanoparticle dose

International Nuclear Information System (INIS)

Hondow, N; Brydson, R; Brown, A

2014-01-01

There are an increasing number of potential applications for nanoparticles in clinical medicine, including targeted drug delivery and contrast agents for biomedical imaging. Current in vitro studies are concerned with the biological impact of nanoparticles, with electron microscopy commonly employed to image their intracellular location. It is critical to quantify the absolute nanoparticle dose internalized by cells in a given exposure, and to understand the factors which affect this. In this work we are aiming to develop a full quantitative description of quantum dot uptake by an in vitro cell line. Transmission electron microscopy of thin cell sections provides the location and number of cellular vesicles per 2-D cell slice plus the number of quantum dots per vesicle. These results can then be correlated to other techniques to quantify the internalized nanoparticle dose distribution for whole cells

Electronic structure of thiolate-covered gold nanoparticles: Au102(MBA)44.

Science.gov (United States)

Li, Yan; Galli, Giulia; Gygi, François

2008-09-23

We present first principles, density functional theory (DFT) calculations of the structural and electronic properties of thiolate-protected gold nanoparticles [Au(102)(MBA)(44) ] that have been recently crystallized and measured by X-ray diffraction. Our calculations yield structural properties in very good agreement with experiment and reveal the impact of thiolate adsorption on both the surface geometry and the electronic structure of the gold core; in particular, within DFT we observe the emergence of an energy gap of about 0.5 eV, upon MBA adsorption. Using a localized orbital analysis, we characterize the electron distribution in the nanoparticle and provide insight into the bonding of thiolates on curved gold surfaces.

Hydrogen treatment as a detergent of electronic trap states in lead chalcogenide nanoparticles

Science.gov (United States)

Voros, Marton; Brawand, Nicholas; Galli, Giulia

Lead chalcogenide (PbX) nanoparticles are promising materials for solar energy conversion. However, the presence of trap states in their electronic gap limits their usability, and developing a universal strategy to remove trap states is a persistent challenge. Using calculations based on density functional theory, we show that hydrogen acts as an amphoteric impurity on PbX nanoparticle surfaces; hydrogen atoms may passivate defects arising from ligand imbalance or off-stoichiometric surface terminations, irrespective of whether they originate from cation or anion excess. In addition, we show, using constrained density functional theory calculations, that hydrogen treatment of defective nanoparticles is also beneficial for charge transport in films. We also find that hydrogen adsorption on stoichiometric nanoparticles leads to electronic doping, preferentially n-type. Our findings suggest that post-synthesis hydrogen treatment of lead chalcogenide nanoparticle films is a viable approach to reduce electronic trap states or to dope well-passivated films. Work supported by the Center for Advanced Solar Photophysics, an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (NB) and U.S. DOE under Contract No. DE-AC02-06CH11357 (MV).

Quantitative detection of gold nanoparticles on individual, unstained cancer cells by Scanning Electron Microscopy

NARCIS (Netherlands)

Hartsuiker, Liesbeth; van Es, Peter; Petersen, Wilhelmina; van Leeuwen, Ton; Terstappen, Leonardus Wendelinus Mathias Marie; Otto, Cornelis

2011-01-01

Gold nanoparticles are rapidly emerging for use in biomedical applications. Characterization of the interaction and delivery of nanoparticles to cells through microscopy is important. Scanning electron microscopes have the intrinsic resolution to visualize gold nanoparticles on cells. A novel sample

Quantitative detection of gold nanoparticles on individual, unstained cancer cells by scanning electron microscopy

NARCIS (Netherlands)

Hartsuiker, L.; van Es, P.; Petersen, W.; van Leeuwen, T. G.; Terstappen, L. W. M. M.; Otto, C.

2011-01-01

Gold nanoparticles are rapidly emerging for use in biomedical applications. Characterization of the interaction and delivery of nanoparticles to cells through microscopy is important. Scanning electron microscopes have the intrinsic resolution to visualize gold nanoparticles on cells. A novel sample

CoPt nanoparticles deposited by electron beam evaporation

International Nuclear Information System (INIS)

Castaldi, L.; Giannakopoulos, K.; Travlos, A.; Niarchos, D.; Boukari, S.; Beaurepaire, E.

2005-01-01

Co 50 Pt 50 nanoparticles were co-deposited on thermally oxidized Si substrates by electron beam evaporation at 750 deg C. The mean particle sizes are between ∼5 and ∼20 nm and depend on the nominal thickness of the layer. Different processing conditions resulted in different structural and morphological properties of the samples which led to superparamagnetic and ferromagnetic behaviors. The post-annealing treatment of the CoPt nanograins resulted in the crystallization of the L1 0 ordered phase and in the magnetic hardening of nanoparticles with a maximum coercivity of ∼7.4 kOe

Structural, magnetic and electronic structure properties of Co doped ZnO nanoparticles

International Nuclear Information System (INIS)

Kumar, Shalendra; Song, T.K.; Gautam, Sanjeev; Chae, K.H.; Kim, S.S.; Jang, K.W.

2015-01-01

Highlights: • XRD and HR-TEM results show the single phase nature of Co doped ZnO nanoparticles. • XMCD and dc magnetization results indicate the RT-FM in Co doped ZnO nanoparticles. • Co L 3,2 NEXAFS spectra infer that Co ions are in 2+ valence state. • O K edge NEXAFS spectra show that O vacancy increases with Co doping in ZnO. - Abstract: We reported structural, magnetic and electronic structure studies of Co doped ZnO nanoparticles. Doping of Co ions in ZnO host matrix has been studied and confirmed using various methods; such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersed X-ray (EDX), high resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, magnetic hysteresis loop measurements and X-ray magnetic circular dichroism (XMCD). From the XRD and HR-TEM results, it is observed that Co doped ZnO nanoparticles have single phase nature with wurtzite structure and exclude the possibility of secondary phase formation. FE-SEM and TEM micrographs show that pure and Co doped nanoparticles are nearly spherical in shape. O K edge NEXAFS spectra indicate that O vacancies increase with Co doping. The Co L 3,2 edge NEXAFS spectra revealed that Co ions are in 2+ valence state. DC magnetization hysteresis loops and XMCD results clearly showed the intrinsic origin of temperature ferromagnetism in Co doped ZnO nanoparticles

Surface chemical and electronic properties of In{sub 2}O{sub 3} and In{sub 2}O{sub 3-x} nanoparticles for ozone detection

Energy Technology Data Exchange (ETDEWEB)

Himmerlich, Marcel; Krischok, Stefan [Institut fuer Physik and Institut fuer Mikro- und Nanotechnologien, TU Ilmenau, PF 100565, 98684 Ilmenau (Germany); Wang, Chunyu; Cimalla, Volker; Ambacher, Oliver [Fraunhofer-Institut fuer Angewandte Festkoerperphysik, Tullastr. 72, 79108 Freiburg im Breisgau (Germany)

2012-07-01

The electrical properties of indium oxide nanoparticle films can be tuned by variation of growth temperature as well as rapid thermal annealing, UV-irradiation and ozone-induced oxidation. The high O{sub 3} sensitivity of indium oxide thin films is strongly linked to their structural and electronic properties. Especially, the alteration of the surface electron accumulation plays an important role in the change of the film resistivity upon O{sub 3} interaction and UV-induced regeneration. We analyse the changes of indium oxide surface properties with respect to varying crystallinity using AFM, XPS and UPS. Compared to stoichiometric In{sub 2}O{sub 3} thin films, indium oxide nanoparticles exhibit a high oxygen deficiency and hence a high defect density at the nanoparticle surface. After growth, these defects are saturated by hydrocarbons due to the incomplete decomposition of precursors during low temperature MOCVD. The defects and the changed stoichiometry have impact on the surface band alignment. Upon ozone-induced oxidation and UV photoreduction a reversible change in band bending, surface dipole and O adsorption density is found and will be discussed in context with electron transport characteristics and thermal properties.

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

International Nuclear Information System (INIS)

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)

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

NARCIS (Netherlands)

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

Electron microscopy localization and characterization of functionalized composite organic-inorganic SERS nanoparticles on leukemia cells.

Science.gov (United States)

Koh, Ai Leen; Shachaf, Catherine M; Elchuri, Sailaja; Nolan, Garry P; Sinclair, Robert

2008-12-01

We demonstrate the use of electron microscopy as a powerful characterization tool to identify and locate antibody-conjugated composite organic-inorganic nanoparticle (COINs) surface enhanced Raman scattering (SERS) nanoparticles on cells. U937 leukemia cells labeled with antibody CD54-conjugated COINs were characterized in their native, hydrated state using wet scanning electron microscopy (SEM) and in their dehydrated state using high-resolution SEM. In both cases, the backscattered electron (BSE) detector was used to detect and identify the silver constituents in COINs due to its high sensitivity to atomic number variations within a specimen. The imaging and analytical capabilities in the SEM were further complemented by higher resolution transmission electron microscopy (TEM) images and scanning Auger electron spectroscopy (AES) data to give reliable and high-resolution information about nanoparticles and their binding to cell surface antigens.

Electron microscopy localization and characterization of functionalized composite organic-inorganic SERS nanoparticles on leukemia cells

International Nuclear Information System (INIS)

Koh, Ai Leen; Shachaf, Catherine M.; Elchuri, Sailaja; Nolan, Garry P.; Sinclair, Robert

2008-01-01

We demonstrate the use of electron microscopy as a powerful characterization tool to identify and locate antibody-conjugated composite organic-inorganic nanoparticle (COINs) surface enhanced Raman scattering (SERS) nanoparticles on cells. U937 leukemia cells labeled with antibody CD54-conjugated COINs were characterized in their native, hydrated state using wet scanning electron microscopy (SEM) and in their dehydrated state using high-resolution SEM. In both cases, the backscattered electron (BSE) detector was used to detect and identify the silver constituents in COINs due to its high sensitivity to atomic number variations within a specimen. The imaging and analytical capabilities in the SEM were further complemented by higher resolution transmission electron microscopy (TEM) images and scanning Auger electron spectroscopy (AES) data to give reliable and high-resolution information about nanoparticles and their binding to cell surface antigens.

Nanoparticle imaging. 3D structure of individual nanocrystals in solution by electron microscopy.

Science.gov (United States)

Park, Jungwon; Elmlund, Hans; Ercius, Peter; Yuk, Jong Min; Limmer, David T; Chen, Qian; Kim, Kwanpyo; Han, Sang Hoon; Weitz, David A; Zettl, A; Alivisatos, A Paul

2015-07-17

Knowledge about the synthesis, growth mechanisms, and physical properties of colloidal nanoparticles has been limited by technical impediments. We introduce a method for determining three-dimensional (3D) structures of individual nanoparticles in solution. We combine a graphene liquid cell, high-resolution transmission electron microscopy, a direct electron detector, and an algorithm for single-particle 3D reconstruction originally developed for analysis of biological molecules. This method yielded two 3D structures of individual platinum nanocrystals at near-atomic resolution. Because our method derives the 3D structure from images of individual nanoparticles rotating freely in solution, it enables the analysis of heterogeneous populations of potentially unordered nanoparticles that are synthesized in solution, thereby providing a means to understand the structure and stability of defects at the nanoscale. Copyright © 2015, American Association for the Advancement of Science.

New insight into nanoparticle precipitation by electron beams in borosilicate glasses

Science.gov (United States)

Sabri, M. M.; Möbus, G.

2017-06-01

Nanoprecipitation in different oxide glasses by means of electron irradiation in transmission electron microscopy (TEM) has been compared in this study. Upon irradiation, groups or patterns of nanoparticles with various morphologies and sizes were formed in borosilicate glasses, loaded with zinc, copper, and silver. The study successfully includes loading ranges for the target metal from doping level (1%) over medium level (20%) to majority phase (60%). It is found that particle patterning resolution is affected by parallel processes of amorphous phase separation, glass ablation, and delocalised precipitation. In addition, via an in-situ study, it is confirmed that by heating alone without irradiation, no precipitate nanoparticles form.

New insight into nanoparticle precipitation by electron beams in borosilicate glasses

Energy Technology Data Exchange (ETDEWEB)

Sabri, M.M.; Moebus, G. [University of Sheffield, Department of Materials Science and Engineering (United Kingdom)

2017-06-15

Nanoprecipitation in different oxide glasses by means of electron irradiation in transmission electron microscopy (TEM) has been compared in this study. Upon irradiation, groups or patterns of nanoparticles with various morphologies and sizes were formed in borosilicate glasses, loaded with zinc, copper, and silver. The study successfully includes loading ranges for the target metal from doping level (1%) over medium level (20%) to majority phase (60%). It is found that particle patterning resolution is affected by parallel processes of amorphous phase separation, glass ablation, and delocalised precipitation. In addition, via an in-situ study, it is confirmed that by heating alone without irradiation, no precipitate nanoparticles form. (orig.)

Mapping the electrostatic potential of Au nanoparticles using hybrid electron holography.

Science.gov (United States)

Ozsoy-Keskinbora, Cigdem; Boothroyd, Chris B; Dunin-Borkowski, Rafal E; van Aken, Peter A; Koch, Christoph T

2016-06-01

Electron holography is a powerful technique for characterizing electrostatic potentials, charge distributions, electric and magnetic fields, strain distributions and semiconductor dopant distributions with sub-nm spatial resolution. Mapping internal electrostatic and magnetic fields within nanoparticles and other low-dimensional materials by TEM requires both high spatial resolution and high phase sensitivity. Carrying out such an analysis fully quantitatively is even more challenging, since artefacts such as dynamical electron scattering may strongly affect the measurement. In-line electron holography, one of the variants of electron holography, features high phase sensitivity at high spatial frequencies, but suffers from inefficient phase recovery at low spatial frequencies. Off-axis electron holography, in contrast, can recover low spatial frequency phase information much more reliably, but is less effective in retrieving phase information at high spatial frequencies when compared to in-line holography. We investigate gold nanoparticles using hybrid electron holography at both atomic-resolution and intermediate magnification. Hybrid electron holography is a novel technique that synergistically combines off-axis and in-line electron holography, allowing the measurement of the complex wave function describing the scattered electrons with excellent signal-to-noise properties at both high and low spatial frequencies. The effect of dynamical electron scattering is minimized by beam tilt averaging. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

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

Science.gov (United States)

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.

Electronic structure, magnetic and structural properties of Ni doped ZnO nanoparticles

International Nuclear Information System (INIS)

Kumar, Shalendra; Vats, Prashant; Gautam, S.; Gupta, V.P.; Verma, K.D.; Chae, K.H.; Hashim, Mohd; Choi, H.K.

2014-01-01

Highlights: • XRD, and HR-TEM results show the single phase nature of Ni doped ZnO nanoparticles. • dc magnetization results indicate the RT-FM in Ni doped ZnO nanoparticles. • Ni L 3,2 edge NEXAFS spectra infer that Ni ions are in +2 valence state. • O K edge NEXAFS spectra show that O vacancy increases with Ni doping in ZnO. - Abstract: We report structural, magnetic and electronic structural properties of Ni doped ZnO nanoparticles prepared by auto-combustion method. The prepared nanoparticles were characterized by using X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and dc magnetization measurements. The XRD and HR-TEM results indicate that Ni doped ZnO nanoparticles have single phase nature with wurtzite lattice and exclude the presence of secondary phase. NEXAFS measurements performed at Ni L 3,2 -edges indicates that Ni ions are in +2 valence state and exclude the presence of Ni metal clusters. O K-edge NEXAFS spectra indicate an increase in oxygen vacancies with Ni-doping, while Zn L 3,2 -edge show the absence of Zn-vacancies. The magnetization measurements performed at room temperature shows that pure and Ni doped ZnO exhibits ferromagnetic behavior

Electron-hole pairs generated in ZrO2 nanoparticle resist upon exposure to extreme ultraviolet radiation

Science.gov (United States)

Kozawa, Takahiro; Santillan, Julius Joseph; Itani, Toshiro

2018-02-01

Metal oxide nanoparticle resists have attracted much attention as the next-generation resist used for the high-volume production of semiconductor devices. However, the sensitization mechanism of the metal oxide nanoparticle resists is unknown. Understanding the sensitization mechanism is important for the efficient development of resist materials. In this study, the energy deposition in a zirconium oxide (ZrO2) nanoparticle resist was investigated. The numbers of electron-hole pairs generated in a ZrO2 core and an methacrylic acid (MAA) ligand shell upon exposure to 1 mJ cm-2 (exposure dose) extreme ultraviolet (EUV) radiations were theoretically estimated to be 0.16 at most and 0.04-0.17 cm2 mJ-1, respectively. By comparing the calculated distribution of electron-hole pairs with the line-and-space patterns of the ZrO2 nanoparticle resist fabricated by an EUV exposure tool, the number of electron-hole pairs required for the solubility change of the resist films was estimated to be 1.3-2.2 per NP. NP denotes a nanoparticle consisting of a metal oxide core with a ligand shell. In the material design of metal oxide nanoparticle resists, it is important to efficiently use the electron-hole pairs generated in the metal oxide core for the chemical change of ligand molecules.

Detection of water and its derivatives on individual nanoparticles using vibrational electron energy-loss spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Crozier, Peter A., E-mail: crozier@asu.edu [School for the Engineering of Matter, Transport and Energy, Arizona State University, 501 E. Tyler Mall, Tempe, AZ 85287-6106 (United States); Aoki, Toshihiro [LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, AZ 85287-1704 (United States); Liu, Qianlang [School for the Engineering of Matter, Transport and Energy, Arizona State University, 501 E. Tyler Mall, Tempe, AZ 85287-6106 (United States)

2016-10-15

Understanding the role of water, hydrate and hydroxyl species on nanoparticle surfaces and interfaces is very important in both physical and life sciences. Detecting the presence of oxygen-hydrogen species with nanometer resolution is extremely challenging at present. Here we show that the recently developed vibrational electron energy-loss spectroscopy using subnanometer focused electron beams can be employed to spectroscopically identify the local presence and variation of OH species on nanoscale surfaces. The hydrogen-oxygen fingerprint can be correlated with highly localized structural and morphological information obtained from electron imaging. Moreover, the current approach exploits the aloof beam mode of spectral acquisition which does not require direct electron irradiation of the sample thus greatly reducing beam damage to the OH bond. These findings open the door for using electron microscopy to probe local hydroxyl and hydrate species on nanoscale organic and inorganic structures. - Highlights: • High spatial resolution spectroscopic detection of water related species in nanoparticles. • Detection of OH stretch modes with vibrational EELS. • Differentiation between hydrate and hydroxide species on or on nanoparticles. • Detection of hydrate on a single 60 nm oxide nanoparticle of MgO. • Use of aloof beam EELS to minimize radiation damage.

Hydrothermal synthesis, off-axis electron holography and magnetic properties of Fe3O4 nanoparticles

DEFF Research Database (Denmark)

Almeida, Trevor P.; Muxworthy, Adrian R.; Williams, Wyn

2014-01-01

The hydrothermal synthesis of Fe3O4 nanoparticles (NPs) (<50 nm) from mixed FeCl3 / FeCl2 precursor solution at pH ~ 12 has been confirmed using complementary characterisation techniques of transmission electron microscopy and X-ray diffractometry. Off-axis electron holography allowed for visuali......The hydrothermal synthesis of Fe3O4 nanoparticles (NPs) (holography allowed...

Efficient electronic structure methods applied to metal nanoparticles

DEFF Research Database (Denmark)

Larsen, Ask Hjorth

of efficient approaches to density functional theory and the application of these methods to metal nanoparticles. We describe the formalism and implementation of localized atom-centered basis sets within the projector augmented wave method. Basis sets allow for a dramatic increase in performance compared....... The basis set method is used to study the electronic effects for the contiguous range of clusters up to several hundred atoms. The s-electrons hybridize to form electronic shells consistent with the jellium model, leading to electronic magic numbers for clusters with full shells. Large electronic gaps...... and jumps in Fermi level near magic numbers can lead to alkali-like or halogen-like behaviour when main-group atoms adsorb onto gold clusters. A non-self-consistent NewnsAnderson model is used to more closely study the chemisorption of main-group atoms on magic-number Au clusters. The behaviour at magic...

Ultrafast electron and energy transfer in dye-sensitized iron oxide and oxyhydroxide nanoparticles

DEFF Research Database (Denmark)

Gilbert, Benjamin; Katz, Jordan E.; Huse, Nils

2013-01-01

photo-initiated interfacial electron transfer. This approach enables time-resolved study of the fate and mobility of electrons within the solid phase. However, complete analysis of the ultrafast processes following dye photoexcitation of the sensitized iron(iii) oxide nanoparticles has not been reported....... We addressed this topic by performing femtosecond transient absorption (TA) measurements of aqueous suspensions of uncoated and DCF-sensitized iron oxide and oxyhydroxide nanoparticles, and an aqueous iron(iii)–dye complex. Following light absorption, excited state relaxation times of the dye of 115...... a four-state model of the dye-sensitized system, finding electron and energy transfer to occur on the same ultrafast timescale. The interfacial electron transfer rates for iron oxides are very close to those previously reported for DCF-sensitized titanium dioxide (for which dye–oxide energy transfer...

Size dependence investigations of hot electron cooling dynamics in metal/adsorbates nanoparticles

International Nuclear Information System (INIS)

Bauer, Christophe; Abid, Jean-Pierre; Girault, Hubert H.

2005-01-01

The size dependence of electron-phonon coupling rate has been investigated by femtosecond transient absorption spectroscopy for gold nanoparticles (NPs) wrapped in a shell of sulfate with diameter varying from 1.7 to 9.2 nm. Broad-band spectroscopy gives an overview of the complex dynamics of nonequilibrium electrons and permits the choice of an appropriate probe wavelength for studying the electron-phonon coupling dynamics. Ultrafast experiments were performed in the weak perturbation regime (less than one photon in average per nanoparticle), which allows the direct extraction of the hot electron cooling rates in order to compare different NPs sizes under the same conditions. Spectroscopic data reveals a decrease of hot electron energy loss rates with metal/adsorbates nanosystem sizes. Electron-phonon coupling time constants obtained for 9.2 nm NPs are similar to gold bulk materials (∼1 ps) whereas an increase of hot electron cooling time up to 1.9 ps is observed for sizes of 1.7 nm. This is rationalized by the domination of surface effects over size (bulk) effects. The slow hot electron cooling is attributed to the adsorbates-induced long-lived nonthermal regime, which significantly reduces the electron-phonon coupling strength (average rate of phonon emission)

Atomic and electronic structure transformations of silver nanoparticles under rapid cooling conditions.

Science.gov (United States)

Lobato, I; Rojas, J; Landauro, C V; Torres, J

2009-02-04

The structural evolution and dynamics of silver nanodrops Ag(2869) (4.4 nm in diameter) under rapid cooling conditions have been studied by means of molecular dynamics simulations and electronic density of state calculations. The interaction of silver atoms is modelled by a tight-binding semiempirical interatomic potential proposed by Cleri and Rosato. The pair correlation functions and the pair analysis technique are used to reveal the structural transition in the process of solidification. It is shown that Ag nanoparticles evolve into different nanostructures under different cooling processes. At a cooling rate of 1.5625 × 10(13) K s(-1) the nanoparticles preserve an amorphous-like structure containing a large amount of 1551 and 1541 pairs which correspond to icosahedral symmetry. For a lower cooling rate (1.5625 × 10(12) K s(-1)), the nanoparticles transform into a crystal-like structure consisting mainly of 1421 and 1422 pairs which correspond to the face centred cubic and hexagonal close packed structures, respectively. The variations of the electronic density of states for the differently cooled nanoparticles are small, but in correspondence with the structural changes.

Synthesis of Specific Nanoparticles for Targeting and Imaging Tumor Angiogenesis Using Electron-Beam Irradiation

Energy Technology Data Exchange (ETDEWEB)

Rizza, G.; Deshayes, S.; Maurizot, V.; Clochard, M. -C.; Berthelot, T.; Baudin, C.; Déléris, G., E-mail: giancarlo.rizza@polytechnique.edu [Commissariat à l' énergie atomique (CEA), Institut Rayonnement Matière de Saclay (IRaMIS), B.P. 52, 91191 Gif Sur Yvette Cedex (France)

2010-07-01

We have succeeded to synthesize PVDF nanoparticles by nanoemulsion polymerization and their functionalization with a peptide that presents an anti-angiogenic activity. Resulted nanoparticles present a radius of 60 nm. From FESEM images and light scattering measurements, we deduced that they were spherical and monodisperse. The alkyl radicals induced from electron beam irradiation combine immediately with the oxygen to form peroxide radicals. Because of a high specific area and small crystallite size, the radical decay with time is evidenced from EPR measurements. Despite this radical decay, electron beam irradiation allows us to graft PAA by radical polymerization onto freshly irradiated PVDF nanoparticles and then to immobilize CBO-P11 by click chemistry via a spacer arm. Evidences of grafting were shown using HRMAS NMR and MALDI-TOF mass spectrometry. Nanoparticles functionalized with an angiogenesis-targeting agent are an attractive option for anti-tumor therapy.

Synthesis of Specific Nanoparticles for Targeting and Imaging Tumor Angiogenesis Using Electron-Beam Irradiation

International Nuclear Information System (INIS)

Rizza, G.; Deshayes, S.; Maurizot, V.; Clochard, M.-C.; Berthelot, T.; Baudin, C.; Déléris, G.

2010-01-01

We have succeeded to synthesize PVDF nanoparticles by nanoemulsion polymerization and their functionalization with a peptide that presents an anti-angiogenic activity. Resulted nanoparticles present a radius of 60 nm. From FESEM images and light scattering measurements, we deduced that they were spherical and monodisperse. The alkyl radicals induced from electron beam irradiation combine immediately with the oxygen to form peroxide radicals. Because of a high specific area and small crystallite size, the radical decay with time is evidenced from EPR measurements. Despite this radical decay, electron beam irradiation allows us to graft PAA by radical polymerization onto freshly irradiated PVDF nanoparticles and then to immobilize CBO-P11 by click chemistry via a spacer arm. Evidences of grafting were shown using HRMAS NMR and MALDI-TOF mass spectrometry. Nanoparticles functionalized with an angiogenesis-targeting agent are an attractive option for anti-tumor therapy

Biological Applications and Transmission Electron Microscopy Investigations of Mesoporous Silica Nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Trewyn, Brian G. [Iowa State Univ., Ames, IA (United States)

2006-01-01

The research presented and discussed within involves the development of novel biological applications of mesoporous silica nanoparticles (MSN) and an investigation of mesoporous material by transmission electron microscopy (TEM). Mesoporous silica nanoparticles organically functionalized shown to undergo endocytosis in cancer cells and drug release from the pores was controlled intracellularly and intercellularly. Transmission electron microscopy investigations demonstrated the variety of morphologies produced in this field of mesoporous silica nanomaterial synthesis. A series of room-temperature ionic liquid (RTIL) containing mesoporous silica nanoparticle (MSN) materials with various particle morphologies, including spheres, ellipsoids, rods, and tubes, were synthesized. By changing the RTIL template, the pore morphology was tuned from the MCM-41 type of hexagonal mesopores to rotational moire type of helical channels, and to wormhole-like porous structures. These materials were used as controlled release delivery nanodevices to deliver antibacterial ionic liquids against Escherichia coli K12. The involvement of a specific organosiloxane function group, covalently attached to the exterior of fluorescein doped mesoporous silica nanoparticles (FITC-MSN), on the degree and kinetics of endocytosis in cancer and plant cells was investigated. The kinetics of endocystosis of TEG coated FITC-MSN is significantly quicker than FITC-MSN as determined by flow cytometry experiments. The fluorescence confocal microscopy investigation showed the endocytosis of TEG coated-FITC MSN triethylene glycol grafted fluorescein doped MSN (TEG coated-FITC MSN) into both KeLa cells and Tobacco root protoplasts. Once the synthesis of a controlled-release delivery system based on MCM-41-type mesoporous silica nanorods capped by disulfide bonds with superparamagnetic iron oxide nanoparticles was completed. The material was characterized by general methods and the dosage and kinetics of the

When Anatase Nanoparticles Become Bulklike: Properties of Realistic TiO2 Nanoparticles in the 1-6 nm Size Range from All Electron Relativistic Density Functional Theory Based Calculations.

Science.gov (United States)

Lamiel-Garcia, Oriol; Ko, Kyoung Chul; Lee, Jin Yong; Bromley, Stefan T; Illas, Francesc

2017-04-11

All electron relativistic density functional theory (DFT) based calculations using numerical atom-centered orbitals have been carried out to explore the relative stability, atomic, and electronic structure of a series of stoichiometric TiO 2 anatase nanoparticles explicitly containing up to 1365 atoms as a function of size and morphology. The nanoparticles under scrutiny exhibit octahedral or truncated octahedral structures and span the 1-6 nm diameter size range. Initial structures were obtained using the Wulff construction, thus exhibiting the most stable (101) and (001) anatase surfaces. Final structures were obtained from geometry optimization with full relaxation of all structural parameters using both generalized gradient approximation (GGA) and hybrid density functionals. Results show that, for nanoparticles of a similar size, octahedral and truncated octahedral morphologies have comparable energetic stabilities. The electronic structure properties exhibit a clear trend converging to the bulk values as the size of the nanoparticles increases but with a marked influence of the density functional employed. Our results suggest that electronic structure properties, and hence reactivity, for the largest anatase nanoparticles considered in this study will be similar to those exhibited by even larger mesoscale particles or by bulk systems. Finally, we present compelling evidence that anatase nanoparticles become effectively bulklike when reaching a size of ∼20 nm diameter.

Cross Linking Polymers (PVA & PEG with TiO2 Nanoparticles for Humidity Sensing

Directory of Open Access Journals (Sweden)

Monika Joshi

2009-11-01

Full Text Available Humidity Sensors of different types are being used for various applications. Resistive Humidity Sensor has advantage over others for being small, low cost, interchangeable and long term stable. This makes them suitable for industrial, commercial and residential applications. In the present investigation humidity sensing behavior of various composite films made of Polyvinyl Alcohol (PVA, Polyethylene glycol (PEG, alkalies and oxide nanoparticles has been studied. It was found that relationship of resistance v/s relative humidity (RH was linear from 40 RH to 60 RH for a composite film made of PVA + PEG+ alkalies .The film can work with reliable efficiency for more than 100 days for the above range of humidity at room temperature. In order to improve the efficiency of composite polymer film TiO2 nanoparticles were added in the film and studied for resistance vs. RH responses. It was found that humidity range expands from 30 RH to 65 RH indicating the proportional decrease in resistance with increase in humidity at both ends as a result of the presence of TiO2 nanoparticles. The composite film with TiO2 nanoparticles can thus be used for wider range of humidity with reasonable stability and consistency. The observed behavior of the film has been attributed to the transportation of charge through TiO2 nanoparticles enhancing the conduction with the cross linked polymers.

Electron Tomography of Nanoparticle Clusters: Implications for Atmospheric Lifetimes and Radiative Forcing of Soot

Science.gov (United States)

vanPoppel, Laura H.; Friedrich, Heiner; Spinsby, Jacob; Chung, Serena H.; Seinfeld, John H.; Buseck, Peter R.

2005-01-01

Nanoparticles are ubiquitous in nature. Their large surface areas and consequent chemical reactivity typically result in their aggregation into clusters. Their chemical and physical properties depend on cluster shapes, which are commonly complex and unknown. This is the first application of electron tomography with a transmission electron microscope to quantitatively determine the three-dimensional (3D) shapes, volumes, and surface areas of nanoparticle clusters. We use soot (black carbon, BC) nanoparticles as an example because it is a major contributor to environmental degradation and global climate change. To the extent that our samples are representative, we find that quantitative measurements of soot surface areas and volumes derived from electron tomograms differ from geometrically derived values by, respectively, almost one and two orders of magnitude. Global sensitivity studies suggest that the global burden and direct radiative forcing of fractal BC are only about 60% of the value if it is assumed that BC has a spherical shape.

In situ transmission electron microscopy and scanning transmission electron microscopy studies of sintering of Ag and Pt nanoparticles

International Nuclear Information System (INIS)

Asoro, M.A.; Ferreira, P.J.; Kovar, D.

2014-01-01

Transmission electron microscopy and scanning transmission electron microscopy studies were conducted in situ on 2–5 nm Pt and 10–40 nm Ag nanoparticles to study mechanisms for sintering and to measure relevant sintering kinetics in nanoscale particles. Sintering between two separated particles was observed to initiate by either (1) diffusion of the particles on the sample support or (2) diffusion of atoms or small clusters of atoms to the neck region between the two particles. After particle contact, the rate of sintering was controlled by atomic surface diffusivity. The surface diffusivity was determined as a function of particle size and temperature from experimental measurements of the rate of neck growth of the particles. The surface diffusivities did not show a strong size effect for the range of particle sizes that were studied. The surface diffusivity for Pt nanoparticles exhibited the expected Arrhenius temperature dependence and did not appear to be sensitive to the presence of surface contaminants. In contrast, the surface diffusivity for Ag nanoparticles was affected by the presence of impurities such as carbon. The diffusivities for Ag nanoparticles were consistent with previous measurements of bulk surface diffusivities for Ag in the presence of C, but were significantly slower than those obtained from pristine Ag

Self-assembled nanoparticles of glycol chitosan – Ergocalciferol succinate conjugate, for controlled release

DEFF Research Database (Denmark)

Quinones, Javier Perez; Gothelf, Kurt Vesterager; Kjems, Jørgen

2012-01-01

Glycol chitosan was linked to vitamin D2 hemisuccinate (ergocalciferol hemisuccinate) for controlled release through water-soluble carbodiimide activation. The resulting conjugate formed self-assembled nanoparticles in aqueous solution with particle size of 279 nm and ergocalciferol hemisuccinate...... content of 8.4% (w/w). Almost spherical 50–90 nm nanoparticles were observed by scanning and transmission electron microscopy upon drying. Drug linking to glycol chitosan was confirmed by FTIR spectroscopy and proton NMR. Particles were also characterized by differential scanning calorimetry and wide...

Energetic electron processes fluorescence effects for structured nanoparticles X-ray analysis and nuclear medicine applications

Energy Technology Data Exchange (ETDEWEB)

Taborda, A.; Desbrée, A. [Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-HOM/SDI/LEDI, BP-17, 31, Avenue de la Division Leclerc, 92262 Fontenay-aux-Roses (France); Carvalho, A. [IEQUALTECS, Lda, Rua Dr. Francisco Sá Carneiro, 36, 2500-065 S. Gregório CLD (Portugal); Chaves, P.C. [C" 2TN, Campus Tecnológico e Nuclear, Instituto Superior Técnico, Universidade de Lisboa, EN10 km 139.7, 2685-066 Bobadela LRS (Portugal); Reis, M.A., E-mail: mareis@ctn.tecnico.ulisboa.pt [IEQUALTECS, Lda, Rua Dr. Francisco Sá Carneiro, 36, 2500-065 S. Gregório CLD (Portugal); C" 2TN, Campus Tecnológico e Nuclear, Instituto Superior Técnico, Universidade de Lisboa, EN10 km 139.7, 2685-066 Bobadela LRS (Portugal)

2016-08-15

Superparamagnetic iron oxide (SPIO) nanoparticles are widely used as contrast agents for nuclear magnetic resonance imaging (MRI), and can be modified for improved imaging or to become tissue-specific or even protein-specific. The knowledge of their detailed elemental composition characterisation and potential use in nuclear medicine applications, is, therefore, an important issue. X-ray fluorescence techniques such as particle induced X-ray emission (PIXE) or X-ray fluorescence spectrometry (XRF), can be used for elemental characterisation even in problematic situations where very little sample volume is available. Still, the fluorescence coefficient of Fe is such that, during the decay of the inner-shell ionised atomic structure, keV Auger electrons are produced in excess to X-rays. Since cross-sections for ionisation induced by keV electrons, for low atomic number atoms, are of the order of 10{sup 3} barn, care should be taken to account for possible fluorescence effects caused by Auger electrons, which may lead to the wrong quantification of elements having atomic number lower than the atomic number of Fe. Furthermore, the same electron processes will occur in iron oxide nanoparticles containing {sup 57}Co, which may be used for nuclear medicine therapy purposes. In the present work, simple approximation algorithms are proposed for the quantitative description of radiative and non-radiative processes associated with Auger electrons cascades. The effects on analytical processes and nuclear medicine applications are quantified for the case of iron oxide nanoparticles, by calculating both electron fluorescence emissions and energy deposition on cell tissues where the nanoparticles may be embedded.

Photoreactivity of ZnO nanoparticles in visible light: Effect of surface states on electron transfer reaction

International Nuclear Information System (INIS)

Baruah, Sunandan; Dutta, Joydeep; Sinha, Sudarson Sekhar; Ghosh, Barnali; Pal, Samir Kumar; Raychaudhuri, A. K.

2009-01-01

Wide band gap metal oxide semiconductors such as zinc oxide (ZnO) show visible band photolysis that has been employed, among others, to degrade harmful organic contaminants into harmless mineral acids. Metal oxides show enhanced photocatalytic activity with the increase in electronic defects in the crystallites. By introducing defects into the crystal lattice of ZnO nanoparticles, we observe a redshift in the optical absorption shifting from the ultraviolet region to the visible region (400-700 nm), which is due to the creation of intermediate defect states that inhibit the electron hole recombination process. The defects were introduced by fast nucleation and growth of the nanoparticles by rapid heating using microwave irradiation and subsequent quenching during the precipitation reaction. To elucidate the nature of the photodegradation process, picosecond resolved time correlated single photon count (TCSPC) spectroscopy was carried out to record the electronic transitions resulting from the de-excitation of the electrons to their stable states. Photodegradation and TCSPC studies showed that defect engineered ZnO nanoparticles obtained through fast crystallization during growth lead to a faster initial degradation rate of methylene blue as compared to the conventionally synthesized nanoparticles

Controllable synthesis and sintering of silver nanoparticles for inkjet-printed flexible electronics

International Nuclear Information System (INIS)

Zhang, Zhiliang; Zhu, Weiyue

2015-01-01

An effective and facile strategy was developed to successfully synthesize nearly uniform silver nanoparticles (AgNPs) with particle size of <10 nm, and demonstrated to achieve the sintering of AgNPs at room temperature for inkjet-printed flexible electronics. In such system, a series of different chain-length alkylamines were exploited as capped molecules to controllable synthesis of uniform AgNPs with the mean nanoparticle size in rang of 8.6 ± 0.9, 8.9 ± 1.2 and 9.2 ± 1.6 nm, and these ultra-small nanoparticles were very favorable to attain an excellent printing fluency. Based on the as-synthesized AgNPs, a sequence of flexible electrocircuits was successfully fabricated by ink-jet printing technique. After the dipped treatment, the printed AgNPs were achieved to spontaneous coalescence and aggregation at room temperature induced by preferential dissolution of capped molecules on AgNPs surfaces into methanol solution. These aggregated AgNPs demonstrated superior controllability, excellent stability and low resistivity in the range of 31.6–26.5 μΩ cm, and would have enormous potential in the application to be tailored for assembly of optoelectronics devices. - Highlights: • Silver nanoparticles with particle size of <10 nm was controllably synthesized. • The sintering of silver nanoparticles was conducted at room temperature. • The resistivity was reached as low as 26.5 μΩ cm for flexible electronics

Structural, Optical, and Electronic Characterization of Fe-Doped Alumina Nanoparticles

Science.gov (United States)

Heiba, Zein K.; Mohamed, Mohamed Bakr; Wahba, Adel Maher; Imam, N. G.

2018-01-01

The effects of iron doping on the structural, optical, and electronic properties of doped alumina have been studied. Single-phase iron-doped alumina Al2- x Fe x O3 ( x = 0.00 to 0.30) nanoparticles were synthesized via citrate-precursor method. Formation of single-phase hexagonal corundum structure with no other separate phases was demonstrated by x-ray diffraction (XRD) analysis and Fourier-transform infrared spectroscopy. The effects of iron doping on the α-Al2O3 structural parameters, viz. atomic coordinates, lattice parameters, crystallite size, and microstrain, were estimated from XRD data by applying the Rietveld profile fitting method. Transmission electron microscopy further confirmed the nanosize nature of the prepared samples with size ranging from 12 nm to 83 nm. The electronic band structure was investigated using density functional theory calculations to explain the decrease in the energy gap of Al2- x Fe x O3 as the amount of Fe was increased. The colored emission peaks in the visible region (blue, red, violet) of the electromagnetic spectrum obtained for the Fe-doped α-Al2O3 nanoparticles suggest their potential application as ceramic nanopigments.

Large area fabrication of plasmonic nanoparticle grating structure by conventional scanning electron microscope

International Nuclear Information System (INIS)

Sudheer,; Tiwari, P.; Rai, V. N.; Srivastava, A. K.; Mukharjee, C.

2015-01-01

Plasmonic nanoparticle grating (PNG) structure of different periods has been fabricated by electron beam lithography using silver halide based transmission electron microscope film as a substrate. Conventional scanning electron microscope is used as a fabrication tool for electron beam lithography. Optical microscope and energy dispersive spectroscopy (EDS) have been used for its morphological and elemental characterization. Optical characterization is performed by UV-Vis absorption spectroscopic technique

Nanoparticle mediated electron transfer across organic layers: from current understanding to applications

Energy Technology Data Exchange (ETDEWEB)

Gooding, J. Justin; Alam, Muhammad Tanzirul; Barfidokht, Abbas; Carter, Lachlan, E-mail: justin.gooding@unsw.edu.au [School of Chemistry and Australian Centre for NanoMedicine, The University of New South Wales, Sydney (Australia)

2014-03-15

In the last few years electrode-organic layer-nanoparticle constructs have attracted considerable research interest for systems where in the absence of the nanoparticles the electrode is passivated. This is because it has been observed that if the organic layer is a good self-assembled monolayer that passivates the electrode, the presence of the nanoparticles 'switches on' faradaic electrochemistry and because electron transfer between the electrode and the nanoparticles is apparently independent of the thickness of the organic layer. This review 1) outlines the full extent of the experimental observations regarding this phenomenon, 2) discusses a recent theoretical description to explain the observations that have just been supported with experimental evidences and 3) provides an overview of the application of these systems in sensing and photovoltaic. (author)

The fabrication and single electron transport of Au nano-particles placed between Nb nanogap electrodes

International Nuclear Information System (INIS)

Nishino, T; Negishi, R; Ishibashi, K; Kawao, M; Nagata, T; Ozawa, H

2010-01-01

We have fabricated Nb nanogap electrodes using a combination of molecular lithography and electron beam lithography. Au nano-particles with anchor molecules were placed in the gap, the width of which could be controlled on a molecular scale (∼2 nm). Three different anchor molecules which connect the Au nano-particles and the electrodes were tested to investigate their contact resistance, and a local gate was fabricated underneath the Au nano-particles. The electrical transport measurements at liquid helium temperatures indicated single electron transistor (SET) characteristics with a charging energy of about ∼ 5 meV, and a clear indication of the effect of superconducting electrodes was not observed, possibly due to the large tunnel resistance.

Nanoparticle sizing: a comparative study using atomic force microscopy, transmission electron microscopy, and ferromagnetic resonance

International Nuclear Information System (INIS)

Lacava, L.M.; Lacava, B.M.; Azevedo, R.B.; Lacava, Z.G.M.; Buske, N.; Tronconi, A.L.; Morais, P.C.

2001-01-01

Atomic force microscopy (AFM), transmission electron microscopy (TEM), and ferromagnetic resonance (FMR) were used to unfold the nanoparticle size of a ferrofluid sample. Compared to TEM, the AFM method showed a nanoparticle diameter (D m ) reduction of 20% and standard deviation (σ) increase of 15%. The differences in D m and σ were associated with the AFM tip and the nanoparticle concentration on the substrate

Theoretical study of ferroelectric nanoparticles using phase reconstructed electron microscopy

Science.gov (United States)

Phatak, C.; Petford-Long, A. K.; Beleggia, M.; De Graef, M.

2014-06-01

Ferroelectric nanostructures are important for a variety of applications in electronic and electro-optical devices, including nonvolatile memories and thin-film capacitors. These applications involve stability and switching of polarization using external stimuli, such as electric fields. We present a theoretical model describing how the shape of a nanoparticle affects its polarization in the absence of screening charges, and quantify the electron-optical phase shift for detecting ferroelectric signals with phase-sensitive techniques in a transmission electron microscope. We provide an example phase shift computation for a uniformly polarized prolate ellipsoid with varying aspect ratio in the absence of screening charges.

In situ growth of SnO2 nanoparticles in heteroatoms doped cross-linked carbon frameworks for lithium ion batteries anodes

International Nuclear Information System (INIS)

Zhou, Xiangyang; Xi, Lihua; Chen, Feng; Bai, Tao; Wang, Biao; Yang, Juan

2016-01-01

Highlights: • A facile hydrothermal method is proposed to prepare cross-linked NSG/CNTs@SnO 2 . • The graphene/CNTs anchored with untrasmall SnO 2 nanoparticles can be obtained. • The N, S are successfully incorporated into the carbon matrix. • The NSG/CNTs@SnO 2 presents enhanced cycling stability and good high-rate capacity. - Abstract: SnO 2 -based nanostructures have attracted considerable interest as a promising high-capacity anode materials for lithium ion batteries. We present herein a facile one step hydrothermal approach for in situ growth of SnO 2 nanoparticles in heteroatoms doped cross-linked carbon framework (NSG/CNTs@SnO 2 ). Thiourea is employed as a single source of nitrogen and sulfur in the cross-linked carbon framework (NSG/CNTs). Characterization shows that the SnO 2 nanoparticles with an average size of 6–10 nm are uniformly anchored on NSG/CNTs matrix. When evaluated for the electrochemical properties in lithium ion batteries, the obtained NSG/CNTs@SnO 2 composite with ultrasmall SnO 2 particle size (6–10 nm) delivers a high reversible capacity of 999 mAh g −1 at 200 mA g −1 after 120 cycles and excellent rate performance. Such outstanding electrochemical performance of the peculiar cross-linked NSG/CNTs@SnO 2 composite can be primarily attributed to the synergistic effect of the ultrasmall anchored SnO 2 nanoparticles and the dual-doped NSG/CNTs matrix. The uniformly distributed SnO 2 nanoparticles can deliver large capacity and the robust dual-doped NSG/CNTs matrix can guarantee the good structural integrity and high electrical conductivity during cycling. Besides, the porous structure can provide free space for the volume expansion of SnO 2 and accommodate the strain formed during repeated lithiation/delithiation processes.

Reliability of Capacitors for DC-Link Applications in Power Electronic Converters

DEFF Research Database (Denmark)

Wang, Huai; Blaabjerg, Frede

2014-01-01

DC-link capacitors are an important part in the majority of power electronic converters which contribute to cost, size and failure rate on a considerable scale. From capacitor users' viewpoint, this paper presents a review on the improvement of reliability of dc link in power electronic converters...... from two aspects: 1) reliability-oriented dc-link design solutions; 2) conditioning monitoring of dc-link capacitors during operation. Failure mechanisms, failure modes and lifetime models of capacitors suitable for the applications are also discussed as a basis to understand the physics......-of-failure. This review serves to provide a clear picture of the state-of-the-art research in this area and to identify the corresponding challenges and future research directions for capacitors and their dc-link applications....

Controllable synthesis, characterization and optical properties of ZnS:Mn nanoparticles as a novel biosensor

International Nuclear Information System (INIS)

Mohagheghpour, E.; Rabiee, M.; Moztarzadeh, F.; Tahriri, M.; Jafarbeglou, M.; Bizari, D.; Eslami, H.

2009-01-01

To be a suitable biolabeling agent (biosensor), the nanoparticles should have high luminescent efficiency and proper surface groups for coupling with biomolecules. In this article, high-quality ZnS:Mn nanoparticles were synthesized from quaternary W/O micro-emulsion system with different Mn% for detecting the best concentration. The addition of biotin and the subsequent specific binding events alter the dielectric environment of the nanoparticle, resulting in a spectral shift of the particle plasmon resonance. Cyclohexane was used as oil, Triton X-100 as surfactant, n-hexanol as a co-surfactant and mercaptoethanol and thioglycolic acid for the best linking of the biological part to the nanoparticle (as linking agents). Surfactant and co-surfactant produce a stable emulsion with connection to the surface of nanoparticles and prevention from contacting together. For qualitative and quantitative analyses of this product scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), inductive coupled plasma (ICP), zeta meter for measurement ZP and spectrograph techniques are used. The results showed that with reducing particle size, emission shifted to the lower wavelengths. In addition, with conjugation between avidin and biotin by mercaptoethanol in biologic media, spectral emission decreased.

The pH sensitive properties of carboxymethyl chitosan nanoparticles cross-linked with calcium ions.

Science.gov (United States)

Kalliola, Simo; Repo, Eveliina; Srivastava, Varsha; Heiskanen, Juha P; Sirviö, Juho Antti; Liimatainen, Henrikki; Sillanpää, Mika

2017-05-01

In environmental applications the applied materials are required to be non-toxic and biodegradable. Carboxymethyl chitosan nanoparticles cross-linked with Ca 2+ ions (CMC-Ca) fulfill these requirements, and they are also renewable. These nanoparticles were applied to oil-spill treatment in our previous study and here we focused on enhancing their properties. It was found that while the divalent Ca 2+ ions are crucial for the formation of the CMC-Ca, the attractive interaction between NH 3 + and COO - groups contributed significantly to the formation and stability of the CMC-Ca. The stability decreased as a function of pH due to the deprotonation of the amino groups. Therefore, the nanoparticles were found to be fundamentally pH sensitive in solution, if the pH deviated from the pH (7-9) that was used in the synthesis of the nanoparticles. The pH sensitive CMC-Ca synthesized in pH 7 and 8 were most stable in the studied conditions and could find applications in oil-spill treatment or controlled-release of substances. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Japan Link Center (JaLC): link management and DOI assignment for Japanese electronic scholarly contents

Science.gov (United States)

Kato, Takafumi; Tsuchiya, Eri; Kubota, Soichi; Miyagawa, Yoshiyuki

JST, cooperated with several national institutes, is currently developing “Japan Link Center”, which manages Japanese electronic scholarly contents (journal articles, books, dissertations etc.) in an integrated fashion using Digital Object Identifier (DOI). Japan Link Center will manage metadata and whereabouts information of the contents in the digital environment and provide domestic and international linking information, cite/cited information to activate dissemination of S&T information, furthermore, to strengthen transmission of S&T information from Japan. Japan Link Center is expected to be appointed as the 9th DOI registration agency (RA) in the world by the International DOI Foundation (IDF) this spring.

Electron spin resonance spectroscopy for immunoassay using iron oxide nanoparticles as probe.

Science.gov (United States)

Jiang, Jia; Tian, Sizhu; Wang, Kun; Wang, Yang; Zang, Shuang; Yu, Aimin; Zhang, Ziwei

2018-02-01

With the help of iron oxide nanoparticles, electron spin resonance spectroscopy (ESR) was applied to immunoassay. Iron oxide nanoparticles were used as the ESR probe in order to achieve an amplification of the signal resulting from the large amount of Fe 3+ ion enclosed in each nanoparticle. Rabbit IgG was used as antigen to test this method. Polyclonal antibody of rabbit IgG was used as antibody to detect the antigen. Iron oxide nanoparticle with a diameter of either 10 or 30 nm was labeled to the antibody, and Fe 3+ in the nanoparticle was probed for ESR signal. The sepharose beads were used as solid phase to which rabbit IgG was conjugated. The nanoparticle-labeled antibody was first added in the sample containing antigen, and the antigen-conjugated sepharose beads were then added into the sample. The nanoparticle-labeled antibody bound to the antigen on sepharose beads was separated from the sample by centrifugation and measured. We found that the detection ranges of the antigen obtained with nanoparticles of different sizes were different because the amount of antibody on nanoparticles of 10 nm was about one order of magnitude higher than that on nanoparticles of 30 nm. When 10 nm nanoparticle was used as probe, the upper limit of detection was 40.00 μg mL -1 , and the analytical sensitivity was 1.81 μg mL -1 . When 30 nm nanoparticle was used, the upper limit of detection was 3.00 μg mL -1 , and the sensitivity was 0.014 and 0.13 μg mL -1 depending on the ratio of nanoparticle to antibody. Graphical abstract Schematic diagram of procedure and ESR spectra.

Quantification of metallic nanoparticle morphology with tilt series imaging by transmission electron microscopy

Science.gov (United States)

Dutta, Aniruddha; Yuan, Biao; Clukay, Christopher J.; Grabill, Christopher N.; Heinrich, Helge; Bhattacharya, Aniket; Kuebler, Stephen M.

2012-02-01

We report on the quantitative analysis of electrolessly deposited Au and Ag nanoparticles (NPs) on SU8 polymer with the help of High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM) in tilt series. Au NPs act as nucleating agents for the electroless deposition of silver. Au NPs were prepared by attachingAu^3+cations to amine functionalized SU8 polymeric surfaces and then reducing it with aqueous NaBH4. The nanoscale morphology of the deposited NPs on the surface of polymer has been studied from the dark field TEM cross sectional images. Ag NPs were deposited on the cross-linked polymeric surface from a silver citrate solution reduced by hydroquinone. HAADF-STEM enables us to determine the distances between the NPs and their exact locations at and near the surface. The particle distribution, sizes and densities provide us with the data necessary to control the parameters for the development of the electroless deposition technique for emerging nanoscale technologies.

Morphology and electronic structure of the oxide shell on the surface of iron nanoparticles.

Science.gov (United States)

Wang, Chongmin; Baer, Donald R; Amonette, James E; Engelhard, Mark H; Antony, Jiji; Qiang, You

2009-07-01

An iron (Fe) nanoparticle exposed to air at room temperature will be instantly covered by an oxide shell that is typically approximately 3 nm thick. The nature of this native oxide shell, in combination with the underlying Fe(0) core, determines the physical and chemical behavior of the core-shell nanoparticle. One of the challenges of characterizing core-shell nanoparticles is determining the structure of the oxide shell, that is, whether it is FeO, Fe(3)O(4), gamma-Fe(2)O(3), alpha-Fe(2)O(3), or something else. The results of prior characterization efforts, which have mostly used X-ray diffraction and spectroscopy, electron diffraction, and transmission electron microscopic imaging, have been framed in terms of one of the known Fe-oxide structures, although it is not necessarily true that the thin layer of Fe oxide is a known Fe oxide. In this Article, we probe the structure of the oxide shell on Fe nanoparticles using electron energy loss spectroscopy (EELS) at the oxygen (O) K-edge with a spatial resolution of several nanometers (i.e., less than that of an individual particle). We studied two types of representative particles: small particles that are fully oxidized (no Fe(0) core) and larger core-shell particles that possess an Fe core. We found that O K-edge spectra collected for the oxide shell in nanoparticles show distinct differences from those of known Fe oxides. Typically, the prepeak of the spectra collected on both the core-shell and the fully oxidized particles is weaker than that collected on standard Fe(3)O(4). Given the fact that the origin of this prepeak corresponds to the transition of the O 1s electron to the unoccupied state of O 2p hybridized with Fe 3d, a weak pre-edge peak indicates a combination of the following four factors: a higher degree of occupancy of the Fe 3d orbital; a longer Fe-O bond length; a decreased covalency of the Fe-O bond; and a measure of cation vacancies. These results suggest that the coordination configuration in

Electron bombardment cross-linking of coating materials

International Nuclear Information System (INIS)

Mileo, J.-C.

1976-01-01

The use of medium-power electron accelerators to cure paints and varnishes and to make them insoluble is described by making a special analysis of the physico-chemical aspect of the process. The following points in particular are examined: the effect of radiation on matter; general aspects of radiochemical polymerization, and the application of radiation polymerization to varnish drying. A quick review is then made of problems linked to the choice of radiation and to the influence of the oxygen in air. An electron accelerator and a method of calorimetric dosimetery are described [fr

Highly Al-doped TiO2 nanoparticles produced by Ball Mill Method: structural and electronic characterization

International Nuclear Information System (INIS)

Santos, Desireé M. de los; Navas, Javier; Sánchez-Coronilla, Antonio; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; Martín-Calleja, Joaquín

2015-01-01

Highlights: • Highly Al-doped TiO 2 nanoparticles were synthesized using a Ball Mill Method. • Al doping delayed anatase to rutile phase transformation. • Al doping allow controlling the structural and electronic properties of nanoparticles. - Abstract: This study presents an easy method for synthesizing highly doped TiO 2 nanoparticles. The Ball Mill method was used to synthesize pure and Al-doped titanium dioxide, with an atomic percentage up to 15.7 at.% Al/(Al + Ti). The samples were annealed at 773 K, 973 K and 1173 K, and characterized using ICP-AES, XRD, Raman spectroscopy, FT-IR, TG, STEM, XPS, and UV–vis spectroscopy. The effect of doping and the calcination temperature on the structure and properties of the nanoparticles were studied. The results show high levels of internal doping due to the substitution of Ti 4+ ions by Al 3+ in the TiO 2 lattice. Furthermore, anatase to rutile transformation occurs at higher temperatures when the percentage of doping increases. Therefore, Al doping allows us to control the structural and electronic properties of the nanoparticle synthesized. So, it is possible to obtain nanoparticles with anatase as predominant phase in a higher range of temperature

Fabrication of Octahedral Gold Nanoparticle embedded Polymer Pattern based on Electron Irradiation and Thermal Treatment

Energy Technology Data Exchange (ETDEWEB)

Kim, Yong Nam; Lee, Hyeok Moo; Cho, Sung Oh [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

2011-05-15

Noble metal nanoparticles (NPs) such as gold (Au), silver, and copper have been a hot research issue due to their unique optical, electronic, and catalytic properties. On account of the size- and shape- dependent properties of the noble metal NPs, most researches are concentrated on tailoring sizes and shapes of the noble metal NPs. In particular, noble metal NPs with Platonic shapes such as tetrahedron, cube, octahedron, dodecahedron, and icosahedron have significant impact on a variety of applications including surface-enhancement spectroscopy, biochemical sensing, and nanodevice fabrication because sharp corners of the metals lead to high local electric-field enhancement. In addition, patterning or controlled assembly of noble metal NPs is indispensible for biological sensors, micro-/nano-electronic devices, photonic and photovoltaic devices, and surface-enhanced Raman scattering (SERS)-active substrates. Although Platonic noble metal NPs with well defined sizes have been intensively studied, patterning of Platonic noble metal NPs has been rarely demonstrated. Here, we present a strategy to fabricate patterned Au nano-octahedra embedded polymer films by selectively irradiating an electron beam onto HAuCl{sub 4}-loadaed poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) block copolymer (BCP) precursor films followed by thermal treatment. The BCP plays a important role for the patterning of the precursor film due to a cross-linking behavior under electron irradiation

Influence of effective electron interaction on critical current of Josephson weak links

International Nuclear Information System (INIS)

Kupriyanov, M.Yu.; Likharev, K.K.; Lukichev, V.F.

1981-01-01

On the basis of microscopic theory of superconductivity, the dc Josphson effect in weak links of the type of variable thickness bridges or high ohmic interlayer sandwiches is studied. The Isub(C)Rsub(N) product is calculatied as a function of temperature T and weak link length L for various amplitudes and both signs of effective electron-electron interaction constant lambda. If the weak link material is superconducting with critical temperature Tsub(C) > 0 (lambda > 0), the maximum value of Isub(C)Rsub(N) product (under condition of the singlevalued Isub(S)(phi) relationship) can be achieved at L approx. <= 3xisup(*) when Tsub(C) approx. <= Tsub(CS)/2, and at L=(4 / 6)xisup(*) when Tsub(C) = Tsub(CS). Electron repulsion inside the weak link (lambda < 0) results in some reduction of the Isub(C)Rsub(N) product in comparison with the case of 'really normal' weak link material (lambda = 0). (orig.)

Cryo-electron tomography investigation of serum albumin-camouflaged tobacco mosaic virus nanoparticles.

Science.gov (United States)

Gulati, Neetu M; Pitek, Andrzej S; Steinmetz, Nicole F; Stewart, Phoebe L

2017-03-09

Nanoparticles offer great potential in drug delivery and imaging, but shielding strategies are necessary to increase circulation time and performance. Structure-function studies are required to define the design rules to achieve effective shielding. With several formulations reaching clinical testing and approval, the ability to assess and detail nanoparticle formulations at the single particle level is becoming increasingly important. To address this need, we use cryo-electron tomography (cryo-ET) to investigate stealth-coated nanoparticles. As a model system, we studied the soft matter nanotubes formed by tobacco mosaic virus (TMV) coated with human serum albumin (SA) stealth proteins. Cryo-ET and subtomogram averaging allow for visualization of individual SA molecules and determination of their orientations relative to the TMV surface, and also for measurement of the surface coverage provided by added stealth proteins. This information fills a critical gap in the understanding of the structural morphology of stealth-coated nanoparticles, and therefore cryo-ET may play an important role in guiding the development of future nanoparticle-based therapeutics.

Preparation of Thermo-Responsive and Cross-Linked Fluorinated Nanoparticles via RAFT-Mediated Aqueous Polymerization in Nanoreactors.

Science.gov (United States)

Ma, Jiachen; Zhang, Luqing; Geng, Bing; Azhar, Umair; Xu, Anhou; Zhang, Shuxiang

2017-01-25

In this work, a thermo-responsive and cross-linked fluoropolymer poly(2,2,2-Trifluoroethyl) methacrylate (PTFEMA) was successfully prepared by reversible addition-fragmentation chain transfer (RAFT) mediated aqueous polymerization with a thermo-responsive diblock poly(dimethylacrylamide- b - N -isopropylacrylamide) (PDMA- b -PNIPAM) that performed a dual function as both a nanoreactor and macro-RAFT agent. The cross-linked polymer particles proved to be in a spherical-like structure of about 50 nm in diameter and with a relatively narrow particle size distribution. ¹H-NMR and 19 F-NMR spectra showed that thermo-responsive diblock P(DMA- b -NIPAM) and cross-linked PTFEMA particles were successfully synthesized. Influence of the amount of ammonium persulfate (APS), the molar ratio of monomers to RAFT agent, influence of the amount of cross-linker on aqueous polymerization and thermo-responsive characterization of the particles are investigated. Monomer conversion increased from 44% to 94% with increasing the molar ratio of APS and P(DMA- b -NIPAM) from 1:9 to1:3. As the reaction proceeded, the particle size increased from 29 to 49 nm due to the consumption of TFEMA monomer. The size of cross-linked nanoparticles sharply decreased from 50.3 to 40.5 nm over the temperature range 14-44 °C, suggesting good temperature sensitivity for these nanoparticles.

Anisotropic Shape Changes of Silica Nanoparticles Induced in Liquid with Scanning Transmission Electron Microscopy

NARCIS (Netherlands)

Zecevic, J.; Hermannsdorfer, Justus; Schuh, Tobias; de Jong, Krijn P.; de Jonge, Niels

2017-01-01

Liquid-phase transmission electron microscopy (TEM) is used for in-situ imaging of nanoscale processes taking place in liquid, such as the evolution of nanoparticles during synthesis or structural changes of nanomaterials in liquid environment. Here, it is shown that the focused electron beam of

Fabrication and evaluation of magnetic phosphodiesterase-5 linked nanoparticles as adsorbent for magnetic dispersive solid-phase extraction of inhibitors from Chinese herbal medicine prior to ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry analysis.

Science.gov (United States)

Tao, Yi; Gu, Xianghui; Li, Weidong; Cai, Baochang

2018-01-12

In the present study, the preparation of the magnetic phosphodiesterase-5 linked Fe 3 O 4 @ SiO 2 nanoparticles was successfully achieved by amide reaction and the magnetic phosphodiesterase-5 linked Fe 3 O 4 @SiO 2 nanoparticles were evaluated as a new adsorbent for magnetic dispersive solid-phase extraction of ligands from medicinal plant samples before the analysis by UHPLC-Q-TOF/MS. The prepared phosphodiesterase-5 linked Fe 3 O 4 @SiO 2 nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, vibration sample magnetometer and potential laser particle size analyzer. The effects of EDC concentration, incubation time and bead-protein ratio on the amount of immobilized protein were studied. The main experimental parameters affect extraction efficiency of ligands, such as wash times, wash solvents, incubation pH, ion strength and incubation temperature, were investigated and optimized by using echinacoside as a model compound. The absolute recovery of echinacoside was ranged from 98.36%-102.16% in Cistanche tubulosa sample under the optimal extraction conditions. Good linearity was observed in the investigated concentration range of 0.006 mgmL -1 -0.97 mgmL -1 (R 2  = 0.9999). The limit of detection was 0.002 mgmL -1 . The RSDs of within-day and between-day precision were less than 2.3%. Due to the excellent magnetic behavior of Fe 3 O 4 @SiO 2 nanoparticles, the proposed method was shown to be simple and rapid. Remarkably, the magnetic phosphodiesterase-5 linked Fe 3 O 4 @SiO 2 nanoparticles could be recycled for ten times with loss of 10% activity. Copyright © 2017 Elsevier B.V. All rights reserved.

Characterization of the electronic and magnetic structure of multifunctional NaREF{sub 4} (RE = rare earth) core-shell nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Schneider, Lilli; Kuepper, Karsten [Physics Department, University of Osnabrueck (Germany); Rinkel, Thorben; Haase, Markus [Institute of Chemistry, University of Osnabrueck (Germany); Chrobak, Artur [Institute of Physics, University of Silesia (Poland)

2014-07-01

Rare earth (RE) based nanoparticles of type NaREF{sub 4} have attracted lot of attention in the last few years due to their upconverting luminescence. Here, we want to concentrate on electronic and magnetic properties of NaREF{sub 4}/NaGdF{sub 4} nanocrystals, since the magnetic behaviour of these fluorescent nanoparticles are of utmost importance from fundamental and applicative point of view as well. Hexagonal β-phase nanocrystals (3-22 nm) were prepared and characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). A detailed study of the electronic structure and magnetic coupling phenomena of the different core-shell nanoparticles is performed using X-ray photoelectron spectroscopy (XPS), magnetometry (SQUID) and X-ray magnetic circular dichroism (XMCD). First SQUID measurements of NaEuF{sub 4}/NaGdF{sub 4} core-shell nanoparticles show butterfly shaped hysteresis loops at low temperature (2 K) in contrast to superparamagnetic behaviour observed for the corresponding ''pure'' NaEuF{sub 4} and NaGdF{sub 4} nanoparticles.

Influence of chemical disorder on the electronic level spacing distribution of the Ag{sub 5083} nanoparticle: A tight-binding study

Energy Technology Data Exchange (ETDEWEB)

Medrano, L.R., E-mail: leonardoms20@gmail.com [Faculty of Physical Sciences, National University of San Marcos, P.O. Box 14-0149, Lima 14 (Peru); Landauro, C.V., E-mail: clandauros@unmsm.edu.pe [Faculty of Physical Sciences, National University of San Marcos, P.O. Box 14-0149, Lima 14 (Peru)

2013-03-01

In the present work we study, employing a tight-binding Hamiltonian, the influence of chemical disorder on the electronic level spacing distribution of a silver nanoparticle containing 5083 atoms (∼ 5.5 nm). This nanoparticle was obtained by molecular dynamics simulations with a tight-binding atomic potential. The results indicate that in the absence of disorder the level spacing distributions are similar to those expected for systems belonging to the Gaussian Orthogonal Ensemble. Whereas, after increasing the chemical disorder, the electronic level spacing distribution and the Σ{sub 2} statistics tend to the corresponding form for the Poisson Ensemble, i.e., the silver nanoparticle acquires an insulating character which is expected for strongly disordered systems. Hence, this kind of disorder produces the localization of the electronic states of the nanoparticle.

First principles study of the electronic and optical properties of GaAs nanoparticles under the influence of external uniform electric field

International Nuclear Information System (INIS)

Bezi Javan, Masoud

2012-01-01

We present electronic and optical properties of the hydrogen terminated gallium arsenide nanoparticles using time dependent density functional theory (TD-DFT). The electronic and optical properties of the GaAs nanoparticles were calculated at presence of the uniform external electric field in the range from 0 to 0.51 V/Å. The induced electric filed can decrease the HOMO–LUMO gap of the nanoparticles and the mount of these reductions increases with gain of the electric field strength. -- Highlights: ► HOMO–LUMO gap of the nanoparticles is significantly more than GaAs bulk band gap. ► HOMO–LUMO gap of the nanoparticles decreases with increase of the nanoparticles size. ► External electric filed decrease the HOMO–LUMO gap of the nanoparticles. ► Dipole moment of nanoparticles increases with gain of the electric field strength. ► Absorption peaks of GaAs nanoparticles shows red shift with applying electric field.

An optimized nanoparticle separator enabled by electron beam induced deposition

International Nuclear Information System (INIS)

Fowlkes, J D; Rack, P D; Doktycz, M J

2010-01-01

Size-based separations technologies will inevitably benefit from advances in nanotechnology. Direct-write nanofabrication provides a useful mechanism for depositing/etching nanoscale elements in environments otherwise inaccessible to conventional nanofabrication techniques. Here, electron beam induced deposition was used to deposit an array of nanoscale features in a 3D environment with minimal material proximity effects outside the beam-interaction region. Specifically, the membrane component of a nanoparticle separator was fabricated by depositing a linear array of sharply tipped nanopillars, with a singular pitch, designed for sub-50 nm nanoparticle permeability. The nanopillar membrane was used in a dual capacity to control the flow of nanoparticles in the transaxial direction of the array while facilitating the sealing of the cellular-sized compartment in the paraxial direction. An optimized growth recipe resulted which (1) maximized the growth efficiency of the membrane (which minimizes proximity effects) and (2) preserved the fidelity of the spacing between nanopillars (which maximizes the size-based gating quality of the membrane) while (3) maintaining sharp nanopillar apexes for impaling an optically transparent polymeric lid critical for device sealing.

An optimized nanoparticle separator enabled by electron beam induced deposition

Science.gov (United States)

Fowlkes, J. D.; Doktycz, M. J.; Rack, P. D.

2010-04-01

Size-based separations technologies will inevitably benefit from advances in nanotechnology. Direct-write nanofabrication provides a useful mechanism for depositing/etching nanoscale elements in environments otherwise inaccessible to conventional nanofabrication techniques. Here, electron beam induced deposition was used to deposit an array of nanoscale features in a 3D environment with minimal material proximity effects outside the beam-interaction region. Specifically, the membrane component of a nanoparticle separator was fabricated by depositing a linear array of sharply tipped nanopillars, with a singular pitch, designed for sub-50 nm nanoparticle permeability. The nanopillar membrane was used in a dual capacity to control the flow of nanoparticles in the transaxial direction of the array while facilitating the sealing of the cellular-sized compartment in the paraxial direction. An optimized growth recipe resulted which (1) maximized the growth efficiency of the membrane (which minimizes proximity effects) and (2) preserved the fidelity of the spacing between nanopillars (which maximizes the size-based gating quality of the membrane) while (3) maintaining sharp nanopillar apexes for impaling an optically transparent polymeric lid critical for device sealing.

188Re labeling and biodistribution of magnetic nanoparticles for the tumor targeting

International Nuclear Information System (INIS)

Li Guiping; Zhang Hui; Wang Yongxian; Zhang Chunfu

2006-01-01

Objective: To prepare 188 Re labeled monoclonal antibody (Herceptin)-coated magnetic nanoparticles for tumor targeting and to study its biodistribution in mice. Methods: Herceptin and histidine were covalently linked to the amine group upon silica-coated magnetic nanoparticles modified by N-[3-(trimethyoxysilyl)prowl]-ethylenediamine using glutaraldehyde method. The Herceptin-coated magnetic nanoparticles and Herceptin were radiolabeled with 188 Re by a direct labelling method, whereas the histidine-coated magnetic nanoparticles was radiolabeled with 188 Re using fac-[ 188 Re(CO) 3 (H 2 0) 3 ] + as a precursor. The labelling efficiency and immunoreactivity as well as labelling stability were determined. Also, the biodistribution of 188 Re-magnetic and 188 Re-Herceptin-magnetic nanoparticles were observed in mice. Results: Herceptin-coated magnetic nanoparticles was characterized by transmission electron microscope (TEM) with diameter about 60 nm, while histidine-coated magnetic nanoparticles about 30 nm. The labeling efficiency for 188 Re-Herceptin, 188 Re-magnetic nanoparticles and 188 Re-Herceptin-magnetic nanoparticles were all > 90% and had a better stability in vitro. The immunoreactivity of Herceptin linked to magnetic nanoparticles was still high. The biodistribution in mice was shown that 188 Re-magnetic nanoparticles and 188 Re-Herceptin- magnetic nanoparticles had higher radioactivity levels in blood. Magnetic nanoparticles with diameter of 30 or 60 nm had a long half-life in blood stream and were accumulated in liver. Conclusion: The efficiency and stability of labelling Herceptin-coated magnetic nanoparticles and labelling magnetic nanoparticles with 188 Re are suitable for in vivo study in tumor-beating nude mice models. (authors)

Enzymatic cellulose oxidation is linked to lignin by long-range electron transfer

DEFF Research Database (Denmark)

Westereng, Bjorge; Cannella, David; Wittrup Agger, Jane

2015-01-01

cell walls. Electron transfer was confirmed by electron paramagnetic resonance spectroscopy showing that LPMO activity on cellulose changes the level of unpaired electrons in the lignin. The discovery of a long-range electron transfer mechanism links the biodegradation of cellulose and lignin and sheds...

Diazonium salt-mediated synthesis of new amino, hydroxy, propargyl, and maleinimido-containing superparamagnetic Fe@C nanoparticles as platforms for linking bio-entities or organocatalytic moieties

International Nuclear Information System (INIS)

Bunge, Alexander; Magerusan, Lidia; Morjan, Ion; Turcu, Rodica; Borodi, Gheorghe; Liebscher, Jürgen

2015-01-01

New magnetic Fe@C nanoparticles in the size range of about 20–50 nm functionalized with amino, hydroxy, propargyl, or maleinimido groups were synthesized by reaction with aryl diazonium salts. Aryl diazonium salts wherein the functional groups are linked via a sulfonamide moiety turned out to be advantageous over those with direct linkage. The obtained Fe@C nanoparticles represent magnetic nanoplatforms for linking bio-entities and organocatalysts using amide formation, CuAAC, or thiol-ene click chemistry as exemplified by selected examples. The Fe@C nanoparticles obtained exhibit supramolecular behavior with high value of saturation magnetization rendering them attractive for practical applications in biomedicine and organocatalysis.

Diazonium salt-mediated synthesis of new amino, hydroxy, propargyl, and maleinimido-containing superparamagnetic Fe@C nanoparticles as platforms for linking bio-entities or organocatalytic moieties

Science.gov (United States)

Bunge, Alexander; Magerusan, Lidia; Morjan, Ion; Turcu, Rodica; Borodi, Gheorghe; Liebscher, Jürgen

2015-09-01

New magnetic Fe@C nanoparticles in the size range of about 20-50 nm functionalized with amino, hydroxy, propargyl, or maleinimido groups were synthesized by reaction with aryl diazonium salts. Aryl diazonium salts wherein the functional groups are linked via a sulfonamide moiety turned out to be advantageous over those with direct linkage. The obtained Fe@C nanoparticles represent magnetic nanoplatforms for linking bio-entities and organocatalysts using amide formation, CuAAC, or thiol-ene click chemistry as exemplified by selected examples. The Fe@C nanoparticles obtained exhibit supramolecular behavior with high value of saturation magnetization rendering them attractive for practical applications in biomedicine and organocatalysis.

Diazonium salt-mediated synthesis of new amino, hydroxy, propargyl, and maleinimido-containing superparamagnetic Fe@C nanoparticles as platforms for linking bio-entities or organocatalytic moieties

Energy Technology Data Exchange (ETDEWEB)

Bunge, Alexander; Magerusan, Lidia [National Institute of Research and Development for Isotopic and Molecular Technologies (Romania); Morjan, Ion [National Institute for Lasers, Plasma and Radiation Physics (Romania); Turcu, Rodica; Borodi, Gheorghe; Liebscher, Jürgen, E-mail: liebscher@chemie.hu-berlin.de [National Institute of Research and Development for Isotopic and Molecular Technologies (Romania)

2015-09-15

New magnetic Fe@C nanoparticles in the size range of about 20–50 nm functionalized with amino, hydroxy, propargyl, or maleinimido groups were synthesized by reaction with aryl diazonium salts. Aryl diazonium salts wherein the functional groups are linked via a sulfonamide moiety turned out to be advantageous over those with direct linkage. The obtained Fe@C nanoparticles represent magnetic nanoplatforms for linking bio-entities and organocatalysts using amide formation, CuAAC, or thiol-ene click chemistry as exemplified by selected examples. The Fe@C nanoparticles obtained exhibit supramolecular behavior with high value of saturation magnetization rendering them attractive for practical applications in biomedicine and organocatalysis.

Revealing the Formation of Copper Nanoparticles from a Homogeneous Solid Precursor by Electron Microscopy

DEFF Research Database (Denmark)

van den Berg, Roy; Elkjær, Christian Fink; Gommes, Cedric J.

2016-01-01

The understanding of processes leading to the formation of nanometer-sized particles is important for tailoring of their size, shape and location. The growth mechanisms and kinetics of nanoparticles from solid precursors are, however, often poorly described. Here we employ transmission electron...... microscopy (TEM) to examine the formation of copper nanoparticles on a silica support during the reduction by H2 of homogeneous copper phyllosilicate platelets, as a prototype precursor for a coprecipitated catalyst. Specifically, time-lapsed TEM image series acquired of the material during the reduction...... process provide a direct visualization of the growth dynamics of an ensemble of individual nanoparticles and enable a quantitative evaluation of the nucleation and growth of the nanoparticles. This quantitative information is compared with kinetic models and found to be best described by a nucleation...

Mining Electronic Health Records using Linked Data.

Science.gov (United States)

Odgers, David J; Dumontier, Michel

2015-01-01

Meaningful Use guidelines have pushed the United States Healthcare System to adopt electronic health record systems (EHRs) at an unprecedented rate. Hospitals and medical centers are providing access to clinical data via clinical data warehouses such as i2b2, or Stanford's STRIDE database. In order to realize the potential of using these data for translational research, clinical data warehouses must be interoperable with standardized health terminologies, biomedical ontologies, and growing networks of Linked Open Data such as Bio2RDF. Applying the principles of Linked Data, we transformed a de-identified version of the STRIDE into a semantic clinical data warehouse containing visits, labs, diagnoses, prescriptions, and annotated clinical notes. We demonstrate the utility of this system though basic cohort selection, phenotypic profiling, and identification of disease genes. This work is significant in that it demonstrates the feasibility of using semantic web technologies to directly exploit existing biomedical ontologies and Linked Open Data.

Activators generated by electron transfer for atom transfer radical polymerization of styrene in the presence of mesoporous silica nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Khezri, Khezrollah, E-mail: kh.khezri@ut.ac.ir [School of Chemistry, University College of Science, University of Tehran, PO Box 14155-6455, Tehran (Iran, Islamic Republic of); Roghani-Mamaqani, Hossein [Department of Polymer Engineering, Sahand University of Technology, PO Box 51335-1996, Tabriz (Iran, Islamic Republic of)

2014-11-15

Graphical abstract: Effect of mesoporous silica nanoparticles (MCM-41) on the activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP) is investigated. Decrement of conversion and number average molecular weight and also increment of polydispersity index (PDI) values are three main results of addition of MCM-41 nanoparticles. Incorporation of MCM-41 nanoparticles in the polystyrene matrix can clearly increase thermal stability and decrease glass transition temperature of the nanocomposites. - Highlights: • Spherical morphology, hexagonal structure, and high surface area with regular pore diameters of the synthesized MCM-41 nanoparticles are examined. • AGET ATRP of styrene in the presence of MCM-41 nanoparticles is performed. • Effect of MCM-41 nanoparticles addition on the polymerization rate, conversion and molecular weights of the products are discussed. • Improvement in thermal stability of the nanocomposites and decreasing T{sub g} values was also observed by incorporation of MCM-41 nanoparticles. - Abstract: Activator generated by electron transfer for atom transfer radical polymerization was employed to synthesize well-defined mesoporous silica nanoparticles/polystyrene composites. Inherent features of spherical mesoporous silica nanoparticles were evaluated by nitrogen adsorption/desorption isotherm, X-ray diffraction and scanning electron microscopy analysis techniques. Conversion and molecular weight evaluations were carried out using gas and size exclusion chromatography respectively. By the addition of only 3 wt% mesoporous silica nanoparticles, conversion decreases from 81 to 58%. Similarly, number average molecular weight decreases from 17,116 to 12,798 g mol{sup −1}. However, polydispersity index (PDI) values increases from 1.24 to 1.58. A peak around 4.1–4.2 ppm at proton nuclear magnetic resonance spectroscopy results clearly confirms the living nature of the polymerization. Thermogravimetric

Cross-linked Composite Gel Polymer Electrolyte using Mesoporous Methacrylate-Functionalized SiO2 Nanoparticles for Lithium-Ion Polymer Batteries

Science.gov (United States)

Shin, Won-Kyung; Cho, Jinhyun; Kannan, Aravindaraj G.; Lee, Yoon-Sung; Kim, Dong-Won

2016-01-01

Liquid electrolytes composed of lithium salt in a mixture of organic solvents have been widely used for lithium-ion batteries. However, the high flammability of the organic solvents can lead to thermal runaway and explosions if the system is accidentally subjected to a short circuit or experiences local overheating. In this work, a cross-linked composite gel polymer electrolyte was prepared and applied to lithium-ion polymer cells as a safer and more reliable electrolyte. Mesoporous SiO2 nanoparticles containing reactive methacrylate groups as cross-linking sites were synthesized and dispersed into the fibrous polyacrylonitrile membrane. They directly reacted with gel electrolyte precursors containing tri(ethylene glycol) diacrylate, resulting in the formation of a cross-linked composite gel polymer electrolyte with high ionic conductivity and favorable interfacial characteristics. The mesoporous SiO2 particles also served as HF scavengers to reduce the HF content in the electrolyte at high temperature. As a result, the cycling performance of the lithium-ion polymer cells with cross-linked composite gel polymer electrolytes employing methacrylate-functionalized mesoporous SiO2 nanoparticles was remarkably improved at elevated temperatures. PMID:27189842

A nanoparticle in plasma

International Nuclear Information System (INIS)

Martynenko, Yu. V.; Nagel', M. Yu.; Orlov, M. A.

2009-01-01

Charge and energy fluxes onto a nanoparticle under conditions typical of laboratory plasmas are investigated theoretically. Here, by a nanoparticle is meant a grain the size of which is much smaller than both the electron Larmor radius and Debye length and the thermionic emission from which is not limited by the space charge. Under conditions at which thermionic emission plays an important role, the electric potential and temperature T p of a nanoparticle are determined by solving a self-consistent set of equations describing the balance of energy and charge fluxes onto the nanoparticle. It is shown that, when the degree of plasma ionization exceeds a critical level, the potential of the nanoparticle and the energy flux onto it increase with increasing nanoparticle temperature, so that, starting from a certain temperature, the nanoparticle potential becomes positive. The critical degree of ionization starting from which the potential of a nanoparticle is always positive is determined as a function of the plasma density and electron temperature. The nanoparticle temperature T p corresponding to the equilibrium state of a positively charged nanoparticle is found as a function of the electron density for different electron temperatures.

Geometrical effects on the electron residence time in semiconductor nano-particles.

Science.gov (United States)

Koochi, Hakimeh; Ebrahimi, Fatemeh

2014-09-07

We have used random walk (RW) numerical simulations to investigate the influence of the geometry on the statistics of the electron residence time τ(r) in a trap-limited diffusion process through semiconductor nano-particles. This is an important parameter in coarse-grained modeling of charge carrier transport in nano-structured semiconductor films. The traps have been distributed randomly on the surface (r(2) model) or through the whole particle (r(3) model) with a specified density. The trap energies have been taken from an exponential distribution and the traps release time is assumed to be a stochastic variable. We have carried out (RW) simulations to study the effect of coordination number, the spatial arrangement of the neighbors and the size of nano-particles on the statistics of τ(r). It has been observed that by increasing the coordination number n, the average value of electron residence time, τ̅(r) rapidly decreases to an asymptotic value. For a fixed coordination number n, the electron's mean residence time does not depend on the neighbors' spatial arrangement. In other words, τ̅(r) is a porosity-dependence, local parameter which generally varies remarkably from site to site, unless we are dealing with highly ordered structures. We have also examined the effect of nano-particle size d on the statistical behavior of τ̅(r). Our simulations indicate that for volume distribution of traps, τ̅(r) scales as d(2). For a surface distribution of traps τ(r) increases almost linearly with d. This leads to the prediction of a linear dependence of the diffusion coefficient D on the particle size d in ordered structures or random structures above the critical concentration which is in accordance with experimental observations.

Opto-electronic devices with nanoparticles and their assemblies

Science.gov (United States)

Nguyen, Chieu Van

Nanotechnology is a fast growing field; engineering matters at the nano-meter scale. A key nanomaterial is nanoparticles (NPs). These sub-wavelength (background noise. The second device is based on a one-dimensional (1-D) self-directed self-assembly of Au NPs mediated by dielectric materials. Depending on the coverage density of the Au NPs assembly deposited on the device, electronic emission was observed at ultra-low bias of 40V, leading to low-power plasma generation in air at atmospheric pressure. Light emitted from the plasma is apparent to the naked eyes. Similarly, 1-D self-assembly of Au NPs mediated by iron oxide was fabricated and exhibits ferro-magnetic behavior. The multi-functional 1-D self-assembly of Au NPs has great potential in modern electronics such as solid state lighting, plasma-based nanoelectronics, and memory devices.

Understanding the formation and growth of Ag nanoparticles on silver chromate induced by electron irradiation in electron microscope: A combined experimental and theoretical study

International Nuclear Information System (INIS)

Fabbro, Maria T.; Gracia, Lourdes; Silva, Gabriela S.; Santos, Luís P.S.; Andrés, Juan; Cordoncillo, Eloisa; Longo, E.

2016-01-01

Ag 2 CrO 4 microcrystals were synthesized using the co-precipitation method. These microcrystals were characterized through X-ray diffraction (XRD) with Rietveld analysis, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) with energy-dispersive spectroscopy (EDS), micro-Raman (MR). XRD patterns and Rietveld refinement data showed that the material exhibits an orthorhombic structure without any deleterious phases. FE-SEM and TEM micrographs revealed the morphology and the growth of Ag nanoparticles on Ag 2 CrO 4 microcrystals during electron beam irradiation. These events were directly monitored in real-time. Their optical properties were investigated using ultraviolet-visible (UV–vis) diffuse reflectance spectroscopy that allowed the calculation of the optical band gap energy. Theoretical analyses based on the density functional theory level indicate that the incorporation of electrons is responsible for structural modifications and formation of defects on the [AgO 6 ] and [AgO 4 ] clusters, generating ideal conditions for the growth of Ag nanoparticles. - Graphical abstract: Theoretical representation of the Ag 2 CrO 4 orthorhombic structure. Display Omitted - Highlights: • The Ag 2 CrO 4 microcrystals indicate an orthorhombic structure. • The formation of Ag 0 promotes Ag-nanoparticle growth on the surface of the Ag 2 CrO 4 . • Electron irradiation of the material induces the formation of Ag vacancies.

Cryo-transmission electron microscopy of Ag nanoparticles grown on an ionic liquid substrate

KAUST Repository

Anjum, Dalaver H.; Stiger, Rebecca M.; Finley, James J.; Conway, James F.

2010-01-01

We report a novel method of growing silver nanostructures by cathodic sputtering onto an ionic liquid (IL) and our visualization by transmission cryo-electron microscopy to avoid beam-induced motion of the nanoparticles. By freezing the IL

Highly Al-doped TiO{sub 2} nanoparticles produced by Ball Mill Method: structural and electronic characterization

Energy Technology Data Exchange (ETDEWEB)

Santos, Desireé M. de los, E-mail: desire.delossantos@uca.es; Navas, Javier, E-mail: javier.navas@uca.es; Sánchez-Coronilla, Antonio; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; Martín-Calleja, Joaquín

2015-10-15

Highlights: • Highly Al-doped TiO{sub 2} nanoparticles were synthesized using a Ball Mill Method. • Al doping delayed anatase to rutile phase transformation. • Al doping allow controlling the structural and electronic properties of nanoparticles. - Abstract: This study presents an easy method for synthesizing highly doped TiO{sub 2} nanoparticles. The Ball Mill method was used to synthesize pure and Al-doped titanium dioxide, with an atomic percentage up to 15.7 at.% Al/(Al + Ti). The samples were annealed at 773 K, 973 K and 1173 K, and characterized using ICP-AES, XRD, Raman spectroscopy, FT-IR, TG, STEM, XPS, and UV–vis spectroscopy. The effect of doping and the calcination temperature on the structure and properties of the nanoparticles were studied. The results show high levels of internal doping due to the substitution of Ti{sup 4+} ions by Al{sup 3+} in the TiO{sub 2} lattice. Furthermore, anatase to rutile transformation occurs at higher temperatures when the percentage of doping increases. Therefore, Al doping allows us to control the structural and electronic properties of the nanoparticle synthesized. So, it is possible to obtain nanoparticles with anatase as predominant phase in a higher range of temperature.

Optical and photoelectrical studies of gold nanoparticle-decorated C{sub 60} films

Energy Technology Data Exchange (ETDEWEB)

Dmitruk, N.L., E-mail: dmitruk@isp.kiev.u [Institute for Physics of Semiconductors, National Academy of Sciences of Ukraine, 45 Nauki Prospect, Kyiv 03028 (Ukraine); Borkovskaya, O.Yu.; Mamykin, S.V.; Naumenko, D.O. [Institute for Physics of Semiconductors, National Academy of Sciences of Ukraine, 45 Nauki Prospect, Kyiv 03028 (Ukraine); Meza-Laguna, V. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (UNAM), Circuito Exterior, Ciudad Universitaria, A. P. 70-186, C. P. 04510 Mexico D.F. (Mexico); Basiuk Golovataya-Dzhymbeeva, E.V. [Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico (UNAM), Circuito exterior S/N Ciudad Universitaria, A. P. 70-186, C. P. 04510 Mexico D.F. (Mexico); Lee, I. Puente [Facultad de Quimica, UNAM, Circuito de la Investigacion Cientifica, Ciudad Universitaria, 04510 Mexico D.F. (Mexico)

2010-01-01

Optical and photoelectrical studies were performed on octane-1,8-dithiol cross-linked fullerene films, with supported gold nanoparticles (C{sub 60}-DT-Au). According to high-resolution transmission electron microscopy observations, the average size of obtained gold nanoparticles was about 5 nm, and the shape was spherical. The comparative investigation of optical properties of pristine and cross-linked with octane-1,8-dithiol C{sub 60} films, decorated with gold nanoparticles, found the difference in the extinction coefficient spectra, which was observed also in the photocurrent spectra of barrier heterostructure Au/C{sub 60}/Si. The analysis of dark current-voltage characteristics for Au/C{sub 60}/Si heterostructures showed that the model for them includes the barrier at the C{sub 60}/Si interface and internal barriers in the C{sub 60} layer, caused by the trapping centers. The hopping mechanism of the current transport in the C{sub 60} layer was supplemented with the Poole-Frenkel emission process on these centers, with the barrier height greater for the fullerene C{sub 60} film cross-linked with octane-1,8-dithiol.

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

International Nuclear Information System (INIS)

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)

Chemical and structural properties of Pd nanoparticle-decorated graphene—Electron spectroscopic methods and QUASES

Energy Technology Data Exchange (ETDEWEB)

Lesiak, B., E-mail: blesiak-orlowska@ichf.edu.pl [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warszawa (Poland); Jiricek, P.; Bieloshapka, I. [Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 6, 162-53 Prague 6 (Czech Republic)

2017-05-15

Highlights: • Pd-decorated graphene oxide (GO), reduced graphene oxide (RGO), graphite (Gr). • Electron spectroscopy (XPS) aided with QUASES and REELS structural analysis. • Pd nanoparticle size decreases with surface hydrophilicity (oxygen group content). • PdO{sub x} overlayer thickness increases with surface hydrophilicity. • GO reduction, Pd decoration by reduction lead to exfoliated graphene structures. - Abstract: Graphite (Gr) and carbon nanomaterials such as graphene oxide (GO) and reduced graphene oxide (RGO) and those decorated with Pd nanoparticles were investigated by photoelectron spectroscopy (XPS) aided with Quantitative Analysis of Surfaces by Electron Spectroscopy (QUASES) and reflected electron energy loss spectroscopy (REELS). Oxidation of Gr decreased the C/O ratio from 10 (Gr) to 2.2 (GO), whereas reduction of GO by N{sub 2}H{sub 4} increased this ratio to 6.6 (RGO) due to decreasing number of oxygen groups (hydroxyl, epoxy, carbonyl and hydroxyl). Graphene materials and those after Pd decoration had 6–11 average number of layers in stacked nanostructures. Pd decoration using NaBH{sub 4}-reducing agents formed nanoparticles of size 6.9 nm (Pd/Gr) > 5.3 nm (Pd/RGO) > 4.25 nm (Pd/GO), with PdO{sub x} overlayer thickness of 2.20 nm (Pd/GO) > 1.42 nm (Pd/Gr) > 1.20 nm (Pd/RGO), decreased number of oxygen groups and average number of layers. Smaller Pd nanoparticles of larger PdO{sub x} overlayer thickness were observed on highly hydrophilic substrates (functional oxygen groups content). Decoration accompanied by reduction using NaBH{sub 4} led to the removal of water attached by hydrogen bonding to graphene interplanes and the formation of PdO{sub x} overlayer from oxygen functional groups. Nanoparticle size obtained from QUASES was confirmed by Pd 3d{sub 5/2} spectra binding energy and full-width at half maximum. Various chemistry and mechanisms of graphene reduction using N{sub 2}H{sub 4} and NaBH{sub 4} were observed, where Na

Intracellular trafficking of superparamagnetic iron oxide nanoparticles conjugated with TAT peptide: 3-dimensional electron tomography analysis

International Nuclear Information System (INIS)

Nair, Baiju G.; Fukuda, Takahiro; Mizuki, Toru; Hanajiri, Tatsuro; Maekawa, Toru

2012-01-01

Highlights: ► We study the intracellular localisation of TAT-SPIONs using 3-D electron tomography. ► 3-D images of TAT-SPIONs in a cell are clearly shown. ► Release of TAT-SPIONs from endocytic vesicles into the cytoplasm is clearly shown. -- Abstract: Internalisation of nanoparticles conjugated with cell penetrating peptides is a promising approach to various drug delivery applications. Cell penetrating peptides such as transactivating transcriptional activator (TAT) peptides derived from HIV-1 proteins are effective intracellular delivery vectors for a wide range of nanoparticles and pharmaceutical agents thanks to their amicable ability to enter cells and minimum cytotoxicity. Although different mechanisms of intracellular uptake and localisation have been proposed for TAT conjugated nanoparticles, it is necessary to visualise the particles on a 3-D plane in order to investigate the actual intracellular uptake and localisation. Here, we study the intracellular localisation and trafficking of TAT peptide conjugated superparamagnetic ion oxide nanoparticles (TAT-SPIONs) using 3-D electron tomography. 3-D tomograms clearly show the location of TAT-SPIONs in a cell and their slow release from the endocytic vesicles into the cytoplasm. The present methodology may well be utilised for further investigations of the behaviours of nanoparticles in cells and eventually for the development of nano drug delivery systems.

Application of Colloidal Palladium Nanoparticles for Labeling in Electron Microscopy

Czech Academy of Sciences Publication Activity Database

Vancová, Marie; Šlouf, Miroslav; Langhans, Jan; Pavlová, Eva; Nebesářová, Jana

2011-01-01

Roč. 17, č. 5 (2011), s. 810-816 ISSN 1431-9276 R&D Projects: GA AV ČR KAN200520704; GA AV ČR KJB600960906; GA ČR GAP205/10/0348 Institutional research plan: CEZ:AV0Z60220518; CEZ:AV0Z40500505 Keywords : electron microscopy * colloidal palladium * nanoparticles * labeling * salivary glands * Ixodes ricinus Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.007, year: 2011

Electronic and structural properties of deposited silver nanoparticles. A STM and GISAXS study

Energy Technology Data Exchange (ETDEWEB)

Sell, Kristian

2010-12-15

The properties of supported Ag nanoparticles are investigated, with the focus on specific structural and electronic qualities. Using a statistical analysis it is shown that large Ag particles move over the surface after being deposited on Si(111)7 x 7. Surface photovoltage measurements reveal the band topology of nanoscale metal-semiconductor systems. The findings are discussed with a band topology model and in terms of current transport mechanisms. Grazing-incidence small angle X-ray scattering is used to monitor in situ the size and shape change of Ag nanoparticles during a catalytic reaction. (orig.)

In situ growth of Ag nanoparticles on α-Ag2WO4 under electron irradiation: probing the physical principles

Science.gov (United States)

San-Miguel, Miguel A.; da Silva, Edison Z.; Zannetti, Sonia M.; Cilense, Mario; Fabbro, Maria T.; Gracia, Lourdes; Andrés, Juan; Longo, Elson

2016-06-01

Exploiting the plasmonic behavior of Ag nanoparticles grown on α-Ag2WO4 is a widely employed strategy to produce efficient photocatalysts, ozone sensors, and bactericides. However, a description of the atomic and electronic structure of the semiconductor sites irradiated by electrons is still not available. Such a description is of great importance to understand the mechanisms underlying these physical processes and to improve the design of silver nanoparticles to enhance their activities. Motivated by this, we studied the growth of silver nanoparticles to investigate this novel class of phenomena using both transmission electron microscopy and field emission scanning electron microscopy. A theoretical framework based on density functional theory calculations (DFT), together with experimental analysis and measurements, were developed to examine the changes in the local geometrical and electronic structure of the materials. The physical principles for the formation of Ag nanoparticles on α-Ag2WO4 by electron beam irradiation are described. Quantum mechanical calculations based on DFT show that the (001) of α-Ag2WO4 displays Ag atoms with different coordination numbers. Some of them are able to diffuse out of the surface with a very low energy barrier (less than 0.1 eV), thus, initiating the growth of metallic Ag nanostructures and leaving Ag vacancies in the bulk material. These processes increase the structural disorder of α-Ag2WO4 as well as its electrical resistance as observed in the experimental measurements.

Molecular tilt-dependent and tyrosine-enhanced electron transfer across ITO/SAM/[DPPC–Au NP–Tyrosine] Janus nanoparticle junction

Energy Technology Data Exchange (ETDEWEB)

Sarangi, Nirod Kumar; Patnaik, Archita, E-mail: archita59@yahoo.com [Indian Institute of Technology Madras, Department of Chemistry (India)

2016-09-15

Enhanced interfacial electron transfer (ET) across the otherwise insulating indium tin oxide/alkanethiol self-assembled monolayer (SAM)/redox molecule junction was accomplished when a Janus gold nanoparticle (JNP) protected by bioinspired phosphatidylcholine (DPPC) lipid and tyrosine amino acid ligands was anchored on it. In addition to the most theoretical and experimental investigations on the distance-dependent ET across Metal–Organic SAM–Nanoparticle (NP) architectures, the current results succinctly illustrate molecular tilt angle of the SAM and the characteristic of JNP as key factors in expediting the ET rate via electron tunneling. In the absence of JNP, electron tunneling with a tunneling factor β = 1.1 Å{sup −1} across the SAM was the rate-limiting step, evidenced from electrochemical impedance spectroscopy (EIS). The apparent electron transfer rate constant (k{sub app}{sup 0}) for anchored SAM was enhanced by at least one order of magnitude than the DPPC-only protected nanoparticle, suggesting the potential role of tyrosine towards the enhanced ET. The asymmetric and biogenic nature of the construct sheds light on a potential bioelectronic device for novel electronic attributes.Graphical abstractEntry of TOC .

Insight on the formation of chitosan nanoparticles through ionotropic gelation with tripolyphosphate.

Science.gov (United States)

Koukaras, Emmanuel N; Papadimitriou, Sofia A; Bikiaris, Dimitrios N; Froudakis, George E

2012-10-01

This work reports details pertaining to the formation of chitosan nanoparticles that we prepare by the ionic gelation method. The molecular interactions of the ionic cross-linking of chitosan with tripolyphosphate have been investigated and elucidated by means of all-electron density functional theory. Solvent effects have been taken into account using implicit models. We have identified primary-interaction ionic cross-linking configurations that we define as H-link, T-link, and M-link, and we have quantified the corresponding interaction energies. H-links, which display high interaction energies and are also spatially broadly accessible, are the most probable cross-linking configurations. At close range, proton transfer has been identified, with maximum interaction energies ranging from 12.3 up to 68.3 kcal/mol depending on the protonation of the tripolyphosphate polyanion and the relative coordination of chitosan with tripolyphosphate. On the basis of our results for the linking types (interaction energies and torsion bias), we propose a simple mechanism for their impact on the chitosan/TPP nanoparticle formation process. We introduce the β ratio, which is derived from the commonly used α ratio but is more fundamental since it additionally takes into account structural details of the oligomers.

Gold nanoparticle assisted assembly of a heme protein for enhancement of long-range interfacial electron transfer

DEFF Research Database (Denmark)

Jensen, Palle Skovhus; Chi, Qijin; Grumsen, Flemming Bjerg

2007-01-01

and characterization of water-soluble gold nanoparticles (AuNPs) with core diameter 3-4 nm and their application for the enhancement of long-range interfacial ET of a heme protein. Gold nanoparticles were electrostatically conjugated with cyt c to form nanoparticle-protein hybrid ET systems with well...... and the protein molecule. When the nanoparticle-protein conjugates are assembled on Au(111) surfaces, long-range interfacial ET across a physical distance of over 50 A via the nanoparticle becomes feasible. Moreover, significant enhancement of the interfacial ET rate by more than an order of magnitude compared...... with that of cyt c in the absence of AuNPs is observed. AuNPs appear to serve as excellent ET relays, most likely by facilitating the electronic coupling between the protein redox center and the electrode surface....

Red emissive cross-linked chitosan and their nanoparticles for imaging the nucleoli of living cells.

Science.gov (United States)

Wang, Ke; Yuan, Xun; Guo, Zhenpeng; Xu, Jiying; Chen, Yi

2014-02-15

Biocompatible glutaraldehyde-cross-linked chitosan with new red fluorescence were prepared for the first time and were shaped into nanoparticles via inverse-microemulsion method. They could luminesce at ca. 670 nm either as powders and nanoparticles or in real and gelling solutions or suspensions, having a lifetime of 1.353 ns and a quantum yield of 0.08 in solution or 0.01 in solid state. The new-formed pyridinium structures and the intramolecular charge transfer effect are considered to be responsible for the new red emission, which have been proved by FTIR, (13)C NMR, and some calculation using Gaussian 09, respectively. Strikingly, they are quite inert and anti-photobleaching, with only nucleoli of living HeLa cells with low cytotoxicity for high contrast imaging inspections. Copyright © 2013 Elsevier Ltd. All rights reserved.

Hot-Electron Intraband Luminescence from Single Hot Spots in Noble-Metal Nanoparticle Films

Science.gov (United States)

Haug, Tobias; Klemm, Philippe; Bange, Sebastian; Lupton, John M.

2015-08-01

Disordered noble-metal nanoparticle films exhibit highly localized and stable nonlinear light emission from subdiffraction regions upon illumination by near-infrared femtosecond pulses. Such hot spot emission spans a continuum in the visible and near-infrared spectral range. Strong plasmonic enhancement of light-matter interaction and the resulting complexity of experimental observations have prevented the development of a universal understanding of the origin of light emission. Here, we study the dependence of emission spectra on excitation irradiance and provide the most direct evidence yet that the continuum emission observed from both silver and gold nanoparticle aggregate surfaces is caused by recombination of hot electrons within the conduction band. The electron gas in the emitting particles, which is effectively decoupled from the lattice temperature for the duration of emission, reaches temperatures of several thousand Kelvin and acts as a subdiffraction incandescent light source on subpicosecond time scales.

Preparation of starch nanoparticles in water in oil microemulsion system and their drug delivery properties.

Science.gov (United States)

Wang, Xinge; Chen, Haiming; Luo, Zhigang; Fu, Xiong

2016-03-15

In this research, 1-hexadecyl-3-methylimidazolium bromide C16mimBr/butan-1-ol/cyclohexane/water ionic liquid microemulsion was prepared. The effects of n-alkyl alcohols, alkanes, water content and temperature on the properties of microemulsion were studied by dilution experiment. The microregion of microemulsion was identified by pseudo-ternary phase diagram and conductivity measurement. Then starch nanoparticles were prepared by water in oil (W/O) microemulsion-cross-linking methods with C16mimBr as surfactant. Starch nanoparticles with a mean diameter of 94.3nm and narrow size distribution (SD=3.3) were confirmed by dynamic light scattering (DLS). Scanning electron microscope (SEM) data revealed that starch nanoparticles were spherical granules with the size about 60nm. Moreover the results of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) demonstrated the formation of cross-linking bonds in starch molecules. Finally, the drug loading and releasing properties of starch nanoparticles were investigated with methylene blue (MB) as drug model. This work may provide an efficient pathway to synthesis starch nanoparticles. Copyright © 2015 Elsevier Ltd. All rights reserved.

Synthesis of nanoparticles in helium droplets—A characterization comparing mass-spectra and electron microscopy data

International Nuclear Information System (INIS)

Thaler, Philipp; Volk, Alexander; Lackner, Florian; Steurer, Johannes; Schnedlitz, Martin; Ernst, Wolfgang E.; Knez, Daniel; Haberfehlner, Georg

2015-01-01

Micrometer sized helium droplets provide an extraordinary environment for the growth of nanoparticles. The method promises great potential for the preparation of core-shell particles as well as one-dimensional nanostructures, which agglomerate along quantum vortices, without involving solvents, ligands, or additives. Using a new apparatus, which enables us to record mass spectra of heavy dopant clusters (>10 4 amu) and to produce samples for transmission electron microscopy simultaneously, we synthesize bare and bimetallic nanoparticles consisting of various materials (Au, Ni, Cr, and Ag). We present a systematical study of the growth process of clusters and nanoparticles inside the helium droplets, which can be described with a simple theoretical model

Synthesis of nanoparticles in helium droplets—A characterization comparing mass-spectra and electron microscopy data

Energy Technology Data Exchange (ETDEWEB)

Thaler, Philipp; Volk, Alexander; Lackner, Florian; Steurer, Johannes; Schnedlitz, Martin; Ernst, Wolfgang E., E-mail: wolfgang.ernst@tugraz.at [Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz (Austria); Knez, Daniel; Haberfehlner, Georg [Institute for Electron Microscopy and Nanoanalysis & Graz Centre for Electron Microscopy, TU Graz, Steyrergasse 17, A-8010 Graz (Austria)

2015-10-07

Micrometer sized helium droplets provide an extraordinary environment for the growth of nanoparticles. The method promises great potential for the preparation of core-shell particles as well as one-dimensional nanostructures, which agglomerate along quantum vortices, without involving solvents, ligands, or additives. Using a new apparatus, which enables us to record mass spectra of heavy dopant clusters (>10{sup 4} amu) and to produce samples for transmission electron microscopy simultaneously, we synthesize bare and bimetallic nanoparticles consisting of various materials (Au, Ni, Cr, and Ag). We present a systematical study of the growth process of clusters and nanoparticles inside the helium droplets, which can be described with a simple theoretical model.

Intracellular trafficking of superparamagnetic iron oxide nanoparticles conjugated with TAT peptide: 3-dimensional electron tomography analysis

Energy Technology Data Exchange (ETDEWEB)

Nair, Baiju G.; Fukuda, Takahiro; Mizuki, Toru; Hanajiri, Tatsuro [Bio-Nano Electronics Research Centre, Toyo University, Saitama 350-8585 (Japan); Maekawa, Toru, E-mail: maekawa@toyo.jp [Bio-Nano Electronics Research Centre, Toyo University, Saitama 350-8585 (Japan)

2012-05-18

Highlights: Black-Right-Pointing-Pointer We study the intracellular localisation of TAT-SPIONs using 3-D electron tomography. Black-Right-Pointing-Pointer 3-D images of TAT-SPIONs in a cell are clearly shown. Black-Right-Pointing-Pointer Release of TAT-SPIONs from endocytic vesicles into the cytoplasm is clearly shown. -- Abstract: Internalisation of nanoparticles conjugated with cell penetrating peptides is a promising approach to various drug delivery applications. Cell penetrating peptides such as transactivating transcriptional activator (TAT) peptides derived from HIV-1 proteins are effective intracellular delivery vectors for a wide range of nanoparticles and pharmaceutical agents thanks to their amicable ability to enter cells and minimum cytotoxicity. Although different mechanisms of intracellular uptake and localisation have been proposed for TAT conjugated nanoparticles, it is necessary to visualise the particles on a 3-D plane in order to investigate the actual intracellular uptake and localisation. Here, we study the intracellular localisation and trafficking of TAT peptide conjugated superparamagnetic ion oxide nanoparticles (TAT-SPIONs) using 3-D electron tomography. 3-D tomograms clearly show the location of TAT-SPIONs in a cell and their slow release from the endocytic vesicles into the cytoplasm. The present methodology may well be utilised for further investigations of the behaviours of nanoparticles in cells and eventually for the development of nano drug delivery systems.

Electron magnetic resonance and magnetooptical studies of nanoparticle-containing borate glasses

Science.gov (United States)

Kliava, Janis; Edelman, Irina; Ivanova, Oxana; Ivantsov, Ruslan; Petrakovskaja, Eleonora; Hennet, Louis; Thiaudière, Dominique; Saboungi, Marie-Louise

2011-03-01

We report electron magnetic resonance (EMR) and magnetooptical studies of borate glasses of molar composition 22.5K 2O-22.5Al 2O 3-55B 2O 3 co-doped with low concentrations of Fe 2O 3 and MnO. In as-prepared samples the paramagnetic ions, as a rule, are in diluted state. However, in the case where the ratio of the iron and manganese oxides in the charge is 3/2, magnetic nanoparticles with characteristics close to those of manganese ferrite are formed already at the first stage of the glass preparation, as evidenced by both magnetic circular dichroism (MCD) and EMR. After thermal treatment all glasses show characteristic MCD and EMR spectra, attesting to the presence of magnetic nanoparticles, predominantly including iron ions. Preliminary EXAFS measurements at the Fe K-absorption edge show an emergence of nanoparticles with a structure close to MnFe 2O 4 after annealing the glasses at 560 °C. By computer simulating the EMR spectra at variable temperatures, a superparamagnetic nature of relatively broad size and shape distribution with the average diameter of ca. 3-4 nm. The characteristic temperature-dependent shift of the apparent resonance field is explained by a strong temperature dependence of the magnetic anisotropy in the nanoparticles. The formation of magnetic nanoparticles confers to the potassium-alumina-borate glasses magnetic and magneto-optical properties typical of magnetically ordered substances. At the same time, they remain transparent in a part of the visible and near infrared spectral range and display a high Faraday rotation value.

Electron magnetic resonance and magnetooptical studies of nanoparticle-containing borate glasses

International Nuclear Information System (INIS)

Kliava, Janis; Edelman, Irina; Ivanova, Oxana; Ivantsov, Ruslan; Petrakovskaja, Eleonora; Hennet, Louis; Thiaudiere, Dominique; Saboungi, Marie-Louise

2011-01-01

We report electron magnetic resonance (EMR) and magnetooptical studies of borate glasses of molar composition 22.5K 2 O-22.5Al 2 O 3 -55B 2 O 3 co-doped with low concentrations of Fe 2 O 3 and MnO. In as-prepared samples the paramagnetic ions, as a rule, are in diluted state. However, in the case where the ratio of the iron and manganese oxides in the charge is 3/2, magnetic nanoparticles with characteristics close to those of manganese ferrite are formed already at the first stage of the glass preparation, as evidenced by both magnetic circular dichroism (MCD) and EMR. After thermal treatment all glasses show characteristic MCD and EMR spectra, attesting to the presence of magnetic nanoparticles, predominantly including iron ions. Preliminary EXAFS measurements at the Fe K-absorption edge show an emergence of nanoparticles with a structure close to MnFe 2 O 4 after annealing the glasses at 560 o C. By computer simulating the EMR spectra at variable temperatures, a superparamagnetic nature of relatively broad size and shape distribution with the average diameter of ca. 3-4 nm. The characteristic temperature-dependent shift of the apparent resonance field is explained by a strong temperature dependence of the magnetic anisotropy in the nanoparticles. The formation of magnetic nanoparticles confers to the potassium-alumina-borate glasses magnetic and magneto-optical properties typical of magnetically ordered substances. At the same time, they remain transparent in a part of the visible and near infrared spectral range and display a high Faraday rotation value. - Research Highlights: →Magnetic nanoparticles are formed in borate glasses co-doped with Fe 2 O 3 and MnO. →The nanoparticle structure is close to that of manganese ferrite. →The particles have large morphological distributions with mean size of 3-4 nm. →These glasses remain transparent in a part of visible and near infrared range. →The glasses show hysteresis in the magnetic field dependence of the

Electron magnetic resonance and magnetooptical studies of nanoparticle-containing borate glasses

Energy Technology Data Exchange (ETDEWEB)

Kliava, Janis, E-mail: j.kliava@cpmoh.u-bordeaux1.f [CPMOH, UMR 5798, Universite Bordeaux 1-CNRS, 351 Cours de la Liberation, 33405 Talence Cedex (France); Edelman, Irina; Ivanova, Oxana; Ivantsov, Ruslan; Petrakovskaja, Eleonora [L.V. Kirensky Institute of Physics, Siberian Branch of the RAS, 660036 Krasnoyarsk (Russian Federation); Hennet, Louis [CEMHTI, UPR3079 CNRS et Universite d' Orleans, 1D Avenue de la Recherche Scientifique, 45071 Orleans Cedex 2 (France); Thiaudiere, Dominique [Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Saboungi, Marie-Louise [CRMD, UMR 6619, Universite d' Orleans-CNRS, 1b Rue de la Ferollerie, 45071 Orleans Cedex 2 (France)

2011-03-15

We report electron magnetic resonance (EMR) and magnetooptical studies of borate glasses of molar composition 22.5K{sub 2}O-22.5Al{sub 2}O{sub 3}-55B{sub 2}O{sub 3} co-doped with low concentrations of Fe{sub 2}O{sub 3} and MnO. In as-prepared samples the paramagnetic ions, as a rule, are in diluted state. However, in the case where the ratio of the iron and manganese oxides in the charge is 3/2, magnetic nanoparticles with characteristics close to those of manganese ferrite are formed already at the first stage of the glass preparation, as evidenced by both magnetic circular dichroism (MCD) and EMR. After thermal treatment all glasses show characteristic MCD and EMR spectra, attesting to the presence of magnetic nanoparticles, predominantly including iron ions. Preliminary EXAFS measurements at the Fe K-absorption edge show an emergence of nanoparticles with a structure close to MnFe{sub 2}O{sub 4} after annealing the glasses at 560 {sup o}C. By computer simulating the EMR spectra at variable temperatures, a superparamagnetic nature of relatively broad size and shape distribution with the average diameter of ca. 3-4 nm. The characteristic temperature-dependent shift of the apparent resonance field is explained by a strong temperature dependence of the magnetic anisotropy in the nanoparticles. The formation of magnetic nanoparticles confers to the potassium-alumina-borate glasses magnetic and magneto-optical properties typical of magnetically ordered substances. At the same time, they remain transparent in a part of the visible and near infrared spectral range and display a high Faraday rotation value. - Research Highlights: >Magnetic nanoparticles are formed in borate glasses co-doped with Fe{sub 2}O{sub 3} and MnO. >The nanoparticle structure is close to that of manganese ferrite. > The particles have large morphological distributions with mean size of 3-4 nm. > These glasses remain transparent in a part of visible and near infrared range. > The glasses show

Integrin-targeting thermally cross-linked superparamagnetic iron oxide nanoparticles for combined cancer imaging and drug delivery

Energy Technology Data Exchange (ETDEWEB)

Yu, Mi Kyung; Park, Jinho; Jon, Sangyong [School of Life Sciences, Gwangju Institute of Science and Technology, 261 Chemdangwagi-ro, Gwangju 500-712 (Korea, Republic of); Jeong, Yong Yeon [Department of Diagnostic Radiology, Jeonnam National University Hwasun Hospital, 160 Ilsim-ri, Hwasun-eup, Jeonnam 519-809 (Korea, Republic of); Moon, Woo Kyung, E-mail: syjon@gist.ac.kr [Diagnostic Radiology, Seoul National University Hospital and the Institute of Radiation Medicine, Medical Research Center Seoul National University, Seoul 110-744 (Korea, Republic of)

2010-10-15

We report multifunctional nanoparticles that are capable of cancer targeting and simultaneous cancer imaging and therapy. The nanoparticles are composed of cyclic arginine-glycine-aspartic acid (cRGD) peptide ligand bioconjugated thermally cross-linked superparamagnetic iron oxide nanoparticles (TCL-SPION) that enable loading of the anticancer drug doxorubicin (Dox). The cyclic RGD-conjugated TCL-SPION (cRGD{sub T}CL-SPION) had a mean hydrodynamic size of 34 {+-} 8 nm with approximately 0.39 wt% of cyclic RGD attached to the surface of the nanoparticles. The cRGD{sub T}CL-SPION exhibited preferential binding towards target cancer cells (U87MG, integrin {alpha}{sub v{beta}3} +) when analyzed by T{sub 2}-weighted magnetic resonance (MR) imaging. When Dox was loaded onto the polymeric coating layers of cRGD{sub T}CL-SPION via ionic interaction, the resulting Dox-loaded cRGD{sub T}CL-SPION (Dox-cRGD{sub T}CL-SPION) showed much higher cytotoxicity in U87MG cells than Dox-TCL-SPION lacking cRGD (IC{sub 50} value of 0.02 {mu}M versus 0.12 {mu}M). These results suggest that Dox-cRGD{sub T}CL-SPION has potential for use as an integrin-targeted, combined imaging and therapeutic agent.

Chemoelectronic circuits based on metal nanoparticles

Science.gov (United States)

Yan, Yong; Warren, Scott C.; Fuller, Patrick; Grzybowski, Bartosz A.

2016-07-01

To develop electronic devices with novel functionalities and applications, various non-silicon-based materials are currently being explored. Nanoparticles have unique characteristics due to their small size, which can impart functions that are distinct from those of their bulk counterparts. The use of semiconductor nanoparticles has already led to improvements in the efficiency of solar cells, the processability of transistors and the sensitivity of photodetectors, and the optical and catalytic properties of metal nanoparticles have led to similar advances in plasmonics and energy conversion. However, metals screen electric fields and this has, so far, prevented their use in the design of all-metal nanoparticle circuitry. Here, we show that simple electronic circuits can be made exclusively from metal nanoparticles functionalized with charged organic ligands. In these materials, electronic currents are controlled by the ionic gradients of mobile counterions surrounding the ‘jammed’ nanoparticles. The nanoparticle-based electronic elements of the circuitry can be interfaced with metal nanoparticles capable of sensing various environmental changes (humidity, gas, the presence of various cations), creating electronic devices in which metal nanoparticles sense, process and ultimately report chemical signals. Because the constituent nanoparticles combine electronic and chemical sensing functions, we term these systems ‘chemoelectronic’. The circuits have switching times comparable to those of polymer electronics, selectively transduce parts-per-trillion chemical changes into electrical signals, perform logic operations, consume little power (on the scale of microwatts), and are mechanically flexible. They are also ‘green’, in the sense that they comprise non-toxic nanoparticles cast at room temperature from alcohol solutions.

Gaining Control over Radiolytic Synthesis of Uniform Sub-3-nanometer Palladium Nanoparticles: Use of Aromatic Liquids in the Electron Microscope

Energy Technology Data Exchange (ETDEWEB)

Abellan Baeza, Patricia; Parent, Lucas R.; Al Hasan, Naila M.; Park, Chiwoo; Arslan, Ilke; Karim, Ayman M.; Evans, James E.; Browning, Nigel D.

2016-01-07

Synthesizing nanomaterials of uniform shape and size is of critical importance to access and manipulate the novel structure-property relationships arising at the nanoscale. In this work we synthesize Pd nanoparticles with well-controlled size using in situ liquid-stage scanning transmission electron microscopy (STEM) and demonstrate a match between the reaction kinetics and products of the radiolytic and chemical syntheses of size-stabilized Pd nanoparticles. We quantify the effect of electron dose on the nucleation kinetics, and compare these results with in situ small angle X-ray scattering (SAXS) experiments investigating the effect of temperature during chemical synthesis. This work introduces methods for precise control of nanoparticle synthesis in the STEM and provides a means to uncover the fundamental processes behind the size and shape stabilization of nanoparticles.

Self-assembled nanogaps via seed-mediated growth of end-to-end linked gold nanorods

DEFF Research Database (Denmark)

Jain, Titoo; Westerlund, Axel Rune Fredrik; Johnson, Erik

2009-01-01

Gold nanorods (AuNRs) are of interest for a wide range of applications, ranging from imaging to molecular electronics, and they have been studied extensively for the past decade. An important issue in AuNR applications is the ability to self-assemble the rods in predictable structures...... on the nanoscale. We here present a new way to end-to-end link AuNRs with a single or few linker molecules. Whereas methods reported in the literature so far rely on modification of the AuNRs after the synthesis, we here dimerize gold nanoparticle seeds with a water-soluble dithiol-functionalized polyethylene...... that a large fraction of the rods are flexible around the hinging molecule in solution, as expected for a molecularly linked nanogap. By using excess of gold nanoparticles relative to the linking dithiol molecule, this method can provide a high probability that a single molecule is connecting the two rods...

In situ electron beam irradiated rapid growth of bismuth nanoparticles in bismuth-based glass dielectrics at room temperature

International Nuclear Information System (INIS)

Singh, Shiv Prakash; Karmakar, Basudeb

2011-01-01

In this study, in situ control growth of bismuth nanoparticles (Bi 0 NPs) was demonstrated in bismuth-based glass dielectrics under an electron beam (EB) irradiation at room temperature. The effects of EB irradiation were investigated in situ using transmission electron microscopy (TEM), selected-area electron diffraction and high-resolution transmission electron microscopy. The EB irradiation for 2–8 min enhanced the construction of bismuth nanoparticles with a rhombohedral structure and diameter of 4–9 nm. The average particle size was found to increase with the irradiation time. Bismuth metal has a melting point of 271 °C and this low melting temperature makes easy the progress of energy induced structural changes during in situ TEM observations. This is a very useful technique in nano-patterning for integrated optics and other applications.

Self-assembled nanoparticles of modified-chitosan conjugates for the sustained release of dl-α-tocopherol

DEFF Research Database (Denmark)

Quinones, Javier Perez; Gothelf, Kurt Vesterager; Kjems, Jørgen

2013-01-01

Synthetic O6-succinylated chitosan and commercial glycol chitosan were covalently linked to dl-α-tocopheryl monoesters for controlled release of vitamin E. These conjugates formed self-assembled nanoparticles in aqueous solution with 254–496 nm mean diameters and dl-α-tocopherol contents between 27...... and 39% (w/w). The particles appeared as 40–75 nm almost spherical nanoparticles when studied by scanning and transmission electron microscopy upon drying. Drug linking to chitosan matrix was confirmed by FTIR spectroscopy and proton NMR. Conjugates were also characterized by differential scanning...... calorimetry and wide-angle X-ray diffraction. In vitro tocopherol release studies performed in water at acid pH indicated a drug release dependence on drug content, hydrated particle sizes and employed chitosan derivative. Almost constant release rates were observed the first 7 h. The obtained nanoparticles...

Dynamic behavior of dual cross-linked nanoparticle networks under oscillatory shear

International Nuclear Information System (INIS)

Iyer, Balaji V S; Yashin, Victor V; Balazs, Anna C

2014-01-01

Via computer simulations, we investigate the linear and nonlinear viscoelastic response of polymer grafted nanoparticle networks subject to oscillatory shear at different amplitudes and frequencies. The individual nanoparticles are composed of a rigid spherical core and a corona of grafted polymers that encompass reactive end groups. With the overlap of the coronas on adjacent particles, the reactive end groups form permanent or labile bonds, and thus form a ‘dual cross-linked’ network. The existing labile bonds between particles can break and reform depending on the bond rupture rate, extent of deformation and the frequency of oscillation. We study how the viscoelastic behavior of the material depends on the energy of the labile bonds and identify the network characteristics that give rise to the observed viscoelastic response. We observe that with an increase in labile bond energy, the storage modulus increases while the loss modulus shows a more complex response depending on the labile bond energy. Specifically, in the case of the samples with the weaker labile bonds, the loss modulus increases monotonically, while for the samples with the stronger labile bonds, the loss modulus exhibits a minimum with an increase in frequency. We show that an increase in the storage modulus corresponds to an enhancement in the average number of bonds in the samples and the characteristics of the loss modulus depend on both the bond kinetics and the mobility of the particles in the network. Furthermore, we determine that the effective contribution of the bonds to the storage modulus decreases with increase in strain amplitude. In particular, while bond formation at small amplitude drives an increase in storage modulus, at large amplitudes it promotes clustering and formation of voids leading to strain softening. Our simulations provide a mesoscopic picture of how the nature of labile bonds affects the performance of cross-linked polymer-grafted nanoparticle networks. (paper)

Efficient electron-induced removal of oxalate ions and formation of copper nanoparticles from copper(II oxalate precursor layers

Directory of Open Access Journals (Sweden)

Kai Rückriem

2016-06-01

Full Text Available Copper(II oxalate grown on carboxy-terminated self-assembled monolayers (SAM using a step-by-step approach was used as precursor for the electron-induced synthesis of surface-supported copper nanoparticles. The precursor material was deposited by dipping the surfaces alternately in ethanolic solutions of copper(II acetate and oxalic acid with intermediate thorough rinsing steps. The deposition of copper(II oxalate and the efficient electron-induced removal of the oxalate ions was monitored by reflection absorption infrared spectroscopy (RAIRS. Helium ion microscopy (HIM reveals the formation of spherical nanoparticles with well-defined size and X-ray photoelectron spectroscopy (XPS confirms their metallic nature. Continued irradiation after depletion of oxalate does not lead to further particle growth giving evidence that nanoparticle formation is primarily controlled by the available amount of precursor.

Enzymatic cellulose oxidation is linked to lignin by long-range electron transfer

DEFF Research Database (Denmark)

Westereng, Bjorge; Cannella, David; Wittrup Agger, Jane

2015-01-01

in biological systems are only partly understood. We show here that insoluble high molecular weight lignin functions as a reservoir of electrons facilitating LPMO activity. The electrons are donated to the enzyme by long-range electron transfer involving soluble low molecular weight lignins present in plant...... cell walls. Electron transfer was confirmed by electron paramagnetic resonance spectroscopy showing that LPMO activity on cellulose changes the level of unpaired electrons in the lignin. The discovery of a long-range electron transfer mechanism links the biodegradation of cellulose and lignin and sheds...

Ultralow-Power Electronic Trapping of Nanoparticles with Sub-10 nm Gold Nanogap Electrodes.

Science.gov (United States)

Barik, Avijit; Chen, Xiaoshu; Oh, Sang-Hyun

2016-10-12

We demonstrate nanogap electrodes for rapid, parallel, and ultralow-power trapping of nanoparticles. Our device pushes the limit of dielectrophoresis by shrinking the separation between gold electrodes to sub-10 nm, thereby creating strong trapping forces at biases as low as the 100 mV ranges. Using high-throughput atomic layer lithography, we manufacture sub-10 nm gaps between 0.8 mm long gold electrodes and pattern them into individually addressable parallel electronic traps. Unlike pointlike junctions made by electron-beam lithography or larger micron-gap electrodes that are used for conventional dielectrophoresis, our sub-10 nm gold nanogap electrodes provide strong trapping forces over a mm-scale trapping zone. Importantly, our technology solves the key challenges associated with traditional dielectrophoresis experiments, such as high voltages that cause heat generation, bubble formation, and unwanted electrochemical reactions. The strongly enhanced fields around the nanogap induce particle-transport speed exceeding 10 μm/s and enable the trapping of 30 nm polystyrene nanoparticles using an ultralow bias of 200 mV. We also demonstrate rapid electronic trapping of quantum dots and nanodiamond particles on arrays of parallel traps. Our sub-10 nm gold nanogap electrodes can be combined with plasmonic sensors or nanophotonic circuitry, and their low-power electronic operation can potentially enable high-density integration on a chip as well as portable biosensing.

Gas-phase synthesis of magnesium nanoparticles : A high-resolution transmission electron microscopy study

NARCIS (Netherlands)

Kooi, B.J.; Palasantzas, G.; de Hosson, J.T.M.

2006-01-01

Magnesium nanoparticles with size above 10 nm, prepared by gas-phase syntheses, were investigated by high-resolution transmission electron microscopy. The dominant particle shape is a hexagonal prism terminated by Mg(0002) and Mg{1010} facets. Oxidation of Mg yields a MgO shell (similar to 3 nm

Electron-irradiation induced changes in the phases and photocatalytic activity of TiO{sub 2} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Sapnar, K.B.; Dhole, S.D. [Department of Physics, University of Pune, Pune 411007 (India); Bhoraskar, V.N., E-mail: vnb@physics.unipune.ac.in [Department of Physics, University of Pune, Pune 411007 (India)

2012-04-01

Highlights: Black-Right-Pointing-Pointer The phases of TiO{sub 2} nanoparticles have been changed by electron irradiation. Black-Right-Pointing-Pointer The photocatalytic activity of TiO{sub 2} gets enhanced after electron irradiation. Black-Right-Pointing-Pointer The brookite phase has appeared in TiO{sub 2} after electron irradiation. - Abstract: Samples of TiO{sub 2} nanoparticles, with mixed anatase and rutile phases, were irradiated with 6.5 MeV electrons at fluences, 1.5, 2.0, 2.5, 3.0, and 3.5 Multiplication-Sign 10{sup 15} e cm{sup -2} and characterized by several methods. With increasing electron fluence, a continuous decrease in the average particle size from {approx}80 nm to around 30 nm were observed along with a decrease in the rutile and the anatase phases of TiO{sub 2}, but at different rates, and growth of the TiO{sub 2} brookite phase at slow rate. The photocatalytic activities of different electron irradiated TiO{sub 2} samples, in the photodegradation of methylene blue, were studied by recording UV-Vis absorption spectra of the respective solutions. On electron irradiation, even though the rutile phase in the TiO{sub 2} was decreasing, the photocatalytic activity of the nanoparticles increased continuously with fluence up to {approx}3.0 Multiplication-Sign 10{sup 15} e cm{sup -2}, but decreased at 3.5 Multiplication-Sign 10{sup 15} e cm{sup -2}. The energy levels introduced by the brookite phase and the electron induced defects in TiO{sub 2} could have effectively reduced the electron-hole recombination rate in the absence of the rutile phase. The observed enhancement in the photocatalytic activity of the irradiated TiO{sub 2} is attributed to the formation of small size particles, the introduction of the oxygen related vacancies and other defects, the growth of the brookite phase, and increased absorption of radiation over the ultraviolet and visible range.

Bio-camouflage of anatase nanoparticles explored by in situ high-resolution electron microscopy.

Science.gov (United States)

Ribeiro, Ana R; Mukherjee, Arijita; Hu, Xuan; Shafien, Shayan; Ghodsi, Reza; He, Kun; Gemini-Piperni, Sara; Wang, Canhui; Klie, Robert F; Shokuhfar, Tolou; Shahbazian-Yassar, Reza; Borojevic, Radovan; Rocha, Luis A; Granjeiro, José M

2017-08-03

While titanium is the metal of choice for most prosthetics and inner body devices due to its superior biocompatibility, the discovery of Ti-containing species in the adjacent tissue as a result of wear and corrosion has been associated with autoimmune diseases and premature implant failures. Here, we utilize the in situ liquid cell transmission electron microscopy (TEM) in a liquid flow holder and graphene liquid cells (GLCs) to investigate, for the first time, the in situ nano-bio interactions between titanium dioxide nanoparticles and biological medium. This imaging and spectroscopy methodology showed the process of formation of an ionic and proteic bio-camouflage surrounding Ti dioxide (anatase) nanoparticles that facilitates their internalization by bone cells. The in situ understanding of the mechanisms of the formation of the bio-camouflage of anatase nanoparticles may contribute to the definition of strategies aimed at the manipulation of these NPs for bone regenerative purposes.

Determination of anisotropy constants of protein encapsulated iron oxide nanoparticles by electron magnetic resonance

International Nuclear Information System (INIS)

Li Hongyan; Klem, Michael T.; Sebby, Karl B.; Singel, David J.; Young, Mark; Douglas, Trevor; Idzerda, Yves U.

2009-01-01

Angle-dependent electron magnetic resonance was performed on 4.9, 8.0, and 19 nm iron oxide nanoparticles encapsulated within protein capsids and suspended in water. Measurements were taken at liquid nitrogen temperature after cooling in a 1 T field to partially align the particles. The angle dependence of the shifts in the resonance field for the iron oxide nanoparticles (synthesized within Listeria-Dps, horse spleen ferritin, and cowpea chlorotic mottle virus) all show evidence of a uniaxial anisotropy. Using a Boltzmann distribution for the particles' easy-axis direction, we are able to use the resonance field shifts to extract a value for the anisotropy energy, showing that the anisotropy energy density increases with decreasing particle size. This suggests that surface anisotropy plays a significant role in magnetic nanoparticles of this size

Determination of anisotropy constants of protein encapsulated iron oxide nanoparticles by electron magnetic resonance

Energy Technology Data Exchange (ETDEWEB)

Li Hongyan [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States); Klem, Michael T.; Sebby, Karl B.; Singel, David J. [Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States); Young, Mark [Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States); Douglas, Trevor [Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States); Idzerda, Yves U. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States)], E-mail: Idzerda@montana.edu

2009-02-15

Angle-dependent electron magnetic resonance was performed on 4.9, 8.0, and 19 nm iron oxide nanoparticles encapsulated within protein capsids and suspended in water. Measurements were taken at liquid nitrogen temperature after cooling in a 1 T field to partially align the particles. The angle dependence of the shifts in the resonance field for the iron oxide nanoparticles (synthesized within Listeria-Dps, horse spleen ferritin, and cowpea chlorotic mottle virus) all show evidence of a uniaxial anisotropy. Using a Boltzmann distribution for the particles' easy-axis direction, we are able to use the resonance field shifts to extract a value for the anisotropy energy, showing that the anisotropy energy density increases with decreasing particle size. This suggests that surface anisotropy plays a significant role in magnetic nanoparticles of this size.

Influence of Structural Defects on Biomineralized ZnS Nanoparticle Dissolution: An In-Situ Electron Microscopy Study

Energy Technology Data Exchange (ETDEWEB)

Eskelsen, Jeremy R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division; Xu, Jie [Univ. of Texas, El Paso, TX (United States). Geological Sciences; Chiu, Michelle Y. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division; Moon, Ji-Won [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division; Wilkins, Branford O. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division; Graham, David E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division; Gu, Baohua [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division; Pierce, Eric M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division

2017-12-19

The dissolution of metal sulfides, such as ZnS, plays an important role in the fate of metal contaminants in the environment. Here we have examined the dissolution behavior of ZnS nanoparticles synthesized via several abiotic and biological pathways. Specifically, the biogenic ZnS nanoparticles were produced by an anaerobic, metal-reducing bacterium Thermoanaerobacter sp. X513 in a Zn-amended, thiosulfate-containing growth medium, whereas the abiogenic ZnS nanoparticles were produced by mixing an aqueous Zn solution with either H₂S-rich gas or Na₂S solution. For biogenic synthesis, we prepared two types of samples, in the presence or absence of trace silver (Ag). The size distribution, crystal structure, aggregation behavior, and internal defects of the synthesized ZnS nanoparticles were primarily examined using high-resolution transmission electron microscopy coupled with X-ray energy dispersive spectroscopy. The characterization results show that both the biogenic and abiogenic samples were dominantly composed of sphalerite. In the absence of Ag, the biogenic ZnS nanoparticles were significantly larger (i.e., ~10 nm) than the abiogenic ones (i.e., ~3–5 nm) and contained structural defects (e.g., twins and stacking faults). The presence of trace Ag showed a restraining effect on the particle size of the biogenic ZnS, resulting in quantum-dot-sized nanoparticles (i.e., ~3 nm). In situ dissolution experiments for the synthesized ZnS were conducted with a liquid-cell coupled to a transmission electron microscope (LCTEM), and the primary factors (i.e., the presence or absence structural defects) were evaluated for their effects on the dissolution behavior using the biogenic and abiogenic ZnS nanoparticle samples with the largest average particle size. Analysis of the dissolution results (i.e., change in particle radius with time) using the Kelvin equation shows that the defect-bearing biogenic ZnS nanoparticles (γ = 0.799 J/m²) have

Characterization of palladium nanoparticles anchored on graphene oxide obtained by electron beam

Energy Technology Data Exchange (ETDEWEB)

Sobrinho, Luiza F.; Garcia, Rafael H.L.; Silva, Flávia R.O.; Neto, Almir O.; Sakata, Solange K., E-mail: lunnaquimica@usp.br, E-mail: sksakata@ipen.br [Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN-SP), São Paulo, SP (Brazil)

2017-07-01

Fuel Cells (FCs) are devices that convert chemical energy directly in electrical and thermal energy. There are two disadvantages in the process that difficult the implementation of these new power supply. The fuel, hydrogen, is highly flammable and it is difficult to transport and the catalyst is costly. FCs have been attracting worldwide attention because they are environmental friendly and potential as clean and efficient power source. However, their durability and cost have being identified as important issues in this power supply. The objective of this work is to provide a new material based on incorporation of palladium graphene oxide as catalyst. Graphene Oxide (GO) was synthesized from graphite by the modified Hummers method, in water/alcohol medium. The one-step method to incorporate nanoparticles on this nanomaterial was developed using by electron beam (EB). Additionally, this method also reduces the Graphene Oxide (GO). This nanocomposite were characterized by thermogravimetry (TG), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), x-rays diffraction (XRD) and its potential for electro catalysis were performed by cyclic voltammetry (CV) and amperometry (CA). The results showed that the incorporation of Pd on reduced GO (rGO) by electron beam was 20-40 % in mass. The process using EB and Pd nanoparticles supported on graphene oxide as a support are an alternative, in substitution of conventional methods to the production of electrodes for fuel cells. (author)

Characterization of palladium nanoparticles anchored on graphene oxide obtained by electron beam

International Nuclear Information System (INIS)

Sobrinho, Luiza F.; Garcia, Rafael H.L.; Silva, Flávia R.O.; Neto, Almir O.; Sakata, Solange K.

2017-01-01

Fuel Cells (FCs) are devices that convert chemical energy directly in electrical and thermal energy. There are two disadvantages in the process that difficult the implementation of these new power supply. The fuel, hydrogen, is highly flammable and it is difficult to transport and the catalyst is costly. FCs have been attracting worldwide attention because they are environmental friendly and potential as clean and efficient power source. However, their durability and cost have being identified as important issues in this power supply. The objective of this work is to provide a new material based on incorporation of palladium graphene oxide as catalyst. Graphene Oxide (GO) was synthesized from graphite by the modified Hummers method, in water/alcohol medium. The one-step method to incorporate nanoparticles on this nanomaterial was developed using by electron beam (EB). Additionally, this method also reduces the Graphene Oxide (GO). This nanocomposite were characterized by thermogravimetry (TG), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), x-rays diffraction (XRD) and its potential for electro catalysis were performed by cyclic voltammetry (CV) and amperometry (CA). The results showed that the incorporation of Pd on reduced GO (rGO) by electron beam was 20-40 % in mass. The process using EB and Pd nanoparticles supported on graphene oxide as a support are an alternative, in substitution of conventional methods to the production of electrodes for fuel cells. (author)

Not all that glitters is gold-Electron microscopy study on uptake of gold nanoparticles in Daphnia magna and related artifacts.

Science.gov (United States)

Jensen, Louise Helene Søgaard; Skjolding, Lars Michael; Thit, Amalie; Sørensen, Sara Nørgaard; Købler, Carsten; Mølhave, Kristian; Baun, Anders

2017-06-01

Increasing use of engineered nanoparticles has led to extensive research into their potential hazards to the environment and human health. Cellular uptake from the gut is sparsely investigated, and microscopy techniques applied for uptake studies can result in misinterpretations. Various microscopy techniques were used to investigate internalization of 10-nm gold nanoparticles in Daphnia magna gut lumen and gut epithelial cells following 24-h exposure and outline potential artifacts (i.e., high-contrast precipitates from sample preparation related to these techniques). Light sheet microscopy confirmed accumulation of gold nanoparticles in the gut lumen. Scanning transmission electron microscopy and elemental analysis revealed gold nanoparticles attached to the microvilli of gut cells. Interestingly, the peritrophic membrane appeared to act as a semipermeable barrier between the lumen and the gut epithelium, permitting only single particles through. Structures resembling nanoparticles were also observed inside gut cells. Elemental analysis could not verify these to be gold, and they were likely artifacts from the preparation, such as osmium and iron. Importantly, gold nanoparticles were found inside holocrine cells with disrupted membranes. Thus, false-positive observations of nanoparticle internalization may result from either preparation artifacts or mistaking disrupted cells for intact cells. These findings emphasize the importance of cell integrity and combining elemental analysis with the localization of internalized nanoparticles using transmission electron microscopy. Environ Toxicol Chem 2017;36:1503-1509. © 2016 SETAC. © 2016 SETAC.

Formation and Characterization of Silver Nanoparticle Composite with Poly(p-Br/F-phenylsilane).

Science.gov (United States)

Roh, Sung-Hee; Noh, Ji Eun; Woo, Hee-Gweon; Cho, Myong-Shik; Sohn, Honglae

2015-02-01

The one-pot production and structural characterization of composites of silver nanoparticles with poly(p-Br/F-phenylsilane), Br/F-PPS, have been performed. The conversion of Ag+ ions to stable Ag0 nanoparticles is mediated by the copolymer Br/F-PPS having both possibly reactive Si-H bonds in the polymer backbone and C-Br bonds in the substituents along with relatively inert C-F bonds. Transmission electron microscopy and field emission scanning electron microscopy analyses show the formation of the composites where silver nanoparticles (less than 30 nm of size) are well dispersed over the Br/F-PPS matrix. X-ray diffraction patterns are consistent with that for face-centered-cubic typed silver. The polymer solubility in toluene implys that the cleavage of C-Br bond and the Si-F dative bonding may not be occurred appreciably at ambient temperature. Nonetheless, thermogravimetric analysis data suggest that some sort of cross-linking could take place at high temperature. Most of the silver particles undergo macroscopic aggregation without Br/F-PPS, which indicates that the polysilane is necessary for stabilizing the silver nanoparticles.

Electrochemical DNA biosensors based on platinum nanoparticles combined carbon nanotubes

International Nuclear Information System (INIS)

Zhu Ningning; Chang Zhu; He Pingang; Fang Yuzhi

2005-01-01

Platinum nanoparticles were used in combination with multi-walled carbon nanotubes (MWCNTs) for fabricating sensitivity-enhanced electrochemical DNA biosensor. Multi-walled carbon nanotubes and platinum nanoparticles were dispersed in Nafion, which were used to fabricate the modification of the glassy carbon electrode (GCE) surface. Oligonucleotides with amino groups at the 5' end were covalently linked onto carboxylic groups of MWCNTs on the electrode. The hybridization events were monitored by differential pulse voltammetry (DPV) measurement of the intercalated daunomycin. Due to the ability of carbon nanotubes to promote electron-transfer reactions, the high catalytic activities of platinum nanoparticles for chemical reactions, the sensitivity of presented electrochemical DNA biosensors was remarkably improved. The detection limit of the method for target DNA was 1.0 x 10 -11 mol l -1

Preparation of starch nanoparticles in a water-in-ionic liquid microemulsion system and their drug loading and releasing properties.

Science.gov (United States)

Zhou, Gang; Luo, Zhigang; Fu, Xiong

2014-08-13

An ionic liquid microemulsion consisting of 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF₆), surfactant TX-100, 1-butanol, and water was prepared. The water-in-[Bmim]PF₆ (W/IL), bicontinuous, and [Bmim]PF₆-in-water (IL/W) microregions of the microemulsion were identified by conductivity measurements. Starch nanoparticles with a mean diameter of 91.4 nm were synthesized with epichlorohydrin as cross-linker through W/IL microemulsion cross-linking reaction at 50 °C for 4 h. Fourier transform infrared spectroscopy (FTIR) data demonstrated the formation of cross-linking bonds in starch molecules. Scanning electron microscopy (SEM) revealed that starch nanoparticles were spherical and that some particles showed aggregation formation. Furthermore, drug loading and releasing properties of starch nanoparticles were investigated with mitoxantrone hydrochloride as a drug model. This work provides an efficient and environmentally friendly approach for the preparation of starch nanoparticles, which is beneficial to their further application.

Design of a versatile chemical assembly method for patterning colloidal nanoparticles

International Nuclear Information System (INIS)

Choi, J H; Adams, S M; Ragan, R

2009-01-01

Poly(methyl methacrylate) (PMMA) domains in phase-separated polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer thin films were chemically modified for controlled placement of solution synthesized Au nanoparticles having a mean diameter of 24 nm. Colloidal Au nanoparticles functionalized with thioctic acid were immobilized on amine functionalized PMMA domains on the PS-b-PMMA template using 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride linking chemistry and N-hydroxy sulfosuccinimide stabilizer. Atomic force microscopy and scanning electron microscopy images demonstrated immobilization of Au nanoparticles commensurate with PMMA domains. Nanoparticles form into clusters of single particles, dimers, and linear chains as directed by the PMMA domain size and shape. Capillary forces influence the spacing between Au nanoparticles on PMMA domains. Inter-particle spacings below 3 nm were achieved and these assemblies of closely spaced nanoparticle clusters are expected to exhibit strong localized electromagnetic fields. Thus, these processes and material systems provide an experimental platform for studying resonantly enhanced excitations of surface plasmons as a function of material and geometric structure as well as utilization in catalytic applications.

Quantitative Transmission Electron Microscopy of Nanoparticles and Thin-Film Formation in Electroless Metallization of Polymeric Surfaces

Science.gov (United States)

Dutta, Aniruddha; Heinrich, Helge; Kuebler, Stephen; Grabill, Chris; Bhattacharya, Aniket

2011-03-01

Gold nanoparticles(Au-NPs) act as nucleation sites for electroless deposition of silver on functionalized SU8 polymeric surfaces. Here we report the nanoscale morphology of Au and Ag nanoparticles as studied by Transmission Electron Microscopy (TEM). Scanning TEM with a high-angle annular dark-field detector is used to obtain atomic number contrast. From the intensity-calibrated plan-view scanning TEM images we determine the mean thickness and the volume distribution of the Au-NPs on the surface of the functionalized polymer. We also report the height and the radius distribution of the gold nanoparticles obtained from STEM images taking into consideration the experimental errors. The cross sectional TEM images yield the density and the average distance of the Au and Ag nanoparticles on the surface of the polymer. Supported by grant NSF, Chemistry Division.

Low temperature sintering of Ag nanoparticles/graphene composites for paper based writing electronics

International Nuclear Information System (INIS)

Wang, Fuliang; He, Hu; Zhu, Haixin

2016-01-01

With the great demand in the applications of flexible electronics, the methods leading to improvements in the electrical and mechanical performance have been widely investigated. In this work, we firstly prepared a hybrid composite ink using Ag nanoparticles and graphene. Then, a hot-press sintering process was deployed to obtain the desired electrical tracks which could be applied in flexible electronics. We have systematically investigated the effects of sintering time, pressure and temperature, as well as the different percentage of weight (wt%) of graphene for the electrical and mechanical performance of sintered electrical tracks. We achieved reasonably low electrical resistivity at low sintering temperature (120 °C). Specifically, the resistivity reaches 6.19  ×  10 −8 Ω · m which is just 3.87 times higher than the value of bulk silver. Additionally, the prepared hybrid composite ink obtained better electrical reliability against bending test comparing with Ag nanoparticle ink. Finally, the optimal wt% of graphene and potential effect to the electrical and mechanical performance were also investigated. (paper)

Mechanical characterization of diesel soot nanoparticles: in situ compression in a transmission electron microscope and simulations

Science.gov (United States)

Jenei, Istvan Zoltan; Dassenoy, Fabrice; Epicier, Thierry; Khajeh, Arash; Martini, Ashlie; Uy, Dairene; Ghaednia, Hamed; Gangopadhyay, Arup

2018-02-01

Incomplete fuel burning inside an internal combustion engine results in the creation of soot in the form of nanoparticles. Some of these soot nanoparticles (SNP) become adsorbed into the lubricating oil film present on the cylinder walls, which adversely affects the tribological performance of the lubricant. In order to better understand the mechanisms underlying the wear caused by SNPs, it is important to understand the behavior of SNPs and to characterize potential changes in their mechanical properties (e.g. hardness) caused by (or during) mechanical stress. In this study, the behavior of individual SNPs originating from diesel engines was studied under compression. The experiments were performed in a transmission electron microscope using a nanoindentation device. The nanoparticles exhibited elasto-plastic behavior in response to consecutive compression cycles. From the experimental data, the Young’s modulus and hardness of the SNPs were calculated. The Young’s modulus and hardness of the nanoparticles increased with the number of compression cycles. Using an electron energy loss spectroscopy technique, it was shown that the sp2/sp3 ratio within the compressed nanoparticle decreases, which is suggested to be the cause of the increase in elasticity and hardness. In order to corroborate the experimental findings, molecular dynamics simulations of a model SNP were performed. The SNP model was constructed using carbon and hydrogen atoms with morphology and composition comparable to those observed in the experiment. The model SNP was subjected to repeated compressions between two virtual rigid walls. During the simulation, the nanoparticle exhibited elasto-plastic behavior like that in the experiments. The results of the simulations confirm that the increase in the elastic modulus and hardness is associated with a decrease in the sp2/sp3 ratio.

Covalent Immobilization of Bacillus licheniformis γ-Glutamyl Transpeptidase on Aldehyde-Functionalized Magnetic Nanoparticles

Directory of Open Access Journals (Sweden)

Meng-Chun Chi

2013-02-01

Full Text Available This work presents the synthesis and use of surface-modified iron oxide nanoparticles for the covalent immobilization of Bacillus licheniformis γ-glutamyl transpeptidase (BlGGT. Magnetic nanoparticles were prepared by an alkaline solution of divalent and trivalent iron ions, and they were subsequently treated with 3-aminopropyltriethoxysilane (APES to obtain the aminosilane-coated nanoparticles. The functional group on the particle surface and the amino group of BlGGT was then cross-linked using glutaraldehyde as the coupling reagent. The loading capacity of the prepared nanoparticles for BlGGT was 34.2 mg/g support, corresponding to 52.4% recovery of the initial activity. Monographs of transmission electron microscopy revealed that the synthesized nanoparticles had a mean diameter of 15.1 ± 3.7 nm, and the covalent cross-linking of the enzyme did not significantly change their particle size. Fourier transform infrared spectroscopy confirmed the immobilization of BlGGT on the magnetic nanoparticles. The chemical and kinetic behaviors of immobilized BlGGT are mostly consistent with those of the free enzyme. The immobilized enzyme could be recycled ten times with 36.2% retention of the initial activity and had a comparable stability respective to free enzyme during the storage period of 30 days. Collectively, the straightforward synthesis of aldehyde-functionalized nanoparticles and the efficiency of enzyme immobilization offer wide perspectives for the practical use of surface-bound BlGGT.

A study on synthesis and properties of Ag nanoparticles immobilized polyacrylamide hydrogel composites

International Nuclear Information System (INIS)

Saravanan, P.; Padmanabha Raju, M.; Alam, Sarfaraz

2007-01-01

Synthesis of Ag nanoparticles containing polyacrylamide (PAm) hydrogel composites was performed by free-radical cross-linking polymerization of acrylamide monomer in an aqueous medium containing Ag + ions. The Ag nanoparticle/PAm composites exhibit faint yellow colour and are found to stable under ambient conditions, without undergoing oxidation. TEM micrographs reveal the presence of nearly spherical and well-separated Ag nanoparticles with diameters in the range of 4-7 nm. UV-vis studies apparently show the characteristic surface plasmon band at ∼415 nm, for the existence of Ag nanoparticles within the hydrogel matrix. The effect of varying Ag + ion concentration within the PAm hydrogels on the amount of formation of Ag nanoparticles, as well as on the bulk properties of hydrogel nanocomposites such as equilibrium swelling, optical and electrical properties are studied. The Ag/PAm hydrogel nanocomposites have higher swelling ratio and lower electron transfer resistance than its corresponding conventional hydrogel

Optical and electronic properties of semiconducting nanoparticles; Optische und elektronische Eigenschaften von halbleitenden Nanopartikeln

Energy Technology Data Exchange (ETDEWEB)

Gondorf, Andreas

2011-10-07

In the present thesis, the electronic properties of semiconducting nanoparticles are investigated. The I-V-characteristics of a submonolayer of silicon nanoparticles, embedded in a Si{sub 3}N{sub 4}-matrix are calculated. The calculated results are compared to those found experimentally by Cho et al. It is investigated whether quantization effects, like the Coulomb blockade, can also be observed in systems, which contain many particles. Compacted silicon and germanium nanoparticle powders are analyzed by reflection measurements. The goal is to determine the carrier density and to find how the core-shell-structure (Ge/Si core and Ge/Si oxide shell) affects the reflection spectra. Furthermore, the influence of doping on the properties of the nanoparticles is investigated. Optical spectroscopy and magneto-transport measurements are performed on thin films, consisting of indium tin oxide nanoparticles (ITO nanoparticles). In optical spectroscopy the dielectric function in the high frequency region is determined. With the known dielectric function the charge carrier concentration as well as the mobility can be calculated. With magnetotransport measurements it is possible to measure the Hall voltage and the macroscopic conductivity. By taking into account the theoretically derived correction factor [Kharitonov, 2008] the carrier density and macroscopic mobility can be determined. Thus, the combination of the two measurement methods allows an insight into the electronic structure of this system. Additionally, layers consisting of ITO nanoparticles exhibit a decreasing resistivity when a magnetic field is applied perpendicular to the current orientation. This effect is called negative transverse magnetoresistance. The experimental results can be explained by the weak localization theory of granular systems. For the dephasing time {tau}{sub H}, however, we find a different dependence on the magnetic field than predicted by theory (experiment: 1/{tau}{sub H} {proportional

A benchmark study of commercially available copper nanoparticle inks for application in organic electronic devices

NARCIS (Netherlands)

Polino, G.; Abbel, R.; Shanmugam, S.; Bex, G.J.P.; Hendriks, R.; Brunetti, F.; Di Carlo, A.; Andriessen, R.; Galagan, Y.

2016-01-01

A set of three commercial copper nanoparticle based inkjet inks has been benchmarked with respect to their potential to form conducting printed structures for future applications in organic electronic devices. Significant differences were observed in terms of jetting properties, spreading behaviour

Colorimetric detection of manganese(II) ions using gold/dopa nanoparticles.

Science.gov (United States)

Narayanan, Kannan Badri; Park, Hyun Ho

2014-10-15

We report here a one-pot, greener, eco-friendly strategy for the synthesis of gold nanoparticles using L-dopa. The as-prepared dopa-functionalized gold nanoparticles (AuNPs/dopa) can detect low concentrations of manganese(II) metal ions in aqueous solution. The binding forces between dopa and Mn(2+) ions cause dopa-functionalized gold nanoparticles to come closer together, decreasing the interparticle distance and aggregating it with a change in color of colloidal solution from red to purplish-blue. Dynamic light scattering (DLS) analysis showed a decreased surface charge on the surface of gold nanoparticles when exposed to Mn(2+) ions, which caused cross-linking aggregation. Transmission electron microscopic (TEM) images also revealed the aggregation of gold nanoparticles with the addition of Mn(2+) ions. The extinction ratio of absorbance at 700-550nm (A700/A550) was linear against the concentration of [Mn(2+)] ions. Thus, the optical absorption spectra of gold colloidal solution before and after the addition of Mn(2+) ions reveal the concentration of Mn(2+) ions in solution. Copyright © 2014 Elsevier B.V. All rights reserved.

Application of polymers cross-linked by electron beam irradiation to electric wire industry

International Nuclear Information System (INIS)

Oda, Eisuke

1976-01-01

Applications of the polymers cross-linked by electron beam irradiation to electric wire industry as an example of dully developed utilization are reviewed. The report is divided into five parts, namely 1) radiation sources and irradiation processes, 2) development of crosslinking materials, 3) accumulation of electric charge and accumulation of heat, 4) examples of application, and 5) future prospect. Such a phenomenon as discharge destruction pattern (Lichtenberg figure) must be solved, when cable insulation materials are cross-linked by electron beam irradiation. The measures for preventing the discharge destruction are required, especially when the layers of polyethylene insulation for high voltage cables are irradiated. The accumulation of heat causes the troubles in foaming, degeneration and wire running of high potential cables, when the layers of insulation are thick. Effective promoters for cross-linking must be studied to reduce the radiation dose. The irradiators capable of irradiating wires uniformly are desirable. Electron beam accelerators will be used, as far as the radiation dose of 10 or more Mrad is required for cross-linking irradiation. If the dose of one tenth or less of the above value is required, gamma-ray sources (RI) are rather easily applicable than focused strong beam. The utilization of spent nuclear fuel is desirable. (Iwakiri, K.)

Comparison effects and electron spin resonance studies of α-Fe2O4 spinel type ferrite nanoparticles.

Science.gov (United States)

Bayrakdar, H; Yalçın, O; Cengiz, U; Özüm, S; Anigi, E; Topel, O

2014-11-11

α-Fe2O4 spinel type ferrite nanoparticles have been synthesized by cetyltrimethylammonium bromide (CTAB) and ethylenediaminetetraacetic acid (EDTA) assisted hydrothermal route by using NaOH solution. Electron spin resonance (ESR/EPR) measurements of α-Fe2O4 nanoparticles have been performed by a conventional x-band spectrometer at room temperature. The comparison effect of nanoparticles prepared by using CTAB and EDTA in different α-doping on the structural and morphological properties have been investigated in detail. The effect of EDTA-assisted synthesis for α-Fe2O4 nanoparticles are refined, and thus the spectroscopic g-factor are detected by using ESR signals. These samples can be considered as great benefits for magnetic recording media, electromagnetic and drug delivery applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Protein Corona Analysis of Silver Nanoparticles Links to Their Cellular Effects.

Science.gov (United States)

Juling, Sabine; Niedzwiecka, Alicia; Böhmert, Linda; Lichtenstein, Dajana; Selve, Sören; Braeuning, Albert; Thünemann, Andreas F; Krause, Eberhard; Lampen, Alfonso

2017-11-03

The breadth of applications of nanoparticles and the access to food-associated consumer products containing nanosized materials lead to oral human exposure to such particles. In biological fluids nanoparticles dynamically interact with biomolecules and form a protein corona. Knowledge about the protein corona is of great interest for understanding the molecular effects of particles as well as their fate inside the human body. We used a mass spectrometry-based toxicoproteomics approach to elucidate mechanisms of toxicity of silver nanoparticles and to comprehensively characterize the protein corona formed around silver nanoparticles in Caco-2 human intestinal epithelial cells. Results were compared with respect to the cellular function of proteins either affected by exposure to nanoparticles or present in the protein corona. A transcriptomic data set was included in the analyses in order to obtain a combined multiomics view of nanoparticle-affected cellular processes. A relationship between corona proteins and the proteomic or transcriptomic responses was revealed, showing that differentially regulated proteins or transcripts were engaged in the same cellular signaling pathways. Protein corona analyses of nanoparticles in cells might therefore help in obtaining information about the molecular consequences of nanoparticle treatment.

Kinetic Transition of Crystal Morphology from Nanoparticles to Dendrites during Electron Beam Induced Deposition of Gold

Science.gov (United States)

Park, Jeung Hun; Schneider, Nicholas; Bau, Haim; Kodambaka, Suneel; Ross, Frances

2015-03-01

We studied the kinetic transition from compact nanoparticle to dendritic morphology during electron beam-induced Au deposition using in situ liquid cell-based transmission electron microcopy. Radiolysis of water by electrons generates radicals and molecular species. Hydrated electrons and hydrogen and hydroxide radicals can act as reducing agents and initiate the reduction of the water-soluble precursor, HAuCl4, resulting in the precipitation of Au as nanostructures. We tracked nucleation, growth, and morphological transition of Au from movies recorded in situ, as a function of irradiated dose and liquid thickness. We identified several distinct regimes that depend on the irradiation time: (1) nucleation; (2) linear volumetric growth; (3) formation of dendritic structures; (4) coalescence and dissolution. A diffusion and reaction model for the radiolytic species and metal ions in the confined geometry of the irradiated volume is used to understand the nucleation sites and morphological transitions. We finally describe how nanoparticles can be made to grow in a stepwise manner by switching the supply of Au ions on and off electrochemically, and discuss possibilities for creating more complex nanostructures. This research was partially funded by the National Science Foundation (DMR-1310639, CMMI-1129722, and CBET-1066573).

Effectiveness of trimethylopropane trimethacrylate for the electron-beam-irradiation-induced cross-linking of polylactic acid

Energy Technology Data Exchange (ETDEWEB)

Ng, Hon-Meng [Department of Chemical Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Genting Kelang, 53300 Setapak, Kuala Lumpur (Malaysia); Bee, Soo-Tueen, E-mail: beest@utar.edu.my [Department of Chemical Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Genting Kelang, 53300 Setapak, Kuala Lumpur (Malaysia); Ratnam, C.T. [Radiation Processing Technology Division, Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor (Malaysia); Sin, Lee Tin; Phang, Yee-Yao; Tee, Tiam-Ting [Department of Chemical Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Genting Kelang, 53300 Setapak, Kuala Lumpur (Malaysia); Rahmat, A.R. [Department of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia)

2014-01-15

Highlights: • Investigation of trimethylopropane trimethacrylate (TMPTMA) on electron beam irradiated PLA. • Irradiated PLA blends were weakened by incorporation of high amount of TMPTMA. • TMPTMA interacts with polymer free radicals to build crosslinking network. -- Abstract: The purpose of this research was to investigate the effects of various loading levels of trimethylopropane trimethacrylate (TMPTMA) on the properties of polylactic acid (PLA) cross-linked via electron-beam irradiation. PLA was compounded with 3–5 wt.% of TMPTMA to induce cross-linking upon subjection to electron-beam irradiation doses of 25–250 kGy. The physical properties of the PLA samples were characterised by means of X-ray diffraction, gel fraction and scanning electron microscopy analyses on fractured surfaces after tensile tests. The presence of TMPTMA in PLA was found to effectively increase the crystallite size and gel fraction. However, higher loading levels of TMPTMA could compromise the properties of the PLA/TMPTMA samples, indicating that a larger amount of monomer free radicals might promote degradation within the substantially cross-linked amorphous phase. Irradiation-induced cross-linking in the samples could improve the cross-linking density while decreasing the elongation and interfering with the crystallisation. These effects are caused by the intensive irradiation-induced chain scission that is responsible for the deterioration of the mechanical and crystalline properties of the samples.

Effectiveness of trimethylopropane trimethacrylate for the electron-beam-irradiation-induced cross-linking of polylactic acid

International Nuclear Information System (INIS)

Ng, Hon-Meng; Bee, Soo-Tueen; Ratnam, C.T.; Sin, Lee Tin; Phang, Yee-Yao; Tee, Tiam-Ting; Rahmat, A.R.

2014-01-01

Highlights: • Investigation of trimethylopropane trimethacrylate (TMPTMA) on electron beam irradiated PLA. • Irradiated PLA blends were weakened by incorporation of high amount of TMPTMA. • TMPTMA interacts with polymer free radicals to build crosslinking network. -- Abstract: The purpose of this research was to investigate the effects of various loading levels of trimethylopropane trimethacrylate (TMPTMA) on the properties of polylactic acid (PLA) cross-linked via electron-beam irradiation. PLA was compounded with 3–5 wt.% of TMPTMA to induce cross-linking upon subjection to electron-beam irradiation doses of 25–250 kGy. The physical properties of the PLA samples were characterised by means of X-ray diffraction, gel fraction and scanning electron microscopy analyses on fractured surfaces after tensile tests. The presence of TMPTMA in PLA was found to effectively increase the crystallite size and gel fraction. However, higher loading levels of TMPTMA could compromise the properties of the PLA/TMPTMA samples, indicating that a larger amount of monomer free radicals might promote degradation within the substantially cross-linked amorphous phase. Irradiation-induced cross-linking in the samples could improve the cross-linking density while decreasing the elongation and interfering with the crystallisation. These effects are caused by the intensive irradiation-induced chain scission that is responsible for the deterioration of the mechanical and crystalline properties of the samples

Data in support of covalent attachment of tyrosinase onto cyanuric chloride crosslinked magnetic nanoparticles

Directory of Open Access Journals (Sweden)

Kourosh Abdollahi

2016-12-01

Full Text Available Preparation and characterization of cross linked amine-functionalized magnetic nanoparticles as an appropriate support for covalent immobilization on tyrosinase was presented in the study "Covalent immobilization of tyrosinase onto cyanuric chloride crosslinked amine-functionalized superparamagnetic nanoparticles: synthesis and characterization of the recyclable nanobiocatalyst" (Abdollahi et al., 2016 [1]. Herein, complementary data regarding X-ray powder diffraction (XRD to characterize the synthesized magnetic nanoparticles, and transmission electron microscopy (TEM to determine the size and morphology of tyrosinase immobilized magnetic nanoparticles (tyrosinase-MNPs were reported. The purification results of the extracted tyrosinase from mushroom Agaricus bisporus were provided in a purification table. The covalent immobilization of tyrosinase onto cyanuric chloride functionalized magnetic nanoparticles was proved by performing thermo-gravimetric and energy-dispersive X-ray spectroscopy analyses. The operational stability of immobilized tyrosinase was investigated by incubating tyrosinase-MNPs at different pH and temperatures.

A novel electrode surface fabricated by directly attaching gold nanoparticles onto NH2+ ions implanted-indium tin oxide substrate

International Nuclear Information System (INIS)

Liu Chenyao; Jiao Jiao; Chen Qunxia; Xia Ji; Li Shuoqi; Hu Jingbo; Li Qilong

2010-01-01

A new type of gold nanoparticle attached to a NH 2 + ion implanted-indium tin oxide surface was fabricated without using peculiar binder molecules, such as 3-(aminopropyl)-trimethoxysilane. A NH 2 /indium tin oxide film was obtained by implantation at an energy of 80 keV with a fluence of 5 x 10 15 ions/cm 2 . The gold nanoparticle-modified film was characterized by X-ray photoelectron spectroscopy, scanning electron microscopy and electrochemical techniques and compared with a modified bare indium tin oxide surface and 3-(aminopropyl)-trimethoxysilane linked surface, which exhibited a relatively low electron transfer resistance and high electrocatalytic activity. The results demonstrate that NH 2 + ion implanted-indium tin oxide films can provide an important route to immobilize nanoparticles, which is attractive in developing new biomaterials.

The effect of reducing agents on the electronic, magnetic and electrocatalytic properties of thiol-capped Pt/Co and Pt/Ni nanoparticles

CSIR Research Space (South Africa)

Mathe, NR

2015-05-01

Full Text Available The electronic, magnetic and electrocatalytic properties of bimetallic thiol-capped Pt/Co and Pt/Ni nanoparticles were synthesised using two reducing agents, NaBH(sub4) and N(sub2)H(sub4). X-ray diffraction analysis of the nanoparticles showed Pt...

Characterization of the Electronic Structure of Silicon Nanoparticles Using X-ray Absorption and Emission

Energy Technology Data Exchange (ETDEWEB)

Vaverka, April Susan Montoya [Univ.of California, Davis, CA (United States)

2008-01-01

Resolving open questions regarding transport in nanostructures can have a huge impact on a broad range of future technologies such as light harvesting for energy. Silicon has potential to be used in many of these applications. Understanding how the band edges of nanostructures move as a function of size, surface termination and assembly is of fundamental importance in understanding the transport properties of these materials. In this thesis work I have investigated the change in the electronic structure of silicon nanoparticle assemblies as the surface termination is changed. Nanoparticles are synthesized using a thermal evaporation technique and sizes are determined using atomic force microscopy (AFM). By passivating the particles with molecules containing alcohol groups we are able to modify the size dependent band edge shifts. Both the valence and conduction bands are measured using synchrotron based x-ray absorption spectroscopy (XAS) and soft x-ray fluorescence (SXF) techniques. Particles synthesized via recrystallization of amorphous silicon/SiO₂ multilayers of thicknesses below 10 nm are also investigated using the synchrotron techniques. These samples also show quantum confinement effects but the electronic structure is different from those synthesized via evaporation methods. The total bandgap is determined for all samples measured. The origins of these differences in the electronic structures are discussed.

Electron transfer dynamics of triphenylamine dyes bound to TiO2 nanoparticles from femtosecond stimulated Raman spectroscopy

KAUST Repository

Hoffman, David P.; Lee, Olivia P.; Millstone, Jill E.; Chen, Mark S.; Su, Timothy A.; Creelman, Mark; Frechet, Jean; Mathies, Richard A.

2013-01-01

Interfacial electron transfer between sensitizers and semiconducting nanoparticles is a crucial yet poorly understood process. To address this problem, we have used transient absorption (TA) and femtosecond stimulated Raman spectroscopy (FSRS

Gas-phase synthesis of magnesium nanoparticles: A high-resolution transmission electron microscopy study

International Nuclear Information System (INIS)

Kooi, B. J.; Palasantzas, G.; De Hosson, J. Th. M.

2006-01-01

Magnesium nanoparticles with size above 10 nm, prepared by gas-phase syntheses, were investigated by high-resolution transmission electron microscopy. The dominant particle shape is a hexagonal prism terminated by Mg(0002) and Mg(1010) facets. Oxidation of Mg yields a MgO shell (∼3 nm thick), which has an orientation relation with the Mg. Inhomogeneous facet oxidation influences their growth kinetics resulting in a relatively broad size and shape distribution. Faceted voids between Mg and MgO shells indicate a fast outward diffusion of Mg and vacancy rearrangement into voids. The faceting of polar (220) planes is assisted by electron irradiation

Long-range interfacial electron transfer and electrocatalysis of molecular scale Prussian Blue nanoparticles linked to Au(111)-electrode surfaces by different chemical contacting groups

DEFF Research Database (Denmark)

Zhu, Nan; Ulstrup, Jens; Chi, Qijin

2017-01-01

We have explored interfacial electrochemical electron transfer (ET) and electrocatalysis of 5–6 nm Prussian Blue nanoparticles (PBNPs) immobilized on Au(111)-electrode surfaces via molecular wiring with variable-length, and differently functionalized thiol-based self-assembled molecular monolayers...... (SAMs). The SAMs contain positively (−NH3+) or negatively charged (–COO–) terminal group, as well an electrostatically neutral hydrophobic terminal group (–CH3). The surface microscopic structures of the immobilized PBNPs were characterized by high-resolution atomic force microscopy (AFM) directly...... in aqueous electrolyte solution under the same conditions as for electrochemical measurements. The PBNPs displayed fast and reversible interfacial ET on all the surfaces, notably in multi-ET steps as reflected in narrow voltammetric peaks. The ET kinetics can be controlled by adjusting the length of the SAM...

Structure and properties of electron-doped Ca1-xSmxMnO3 nanoparticles

International Nuclear Information System (INIS)

Sanmathi, C.S.; Retoux, R.; Singh, M.P.; Noudem, J.

2009-01-01

In this paper, we report the structural and magnetic properties of electron-doped Ca 1-x Sm x MnO 3 (CSM) nanoparticles. The samarium's composition 'x' was varied from 0 to 0.2 with the special attention up to 0.05. Spherical 60-70 nm polycrystalline CSM nanoparticles were synthesised by chemical co-precipitation technique. Doping of Sm 3+ in antiferromagnetic CaMnO 3 has drastically altered its magnetic behavior due to the formation of ferromagnetic clusters. For example, the CSM powder with x = 0.04 displays about 115 K magnetic Curie temperature and about 0.1 emu/mole saturation magnetization. Physical properties of our nano-CSM powders are also compared with identical bulk-samples. To understand the differences, we invoked the intra-grain and inter-grain magnetic coupling process that facilitates to enhance their ferromagnetic behaviors. Unlike the bulk samples, such magnetic couplings in nanoparticles are favored by the presence of low-level crystal and interfacial defects

Direct hierarchical assembly of nanoparticles

Science.gov (United States)

Xu, Ting; Zhao, Yue; Thorkelsson, Kari

2014-07-22

The present invention provides hierarchical assemblies of a block copolymer, a bifunctional linking compound and a nanoparticle. The block copolymers form one micro-domain and the nanoparticles another micro-domain.

Contrast of Backscattered Electron SEM Images of Nanoparticles on Substrates with Complex Structure.

Science.gov (United States)

Kowoll, Thomas; Müller, Erich; Fritsch-Decker, Susanne; Hettler, Simon; Störmer, Heike; Weiss, Carsten; Gerthsen, Dagmar

2017-01-01

This study is concerned with backscattered electron scanning electron microscopy (BSE SEM) contrast of complex nanoscaled samples which consist of SiO 2 nanoparticles (NPs) deposited on indium-tin-oxide covered bulk SiO 2 and glassy carbon substrates. BSE SEM contrast of NPs is studied as function of the primary electron energy and working distance. Contrast inversions are observed which prevent intuitive interpretation of NP contrast in terms of material contrast. Experimental data is quantitatively compared with Monte-Carlo- (MC-) simulations. Quantitative agreement between experimental data and MC-simulations is obtained if the transmission characteristics of the annular semiconductor detector are taken into account. MC-simulations facilitate the understanding of NP contrast inversions and are helpful to derive conditions for optimum material and topography contrast.

An electric detection of immunoglobulin G in the enzyme-linked immunosorbent assay using an indium oxide nanoparticle ion-sensitive field-effect transistor

International Nuclear Information System (INIS)

Lee, Dongjin; Cui, Tianhong

2012-01-01

Semiconducting nanoparticle ion-sensitive field-effect transistors (ISFETs) are used to detect immunoglobulin G (IgG) in the conventional enzyme-linked immunosorbent assay (ELISA). Indium oxide and silica nanoparticles were layer-by-layer self-assembled with the oppositely charged polyelectrolyte as the electrochemical transducer and antibody immobilization site, respectively. The assay was conducted on a novel platform of indium oxide nanoparticle ISFETs, where the electric signals are generated in response to the concentration of target IgG using the labeled detecting antibody. The sandwiched ELISA structure catalyzed the conversion of the acidic substrate into neutral substance with the aid of horseradish peroxidase. The pH change in the substrate solution was detected by nanoparticle ISFETs. Normal rabbit IgG was used as a model antigen whose detection limit of 0.04 ng ml −1 was found. The facile electric detection in the conventional assay through the semiconducting nanoparticle ISFET has potential applications as a point-of-care detection or a sensing element in a lab-on-a-chip system

Cross-Linked Fluorescent Supramolecular Nanoparticles as Finite Tattoo Pigments with Controllable Intradermal Retention Times.

Science.gov (United States)

Choi, Jin-Sil; Zhu, Yazhen; Li, Hongsheng; Peyda, Parham; Nguyen, Thuy Tien; Shen, Mo Yuan; Yang, Yang Michael; Zhu, Jingyi; Liu, Mei; Lee, Mandy M; Sun, Shih-Sheng; Yang, Yang; Yu, Hsiao-Hua; Chen, Kai; Chuang, Gary S; Tseng, Hsian-Rong

2017-01-24

Tattooing has been utilized by the medical community for precisely demarcating anatomic landmarks. This practice is especially important for identifying biopsy sites of nonmelanoma skin cancer (NMSC) due to the long interval (i.e., up to 3 months) between the initial diagnostic biopsy and surgical treatment. Commercially available tattoo pigments possess several issues, which include causing poor cosmesis, being mistaken for a melanocytic lesion, requiring additional removal procedures when no longer desired, and potentially inducing inflammatory responses. The ideal tattoo pigment for labeling of skin biopsy sites for NMSC requires (i) invisibility under ambient light, (ii) fluorescence under a selective light source, (iii) a finite intradermal retention time (ca. 3 months), and (iv) biocompatibility. Herein, we introduce cross-linked fluorescent supramolecular nanoparticles (c-FSNPs) as a "finite tattoo" pigment, with optimized photophysical properties and intradermal retention time to achieve successful in vivo finite tattooing. Fluorescent supramolecular nanoparticles encapsulate a fluorescent conjugated polymer, poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene] (MPS-PPV), into a core via a supramolecular synthetic approach. FSNPs which possess fluorescent properties superior to those of the free MPS-PPV are obtained through a combinatorial screening process. Covalent cross-linking of FSNPs results in micrometer-sized c-FSNPs, which exhibit a size-dependent intradermal retention. The 1456 nm sized c-FSNPs display an ideal intradermal retention time (ca. 3 months) for NMSC lesion labeling, as observed in an in vivo tattoo study. In addition, the c-FSNPs induce undetectable inflammatory responses after tattooing. We believe that the c-FSNPs can serve as a "finite tattoo" pigment to label potential malignant NMSC lesions.

Facilitated extracellular electron transfer of Shewanella loihica PV-4 by antimony-doped tin oxide nanoparticles as active microelectrodes.

Science.gov (United States)

Zhang, Xiaojian; Liu, Huan; Wang, Jinrong; Ren, Guangyuan; Xie, Beizhen; Liu, Hong; Zhu, Ying; Jiang, Lei

2015-11-28

Dissimilatory metal reducing bacteria are capable of extracellular electron transfer (EET) to insoluble metal oxides as external electron acceptors for their anaerobic respiration, which is recognized as an important energy-conversion process in natural and engineered environments, such as in mineral cycling, bioremediation, and microbial fuel/electrolysis cells. However, the low EET efficiency remains one of the major bottlenecks for its practical application. We report firstly that the microbial current generated by Shewanella loihica PV-4 (S. loihica PV-4) could be greatly improved that is up to ca. 115 fold, by adding antimony-doped tin oxide (ATO) nanoparticles in the electrochemical reactor. The results demonstrate that the biocompatible, electrically conductive ATO nanoparticles acted as active microelectrodes could facilitate the formation of a cells/ATO composite biofilm and the reduction of the outer membrane c-type cytochromes (OM c-Cyts) that are beneficial for the electron transfer from cells to electrode. Meanwhile, a synergistic effect between the participation of OM c-Cyts and the accelerated EET mediated by cell-secreted flavins may play an important role for the enhanced current generation in the presence of ATO nanoparticles. Moreover, it is worth noting that the TCA cycle in S. loihica PV-4 cells is activated by adding ATO nanoparticles, even if the potential is poised at +0.2 V, thereby also improving the EET process. The results presented here may provide a simple and effective strategy to boost the EET of S. loihica PV-4 cells, which is conducive to providing potential applications in bioelectrochemical systems.

Radioactive gold nanoparticles with beta energy and auger electron cascades in nanomedicine: green nanotechnology and radiochemical approaches

International Nuclear Information System (INIS)

Katti, Kattesh V.

2016-01-01

In our continued efforts to apply Green Nanotechnology for the development of therapeutic radioactive gold nanoparticles, we have developed a new generation of 198 Au theranostic probes. Laminin receptors are overexpressed in a large number of human tumors and the high in vivo affinity of EGCG toward Laminin receptors has allowed us to develop Laminin receptor specific radioactive gold nanoparticles to achieve tumor specificity. This lecture will provide: (a) Oncological aspects of Auger electrons through nanomedicine; (b) details on the intervention of nuclear activation analysis and various radioanalytical approaches for the production of tumor specific radioactive gold-198 nanoparticles; and (c) full in vivo investigations on therapeutic properties of EGCG-198-AuNP agent in treating prostate tumors

Surface-enhanced Raman scattering active gold nanoparticle/nanohole arrays fabricated through electron beam lithography

Science.gov (United States)

Wu, Tsunghsueh; Lin, Yang-Wei

2018-03-01

Effective surface-enhanced Raman scattering (SERS)-active substrates from gold nanoparticle and gold nanohole arrays were successfully fabricated through electron beam lithography with precise computer-aided control of the unit size and intergap distance. Their SERS performance was evaluated using 4-mercaptobenzoic acid (4-MBA). These gold arrays yielded strong SERS signals under 785 nm laser excitation. The enhancement factors for 4-MBA molecules on the prepared gold nanoparticle and nanohole arrays maxed at 1.08 × 107 and 8.61 × 106, respectively. The observed increase in SERS enhancement was attributed to the localized surface plasmon resonance (LSPR) wavelength shifting toward the near-infrared regime when the gold nanohole diameter increased, in agreement with the theoretical prediction in this study. The contribution of LSPR to the Raman enhancement from nanohole arrays deposited on fluorine-doped tin oxide glass was elucidated by comparing SERS and transmission spectra. This simple fabrication procedure, which entails employing electron beam lithography and the controllability of the intergap distance, suggests highly promising uses of nanohole arrays as functional components in sensing and photonic devices.

Effect of gold nanoparticles on the structure and electron-transfer characteristics of glucose oxidase redox polyelectrolyte-surfactant complexes.

Science.gov (United States)

Cortez, M Lorena; Marmisollé, Waldemar; Pallarola, Diego; Pietrasanta, Lía I; Murgida, Daniel H; Ceolín, Marcelo; Azzaroni, Omar; Battaglini, Fernando

2014-10-06

Efficient electrical communication between redox proteins and electrodes is a critical issue in the operation and development of amperometric biosensors. The present study explores the advantages of a nanostructured redox-active polyelectrolyte-surfactant complex containing [Os(bpy)2Clpy](2+) (bpy=2,2'-bipyridine, py= pyridine) as the redox centers and gold nanoparticles (AuNPs) as nanodomains for boosting the electron-transfer propagation throughout the assembled film in the presence of glucose oxidase (GOx). Film structure was characterized by grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM), GOx incorporation was followed by surface plasmon resonance (SPR) and quartz-crystal microbalance with dissipation (QCM-D), whereas Raman spectroelectrochemistry and electrochemical studies confirmed the ability of the entrapped gold nanoparticles to enhance the electron-transfer processes between the enzyme and the electrode surface. Our results show that nanocomposite films exhibit five-fold increase in current response to glucose compared with analogous supramolecular AuNP-free films. The introduction of colloidal gold promotes drastic mesostructural changes in the film, which in turn leads to a rigid, amorphous interfacial architecture where nanoparticles, redox centers, and GOx remain in close proximity, thus improving the electron-transfer process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tuning the Electronic Structure of Titanium Oxide Support to Enhance the Electrochemical Activity of Platinum Nanoparticles

KAUST Repository

Shi, Feifei; Baker, L. Robert; Hervier, Antoine; Somorjai, Gabor A.; Komvopoulos, Kyriakos

2013-01-01

on pristine TiO2 support were achieved by tuning the electronic structure of the titanium oxide support of Pt nanoparticle catalysts. This was accomplished by adding oxygen vacancies or doping with fluorine. Experimental trends are interpreted in the context

Controllable fabrication of Pt nanocatalyst supported on N-doped carbon containing nickel nanoparticles for ethanol oxidation.

Science.gov (United States)

Yu, Jianguo; Dai, Tangming; Cao, Yuechao; Qu, Yuning; Li, Yao; Li, Juan; Zhao, Yongnan; Gao, Haiyan

2018-08-15

In this paper, platinum nanoparticles were deposited on a carbon carrier with the partly graphitized carbon and the highly dispersive carbon-coated nickel particles. An efficient electron transfer structure can be fabricated by controlling the contents of the deposited platinum. The high resolution transmission electron microscopy images of Pt 2 /Ni@C N-doped sample prove the electron transfer channel from Pt (1 1 1) crystal planes to graphite (1 0 0) or Ni (1 1 1) crystal planes due to these linked together crystal planes. The Pt 3 /Ni@C N-doped with low Pt contents cannot form the electron transfer structure and the Pt 1 /Ni@C N-doped with high Pt contents show an obvious aggregation of Pt nanoparticles. The electrochemical tests of all the catalysts show that the Pt 2 /Ni@C N-doped sample presents the highest catalytic activity, the strongest CO tolerance and the best catalytic stability. The high performance is attributed to the efficient electronic transport structure of the Pt 2 /Ni@C N-doped sample and the synergistic effect between Pt and Ni nanoparticles. This paper provides a promising method for enhancing the conductivity of electrode material. Copyright © 2018 Elsevier Inc. All rights reserved.

Platinum nanoparticles on gallium nitride surfaces: effect of semiconductor doping on nanoparticle reactivity.

Science.gov (United States)

Schäfer, Susanne; Wyrzgol, Sonja A; Caterino, Roberta; Jentys, Andreas; Schoell, Sebastian J; Hävecker, Michael; Knop-Gericke, Axel; Lercher, Johannes A; Sharp, Ian D; Stutzmann, Martin

2012-08-01

Platinum nanoparticles supported on n- and p-type gallium nitride (GaN) are investigated as novel hybrid systems for the electronic control of catalytic activity via electronic interactions with the semiconductor support. In situ oxidation and reduction were studied with high pressure photoemission spectroscopy. The experiments revealed that the underlying wide-band-gap semiconductor has a large influence on the chemical composition and oxygen affinity of supported nanoparticles under X-ray irradiation. For as-deposited Pt cuboctahedra supported on n-type GaN, a higher fraction of oxidized surface atoms was observed compared to cuboctahedral particles supported on p-type GaN. Under an oxygen atmosphere, immediate oxidation was recorded for nanoparticles on n-type GaN, whereas little oxidation was observed for nanoparticles on p-type GaN. Together, these results indicate that changes in the Pt chemical state under X-ray irradiation depend on the type of GaN doping. The strong interaction between the nanoparticles and the support is consistent with charge transfer of X-ray photogenerated free carriers at the semiconductor-nanoparticle interface and suggests that GaN is a promising wide-band-gap support material for photocatalysis and electronic control of catalysis.

IN SITU PREPARED TiO2 NANOPARTICLES CROSS-LINKED SULFONATED PVA MEMBRANES WITH HIGH PROTON CONDUCTIVITY FOR DMFC

Directory of Open Access Journals (Sweden)

Jignasa N. Solanki

2016-07-01

Full Text Available Organic/inorganic membranes based on sulfonated poly(vinyl alcohol (SPVA and in situ prepared TiO2 nanoparticles nanocomposite membranes with various compositions were prepared to use as proton exchange membranes in direct membrane fuel cells. Poly(vinyl alcohol (PVA was sulfonated and cross-linked separately by 4-formylbenzene-1,3-disulfonic acid disodium salt hydrate and glutaraldehyde. The ion exchange capacity and proton conductivity of the membranes increased with increasing amount of TiO2 nanoparticles. The composite membranes with 15 wt% TiO2 exhibited excellent proton conductivity of 0.0822 S cm-1, as well as remarkably low methanol permeability of 1.11×10-9 cm2 s-1. The thermal stability and durability were also superior and performance in methanol fuel cell was also reasonably good

Optimization of the fabrication of novel stealth PLA-based nanoparticles by dispersion polymerization using D-optimal mixture design.

Science.gov (United States)

Adesina, Simeon K; Wight, Scott A; Akala, Emmanuel O

2014-11-01

Nanoparticle size is important in drug delivery. Clearance of nanoparticles by cells of the reticuloendothelial system has been reported to increase with increase in particle size. Further, nanoparticles should be small enough to avoid lung or spleen filtering effects. Endocytosis and accumulation in tumor tissue by the enhanced permeability and retention effect are also processes that are influenced by particle size. We present the results of studies designed to optimize cross-linked biodegradable stealth polymeric nanoparticles fabricated by dispersion polymerization. Nanoparticles were fabricated using different amounts of macromonomer, initiators, crosslinking agent and stabilizer in a dioxane/DMSO/water solvent system. Confirmation of nanoparticle formation was by scanning electron microscopy (SEM). Particle size was measured by dynamic light scattering (DLS). D-optimal mixture statistical experimental design was used for the experimental runs, followed by model generation (Scheffe polynomial) and optimization with the aid of a computer software. Model verification was done by comparing particle size data of some suggested solutions to the predicted particle sizes. Data showed that average particle sizes follow the same trend as predicted by the model. Negative terms in the model corresponding to the cross-linking agent and stabilizer indicate the important factors for minimizing particle size.

X-ray imaging and spectroscopy of individual cobalt nanoparticles using photoemission electron microscopy

International Nuclear Information System (INIS)

Fraile Rodriguez, A.; Nolting, F.; Bansmann, J.; Kleibert, A.; Heyderman, L.J.

2007-01-01

Photoemission electron microscopy (PEEM) was employed for X-ray imaging and absorption spectroscopy of individual cobalt nanoparticles as small as 8 nm grown using an arc ion cluster source. Using lithographic markers on the samples we were able to identify the same particles with PEEM and scanning electron microscopy. Significant variations in the shape of the X-ray absorption spectra between different cobalt particles were detected. Furthermore, our data suggest that distinctive spectral information about the individual particles, such as the quenching of oxide-related features and changes in the cobalt L 3 -edge intensity, cancel out and cannot be detected in the measurement over an ensemble of particles

Contrast of Backscattered Electron SEM Images of Nanoparticles on Substrates with Complex Structure

Directory of Open Access Journals (Sweden)

Thomas Kowoll

2017-01-01

Full Text Available This study is concerned with backscattered electron scanning electron microscopy (BSE SEM contrast of complex nanoscaled samples which consist of SiO2 nanoparticles (NPs deposited on indium-tin-oxide covered bulk SiO2 and glassy carbon substrates. BSE SEM contrast of NPs is studied as function of the primary electron energy and working distance. Contrast inversions are observed which prevent intuitive interpretation of NP contrast in terms of material contrast. Experimental data is quantitatively compared with Monte-Carlo- (MC- simulations. Quantitative agreement between experimental data and MC-simulations is obtained if the transmission characteristics of the annular semiconductor detector are taken into account. MC-simulations facilitate the understanding of NP contrast inversions and are helpful to derive conditions for optimum material and topography contrast.

Albumin nanoparticles for glutathione-responsive release of cisplatin: New opportunities for medulloblastoma.

Science.gov (United States)

Catanzaro, Giuseppina; Curcio, Manuela; Cirillo, Giuseppe; Spizzirri, Umile Gianfranco; Besharat, Zein Mersini; Abballe, Luana; Vacca, Alessandra; Iemma, Francesca; Picci, Nevio; Ferretti, Elisabetta

2017-01-30

Redox-responsive nanoparticles were synthesized by desolvation of bovine serum albumin followed by disulfide-bond crosslinking with N, N'-Bis (acryloyl) cystamine. Dynamic light scattering and transmission electron microscopy studies revealed spherical nanoparticles (mean diameter: 83nm, polydispersity index: 0.3) that were glutathione-responsive. Confocal microscopy revealed rapid, efficient internalization of the nanoparticles by Daoy medulloblastoma cells and healthy controls (HaCaT keratinocytes). Cisplatin-loaded nanoparticles with drug:carrier ratios of 5%, 10%, and 20% were tested in both cell lines. The formulation with the highest drug:carrier ratio reduced Daoy and HaCaT cell viability with IC 50 values of 6.19 and 11.17μgmL -1 , respectively. The differential cytotoxicity reflects the cancer cells' higher glutathione content, which triggers more extensive disruption of the disulfide bond-mediated intra-particle cross-links, decreasing particle stability and increasing their cisplatin release. These findings support continuing efforts to improve the safety and efficacy of antineoplastic drug therapy for pediatric brain tumors using selective nanoparticle-based drug delivery systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Size effects in electronic and catalytic properties of unsupported palladium nanoparticles in electrooxidation of formic acid.

Science.gov (United States)

Zhou, Wei Ping; Lewera, Adam; Larsen, Robert; Masel, Rich I; Bagus, Paul S; Wieckowski, Andrzej

2006-07-13

We report a combined X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and chronoamperometry (CA) study of formic acid electrooxidation on unsupported palladium nanoparticle catalysts in the particle size range from 9 to 40 nm. The CV and CA measurements show that the most active catalyst is made of the smallest (9 and 11 nm) Pd nanoparticles. Besides the high reactivity, XPS data show that such nanoparticles display the highest core-level binding energy (BE) shift and the highest valence band (VB) center downshift with respect to the Fermi level. We believe therefore that we found a correlation between formic acid oxidation current and BE and VB center shifts, which, in turn, can directly be related to the electronic structure of palladium nanoparticles of different particle sizes. Clearly, such a trend using unsupported catalysts has never been reported. According to the density functional theory of heterogeneous catalysis, and mechanistic considerations, the observed shifts are caused by a weakening of the bond strength of the COOH intermediate adsorption on the catalyst surface. This, in turn, results in the increase in the formic acid oxidation rate to CO2 (and in the associated oxidation current). Overall, our measurements demonstrate the particle size effect on the electronic properties of palladium that yields different catalytic activity in the HCOOH oxidation reaction. Our work highlights the significance of the core-level binding energy and center of the d-band shifts in electrocatalysis and underlines the value of the theory that connects the center of the d-band shifts to catalytic reactivity.

Biological synthesis of silver nanoparticles

International Nuclear Information System (INIS)

Maliszewska, I; Szewczyk, K; Waszak, K

2009-01-01

Fungus-mediated synthesis of silver nanoparticles is reported. The nanosilver was formed in contact with the cell-free filtrate of Penicillium strain studied. The nanoparticles were characterized by means of the UV-Vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The synthesized nanosilver showed a absorbed maximum at 425 nm in the visible region. The SEM characterization of the fungus cells treated with silver nitrite indicated that the protein might be responsible for the reduction of silver ions. Transmission electron microscopy (TEM) micrograph showed formation of silver nanoparticles in the range of 10-100 nm.

Not all that glitters is gold - Electron microscopy study on uptake of gold nanoparticles in Daphnia magna and related artefacts

DEFF Research Database (Denmark)

Jensen, Louise Helene Søgaard; Skjolding, Lars Michael; Thit, Amalie

2017-01-01

techniques are used to investigate internalization of 10 nm gold nanoparticles in Daphnia magna gut lumen and gut epithelial cells upon 24h exposure and outline potential artefacts, i.e. high contract precipitates from sample preparation related to these techniques. Light sheet microscopy confirmed...... accumulation of gold nanoparticles in the gut lumen. Scanning transmission electron microscopy and elemental analysis revealed gold nanoparticles attached to the microvilli of gut cells. Interestingly, the peritrophic membrane appeared to act as a semipermeable barrier between the lumen and the gut epithelium...

Structural, magnetic and electronic structural properties of Mn doped CeO2 nanoparticles

Science.gov (United States)

Kumari, Kavita; Vij, Ankush; Hashim, Mohd.; Chae, K. H.; Kumar, Shalendra

2018-05-01

Nanoparticles of Ce1-xMnxO2, (x=0.0, 0.01, and 0.05) have been synthesized by using co-precipitation method, and then characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), near edge x-ray absorption fine structure (NEXAFS) spectroscopy and dc magnetization measurements. XRD results clearly showed that the all the samples have single phase nature and exclude the presence of any secondary phase. The average particle size calculated using XRD TEM measurements found to decrease with increase in Mn doping in the range of 4.0 - 9.0 nm. The structural parameters such as strain, interplaner distance and lattice parameter is observed to decrease with increase in doping. The morphology of Ce1-xMnxO2 nanoparticles measured using TEM micrographs indicate that nanoparticle have spherical shape morphology. Magnetic hysteresis curve for Ce1-xMnxO2, (x = 0.0, 0.01, and 0.05) confirms the ferromagnetic ordering room temperature. The value of saturation magnetization is observed to decrease with increase in temperature from 10 K to 300 K. The NEXAFS spectra measured at Ce M4,5 edge reveals that Ce-ions are in +4 valance state.

Electronic structure, charge transfer, and intrinsic luminescence of gadolinium oxide nanoparticles: Experiment and theory

Science.gov (United States)

Zatsepin, D. A.; Boukhvalov, D. W.; Zatsepin, A. F.; Kuznetsova, Yu. A.; Mashkovtsev, M. A.; Rychkov, V. N.; Shur, V. Ya.; Esin, A. A.; Kurmaev, E. Z.

2018-04-01

The cubic (c) and monoclinic (m) polymorphs of Gd2O3 were studied using the combined analysis of several materials science techniques - X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. Density functional theory (DFT) based calculations for the samples under study were performed as well. The cubic phase of gadolinium oxide (c-Gd2O3) synthesized using a precipitation method exhibits spheroidal-like nanoclusters with well-defined edges assembled from primary nanoparticles with an average size of 50 nm, whereas the monoclinic phase of gadolinium oxide (m-Gd2O3) deposited using explosive pyrolysis has a denser structure compared with natural gadolinia. This phase also has a structure composed of three-dimensional complex agglomerates without clear-edged boundaries that are ∼21 nm in size plus a cubic phase admixture of only 2 at.% composed of primary edge-boundary nanoparticles ∼15 nm in size. These atomic features appear in the electronic structure as different defects ([Gd…Osbnd OH] and [Gd…Osbnd O]) and have dissimilar contributions to the charge-transfer processes among the appropriate electronic states with ambiguous contributions in the Gd 5р - O 2s core-like levels in the valence band structures. The origin of [Gd…Osbnd OH] defects found by XPS was well-supported by PL analysis. The electronic and atomic structures of the synthesized gadolinias calculated using DFT were compared and discussed on the basis of the well-known joint OKT-van der Laan model, and good agreement was established.

Predicting the Oxygen-Binding Properties of Platinum Nanoparticle Ensembles by Combining High-Precision Electron Microscopy and Density Functional Theory.

Science.gov (United States)

Aarons, Jolyon; Jones, Lewys; Varambhia, Aakash; MacArthur, Katherine E; Ozkaya, Dogan; Sarwar, Misbah; Skylaris, Chris-Kriton; Nellist, Peter D

2017-07-12

Many studies of heterogeneous catalysis, both experimental and computational, make use of idealized structures such as extended surfaces or regular polyhedral nanoparticles. This simplification neglects the morphological diversity in real commercial oxygen reduction reaction (ORR) catalysts used in fuel-cell cathodes. Here we introduce an approach that combines 3D nanoparticle structures obtained from high-throughput high-precision electron microscopy with density functional theory. Discrepancies between experimental observations and cuboctahedral/truncated-octahedral particles are revealed and discussed using a range of widely used descriptors, such as electron-density, d-band centers, and generalized coordination numbers. We use this new approach to determine the optimum particle size for which both detrimental surface roughness and particle shape effects are minimized.

Preparation of TiO2-based nanotubes/nanoparticles composite thin film electrodes for their electron transport properties

International Nuclear Information System (INIS)

Zhao, Wanyu; Fu, Wuyou; Chen, Jingkuo; Li, Huayang; Bala, Hari; Wang, Xiaodong; Sun, Guang; Cao, Jianliang; Zhang, Zhanying

2015-01-01

The composite thin film electrodes were prepared with one-dimensional (1D) TiO 2 -B nanotubes (NTs) and zero-dimensional TiO 2 nanoparticles (NPs) based on different weight ratios. The electron transport properties of the NTs/NPs composite thin film electrodes applied for dye-sensitized solar cells had been investigated systematically. The results indicated that although the amount of dye adsorption decreased slightly, the devices with the NTs/NPs composite thin film electrodes could obtain higher open-circuit voltage and overall conversion efficiency compared to devices with pure TiO 2 NPs electrodes by rational tuning the weight ratio of TiO 2 -B NTs and TiO 2 NPs. When the weight ratio of TiO 2 -B NTs in the NTs/NPs composite thin film electrodes increased, the density of states and recombination rate decreased. The 1D structure of TiO 2 -B NTs can provide direct paths for electron transport, resulting in higher electron lifetime, electron diffusion coefficient and electron diffusion length. The composite thin film electrodes possess the merits of the rapid electron transport of TiO 2 -B NTs and the high surface area of TiO 2 NPs, which has great applied potential in the field of photovoltaic devices. - Highlights: • The composite thin film electrodes (CTFEs) were prepared with nanotubes and nanoparticles. • The CTFEs possess the rapid electron transport and high surface area. • The CTFEs exhibit lower recombination rate and longer electron life time. • The CTFEs have great applied potential in the field of photovoltaic devices

Exceptionally Slow Movement of Gold Nanoparticles at a Solid/Liquid Interface Investigated by Scanning Transmission Electron Microscopy.

Science.gov (United States)

Verch, Andreas; Pfaff, Marina; de Jonge, Niels

2015-06-30

Gold nanoparticles were observed to move at a liquid/solid interface 3 orders of magnitude slower than expected for the movement in a bulk liquid by Brownian motion. The nanoscale movement was studied with scanning transmission electron microscopy (STEM) using a liquid enclosure consisting of microchips with silicon nitride windows. The experiments involved a variation of the electron dose, the coating of the nanoparticles, the surface charge of the enclosing membrane, the viscosity, and the liquid thickness. The observed slow movement was not a result of hydrodynamic hindrance near a wall but instead explained by the presence of a layer of ordered liquid exhibiting a viscosity 5 orders of magnitude larger than a bulk liquid. The increased viscosity presumably led to a dramatic slowdown of the movement. The layer was formed as a result of the surface charge of the silicon nitride windows. The exceptionally slow motion is a crucial aspect of electron microscopy of specimens in liquid, enabling a direct observation of the movement and agglomeration of nanoscale objects in liquid.

Emerging synthetic strategies for core cross-linked star (CCS) polymers and applications as interfacial stabilizers: bridging linear polymers and nanoparticles.

Science.gov (United States)

Chen, Qijing; Cao, Xueteng; Xu, Yuanyuan; An, Zesheng

2013-10-01

Core cross-linked star (CCS) polymers become increasingly important in polymer science and are evaluated in many value-added applications. However, limitations exist to varied degrees for different synthetic methods. It is clear that improvement in synthetic efficiency is fundamental in driving this field moving even further. Here, the most recent advances are highlighted in synthetic strategies, including cross-linking with cross-linkers of low solubility, polymerization-induced self-assembly in aqueous-based heterogeneous media, and cross-linking via dynamic covalent bonds. The understanding of CCS polymers is also further refined to advocate their role as an intermediate between linear polymers and polymeric nanoparticles, and their use as interfacial stabilizers is rationalized within this context. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Calculating electronic tunnel currents in networks of disordered irregularly shaped nanoparticles by mapping networks to arrays of parallel nonlinear resistors

Energy Technology Data Exchange (ETDEWEB)

Aghili Yajadda, Mir Massoud [CSIRO Manufacturing Flagship, P.O. Box 218, Lindfield NSW 2070 (Australia)

2014-10-21

We have shown both theoretically and experimentally that tunnel currents in networks of disordered irregularly shaped nanoparticles (NPs) can be calculated by considering the networks as arrays of parallel nonlinear resistors. Each resistor is described by a one-dimensional or a two-dimensional array of equal size nanoparticles that the tunnel junction gaps between nanoparticles in each resistor is assumed to be equal. The number of tunnel junctions between two contact electrodes and the tunnel junction gaps between nanoparticles are found to be functions of Coulomb blockade energies. In addition, the tunnel barriers between nanoparticles were considered to be tilted at high voltages. Furthermore, the role of thermal expansion coefficient of the tunnel junction gaps on the tunnel current is taken into account. The model calculations fit very well to the experimental data of a network of disordered gold nanoparticles, a forest of multi-wall carbon nanotubes, and a network of few-layer graphene nanoplates over a wide temperature range (5-300 K) at low and high DC bias voltages (0.001 mV–50 V). Our investigations indicate, although electron cotunneling in networks of disordered irregularly shaped NPs may occur, non-Arrhenius behavior at low temperatures cannot be described by the cotunneling model due to size distribution in the networks and irregular shape of nanoparticles. Non-Arrhenius behavior of the samples at zero bias voltage limit was attributed to the disorder in the samples. Unlike the electron cotunneling model, we found that the crossover from Arrhenius to non-Arrhenius behavior occurs at two temperatures, one at a high temperature and the other at a low temperature.

Structure and function of nanoparticle-protein conjugates

International Nuclear Information System (INIS)

Aubin-Tam, M-E; Hamad-Schifferli, K

2008-01-01

Conjugation of proteins to nanoparticles has numerous applications in sensing, imaging, delivery, catalysis, therapy and control of protein structure and activity. Therefore, characterizing the nanoparticle-protein interface is of great importance. A variety of covalent and non-covalent linking chemistries have been reported for nanoparticle attachment. Site-specific labeling is desirable in order to control the protein orientation on the nanoparticle, which is crucial in many applications such as fluorescence resonance energy transfer. We evaluate methods for successful site-specific attachment. Typically, a specific protein residue is linked directly to the nanoparticle core or to the ligand. As conjugation often affects the protein structure and function, techniques to probe structure and activity are assessed. We also examine how molecular dynamics simulations of conjugates would complete those experimental techniques in order to provide atomistic details on the effect of nanoparticle attachment. Characterization studies of nanoparticle-protein complexes show that the structure and function are influenced by the chemistry of the nanoparticle ligand, the nanoparticle size, the nanoparticle material, the stoichiometry of the conjugates, the labeling site on the protein and the nature of the linkage (covalent versus non-covalent)

Link between the photonic and electronic topological phases in artificial graphene

Science.gov (United States)

Lannebère, Sylvain; Silveirinha, Mário G.

2018-04-01

In recent years the study of topological phases of matter has emerged as a very exciting field of research, both in photonics and in electronics. However, up to now the electronic and photonic properties have been regarded as totally independent. Here we establish a link between the electronic and the photonic topological phases of the same material system and theoretically demonstrate that they are intimately related. We propose a realization of the Haldane model as a patterned two-dimensional electron gas and determine its optical response using the Kubo formula. It is shown that the electronic and photonic phase diagrams of the patterned electron gas are strictly related. In particular, the system has a trivial photonic topology when the inversion symmetry is the prevalent broken symmetry, whereas it has a nontrivial photonic topology for a dominant broken time-reversal symmetry, similar to the electronic case. To confirm these predictions, we numerically demonstrate the emergence of topologically protected unidirectional electromagnetic edge states at the interface with a trivial photonic material.

Synthesis and characterisation of cross-linked chitosan composites functionalised with silver and gold nanoparticles for antimicrobial applications

Science.gov (United States)

Ryan, Catherine; Alcock, Emma; Buttimer, Finbarr; Schmidt, Michael; Clarke, David; Pemble, Martyn; Bardosova, Maria

2017-12-01

We present a study of a range of cross-linked chitosan composites with potential antimicrobial applications. They were formed by cross-linking chitosan and siloxane networks and by introducing silver and gold nanoparticles (NPs). The aim was to investigate whether adding the metal NPs to the chitosan-siloxane composite would lead to a material with enhanced antimicrobial ability as compared to chitosan itself. The composites were synthesised in hydrogel form with the metal NPs embedded in the cross-linked chitosan network. Spectroscopic and microscopic techniques were employed to investigate the structural properties of the composite and the tensile strength of the structures was measured. It was found that the addition of metal NPs did not influence the mechanical strength of the composite. A crystal violet attachment assay results displayed a significant reduction in the attachment of E. coli to the cross-linked chitosan surfaces. Release profile tests suggest that the metal NPs do not contribute to the overall antimicrobial activity under neutral conditions. The contribution to the mechanical and antimicrobial properties from cross-linking with siloxane is significant, giving rise to a versatile, durable, antimicrobial material suitable for thin film formation, wound dressings or the coating of various surfaces where robustness and antimicrobial control are required.

Protein–nanoparticle interaction in bioconjugated silver nanoparticles: A transmission electron microscopy and surface enhanced Raman spectroscopy study

Energy Technology Data Exchange (ETDEWEB)

Reymond-Laruinaz, Sébastien; Saviot, Lucien; Potin, Valérie; Marco de Lucas, María del Carmen, E-mail: delucas@u-bourgogne.fr

2016-12-15

Highlights: • Synthesis of protein-conjugated Ag nanoparticles (NPs) in absence of citrates. • NPs size and protein layer thickness determined by TEM. • SERS spectra showed the chemisorption of proteins on the surface of Ag-NPs. - Abstract: Understanding the mechanisms of interaction between proteins and noble metal nanoparticles (NPs) is crucial to extend the use of NPs in biological applications and nanomedicine. We report the synthesis of Ag-NPs:protein bioconjugates synthesized in total absence of citrates or other stabilizing agents in order to study the NP-protein interaction. Four common proteins (lysozyme, bovine serum albumin, cytochrome-C and hemoglobin) were used in this work. Transmission electron microscopy (TEM) and surface enhanced Raman spectroscopy (SERS) were mainly used to study these bioconjugated NPs. TEM images showed Ag NPs with sizes in the 5–40 nm range. The presence of a protein layer surrounding the Ag NPs was also observed by TEM. Moreover, the composition at different points of single bioconjugated NPs was probed by electron energy loss spectroscopy (EELS). The thickness of the protein layer varies in the 3–15 nm range and the Ag NPs are a few nanometers away. This allowed to obtain an enhancement of the Raman signal of the proteins in the analysis of water suspensions of bioconjugates. SERS results showed a broadening of the Raman bands of the proteins which we attribute to the contribution of different configurations of the proteins adsorbed on the Ag NPs surface. Moreover, the assignment of an intense and sharp peak in the low-frequency range to Ag–N vibrations points to the chemisorption of the proteins on the Ag-NPs surface.

Protein–nanoparticle interaction in bioconjugated silver nanoparticles: A transmission electron microscopy and surface enhanced Raman spectroscopy study

International Nuclear Information System (INIS)

Reymond-Laruinaz, Sébastien; Saviot, Lucien; Potin, Valérie; Marco de Lucas, María del Carmen

2016-01-01

Highlights: • Synthesis of protein-conjugated Ag nanoparticles (NPs) in absence of citrates. • NPs size and protein layer thickness determined by TEM. • SERS spectra showed the chemisorption of proteins on the surface of Ag-NPs. - Abstract: Understanding the mechanisms of interaction between proteins and noble metal nanoparticles (NPs) is crucial to extend the use of NPs in biological applications and nanomedicine. We report the synthesis of Ag-NPs:protein bioconjugates synthesized in total absence of citrates or other stabilizing agents in order to study the NP-protein interaction. Four common proteins (lysozyme, bovine serum albumin, cytochrome-C and hemoglobin) were used in this work. Transmission electron microscopy (TEM) and surface enhanced Raman spectroscopy (SERS) were mainly used to study these bioconjugated NPs. TEM images showed Ag NPs with sizes in the 5–40 nm range. The presence of a protein layer surrounding the Ag NPs was also observed by TEM. Moreover, the composition at different points of single bioconjugated NPs was probed by electron energy loss spectroscopy (EELS). The thickness of the protein layer varies in the 3–15 nm range and the Ag NPs are a few nanometers away. This allowed to obtain an enhancement of the Raman signal of the proteins in the analysis of water suspensions of bioconjugates. SERS results showed a broadening of the Raman bands of the proteins which we attribute to the contribution of different configurations of the proteins adsorbed on the Ag NPs surface. Moreover, the assignment of an intense and sharp peak in the low-frequency range to Ag–N vibrations points to the chemisorption of the proteins on the Ag-NPs surface.

Tuning the Electronic Structure of Titanium Oxide Support to Enhance the Electrochemical Activity of Platinum Nanoparticles

KAUST Repository

Shi, Feifei

2013-09-11

Two times higher activity and three times higher stability in methanol oxidation reaction, a 0.12 V negative shift of the CO oxidation peak potential, and a 0.07 V positive shift of the oxygen reaction potential compared to Pt nanoparticles on pristine TiO2 support were achieved by tuning the electronic structure of the titanium oxide support of Pt nanoparticle catalysts. This was accomplished by adding oxygen vacancies or doping with fluorine. Experimental trends are interpreted in the context of an electronic structure model, showing an improvement in electrochemical activity when the Fermi level of the support material in Pt/TiOx systems is close to the Pt Fermi level and the redox potential of the reaction. The present approach provides guidance for the selection of the support material of Pt/TiOx systems and may be applied to other metal-oxide support materials, thus having direct implications in the design and optimization of fuel cell catalyst supports. © 2013 American Chemical Society.

Quantitative annular dark field scanning transmission electron microscopy for nanoparticle atom-counting: What are the limits?

International Nuclear Information System (INIS)

De Backer, A; De Wael, A; Gonnissen, J; Martinez, G T; Béché, A; Van Aert, S; MacArthur, K E; Jones, L; Nellist, P D

2015-01-01

Quantitative atomic resolution annular dark field scanning transmission electron microscopy (ADF STEM) has become a powerful technique for nanoparticle atom-counting. However, a lot of nanoparticles provide a severe characterisation challenge because of their limited size and beam sensitivity. Therefore, quantitative ADF STEM may greatly benefit from statistical detection theory in order to optimise the instrumental microscope settings such that the incoming electron dose can be kept as low as possible whilst still retaining single-atom precision. The principles of detection theory are used to quantify the probability of error for atom-counting. This enables us to decide between different image performance measures and to optimise the experimental detector settings for atom-counting in ADF STEM in an objective manner. To demonstrate this, ADF STEM imaging of an industrial catalyst has been conducted using the near-optimal detector settings. For this experiment, we discussed the limits for atomcounting diagnosed by combining a thorough statistical method and detailed image simulations. (paper)

Transmission electron microscopy and Raman characterization of copper (I) oxide microspheres composed of nanoparticles

International Nuclear Information System (INIS)

Wang Wenzhong; Tu Ya; Wang Lijuan; Liang Yujie; Shi Honglong

2013-01-01

Highlights: ► Raman spectroscopy of copper (I) oxide microspheres were investigated. ► Infrared active mode is greatly activated in Raman scattering spectrum. ► Infrared active mode shows up in Raman spectrum of copper (I) oxide microspheres. ► The defects existed in spheres could be responsible for the observed Raman property. - Abstract: The high-resolution transmission electron microscope and Raman spectroscopy were used to investigate the microstructures and Raman scattering property of copper (I) oxide microspheres composed of nanoparticles. High-resolution transmission electron microscope images indicate that the copper (I) oxide microspheres are composed of nanoparticles with random growth direction, indicating that there are many defects in microspheres. The Raman spectrum shows that infrared active mode, which must be odd parity and is Raman forbidden for bulk crystal due to its inversion symmetry, is activated and shows up in Raman scattering spectrum. On the basis of investigations of the microstructure features of copper (I) oxide microspheres, we attribute the appearance of IR active mode in Raman scattering spectrum to the breakdown of the symmetry of the lattice due to the presence of defects in the prepared copper (I) oxide microspheres as observed in HRTEM images.

pH-sensitive degradable nanoparticles for highly efficient intracellular delivery of exogenous protein

Directory of Open Access Journals (Sweden)

Xu D

2013-09-01

Full Text Available Dan Xu,1 Fei Wu,1 Yinghui Chen,2,* Liangming Wei,3,* Weien Yuan1,* 1School of Pharmacy, Shanghai Jiao Tong University, Shanghai, 2Department of Neurology, Jinshan Hospital, Fudan University, Shanghai, 3Key Laboratory for Thin Film and Microfabrication of the Ministry of Education, Institute of Micro/Nano Science and Technology, Shanghai Jiao Tong University, Shanghai, People's Republic of China*These authors contributed equally to this workBackground: Encapsulating exogenous proteins into a nanosized particulate system for delivery into cells is a great challenge. To address this issue, we developed a novel nanoparticle delivery method that differs from the nanoparticles reported to date because its core was composed of cross-linked dextran glassy nanoparticles which had pH in endosome-responsive environment and the protein was loaded in the core of cross-linked dextran glassy nanoparticles.Methods: In this study, dextran in a poly(ethylene glycol aqueous two-phase system created a different chemical environment in which proteins were encapsulated very efficiently (84.3% and 89.6% for enhanced green fluorescent protein and bovine serum albumin, respectively by thermodynamically favored partition. The structures of the nanoparticles were confirmed by confocal laser scanning microscopy and scanning electron microscopy.Results: The nanoparticles had a normal size distribution and a mean diameter of 186 nm. MTT assays showed that the nanoparticles were nontoxic up to a concentration of 2000 µg/mL in human hepatocarcinoma cell line SMMC-7721, HeLa, and BRL-3A cells. Of note, confocal laser scanning microscopy studies showed that nanoparticles loaded with fluorescein isothiocyanate-bovine serum albumin were efficiently delivered and released proteins into the cytoplasm of HeLa cells. Flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling assays showed that nanoparticles with a functional protein (apoptin efficiently induced

Wrinkling of graphene membranes supported by silica nanoparticles on substrates

Science.gov (United States)

Yamamoto, Mahito; Cullen, William; Fuhrer, Michael; Einstein, Theodore; Department of Physics, University of Maryland Team

2011-03-01

The challenging endeavor of modulating the morphology of graphene via a patterned substrate to produce a controlled deformation has great potential importance for strain engineering the electronic properties of graphene. An essential step in this direction is to understand the response of graphene to substrate features of known geometry. Here we employ silica nanoparticles with a diameter of 10-100 nm to uniformly decorate Si O2 and mica substrates before depositing graphene, to promote nanoscale modulation of graphene geometry. The morphology of graphene on this modified substrate is then characterized by atomic force spectroscopy. We find that graphene on the substrate is locally raised by the supporting nanoparticles, and wrinkling propagates radially from the protrusions to form a ridge network which links the protrusions. We discuss the dependence of the wrinkled morphology on nanoparticle diameter and graphene thickness in terms of graphene elasticity and adhesion energy. Supported by NSF-MRSEC, Grant DMR 05-20471

Fabrication and Characterization of Chitosan Nanoparticle-Incorporated Quaternized Poly(Vinyl Alcohol) Composite Membranes as Solid Electrolytes for Direct Methanol Alkaline Fuel Cells

International Nuclear Information System (INIS)

Li, Pin-Chieh; Liao, Guan–Ming; Kumar, S. Rajesh; Shih, Chao-Ming; Yang, Chun-Chen; Wang, Da-Ming; Lue, Shingjiang Jessie

2016-01-01

Highlights: • Preparation of chitosan nanoparticles from bulk to enhance the degree of deacetylation. • The incorporation of chitosan nanoparticles into a QPVA matrix to form a nanocomposite membrane. • The nanocomposite constructed into thin-film membranes using the solution casting method. • To improve permeability, glutaraldehyde was cross-linked with the nanocomposite membranes. • A direct methanol alkaline fuel cell was studied at different temperatures. - Abstract: In this study, we designed a method for the preparation of chitosan nanoparticles incorporated into a quaternized poly(vinyl alcohol) (QPVA) matrix for direct methanol alkaline fuel cells (DMAFCs). The structural and morphological properties of the prepared nanocomposites were studied using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM) and dynamic laser-light scattering (DLS). The crystallinity of the nanocomposite solid electrolytes containing 0 and 10% chitosan nanoparticles were investigated using differential scanning calorimetry (DSC). The electrochemical measurement of resulting nanocomposite membranes were analyzed according to the following parameters: methanol permeability, liquid uptakes, ionic conductivity and cell performances. The composite membranes with 10% chitosan nanoparticles in a QPVA matrix (CQPVA) show suppressed methanol permeability and higher ionic conductivity than pristine QPVA. In addition, the glutaraldehyde cross-linked nanocomposite film exhibited improvement on the methanol barrier property at 80 °C. The peak power density of the DMAFCs reached 67 mW cm −2 when fed into 1 M of methanol in 6 M of KOH.

Photocatalytic inactivation of hospital-associated bacteria using titania nanoparticle coated textiles

International Nuclear Information System (INIS)

Tahir, T.; Qazi, I.A.; Hashmi, I.; Baig, M.A.

2017-01-01

Modification in hospital textiles to include disinfection properties may help in the reduction of nosocomial infections. In this study, antibacterial properties were imparted to cotton fabric by modifying it with pure and (1%) silver doped titania nanoparticles. The nanoparticles were prepared by liquid impregnation process and characterized using X-ray Diffraction (XRD) spectroscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). These nanoparticles were attached to cotton fabric using a cross linking agent succinic acid. Samples were washed at three different temperatures (30, 60 and 90 degree C), with and without detergent and for different number of cycles to test the durability of nanoparticles to the fabric. Scanning Electron Microscopy (SEM) was used for studying surface topography of fabric. Energy Dispersive X-ray fluorescence (ED-XRF) spectrometer was used to detect the titanium present on the fabric. Catalytic spectrophotometry using UV/visible spectrophotometer was used to determine titania concentration in washing effluent. The antibacterial activity of the modified fabric was examined against Methicillin Resistant Staphylococcus aureus (MRSA) under UV and fluorescent light. The maximum durability of titania nanoparticles to the fabric was retained after washing without detergent at 30 degree C. The overall results of durability testing showed that coating of nanoparticles on fabric was durable against washing at various conditions, hence suitable from an environmental perspective. Antibacterial testing showed 100% photocatalytic inactivation of MRSA after 4 and 24 h of UV and fluorescent light exposure respectively. The potential of using such textiles in hospital environment was validated through the use of modified bed linen in a local hospital for a period of three days consecutively. The viable count indicated the reduced bacterial contamination on nano-coated fabric as compared to uncoated fabric. Bed linen, curtains

Manipulation of nanoparticles of different shapes inside a scanning electron microscope

Directory of Open Access Journals (Sweden)

Boris Polyakov

2014-02-01

Full Text Available In this work polyhedron-like gold and sphere-like silver nanoparticles (NPs were manipulated on an oxidized Si substrate to study the dependence of the static friction and the contact area on the particle geometry. Measurements were performed inside a scanning electron microscope (SEM that was equipped with a high-precision XYZ-nanomanipulator. To register the occurring forces a quartz tuning fork (QTF with a glued sharp probe was used. Contact areas and static friction forces were calculated by using different models and compared with the experimentally measured force. The effect of NP morphology on the nanoscale friction is discussed.

A novel electrode surface fabricated by directly attaching gold nanoparticles onto NH{sub 2}{sup +} ions implanted-indium tin oxide substrate

Energy Technology Data Exchange (ETDEWEB)

Liu Chenyao; Jiao Jiao; Chen Qunxia [College of Chemistry, Beijing Normal University, Beijing 100875 (China); Xia Ji [Key Laboratory of Beam Technology and Material Modification of Ministry of Education, Beijing Normal University, Beijing 100875 (China); Li Shuoqi [College of Chemistry, Beijing Normal University, Beijing 100875 (China); Hu Jingbo, E-mail: hujingbo@bnu.edu.c [College of Chemistry, Beijing Normal University, Beijing 100875 (China); Li Qilong [College of Chemistry, Beijing Normal University, Beijing 100875 (China)

2010-12-01

A new type of gold nanoparticle attached to a NH{sub 2}{sup +} ion implanted-indium tin oxide surface was fabricated without using peculiar binder molecules, such as 3-(aminopropyl)-trimethoxysilane. A NH{sub 2}/indium tin oxide film was obtained by implantation at an energy of 80 keV with a fluence of 5 x 10{sup 15} ions/cm{sup 2}. The gold nanoparticle-modified film was characterized by X-ray photoelectron spectroscopy, scanning electron microscopy and electrochemical techniques and compared with a modified bare indium tin oxide surface and 3-(aminopropyl)-trimethoxysilane linked surface, which exhibited a relatively low electron transfer resistance and high electrocatalytic activity. The results demonstrate that NH{sub 2}{sup +} ion implanted-indium tin oxide films can provide an important route to immobilize nanoparticles, which is attractive in developing new biomaterials.

Nanoparticle movement: Plasmonic forces and physical constraints

International Nuclear Information System (INIS)

Batson, P.E.; Reyes-Coronado, A.; Barrera, R.G.; Rivacoba, A.; Echenique, P.M.; Aizpurua, J.

2012-01-01

Nanoparticle structures observed in aberration-corrected electron microscopes exhibit many types of behavior, some of which are dominated by intrinsic conditions, unrelated to the microscope environment. Some behaviors are clearly driven by the electron beam, however, and the question arises as to whether these are similar to intrinsic mechanisms, useful for understanding nanoscale behavior, or whether they should be regarded as unwanted modification of as-built specimens. We have studied a particular kind of beam–specimen interaction – plasmon dielectric forces caused by the electric fields imposed by a passing swift electron – identifying four types of forced motion, including both attractive and repulsive forces on single nanoparticles, and coalescent and non-coalescent forces in groups of two or more nanoparticles. We suggest that these forces might be useful for deliberate electron beam guided movement of nanoparticles. -- Highlights: ► We investigate the interaction of metal nanoparticles with a high energy electron beam. ► We find forces ranging from 0.1 to 50 pN forces between the metal particles and the beam. ► At moderate distances, dielectric forces are usually small and attractive. ► At sub-Nm distances the forces become repulsive, pushing nanoparticles away from the electron beam. ► While the repulsive behavior is predicted by electromagnetic theory, the detailed origin of the behavior is not yet understood.

Dual-color plasmonic enzyme-linked immunosorbent assay based on enzyme-mediated etching of Au nanoparticles

Science.gov (United States)

Guo, Longhua; Xu, Shaohua; Ma, Xiaoming; Qiu, Bin; Lin, Zhenyu; Chen, Guonan

2016-09-01

Colorimetric enzyme-linked immunosorbent assay utilizing 3‧-3-5‧-5-tetramethylbenzidine(TMB) as the chromogenic substrate has been widely used in the hospital for the detection of all kinds of disease biomarkers. Herein, we demonstrate a strategy to change this single-color display into dual-color responses to improve the accuracy of visual inspection. Our investigation firstly reveals that oxidation state of 3‧-3-5‧-5-tetramethylbenzidine (TMB2+) can quantitatively etch gold nanoparticles. Therefore, the incorporation of gold nanoparticles into a commercial TMB-based ELISA kit could generate dual-color responses: the solution color varied gradually from wine red (absorption peak located at ~530 nm) to colorless, and then from colorless to yellow (absorption peak located at ~450 nm) with the increase amount of targets. These dual-color responses effectively improved the sensitivity as well as the accuracy of visual inspection. For example, the proposed dual-color plasmonic ELISA is demonstrated for the detection of prostate-specific antigen (PSA) in human serum with a visual limit of detection (LOD) as low as 0.0093 ng/mL.

Assessment of a nanoparticle bridge platform for molecular electronics measurements

International Nuclear Information System (INIS)

Jafri, S H M; Blom, T; Leifer, K; Stroemme, M; Welch, K; Loefaas, H; Grigoriev, A; Ahuja, R

2010-01-01

A combination of electron beam lithography, photolithography and focused ion beam milling was used to create a nanogap platform, which was bridged by gold nanoparticles in order to make electrical measurements and assess the platform under ambient conditions. Non-functionalized electrodes were tested to determine the intrinsic response of the platform and it was found that creating devices in ambient conditions requires careful cleaning and awareness of the contributions contaminants may make to measurements. The platform was then used to make measurements on octanethiol (OT) and biphenyldithiol (BPDT) molecules by functionalizing the nanoelectrodes with the molecules prior to bridging the nanogap with nanoparticles. Measurements on OT show that it is possible to make measurements on relatively small numbers of molecules, but that a large variation in response can be expected when one of the metal-molecule junctions is physisorbed, which was partially explained by attachment of OT molecules to different sites on the surface of the Au electrode using a density functional theory calculation. On the other hand, when dealing with BPDT, high yields for device creation are very difficult to achieve under ambient conditions. Significant hysteresis in the I-V curves of BPDT was also observed, which was attributed primarily to voltage induced changes at the interface between the molecule and the metal.

Synthesis of pure colloidal silver nanoparticles with high electroconductivity for printed electronic circuits: the effect of amines on their formation in aqueous media.

Science.gov (United States)

Natsuki, Jun; Abe, Takao

2011-07-01

This paper describes a practical and convenient method to prepare stable colloidal silver nanoparticles for use in printed electronic circuits. The method uses a dispersant and two kinds of reducing agents including 2-(dimethylamino) ethanol (DMAE), which play important roles in the reduction of silver ions in an aqueous medium. The effect of DMAE and dispersant, as well as the factors affecting particle size and morphology are investigated. In the formation of the silver nanoparticles, reduction occurs rapidly at room temperature and the silver particles can be separated easily from the mixture in a short time. In addition, organic solvents are not used. Pure, small and relatively uniform particles with a diameter less than 10 nm can be obtained that exhibit high electroconductivity. The silver nanoparticles are stable, and can be isolated as a dried powder that can be fully redispersed in deionized water. This method of producing colloidal silver nanoparticles will find practical use in electronics applications. Copyright © 2011 Elsevier Inc. All rights reserved.

Influence of Fe nanoparticles diameters on the structure and electron emission studies of carbon nanotubes and multilayer graphene

International Nuclear Information System (INIS)

Sharma, Himani; Shukla, A.K.; Vankar, V.D.

2013-01-01

In this paper we report the effect of Fe film thickness on the growth, structure and electron emission characteristics of carbon nanotubes (CNTs) and multilayer graphene deposited on Si substrate. It is observed that the number of graphitic shells in carbon nanostructures (CNs) varies with the thickness of the catalyst depending on the average size of nanoparticles. Further, the Fe nanoparticles do not catalyze beyond a particular size of nanoclusters leading to the formation of multilayer graphene structure, instead of carbon nanotubes (CNTs). It is observed that the crystallinity of CNs enhances upon increasing the catalyst thickness. Multilayer graphene structures show improved crystallinity in comparison to CNTs as graphitic to defect mode intensity ratio (I D /I G ) decreases from 1.2 to 0.8. However, I 2D /I G value for multilayer graphene is found to be 1.1 confirming the presence of at least 10 layers of graphene in these samples. CNTs with smaller diameter show better electron emission properties with enhancement factor (γ C = 2.8 × 10 3 ) in comparison to multilayer graphene structure (γ C = 1.5 × 10 3 ). The better emission characteristics in CNTs are explained due to combination of electrons from edges as well as centers in comparison to the multilayer graphene. Highlights: ► Graphitic shells in CNTs and graphene depend on the size of Fe nanoparticles. ► The diameter of nanoparticles decides the morphology of CNTs and graphene. ► Multilayer graphene structures show improved crystallinity in comparison to CNTs. ► Multilayer graphene (MLG) has the γ C factor of 1.5 × 10 3 and CNTs has 2.8 × 10 3 . ► The nonlinearity in MLG may occur through change in work function.

Size-controlled synthesis of nickel nanoparticles

International Nuclear Information System (INIS)

Hou, Y.; Kondoh, H.; Ohta, T.; Gao, S.

2005-01-01

A facile reduction approach with nickel acetylacetonate, Ni(acac) 2 , and sodium borohydride or superhydride leads to monodisperse nickel nanoparticles in the presence of hexadecylamine (HDA) and trioctylphosphine oxide (TOPO). The combination of HDA and TOPO used in the conventional synthesis of semiconductor nanocrystals also provides better control over particle growth in the metal nanoparticle synthesis. The size of Ni nanoparticles can be readily tuned from 3 to 11 nm, depending on the ratio of HDA to TOPO in the reaction system. As-synthesized Ni nanoparticles have a cubic structure as characterized by power X-ray diffraction (XRD), selected-area electron diffraction (SAED). Transmission electron microscopy (TEM) images show that Ni nanoparticles have narrow size distribution. SQUID magnetometry was also used in the characterization of Ni nanoparticles. The synthetic procedure can be extended to the preparation of high quality metal or alloy nanoparticles

Characterization of magnetic core-shell nanoparticles by fluxgate magnetorelaxometry, ac susceptibility, transmission electron microscopy and photon correlation spectroscopy-A comparative study

International Nuclear Information System (INIS)

Ludwig, Frank; Heim, Erik; Schilling, Meinhard

2009-01-01

We have compared the structure parameters of magnetic core-shell nanoparticles determined from fluxgate magnetorelaxometry measurements applying the moment superposition model with the results from other methods. For the characterization of the magnetic cores, the nanoparticles are immobilized by freeze-drying. The core size distribution estimated for superparamagnetic Fe 3 O 4 magnetic nanoparticles (MNPs) with polyacrylic acid shell agrees well with that from transmission electron microscopy measurements. The distribution of hydrodynamic diameters of nanoparticle suspensions estimated from magnetorelaxometry measurements is in good agreement with that obtained from ac susceptibility and photon correlation spectroscopy measurements. Advantages of magnetorelaxometry compared to the other two integral techniques are that it is fast and the signal is less dominated by larger particles.

Charging of nanoparticles in stationary plasma in a gas aggregation cluster source

Science.gov (United States)

Blažek, J.; Kousal, J.; Biederman, H.; Kylián, O.; Hanuš, J.; Slavínská, D.

2015-10-01

Clusters that grow into nanoparticles near the magnetron target of the gas aggregation cluster source (GAS) may acquire electric charge by collecting electrons and ions or through other mechanisms like secondary- or photo-electron emissions. The region of the GAS close to magnetron may be considered as stationary plasma. The steady state charge distribution on nanoparticles can be determined by means of three possible models—fluid model, kinetic model and model employing Monte Carlo simulations—of cluster charging. In the paper the mathematical and numerical aspects of these models are analyzed in detail and close links between them are clarified. Among others it is shown that Monte Carlo simulation may be considered as a particular numerical technique of solving kinetic equations. Similarly the equations of the fluid model result, after some approximation, from averaged kinetic equations. A new algorithm solving an in principle unlimited set of kinetic equations is suggested. Its efficiency is verified on physical models based on experimental input data.

Green synthesis of silver nanoparticles using tannins

Science.gov (United States)

Raja, Pandian Bothi; Rahim, Afidah Abdul; Qureshi, Ahmad Kaleem; Awang, Khalijah

2014-09-01

Colloidal silver nanoparticles were prepared by rapid green synthesis using different tannin sources as reducing agent viz. chestnut (CN), mangrove (MG) and quebracho (QB). The aqueous silver ions when exposed to CN, MG and QB tannins were reduced which resulted in formation of silver nanoparticles. The resultant silver nanoparticles were characterized using UV-Visible, X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), and transmission electron microscopy (TEM) techniques. Furthermore, the possible mechanism of nanoparticles synthesis was also derived using FT-IR analysis. Spectroscopy analysis revealed that the synthesized nanoparticles were within 30 to 75 nm in size, while XRD results showed that nanoparticles formed were crystalline with face centered cubic geometry.

Synthesis and characterization of retrograded starch nanoparticles through homogenization and miniemulsion cross-linking.

Science.gov (United States)

Ding, Yongbo; Zheng, Jiong; Zhang, Fusheng; Kan, Jianquan

2016-10-20

A new and convenient route to synthesizing retrograded starch nanoparticles (RS3NPs) through homogenization combined with a water-in-oil miniemulsion cross-linking technique was developed. The RS3NPs were optimized using Box-Behnken experimental design. Homogenization pressure (X1), oil/water ratio (X2), and surfactant (X3) were selected as independent variables, whereas particle size was considered as a dependent variable. Results indicated that homogenization pressure was the main contributing variable for particle size. The optimum values for homogenization pressure, oil/water ratio, and surfactant were 30MPa, 9.34:1, and 2.54g, respectively, whereas the particle size was predicted to be 288.2 nm. Morphological, physical, chemical, and functional properties of the RS3NPs were the assessed. Scanning electron microscopy and dynamic light scattering images showed that RS3NP granules were broken down to size of about 222.2nm. X-ray diffraction results revealed a disruption in crystallinity. The RS3NPs exhibited a slight decrease in To, but Tp and Tc increased and narrowest Tc-To. The solubility and swelling power were also increased. New peaks at 1594.84 and 1403.65cm(-1) were observed in the FTIR graph. However, homogenization minimally influenced the antidigestibility of RS3NPs. The absorption properties improved, and the adsorption kinetic described the contact time on the adsorption of captopril onto RS3NPs. In vitro release experiment indicated that the drug was released as follows: 21% after 2h in SGF, 42.78% at the end of 8h (2h in SGF and 6h in SIF), and 92.55% after 12h in SCF. These findings may help better utilize RS3NP in biomedical applications as a drug delivery material. Copyright © 2016 Elsevier Ltd. All rights reserved.

Magnetic properties of electron-doped La0.23Ca0.77MnO3 nanoparticles

Science.gov (United States)

Markovich, V.; Jung, G.; Wisniewski, A.; Mogilyansky, D.; Puzniak, R.; Kohn, A.; Wu, X. D.; Suzuki, K.; Gorodetsky, G.

2012-09-01

Magnetic properties of electron-doped La0.23Ca0.77MnO3 manganite nanoparticles, with average size of 12 and 60 nm, prepared by the glycine-nitrate method, have been investigated in the temperature range 5-300 K and magnetic fields up to 90 kOe. It is suggested that weak ferromagnetic moment results from ferromagnetic shells of the basically antiferromagnetic nanoparticles and from domains of frustrated disordered phase in the core. Assumption of two distinct sources of ferromagnetism is supported by the appearance of two independent ferromagnetic contributions in the fit of the T 3/2 Bloch law to spontaneous magnetization. The ferromagnetic components, which are more pronounced in smaller particles, occupy only a small fraction of the nanoparticle volume and the antiferromagnetic ground state remains stable. It is found that the magnetic hysteresis loops following field cooled processes, display size-dependent horizontal and vertical shifts, namely, exhibiting exchange bias effect. Time-dependent magnetization dynamics demonstrating two relaxation rates were observed at constant magnetic fields upon cooling to T K.

Electronic Tongue Based on Nanostructured Hybrid Films of Gold Nanoparticles and Phthalocyanines for Milk Analysis

Directory of Open Access Journals (Sweden)

Luiza A. Mercante

2015-01-01

Full Text Available The use of gold nanoparticles combined with other organic and inorganic materials for designing nanostructured films has demonstrated their versatility for various applications, including optoelectronic devices and chemical sensors. In this study, we reported the synthesis and characterization of gold nanoparticles stabilized with poly(allylamine hydrochloride (Au@PAH NPs, as well as the capability of this material to form multilayer Layer-by-Layer (LbL nanostructured films with metal tetrasulfonated phthalocyanines (MTsPc. Film growth was monitored by UV-Vis absorption spectroscopy, atomic force microscopy (AFM, and Fourier transform infrared spectroscopy (FTIR. Once LbL films have been applied as active layers in chemical sensors, Au@PAH/MTsPc and PAH/MTsPc LbL films were used in an electronic tongue system for milk analysis regarding fat content. The capacitance data were treated using Principal Component Analysis (PCA, revealing the role played by the gold nanoparticles on the LbL films electrical properties, enabling this kind of system to be used for analyzing complex matrices such as milk without any prior pretreatment.

Seed-mediated synthesis of cross-linked Pt-NiO nanochains for methanol oxidation

Science.gov (United States)

Gu, Zhulan; Bin, Duan; Feng, Yue; Zhang, Ke; Wang, Jin; Yan, Bo; Li, Shumin; Xiong, Zhiping; Wang, Caiqin; Shiraishi, Yukihide; Du, Yukou

2017-07-01

A simple method was reported for employing NiO nanoparticles act as seeds and then different amounts of Pt2+ were reduced on the NiO nanoparticles, forming a cross-linked Pt-NiO nanocatalysts. These as-prepared catalysts were characterized using different physical-chemical techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results indicate that the morphology of the cross-linked Pt-NiO nanochain was successfully produced regardless of the molar ratio of Pt2+ to NiO precursors. The electrochemical characteristics of Pt-NiO nanochain catalysts were evaluated for the oxidation of methanol as a model reaction, which verify that the Pt-NiO catalysts show enhanced activity and high stability in comparison with the commercial Pt/C catalyst. The optimized ratio of Pt to NiO is 1:1, then tuned by simple adjusting the feed ratio of the precursors as well. The synthesized nanocatalysts will be found the great potential applications as electrocatalysts for fuel cells owe to their enhanced catalytic performance and long-term stability.

Electronic structure and size of TiO sub 2 nanoparticles of controlled size prepared by aerosol methods

CERN Document Server

Soriano, L; Sanchez-Agudo, M; Sanz, J M; Ahonen, P P; Kauppinen, E I; Palomares, F J; Bressler, P R

2002-01-01

A complete characterization of nanostructures has to deal both with electronic structure and dimensions. Here we present the characterization of TiO sub 2 nanoparticles of controlled size prepared by aerosol methods. The electronic structure of these nanoparticles was probed by x-ray absorption spectroscopy (XAS), the particle size by atomic force microscopy (AFM). XAS spectra show that the particles crystallize in the anatase phase upon heating at 500 sup o C, whereas further annealing at 700 sup o C give crystallites of 70 % anatase and 30 % rutile phases. Raising the temperature to 900 sup o C results in a complete transformation of the particles to rutile. AFM images reveal that the mean size of the anatase particles formed upon heating at 500 sup o C is 30 nm, whereas for the rutile particles formed upon annealing at 900 sup o C 90 nm were found. The results obtained by these techniques agree with XRD data. (author)

Disappearance of electron-hole asymmetry in nanoparticles of Nd1−xCaxMnO3(x=0.6,0.4): magnetization and electron paramagnetic resonance evidence

International Nuclear Information System (INIS)

Bhagyashree, K. S.; Bhat, S. V.

2015-01-01

We study and compare magnetic and electron paramagnetic resonance behaviors of bulk and nanoparticles of Nd 1−x Ca x MnO 3 in hole doped (x=0.4;NCMOH) and electron doped (x=0.6;NCMOE) samples. NCMOH in bulk form shows a complex temperature dependence of magnetization M(T), with a charge ordering transition at ∼250 K, an antiferromagnetic (AFM) transition at ∼150 K, and a transition to a canted AFM phase/mixed phase at ∼80 K. Bulk NCMOE behaves quite differently with just a charge ordering transition at ∼280 K, thus providing a striking example of the so called electron-hole asymmetry. While our magnetization data on bulk samples are consistent with the earlier reports, the new results on the nanoparticles bring out drastic effects of size reduction. They show that M(T) behaviors of the two nanosamples are essentially similar in addition to the absence of the charge order in them thus providing strong evidence for vanishing of the electron-hole asymmetry in nanomanganites. This conclusion is further corroborated by electron paramagnetic resonance studies which show that the large difference in the “g” values and their temperature dependences found for the two bulk samples disappears as they approach a common behavior in the corresponding nanosamples

Probing cytotoxicity of nanoparticles and organic compounds using scanning proton microscopy, scanning electron microscopy and fluorescence microscopy

Energy Technology Data Exchange (ETDEWEB)

Tong Yongpeng [Institute of Nuclear Techniques, Shenzhen University, Nanhai Avenue 3688, Shenzhen 518060 (China)], E-mail: yongpengt@yahoo.com.cn; Li Changming [School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637457 (Singapore); Liang Feng [Institute Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai 200025 (China); Chen Jianmin [Shenzhen Municipal Hospital for Chronic Disease Control and Prevention, Guangdong 518020 (China); Zhang Hong; Liu Guoqing; Sun Huibin [Institute of Nuclear Techniques, Shenzhen University, Nanhai Avenue 3688, Shenzhen 518060 (China); Luong, John H.T. [Biotechnology Research Institute, National Research Council Canada, Montreal, Quebec, H4P 2R2 (Canada)

2008-12-15

Scanning proton microscopy, scanning electron microscopy (SEM) and fluorescence microscopy have been used to probe the cytotoxicity effect of benzo[a]pyrene (BaP), ethidium bromide (EB) and nanoparticles (ZnO, Al{sub 2}O{sub 3} and TiO{sub 2}) on a T lymphoblastic leukemia Jurkat cell line. The increased calcium ion (from CaCl{sub 2}) in the culture medium stimulated the accumulation of BaP and EB inside the cell, leading to cell death. ZnO, Al{sub 2}O{sub 3} and TiO{sub 2} nanoparticles, however, showed a protective effect against these two organic compounds. Such inorganic nanoparticles complexed with BaP or EB which became less toxic to the cell. Fe{sub 2}O{sub 3} nanoparticles as an insoluble particle model scavenged by macrophage were investigated in rats. They were scavenged out of the lung tissue about 48 h after infection. This result suggest that some insoluble inorganic nanoparticles of PM (particulate matters) showed protective effects on organic toxins induced acute toxic effects as they can be scavenged by macrophage cells. Whereas, some inorganic ions such as calcium ion in PM may help environmental organic toxins to penetrate cell membrane and induce higher toxic effect.

Crystal and electronic structure study of Mn doped wurtzite ZnO nanoparticles

Directory of Open Access Journals (Sweden)

O.M. Ozkendir

2016-08-01

Full Text Available The change in the crystal and electronic structure properties of wurtzite ZnO nanoparticles was studied according to Mn doping in the powder samples. The investigations were conducted by X-ray Absorption Fine Structure Spectroscopy (XAFS technique for the samples prepared with different heating and doping processes. Electronic analysis was carried out by the collected data from the X-ray Absorption Near-Edge Structure Spectroscopy (XANES measurements. Additional crystal structure properties were studied by Extended-XAFS (EXAFS analysis. Longer heating periods for the undoped wurtzite ZnO samples were determined to own stable crystal geometries. However, for some doped samples, the distortions in the crystal were observed as a result of the low doping amounts of Mn which was treated as an impurity. Besides, the changes in oxygen locations were determined to create defects and distortions in the samples.

Electronic-level interactions of tungsten oxide with unsupported Se/Ru electrocatalytic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Lewera, Adam; Miecznikowski, Krzysztof [Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw (Poland); Hunger, Ralf [Institute of Materials Science, Darmstadt University of Technology, Darmstadt (Germany); Kolary-Zurowska, Aneta [Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw (Poland); Wieckowski, Andrzej [Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Kulesza, Pawel J., E-mail: pkulesza@chem.uw.edu.p [Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw (Poland)

2010-11-01

Se/Ru nanoparticles - a potent non-platinum catalyst towards oxygen reduction reaction - were modified by hydrated WO{sub 3} and investigated using the rotating disk/ring electrode methods and by synchrotron X-ray photoelectron spectroscopy. The modification resulted in an enhanced catalytic activity towards oxygen reduction reaction (ORR). Our data indicate that the oxygen reduction current starts ca. 70 mV more positive and formation of undesirable hydrogen peroxide has significantly decreased following the modification of Se/Ru with WO{sub 3}. X-ray photoelectron spectroscopy reveals that WO{sub 3} interacts electronically with Se/Ru as the W 4f and Se 3d line-shapes change. We therefore conclude that the electronic interactions between Se/Ru and WO{sub 3} are primarily responsible for the increase in activity and selectivity of the WO{sub 3}-modified Se/Ru towards ORR.

Electronic-level interactions of tungsten oxide with unsupported Se/Ru electrocatalytic nanoparticles

International Nuclear Information System (INIS)

Lewera, Adam; Miecznikowski, Krzysztof; Hunger, Ralf; Kolary-Zurowska, Aneta; Wieckowski, Andrzej; Kulesza, Pawel J.

2010-01-01

Se/Ru nanoparticles - a potent non-platinum catalyst towards oxygen reduction reaction - were modified by hydrated WO 3 and investigated using the rotating disk/ring electrode methods and by synchrotron X-ray photoelectron spectroscopy. The modification resulted in an enhanced catalytic activity towards oxygen reduction reaction (ORR). Our data indicate that the oxygen reduction current starts ca. 70 mV more positive and formation of undesirable hydrogen peroxide has significantly decreased following the modification of Se/Ru with WO 3 . X-ray photoelectron spectroscopy reveals that WO 3 interacts electronically with Se/Ru as the W 4f and Se 3d line-shapes change. We therefore conclude that the electronic interactions between Se/Ru and WO 3 are primarily responsible for the increase in activity and selectivity of the WO 3 -modified Se/Ru towards ORR.

Formation of palladium(0) nanoparticles at microbial surfaces

DEFF Research Database (Denmark)

Bunge, Michael; Søbjerg, Lina S; Rotaru, Amelia-Elena

2010-01-01

) nanoparticles were still deposited on autoclaved cells of C. necator that had no hydrogenase activity, suggesting a hydrogenase-independent formation mechanism. The catalytic properties of Pd(0) and bioPd(0) were determined by the amount of hydrogen released in a reaction with hypophosphite. Generally, bioPd(0...... potential. Hitherto, bacteria with the property of dissimilatory metal reduction have been in focus, although the biochemical reactions linking enzymatic Pd(II) reduction and Pd(0) deposition have not yet been identified. In this study we investigated Pd(II) reduction with formate as the electron donor......) demonstrated a lower level of activity than the Pd(0) control, possibly due to the inaccessibility of the Pd(0) fraction embedded in the cell envelope. Our results demonstrate the suitability of bacterial cells for the recovery of Pd(0), and formation and immobilization of Pd(0) nanoparticles inside the cell...

Fabrication of large area plasmonic nanoparticle grating structure on silver halide based transmission electron microscope film and its application as a surface enhanced Raman spectroscopy substrate

International Nuclear Information System (INIS)

Sudheer,; Tiwari, P.; Singh, M. N.; Sinha, A. K.; Rai, V. N.; Srivastava, A. K.; Bhartiya, S.; Mukherjee, C.

2015-01-01

The plasmonic responses of silver nanoparticle grating structures of different periods made on silver halide based electron microscope film are investigated. Raster scan of the conventional scanning electron microscope (SEM) is used to carry out electron beam lithography for fabricating the plasmonic nanoparticle grating (PNG) structures. Morphological characterization of the PNG structures, carried out by the SEM and the atomic force microscope, indicates that the depth of the groove decreases with a decrease in the grating period. Elemental characterization performed by the energy dispersive spectroscopy and the x-ray diffraction shows the presence of nanoparticles of silver in the PNG grating. The optical characterization of the gratings shows that the localized surface plasmon resonance peak shifts from 366 to 378 nm and broadens with a decrease in grating period from 10 to 2.5 μm. The surface enhanced Raman spectroscopy of the Rhodamine-6G dye coated PNG structure shows the maximum enhancement by two orders of magnitude in comparison to the randomly distributed silver nanoparticles having similar size and shape as the PNG structure

Study on growth kinetics of hexadecylamine capped CdSe nanoparticles using its electronic properties

Energy Technology Data Exchange (ETDEWEB)

Oluwafemi, S.O., E-mail: tobi_55@yahoo.co [Department of Chemistry, University of Zululand, Private Bag X1001, Kwadlangezwa 3886 (South Africa); Revaprasadu, N. [Department of Chemistry, University of Zululand, Private Bag X1001, Kwadlangezwa 3886 (South Africa)

2009-05-01

The growth kinetics of hexadecylamine (HDA) capped CdSe synthesised via a novel, mild, effective, and facile non-organometallic route was studied using its electronic properties. The emission and optical maxima of all the nanoparticles synthesised are blue-shifted as the reaction time increases indicating decrease in particle size. The UV spectra show distinct excitonic features which can be attributed to the first electronic transition [1S{sub 3/2}(h)-1S(e)] occurring in CdSe nanoparticles with band-edge luminescence in their emission spectra. The extinction coefficient was determined for convenient and accurate measurements of the concentration of the nanocrystals. Nucleation is very fast and well separated from particle growth under this reaction condition. Two distinguishable stages of growth were observed: an early stage 0-10 min characterised by fast growth, with narrow size distribution and the late stage characterised by slow growth with slight defocusing of size distribution and large particle sizes. The diameter of the size ranges from 2.2 to 3.0 nm. About 94% of the available monomer concentration was consumed during the growth and the solubility of 3.0 nm CdSe in hexadecylamine is measured to be 9.216x10{sup -7} M{sup 2} at 433 deg. K.

Understanding Atom Probe Tomography of Oxide-Supported Metal Nanoparticles by Correlation with Atomic-Resolution Electron Microscopy and Field Evaporation Simulation.

Science.gov (United States)

Devaraj, Arun; Colby, Robert; Vurpillot, François; Thevuthasan, Suntharampillai

2014-04-17

Oxide-supported metal nanoparticles are widely used in heterogeneous catalysis. The increasingly detailed design of such catalysts necessitates three-dimensional characterization with high spatial resolution and elemental selectivity. Laser-assisted atom probe tomography (APT) is uniquely suited to the task but faces challenges with the evaporation of metal/insulator systems. Correlation of APT with aberration-corrected scanning transmission electron microscopy (STEM), for Au nanoparticles embedded in MgO, reveals preferential evaporation of the MgO and an inaccurate assessment of nanoparticle composition. Finite element field evaporation modeling is used to illustrate the evolution of the evaporation front. Nanoparticle composition is most accurately predicted when the MgO is treated as having a locally variable evaporation field, indicating the importance of considering laser-oxide interactions and the evaporation of various molecular oxide ions. These results demonstrate the viability of APT for analysis of oxide-supported metal nanoparticles, highlighting the need for developing a theoretical framework for the evaporation of heterogeneous materials.

Transformations of gold nanoparticles investigated using variable temperature high-resolution transmission electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Young, N.P. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Huis, M.A. van; Zandbergen, H.W. [Kavli Institute of Nanoscience, Delft University of Technolgy, Lorentzweg 1, NL-2628CJ, Delft, The Netherlands. (Netherlands); Xu, H. [Department of Geology and Geophysics, and Materials Science Program, University of Wisconsin-Madison, Madison, WI (United States); Kirkland, A.I., E-mail: angus.kirkland@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

2010-04-15

Recently designed advanced in-situ specimen holders for transmission electron microscopy (TEM) have been used in studies of gold nanoparticles. We report results of variable temperature TEM experiments in which structural transformations have been correlated with specimen temperature, allowing general trends to be identified. Transformation to a decahedral morphology for particles in the size range 5-12 nm was observed for the majority of particles regardless of their initial structure. Following in-situ annealing, decahedra were found to be stable at room temperature, confirming this as the equilibrium morphology, in agreement with recently calculated phase diagrams. Other transitions at low temperature in addition to surface roughening have also been observed and correlated with the same nanoscale phase diagram. Investigations of gold particles at high temperature have revealed evidence for co-existing solid and liquid phases. Overall, these results are important in a more precise understanding of the structure and action of catalytic gold nanoparticles and in the experimental verification of theoretical calculations.

Microfluidic conceived Trojan microcarriers for oral delivery of nanoparticles.

Science.gov (United States)

Khan, Ikram Ullah; Serra, Christophe A; Anton, Nicolas; Er-Rafik, Mériem; Blanck, C; Schmutz, Marc; Kraus, Isabelle; Messaddeq, Nadia; Sutter, Christophe; Anton, Halina; Klymchenko, Andrey S; Vandamme, Thierry F

2015-09-30

In this study, we report on a novel method for the synthesis of poly(acrylamide) Trojan microparticles containing ketoprofen loaded poly(ethyl acrylate) or poly(methyl acrylate) nanoparticles. To develop these composite particles, a polymerizable nanoemulsion was used as a template. This nanoemulsion was obtained in an elongational-flow micromixer (μRMX) which was linked to a capillary-based microfluidic device for its emulsification into micron range droplets. Downstream, the microdroplets were hardened into Trojan particles in the size range of 213-308 μm by UV initiated free radical polymerization. The nanoemulsion size varied from 98 -132 nm upon changes in surfactant concentration and number of operating cycles in μRMX. SEM and confocal microscopy confirmed the Trojan morphology. Under SEM it was observed that the polymerization reduced the size of the nanoemulsion down to 20-32 nm for poly(ethyl acrylate) and 10-15 nm for poly(methyl acrylate) nanoparticles. This shrinkage was confirmed by cryo-TEM studies. We further showed that Trojan microparticles released embedded nanoparticles on contact with suitable media as confirmed by transmission electron microscopy. In a USP phosphate buffer solution of pH 6.8, Trojan microparticles containing poly(ethyl acrylate) nanoparticles released 35% of encapsulated ketoprofen over 24h. The low release of the drug was attributed to the overall low concentration of nanoparticles and attachment of some of nanoparticles to the poly(acrylamide) matrix. Thus, this novel method has shown possibility to develop Trojan particles convieniently with potential to deliver nanoparticles in the gastrointestinal tract. Copyright © 2015 Elsevier B.V. All rights reserved.

Gum arabic modified Fe3O4 nanoparticles cross linked with collagen for isolation of bacteria

Directory of Open Access Journals (Sweden)

Chittor Raghuraman

2010-12-01

Full Text Available Abstract Background Multifunctional magnetic nanoparticles are important class of materials in the field of nanobiotechnology, as it is an emerging area of research for material science and molecular biology researchers. One of the various methods to obtain multifunctional nanomaterials, molecular functionalization by attaching organic functional groups to nanomagnetic materials is an important technique. Recently, functionalized magnetic nanoparticles have been demonstrated to be useful in isolation/detection of dangerous pathogens (bacteria/viruses for human life. Iron (Fe based material especially FePt is used in the isolation of ultralow concentrations (2 cfu/ml of bacteria in less time and it has been demonstrated that van-FePt may be used as an alternative fast detection technique with respect to conventional polymerase chain reaction (PCR method. However, still further improved demonstrations are necessary with interest to biocompatibility and green chemistry. Herein, we report the synthesis of Fe3O4 nanoparticles by template medication and its application for the detection/isolation of S. aureus bacteria. Results The reduction of anhydrous Iron chloride (FeCl3 in presence of sodium borohydride and water soluble polyelectrolyte (polydiallyldimethyl ammonium chloride, PDADMAC produces black precipitates. The X-ray diffraction (XRD, XPS and TEM analysis of the precipitates dried at 373 K demonstrated the formation of nanocrystalline Fe3O4. Moreover, scanning electron microscopy (SEM showed isolated staphylococcous aureus (S. aureus bacteria at ultralow concentrations using collagen coated gum arabic modified iron oxide nanoparticles (CCGAMION. Conclusion We are able to synthesize nanocrystalline Fe3O4 and CCGAMION was able to isolate S. aureus bacteria at 8-10 cfu (colony forming units/ml within ~3 minutes.

Water-soluble PEGylated silicon nanoparticles and their assembly into swellable nanoparticle aggregates

International Nuclear Information System (INIS)

Xu, Zejing; Li, Yejia; Zhang, Boyu; Purkait, Tapas; Alb, Alina; Mitchell, Brian S.; Grayson, Scott M.; Fink, Mark J.

2015-01-01

Water-soluble silicon nanoparticles were synthesized by grafting PEG polymers onto functionalized silicon nanoparticles with distal alkyne or azide moieties. The surface-functionalized silicon nanoparticles were produced in one step from the reactive high-energy ball milling (RHEBM) of silicon wafers with a mixture of either 5-chloro-1-pentyne in 1-pentyne or 1,7 octadiyne in 1-hexyne to afford air and water-stable chloroalkyl or alkynyl-terminated nanoparticles, respectively. Nanoparticles with the ω-chloroalkyl substituents were easily converted to ω-azidoalkyl groups through the reaction of the Si nanoparticles with sodium azide in DMF. The azido-terminated nanoparticles were then grafted with mono-alkynyl-PEG polymers using a copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction to afford core–shell silicon nanoparticles with a covalently attached PEG shell. Covalently linked Si nanoparticle clusters were synthesized via the CuAAC “click” reaction of functional Si NPs with α,ω-functional PEG polymers of various lengths. Dynamic light scattering studies show that the flexible globular nanoparticle aggregates undergo a solvent-dependent change in volume (ethanol > dichloromethane > toluene) similar in behavior to hydrogel nanocomposites

Avoiding drying-artifacts in transmission electron microscopy: Characterizing the size and colloidal state of nanoparticles

Science.gov (United States)

Michen, Benjamin; Geers, Christoph; Vanhecke, Dimitri; Endes, Carola; Rothen-Rutishauser, Barbara; Balog, Sandor; Petri-Fink, Alke

2015-01-01

Standard transmission electron microscopy nanoparticle sample preparation generally requires the complete removal of the suspending liquid. Drying often introduces artifacts, which can obscure the state of the dispersion prior to drying and preclude automated image analysis typically used to obtain number-weighted particle size distribution. Here we present a straightforward protocol for prevention of the onset of drying artifacts, thereby allowing the preservation of in-situ colloidal features of nanoparticles during TEM sample preparation. This is achieved by adding a suitable macromolecular agent to the suspension. Both research- and economically-relevant particles with high polydispersity and/or shape anisotropy are easily characterized following our approach (http://bsa.bionanomaterials.ch), which allows for rapid and quantitative classification in terms of dimensionality and size: features that are major targets of European Union recommendations and legislation. PMID:25965905

Durable antibacterial and cross-linking cotton with colloidal silver nanoparticles and butane tetracarboxylic acid without yellowing.

Science.gov (United States)

Montazer, Majid; Alimohammadi, Farbod; Shamei, Ali; Rahimi, Mohammad Karim

2012-01-01

Colloidal nano silver was applied on the surface of cotton fabric and stabilized using 1,2,3,4-butanetetracarboxylic acid (BTCA). The two properties of antimicrobial activity and resistance against creasing were imparted to the samples of fabric as a result of the treatment with silver nano colloid and BTCA. The antimicrobial property of samples was evaluated using two pathogenic bacteria including Escherichia coli and Staphylococcus aureus as outstanding barometers in this field. The durability of applied nanoparticles, color variation, wettability and wrinkle recovery angle of the treated samples were investigated employing related credible standards. The presence of nano silver particles on the surface of treated cotton fabric was proved using EDS spectrum as well as the SEM images. Furthermore, the creation of cross-links was confirmed by the means of both ATR-FTIR and Raman spectra. In conclusion, it was observed that BTCA plays a prominent role in stabilizing silver nanoparticle. Besides, Wettability and winkle recovery angle of finished samples decreased and increased, respectively. In addition, it is noteworthy that no obvious color variation was observed. Copyright © 2011 Elsevier B.V. All rights reserved.

Large patternable metal nanoparticle sheets by photo/e-beam lithography

Science.gov (United States)

Saito, Noboru; Wang, Pangpang; Okamoto, Koichi; Ryuzaki, Sou; Tamada, Kaoru

2017-10-01

Techniques for micro/nano-scale patterning of large metal nanoparticle sheets can potentially be used to realize high-performance photoelectronic devices because the sheets provide greatly enhanced electrical fields around the nanoparticles due to localized surface plasmon resonances. However, no single metal nanoparticle sheet currently exists with sufficient durability for conventional lithographical processes. Here, we report large photo and/or e-beam lithographic patternable metal nanoparticle sheets with improved durability by incorporating molecular cross-linked structures between nanoparticles. The cross-linked structures were easily formed by a one-step chemical reaction; immersing a single nanoparticle sheet consisting of core metals, to which capping molecules ionically bond, in a dithiol ethanol solution. The ligand exchange reaction processes were discussed in detail, and we demonstrated 20 μm wide line and space patterns, and a 170 nm wide line of the silver nanoparticle sheets.

Data Mining as a Guide for the Construction of Cross-Linked Nanoparticles with Low Immunotoxicity via Control of Polymer Chemistry and Supramolecular Assembly.

Science.gov (United States)

Elsabahy, Mahmoud; Wooley, Karen L

2015-06-16

The potential immunotoxicity of nanoparticles that are currently being approved, in different phases of clinical trials, or undergoing rigorous in vitro and in vivo characterizations in several laboratories has recently raised special attention. Products with no apparent in vitro or in vivo toxicity may still trigger various components of the immune system unintentionally and lead to serious adverse reactions. Cytokines are one of the useful biomarkers for predicting the effect of biotherapeutics on modulation of the immune system and for screening the immunotoxicity of nanoparticles both in vitro and in vivo, and they were recently found to partially predict the in vivo pharmacokinetics and biodistribution of nanomaterials. Control of polymer chemistry and supramolecular assembly provides a great opportunity for the construction of biocompatible nanoparticles for biomedical clinical applications. However, the sources of data collected regarding immunotoxicities of nanomaterials are diverse, and experiments are usually conducted using different assays under specific conditions. As a result, making direct comparisons nearly impossible, and thus, tailoring the properties of nanomaterials on the basis of the available data is challenging. In this Account, the effects of chemical structure, cross-linking, degradability, morphology, concentration, and surface chemistry on the immunotoxicity of an expansive array of polymeric nanomaterials will be highlighted, with a focus on assays conducted using the same in vitro and in vivo models and experimental conditions. Furthermore, numerical descriptive values have been utilized uniquely to stand for induction of cytokines by nanoparticles. This treatment of available data provides a simple way to compare the immunotoxicities of various nanomaterials, and the values were found to correlate well with published data. On the basis of the polymeric systems investigated in this study, valuable information has been collected that

Synthesis, characterization, and ecotoxicity of CeO{sub 2} nanoparticles with differing properties

Energy Technology Data Exchange (ETDEWEB)

Alam, Bushra [Aero Shade Technologies Inc (United States); Philippe, Allan, E-mail: philippe@uni-landau.de; Rosenfeldt, Ricki R.; Seitz, Frank [University of Koblenz-Landau, Group of Environmental and Soil Chemistry, Institute for Environmental Sciences (Germany); Dey, Sonal [SUNY Polytechnic Institute, Colleges of Nanoscale Science and Engineering (United States); Bundschuh, Mirco; Schaumann, Gabriele E. [University of Koblenz-Landau, Group of Environmental and Soil Chemistry, Institute for Environmental Sciences (Germany); Brenner, Sara A. [SUNY Polytechnic Institute, Colleges of Nanoscale Science and Engineering (United States)

2016-10-15

CeO{sub 2} nanoparticles with various characteristics find an increasing number of applications in the electronic, medical, and other industries and are therefore likely released in the environment. This calls for investigations linking the physicochemical properties of these particles with their potential environmental impacts. In this study, CeO{sub 2} nanoparticle powders were prepared using three different precursors [Ce(NO{sub 3}){sub 3}, CeCl{sub 3}, and Ce(CH{sub 3}COO){sub 3}] and annealing temperatures (300, 500, and 700 °C). This procedure resulted in nine different types of nanoparticles with differing size (5–90 nm), morphology, surface Ce{sup 3+}/Ce{sup 4+} ratio, and slightly different crystal structures as characterized using transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, and X-ray diffraction measurements with Rietveld refinement. These CeO{sub 2} nanoparticles underwent toxicity testing at concentrations up to 64 mg L{sup −1} using Daphnia magna. Toxic effects were observed for three particle types with EC50 values between 5 and 64 mg L{sup −1}. No clear correlation was observed between the physicochemical properties (size, shape, oxygen occupancy, Ce{sup 3+}/Ce{sup 4+} ratio) of the nanoparticles and their toxicity. However, toxicity was correlated with the amount of Ce remaining suspended in the test medium after 24 h. This indicated that toxic effects may depend on the colloidal stability of CeO{sub 2} nanoparticles during the first day of exposure. Therefore, being readily suspended and remaining stable for several days in the aquatic media increases the likelihood that CeO{sub 2} nanoparticles will cause unwanted adverse effects.

PREPARATIONS AND APPLICATION OF METAL NANOPARTICLES

Directory of Open Access Journals (Sweden)

Adlim Adlim

2010-06-01

Full Text Available Terminology of metal nanoparticles, the uniqueness properties in terms of the surface atom, the quantum dot, and the magnetism are described. The further elaboration was on the synthesis of nanoparticles. Applications of metal nanoparticles in electronic, ceramic medical and catalysis were overviewed. The bibliography includes 81 references with 99% are journal articles.   Keywords: metal nanoparticles

PREPARATIONS AND APPLICATION OF METAL NANOPARTICLES

OpenAIRE

Adlim, Adlim

2010-01-01

Terminology of metal nanoparticles, the uniqueness properties in terms of the surface atom, the quantum dot, and the magnetism are described. The further elaboration was on the synthesis of nanoparticles. Applications of metal nanoparticles in electronic, ceramic medical and catalysis were overviewed. The bibliography includes 81 references with 99% are journal articles.   Keywords: metal nanoparticles

CdSe nanoparticles grown via radiolytic methods in aqueous solutions

International Nuclear Information System (INIS)

Singh, Shalini; Rath, M.C.; Singh, A.K.; Mukherjee, T.; Jayakumar, O.D.; Tyagi, A.K.; Sarkar, S.K.

2011-01-01

Cadmium selenide, CdSe, nanoparticles have been synthesized in aqueous solution containing equimolar ammoniated CdSO 4 and Na 2 SeSO 3 as the starting materials without any capping agents, using gamma and electron beam irradiation under a reducing condition. The radiolytic processes occurring in water result in the formation of CdSe nanoparticles through the reactions mediated by hydrated electrons, e aq - . TEM measurements revealed that the CdSe nanoparticles were found to exist in agglomerates of dimension of about 100 nm, consisting of primary nanoparticles of dimensions within 5 nm. The as-grown nanoparticles were of cubic crystalline phase as supported by the XRD measurements. These bare CdSe nanoparticles exhibit room temperature ferromagnetic (RTFM) behavior. However, the RTFM behavior was found to be 30% higher in the case of CdSe nanoparticles prepared on electron beam irradiation as compared to those obtained by gamma irradiation, which was attributed to their relatively smaller size (2-3 nm) and disordered structures as compared to those obtained in the later case (3-5 nm). -- Research highlights: → CdSe nanoparticles could be synthesized in aqueous solutions containing equimolar ammoniated CdSO 4 and Na 2 SeSO 3 as the starting materials using gamma and electron beam irradiation under a reducing condition. → CdSe nanoparticles were found to exist in agglomerates of dimension of about 100 nm, consisting of primary nanoparticles of dimensions within 5 nm. → CdSe nanoparticles exhibit room temperature ferromagnetic (RTFM) behavior. → The RTFM behavior was found to be 30% higher in the case of CdSe nanoparticles prepared on electron beam irradiation as compared to those obtained by gamma irradiation.

Effect of Interface energy and electron transfer on shape, plasmon resonance and SERS activity of supported surfactant-free gold nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Giangregorio, Maria M. [Institute of Inorganic Methodologies and of Plasmas, CNR-IMIP; Dastmalchi, Babak [Ames Laboratory; Suvorova, Alexandra [University of Western Australia; Bianco, Giuseppe V. [Institute of Inorganic Methodologies and of Plasmas, CNR-IMIP; Hingerl, Kurt [Johannes Kepler University Linz; Bruno, Giovanni [Institute of Inorganic Methodologies and of Plasmas, CNR-IMIP; Losurdo, Maria [Institute of Inorganic Methodologies and of Plasmas, CNR-IMIP

2014-01-01

For device integration purposes plasmonic metal nanoparticles must be supported/deposited on substrates. Therefore, it is important to understand the interaction between surfactant-free plasmonic metal nanoparticles and different substrates, as well as to identify factors that drive nanoparticles nucleation and formation. Here we show that for nanoparticles grown directly on supports, the substrate/nanoparticle interfacial energy affects the equilibrium shape of nanoparticles. Therefore, oblate, spherical and prolate Au nanoparticles (NPs) with different shapes have been deposited by radiofrequency sputtering on substrates with different characteristics, namely a dielectric oxide Al2O3 (0001), a narrow bandgap semiconductor Si (100), and a polar piezoelectric wide bandgap semiconductor 4H–SiC (0001). We demonstrate that the higher the substrate surface energy, the higher the interaction with the substrate, resulting in flat prolate Au nanoparticles. The resulting localized surface plasmon resonance characteristics of Au NPs/Al2O3, Au NPs/Si and Au NPs/SiC have been determined by spectroscopic ellipsometry and correlated with their structure and shape studied by transmission electron microscopy. Finally, we have demonstrated the diverse response of the tailored plasmonic substrates as ultrasensitive SERS chemical sensors. Flat oblates Au NPs on SiC result in an enhanced and more stable SERS response. The experimental findings are validated by numerical simulations of electromagnetic fields.

Transport in nanoparticle chains influenced by reordering

International Nuclear Information System (INIS)

Luedtke, T.; Mirovsky, P.; Huether, R.; Govor, L.; Bauer, G.H.; Parisi, J.; Haug, R.J.

2011-01-01

Nanoparticles are deposited onto a mica substrate in a dewetting process of hexane solution containing the nanoparticles. The array of nanoparticles was measured inside an electron beam microscope containing a self-developed probing-tip setup. Transport measurements performed under vacuum conditions at room temperature show a power law behavior as expected for low-dimensional cluster systems. During the measurement a variation of the threshold voltage in the nonlinear current-voltage (I-V) characteristic was observed which we attribute to a reordering of the system by an applied electric field. - Highlights: → Fabrication of chains of ordered Au-nanoparticles. → Contact these nanoparticles without further chemical treatment with probing tips inside an electron microscope. → Observation of low-dimensional transport and Coulomb blockade. → Reordering of nanoparticles due to the applied electric field between the tips.

Studying the Kinetics of Crystalline Silicon Nanoparticle Lithiation with In Situ Transmission Electron Microscopy

KAUST Repository

McDowell, Matthew T.; Ryu, Ill; Lee, Seok Woo; Wang, Chongmin; Nix, William D.; Cui, Yi

2012-01-01

In situ transmission electron microscopy (TEM) is used to study the electrochemical lithiation of high-capacity crystalline Si nanoparticles for use in Li-ion battery anodes. The lithiation reaction slows down as it progresses into the particle interior, and analysis suggests that this behavior is due not to diffusion limitation but instead to the influence of mechanical stress on the driving force for reaction. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Studying the Kinetics of Crystalline Silicon Nanoparticle Lithiation with In Situ Transmission Electron Microscopy

KAUST Repository

McDowell, Matthew T.

2012-09-04

In situ transmission electron microscopy (TEM) is used to study the electrochemical lithiation of high-capacity crystalline Si nanoparticles for use in Li-ion battery anodes. The lithiation reaction slows down as it progresses into the particle interior, and analysis suggests that this behavior is due not to diffusion limitation but instead to the influence of mechanical stress on the driving force for reaction. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reflection electron energy loss spectroscopy as efficient technique for the determination of optical properties of polystyrene intermixed with gold nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Deris, Jamileh [Department of Physics, Yasouj University, Yasouj 75918-74831 (Iran, Islamic Republic of); Hajati, Shaaker, E-mail: Hajati@mail.yu.ac.ir [Department of Physics, Yasouj University, Yasouj 75918-74831 (Iran, Islamic Republic of); Department of Semiconductors, Materials and Energy Research Center, Karaj 3177983634 (Iran, Islamic Republic of)

2017-01-15

Highlights: • Reflection Electron Energy Loss Spectroscopy of nano-metalized polymer. • Determination of real part of the dielectric function of nanostructured sample. • Determination of imaginary part of the dielectric function of nanostructured sample. • Determination of refractive index and coefficient of extinction of the sample. • Determination of reflection and absorption coefficients of nano-metalized Polymer. - Abstract: The electronic properties (electron inelastic cross section, energy loss function) of a nano-metalized polystyrene obtained by reflection electron energy loss spectroscopy (REELS) in a previous study [J. Deris, S. Hajati, S. Tougaard, V. Zaporojtchenko, Appl. Surf. Sci. 377 (2016) 44–47], which relies on the Yubero-Tougaard method, were used in the complementary application of Kramers-Kronig transformation to determine its optical properties such as the real part (ε{sub 1}) and imaginary part (ε{sub 2}) of the dielectric function (ε), refractive index (n), coefficients of extinction (k), reflection (R) and absorption (μ). The degree of intermixing of polystyrene thin film and gold nanoparticles of sizes 5.5 nm was controlled by annealing the sample to achieve a morphology in which the nanoparticles were homogeneously distributed within polystyrene. It is worth noting that no data are available on the optical properties of metalized polymers such as gold nanoparticles intermixed with polystyrene. Therefore, this work is of high importance in terms of both the sample studied here and the method applied. The advantage of the method applied here is that no information on the lateral distribution of the nanocomposite sample is required. This means that the REELS technique has been presented here to suitably, efficiently and easily obtain the optical properties of such nano-metalized polymer in which the metal nanoparticles have been vertically well distributed (homogeneous in depth). Therefore, for vertically homogeneous and

Synthesis of Thermally Spherical CuO Nanoparticles

Directory of Open Access Journals (Sweden)

Nittaya Tamaekong

2014-01-01

Full Text Available Copper oxide (CuO nanoparticles were successfully synthesized by a thermal method. The CuO nanoparticles were further characterized by thermogravimetric analysis (TGA, differential thermal analysis (DTA, X-ray diffraction (XRD, scanning electron microscopy (SEM, energy dispersive X-ray spectrometry (EDS, and high resolution transmission electron microscopy (HRTEM, respectively. The specific surface area (SSABET of CuO nanoparticles was determined by nitrogen adsorption. The SSABET was found to be 99.67 m2/g (dBET of 9.5 nm. The average diameter of the spherical CuO nanoparticles was approximately 6–9 nm.

Sensing the quantum behaviour of magnetic nanoparticles by electron magnetic resonance.

Science.gov (United States)

Fittipaldi, M; Mercatelli, R; Sottini, S; Ceci, P; Falvo, E; Gatteschi, D

2016-02-07

We have investigated Magnetic Nanoparticles (MNPs) of spinel type iron oxide (of approximately 8 nm) mineralized in the internal cavity of the bioreactor ferritin nanocage. In particular, we have used Electron Magnetic Resonance, EMR, spectroscopy and taken advantage of the capacity of the protein shells to control the size of the MNPs. EMR measurements in perpendicular and parallel configurations have been recorded at various temperatures. A model based on the giant spin is used to interpret the experimental results. The analysis indicates that the observed quantum behaviour has to be ascribed to the whole MNP and that the thermal population of excited spin states has a strong influence in the EMR behaviour of MNPs.

Preparation of an Environmentally Friendly Formulation of the Insecticide Nicotine Hydrochloride through Encapsulation in Chitosan/Tripolyphosphate Nanoparticles.

Science.gov (United States)

Yang, Ying; Cheng, Jiagao; Garamus, Vasil M; Li, Na; Zou, Aihua

2018-02-07

Insecticide nicotine hydrochloride (NCT) was formulated as nanoparticles composed of chitosan (CS) and sodium tripolyphosphate (TPP) to undermine its adverse impacts on human health and reinforce its physicochemical stability. The study investigated the preparation and characterization of chitosan/tripolyphosphate nanoparticles (CS/TPP NPs) with good encapsulation efficiency (55%), uniform morphology, and physicochemical stability (45 days) through dynamic light scattering (DLS), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS) measurements. A bioassay against Musca domestica NCT CS/TPP NPs exhibited good bioactivity and thermal stability. The effect of the monovalent salt (NaCl) on manipulating the formation and size distribution of ionically cross-linked nanoparticles was demonstrated as well. The formulation of NCT CS/TPP NPs could be a utility candidate in public health and agriculture.

Thiolated chitosan nanoparticles: transfection study in the Caco-2 differentiated cell culture

International Nuclear Information System (INIS)

Martien, Ronny; Loretz, Brigitta; Sandbichler, Adolf Michael; Schnuerch, Andreas Bernkop

2008-01-01

The aim of this study was to monitor the expression of secreted protein in differentiated Caco-2 cells after transfection with nanoparticles, in order to improve gene delivery. Based on unmodified chitosan and thiolated chitosan conjugates, nanoparticles with the gene reporter pSEAP (recombinant Secreted Alkaline Phosphatase) were generated at pH 4.0. Transfection studies of thiolated chitosan in Caco-2 cells during the exponential growth phase and differentiation growth phase of the cells led to a 5.0-fold and 2.0-fold increase in protein expression when compared to unmodified chitosan nanoparticles. The mean particle size for both unmodified chitosan and cross-linked thiolated chitosan nanoparticles is 212.2 ± 86 and 113.6 ± 40 nm, respectively. The zeta potential of nanoparticles was determined to be 7.9 ± 0.38 mV for unmodified chitosan nanoparticles and 4.3 ± 0.74 mV for cross-linked thiolated chitosan nanoparticles. Red blood cell lysis evaluation was used to evaluate the membrane damaging properties of unmodified and thiolated chitosan nanoparticles and led to 4.61 ± 0.36% and 2.29 ± 0.25% lysis, respectively. Additionally, cross-linked thiolated chitosan nanoparticles were found to exhibit higher stability toward degradation in gastric juices. Furthermore the reversible effect of thiolated chitosan on barrier properties was monitored by measuring the transepithelial electrical resistance (TEER) and is supported by immunohistochemical staining for the tight junction protein claudin. According to these results cross-linked thiolated chitosan nanoparticles have the potential to be used as a non-viral vector system for gene therapy

Correlation of electronic and magnetic properties of thin polymer layers with cobalt nanoparticles

DEFF Research Database (Denmark)

Kharchenko, A.; Lukashevich, M.; Popok, Vladimir

2013-01-01

Nanoparticles (NPs) of cobalt are synthesized in shallow layers of polyimide using 40 keV implantation of Co+ ions with a few different fluences at various ion current densities. Nucleation of individual NPs at low fluencies and their percolation at high fluencies are crucial processes governing...... of the magnetoresistance on the applied magnetic field allows to suggest spin-dependent domain wall scattering affecting the electron transport. The samples implanted with low fluencies demonstrate superparamagnetic behavior down to very low blocking temperatures. While for high fluence (1.25x1017 cm-2) the transition...

A layer-by-layer ZnO nanoparticle-PbS quantum dot self-assembly platform for ultrafast interfacial electron injection

KAUST Repository

Eita, Mohamed Samir

2014-08-28

Absorbent layers of semiconductor quantum dots (QDs) are now used as material platforms for low-cost, high-performance solar cells. The semiconductor metal oxide nanoparticles as an acceptor layer have become an integral part of the next generation solar cell. To achieve sufficient electron transfer and subsequently high conversion efficiency in these solar cells, however, energy-level alignment and interfacial contact between the donor and the acceptor units are needed. Here, the layer-by-layer (LbL) technique is used to assemble ZnO nanoparticles (NPs), providing adequate PbS QD uptake to achieve greater interfacial contact compared with traditional sputtering methods. Electron injection at the PbS QD and ZnO NP interface is investigated using broadband transient absorption spectroscopy with 120 femtosecond temporal resolution. The results indicate that electron injection from photoexcited PbS QDs to ZnO NPs occurs on a time scale of a few hundred femtoseconds. This observation is supported by the interfacial electronic-energy alignment between the donor and acceptor moieties. Finally, due to the combination of large interfacial contact and ultrafast electron injection, this proposed platform of assembled thin films holds promise for a variety of solar cell architectures and other settings that principally rely on interfacial contact, such as photocatalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Uncorrelated electron-hole transition energy in GaN|InGaN|GaN spherical QDQW nanoparticles

International Nuclear Information System (INIS)

Haddou El Ghazi; Anouar Jorio and Izeddine Zorkani

2013-01-01

The electron (hole) energy and uncorrelated 1S e - 1S h electron-hole transition in Core(GaN)|well(In x Ga 1-x N)|shell(GaN) spherical QDQW nanoparticles is investigated as a function of the inner and the outer radii. The calculations are performed within the framework of the effective-mass approximation and the finite parabolic potential confinement barrier in which two confined parameters are taking account. The Indium composition effect is also investigated. A critical value of the outer and the inner ratio is obtained which constitutes the turning point of two indium composition behaviors. (author)

Characterization of nanoparticles released during construction of photocatalytic pavements using engineered nanoparticles

International Nuclear Information System (INIS)

Dylla, Heather; Hassan, Marwa M.

2012-01-01

With the increasing use of titanium dioxide (TiO 2 ) nanoparticles in self-cleaning materials such as photocatalytic concrete pavements, the release of nanoparticles into the environment is inevitable. Nanoparticle concentration, particle size, surface area, elemental composition, and surface morphology are pertinent to determine the associated risks. In this study, the potential of exposure to synthetic nanoparticles released during construction activities for application of photocatalytic pavements was measured during laboratory-simulated construction activities of photocatalytic mortar overlays and in an actual field application of photocatalytic spray coat. A scanning mobility particle sizer system measured the size distribution of nanoparticles released during laboratory and field activities. Since incidental nanoparticles are released during construction activities, nanoparticle emissions were compared to those from similar activities without nano-TiO 2 . Nanoparticle counts and size distribution suggest that synthetic nanoparticles are released during application of photocatalytic pavements. In order to identify the nanoparticle source, nanoparticles were also collected for offline characterization using transmission electron microscopy. However, positive identification of synthetic nanoparticles was not possible due to difficulties in obtaining high-resolution images. As a result, further research is recommended to identify nanoparticle composition and sources.

Irradiation of gold nanoparticles by x-rays: Monte Carlo simulation of dose enhancements and the spatial properties of the secondary electrons production.

Science.gov (United States)

Leung, Michael K K; Chow, James C L; Chithrani, B Devika; Lee, Martin J G; Oms, Barbara; Jaffray, David A

2011-02-01

The aim of this study is to understand the characteristics of secondary electrons generated from the interaction of gold nanoparticles (GNPs) with x-rays as a function of nanoparticle size and beam energy and thereby further the understanding of GNP-enhanced radiotherapy. The effective range, deflection angle, dose deposition, energy, and interaction processes of electrons produced from the interaction of x-rays with a GNP were calculated by Monte Carlo simulations. The GEANT4 code was used to simulate and track electrons generated from a 2, 50, and 100 nm diameter GNP when it is irradiated with a 50 kVp, 250 kVp, cobalt-60, and 6 MV photon beam in water. When a GNP was present, depending on the beam energies used, secondary electron production was increased by 10- to 2000-fold compared to an absence of a GNP. Low-energy photon beams were much more efficient at interacting with the GNP by two to three orders of magnitude compared to MV energies and increased the deflection angle. GNPs with larger diameters also contributed more dose. The majority of the energy deposition was outside the GNP, rather than self-absorbed by the nanoparticle. The mean effective range of electron tracks for the beams tested ranged from approximately 3 microm to 1 mm. These simulated results yield important insights concerning the spatial distributions and elevated dose in GNP-enhanced radiotherapy. The authors conclude that the irradiation of GNP at lower photon energies will be more efficient for cell killing. This conclusion is consistent with published studies.

CdSe nanoparticles grown via radiolytic methods in aqueous solutions

Energy Technology Data Exchange (ETDEWEB)

Singh, Shalini [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Rath, M.C., E-mail: madhab@barc.gov.i [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Singh, A.K. [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Mukherjee, T. [Chemistry Group, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Jayakumar, O.D.; Tyagi, A.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Sarkar, S.K. [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2011-06-15

Cadmium selenide, CdSe, nanoparticles have been synthesized in aqueous solution containing equimolar ammoniated CdSO{sub 4} and Na{sub 2}SeSO{sub 3} as the starting materials without any capping agents, using gamma and electron beam irradiation under a reducing condition. The radiolytic processes occurring in water result in the formation of CdSe nanoparticles through the reactions mediated by hydrated electrons, e{sub aq}{sup -}. TEM measurements revealed that the CdSe nanoparticles were found to exist in agglomerates of dimension of about 100 nm, consisting of primary nanoparticles of dimensions within 5 nm. The as-grown nanoparticles were of cubic crystalline phase as supported by the XRD measurements. These bare CdSe nanoparticles exhibit room temperature ferromagnetic (RTFM) behavior. However, the RTFM behavior was found to be 30% higher in the case of CdSe nanoparticles prepared on electron beam irradiation as compared to those obtained by gamma irradiation, which was attributed to their relatively smaller size (2-3 nm) and disordered structures as compared to those obtained in the later case (3-5 nm). -- Research highlights: {yields} CdSe nanoparticles could be synthesized in aqueous solutions containing equimolar ammoniated CdSO{sub 4} and Na{sub 2}SeSO{sub 3} as the starting materials using gamma and electron beam irradiation under a reducing condition. {yields} CdSe nanoparticles were found to exist in agglomerates of dimension of about 100 nm, consisting of primary nanoparticles of dimensions within 5 nm. {yields} CdSe nanoparticles exhibit room temperature ferromagnetic (RTFM) behavior. {yields} The RTFM behavior was found to be 30% higher in the case of CdSe nanoparticles prepared on electron beam irradiation as compared to those obtained by gamma irradiation.

Microwave absorption enhancement, magnetic coupling and ab initio electronic structure of monodispersed (Mn1-xCox)3O4 nanoparticles

Science.gov (United States)

Zhao, Pengfei; Liang, Chongyun; Gong, Xiwen; Gao, Ran; Liu, Jiwei; Wang, Min; Che, Renchao

2013-08-01

Monodispersed manganese oxide (Mn1-xCox)3O4 (0 nanoparticles, less than 10 nm size, are respectively synthesized via a facile thermolysis method at a rather low temperature, ranging from 90 to 100 °C, without any inertia gas for protection. The influences of the Co dopant content on the critical reaction temperature required for the nanoparticle formation, electronic band structures, magnetic properties, and the microwave absorption capability of (Mn1-xCox)3O4 are comprehensively investigated by means of both experimental and theoretical approaches including powder X-ray diffraction (XRD), electron energy loss spectroscopy (EELS), super conductivity quantum interference device (SQUID) examination, and first-principle simulations. Co is successfully doped into the Mn atomic sites of the (Mn1-xCox)3O4 lattice, which is further confirmed by EELS data acquired from one individual nanoparticle. Therefore, continuous solid solutions of well-crystallized (Mn1-xCox)3O4 products are achieved without any impurity phase or phase separation. With increases in the Co dopant concentration x from 0 to 0.5, the lattice parameters change systemically, where the overall saturation magnetization at 30 K increases due to the more intense coupling of the 3d electrons between Mn and Co, as revealed by simulations. The microwave absorption properties of the (Mn1-xCox)3O4 nanoparticles are examined between 2 and 18 GHz. The maximum absorption peak -11.0 dB of the x = 0 sample is enhanced to -11.5 dB for x = 0.2, -12.7 dB for x = 0.25, -15.6 dB for x = 0.33, and -24.0 dB for x = 0.5 respectively, suggesting the Co doping effects. Our results might provide novel insights into the understanding of the influences of metallic ion doping on the electromagnetic properties of metallic oxide nanomaterials.Monodispersed manganese oxide (Mn1-xCox)3O4 (0 nanoparticles, less than 10 nm size, are respectively synthesized via a facile thermolysis method at a rather low temperature, ranging from 90 to

Progress toward clonable inorganic nanoparticles

Science.gov (United States)

Ni, Thomas W.; Staicu, Lucian C.; Nemeth, Richard S.; Schwartz, Cindi L.; Crawford, David; Seligman, Jeffrey D.; Hunter, William J.; Pilon-Smits, Elizabeth A. H.; Ackerson, Christopher J.

2015-10-01

Pseudomonas moraviensis stanleyae was recently isolated from the roots of the selenium (Se) hyperaccumulator plant Stanleya pinnata. This bacterium tolerates normally lethal concentrations of SeO32- in liquid culture, where it also produces Se nanoparticles. Structure and cellular ultrastructure of the Se nanoparticles as determined by cellular electron tomography shows the nanoparticles as intracellular, of narrow dispersity, symmetrically irregular and without any observable membrane or structured protein shell. Protein mass spectrometry of a fractionated soluble cytosolic material with selenite reducing capability identified nitrite reductase and glutathione reductase homologues as NADPH dependent candidate enzymes for the reduction of selenite to zerovalent Se nanoparticles. In vitro experiments with commercially sourced glutathione reductase revealed that the enzyme can reduce SeO32- (selenite) to Se nanoparticles in an NADPH-dependent process. The disappearance of the enzyme as determined by protein assay during nanoparticle formation suggests that glutathione reductase is associated with or possibly entombed in the nanoparticles whose formation it catalyzes. Chemically dissolving the nanoparticles releases the enzyme. The size of the nanoparticles varies with SeO32- concentration, varying in size form 5 nm diameter when formed at 1.0 μM [SeO32-] to 50 nm maximum diameter when formed at 100 μM [SeO32-]. In aggregate, we suggest that glutathione reductase possesses the key attributes of a clonable nanoparticle system: ion reduction, nanoparticle retention and size control of the nanoparticle at the enzyme site.Pseudomonas moraviensis stanleyae was recently isolated from the roots of the selenium (Se) hyperaccumulator plant Stanleya pinnata. This bacterium tolerates normally lethal concentrations of SeO32- in liquid culture, where it also produces Se nanoparticles. Structure and cellular ultrastructure of the Se nanoparticles as determined by cellular

Au nanoparticle-decorated silicon pyramids for plasmon-enhanced hot electron near-infrared photodetection

Science.gov (United States)

Qi, Zhiyang; Zhai, Yusheng; Wen, Long; Wang, Qilong; Chen, Qin; Iqbal, Sami; Chen, Guangdian; Xu, Ji; Tu, Yan

2017-07-01

The heterojunction between metal and silicon (Si) is an attractive route to extend the response of Si-based photodiodes into the near-infrared (NIR) region, so-called Schottky barrier diodes. Photons absorbed into a metallic nanostructure excite the surface plasmon resonances (SPRs), which can be damped non-radiatively through the creation of hot electrons. Unfortunately, the quantum efficiency of hot electron detectors remains low due to low optical absorption and poor electron injection efficiency. In this study, we propose an efficient and low-cost plasmonic hot electron NIR photodetector based on a Au nanoparticle (Au NP)-decorated Si pyramid Schottky junction. The large-area and lithography-free photodetector is realized by using an anisotropic chemical wet etching and rapid thermal annealing (RTA) of a thin Au film. We experimentally demonstrate that these hot electron detectors have broad photoresponsivity spectra in the NIR region of 1200-1475 nm, with a low dark current on the order of 10-5 A cm-2. The observed responsivities enable these devices to be competitive with other reported Si-based NIR hot electron photodetectors using perfectly periodic nanostructures. The improved performance is attributed to the pyramid surface which can enhance light trapping and the localized electric field, and the nano-sized Au NPs which are beneficial for the tunneling of hot electrons. The simple and large-area preparation processes make them suitable for large-scale thermophotovoltaic cell and low-cost NIR detection applications.

Ultrafast chemical interface scattering as an additional decay channel for nascent nonthermal electrons in small metal nanoparticles.

Science.gov (United States)

Bauer, Christophe; Abid, Jean-Pierre; Fermin, David; Girault, Hubert H

2004-05-15

The use of 4.2 nm gold nanoparticles wrapped in an adsorbates shell and embedded in a TiO2 metal oxide matrix gives the opportunity to investigate ultrafast electron-electron scattering dynamics in combination with electronic surface phenomena via the surface plasmon lifetimes. These gold nanoparticles (NPs) exhibit a large nonclassical broadening of the surface plasmon band, which is attributed to a chemical interface damping. The acceleration of the loss of surface plasmon phase coherence indicates that the energy and the momentum of the collective electrons can be dissipated into electronic affinity levels of adsorbates. As a result of the preparation process, gold NPs are wrapped in a shell of sulfate compounds that gives rise to a large density of interfacial molecules confined between Au and TiO2, as revealed by Fourier-transform-infrared spectroscopy. A detailed analysis of the transient absorption spectra obtained by broadband femtosecond transient absorption spectroscopy allows separating electron-electron and electron-phonon interaction. Internal thermalization times (electron-electron scattering) are determined by probing the decay of nascent nonthermal electrons (NNEs) and the build-up of the Fermi-Dirac electron distribution, giving time constants of 540 to 760 fs at 0.42 and 0.34 eV from the Fermi level, respectively. Comparison with literature data reveals that lifetimes of NNEs measured for these small gold NPs are more than four times longer than for silver NPs with similar sizes. The surprisingly long internal thermalization time is attributed to an additional decay mechanism (besides the classical e-e scattering) for the energy loss of NNEs, identified as the ultrafast chemical interface scattering process. NNEs experience an inelastic resonant scattering process into unoccupied electronic states of adsorbates, that directly act as an efficient heat bath, via the excitation of molecular vibrational modes. The two-temperature model is no longer

Shielding of Sensitive Electronic Devices in Magnetic Nanoparticle Hyperthermia Using Arrays of Coils

International Nuclear Information System (INIS)

Spirou, S V; Tsialios, P; Loudos, G

2015-01-01

In Magnetic Nanoparticle Hyperthermia (MNH) an externally applied electromagnetic field transfers energy to the magnetic nanoparticles in the body, which in turn convert this energy into heat, thus locally heating the tissue they are located in. This external electromagnetic field is sufficiently strong so as to cause interference and affect sensitive electronic equipment. Standard shielding of magnetic fields involves Faraday cages or coating with high-permeability shielding alloys; however, these techniques cannot be used with optically sensitive devices, such as those employed in Optical Coherence Tomography or radionuclide imaging. In this work we present a method to achieve magnetic shielding using an array of coils. The magnetic field generated by a single coil was calculated using the COMSOL physics simulation toolkit. Software was written in C/C++ to import the single-coil data, and then calculate the positions, number of turns and currents in the shielding coils in order to minimize the magnetic field strength at the desired location. Simulations and calculations have shown that just two shielding coils can reduce the magnetic field by 2-3 orders of magnitude. (paper)

Shielding of Sensitive Electronic Devices in Magnetic Nanoparticle Hyperthermia Using Arrays of Coils

Science.gov (United States)

Spirou, S. V.; Tsialios, P.; Loudos, G.

2015-09-01

In Magnetic Nanoparticle Hyperthermia (MNH) an externally applied electromagnetic field transfers energy to the magnetic nanoparticles in the body, which in turn convert this energy into heat, thus locally heating the tissue they are located in. This external electromagnetic field is sufficiently strong so as to cause interference and affect sensitive electronic equipment. Standard shielding of magnetic fields involves Faraday cages or coating with high-permeability shielding alloys; however, these techniques cannot be used with optically sensitive devices, such as those employed in Optical Coherence Tomography or radionuclide imaging. In this work we present a method to achieve magnetic shielding using an array of coils. The magnetic field generated by a single coil was calculated using the COMSOL physics simulation toolkit. Software was written in C/C++ to import the single-coil data, and then calculate the positions, number of turns and currents in the shielding coils in order to minimize the magnetic field strength at the desired location. Simulations and calculations have shown that just two shielding coils can reduce the magnetic field by 2-3 orders of magnitude.

All-inkjet-printed flexible electronics fabrication on a polymer substrate by low-temperature high-resolution selective laser sintering of metal nanoparticles

International Nuclear Information System (INIS)

Ko, Seung H; Pan Heng; Grigoropoulos, Costas P; Luscombe, Christine K; Frechet, Jean M J; Poulikakos, Dimos

2007-01-01

All-printed electronics is the key technology to ultra-low-cost, large-area electronics. As a critical step in this direction, we demonstrate that laser sintering of inkjet-printed metal nanoparticles enables low-temperature metal deposition as well as high-resolution patterning to overcome the resolution limitation of the current inkjet direct writing processes. To demonstrate this process combined with the implementation of air-stable carboxylate-functionalized polythiophenes, high-resolution organic transistors were fabricated in ambient pressure and room temperature without utilizing any photolithographic steps or requiring a vacuum deposition process. Local thermal control of the laser sintering process could minimize the heat-affected zone and the thermal damage to the substrate and further enhance the resolution of the process. This local nanoparticle deposition and energy coupling enable an environmentally friendly and cost-effective process as well as a low-temperature manufacturing sequence to realize large-area, flexible electronics on polymer substrates

Magnetic nanoparticles coated with polyaniline to stabilize immobilized trypsin

Energy Technology Data Exchange (ETDEWEB)

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.

Synthesis of gold and silver nanoparticles by electron irradiation at 5-15 keV energy

Energy Technology Data Exchange (ETDEWEB)

Mahapatra, S K; Bogle, K A; Dhole, S D; Bhoraskar, V N [Microtron Accelerator Laboratory, Department of Physics, University of Pune, Pune-411007 (India)

2007-04-04

Thin coatings ({approx}10 {mu}m) made from a mixture of polyvinyl alcohol (PVA) and HAuCl{sub 4} or PVA and AgNO{sub 3} on quartz plates were irradiated with 5-15 keV electrons, at room temperature. The electron energy was varied from coating to coating in the range of 5-15 keV, but electron fluence was kept constant at {approx}10{sup 15} e cm{sup -2}. Samples were characterized by the UV-vis, XRD, SEM and TEM techniques. The plasmon absorption peaks at {approx}511 and {approx}442 nm confirmed the formation of gold and silver nanoparticles in the respective electron-irradiated coatings. The XRD, SEM and TEM measurements reveal that the average size of the particles could be tailored in the range of 130-50 nm for gold and from 150-40 nm for silver by varying the electron energy in the range of 5-15 keV. These particles of gold and silver embedded in the polymer could also be separated by dissolving the coatings in distilled water.

Lactobacillusassisted synthesis of titanium nanoparticles

Directory of Open Access Journals (Sweden)

Jha Anal

2007-01-01

Full Text Available AbstractAn eco-friendlylactobacillussp. (microbe assisted synthesis of titanium nanoparticles is reported. The synthesis is performed at room temperature. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of Ti nanoparticles. Individual nanoparticles as well as a number of aggregates almost spherical in shape having a size of 40–60 nm are found.

Antimicrobial activity of silver nanoparticles encapsulated in poly-N-isopropylacrylamide-based polymeric nanoparticles.

Science.gov (United States)

Qasim, Muhammad; Udomluck, Nopphadol; Chang, Jihyun; Park, Hansoo; Kim, Kyobum

2018-01-01

In this study, we analyzed the antimicrobial activities of poly- N -isopropylacrylamide (pNIPAM)-based polymeric nanoparticles encapsulating silver nanoparticles (AgNPs). Three sizes of AgNP-encapsulating pNIPAM- and pNIPAM-NH 2 -based polymeric nanoparticles were fabricated. Highly stable and uniformly distributed AgNPs were encapsulated within polymeric nanoparticles via in situ reduction of AgNO 3 using NaBH 4 as the reducing agent. The formation and distribution of AgNPs was confirmed by UV-visible spectroscopy, transmission electron microscopy, and inductively coupled plasma optical emission spectrometry, respectively. Both polymeric nanoparticles showed significant bacteriostatic activities against Gram-negative ( Escherichia coli ) and Gram-positive ( Staphylococcus aureus ) bacteria depending on the nanoparticle size and amount of AgNO 3 used during fabrication.

Nanoparticle Metamorphosis: An in Situ High-Temperature Transmission Electron Microscopy Study of the Structural Evolution of Heterogeneous Au:Fe 2 O 3 Nanoparticles

KAUST Repository

Baumgardner, William J.

2014-05-27

High-temperature in situ electron microscopy and X-ray diffraction have revealed that Au and Fe2O3 particles fuse in a fluid fashion at temperatures far below their size-reduced melting points. With increasing temperature, the fused particles undergo a sequence of complex structural transformations from surface alloy to phase segregated and ultimately core-shell structures. The combination of in situ electron microscopy and spectroscopy provides insights into fundamental thermodynamic and kinetic aspects governing the formation of heterogeneous nanostructures. The observed structural transformations present an interesting analogy to thin film growth on the curved surface of a nanoparticle. Using single-particle observations, we constructed a phase diagram illustrating the complex relationships among composition, morphology, temperature, and particle size. © 2014 American Chemical Society.

Nanoparticle Metamorphosis: An in Situ High-Temperature Transmission Electron Microscopy Study of the Structural Evolution of Heterogeneous Au:Fe 2 O 3 Nanoparticles

KAUST Repository

Baumgardner, William J.; Yu, Yingchao; Hovden, Robert; Honrao, Shreyas; Hennig, Richard G.; Abruñ a, Hé ctor D.; Muller, David; Hanrath, Tobias

2014-01-01

High-temperature in situ electron microscopy and X-ray diffraction have revealed that Au and Fe2O3 particles fuse in a fluid fashion at temperatures far below their size-reduced melting points. With increasing temperature, the fused particles undergo a sequence of complex structural transformations from surface alloy to phase segregated and ultimately core-shell structures. The combination of in situ electron microscopy and spectroscopy provides insights into fundamental thermodynamic and kinetic aspects governing the formation of heterogeneous nanostructures. The observed structural transformations present an interesting analogy to thin film growth on the curved surface of a nanoparticle. Using single-particle observations, we constructed a phase diagram illustrating the complex relationships among composition, morphology, temperature, and particle size. © 2014 American Chemical Society.

Effects of Short-Term Exposure to Sublethal Concentrations of Silver Nanoparticles on Histopathology and Electron Microscope Ultrastructure of Zebrafish (Danio Rerio Gills

Directory of Open Access Journals (Sweden)

Borhan Mansouri

2015-11-01

Full Text Available Background: The increasing use of nanomaterials and nanoproducts has increased the possibility of contamination of the environment, which may have adverse effects on different organisms. The aim of this study was to evaluate the effects of silver nanoparticles on histopathology and gill ultrastructure of zebrafish (Danio rerio under laboratory conditions. Methods: Zebrafish were exposed to four concentrations of silver nanoparticles (0.0015, 0.00375, 0.0075, and 0.015 mg/l for a period of 4 days. Gill ultrastructure and histopathological changes were studied using scanning electron microscope and haematoxylin - eosin staining. Results: Exposure to silver nanoparticles significantly (P < 0.001 increased the diameter of gill filaments and secondary lamellae, while silver nanoparticles significantly reduced the length of the secondary gills in zebrafish. Moreover, other changes such as vacuolization, dilated and clubbed tips, hyperplasia, edema, fusion, swelling of mucocytes, hypertrophy, and necrosis were observed. The effects of silver nanoparticles in zebrafish gills were dose dependent. Conclusion: Based on the adverse effects of AgNPs on zebrafish gills, silver nanoparticle solutions can be hazardous pollutants for the environment.

High energy-resolution electron energy-loss spectroscopy study of the dielectric properties of bulk and nanoparticle LaB6 in the near-infrared region

International Nuclear Information System (INIS)

Sato, Yohei; Terauchi, Masami; Mukai, Masaki; Kaneyama, Toshikatsu; Adachi, Kenji

2011-01-01

The dielectric properties of LaB 6 crystals and the plasmonic behavior of LaB 6 nanoparticles, which have been applied to solar heat-shielding filters, were studied by high energy-resolution electron energy-loss spectroscopy (HR-EELS). An EELS spectrum of a LaB 6 crystal showed a peak at 2.0 eV, which was attributed to volume plasmon excitation of carrier electrons. EELS spectra of single LaB 6 nanoparticles showed peaks at 1.1-1.4 eV depending on the dielectric effect from the substrates. The peaks were assigned to dipole oscillation excitations. These peak energies almost coincided with the peak energy of optical absorption of a heat-shielding filter with LaB 6 nanoparticles. On the other hand, those energies were a smaller than a dipole oscillation energy predicted using the dielectric function of bulk LaB 6 crystal. It is suggested that the lower energy than expected is due to an excitation at 1.2 eV, which was observed for oxidized LaB 6 area. -- Highlights: → The dielectric properties of LaB 6 nanoparticles applied to solar heat-shielding filters were studied by HR-EELS. → Plasmon peak energies of the LaB 6 nanoparticles were almost equal to optical absorption energy of a heat-shielding filter. → From this result, near-infrared optical absorption of the filter is due to the surface dipole mode of the nanoparticles.

Electrodeposition of silver nanoparticle arrays on transparent conductive oxides

International Nuclear Information System (INIS)

Zhang, Dezhong; Tang, Yang; Jiang, Fuguo; Han, Zhihua; Chen, Jie

2016-01-01

Highlights: • The sliver nanoparticles' size and the distance between nanoparticles are tunable. - Abstract: In this paper, we present a facile method for the preparation of silver nanoparticles on aluminum-doped zinc oxide (AZO) via electrodeposition techniques at room temperature. The morphology and structure of silver nanoparticles are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), respectively. Due to localized surface plasmon resonances, as-prepared silver nanoparticles on AZO glass exhibited different reflectivity in contrast with bare AZO glass. The weighted reflection of AZO substrate increased from 10.2% to 12.8%. The high reflection property of silver nanoparticle arrays on AZO substrate might be applicable for thin film solar cells and other optoelectronics applications.

Electrodeposition of silver nanoparticle arrays on transparent conductive oxides

Energy Technology Data Exchange (ETDEWEB)

Zhang, Dezhong; Tang, Yang, E-mail: tangyang@nicenergy.com; Jiang, Fuguo; Han, Zhihua; Chen, Jie

2016-04-30

Highlights: • The sliver nanoparticles' size and the distance between nanoparticles are tunable. - Abstract: In this paper, we present a facile method for the preparation of silver nanoparticles on aluminum-doped zinc oxide (AZO) via electrodeposition techniques at room temperature. The morphology and structure of silver nanoparticles are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), respectively. Due to localized surface plasmon resonances, as-prepared silver nanoparticles on AZO glass exhibited different reflectivity in contrast with bare AZO glass. The weighted reflection of AZO substrate increased from 10.2% to 12.8%. The high reflection property of silver nanoparticle arrays on AZO substrate might be applicable for thin film solar cells and other optoelectronics applications.

Implementation of an electronic fingerprint-linked data collection system: a feasibility and acceptability study among Zambian female sex workers.

Science.gov (United States)

Wall, Kristin M; Kilembe, William; Inambao, Mubiana; Chen, Yi No; Mchoongo, Mwaka; Kimaru, Linda; Hammond, Yuna Tiffany; Sharkey, Tyronza; Malama, Kalonde; Fulton, T Roice; Tran, Alex; Halumamba, Hanzunga; Anderson, Sarah; Kishore, Nishant; Sarwar, Shawn; Finnegan, Trisha; Mark, David; Allen, Susan A

2015-06-27

Patient identification within and between health services is an operational challenge in many resource-limited settings. When following HIV risk groups for service provision and in the context of vaccine trials, patient misidentification can harm patient care and bias trial outcomes. Electronic fingerprinting has been proposed to identify patients over time and link patient data between health services. The objective of this study was to determine 1) the feasibility of implementing an electronic-fingerprint linked data capture system in Zambia and 2) the acceptability of this system among a key HIV risk group: female sex workers (FSWs). Working with Biometrac, a US-based company providing biometric-linked healthcare platforms, an electronic fingerprint-linked data capture system was developed for use by field recruiters among Zambian FSWs. We evaluated the technical feasibility of the system for use in the field in Zambia and conducted a pilot study to determine the acceptability of the system, as well as barriers to uptake, among FSWs. We found that implementation of an electronic fingerprint-linked patient tracking and data collection system was feasible in this relatively resource-limited setting (false fingerprint matching rate of 1/1000 and false rejection rate of lodges) could be addressed by recruiting women during less busy hours, in their own homes, in the presence of "Queen Mothers" (FSW organizers), or in the presence of a FSW that has already been fingerprinted. Our findings have major implications for key population research and improved health services provision. However, more work needs to be done to increase the acceptability of the electronic fingerprint-linked data capture system during field recruitment. This study indicated several potential avenues that will be explored to increase acceptability.

Deterministic nanoparticle assemblies: from substrate to solution

International Nuclear Information System (INIS)

Barcelo, Steven J; Gibson, Gary A; Yamakawa, Mineo; Li, Zhiyong; Kim, Ansoon; Norris, Kate J

2014-01-01

The deterministic assembly of metallic nanoparticles is an exciting field with many potential benefits. Many promising techniques have been developed, but challenges remain, particularly for the assembly of larger nanoparticles which often have more interesting plasmonic properties. Here we present a scalable process combining the strengths of top down and bottom up fabrication to generate deterministic 2D assemblies of metallic nanoparticles and demonstrate their stable transfer to solution. Scanning electron and high-resolution transmission electron microscopy studies of these assemblies suggested the formation of nanobridges between touching nanoparticles that hold them together so as to maintain the integrity of the assembly throughout the transfer process. The application of these nanoparticle assemblies as solution-based surface-enhanced Raman scattering (SERS) materials is demonstrated by trapping analyte molecules in the nanoparticle gaps during assembly, yielding uniformly high enhancement factors at all stages of the fabrication process. (paper)

Magnetic irone oxide nanoparticles in photosynthetic systems

International Nuclear Information System (INIS)

Khalilov, R.I.; Nasibova, A.N.; Khomutov, G.B.

2014-01-01

Full text : It was found and studied the effect of biogenic formation of magnetic inclusions in photosynthetic systems - in various higher plants under the influence of some external stress factors (radiation impact, moisture deficit) and in a model system - a suspension of chloroplasts. For registration and characterization of magnetic nanoparticles in the samples used EPR spectrometer because superparamagnetic and ferromagnetic nanoparticles have a chcracteristic signals of electron magnetic resonance. For direct visualization of magnetic nanoparticles it was used the method of transmission electron microscopy

Seed-mediated synthesis of cross-linked Pt-NiO nanochains for methanol oxidation

Energy Technology Data Exchange (ETDEWEB)

Gu, Zhulan; Bin, Duan; Feng, Yue; Zhang, Ke; Wang, Jin; Yan, Bo; Li, Shumin; Xiong, Zhiping; Wang, Caiqin; Shiraishi, Yukihide; Du, Yukou, E-mail: duyk@suda.edu.cn

2017-07-31

Highlights: • Cross-linked Pt-NiO nanochains using seed-mediated growth method are synthesized. • The as-prepared catalysts exhibit higher electrocatalytic activity than Pt/C for MOR. • The Pt-NiO(1:1 by molar) catalyst shows the best electrocatalytic property towards MOR. - Abstract: A simple method was reported for employing NiO nanoparticles act as seeds and then different amounts of Pt{sup 2+} were reduced on the NiO nanoparticles, forming a cross-linked Pt-NiO nanocatalysts. These as-prepared catalysts were characterized using different physical-chemical techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results indicate that the morphology of the cross-linked Pt-NiO nanochain was successfully produced regardless of the molar ratio of Pt{sup 2+} to NiO precursors. The electrochemical characteristics of Pt-NiO nanochain catalysts were evaluated for the oxidation of methanol as a model reaction, which verify that the Pt-NiO catalysts show enhanced activity and high stability in comparison with the commercial Pt/C catalyst. The optimized ratio of Pt to NiO is 1:1, then tuned by simple adjusting the feed ratio of the precursors as well. The synthesized nanocatalysts will be found the great potential applications as electrocatalysts for fuel cells owe to their enhanced catalytic performance and long-term stability.

Seed-mediated synthesis of cross-linked Pt-NiO nanochains for methanol oxidation

International Nuclear Information System (INIS)

Gu, Zhulan; Bin, Duan; Feng, Yue; Zhang, Ke; Wang, Jin; Yan, Bo; Li, Shumin; Xiong, Zhiping; Wang, Caiqin; Shiraishi, Yukihide; Du, Yukou

2017-01-01

Highlights: • Cross-linked Pt-NiO nanochains using seed-mediated growth method are synthesized. • The as-prepared catalysts exhibit higher electrocatalytic activity than Pt/C for MOR. • The Pt-NiO(1:1 by molar) catalyst shows the best electrocatalytic property towards MOR. - Abstract: A simple method was reported for employing NiO nanoparticles act as seeds and then different amounts of Pt 2+ were reduced on the NiO nanoparticles, forming a cross-linked Pt-NiO nanocatalysts. These as-prepared catalysts were characterized using different physical-chemical techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results indicate that the morphology of the cross-linked Pt-NiO nanochain was successfully produced regardless of the molar ratio of Pt 2+ to NiO precursors. The electrochemical characteristics of Pt-NiO nanochain catalysts were evaluated for the oxidation of methanol as a model reaction, which verify that the Pt-NiO catalysts show enhanced activity and high stability in comparison with the commercial Pt/C catalyst. The optimized ratio of Pt to NiO is 1:1, then tuned by simple adjusting the feed ratio of the precursors as well. The synthesized nanocatalysts will be found the great potential applications as electrocatalysts for fuel cells owe to their enhanced catalytic performance and long-term stability.

Alloy nanoparticle synthesis using ionizing radiation

Science.gov (United States)

Nenoff, Tina M [Sandia Park, NM; Powers, Dana A [Albuquerque, NM; Zhang, Zhenyuan [Durham, NC

2011-08-16

A method of forming stable nanoparticles comprising substantially uniform alloys of metals. A high dose of ionizing radiation is used to generate high concentrations of solvated electrons and optionally radical reducing species that rapidly reduce a mixture of metal ion source species to form alloy nanoparticles. The method can make uniform alloy nanoparticles from normally immiscible metals by overcoming the thermodynamic limitations that would preferentially produce core-shell nanoparticles.

A new metal electrocatalysts supported matrix: Palladium nanoparticles supported silicon carbide nanoparticles and its application for alcohol electrooxidation

International Nuclear Information System (INIS)

Dai Hong; Chen Yanling; Lin Yanyu; Xu Guifang; Yang Caiping; Tong Yuejin; Guo Longhua; Chen Guonan

2012-01-01

In this paper, we propose a facile approach for palladium nanoparticles load using silicon carbide nanoparticles as the new supported matrix and a familiar NaBH 4 as reducer. Detailed X-ray photoelectron spectrum (XPS) and transmission electron microscopy (TEM) analysis of the resultant products indicated that palladium nanoparticles are successfully immobilized onto the surface of the silicon carbide nanoparticles with uniform size distribution between 5 and 7 nm. The relative electrochemical characterization clearly demonstrated excellent electrocatalytic activity of this material toward alcohol in alkaline electrolytes. Investigation on the characteristics of the electrocatalytic activity of this material further indicated that the palladium nanoparticles supporting on SiC are very promising for direct alcohol fuel cells (DMFCs), biosensor and electronic devices. Moreover, it was proved that silicon carbide nanoparticles with outstanding properties as support for catalysis are of strong practical interest. And the silicon carbide could perform attractive role in adsorbents, electrodes, biomedical applications, etc.

Crystal structure of TiNi nanoparticles obtained by Ar ion beam deposition

International Nuclear Information System (INIS)

Castro, A. Torres; Cuellar, E. Lopez; Mendez, U. Ortiz; Yacaman, M. Jose

2008-01-01

Nanoparticles are a state of matter that have properties different from either molecules or bulk solids, turning them into a very interesting class of materials to study. In the present work, the crystal structure of TiNi nanoparticles obtained by ion beam deposition is characterized. TiNi nanoparticles were obtained from TiNi wire samples by sputtering with Ar ions using a Gatan precision ion polishing system. The TiNi nanoparticles were deposited on a Lacey carbon film that was used for characterization by transmission electron microscopy. The nanoparticles were characterized by high-resolution transmission electron microscopy, high-angle annular dark-field imaging, electron diffraction, scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy. Results of nanodiffraction seem to indicate that the nanoparticles keep the same B2 crystal structure as the bulk material but with a decreased lattice parameter

ENHANCING DIRECT ELECTRON TRANSFER OF GLUCOSE OXIDASE USING A GOLD NANOPARTICLE |TITANATE NANOTUBE NANOCOMPOSITE ON A BIOSENSOR

International Nuclear Information System (INIS)

Zhao, Ruoxia; Liu, Xiaoqiang; Zhang, Jiamei; Zhu, Jie; Wong, Danny K.Y.

2015-01-01

ABSTRACT: In this paper, we have developed a gold nanoparticle (GNP) decorated titanate nanotubes (TNT) nanocomposite that aids in the direct electron transfer of a large enzyme, such as glucose oxidase (GOD), in which the electroactive site of flavin adenine dinucleotide is deeply buried within the enzyme. The ionic liquid, brominated 1-decyl-3-methyl imidazole, was used to immobilise the nanocomposite and the enzyme on a glassy carbon electrode to further aid in the electron transfer between GOD and the electrode surface. Nafion was also added to anchor the biosensor scaffold. Initially, the tubiform geometry of titanate nanomaterials and the GNP-TNT nanocomposite was confirmed by microscopic and spectroscopic techniques before glucose oxidase was entrapped in the nanocomposite. Based on voltammetric results, this biosensor showed a strong electrocatalytic capability towards glucose (with a heterogeneous electron transfer rate constant of 7.1 s −1 at 180 mV s −1 ) and the calibration for glucose exhibited a high sensitivity (5.1 μA mM −1 ) and a wide linear range (0.01–1.2 mM). These results demonstrated superior analytical performance of our biosensor over others fabricated using bulkier TiO 2 nanoparticles or nanobundles, which could be attributed to a high degree of biocompatibility to glucose oxidase and electrical conductivity of the nanocomposite

Preparation and characterization of zinc oxide nanoparticles and their sensor applications for electrochemical monitoring of nucleic acid hybridization.

Science.gov (United States)

Yumak, Tugrul; Kuralay, Filiz; Muti, Mihrican; Sinag, Ali; Erdem, Arzum; Abaci, Serdar

2011-09-01

In this study, ZnO nanoparticles (ZNP) of approximately 30 nm in size were synthesized by the hydrothermal method and characterized by X-ray diffraction (XRD), Braun-Emmet-Teller (BET) N2 adsorption analysis and transmission electron microscopy (TEM). ZnO nanoparticles enriched with poly(vinylferrocenium) (PVF+) modified single-use graphite electrodes were then developed for the electrochemical monitoring of nucleic acid hybridization related to the Hepatitis B Virus (HBV). Firstly, the surfaces of polymer modified and polymer-ZnO nanoparticle modified single-use pencil graphite electrodes (PGEs) were characterized using scanning electron microscopy (SEM). The electrochemical behavior of these electrodes was also investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Subsequently, the polymer-ZnO nanoparticle modified PGEs were evaluated for the electrochemical detection of DNA based on the changes at the guanine oxidation signals. Various modifications in DNA oligonucleotides and probe concentrations were examined in order to optimize the electrochemical signals that were generated by means of nucleic acid hybridization. After the optimization studies, the sequence-selective DNA hybridization was investigated in the case of a complementary amino linked probe (target), or noncomplementary (NC) sequences, or target and mismatch (MM) mixture in the ratio of (1:1). Copyright © 2011 Elsevier B.V. All rights reserved.

Nanoparticle Netpoints for Shape-Memory Polymers

KAUST Repository

Agarwal, Praveen

2011-08-02

Forget-me-not: Nanoparticle fillers in shape-memory polymers usually improve mechanical properties at the expense of shape-memory performance. A new approach overcomes these drawbacks by cross-linking the functionalized poly(ethylene glycol) tethers on silica nanoparticles (see picture). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Environmental transmission electron microscopy investigations of Pt-Fe2O3 nanoparticles for nucleating carbon nanotubes

DEFF Research Database (Denmark)

He, Maoshuai; Jin, Hua; Zhang, Lili

2016-01-01

electron microscopy, restructuring of the acorn-like Pt-Fe2O3 nanoparticles at reaction conditions is investigated. Upon heating to reaction temperature, ε-Fe2O3 is converted to β-Fe2O3, which can be subsequently reduced to metallic Fe once introducing CO. As Pt promotes the carburization of Fe, part...... of the metallic Fe reacts with active carbon atoms to form Fe2.5C instead of Fe3C, catalyzing the nucleation of carbon nanotubes. Nanobeam electron diffraction characterizations on SWCNTs grown under ambient pressure at 800 °C demonstrate that their chiral angle and diameter distributions are similar to those...

Influences of surfactants on the preparation of copper nanoparticles by electron beam irradiation

Energy Technology Data Exchange (ETDEWEB)

Zhou Ruimin [Shanghai Applied Radiation Institute, Shanghai University, Shanghai 201800 (China)], E-mail: zhourm47@staff.shu.edu.cn; Wu Xinfeng; Hao Xufeng; Zhou Fei [Shanghai Applied Radiation Institute, Shanghai University, Shanghai 201800 (China); Li Hongbin [Department of Chemical Engineering and Technology, Shanghai University, Shanghai 201800 (China); Rao Weihong [Shenzhen Tianding Fine Chemical Engineering Manufacturing Co., Ltd., Shenzhen, Guangdong 518057 (China)

2008-02-15

Electron beam radiation was applied to prepare nano-size copper in water system using polyvinyl alcohol, sodium dodecyl benzene sulfonate, gluten and polyethylene glycol as the surfactants, respectively. The irradiated products were characterized by XRD, TEM and LSPSDA. The XRD and TEM showed that relative pure copper products with an average size of 20 nm, 40 nm and 20 nm can be obtained by using gluten, PEG and SDBS as surfactant, respectively. An admixture of copper and cuprous oxide was obtained in PVA system. The LSPSDA showed that the size of the Cu nanoparticles decreased with increasing the glutin concentration.

Biosynthesis of extracellular and intracellular gold nanoparticles by Aspergillus fumigatus and A. flavus.

Science.gov (United States)

Gupta, Saurabh; Bector, Shruti

2013-05-01

Green chemistry is a boon for the development of safe, stable and ecofriendly nanostructures using biological tools. The present study was carried out to explore the potential of selected fungal strains for biosynthesis of intra- and extracellular gold nanostructures. Out of the seven cultures, two fungal strains (SBS-3 and SBS-7) were selected on the basis of development of dark pink colour in cell free supernatant and fungal beads, respectively indicative of extra- and intracellular gold nanoparticles production. Both biomass associated and cell free gold nanoparticles were characterized using X-ray diffractogram (XRD) analysis and transmission electron microscopy (TEM). XRD analysis confirmed crystalline, face-centered cubic lattice of metallic gold nanoparticles along with average crystallite size. A marginal difference in average crystallite size of extracellular (17.76 nm) and intracellular (26 and 22 nm) Au-nanostructures was observed using Scherrer equation. In TEM, a variety of shapes (triangles, spherical, hexagonal) were observed in both extra- and intracellular nanoparticles. 18S rRNA gene sequence analysis by multiple sequence alignment (BLAST) indicated 99 % homology of SBS-3 to Aspergillus fumigatus with 99 % alignment coverage and 98 % homology of SBS-7 to Aspergillus flavus with 98 % alignment coverage respectively. Native-PAGE and activity staining further confirmed enzyme linked synthesis of gold nanoparticles.

Direct Measurement of the Surface Energy of Bimetallic Nanoparticles: Evidence of Vegard's Rulelike Dependence.

Science.gov (United States)

Chmielewski, Adrian; Nelayah, Jaysen; Amara, Hakim; Creuze, Jérôme; Alloyeau, Damien; Wang, Guillaume; Ricolleau, Christian

2018-01-12

We use in situ transmission electron microscopy to monitor in real time the evaporation of gold, copper, and bimetallic copper-gold nanoparticles at high temperature. Besides, we extend the Kelvin equation to two-component systems to predict the evaporation rates of spherical liquid mono- and bimetallic nanoparticles. By linking this macroscopic model to experimental TEM data, we determine the surface energies of pure gold, pure copper, Cu_{50}Au_{50}, and Cu_{25}Au_{75} nanoparticles in the liquid state. Our model suggests that the surface energy varies linearly with the composition in the liquid Cu-Au nanoalloy; i.e., it follows a Vegard's rulelike dependence. To get atomic-scale insights into the thermodynamic properties of Cu-Au alloys on the whole composition range, we perform Monte Carlo simulations employing N-body interatomic potentials. These simulations at a microscopic level confirm the Vegard's rulelike behavior of the surface energy obtained from experiments combined with macroscopic modeling.

Factors influencing the charge distribution on Pd x Pt y bimetallic nanoparticles

Directory of Open Access Journals (Sweden)

Carlos M. Celis-Cornejo

2013-12-01

Full Text Available We performed quantum mechanics calculations to elucidate the electronic behavior of Pd-Pt bimetallic nanoparticles, using density functional theory, in response to particle size and stoichiometric composition. Using neutrally charged nanoparticles and the Bader charge analysis, we found that external Pd atoms were positively charged, which agrees with previous XPS observations of supported Pd-Pt nanoparticles. From the calculations, unsupported nanoparticles exhibit an electron transfer from Pd to Pt. This result supports the idea that Pd electron-deficient species are possibly responsible of the hydrogenating function of these catalysts, in the hydrodesulfurization of dibenzothiophene. Additionally, it was found that the particle size does not affect the electronic charge distribution and the stoichiometric composition is the factor that greatly influences this property in nanoparticles.

Electronic cigarette aerosols and copper nanoparticles induce mitochondrial stress and promote DNA fragmentation in lung fibroblasts

Energy Technology Data Exchange (ETDEWEB)

Lerner, Chad A.; Rutagarama, Pierrot; Ahmad, Tanveer; Sundar, Isaac K.; Elder, Alison; Rahman, Irfan, E-mail: irfan_rahman@urmc.rochester.edu

2016-09-02

Oxidants or nanoparticles have recently been identified as constituents of aerosols released from various styles of electronic cigarettes (E-cigs). Cells in the lung may be directly exposed to these constituents and harbor reactive properties capable of incurring acute cell injury. Our results show mitochondria are sensitive to both E-cig aerosols and aerosol containing copper nanoparticles when exposed to human lung fibroblasts (HFL-1) using an Air-Liquid Interface culture system, evident by elevated levels of mitochondrial ROS (mtROS). Increased mtROS after aerosol exposure is associated with reduced stability of OxPhos electron transport chain (ETC) complex IV subunit and nuclear DNA fragmentation. Increased levels of IL-8 and IL-6 in HFL-1 conditioned media were also observed. These findings reveal both mitochondrial, genotoxic, and inflammatory stresses are features of direct cell exposure to E-cig aerosols which are ensued by inflammatory duress, raising a concern on deleterious effect of vaping. - Graphical abstract: Oxidants and possibly reactive properties of metal particles in E-cig aerosols impart mitochondrial oxidative stress and DNA damage. These biological effects accompany inflammatory response which may raise concern regarding long term E-cig use. Mitochondria may be particularly sensitive to reactive properties of E-cig aerosols in addition to the potential for them to induce genotoxic stress by generating increased ROS. - Highlights: • Mitochondria are sensitive to both E-cig aerosols and metal nanoparticles. • Increased mtROS by E-cig aerosol is associated with disrupted mitochondrial energy. • E-cig causes nuclear DNA fragmentation. • E-cig aerosols induce pro-inflammatory response in human fibroblasts.

Electronic cigarette aerosols and copper nanoparticles induce mitochondrial stress and promote DNA fragmentation in lung fibroblasts

International Nuclear Information System (INIS)

Lerner, Chad A.; Rutagarama, Pierrot; Ahmad, Tanveer; Sundar, Isaac K.; Elder, Alison; Rahman, Irfan

2016-01-01

Oxidants or nanoparticles have recently been identified as constituents of aerosols released from various styles of electronic cigarettes (E-cigs). Cells in the lung may be directly exposed to these constituents and harbor reactive properties capable of incurring acute cell injury. Our results show mitochondria are sensitive to both E-cig aerosols and aerosol containing copper nanoparticles when exposed to human lung fibroblasts (HFL-1) using an Air-Liquid Interface culture system, evident by elevated levels of mitochondrial ROS (mtROS). Increased mtROS after aerosol exposure is associated with reduced stability of OxPhos electron transport chain (ETC) complex IV subunit and nuclear DNA fragmentation. Increased levels of IL-8 and IL-6 in HFL-1 conditioned media were also observed. These findings reveal both mitochondrial, genotoxic, and inflammatory stresses are features of direct cell exposure to E-cig aerosols which are ensued by inflammatory duress, raising a concern on deleterious effect of vaping. - Graphical abstract: Oxidants and possibly reactive properties of metal particles in E-cig aerosols impart mitochondrial oxidative stress and DNA damage. These biological effects accompany inflammatory response which may raise concern regarding long term E-cig use. Mitochondria may be particularly sensitive to reactive properties of E-cig aerosols in addition to the potential for them to induce genotoxic stress by generating increased ROS. - Highlights: • Mitochondria are sensitive to both E-cig aerosols and metal nanoparticles. • Increased mtROS by E-cig aerosol is associated with disrupted mitochondrial energy. • E-cig causes nuclear DNA fragmentation. • E-cig aerosols induce pro-inflammatory response in human fibroblasts.

Diamond nanoparticles as a way to improve electron transfer in sol–gel L-lactate biosensing platforms

Energy Technology Data Exchange (ETDEWEB)

Briones, M.; Casero, E. [Departamento de Química Analítica y Análisis Instrumental, Facultad de Ciencias, c/Francisco Tomás y Valiente, No7, Campus de Excelencia de la Universidad Autónoma de Madrid, 28049 Madrid (Spain); Vázquez, L. [Instituto de Ciencia de Materiales de Madrid (CSIC), c/Sor Juana Inés de la Cruz No3, Campus de Excelencia de la Universidad Autónoma de Madrid, 28049 Madrid (Spain); Pariente, F.; Lorenzo, E. [Departamento de Química Analítica y Análisis Instrumental, Facultad de Ciencias, c/Francisco Tomás y Valiente, No7, Campus de Excelencia de la Universidad Autónoma de Madrid, 28049 Madrid (Spain); Petit-Domínguez, M.D., E-mail: mdolores.petit@uam.es [Departamento de Química Analítica y Análisis Instrumental, Facultad de Ciencias, c/Francisco Tomás y Valiente, No7, Campus de Excelencia de la Universidad Autónoma de Madrid, 28049 Madrid (Spain)

2016-02-18

In the present work, we have included for the first time diamond nanoparticles (DNPs) in a sol–gel matrix derived from (3-mercaptopropyl)-trimethoxysilane (MPTS) in order to improve electron transfer in a lactate oxidase (LOx) based electrochemical biosensing platform. Firstly, an exhaustive AFM study, including topographical, surface potential (KFM) and capacitance gradient (CG) measurements, of each step involved in the biosensing platform development was performed. The platform is based on gold electrodes (Au) modified with the sol–gel matrix (Au/MPTS) in which diamond nanoparticles (Au/MPTS/DNPs) and lactate oxidase (Au/MPTS/DNPs/LOx) have been included. For the sake of comparison, we have also characterized a gold electrode directly modified with DNPs (Au/DNPs). Secondly, the electrochemical behavior of a redox mediator (hydroxymethyl-ferrocene, HMF) was evaluated at the platforms mentioned above. The response of Au/MPTS/DNPs/LOx towards lactate was obtained. A linear concentration range from 0.053 mM to 1.6 mM, a sensitivity of 2.6 μA mM{sup −1} and a detection limit of 16 μM were obtained. These analytical properties are comparable to other biosensors, presenting also as advantages that DNPs are inexpensive, environment-friendly and easy-handled nanomaterials. Finally, the developed biosensor was applied for lactate determination in wine samples. - Highlights: • We have included for the first time diamond nanoparticles (DNPs) in a sol–gel matrix for developing lactate biosensors. • DNPs facilitate electron-transfer within the sol–gel network in electrochemical biosensors. • Lactate biosensors show good sensitivity, detection limit, reproducibility and stability.

Bulk tungsten with uniformly dispersed La2O3 nanoparticles sintered from co-precipitated La2O3/W nanoparticles

International Nuclear Information System (INIS)

Xia, Min; Yan, Qingzhi; Xu, Lei; Guo, Hongyan; Zhu, Lingxu; Ge, Changchun

2013-01-01

Graphical abstract: La 2 O 3 doped La 2 O 3 /W nanoparticles with high-purity and uniform diameters have been fabricated by a co-precipitation process. The as-prepared nanoparticles demonstrate the potential of this method for fabricating uniformly structured bulk tungsten materials. -- Abstract: We report the preparation of 1 wt% La 2 O 3 doped La 2 O 3 /W nanoparticles by a co-precipitation process, using ammonium metatungstate (AMT) and lanthanum nitrate as raw materials. The as-synthesized nanoparticles were characterized by X-ray diffraction, Filed-emission scanning electron microscopy, Transmission electron microscopy (TEM), energy dispersive spectroscopy. Our results reveal that the as-synthesized particles possess uniform diameters of about 70 nm, and are of high purity. The TEM and the corresponding fast Fourier transform images demonstrated that La 2 O 3 precipitates were homogeneously doped into the nano-sized tungsten particles. When the as-synthesized nanoparticles were sintered by spark plasma sintering, the electron backscatter diffraction images of the bulk material reveal that La 2 O 3 nanoparticles were homogenously distributed in both the tungsten grains and the grain boundaries, and the sample exhibit a narrow micro-hardness distribution

Photocatalytic activity enhancement by electron irradiation of fullerene derivative-TiO2 nanoparticles under visible light illumination

International Nuclear Information System (INIS)

Cho, Sung Oh; Yoo, Seung Hwa; Lee, Dong Hoon

2011-01-01

Photocatalytic decomposition of aqueous organic pollutant have attracted many interest due to its simple, low cost, and clean procedure. By only using the sun light and photocatalyst, especially TiO 2 nanoparticles based systems have been extensively studied and commercialized for real life application. However, TiO 2 has a critical disadvantage, which can only absorb the ultra-violet region of the solar spectrum, due to the large band-gap of 3.2 eV. Extensive studies have been preformed to expand the light absorption of TiO 2 to the visible light region of the solar spectrum, by doping metal or non-metal elements on TiO 2 or attaching small band-gap semiconductors on TiO 2 . In this study, a fullerene derivative 1-(3- carboxypropyl)-1-phenyl[6,6]C 61 (PCBA) was attached on the surface of TiO 2 nanoparticles, and its photocatalytic activity was evaluated by decomposition of methyl orange under visible light. Furthermore, enhancement in the photocatalytic activity of these nanoparticles by electron irradiation is discussed

Hydrothermal synthesis and physicochemical properties of ruthenium(0) nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Dikhtiarenko, A., E-mail: dikhtiarenkoalla@uniovi.es [Departamento de Quimica Organica e Inorganica, Universidad de Oviedo - CINN, 33006 Oviedo (Spain); Khainakov, S.A.; Garcia, J.R.; Gimeno, J. [Departamento de Quimica Organica e Inorganica, Universidad de Oviedo - CINN, 33006 Oviedo (Spain); Pedro, I. de; Fernandez, J. Rodriguez [CITIMAC, Facultad de Ciencias, Universidad de Cantabria, 39005 Santander (Spain); Blanco, J.A. [Departamento de Fisica, Universidad de Oviedo, 33007 Oviedo (Spain)

2012-09-25

Highlights: Black-Right-Pointing-Pointer Ruthenium nanoparticles were synthesized by hydrothermal technique. Black-Right-Pointing-Pointer The average size of the nanoparticles are depend on the reducing agent used. Black-Right-Pointing-Pointer The magnetic response seems to be dominated by a paramagnetic contribution characteristic of the band electronic magnetism of the ruthenium(0) nanoparticles. - Abstract: The synthesis of ruthenium nanoparticles in hydrothermal conditions using mild reducing agents (succinic acid, ascorbic acid and sodium citrate) is reported. The shape of the nanoparticles depends on the type of the reducing agent, while the size is more influenced by the pH of the medium. The magnetic response seems to be dominated by a paramagnetic contribution characteristic of the band electronic magnetism of the nanoparticles.

Room temperature ferromagnetism in Mg-doped ZnO nanoparticles

International Nuclear Information System (INIS)

Singh, Jaspal; Vashihth, A.; Gill, Pritampal Singh; Verma, N. K.

2015-01-01

Zn 1-x Mg x O (x = 0, 0,10) nanoparticles were successfully synthesized using sol-gel method. X-ray diffraction (XRD) confirms that the synthesized nanoparticles possess wurtzite phase having hexagonal structure. Morphological analysis was carried out using transmission electron microscopy (TEM) which depicts the spherical morphology of ZnO nanoparticles. Energy dispersive spectroscopy (EDS) showed the presence of Mg in ZnO nanoparticles. Electron spin resonance (ESR) signal was found to be decreasing with increasing of Mg-doping concentration. The room temperature ferromagnetism was observed in undoped and Mg-doped ZnO nanoparticles. The increase of Mg-doping concentration resulted in decrease of saturation magnetization value which could be attributed to decrease of oxygen vacancies present in host nanoparticles

Passive linear nanoscale optical and molecular electronics device synthesis from nanoparticles

International Nuclear Information System (INIS)

Yurke, Bernard; Kuang Wan

2010-01-01

Arrays of nanoparticles whose interactions can be characterized by hopping Hamiltonians can serve as excitation transmission lines. Here we show, that in addition suitable arrangements of nanoparticles can form beam splitters, phase shifters, and crossover splitters. With these elements, any discrete unitary transformation can be implemented on input modes via a network of nanoparticles in which all the components lie in the same plane. These nanoparticle networks can produce optical functionalities at a length scale much smaller than 1 μm.

Instant synthesis of gold nanoparticles at room temperature and SERS applications

International Nuclear Information System (INIS)

Britto Hurtado, R.; Cortez-Valadez, M.; Ramírez-Rodríguez, L.P.; Larios-Rodriguez, Eduardo; Alvarez, Ramón A.B.; Rocha-Rocha, O.; Delgado-Beleño, Y.; Martinez-Nuñez, C.E.; Arizpe-Chávez, H.; Hernández-Martínez, A.R.; Flores-Acosta, M.

2016-01-01

Nowadays, gold nanoparticles (AuNps) can be used in a variety of applications, thus efficient methods to produce them are necessary. Several methods have been proposed in this area, but NPs production time is one limitation of these approaches. In this study, we propose a high competitive method to synthesize gold colloidal nanoparticles, instantaneously, using no-toxic reducing agents. These substances allow the instantaneous synthesis at room temperature, even without magnetic stirrers, ovens or ultrasonic baths. Optic analysis showed two absorption bands, associated with surface Plasmon as function of HAuCl_4 concentration. The nanoparticles synthesized have a 10–20 nm size, seen by the transmission electron microscopy (TEM). Therefore, it was possible to obtain several geometric patterns of AuNps, and the synthesis was performed reducing significantly processing time. Additionally, Mie and Fuchs theories were used to predict the location of the absorption bands linked to the plasmon surface in gold nanoparticles. The Surface Enhanced Raman Spectroscopy (SERS) effect was analyzed considering natural zeolite (Chabazite) as analyte, in order to determinate its possible application in soil analysis. - Highlights: • Cubic and spherical morphologies in AuNp. • Surface plasmon prediction in cubic and spherical AuNp. • Instant synthesis of AuNp. • SERS applications in soil analysis.

Instant synthesis of gold nanoparticles at room temperature and SERS applications

Energy Technology Data Exchange (ETDEWEB)

Britto Hurtado, R. [Departamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-88, 83190, Hermosillo, Sonora (Mexico); Cortez-Valadez, M., E-mail: jose.cortez@unison.mx [CONACYT-Departamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-88, 83190, Hermosillo, Sonora (Mexico); Ramírez-Rodríguez, L.P. [Departamento de Física, Universidad de Sonora, Apdo. Postal 5-88, 83190, Hermosillo, Sonora (Mexico); Larios-Rodriguez, Eduardo [Departamento de Ingeniería Química y Metalurgia, Universidad de Sonora, Rosales y Luis Encinas S/N, Hermosillo, Sonora (Mexico); Alvarez, Ramón A.B.; Rocha-Rocha, O.; Delgado-Beleño, Y.; Martinez-Nuñez, C.E.; Arizpe-Chávez, H. [Departamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-88, 83190, Hermosillo, Sonora (Mexico); Hernández-Martínez, A.R. [Centro de Física Aplicada y Tecnología Avanzada (CFATA), Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro C.P. 76130 (Mexico); Flores-Acosta, M. [Departamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-88, 83190, Hermosillo, Sonora (Mexico)

2016-08-06

Nowadays, gold nanoparticles (AuNps) can be used in a variety of applications, thus efficient methods to produce them are necessary. Several methods have been proposed in this area, but NPs production time is one limitation of these approaches. In this study, we propose a high competitive method to synthesize gold colloidal nanoparticles, instantaneously, using no-toxic reducing agents. These substances allow the instantaneous synthesis at room temperature, even without magnetic stirrers, ovens or ultrasonic baths. Optic analysis showed two absorption bands, associated with surface Plasmon as function of HAuCl{sub 4} concentration. The nanoparticles synthesized have a 10–20 nm size, seen by the transmission electron microscopy (TEM). Therefore, it was possible to obtain several geometric patterns of AuNps, and the synthesis was performed reducing significantly processing time. Additionally, Mie and Fuchs theories were used to predict the location of the absorption bands linked to the plasmon surface in gold nanoparticles. The Surface Enhanced Raman Spectroscopy (SERS) effect was analyzed considering natural zeolite (Chabazite) as analyte, in order to determinate its possible application in soil analysis. - Highlights: • Cubic and spherical morphologies in AuNp. • Surface plasmon prediction in cubic and spherical AuNp. • Instant synthesis of AuNp. • SERS applications in soil analysis.

Synthesis, Structural Characterization, and Preclinical Efficacy of a Novel Paclitaxel-Loaded Alginate Nanoparticle for Breast Cancer Treatment

Directory of Open Access Journals (Sweden)

Ahmed A. Markeb

2016-01-01

Full Text Available Purpose. The antitumor activity of a novel alginate (ALG polymer-based particle that contained paclitaxel (PTX was evaluated using human primary breast cancer cells. Materials and Methods. PTX was combined with ALG in a nanoparticle as a drug delivery system designed to improve breast cancer tumor cell killing. PTX-ALG nanoparticles were first synthesized by nanoemulsification polymer cross-linking methods that improved the aqueous solubility. Structural and biophysical properties of the PTX-ALG nanoparticles were then determined by transmission electron microscopy (TEM and high performance liquid chromatography (HPLC fluorescence. The effect on cell cycle progression and apoptosis was determined using flow cytometry. Results. PTX-ALG nanoparticles were prepared and characterized by ultraviolet (UV/visible (VIS, HPLC fluorescence, and TEM. PTX-ALG nanoparticles demonstrated increased hydrophobicity and solubility over PTX alone. Synthetically engineered PTX-ALG nanoparticles promoted cell-cycle arrest, reduced viability, and induced apoptosis in human primary patient breast cancer cells superior to those of PTX alone. Conclusion. Taken together, our results demonstrate that PTX-ALG nanoparticles represent an innovative, nanoscale delivery system for the administration of anticancer agents that may avoid the adverse toxicities with enhanced antitumor effects to improve the treatment of breast cancer patients.

Transformation mechanism of n-butyl terminated Si nanoparticles embedded into Si1-xCx nanocomposites mixed with Si nanoparticles and C atoms

International Nuclear Information System (INIS)

Shin, J.W.; Oh, D.H.; Kim, T.W.; Cho, W.J.

2009-01-01

Bright-field transmission electron microscopy (TEM) images, high-resolution TEM (HRTEM) images, and fast-Fourier transformed electron-diffraction patterns showed that n-butyl terminated Si nanoparticles were aggregated. The formation of Si 1-x C x nanocomposites was mixed with Si nanoparticles and C atoms embedded in a SiO 2 layer due to the diffusion of C atoms from n-butyl termination shells into aggregated Si nanoparticles. Atomic force microscopy (AFM) images showed that the Si 1-x C x nanocomposites mixed with Si nanoparticles and C atoms existed in almost all regions of the SiO 2 layer. The formation mechanism of Si nanoparticles and the transformation mechanism of n-butyl terminated Si nanoparticles embedded into Si 1-x C x nanocomposites mixed with Si nanoparticles and C atoms are described on the basis of the TEM, HRTEM, and AFM results. These results can help to improve the understanding of the formation mechanism of Si nanoparticles.

Biosynthesis of silver nanoparticles by Aspergillus niger , Fusarium ...

African Journals Online (AJOL)

... scanning electron microscope (SEM). Results indicate the synthesis of silver nanoparticles in the reaction mixture. The synthesis of nanoparticles would be suitable for developing a microbial nanotechnology biosynthesis process for mass scale production. Keywords: Silver nanoparticles, biosynthesis, fungi, Aspergillus.

Efficient sampling of reversible cross-linking polymers: Self-assembly of single-chain polymeric nanoparticles

Science.gov (United States)

Oyarzún, Bernardo; Mognetti, Bortolo Matteo

2018-03-01

We present a new simulation technique to study systems of polymers functionalized by reactive sites that bind/unbind forming reversible linkages. Functionalized polymers feature self-assembly and responsive properties that are unmatched by the systems lacking selective interactions. The scales at which the functional properties of these materials emerge are difficult to model, especially in the reversible regime where such properties result from many binding/unbinding events. This difficulty is related to large entropic barriers associated with the formation of intra-molecular loops. In this work, we present a simulation scheme that sidesteps configurational costs by dedicated Monte Carlo moves capable of binding/unbinding reactive sites in a single step. Cross-linking reactions are implemented by trial moves that reconstruct chain sections attempting, at the same time, a dimerization reaction between pairs of reactive sites. The model is parametrized by the reaction equilibrium constant of the reactive species free in solution. This quantity can be obtained by means of experiments or atomistic/quantum simulations. We use the proposed methodology to study the self-assembly of single-chain polymeric nanoparticles, starting from flexible precursors carrying regularly or randomly distributed reactive sites. We focus on understanding differences in the morphology of chain nanoparticles when linkages are reversible as compared to the well-studied case of irreversible reactions. Intriguingly, we find that the size of regularly functionalized chains, in good solvent conditions, is non-monotonous as a function of the degree of functionalization. We clarify how this result follows from excluded volume interactions and is peculiar of reversible linkages and regular functionalizations.

Ligand-Modified Human Serum Albumin Nanoparticles for Enhanced Gene Delivery.

Science.gov (United States)

Look, Jennifer; Wilhelm, Nadine; von Briesen, Hagen; Noske, Nadja; Günther, Christine; Langer, Klaus; Gorjup, Erwin

2015-09-08

The development of nonviral gene delivery systems is a great challenge to enable safe gene therapy. In this study, ligand-modified nanoparticles based on human serum albumin (HSA) were developed and optimized for an efficient gene therapy. Different glutaraldehyde cross-linking degrees were investigated to optimize the HSA nanoparticles for gene delivery. The peptide sequence arginine-glycine-aspartate (RGD) and the HIV-1 transactivator of transduction sequence (Tat) are well-known as promising targeting ligands. Plasmid DNA loaded HSA nanoparticles were covalently modified on their surface with these different ligands. The transfection potential of the obtained plasmid DNA loaded RGD- and Tat-modified nanoparticles was investigated in vitro, and optimal incubation conditions for these preparations were studied. It turned out that Tat-modified HSA nanoparticles with the lowest cross-linking degree of 20% showed the highest transfection potential. Taken together, ligand-functionalized HSA nanoparticles represent promising tools for efficient and safe gene therapy.

Comparison of four functionalization methods of gold nanoparticles for enhancing the enzyme-linked immunosorbent assay (ELISA

Directory of Open Access Journals (Sweden)

Paula Ciaurriz

2017-01-01

Full Text Available The enzyme-linked immunosorbent assay (ELISA technique is based on the specific recognition ability of the molecular structure of an antigen (epitope by an antibody and is likely the most important diagnostic technique used today in bioscience. With this methodology, it is possible to diagnose illness, allergies, alimentary fraud, and even to detect small molecules such as toxins, pesticides, heavy metals, etc. For this reason, any procedures that improve the detection limit, sensitivity or reduce the analysis time could have an important impact in several fields. In this respect, many methods have been developed for improving the technique, ranging from fluorescence substrates to methods for increasing the number of enzyme molecules involved in the detection such as the biotin–streptavidin method. In this context, nanotechnology has offered a significant number of proposed solutions, mainly based on the functionalization of nanoparticles from gold to carbon which could be used as antibody carriers as well as reporter enzymes like peroxidase. However, few works have focused on the study of best practices for nanoparticle functionalization for ELISA enhancement. In this work, we use 20 nm gold nanoparticles (AuNPs as a vehicle for secondary antibodies and peroxidase (HRP. The design of experiments technique (DOE and four different methods for biomolecule loading were compared using a rabbit IgG/goat anti-rabbit IgG ELISA model (adsorption, directional, covalent and a combination thereof. As a result, AuNP probes prepared by direct adsorption were the most effective method. AuNPs probes were then used to detect gliadin, one of the main components of wheat gluten, the protein composite that causes celiac disease. With this optimized approach, our data showed a sensitivity increase of at least five times and a lower detection limit with respect to a standard ELISA of at least three times. Additionally, the assay time was remarkably decreased.

Cancer nanomedicine: gold nanoparticle mediated combined cancer therapy

Science.gov (United States)

Yang, C.; Bromma, Kyle; Chithrani, B. D.

2018-02-01

Recent developments in nanotechnology has provided new tools for cancer therapy and diagnosis. Among other nanomaterial systems, gold nanoparticles are being used as radiation dose enhancers and anticancer drug carriers in cancer therapy. Fate of gold nanoparticles within biological tissues can be probed using techniques such as TEM (transmission electron microscopy) and SEM (Scanning Electron Microscopy) due to their high electron density. We have shown for the first time that cancer drug loaded gold nanoparticles can reach the nucleus (or the brain) of cancer cells enhancing the therapeutic effect dramatically. Nucleus of the cancer cells are the most desirable target in cancer therapy. In chemotherapy, smart delivery of highly toxic anticancer drugs through packaging using nanoparticles will reduce the side effects and improve the quality and care of cancer patients. In radiation therapy, use of gold nanoparticles as radiation dose enhancer is very promising due to enhanced localized dose within the cancer tissue. Recent advancement in nanomaterial characterization techniques will facilitate mapping of nanomaterial distribution within biological specimens to correlate the radiobiological effects due to treatment. Hence, gold nanoparticle mediated combined chemoradiation would provide promising tools to achieve personalized and tailored cancer treatments in the near future.

Magnetic nanoparticle imaging using multiple electron paramagnetic resonance activation sequences

International Nuclear Information System (INIS)

Coene, A.; Dupré, L.; Crevecoeur, G.

2015-01-01

Magnetic nanoparticles play an important role in several biomedical applications such as hyperthermia, drug targeting, and disease detection. To realize an effective working of these applications, the spatial distribution of the particles needs to be accurately known, in a non-invasive way. Electron Paramagnetic Resonance (EPR) is a promising and sensitive measurement technique for recovering these distributions. In the conventional approach, EPR is applied with a homogeneous magnetic field. In this paper, we employ different heterogeneous magnetic fields that allow to stabilize the solution of the associated inverse problem and to obtain localized spatial information. A comparison is made between the two approaches and our novel adaptation shows an average increase in reconstruction quality by 5% and is 12 times more robust towards noise. Furthermore, our approach allows to speed up the EPR measurements while still obtaining reconstructions with an improved accuracy and noise robustness compared to homogeneous EPR

Linking Data for Mothers and Babies in De-Identified Electronic Health Data.

Science.gov (United States)

Harron, Katie; Gilbert, Ruth; Cromwell, David; van der Meulen, Jan

2016-01-01

Linkage of longitudinal administrative data for mothers and babies supports research and service evaluation in several populations around the world. We established a linked mother-baby cohort using pseudonymised, population-level data for England. Retrospective linkage study using electronic hospital records of mothers and babies admitted to NHS hospitals in England, captured in Hospital Episode Statistics between April 2001 and March 2013. Of 672,955 baby records in 2012/13, 280,470 (42%) linked deterministically to a maternal record using hospital, GP practice, maternal age, birthweight, gestation, birth order and sex. A further 380,164 (56%) records linked using probabilistic methods incorporating additional variables that could differ between mother/baby records (admission dates, ethnicity, 3/4-character postcode district) or that include missing values (delivery variables). The false-match rate was estimated at 0.15% using synthetic data. Data quality improved over time: for 2001/02, 91% of baby records were linked (holding the estimated false-match rate at 0.15%). The linked cohort was representative of national distributions of gender, gestation, birth weight and maternal age, and captured approximately 97% of births in England. Probabilistic linkage of maternal and baby healthcare characteristics offers an efficient way to enrich maternity data, improve data quality, and create longitudinal cohorts for research and service evaluation. This approach could be extended to linkage of other datasets that have non-disclosive characteristics in common.

Synthesis and Characterization of Metal Sulfides Nanoparticles/Poly(methyl methacrylate) Nanocomposites

OpenAIRE

Ajibade, Peter A.; Mbese, Johannes Z.

2014-01-01

Metal sulfides nanoparticles in poly(methyl methacrylate) matrices were prepared and characterized by infrared spectroscopy, thermogravimetric analysis, powder X-ray diffraction, scanning electron microscope (SEM), and transmission electron microscope (TEM). The FTIR confirms the dispersion of the nanoparticles in PMMA matrices with the C=O and C–O–C bonds of the PMMA shifting slightly which may be attributed to the interactions between the nanoparticles and PMMA. The ZnS nanoparticles in PMM...

Linked-cluster formulation of electron-hole interaction kernel in real-space representation without using unoccupied states.

Science.gov (United States)

Bayne, Michael G; Scher, Jeremy A; Ellis, Benjamin H; Chakraborty, Arindam

2018-05-21

Electron-hole or quasiparticle representation plays a central role in describing electronic excitations in many-electron systems. For charge-neutral excitation, the electron-hole interaction kernel is the quantity of interest for calculating important excitation properties such as optical gap, optical spectra, electron-hole recombination and electron-hole binding energies. The electron-hole interaction kernel can be formally derived from the density-density correlation function using both Green's function and TDDFT formalism. The accurate determination of the electron-hole interaction kernel remains a significant challenge for precise calculations of optical properties in the GW+BSE formalism. From the TDDFT perspective, the electron-hole interaction kernel has been viewed as a path to systematic development of frequency-dependent exchange-correlation functionals. Traditional approaches, such as MBPT formalism, use unoccupied states (which are defined with respect to Fermi vacuum) to construct the electron-hole interaction kernel. However, the inclusion of unoccupied states has long been recognized as the leading computational bottleneck that limits the application of this approach for larger finite systems. In this work, an alternative derivation that avoids using unoccupied states to construct the electron-hole interaction kernel is presented. The central idea of this approach is to use explicitly correlated geminal functions for treating electron-electron correlation for both ground and excited state wave functions. Using this ansatz, it is derived using both diagrammatic and algebraic techniques that the electron-hole interaction kernel can be expressed only in terms of linked closed-loop diagrams. It is proved that the cancellation of unlinked diagrams is a consequence of linked-cluster theorem in real-space representation. The electron-hole interaction kernel derived in this work was used to calculate excitation energies in many-electron systems and results

Electronic structure study of Co doped CeO2 nanoparticles using X-ray absorption fine structure spectroscopy

International Nuclear Information System (INIS)

Kumar, Shalendra; Gautam, Sanjeev; Song, T.K.; Chae, Keun Hwa; Jang, K.W.; Kim, S.S.

2014-01-01

Highlights: • The electronic structural of Co–CeO 2 nanoparticles is investigated using XAFS. • Ce M 5,4 , Ce L 3 and O K edge NEXAFS reveal that the Ce-ions are in +4 valence state. • The NEXAFS spectrum performed at Co L3,2-edge confirms Co-ion in 2+ state. • The EXAFS analysis also show that Co ions are occupying Ce position in doped CeO 2 . • The distances between Ce–O and Ce–Ce/Co in all shells decreases with Co doping. - Abstract: We investigated the electronic structure of well characterized Co doped CeO 2 nanoparticles using X-ray absorption fine structure (XAFS) spectroscopy. Near edge X-ray absorption fine structure (NEXAFS) spectra at Ce M 5,4 , Ce L 3 and O K-edge conclude that the Ce-ions are in +4 valence state in pure as well as in Co doped CeO 2 nanoparticles. The local structure around Ce-atom in Co doped CeO 2 nanoparticles was also determined using extended X-ray absorption fine structure (EXAFS) spectroscopy at Ce L 3 edge. The EXAFS analysis suggest that the inter-atomic distance of Ce–O, Ce–Ce/Co decreases with Co doping, which indicate a contraction of the lattice. The decease in Ce–O distance also reflect that there is a formation of oxygen vacancies in CeO 2 matrix. The Debye–Waller factor also shows the consistent behaviour for all the coordination shells. The atomic multiplet calculations for Co L 3,2 -edge was performed to determine the valence state, symmetry and field splitting, which reflect that Co-ions are in 2+ state and substituted at Ce-site with crystal field splitting of 10Dq=-0.57eV. The XAFS measurements reveal that the Co-ions occupy the Ce position in the CeO 2 host matrix and create a oxygen vacancy

Antimicrobial active silver nanoparticles and silver/polystyrene core-shell nanoparticles prepared in room-temperature ionic liquid

International Nuclear Information System (INIS)

An Jing; Wang Desong; Luo Qingzhi; Yuan Xiaoyan

2009-01-01

Uniform silver nanoparticles and silver/polystyrene core-shell nanoparticles were successfully synthesized in a room temperature ionic liquid, 1-n-butyl-3-methylimidazolium tetrafluoroborate ([BMIM].BF 4 ). [BMIM].BF 4 plays a protective role to prevent the nanoparticles from aggregation during the preparation process. Transmission electron micrographs confirm that both silver nanoparticles and core-shell nanoparticles are regular spheres with the sizes in the range of 5-15 nm and 15-25 nm, respectively. The X-ray diffraction analysis reveals the face-centered cubic geometry of silver nanoparticles. The as-prepared nanoparticles were also characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, UV-vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. In addition, antimicrobial activities against E. coli and S. aureus were studied and the results show that both silver nanoparticles and core-shell nanoparticles possess excellent antimicrobial activities. The antimicrobial mechanism of the as-prepared nanoparticles was discussed.

Dynamics of Supported Metal Nanoparticles Observed in a CS Corrected Environmental Transmission Electron Microscope

DEFF Research Database (Denmark)

Hansen, Thomas Willum; Dunin-Borkowski, Rafal E.; Wagner, Jakob Birkedal

resulting in the formation of larger particles and a loss of catalytic performance. Several models of sintering in different systems have been put forward [1,2]. However, most investigations have been post mortem studies, revealing only the final state of the catalyst. Transmission electron microscopy (TEM....... The combined capabilities of ETEM and image CS correction provide unique possibilities to study this relationship. However, in order to fully quantify image contrast from such experiments, a deeper understanding of the scattering of fast electrons in the presence of gas molecules in the pole piece gap...... of the microscope is needed. As industrial catalysts are usually complex high surface area materials, they are often not suited for fundamental studies. For this purpose, model systems consisting of gold nanoparticles on sheets of low surface area boron nitride and graphite supports were produced. Sheets...

Assessing protein oxidation by inorganic nanoparticles with enzyme-linked immunosorbent assay (ELISA).

Science.gov (United States)

Sun, Wenjie; Luna-Velasco, Antonia; Sierra-Alvarez, Reyes; Field, Jim A

2013-03-01

Growth in the nanotechnology industry is leading to increased production of engineered nanoparticles (NPs). This has given rise to concerns about the potential adverse and toxic effects to biological system and the environment. An important mechanism of NP toxicity is oxidative stress caused by the formation of reactive oxygen species (ROS) or via direct oxidation of biomolecules. In this study, a protein oxidation assay was developed as an indicator of biomolecule oxidation by NPs. The oxidation of the protein, bovine serum albumin (BSA) was evaluated with an enzyme-linked immunosorbent assay (ELISA) to measure the protein carbonyl derivatives formed from protein oxidation. The results showed that some NPs such as Cu(0), CuO, Mn(2)O(3), and Fe(0) caused oxidation of BSA; whereas, many of the other NPs tested were not reactive or very slowly reactive with BSA. The mechanisms involved in the oxidation of BSA protein by the reactive NPs could be attributed to the combined effects of ROS-dependent and direct protein oxidation mechanisms. The ELISA assay is a promising method for the assessment of protein oxidation by NPs, which can provide insights on NP toxicity mechanisms. Copyright © 2012 Wiley Periodicals, Inc.

Synthesis and characterization of dextran-coated iron oxide nanoparticles

Science.gov (United States)

Predescu, Andra Mihaela; Matei, Ecaterina; Berbecaru, Andrei Constantin; Pantilimon, Cristian; Drăgan, Claudia; Vidu, Ruxandra; Predescu, Cristian; Kuncser, Victor

2018-03-01

Synthesis and characterization of iron oxide nanoparticles coated with a large molar weight dextran for environmental applications are reported. The first experiments involved the synthesis of iron oxide nanoparticles which were coated with dextran at different concentrations. The synthesis was performed by a co-precipitation technique, while the coating of iron oxide nanoparticles was carried out in solution. The obtained nanoparticles were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction spectrometry, Fourier transform infrared spectroscopy and superconducting quantum interference device magnetometry. The results demonstrated a successful coating of iron oxide nanoparticles with large molar weight dextran, of which agglomeration tendency depended on the amount of dextran in the coating solution. SEM and TEM observations have shown that the iron oxide nanoparticles are of about 7 nm in size.

An electron microscopic study of the photochemical cross-linking of DNA in guinea pig epidermis by psoralen derivatives

International Nuclear Information System (INIS)

Cech, T.; Pathak, M.A.; Biswas, R.K.

1979-01-01

Albino guinea pigs were treated with psoralen derivatives plus 320-400 nm ultraviolet radiation, and DNA was extracted from their epidermis. The DNA was assayed for the presence of interstrand cross-links by standard denaturation-renaturation assays and by a new technique, electron microscopy of the DNA under totally denaturing conditions. The latter method allows individual cross-links to be directly observed and counted. When either 4,5',8-trimethylpsoralen or 8-methoxypsoralen was applied topically to the skin (8-20 μg/cm 2 ) or administered orally (10-12 mg/kg body weight), followed by exposure to 320-400 nm ultraviolet radiation, most of the epidermal DNA was found to contain a high frequency of cross-links. For example, oral or topical trimethylpsoralen treatment gave an average of one cross-link per 250 nucleotide pairs or about 3 . 10 5 cross-links per guinea pig chromosome. When the dose of either drug was decreased 20-fold to the level used in the clinical treatment of psoriasis, however, no cross-links could be detected in the epidermal DNA. The electron microscopic assay is sensitive enough that one can put an upper limit of 1 cross-link per 10 6 nucleotide pairs (80 cross-links per chromosome) for the low dose studies. The significance of these findings to the understanding of the effectiveness of psoralens in psoriasis therapy is discussed. (Auth.)

Kinetics of laser irradiated nanoparticles cloud

Science.gov (United States)

Mishra, S. K.; Upadhyay Kahaly, M.; Misra, Shikha

2018-02-01

A comprehensive kinetic model describing the complex kinetics of a laser irradiated nanoparticle ensemble has been developed. The absorbed laser radiation here serves dual purpose, viz., photoenhanced thermionic emission via rise in its temperature and direct photoemission of electrons. On the basis of mean charge theory along with the equations for particle (electron) and energy flux balance over the nanoparticles, the transient processes of charge/temperature evolution over its surface and mass diminution on account of the sublimation (phase change) process have been elucidated. Using this formulation phenomenon of nanoparticle charging, its temperature rise to the sublimation point, mass ablation, and cloud disintegration have been investigated; afterwards, typical timescales of disintegration, sublimation and complete evaporation in reference to a graphite nanoparticle cloud (as an illustrative case) have been parametrically investigated. Based on a numerical analysis, an adequate parameter space describing the nanoparticle operation below the sublimation temperature, in terms of laser intensity, wavelength and nanoparticle material work function, has been identified. The cloud disintegration is found to be sensitive to the nanoparticle charging through photoemission; as a consequence, it illustrates that radiation operating below the photoemission threshold causes disintegration in the phase change state, while above the threshold, it occurs with the onset of surface heating.

Biosynthesis of selenium nanoparticles by Pantoea agglomerans and their antioxidant activity

Energy Technology Data Exchange (ETDEWEB)

Torres, S. K.; Campos, V. L., E-mail: vcampos@udec.cl; Leon, C. G. [Universidad de Concepcion, Laboratorio de Microbiologia Ambiental, Departamento de Microbiologia (Chile); Rodriguez-Llamazares, S. M. [Centro de Investigacion de Polimeros Avanzados (CIPA) (Chile); Rojas, S. M.; Gonzalez, M. [Universidad de Concepcion, Laboratorio de Fisiologia Vascular, Departamento de Fisiologia (Chile); Smith, C. [Universidad de Concepcion, Departamento de Microbiologia (Chile); Mondaca, M. A. [Universidad de Concepcion, Laboratorio de Microbiologia Ambiental, Departamento de Microbiologia (Chile)

2012-11-15

The bio-reduction of selenite (Se (IV)) generates nanoparticles with sizes ranging between 30 and 300 nm. Biologic properties of Se nanoparticles, e.g., antioxidant activity, are dependent on the nanoparticle size; smaller particles have greater activity. In this study, the bio-reduction of selenite by Pantoea agglomerans strain UC-32 under aerobic conditions and room temperature to produce bioactive Se nanoparticles smaller than 100 nm was demonstrated. Isolation and purification of the nanoparticles was performed by alkaline lysis. These purified nanoparticles were stabilized with l-cysteine (4 mM). The visualization and characterization of nanoparticles were performed by transmission electron microscopy, energy dispersive X-ray spectroscopy, and scanning electron microscopy. The antioxidant activity of nanoparticles was determined by production of reactive oxygen species using human umbilical vein endothelial cells. Transmission electron microscopy images showed the accumulation of spherical selenium nanoparticles as intracellular and extracellular deposits. The size of Se nanoparticles varied with incubation time. Amorphous Se nanoparticles with size in the order of 100 nm were obtained before 24 h of incubation; but, at 24 h of incubation, the size of the majority of the nanoparticles was in the desirable order of 100 nm and they were not aggregated. Energy dispersive spectroscopy spectra indicated that nanoparticles were composed entirely of selenium. Antioxidant activity of stabilized selenium nanoparticles demonstrated high antioxidant activity when compared to selenite and selenium nanoparticles without stabilization. Stabilized biologically synthetized selenium (0) nanoparticles with size less than 100 nm have a potential application as a food additive with antioxidant properties relevant to human health.

Biosynthesis of selenium nanoparticles by Pantoea agglomerans and their antioxidant activity

International Nuclear Information System (INIS)

Torres, S. K.; Campos, V. L.; León, C. G.; Rodríguez-Llamazares, S. M.; Rojas, S. M.; González, M.; Smith, C.; Mondaca, M. A.

2012-01-01

The bio-reduction of selenite (Se (IV)) generates nanoparticles with sizes ranging between 30 and 300 nm. Biologic properties of Se nanoparticles, e.g., antioxidant activity, are dependent on the nanoparticle size; smaller particles have greater activity. In this study, the bio-reduction of selenite by Pantoea agglomerans strain UC-32 under aerobic conditions and room temperature to produce bioactive Se nanoparticles smaller than 100 nm was demonstrated. Isolation and purification of the nanoparticles was performed by alkaline lysis. These purified nanoparticles were stabilized with l-cysteine (4 mM). The visualization and characterization of nanoparticles were performed by transmission electron microscopy, energy dispersive X-ray spectroscopy, and scanning electron microscopy. The antioxidant activity of nanoparticles was determined by production of reactive oxygen species using human umbilical vein endothelial cells. Transmission electron microscopy images showed the accumulation of spherical selenium nanoparticles as intracellular and extracellular deposits. The size of Se nanoparticles varied with incubation time. Amorphous Se nanoparticles with size in the order of 100 nm were obtained before 24 h of incubation; but, at 24 h of incubation, the size of the majority of the nanoparticles was in the desirable order of 100 nm and they were not aggregated. Energy dispersive spectroscopy spectra indicated that nanoparticles were composed entirely of selenium. Antioxidant activity of stabilized selenium nanoparticles demonstrated high antioxidant activity when compared to selenite and selenium nanoparticles without stabilization. Stabilized biologically synthetized selenium (0) nanoparticles with size less than 100 nm have a potential application as a food additive with antioxidant properties relevant to human health.

Controlling Hydrogel Mechanics via Bio-Inspired Polymer-Nanoparticle Bond Dynamics.

Science.gov (United States)

Li, Qiaochu; Barrett, Devin G; Messersmith, Phillip B; Holten-Andersen, Niels

2016-01-26

Interactions between polymer molecules and inorganic nanoparticles can play a dominant role in nanocomposite material mechanics, yet control of such interfacial interaction dynamics remains a significant challenge particularly in water. This study presents insights on how to engineer hydrogel material mechanics via nanoparticle interface-controlled cross-link dynamics. Inspired by the adhesive chemistry in mussel threads, we have incorporated iron oxide nanoparticles (Fe3O4 NPs) into a catechol-modified polymer network to obtain hydrogels cross-linked via reversible metal-coordination bonds at Fe3O4 NP surfaces. Unique material mechanics result from the supra-molecular cross-link structure dynamics in the gels; in contrast to the previously reported fluid-like dynamics of transient catechol-Fe(3+) cross-links, the catechol-Fe3O4 NP structures provide solid-like yet reversible hydrogel mechanics. The structurally controlled hierarchical mechanics presented here suggest how to develop hydrogels with remote-controlled self-healing dynamics.

Electron irradiation induced nanocrystal formation in Cu-borosilicate glass

Energy Technology Data Exchange (ETDEWEB)

Sabri, Mohammed Mohammed; Möbus, Günter, E-mail: g.moebus@sheffield.ac.uk [University of Sheffield, Department of Materials Science and Engineering (United Kingdom)

2016-03-15

Nanoscale writing of Cu nanoparticles in glasses is introduced using focused electron irradiation by transmission electron microscopy. Two types of copper borosilicate glasses, one with high and another with low Cu loading, have been tested at energies of 200–300 keV, and formation of Cu nanoparticles in a variety of shapes and sizes using different irradiation conditions is achieved. Electron energy loss spectroscopy analysis, combined with high-resolution transmission electron microscopy imaging, confirmed the irradiation-induced precipitated nanoparticles as metallic, while furnace annealing of the glass triggered dendrite-shaped particles of copper oxide. Unusual patterns of nanoparticle rings and chains under focused electron beam irradiation are also presented. Conclusively, electron beam patterning of Cu-loaded glasses is a promising alternative route to well-established femtosecond laser photoreduction of Cu ions in glass.

Linking Informal and Formal Electronics Recycling via an Interface Organization

Directory of Open Access Journals (Sweden)

Yoshiaki Totoki

2013-07-01

Full Text Available Informal recycling of electronics in the developing world has emerged as a new global environmental concern. The primary approach to address this problem has been command-and-control policies that ban informal recycling and international trade in electronic scrap. These bans are difficult to enforce and also have negative effects by reducing reuse of electronics, and employment for people in poverty. An alternate approach is to link informal and formal sectors so as to maintain economic activity while mitigating environmental damages. This article explores the idea of an interface organization that purchases components and waste from informal dismantlers and passes them on to formal processors. Environmental, economic and social implications of interface organizations are discussed. The main environmental questions to resolve are what e-scrap components should be targeted by the interface organization, i.e., circuit boards, wires, and/or plastic parts. Economically, when formal recycling is more profitable (e.g., for circuit boards, the interface organization is revenue positive. However, price subsidies are needed for copper wires and residual waste to incentivize informal dismantlers to turn in for formal processing. Socially, the potential for corruption and gaming of the system is critical and needs to be addressed.

The extraction of gold nanoparticles from oat and wheat biomasses using sodium citrate and cetyltrimethylammonium bromide, studied by x-ray absorption spectroscopy, high-resolution transmission electron microscopy, and UV-visible spectroscopy

International Nuclear Information System (INIS)

Armendariz, Veronica; Parsons, Jason G; Lopez, Martha L; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L; Jose-Yacaman, Miguel

2009-01-01

Gold (Au) nanoparticles can be produced through the interaction of Au(III) ions with oat and wheat biomasses. This paper describes a procedure to recover gold nanoparticles from oat and wheat biomasses using cetyltrimethylammonium bromide or sodium citrate. Extracts were analyzed using UV-visible spectroscopy, high-resolution transmission electron microscopy (HRTEM), and x-ray absorption spectroscopy. The HRTEM data demonstrated that smaller nanoparticles are extracted first, followed by larger nanoparticles. In the fourth extraction, coating of chelating agents is visible on the extracted nanoparticles.

The extraction of gold nanoparticles from oat and wheat biomasses using sodium citrate and cetyltrimethylammonium bromide, studied by x-ray absorption spectroscopy, high-resolution transmission electron microscopy, and UV-visible spectroscopy.

Science.gov (United States)

Armendariz, Veronica; Parsons, Jason G; Lopez, Martha L; Peralta-Videa, Jose R; Jose-Yacaman, Miguel; Gardea-Torresdey, Jorge L

2009-03-11

Gold (Au) nanoparticles can be produced through the interaction of Au(III) ions with oat and wheat biomasses. This paper describes a procedure to recover gold nanoparticles from oat and wheat biomasses using cetyltrimethylammonium bromide or sodium citrate. Extracts were analyzed using UV-visible spectroscopy, high-resolution transmission electron microscopy (HRTEM), and x-ray absorption spectroscopy. The HRTEM data demonstrated that smaller nanoparticles are extracted first, followed by larger nanoparticles. In the fourth extraction, coating of chelating agents is visible on the extracted nanoparticles.

Structure determination of chitosan-stabilized Pt and Pd based bimetallic nanoparticles by X-ray photoelectron spectroscopy and transmission electron microscopy

International Nuclear Information System (INIS)

Wu, Lihua; Shafii, Salimah; Nordin, Mohd Ridzuan; Liew, Kong Yong; Li, Jinlin

2012-01-01

Chitosan (CTS)-stabilized bimetallic nanoparticles were prepared at room temperature (rt.) in aqueous solution. Palladium (Pd) and platinum (Pt) were selected as the first metals while iron (Fe) and nickel (Ni) functioned as the second metals. In order to obtain the noble metal core-transition metal shell structures, bimetallic nanoparticles were prepared in a two-step process: the preparation of mono noble metallic (Pd or Pt) nanoparticles and the deposition of transition metals (Fe or Ni) on the surface of the monometallic nanoparticles. The structures of the nanoparticles were studied using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The XPS results show that Pd and Pt exist mainly in zero valences. The presence of Fe and Ni in the bimetallic nanoparticles affects the binding energy of Pd and Pt. Moreover, the studies of O 1s spectra indicate the presence of Fe or Ni shells. The analyses of TEM micrographs give the particle size and size distributions while the high-resolution TEM (HRTEM) micrographs show the existence of noble metal core lattices. The results confirm the formation of noble metal core-transition metal shell structures. -- Highlights: ► Chitosan-stabilized bimetallic nanoparticles were prepared at room temperature in aqueous solution. ► The presence of Fe or Ni shells was proven by XPS study. ► The existence of noble metal cores covered by amorphous shells was indicated by TEM study. ► The formation of noble metal core-transition metal shell structures was confirmed.

X-Ray Spectroscopy of Gold Nanoparticles

Science.gov (United States)

Nahar, Sultana N.; Montenegro, M.; Pradhan, A. K.; Pitzer, R.

2009-06-01

Inner shell transitions, such as 1s-2p, in heavy elements can absorb or produce hard X-rays, and hence are widely used in nanoparticles. Bio-medical research for cancer treatment has been using heavy element nanoparticles, embeded in malignant tumor, for efficient absorption of irradiated X-rays and leading emission of hard X-rays and energetic electrons to kill the surrounding cells. Ejection of a 1s electron during ionization of the element by absorption of a X-ray photon initiates the Auger cascades of emission of photons and electrons. We have investigated gold nanoparticles for the optimal energy range, below the K-edge (1s) ionization threshold, that corresponds to resonant absorption of X-rays with large attenuation coefficients, orders of magnitude higher over the background as well as to that at K-edge threshold. We applied these attenuation coefficients in Monte Carlo simulation to study the intensities of emission of photons and electrons by Auger cascades. The numerical experiments were carried out in a phantom of water cube with a thin layer, 0.1mm/g, of gold nanoparticles 10 cm inside from the surface using the well-known code Geant4. We will present results on photon and electron emission spectra from passing monochromatic X-ray beams at 67 keV, which is the resonant energy for resonant K_{α} lines, at 82 keV, the K-shell ionization threshold, and at 2 MeV where the resonant effect is non-existent. Our findings show a high peak in the gold nanoparticle absorption curve indicating complete absorption of radiation within the gold layer. The photon and electron emission spectra show resonant features. Acknowledgement: Partially supported by a Large Interdisciplinary Grant award of the Ohio State University and NASA APRA program (SNN). The computational work was carried out on the Cray X1 and Itanium 4 cluster at the Ohio Supercomputer Center, Columbus Ohio. "Resonant X-ray Irradiation of High-Z Nanoparticles For Cancer Theranostics" (refereed

Structural, optical, morphological and dielectric properties of cerium oxide nanoparticles

International Nuclear Information System (INIS)

Prabaharan, Devadoss Mangalam Durai Manoharadoss; Sadaiyandi, Karuppasamy; Mahendran, Manickam; Sagadevan, Suresh

2016-01-01

Cerium oxide (CeO 2 ) nanoparticles were prepared by the precipitation method. The average crystallite size of cerium oxide nanoparticles was calculated from the X-ray diffraction (XRD) pattern and found to be 11 nm. The FT-IR spectrum clearly indicated the strong presence of cerium oxide nanoparticles. Raman spectrum confirmed the cubic nature of the cerium oxide nanoparticles. The Scanning Electron Microscopy (SEM) analysis showed that the nanoparticles agglomerated forming spherical-shaped particles. The Transmission Electron Microscopic (TEM) analysis confirmed the prepared cerium oxide nanoparticles with the particle size being found to be 16 nm. The optical absorption spectrum showed a blue shift by the cerium oxide nanoparticles due to the quantum confinement effect. The dielectric properties of cerium oxide nanoparticles were studied for different frequencies at different temperatures. The dielectric constant and the dielectric loss of the cerium oxide nanoparticles decreased with increase in frequency. The AC electrical conductivity study revealed that the conduction depended on both the frequency and the temperature. (author)

Structural, optical, morphological and dielectric properties of cerium oxide nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Prabaharan, Devadoss Mangalam Durai Manoharadoss [Department of Physics, NPR College of Engineering and Technology, Natham, Dindigul, Tamil Nadu (India); Sadaiyandi, Karuppasamy [Department of Physics, Alagappa Government Arts College, Karaikudi, Sivaganga, Tamil Nadu (India); Mahendran, Manickam [Department of Physics, Thiagarajar College of Engineering, Madurai, Tamil Nadu (India); Sagadevan, Suresh, E-mail: duraiphysics2011@gmail.com [Department of Physics, AMET University (India)

2016-03-15

Cerium oxide (CeO{sub 2}) nanoparticles were prepared by the precipitation method. The average crystallite size of cerium oxide nanoparticles was calculated from the X-ray diffraction (XRD) pattern and found to be 11 nm. The FT-IR spectrum clearly indicated the strong presence of cerium oxide nanoparticles. Raman spectrum confirmed the cubic nature of the cerium oxide nanoparticles. The Scanning Electron Microscopy (SEM) analysis showed that the nanoparticles agglomerated forming spherical-shaped particles. The Transmission Electron Microscopic (TEM) analysis confirmed the prepared cerium oxide nanoparticles with the particle size being found to be 16 nm. The optical absorption spectrum showed a blue shift by the cerium oxide nanoparticles due to the quantum confinement effect. The dielectric properties of cerium oxide nanoparticles were studied for different frequencies at different temperatures. The dielectric constant and the dielectric loss of the cerium oxide nanoparticles decreased with increase in frequency. The AC electrical conductivity study revealed that the conduction depended on both the frequency and the temperature. (author)

Carboxymethyl starch cross-linked by electron beam radiation in presence of acrylic acid sensitizer

International Nuclear Information System (INIS)

Doan Binh; Nguyen Thanh Duoc; Pham Thi Thu Hong

2013-01-01

Carboxymethyl starch (CMS) can be cross-linked by electron beam radiation to form a biocompatible and environment-friendly hydrogel at a high absorbed dose and a condensed CMS concentration. Acrylic acid (AAc) can be used as a sensitizer in order to reduce the absorbed doses to an acceptable certain level. At an absorbed dose of 3-4 kGy, the gel content of crosslinked CMS can be obtained about 50% with 5% (w/w) AAc concentration used. The compressive strength of CMS samples increased with increasing their cross-linked densities due to raising absorbed doses. The swelling ratio of cross-linked CMS was also attainable at a maximum of 50 times in the distilled water. The enzymatic degradation of cross-linked CMS was carried out in acetate buffer pH 4.6 with 0.1% α-amylase enzymatic solution incubated at 40℃ for 6 h. The crosslinked CMS samples were degraded slower than uncrosslinked CMS ones. The results indicated that the highly cross-linked CMS was almost fully degradable when the enzymatic hydrolysis was performed during 6 h. The FT IR spectra of cross-linked CMS in the presence of AAc were examined to observe the carboxyl group of AAc in the structure of cross-linked CMS. The hydrophilic of cross-linked CMS surface was determined by a contact-angle analysis. (authors)

A Biphasic Ligand Exchange Reaction on Cdse Nanoparticles: Introducing Undergraduates to Functionalizing Nanoparticles for Solar Cells

Science.gov (United States)

Zemke, Jennifer M.; Franz, Justin

2016-01-01

Semiconductor nanoparticles, including cadmium selenide (CdSe) particles, are attractive as light harvesting materials for solar cells. In the undergraduate laboratory, the size-tunable optical and electronic properties can be easily investigated; however, these nanoparticles (NPs) offer another platform for application-based tunability--the NP…

Inverter circuits on freestanding flexible substrate using ZnO nanoparticles for cost-efficient electronics

Science.gov (United States)

Vidor, Fábio F.; Meyers, Thorsten; Müller, Kathrin; Wirth, Gilson I.; Hilleringmann, Ulrich

2017-11-01

Driven by the Internet of Things (IoT), flexible and transparent smart systems have been intensively researched by the scientific community and by several companies. This technology is already available for consumers in a wide range of innovative products, e.g., flexible displays, radio-frequency identification tags and wearable electronic skins which, for instance, collect and analyze data for medical applications. For these systems, thin-film transistors (TFTs) are the key elements responsible for the driving currents. Solution-based materials such as nanoparticle dispersions avail the fabrication on large-area substrates with high throughput processes. In this study, we discuss the integration of ZnO nanoparticle thin-film transistors and inverter circuits on freestanding polymeric substrates enclosing the main issues concerning the transfer of the integration process from a rigid substrate to a flexible one. The TFTs depict VON between -0.2 and 1 V, ION/IOFF > 104 and field-effect mobility >0.5 cm2 V-1 s-1. Additionally, in order to enhance the transistors and inverters performance, an adaptation on the device configuration, from an inverted coplanar to an inverted staggered setup, was conducted and analyzed. By employing the inverted staggered setup a considerable increase in the contact quality between the semiconductor and the drain and source electrodes was observed. As the integrated devices depict electrical characteristics which enable the fabrication of electronic circuits for the low-cost sector, inverters were fabricated and characterized, evaluating the circuit's gain as function of the applied supply voltage and circuit's geometric ratio.

Supercooled smectic nanoparticles

DEFF Research Database (Denmark)

Kuntsche, Judith; Koch, Michel H J; Fahr, Alfred

2009-01-01

Cholesteryl nonanoate (CN), myristate (CM), palmitate (CP) and oleate (CO) alone or in combination were evaluated as matrix lipids for the preparation of supercooled smectic nanoparticles with a high stability against recrystallization during storage. The phase behavior of the cholesterol esters......, laser diffraction combined with polarizing intensity differential scattering, DSC and SAXS. The morphology of selected formulations was studied by freeze-fracture electron microscopy. All smectic nanoparticles with a mixed cholesterol ester matrix were stable against recrystallization when stored...... at room temperature. Nanoparticles with a pure CN and mixed CM/CN matrix with a high fraction of CN (60% of the whole lipid matrix) could even be stored at 4 degrees C for at least 18 months without any recrystallization. As smectic nanoparticles are studied especially with regard to parenteral...

Microwave-Assisted Synthesis of Alumina Nanoparticles Using Some Plants Extracts

Directory of Open Access Journals (Sweden)

Meisam Hasanpoor

2017-01-01

Full Text Available In present study we used five green plants for microwave assisted synthesis of Alumina nanoparticles from Aluminum nitrate. Structural characterization was studied using x-ray diffraction that showed semi- crystalline and possibly, amorphous structure. Fourier infrared spectroscopy was used to determine Al-O bond and functional groups responsible for synthesis of nanoparticles. FTIR confirmed existence of Al-O band and bio-functional groups, originated from plant extract. Morphology and size of nanoparticles were investigated using scanning electron microscopy, transmission electron microscopy and atomic force microscopy techniques. It was observed that nanoparticles have near-spherical shape. Average size of clusters of nanoparticles varied with different routes from of 60 nm to 300 nm. AFM images showed that Individual nanoparticles were less than 10 nm.

One-dimensional self-assembly of gold nanoparticles for tunable surface plasmon resonance properties

International Nuclear Information System (INIS)

Yang Yong; Matsubara, Shigemasha; Nogami, Masayuki; Shi Jianlin; Huang Weiming

2006-01-01

The localized surface plasmon resonance (LSPR) is a collective oscillation of the nanoparticle conduction electrons. LSPR excitation in silver and gold nanoparticles produces strong extinction and scattering spectra that in recent years have been used for important sensing and spectroscopy applications. Tuning the optoelectronic properties by controlling coupled SP modes in metals is one of the major challenges in the area of metal nanomaterials. Here we develop a simple method to fabricate linear-chainlike aggregates of gold nanoparticles (so-called nanochains), tuning the linear optical properties in a wide wavelength range from visible to the near infrared. The aggregation behaviour and linear self-assembly mechanism of citrate-stabilized gold colloids as provoked by the addition of cetyltrimethylammonium bromide (CTAB) are also analysed. The CTAB with appropriate concentration serves as the 'glue' that can link the {100} facets of two neighbour Au NPs, which leads to an anisotropic distribution of the residual surface charge, and this extrinsic electric dipole formation is responsible for the linear organization of the gold NPs into short chains

Ultrahigh Voltage Electron Microscopy Links Neuroanatomy and Neuroscience/Neuroendocrinology

Directory of Open Access Journals (Sweden)

Hirotaka Sakamoto

2012-01-01

Full Text Available The three-dimensional (3D analysis of anatomical ultrastructures is extremely important in most fields of biological research. Although it is very difficult to perform 3D image analysis on exact serial sets of ultrathin sections, 3D reconstruction from serial ultrathin sections can generally be used to obtain 3D information. However, this technique can only be applied to small areas of a specimen because of technical and physical difficulties. We used ultrahigh voltage electron microscopy (UHVEM to overcome these difficulties and to study the chemical neuroanatomy of 3D ultrastructures. This methodology, which links UHVEM and light microscopy, is a useful and powerful tool for studying molecular and/or chemical neuroanatomy at the ultrastructural level.

Structural characterization of copolymer embedded magnetic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Nedelcu, G.G., E-mail: ggnedelcu@yahoo.com [Faculty of Physics, University “Alexandru Ioan Cuza”, Carol I Bulevard, Nr.11, 700506 Iasi (Romania); Nastro, A.; Filippelli, L. [Department of Chemistry and Chemical Technology, University of Calabria, Via P. Bucci, 87036 Arcavacata di Rende, Cosenza (Italy); Cazacu, M.; Iacob, M. [Institute of Macromolecular Chemistry “Petru Poni”, Aleea Grigore Ghica Voda, nr. 41A, 700487 Iasi (Romania); Rossi, C. Oliviero [Department of Chemistry and Chemical Technology, University of Calabria, Via P. Bucci, 87036 Arcavacata di Rende, Cosenza (Italy); Popa, A.; Toloman, D. [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath Str., 400293 Cluj-Napoca 5 (Romania); Dobromir, M.; Iacomi, F. [Faculty of Physics, University “Alexandru Ioan Cuza”, Carol I Bulevard, Nr.11, 700506 Iasi (Romania)

2015-10-15

Highlights: • The emulsion polymerization method was used to synthesize three samples of poly(methyl methacrylate-co-acrylic acid) coated magnetite obtained before through co-precipitation technique. • Poly(methyl methacrylate-co-acrylic acid) coated magnetite nanoparticles were prepared having spherical shape and dimensions between 13 and 16 nm without agglomerations. • Fourier transform infrared spectra have found that the magnetite was pure and spectral characteristics of PMMA-co-AAc were present. • The electron spin resonance spectra revealed that interactions between nanoparticles are very weak due to the fact that the nanoparticles have been individually embedded in polymer. • The resonance field values as function of temperature demonstrate that the presence of polymer has not modified essentially its magnetic properties, except that at temperatures below 140 K there was a change due to decreasing of the magnetic anisotropy. - Abstract: Small magnetic nanoparticles (Fe{sub 3}O{sub 4}) were synthesized by co-precipitation and coated by emulsion polymerization with poly(methyl methacrylate-co-acrylic acid) (PMMA-co-AAc) to create surface functional groups that can attach drug molecules and other biomolecules. The coated and uncoated magnetite nanoparticles were stored for two years in normal closed ships and than characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, vibrating sample magnetometry, and electron paramagnetic resonance spectroscopy. The solid phase transformation of magnetite to maghemite, as well as an increase in particle size were evidenced for the uncoated nanoparticles. The coated nanoparticles preserved their magnetite structure and magnetic properties. The influences of monomers and surfactant layers on interactions between the magnetic nanoparticles evidenced that the thickness of the polymer has a significant effect on magnetic properties.

Magnetic properties of electron-doped La{sub 0.23}Ca{sub 0.77}MnO{sub 3} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Markovich, V., E-mail: markoviv@bgu.ac.il; Jung, G. [Ben-Gurion University of the Negev, Department of Physics (Israel); Wisniewski, A. [Polish Academy of Sciences, Institute of Physics (Poland); Mogilyansky, D. [Ben-Gurion University of the Negev, Ilse Katz Institute for Nanoscale Science and Technology (Israel); Puzniak, R. [Polish Academy of Sciences, Institute of Physics (Poland); Kohn, A. [Ben-Gurion University of the Negev, Ilse Katz Institute for Nanoscale Science and Technology (Israel); Wu, X. D.; Suzuki, K. [Monash University, Department of Materials Engineering (Australia); Gorodetsky, G. [Ben-Gurion University of the Negev, Department of Physics (Israel)

2012-09-15

Magnetic properties of electron-doped La{sub 0.23}Ca{sub 0.77}MnO{sub 3} manganite nanoparticles, with average size of 12 and 60 nm, prepared by the glycine-nitrate method, have been investigated in the temperature range 5-300 K and magnetic fields up to 90 kOe. It is suggested that weak ferromagnetic moment results from ferromagnetic shells of the basically antiferromagnetic nanoparticles and from domains of frustrated disordered phase in the core. Assumption of two distinct sources of ferromagnetism is supported by the appearance of two independent ferromagnetic contributions in the fit of the T{sup 3/2} Bloch law to spontaneous magnetization. The ferromagnetic components, which are more pronounced in smaller particles, occupy only a small fraction of the nanoparticle volume and the antiferromagnetic ground state remains stable. It is found that the magnetic hysteresis loops following field cooled processes, display size-dependent horizontal and vertical shifts, namely, exhibiting exchange bias effect. Time-dependent magnetization dynamics demonstrating two relaxation rates were observed at constant magnetic fields upon cooling to T < 100 K.

Graphene-enhanced Raman imaging of TiO2 nanoparticles

International Nuclear Information System (INIS)

Naumenko, Denys; Snitka, Valentinas; Snopok, Boris; Arpiainen, Sanna; Lipsanen, Harri

2012-01-01

The interaction of anatase titanium dioxide (TiO 2 ) nanoparticles with chemical vapour deposited graphene sheets transferred on glass substrates is investigated by using atomic force microscopy, Raman spectroscopy and imaging. Significant electronic interactions between the nanoparticles of TiO 2 and graphene were found. The changes in the graphene Raman peak positions and intensity ratios indicate that charge transfer between graphene and TiO 2 nanoparticles occurred, increasing the Raman signal of the TiO 2 nanoparticles up to five times. The normalized Raman intensity of TiO 2 nanoparticles per their volume increased with the disorder of the graphene structure. The complementary reason for the observed enhancement is that due to the higher density of states in the defect sites of graphene, a higher electron transfer occurs from the graphene to the anatase TiO 2 nanoparticles. (paper)

Biosynthesis of gold nanoparticles using diatoms-silica-gold and EPS-gold bionanocomposite formation

OpenAIRE

Schröfel, Adam; Kratošová, Gabriela; Bohunická, Markéta; Dobročka, Edmund; Vávra, Ivo

2011-01-01

Novel synthesis of gold nanoparticles, EPS-gold, and silica-gold bionanocomposites by biologically driven processes employing two diatom strains (Navicula atomus, Diadesmis gallica) is described. Transmission electron microscopy (TEM) and electron diffraction analysis (SAED) revealed a presence of gold nanoparticles in the experimental solutions of the diatom culture mixed with tetrachloroaureate. Nature of the gold nanoparticles was confirmed by X-ray diffraction studies. Scanning electron m...

Linking Data for Mothers and Babies in De-Identified Electronic Health Data.

Directory of Open Access Journals (Sweden)

Katie Harron

Full Text Available Linkage of longitudinal administrative data for mothers and babies supports research and service evaluation in several populations around the world. We established a linked mother-baby cohort using pseudonymised, population-level data for England.Retrospective linkage study using electronic hospital records of mothers and babies admitted to NHS hospitals in England, captured in Hospital Episode Statistics between April 2001 and March 2013.Of 672,955 baby records in 2012/13, 280,470 (42% linked deterministically to a maternal record using hospital, GP practice, maternal age, birthweight, gestation, birth order and sex. A further 380,164 (56% records linked using probabilistic methods incorporating additional variables that could differ between mother/baby records (admission dates, ethnicity, 3/4-character postcode district or that include missing values (delivery variables. The false-match rate was estimated at 0.15% using synthetic data. Data quality improved over time: for 2001/02, 91% of baby records were linked (holding the estimated false-match rate at 0.15%. The linked cohort was representative of national distributions of gender, gestation, birth weight and maternal age, and captured approximately 97% of births in England.Probabilistic linkage of maternal and baby healthcare characteristics offers an efficient way to enrich maternity data, improve data quality, and create longitudinal cohorts for research and service evaluation. This approach could be extended to linkage of other datasets that have non-disclosive characteristics in common.

Linking Data for Mothers and Babies in De-Identified Electronic Health Data

Science.gov (United States)

Gilbert, Ruth; Cromwell, David; van der Meulen, Jan

2016-01-01

Objective Linkage of longitudinal administrative data for mothers and babies supports research and service evaluation in several populations around the world. We established a linked mother-baby cohort using pseudonymised, population-level data for England. Design and Setting Retrospective linkage study using electronic hospital records of mothers and babies admitted to NHS hospitals in England, captured in Hospital Episode Statistics between April 2001 and March 2013. Results Of 672,955 baby records in 2012/13, 280,470 (42%) linked deterministically to a maternal record using hospital, GP practice, maternal age, birthweight, gestation, birth order and sex. A further 380,164 (56%) records linked using probabilistic methods incorporating additional variables that could differ between mother/baby records (admission dates, ethnicity, 3/4-character postcode district) or that include missing values (delivery variables). The false-match rate was estimated at 0.15% using synthetic data. Data quality improved over time: for 2001/02, 91% of baby records were linked (holding the estimated false-match rate at 0.15%). The linked cohort was representative of national distributions of gender, gestation, birth weight and maternal age, and captured approximately 97% of births in England. Conclusion Probabilistic linkage of maternal and baby healthcare characteristics offers an efficient way to enrich maternity data, improve data quality, and create longitudinal cohorts for research and service evaluation. This approach could be extended to linkage of other datasets that have non-disclosive characteristics in common. PMID:27764135

Synthesis and Characterization of BSA Conjugated Silver Nanoparticles (Ag/BSA Nanoparticles) and Evaluation of Biological Properties of Ag/BSA Nanoparticles and Ag/BSA Nanoparticles Loaded Poly(hydroxy butyrate valerate) PHBV Films

Science.gov (United States)

Ambaye, Almaz

Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa are the etiological agents of several infectious diseases. Antibiotic resistance by these three microbes has emerged as a prevalent problem due in part to the misuse of existing antibiotics and the lack of novel antibiotics. Nanoparticles have emerged as an alternative antibacterial agents to conventional antibiotics owing to their high surface area to volume ratio and their unique chemical and physical properties. Among the nanoparticles, silver nanoparticles have gained increasing attention because silver nanoparticles exhibit antibacterial activity against a range of gram positive and gram negative bacteria. Nanoparticles of well-defined chemistry and morphology can be used in broad biomedical applications, especially in bone tissue engineering applications, where bone infection by bacteria can be acute and lethal. It is commonly noted in the literature that the activity of nanoparticles against microorganisms is dependent upon the size and concentration of the nanoparticles as well as the chemistry of stabilizing agent. To the best of our knowledge, a comprehensive study that evaluates the antibacterial activity of well characterized silver nanoparticles in particular Bovine Serum Albumin (BSA) stabilized against S. aureus and E. coli and cytotoxicity level of BSA stabilized silver nanoparticles towards osteoblast cells (MC3T3-E1) is currently lacking. Therefore, the primary objective of this study was to characterize protein conjugated silver nanoparticles prepared by chemical reduction of AgNO3 and BSA mixture. The formation of Ag/BSA nanoparticles was studied by UV-Vis spectroscopy. The molar ratio of silver to BSA in the Ag/BSA nanoparticles was established to be 27+/- 3: 1, based on Thermogravimetric Analysis and Atomic Absorption Spectroscopy. Based on atomic force microscopy, dynamic light scattering,and transmission electron microscopy(TEM) measurements, the particle size (diameter) of

Inhibition effects of protein-conjugated amorphous zinc sulfide nanoparticles on tumor cells growth

International Nuclear Information System (INIS)

Cao Ying; Wang Huajie; Cao Cui; Sun Yuanyuan; Yang Lin; Wang Baoqing; Zhou Jianguo

2011-01-01

In this article, a facile and environmentally friendly method was applied to fabricate BSA-conjugated amorphous zinc sulfide (ZnS) nanoparticles using bovine serum albumin (BSA) as the matrix. Transmission electron microscopy analysis indicated that the stable and well-dispersed nanoparticles with the diameter of 15.9 ± 2.1 nm were successfully prepared. The energy dispersive X-ray, X-ray powder diffraction, Fourier transform infrared spectrograph, high resolution transmission electron microscope, and selected area electron diffraction measurements showed that the obtained nanoparticles had the amorphous structure and the coordination occurred between zinc sulfide surfaces and BSA in the nanoparticles. In addition, the inhibition effects of BSA-conjugated amorphous zinc sulfide nanoparticles on tumor cells growth were described in detail by cell viability analysis, optical and electron microscopy methods. The results showed that BSA-conjugated amorphous zinc sulfide nanoparticles could inhibit the metabolism and proliferation of human hepatocellular carcinoma cells, and the inhibition was dose dependent. The half maximal inhibitory concentration (IC50) was 0.36 mg/mL. Overall, this study suggested that BSA-conjugated amorphous zinc sulfide nanoparticles had the application potential as cytostatic agents and BSA in the nanoparticles could provide the modifiable site for the nanoparticles to improve their bioactivity or to endow them with the target function.

Increased apoptotic potential and dose-enhancing effect of gold nanoparticles in combination with single-dose clinical electron beams on tumor-bearing mice

International Nuclear Information System (INIS)

Chang Mengya; Chen Yuhung; Chang Chihjui; Chen Helen H-W; Wu Chaoliang; Shiau Aili

2008-01-01

High atomic number material, such as gold, may be used in conjunction with radiation to provide dose enhancement in tumors. In the current study, we investigated the dose-enhancing effect and apoptotic potential of gold nanoparticles in combination with single-dose clinical electron beams on B16F10 melanoma tumor-bearing mice. We revealed that the accumulation of gold nanoparticles was detected inside B16F10 culture cells after 18 h of incubation, and moreover, the gold nanoparticles were shown to be colocalized with endoplasmic reticulum and Golgi apparatus in cells. Furthermore, gold nanoparticles radiosensitized melanoma cells in the colony formation assay (P=0.02). Using a B16F10 tumor-bearing mouse model, we further demonstrated that gold nanoparticles in conjunction with ionizing radiation significantly retarded tumor growth and prolonged survival compared to the radiation alone controls (P<0.05). Importantly, an increase of apoptotic signals was detected inside tumors in the combined treatment group (P<0.05). Knowing that radiation-induced apoptosis has been considered a determinant of tumor responses to radiation therapy, and the length of tumor regrowth delay correlated with the extent of apoptosis after single-dose radiotherapy, these results may suggest the clinical potential of gold nanoparticles in improving the outcome of melanoma radiotherapy. (author)

Paclitaxel Albumin-stabilized Nanoparticle Formulation

Science.gov (United States)

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.

Mn doped GaN nanoparticles synthesized by rapid thermal treatment in ammonia

International Nuclear Information System (INIS)

Šimek, P.; Sedmidubský, D.; Huber, Š.; Klímová, K.; Maryško, M.; Mikulics, M.; Sofer, Z.

2015-01-01

We present a novel route for the synthesis of manganese doped GaN nanoparticles. Nanoparticles in the form of hexagonal discs were synthesized by rapid thermal treatment of manganese doped ammonium hexafluorogallate in ammonium atmosphere. The morphology of GaN:Mn nanoparticles was investigated using scanning electron microscopy. A concentration over 0.7 wt.% of Mn was observed by X-ray fluorescence and electron microprobe. Structural and electronic properties were investigated using X-ray diffraction, Raman spectroscopy and micro-photoluminescence with excitation wavelength of 325 nm and 532 nm. The magnetic properties between 4.5 K and 300 K were investigated by a superconducting quantum interference device (SQUID) magnetometer. GaN:Mn nanoparticles show a purely paramagnetic behavior which can be interpreted in terms of Mn 2+ ions exhibiting an antiferromagnetic interaction. - Highlights: • A new method for the synthesis of Mn doped GaN nanoparticles. • GaN:Mn nanoparticles form hexagonal discs. • None ferromagnetic ordering observed in GaN:Mn nanoparticles. • The concentration of Mn in GaN:Mn nanoparticles reach up to 0.8 wt.%

BiVO4 nanoparticles: Preparation, characterization and photocatalytic activity

Directory of Open Access Journals (Sweden)

Venkataraman Sivakumar

2015-12-01

Full Text Available Bismuth vanadate (BiVO4 nanoparticles were synthesized by a simple thermal decomposition method. The synthesized bismuth vanadate nanoparticles were characterized by X-ray diffraction analysis, it is found that the synthesized sample belongs to monoclinic BiVO4. Fourier transform infrared spectroscopy confirms the formation of Bi-O bond in the sample. Ultraviolet–Visible (DRS-UV–Visible spectroscopy and photoluminescence spectroscopy reveal the optical property of the BiVO4 nanoparticles. The morphology was identified by both scanning electron microscopy and high-resolution transmission electron microscopy. Further, the photocatalytic activity of BiVO4 nanoparticles was investigated by photodegradation of methylene blue as a model organic pollutant.

Bio-synthesis of gold nanoparticles by human epithelial cells, in vivo

International Nuclear Information System (INIS)

Larios-Rodriguez, E; Rangel-Ayon, C; Herrera-Urbina, R; Castillo, S J; Zavala, G

2011-01-01

Healthy epithelial cells, in vivo, have the ability to synthesize gold nanoparticles when aqueous tetrachloroauric acid is made to react with human skin. Neither a reducing agent nor a protecting chemical is needed for this bio-synthesis method. The first indication of gold nanoparticle formation is the staining of the skin, which turns deep purple. Stereoscopic optical micrographs of human skin tissue in contact with aqueous tetrachloroauric acid clearly show the staining of the epithelial cells. The UV-Vis spectrum of these epithelial cells shows an absorption band with a maximum at 553 nm. This absorption peak is within the wavelength region where the surface plasmon resonance (SPR) band of aqueous colloidal gold exhibits a maximum. Transmission electron micrographs show that gold nanoparticles synthesized by epithelial cells have sizes between 1 and 100 nm. The electron diffraction pattern of these nanoparticles reveals a crystalline structure whose interplanar distances correspond to fcc metallic gold. Transmission electron micrographs of ultra-thin (70 nm thick) slices of epithelial cells clearly and undoubtedly demonstrate that gold nanoparticles are inside the cell. According to high resolution transmission electron micrographs of intracellular single gold nanoparticles, they have the shape of a polyhedron.

Bio-synthesis of gold nanoparticles by human epithelial cells, in vivo

Energy Technology Data Exchange (ETDEWEB)

Larios-Rodriguez, E; Rangel-Ayon, C; Herrera-Urbina, R [Departamento de Ingenieria Quimica y Metalurgia, Universidad de Sonora, Rosales y Luis Encinas S/N, Hermosillo, Sonora, C.P. 83000 (Mexico); Castillo, S J [Departamento de Investigacion en Fisica, Universidad de Sonora, Rosales y Luis Encinas S/N, Hermosillo, Sonora, C.P. 83000 (Mexico); Zavala, G, E-mail: elarios@polimeros.uson.mx [Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Cuernavaca, Morelos (Mexico)

2011-09-02

Healthy epithelial cells, in vivo, have the ability to synthesize gold nanoparticles when aqueous tetrachloroauric acid is made to react with human skin. Neither a reducing agent nor a protecting chemical is needed for this bio-synthesis method. The first indication of gold nanoparticle formation is the staining of the skin, which turns deep purple. Stereoscopic optical micrographs of human skin tissue in contact with aqueous tetrachloroauric acid clearly show the staining of the epithelial cells. The UV-Vis spectrum of these epithelial cells shows an absorption band with a maximum at 553 nm. This absorption peak is within the wavelength region where the surface plasmon resonance (SPR) band of aqueous colloidal gold exhibits a maximum. Transmission electron micrographs show that gold nanoparticles synthesized by epithelial cells have sizes between 1 and 100 nm. The electron diffraction pattern of these nanoparticles reveals a crystalline structure whose interplanar distances correspond to fcc metallic gold. Transmission electron micrographs of ultra-thin (70 nm thick) slices of epithelial cells clearly and undoubtedly demonstrate that gold nanoparticles are inside the cell. According to high resolution transmission electron micrographs of intracellular single gold nanoparticles, they have the shape of a polyhedron.

Wood Sawdust/Natural Rubber Ecocomposites Cross-Linked by Electron Beam Irradiation

Directory of Open Access Journals (Sweden)

Elena Manaila

2016-06-01

Full Text Available The obtaining and characterization of some polymeric eco-composites based on wood sawdust and natural rubber is presented. The natural rubber was cross-linked using the electron beam irradiation. The irradiation doses were of 75, 150, 300 and 600 kGy and the concentrations of wood sawdust were of 10 and 20 phr, respectively. As a result of wood sawdust adding, the physical and mechanical properties such as hardness, modulus at 100% elongation and tensile strength, showed significant improvements. The presence of wood sawdust fibers has a reinforcing effect on natural rubber, similar or better than of mineral fillers. An increase in the irradiation dose leads to the increasing of cross-link density, which is reflected in the improvement of hardness, modulus at 100% elongation and tensile strength of blends. The cross-linking rates, appreciated using the Flory-Rehner equation, have increased with the amount of wood sawdust in blends and with the irradiation dose. Even if the gel fraction values have varied irregularly with the amount of wood sawdust and irradiation dose it was over 90% for all blends, except for the samples without wood sawdust irradiated with 75 kGy. The water uptake increased with increasing of fiber content and decreased with the irradiation dose.

Stability and electronic structure of iron nanoparticle anchored on defective hexagonal boron nitrogen nanosheet: A first-principle study

International Nuclear Information System (INIS)

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

Determination of dose enhancement caused by gold-nanoparticles irradiated with proton, X-rays (kV and MV) and electron beams, using alanine/EPR dosimeters

International Nuclear Information System (INIS)

Smith, Clare L.; Ackerly, Trevor; Best, Stephen P.; Gagliardi, Frank; Kie, Katahira; Little, Peter J.; McCorkell, Giulia; Sale, Charlotte A.; Tsunei, Yusuke; Tominaga, Takahiro; Volaric, Sioe See; Geso, Moshi

2015-01-01

The main aims of this research was to employ alanine doped with gold-nanoparticles “AuNPs” to determine the levels of dose enhancement caused by these particles when irradiated with proton beams, low and high energy X-rays and electrons. DL-alanine was impregnated with 5 nm gold-nanoparticles (3% by weight) and added as a uniform layer within a wax pellet of dimensions 10 × 5 × 5 mm. Control pellets, containing DL-Alanine were also produced, and placed within a phantom, and exposed to various types of radiations: low energy (kV ranges) X-rays were obtained from a superficial machine, high energy (MV) X-rays and electrons derived from a linear accelerator, and protons were produced by the Hyogo Ion Beam Centre in Japan. Nominal doses received ranged from 2 to 20 Gy (within clinical range). The Electron Paramagnetic Resonance (EPR) spectra of the irradiated samples were recorded on a BRUKER Elexsys 9.5 MHz. The dose enhancement caused by gold nanoparticles for 80 kV x-rays was found to be more than 60% at about 5 Gy. Smaller dose enhancements (under the same measurement conditions) were observed for megavoltage x-ray beams (up to 10%). Dose enhancement caused by charged particles indicated minimal values for 6 MeV electrons (approximately 5%) whilst less than that is obtained with protons of 150 MeV. The proton results validate the latest simulation results based on Monte Carlo calculations but the dose enhancement is significantly less than that reported in cell and animal model systems, (about 20%). We attribute this difference to the fact that alanine only measures the levels of free radicals generated by the inclusion of nanoparticles and not the redox type radicals (such as reactive oxygen species) generated from aqueous media in cells. Dose enhancement caused by 5 nm gold-nanoparticles with radiotherapy type proton beams has been found to be less than 5% as determined when using alanine/wax as both a phantom and dosimeter. This agrees well

Synthesis and characterization of cobalt/gold bimetallic nanoparticles

International Nuclear Information System (INIS)

Cheng, Guangjun; Hight Walker, Angela R.

2007-01-01

Cobalt/gold (Co/Au) bimetallic nanoparticles are prepared by chemically reducing gold (III) chloride to gold in the presence of pre-synthesized Co nanoparticles. Transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption spectrometry, and a superconducting quantum interference device (SQUID) magnetometer have been used to characterize as-prepared bimetallic nanoparticles. Our findings demonstrate Au not only grows onto Co nanoparticles, forming a surface coating, but also diffuses into Co nanoparticles. The introduction of Au alters the crystalline structure of Co nanoparticles and changes their magnetic properties. Dodecanethiols induce a reorganization of as-prepared Co/Au bimetallic nanoparticles

Magnetization, magnetotransport and electron magnetic resonance studies of nanoparticles and nanowires of Pr0.5Sr0.5MnO3

International Nuclear Information System (INIS)

Rao, S S; Bhat, S V

2009-01-01

In this paper, we present the preparation and characterization of nanoparticles and nanowires of Pr 0.5 Sr 0.5 MnO 3 (PSMO). The main results of this investigation are as follows: (a) a comparison with the properties of the bulk material shows that the ferromagnetic (FM) transition at 270 K remains unaffected but the anti-ferromagnetic (AFM) transition at T N = 150 K disappears in the nanoparticles, (b) the size induced ground state magnetic phase (below 150 K) is predominantly FM, coexisting with a residual AFM phase, and (c) the temperature dependence of magnetic anisotropy shows complex behaviour, being higher in the nanoparticles at high temperatures and lower at moderately lower temperatures in comparison with the bulk. The results obtained from the extensive magnetization, magnetotransport and electron magnetic resonance studies made on various samples are presented and discussed in detail.

Radiation-induced synthesis of gold, iron-oxide composite nanoparticles

International Nuclear Information System (INIS)

Seino, Satoshi; Yamamoto, Takao; Nakagawa, Takashi; Kinoshita, Takuya; Kojima, Takao; Taniguchi, Ryoichi; Okuda, Shuichi

2007-01-01

Composite nanoparticles consisting of magnetic iron oxide nanoparticles and gold nanoparticles were synthesized using gamma-rays or electron beam. Ionizing irradiation induces the generation of reducing species inside the aqueous solution, and gold ions are reduced to form metallic Au nanoparticles. The size of Au nanoparticles depended on the dose rate and the concentration of support iron oxide. The gold nanoparticles on iron oxide nanoparticles selectively adsorb biomolecules via Au-S bonding. By using magnetic property of the support iron oxide nanoparticles, the composite nanoparticles are expected as a new type of magnetic nanocarrier for biomedical applications. (author)

Size effect on the magnetic properties of antiferromagnetic La0.2Ca0.8MnO3 nanoparticles

Science.gov (United States)

Markovich, V.; Fita, I.; Wisniewski, A.; Mogilyansky, D.; Puzniak, R.; Titelman, L.; Martin, C.; Gorodetsky, G.

2010-03-01

Magnetic properties of electron-doped La0.2Ca0.8MnO3 manganite nanoparticles with average particle size ranging from 15 to 37 nm, prepared by the glycine-nitrate method, have been investigated in temperature range 5-300 K and in magnetic fields up to 90 kOe. A monotonous enhancement of weak ferromagnetism linked to the reduction in the particle size was observed for all nanoparticles. Magnetic hysteresis loops also indicate size-dependent exchange bias effect displayed by horizontal and vertical shifts in field-cooled processes. The magnetization data reveal two ferromagnetic components: first one appears at T˜200K and may be attributed to surface magnetization and second one appears as a result of spin canting of antiferromagnetic core or is developed at some interfaces inside nanoparticles. Time evolution of magnetization recorded in magnetic fields after the field cooling to low temperatures exhibits a very noisy behavior that may be caused by formation of collective state of nanoparticles with no clear tendency to reach equilibrium state. Magnetic properties of the nanoparticle samples are compared with those of the bulk La0.2Ca0.8MnO3 .

Size and composition tunable Ag-Au alloy nanoparticles by replacement reactions

International Nuclear Information System (INIS)

Zhang Qingbo; Lee, J Y; Yang Jun; Boothroyd, Chris; Zhang Jixuan

2007-01-01

Ag-Au alloy nanoparticles with tunable size and composition were prepared by a replacement reaction between Ag nanoparticles and HAuCl 4 at elevated temperatures. The formation of homogeneous alloy nanoparticles was confirmed by selected-area energy-dispersive x-ray spectroscopy (SAEDX), UV-visible absorption spectroscopy, high resolution transmission electron microscopy (HRTEM) and electron diffraction. This method leverages upon the rapid interdiffusion of Ag and Au atoms in the reduced dimension of a nanoparticle, elevated temperatures and the large number of vacancy defects created in the replacement reaction. This method of preparation has several notable advantages: (1) independent tuning of the size and composition of alloy nanoparticles; (2) production of alloy nanoparticles in high concentrations; (3) general utility in the synthesis of alloy nanoparticles that cannot be obtained by the co-reduction method

Single-Nanoparticle Photoelectrochemistry at a Nanoparticulate TiO2 -Filmed Ultramicroelectrode.

Science.gov (United States)

Peng, Yue-Yi; Ma, Hui; Ma, Wei; Long, Yi-Tao; Tian, He

2018-03-26

An ultrasensitive photoelectrochemical method for achieving real-time detection of single nanoparticle collision events is presented. Using a micrometer-thick nanoparticulate TiO 2 -filmed Au ultra-microelectrode (TiO 2 @Au UME), a sub-millisecond photocurrent transient was observed for an individual N719-tagged TiO 2 (N719@TiO 2 ) nanoparticle and is due to the instantaneous collision process. Owing to a trap-limited electron diffusion process as the rate-limiting step, a random three-dimensional diffusion model was developed to simulate electron transport dynamics in TiO 2 film. The combination of theoretical simulation and high-resolution photocurrent measurement allow electron-transfer information of a single N719@TiO 2 nanoparticle to be quantified at single-molecule accuracy and the electron diffusivity and the electron-collection efficiency of TiO 2 @Au UME to be estimated. This method provides a test for studies of photoinduced electron transfer at the single-nanoparticle level. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photovoltaic devices having nanoparticle dipoles for enhanced performance and methods for making same

Science.gov (United States)

Williams, George M [Portland, OR; Schut, David M [Philomath, OR; Stonas, Andreas [Albany, OR

2011-08-09

A photovoltaic device has nanoparticles sandwiched between a conductive substrate and a charge selective transport layer. Each of the nanoparticles has a ligand shell attached to the nanoparticle core. A first type of ligand is electron rich and attached to one hemisphere of the nanoparticle core, while a second type of ligand is electron poor and attached to an opposite hemisphere of the core. Consequently, the ligand shell induces an electric field within the nanoparticle, enhancing the photovoltaic effect. The arrangement of ligands types on different sides of the nanoparticle is obtained by a process involving ligand substitution after adhering the nanoparticles to the conductive substrate.

Photochemical synthesis of UO2 nanoparticles

International Nuclear Information System (INIS)

Rath, M.C.; Keny, Sangeeta; Naik, D.B.

2014-01-01

UO 2 nanoparticles have been recently synthesized by us from aqueous solutions of uranyl nitrate through radiolytic method on high-energy electron beam irradiation. In this study, the synthesis of UO 2 nanoparticles through photochemical method is reported which is a complementary route to radiation chemical method

X-ray spectroscopy study of electronic structure of laser-irradiated Au nanoparticles in a silica film

International Nuclear Information System (INIS)

Jonnard, P.; Bercegol, H.; Lamaignere, L.; Morreeuw, J.-P.; Rullier, J.-L.; Cottancin, E.; Pellarin, M.

2005-01-01

The electronic structure of gold nanoparticles embedded in a silica film is studied, both before and after irradiation at 355 nm by a laser. The Au 5d occupied valence states are observed by x-ray emission spectroscopy. They show that before irradiation the gold atoms are in metallic states within the nanoparticles. After irradiation with a fluence of 0.5 J/cm 2 , it is found that gold valence states are close to those of a metal-poor gold silicide; thanks to a comparison of the experimental Au 5d states with the calculated ones for gold silicides using the density-functional theory. The formation of such a compound is driven by the diffusion of the gold atoms into the silica film upon the laser irradiation. At higher fluence, 1 J/cm 2 , we find a higher percentage of metallic gold that could be attributed to annealing in the silica matrix

Self-Assembly of Gold Nanoparticles at the Liquid/Liquid Interface

International Nuclear Information System (INIS)

Lee, Kang Yeol; Han, Sang Woo

2005-01-01

We have shown that the crown ether derivative can mediate the transfer of gold nanoparticles in water solution to water/oil interface, results in directing the self-assembly of nanoparticles in the form of a novel nanocomposite film. The interfacial film of nanoparticles could be transferred to various solid substrates. The experimental results indicate the formation of nanoparticles monolayers at water/oil interfaces. Our work is an important step towards interfacial entrapment and self-assembly of nanoparticles for efficient creation of 2D nanostructures. These types of materials may be used in developing catalysts, sensors, and nanoelectronic devices. Currently, we are attempting to synthesize other composite films by using specific interactions between suitable organic or inorganic ligands and various nanoparticles. The intense research activity in the field of nanoparticles is motivated by the search for new materials in order to further miniaturize electronic devices, as well as by the fundamental question of how molecular electronic properties evolve with increasing size in this intermediate region between molecular and solid-state physics. In this respect, molecularly bridged nanoparticle aggregates have been attracting growing interest. The properties of two-dimensional assemblies of metal nanoparticles are controlled by the composition, geometry, and spatial arrangement of the nanoparticle building blocks. Such structures have been used for a variety of important applications in catalysis, photonics, electronics, and biological sensing. The 2D/3D control over the spatial arrangement of nanoparticles is primarily based on the thiolamphilic nature of metal nanoparticles, hydrogenbonding interactions, the highly specific recognition interaction of antigens/antibodies, and specific base-pairing interactions between DNA and its complementary strand

Copper nanoparticles functionalized PE: Preparation, characterization and magnetic properties

International Nuclear Information System (INIS)

Reznickova, A.; Orendac, M.; Kolska, Z.; Cizmar, E.; Dendisova, M.; Svorcik, V.

2016-01-01

Highlights: • Polyethylene (PE) surface was activated by argon plasma discharge. • Copper nanoparticles were coated on polyethylene via dithiol interlayer. • Prepared samples exhibit excellent structural and magnetic properties. • Studied properties may be utilized in design and fabrication of electronic devices. - Abstract: We report grafting of copper nanoparticles (CuNP) on plasma activated high density polyethylene (HDPE) via dithiol interlayer pointing out to the structural and magnetic properties of those composites. The as-synthesized Cu nanoparticles have been characterized by high-resolution transmission electron microscopy (HRTEM/TEM) and UV–vis spectroscopy. Properties of pristine PE and their plasma treated counterparts were studied by different experimental techniques: X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy, energy dispersive X-ray spectroscopy (EDS), zeta potential, electron spin resonance (ESR) and SQUID magnetometry. From TEM and HRTEM analyses, it is found that the size of high purity Cu nanoparticles is (12.2 ± 5.2) nm. It was determined that in the CuNPs, the copper atoms are arranged mostly in the (111) and (200) planes. Absorption in UV–vis region by these nanoparticles is ranging from 570 to 670 nm. EDS revealed that after 1 h of grafting are Cu nanoparticles homogeneously distributed over the whole surface and after 24 h of grafting Cu nanoparticles tend to aggregate slightly. The combined investigation of magnetic properties using ESR spectrometry and SQUID magnetometry confirmed the presence of copper nanoparticles anchored on PE substrate and indicated ferromagnetic interactions.

Copper nanoparticles functionalized PE: Preparation, characterization and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Reznickova, A., E-mail: alena.reznickova@vscht.cz [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague 6 (Czech Republic); Orendac, M., E-mail: martin.orendac@upjs.sk [Faculty of Science, P.J. Safarik University, Park Angelinum 9, 04013 Kosice (Slovakia); Kolska, Z., E-mail: zdenka.kolska@seznam.cz [Faculty of Science, J.E. Purkyne University, 400 96 Usti nad Labem (Czech Republic); Cizmar, E., E-mail: erik.cizmar@upjs.sk [Faculty of Science, P.J. Safarik University, Park Angelinum 9, 04013 Kosice (Slovakia); Dendisova, M., E-mail: vyskovsm@vscht.cz [Department of Physical Chemistry, University of Chemistry and Technology Prague, 166 28 Prague 6 (Czech Republic); Svorcik, V., E-mail: vaclav.svorcik@vscht.cz [Department of Solid State Engineering, University of Chemistry and Technology, 166 28 Prague 6 (Czech Republic)

2016-12-30

Highlights: • Polyethylene (PE) surface was activated by argon plasma discharge. • Copper nanoparticles were coated on polyethylene via dithiol interlayer. • Prepared samples exhibit excellent structural and magnetic properties. • Studied properties may be utilized in design and fabrication of electronic devices. - Abstract: We report grafting of copper nanoparticles (CuNP) on plasma activated high density polyethylene (HDPE) via dithiol interlayer pointing out to the structural and magnetic properties of those composites. The as-synthesized Cu nanoparticles have been characterized by high-resolution transmission electron microscopy (HRTEM/TEM) and UV–vis spectroscopy. Properties of pristine PE and their plasma treated counterparts were studied by different experimental techniques: X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy, energy dispersive X-ray spectroscopy (EDS), zeta potential, electron spin resonance (ESR) and SQUID magnetometry. From TEM and HRTEM analyses, it is found that the size of high purity Cu nanoparticles is (12.2 ± 5.2) nm. It was determined that in the CuNPs, the copper atoms are arranged mostly in the (111) and (200) planes. Absorption in UV–vis region by these nanoparticles is ranging from 570 to 670 nm. EDS revealed that after 1 h of grafting are Cu nanoparticles homogeneously distributed over the whole surface and after 24 h of grafting Cu nanoparticles tend to aggregate slightly. The combined investigation of magnetic properties using ESR spectrometry and SQUID magnetometry confirmed the presence of copper nanoparticles anchored on PE substrate and indicated ferromagnetic interactions.

Surface plasmon enhanced quantum transport in a hybrid metal nanoparticle array

International Nuclear Information System (INIS)

Sun, Lin; Nan, Yali; Xu, Shang; Zhang, Sishi; Han, Min

2014-01-01

Hybrid Pd–Ag nanoparticle arrays composed of randomly distributed Pd nanoparticles in dense packing and a small number of dispersed Ag nanoparticles were fabricated with controlled coverage. Photo-enhanced conductance was observed in the nanoparticle arrays. Largest enhancement, which can be higher than 20 folds, was obtained with 450 nm light illumination. This wavelength was found to correlate with the surface plasmon resonance of the Ag nanoparticles. Electron transport measurements showed there were significant Coulomb blockade in the nanoparticle arrays and the blockade could be overcome with the surface plasmon enhanced local field of Ag nanoparticles induced by light illumination. - Highlights: • We study photo-enhanced electron conductance of a hybrid Pd–Ag nanoparticle array. • The light-induced conductance enhancement is as high as 20 folds at 10 K. • The enhancement is correlate with the surface plasmon resonance of Ag nanoparticles. • Coulomb blockades is overcome with the surface plasmon enhanced local field

21 CFR 11.70 - Signature/record linking.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Signature/record linking. 11.70 Section 11.70 Food... RECORDS; ELECTRONIC SIGNATURES Electronic Records § 11.70 Signature/record linking. Electronic signatures and handwritten signatures executed to electronic records shall be linked to their respective...

Structure and magnetic properties of Cr nanoparticles and Cr2O3 nanoparticles

International Nuclear Information System (INIS)

Zhang, W.S.; Brueck, E.; Zhang, Z.D.; Tegus, O.; Li, W.F.; Si, P.Z.; Geng, D.Y.; Buschow, K.H.J.

2005-01-01

We have synthesized Cr nanoparticles by arc-discharge and Cr 2 O 3 nanoparticles by subsequent annealing the as-prepared Cr nanoparticles. The structure of these nanoparticles is studied by means of X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscope. Most of the particles show a good crystal habit of well-defined cubic or orthorhombic shape, while some small particles show spherical shape. The as-prepared Cr nanoparticles have a BCC Cr core coated with a thin Cr 2 O 3 layer. Cr in the core of the particles heated at 873 K for 4 h is changed to Cr 2 O 3 . The results of magnetic measurements show that the Cr nanoparticles exhibit mainly antiferromagnetic properties, in addition to a weak-ferromagnetic component at lower fields. The weak-ferromagnetic component may be ascribed to uncompensated surface spins. For the field-cooled Cr 2 O 3 nanoparticles, an exchange bias is observed in the hysteresis loops, which can be interpreted as the exchange coupling between the uncompensated spins at the surface and the spins in the core of the Cr 2 O 3 nanoparticles

Palladium nanoparticles produced by CW and pulsed laser ablation in water

Energy Technology Data Exchange (ETDEWEB)

Boutinguiza, M., E-mail: mohamed@uvigo.es [Applied Physics Department, University of Vigo EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain); Comesaña, R. [Materials Engineering, Applied Mechanics and Construction Department, University of Vigo, EEI, Lagoas-Marcosende, Vigo 36310 (Spain); Lusquiños, F. [Applied Physics Department, University of Vigo EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain); Riveiro, A. [Applied Physics Department, University of Vigo EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain); Centro Universitario de la Defensa, Escuela Naval Militar, Plaza de España 2, 36920 Marín (Spain); Val, J. del; Pou, J. [Applied Physics Department, University of Vigo EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain)

2014-05-01

Palladium nanoparticles are receiving important interest due to its application as catalyst. In this work Pd nanoparticles have been obtained by ablating a Pd target submerged in de-ionized using both, pulsed as well as continuous wave (CW) laser. The influence of laser parameters involved in the formation in nanoparticles has been studied. Crystalline phases, morphology and optical properties of the obtained colloidal nanoparticles were characterized by means of transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and UV/vis absorption spectroscopy. The obtained colloidal suspensions consisted of pure Pd nanoparticles showing spherical shape with diameters ranging from few nanometers to 5–60 nm. The moderate irradiance delivered by the CW laser favours high production of uniform nanoparticles.