WorldWideScience

Sample records for monodisperse spiro-bridged ladder-type

  1. Towards Monodisperse Star-Shaped Ladder-Type Conjugated Systems: Design, Synthesis, Stabilized Blue Electroluminescence and Amplified Spontaneous Emission.

    Science.gov (United States)

    Lai, Wen-Yong; Jiang, Yi; Fang, Mei; Chang, Si-Ju; Huang, Jin-Jin; Chu, Shuang-Quan; Hu, Shan-Ming; Liu, Cheng-Fang; Huang, Wei

    2017-02-14

    A novel series of monodisperse star-shaped ladder-type oligo(p-phenylene)s, named as TrL-n (n = 1-3), have been explored. Their thermal and electrochemical properties, fluorescence transients, photoluminescence quantum yields, density functional theory calculations, electroluminescence (EL) and amplified spontaneous emission (ASE) properties have been systematically investigated to unravel the molecular design on optoelectronic properties. The resulting materials showed excellent structural perfection free of chemical defects, exhibiting great thermal stability (Td: 404-418°C and Tg:147-184°C) and amorphous glassy morphologies. Compared with their corresponding linear counterparts FL-m (m = 1-3), TrL-n showed only little bathochromic shifts (5-12 nm) for the absorption maxima λmax in both solution and films. The star-shaped ladder-type compounds exhibited enhanced optical stability and suppressed low-energy emission. Their EL spectra exhibited excellent stability with increasing the driving voltage from 6 to 12 V. Moreover, superior low ASE thresholds were recorded for TrL-n compared with FL-m. Rather low ASE threshold (29 nJ/pulse or 1.60 μJ/cm2) was recorded for TrL-3, demonstrating their promising potential as excellent gain media. This study provides a novel design concept to develop monodisperse star-shaped ladder-type materials with excellent structural perfection, which are vital for shedding light on exploring robust organic emitters for optoelectronic applications.

  2. Genus distribution of ladder type and cross type graphs

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In this paper a method is given to calculate the explicit expressions of embedding genus distribution for ladder type graphs and cross type graphs. As an example, we refind the genus distri- bution of the graph Jn which is the first class of graphs studied for genus distribution where its genus depends on n.

  3. Genus distribution of ladder type and cross type graphs

    Institute of Scientific and Technical Information of China (English)

    WAN LiangXia; FENG KeQin; LIU YanPei; WANG DianJun

    2009-01-01

    In this paper a method is given to calculate the explicit expressions of embedding genus distribution for ladder type graphs and cross type graphs.As an example,we refind the genus distribution of the graph Jn which is the first class of graphs studied for genus distribution where its genus depends on n.

  4. Design of a 325 MHz ladder - type RFQ for FAIR

    Energy Technology Data Exchange (ETDEWEB)

    Schuett, Maximilian; Brodhage, Robert; Almomani, Ali; Ratzinger, Ulrich [Institut fuer Angewandte Physik, Goethe-Universitaet Frankfurt, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany)

    2014-07-01

    For the research program with cooled antiprotons at FAIR a dedicated 70 MeV, 70 mA proton injector is required. The first rf accelerator element is a 325 MHz RFQ accelerating from 95 keV to 3.0 MeV. RFQ's beyond 300 MHz were realized in 4-Vane-type geometry so far. At IAP there is a tradition in 4-Rod-type RFQ development. This RFQ-type is dominating at lower frequencies. Very promising results have been reached with a ladder type-RFQ, which has been investigated during 2013. We show most recent 3D simulations of the general layout and of a whole cavity demonstrating the power of a ladder type RFQ. An RFQ layout for the new FAIR proton injector is presented. In comparison with a traditional 4-Rod RFQ approach the geometry is more convenient at high frequencies.

  5. Comparison of up ladder type and terraced type normalizing heat treatments of heavy cylinder

    Institute of Scientific and Technical Information of China (English)

    孙建亮; 彭艳; 邱丑武; 张永振

    2016-01-01

    Because of the mixed grain and coarse grain structure, the long heat treatment cycle and large energy conservation in the heavy cylinder heat treatment process, the up ladder type and terraced type normalizing heat treatment of heavy cylinder after rolling were put forward. The microstructure and mechanical properties of 2.25Cr1Mo0.25V steel after the up ladder type normalizing, terraced type normalizing and isothermal type normalizing were studied. Experimental results show that: 1) For the grain refinement, the twice terraced type normalizing is better than the up ladder type and isothermal type normalizing, and the average grain size is 18μm; 2) The yield strength, tensile strength and−30 °C charpy impact energy after twice terraced type normalizing are 681 MPa, 768 MPa and 181 J, respectively, and the mechanical properties are better than those of the up ladder type and isothermal type normalizing; 3) Compared with the isothermal type normalizing, the holding time of terraced type normalizing can be shortened by 30%, which greatly reduces the energy consumption.

  6. Atomic coherence effects in four-wave mixing process of a ladder-type atomic system.

    Science.gov (United States)

    Lee, Yoon-Seok; Moon, Han Seb

    2016-05-16

    We investigate the effects of atomic coherence on four-wave mixing (FWM), with respect to the transition routes between the hyperfine states in the 5S1/2-5P3/2-5D5/2 transition of 87Rb atoms. By comparing the FWM spectra with the electromagnetically induced transparency (EIT) spectra of the hyperfine states, we confirm that the FWM process is significantly influenced by both ladder-type and V-type two-photon coherences. From the observed FWM signal of each hyperfine structure, we clarify the role of two-photon coherence in the FWM process under EIT, double-resonance optical pumping (DROP), and two-photon absorption (TPA) conditions in a ladder-type atomic system, which is dependent on the open degree of the hyperfine states, the laser intensity, and the laser frequency detuning.

  7. Effects of spontaneously induced coherence on absorption of a ladder-type atom

    Institute of Scientific and Technical Information of China (English)

    Ma Hong-Mei; Gong Shang-Qing; Sun Zhen-Rong; Li Ru-Xin; Xu Zhi-Zhan

    2006-01-01

    This paper investigates the effects of spontaneously induced coherence on absorption properties in a nearly equispaced three-level ladder-type system driven by two coherent fields. It find that the absorption properties of this system with the probe field applied on the lower transition can be significantly modified if this coherence is optimized. In the case of small spontaneous decay rate in the upper excited state, it finds that such coherence does not destroy the electromagnetically induced transparency (EIT). Nevertheless, the absorption peak on both sides of zero detuning and the linewidth of absorption line become larger and narrower than those in the case corresponding to the effects of spontaneously induced coherence; while in the case of large decay rate, it finds that, instead of EIT with low resonant absorption, a sharp absorption peak at resonance appears. That is, electromagnetically induced absorption in the nearly equispaced ladder-type system can occur due to such coherent effects.

  8. Ladder-type electromagnetically induced transparency using nanofiber-guided light in a warm atomic vapor

    CERN Document Server

    Jones, D E; Pittman, T B

    2015-01-01

    We demonstrate ladder-type electromagnetically induced transparency (EIT) using an optical nanofiber suspended in a warm rubidium vapor. The signal and control fields are both guided along the nanofiber, which enables strong nonlinear interactions with the surrounding atoms at relatively low powers. Transit-time broadening is found to be a significant EIT decoherence mechanism in this tightly-confined waveguiding geometry. Nonetheless, we observe significant EIT and controlled polarization rotation using control-field powers of only a few microWatts in this relatively robust warm-atom nanofiber system.

  9. Thermoelectric Properties of Solution-Processed n-Doped Ladder-Type Conducting Polymers

    DEFF Research Database (Denmark)

    Wang, Suhao; Sun, Hengda; Ail, Ujwala;

    2016-01-01

    Ladder-type "torsion-free" conducting polymers (e.g., polybenzimidazobenzophenanthroline (BBL)) can outperform "structurally distorted" donor-acceptor polymers (e.g., P(NDI2OD-T2)), in terms of conductivity and thermoelectric power factor. The polaron delocalization length is larger in BBL than...... in P(NDI2OD-T2), resulting in a higher measured polaron mobility. Structure-function relationships are drawn, setting material-design guidelines for the next generation of conducting thermoelectric polymers....

  10. Population transfer by femtosecond laser pulses in a ladder-type atomic system

    Institute of Scientific and Technical Information of China (English)

    Fan Xi-Jun; Li Ai-Yun; Tong Dian-Min; Liu Cheng-Pu

    2008-01-01

    The population transfer in a ladder-type atomic system driven by linearly polarized sech-shape femtosecond laser pulses is investigated by numerically solving Schrodinger equation without including the rotating wave approximation (RWA). It is shown that population transfer is mainly determined by the Rabi frequency (strength) of the driving laser field and the chirp rate, and that the ratio of the dipole moments and the pulse width also have a prominent effect on the population transfer. By choosing appropriate values of the above parameters, complete population transfer can be realized.

  11. Theoretical Design of a 104 MHz Ladder Type IH-RFQ Accelerator

    Institute of Scientific and Technical Information of China (English)

    NIE Yuan-Cun; LU Yuan-Rong; CHEN Jia-Er; YAN Xue-Qing; GAO Shu-Li; ZHU Kun; LIU Ke-Xin; GUO Zhi-Yu

    2010-01-01

    @@ Beam dynamics and rf designs of a 104 MHz ladder type IH-RFQ (L-IH-RFQ) accelerator are finished at Peking University for the acceleration of 14C+ from 40 keV to 500 keV. As a specific feature, the output beam energy spread is as low as 0.6% achieved with the internal discrete bunching method, which makes potential applications of RFQ feasible, such as accelerator mass spectrometry and ion implantation. Tolerances of the beam dynamics design are studied by means of changing the input beam parameters, and the results are quite satisfying. On the other hand, the L-IH-RFQ structure is employed, taking advantage of its mechanical stability and the absence of inter-electrode voltage asymmetry. Radio-frequency properties are studied and optimized for reducing power loss with Microwave Studio (MWS). Tuning of the field fiatness and frequency is investigated in principle.

  12. Donor-acceptor conjugated polymers based on multifused ladder-type arenes for organic solar cells.

    Science.gov (United States)

    Wu, Jhong-Sian; Cheng, Sheng-Wen; Cheng, Yen-Ju; Hsu, Chain-Shu

    2015-03-07

    Harvesting solar energy from sunlight to generate electricity is considered as one of the most important technologies to address the future sustainability of humans. Polymer solar cells (PSCs) have attracted tremendous interest and attention over the past two decades due to their potential advantage to be fabricated onto large area and light-weight flexible substrates by solution processing at a lower cost. PSCs based on the concept of bulk heterojunction (BHJ) configuration where an active layer comprises a composite of a p-type (donor) and an n-type (acceptor) material represents the most useful strategy to maximize the internal donor-acceptor interfacial area allowing for efficient charge separation. Fullerene derivatives such as [6,6]-phenyl-C61 or 71-butyric acid methyl ester (PCBM) are the ideal n-type materials ubiquitously used for BHJ solar cells. The major effort to develop photoactive materials is numerously focused on the p-type conjugated polymers which are generally synthesized by polymerization of electron-rich donor and electron-deficient acceptor monomers. Compared to the development of electron-deficient comonomers (acceptor segments), the development of electron-rich donor materials is considerably flourishing. Forced planarization by covalently fastening adjacent aromatic and heteroaromatic subunits leads to the formation of ladder-type conjugated structures which are capable of elongating effective conjugation, reducing the optical bandgap, promoting intermolecular π-π interactions and enhancing intrinsic charge mobility. In this review, we will summarize the recent progress on the development of various well-defined new ladder-type conjugated materials. These materials serve as the superb donor monomers to prepare a range of donor-acceptor semi-ladder copolymers with sufficient solution-processability for solar cell applications.

  13. Theoretical study of anisotropic mobility in ladder-type molecule organic semiconductors

    Science.gov (United States)

    Wei, Hui-Ling; Liu, Yu-Fang

    2014-09-01

    The properties of two ladder-type semiconductors {M1: 2,2'-(2,7-dihexy1-4,9-dihydro- s-indaceno[1,2- b:5,6- b']dithiophene-4,9-diylidene) dimalononitrile and M2: 2,7-dihexy1-4,9-dihydro- s-indaceno[1,2- b:5,6- b']dithiophene-4,9-dione} as the n-type and ambipolar organic materials are systematically investigated using the first-principle density functional theory combined with the Marcus-Hush electron transfer theory. It is found that the substitution of M1 induces large changes in its electron-transfer mobility of 1.370 cm2 V-1 s-1. M2 has both large electron- and hole-transfer mobility of 0.420 and 0.288 cm2 V-1 s-1, respectively, which indicates that M2 is potentially a high efficient ambipolar organic semiconducting material. Both the M1 and M2 crystals show remarkable anisotropic behavior. A proper design of the n-type and ambipolar organic electronic materials, which may have high mobility performance, is suggested based on the investigated two molecules.

  14. Effects of relative phase on transient evolution in an open resonant ladder-type atomic system

    Institute of Scientific and Technical Information of China (English)

    Yang Yan-Ling; Liu Zhong-Bo; Wang Lei; Tong Dian-Min; Fan Xi-Jun

    2009-01-01

    In an open ladder-type resonant atomic system, variation in relative phase between probe and driving fields does not affect the transient evolution of populations, but it has remarkable effects on gain and dispersion of the probe field. No matter whether an incoherent pump is present or absent, transient and stationary gains without inversion (GWI) always can be obtained by choosing an appropriate value of the relative phase. When the incoherent pump is absent, the values of transient and stationary GWIs are much larger and the time interval required to reach the stationary value is longer than those when the incoherent pump is present. Varying the exit rate and the ratio between injection rates can obviously change the phase-dependent GWI. In addition, in the transient evolution process, the phenomenon of high dispersion (refractive index) without absorption occurs at some values of relative phase. In the corresponding closed system, the stationary GWI can be obtained by choosing an appropriate value of relative phase only when incoherent pump exists, moreover the gain is smaller than that in the open system.

  15. Generation of non-classical correlated photon pairs via a ladder-type atomic configuration: theory and experiment.

    Science.gov (United States)

    Ding, Dong-Sheng; Zhou, Zhi-Yuan; Shi, Bao-Sen; Zou, Xu-Bo; Guo, Guang-Can

    2012-05-07

    We experimentally generate a non-classical correlated two-color photon pair at 780 and 1529.4 nm in a ladder-type configuration using a hot 85Rb atomic vapor with the production rate of ~10(7)/s. The non-classical correlation between these two photons is demonstrated by strong violation of Cauchy-Schwarz inequality by the factor R = 48 ± 12. Besides, we experimentally investigate the relations between the correlation and some important experimental parameters such as the single-photon detuning, the powers of pumps. We also make a theoretical analysis in detail and the theoretical predictions are in reasonable agreement with our experimental results.

  16. Four-Wave Mixing Scheme in a Four-Level Ladder-Type Atomic System Based on Electromagnetically Induced Transparency

    Institute of Scientific and Technical Information of China (English)

    LI Jia-Hua; CHEN Ai-Xi; PENG Ju-Cun

    2004-01-01

    @@ A nonlinear optical four-wave mixing scheme is presented and analysed for the generation of coherent light in a nearly four-level ladder-type atomic system in the context of electromagnetically induced transparency (EIT).We find that EIT can suppress nonlinear photon absorption and the peak of the generated mixing field is located at the centre of the transparency window where the loss is minimal, though there is a dip in the centre. Such a nonlinear optical process can also be used for generating coherent short-wavelength radiation.

  17. Direct Observation of Ultrafast Field-Induced Charge Generation in Ladder-Type Poly(Para-Phenylene)

    Science.gov (United States)

    Graupner, W.; Cerullo, G.; Lanzani, G.; Nisoli, M.; List, E. J. W.; Leising, G.; de Silvestri, S.

    1998-10-01

    Electric field-induced charge photogeneration in ladder-type poly(para-phenylene) is investigated by field-assisted femtosecond pump-probe experiments carried out on light emitting diodes. The characteristic photoinduced absorption band at 1.9 eV allows one to directly monitor the polaron population. We find that polarons are formed by exciton fission without intermediate states on a time scale of 10 ps. The buildup kinetics of the polaron population suggests a dissociation driven by exciton diffusion during interchain thermalization.

  18. Photogeneration Action Spectroscopy of Neutral and Charged Excitations in Films of a Ladder-Type Poly(Para-Phenylene)

    Science.gov (United States)

    Wohlgenannt, M.; Graupner, W.; Leising, G.; Vardeny, Z. V.

    1999-04-01

    The photogeneration quantum efficiency action spectra of long-lived neutral and charged excitations in films of a ladder-type poly(para-phenylene) were measured. We found that both triplet and polaron action spectra show, in addition to a step function increase at the optical gap, a monotonic rise at higher energies. For triplets this rise is explained by singlet exciton fission into triplet pairs from which the triplet exciton energy in the gap was obtained; this energy was also confirmed by measuring the weak phosphorescence band. For polarons the photogeneration increase at high energies is modeled by a novel hot electron interchain tunneling process.

  19. Alkylated selenophene-based ladder-type monomers via a facile route for high performance thin-film transistor applications

    KAUST Repository

    Fei, Zhuping

    2017-05-26

    We report the synthesis of two new selenophene containing ladder-type monomers, cyclopentadiselenophene (CDS) and indacenodiselenophene (IDSe), via a twofold and fourfold Pd catalyzed coupling with a 1,1-diborylmethane derivative. Co-polymers with benzothiadiazole (BT) were prepared in high yield by Suzuki polymerization to afford co-polymers which exhibited excellent solubility in a range of non-chlorinated solvents. The CDS co-polymer exhibited a band gap of just 1.18 eV, which is amongst the lowest reported for donor-acceptor polymers. Thin-film transistors were fabricated using environmentally benign, non-chlorinated solvents with the CDS and IDSe co-polymers exhibiting hole mobility up to 0.15 and 6.4 cm2 /Vs, respectively. This high performance was achieved without the undesirable peak in mobility often observed at low gate voltages due to parasitic contact resistance.

  20. Engineered monodisperse mesoporous materials

    Energy Technology Data Exchange (ETDEWEB)

    Saunders, R.S.; Small, J.H.; Lagasse, R.R.; Schroeder, J.L.; Jamison, G.M.

    1997-08-01

    Porous materials technology has developed products with a wide variety of pore sizes ranging from 1 angstrom to 100`s of microns and beyond. Beyond 15{angstrom} it becomes difficult to obtain well ordered, monodisperse pores. In this report the authors describe efforts in making novel porous material having monodisperse, controllable pore sizes spanning the mesoporous range (20--500 {angstrom}). They set forth to achieve this by using unique properties associated with block copolymers--two linear homopolymers attached at their ends. Block copolymers phase separate into monodisperse mesophases. They desired to selectively remove one of the phases and leave the other behind, giving the uniform monodisperse pores. To try to achieve this the authors used ring-opening metathesis polymerization to make the block copolymers. They synthesized a wide variety of monomers and surveyed their polymers by TGA, with the idea that one phase could be made thermally labile while the other phase would be thermally stable. In the precipitated and sol-gel processed materials, they determined by porosimetry measurements that micropores, mesopores, and macropores were created. In the film processed sample there was not much porosity present. They moved to a new system that required much lower thermal treatments to thermally remove over 90% of the labile phase. Film casting followed by thermal treatment and solvent extraction produced the desired monodisperse materials (based solely on SEM results). Modeling using Density Functional Theory was also incorporated into this project. The modeling was able to predict accurately the domain size and spacing vs. molecular weight for a model system, as well as accurate interfacial thicknesses.

  1. Photogeneration and recombination processes of neutral and charged excitations in films of a ladder-type poly(para-phenylene)

    Science.gov (United States)

    Wohlgenannt, M.; Graupner, W.; Leising, G.; Vardeny, Z. V.

    1999-08-01

    We introduce a version of the cw photomodulation technique, measured far from the steady state, for obtaining the quantum efficiency, η, of long-lived photoexcitations in π-conjugated polymers. We apply this technique to films of a ladder-type poly(para-phenylene) [mLPPP] for studying the photogeneration action spectra, η(E), and recombination kinetics of photogenerated neutral and charged excitations such as singlet and triplet excitons and charged polarons. Whereas the η(E) spectrum for singlet excitons shows a step function increase at a photon energy, E, close to the optical gap (~=2.6 eV), both triplet and polaron η(E) spectra show, in addition, a monotonous rise at higher E. The rise for triplets is explained by singlet exciton fission into triplet pairs, and from a model fit we get the triplet exciton energy (~=1.6 eV). For polarons this rise is modeled by an electron intersegment tunneling process. The electroabsorption spectrum is also measured and analyzed in terms of Stark shift of the lowest lying exciton, 1Bu, and enhanced oscillator strength of the important mAg exciton. A consistent picture for the lowest excited state energy levels and optical transitions in the neutral (singlet and triplet) and charged manifolds is presented. From both the exciton binding energy of ~=0.6 eV and the singlet-triplet energy splitting of ~=1 eV, we conclude that the e-e interaction in mLPPP is relatively strong. Our results are in good agreement with recent ab initio band structure calculations for several π-conjugated polymers.

  2. Mathematical model analysis on the enhancement of aeration efficiency using ladder-type flat membrane module forms in the Submerged Membrane Bio-reactor(SMBR)

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The cross-flow shearing action produced from the inferior aeration in the Submerged Membrane Bio-reactor(SMBR) is an effective way to further improve anti-fouling effects of membrane modules.Based on the widely-applied vertical structure of flat membrane modules,improvements are made that ladder-type flat membrane structure is designed with a certain inclined angle θ so that the cross-flow velocity of bubble near the membrane surface can be held,and the intensity and times of elastic colli-sion between bubbles and membrane surface can be increased.This can improve scouring action of membrane surface on aeration and reduce energy consumption of strong aeration in SMBR.By de-ducing and improving the mathematics model of collision between bubble and vertical flat put forward by Vries,the relatively suitable incline angle θ under certain aeration place and in certain size rang of bubble can be obtained with the computer iterative calculation technology.Finally,for many groups of ladder-type flat membrane in parallel placement in the practical application of SMBR,some sugges-tions are offered:the interval distance of membrane modules is 8―15 mm,and aeration should be op-erated at 5―7 mm among membrane modules,and the optimal design angle of trapeziform membrane is 1.7°―2.5°.

  3. Mathematical model analysis on the enhancement of aeration efficiency using ladder-type flat membrane module forms in the Submerged Membrane Bio-reactor (SMBR)

    Institute of Scientific and Technical Information of China (English)

    LI Bo; YE MaoSheng; YANG FengLin; MA Hui

    2009-01-01

    The cross-flow shearing action produced from the inferior aeration in the Submerged Membrane Bio-reactor (SMBR) Is an effective way to further improve anti-fouling effects of membrane modules.Based on the widely-applied vertical structure of flat membrane modules, improvements are made that ladder-type flat membrane structure is designed with a certain inclined angle θ so that the cross-flow velocity of bubble near the membrane surface can be held, and the intensity and times of elastic colli-sion between bubbles and membrane surface can be increased. This can improve scouring action ofmembrane surface on aeration and reduce energy consumption of strong aeration in SMBR. By de-ducing and improving the mathematics model of collision between bubble and vertical flat put forward by Vries, the relatively suitable Incline angle θ under certain aeration place and in certain size rang ofbubble can be obtained with the computer iterative calculation technology. Finally, for many groups of ladder-type flat membrane in parallel placement in the practical application of SMBR, some sugges-tions are offered: the interval distance of membrane modules is 8--15 mm, and aeration should be op-erated at 5--7 mm among membrane modules, and the optimal design angle of trapeziform membrane is 1.7°--2.5°.

  4. Preparation of large monodisperse vesicles.

    Directory of Open Access Journals (Sweden)

    Ting F Zhu

    Full Text Available Preparation of monodisperse vesicles is important both for research purposes and for practical applications. While the extrusion of vesicles through small pores (approximately 100 nm in diameter results in relatively uniform populations of vesicles, extrusion to larger sizes results in very heterogeneous populations of vesicles. Here we report a simple method for preparing large monodisperse multilamellar vesicles through a combination of extrusion and large-pore dialysis. For example, extrusion of polydisperse vesicles through 5-microm-diameter pores eliminates vesicles larger than 5 microm in diameter. Dialysis of extruded vesicles against 3-microm-pore-size polycarbonate membranes eliminates vesicles smaller than 3 microm in diameter, leaving behind a population of monodisperse vesicles with a mean diameter of approximately 4 microm. The simplicity of this method makes it an effective tool for laboratory vesicle preparation with potential applications in preparing large monodisperse liposomes for drug delivery.

  5. Effect of Cavity Decay on Entanglement of Ladder-Type Three-Level Atoms and a Two-Mode Cavity Field

    Institute of Scientific and Technical Information of China (English)

    GAO Cheng-Yuan; LIU Jin-Ming; MA Lei

    2008-01-01

    Considering the adiabatical approximation and the large detuning condition, we give the effective Hamil-tonian of a ladder-type three levels atom interacting with a bimodal cavity field. If two identical three-level atoms are sent through the cavity one by one, a two-atom entangled state can be generated. With the choice of the appropriate interaction time, a maximally entangled state of two atoms can be obtained if decoherence effect is ignored. Moreover, we discuss the effect of cavity decay on four physical quantities including atomic population probability, residual entan-glement of the first atom and the cavity field, concurrence between the two atoms, and fidelity for generating atomic EPR state, all of which decrease with the increase of cavity decay when the other parameters are fixed.

  6. The Influence of Oxygen Atoms on Conformation and π-π Stacking of Ladder-Type Donor-Based Polymers and Their Photovoltaic Properties.

    Science.gov (United States)

    Qin, Tong; Zang, Yue; Bai, Wei-Yun; Yao, Kai; Xu, Yun-Xiang

    2017-08-01

    A novel ladder-type donor pyran-bridged indacenodithiophene (IDTP) is developed by introducing two oxygen atoms into indacenodithiophene unit. IDTP possesses a twisted backbone and leads to facially asymmetric arrangement of side chains, resulting in enhanced local π-π stacking of according polymer poly[(5,5,11,11-tetrakis(4-octylphenyl)-5,11-dihydrothieno[2',3':5,6]pyrano[3,4-g]thieno[3,2-c]isochromene)-alt-4,7-(5-fluoro-2,1,3-benzothiadiazole)] (PIDTP)-FBT, which shows extended absorption range. Moreover, oxygen atoms render deeper highest occupied molecular orbital (HOMO) levels of poly[indacenodithiophene-alt-4,7-(5-fluoro-2,1,3-benzothiadiazole)] (PIDTP)-FBT compared with PIDT-FBT, therefore bringing a higher open-circuit voltage (Voc ). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Preparation of artificial canine femoral stem with HA-Ti ladder-type coating on plasma-sprayed pure Ti substrate and its performance evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Zeng Xianlin, E-mail: zxlxhh@163.com [Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022 (China); Li Jingfeng; Yang Shuhua; Zheng Qixin; Zou Zhenwei [Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022 (China)

    2012-03-01

    An ideal, biological-type, artificial femoral stem prosthesis has good stability and improved bone-prosthesis bonding capacity. In the current study, pure hydroxyapatite (HA)-coated, cementless, artificial femoral stems were prepared by adopting different plasma spray powers and distances and were tested in terms of shear strength. The pure titanium (Ti) substrates, HA coatings, and composite Ti-HA ladder-type coatings prepared under vacuum and atmospheric conditions were examined to compare the shear strengths, microscopic constitutions, and structures of the coatings. The coating was fabricated and the bond strength was improved by adopting 35 kW of spray power and an 80 mm spray distance. The comparisons show that the shear strength of the Ti coating prepared under vacuum conditions was higher than that of the coating prepared under atmospheric conditions (P < 0.05). Moreover, the pressure-shear strength of the Ti + HAG + Ti + V group coating was statistically significantly different from those of the HA + Ti + V and HA + Ti + A groups (P < 0.05). The coatings were compared using scanning electron microscopy, X-ray diffraction, and infrared spectrum analysis. The composite HA-Ti ladder-type coating group, where pure Ti substrate was sprayed onto the Ti alloy under vacuum conditions, had a successive laminate structure. In addition, the intergranular bond in the HA surface layer on the gradient coating was compact and highly crystallized. Under vacuum conditions, the plasma-sprayed layer was characterized by higher tightness, moderate porosity, higher bonding strength to HA, and higher HA crystallinity. The proposed coating can be used in new, cementless, artificial femoral stems with improved bone-prosthesis bonding capacity and stability.

  8. Aerosol fabrication methods for monodisperse nanoparticles

    Science.gov (United States)

    Jiang, Xingmao; Brinker, C Jeffrey

    2014-10-21

    Exemplary embodiments provide materials and methods for forming monodisperse particles. In one embodiment, the monodisperse particles can be formed by first spraying a nanoparticle-containing dispersion into aerosol droplets and then heating the aerosol droplets in the presence of a shell precursor to form core-shell particles. By removing either the shell layer or the nanoparticle core of the core-shell particles, monodisperse nanoparticles can be formed.

  9. Spontaneous Breakup of Extended Monodisperse Polymer Melts

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Yu, Kaijia

    2011-01-01

    We apply continuum mechanical based, numerical modeling to study the dynamics of extended monodisperse polymer melts during the relaxation. The computations are within the ideas of the microstructural ‘‘interchain pressure’’ theory. The computations show a delayed necking resulting in a rupture...

  10. Template synthesis of monodisperse carbon nanodots

    Science.gov (United States)

    Kurdyukov, D. A.; Eurov, D. A.; Stovpiaga, E. Yu.; Kirilenko, D. A.; Konyakhin, S. V.; Shvidchenko, A. V.; Golubev, V. G.

    2016-12-01

    Monodisperse carbon nanodots in pores of mesoporous silica particles are obtained by template synthesis. This method is based on introducing a precursor (organosilane) into pores, its thermal decomposition with formation of carbon nanodots, and the template removal. Structural analysis of the nanomaterial has been performed, which showed that carbon nanodots have an approximately spherical form and a graphite-like structure. According to dynamic light scattering data, the size of carbon nanodots is 3.3 ± 0.9 nm.

  11. Investigation of two-color magneto-optical trap with cesium 6S1/2-6P3/2-7S1/2 ladder-type system

    CERN Document Server

    Wang, Jie; Yang, Baodong; He, Jun; Wang, Junmin

    2016-01-01

    A novel cesium (Cs) two-color magneto-optical trap (TC-MOT), which partially employs the optical radiation forces due to photon scattering of the 6P3/2 (F'=5) - 7S1/2 (F"=4) excited-state transition in the Cs 6S1/2 - 6P3/2 - 7S1/2 (852 + 1470 nm) ladder-type system, has been proposed and experimentally investigated. One of the three pairs of 852 nm cooling/trapping beams (CTBs) in a conventional Cs MOT is replaced with a pair of the 1470 nm CTBs (type-I) or with one 852 nm CTB plus another counter-propagating 1470 nm CTB (type-II). Both the type-I and type-II Cs TC-MOTs can cool and trap atoms on both the red- and blue-detuning sides of the two-photon resonance. The Cs TC-MOT demonstrated in this work may have applications in the background-free detection of cooled and trapped atoms, and the photon-pair sources compatible with the ensemble-based quantum memory and the long-distance quantum communication via optical fiber.

  12. Microfluidic Production of Monodisperse Perfluorocarbon Microdroplets

    Science.gov (United States)

    Li, David; Schalte, Kevin; Fowlkes, J. Brian; Bull, Joseph

    2010-11-01

    Acoustic droplet vaporization (ADV) is process in which liquid perfluorocarbon (PFC) microdroplets are vaporized using focused ultrasound to form gas bubbles that are approximately 125 times larger in volume. Gas embolotherapy is a novel cancer treatment that uses ADV in vivo to strategically form gas emoboli, which can lodge in the microcirculation and starve tumors. Current methods to produce PFC microdroplets, such has high speed shaking or sonication, result in polydisperse droplet distributions where a fraction of droplets fall within the 2-10 microns range. In the clinical application with such a droplet distribution, large droplets are filtered by the lungs and small droplets result in bubbles that are too small to lodge in the tumor vasculature. Consequently, there is a need for a monodisperse droplet distribution. A microfluidic based device has been developed in order to produce such monodisperse PFC microdroplets. The device used hydrodynamic flow focusing to create droplets with a mean diameter less than 10 microns in diameter. This work is supported by NIH grant R01EB006476.

  13. Elongational viscosity of monodisperse and bidisperse polystyrene melts

    DEFF Research Database (Denmark)

    Nielsen, Jens Kromann; Rasmussen, Henrik K.; Hassager, Ole

    2006-01-01

    The start-up and steady uniaxial elongational viscosity have been measured for two monodisperse polystyrene melts with molecular weights of 52 and 103 kg/mole, and for three bidisperse polystyrene melts. The monodisperse melts show a maximum in the steady elongational viscosity vs. the elongation...

  14. Synthesis of monodisperse crosslinked polystyrene microspheres

    Institute of Scientific and Technical Information of China (English)

    Jiang Kai; Chen Sheng-Li; Dong Peng; Liu Renxiao

    2008-01-01

    Monodisperse crosslinked polystyrene (CPS) particles were prepared through the normal emulsion polymerization method by adding crosslinker-divinylbenzene (DVB) into the reaction system after polystyrene (PS) particles grew to ~80% of the final size. When the amount of crosslinker DVB added was less than 6.17 wt% based on styrene, the prepared CPS particles were spherical and uniform and the size of the CPS particles could be predicted through the normal emulsion method. The glass transition temperature (Tg) of the prepared CPS particles was higher than that of un-crosslinked PS particles and, the more crosslinker that was added, the higher the Tg of CPS Particles. The prepared CPS particles had strong resistance to organic solvents.

  15. Monodisperse microdroplet generation and stopping without coalescence

    Energy Technology Data Exchange (ETDEWEB)

    Beer, Neil Reginald

    2016-02-23

    A system for monodispersed microdroplet generation and trapping including providing a flow channel in a microchip; producing microdroplets in the flow channel, the microdroplets movable in the flow channel; providing carrier fluid in the flow channel using a pump or pressure source; controlling movement of the microdroplets in the flow channel and trapping the microdroplets in a desired location in the flow channel. The system includes a microchip; a flow channel in the microchip; a droplet maker that generates microdroplets, the droplet maker connected to the flow channel; a carrier fluid in the flow channel, the carrier fluid introduced to the flow channel by a source of carrier fluid, the source of carrier fluid including a pump or pressure source; a valve connected to the carrier fluid that controls flow of the carrier fluid and enables trapping of the microdroplets.

  16. Facile Method for Preparation of Silica Coated Monodisperse Superparamagnetic Microspheres

    Directory of Open Access Journals (Sweden)

    Xuan-Hung Pham

    2016-01-01

    Full Text Available This paper presents a facile method for preparation of silica coated monodisperse superparamagnetic microsphere. Herein, monodisperse porous polystyrene-divinylbenzene microbeads were prepared by seeded emulsion polymerization and subsequently sulfonated with acetic acid/H2SO4. The as-prepared sulfonated macroporous beads were magnetized in presence of Fe2+/Fe3+ under alkaline condition and were subjected to silica coating by sol-gel process, providing water compatibility, easily modifiable surface form, and chemical stability. FE-SEM, TEM, FT-IR, and TGA were employed to characterize the silica coated monodisperse magnetic beads (~7.5 μm. The proposed monodisperse magnetic beads can be used as mobile solid phase particles candidate for protein and DNA separation.

  17. Rapid enumeration of phage in monodisperse emulsions.

    Science.gov (United States)

    Tjhung, Katrina F; Burnham, Sean; Anany, Hany; Griffiths, Mansel W; Derda, Ratmir

    2014-06-17

    Phage-based detection assays have been developed for the detection of viable bacteria for applications in clinical diagnosis, monitoring of water quality, and food safety. The majority of these assays deliver a positive readout in the form of newly generated progeny phages by the bacterial host of interest. Progeny phages are often visualized as plaques, or holes, in a lawn of bacteria on an agar-filled Petri dish; however, this rate-limiting step requires up to 12 h of incubation time. We have previously described an amplification of bacteriophages M13 inside droplets of media suspended in perfluorinated oil; a single phage M13 in a droplet yields 10(7) copies in 3-4 h. Here, we describe that encapsulation of reporter phages, both lytic T4-LacZ and nonlytic M13, in monodisperse droplets can also be used for rapid enumeration of phage. Compartmentalization in droplets accelerated the development of the signal from the reporter enzyme; counting of "positive" droplets yields accurate enumeration of phage particles ranging from 10(2) to 10(6) pfu/mL. For enumeration of T4-LacZ phage, the fluorescent signal appeared in as little as 90 min. Unlike bulk assays, quantification in emulsion is robust and insensitive to fluctuations in environmental conditions (e.g., temperature). Power-free emulsification using gravity-driven flow in the absence of syringe pumps and portable fluorescence imaging solutions makes this technology promising for use at the point of care in low-resource environments. This droplet-based phage enumeration method could accelerate and simplify point-of-care detection of the pathogens for which reporter bacteriophages have been developed.

  18. Design, synthesis, and characterization of ladder-type molecules and polymers. Air-stable, solution-processable n-channel and ambipolar semiconductors for thin-film transistors via experiment and theory.

    Science.gov (United States)

    Usta, Hakan; Risko, Chad; Wang, Zhiming; Huang, Hui; Deliomeroglu, Murat K; Zhukhovitskiy, Aleksandr; Facchetti, Antonio; Marks, Tobin J

    2009-04-22

    The design, synthesis, and characterization of new high-performance n-channel molecular/polymeric semiconductors that are solution-processable and air-stable is of great interest for the development of p-n junctions, bipolar transistors, and organic complementary circuitry (CMOS). While over the past two decades there have been many reports on n-channel materials, solution-processability and air-stability still remain as major challenges. We report here the synthesis and detailed characterization of a highly electron-deficient class of indeno[1,2-b]fluorene-6,12-dione, 2,2'-(indeno[1,2-b]fluorene-6,12-diylidene) dimalononitrile, bisindenofluorene-12,15-dione, and 2,2'-(bisindenofluorene-12,15-diylidene) dimalononitrile-based ladder-type building blocks (1-12) and their corresponding homo- and copolymers (P1-P14), and examine in detail the effects of core size, thiophene vs core regiochemistry, carbonyl vs dicyanovinylene functionality, and alkyl chain orientation on the physicochemical properties, thin film microstructures, and OFET device performance. New compounds are characterized by DSC, TGA, melting point, single-crystal X-ray diffraction (XRD), solution/thin film optical, PL, and cyclic voltammetry measurements to evaluate frontier molecular orbital energetics and intermolecular cohesive forces. Thin films are grown by vacuum deposition and spin-coating, and investigated by X-ray diffraction (XRD) and AFM. By tuning the HOMO/LUMO energetics of the present materials over a 1.1 eV range, p-type, n-type, or ambipolar charge transport characteristics can be observed, thus identifying the MO energetic windows governing majority carrier polarity and air stability. One of these systems, thiophene-terminated indenofluorenedicyanovinylene 10 exhibits an electron mobility of 0.16 cm(2)/V x s and an I(on)/I(off) ratio of 10(7)-10(8), one of the highest to date for a solution-cast air-stable n-channel semiconductor. Here we also report solution-processed ambipolar films

  19. Growth Kinetics of Monodisperse Polystyrene Microspheres Prepared by Dispersion Polymerization

    Directory of Open Access Journals (Sweden)

    Fan Li

    2013-01-01

    Full Text Available Dispersion polymerization has been widely applied to the synthesis of monodisperse micron-sized polymer colloidal spheres. Many efforts have been devoted to studying the influence of initial conditions on the size and uniformity of the resultant microspheres, aiming to synthesize micron-size monodisperse colloidal spheres. However, the inner contradiction between the size and the size distribution of colloidal spheres hinders the realization of this goal. In this work, we drew our attention from the initial conditions to the growth stage of dispersion polymerization. We tracked the size evolution of colloidal sphere during the dispersion polymerization, through which we established a kinetic model that described the relationship between the monomer concentration and the reaction time. The model may provide a guideline to prepare large polymer colloidal spheres with good monodispersity by continuous monomer feeding during the growth stage to maintain the concentration of monomer at a constant value in a dispersion polymerization process.

  20. Spontaneous droplet formation techniques for monodisperse emulsions preparation – Perspectives for food applications

    NARCIS (Netherlands)

    Maan, A.A.; Schroën, C.G.P.H.; Boom, R.M.

    2011-01-01

    Spontaneous droplet formation through Laplace pressure differences is a simple method for making monodisperse emulsions and is claimed to be suited for shear and temperature sensitive products, and those requiring high monodispersity. Techniques belonging to this category include (grooved) microchan

  1. Thermoplastic polyurethanes with TDI-based monodisperse hard segments

    NARCIS (Netherlands)

    De, D.; Araichimani, A.; ten Hoopen, Hermina W.M.; Gaymans, R.J.

    2009-01-01

    Polyurethanes with PTMO soft segments and toluene diisocyanate diamide as urethane segment were studied. The toluene diisocyanate diamide urethane segment was monodisperse in length. The soft segment length was changed by extending PTMO with TDI units to a soft segment length varying from 2 250 to

  2. Highly monodisperse bismuth nanoparticles and their three-dimensional superlattices.

    Science.gov (United States)

    Yarema, Maksym; Kovalenko, Maksym V; Hesser, Günter; Talapin, Dmitri V; Heiss, Wolfgang

    2010-11-01

    A simple and reproducible synthesis of highly monodisperse and ligand-protected bismuth nanoparticles (Bi NPs) is reported. The size of the single-crystalline and spherically shaped NPs is controlled between 11 and 22 nm mainly by the reaction temperature. The high uniformity of the NPs allows their self-assembly into long-range-ordered two- and three-dimensional superstructures.

  3. A general approach for monodisperse colloidal perovskites, Chemistry of Materials

    NARCIS (Netherlands)

    Demirors, A.F.; Imhof, A.

    2009-01-01

    We describe a novel general method for synthesizing monodisperse colloidal perovskite particles at room temperature by postsynthesis addition of metal hydroxides to amorphous titania colloids. In previous work, we used titania particles to synthesize homogenously mixed silica-titania composite parti

  4. A co-flow-focusing monodisperse microbubble generator

    KAUST Repository

    Zhang, Jiaming

    2014-02-14

    We use a simple and inexpensive microfluidic device, which is based on microscope glass slides and two tapered glass capillaries, to produce monodisperse microbubbles. The innermost capillary used for transporting the gas is inserted into the second capillary, with its 2 μm sharp tip aligned with the center of the converging-diverging throat of the second capillary. This configuration provides a small and smooth gas flow rate, and a high velocity gradient at the tube outlet. Highly monodisperse microbubbles with diameters ranging from 3.5 to 60 microns have been successfully produced at a rate of up to 40 kHz. A simple scaling law, which is based on the capillary number and liquid-to-gas flow rate ratio, successfully predicts the bubble size. © 2014 IOP Publishing Ltd.

  5. Synthesis and antimicrobial activity of monodisperse copper nanoparticles.

    Science.gov (United States)

    Kruk, Tomasz; Szczepanowicz, Krzysztof; Stefańska, Joanna; Socha, Robert P; Warszyński, Piotr

    2015-04-01

    Metallic monodisperse copper nanoparticles at a relatively high concentration (300 ppm CuNPs) have been synthesized by the reduction of copper salt with hydrazine in the aqueous SDS solution. The average particles size and the distribution size were characterized by Dynamic Light Scattering (DLS), Nanosight-Nanoparticle Tracking Analysis (NTA). The morphology and structure of nanoparticles were investigated using Scanning Electron Microscopy (SEM). The chemical composition of the copper nanoparticles was determined by X-ray Photoelectron Spectroscopy (XPS). Monodisperse copper nanoparticles with average diameter 50 nm were received. UV/vis absorption spectra confirmed the formation of the nanoparticles with the characteristic peak 550 nm. The antimicrobial studies showed that the copper nanoparticles had high activity against Gram-positive bacteria, standard and clinical strains, including methicillin-resistant Staphylococcus aureus, comparable to silver nanoparticles and some antibiotics. They also exhibited antifungal activity against Candida species. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Synthesis of Monodisperse Iron Oxide Nanoparticles without Surfactants

    Directory of Open Access Journals (Sweden)

    Xiao-Chen Yang

    2014-01-01

    Full Text Available Monodisperse iron oxide nanoparticles could be successfully synthesized with two kinds of precipitants through a precipitation method. As-prepared nanoparticles in the size around 10 nm with regular spherical-like shape were achieved by adjusting pH values. NaOH and NH3·H2O were used as two precipitants for comparison. The average size of nanoparticles with NH3·H2O precipitant got smaller and represented better dispersibility, while nanoparticles with NaOH precipitant represented better magnetic property. This work provided a simple method without using any organic solvents, organic metal salts, or surfactants which could easily obtain monodisperse nanoparticles with tunable morphology.

  7. Preparation and Characterization of Monodisperse Nickel Nanoparticles by Polyol Process

    Institute of Scientific and Technical Information of China (English)

    LI Peng; GUAN Jianguo; ZHANG Qingjie; ZHAO Wenyu

    2005-01-01

    Polymer-protected monodisperse nickel nanoparticles were synthesized by a modified polyol reduction method in the presence of poly ( N-vinyl- 2-pyrrolidone ). These nanoparticles were characterized by transmission electron microscopy (TEM), X- ray diffraction ( XRD ), selected area electron diffraction ( SAED ), as well as vibrating sample magnetometer (VSM). The experimental results show that the addition of PVP and the concentration of NaOH have strong influences on the size, agglomeration and uniformity of nanoparticles. In the presence of PVP and NaOH with low concentrations, monodisperse nickel nanoparticles with average diameters about 42 nm were obtained and characterized to be pure nickel crystalline with fcc structure. Secondary structures such as clusters, loops, and strings resulted from magnetic interactions between particles were observed. The chemical interaction between the PVP and nickel nanoparticles was found by FTIR. The saturation magnetization ( Ms ), remanent magnetization (Mr) and coercivity ( Hc ) of these nickel nanoparticles are lower than those of bulk nickel.

  8. Monodispersive CoPt Nanoparticles Synthesized Using Chemical Reduction Method

    Institute of Scientific and Technical Information of China (English)

    SHEN Cheng-Min; HUI Chao; YANG Tian-Zhong; XIAO Cong-Wen; CHEN Shu-Tang; DING Hao; GAO Hong-Jun

    2008-01-01

    @@ Monodispersive CoPt nanoparticles in sizes of about 2.2 nm are synthesized by superhydride reduction of CoCl2 and PtCl2 in diphenyl ether. The as-prepared nanoparticles show a chemically disordered A1 structure and are superparamagnetic. Thermal annealing transforms the A1 structure into chemically ordered L1o structure and the particles are ferromagnetic at room temperature.

  9. Monodisperse magnesium hydride nanoparticles uniformly self-assembled on graphene.

    Science.gov (United States)

    Xia, Guanglin; Tan, Yingbin; Chen, Xiaowei; Sun, Dalin; Guo, Zaiping; Liu, Huakun; Ouyang, Liuzhang; Zhu, Min; Yu, Xuebin

    2015-10-21

    Monodisperse MgH2 nanoparticles with homogeneous distribution and a high loading percent are developed through hydrogenation-induced self-assembly under the structure-directing role of graphene. Graphene acts not only as a structural support, but also as a space barrier to prevent the growth of MgH2 nanoparticles and as a thermally conductive pathway, leading to outstanding performance.

  10. Facile Synthesis of Monodisperse CdS Nanocrystals via Microreaction

    Directory of Open Access Journals (Sweden)

    Zhou Xinggui

    2009-01-01

    Full Text Available Abstract CdS-based nanocrystals (NCs have attracted extensive interest due to their potential application as key luminescent materials for blue and white LEDs. In this research, the continuous synthesis of monodisperse CdS NCs was demonstrated utilizing a capillary microreactor. The enhanced heat and mass transfer in the microreactor was useful to reduce the reaction temperature and residence time to synthesize monodisperse CdS NCs. The superior stability of the microreactor and its continuous operation allowed the investigation of synthesis parameters with high efficiency. Reaction temperature was found to be a key parameter for balancing the reactivity of CdS precursors, while residence time was shown to be an important factor that governs the size and size distribution of the CdS NCs. Furthermore, variation of OA concentration was demonstrated to be a facile tuning mechanism for controlling the size of the CdS NCs. The variation of the volume percentage of OA from 10.5 to 51.2% and the variation of the residence time from 17 to 136 s facilitated the synthesis of monodisperse CdS NCs in the size range of 3.0–5.4 nm, and the NCs produced photoluminescent emissions in the range of 391–463 nm.

  11. Morphologically and size uniform monodisperse particles and their shape-directed self-assembly

    Science.gov (United States)

    Collins, Joshua E.; Bell, Howard Y.; Ye, Xingchen; Murray, Christopher Bruce

    2015-11-17

    Monodisperse particles having: a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology are disclosed. Due to their uniform size and shape, the monodisperse particles self assemble into superlattices. The particles may be luminescent particles such as down-converting phosphor particles and up-converting phosphors. The monodisperse particles of the invention have a rare earth-containing lattice which in one embodiment may be an yttrium-containing lattice or in another may be a lanthanide-containing lattice. The monodisperse particles may have different optical properties based on their composition, their size, and/or their morphology (or shape). Also disclosed is a combination of at least two types of monodisperse particles, where each type is a plurality of monodisperse particles having a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology; and where the types of monodisperse particles differ from one another by composition, by size, or by morphology. In a preferred embodiment, the types of monodisperse particles have the same composition but different morphologies. Methods of making and methods of using the monodisperse particles are disclosed.

  12. Morphologically and size uniform monodisperse particles and their shape-directed self-assembly

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Joshua E.; Bell, Howard Y.; Ye, Xingchen; Murray, Christopher Bruce

    2017-09-12

    Monodisperse particles having: a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology are disclosed. Due to their uniform size and shape, the monodisperse particles self assemble into superlattices. The particles may be luminescent particles such as down-converting phosphor particles and up-converting phosphors. The monodisperse particles of the invention have a rare earth-containing lattice which in one embodiment may be an yttrium-containing lattice or in another may be a lanthanide-containing lattice. The monodisperse particles may have different optical properties based on their composition, their size, and/or their morphology (or shape). Also disclosed is a combination of at least two types of monodisperse particles, where each type is a plurality of monodisperse particles having a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology; and where the types of monodisperse particles differ from one another by composition, by size, or by morphology. In a preferred embodiment, the types of monodisperse particles have the same composition but different morphologies. Methods of making and methods of using the monodisperse particles are disclosed.

  13. A Facile Solvothermal Synthesis of Monodisperse Ni Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    YU Peng-fei; CUI Bin; ZHANG Yan; SHI Qi-zhen

    2008-01-01

    A simple solvothermal approach was developed to synthesize uniform spherical monodisperse Ni nanoparticles, which can easily disperse in nonpolar solvents to form homogenous colloidal solution. The as-prepared sample was characterized by XRD, TEM, and FTIR. The results indicate that Ni nanoparticles have the structure of face-centered cube and a narrow distribution with a diameter of (3.5±0.5) nm. The FTIR spectrum reveals that the as a surfactant. The probable formation mechanism of the spherical nanoparticles was also discussed.

  14. Structural disorder versus spin canting in monodisperse maghemite nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Kubickova, S.; Vejpravova, J., E-mail: vejpravo@fzu.cz [Department of Magnetic Nanosystems, Institute of Physics of the ASCR, v.v.i., Na Slovance 2, 182 21 Prague (Czech Republic); Niznansky, D. [Faculty of Science, Department of Inorganic Chemistry, Charles University in Prague, Albertov 2030, 128 40 Prague (Czech Republic); Morales Herrero, M. P. [Instituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana Ins de la Cruz 3, Campus de Cantoblanco, 28049 Madrid (Spain); Salas, G. [Instituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana Ins de la Cruz 3, Campus de Cantoblanco, 28049 Madrid (Spain); Instituto Madrileno de Estudios Avanzados en Nanociencia, Campus Universitario de Cantoblanco, 28049 Madrid (Spain)

    2014-06-02

    Monodisperse maghemite nanoparticles with diameter ranging from 7 to 20 nm were examined by the In-field Mössbauer Spectroscopy (IFMS) in varying external magnetic field up to 6 T. Surprisingly, the small-sized particles (7 nm) exhibit nearly no spin canting in contrast to the larger particles with lower surface-to-volume ratio. We demonstrate that the observed phenomenon is originated by lower relative crystallinity of the larger particles with different internal structure. Hence, the persistence of the 2nd and 5th absorption lines in the IFMS cannot be unambiguously assigned to the surface spins.

  15. Monodisperse Silver Nanoparticles Synthesized by a Microwave-Assisted Method

    Institute of Scientific and Technical Information of China (English)

    ZHU Shao-Peng; TANG Shao-Chun; MENG Xiang-Kang

    2009-01-01

    Silver nanoparticles with an average size of about 2Onto are synthesized in a colloidal solution with the aid of microwave irradiation. Neither additional reductant nor stabilizer is required in this microwave-assisted method.The color of the colloidal solution is found to be dark green, different from the characteristic yellow of silver colloidal solutions. The silver nanoparticles in the colloidal solution have a narrow size distribution and large yield quantity. UV-visible absorption spectroscopy analysis reveals that the as-synthesized monodisperse silver nanoparticles have exceptional optical properties. Raman spectroscopy measurements demonstrate that these silver nanoparticles exhibit a notable surface-enhanced Raman scattering ability.

  16. MONODISPERSE MICRON-SIZED POLYACRYLAMIDE PARTICLES SYNTHESIZED BY DISPERSION POLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    Xin Hou; Bo Gao; Zhe-guo Zhang; Kang-de Yao

    2007-01-01

    Monodisperse micron-sized polyacrylamide (PAM) particles with a regular shape have been successfully prepared through dispersion polymerization of the monomer using a rotary reactor. FTIR and NMR spectroscopic results demonstrated the formation of PAM. POM and TEM observations revealed that PAM particles had a regular shape and good dispersity. A thick layer of surfactant (PVP) still existed on PAM particles after multiple centrifugation and ultrasonic re-dispersion in ethanol, which indicates a strong interaction between PVP and PAM. The effects of various polymerization factors on the average size of PAM particles have also been studied.

  17. A novel method for preparing monodispersed polystyrene nanoparticles

    Institute of Scientific and Technical Information of China (English)

    LIU Kaiyi; WANG Zhaoqun

    2007-01-01

    A preparation manner for monodispersed polystyrene(PS)nanoparticles polymerized by using a novel addition procedure of a monomer is suggested.In systems containing a smaller amount of surfactant compared with conventional microemulsion polymerization,the polymerization processes consists of three stages:adding dropwise the first part of the monomer for a few minutes at 80℃ and polymerizing for 1 h;adding collectively the residual part of the monomer and polymerizing at the same temperature for another 1 h;and then polymerizing at 85℃ for another 1 h.Based on discussions on the nucleation mechanism of particles in the polymerization system,the influences of monomer weight added dropwise,and amounts of initiator and emulsifier on the size and distribution of PS particles were investigated.PS nanoparticles with smaller diameter such as a number-average diameter of 18.7 nm and better monodispersity were obtained since the dropped styrene amount was suitable under 20wt-% emulsifier amount and 3wt-% initiator amount based on the monomer.

  18. Interchain tube pressure effect in extensional flows of oligomer diluted nearly monodisperse polystyrene melts

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Huang, Qian

    2014-01-01

    We have derived a constitutive equation to explain the extensional dynamics of oligomer-diluted monodisperse polymers, if the length of the diluent has at least two Kuhn steps. These polymer systems have a flow dynamics which distinguish from pure monodisperse melts and solutions thereof, if the ...

  19. Monodisperse Femto- to Atto-liter Droplet Formation Using a Nano-Microchannel Interface

    NARCIS (Netherlands)

    Shui, Lingling; Berg, van den Albert; Eijkel, Jan C.T.; Kim, Tae Song; Lee, Yoon-Sik; Chung, Taek-Dong; Jeon, Noo Li; Suh, Kahp-Yang; Choo, Jaebum; Kim, Yong-Kweon

    2009-01-01

    We demonstrate the production of sub-micrometer diameter monodisperse droplets by using a nano-micro channel interface. A perfectly steady nanoscopic liquid filament can be formed by a geometric confinement which eventually gives rise to a stable production of nearly perfectly monodisperse droplets.

  20. Surface properties of poly(ethylene oxide)-based segmented block copolymers with monodisperse hard segments

    NARCIS (Netherlands)

    Husken, D.; Feijen, Jan; Gaymans, R.J.

    2009-01-01

    The surface properties of segmented block copolymers based on poly(ethylene oxide) (PEO) segments and monodisperse crystallizable tetra-amide segments were studied. The monodisperse crystallizable segments (T6T6T) were based on terephthalate (T) and hexamethylenediamine (6). Due to the crystallinity

  1. MONODISPERSED AND NANOSIZED DENDRIMER/POLYSTYRENE LATEX PARTICLES

    Institute of Scientific and Technical Information of China (English)

    Changfeng Yi; Zushun Xu; Warren T. Ford

    2004-01-01

    Emulsion polymerization of styrene was carried out using dendrimer DAB-dendr-(NH2)64 as seed. The size and size distribution of the emulsion particles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS), and the effects of emulsion polymerization conditions on the preparation of emulsion particle were investigated. It has been found that the nanosized dendrimer/polystyrene polymer emulsion particles obtained were in the range of 26~64 nm in diameter, and were monodisperse; the size and size distribution of emulsion particles were influenced by the contents of dendrimer DAB-dendr-(NH2)64, emulsifier and initiator, as well as the pH value.

  2. Selection of quasi-monodisperse super-micron aerosol particles

    Science.gov (United States)

    Rösch, Michael; Pfeifer, Sascha; Wiedensohler, Alfred; Stratmann, Frank

    2014-05-01

    Size-segregated quasi monodisperse particles are essential for e.g. fundamental research concerning cloud microphysical processes. Commonly a DMA (Differential Mobility Analyzer) is used to produce quasi-monodisperse submicron particles. Thereto first, polydisperse aerosol particles are bipolarly charged by a neutralizer, and then selected according to their electrical mobility with the DMA [Knutson et al. 1975]. Selecting a certain electrical mobility with a DMA results in a particle size distribution, which contains singly charged particles as well as undesired multiply charged larger particles. Often these larger particles need to either be removed from the generated aerosol or their signals have to be corrected for in the data inversion and interpretation process. This problem becomes even more serious when considering super-micron particles. Here we will present two different techniques for generating quasi-monodisperse super-micron aerosol particles with no or only an insignificant number of larger sized particles being present. First, we use a combination of a cyclone with adjustable aerodynamic cut-off diameter and our custom-built Maxi-DMA [Raddatz et al. 2013]. The cyclone removes particles larger than the desired ones prior to mobility selection with the DMA. This results in a reduction of the number of multiply charged particles of up to 99.8%. Second, we utilize a new combination of cyclone and PCVI (Pumped Counterflow Virtual Impactor), which is based on purely inertial separation and avoids particle charging. The PCVI instrument was previously described by Boulter et al. (2006) and Kulkarni et al. (2011). With our two setups we are able to produce quasi-monodisperse aerosol particles in the diameter range from 0.5 to 4.4 µm without a significant number of larger undesired particles being present. Acknowledgements: This work was done within the framework of the DFG funded Ice Nucleation research UnIT (INUIT, FOR 1525) under WE 4722/1-1. References

  3. Monodisperse Clusters in Charged Attractive Colloids: Linear Renormalization of Repulsion.

    Science.gov (United States)

    Růžička, Štěpán; Allen, Michael P

    2015-08-11

    Experiments done on polydisperse particles of cadmium selenide have recently shown that the particles form spherical isolated clusters with low polydispersity of cluster size. The computer simulation model of Xia et al. ( Nat. Nanotechnol. 2011 , 6 , 580 ) explaining this behavior used a short-range van der Waals attraction combined with a variable long-range screened electrostatic repulsion, depending linearly on the volume of the clusters. In this work, we term this dependence "linear renormalization" of the repulsive term, and we use advanced Monte Carlo simulations to investigate the kinetically slowed down phase separation in a similar but simpler model. We show that amorphous drops do not dissolve and crystallinity evolves very slowly under linear renormalization, and we confirm that low polydispersity of cluster size can also be achieved using this model. The results indicate that the linear renormalization generally leads to monodisperse clusters.

  4. Solvent: A Key in Digestive Ripening for Monodisperse Au Nanoparticles

    Science.gov (United States)

    Wang, Peng; Qi, Xuan; Zhang, Xuemin; Wang, Tieqiang; Li, Yunong; Zhang, Kai; Zhao, Shuang; Zhou, Jun; Fu, Yu

    2017-01-01

    This work has mainly investigated the influence of the solvent on the nanoparticles distribution in digestive ripening. The experiments suggested that the solvents played a key role in digestive ripening of Au nanoparticles (Au NPs). For the benzol solvents, the resulting size distribution of Au NPs was inversely related to the solvent polarity. It may be interpreted by the low Gibbs free energy of nanoparticles in the high polarity medium, which was supposedly in favor of reducing the nanoparticles distribution. Through digestive ripening in the highly polar benzol solvent of p-chlorotoluene, monodisperse Au NPs with relative standard deviation (RSD) of 4.8% were achieved. This indicated that digestive ripening was an effective and practical way to prepare high-quality nanoparticles, which holds great promise for the nanoscience and nanotechnology.

  5. Structure and Hydration of Highly Branched, Monodisperse Phytoglycogen Nanoparticles

    Science.gov (United States)

    Atkinson, John; Nickels, Jonathan; Stanley, Christopher; Diallo, Souleymane; Katsaras, John; Dutcher, John

    Monodisperse phytoglycogen nanoparticles are a promising, new soft colloidal nanomaterial with many applications in the personal care, food, nutraceutical and pharmaceutical industries. These applications rely on exceptional properties that emerge from the highly branched structure of phytoglycogen and its interaction with water, such as extraordinarily high water retention, and low viscosity and exceptional stability in water. The structure and hydration of the nanoparticles was characterized using small angle neutron scattering (SANS) and quasielastic neutron scattering (QENS). SANS allowed us to determine the size of the nanoparticles, evaluate their radial density profile, quantify the particle-to-particle spacing, and determine their water content. The results show clearly that the nanoparticles are highly hydrated, with each nanoparticle containing 250% of its mass in water, and that aqueous dispersions approach a jamming transition at ~ 25% (w/w). QENS experiments provided an independent and consistent measure of the high level of hydration of the particles.

  6. Monodispersed Zinc Oxide Nanoparticle-Dye Dyads and Triads

    Energy Technology Data Exchange (ETDEWEB)

    Gladfelter, Wayne L. [Univ. of Minnesota, Minneapolis, MN (United States); Blank, David A. [Univ. of Minnesota, Minneapolis, MN (United States); Mann, Kent R. [Univ. of Minnesota, Minneapolis, MN (United States)

    2017-06-22

    events at a fundamental level. This was combined with the synthesis of a broad range of sensitizers that provide systematic variation of the energetics, excited state dynamics, structure and interfacial bonding. The key is that the monodisperse nature and high dispersibility of the ZnO NCs made these experiments reproducible; in essence, the measurements were on discrete molecular species rather than on the complicated mixtures that resulted from the typical fabrication of functional photovoltaic cells. The monodispersed nature of the NCs also allowed the use of quantum confinement to investigate the role of donor/acceptor energetic alignment in chemically identical systems. The results added significantly to our basic understanding of energy and charge transfer events at molecule-semiconductor interfaces and will help the R&D community realize zinc oxide's full potential in solar cell applications.

  7. Efficient thermolysis route to monodisperse Cu₂ZnSnS₄ nanocrystals with controlled shape and structure

    National Research Council Canada - National Science Library

    Zhang, Xiaoyan; Guo, Guobiao; Ji, Cheng; Huang, Kai; Zha, Chenyang; Wang, Yifeng; Shen, Liming; Gupta, Arunava; Bao, Ningzhong

    2014-01-01

    Monodisperse Cu2ZnSnS4 (CZTS) nanocrystals with tunable shape, crystalline phase, and composition are synthesized by efficient thermolysis of a single source precursor of mixed metal-oleate complexes in hot organic solvents...

  8. Cr/alpha-Cr2O3 monodispersed spherical core-shell particles based solar absorbers

    CSIR Research Space (South Africa)

    Khamlich, S

    2011-07-01

    Full Text Available Monodispersed spherical core-shell particles of Cr/alpha-Cr2O3 cermet ACG coatings investigated within this contribution could be successfully employed in thermal converters. Their selectivity depends on their chemical, physical and structural...

  9. Facile and Scalable Synthesis of Monodispersed Spherical Capsules with a Mesoporous Shell

    KAUST Repository

    Qi, Genggeng

    2010-05-11

    Monodispersed HMSs with tunable particle size and shell thickness were successfully synthesized using relatively concentrated polystyrene latex templates and a silica precursor in a weakly basic ethanol/water mixture. The particle size of the capsules can vary from 100 nm to micrometers. These highly engineered monodispersed capsules synthesized by a facile and scalable process may find applications in drug delivery, catalysis, separationm or as biological and chemical microreactors. © 2010 American Chemical Society.

  10. Preparation of Monodisperse Nanoparticle of Layered Double Hydroxides and Polyoxyethylene Sulfate

    Institute of Scientific and Technical Information of China (English)

    XU Huizhong; QIN Lianjie; ZHANG Hong; YANG Qinzheng; YANG Jing

    2005-01-01

    In order to obtain the bio-molecule/ LDHs nanocomposites having regular crystal structure,three nanocomposites of layered double hydroxides and polyoxyethylene sulfates were prepared by ion-exchange method. TEM analysis reveals that the monodisperse rigid .sphere of approximately 200 nm in diameter could be gotten when the intergallery anion was PEGS-400. Such monodisperse nanoparticle could be used as a promising precursor for preparing bio-molecule/LDHs nanocomposites.

  11. Periodic jetting and monodisperse jet drops from oblique gas injection

    Science.gov (United States)

    McRae, Oliver; Gaillard, Antoine; Bird, James C.

    2017-07-01

    When air is blown in a straw or tube near an air-liquid interface, typically one of two behaviors is observed: a dimple in the liquid's surface, or a frenzy of sputtering bubbles, waves, and spray. Here we report and characterize an intermediate regime that can develop when a confined air jet enters the interface at an angle. This regime is oscillatory with a distinct characteristic frequency and can develop periodic angled jets that can break up into monodisperse aerosols. The underlying mechanisms responsible for this highly periodic regime are not well understood. Here we flow a continuous stream of gas through a tube near a liquid surface, observing both optically and acoustically the deformation of the liquid-air interface as various parameters are systematically adjusted. We show that the Kelvin-Helmholtz instability is responsible for the inception of waves within a cavity formed by the gas. Inertia, gravity, and capillary forces both shape the cavity and govern the frequency and amplitude of these gas-induced cavity waves. The flapping cavity focuses the waves into a series of periodic jets that can break up into droplets following the Rayleigh-Plateau instability. We present scaling arguments to rationalize the fundamental frequencies driving this system, as well as the conditions that bound the periodic regime. These frequencies and conditions compare well with our experimental results.

  12. Jamming of Monodisperse Cylindrical Grains in Featureless Vertical Channels

    Science.gov (United States)

    Friedl, Nicholas; Baxter, G. William

    2014-03-01

    We study jamming of low aspect-ratio cylindrical Delrin grains falling through a featureless vertical channel under the influence of gravity. These grains have an aspect-ratio less than two (H/D aspirin tablets, 35mm film canisters, poker chips, or coins. Monodisperse grains are allowed to fall under the influence of gravity through a uniform channel of square cross-section where the channel width is greater than the grain size and constant along the length of the channel. No combination of grain heights and diameters is equal to the channel width. Collections of grains sometimes form jams, stable structures in which the grains are supported by the channel walls and not by grains or walls beneath them. The probability of a jam occurring and the jam's strength are influenced by the grain dimensions and channel width. We will present experimental measurements of the jamming probability and jam strength and discuss the relationship of these results to other experiments and theories. Supported by an Undergraduate Research Grant from Penn State Erie, The Behrend College.

  13. Biotemplate synthesis of monodispersed iron phosphate hollow microspheres.

    Science.gov (United States)

    Cao, Feng; Li, Dongxu

    2010-03-01

    Monodispersed iron phosphate hollow microspheres with a high degree of crystallization were prepared through a facile in situ deposition method using rape pollen grains as a biotemplate. The functional group on the surface of the pollen grains could adsorb Fe(3+), which provided the nucleation sites for growth of iron phosphate nanoparticles. After being sintered at 600 degrees C for 10 h, the pollen grains were removed and iron phosphate hollow microspheres were obtained. A scanning electron microscope and x-ray diffraction were applied to characterize the morphology and crystalline structure of the pollen grains, iron phosphate-coated pollen grains and iron phosphate hollow microspheres. Differential scanning calorimetry and thermogravity analyses were performed to investigate the thermal behavior of the iron phosphate-coated pollen grains during the calcinations. Energy dispersive spectroscopy and Fourier transform infrared spectroscopy were utilized to investigate the interaction between the pollen grains and iron phosphate. The effect of the pollen wall on the surface morphology of these iron phosphate hollow microspheres was also proven in this work.

  14. Monodisperse Platinum and Rhodium Nanoparticles as Model Heterogeneous Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Grass, Michael Edward [Univ. of California, Berkeley, CA (United States)

    2008-09-01

    Model heterogeneous catalysts have been synthesized and studied to better understand how the surface structure of noble metal nanoparticles affects catalytic performance. In this project, monodisperse rhodium and platinum nanoparticles of controlled size and shape have been synthesized by solution phase polyol reduction, stabilized by polyvinylpyrrolidone (PVP). Model catalysts have been developed using these nanoparticles by two methods: synthesis of mesoporous silica (SBA-15) in the presence of nanoparticles (nanoparticle encapsulation, NE) to form a composite of metal nanoparticles supported on SBA-15 and by deposition of the particles onto a silicon wafer using Langmuir-Blodgett (LB) monolayer deposition. The particle shapes were analyzed by transmission electron microscopy (TEM) and high resolution TEM (HRTEM) and the sizes were determined by TEM, X-ray diffraction (XRD), and in the case of NE samples, room temperature H2 and CO adsorption isotherms. Catalytic studies were carried out in homebuilt gas-phase reactors. For the nanoparticles supported on SBA-15, the catalysts are in powder form and were studied using the homebuilt systems as plug-flow reactors. In the case of nanoparticles deposited on silicon wafers, the same systems were operated as batch reactors. This dissertation has focused on the synthesis, characterization, and reaction studies of model noble metal heterogeneous catalysts. Careful control of particle size and shape has been accomplished though solution phase synthesis of Pt and Rh nanoparticles in order to elucidate further structure-reactivity relationships in noble metal catalysis.

  15. Facile Synthesis of Monodisperse Gold Nanocrystals Using Virola oleifera

    Science.gov (United States)

    Milaneze, Bárbara A.; Oliveira, Jairo P.; Augusto, Ingrid; Keijok, Wanderson J.; Côrrea, Andressa S.; Ferreira, Débora M.; Nunes, Otalíbio C.; Gonçalves, Rita de Cássia R.; Kitagawa, Rodrigo R.; Celante, Vinícius G.; da Silva, André Romero; Pereira, Ana Claudia H.; Endringer, Denise C.; Schuenck, Ricardo P.; Guimarães, Marco C. C.

    2016-10-01

    The development of new routes and strategies for nanotechnology applications that only employ green synthesis has inspired investigators to devise natural systems. Among these systems, the synthesis of gold nanoparticles using plant extracts has been actively developed as an alternative, efficient, cost-effective, and environmentally safe method for producing nanoparticles, and this approach is also suitable for large-scale synthesis. This study reports reproducible and completely natural gold nanocrystals that were synthesized using Virola oleifera extract. V. oleifera resin is rich in epicatechin, ferulic acid, gallic acid, and flavonoids (i.e., quercetin and eriodictyol). These gold nanoparticles play three roles. First, these nanoparticles exhibit remarkable stability based on their zeta potential. Second, these nanoparticles are functionalized with flavonoids, and third, an efficient, economical, and environmentally friendly mechanism can be employed to produce green nanoparticles with organic compounds on the surface. Our model is capable of reducing the resin of V. oleifera, which creates stability and opens a new avenue for biological applications. This method does not require painstaking conditions or hazardous agents and is a rapid, efficient, and green approach for the fabrication of monodisperse gold nanoparticles.

  16. Ultrasonically Aided Electrospray source for monodisperse, charged nanoparticles

    Science.gov (United States)

    Song, Weidong

    This dissertation presents a new method of producing nearly monodisperse electrospray using charged capillary standing waves. This method, based on the Ultrasonically Aided Electrospraying (UAE) technology concept invented by the author, includes the steps of dispensing a liquid on the top surface of a diaphragm so as to form a liquid film on the surface of the diaphragm, setting the diaphragm into vibration using piezoelectric transducers so as to induce capillary standing waves in the liquid film, applying electric charge to the capillary standing waves so that electrospray is extracted from the crests of the capillary standing waves. Theoretical analysis on the formation of charged particles from charged capillary standing waves at critically stable condition is performed. An experimental UAE system is designed, built, and tested and the performance of this new technology concept is assessed. Experimental results validate the capabilities of the UAE concept. The method has several applications including electric space propulsion, nano particulate technologies, nanoparticle spray coating and painting techniques, semiconductor fabrication and biomedical processes. Two example applications in electric space propulsion and nanoparticle spray coating are introduced.

  17. Spark Ignition of Monodisperse Fuel Sprays. Ph.D. Thesis

    Science.gov (United States)

    Danis, Allen M.; Cernansky, Nicholas P.; Namer, Izak

    1987-01-01

    A study of spark ignition energy requirements was conducted with a monodisperse spray system allowing independent control of droplet size, equivalent ratio, and fuel type. Minimum ignition energies were measured for n-heptane and methanol sprays characterized at the spark gap in terms of droplet diameter, equivalence ratio (number density) and extent of prevaporization. In addition to sprays, minimum ignition energies were measured for completely prevaporized mixtures of the same fuels over a range of equivalence ratios to provide data at the lower limit of droplet size. Results showed that spray ignition was enhanced with decreasing droplet size and increasing equivalence ratio over the ranges of the parameters studied. By comparing spray and prevaporized ignition results, the existence of an optimum droplet size for ignition was indicated for both fuels. Fuel volatility was seen to be a critical factor in spray ignition. The spray ignition results were analyzed using two different empirical ignition models for quiescent mixtures. Both models accurately predicted the experimental ignition energies for the majority of the spray conditions. Spray ignition was observed to be probabilistic in nature, and ignition was quantified in terms of an ignition frequency for a given spark energy. A model was developed to predict ignition frequencies based on the variation in spark energy and equivalence ratio in the spark gap. The resulting ignition frequency simulations were nearly identical to the experimentally observed values.

  18. Biotemplate synthesis of monodispersed iron phosphate hollow microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Cao Feng; Li Dongxu, E-mail: dongxuli@njut.edu.c [College of Materials Science and Engineering, Nanjing University of Technology, Jiangsu Nanjing 210009 (China)

    2010-03-15

    Monodispersed iron phosphate hollow microspheres with a high degree of crystallization were prepared through a facile in situ deposition method using rape pollen grains as a biotemplate. The functional group on the surface of the pollen grains could adsorb Fe{sup 3+}, which provided the nucleation sites for growth of iron phosphate nanoparticles. After being sintered at 600 deg. C for 10 h, the pollen grains were removed and iron phosphate hollow microspheres were obtained. A scanning electron microscope and x-ray diffraction were applied to characterize the morphology and crystalline structure of the pollen grains, iron phosphate-coated pollen grains and iron phosphate hollow microspheres. Differential scanning calorimetry and thermogravity analyses were performed to investigate the thermal behavior of the iron phosphate-coated pollen grains during the calcinations. Energy dispersive spectroscopy and Fourier transform infrared spectroscopy were utilized to investigate the interaction between the pollen grains and iron phosphate. The effect of the pollen wall on the surface morphology of these iron phosphate hollow microspheres was also proven in this work.

  19. Formation of monodisperse mesoporous silica microparticles via spray-drying.

    Science.gov (United States)

    Waldron, Kathryn; Wu, Winston Duo; Wu, Zhangxiong; Liu, Wenjie; Selomulya, Cordelia; Zhao, Dongyuan; Chen, Xiao Dong

    2014-03-15

    In this work, a protocol to synthesize monodisperse mesoporous silica microparticles via a unique microfluidic jet spray-drying route is reported for the first time. The microparticles demonstrated highly ordered hexagonal mesostructures with surface areas ranging from ~900 up to 1500 m(2)/g and pore volumes from ~0.6 to 0.8 cm(3)/g. The particle size could be easily controlled from ~50 to 100 μm from the same diameter nozzle via changing the initial solute content, or changing the drying temperature. The ratio of the surfactant (CTAB) and silica (TEOS), and the amount of water in the precursor were found to affect the degree of ordering of mesopores by promoting either the self-assembly of the surfactant-silica micelles or the condensation of the silica as two competing processes in evaporation induced self-assembly. The drying rate and the curvature of particles also affected the self-assembly of the mesostructure. The particle mesostructure is not influenced by the inlet drying temperature in the range of 92-160 °C, with even a relatively low temperature of 92 °C producing highly ordered mesoporous microparticles. The spray-drying derived mesoporous silica microparticles, while of larger sizes and more rapidly synthesized, showed a comparable performance with the conventional mesoporous silica MCM-41 in controlled release of a dye, Rhodamine B, indicating that these spray dried microparticles could be used for the immobilisation and controlled release of small molecules.

  20. Monodisperse droplet generation for microscale mass transfer studies

    Science.gov (United States)

    Roberts, Christine; Rao, Rekha; Grillet, Anne; Jove-Colon, Carlos; Brooks, Carlton; Nemer, Martin

    2011-11-01

    Understanding interfacial mass transport on a droplet scale is essential for modeling liquid-liquid extraction processes. A thin flow-focusing microfluidic channel is evaluated for generating monodisperse liquid droplets for microscale mass transport studies. Surface treatment of the microfluidic device allows creation of both oil in water and water in oil emulsions, facilitating a large parameter study of viscosity and flow rate ratios. The unusually thin channel height promotes a flow regime where no droplets form. Through confocal microscopy, this regime is shown to be highly influenced by the contact angle of the liquids with the channel. Drop sizes are found to scale with a modified capillary number. Liquid streamlines within the droplets are inferred by high speed imagery of microparticles dispersed in the droplet phase. Finally, species mass transfer to the droplet fluid is quantitatively measured using high speed imaging. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85.

  1. Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

    Directory of Open Access Journals (Sweden)

    Sumeet Kumar

    2015-02-01

    Full Text Available In the present study, monodispersed CeO2 nanoparticles (NPs of size 8.5 ± 1.0, 11.4 ± 1.0 and 15.4 ± 1.0 nm were synthesized using the sol-gel method. Size-dependent structural, optical and magnetic properties of as-prepared samples were investigated by X-ray diffraction (XRD, field emission scanning electron microscope (FE-SEM, high resolution transmission electron microscopy (HR-TEM, ultra-violet visible (UV-VIS spectroscopy, Raman spectroscopy and vibrating sample magnetometer (VSM measurements. The value of optical band gap is calculated for each particle size. The decrease in the value of optical band gap with increase of particle size may be attributed to the quantum confinement, which causes to produce localized states created by the oxygen vacancies due to the conversion of Ce4+ into Ce3+ at higher calcination temperature. The Raman spectra showed a peak at ∼461 cm-1 for the particle size 8.5 nm, which is attributed to the 1LO phonon mode. The shift in the Raman peak could be due to lattice strain developed due to variation in particle size. Weak ferromagnetism at room temperature is observed for each particle size. The values of saturation magnetization (Ms, coercivity (Hc and retentivity (Mr are increased with increase of particle size. The increase of Ms and Mr for larger particle size may be explained by increase of density of oxygen vacancies at higher calcination temperature. The latter causes high concentrations of Ce3+ ions activate more coupling between the individual magnetic moments of the Ce ions, leading to an increase of Ms value with the particle size. Moreover, the oxygen vacancies may also produce magnetic moment by polarizing spins of f electrons of cerium (Ce ions located around oxygen vacancies, which causes ferromagnetism in pure CeO2 samples.

  2. Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sumeet; Ojha, Animesh K. [Department of Physics, Motilal Nehru National Institute of Technology, Allahabad-211004 (India); Srivastava, Manish, E-mail: 84.srivastava@gmail.com, E-mail: manish-mani84@rediffmail.com [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India); Singh, Jay [Department of Applied Chemistry and Polymer Technology, Delhi Technological University, Shahbad Daulatpur, Main Bawana Road, Delhi 110042 (India); Layek, Samar [Department of Physics, Indian Institute of Technology, Kanpur 208016 (India); Yashpal, Madhu [Electron Microscope Facility, Department of Anatomy Institute of Medical Sciences, Banaras Hindu University, Varanasi 221005 (India); Materny, Arnulf [Center for Functional Materials and Nanomolecular Science, Jacobs University Bremen, Campus Ring, 28759 Bremen (Germany)

    2015-02-15

    In the present study, monodispersed CeO{sub 2} nanoparticles (NPs) of size 8.5 ± 1.0, 11.4 ± 1.0 and 15.4 ± 1.0 nm were synthesized using the sol-gel method. Size-dependent structural, optical and magnetic properties of as-prepared samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscopy (HR-TEM), ultra-violet visible (UV-VIS) spectroscopy, Raman spectroscopy and vibrating sample magnetometer (VSM) measurements. The value of optical band gap is calculated for each particle size. The decrease in the value of optical band gap with increase of particle size may be attributed to the quantum confinement, which causes to produce localized states created by the oxygen vacancies due to the conversion of Ce{sup 4+} into Ce{sup 3+} at higher calcination temperature. The Raman spectra showed a peak at ∼461 cm{sup -1} for the particle size 8.5 nm, which is attributed to the 1LO phonon mode. The shift in the Raman peak could be due to lattice strain developed due to variation in particle size. Weak ferromagnetism at room temperature is observed for each particle size. The values of saturation magnetization (Ms), coercivity (Hc) and retentivity (Mr) are increased with increase of particle size. The increase of Ms and Mr for larger particle size may be explained by increase of density of oxygen vacancies at higher calcination temperature. The latter causes high concentrations of Ce{sup 3+} ions activate more coupling between the individual magnetic moments of the Ce ions, leading to an increase of Ms value with the particle size. Moreover, the oxygen vacancies may also produce magnetic moment by polarizing spins of f electrons of cerium (Ce) ions located around oxygen vacancies, which causes ferromagnetism in pure CeO{sub 2} samples.

  3. Ladder型三能级介质中传播的少周期激光脉冲的空间分布%Spatial Distribution of Few-cycle Laser Pulses Propagating in a Ladder-type Three-level Medium

    Institute of Scientific and Technical Information of China (English)

    王蕾; 王振东; 梁变; 樊锡君

    2011-01-01

    利用由时域有限差分法和预估校正法求得全波Maxwell-Bloch 方程的数值解,研究少周期超短激光脉冲在Ladder型三能级原子介质中传播时脉冲及介质粒子布居的空间分布.结果表明,脉冲及介质粒子布居的空间分布规律随脉冲面积的改变而发生明显的变化.当脉冲面积较小时,脉冲形状不规则,振荡次数较多;当脉冲面积较大时,脉冲形状变得较为规则,振荡次数明显减少.随着脉冲面积的增大,脉冲振幅和传播速度逐渐增大,各能级粒子布居振荡次数增多,不同时刻的脉冲和粒子布居空间分布的变化明显减小.粒子布居的空间分布与脉冲的空间分布密切相关.%With numerical solution of full Maxwell-Bloch equations obtained by finite-difference time-domain method and iterative predictor-corrector method, spatial distributions of pulse and populations of few-cycle laser pulse propagates in a ladder-type three-level atomic medium are investigated. It shows that, spatial distributions changes evidently with pulse area. As the pulse area is smallr, the pulse shape is irregular and oscillation time increases. As the pulse area is large, the pulse shape becomes relatively regular and oscillation times decreases evidently. With increasing of pulse area, amplitude and group velocity of pulse increase progressively,oscillation times of populations increase gradually and variation of spatial distributions of the pulse and populations at different moments decreases considerably. Moreover, spatial distribution of populations correlates closely to spatial distribution of the pulse.

  4. Solvothermal synthesis and characterization of monodisperse superparamagnetic iron oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shichuan; Zhang, Tonglai; Tang, Runze; Qiu, Hao [State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081 (China); Wang, Caiqin [Shandong Special Industry Group Co., Ltd, Shandong 255201 (China); Zhou, Zunning [State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081 (China)

    2015-04-01

    A series of magnetic iron oxide nanoparticle clusters with different structure guide agents were synthesized by a modified solvothermal method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analyses (TG), a vibrating sample magnetometer (VSM) and Fourier transform infrared spectroscopy (FTIR). It is found that the superparamagnetic nanoparticles guided by NaCit (sodium citrate) have high saturation magnetization (M{sub s}) of 69.641 emu/g and low retentivity (M{sub r}) of 0.8 emu/g. Guiding to form superparamagnetic clusters with size range of 80–110 nm, the adherent small-molecule citrate groups on the surface prevent the prefabricated ferrite crystals growing further. In contrast, the primary small crystal guided and stabilized by the PVP long-chain molecules assemble freely to larger ones and stop growing in size range of 100–150 nm, which has saturation magnetization (M{sub s}) of 97.979 emu/g and retentivity (M{sub r}) of 46.323 emu/g. The relevant formation mechanisms of the two types of samples are proposed at the end. The superparamagnetic ferrite clusters guided by sodium citrate are expected to be used for movement controlling of passive interference particles to avoid aggregation and the sample guided by PVP will be a candidate of nanometer wave absorbing material. - Highlights: • A facile synthesis of two kinds of monodisperse iron oxide nano-particle clusters was performed via a modified one-step solvothermal method in this work. • The NaCit and PVP as different guiding agents are used to control the formation and aggregation of nano-crystals during reacting and the ripening processes. • The superparamagnetic NaCit–Fe{sub 3}O{sub 4} samples have high saturation magnetization (M{sub s}) of 69.641 emu/g and low retentivity (M{sub r}) of 0.8 emu/g. • The relevant formation mechanisms of the two types of samples are proposed.

  5. Monodisperse, submicrometer droplets via condensation of microfluidic-generated gas bubbles.

    Science.gov (United States)

    Seo, Minseok; Matsuura, Naomi

    2012-09-10

    Microfluidics (MFs) can produce monodisperse droplets with precise size control. However, the synthesis of monodisperse droplets much smaller than the minimum feature size of the microfluidic device (MFD) remains challenging, thus limiting the production of submicrometer droplets. To overcome the minimum micrometer-scale droplet sizes that can be generated using typical MFDs, the droplet material is heated above its boiling point (bp), and then MFs is used to produce monodisperse micrometer-scale bubbles (MBs) that are easily formed in the size regime where standard MFDs have excellent size control. After MBs are formed, they are cooled, condensing into dramatically smaller droplets that are beyond the size limit achievable using the original MFD, with a size decrease corresponding to the density difference between the gas and liquid phases of the droplet material. Herein, it is shown experimentally that monodisperse, submicrometer droplets of predictable sizes can be condensed from a monodisperse population of MBs as generated by MFs. Using perfluoropentane (PFP) as a representative solvent due to its low bp (29.2 °C), it is demonstrated that monodisperse PFP MBs can be produced at MFD temperatures >3.6 °C above the bp of PFP over a wide range of sizes (i.e., diameters from 2 to 200 μm). Independent of initial size, the generated MBs shrink rapidly in size from about 3 to 0 °C above the bp of PFP, corresponding to a phase change from gas to liquid, after which they shrink more slowly to form fully condensed droplets with diameters 5.0 ± 0.1 times smaller than the initial size of the MBs, even in the submicrometer size regime. This new method is versatile and flexible, and may be applied to any type of low-bp solvent for the manufacture of different submicrometer droplets for which precisely controlled dimensions are required.

  6. PREPARATION OF MONODISPERSE CROSSLINKED POLYMER MICROSPHERES HAVING CHLOROMETHYL GROUP BY DISTILLATION-PRECIPITATION POLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    Shu-Feng Li; Xin-Lin Yang; Wen-Qiang Huang

    2005-01-01

    Monodisperse crosslinked poly(chloromethylstyrene-co-divinylbenzene) (poly(CMSt-co-DVB)) microspheres were prepared by distillation-precipitation copolymerization of chloromethylstyrene (CMSt) and divinylbenzene (DVB) in neat acetonitrile. The polymer particles had clean surfaces due to the absence of any added stabilizer. The size of the particles ranges from 2.59 μm to 3.19 μm and with mono-dispersity around 1.002-1.014. The effects of monomer feed in copolymerization on the microsphere formation were described. The polymer microspheres were characterized by SEM and chlorinity elemental analysis.

  7. A facile method to produce highly monodispersed nanospheres of cystine aggregates

    Science.gov (United States)

    Han, Hongliang; Wang, Chungang; Ma, Zhanfang; Su, Zhongmin

    2006-10-01

    Multiple shapes of nano- and micro-structured cystine aggregates, including spheres, rods, spindles, dendrites, and multipods, were easily synthesized just by adjusting the concentrations and pH values of L-Cysteine solutions under ultrasonic irritation. Importantly, highly monodispersed nanospheres of cystine aggregates 225 nm in diameter without any other shapes were easily obtained for the system of 0.1 M L-Cysteine with pH 8. This will provide a very simple and effective approach to produce monodispersed cystine microspheres, which could promote new possibilities for future applications in biosensor, drug delivery, medicine, and the production of nanomaterials.

  8. A facile method to produce highly monodispersed nanospheres of cystine aggregates

    Energy Technology Data Exchange (ETDEWEB)

    Han Hongliang; Wang Chungang; Ma Zhanfang; Su Zhongmin [Chemistry Department, Northeast Normal University, Changchun 130024 (China)

    2006-10-28

    Multiple shapes of nano- and micro-structured cystine aggregates, including spheres, rods, spindles, dendrites, and multipods, were easily synthesized just by adjusting the concentrations and pH values of L-Cysteine solutions under ultrasonic irritation. Importantly, highly monodispersed nanospheres of cystine aggregates 225 nm in diameter without any other shapes were easily obtained for the system of 0.1 M L-Cysteine with pH 8. This will provide a very simple and effective approach to produce monodispersed cystine microspheres, which could promote new possibilities for future applications in biosensor, drug delivery, medicine, and the production of nanomaterials.

  9. Conventional and microwave hydrothermal synthesis of monodispersed metal oxide nanoparticles at liquid-liquid interface

    Science.gov (United States)

    Monodispersed nanoparticles of metal oxide including ferrites MFe2O4 (M=, Ni, Co, Mn) and γ-Fe2O3, Ta2O5 etc. have been synthesized using a water-toluene interface under both conventional and microwave hydrothermal conditions. This general synthesis procedure uses readily availab...

  10. Monodispersed water-in-oil emulsions prepared with semi-metal microfluidic EDGE systems

    NARCIS (Netherlands)

    Maan, A.A.; Schroën, C.G.P.H.; Boom, R.M.

    2013-01-01

    Monodispersed water-in-oil emulsions were prepared with EDGE (Edge based Droplet GEneration) systems, which generate many droplets simultaneously from one junction. The devices (with plateau height of 1.0 µm) were coated with Cu and CuNi having the same hydrophobicity but different surface

  11. Lock and key colloids through polymerization-induced buckling of monodisperse silicon oil droplets

    NARCIS (Netherlands)

    Sacanna, S.|info:eu-repo/dai/nl/311471676; Irvine, W.T.M.; Rossi, L.|info:eu-repo/dai/nl/314410376; Pine, D.J.

    2011-01-01

    We have developed a new simple method to fabricate bulk amounts of colloidal spheres with well defined cavities from monodisperse emulsions. Herein, we describe the formation mechanism of ‘‘reactive’’ silicon oil droplets that deform to reproducible shapes via a polymerization-induced buckling

  12. Effect of Mixed Solvent on Fabrication, Morphology and Monodispersity of Microspheres with Hydrophobic Poly(butyl methacrylate) Shells

    Institute of Scientific and Technical Information of China (English)

    XIAO Xincai; LU Cheng

    2012-01-01

    Monodisperse microspheres (mean diameter 200-300 nm) with polystyrene cores and poly(acrylamide-co-buty1 methacrylate) shells were prepared by using a free radical polymerization method.Moreover,the effect of mixed solvent on the preparation,morphology and monodispersity was investigated.The experimental results showed that solubility parameter of butyl methacrylate and solvent affected mainly the molding of monodisperse core-shell microspheres.When the microspheres were fabricated in a sequential synthesis process,addition of hydrophilic and organic solvent including butyl methacrylate led to spherical degree of the particles becoming worse,and the mean diameter of the microspheres decreased and the monodispersity became better with increasing the crosslinker methylenebisacrylamide dosage.

  13. Formation mechanism of monodisperse, low molecular weight chitosan nanoparticles by ionic gelation technique.

    Science.gov (United States)

    Fan, Wen; Yan, Wei; Xu, Zushun; Ni, Hong

    2012-02-01

    Chitosan nanoparticles have been extensively studied for drug and gene delivery. In this paper, monodisperse, low molecular weight (LMW) chitosan nanoparticles were prepared by a novel method based on ionic gelation using sodium tripolyphosphate (TPP) as cross-linking agent. The objective of this study was to solve the problem of preparation of chitosan/TPP nanoparticles with high degree of monodispersity and stability, and investigate the effect of various parameters on the formation of LMW chitosan/TPP nanoparticles. It was found that the particle size distribution of the nanoparticles could be significantly narrowed by a combination of decreasing the concentration of acetic acid and reducing the ambient temperature during cross-linking process. The optimized nanoparticles exhibited a mean hydrodynamic diameter of 138 nm with a polydispersity index (PDI) of 0.026 and a zeta potential of +35 mV, the nanoparticles had good storage stability at room temperature up to at least 20 days.

  14. Controlled Synthesis and Characterization of Monodisperse Fe3O4 Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    SHI,Rongrong; GAO,Guanhua; YI,Ran; ZHOU,Kechao; QIU,Guanzhou; LIU,Xiaohe

    2009-01-01

    Monodisperse Fe3O4 nanoparticles were successfully synthesized through the thermal decomposition of iron acetylacetonate in octadecene solvent in the presence of oleic acid and oleylamine.The influences of experimental parameters,such as reacting temperature,amounts and kinds of surfactants,solvents,oleic acid and oleylamine,on the size and shape of monodisperse Fe3O4 nanoparticles were discussed.The phase structures,morphology,and size of the as-prepared products were investigated in detail by X-ray diffraction (XRD),transmission electron microscopy (TEM),selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM).Magnetic property was measured using a vibrating sample magnetometer (VSM) at room temperature,which revealed that Fe3O4 nanoparticles were of ferromagnetism with a saturation magnetization (Ms) of 74.0 emu/g and coercivity (Hc) of 72.6 Oe.

  15. Simple and inexpensive microfluidic devices for the generation of monodisperse multiple emulsions

    KAUST Repository

    Li, Erqiang

    2013-12-16

    Droplet-based microfluidic devices have become a preferred versatile platform for various fields in physics, chemistry and biology. Polydimethylsiloxane soft lithography, the mainstay for fabricating microfluidic devices, usually requires the usage of expensive apparatus and a complex manufacturing procedure. Here, we report the design and fabrication of simple and inexpensive microfluidic devices based on microscope glass slides and pulled glass capillaries, for generating monodisperse multiple emulsions. The advantages of our method lie in a simple manufacturing procedure, inexpensive processing equipment and flexibility in the surface modification of the designed microfluidic devices. Different types of devices have been designed and tested and the experimental results demonstrated their robustness for preparing monodisperse single, double, triple and multi-component emulsions. © 2014 IOP Publishing Ltd.

  16. Micro-spherical cochleate composites: method development for monodispersed cochleate system.

    Science.gov (United States)

    Nagarsekar, Kalpa; Ashtikar, Mukul; Steiniger, Frank; Thamm, Jana; Schacher, Felix H; Fahr, Alfred

    2017-03-01

    Cochleates have been of increasing interest in pharmaceutical research due to their extraordinary stability. However the existing techniques used in the production of cochleates still need significant improvements to achieve sufficiently monodispersed formulations. In this study, we report a simple method for the production of spherical composite microparticles (3-5 μm in diameter) made up of nanocochleates from phosphatidylserine and calcium (as binding agent). Formulations obtained from the proposed method were evaluated using electron microscopy and small angle X-ray scattering and were compared with conventional cochleate preparation techniques. In this new method, an ethanolic lipid solution and aqueous solution of a binding agent is subjected to rapid and uniform mixing with a microfluidic device. The presence of high concentration of organic solvent promotes the formation of composite microparticles made of nanocochleates. This simple methodology eliminates elaborate preparation methods, while providing a monodisperse cochleate system with analogous quality.

  17. Enhanced thermal stability of monodispersed silver cluster arrays assembled on block copolymer scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Xu, C H; Chen, X; Liu, Y J; Xie, B; Han, M [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Song, F Q; Wang, G H, E-mail: sjhanmin@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China)

    2010-05-14

    Triblock copolymer poly(styrene-b-butadiene-b-styrene) (SBS) films with long-range ordered self-assembled nanopatterns are used as templates to selectively adsorb soft-landing silver clusters. Closely spaced cluster arrays with high monodispersity are formed through the confinement of the block copolymer scaffolds, and show a much enhanced thermal stability as compared with the cluster assemblies on the surfaces of covalent amorphous solids, or even on the disordered SBS films. Their morphologies are barely influenced by long time thermal annealing at a temperature as high as 180 deg. C, while in the latter case intense aggregations and coalescences of silver clusters are commonly observed upon annealing. The different thermal stabilities of the cluster assemblies also induce different evolutions of their optical extinction spectra under annealing. This promises a simple way to control the monodispersity and thermal stability of metal cluster assembly via self-assembled block copolymer template.

  18. A granocentric model captures the statistical properties of monodisperse random packings

    CERN Document Server

    Newhall, Katherine A; Vanden-Eijnden, Eric; Brujic, Jasna

    2012-01-01

    We present a generalization of the granocentric model proposed in [Clusel et al., Nature, 2009, 460, 611615] that is capable of describing the local fluctuations inside not only polydisperse but also monodisperse packings of spheres. This minimal model does not take into account the relative particle positions, yet it captures positional disorder through local stochastic processes sampled by efficient Monte Carlo methods. The disorder is characterized by the distributions of local parameters, such as the number of neighbors and contacts, filled solid angle around a central particle and the cell volumes. The model predictions are in good agreement with our experimental data on monodisperse random close packings of PMMA particles. Moreover, the model can be used to predict the distributions of local fluctuations in any packing, as long as the average number of neighbors, contacts and the packing fraction are known. These distributions give a microscopic foundation to the statistical mechanics framework for jamm...

  19. Understanding and Controlling the Growth of Monodisperse CdS Nanowires in Solution

    DEFF Research Database (Denmark)

    Xi, Lifei; Tan, Winnie Xiu Wen; Boothroyd, Chris;

    2008-01-01

    diffusion rate of the precursor and hence low reactivity. Therefore, ODPA is good for generating nearly monodisperse and high aspect ratio US nanowires. Our nanowires have a high degree of dispersibility and thus can be easily processed for potential applications as solar cells and transistors. Finally......Cadmium sulfide (CdS) nanowires with a monodisperse diameter of 3.5 nm and length of about 600 nm were successfully synthesized using a simple and reproducible hot coordination solvents method. Structural characterization showed that the one-dimensional nanowires grow along the [001] direction......, we propose that the ODPA-to-Cd mole ratio is the key factor affecting the morphology of the nanowires because it affects both the cleavage rate of the P=S double bond and the nucleation/growth rate of the anisotropic nanocrystals. In addition, it was found that Cd-ODPA complexes give rise to a low...

  20. Fabrication of monodisperse magnetic nanoparticles released in solution using a block copolymer template

    Science.gov (United States)

    Morcrette, Mélissa; Ortiz, Guillermo; Tallegas, Salomé; Joisten, Hélène; Tiron, Raluca; Baron, Thierry; Hou, Yanxia; Lequien, Stéphane; Bsiesy, Ahmad; Dieny, Bernard

    2017-07-01

    This paper describes a fabrication process of monodisperse magnetic nanoparticles released in solution, based on combined ‘top-down’ and ‘bottom-up’ approaches. The process involves the use of a self-assembled PS-PMMA block copolymer formed on a sacrificial layer. Such an approach was so far mostly explored for the preparation of patterned magnetic media for ultrahigh density magnetic storage. It is here extended to the preparation of released monodisperse nanoparticles for biomedical applications. A special sacrificial layer had to be developed compatible with the copolymer self-organization. The resulting nanoparticles exhibit very narrow size dispersion (≈7%) and can be good candidates as contrast agents for medical imaging i.e. magnetic resonance imaging or magnetic particle imaging. The approach provides a great freedom in the choice of the particles shapes and compositions. In particular, they can be made of biocompatible magnetic material.

  1. Towards Cluster-Assembled Materials of True Monodispersity in Size and Chemical Environment: Synthesis, Dynamics and Activity

    Science.gov (United States)

    2016-10-27

    pathway Status: not yet published Diverse technologies, from catalyst coking to graphene synthesis , entail hydrocarbon dehydrogena- tion and...AFRL-AFOSR-UK-TR-2016-0037 Towards cluster-assembled materials of true monodispersity in size and chemical environment: Synthesis , Dynamics and...Towards cluster-assembled materials of true monodispersity in size and chemical environment: synthesis , dynamics and activity 5a.  CONTRACT NUMBER 5b

  2. Size reduction of cosolvent-infused microbubbles to form acoustically responsive monodisperse perfluorocarbon nanodroplets.

    Science.gov (United States)

    Seo, Minseok; Williams, Ross; Matsuura, Naomi

    2015-09-07

    Perfluorocarbon (PFC) nanodroplet agents are exciting new biomaterials that can be remotely vapourized by ultrasound or light to change into micron-scale gas bubbles in situ. After PFC nanodroplet vapourization, the micron-scale gas bubble can interact strongly with ultrasound radiation, such that the bubbles can be used for cancer imaging and therapy. For these phase-change agents to be useful, however, PFC nanodroplets must be produced in the range of 100 to 400 nm in diameter with high size control and monodispersity, restrictions that remain a challenge. Here, we address this challenge by taking advantage of the size control offered by microfluidics, in combination with the size reduction provided by cosolvent-infused PFC bubbles through both condensation and cosolvent dissolution. In this approach, PFC bubbles with a high percentage of cosolvent (in this study, diethyl ether, DEE) are produced using microfluidics at a temperature above the boiling point. After synthesis, these bubbles become much smaller through both condensation of the gas into liquid droplets and from dissolution of the DEE into the continuous phase. This approach demonstrates that monodisperse, cosolvent-incorporated PFC bubbles can directly form monodisperse PFC nanodroplets a factor of 24 times smaller than the precursor bubbles. We also demonstrate that these nanoscale droplets can be converted to echogenic microbubbles after exposure to ultrasound, showing that these PFC nanodroplets are viable for the in situ production of ultrasound contrast agents. We show that this system can overcome the minimum droplet size limit of standard microfluidics, and is a powerful new tool for generating monodisperse, PFC phase-change ultrasound contrast agents for treating and imaging cancer.

  3. Aerosol-Assisted Synthesis of Monodisperse Single-Crystalline α-Cristobalite Nanospheres

    OpenAIRE

    Jiang, Xingmao; Bao, Lihong; Cheng, Yung-Sung; Dunphy, Darren R.; Li, Xiaodong; Brinker, C. Jeffrey

    2011-01-01

    Monodisperse single-crystalline α-cristobalite nanospheres have been synthesized by hydrocarbon-pyrolysis-induced carbon deposition on amorphous silica aerosol nanoparticles, devitrification of the coated silica at high temperature, and subsequent carbon removal by oxidation. The nanosphere size can be well controlled by tuning the size of the colloidal silica precursor. Uniform, high-purity nanocrystalline α-cristobalite is important for catalysis, nanocomposites, advanced polishing, and und...

  4. On sufficient stability conditions of the Couette — Poiseuille flow of monodisperse mixture

    Science.gov (United States)

    Popov, D. I.; Sagalakov, A. M.; Nikitenko, N. G.

    2011-06-01

    The stability of the Couette — Poiseuille flow of a monodisperse mixture is considered. Sufficient stability conditions are derived. Results of the computation of the spectrum are presented. A considerable stabilization of the flow with particles admixture to small disturbances is observed. It is found that the regions of instability generation may have complex geometry. The influence of the main velocity profile and admixture parameters on the stability conditions is considered.

  5. Enhancement of magnetic coercivity and macroscopic quantum tunneling in monodispersed Co/CoO cluster assemblies

    OpenAIRE

    Peng, D. L.; Sumiyama, Kenji; Hihara, Takehiko; Yamamuro, S.; ヒハラ, タケヒコ; スミヤマ, ケンジ; 日原, 岳彦; 隅山, 兼治; Hihara, T.; Sumiyama, K.

    1999-01-01

    Magnetic properties have been measured for monodisperse-sized Co/CoO cluster assemblies prepared by a plasma-gas-condensation-type cluster beam deposition technique. The clear correlation obtained between exchange bias field and coercivity suggests the enhancement of uniaxial anisotropy owing to the exchange coupling between the ferromagnetic Co core and antiferromagnetic CoO shell, and magnetic disorder at the core-shell interface. A nonthermal magnetic relaxation observed below 8 K, being r...

  6. Aqueous dispersion of monodisperse magnetic iron oxide nanocrystals through phase transfer

    Energy Technology Data Exchange (ETDEWEB)

    Yu, William W [Department of Chemistry, Rice University, Houston, TX 77005 (United States); Chang, Emmanuel [Department of Bioengineering, Rice University, Houston, TX 77005 (United States); Sayes, Christie M [Department of Chemistry, Rice University, Houston, TX 77005 (United States); Drezek, Rebekah [Department of Bioengineering, Rice University, Houston, TX 77005 (United States); Colvin, Vicki L [Department of Chemistry, Rice University, Houston, TX 77005 (United States)

    2006-09-14

    A facile method was developed for completely transferring high quality monodisperse iron oxide nanocrystals from organic solvents to water. The as-prepared aqueous dispersions of iron oxide nanocrystals were extremely stable and could be functionalized for bioconjugation with biomolecules. These iron oxide nanocrystals showed negligible cytotoxicity to human breast cancer cells (SK-BR-3) and human dermal fibroblast cells. This method is general and versatile for many organic solvent-synthesized nanoparticles, including fluorescent semiconductor nanocrystals.

  7. Monodisperse spherical meso-macroporous silica particles: Synthesis and adsorption of biological macromolecules

    Science.gov (United States)

    Stovpiaga, E. Yu.; Grudinkin, S. A.; Kurdyukov, D. A.; Kukushkina, Yu. A.; Nashchekin, A. V.; Sokolov, V. V.; Yakovlev, D. R.; Golubev, V. G.

    2016-11-01

    Monodispersed spherical silica particles, including large mesopores (over 10 nm) and macropores (up to 100 nm) were obtained by chemical etching in an autoclave. A method for introducing globular protein myoglobin molecules into the pores is developed. The method of filling is based on a high adsorption capacity of the developed internal pore structure of the particles. The structure and adsorption properties of the materials are studied.

  8. Monodispersed bimetallic PdAg nanoparticles with twinned structures: Formation and enhancement for the methanol oxidation

    OpenAIRE

    Zhen Yin; Yining Zhang; Kai Chen; Jing Li; Wenjing Li; Pei Tang; Huabo Zhao; Qingjun Zhu; Xinhe Bao; Ding Ma

    2014-01-01

    Monodispersed bimetallic PdAg nanoparticles can be fabricated through the emulsion-assisted ethylene glycol (EG) ternary system. Different compositions of bimetallic PdAg nanoparticles, Pd80Ag20, Pd65Ag35 and Pd46Ag54 can be obtained via adjusting the reaction parameters. For the formation process of the bimetallic PdAg nanoparticles, there have two-stage growth processes: firstly, nucleation and growth of the primary nanoclusters; secondly, formation of the secondary nanoparticles with the s...

  9. In-site synthesis of monodisperse, oleylamine-capped Ag nanoparticles through microemulsion approach

    Science.gov (United States)

    Chen, Shun; Ju, Yanyun; Guo, Yi; Xiong, Chuanxi; Dong, Lijie

    2017-03-01

    Ag NPs were in-site synthesized through microemulsion method by reducing silver acetate with oleylamine-mediated at 70 °C with highly monodisperse and narrow size from 10 to 20 nm. The synthesis of Ag NPs was aided by oleylamine and the role of oleylamine was researched. This in-site synthesis approach to Ag NPs was reproducibility and high yield more than 80% with stable store about 6 months.

  10. One-pot polyol synthesis of highly monodisperse short green silver nanorods.

    Science.gov (United States)

    Patarroyo, Javier; Genç, Aziz; Arbiol, Jordi; Bastús, Neus G; Puntes, Victor

    2016-09-21

    Green silver nanorods (Ag NRs) of a low aspect ratio (2.8) have been produced in high yields via an optimized, simple, and robust one-pot polyol method in the presence of tannic acid, which favors the nucleation of decahedral seeds needed for the production of monodisperse Ag NRs. These Ag NRs were further used as sacrificial templates to produce Au hollow nanostructures via galvanic replacement reaction with HAuCl4 at room temperature.

  11. Effects of PVP on the preparation and growth mechanism of monodispersed Ni nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Monodispersed Ni nanoparticles were successfully prepared by chemical reduction with hydrazine hydrate in ethylene glycol.The effect of the amount of polyvinylpyrrolidone (PVP-K30) on the preparation of Ni nanoparticles was investigated.X-ray diffraction (XRD),transmission electron microscopy (TEM),and high resolution transmission electron microscopy (HRTEM) were employed to characterize the nickel particles are spherical in shape and are not agglomerated.A possible extensive mechanism of nickel nanoparticle formation has been suggested.

  12. Studies on Monodispersed Microspheres of Zinc Sulfide Doped with Mn2+

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this paper, zinc acetate, manganese acetate and thiacetamide are used as raw materials to successfully synthesize monodispersed ZnS:Mn2+ microspheres by using hydrothermal method and taking P123 surfactant as a template. The products were characterized by XRD, STEM,FT-IR and N2 adsorption-desorption. And the results show that the diameter of this microsphere is 1.0 μm or so, which is larger than that of ZnS microsphere without Mn2+ doping, and it has monodispersion, smooth surface and uniform size. The doping of Mn2+ does not obviously change the structure of monodispersed ZnS microsphere. The photoluminescence peak lies in a wide band ranging from 450 to 650 nm, and the microspheres emit orange light;with the increase of Mn2+concentration, fluorescence intensity of ZnS:Mn2+ microsphere changes, and when the mole ratio of Mn2+:Zn2+is 0.3:1, the fluorescence intensity is the strongest.

  13. Monodispersity of recombinant Cre recombinase correlates with its effectiveness in vivo

    Directory of Open Access Journals (Sweden)

    Edenhofer Frank

    2009-09-01

    Full Text Available Abstract Background Cre recombinase is a common reagent used for the in vivo on/off switching of the expression of target genes flanked by loxP sites. In particular, recombinant TAT-Cre fusion constructs purified from bacteria have been used to promote the cell uptake of the enzyme. However, the recovery of active TAT-Cre remains a demanding process and its specific activity varies significantly among batches, making difficult data comparison. Results We noticed a strong correlation between recombinase activity and enzyme monodispersity. The existence of such correlation enabled us to indirectly monitor the TAT-Cre recombinase activity during the multi-step purification process by measuring its monodispersity, a parameter detectable by means of a spectrofluorimetric assay that allows the calculation of the Aggregation Index (AI in an easy and rapid way. AI values were recorded after each purification passage to identify the critical steps and to choose optimal alternatives for chromatographic conditions, desalting procedures, and protocols for bacterial endotoxin removal. Furthermore, the effect of metal ions and temperature on TAT-Cre aggregation and inactivation was characterized in vitro. Finally, we optimized the enzyme delivery protocol in vivo by following the accumulation tuning of the reporter protein β-catenin. Conclusion A rational purification protocol for TAT-Cre has been developed by choosing the options that minimize the enzyme aggregation. Our data suggest that AI measurement should support the optimization of any protocol aiming at the recovery of monodispersed protein.

  14. Existence of isostatic, maximally random jammed monodisperse hard-disk packings.

    Science.gov (United States)

    Atkinson, Steven; Stillinger, Frank H; Torquato, Salvatore

    2014-12-30

    We generate jammed packings of monodisperse circular hard-disks in two dimensions using the Torquato-Jiao sequential linear programming algorithm. The packings display a wide diversity of packing fractions, average coordination numbers, and order as measured by standard scalar order metrics. This geometric-structure approach enables us to show the existence of relatively large maximally random jammed (MRJ) packings with exactly isostatic jammed backbones and a packing fraction (including rattlers) of [Formula: see text]. By contrast, the concept of random close packing (RCP) that identifies the most probable packings as the most disordered misleadingly identifies highly ordered disk packings as RCP in 2D. Fundamental structural descriptors such as the pair correlation function, structure factor, and Voronoi statistics show a strong contrast between the MRJ state and the typical hyperstatic, polycrystalline packings with [Formula: see text] that are more commonly obtained using standard packing protocols. Establishing that the MRJ state for monodisperse hard disks is isostatic and qualitatively distinct from commonly observed polycrystalline packings contradicts conventional wisdom that such a disordered, isostatic packing does not exist due to a lack of geometrical frustration and sheds light on the nature of disorder. This prompts the question of whether an algorithm may be designed that is strongly biased toward generating the monodisperse disk MRJ state.

  15. Synthesis of monodisperse silver nanoparticles for ink-jet printed flexible electronics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Zhiliang; Zhang Xingye; Xin Zhiqing; Deng Mengmeng; Wen Yongqiang; Song Yanlin, E-mail: zhangxy@iccas.ac.cn, E-mail: ylsong@iccas.ac.cn [Beijing National Laboratory for Molecular Sciences (BNLMS), Key Lab of Organic Solids, Laboratory of New Materials, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2011-10-21

    In this study, monodisperse silver nanoparticles were synthesized with a new reduction system consisting of adipoyl hydrazide and dextrose at ambient temperature. By this facile and rapid approach, high concentration monodisperse silver nanoparticles were obtained on a large scale at low protectant/AgNO{sub 3} mass ratio which was highly beneficial to low cost and high conductivity. Based on the synthesized monodisperse silver nanoparticles, conductive inks were prepared with water, ethanol and ethylene glycol as solvents, and were expected to be more environmentally friendly. A series of electrocircuits were fabricated by ink-jet printing silver nanoparticle ink on paper substrate with a commercial printer, and they had low resistivity in the range of 9.18 x 10{sup -8}-8.76 x 10{sup -8} {Omega} m after thermal treatment at 160 {sup 0}C for 30 min, which was about five times that of bulk silver (1.586 x 10{sup -8} {Omega} m). Moreover, a radio frequency identification (RFID) antenna was fabricated by ink-jet printing, and 6 m wireless identification was realized after an Alien higgs-3 chip was mounted on the printed antenna by the flip-chip method. These flexible electrocircuits produced by ink-jet printing would have enormous potential for low cost electrodes and sensor devices.

  16. Synthesis of monodisperse silver nanoparticles for ink-jet printed flexible electronics.

    Science.gov (United States)

    Zhang, Zhiliang; Zhang, Xingye; Xin, Zhiqing; Deng, Mengmeng; Wen, Yongqiang; Song, Yanlin

    2011-10-21

    In this study, monodisperse silver nanoparticles were synthesized with a new reduction system consisting of adipoyl hydrazide and dextrose at ambient temperature. By this facile and rapid approach, high concentration monodisperse silver nanoparticles were obtained on a large scale at low protectant/AgNO(3) mass ratio which was highly beneficial to low cost and high conductivity. Based on the synthesized monodisperse silver nanoparticles, conductive inks were prepared with water, ethanol and ethylene glycol as solvents, and were expected to be more environmentally friendly. A series of electrocircuits were fabricated by ink-jet printing silver nanoparticle ink on paper substrate with a commercial printer, and they had low resistivity in the range of 9.18 × 10( - 8)-8.76 × 10( - 8) Ω m after thermal treatment at 160 °C for 30 min, which was about five times that of bulk silver (1.586 × 10( - 8) Ω m). Moreover, a radio frequency identification (RFID) antenna was fabricated by ink-jet printing, and 6 m wireless identification was realized after an Alien higgs-3 chip was mounted on the printed antenna by the flip-chip method. These flexible electrocircuits produced by ink-jet printing would have enormous potential for low cost electrodes and sensor devices.

  17. Seed mediated synthesis of highly mono-dispersed gold nanoparticles in the presence of hydroquinone

    Science.gov (United States)

    Kumar, Dhiraj; Mutreja, Isha; Sykes, Peter

    2016-09-01

    Gold nanoparticles (AuNPs) are being studied for several biomedical applications, including drug delivery, biomedical imaging, contrast agents and tumor targeting. The synthesis of nanoparticles with a narrow size distribution is critical for these applications. We report the synthesis of highly mono-dispersed AuNPs by a seed mediated approach, in the presence of tri-sodium citrate and hydroquinone (HQ). AuNPs with an average size of 18 nm were used for the synthesis of highly mono-dispersed nanocrystals of an average size 40 nm, 60 nm, 80 nm and ˜100 nm; but the protocol is not limited to these sizes. The colloidal gold was subjected to UV-vis absorbance spectroscopy, showing a red shift in lambda max wavelength, peaks at 518.47 nm, 526.37 nm, 535.73 nm, 546.03 nm and 556.50 nm for AuNPs seed (18 nm), 40 nm, 60 nm, 80 nm and ˜100 nm respectively. The analysis was consistent with dynamic light scattering and electron microscopy. Hydrodynamic diameters measured were 17.6 nm, 40.8 nm, 59.8 nm, 74.1 nm, and 91.4 nm (size by dynamic light scattering—volume %); with an average poly dispersity index value of 0.088, suggesting mono-dispersity in the size distribution, which was also confirmed by transmission electron microscopy analysis. The advantage of a seed mediated approach is a multi-step growth of nanoparticle size that enables us to control the number of nanoparticles in the suspension, for size ranging from 24.5 nm to 95.8 nm. In addition, the HQ-based synthesis of colloidal nanocrystals allowed control of the particle size and size distribution by tailoring either the number of seeds, amount of gold precursor or reducing agent (HQ) in the final reaction mixture.

  18. Microfluidic separation of satellite droplets as the basis of a monodispersed micron and submicron emulsification system.

    Science.gov (United States)

    Tan, Yung-Chieh; Lee, Abraham Phillip

    2005-10-01

    Emulsions are widely used to produce sol-gel, drugs, synthetic materials, and food products. Recent advancements in microfluidic droplet emulsion technology has enabled the precise sampling and processing of small volumes of fluids (picoliter to femtoliter) by the controlled viscous shearing in microchannels. However the generation of monodispersed droplets smaller than 1 microm without surfactants has been difficult to achieve. Normally, the generation of satellite droplets along with parent droplets is undesirable and makes it difficult to control volume and purity of samples in droplets. In this paper, however, several methods are presented to passively filter out satellite droplets from the generation of parent droplets and use these satellite droplets as the source for monodispersed production of submicron emulsions. A passive satellite droplet filtration system and a dynamic satellite droplet separation system are demonstrated. Satellite droplets are filtered from parent droplets with a two-layer channel geometry. This design allows the creation and collection of droplets that are less than 100 nm in diameter. In the dynamic separation system, satellite droplets of defined sizes can be selectively separated into different collecting zones. The separation of the satellite droplets into different collecting zones correlates with the cross channel position of the satellite droplets during the breakup of the liquid thread. The delay time for droplets to switch between the different alternating collecting zones is nominally 1 min and is proportional to the ratio of the oil shear flows. With our droplet generation system, monodispersed satellite droplets with an average radius of 2.23 +/- 0.11 microm, and bidispersed secondary and tertiary satellite droplets with radii of 1.55 +/- 0.07 microm and 372 +/- 46 nm respectively, have been dynamically separated and collected.

  19. Seed mediated synthesis of highly mono-dispersed gold nanoparticles in the presence of hydroquinone.

    Science.gov (United States)

    Kumar, Dhiraj; Mutreja, Isha; Sykes, Peter

    2016-09-02

    Gold nanoparticles (AuNPs) are being studied for several biomedical applications, including drug delivery, biomedical imaging, contrast agents and tumor targeting. The synthesis of nanoparticles with a narrow size distribution is critical for these applications. We report the synthesis of highly mono-dispersed AuNPs by a seed mediated approach, in the presence of tri-sodium citrate and hydroquinone (HQ). AuNPs with an average size of 18 nm were used for the synthesis of highly mono-dispersed nanocrystals of an average size 40 nm, 60 nm, 80 nm and ∼100 nm; but the protocol is not limited to these sizes. The colloidal gold was subjected to UV-vis absorbance spectroscopy, showing a red shift in lambda max wavelength, peaks at 518.47 nm, 526.37 nm, 535.73 nm, 546.03 nm and 556.50 nm for AuNPs seed (18 nm), 40 nm, 60 nm, 80 nm and ∼100 nm respectively. The analysis was consistent with dynamic light scattering and electron microscopy. Hydrodynamic diameters measured were 17.6 nm, 40.8 nm, 59.8 nm, 74.1 nm, and 91.4 nm (size by dynamic light scattering-volume %); with an average poly dispersity index value of 0.088, suggesting mono-dispersity in the size distribution, which was also confirmed by transmission electron microscopy analysis. The advantage of a seed mediated approach is a multi-step growth of nanoparticle size that enables us to control the number of nanoparticles in the suspension, for size ranging from 24.5 nm to 95.8 nm. In addition, the HQ-based synthesis of colloidal nanocrystals allowed control of the particle size and size distribution by tailoring either the number of seeds, amount of gold precursor or reducing agent (HQ) in the final reaction mixture.

  20. Approximate Bayesian computation for estimating number concentrations of monodisperse nanoparticles in suspension by optical microscopy

    Science.gov (United States)

    Röding, Magnus; Zagato, Elisa; Remaut, Katrien; Braeckmans, Kevin

    2016-06-01

    We present an approximate Bayesian computation scheme for estimating number concentrations of monodisperse diffusing nanoparticles in suspension by optical particle tracking microscopy. The method is based on the probability distribution of the time spent by a particle inside a detection region. We validate the method on suspensions of well-controlled reference particles. We illustrate its usefulness with an application in gene therapy, applying the method to estimate number concentrations of plasmid DNA molecules and the average number of DNA molecules complexed with liposomal drug delivery particles.

  1. Memory effects in metal-oxide-semiconductor capacitors incorporating dispensed highly monodisperse 1 nm silicon nanoparticles

    Science.gov (United States)

    Nayfeh, Osama M.; Antoniadis, Dimitri A.; Mantey, Kevin; Nayfeh, Munir H.

    2007-04-01

    Metal-oxide-semiconductor capacitors containing various densities of ex situ produced, colloidal, highly monodisperse, spherical, 1nm silicon nanoparticles were fabricated and evaluated for potential use as charge storage elements in future nonvolatile memory devices. The capacitance-voltage characteristics are well behaved and agree with similarly fabricated zero-nanoparticle control samples and with an ideal simulation. Unlike larger particle systems, the demonstrated memory effect exhibits effectively pure hole storage. The nature of charging, hole type versus electron type may be understood in terms of the characteristics of ultrasmall silicon nanoparticles: large energy gap, large charging energy, and consequently a small electron affinity.

  2. The Synthesis, Characterization and Catalytic Reaction Studies of Monodisperse Platinum Nanoparticles in Mesoporous Oxide Materials

    Energy Technology Data Exchange (ETDEWEB)

    Rioux, Robert M. [Univ. of California, Berkeley, CA (United States)

    2006-01-01

    A catalyst design program was implemented in which Pt nanoparticles, either of monodisperse size and/or shape were synthesized, characterized and studied in a number of hydrocarbon conversion reactions. The novel preparation of these materials enables exquisite control over their physical and chemical properties that could be controlled (and therefore rationally tuned) during synthesis. The ability to synthesize rather than prepare catalysts followed by thorough characterization enable accurate structure-function relationships to be elucidated. This thesis emphasizes all three aspects of catalyst design: synthesis, characterization and reactivity studies. The precise control of metal nanoparticle size, surface structure and composition may enable the development of highly active and selective heterogeneous catalysts.

  3. Synthesis of 3-D ordered macroporous silicate using the template formed from monodispersed polystyrene latex

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Based on the template formed from monodispersed polystyrene (PS) latex, a modified fast sol-gel process was employed to synthesize a three-dimensional ( 3-D ) ordered macroporous silica material after removing the template by calcination at high temperature. It was indicated that there existed highly ordered packed pores within the whole silica material by SEM morphology observation. It was also found that the pores were interconnected. The pore size could be controlled mainly by varying the particle size of the latex ranging from 101 to 102 nm. The formation process of the ordered pores was also preliminarily discussed.

  4. A Facile Synthesis of Monodisperse Au Nanoparticles and Their Catalysis of CO Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Sheng [ORNL; Peng, Sheng [Brown University; Lee, Youngmin [Brown University; Wang, Chao [Brown University; Yin, Hongfeng [ORNL; Sun, Shouheng [ORNL

    2008-01-01

    Monodisperse Au nanoparticles (NPs) have been synthesized at room temperature via a burst nucleation of Au upon injection of the reducing agent t-butylamine-borane complex into a 1, 2, 3, 4-tetrahydronaphthalene solution of HAuCl{sub 4} {center_dot} 3H{sub 2}O in the presence of oleylamine. The as-synthesized Au NPs show size-dependent surface plasmonic properties between 520 and 530 nm. They adopt an icosahedral shape and are polycrystalline with multiple-twinned structures. When deposited on a graphitized porous carbon support, the NPs are highly active for CO oxidation, showing 100% CO conversion at -45 C.

  5. Shape-dependent electrocatalytic activity of monodispersed palladium nanocrystals toward formic acid oxidation.

    Science.gov (United States)

    Zhang, Xuwei; Yin, Huajie; Wang, Jinfeng; Chang, Lin; Gao, Yan; Liu, Wei; Tang, Zhiyong

    2013-09-21

    The catalytic activity of different-shaped and monodispersed palladium nanocrystals, including cubes, octahedra and rhombic dodecahedra, toward the electrochemical oxidation of formic acid has been systematically evaluated in both HClO4 and H2SO4 solutions. Notably, the cubic palladium nanocrystals wholly exposed with {100} facets exhibit the highest activity, while the rhombic dodecahedra with {110} facets show the lowest electrocatalytic performance. Furthermore, compared with HClO4 electrolyte, the catalytic activity is found to be obviously lower in H2SO4 solution likely due to the competitive adsorption of SO4(2-) ions and formic acid on the surface of Pd nanocrystals.

  6. In situ Gelation of Monodisperse Alginate Hydrogel in Microfluidic Channel Based on Mass Transfer of Calcium Ions

    Energy Technology Data Exchange (ETDEWEB)

    Song, YoungShin; Lee, Chang-Soo [Chungnam National University, Daejeon (Korea, Republic of)

    2014-10-15

    A microfluidic method for the in situ production of monodispersed alginate hydrogels using biocompatible polymer gelation by crosslinker mass transfer is described. Gelation of the hydrogel was achieved in situ by the dispersed calcium ion in the microfluidic device. The capillary number (Ca) and the flow rate of the disperse phase which are important operating parameters mainly influenced the formation of three distinctive flow regions, such as dripping, jetting, and unstable dripping. Under the formation of dripping region, monodispersed alginate hydrogels having a narrow size distribution (C.V=2.71%) were produced in the microfluidic device and the size of the hydrogels, ranging from 30 to 60 µm, could be easily controlled by varying the flow rate, viscosity, and interfacial tension. This simple microfluidic method for the production of monodisperse alginate hydrogels shows strong potential for use in delivery systems of foods, cosmetics, inks, and drugs, and spherical alginate hydrogels which have biocompatibility will be applied to cell transplantation.

  7. Facile Synthesis of Mono-Dispersed Polystyrene (PS/Ag Composite Microspheres via Modified Chemical Reduction

    Directory of Open Access Journals (Sweden)

    Wen Zhu

    2013-12-01

    Full Text Available A modified method based on in situ chemical reduction was developed to prepare mono-dispersed polystyrene/silver (PS/Ag composite microspheres. In this approach; mono-dispersed PS microspheres were synthesized through dispersion polymerization using poly-vinylpyrrolidone (PVP as a dispersant at first. Then, poly-dopamine (PDA was fabricated to functionally modify the surfaces of PS microspheres. With the addition of [Ag(NH32]+ to the PS dispersion, [Ag(NH32]+ complex ions were absorbed and reduced to silver nanoparticles on the surfaces of PS-PDA microspheres to form PS/Ag composite microspheres. PVP acted both as a solvent of the metallic precursor and as a reducing agent. PDA also acted both as a chemical protocol to immobilize the silver nanoparticles at the PS surface and as a reducing agent. Therefore, no additional reducing agents were needed. The resulting composite microspheres were characterized by TEM, field emission scanning electron microscopy (FESEM, energy-dispersive X-ray spectroscopy (EDS, XRD, UV-Vis and surface-enhanced Raman spectroscopy (SERS. The results showed that Ag nanoparticles (NPs were homogeneously immobilized onto the PS microspheres’ surface in the presence of PDA and PVP. PS/Ag composite microspheres were well formed with a uniform and compact shell layer and were adjustable in terms of their optical property.

  8. Preparation of monodisperse, superparamagnetic, luminescent, and multifunctional PGMA microspheres with amino-groups

    Institute of Scientific and Technical Information of China (English)

    WANG WeiCai; ZHANG Qi; ZHANG BingBo; LI DeNa; DONG XiaoQing; ZHANG Lei; CHANG Jin

    2008-01-01

    Micron-sized, monodisperse, superparamagnetic, luminescent composite poly(glycidyl methacrylate) (PGMA) microspheres with functional amino-groups were successfully synthesized in this study. The process of preparation was as follows: preparation of monodisperse poly(glycidyl methacrylate) mi-crospheres by dispersion polymerization method; modification of poly(glycidyl methacrylate) micro-spheres with ethylene diamine to form amino-groups; impregnation of iron ions (Fe2+ and Fe3+) inside the microspheres and subsequently precipitating them with ammonium hydroxide to form magnetite (Fe3O,4>) nanoparticles within the polymer microspheres; infusion of CdSe/CdS core-shell quantum dots (QDs) into magnetic polymer microspheres. Scanning electron microscopy (SEM) was used to char-acterize surface morphology and size distribution of composite microspheres. The average size of mi-crospheres was 1.42μm with a size variation of 3.8%, The composite microspheres were bright enough and easily observed using a conventional fluorescence microscope, The composite microspheres were easily separated from solution by magnetic decantation using a permanent magnet. The new multi-functional composite microspheres are promising to be used in a variety of bioanalytical assays in-volving luminescence detection and magnetic separation.

  9. On-demand one-step synthesis of monodisperse functional polymeric microspheres with droplet microfluidics.

    Science.gov (United States)

    Yu, Xu; Cheng, Gong; Zhou, Ming-Da; Zheng, Si-Yang

    2015-04-07

    A simple and robust method for one-step synthesis of monodisperse functional polymeric microspheres was established by generation of reversed microemulsion droplets in aqueous phase inside microfluidic chips and controlled evaporation of the organic solvent. Using this method, water-soluble nanomaterials can be easily encapsulated into biodegradable Poly(D,L-lactic-co-glycolic acid) (PLGA) to form functional microspheres. By controlling the flow rate of microemulsion phase, PLGA polymeric microspheres with narrow size distribution and diameters in the range of ∼50-100 μm were obtained. As a demonstration of the versatility of the approach, high-quality fluorescent CdTe:Zn(2+) quantum dots (QDs) of various emission spectra, superparamagnetic Fe3O4 nanoparticles, and water-soluble carbon nanotubes (CNTs) were used to synthesize fluorescent PLGA@QDs, magnetic PLGA@Fe3O4, and PLGA@CNTs polymeric microspheres, respectively. In order to show specific applications, the PLGA@Fe3O4 were modified with polydopamine (PDA), and then the silver nanoparticles grew on the surfaces of the PLGA@Fe3O4@PDA polymeric microspheres by reducting the Ag(+) to Ag(0). The as-prepared PLGA@Fe3O4@PDA-Ag microspheres showed a highly efficient catalytic reduction of the 4-nitrophenol, a highly toxic substance. The monodisperse uniform functional PLGA polymeric microspheres can potentially be critically important for multiple biomedical applications.

  10. Microwave Synthesized Monodisperse CdS Spheres of Different Size and Color for Solar Cell Applications

    Directory of Open Access Journals (Sweden)

    Carlos A. Rodríguez-Castañeda

    2015-01-01

    Full Text Available Monodisperse CdS spheres of size of 40 to 140 nm were obtained by microwave heating from basic solutions. It is observed that larger CdS spheres were formed at lower solution pH (8.4–8.8 and smaller ones at higher solution pH (10.8–11.3. The color of CdS products changed with solution pH and reaction temperature; those synthesized at lower pH and temperature were of green-yellow color, whereas those formed at higher pH and temperature were of orange-yellow color. A good photovoltage was observed in CdS:poly(3-hexylthiophene solar cells with spherical CdS particles. This is due to the good dispersion of CdS nanoparticles in P3HT solution that led to a large interface area between the organic and inorganic semiconductors. Higher photocurrent density was obtained in green-yellow CdS particles of lower defect density. The efficient microwave chemistry accelerated the hydrolysis of thiourea in pH lower than 9 and produced monodisperse spherical CdS nanoparticles suitable for solar cell applications.

  11. Monodisperse polyvinylpyrrolidone-coated CoFe2O4 nanoparticles: Synthesis, characterization and cytotoxicity study

    Science.gov (United States)

    Wang, Guangshuo; Ma, Yingying; Mu, Jingbo; Zhang, Zhixiao; Zhang, Xiaoliang; Zhang, Lina; Che, Hongwei; Bai, Yongmei; Hou, Junxian; Xie, Hailong

    2016-03-01

    In this study, monodisperse cobalt ferrite (CoFe2O4) nanoparticles were prepared successfully with various additions of polyvinylpyrrolidone (PVP) by sonochemical method, in which PVP served as a stabilizer and dispersant. The effects and roles of PVP on the morphology, microstructure and magnetic properties of the obtained CoFe2O4 were investigated in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID). It was found that PVP-coated CoFe2O4 showed relatively well dispersion with narrow size distribution. The field-dependent magnetization curves indicated superparamagnetic behavior of PVP-coated CoFe2O4 with moderate saturation magnetization and hydrophilic character at room temperature. More importantly, the in vitro cytotoxicity testing exhibited negligible cytotoxicity of as-prepared PVP-CoFe2O4 even at the concentration as high as 150 μg/mL after 24 h treatment. Considering the superparamagnetic properties, hydrophilic character and negligible cytotoxicity, the monodisperse CoFe2O4 nanoparticles hold great potential in a variety of biomedical applications.

  12. DMSO as a solvent/ligand to monodisperse CdS spherical nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Kaijun [China Pharmaceutical University, Physical Chemistry Lab, School of Science (China); Han, Qiaofeng, E-mail: hanqiaofeng@njust.edu.cn [Nanjing University of Science and Technology, Key Laboratory for Soft Chemistry and Functional Materials, Ministry of Education (China)

    2016-01-15

    Monodisperse CdS nanospheres assembled by small nanoparticles were prepared using dimethyl sulfoxide (DMSO) as a solvent through several routes including thermolysis of xanthate, the reaction of cadmium acetate (Cd(CH{sub 3}CO{sub 2}){sub 2}) with thiourea, and interfacial reaction of CS{sub 2} and Cd(CH{sub 3}CO{sub 2}){sub 2}/DMSO. The corresponding products possessed the particle sizes ranging from around 35 to 45 nm, 63 to 73 nm, and 240 to 280 nm, respectively. These products presented uniform spherical morphology, which provide insights into the effect of DMSO on CdS morphology. DMSO, as an aprotic and polar solvent, possesses unique properties. The oxygen and sulfur atoms in DMSO can coordinate to metal ions on nanoparticles surface, and the high polarity of DMSO is favorable to fast reaction, nucleation, growth, and Ostwald ripening, forming monodisperse nanospheres with narrow size distribution. The influence of CdS size on its photocatalytic activity was evaluated using Rhodamine B (RhB) as a model compound under visible light irradiation.

  13. Preparation of monodisperse magnetic polymer microspheres by swelling and thermolysis technique.

    Science.gov (United States)

    Yang, Chengli; Shao, Qian; He, Jie; Jiang, Biwang

    2010-04-06

    A novel process for the preparation of monodisperse magnetic polymer microspheres by uniquely combining swelling and thermolysis technique was reported. The monodisperse polystyrene microspheres were first prepared by dispersion polymerization and swelled in chloroform. Then, ferric oleate was dispersed in chloroform as a precursor and impregnated into the swollen polymer microspheres. Subsequently, the iron oxide nanoparticles were formed within the polymer matrix by thermal decomposition of ferric oleate. The morphology, inner structure, and magnetic properties of the magnetic polymer microspheres were studied with a field emission scanning electron microscope (SEM), transmission electron microscope (TEM), and superconducting quantum interference device (SQUID) magnetometer. The results showed that the average diameter of the magnetic polymer microspheres was 5.1 microm with a standard deviation of 0.106, and the magnetic polymer microspheres with saturation magnetization of 12.6 emu/g exhibited distinct superparamagnetic characteristics at room temperature. More interestingly, the magnetite nanoparticles with a spinel structure are evenly distributed over the whole area of the polymer microspheres. These magnetic polymer microspheres have potential applications in biotechnology.

  14. Random-close packing limits for monodisperse and polydisperse hard spheres.

    Science.gov (United States)

    Baranau, Vasili; Tallarek, Ulrich

    2014-06-07

    We investigate how the densities of inherent structures, which we refer to as the closest jammed configurations, are distributed for packings of 10(4) frictionless hard spheres. A computational algorithm is introduced to generate closest jammed configurations and determine corresponding densities. Closest jamming densities for monodisperse packings generated with high compression rates using Lubachevsky-Stillinger and force-biased algorithms are distributed in a narrow density range from φ = 0.634-0.636 to φ≈ 0.64; closest jamming densities for monodisperse packings generated with low compression rates converge to φ≈ 0.65 and grow rapidly when crystallization starts with very low compression rates. We interpret φ≈ 0.64 as the random-close packing (RCP) limit and φ≈ 0.65 as a lower bound of the glass close packing (GCP) limit, whereas φ = 0.634-0.636 is attributed to another characteristic (lowest typical, LT) density φLT. The three characteristic densities φLT, φRCP, and φGCP are determined for polydisperse packings with log-normal sphere radii distributions.

  15. Preparation and Characterization of Gd3+-doped Monodisperse TiO2 Hollow Microsphere

    Institute of Scientific and Technical Information of China (English)

    JI; Feng; SHANG; Pengbo; ZHENG; Yuying

    2015-01-01

    Gd3+-doped monodisperse TiO2 hollow microspheres with various molar ratios of Gd3+/TBOT were synthesized via a novel process, which involved the preparation of SiO2 templates, deposition of Gd3+-doped TiO2 by sol-gel, SiO2 coating, heat treatment to induce crystallization of TiO2, and finally etching away the inner SiO2 templates and outer SiO2 layers. The synthesized samples were characterized by transmission electron microscopy(TEM), scanning electron microscopy(SEM), X-ray diffraction(XRD), diffuse reflection spectroscopy(DRS), specific surface area measurement(BET) and X-ray photoelectron spectroscopy(XPS), respectively. The photocatalytic activity of Gd3+-doped samples was evaluated via photocatalytic degradation of Methyl orange under UV irradiation. The results show that the SiO2 layers prevent aggregation of TiO2 hollow microspheresand improve the thermal stability of the synthesized samples. Also, the photocatalytic activity of monodisperse TiO2 hollow microspheres can be enhanced at the optimal molar ration of Gd3+/TBOT of 0.7%.

  16. Shape-dependent electrocatalytic activity of monodispersed palladium nanocrystals toward formic acid oxidation

    Science.gov (United States)

    Zhang, Xuwei; Yin, Huajie; Wang, Jinfeng; Chang, Lin; Gao, Yan; Liu, Wei; Tang, Zhiyong

    2013-08-01

    The catalytic activity of different-shaped and monodispersed palladium nanocrystals, including cubes, octahedra and rhombic dodecahedra, toward the electrochemical oxidation of formic acid has been systematically evaluated in both HClO4 and H2SO4 solutions. Notably, the cubic palladium nanocrystals wholly exposed with {100} facets exhibit the highest activity, while the rhombic dodecahedra with {110} facets show the lowest electrocatalytic performance. Furthermore, compared with HClO4 electrolyte, the catalytic activity is found to be obviously lower in H2SO4 solution likely due to the competitive adsorption of SO42- ions and formic acid on the surface of Pd nanocrystals.The catalytic activity of different-shaped and monodispersed palladium nanocrystals, including cubes, octahedra and rhombic dodecahedra, toward the electrochemical oxidation of formic acid has been systematically evaluated in both HClO4 and H2SO4 solutions. Notably, the cubic palladium nanocrystals wholly exposed with {100} facets exhibit the highest activity, while the rhombic dodecahedra with {110} facets show the lowest electrocatalytic performance. Furthermore, compared with HClO4 electrolyte, the catalytic activity is found to be obviously lower in H2SO4 solution likely due to the competitive adsorption of SO42- ions and formic acid on the surface of Pd nanocrystals. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03100d

  17. Coalescence of functional gold and monodisperse silver nanoparticles mediated by black Panax ginseng Meyer root extract

    Science.gov (United States)

    Wang, Dandan; Markus, Josua; Kim, Yeon-Ju; Wang, Chao; Jiménez Pérez, Zuly Elizabeth; Ahn, Sungeun; Aceituno, Verónica Castro; Mathiyalagan, Ramya; Yang, Deok Chun

    2016-01-01

    A rapid biological synthesis of multifunctional gold nanoparticle (AuNp) and monodisperse silver nanoparticle (AgNp) was achieved by an aqueous extract of black Panax ginseng Meyer root. The physicochemical transformation into black ginseng (BG) greatly enhanced the pharmacological activities of white ginseng and its minor ginsenoside content. The optimal temperature conditions and kinetics of bioreduction were investigated. Formation of BG-AuNps and BG-AgNps was verified by ultraviolet–visible spectrophotometry at 548 and 412 nm, respectively. The biosynthesized BG-AgNps were spherical and monodisperse with narrow distribution, while BG-AuNps were icosahedral-shaped and moderately polydisperse. Synthesized nanoparticles exhibited long-term stability in buffers of pH 7.0–8.0 and biological media (5% bovine serum albumin) at an ambient temperature and at 37°C. BG-AgNps showed effective antibacterial activity against Escherichia coli and Staphylococcus aureus. BG-AuNps and BG-AgNps demonstrated increased scavenging activity against 2,2-diphenyl-1-picrylhydrazyl free radicals. In addition, BG-AuNps and BG-AgNps were nontoxic to HaCaT and MCF-7 cells; the latter showed no cytotoxicity at concentrations lower than 10 µg/mL. At higher concentrations, BG-AgNps exhibited apparent apoptotic activity in MCF-7 breast cancer cell line through reactive oxygen species generation and nuclear fragmentation. PMID:28008248

  18. Development of monodispersed and functional magnetic polymeric liposomes via simple liposome method

    Energy Technology Data Exchange (ETDEWEB)

    Liang Xiaofei; Wang Hanjie [Tianjin University and Tianjin Key Laboratory of Composites and Functional Materials, Institute of Nanobiotechnology, School of Materials Science and Engineering (China); Jiang Xinguo [Fudan University, School of Pharmacy (China); Chang Jin, E-mail: jinchang@tju.edu.c [Tianjin University and Tianjin Key Laboratory of Composites and Functional Materials, Institute of Nanobiotechnology, School of Materials Science and Engineering (China)

    2010-06-15

    We are reporting a simple and rapid method to prepare superparamagnetic, controlled size, and monodispersed magnetic cationic polymeric liposomes (MCPL) by octadecyl quaternized carboxymethyl chitosan (OQCMC) and cholesterol. The whole process is only about 25 min with simple thin-film dispersion and solvent evaporation method. Hydrophilic magnetic nanoparticles (LM) and hydrophobic magnetic nanoparticles (BM) can be encapsulated into these cationic polymeric liposomes, simultaneously or respectively. A model hydrophobic drug indomethacin can be successfully filled in MCPL with high drug loading capacity 22%. MCPL encapsulating BM also showed strong DNA (pEGFP) binding ability. Drug-loaded MCPL have a long and controlled sustained release profile by changing the number of polymeric lipid layer. These functional MCPL nanospheres can be allowed to serve as ideal candidates for many biomedical applications.Graphical AbstractA simple and rapid liposome method was reported to prepare superparamagnetic, controlled size, and monodispersed magnetic cationic polymeric liposomes (MCPL) by polymeric surfactant, octadecyl quaternized carboxymethyl chitosan (OQCMC), and cholesterol. Hydrophilic Fe{sub 3}O{sub 4} ferrofluid and hydrophobic magnetic nanoparticles can be encapsulated into these cationic polymeric liposomes, simultaneously or respectively. Hydrophobic drug indomethacin can be encapsulated into this MCPL with high encapsulating efficiency and with controlled release profile by changing the number of polymeric lipid layer.

  19. Fabrication of monodispersive nanoscale alginate–chitosan core–shell particulate systems for controlled release studies

    Energy Technology Data Exchange (ETDEWEB)

    Körpe, Didem Aksoy; Malekghasemi, Soheil; Aydın, Uğur; Duman, Memed, E-mail: memedduman@gmail.com [Hacettepe University, Institute of Science, Nanotechnology and Nanomedicine Division (Turkey)

    2014-12-15

    Biopolymers such as chitosan and alginate are widely used for controlled drug delivery systems. The present work aimed to develop a new protocol for preparation of monodisperse alginate-coated chitosan nanoparticles at nanoscale. Modifications of preparation protocol contain changing the pH of polymer solutions and adding extra centrifugation steps into the procedure. While chitosan nanoparticles were synthesized by ionic gelation method, they were coated with alginate by electrostatic interaction. The size, morphology, charge, and structural characterization of prepared core–shell nanoparticulated system were performed by AFM, Zeta sizer, and FTIR. BSA and DOX were loaded as test biomolecules to core and shell part of the nanoparticle, respectively. Release profiles of BSA and DOX were determined by spectrophotometry. The sizes of both chitosan and alginate-coated chitosan nanoparticles which were prepared by modified protocol were measured to be 50 ± 10 and 60 ± 3 nm, respectively. After loading BSA and DOX, the average size of the particles increased to 80 ± 7 nm. Moreover, while the zeta potential of chitosan nanoparticles was positive value, the value was inverted to negative after alginate coating. Release profile measurements of BSA and DOX were determined during 57 and 2 days, respectively. Our results demonstrated that monodisperse alginate-coated nanoparticles were synthesized and loaded successfully using our modified protocol.

  20. Fabrication of monodispersive nanoscale alginate-chitosan core-shell particulate systems for controlled release studies

    Science.gov (United States)

    Körpe, Didem Aksoy; Malekghasemi, Soheil; Aydın, Uğur; Duman, Memed

    2014-12-01

    Biopolymers such as chitosan and alginate are widely used for controlled drug delivery systems. The present work aimed to develop a new protocol for preparation of monodisperse alginate-coated chitosan nanoparticles at nanoscale. Modifications of preparation protocol contain changing the pH of polymer solutions and adding extra centrifugation steps into the procedure. While chitosan nanoparticles were synthesized by ionic gelation method, they were coated with alginate by electrostatic interaction. The size, morphology, charge, and structural characterization of prepared core-shell nanoparticulated system were performed by AFM, Zeta sizer, and FTIR. BSA and DOX were loaded as test biomolecules to core and shell part of the nanoparticle, respectively. Release profiles of BSA and DOX were determined by spectrophotometry. The sizes of both chitosan and alginate-coated chitosan nanoparticles which were prepared by modified protocol were measured to be 50 ± 10 and 60 ± 3 nm, respectively. After loading BSA and DOX, the average size of the particles increased to 80 ± 7 nm. Moreover, while the zeta potential of chitosan nanoparticles was positive value, the value was inverted to negative after alginate coating. Release profile measurements of BSA and DOX were determined during 57 and 2 days, respectively. Our results demonstrated that monodisperse alginate-coated nanoparticles were synthesized and loaded successfully using our modified protocol.

  1. Small silicon, big opportunities: the development and future of colloidally-stable monodisperse silicon nanocrystals.

    Science.gov (United States)

    Mastronardi, Melanie L; Henderson, Eric J; Puzzo, Daniel P; Ozin, Geoffrey A

    2012-11-14

    Nanomaterials are becoming increasingly widespread in consumer technologies, but there is global concern about the toxicity of nanomaterials to humans and the environment as they move rapidly from the research laboratory to the market place. With this in mind, it makes sense to intensify the nanochemistry community's global research effort on the synthesis and study of nanoparticles that are purportedly "green". One potentially green nanoparticle that seems to be a most promising candidate in this context is silicon, whose appealing optical, optoelectronic, photonic, and biomedical attributes are recently gaining much attention. In this paper, we outline some of our recent contributions to the development of the growing field of silicon nanocrystals (ncSi) in order to stress the importance of continued study of ncSi as a green alternative to the archetypal semiconductor nanocrystals like CdSe, InAs, and PbS. While a variety of developments in synthetic methods, characterization techniques, and applications have been reported in recent years, the ability to prepare colloidally-stable monodisperse ncSi samples may prove to have the largest impact on the field, as it opens the door to study and access the tunable size-dependent properties of ncSi. Here, we summarize our recent contributions in size-separation methods to achieve monodisperse samples, the characterization of size-dependant property trends, the development of ncSi applications, and their potential impact on the promising future of ncSi.

  2. An alternative route towards monodisperse CdS quantum dots for hybrid solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Fengfeng; Wang, Hao [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Xia, Zhouhui [Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123 (China); Dai, Xiao; Cong, Shan [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Dong, Chao [Department of Chemistry and Biology, University of New Mexico, ABQ 87120 (United States); Sun, Baoquan [Institute of Functional Nano and Soft Materials, Soochow University, Suzhou 215123 (China); Lou, Yanhui, E-mail: yhlou@suda.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Sun, Yinghui; Zhao, Jie [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Zou, Guifu, E-mail: zouguifu@suda.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China)

    2015-01-15

    Monodisperse CdS quantum dots (QDs) are synthesized by thermal decomposition of organic complexes in the system of the cost-effective commercial 0{sup #} diesel at 200 °C. The prepared CdS QDs have a good dispersion and high crystallization. When the CdS QDs are doped into the blends of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6, 6)C61 (PCBM) for hybrid solar cells (HSCs), the HSCs achieve about 25% increase of power conversion efficiency in comparison to the reference device without the CdS QDs. The improvement of the cell performance mainly attributes to the increased short-circuit current density arising from the absorption enhancement in the wavelength range of 350–550 nm by introducing the synthesized CdS QDs into the P3HT: PCBM active layer. - Highlights: • Monodisperse CdS quantum dots. • A cost-effective route to synthesize crystalline CdS quantum dots. • CdS quantum dots based hybrid solar cells with power conversion efficiency enhancement.

  3. Low temperature synthesis of monodispersed YAG:Eu crystallites by hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Mengmeng [Shanghai Institute of Ceramics, Chinese Academy of Sciences, No. 1295 Dingxi Road, Shanghai, 200050 (China); University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049 (China); Zhang, Zhijun, E-mail: zhangzhijun@shu.edu.cn [School of Materials Science and Engineering, Shanghai University, No. 99 Shangda Road, Shanghai, 200072 (China); Zhao, Jingtai, E-mail: jtzhao@shu.edu.cn [School of Materials Science and Engineering, Shanghai University, No. 99 Shangda Road, Shanghai, 200072 (China); Zhang, Jiazhi [Shanghai Institute of Ceramics, Chinese Academy of Sciences, No. 1295 Dingxi Road, Shanghai, 200050 (China); University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049 (China); Liu, Zhiwei [Shanghai Institute of Ceramics, Chinese Academy of Sciences, No. 1295 Dingxi Road, Shanghai, 200050 (China)

    2015-10-25

    Single phase europium doped yttrium aluminum garnet (YAG:Eu) crystallites with good dispersity were successfully synthesized by a facile hydrothermal method at 300 °C for 24 h. The influences of the molar ratio of (Y + Eu) to Al (denoted by Ln/Al) in the raw material on the phase, morphology, crystallinity, local environment of Eu ions and photoluminescence properties were investigated. It was found that the monodispersed single phase YAG:Eu crystallites with terminating faces of {110} can be obtained when Ln/Al is 3:4. Eu ions in all the samples are trivalent regardless of Ln/Al, while the local environment of Eu ions is more symmetric when Ln/Al is 3:4. Moreover, the YAG:Eu crystallites obtained when Ln/Al is 3:4 exhibit improved crystallinity, which contributes to the enhanced luminescence intensity. - Highlights: • Single phase YAG:Eu was synthesized by the hydrothermal method at 300 °C. • The YAG:Eu crystallites are monodispersed and exhibit improved crystallinity. • The YAG:Eu crystallites exhibit improved luminescence intensity. • XAFS and VUV were used to investigate the local structure of Eu.

  4. Silicon-based megahertz ultrasonic nozzles for production of monodisperse micrometer-sized droplets.

    Science.gov (United States)

    Tsai, Shirley C; Cheng, Chih H; Wang, Ning; Song, Yu L; Lee, Ching T; Tsai, Chen S

    2009-09-01

    Monodisperse ethanol droplets 2.4 microm and water droplets 4.5 microm in diameter have been produced in ultrasonic atomization using 1.5- and 1.0-MHz microelectromechanical system (MEMS)-based silicon nozzles, respectively. The 1.5- and 1.0-MHz nozzles, each consisting of 3 Fourier horns in resonance, measured 1.20 cm x 0.15 cm x .11 cm and 1.79 cm x 0.21 cm x 0.11 cm, respectively, required electrical drive power as low as 0.25 W and could accommodate flow rates as high as 350 microl/min. As the liquid issues from the nozzle tip that vibrates longitudinally at the nozzle resonance frequency, a liquid film is maintained on the end face of the nozzle tip and standing capillary waves are formed on the free surface of the liquid film when the tip vibration amplitude exceeds a critical value due to Faraday instability. Temporal instability of the standing capillary waves, treated in terms of the unstable solutions (namely, time-dependant function with a positive Floquet exponent) to the corresponding Mathieu differential equation, is shown to be the underlying mechanism for atomization and production of such monodisperse droplets. The experimental results of nozzle resonance and atomization frequencies, droplet diameter, and critical vibration amplitude are all in excellent agreement with the predictions of the 3-D finite element simulation and the theory of Faraday instability responsible for atomization.

  5. Time Resolved Nucleation and Growth of Monodisperse FeOOH Nanoparticles Observed in situ

    Science.gov (United States)

    Legg, B. A.; Zhu, M.; Zhang, H.; Waychunas, G.; Banfield, J. F.

    2012-12-01

    The nucleation and growth of oxide minerals from aqueous solution is a poorly understood process. Complexities such as two-stage precipitation, phase transformation, and hydrolysis often inhibit simple interpretation. In this study, we track the thermally induced nucleation and growth of akaganeite (β-FeOOH) nanoparticles from FeCl3 solutions, using in situ time resolved small angle x-ray scattering (SAXS) and transmission electron microscopy (TEM). Variations in reaction temperature (from 37 deg C to 80 deg C) and FeCl3 concentration (from 5 mM to 800 mM) produce systematic changes in nucleation rate, growth rate, particle size distribution, and aspect ratio. Low FeCl3 concentrations and high temperatures lead to formation of very small particles via rapid nucleation. (FeCl3 solutions are actually more supersaturated with respect to akaganeite when concentrations are low, due to the acid-base chemistry of ferric iron.) Increasing the FeCl3 concentration leads to large, highly monodisperse particles via size focused growth. Suspensions of highly monodisperse, elongated particles are found to self-organize into two dimensional colloidal crystals. The well-controlled growth processes in this system make it possible to conduct detailed kinetic modeling, and determine how both nucleation and growth rate respond to changes in the experimental conditions.

  6. Controlled synthesis of monodisperse gold nanorods with different aspect ratios in the presence of aromatic additives

    Science.gov (United States)

    Wang, Yun; Wang, Feihu; Guo, Yuan; Chen, Rongjun; Shen, Yuanyuan; Guo, Aijie; Liu, Jieying; Zhang, Xiao; Zhou, Dejian; Guo, Shengrong

    2014-12-01

    This paper reports the synthesis of monodisperse gold nanorods (GNRs) via a simple seeded growth approach in the presence of different aromatic additives, such as 7-bromo-3-hydroxy-2-naphthoic acid (7-BrHNA), 3-hydroxy-2-naphthoic acid (HNA), 5-bromosalicylic acid (5-BrSA), salicylic acid (SA), or phenol (PhOH). Effects of the aromatic additives and hydrochloric acid (HCl) on the structure and optical properties of the synthesized GNRs were investigated. The longitudinal surface plasmon resonance (LSPR) peak wavelength of the resulting GNRs was found to be dependent on the aromatic additive in the following sequence: 5-BrSA (778 nm) > 7-BrHNA (706 nm) > SA (688 nm) > HNA (676 nm) > PhOH (638 nm) without the addition of HCl, but this was changed to 7-BrHNA (920 nm) > SA (890 nm) > HNA (872 nm) > PhOH (858 nm) > 5-BrSA (816 nm) or 7-BrHNA (1,005 nm) > PhOH (995 nm) > SA (990 nm) > HNA (980 nm) > 5-BrSA (815 nm) with the addition of HCl or HNO3, respectively. The LSPR peak wavelength was increased with the increasing concentration of 7-BrHNA without HCl addition; however, there was a maximum LSPR peak wavelength when HCl was added. Interestingly, the LSPR peak wavelength was also increased with the amount of HCl added. The results presented here thus established a simple approach to synthesize monodisperse GNRs of different LSPR wavelengths.

  7. Monodisperse Au nanoparticles for selective electrocatalytic reduction of CO2 to CO.

    Science.gov (United States)

    Zhu, Wenlei; Michalsky, Ronald; Metin, Önder; Lv, Haifeng; Guo, Shaojun; Wright, Christopher J; Sun, Xiaolian; Peterson, Andrew A; Sun, Shouheng

    2013-11-13

    We report selective electrocatalytic reduction of carbon dioxide to carbon monoxide on gold nanoparticles (NPs) in 0.5 M KHCO3 at 25 °C. Among monodisperse 4, 6, 8, and 10 nm NPs tested, the 8 nm Au NPs show the maximum Faradaic efficiency (FE) (up to 90% at -0.67 V vs reversible hydrogen electrode, RHE). Density functional theory calculations suggest that more edge sites (active for CO evolution) than corner sites (active for the competitive H2 evolution reaction) on the Au NP surface facilitates the stabilization of the reduction intermediates, such as COOH*, and the formation of CO. This mechanism is further supported by the fact that Au NPs embedded in a matrix of butyl-3-methylimidazolium hexafluorophosphate for more efficient COOH* stabilization exhibit even higher reaction activity (3 A/g mass activity) and selectivity (97% FE) at -0.52 V (vs RHE). The work demonstrates the great potentials of using monodisperse Au NPs to optimize the available reaction intermediate binding sites for efficient and selective electrocatalytic reduction of CO2 to CO.

  8. Microfluidic fabrication of monodisperse polylactide microcapsules with tunable structures through rapid precipitation.

    Science.gov (United States)

    Watanabe, Takaichi; Kimura, Yukitaka; Ono, Tsutomu

    2013-11-19

    We describe a versatile and facile route to the continuous production of monodisperse polylactide (PLA) microcapsules with controllable structures. With the combination of microfluidic emulsification, solvent diffusion, and internal phase separation, uniform PLA microcapsules with a perfluorooctyl bromide (PFOB) core were successfully obtained by simply diluting monodisperse ethyl acetate (EA)-in-water emulsion with pure water. Rapid extraction of EA from the droplets into the aqueous phase enabled the solidification of the polymer droplets in a nonequilibrium state during internal phase separation between a concentrated PLA/EA phase and a PFOB phase. Higher-molecular-weight PLA generated structural complexity of the microcapsules, yielding core-shell microcapsules with covered with small PFOB droplets. Removal of the PFOB via freeze drying gave hollow microcapsules with dimpled surfaces. The core-shell ratios and the diameter of these microcapsules could be finely tuned by just adjusting the concentration of PFOB and flow rates on emulsification, respectively. These biocompatible microcapsules with controllable size and structures are potentially applicable in biomedical fields such as drug delivery carriers of many functional molecules.

  9. Linear theory on temporal instability of megahertz faraday waves for monodisperse microdroplet ejection.

    Science.gov (United States)

    Tsai, Shirley C; Tsai, Chen S

    2013-08-01

    A linear theory on temporal instability of megahertz Faraday waves for monodisperse microdroplet ejection based on mass conservation and linearized Navier-Stokes equations is presented using the most recently observed micrometer- sized droplet ejection from a millimeter-sized spherical water ball as a specific example. The theory is verified in the experiments utilizing silicon-based multiple-Fourier horn ultrasonic nozzles at megahertz frequency to facilitate temporal instability of the Faraday waves. Specifically, the linear theory not only correctly predicted the Faraday wave frequency and onset threshold of Faraday instability, the effect of viscosity, the dynamics of droplet ejection, but also established the first theoretical formula for the size of the ejected droplets, namely, the droplet diameter equals four-tenths of the Faraday wavelength involved. The high rate of increase in Faraday wave amplitude at megahertz drive frequency subsequent to onset threshold, together with enhanced excitation displacement on the nozzle end face, facilitated by the megahertz multiple Fourier horns in resonance, led to high-rate ejection of micrometer- sized monodisperse droplets (>10(7) droplets/s) at low electrical drive power (<;1 W) with short initiation time (<;0.05 s). This is in stark contrast to the Rayleigh-Plateau instability of a liquid jet, which ejects one droplet at a time. The measured diameters of the droplets ranging from 2.2 to 4.6 μm at 2 to 1 MHz drive frequency fall within the optimum particle size range for pulmonary drug delivery.

  10. Dynamics of polyelectrolyte adsorption and colloidal flocculation upon mixing studied using mono-dispersed polystyrene latex particles

    NARCIS (Netherlands)

    Feng, Lili; Cohen Stuart, Martien; Adachi, Yasuhisa

    2015-01-01

    The dynamic behavior of polyelectrolytes just after their encounter with the surface of bare colloidal particles is analyzed, using the flocculation properties of mono-dispersed polystyrene latex (PSL) particles. Applying a Standardized Colloid Mixing (SCM) approach, effects of ionic strength and

  11. Characteristic tunnel-type conductivity and magnetoresistance in a CoO-coated monodispersive Co cluster assembly

    OpenAIRE

    Peng, D. L.; Sumiyama, Kenji; Yamamuro, S.; Hihara, Takehiko; Konno, T. J.; ヒハラ, タケヒコ; スミヤマ, ケンジ; 隅山, 兼治; 日原, 岳彦; Sumiyama, K.; Hihara, T.

    1999-01-01

    We have studied electrical conductivity, σ, and magnetoresistance in a CoO-coated monodispersive Co cluster assembly fabricated by a plasma-gas-aggregation-type cluster beam deposition technique. The temperature dependence of σ is described in the form of log σ vs 1/T for 7

  12. Monodisperse embedded nanoparticles derived from an atomic metal-dispersed precursor of layered double hydroxide for architectured carbon nanotube formation

    DEFF Research Database (Denmark)

    Tian, Gui-Li; Zhao, Meng-Qiang; Zhang, Bingsen

    2014-01-01

    Monodisperse metal nanoparticles (NPs) with high activity and selectivity are among the most important catalytic materials. However, the intrinsic process to obtain well-dispersed metal NPs with tunable high density (ranging from 10(13) to 10(16) m(-2)) and thermal stability is not yet well under...

  13. Facile Hydrothermal Synthesis of Monodispersed MoS2 Ultrathin Nanosheets Assisted by Ionic Liquid Brij56

    Directory of Open Access Journals (Sweden)

    Guan-Qun Han

    2015-01-01

    Full Text Available Monodispersed MoS2 ultrathin nanosheets have been successfully fabricated by a facile hydrothermal process assisted by ionic liquid Brij56. The effect of Brij56 on the morphology and structure of MoS2 has been obviously observed. XRD shows that the as-prepared MoS2 assisted by Brij56 has the weak and broad peak of (002 planes, which implies the small size and well dispersed structure of MoS2 nanosheets. TEM and SEM images reveal that MoS2 ultrathin nanosheets have small size and few stacking layers with the adding of Brij56. HRTEM images prove that MoS2 appears to have a highly monodispersed morphology and to be monolayer ultrathin nanosheets with the length about 5–8 nm, which can provide more exposed rims and edges as active sites for hydrogen evolution reaction. Brij56 has played a crucial role in preparing monodispersed MoS2 ultrathin nanosheets as excellent electrocatalysts. The growth mechanism of monodispersed MoS2 has been discussed in detail.

  14. Annealing effect on the structural and optical properties of Cr/ -Cr2O3 monodispersed particles based solar absorbers

    CSIR Research Space (South Africa)

    Khamlich, S

    2013-01-01

    Full Text Available A cost-effective and environmentally friendly green chemical method, the so-called aqueous chemical growth (ACG) method, was used to deposit chromium/alpha-chromium(III) oxide, Cr/a-Cr2O3, monodispersed particles, for solar absorbers applications...

  15. Sustainable and scalable production of monodisperse and highly uniform colloidal carbonaceous spheres using sodium polyacrylate as the dispersant.

    Science.gov (United States)

    Gong, Yutong; Xie, Lei; Li, Haoran; Wang, Yong

    2014-10-28

    Monodisperse, uniform colloidal carbonaceous spheres were fabricated by the hydrothermal treatment of glucose with the help of a tiny amount of sodium polyacrylate (PAANa). This synthetic strategy is effective at high glucose concentration and for scale-up experiments. The sphere size can be easily tuned by the reaction time, temperature and glucose concentration.

  16. Synthesis of monodispersed silver nanoparticles using Hibiscus cannabinus leaf extract and its antimicrobial activity

    Science.gov (United States)

    Bindhu, M. R.; Umadevi, M.

    2013-01-01

    Synthesis of silver nanoparticles using leaf extract of Hibiscus cannabinus has been investigated. The influences of different concentration of H. cannabinus leaf extract, different metal ion concentration and different reaction time on the above cases on the synthesis of nanoparticles were evaluated. The synthesized nanoparticles were characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The prepared silver nanoparticles were monodispersed, spherical in shape with the average particle size of 9 nm and shows surface plasmon peak at 446 nm. The study also reveals that the ascorbic acid present in H. cannabinus leaf extract has been used as reducing agent. The prepared silver nanoparticle shows good antimicrobial activity against Escherichia coli, Proteus mirabilis and Shigella flexneri.

  17. Synthesis and characterization of monodispersed inorganic/organic core/shell microspheres with fluorescence

    Institute of Scientific and Technical Information of China (English)

    ZHANG Kai; HAN Kun; ZHANG Xuehai; YANG Bai

    2005-01-01

    @@ In recent years, the semiconductor nanocrystals (NCs) have attracted great interest due to their potentials in photonics, electronics, magnetics and catalysis, and the monodispersed organic or inorganic microspheres doped NCs display predominant characteristics in the fabrication and study for photonic crystals[1,2], and considerable effort has been devoted to the design and synthesis of CdTe NCs doped colloid with well fluorescence[3-8]. For example, CdTe NCs were fabricated on the surfaces of silica or polymer microspheres by the methods of layer-by-layer assembly, and CdTe NCs were also doped into inorganic or organic microspheres through sol-gel process or swell- ing.

  18. Synthesis of Monodisperse Walnut-Like SnO2 Spheres and Their Photocatalytic Performances

    Directory of Open Access Journals (Sweden)

    Jing Wang

    2015-01-01

    Full Text Available Novel walnut-like SnO2 spheres have been synthesized using a one-step hydrothermal reaction with SnCl2·2H2O and KOH as raw materials. The morphology, microstructure, and optical properties of the products were characterized by X-ray powder diffraction (XRD, Raman spectrum, scanning electron microscopy (SEM, transmission electron microscopy (TEM, selected area electron diffraction (SAED, and ultraviolet-visible (UV-Vis absorption spectroscopy. The detailed studies revealed that these synthesized spheres are highly monodisperse and have a uniform size of approximately 250 nm. Photocatalytic activity of the prepared SnO2 spheres was evaluated by the degradation of methylene orange. The synthesized SnO2 spheres exhibited excellent photocatalytic degradation. In addition, a possible formation mechanism of the walnut-like nanostructures was proposed based on reaction time-dependent experiments.

  19. Sonochemical synthesis of monodispersed magnetite nanoparticles by using an ethanol-water mixed solvent.

    Science.gov (United States)

    Dang, Feng; Enomoto, Naoya; Hojo, Junichi; Enpuku, Keiji

    2009-06-01

    The magnetite nanoparticles were synthesized in an ethanol-water solution under ultrasonic irradiation from a Fe(OH)(2) precipitate. XRD, TEM, TG, IR, VSM and UV/vis absorption spectrum were used to characterize the magnetite nanoparticles. It was found that the formation of magnetite was accelerated in ethanol-water solution in the presence of ultrasonic irradiation, whereas, it was limited in ethanol-water solution under mechanical stirring. The monodispersibility of magnetite particles was improved significantly through the sonochemical synthesis in ethanol-water solution. The magnetic properties were improved for the samples synthesized under ultrasonic irradiation. This would be attributed to high Fe(2+) concentration in the magnetite cubic structure.

  20. Recent Progress in the Design of Monodisperse, Sequence-Defined Macromolecules.

    Science.gov (United States)

    Solleder, Susanne C; Schneider, Rebekka V; Wetzel, Katharina S; Boukis, Andreas C; Meier, Michael A R

    2017-05-01

    This review describes different synthetic strategies towards sequence-defined, monodisperse macromolecules, which are built up by iterative approaches and lead to linear non-natural polymer structures. The review is divided in three parts: solution phase-, solid phase-, and fluorous- and polymer-tethered approaches. Moreover, synthesis procedures leading to conjugated and non-conjugated macromolecules are considered and discussed in the respective sections. A major focus in the evaluation is the applicability of the different approaches in polymer chemistry. In this context, simple procedures for monomer and oligomer synthesis, overall yields, scalability, purity of the oligomers, and the achievable level of control (side-chains, backbone, stereochemistry) are important benchmarks. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. XAFS studies of monodisperse Au nanoclusters formation in the etching process

    Science.gov (United States)

    Yang, Lina; Huang, Ting; Liu, Wei; Bao, Jie; Huang, Yuanyuan; Cao, Yuanjie; Yao, Tao; Sun, Zhihu; Wei, Shiqiang

    2016-05-01

    Understanding the formation mechanism of gold nanoclusters is essential to the development of their synthetic chemistry. Here, by using x-ray absorption fine-structure (XAFS) spectroscopy, UV-Vis and MS spectra, the formation process of monodisperse Au13 nanoclusters is investigated. We find that a critical step involving the formation of smaller Au8-Au11 metastable intermediate clusters induced by the HCl + HSR etching of the polydisperse Aun precursor clusters occurs firstly. Then these intermediate species undergo a size-growth to Au13 cores, followed by a slow structure rearrangement to reach the final stable structure. This work enriches the understanding of cluster formation chemistry and may guide the way towards the design and the controllable synthesis of nanoclusters.

  2. Efficient thermolysis route to monodisperse Cu₂ZnSnS₄ nanocrystals with controlled shape and structure.

    Science.gov (United States)

    Zhang, Xiaoyan; Guo, Guobiao; Ji, Cheng; Huang, Kai; Zha, Chenyang; Wang, Yifeng; Shen, Liming; Gupta, Arunava; Bao, Ningzhong

    2014-05-28

    Monodisperse Cu2ZnSnS4 (CZTS) nanocrystals with tunable shape, crystalline phase, and composition are synthesized by efficient thermolysis of a single source precursor of mixed metal-oleate complexes in hot organic solvents with dissolved sulfur sources. Suitable tuning of the synthetic conditions and the Cu/(Zn + Sn) ratio of the precursor has enabled precise control of the crystalline phase in the form of kesterite, or a newly observed wurtzite structure. Nanocrystals with morphology in the form of spherical, rice-like, or rod-like shapes are obtained over a wide range of compositions (0.5 ≤ Cu/(Zn + Sn) ≤ 1.2). Both the final products and intermediates for each shape exhibit consistent composition and structure, indicating homogenous nucleation and growth of single-phase nanocrystals. Thin films prepared from colloidal nanocrystal suspensions display interesting shape-dependent photoresponse behavior under white light illumination from a solar simulator.

  3. Synthesis and characterization of monodisperse CdSe quantum dots in different organic solvents

    Institute of Scientific and Technical Information of China (English)

    He Rong; You Xiaogang; Tian Hongye; Gao Feng; Cui Daxiang; Gu Hongchen

    2006-01-01

    Nearly monodisperse CdSe quantum dots (QDs)have been prepared by a soft solution approach using air-stable reagents in different organic solvents.This scheme is a supplement to the conventional thermal decomposition of organometailic compounds at higher temperatures.CdSe nanocrystals of different sizes could be obtained by simply changing the solvent.This method is reproducible and simple and thus can be readily scaled up for industrial production.The reaction process was monitored by the temporal evolution of the UV-Vis absorption and room temperature photoluminensce spectra.The structures of the CdSe quantum dots were determined by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM).The phase-transfer of oleic acid-stabilized CdSe nanocrystals into PBS buffer solutions was also studied for their potentials in biological applications.

  4. Straightforward and robust synthesis of monodisperse surface-functionalized gold nanoclusters

    Directory of Open Access Journals (Sweden)

    Silvia Varela-Aramburu

    2016-09-01

    Full Text Available Gold nanoclusters are small (1–3 nm nanoparticles with a high surface area that are useful for biomedical studies and drug delivery. The synthesis of small, surface-functionalized gold nanoclusters is greatly dependent on the reaction conditions. Here, we describe a straightforward, efficient and robust room temperature one-pot synthesis of 2 nm gold nanoclusters using thioglucose as a reducing and stabilizing agent, which was discovered by serendipity. The resultant monodisperse gold nanoclusters are more stable than those generated using some other common methods. The carboxylic acid contained in the stabilizing agent on the cluster surface serves as anchor for nanocluster functionalization. Alternatively, the addition of thiols serves to functionalize the nanoclusters. The resulting non-cytotoxic nanoclusters are taken up by cells and constitute a tuneable platform for biomedical applications including drug delivery.

  5. Shape-controlled synthesis of highly monodisperse and small size gold nanoparticles

    Institute of Scientific and Technical Information of China (English)

    FU YunZhi; DU YuKou; YANG Ping; LI JinRu; JIANG Long

    2007-01-01

    We describe here that fine control of nanoparticle shape and size can be achieved by systematic variation of experimental parameters in the seeded growth procedure in aqueous solution. Cubic and spherical gold nanoparticles are obtained respectively. In particularly, the Au cubes are highly monodisperse in 33±2 nm diameter. The experimental methods involve the preparation of Au seed particles and the subsequent addition of an appropriate quantity of Au seed solution to the aqueous growth solutions containing desired quantities of CTAB and ascorbic acid (AA). Here, AA is a weak reducing agent and CTAB is not only a stable agent for nanoparticles but also an inductive agent for leading increase in the face of nanoparticle. Ultraviolet visible spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM) are used to characterize the nanoparticles. The results show that the different size gold nanoparticles displayed high size homogenous distribution and formed mono-membrane at the air/solid interface.

  6. Straightforward and robust synthesis of monodisperse surface-functionalized gold nanoclusters

    Science.gov (United States)

    Varela-Aramburu, Silvia; Wirth, Richard; Lai, Chian-Hui; Orts-Gil, Guillermo

    2016-01-01

    Summary Gold nanoclusters are small (1–3 nm) nanoparticles with a high surface area that are useful for biomedical studies and drug delivery. The synthesis of small, surface-functionalized gold nanoclusters is greatly dependent on the reaction conditions. Here, we describe a straightforward, efficient and robust room temperature one-pot synthesis of 2 nm gold nanoclusters using thioglucose as a reducing and stabilizing agent, which was discovered by serendipity. The resultant monodisperse gold nanoclusters are more stable than those generated using some other common methods. The carboxylic acid contained in the stabilizing agent on the cluster surface serves as anchor for nanocluster functionalization. Alternatively, the addition of thiols serves to functionalize the nanoclusters. The resulting non-cytotoxic nanoclusters are taken up by cells and constitute a tuneable platform for biomedical applications including drug delivery. PMID:27826501

  7. One-Step Synthesis of Monodisperse In-Doped ZnO Nanocrystals

    Directory of Open Access Journals (Sweden)

    Wang QingLing

    2010-01-01

    Full Text Available Abstract A method for the synthesis of high quality indium-doped zinc oxide (In-doped ZnO nanocrystals was developed using a one-step ester elimination reaction based on alcoholysis of metal carboxylate salts. The resulting nearly monodisperse nanocrystals are well-crystallized with typically crystal structure identical to that of wurtzite type of ZnO. Structural, optical, and elemental analyses on the products indicate the incorporation of indium into the host ZnO lattices. The individual nanocrystals with cubic structures were observed in the 5% In–ZnO reaction, due to the relatively high reactivity of indium precursors. Our study would provide further insights for the growth of doped oxide nanocrystals, and deepen the understanding of doping process in colloidal nanocrystal syntheses.

  8. Two typical structure patterns in jammed monodisperse disk packings at high densities

    Science.gov (United States)

    Yuan, Ye; Jin, Weiwei; Liu, Lufeng; Li, Shuixiang

    2016-11-01

    We generate a large number of monodisperse disk packings in two dimensions via geometric-based packing algorithms including the relaxation algorithm and the Torquato-Jiao algorithm. Using the geometric-structure approach, a clear boundary of the geometrical feasible region in the order map is found which quite differs from that of the jammed region. For a certain packing density higher than 0.83, the crystalline degree varies in different packing samples. We find that the local hexatic order may increase in two fairly different ways as the system densifies. Therefore, two typical non-equilibrium jammed patterns, termed polycrystal and distorted crystal, are defined at high packing densities. Furthermore, their responses to isotropic compression are investigated using a compression-relaxation molecular dynamic protocol. The distorted crystal pattern is more stable than the polycrystal one with smaller displacements despite its low occurrence frequency. The results are helpful in understanding the structure and phase transition of disk packings.

  9. Formation and spectroscopic characterization of mono-dispersed CdSe nanocrystals

    Institute of Scientific and Technical Information of China (English)

    Miao Yan-Ming; Li Chao-Rong; Cao Li; Liu Rui-Bin; He Yu-Ping; Xie Si-Shen; Zou Bing-Suo

    2005-01-01

    In this article, mono-dispersed hexagonal structure CdSe nanocrystals with polyhedron shape were prepared by an open solvent thermal reaction. They show a discrete excitonic transition structure in the absorption spectra and the minimal photoluminescence (PL) peak full-width at half-maximum of 19nm. The PL quantum yield is about 60%. Transmission electron micrographs, high-resolution transmission electron micrographs, x-ray powder diffraction patterns, UV-vis absorption spectra and PL spectra were obtained for the as-prepared CdSe nanocrystals. The size of the CdSe nanocrystals can be tuned by changing the reaction temperature or time. Due to the improved synthesis method, a different growth mechanism of the CdSe nanocrystals is discussed.

  10. Direct Dry-Grinding Synthesis of Monodisperse Lipophilic CuS Nanoparticles.

    Science.gov (United States)

    Li, Yajuan; Scott, Julie; Chen, Yi-Tzai; Guo, Liangran; Zhao, Mingyang; Wang, Xiaodong; Lu, Wei

    2015-07-15

    Copper sulfide nanoparticles, effective absorbers of near-infrared light, are recently attracting broad interest as a photothermal coupling agent for cancer therapy. Lipophilic copper sulfide nanoparticles are preferred for high performance biomedical applications due to high tissue affinity. Synthesis of lipophilic copper sulfide nanoparticles requires complicated multi-step processes under severe conditions. Here, we describe a new synthetic process, developed by direct dry-grinding of copper(II) acetylacetonate with sulfur under ambient environment at low temperature. The formed CuS nanoparticles are of uniform size, ~10 nm in diameter, and are monodispersed in chloroform. Each covellite CuS nanocrystal surface is modified with oleylamine through hydrogen bonding between sulfur atoms and amine groups of oleylamine. The nanoparticles demonstrate near-infrared light absorption for photothermal applications. The synthetic methodology described here is more convenient and less extreme than previous methods, and should thus greatly facilitate the preparation of photothermal lipophilic copper sulfide nanomaterials for cancer therapy.

  11. Facile synthesis of monodisperse thermally immiscible Ag–Ni alloy nanoparticles at room temperature

    Indian Academy of Sciences (India)

    S Tabatabaei; S K Sadrnezhaad

    2014-10-01

    Ag and Ni are immiscible, mainly due to their large lattice mismatch. This paper reports on their nanoscale formation of solid solution at room temperature by simple reduction reactions which lead to the amorphous Ag–Ni alloy nanoparticles (ANPs) with mono-disperse distribution. Microscopic and spectroscopic studies confirmed dependence of the alloy composition on size of nanoparticles. In the presence of different ligands such as sodium citrate, polyvinyl alcohol and potassium carbonate a mixture of silver oxide and Ag–Ni ANPs was achieved. Stoichiometry of the Ag–Ni ANPs was also found to be strongly dependent on ligands of the reduction reaction and further study shows without any ligand 100% Ag–Ni ANPs was observed in the system. Using Tetrakis hydroxymethyl phosphonium chloride resulted in construction of near-uniform ANPs in the easily controllable conditions of the present alloying procedure. Nanoparticles having up to 65% Ni were observed for the first time in this research.

  12. Microwave Synthesis of Nearly Monodisperse Core/Multishell Quantum Dots with Cell Imaging Applications

    Directory of Open Access Journals (Sweden)

    Xu Hengyi

    2010-01-01

    Full Text Available Abstract We report in this article the microwave synthesis of relatively monodisperse, highly crystalline CdSe quantum dots (QDs overcoated with Cd0.5Zn0.5S/ZnS multishells. The as-prepared QDs exhibited narrow photoluminescence bandwidth as the consequence of homogeneous size distribution and uniform crystallinity, which was confirmed by transmission electron microscopy. A high photoluminescence quantum yield up to 80% was measured for the core/multishell nanocrystals. Finally, the resulting CdSe/Cd0.5Zn0.5S/ZnS core/multishell QDs have been successfully applied to the labeling and imaging of breast cancer cells (SK-BR3.

  13. Monodisperse core-shell particles composed of magnetite and dye-functionalized mesoporous silica

    Science.gov (United States)

    Eurov, D. A.; Kurdyukov, D. A.; Medvedev, A. V.; Kirilenko, D. A.; Yakovlev, D. R.; Golubev, V. G.

    2017-08-01

    Hybrid particles with a core-shell structure have been obtained in the form of monodisperse spherical mesoporous silica particles filled with magnetite and covered with a mesoporous silica shell functionalized with a luminescent dye. The particles have a small root-mean-square size deviation (at most 10%), possess a specific surface area and specific pore volume of up to 250 m2/g and 0.15 cm3/g, respectively, and exhibit visible luminescence peaked at a wavelength of 530 nm. The particles can be used in diagnostics of cancerous diseases, serving simultaneously for therapeutic (magnetic hyperthermia and targeted drug delivery) and diagnostic (contrast agent for magnetic-resonance tomography and luminescent marker) purposes.

  14. Hydrothermal synthesis of monodisperse α-Fe2O3 hexagonal platelets

    Institute of Scientific and Technical Information of China (English)

    Dengfeng Peng; Sadeh Beysen; Qiang Li; Yanfei Sun; Linyu Yang

    2010-01-01

    Uniformly sized α-Fe2O3 hexagonal platelets were synthesized by a hydrothermal process using Fe(OH)3suspension and large amount of NaOH.The reaction products were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),selected area electron diffraction(SAED),and a vibrating sample magnetometer(VSM).The results show that the hexagonal platelets are fine,monodisperse and consisting of single-crystals.The magnetic hysteresis(M-H)curve of the samples measured at room temperature indicates that the α-Fe2O3 micro-platelets exhibit ferromagnetic behaviors with relatively low coercivity.

  15. Synthesis of mono-dispersed Fe-Co nanoparticles with precise composition control

    Science.gov (United States)

    Wang, Yufeng; Zheng, Yi; Hu, Shuchun

    2017-01-01

    Monodispersed Fe-Co nanoparticles are synthesized by reducing FeCl2 and CoCl2 in diphenyl ether, with n-butyllithium as reducing agent and oleic acid as surfactant. The body centered cubic (BCC) crystal structure of Fe-Co nanoparticles is confirmed by both XRD patterns and TEM diffraction patterns. The average nanoparticle size is 10 nm at the reported experimental condition. The magnetization of the Fe-Co increases with increased cobalt atomic percentage. XPS technique is used to investigate the surface chemical states of Fe-Co nanoparticles. Finally, the composition of Fe-Co nanoparticles is investigated through EDX, confirming the molar ratio of Fe/Co in nanoparticles could be accurately controlled by changing the composition of the precursors.

  16. Glass Transitions in Monodisperse Cluster-Forming Ensembles: Vortex Matter in Type-1.5 Superconductors

    Science.gov (United States)

    Díaz-Méndez, Rogelio; Mezzacapo, Fabio; Lechner, Wolfgang; Cinti, Fabio; Babaev, Egor; Pupillo, Guido

    2017-02-01

    At low enough temperatures and high densities, the equilibrium configuration of an ensemble of ultrasoft particles is a self-assembled, ordered, cluster crystal. In the present Letter, we explore the out-of-equilibrium dynamics for a two-dimensional realization, which is relevant to superconducting materials with multiscale intervortex forces. We find that, for small temperatures following a quench, the suppression of the thermally activated particle hopping hinders the ordering. This results in a glass transition for a monodispersed ensemble, for which we derive a microscopic explanation in terms of an "effective polydispersity" induced by multiscale interactions. This demonstrates that a vortex glass can form in clean systems of thin films of "type-1.5" superconductors. An additional setup to study this physics can be layered superconducting systems, where the shape of the effective vortex-vortex interactions can be engineered.

  17. The synthesis of clusters of iron oxides in mesopores of monodisperse spherical silica particles

    Science.gov (United States)

    Stovpiaga, E. Yu.; Eurov, D. A.; Kurdyukov, D. A.; Smirnov, A. N.; Yagovkina, M. A.; Grigorev, V. Yu.; Romanov, V. V.; Yakovlev, D. R.; Golubev, V. G.

    2017-08-01

    The method of obtaining nanoclusters α-Fe2O3 in the pores of monodisperse spherical particles of mesoporous silica ( mSiO2) by a single impregnation of the pores with a melt of crystalline hydrate of ferric nitrate and its subsequent thermal destruction has been proposed. Fe3O4 nanoclusters are synthesized from α-Fe2O3 in the pores by reducing in thermodynamically equilibrium conditions. Then particles containing Fe3O4 were annealed in oxygen for the conversion of Fe3O4 back to α-Fe2O3. In the result, the particles with the structure of the core-shell mSiO2/Fe3O4@ mSiO2/α-Fe2O3 are obtained. The composition and structure of synthesized materials as well as the field dependence of the magnetic moment on the magnetic field strength have been investigated.

  18. Size-controlled synthesis of monodispersed gold nanoparticles via carbon monoxide gas reduction

    Directory of Open Access Journals (Sweden)

    Lewinski Nastassja

    2011-01-01

    Full Text Available Abstract An in depth analysis of gold nanoparticle (AuNP synthesis and size tuning, utilizing carbon monoxide (CO gas as a reducing agent, is presented for the first time. The sizes of the AuNPs are tunable from ~4 to 100 nm by altering the concentration of HAuCl4 and inlet CO gas-injection flow rate. It is also found that speciation of aqueous HAuCl4, prior to reduction, influences the size, morphology, and properties of AuNPs when reduced with CO gas. Ensemble extinction spectra and TEM images provide clear evidence that CO reduction offers a high level of monodispersity with standard deviations as low as 3%. Upon synthesis, no excess reducing agent remains in solution eliminating the need for purification. The time necessary to synthesize AuNPs, using CO, is less than 2 min.

  19. A Convenient and Templated Method for the Fabrication of Monodisperse Micrometer Hollow Titania Spheres

    Directory of Open Access Journals (Sweden)

    Haibo Yao

    2013-01-01

    Full Text Available A simple and widely applicable methodology was presented to synthesize monodisperse micrometer hollow titania spheres (HTS based on the templating method. It was performed by using the preformed poly(styrene-acrylic acid (PSA as template spheres which was mixed with tetrabutyltitanate (TBOT in an ethanol solvent under steam treatment. The HTS which were obtained by the calcination of PSA/TiO2 composite core-shell spheres had a narrow particle size distribution and commendable surface topography characterized by SEM. The calcined HTS at 500°C displayed crystalline reflection peaks that were characteristic to the anatase phase by XRD. Moreover, some key influencing factors including TBOT concentration and reaction time were analyzed. As expected, the diameter of HTS could be readily controlled by altering the size of PSA template spheres. In addition, the approach was also applied to fabricate hollow zirconia spheres and other inorganic spheres.

  20. Photoelectrochemical performance of DSSC with monodisperse and polydisperse ZnO SPs

    Energy Technology Data Exchange (ETDEWEB)

    Wahyuono, Ruri Agung, E-mail: r-agung-w@ep.its.ac.id; Risanti, Doty D., E-mail: r-agung-w@ep.its.ac.id [Department of Engineering Physics, Institut Teknologi Sepuluh Nopember (Indonesia); Shirosaki, Tomohiro; Nagaoka, Shoji [Kumamoto Industrial Research Institute (Japan); Takafuji, Makoto; Ihara, Hirotaka [Department of Applied Chemistry and Biochemistry, Kumamoto University (Japan)

    2014-02-24

    Zinc oxide, ZnO, is one of oxide semiconductors being used in DSSC. ZnO is promising material for having fairly higher energy band gap and much higher bulk electron mobility than that of anatase TiO{sub 2}, the most widely used semiconductor for DSSC photoelectrode. This study introduces the synthesis of ZnO by precipitation method. The synthesis involves ZnAc dihydrate and diethylene glycol (DEG) for the chemicals. Various size of ZnO spherical particles (SPs) are obtained in polydisperse and monodisperse particles. Monolayer and bilayer DSSCs are fabricated in sandwich structure and sensitized with N719 dye for 3 and 5 hours. Monolayer DSSC using monodisperse particles (422 nm) is able to generate highest conversion efficiency of 0.569% (V{sub oc} = 541.3 mV, J{sub sc} = 1.92 mA/cm{sup 2}, and fill factor of 54.78%). Bilayer DSSC, i.e. combined 422 - 185 nm ZnO layer, can optimize the photocurrent action spectra in UV regime leading to high conversion efficiency of 0.568 (V{sub oc} = 568.2 mV, J{sub sc} = 2.22 mA/cm{sup 2}, and fill factor of 47.25%). The longer sensitizing time does not always produce better conversion efficiency since it can induce the dissolution of Zn atoms and formation of Zn{sup 2+} - dye resisting the electron transport from dye to ZnO photoelectrode.

  1. Preparation and characterization of monodisperse large-porous silica microspheres as the matrix for protein separation.

    Science.gov (United States)

    Xia, Hongjun; Wan, Guangping; Zhao, Junlong; Liu, Jiawei; Bai, Quan

    2016-11-04

    High performance liquid chromatography (HPLC) is a kind of efficient separation technology and has been used widely in many fields. Micro-sized porous silica microspheres as the most popular matrix have been used for fast separation and analysis in HPLC. In this paper, the monodisperse large-porous silica microspheres with controllable size and structure were successfully synthesized with polymer microspheres as the templates and characterized. First, the poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate) microspheres (PGMA-EDMA) were functionalized with tetraethylenepentamine (TEPA) to generate amino groups which act as a catalyst in hydrolysis of tetraethyl orthosilicate (TEOS) to form Si-containing low molecular weight species. Then the low molecular weight species diffused into the functionalized PGMA-EDMA microspheres by induction force of the amino groups to form polymer/silica hybrid microspheres. Finally, the organic polymer templates were removed by calcination, and the large-porous silica microspheres were obtained. The compositions, morphology, size distribution, specific surface area and pore size distribution of the porous silica microspheres were characterized by infrared analyzer, scanning-electron microscopy, dynamic laser scattering, the mercury intrusion method and thermal gravimetric analysis, respectively. The results show that the agglomeration of the hybrid microspheres can be overcome when the templates were functionalized with TEPA as amination reagent, and the yield of 95.7% of the monodisperse large-porous silica microspheres can be achieved with high concentration of polymer templates. The resulting large-porous silica microspheres were modified with octadecyltrichlorosilane (ODS) and the chromatographic evaluation was performed by separating the proteins and the digest of BSA. The baseline separation of seven kinds of protein standards was achieved, and the column delivered a better performance when separating BSA digests

  2. Controlled synthesis of monodisperse gold nanorods with different aspect ratios in the presence of aromatic additives

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yun; Wang, Feihu [Shanghai Jiao Tong University, School of Pharmacy (China); Guo, Yuan [University of Leeds, School of Chemistry and Astbury Centre for Structural Molecular Biology (United Kingdom); Chen, Rongjun, E-mail: rongjun.chen@imperial.ac.uk [Imperial College London, Department of Chemical Engineering (United Kingdom); Shen, Yuanyuan; Guo, Aijie; Liu, Jieying; Zhang, Xiao [Shanghai Jiao Tong University, School of Pharmacy (China); Zhou, Dejian, E-mail: d.zhou@leeds.ac.uk [University of Leeds, School of Chemistry and Astbury Centre for Structural Molecular Biology (United Kingdom); Guo, Shengrong, E-mail: srguo@sjtu.edu.cn [Shanghai Jiao Tong University, School of Pharmacy (China)

    2014-12-15

    This paper reports the synthesis of monodisperse gold nanorods (GNRs) via a simple seeded growth approach in the presence of different aromatic additives, such as 7-bromo-3-hydroxy-2-naphthoic acid (7-BrHNA), 3-hydroxy-2-naphthoic acid (HNA), 5-bromosalicylic acid (5-BrSA), salicylic acid (SA), or phenol (PhOH). Effects of the aromatic additives and hydrochloric acid (HCl) on the structure and optical properties of the synthesized GNRs were investigated. The longitudinal surface plasmon resonance (LSPR) peak wavelength of the resulting GNRs was found to be dependent on the aromatic additive in the following sequence: 5-BrSA (778 nm) > 7-BrHNA (706 nm) > SA (688 nm) > HNA (676 nm) > PhOH (638 nm) without the addition of HCl, but this was changed to 7-BrHNA (920 nm) > SA (890 nm) > HNA (872 nm) > PhOH (858 nm) > 5-BrSA (816 nm) or 7-BrHNA (1,005 nm) > PhOH (995 nm) > SA (990 nm) > HNA (980 nm) > 5-BrSA (815 nm) with the addition of HCl or HNO{sub 3}, respectively. The LSPR peak wavelength was increased with the increasing concentration of 7-BrHNA without HCl addition; however, there was a maximum LSPR peak wavelength when HCl was added. Interestingly, the LSPR peak wavelength was also increased with the amount of HCl added. The results presented here thus established a simple approach to synthesize monodisperse GNRs of different LSPR wavelengths.

  3. Synthesis of phase-pure and monodisperse iron oxide nanoparticles by thermal decomposition

    Science.gov (United States)

    Hufschmid, Ryan; Arami, Hamed; Ferguson, R. Matthew; Gonzales, Marcela; Teeman, Eric; Brush, Lucien N.; Browning, Nigel D.; Krishnan, Kannan M.

    2015-06-01

    Superparamagnetic iron oxide nanoparticles (SPIONs) are used for a wide range of biomedical applications requiring precise control over their physical and magnetic properties, which are dependent on their size and crystallographic phase. Here we present a comprehensive template for the design and synthesis of iron oxide nanoparticles with control over size, size distribution, phase, and resulting magnetic properties. We investigate critical parameters for synthesis of monodisperse SPIONs by organic thermal decomposition. Three different, commonly used, iron containing precursors (iron oleate, iron pentacarbonyl, and iron oxyhydroxide) are evaluated under a variety of synthetic conditions. We compare the suitability of these three kinetically controlled synthesis protocols, which have in common the use of iron oleate as a starting precursor or reaction intermediate, for producing nanoparticles with specific size and magnetic properties. Monodisperse particles were produced over a tunable range of sizes from approximately 2-30 nm. Reaction parameters such as precursor concentration, addition of surfactant, temperature, ramp rate, and time were adjusted to kinetically control size and size-distribution, phase, and magnetic properties. In particular, large quantities of excess surfactant (up to 25 : 1 molar ratio) alter reaction kinetics and result in larger particles with uniform size; however, there is often a trade-off between large particles and a narrow size distribution. Iron oxide phase, in addition to nanoparticle size and shape, is critical for establishing magnetic properties such as differential susceptibility (dm/dH) and anisotropy. As an example, we show the importance of obtaining the required size and iron oxide phase for application to Magnetic Particle Imaging (MPI), and describe how phase purity can be controlled. These results provide much of the information necessary to determine which iron oxide synthesis protocol is best suited to a particular

  4. Structure-transport correlation for the diffusive tortuosity of bulk, monodisperse, random sphere packings.

    Science.gov (United States)

    Khirevich, Siarhei; Höltzel, Alexandra; Daneyko, Anton; Seidel-Morgenstern, Andreas; Tallarek, Ulrich

    2011-09-16

    The mass transport properties of bulk random sphere packings depend primarily on the bed (external) porosity ε, but also on the packing microstructure. We investigate the influence of the packing microstructure on the diffusive tortuosity τ=D(m)/D(eff), which relates the bulk diffusion coefficient (D(m)) to the effective (asymptotic) diffusion coefficient in a porous medium (D(eff)), by numerical simulations of diffusion in a set of computer-generated, monodisperse, hard-sphere packings. Variation of packing generation algorithm and protocol yielded four Jodrey-Tory and two Monte Carlo packing types with systematically varied degrees of microstructural heterogeneity in the range between the random-close and the random-loose packing limit (ε=0.366-0.46). The distinctive tortuosity-porosity scaling of the packing types is influenced by the extent to which the structural environment of individual pores varies in a packing, and to quantify this influence we propose a measure based on Delaunay tessellation. We demonstrate that the ratio of the minimum to the maximum void face area of a Delaunay tetrahedron around a pore between four adjacent spheres, (A(min)/A(max))(D), is a measure for the structural heterogeneity in the direct environment of this pore, and that the standard deviation σ of the (A(min)/A(max))(D)-distribution considering all pores in a packing mimics the tortuosity-porosity scaling of the generated packing types. Thus, σ(A(min)/A(max))(D) provides a structure-transport correlation for diffusion in bulk, monodisperse, random sphere packings. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. Production of monodisperse epigallocatechin gallate (EGCG) microparticles by spray drying for high antioxidant activity retention.

    Science.gov (United States)

    Fu, Nan; Zhou, Zihao; Jones, Tyson Byrne; Tan, Timothy T Y; Wu, Winston Duo; Lin, Sean Xuqi; Chen, Xiao Dong; Chan, Peggy P Y

    2011-07-15

    Epigallocatechin gallate (EGCG) originated from green tea is well-known for its pharmaceutical potential and antiproliferating effect on carcinoma cells. For drug delivery, EGCG in a micro-/nanoparticle form is desirable for their optimized chemopreventive effect. In this study, first time reports that EGCG microparticles produced by low temperature spray drying can maintain high antioxidant activity. A monodisperse droplet generation system was used to realize the production of EGCG microparticles. EGCG microparticles were obtained with narrow size distribution and diameter of 30.24 ± 1.88 μM and 43.39 ± 0.69 μM for pure EGCG and lactose-added EGCG, respectively. The EC50 value (the amount of EGCG necessary to scavenge 50% of free radical in the medium) of spray dried pure EGCG particles obtained from different temperature is in the range of 3.029-3.075 μM compared to untreated EGCG with EC50 value of 3.028 μM. Varying the drying temperatures from 70°C and 130°C showed little detrimental effect on EGCG antioxidant activity. NMR spectrum demonstrated the EGCG did not undergo chemical structural change after spray drying. The major protective mechanism was considered to be: (1) the use of low temperature and (2) the heat loss from water evaporation that kept the particle temperature at low level. With further drier optimization, this monodisperse spray drying technique can be used as an efficient and economic approach to produce EGCG micro-/nanoparticles.

  6. Preparation of highly monodisperse fluorescent polymer particles by miniemulsion polymerization of styrene with a polymerizable surfactant.

    Science.gov (United States)

    Taniguchi, Tatsuo; Takeuchi, Naoki; Kobaru, Shotaro; Nakahira, Takayuki

    2008-11-01

    Miniemulsion polymerization of styrene (St) in the presence of a hydrophobe (hexadecane:HD) using a cationic polymerizable surfactant (N,N-dimethyl-N-n-dodecyl-N-2-methacryloyloxyethylammonium bromide:C(12)Br) and a cationic initiator (2,2'-azobis(2-amidinopropane) dihydrochloride:V50), called St/C(12)Br/V50 hereafter, proceeded efficiently compared with that using sodium dodecyl sulfate (SDS) and potassium persulfate (KPS), i.e., St/SDS/KPS, providing monodisperse polystyrene latex particles with a narrower particle size distribution. In St/C(12)Br/AIBN, where an oil-soluble initiator, i.e., 2,2'-azobisisobutyronitrile (AIBN), was used in place of V50, little changes in polymerization kinetics or in particle size distribution were observed, while a significant drop in polymerization rate and a broad particle size distribution were observed with St/SDS/AIBN. A polymerizable pyrene derivative (1-pyrenylmethyl methacrylate: PyMMA) was quantitatively incorporated into monodisperse latex particles in St/PyMMA/C(12)Br/V50 compared to pyrene (Py) in St/Py/C(12)Br/V50. Contrary to our expectation, however, increased excimer emission was observed with St/PyMMA/C(12)Br/V50 particles, indicating less evenly distributed pyrene chromophores in the particles. The fluorescence lifetime of pyrene chromophores in St/Py/C(12)Br/V50 particles was determined to be 286 ns, which was 17 times longer than that of pyrene in THF solution.

  7. Highly monodisperse low-magnetization magnetite nanocubes as simultaneous T1-T2 MRI contrast agents

    Science.gov (United States)

    Sharma, V. K.; Alipour, A.; Soran-Erdem, Z.; Aykut, Z. G.; Demir, H. V.

    2015-06-01

    We report the first study of highly monodisperse and crystalline iron oxide nanocubes with sub-nm controlled size distribution (9.7 +/- 0.5 nm in size) that achieve simultaneous contrast enhancement in both T1- and T2-weighted magnetic resonance imaging (MRI). Here, we confirmed the magnetite structure of iron oxide nanocubes by X-ray diffraction (XRD), selected area electron diffraction (SAED) pattern, optical absorption and Fourier transformed infrared (FT-IR) spectra. These magnetite nanocubes exhibit superparamagnetic and paramagnetic behavior simultaneously by virtue of their finely controlled shape and size. The magnetic measurements reveal that the magnetic moment values are favorably much lower because of the small size and cubic shape of the nanoparticles, which results in an enhanced spin canting effect. As a proof-of-concept demonstration, we showed their potential as dual contrast agents for both T1- and T2-weighted MRI via phantom studies, in vivo imaging and relaxivity measurements. Therefore, these low-magnetization magnetite nanocubes, while being non-toxic and bio-compatible, hold great promise as excellent dual-mode T1 and T2 contrast agents for MRI.We report the first study of highly monodisperse and crystalline iron oxide nanocubes with sub-nm controlled size distribution (9.7 +/- 0.5 nm in size) that achieve simultaneous contrast enhancement in both T1- and T2-weighted magnetic resonance imaging (MRI). Here, we confirmed the magnetite structure of iron oxide nanocubes by X-ray diffraction (XRD), selected area electron diffraction (SAED) pattern, optical absorption and Fourier transformed infrared (FT-IR) spectra. These magnetite nanocubes exhibit superparamagnetic and paramagnetic behavior simultaneously by virtue of their finely controlled shape and size. The magnetic measurements reveal that the magnetic moment values are favorably much lower because of the small size and cubic shape of the nanoparticles, which results in an enhanced spin

  8. Monodispersed calcium carbonate nanoparticles modulate local pH and inhibit tumor growth in vivo

    Science.gov (United States)

    Som, Avik; Raliya, Ramesh; Tian, Limei; Akers, Walter; Ippolito, Joseph E.; Singamaneni, Srikanth; Biswas, Pratim; Achilefu, Samuel

    2016-06-01

    The acidic extracellular environment of tumors potentiates their aggressiveness and metastasis, but few methods exist to selectively modulate the extracellular pH (pHe) environment of tumors. Transient flushing of biological systems with alkaline fluids or proton pump inhibitors is impractical and nonselective. Here we report a nanoparticles-based strategy to intentionally modulate the pHe in tumors. Biochemical simulations indicate that the dissolution of calcium carbonate nanoparticles (nano-CaCO3) in vivo increases pH asymptotically to 7.4. We developed two independent facile methods to synthesize monodisperse non-doped vaterite nano-CaCO3 with distinct size range between 20 and 300 nm. Using murine models of cancer, we demonstrate that the selective accumulation of nano-CaCO3 in tumors increases tumor pH over time. The associated induction of tumor growth stasis is putatively interpreted as a pHe increase. This study establishes an approach to prepare nano-CaCO3 over a wide particle size range, a formulation that stabilizes the nanomaterials in aqueous solutions, and a pH-sensitive nano-platform capable of modulating the acidic environment of cancer for potential therapeutic benefits.The acidic extracellular environment of tumors potentiates their aggressiveness and metastasis, but few methods exist to selectively modulate the extracellular pH (pHe) environment of tumors. Transient flushing of biological systems with alkaline fluids or proton pump inhibitors is impractical and nonselective. Here we report a nanoparticles-based strategy to intentionally modulate the pHe in tumors. Biochemical simulations indicate that the dissolution of calcium carbonate nanoparticles (nano-CaCO3) in vivo increases pH asymptotically to 7.4. We developed two independent facile methods to synthesize monodisperse non-doped vaterite nano-CaCO3 with distinct size range between 20 and 300 nm. Using murine models of cancer, we demonstrate that the selective accumulation of nano-CaCO3

  9. Tribological characteristics of monodispersed cerium borate nanospheres in biodegradable rapeseed oil lubricant

    Energy Technology Data Exchange (ETDEWEB)

    Boshui, Chen, E-mail: boshuichen@163.com; Kecheng, Gu; Jianhua, Fang; Jiang, Wu; Jiu, Wang; Nan, Zhang

    2015-10-30

    Graphical abstract: - Highlights: • Monodispersed stearic acid-capped cerium borate composite nanoparticles were prepared by hydrothermal method. Their morphologies, element compositions, size distributions, crystal and chemical structures, hydrophobic characteristics were also characterized. • The surface-capped cerium borate nanoparticles exhibited excellent dispersing stability in rapeseed oil. As new lubricating additives, they were also outstanding in enhancing friction-reducing and anti-wear capacities of rapeseed oil in biodegradable rapeseed oil. The results presented in this paper would be of important significance for developing green lubricants and lubricant additives. • The prominent tribological performances of SA/CeBO{sub 3} in rapeseed oil were investigated and attributed to the formation of a composite boundary lubrication film mainly composed of lubricous tribochemical species on the tribo-surfaces. - Abstract: Stearic acid-capped cerium borate composite nanoparticles, abbreviated as SA/CeBO{sub 3}, were prepared by hydrothermal method. The morphologies, element compositions, size distributions, crystal and chemical structures, hydrophobic characteristics, of SA/CeBO{sub 3} were characterized by scanning electron microscope, energy dispersive X-ray spectrometer, dynamic laser particle size analyzer, X-ray diffraction, and Fourier transform infrared spectrometer, respectively. The friction and wear performances of SA/CeBO{sub 3} as a lubricating additive in a rapeseed oil were evaluated on a four-ball tribo-tester. The tribochemical characteristics of the worn surfaces were investigated by X-ray photoelectron spectroscopy. The results showed that the hydrophobic SA/CeBO{sub 3} were monodispersed nanospheres with an average diameter of 8 nm, and exhibited excellent dispersing stability in rapeseed oil. Meanwhile, SA/CeBO{sub 3} nanospheres were outstanding in enhancing friction-reducing and anti-wear capacities of rapeseed oil. The prominent

  10. Generation and stabilization of whey-based monodisperse naoemulsions using ultra-high pressure homogenization and small amphipathic co-emulsifier combinations

    Science.gov (United States)

    Ultra-high-pressure homogenization (UHPH) was used to generate monodisperse stable peanut oil nanoemulsions within a desired nanosize range (whey protein concentrate (WPC), sodium dodecyl sulfate, Triton X-100 (X100), and zwitterionic sulfobetaine-base...

  11. Influence of Monodisperse Fe3O4 Nanoparticle Size on Electrical Properties of Vegetable Oil-Based Nanofluids

    Directory of Open Access Journals (Sweden)

    Bin Du

    2015-01-01

    Full Text Available Insulating oil modified by nanoparticles (often called nanofluids has recently drawn considerable attention, especially concerning the improvement of electrical breakdown and thermal conductivity of the nanofluids. In this paper, three sized monodisperse Fe3O4 nanoparticles were prepared and subsequently dispersed into insulating vegetable oil to achieve nanofluids. The dispersion stability of nanoparticles in nanofluids was examined by natural sedimentation and zeta potential measurement. The electrical breakdown strength, space charge distribution, and several dielectric characteristics, for example, permittivity, dielectric loss, and volume resistivity of these nanofluids, were comparatively investigated. Experimental results show that the monodisperse Fe3O4 nanoparticles not only enhance the dielectric strength but also uniform the electric field of the nanofluids. The depth of electrical potential well of insulating vegetable oils and nanofluids were analyzed to clarify the influence of nanoparticles on electron trapping and on insulation improvement of the vegetable oil.

  12. Hydrothermal growth of highly monodispersed TiO2 nanoparticles: Functional properties and dye-sensitized solar cell performance

    Science.gov (United States)

    Navaneethan, M.; Nithiananth, S.; Abinaya, R.; Harish, S.; Archana, J.; Sudha, L.; Ponnusamy, S.; Muthamizhchelvan, C.; Ikeda, H.; Hayakawa, Y.

    2017-10-01

    Monodispersed anatase TiO2 nanoparticles were synthesized by hydrothermal method using citric acid as a capping agent. The effect of citric acid and the growth time on the formation of TiO2, functional properties and dye-sensitized solar cell performances were investigated. X-ray diffraction pattern (XRD) and Raman spectroscopy results revealed that the TiO2 nanoparticles possess the anatase phase. Transmission electron microscopy (TEM) measurement revealed the formation of spherical nanoparticles with monodispersity in size and morphology. An average size of 14 nm was obtained for the growth period of 15 h. The maximum efficiency (η) of dye-sensitized solar cell was achieved for TiO2 nanoparticles grown for 15 h as 7.66% which was higher than that of commercial P25 TiO2 (5.23%) and uncapped nanoparticles (3.68%).

  13. Organoclay-assisted interfacial polymerization for microfluidic production of monodisperse PEG-microdroplets and in situ encapsulation of E. coli.

    Science.gov (United States)

    Wang, Kye Won; Lee, Kyoung G; Park, Tae Jung; Lee, Young-Chul; Yang, Ji-Won; Kim, Do Hyun; Lee, Seok Jae; Park, Jung Youn

    2012-01-01

    We developed a novel one-pot synthetic strategy for preparing monodisperse polyethylene glycol diacrylate (PEGDA) microdroplets via organoclay-assisted interfacial polymerization approach for Escherichia coli encapsulation. Based on the mechanism of spontaneous and rapid polymerization of PEGDA precursor solution with Mg-organoclay, the prepared PEGDA microdroplets have uniform size and fine round shape, with size range of 74-118 µm. The size of microdroplets can be controlled through the changing continuous phase flow rate. Organoclay-assisted polymerization method provides a unique environment to produce non-toxic ways of fabricating microorganism encapsulated microdroplets and to prohibit microdroplets merge during the processes. Furthermore, we successfully carried out to entrap E. coli inside of the PEGDA microdroplets. E. coli expressing a green fluorescent protein shows a good viability inside the PEGDA microdroplets. The in situ microfluidic synthetic method provides a novel approach for the preparation of monodisperse PEGDA microdroplets via a one-pot route.

  14. Direct incorporation of lipophilic nanoparticles into monodisperse perfluorocarbon nanodroplets via solvent dissolution from microfluidic-generated precursor microdroplets.

    Science.gov (United States)

    Seo, Minseok; Matsuura, Naomi

    2014-10-28

    Multifunctional medical agents based on imaging or therapy nanoparticles (NPs) incorporated into perfluorocarbon (PFC) droplets are promising new agents for cancer detection and treatment. For the first time, monodisperse PFC nanodroplets labeled with NPs have been produced. Lipophilic, as-synthesized, hydrocarbon-stabilized NPs are directly miscibilized into lipophobic PFCs using a removable cosolvent, diethyl ether (DEE), which eliminates the need of the typical time-consuming and expertise-specific NP surface modification steps previously required for NP incorporation into PFCs. This NP-DEE/PFC solution is then used to synthesize monodisperse, micrometer-scale, DEE-infused NP-PFC precursor droplets in water using microfluidics. After precursor microdroplet generation, the DEE cosolvent is removed by dissolution and evaporation, resulting in dramatically smaller, monodisperse, NP-labeled nanodroplets, with final droplet sizes far smaller than the minimum droplet size limit of the microfluidic system, and easily controlled by the amount of DEE mixed in the PFC phase prior to precursor droplet synthesis. Using this technique, unmodified lipophilic quantum dot (QD) NPs were integrated into monodisperse and PFC nanodroplets 165 times smaller in volume than the precursor microdroplets, with dimensions down to 470 nm. The final droplet sizes scaled with the PFC concentrations in the precursor microdroplets, and the QDs remain localized within the droplets after DEE is removed from the system. This method is robust and versatile, and it comprises a platform technology for other unmodified lipophilic NPs and molecules to be incorporated into different types of PFC droplets for the production of new NP-PFC hybrid agents for medical imaging and therapy applications.

  15. Facile Synthesis of Monodispersed Polysulfide Spheres for Building Structural Colors with High Color Visibility and Broad Viewing Angle.

    Science.gov (United States)

    Li, Feihu; Tang, Bingtao; Wu, Suli; Zhang, Shufen

    2017-01-01

    The synthesis and assembly of monodispersed colloidal spheres are currently the subject of extensive investigation to fabricate artificial structural color materials. However, artificial structural colors from general colloidal crystals still suffer from the low color visibility and strong viewing angle dependence which seriously hinder their practical application in paints, colorimetric sensors, and color displays. Herein, monodispersed polysulfide (PSF) spheres with intrinsic high refractive index (as high as 1.858) and light-absorbing characteristics are designed, synthesized through a facile polycondensation and crosslinking process between sodium disulfide and 1,2,3-trichloropropane. Owing to their high monodispersity, sufficient surface charge, and good dispersion stability, the PSF spheres can be assembled into large-scale and high-quality 3D photonic crystals. More importantly, high structural color visibility and broad viewing angle are easily achieved because the unique features of PSF can remarkably enhance the relative reflectivity and eliminate the disturbance of scattering and background light. The results of this study provide a simple and efficient strategy to create structural colors with high color visibility, which is very important for their practical application.

  16. Hands-off preparation of monodisperse emulsion droplets using a poly(dimethylsiloxane) microfluidic chip for droplet digital PCR.

    Science.gov (United States)

    Tanaka, Hironari; Yamamoto, Shunsuke; Nakamura, Arichika; Nakashoji, Yuta; Okura, Naoaki; Nakamoto, Norimitsu; Tsukagoshi, Kazuhiko; Hashimoto, Masahiko

    2015-04-21

    A fully autonomous method of creating highly monodispersed emulsion droplets with a low sample dead volume was realized using a degassed poly(dimethylsiloxane) (PDMS) microfluidic chip possessing a simple T-junction channel geometry with two inlet reservoirs for oil and water to be loaded and one outlet reservoir for the collection of generated droplets. Autonomous transport of oil and water phases in the channel was executed by permeation of air confined inside the outlet reservoir into the degassed PDMS. The only operation required for droplet creation was simple pipetting of oil and aqueous solutions into the inlet reservoirs. Long-lasting fluid transport in the current system enabled us to create ca. 51,000 monodispersed droplets (with a coefficient of variation of droplet diameter) in 80 min with a maximum droplet generation rate of ca. 12 Hz using a PDMS chip that had been degassed overnight. With multiple time-course measurements, the reproducibility in the current method of droplet preparation was confirmed, with tunable droplet sizes achieved simply by changing the cross-sectional dimensions of the microchannel. Furthermore, it was verified that the resultant droplets could serve as microreactors for digital polymerase chain reactions. This hands-free technique for preparing monodispersed droplets in a very facile and inexpensive fashion is intended for, but not limited to, bioanalytical applications and is also applicable to material syntheses.

  17. Kinetics of successive seeding of monodisperse polystyrene latexes. I - Initiation via potassium persulfate. II - Azo initiators with and without inhibitors

    Science.gov (United States)

    Sudol, E. D.; El-Aasser, M. S.; Vanderhoff, J. W.

    1986-01-01

    The polymerization kinetics of monodisperse polystyrene latexes with diameters of 1 micron are studied. The monodisperse latexes were prepared by the successive seeding method using 1 mM K2S2O8 with an 8 percent emulsifier surface coverage and 0.5 mM K2S2O8 with a 4 percent emulsifier surface coverage, and the kinetics were measured in a piston/cylinder dialometer. The data reveal that the polymerization rate decreases with increasing particle size; and the surface charge decreases with increasing particle size. The effects of initiators (AIBN and AMBN) and inhibitors (NH24SCN, NaNO2, and hydroquinone) on the product monodispersity and polymerization kinetics of latexes with diameters greater than 1 micron are investigated in a second experiment. It is observed that hydroquinone combined with AMBN are most effective in reducing nucleation without causing flocculation. It is noted that the kinetic transition from emulsion to bulk is complete for a particle size exceeding 1 micron in which the polymerization rate is independent of the particle size.

  18. Formation of nearly monodisperse In2O3 nanodots and oriented-attached nanoflowers: hydrolysis and alcoholysis vs pyrolysis.

    Science.gov (United States)

    Narayanaswamy, Arun; Xu, Huifang; Pradhan, Narayan; Kim, Myeongseob; Peng, Xiaogang

    2006-08-01

    Single crystalline and nearly monodisperse In2O3 nanocrystals with both dot and flower shapes were synthesized in a simple reaction system. This system used indium carboxylates as the precursors with or without alcohol as the activating reagents in a hydrocarbon solvent under elevated temperatures. Limited ligand protection (LLP) led to three-dimensional (3D) oriented attachment of nanodots, resulting in 3D nanoflowers. When the system had sufficient ligand protection for the nanocrystals, nanodots were found to be the stable products. The diameters of nearly monodisperse nanodots and nanoflowers were varied in a range from approximately 5 to approximately 15 nm and approximately 15 to approximately 60 nm, respectively. The simple reaction system made it possible to have a systematic study of the reaction mechanisms along with the growth kinetics of nanocrystals. Hydrolysis and alcoholysis were identified as the major paths for this system, as opposed to pyrolysis. Both nearly monodispersed nanodots and nanoflowers can be made through either of the reaction pathways. Hydrolysis was found as a reversible pathway, and alcoholysis was confirmed to be irreversible. Consequently, a sufficient amount of alcohol was able to force the yield of nanocrystals, both dots and flowers, to unity.

  19. Facile synthesis of monodisperse superparamagnetic Fe3O4/PMMA composite nanospheres with high magnetization

    Science.gov (United States)

    Lan, Fang; Liu, Ke-Xia; Jiang, Wen; Zeng, Xiao-Bo; Wu, Yao; Gu, Zhong-Wei

    2011-06-01

    Monodisperse superparamagnetic Fe3O4/polymethyl methacrylate (PMMA) composite nanospheres with high saturation magnetization were successfully prepared by a facile novel miniemulsion polymerization method. The ferrofluid, MMA monomer and surfactants were co-sonicated and emulsified to form stable miniemulsion for polymerization. The samples were characterized by DLS, TEM, FTIR, XRD, TGA and VSM. The diameter of the Fe3O4/PMMA composite nanospheres by DLS was close to 90 nm with corresponding polydispersity index (PDI) as small as 0.099, which indicated that the nanospheres have excellent homogeneity in aqueous medium. The TEM results implied that the Fe3O4/PMMA composite nanospheres had a perfect core-shell structure with about 3 nm thin PMMA shells, and the core was composed of many homogeneous and closely packed Fe3O4 nanoparticles. VSM and TGA showed that the Fe3O4/PMMA composite nanospheres with at least 65% high magnetite content were superparamagnetic, and the saturation magnetization was as high as around 39 emu g - 1 (total mass), which was only decreased by 17% compared with the initial bare Fe3O4 nanoparticles.

  20. Monodisperse sodium oleate coated magnetite high susceptibility nanoparticles for hyperthermia applications

    Science.gov (United States)

    Araújo-Neto, R. P.; Silva-Freitas, E. L.; Carvalho, J. F.; Pontes, T. R. F.; Silva, K. L.; Damasceno, I. H. M.; Egito, E. S. T.; Dantas, Ana L.; Morales, Marco A.; Carriço, Artur S.

    2014-09-01

    We report a simple and low cost methodology to synthesize sodium oleate coated magnetite nanoparticles for hyperthermia applications. The system consists of oleate coated magnetite nanoparticles with large susceptibility (1065 emu/gT), induced by the dipolar inter-particle interaction, with a magnetic core diameter in the 6 nm-12 nm size range. In aqueous medium, the nanoparticles agglomerate to form a monodisperse system, exhibiting a mean hydrodynamic diameter of 60.6 nm±4.1 nm, with a low average polydispersity index of 0.128±0.003, as required for intravenous applications. The system exhibits promising efficiency for magnetic hyperthermia, with a specific absorption rate of 14 W/g at a low field amplitude of 15.9 kA/m and frequency of 62 kHz. In a 50 mg/mL density in 1 mL, the temperature rises to 42.5 °C in 1.9 min.

  1. Monodisperse porous silicon spheres as anode materials for lithium ion batteries.

    Science.gov (United States)

    Wang, Wei; Favors, Zachary; Ionescu, Robert; Ye, Rachel; Bay, Hamed Hosseini; Ozkan, Mihrimah; Ozkan, Cengiz S

    2015-03-05

    Highly monodisperse porous silicon nanospheres (MPSSs) are synthesized via a simple and scalable hydrolysis process with subsequent surface-protected magnesiothermic reduction. The spherical nature of the MPSSs allows for a homogenous stress-strain distribution within the structure during lithiation and delithiation, which dramatically improves the electrochemical stability. To fully extract the real performance of the MPSSs, carbon nanotubes (CNTs) were added to enhance the electronic conductivity within the composite electrode structure, which has been verified to be an effective way to improve the rate and cycling performance of anodes based on nano-Si. The Li-ion battery (LIB) anodes based on MPSSs demonstrate a high reversible capacity of 3105 mAh g(-1). In particular, reversible Li storage capacities above 1500 mAh g(-1) were maintained after 500 cycles at a high rate of C/2. We believe this innovative approach for synthesizing porous Si-based LIB anode materials by using surface-protected magnesiothermic reduction can be readily applied to other types of SiOx nano/microstructures.

  2. Prediction of permeability of monodisperse granular materials with a micromechanics approach

    Science.gov (United States)

    Yang, Rongwei; Lemarchand, Eric; Fen-Chong, Teddy; Li, Kefei

    2016-04-01

    Prediction of the permeability of porous media is of vital importance to such fields as petroleum engineering, agricultural engineering and civil engineering. The liquid water within unsaturated granular materials is distinguished as the intergranular layer, the wetting layer and the water film. By means of the micromechanics approach, a physical conceptual model is developed to predict the permeability (intrinsic and relative permeabilities) of the monodisperse granular materials. The proposed model has been validated by comparing the available experimental data and the empirical models, and has been used to re-interpret the Kozeny-Carman's relation in particular. The results obtained with this model show that the intergranular water will dominate the flow transport when the saturation degree is higher than the residual saturation degree; when the saturation degree is below the residual saturation degree, the wetting layer will govern the flow transport and the relative permeability will decrease by 3 to 8 orders of magnitude depending on the connectivity of the wetting layer.

  3. Preparation and characterization of monodispersed PS/Ag composite microspheres through modified electroless plating

    Energy Technology Data Exchange (ETDEWEB)

    Ma Yuehui [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China); Zhang Qinghua, E-mail: qhzhang@dhu.edu.cn [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China)

    2012-07-15

    A modified electroless silver-plating process has been devised for the preparation of monodispersed, polystyrene/silver (PS/Ag) composite microspheres with tunable shell thickness. Tailoring was achieved by altering the concentration of the silver precursor in the plating bath. PS/Ag composite microspheres were characterized by field-emission scanning electron microscopy, ultraviolet-visible absorption, X-ray diffraction and thermogravimetric analysis. The results showed that a dense, stable and uniform silver nanoshell was formed on the surface of PS microspheres in the presence of poly(vinylpyrrolidone) and glucose. The bulk conductivity of the PS/Ag composites increased from 1.16 S/m to 3.57 Multiplication-Sign 10{sup 4} S/m, corresponding to a shell thickness of 35-198 nm. The PS/Ag composite microspheres with diameters of ca. 3 {mu}m might have great potential to be used as fillers in anisotropic conductive films because of the uniform diameter, low density and good conductivity of the microspheres.

  4. Controllable synthesis of gold nanoparticles with ultrasmall size and high monodispersity via continuous supplement of precursor.

    Science.gov (United States)

    Li, Yuanyuan; Liu, Shoujie; Yao, Tao; Sun, Zhihu; Jiang, Zheng; Huang, Yuying; Cheng, Hao; Huang, Yuanyuan; Jiang, Yong; Xie, Zhi; Pan, Guoqiang; Yan, Wensheng; Wei, Shiqiang

    2012-10-14

    Synthesis of monodisperse small Au nanoparticles in a controllable manner is of great importance for fundamental science and technical applications. Here, we report a "precursor continuous-supply" strategy for controllable synthesis of 0.9-3.3 nm Au nanoparticles with a narrow size distribution of 0.1-0.2 nm, using a weak reductant to slow-down the reducing rate of AuClPPh(3) precursor in ethanol. Time-dependent X-ray absorption and UV-Vis absorption measurements revealed that owing to the joint use of AuClPPh(3) and ethanol, the remnant AuClPPh(3) was self-supplied and the precursor concentration was maintained at a level near to its equilibrium solubility (ca. 1.65 mmol L(-1)) in ethanol. Hence the nucleation duration was extended that focused the initial size distribution of the Au clusters. With reaction going on for 58 min, most of AuClPPh(3) with a nominal Au concentration of 17.86 mmol L(-1) was converted to ethanol-soluble Au clusters with a size of about 1.0 nm, resulting in a high-yield synthesis.

  5. Bulk synthesis of monodisperse magnetic FeNi3 nanopowders by flow levitation method.

    Science.gov (United States)

    Chen, Shanjun; Chen, Yan; Kang, Xiaoli; Li, Song; Tian, Yonghong; Wu, Weidong; Tang, Yongjian

    2013-10-01

    In this work, a novel bulk synthesis method for monodisperse FeNi3 nanoparticles was developed by flow levitation method (FL). The Fe and Ni vapours ascending from the high temperature levitated droplet was condensed by cryogenic Ar gas under atmospheric pressure. X-ray diffraction was used to identify and characterize the crystal phase of prepared powders exhibiting a FeNi3 phase. The morphology and size of nanopowders were observed by transmission electron microscopy (TEM). The chemical composition of the nanoparticles was determined with energy dispersive spectrometer (EDS). The results indicated that the FeNi3 permalloy powders are nearly spherical-shaped with diameter about 50-200 nm. Measurement of the magnetic property of nanopowders by a superconducting quantum interference device (SQUID, Quantum Design MPMS-7) showed a symmetric hysteresis loop of ferromagnetic behavior with coercivity of 220 Oe and saturation magnetization of 107.17 emu/g, at 293 K. At 5 K, the obtained saturation magnetization of the sample was 102.16 emu/g. The production rate of FeNi3 nanoparticles was estimated to be about 6 g/h. This method has great potential in mass production of FeNi3 nannoparticles.

  6. Mono-dispersed cross-linked polystyrene micro-spheres prepared by seed swelling polymerization method

    Institute of Scientific and Technical Information of China (English)

    Dongsha WANG; Yanjun LIU

    2008-01-01

    A two-step swelling procedure was adopted to synthesize mono-dispersed and highly cross-linked poly (St-divinylbenzene) particles with PSt micro-spheres (1.80 μmin diameter). The PSt micro-spheres were prepared by a dispersion polymerization method and used as seeds. The effects of monomer concentration, ratio of ethanol to water, swelling reagents, crosslinking reagents, swelling temper-ature and agitation speed on particle size were investigated in detail. The morphologies and size distributions of these micro-spheres were examined by SEM and particle size analysis (PSA). The Tg of the micro-spheres was measured by DSC. The results indicate that the particles (6.20 μm in diameter) exhibit excellent mono dispersed property and high crosslinking degree when the concentration of the swelling reagent was 25%, the concentration of the cross-linking reagents was 23%, the swelling temperature was 30℃ and the stirring speed was 150 r/min.

  7. Synthesis of Monodisperse Nanocrystals via Microreaction: Open-to-Air Synthesis with Oleylamine as a Coligand

    Directory of Open Access Journals (Sweden)

    Yang Hongwei

    2009-01-01

    Full Text Available Abstract Microreaction provides a controllable tool to synthesize CdSe nanocrystals (NCs in an accelerated fashion. However, the surface traps created during the fast growth usually result in low photoluminescence (PL efficiency for the formed products. Herein, the reproducible synthesis of highly luminescent CdSe NCs directly in open air was reported, with a microreactor as the controllable reaction tool. Spectra investigation elucidated that applying OLA both in Se and Cd stock solutions could advantageously promote the diffusion between the two precursors, resulting in narrow full-width-at-half maximum (FWHM of PL (26 nm. Meanwhile, the addition of OLA in the source solution was demonstrated helpful to improve the reactivity of Cd monomer. In this case, the focus of size distribution was accomplished during the early reaction stage. Furthermore, if the volume percentage (vol.% of OLA in the precursors exceeded a threshold of 37.5%, the resulted CdSe NCs demonstrated long-term fixing of size distribution up to 300 s. The observed phenomena facilitated the preparation of a size series of monodisperse CdSe NCs merely by the variation of residence time. With the volume percentage of OLA as 37.5% in the source solution, a 78 nm tuning of PL spectra (from 507 to 585 was obtained through the variation of residence time from 2 s to 160 s, while maintaining narrow FMWH of PL (26–31 nm and high QY of PL (35–55%.

  8. Efficient one-pot synthesis of monodisperse alkyl-terminated colloidal germanium nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Carolan, Darragh, E-mail: darragh.carolan@tyndall.ie; Doyle, Hugh, E-mail: hugh.doyle@tyndall.ie [University College Cork, Tyndall National Institute (Ireland)

    2014-12-15

    An efficient one-pot method for fabricating alkyl-capped germanium nanocrystals (Ge NCs) is reported. Ge NCs with a size of 3.9 ± 0.5 nm, are formed by co-reduction of germanium tetrachloride in the presence of n-butyltrichlorogermane, producing NCs with butyl-terminated surfaces. The advantage of this method is that it allows rapid synthesis and functionalisation of NCs with minimal post-synthetic purification requirements. TEM imaging showed that the Ge NCs are monodisperse and highly crystalline, while EDX and SAED confirmed the chemical identity and crystal phase of the NCs. FTIR and XPS confirmed that the Ge NCs were well passivated, with some oxidation of the nanocrystal surface. Optical spectroscopy of the NCs showed a strong absorbance in the UV region and an excitation wavelength dependent photoluminescence in the UV/violet. Time resolved photoluminescence measurements showed the presence of two nanosecond lifetime components, consistent with recombination of photogenerated excitons at low lying energy states present at the nanocrystal surface. Photoluminescence quantum yields were determined to be 37 %, one of the highest values reported for organically terminated Ge NCs.

  9. Monodispersed magnetite nanoparticles optimized for magnetic fluid hyperthermia: Implications in biological systems

    Science.gov (United States)

    Khandhar, Amit P.; Ferguson, R. Matthew; Krishnan, Kannan M.

    2011-04-01

    Magnetite (Fe3O4) nanoparticles (MNPs) are suitable materials for Magnetic Fluid Hyperthermia (MFH), provided their size is carefully tailored to the applied alternating magnetic field (AMF) frequency. Since aqueous synthesis routes produce polydisperse MNPs that are not tailored for any specific AMF frequency, we have developed a comprehensive protocol for synthesizing highly monodispersed MNPs in organic solvents, specifically tailored for our field conditions (f = 376 kHz, H0 = 13.4 kA/m) and subsequently transferred them to water using a biocompatible amphiphilic polymer. These MNPs (σavg. = 0.175) show truly size-dependent heating rates, indicated by a sharp peak in the specific loss power (SLP, W/g Fe3O4) for 16 nm (diameter) particles. For broader size distributions (σavg. = 0.266), we observe a 30% drop in overall SLP. Furthermore, heating measurements in biological medium [Dulbecco's modified Eagle medium (DMEM) + 10% fetal bovine serum] show a significant drop for SLP (˜30% reduction in 16 nm MNPs). Dynamic Light Scattering (DLS) measurements show particle hydrodynamic size increases over time once dispersed in DMEM, indicating particle agglomeration. Since the effective magnetic relaxation time of MNPs is determined by fractional contribution of the Neel (independent of hydrodynamic size) and Brownian (dependent on hydrodynamic size) components, we conclude that agglomeration in biological medium modifies the Brownian contribution and thus the net heating capacity of MNPs.

  10. Tribological characteristics of monodispersed cerium borate nanospheres in biodegradable rapeseed oil lubricant

    Science.gov (United States)

    Boshui, Chen; Kecheng, Gu; Jianhua, Fang; Jiang, Wu; Jiu, Wang; Nan, Zhang

    2015-10-01

    Stearic acid-capped cerium borate composite nanoparticles, abbreviated as SA/CeBO3, were prepared by hydrothermal method. The morphologies, element compositions, size distributions, crystal and chemical structures, hydrophobic characteristics, of SA/CeBO3 were characterized by scanning electron microscope, energy dispersive X-ray spectrometer, dynamic laser particle size analyzer, X-ray diffraction, and Fourier transform infrared spectrometer, respectively. The friction and wear performances of SA/CeBO3 as a lubricating additive in a rapeseed oil were evaluated on a four-ball tribo-tester. The tribochemical characteristics of the worn surfaces were investigated by X-ray photoelectron spectroscopy. The results showed that the hydrophobic SA/CeBO3 were monodispersed nanospheres with an average diameter of 8 nm, and exhibited excellent dispersing stability in rapeseed oil. Meanwhile, SA/CeBO3 nanospheres were outstanding in enhancing friction-reducing and anti-wear capacities of rapeseed oil. The prominent tribological performances of SA/CeBO3 in rapeseed oil were attributed to the formation of a composite boundary lubrication film mainly composed of lubricous tribochemical species of B2O3, CeO2 and Fe2O3, and the adsorbates of SA/CeBO3 and rapeseed oil, on the tribo-surfaces.

  11. Synthetic Polymers at Interfaces: Monodisperse Emulsions Multiple Emulsions and Liquid Marbles

    Science.gov (United States)

    Sun, Guanqing

    The adsorption of polymeric materials at interfaces is an energetically favorable process which is investigated in much diversified fields, such as emulsions, bubbles, foams, liquid marbles. Pickering emulsion, which is emulsion stabilized by solid particles has been investigated for over one century and preparation of Pickering emulsion with narrow size distribution is crucial for both the theoretical study of the stabilization mechanism and practical application, such as templated fabrication of colloidosomes. The precise control over the size and functionality of polymer latices allows the preparation of monodisperse Pickering emulsions with desired sizes through SPG membrane emulsification at rather rapid rate compared to microfludic production. Double or multiple emulsions have long been investigated but its rapid destabilization has always been a major obstacle in applying them into practical applications. The modern living polymerization techniques allow us to prepare polymers with designed structure of block copolymers which makes it possible to prepare ultra-stable multiple emulsions. The precise tuning of the ratio of hydrophobic part over the hydrophilic can unveil the stabilization mechanism. Liquid marble is a new type of materials of which liquid droplets are coated by dry particles. The coating of an outer layer of dry particles renders the liquid droplets non-sticky at solid surface which is useful in transportation of small amount of liquid without leakage at extreme low friction force. The property of liquid marbles relies largely on the stabilizers and the drying condition of polymeric latices is shown to have great influence on the property of liquid marbles. Firstly, an introduction to the interfacial and colloidal science with special attention to topics on emulsions, multiple emulsion and liquid marbles is given in Chapter 1. The unique features of an interface and a discussion on the definition of colloids are introduced prior to the

  12. HIGH IMMOBILIZATION OF ANTIBACTERIAL MOIETIES ONTO MONODISPERSE MICROSPHERES BY DISPERSION POLYMERIZATION USING BICATIONIC VIOLOGEN SURFMER

    Institute of Scientific and Technical Information of China (English)

    Sheng-liu Wang; Xiao-fang Yang; Lian-ying Liu; Wan-tai Yang

    2012-01-01

    In order to achieve monodisperse particles with high content of antibacterial groups covalently bonded on surface,a bicationic viologen,N-hexyl-N'-(4-vinylbenzyl)-4,4'-bipyridinium bromide chloride (HVV) was devised as a surfmer in dispersion polymerization of styrene (St) using a mixture of methanol (or ethylene glycol) and water as media.Effects of content of HVV,its addition profile and composition of reaction media on particles size and incorporation of HVV moieties were mainly investigated.The attachment of silver and gold nanoparticles on particle surface under UV irradiation ascertained the surface-bonded HVV segments.SEM,TEM observations and XPS,zata potential measurements indicated that increase of initial HVV contents and addition of HVV (when polymerization had been performed for 3 h) led to grown particles and enhanced immobilization of HVV moieties.Using a mixture of ethylene glycol and water as reaction media,small particles (520-142 nm) with highly attached HVV moieties were prepared.Furthermore,antibacterial efficacy of the resultant particles against S.aureus was assayed,and particles with more HVV moieties anchored on surface demonstrated greater efficiency of antibacterial activity.

  13. Global stability of stretched jets: conditions for the generation of monodisperse micro-emulsions using coflows

    CERN Document Server

    Gordillo, José Manuel; Campo-Cortés, Francisco

    2014-01-01

    In this paper we reveal the physics underlying the conditions needed for the generation of emulsions composed of uniformly sized drops of micrometric or submicrometric diameters when two immiscible streams flow in parallel under the so-called tip streaming regime after Suryo & Basaran (2006). Indeed, when inertial effects in both liquid streams are negligible, the inner to outer flow-rate and viscosity ratios are small enough and the capillary number is above an experimentally determined threshold which is predicted by our theoretical results with small relative errors, a steady micron-sized jet is issued from the apex of a conical drop. Under these conditions, the jet disintegrates into drops with a very well defined mean diameter, giving rise to a monodisperse micro-emulsion. Here, we demonstrate that the regime in which uniformly-sized drops are produced corresponds to values of the capillary number for which the cone-jet system is globally stable. Interestingly enough, our general stability theory rev...

  14. Size-Controlled and Optical Properties of Monodispersed Silver Nanoparticles Synthesized by the Radiolytic Reduction Method

    Directory of Open Access Journals (Sweden)

    Kazem Naghavi

    2013-04-01

    Full Text Available Size-controlled and monodispersed silver nanoparticles were synthesized from an aqueous solution containing silver nitrate as a metal precursor, polyvinyl alcohol as a capping agent, isopropyl alcohol as hydrogen and hydroxyl radical scavengers, and deionized water as a solvent with a simple radiolytic method. The average particle size decreased with an increase in dose due to the domination of nucleation over ion association in the formation of the nanoparticles by gamma reduction. The silver nanoparticles exhibit a very sharp and strong absorption spectrum with the absorption maximum λmax blue shifting with an increased dose, owing to a decrease in particle size. The absorption spectra of silver nanoparticles of various particle sizes were also calculated using a quantum physics treatment and an agreement was obtained with the experimental absorption data. The results suggest that the absorption spectrum of silver nanoparticles possibly derived from the intra-band excitations of conduction electrons from the lowest energy state (n = 5, l = 0 to higher energy states (n ≥ 6; Δl = 0, ±1; Δs = 0, ±1, allowed by the quantum numbers principle. This demonstrates that the absorption phenomenon of metal nanoparticles based on a quantum physics description could be exploited to be added into the fundamentals of metal nanoparticles and the related fields of nanoscience and nanotechnology.

  15. A new method for preparing mono-dispersed nanoparticles using magnetized water

    Science.gov (United States)

    Nakhaei Pour, Ali; Gholizadeh, Mostafa; Housaindokht, Mohammadreza; Moosavi, Fatemeh; Monhemi, Hasan

    2017-04-01

    We studied the use of magnetized water on the size of the nanoparticles. Magnetized water found to reduce the diameter of the nanoparticles during a homogeneous precipitation process, which is a combination of nucleation and nuclei growth processes. We found that the modified water, which demonstrated different physical properties especially on the surface tension and viscosity, significantly influenced the both processes. Therefore, the nucleation process was initially prolonged in the homogeneous precipitation process due to the lower critical size of nucleus and higher rate of nucleation, and consequently formed smaller particles and a larger number of particles. Furthermore, the growth rate of nanoparticles was hindered owing to the higher viscosity of the water and restriction in the mass transport process. As a result, the precipitated particles with the magnetized water were eventually structured smaller particle diameter compared to the bulk. The presented method in here indicated a low cost, straightforward, and feasible technique for industrial application. In addition, this method could open a new promising perspective on nanomaterial synthesis in order to facilitate the production of monodispersed nanoparticles. Molecular dynamic confirmed that surface tension decreased as the external magnetic field was applied. Moreover, the density profile illustrated that the average number of hydrogen atoms is greater than oxygen atoms.

  16. Synthesis of highly monodisperse Ge crystals in a capacitively coupled flow through reactor for photovoltaic applications

    Science.gov (United States)

    Gresback, Ryan; Kortshagen, Uwe

    2006-10-01

    Germanium nanocrystals are interesting candidates for quantum dot-based solar cells. While the band gap of bulk Ge is ˜0.7 eV, the energy gap can be increased due to quantum confinement to ˜ 2eV for Ge particles of ˜3 nm in size. With a single material, Ge nanocrystals of sizes from 3 -15 nm would thus allow to span the entire range of band gaps that is of interest for photovoltaic devices. Moreover, compared to many other quantum dot materials that are currently studied for photovoltaic applications, Ge is perceived as non-toxic and environmentally benign. Ge nanocrystals are synthesized in a tubular, capacitively coupled flow through reactor. Germanium tetrachloride is used as a precursor. It is introduced into the plasma by a flow of argon and hydrogen. At typical pressures of 2 Torr and 40 W of RF power at 13.56 MHz, Ge crystals are generated and reside in the plasma for several tens of milliseconds. The size of the nanocrystals can be controlled in a range from 3-20 nm through the residence time. Particles are highly monodisperse. Organically passivated Ge nanocrystals self-assemble into monolayers when cast from colloidal solutions.

  17. Shape-controlled synthesis of highly monodisperse and small size gold nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We describe here that fine control of nanoparticle shape and size can be achieved by systematic varia-tion of experimental parameters in the seeded growth procedure in aqueous solution. Cubic and spherical gold nanoparticles are obtained respectively. In particularly, the Au cubes are highly mono-disperse in 33±2 nm diameter. The experimental methods involve the preparation of Au seed particles and the subsequent addition of an appropriate quantity of Au seed solution to the aqueous growth solutions containing desired quantities of CTAB and ascorbic acid (AA). Here, AA is a weak reducing agent and CTAB is not only a stable agent for nanoparticles but also an inductive agent for leading increase in the face of nanoparticle. Ultraviolet visible spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM) are used to characterize the nanoparticles. The results show that the different size gold nanoparticles displayed high size homogenous distribution and formed mono-membrane at the air/solid interface.

  18. Electrohydrodynamic Generation and Delivery of Monodisperse Pico-Liter Droplets Using PDMS Microchip

    Science.gov (United States)

    Kim, Sung Jae; Song, Yong-Ak; Skipper, Paul L.; Han, Jongyoon

    2008-01-01

    We developed a drop-on-demand microdroplet generator for the discrete dispensing of biosamples into a bio-analytical unit. This disposable PDMS microfluidic device can generate monodisperse droplets of pico-liter volume directly out of a plane sidewall of the microfluidic chip by an electrohydrodynamic mechanism. The droplet generation was accomplished without using either an inserted capillary or monolithically built-in tip. The minimum droplet volume was around 4 pico-liters, and the droplet generation was repeatable and stable for at least 30 minutes, with a typical variation of less than 2.0% of drop size. The Taylor cone, which is usually observed in electrospray, was suppressed by controlling the surface wetting property of the PDMS device as well as the surface tension of the sample liquids. A modification of the channel geometry right before the opening of the microchannel also enhanced the continuous droplet generation without applying any external pumping. A simple numerical simulation of the droplet generation verified the importance of controlling the surface wetting conditions for the droplet formation. Our microdroplet generator can be effectively applied to a direct interface of a microfluidic chip to a bio-sensing unit, such as AMS, MALDI-MS or protein microarray-type biochips. PMID:17134134

  19. Sedimentation of concentrated monodisperse colloidal suspensions: role of collective particle interaction forces.

    Science.gov (United States)

    Vesaratchanon, Jan S; Nikolov, Alex; Wasan, Darsh T

    2008-06-01

    The sedimentation velocities and concentration profiles of low-charge, monodisperse hydroxylate latex particle suspensions were investigated experimentally as a function of the particle concentration to study the effects of the collective particle interactions on suspension stability. We used the Kossel diffraction technique to measure the particle concentration profile and sedimentation rate. We conducted the sedimentation experiments using three different particle sizes. Collective hydrodynamic interactions dominate the particle-particle interactions at particle concentrations up to 6.5 vol%. However, at higher particle concentrations, additional collective particle-particle interactions resulting from the self-depletion attraction cause particle aggregation inside the suspension. The collective particle-particle interaction forces play a much more important role when relatively small particles (500 nm in diameter or less) are used. We developed a theoretical model based on the statistical particle dynamics simulation method to examine the role of the collective particle interactions in concentrated suspensions in the colloidal microstructure formation and sedimentation rates. The theoretical results agree with the experimentally-measured values of the settling velocities and concentration profiles.

  20. Preparation of monodisperse aqueous microspheres containing high concentration of l-ascorbic acid by microchannel emulsification.

    Science.gov (United States)

    Khalid, Nauman; Kobayashi, Isao; Neves, Marcos A; Uemura, Kunihiko; Nakajima, Mitsutoshi; Nabetani, Hiroshi

    2015-01-01

    Monodisperse aqueous microspheres containing high concentrations of l-ascorbic acid with different concentrations of sodium alginate (Na-ALG) and magnesium sulfate (MgSO4) were prepared by using microchannel emulsification (MCE). The continuous phase was water-saturated decane containing a 5% (w/w) hydrophobic emulsifier. The flow rate of the continuous phase was maintained at 10 mL h(-1), whereas the pressure applied to the disperse phase was varied between 3 and 25 kPa. The disperse phase optimized for successfully generating aqueous microspheres included 2% (w/w) Na-ALG and 1% (w/w) MgSO4. At a higher MgSO4 concentration, the generated microspheres resulted in coalescence and subsequent bursting. At a lower MgSO4 concentration, unstable and polydisperse microspheres were obtained. The aqueous microspheres generated from the MCs under optimized conditions had a mean particle diameter (dav) of 14-16 µm and a coefficient of variation (CV) of less than 8% at the disperse phase pressures of 5-15 kPa.

  1. Direct dry-grinding synthesis of monodisperse lipophilic CuS nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yajuan; Scott, Julie; Chen, Yi-Tzai; Guo, Liangran; Zhao, Mingyang; Wang, Xiaodong [Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, The University of Rhode Island, Kingston, RI 02881 (United States); Lu, Wei, E-mail: weilu@uri.edu [Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, The University of Rhode Island, Kingston, RI 02881 (United States); School of Pharmacy, Fudan University, Shanghai 201203 (China)

    2015-07-15

    Copper sulfide nanoparticles, effective absorbers of near-infrared light, are recently attracting broad interest as a photothermal coupling agent for cancer therapy. Lipophilic copper sulfide nanoparticles are preferred for high performance biomedical applications due to high tissue affinity. Synthesis of lipophilic copper sulfide nanoparticles requires complicated multi-step processes under severe conditions. Here, we describe a new synthetic process, developed by direct dry-grinding of copper(II) acetylacetonate with sulfur under ambient environment at low temperature. The formed CuS nanoparticles are of uniform size, ∼10 nm in diameter, and are monodispersed in chloroform. Each covellite CuS nanocrystal surface is modified with oleylamine through hydrogen bonding between sulfur atoms and amine groups of oleylamine. The nanoparticles demonstrate near-infrared light absorption for photothermal applications. The synthetic methodology described here is more convenient and less extreme than previous methods, and should thus greatly facilitate the preparation of photothermal lipophilic copper sulfide nanomaterials for cancer therapy. - Highlights: • We make lipophilic CuS nanoparticles by mechanical grinding method in large scale. • The reaction condition is studied to obtain high yield and uniform size. • The synthesis does not need nitrogen protection or high temperature. • Lipophilic CuS nanoparticles show significant near-infrared absorbance.

  2. Synthesis of single-walled carbon nanotube networks using monodisperse metallic nanocatalysts encapsulated in reverse micelles

    Directory of Open Access Journals (Sweden)

    Gayduchenko Igor A.

    2016-01-01

    Full Text Available We report on a method of synthesis of single-walled carbon nanotubes percolated networks on silicon dioxide substrates using monodisperse Co and Ni catalyst. The catalytic nanoparticles were obtained by modified method of reverse micelles of bis-(2-ethylhexyl sulfosuccinate sodium in isooctane solution that provides the nanoparticle size control in range of 1 to 5 nm. The metallic nanoparticles of Ni and Co were characterized using transmission electron microscopy (TEM and atomic-force microscopy (AFM. Carbon nanotubes were synthesized by chemical vapor deposition of CH4/H2 composition at temperature 1000 °С on catalysts pre-deposited on silicon dioxide substrate. Before temperature treatment during the carbon nanotube synthesis most of the catalyst material agglomerates due to magnetic forces while during the nanotube growth disintegrates into the separate nanoparticles with narrow diameter distribution. The formed nanotube networks were characterized using AFM, scanning electron microscopy (SEM and Raman spectroscopy. We find that the nanotubes are mainly single-walled carbon nanotubes with high structural perfection up to 200 μm long with diameters from 1.3 to 1.7 nm consistent with catalyst nanoparticles diameter distribution and independent of its material.

  3. Monodispersed bimetallic PdAg nanoparticles with twinned structures: formation and enhancement for the methanol oxidation.

    Science.gov (United States)

    Yin, Zhen; Zhang, Yining; Chen, Kai; Li, Jing; Li, Wenjing; Tang, Pei; Zhao, Huabo; Zhu, Qingjun; Bao, Xinhe; Ma, Ding

    2014-03-10

    Monodispersed bimetallic PdAg nanoparticles can be fabricated through the emulsion-assisted ethylene glycol (EG) ternary system. Different compositions of bimetallic PdAg nanoparticles, Pd₈₀Ag₂₀, Pd₆₅Ag₃₅ and Pd₄₆Ag₅₄ can be obtained via adjusting the reaction parameters. For the formation process of the bimetallic PdAg nanoparticles, there have two-stage growth processes: firstly, nucleation and growth of the primary nanoclusters; secondly, formation of the secondary nanoparticles with the size-selection and relax process via the coalescence or aggregation of the primary nanoclusters. The as-prepared PdAg can be supported on the carbon black without any post-treatment, which exhibited high electro-oxidation activity towards methanol oxidation under alkaline media. More importantly, carbon-supported Pd₈₀Ag₂₀ nanoparticles reveal distinctly superior activities for the methanol oxidation, even if compared with commercial Pt/C electro-catalyst. It is concluded that the enhanced activity is dependant on the unique twinning structure with heterogeneous phase due to the dominating coalescence growth in EG ternary system.

  4. A new and facile method for measurement of apparent density of monodisperse polymer beads.

    Science.gov (United States)

    Zhang, Qi; Srinivasan, Balasubramanian; Li, Yuanpeng; Jing, Ying; Xing, Chengguo; Chang, Jin; Wang, Jian-Ping

    2010-03-15

    The apparent density, an intrinsic physical property of polymer beads, plays an important role in the application of beads in micro-total analysis systems and separation. Here we have developed a new, facile and milligram-scale method to describe the motion of beads in aqueous solution and further detect the apparent density of beads. The motion of beads in solutions is determined by the viscosity of solutions and the density difference between beads and solutions. In this study, using various glycerol aqueous solutions with certain viscosities and densities, the motion time (i.e. floating or sedimentation time) of hybrid polymer beads was experimentally measured and theoretically deduced, and consequently, the apparent density of monodisperse beads can be quickly and easily calculated. The results indicated that the present method provided a more precise way to predict the movement of hybrid beads in aqueous solution compared with the approach for commercial use. This new method can be potentially employed in flow cytometry, suspension stability, and particle analysis systems.

  5. Effect of colloidal particle size on adsorbed monodisperse and bidisperse monolayers.

    Science.gov (United States)

    Rosenberg, Rachel T; Dan, Nily

    2011-07-19

    Coating hydrogel films or microspheres by an adsorbed colloidal shell is one synthesis method for forming colloidosomes. The colloidal shell allows control of the release rate of encapsulated materials, as well as selective transport. Previous studies found that the packing density of self-assembled, adsorbed colloidal monolayers is independent of the colloidal particle size. In this paper we develop an equilibrium model that correlates the packing density of charged colloidal particles in an adsorbed shell to the particle dimensions in monodisperse and bidisperse systems. In systems where the molar concentration in solution is fixed, the increase in adsorption energy with increasing particle size leads to a monotonic increase in the monolayer packing density with particle radius. However, in systems where the mass fraction of the particles in the adsorbing solutions is fixed, increasing particle size also reduces the molar concentration of particles in solution, thereby reducing the probability of adsorption. The result is a nonmonotonic dependence of the packing density in the adsorbed layer on the particle radius. In bidisperse monolayers composed of two particle sizes, the packing density in the layer increases significantly with size asymmetry. These results may be utilized to design the properties of colloidal shells and coatings to achieve specific properties such as transport rate and selectivity.

  6. Monodisperse lignin fractions as standards in size-exclusion analysis: comparison with polystyrene standards.

    Science.gov (United States)

    Botaro, Vagner Roberto; Curvelo, Antonio Aprígio da Silva

    2009-05-01

    The difficulty of preparing monodisperse lignin fractions on a large scale is a limiting factor in many applications. The present paper addresses this problem by examining the properties and size-exclusion behavior of lignin isolated by the acetosolv pulping process from post-extraction crushed sugarcane bagasse. The isolated lignin was subjected to a solvent pretreatment, followed by preparative gel permeation chromatography fractionation. The fractions were analyzed by high-performance size-exclusion chromatography (HPSEC) and these samples showed a great decrease in polydispersity, compared to the original acetosolv lignin. Several fractions of very low polydispersity, close to unity, were employed as calibration curve standards in HPSEC analysis. This original analytical approach allowed calibration with these lignin fractions to be compared with the polystyrene standards that are universally employed for lignin molecular mass determination. This led to a noteworthy result, namely that the lignin fractions and polystyrene standards showed very similar behavior over a large range of molecular masses in a typical HPSEC analysis of acetosolv lignin.

  7. Magnetic Behaviour and Heating Effect of Fe3O4 Ferrofluids Composed of Monodisperse Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    ZHANG Li-Ying; DOU Yong-Hua; ZHANG Ling; GU Hong-Chen

    2007-01-01

    Fe3O4 ferrofluids containing monodisperse Fe3O4 nanoparticles with different diameters of 8, 12, 16 and 18 nm are prepared by using high-temperature solution phase reaction. The particles have single crystal structures with narrow size distributions. At room temperature, the 8-nm ferrofluid shows superparamagnetic behaviour,whereas the others display hysteresis properties and the coercivity increases with the increasing particle size.The spin glass-like behaviour and cusps near 190K are observed on all ferrofluids according to the temperature variation of field-cooled (FC) and zero-field-cooled (ZFC) magnetization measurements. The cusps are found to be associated with the freezing point of the solvent. As a comparison, the ferrofluids are dried and the FC and ZFC magnetization curves of powdery samples are also investigated. It is found that the blocking temperatures for the powdery samples are higher than those for their corresponding ferrofluids. Moreover, the size dependent heating effect of the ferrofluids is also investigated in ac magnetic field with a frequency of 55 kHz and amplitude of 200 Oe.

  8. Structural and optical properties of solvothermal synthesized nearly monodispersed CdSe nanocrystals

    Science.gov (United States)

    Shahi, A. K.; Pandey, B. K.; Singh, B. P.; Gopal, R.

    2016-09-01

    Water soluble nearly monodisperse CdSe nanocrystals have been successfully synthesized via aqueous phase solvothermal route in non ionic surfactant glycolic acid ethoxylate 4-non phenyl ether (GAEPE). X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) are used to determine the phase, structural parameters such as lattice constants, strain, x-ray density and specific surface area, morphology, shape and size distribution, respectively, whereas optical properties are studied by UV-visible absorption and photoluminescence (PL) spectroscopy. All the diffraction peaks of XRD pattern indexed to wurtzite phase of hexagonal system of CdSe and crystallite sizes estimated to be 13-29 nm along some stronger and narrower peaks which is also consistent with TEM measurement while crystallinity and defects have been analyzed with selective area electron diffraction (SAED) pattern. Optical absorption spectrum shows that the as prepared sample exhibits primary and secondary absorption band centered at 2.15 eV and 1.82 eV, respectively, which is blue shifted as compared to bulk value (1.74 eV) of band gap due to quantum confinement effect. Photoluminescence spectrum shows sharp excitonic emission band centered at 583 nm which is nearer to primary band gap energy.

  9. Preparation and Evaluation of Monodisperse Nonionic Surfactants Based on Fluorine-Containing Dicarbamates.

    Science.gov (United States)

    Mureau; Trabelsi; Guittard; Geribaldi

    2000-09-15

    Novel bipodal surfactants of fluorine-containing carbamate type were synthesized with satisfactory yields from the action of fluorinated diisocyanates on oligooxyethylmonomethylated ethers without solvent. The synthetic pathways via malonic intermediates were elaborated in order to use low-price commercially available compounds such as 2-F-alkylethyl iodides and oligooxyethylmonomethylated ethers as starting materials. This new class of nonionic surfactants contains one hydrophobic part and one oleophobic part, and shows peculiar properties due to the presence of two hydrophilic parts (bipodal). All these compounds are monodisperse, i.e, include a perfectly defined number of oxyethylene units. Compared with their bipodal homologues previously described within the F-alkylated series, these new structures were easily obtained from commercial raw materials and are stable against pH media. The evaluation of their behavior at the air-water interface has been studied by measurements of surface tension versus concentration. This allows us to show clearly the variation of the critical micelle concentration (cmc) from 1.1x10(-5) to 9.8x10(-3) mol.l(-1), and of the surface area per surfactant molecule versus studied structures. The dicarbamates of oligooxyethylmonomethylether of 3-(F-alkyl)propyl so realized exhibit noteworthy properties as nonionic fluorinated surfactants. Copyright 2000 Academic Press.

  10. Monodisperse Dual-Functional Upconversion Nanoparticles Enabled Near-Infrared Organolead Halide Perovskite Solar Cells.

    Science.gov (United States)

    He, Ming; Pang, Xinchang; Liu, Xueqin; Jiang, Beibei; He, Yanjie; Snaith, Henry; Lin, Zhiqun

    2016-03-18

    Extending the spectral absorption of organolead halide perovskite solar cells from visible into near-infrared (NIR) range renders the minimization of non-absorption loss of solar photons with improved energy alignment. Herein, we report on, for the first time, a viable strategy of capitalizing on judiciously synthesized monodisperse NaYF4 :Yb/Er upconversion nanoparticles (UCNPs) as the mesoporous electrode for CH3 NH3 PbI3 perovskite solar cells and more importantly confer perovskite solar cells to be operative under NIR light. Uniform NaYF4 :Yb/Er UCNPs are first crafted by employing rationally designed double hydrophilic star-like poly(acrylic acid)-block-poly(ethylene oxide) (PAA-b-PEO) diblock copolymer as nanoreactor, imparting the solubility of UCNPs and the tunability of film porosity during the manufacturing process. The subsequent incorporation of NaYF4 :Yb/Er UCNPs as the mesoporous electrode led to a high efficiency of 17.8 %, which was further increased to 18.1 % upon NIR irradiation. The in situ integration of upconversion materials as functional components of perovskite solar cells offers the expanded flexibility for engineering the device architecture and broadening the solar spectral use.

  11. Magnetically Triggered Monodispersed Nanocomposite Fabricated by Microfluidic Approach for Drug Delivery

    KAUST Repository

    Yassine, Omar

    2016-01-01

    Responsive microgel poly(N-isopropylacrylamide) or PNIPAM is a gel that can swell or shrink in response to external stimuli (temperature, pH, etc.). In this work, a nanocomposite gel is developed consisting of PNIPAM and magnetic iron oxide nanobeads for controlled release of liquids (like drugs) upon exposure to an alternating magnetic field. Microparticles of the nanocomposite are fabricated efficiently with a monodisperse size distribution and a diameter ranging from 20 to 500  µ m at a rate of up to 1 kHz using a simple and inexpensive microfluidic system. The nanocomposite is heated through magnetic losses, which is exploited for a remotely stimulated liquid release. The efficiency of the microparticles for controlled drug release applications is tested with a solution of Rhodamine B as a liquid drug model. In continuous and pulsatile mode, a release of 7% and 80% was achieved, respectively. Compared to external thermal actuation that heats the entire surrounding or embedded heaters that need complex fabrication steps, the magnetic actuation provides localized heating and is easy to implement with our microfluidic fabrication method.

  12. Precisely Size-Tunable Monodisperse Hairy Plasmonic Nanoparticles via Amphiphilic Star-Like Block Copolymers.

    Science.gov (United States)

    Chen, Yihuang; Yoon, Young Jun; Pang, Xinchang; He, Yanjie; Jung, Jaehan; Feng, Chaowei; Zhang, Guangzhao; Lin, Zhiqun

    2016-12-01

    In situ precision synthesis of monodisperse hairy plasmonic nanoparticles with tailored dimensions and compositions by capitalizing on amphiphilic star-like diblock copolymers as nanoreactors are reported. Such hairy plasmonic nanoparticles comprise uniform noble metal nanoparticles intimately and perpetually capped by hydrophobic polymer chains (i.e., "hairs") with even length. Interestingly, amphiphilic star-like diblock copolymer nanoreactors retain the spherical shape under reaction conditions, and the diameter of the resulting plasmonic nanoparticles and the thickness of polymer chains situated on the surface of the nanoparticle can be readily and precisely tailored. These hairy nanoparticles can be regarded as hard/soft core/shell nanoparticles. Notably, the polymer "hairs" are directly and permanently tethered to the noble metal nanoparticle surface, thereby preventing the aggregation of nanoparticles and rendering their dissolution in nonpolar solvents and the homogeneous distribution in polymer matrices with long-term stability. This amphiphilic star-like block copolymer nanoreactor-based strategy is viable and robust and conceptually enables the design and synthesis of a rich variety of hairy functional nanoparticles with new horizons for fundamental research on self-assembly and technological applications in plasmonics, catalysis, energy conversion and storage, bioimaging, and biosensors.

  13. Magnetically Triggered Monodispersed Nanocomposite Fabricated by Microfluidic Approach for Drug Delivery

    Directory of Open Access Journals (Sweden)

    O. Yassine

    2016-01-01

    Full Text Available Responsive microgel poly(N-isopropylacrylamide or PNIPAM is a gel that can swell or shrink in response to external stimuli (temperature, pH, etc.. In this work, a nanocomposite gel is developed consisting of PNIPAM and magnetic iron oxide nanobeads for controlled release of liquids (like drugs upon exposure to an alternating magnetic field. Microparticles of the nanocomposite are fabricated efficiently with a monodisperse size distribution and a diameter ranging from 20 to 500 µm at a rate of up to 1 kHz using a simple and inexpensive microfluidic system. The nanocomposite is heated through magnetic losses, which is exploited for a remotely stimulated liquid release. The efficiency of the microparticles for controlled drug release applications is tested with a solution of Rhodamine B as a liquid drug model. In continuous and pulsatile mode, a release of 7% and 80% was achieved, respectively. Compared to external thermal actuation that heats the entire surrounding or embedded heaters that need complex fabrication steps, the magnetic actuation provides localized heating and is easy to implement with our microfluidic fabrication method.

  14. Large-scale, low-cost synthesis of monodispersed gold nanorods using a gemini surfactant

    Science.gov (United States)

    Xu, Yong; Zhao, Yang; Chen, Lei; Wang, Xuchun; Sun, Jianxia; Wu, Haihua; Bao, Feng; Fan, Jian; Zhang, Qiao

    2015-04-01

    In this work, we demonstrate that monodispersed gold nanorods (AuNRs) can be obtained in a large-scale and cost-effective way. By using an industrial grade gemini surfactant (P16-8-16), the cost of the synthesis of high-quality AuNRs can be significantly reduced by 90%. The synthesis can be scaled up to over 4 L. The aspect ratio of AuNRs can be well tuned from ~2.4 to ~6.3, resulting in a wide tunability of the SPR properties. Systematic studies reveal that P16-8-16 could have a dual function: it can not only act as a capping ligand to stabilize AuNRs but also it can pre-reduce Au3+ to Au+ by the unsaturated C&z.dbd;C bond. Furthermore, the shape of AuNRs can be tailored from straight nanorods to ``dog-bones'' by simply varying the concentration of the surfactant. A mechanistic study shows that the shape change can be attributed to the presence of excess bromide ions because of the complex effect between bromide ions and gold ions. This work will not only help to achieve the industrial production of AuNRs, but also promote research into practical applications of various nanomaterials.In this work, we demonstrate that monodispersed gold nanorods (AuNRs) can be obtained in a large-scale and cost-effective way. By using an industrial grade gemini surfactant (P16-8-16), the cost of the synthesis of high-quality AuNRs can be significantly reduced by 90%. The synthesis can be scaled up to over 4 L. The aspect ratio of AuNRs can be well tuned from ~2.4 to ~6.3, resulting in a wide tunability of the SPR properties. Systematic studies reveal that P16-8-16 could have a dual function: it can not only act as a capping ligand to stabilize AuNRs but also it can pre-reduce Au3+ to Au+ by the unsaturated C&z.dbd;C bond. Furthermore, the shape of AuNRs can be tailored from straight nanorods to ``dog-bones'' by simply varying the concentration of the surfactant. A mechanistic study shows that the shape change can be attributed to the presence of excess bromide ions because of the

  15. Monodisperse mesoporous anatase beads as high performance and safer anodes for lithium ion batteries

    Science.gov (United States)

    Rodriguez, Erwin F.; Chen, Dehong; Hollenkamp, Anthony F.; Cao, Lu; Caruso, Rachel A.

    2015-10-01

    To achieve high efficiency lithium ion batteries (LIBs), an effective active material is important. In this regard, monodisperse mesoporous titania beads (MMTBs) featuring well interconnected nanoparticles were synthesised, and their mesoporous properties were tuned to study how these affect the electrochemical performance in LIBs. Two pore diameters of 15 and 25 nm, three bead diameters of 360, 800 and 2100 nm, and various annealing temperatures (from 300 to 650 °C) were investigated. The electrochemical results showed that while the pore size does not significantly influence the electrochemical behaviour, the specific surface area and the nanocrystal size affect the performance. Also, there is an optimum annealing temperature that enhances electron transfer across the titania bead structure. The carbon content employed in the electrode was varied, showing that the bead diameter strongly influences the minimal content of the conductive carbon required to fabricate the electrode. As a general rule, the smaller the bead diameter, the more carbon was required in the electrode. A large energy capacity and high current rate performance were achieved on the MMTBs featuring high surface area, nano-sized anatase crystals and well-sintered connections between the nanocrystals. The high stability of these mesoporous structures was demonstrated by charge/discharge cycling up to 500 cycles. Devices constructed with the MMTBs retained more than 80% of the initial capacity, indicating an excellent performance.To achieve high efficiency lithium ion batteries (LIBs), an effective active material is important. In this regard, monodisperse mesoporous titania beads (MMTBs) featuring well interconnected nanoparticles were synthesised, and their mesoporous properties were tuned to study how these affect the electrochemical performance in LIBs. Two pore diameters of 15 and 25 nm, three bead diameters of 360, 800 and 2100 nm, and various annealing temperatures (from 300 to 650

  16. Atomically monodisperse nickel nanoclusters as highly active electrocatalysts for water oxidation

    Science.gov (United States)

    Joya, Khurram S.; Sinatra, Lutfan; Abdulhalim, Lina G.; Joshi, Chakra P.; Hedhili, M. N.; Bakr, Osman M.; Hussain, Irshad

    2016-05-01

    Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these Ni NCs are found to be Ni4(PET)8 and Ni6(PET)12 and are highly active electrocatalysts for oxygen evolution without any pre-conditioning. Ni4(PET)8 are slightly better catalysts than Ni6(PET)12 which initiate oxygen evolution at an amazingly low overpotential of ~1.51 V (vs. RHE; η ~ 280 mV). The peak oxygen evolution current density (J) of ~150 mA cm-2 at 2.0 V (vs. RHE) with a Tafel slope of 38 mV dec-1 is observed using Ni4(PET)8. These results are comparable to the state-of-the-art RuO2 electrocatalyst, which is highly expensive and rare compared to Ni-based materials. Sustained oxygen generation for several hours with an applied current density of 20 mA cm-2 demonstrates the long-term stability and activity of these Ni NCs towards electrocatalytic water oxidation. This unique approach provides a facile method to prepare cost-effective, nanoscale and highly efficient electrocatalysts for water oxidation.Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these

  17. Synthesis, photocatalytic activity, and photogenerated hydroxyl radicals of monodisperse colloidal ZnO nanospheres

    Science.gov (United States)

    Yang, Chong; Li, Qingsong; Tang, Limei; Xin, Kun; Bai, Ailing; Yu, Yingmin

    2015-12-01

    In the present study, monodisperse colloidal zinc oxide (ZnO) nanospheres were successfully synthesized via a newly developed two-stage solution method followed by facile calcination at various temperatures. The effects of calcination temperature on the structure, morphology, and optical properties as well as the photocatalytic activity of the as-made ZnO samples were investigated systematically by Fourier transform infrared spectrometry, X-ray diffraction, field emission scanning electron microscopy, nitrogen adsorption/desorption isotherms, diffuse reflectance UV-visible spectroscopy (DRS), photoluminescence, and related photocatalytic activity tests. The thermal decomposition was analyzed by thermogravimetric analysis. The crystallinity was found to gradually increase with increasing calcination temperature, whereas the decrease in the Brunauer-Emmett-Teller specific surface area of the samples with calcination may be ascribed to the increased particle size. The DRS results provided clear evidence for the decrease in band gap energy of ZnO samples with an increase in calcination temperature. The photoluminescence spectra demonstrated the calcination-dependent emission features, especially the UV emission intensity. In particular, the ZnO product calcined at 400 °C exhibited the highest photocatalytic activity, degrading methylene blue by almost 99.1% in 70 min, which is ascribed to the large specific surface area and pore volume, high electron-hole pair separation efficient, and great redox potential of the obtained ZnO nanoparticles. In addition, the production of photogenerated hydroxyl radicals (•OH) was consistent with the methylene blue degradation efficiency over the as-made ZnO nanoparticles. Using isopropanol as a hydroxyl radical scavenger, •OH was determined to be the main active oxygen species in the photocatalytic process. A possible mechanism of photodegradation under UV light irradiation also is proposed.

  18. Optical properties of gold nanoshells on monodisperse silica cores: Experiment and simulations

    Science.gov (United States)

    Khanadeev, Vitaly A.; Khlebtsov, Boris N.; Khlebtsov, Nikolai G.

    2017-01-01

    Gold nanoshells (GNSs) on silica cores are widely used in various biomedical applications that need the spectral tunability and controlled absorption/scattering ratio. However, the plasmonic quality of experimental extinction spectra of GNS colloids differs from that predicted by Mie theory. In this work, we fabricated highly monodisperse silica nanospheres to use them further as cores for synthesis of silica/gold nanoshells. Four GNS samples with 116-nm core and gold shell thickness ranging from 16 to 34 nm (116/16, 18, 25, 34) were additionally separated in glycerol gradient solutions to obtain fractions with dominant percentage of single particles or aggregates of various sizes. The separated samples demonstrated extinction spectra with a high extinction maximum to minimum ratio about 3. Optical properties of GNS monomers and aggregates with fixed and random orientations were calculated by Mie theory for polydisperse GNSs, by a generalized multiparticle Mie (GMM) theory for aggregates of separated GNSs, and by the finite-difference time-domain (FDTD) method for aggregates of overlapped GNSs. The extinction spectra of upper fractions from 116/25 and 116/34 samples are shown to be well described by Mie theory for GNSs with polydisperse shell thickness. However, for as prepared 116/16 sample this approach fails because of strong near infrared (NIR) contribution from GNS dimers and trimers. The formation of such aggregates is due to coupling of silica cores at early stages of nanoshell synthesis, thus leading to peanut structures with overlapped gold shells. We suggested TEM-based ensemble model with single particles and small dimer and trimer aggregates, which gives satisfactory agreement between measured and FDTD simulated spectra in the vis-NIR region. Thus, the proposed synthetic technology produces high quality gold nanoshells, which remarkable optical properties are in good agreement with electromagnetic simulations based on TEM data.

  19. Green synthesis and antimicrobial activity of monodisperse silver nanoparticles synthesized using Ginkgo Biloba leaf extract

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Yan-yu [School of Food and Biological Engineering, Shaanxi University of Science & Technology, Xi' an 710021 (China); Yang, Hui, E-mail: 549456369@qq.com [School of Food and Biological Engineering, Shaanxi University of Science & Technology, Xi' an 710021 (China); Wang, Tao [School of Food and Biological Engineering, Shaanxi University of Science & Technology, Xi' an 710021 (China); Wang, Chuang [Department of Highway & Bridge, Shaanxi Railway Institute, Weinan 714000 (China)

    2016-11-25

    Various parts of plants can be used as a raw material for the synthesis of nanoparticles, which is eco-friendly way and does not involve any harmful chemicals. In this project, Ginkgo biloba leaf, an abundantly available medicinal plant in China, was for the first time adopted as a reducing and stabilizing agent to synthesize smaller sized and stable silver nanoparticles (AgNPs). To improve the quality of AgNPs, the reduction was accelerated by changing the concentrations of initial Ag{sup +} (0.02, 0.04, 0.06 and 0.08 mol/L) of the reaction mixture consisting of silver nitrate solution (AgNO{sub 3}) and Ginkgo biloba leaf extract. At pH = 8 and lower AgNO{sub 3} concentration (0.02 mol/L), a colloid consisting of well-dispersed spherical nanoparticles was obtained. The synthesized nanocrystals were successfully characterized by UV–vis and XRD. TEM images revealed the size of the spherical AgNPs ranged between 10–16 nm. FTIR analysis revealed that biological macromolecules with groups of −NH{sub 2}, −OH, and others were distributed on the surface of the nanoparticles. The biosynthesized AgNPs exhibited good antibacterial activities against gram-negative bacteria and gram-positive bacteria. Compared to traditional chemical methods, Ginkgo biloba leaf extract provides an easy green synthetical way. It is anticipated that the biosynthesized AgNPs can be used in areas such as cosmetics, foods and medical applications. - Highlights: • Monodisperse silver nanoparticles were first prepared by a green synthetical way through Ginkgo Biloba leaf extract. • The synthesized AgNPs is of high crystallinity, stable and good dispersion with smaller sizes between 10–16 nm. • The achieved AgNPs exhibits good antibacterial activities. • The biosynthesis method is advantageous for its cost effectiveness, availability, portability, nontoxic and environmentally benign.

  20. Monodisperse granular flows in viscous dispersions in a centrifugal acceleration field

    Science.gov (United States)

    Cabrera, Miguel Angel; Wu, Wei

    2016-04-01

    Granular flows are encountered in geophysical flows and innumerable industrial applications with particulate materials. When mixed with a fluid, a complex network of interactions between the particle- and fluid-phase develops, resulting in a compound material with a yet unclear physical behaviour. In the study of granular suspensions mixed with a viscous dispersion, the scaling of the stress-strain characteristics of the fluid phase needs to account for the level of inertia developed in experiments. However, the required model dimensions and amount of material becomes a main limitation for their study. In recent years, centrifuge modelling has been presented as an alternative for the study of particle-fluid flows in a reduced scaled model in an augmented acceleration field. By formulating simple scaling principles proportional to the equivalent acceleration Ng in the model, the resultant flows share many similarities with field events. In this work we study the scaling principles of the fluid phase and its effects on the flow of granular suspensions. We focus on the dense flow of a monodisperse granular suspension mixed with a viscous fluid phase, flowing down an inclined plane and being driven by a centrifugal acceleration field. The scaled model allows the continuous monitoring of the flow heights, velocity fields, basal pressure and mass flow rates at different Ng levels. The experiments successfully identify the effects of scaling the plastic viscosity of the fluid phase, its relation with the deposition of particles over the inclined plane, and allows formulating a discussion on the suitability of simulating particle-fluid flows in a centrifugal acceleration field.

  1. Synthesis, characterization and magnetic properties of monodisperse Ni, Zn-ferrite nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sanjeev, E-mail: sanjeevkumar.dubey2@gmail.com [University of Petroleum and Energy Studies, Dehradun, Uttarakhand (India); Kumar, Pankaj [University of Petroleum and Energy Studies, Dehradun, Uttarakhand (India); Singh, Vaishali [University School of Basic and Applied Science (India); Kumar Mandal, Uttam [University of Chemical Technology, GGS Indraprastha University, Sector 16, Dwarka, Delhi 110403 (India); Kumar Kotnala, Ravinder [National Physical laboratory, New Delhi 110012 (India)

    2015-04-01

    Synthesization of monodisperse Ni, Zn-ferrite (Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4}, x=1, 0.8, 0.6, 0.5, 0.4, 0.2, 0.0) nanocrystals has been achieved by the inverse microemulsion method using CTAB as surfactant and kerosene as an oil phase. The detailed characterization of the synthesized nanocrystals and measurement of the magnetic properties has been done by techniques like X-ray diffraction (XRD), field emission transmission electron microscopy (FETEM), Fourier transform infrared spectroscopy (FITR) and Vibrating Sample Magnetometer (VSM) respectively. The relationship between the structure and composition of the nanocrystals with magnetic properties has been investigated. The nanocrystals size is found to be in the range 1–5 nm. The effect of Zn substitution on size and magnetic properties has been studied. It has been observed that magnetism changed from ferromagnetic at X= 0 to super paramagnetic to paramagnetic at X=1 as Zn concentration increased. The Curie temperature is found to decrease with an increase in Zn concentration. - Highlights: • Reverse microemulsion route is very facile route for synthesis of Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} ferrite. • Presence of Zn changes the structural and magnetic properties of the Zn substituted NiFe{sub 2}O{sub 4.} • The lattice constant increases with the increase in Zn substitution. • The curie temperature decreases with Zn concentration appreciably. • Magnetic behavior varies from ferromagnetic at x=0 to superparamagnetic to paramagnetic at x=1.

  2. Synthesis of monodisperse TiO2-paraffin core-shell nanoparticles for improved dielectric properties.

    Science.gov (United States)

    Balasubramanian, Balamurugan; Kraemer, Kristin L; Reding, Nicholas A; Skomski, Ralph; Ducharme, Stephen; Sellmyer, David J

    2010-04-27

    Core-shell structures of oxide nanoparticles having a high dielectric constant, and organic shells with large breakdown field are attractive candidates for large electrical energy storage applications. A high growth temperature, however, is required to obtain the dielectric oxide nanoparticles, which affects the process of core-shell formation and also leads to poor control of size, shape, and size-distribution. In this communication, we report a new synthetic process to grow core-shell nanoparticles by means of an experimental method that can be easily adapted to synthesize core-shell structures from a variety of inorganic-organic or inorganic-inorganic materials. Monodisperse and spherical TiO2 nanoparticles were produced at room temperature as a collimated cluster beam in the gas phase using a cluster-deposition source and subsequently coated with uniform paraffin nanoshells using in situ thermal evaporation, prior to deposition on substrates for further characterization and device processing. The paraffin nanoshells prevent the TiO2 nanoparticles from contacting each other and also act as a matrix in which the volume fraction of TiO2 nanoparticles was varied by controlling the thickness of the nanoshells. Parallel-plate capacitors were fabricated using dielectric core-shell nanoparticles having different shell thicknesses. With respect to the bulk paraffin, the effective dielectric constant of TiO2-paraffin core-shell nanoparticles is greatly enhanced with a decrease in the shell thickness. The capacitors show a minimum dielectric dispersion and low dielectric losses in the frequency range of 100 Hz-1 MHz, which are highly desirable for exploiting these core-shell nanoparticles for potential applications.

  3. Unraveling the Driving Forces in the Self-Assembly of Monodisperse Naphthalenediimide-Oligodimethylsiloxane Block Molecules.

    Science.gov (United States)

    Berrocal, José Augusto; Zha, R Helen; de Waal, Bas F M; Lugger, Jody A M; Lutz, Martin; Meijer, E W

    2017-04-25

    Block molecules belong to a rapidly growing research field in materials chemistry in which discrete macromolecular architectures bridge the gap between block copolymers (BCP) and liquid crystals (LCs). The merging of characteristics from both BCP and LCs is expected to result in exciting breakthroughs, such as the discovery of unexpected morphologies or significant shrinking of domain spacings in materials that possess the high definition of organic molecules and the processability of polymers. Here we report the bulk self-assembly of two families of monodisperse block molecules comprised of naphthalenediimides (NDIs) and oligodimethylsiloxanes (ODMS). These materials are characterized by waxy texture, strong long-range order, and very low mobility, typical properties of conformationally disordered crystals. Our investigation unambiguously reveals that thermodynamic immiscibility and crystallization direct the self-assembly of ODMS-based block molecules. We show that a synergy of high incompatibility between the blocks and crystallization of the NDIs causes nanophase separation, giving access to hexagonally packed columnar (Colh) and lamellar (LAM) morphologies with sub-10 nm periodicities. The domain spacings can be tuned by mixing molecules with different ODMS lengths and the same number of NDIs, introducing an additional layer of control. X-ray scattering experiments reveal macrophase separation whenever this constitutional bias is not observed. Finally, we highlight our "ingredient approach" to obtain perfect order in sub-10 nm structured materials with a simple strategy built on a crystalline "hard" moiety and an incompatible "soft" ODMS partner. Following this simple rule, our recipe can be extended to a number of systems.

  4. Synthesis and characterization of stable monodisperse silica nanoparticle sols for in vitro cytotoxicity testing.

    Science.gov (United States)

    Thomassen, Leen C J; Aerts, Alexander; Rabolli, Virginie; Lison, Dominique; Gonzalez, Laetitia; Kirsch-Volders, Micheline; Napierska, Dorota; Hoet, Peter H; Kirschhock, Christine E A; Martens, Johan A

    2010-01-05

    For the investigation of the interaction of nanoparticles with biomolecules, cells, organs, and animal models there is a need for well-characterized nanoparticle suspensions. In this paper we report the preparation of monodisperse dense amorphous silica nanoparticles (SNP) suspended in physiological media that are sterile and sufficiently stable against aggregation. SNP sols with various particle sizes (2-335 nm) were prepared via base-catalyzed hydrolysis and polymerization of tetraethyl orthosilicate under sterile conditions using either ammonia (Stober process (1) ) or lysine catalyst (Lys-Sil process (2) ). The series was complemented with commercial silica sols (Ludox). Silica nanoparticle suspensions were purified by dialysis and dispersed without using any dispersing agent into cell culture media (Dulbecco's Modified Eagle's medium) containing antibiotics. Particle sizes were determined by dynamic light scattering. SNP morphology, surface area, and porosity were characterized using electron microscopy and nitrogen adsorption. The SNP sols in cell culture medium were stable for several days. The catalytic activity of the SNP in the conversion of hydrogen peroxide into hydroxyl radicals was investigated using electron paramagnetic resonance. The catalytic activity per square meter of exposed silica surface area was found to be independent of particle size and preparation method. Using this unique series of nanoparticle suspensions, the relationship between cytotoxicity and particle size was investigated using human endothelial and mouse monocyte-macrophage cells. The cytotoxicity of the SNP was strongly dependent on particle size and cell type. This unique methodology and the collection of well-characterized SNP will be useful for further in vitro studies exploring the physicochemical determinants of nanoparticle toxicity.

  5. Templated synthesis of monodisperse mesoporous maghemite/silica microspheres for magnetic separation of genomic DNA

    Science.gov (United States)

    Chen, Feng; Shi, Ruobing; Xue, Yun; Chen, Lei; Wan, Qian-Hong

    2010-08-01

    A novel method is described for the preparation of superparamagnetic mesoporous maghemite (γ-Fe 2O 3)/silica (SiO 2) composite microspheres to allow rapid magnetic separation of DNA from biological samples. With magnetite (Fe 3O 4) and silica nanoparticles as starting materials, such microspheres were synthesized by the following two consecutive steps: (1) formation of monodispersed organic/inorganic hybrid microspheres through urea-formaldedyde (UF) polymerization and (2) removal of the organic template and phase transformation of Fe 3O 4 to γ-Fe 2O 3 by calcination at elevated temperatures. The as-synthesized particles obtained by heating at temperature 300 °C feature spherical shape and uniform particle size ( dparticle=1.72 μm), high saturation magnetization ( Ms=17.22 emu/g), superparamagnetism ( Mr/ Ms=0.023), high surface area ( SBET=240 m 2/g), and mesoporosity ( dpore=6.62 nm). The composite microsphere consists of interlocked amorphous SiO 2 nanoparticles, in which cubic γ-Fe 2O 3 nanocrystals are homogeneously dispersed and thermally stable against γ- to α-phase transformation at temperatures up to 600 °C. With the exposed iron oxide nanoparticles coated with a thin layer of silica shell, the magnetic microspheres were used as a solid-phase adsorbent for rapid extraction of genomic DNA from plant samples. The results show that the DNA templates isolated from pea and green pepper displayed single bands with molecular weights greater than 8 kb and A260/ A280 values of 1.60-1.72. The PCR amplification of a fragment encoding the endogenous chloroplast ndhB gene confirmed that the DNA templates obtained were inhibitor-free and amenable to sensitive amplification-based DNA technologies.

  6. Atomically Monodisperse Nickel Nanoclusters as Highly Active Electrocatalysts for Water Oxidation

    KAUST Repository

    Joya, Khurram

    2016-04-08

    Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these Ni NCs are found to be Ni4(PET)8 and Ni6(PET)12 and are highly active electrocatalysts for oxygen evolution without any pre-conditioning. Ni4(PET)8 are slightly better catalysts than Ni6(PET)12 and initiate the oxygen evolution at an amazingly low overpotential of ~1.51 V (vs RHE; η ≈ 280 mV). The peak oxygen evolution current density (J) of ~150 mA cm–2 at 2.0 V (vs. RHE) with a Tafel slope of 38 mV dec–1 is observed using Ni4(PET)8. These results are comparable to the state-of-the art RuO2 electrocatalyst, which is highly expensive and rare compared to Ni-based materials. Sustained oxygen generation for several hours with an applied current density of 20 mA cm–2 demonstrates the long-term stability and activity of these Ni NCs towards electrocatalytic water oxidation. This unique approach provides a facile method to prepare cost-effective, nanoscale and highly efficient electrocatalysts for water oxidation.

  7. Solvothermal synthesis and controlled self-assembly of monodisperse titanium-based perovskite colloidal nanocrystals

    Science.gov (United States)

    Caruntu, Daniela; Rostamzadeh, Taha; Costanzo, Tommaso; Salemizadeh Parizi, Saman; Caruntu, Gabriel

    2015-07-01

    The rational design of monodisperse ferroelectric nanocrystals with controlled size and shape and their organization into hierarchical structures has been a critical step for understanding the polar ordering in nanoscale ferroelectrics, as well as the design of nanocrystal-based functional materials which harness the properties of individual nanoparticles and the collective interactions between them. We report here on the synthesis and self-assembly of aggregate-free, single-crystalline titanium-based perovskite nanoparticles with controlled morphology and surface composition by using a simple, easily scalable and highly versatile colloidal route. Single-crystalline, non-aggregated BaTiO3 colloidal nanocrystals, used as a model system, have been prepared under solvothermal conditions at temperatures as low as 180 °C. The shape of the nanocrystals was tuned from spheroidal to cubic upon changing the polarity of the solvent, whereas their size was varied from 16 to 30 nm for spheres and 5 to 78 nm for cubes by changing the concentration of the precursors and the reaction time, respectively. The hydrophobic, oleic acid-passivated nanoparticles exhibit very good solubility in non-polar solvents and can be rendered dispersible in polar solvents by a simple process involving the oxidative cleavage of the double bond upon treating the nanopowders with the Lemieux-von Rudloff reagent. Lattice dynamic analysis indicated that regardless of their size, BaTiO3 nanocrystals present local disorder within the perovskite unit cell, associated with the existence of polar ordering. We also demonstrate for the first time that, in addition to being used for fabricating large area, crack-free, highly uniform films, BaTiO3 nanocubes can serve as building blocks for the design of 2D and 3D mesoscale structures, such as superlattices and superparticles. Interestingly, the type of superlattice structure (simple cubic or face centered cubic) appears to be determined by the type of solvent

  8. Coherent Phase Control of Multiphoton Ionization in Three-Level Ladder-Type System

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shi-An; CHEN Yu-Ting; WANG Zu-Geng; SUN Zhen-Rong

    2009-01-01

    We present the theoretical investigation of photoelectron spectroscopy resulting from the strong field induced multiphoton ionization in a typical three-level ladder-style system.Our theoretical results show that the photoelectron spectral structure can be alternatively steered by spectral phase modulation.This physical mechanism for strong field quantum control is explicitly exploited by the time-dependent dressed state population.It is concluded that the phase-shaped laser pulses can be used to selectively manipulate the multiphoton ionization process in complicated quantum systems.

  9. Magneto-optical polarization rotation in a ladder-type atomic system for tunable offset locking

    CERN Document Server

    Parniak, Michał; Wasilewski, Wojciech

    2016-01-01

    We demonstrate an easily tunable locking scheme for stabilizing frequency-sum of two lasers on a two-photon ladder transition based on polarization rotation in warm rubidium vapors induced by magnetic field and circularly polarized driving field. In principle unlimited tunability of the two-photon offset frequency is due to strong splitting and shifting of magnetic states in external field. We achieve two-photon detuning of 120 MHz with the single-photon detuning of up to 20 GHz, as well as strong rotation signal.

  10. Monodisperse polyvinylpyrrolidone-coated CoFe{sub 2}O{sub 4} nanoparticles: Synthesis, characterization and cytotoxicity study

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guangshuo, E-mail: wgs8136@163.com; Ma, Yingying, E-mail: bzhjgcmyy@163.com; Mu, Jingbo; Zhang, Zhixiao; Zhang, Xiaoliang; Zhang, Lina; Che, Hongwei; Bai, Yongmei; Hou, Junxian; Xie, Hailong

    2016-03-01

    Graphical abstract: - Highlights: • Monodisperse cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles were prepared with various additions of polyvinylpyrrolidone (PVP) by a facile sonochemical method. • PVP-coated CoFe{sub 2}O{sub 4} showed relatively well dispersion and homogeneous shape with narrow size distribution. • PVP-coated CoFe{sub 2}O{sub 4} exhibited superparamagnetism with moderate saturation magnetization and hydrophilic character at room temperature. • Negligible cytotoxicity of PVP-coated CoFe{sub 2}O{sub 4} was observed even at high sample concentration after 24 h treatment. - Abstract: In this study, monodisperse cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles were prepared successfully with various additions of polyvinylpyrrolidone (PVP) by sonochemical method, in which PVP served as a stabilizer and dispersant. The effects and roles of PVP on the morphology, microstructure and magnetic properties of the obtained CoFe{sub 2}O{sub 4} were investigated in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID). It was found that PVP-coated CoFe{sub 2}O{sub 4} showed relatively well dispersion with narrow size distribution. The field-dependent magnetization curves indicated superparamagnetic behavior of PVP-coated CoFe{sub 2}O{sub 4} with moderate saturation magnetization and hydrophilic character at room temperature. More importantly, the in vitro cytotoxicity testing exhibited negligible cytotoxicity of as-prepared PVP-CoFe{sub 2}O{sub 4} even at the concentration as high as 150 μg/mL after 24 h treatment. Considering the superparamagnetic properties, hydrophilic character and negligible cytotoxicity, the monodisperse CoFe{sub 2}O{sub 4} nanoparticles hold great potential in a variety of biomedical applications.

  11. In Situ Monitoring of the Generation of Monodisperse Silica Particles during the Hydrolysis of Tetraethyl Orthosilicate with Piezoelectric Quartz Crystal Impedance Analyzer

    Institute of Scientific and Technical Information of China (English)

    姚守拙; 张友玉; 谢青季

    2003-01-01

    The piezoelectric quartz crystal(PQC)impedance analyzer was used to monitor in situ the generation of monodisperse silica particles during the hydrolysis of tetraethyl orthosilicate (TEOS) and their adsorption onto and Au electrode in alcohol solutions containing water(6-15mol/L)and ammonia(0.2-2.0 mol/L).The equivalent circuit parameters,the resonance frequencies and the half-peak width values of the conductance spectra of the PQC resonance were obtained.The resonant frequency decreased notably while the motional resistance changed very slightly(within 1Ω during the hydrolysis reaction,suggesting that the mass effect dominated the adsorption of generated monodisperse silica particles on the gold electrode in this system.Changes in f0 indicated that the ammonia concentration affected the hydrolytic reaction obviously,and the influence of water concentration on the reaction was small while the water was significantly excessive.Kinetics of monodisperse silica particle adsorption occurring at the electrode i solution interface was analyzed using a first-order reaction scheme.In addition,the electrolyte-induced precipitation of the monodisperse silica of adsorbed particles per area and the converge of monodisperse silica particles were obtained from scanning electron nicroscope(SEM)observations.

  12. Comparative DNA isolation behaviours of silica and polymer based sorbents in batch fashion: monodisperse silica microspheres with bimodal pore size distribution as a new sorbent for DNA isolation.

    Science.gov (United States)

    Günal, Gülçin; Kip, Çiğdem; Eda Öğüt, S; İlhan, Hasan; Kibar, Güneş; Tuncel, Ali

    2017-03-22

    Monodisperse silica microspheres with bimodal pore-size distribution were proposed as a high performance sorbent for DNA isolation in batch fashion under equilibrium conditions. The proposed sorbent including both macroporous and mesoporous compartments was synthesized 5.1 μm in-size, by a "staged shape templated hydrolysis and condensation method". Hydrophilic polymer based sorbents were also obtained in the form of monodisperse-macroporous microspheres ca 5.5 μm in size, with different functionalities, by a developed "multi-stage microsuspension copolymerization" technique. The batch DNA isolation performance of proposed material was comparatively investigated using polymer based sorbents with similar morphologies. Among all sorbents tried, the best DNA isolation performance was achieved with the monodisperse silica microspheres with bimodal pore size distribution. The collocation of interconnected mesoporous and macroporous compartments within the monodisperse silica microspheres provided a high surface area and reduced the intraparticular mass transfer resistance and made easier both the adsorption and desorption of DNA. Among the polymer based sorbents, higher DNA isolation yields were achieved with the monodisperse-macroporous polymer microspheres carrying trimethoxysilyl and quaternary ammonium functionalities. However, batch DNA isolation performances of polymer based sorbents were significantly lower with respect to the silica microspheres.

  13. Preparation of Weak Cation Exchange Packings Based on Monodisperse Poly (chloromethylstyrene-co-divinylbenzene) Particles and Its Chromatographic Properties

    Institute of Scientific and Technical Information of China (English)

    卫引茂; 陈强; 耿信笃

    2001-01-01

    Monodisperse poly ( chloromethylstyrene-co-divinylbenzene )particles were firstly prepared by a two-step swelling method.Based on this media, one kind of weak cation ion exchange packings was prepared. It was demonstrated that the prepared packings have comparative advantages for biopolymer separation with high column efficiency, low interstitial volume and low column backpressure, and have good resolution to proteins. The effects of salt concentration and pH of mobile phase on protein retentions were investigated. The properties of the weak cation ion exchange packings were evaluated by the unified retention model for mixed-mode interaction mechanison in ion exchange and hydrophobic interaction chromatography.

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

    Directory of Open Access Journals (Sweden)

    Alaaldin M. Alkilany

    2015-01-01

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

  15. Near-Monodisperse Ni-Cu Bimetallic Nanocrystals of Variable Composition: Controlled Synthesis and Catalytic Activity for H2 Generation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yawen; Huang, Wenyu; Habas, Susan E.; Kuhn, John N.; Grass, Michael E.; Yamada, Yusuke; Yang, Peidong; Somorjai, Gabor A.

    2008-07-22

    Near-monodisperse Ni{sub 1-x}Cu{sub x} (x = 0.2-0.8) bimetallic nanocrystals were synthesized by a one-pot thermolysis approach in oleylamine/1-octadecene, using metal acetylacetonates as precursors. The nanocrystals form large-area 2D superlattices, and display a catalytic synergistic effect in the hydrolysis of NaBH{sub 4} to generate H{sub 2} at x = 0.5 in a strongly basic medium. The Ni{sub 0.5}Cu{sub 0.5} nanocrystals show the lowest activation energy, and also exhibit the highest H{sub 2} generation rate at 298 K.

  16. Monodispersed fabrication and dielectric studies on ethylenediamine passivated α-manganese dioxide nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, A. Martin [Research and Development Centre, Bharathiar University, Coimbatore, Tamilnadu (India); Kumar, R. Thilak, E-mail: manojthilak@yahoo.com [Periyar Arts College, Cuddalore-607001, Tamilnadu (India)

    2016-09-15

    Highlights: • Monodispersed ethylenediamine (EDA) passivated α-MnO{sub 2} nanorods were fabricated by inexpensive wet chemical method. • FTIR analysis indicated that surface passivation is strongly influenced by the introduction of the organic ligand. • XRD and HR-SEM revealed the structure and morphology of the fabricated α-MnO{sub 2} nanorods with an average size of about 40 × 200 nm. • Dielectric studies pointed out that the fabricated α-MnO{sub 2} is semiconducting in nature with resistivity, ρ = 1.46 to 5.76 × 10{sup 3} Ωcm. • The optical energy gap for the fabricated α-MnO{sub 2} nanorods is found to be around 1.37 eV. - Abstract: In this present work, pure α-MnO{sub 2} nanorods were fabricated by the reduction of 0.2 m/L of KMnO{sub 4} with 0.2 m/L of Na{sub 2}S{sub 2}O{sub 3}·5H{sub 2}O and by passivating with the organic ligand Ethylenediamine (EDA). The structural, functional, morphological and chemical composition of the nanorods were investigated by X-Ray Diffractometer (XRD), Fourier Transform Infrared Spectrometer (FTIR), High Resolution Scanning Electron Microscope (HR-SEM) and Energy Dispersive X-Ray Spectrometry (EDX). The XRD analysis indicated high crystalline nature of the product and FTIR confirmed the contribution of the organic ligand in surface passivation. HR-SEM image revealed the morphology of the α-MnO{sub 2} nanorods with an average size of about 40 × 200 nm. EDX confirmed the presence of Mn and O in the material. UV–visible spectrophotometery was used to determine the absorption behavior of the nanorods and an indirect band gap of 1.37 eV was acquired by Taucplot. Dielectric studies were carried out using Broadband Dielectric Spectrometer(BDS) and the resistivity was found to be around the semiconductor range (ρ = 1.46 to 5.76 × 10{sup 3} Ωcm).

  17. Monodisperse metal nanoparticle catalysts on silica mesoporous supports: synthesis, characterizations, and catalytic reactions

    Energy Technology Data Exchange (ETDEWEB)

    Somorjai, G.A.

    2009-09-14

    The design of high performance catalyst achieving near 100% product selectivity at maximum activity is one of the most important goals in the modern catalytic science research. To this end, the preparation of model catalysts whose catalytic performances can be predicted in a systematic and rational manner is of significant importance, which thereby allows understanding of the molecular ingredients affecting the catalytic performances. We have designed novel 3-dimensional (3D) high surface area model catalysts by the integration of colloidal metal nanoparticles and mesoporous silica supports. Monodisperse colloidal metal NPs with controllable size and shape were synthesized using dendrimers, polymers, or surfactants as the surface stabilizers. The size of Pt, and Rh nanoparticles can be varied from sub 1 nm to 15 nm, while the shape of Pt can be controlled to cube, cuboctahedron, and octahedron. The 3D model catalysts were generated by the incorporation of metal nanoparticles into the pores of mesoporous silica supports via two methods: capillary inclusion (CI) and nanoparticle encapsulation (NE). The former method relies on the sonication-induced inclusion of metal nanoparticles into the pores of mesoporous silica, whereas the latter is performed by the encapsulation of metal nanoparticles during the hydrothermal synthesis of mesoporous silica. The 3D model catalysts were comprehensively characterized by a variety of physical and chemical methods. These catalysts were found to show structure sensitivity in hydrocarbon conversion reactions. The Pt NPs supported on mesoporous SBA-15 silica (Pt/SBA-15) displayed significant particle size sensitivity in ethane hydrogenolysis over the size range of 1-7 nm. The Pt/SBA-15 catalysts also exhibited particle size dependent product selectivity in cyclohexene hydrogenation, crotonaldehyde hydrogenation, and pyrrole hydrogenation. The Rh loaded SBA-15 silica catalyst showed structure sensitivity in CO oxidation reaction. In

  18. Templated synthesis of monodisperse mesoporous maghemite/silica microspheres for magnetic separation of genomic DNA

    Energy Technology Data Exchange (ETDEWEB)

    Chen Feng; Shi Ruobing; Xue Yun; Chen Lei [School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072 (China); Wan Qianhong, E-mail: qhwan@tju.edu.c [School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072 (China)

    2010-08-15

    A novel method is described for the preparation of superparamagnetic mesoporous maghemite (gamma-Fe{sub 2}O{sub 3})/silica (SiO{sub 2}) composite microspheres to allow rapid magnetic separation of DNA from biological samples. With magnetite (Fe{sub 3}O{sub 4}) and silica nanoparticles as starting materials, such microspheres were synthesized by the following two consecutive steps: (1) formation of monodispersed organic/inorganic hybrid microspheres through urea-formaldedyde (UF) polymerization and (2) removal of the organic template and phase transformation of Fe{sub 3}O{sub 4} to gamma-Fe{sub 2}O{sub 3} by calcination at elevated temperatures. The as-synthesized particles obtained by heating at temperature 300 deg. C feature spherical shape and uniform particle size (d{sub particle}=1.72 mum), high saturation magnetization (M{sub s}=17.22 emu/g), superparamagnetism (M{sub r}/M{sub s}=0.023), high surface area (S{sub BET}=240 m{sup 2}/g), and mesoporosity (d{sub pore}=6.62 nm). The composite microsphere consists of interlocked amorphous SiO{sub 2} nanoparticles, in which cubic gamma-Fe{sub 2}O{sub 3} nanocrystals are homogeneously dispersed and thermally stable against gamma- to alpha-phase transformation at temperatures up to 600 deg. C. With the exposed iron oxide nanoparticles coated with a thin layer of silica shell, the magnetic microspheres were used as a solid-phase adsorbent for rapid extraction of genomic DNA from plant samples. The results show that the DNA templates isolated from pea and green pepper displayed single bands with molecular weights greater than 8 kb and A{sub 260}/A{sub 280} values of 1.60-1.72. The PCR amplification of a fragment encoding the endogenous chloroplast ndhB gene confirmed that the DNA templates obtained were inhibitor-free and amenable to sensitive amplification-based DNA technologies.

  19. Antisolvent Precipitation for the Synthesis of Monodisperse Mesoporous Niobium Oxide Spheres as Highly Effective Solid Acid Catalysts

    KAUST Repository

    Li, Cheng Chao

    2012-03-20

    We have developed a low-cost reaction protocol to synthesize mesoporous Nb 2O 5-based solid acid catalysts with external shape control. In the synthesis, monodisperse glycolated niobium oxide spheres (GNOS) were prepared by means of a simple antisolvent precipitation approach and subsequently converted to mesoporous niobium oxide spheres (MNOS) with a large surface area of 312m 2g -1 by means of the hydrothermal treatment. The antisolvent acetone used to obtain GNOS was recovered through distillation at high purity. The obtained mesoporous MNOS were functionalized further with sulfate anions at different temperatures or incorporated with tungstophosphoric acid to obtain recyclable solid acid catalysts. These MNOS-based catalysts showed excellent performance in a wide range of acid-catalyzed reactions, such as Friedel-Crafts alkylation, esterification, and hydrolysis of acetates. As they are monodisperse spheres with diameters in the submicrometer range, the catalysts can be easily separated and reused. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Monodisperse Ag@SiO2 core-shell nanoparticles as active inhibitors for marine anticorrosion applications.

    Science.gov (United States)

    Zhang, Xin-Sheng; Wang, Jie-Xin; Xu, Ke; Le, Yuan; Chen, Jian-Feng

    2011-04-01

    Monodisperse Ag@SiO2 core-shell structured nanoparticles were firstly utilized as a novel corrosion inhibitor for marine anticorrosion applications. The related marine anticorrosion properties were evaluated with an electrochemical noise (ECN) analysis during 2 weeks of accelerated immersion tests in natural seawater with the addition of various inorganic salts and nutriments. The experimental results indicate that the corrosion activity is markedly reduced by nearly 1-3 orders of magnitude owing to the introduction of Ag@SiO2 core-shell nanoparticles into coating. The inhibition efficiency of corrosion can reach as high as about 99%. More importantly, such a coating exhibits an excellent long-term sustained marine anticorrosion effect. So it could be reasonably inferred that silver cores as active inhibitors effectively prevent the corrosion damage from microorganisms, while silica shells act as a good protection for silver nanoparticles, delay the release of silver ions, and also function as the corrosion inhibiting action for inorganic salts. Therefore, this would make monodisperse Ag@SiO2 core-shell nanoparticles a potential and promising corrosion inhibitor for developing future advanced multifunctional coatings.

  1. Highly monodispersed tin oxide/mesoporous starbust carbon composite as high-performance Li-ion battery anode.

    Science.gov (United States)

    Chen, Jiajun; Yano, Kazuhisa

    2013-08-28

    The widespread commercialization of today's plug-in hybrid and all electric vehicles will rely on improved lithium batteries with higher energy density, greater power, and durability.To take advantage of the high density of SnO2 anodes for Li ion batteries, we achieved a smart design of monodispersed SnO2/MSCS composite with very high content of SnO2 by a simple infiltration procedure. The synergistic effects of the unique nanoarchitecture of MSCS and the ultrafine size of SnO2 nanoparticle endowed the composite with superior electrochemical performance. Because of the high density of the composite resulting from its monodispersed submicrometer spherical morphology, an exceptionally high reversible lithium storage capacity (both gravimetric and volumetric), very close to the theoretical capacity (1491 mA h/g), can be achieved with good cyclability (capacity retention of 92.5% after 15 cycles). The SnO2/MSCS composite anode exhibited a high reversible average capacity of about 1200 mAh/g over 30 cycles at a current of 80 mAh/g, which corresponds to about 1440 mAh/cm(3) (practical volumetric capacity). In addition, a Coulombic efficiency close to 100% was achieved, and less than 25% first irreversible capacity loss was observed.

  2. Newly designed silver coated-magnetic, monodisperse polymeric microbeads as SERS substrate for low-level detection of amoxicillin

    Science.gov (United States)

    Kibar, Güneş; Topal, Ahmet Emin; Dana, Aykutlu; Tuncel, Ali

    2016-09-01

    We report the preparation of silver-coated magnetic polymethacrylate core-shell nanoparticles for use in surface-enhanced Raman scattering based drug detection. Monodisperse porous poly (mono-2-(methacryloyloxy)ethyl succinate-co-glycerol dimethacrylate), poly (MMES-co-GDMA) microbeads of ca. 5 μm diameter were first synthesized through a multistage microsuspension polymerization technique to serve as a carboxyl-bearing core region. Microspheres were subsequently magnetized by the co-precipitation of ferric ions, aminated through the surface hydroxyl groups and decorated with Au nanoparticles via electrostatic attraction. An Ag shell was then formed on top of the Au layer through a seed-mediated growth process, resulting in micron-sized monodisperse microbeads that exhibit Raman enhancement effects due to the roughness of the Ag surface layer. The core-shell microspheres were used as a new substrate for the detection of amoxicillin at trace concentrations up to 10-8 M by SERS. The proposed SERS platform can be evaluated as a useful tool for the follow-up amoxicillin pollution and low-level detection of amoxicillin in aqueous media.

  3. High surface area monodispersed Fe3O4 nanoparticles alone and on physical exfoliated graphite for improved supercapacitors

    Science.gov (United States)

    Sarno, Maria; Ponticorvo, Eleonora; Cirillo, Claudia

    2016-12-01

    Highly conductive, unsophisticated and easy to be obtained physical exfoliated graphite (PHG) supporting well dispersed magnetite, Fe3O4/PHG nanocomposite, has been prepared by a one-step chemical strategy and physico-chemical characterized. The nanocomposite, favoured by the a-polar nanoparticles (NPs) capping, results in a self-assembled monolayer of monodispersed Fe3O4, covering perfectly the hydrophobic surfaces of PHG. The nanocomposite as an electrode material was fabricated into a supercapacitor and characterized by cyclic voltammetry (CV) and galvanostatic charge-discharge measurements. It shows, after a suitable annealing, significant electrochemical properties (capacitance value of 787 F/g at 0.5 A g-1 and a Fe3O4/PHG weight ratio of 0.31) and good cycling stability (retention 91% after 30,000 cycles). Highly monodispersed very fine Fe3O4 NPs, covered by organic chains, have been also synthesized. The high surface area Fe3O4 NPs, after washing to leave a low content of organic chains able to avoid aggregation without excessively affecting the electrical properties of the material, exhibit remarkable pseudocapacitive activities, including the highest specific capacitance over reported for Fe3O4 (300 F/g at 0.5 A g-1).

  4. Light-induced growth of monodisperse silver nanoparticles with tunable SPR properties and wavelength self-limiting effect

    Science.gov (United States)

    Zheng, Xianliang; Lombardi, John R.

    2008-08-01

    We present a technique for the tunable synthesis of a variety of monodisperse silver nanoparticles. Utilizing different optical wavelengths to irradiate initially grown seed crystals, the size and shape of the products can be controlled. Monitoring the absorption spectrum during growth, we observe that initially the absorption maximum shifts to longer wavelengths and broadens, indicating increasing particle size and dispersion. Remarkably, this effect gradually comes to a halt and reverses, displaying a shift to shorter wavelengths and simultaneously narrower bandwidths, until on completion, a final size and relatively narrow distribution is reached. The final morphology is found to depend on control of the laser wavelength and power. Discs, triangular prisms as well as pyramidal and pentagonal prisms may be produced. A process based on a wavelength dependent self-limiting mechanism governed by the surface plasmon resonance controlling the photochemical reduction of particles is suggested. By a similar mechanism, we show that by using a sodium lamp instead of a laser as an excitation source, a monodisperse sample of nanotetrahedra can be produced.

  5. Fabrication of and drug delivery by an upconversion emission nanocomposite with monodisperse LaF3:Yb,Er core / mesoporous silica shell structure

    NARCIS (Netherlands)

    Yang, Y.; Qu, Y.; Zhao, J.; Zeng, Q.; Ran, Y.; Zhang, Q.; Kong, X.; Zhang, H.

    2010-01-01

    Monodisperse, uniform, encapsulated mesoporous silicananocomposites with a LaF3:Yb,Er core and a mesoporous silica shell structure, which still exhibit green upconversion photoluminescence (PL) under 980 nm irradiation, have been successfully synthesized and investigated as potential drug delivery s

  6. Monodisperse Water-in-Oil-in-Water (W/O/W Double Emulsion Droplets as Uniform Compartments for High-Throughput Analysis via Flow Cytometry

    Directory of Open Access Journals (Sweden)

    Jing Yan

    2013-12-01

    Full Text Available Here we report the application of monodisperse double emulsion droplets, produced in a single step within partially hydrophilic/partially hydrophobic microfluidic devices, as defined containers for quantitative flow cytometric analysis. Samples with varying fluorophore concentrations were generated, and a clear correlation between dye concentration and fluorescence signals was observed.

  7. Solvothermal synthesis of monodispersed CoZr{sub 4}(PO{sub 4}){sub 6} microspheres and their application as microwave absorber

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Tingting [College of Chemistry, Beijing Normal University, Beijing 100875 (China); Sun, Genban, E-mail: gbsun@bnu.edu.cn [College of Chemistry, Beijing Normal University, Beijing 100875 (China); Ma, Shulan; Yang, Xiaojing [College of Chemistry, Beijing Normal University, Beijing 100875 (China); Hu, Changwen [Key Laboratory of Cluster Science, Ministry of Education of China and Department of Chemistry, Beijing Institute of Technology, Beijing 100081 (China)

    2012-03-15

    Graphical abstract: Monodispersed CoZr{sub 4}(PO{sub 4}){sub 6} porous microspheres with shell structure were synthesized via a combined solvothermal method and calcination route. The radar-wave absorbability of the purple sample calcined at 900 Degree-Sign C was strongest at the frequency of about 8.5 GHz. Highlights: Black-Right-Pointing-Pointer In this study we synthesized monodispersed CoZr{sub 4}(PO{sub 4}){sub 6} porous microspheres as microwave absorber. Black-Right-Pointing-Pointer The relationship between microstructures and the electromagnetic properties was indicated. Black-Right-Pointing-Pointer The radar-wave absorbability of the sample was included. -- Abstract: Monodispersed CoZr{sub 4}(PO{sub 4}){sub 6} microspheres with a diameter of 40 {mu}m were achieved via a combining solvothermal and calcination route. The crystallinity of the calcined microspheres with shell structure was improved, while the monodisperse property and morphologies remained. The possible formation mechanism of the porous CoZr{sub 4}(PO{sub 4}){sub 6} microspheres with nanoshell was proposed. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra (FT-IR) technologies, thermal analysis (TG and DSC), nitrogen adsorption-desorption isotherms and network analyzer. The sample calcined at 900 Degree-Sign C shows a strongest absorbability in the radar-wave absorbability test.

  8. Consequences of using different pair-correlation funtions on the stability properties of the Homogeneous Cooling State for a monodisperse system of near-elastic disks

    NARCIS (Netherlands)

    Gonzalez Briones, Sebastián; González, Sebastián; Luding, Stefan

    2010-01-01

    We show the differences in the stability properties of the Homogeneous Cooling State (HCS) of a two-dimensional monodisperse collection of rigid and near-elastic disks, obtained by using different formulae for the pair-correlation function.For an equation of state that takes into account the

  9. Facile Droplet-based Microfluidic Synthesis of Monodisperse IV-VI Semiconductor Nanocrystals with Coupled In-Line NIR Fluorescence Detection

    NARCIS (Netherlands)

    Lignos, Ioannis; Protesescu, Loredana; Stavrakis, Stavros; Piveteau, Laura; Speirs, Mark J.; Loi, Maria A.; Kovalenko, Maksym V.; deMello, Andrew J.

    2014-01-01

    We describe the realization of a droplet-based microfluidic platform for the controlled and reproducible synthesis of lead chalcogenide (PbS, PbSe) nanocrystal quantum dots (QDs). Monodisperse nanocrystals were synthesized over a wide range of experimental conditions, with real-time assessment and f

  10. Annealing effect on the structural and optical properties of Cr/a-Cr2O3 monodispersed particles based solar absorbers

    CSIR Research Space (South Africa)

    Khamlich, S

    2013-01-01

    Full Text Available A cost-effective and environmentally friendly green chemical method, the so-called aqueous chemical growth (ACG) method, was used to deposit chromium/alpha-chromium(III) oxide, Cr/a-Cr2O3, monodispersed particles, for solar absorbers applications...

  11. Nearly Monodispersion CoSm Alloy Nanoparticles Formed by an In-situ Rapid Cooling and Passivating Microfluidic Process

    Directory of Open Access Journals (Sweden)

    Henry Laurence

    2009-01-01

    Full Text Available Abstract An in siturapid cooling and passivating microfluidic processhas been developed for the synthesis of nearly monodispersed cobalt samarium nanoparticles (NPs with tunable crystal structures and surface properties. This process involves promoting the nucleation and growth of NPs at an elevated temperature and rapidly quenching the NP colloids in a solution containing a passivating reagent at a reduced temperature. We have shown that Cobalt samarium NPs having amorphous crystal structures and a thin passivating layer can be synthesized with uniform nonspherical shapes and size of about 4.8 nm. The amorphous CoSm NPs in our study have blocking temperature near 40 K and average coercivity of 225 Oe at 10 K. The NPs also exhibit high anisotropic magnetic properties with a wasp-waist hysteresis loop and a bias shift of coercivity due to the shape anisotropy and the exchange coupling between the core and the thin oxidized surface layer.

  12. Preparation of Size-tunable, Highly Monodisperse PVP-Protected Pt-nanoparticles by Seed-mediated Growth

    Energy Technology Data Exchange (ETDEWEB)

    Koebel, Matthias Michael; Jones, Louis C.; Somorjai, Gabor A.

    2008-04-02

    We demonstrate a preparative method which produces highly-monodisperse Pt-nanoparticles of tunable size without the external addition of seed particles. Hexachloroplatinic acid is dosed slowly to an ethylene glycol solution at 120 C and reduced in the presence of a stabilizing polymer poly-N-vinylpyrollidone (PVP). Slow addition of the Pt-salt first will first lead to the formation of nuclei (seeds) which then grow further to produce larger particles of any desired size between 3 and 8nm. The amount of added hexachloroplatinic acid precursor controls the size of the final nanoparticle product. TEM was used to determine size and morphology and to confirm the crystalline nature of the nanoparticles. Good reproducibility of the technique was demonstrated. Above 7nm, the particle shape and morphology changes suddenly indicating a change in the deposition selectivity of the Pt-precursor from (100) towards (111) crystal faces and breaking up of larger particles into smaller entities.

  13. Composite Electroplating to Obtain Ni-ZrO2 Nanocomposite Coatings Containing Monodispersed ZrO2 Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; HOU Feng-yan; GUO He-tong

    2004-01-01

    The Zirconia nanoparticles are dispersed well in the plating bath using polyelectrolyte dispersant and NiZrO2 nanocomposite coatings containing monodispersed ZrO2 nanoparticles are successfully prepared under DC electrodeposition condition. The effects of the dispersant concentration on the dispersibility of Zirconia nanoparticles in the plating bath and the hardness of nanocomposite coatings have been investigated. The results shows that the hardness of nanocomposite coatings are strongly influenced by the dispersion state of ZrO2 nanoparticles in the composite coatings and only a very low volume percent of monodispered ZrO2 nanoparticles in Ni-ZrO2 composite coatings will result in higher hardness of the coating.

  14. Efficient Thermolysis Route to Monodisperse Cu2ZnSnS4 Nanocrystals with Controlled Shape and Structure

    Science.gov (United States)

    Zhang, Xiaoyan; Guo, Guobiao; Ji, Cheng; Huang, Kai; Zha, Chenyang; Wang, Yifeng; Shen, Liming; Gupta, Arunava; Bao, Ningzhong

    2014-05-01

    Monodisperse Cu2ZnSnS4 (CZTS) nanocrystals with tunable shape, crystalline phase, and composition are synthesized by efficient thermolysis of a single source precursor of mixed metal-oleate complexes in hot organic solvents with dissolved sulfur sources. Suitable tuning of the synthetic conditions and the Cu/(Zn + Sn) ratio of the precursor has enabled precise control of the crystalline phase in the form of kesterite, or a newly observed wurtzite structure. Nanocrystals with morphology in the form of spherical, rice-like, or rod-like shapes are obtained over a wide range of compositions (0.5 <= Cu/(Zn + Sn) <= 1.2). Both the final products and intermediates for each shape exhibit consistent composition and structure, indicating homogenous nucleation and growth of single-phase nanocrystals. Thin films prepared from colloidal nanocrystal suspensions display interesting shape-dependent photoresponse behavior under white light illumination from a solar simulator.

  15. Hybrid thin films derived from UV-curable acrylate-modified waterborne polyurethane and monodispersed colloidal silica

    Directory of Open Access Journals (Sweden)

    C. H. Yang

    2012-01-01

    Full Text Available Hybrid thin films containing nano-sized inorganic domains were synthesized from UV-curable acrylate-modified waterborne polyurethane (WPU-AC and monodispersed colloidal silica with coupling agent. The coupling agent, 3-(trimethoxysilylpropyl methacrylate (MSMA, was bonded onto colloidal silica first, and then mixed with WPU-AC to form a precursor solution. This precursor was spin coated, dried and UV-cured to generate the hybrid films. The silica content in the hybrid thin films was varied from 0 to 30 wt%. Experimental results showed the aggregation of silica particles in the hybrid films. Thus, the silica domain in the hybrid films was varied from 30 to 50 nm by the different ratios of MSMAsilica to WPU-AC. The prepared hybrid films from the crosslinked WPU-AC/MSMA-silica showed much better thermal stability and mechanical properties than pure WPU-AC.

  16. Facile preparation of monodisperse, impurity-free, and antioxidation copper nanoparticles on a large scale for application in conductive ink.

    Science.gov (United States)

    Zhang, Yu; Zhu, Pengli; Li, Gang; Zhao, Tao; Fu, Xianzhu; Sun, Rong; Zhou, Feng; Wong, Ching-ping

    2014-01-08

    Monodisperse copper nanoparticles with high purity and antioxidation properties are synthesized quickly (only 5 min) on a large scale (multigram amounts) by a modified polyol process using slightly soluble Cu(OH)2 as the precursor, L-ascorbic acid as the reductant, and PEG-2000 as the protectant. The resulting copper nanoparticles have a size distribution of 135 ± 30 nm and do not suffer significant oxidation even after being stored for 30 days under ambient conditions. The copper nanoparticles can be well-dispersed in an oil-based ink, which can be silk-screen printed onto flexible substrates and then converted into conductive patterns after heat treatment. An optimal electrical resistivity of 15.8 μΩ cm is achieved, which is only 10 times larger than that of bulk copper. The synthesized copper nanoparticles could be considered as a cheap and effective material for printed electronics.

  17. Synthesis of monodisperse nimesulide nanoparticles in microemulsions E170/isopropyl myristate/water/n-butanol (or isopropanol).

    Science.gov (United States)

    Debuigne, F; Cuisenaire, J; Jeunieau, L; Masereel, B; Nagy, J B

    2000-01-01

    Nanoparticles of nimesulide have been synthesized in two systems of microemulsion: E170/isopropyl myristate/water/n-butanol (or isopropanol). Nanoparticles are monodisperse. In the two microemulsions, the size of the nanoparticles is comprised between 45 and 60 A and also seems to be independent of the factor R ([water]/[E170]) and of the concentration of the nimesulide solubilized in chloroform. The constancy of the size suggests that the size is controlled by thermodynamic stabilization of the nanoparticles with the surfactant. The nature of the cosurfactant does not have an obvious influence on the nanoparticle size. The nanoparticles are instantaneously formed and stay stable during a long period of time (several months).

  18. One-pot synthesis of graphene-supported monodisperse Pd nanoparticles as catalyst for formic acid electro-oxidation.

    Science.gov (United States)

    Yang, Sudong; Dong, Jing; Yao, Zhaohui; Shen, Chengmin; Shi, Xuezhao; Tian, Yuan; Lin, Shaoxiong; Zhang, Xiaogang

    2014-03-28

    To synthesize monodisperse palladium nanoparticles dispersed on reduced graphene oxide (RGO) sheets, we have developed an easy and scalable solvothermal reduction method from an organic solution system. The RGO-supported palladium nanoparticles with a diameter of 3.8 nm are synthesized in N-methyl-2-pyrrolidone (NMP) and in the presence of oleylamine and trioctylphosphine, which facilitates simultaneous reduction of graphene oxide and formation of Pd nanocrystals. So-produced Pd/RGO was tested for potential use as electrocatalyst for the electro-oxidation of formic acid. Pd/RGO catalyzes formic acid oxidation very well compared to Pd/Vulcan XC-72 catalyst. This synthesis method is a new way to prepare excellent electrocatalysts, which is of great significance in energy-related catalysis.

  19. One-Pot Synthesis of Graphene-Supported Monodisperse Pd Nanoparticles as Catalyst for Formic Acid Electro-oxidation

    Science.gov (United States)

    Yang, Sudong; Dong, Jing; Yao, Zhaohui; Shen, Chengmin; Shi, Xuezhao; Tian, Yuan; Lin, Shaoxiong; Zhang, Xiaogang

    2014-03-01

    To synthesize monodisperse palladium nanoparticles dispersed on reduced graphene oxide (RGO) sheets, we have developed an easy and scalable solvothermal reduction method from an organic solution system. The RGO-supported palladium nanoparticles with a diameter of 3.8 nm are synthesized in N-methyl-2-pyrrolidone (NMP) and in the presence of oleylamine and trioctylphosphine, which facilitates simultaneous reduction of graphene oxide and formation of Pd nanocrystals. So-produced Pd/RGO was tested for potential use as electrocatalyst for the electro-oxidation of formic acid. Pd/RGO catalyzes formic acid oxidation very well compared to Pd/Vulcan XC-72 catalyst. This synthesis method is a new way to prepare excellent electrocatalysts, which is of great significance in energy-related catalysis.

  20. Controllable 5-sulfosalicylic acid assisted solvothermal synthesis of monodispersed superparamagnetic Fe3O4 nanoclusters with tunable size

    Science.gov (United States)

    Wang, Wentao; Tang, Bingtao; Wu, Suli; Gao, Zhanming; Ju, Benzhi; Teng, Xiaoxu; Zhang, Shufen

    2017-02-01

    Monodispersed Fe3O4 nanoclusters were synthesized in a one-pot solvothermal route with 5-sulfosalicylic acid (SSA) as the functional ligand in a mixed-solvent system of diethylene glycol/ethylene glycol (DEG/EG). Nucleation and aggregation growth model was responsible for the formation of secondary structure of the clusters. In the process, the size of the clusters can be effectively controlled by varying the amounts of SSA and the volume ratio of DEG/EG. The nanoclusters exhibited superparamagnetic properties with high saturation magnetization value of about 68.7 emu g-1 at room temperature. The water-soluble small-molecule SSA grafted on the surface of Fe3O4 nanocrystals rendered the superparamagnetic clusters dispersible in water, which is crucial for potential applications in biomedical fields.

  1. Highly efficient synthesis of monodisperse poly(ethylene glycols) and derivatives through macrocyclization of oligo(ethylene glycols).

    Science.gov (United States)

    Zhang, Hua; Li, Xuefei; Shi, Qiuyan; Li, Yu; Xia, Guiquan; Chen, Long; Yang, Zhigang; Jiang, Zhong-Xing

    2015-03-16

    A macrocyclic sulfate (MCS)-based approach to monodisperse poly(ethylene glycols) (M-PEGs) and their monofunctionalized derivatives has been developed. Macrocyclization of oligo(ethylene glycols) (OEGs) provides MCS (up to a 62-membered macrocycle) as versatile precursors for a range of monofunctionalized M-PEGs. Through iterative nucleophilic ring-opening reactions of MCS without performing group protection and activation, a series of M-PEGs, including the unprecedented 64-mer (2850 Da), can be readily prepared. Synthetic simplicity coupled with versatility of this new strategy may pave the way for broader applications of M-PEGs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Monodisperse and LPS-free Aggregatibacter actinomycetemcomitans leukotoxin: Interactions with human β2 integrins and erythrocytes

    DEFF Research Database (Denmark)

    Reinholdt, Jesper; Poulsen, Knud; Brinkmann, Christel Rothe

    2013-01-01

    Aggregatibacter actinomycetemcomitans is a gram-negative, facultatively anaerobic cocco-bacillus and a frequent member of the human oral flora. It produces a leukotoxin, LtxA, belonging to the repeats-in-toxin (RTX) family of bacterial cytotoxins. LtxA efficiently kills neutrophils and mononuclear...... structure. Here, we describe a protocol for the purification of LtxA from bacterial culture supernatant, which does not involve denaturing procedures. The purified LtxA was monodisperse, well folded as judged by the combined use of synchrotron radiation circular dichroism spectroscopy (SRCD) and in silico...... prediction of the secondary structure content, and free of bacterial lipopolysaccharide. The analysis by SRCD and similarity to a lipase from Pseudomonas with a known three dimensional structure supports the presence of a so-called beta-ladder domain in the C-terminal part of LtxA. LtxA rapidly killed K562...

  3. H2/D2 exchange reaction on mono-disperse Pt clusters: enhanced activity from minute O2 concentrations

    DEFF Research Database (Denmark)

    Riedel, Jakob Nordheim; Rötzer, Marian David; Jørgensen, Mikkel;

    2016-01-01

    The H2/D2 exchange reaction was studied on mono-disperse Pt8 clusters in a μ-reactor. The chemical activity was studied at temperatures varying from room temperature to 180 °C using mass spectrometry. It was found that minute amounts of O2 in the gas stream increased the chemical activity...... significantly. XPS and ISS before and after reaction suggest little or no sintering during reaction. A reaction pathway is suggested based on DFT. H2 desorption is identified as the rate-limiting step and O2 is confirmed as the source of the increased activity. The binding energy of platinum atoms in a SiO2...... supported Pt8 cluster is found to be comparable to the interatomic binding energies of bulk platinum, underlining the stability of the model system....

  4. Preparation and sonocatalytic activity of monodisperse porous bread-like CuO via thermal decomposition of copper oxalate precursors

    Science.gov (United States)

    Zhang, Lihui; Liu, Rong; Yang, Heqing

    2012-04-01

    Porous bread-like CuO have been obtained via the thermal decomposition of copper oxalate precursor synthesized by the room temperature reaction of Cu(NO3)2 with Na2C2O4 in water. These bread-like CuO with the monoclinic structure are well dispersed with good monodispersity, their diameters are about 1.5 μm. The sonocatalytic activity of porous CuO for the degradation of acid scarlet dye was studied. It was found that the as-prepared porous CuO nanostructures exhibit efficient sonocatalytic ability for the degradation of acid scarlet dye in the presence of H2O2, which are expected to be useful in the treatment of non- or low-transparent wastewaters.

  5. Self-assembly of monodisperse polymer microspheres from PPQ-b-PEG rod-coil block copolymers in selective solvents

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xueao; CHEN Ke; XIE Kai; LONG Yongfu

    2005-01-01

    Poly(phenylquinoline)-block-poly(ethylene glycol)(PPQ-b-PEG) rod-coil block copolymers possess the self-assembly behavior in selective solvents. The copolymers in the mixed solvents of V(trifluoroacetic acid, TFA):V(dichloromethane, DCM)=1:1 can self-assemble into polymer hollow microspheres with diameters of a few micrometers. The polymer hollow microspheres are monodisperse, and the diameters of them increase with an increased polymerization degree of the PPQ rigid-rod block. The solution concentration has no effect on the microsphere diameter, but spherical surface shows burrs when the solution concentration is too low. It has been found that the obtained dilute solution has the strongest absorption peak at 376 nm and strongest emission peak at 604 nm by the spectroscopy analysis.

  6. Synthesis and Magnetic Properties of Nearly Monodisperse CoFe2O4Nanoparticles Through a Simple Hydrothermal Condition

    Directory of Open Access Journals (Sweden)

    Li Xing-Hua

    2010-01-01

    Full Text Available Abstract Nearly monodisperse cobalt ferrite (CoFe2O4 nanoparticles without any size-selection process have been prepared through an alluring method in an oleylamine/ethanol/water system. Well-defined nanospheres with an average size of 5.5 nm have been synthesized using metal chloride as the law materials and oleic amine as the capping agent, through a general liquid–solid-solution (LSS process. Magnetic measurement indicates that the particles exhibit a very high coercivity at 10 K and perform superparamagnetism at room temperature which is further illuminated by ZFC/FC curves. These superparamagnetic cobalt ferrite nanomaterials are considered to have potential application in the fields of biomedicine. The synthesis method is possible to be a general approach for the preparation of other pure binary and ternary compounds.

  7. Simulation study of electric-guided delivery of 0.4µm monodisperse and polydisperse aerosols to the ostiomeatal complex.

    Science.gov (United States)

    Xi, Jinxiang; Yuan, Jiayao Eddie; Si, Xiuhua April

    2016-05-01

    Despite the high prevalence of rhinosinusitis, current inhalation therapy shows limited efficacy due to extremely low drug delivery efficiency to the paranasal sinuses. Novel intranasal delivery systems are needed to enhance targeted delivery to the sinus with therapeutic dosages. An optimization framework for intranasal drug delivery was developed to target polydisperse charged aerosols to the ostiomeatal complex (OMC) with electric guidance. The delivery efficiency of a group of charged aerosols recently reported in the literature was numerically assessed and optimized in an anatomically accurate nose-sinus model. Key design variables included particle charge number, particle size and distribution, electrode strength, and inhalation velocity. Both monodisperse and polydisperse aerosol profiles were considered. Results showed that the OMC delivery efficiency was highly sensitive to the applied electric field and electrostatic charges carried by the particles. Through the synthesis of electric-guidance and point drug release, focused deposition with significantly enhanced dosage in the OMC can be achieved. For 0.4 µm charged aerosols, an OMC delivery efficiency of 51.6% was predicted for monodisperse aerosols and 34.4% for polydisperse aerosols. This difference suggested that the aerosol profile exerted a notable effect on intranasal deliveries. Sensitivity analysis indicated that the OMC deposition fraction was highly sensitive to the charge and size of particles and was less sensitive to the inhalation velocity considered in this study. Experimental studies are needed to validate the numerically optimized designs. Further studies are warranted to investigate the targeted OMC delivery with both electric and acoustics controls, the latter of which has the potential to further deliver the drug particles into the sinus cavity.

  8. Synthesis of monodispersed ZnAl{sub 2}O{sub 4} nanoparticles and their tribology properties as lubricant additives

    Energy Technology Data Exchange (ETDEWEB)

    Song, Xiaoyun; Zheng, Shaohua; Zhang, Jun; Li, Wei; Chen, Qiang [Key Laboratory of Inorganic Functional Materials in Universities of Shandong, School of Material Science and Engineering, University of Jinan, Jinan 250022 (China); Cao, Bingqiang, E-mail: mse_caobq@ujn.edu.cn [Key Laboratory of Inorganic Functional Materials in Universities of Shandong, School of Material Science and Engineering, University of Jinan, Jinan 250022 (China)

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► The preparation of ZnAl{sub 2}O{sub 4} nanoparticles was realized by hydrothermal method. ► After surface modification, ZnAl{sub 2}O{sub 4} nanoparticles of narrow size distribution can disperse in lubricating oil stably. ► The modified ZnAl{sub 2}O{sub 4} nanoparticles as lubricating oil additives exhibit good tribology properties. -- Abstract: Monodispersed spherical zinc aluminate spinel (ZnAl{sub 2}O{sub 4}) nanoparticles were synthesized via a solvothermal method and modified by oleic acid in cyclohexanol solution. The nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and infrared spectrum (IR). The dispersion ability of nanoparticles in lubricant oil was measured with optical absorbance spectrum. The results show that the modified nanoparticles are nearly monodispersed and can stably disperse in lubricant oil. The tribological properties of the ZnAl{sub 2}O{sub 4} nanoparticles as an additive in lubricant oil were evaluated with four-ball test and thrust-ring test. For comparison, ZnO and Al{sub 2}O{sub 3} nanoparticles as additive in lubricant oil were also tested respectively. The results show that ZnAl{sub 2}O{sub 4} nanoparticles exhibit better tribology properties in terms of anti-wear and anti-friction than ZnO or Al{sub 2}O{sub 3} nanoparticles. The anti-friction and anti-wear mechanisms were discussed and the lubricating effect of ZnAl{sub 2}O{sub 4} nanoparticles can be attributed to nano-bearings effect and tribo-sintering mechanism.

  9. Facile preparation and visible light photocatalytic activity of CdIn{sub 2}S{sub 4} monodispersed spherical particles

    Energy Technology Data Exchange (ETDEWEB)

    Mu Jin, E-mail: mujin@sit.edu.cn [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China); Wei Qinglian; Yao Pingping; Zhao Xueling [School of Chemistry and Molecular Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China); Kang Shizhao; Li Xiangqing [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China)

    2012-02-05

    Highlights: Black-Right-Pointing-Pointer CdIn{sub 2}S{sub 4} monodispersed spherical particles were prepared by a soft solution method. Black-Right-Pointing-Pointer Mercaptoacetic acid was used as capping agent to hinder the fast crystal growth. Black-Right-Pointing-Pointer Thioacetamide as sulfur source resulted in the slow growth of particles. Black-Right-Pointing-Pointer CdIn{sub 2}S{sub 4} spheres showed high visible light photocatalytic activity. - Abstract: We developed a facile method to prepare CdIn{sub 2}S{sub 4} monodispersed spherical particles by using mercaptoacetic acid as capping agent and thioacetamide as sulfur source. The results indicated that the size and morphology of CdIn{sub 2}S{sub 4} particles were related to reaction time. The CdIn{sub 2}S{sub 4} spherical particles with an average size of about 236 nm and a narrow size distribution were formed after reacting for 7 h. The photocatalytic activity of as-synthesized CdIn{sub 2}S{sub 4} spherical particles was evaluated by the photocatalytic degradation of methyl orange under visible light illumination. The results showed that the photocatalytic activity increased with prolonging reaction time in the preparation of CdIn{sub 2}S{sub 4} spherical particles. The CdIn{sub 2}S{sub 4} spherical particles prepared after reacting for 7 h exhibited a 98% degradation efficiency of methyl orange after 15 min visible light irradiation.

  10. Rapid Synthesis of Highly Monodisperse Au x Ag 1− x Alloy Nanoparticles via a Half-Seeding Approach

    KAUST Repository

    Chng, Ting Ting

    2011-05-03

    Gold-silver alloy AuxAg1-x is an important class of functional materials promising new applications across a wide array of technological fields. In this paper, we report a fast and facile synthetic protocol for preparation of highly monodisperse AuxAg1-x alloy nanoparticles in the size range of 3-6 nm. The precursors employed in this work are M(I)-alkanethiolates (M = Au and Ag), which can be easily prepared by mixing common chemicals such as HAuCl4 or AgNO3 with alkanethiols at room temperature. In this half-seeding approach, one of the M(I)-alkanethiolates is first heated and reduced in oleylamine solvent, and freshly formed metal clusters will then act as premature seeds on which both the first and second metals (from M(I)-alkanethiolates, M = Au and Ag) can grow accordingly without additional nucleation and thus achieve high monodispersity for product alloy nanoparticles. Unlike in other prevailing methods, both Au and Ag elements present in these solid precursors are in the same monovalent state and have identical supramolecular structures, which may lead to a more homogeneous reduction and complete interdiffusion at elevated reaction temperatures. When the M(I)-alkanethiolates are reduced to metallic forms, the detached alkanethiolate ligands will serve as capping agent to control the growth. More importantly, composition, particle size, and optical properties of AuxAg1-x alloy nanoparticles can be conveniently tuned with this approach. The optical limiting properties of the prepared particles have also been investigated at 532 and 1064 nm using 7 ns laser pulses, which reveals that the as-prepared alloy nanoparticles exhibit outstanding broadband optical limiting properties with low thresholds. © 2011 American Chemical Society.

  11. Metal Fe{sup 3+} ions assisted synthesis of highly monodisperse Ag/SiO{sub 2} nanohybrids and their antibacterial activity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Nianchun; Xue, Feng [College of Material Science and Engineering, South China University of Technology, Guangzhou 510641 (China); Yu, Xiang [Analytical and Testing Center, Jinan University, Guangzhou 510632 (China); Zhou, Huihua [Guangdong East Sunshine Pharmaceutical Co., Ltd., Dongguan 523871 (China); Ding, Enyong, E-mail: eyding@scut.edu.cn [College of Material Science and Engineering, South China University of Technology, Guangzhou 510641 (China)

    2013-02-15

    Graphical abstract: TEM images of the Ag/SiO{sub 2}-2 nanohybrids. The homogeneous and more mono-disperse Ag nanoparticles deposit on SiO{sub 2} spheres. Through this method, Ag nanoparticles are easily formed on the surface of SiO{sub 2} compared to other methods. Highlights: Black-Right-Pointing-Pointer We prepared homogeneous and mono-dispersed Ag/SiO{sub 2}-2 nanohybrids by adding Fe{sup 3+} ions. Black-Right-Pointing-Pointer The Ag/SiO{sub 2}-2 nanohybrids had core(SiO{sub 2})-shell(Ag) structure. Black-Right-Pointing-Pointer The Ag/SiO{sub 2}-2 nanohybrids exhibited excellent antibacterial activity against bacteria. Black-Right-Pointing-Pointer The reaction temperature was lower and the yield of Ag/SiO{sub 2}-2 nanohybrids were higher. - Abstract: Highly monodispersed Ag/SiO{sub 2} nanohybrids with excellent antibacterial property were synthesized by using DMF as a reducing agent and employing an additional redox potential of metal Fe{sup 3+} ion as a catalytic agent. The obtained Ag/SiO{sub 2}-2 nanohybrids of about 240 nm were highly monodispersity and uniformity by adding trace Fe{sup 3+} ions into the reaction which Ag{sup +} reacted with N,N-dimethyl formamide (DMF) at 70 Degree-Sign C. Compared to the conventional techniques, which need long time and high temperature for silica coating of Ag nanoparticles, this new method was capable of synthesizing monodispersed, uniform, high yield Ag/SiO{sub 2} nanohybrids. The electron was transferred from the Fe{sup 2+} ion to the Ag{sup +} ion to accelerate the nucleation of silver nanoparticles. The chemical structures, morphologies and properties of the Ag/SiO{sub 2} nanohybrids were characterized by X-ray diffraction (XRD), (High-resolution, Scanning transmission) transmission electron microscopy (TEM, HRTEM and STEM), and X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy (UV-vis) and test of antibacterial. The results demonstrated that the silver nanoparticles supported on the surface of Si

  12. Final Report for Fractionation and Separation of Polydisperse Nanoparticles into Distinct Monodisperse Fractions Using CO2 Expanded Liquids

    Energy Technology Data Exchange (ETDEWEB)

    Chistopher Roberts

    2007-08-31

    The overall objective of this project was to facilitate efficient fractionation and separation of polydisperse metal nanoparticle populations into distinct monodisperse fractions using the tunable solvent properties of gas expanded liquids. Specifically, the dispersibility of ligand-stabilized nanoparticles in an organic solution was controlled by altering the ligand-solvent interaction (solvation) by the addition of carbon dioxide (CO{sub 2}) gas as an antisolvent (thereby tailoring the bulk solvent strength) in a custom high pressure apparatus developed in our lab. This was accomplished by adjusting the CO{sub 2} pressure over the liquid dispersion, resulting in a simple means of tuning the nanoparticle precipitation by size. Overall, this work utilized the highly tunable solvent properties of organic/CO{sub 2} solvent mixtures to selectively size-separate dispersions of polydisperse nanoparticles (ranging from 1 to 20 nm in size) into monodisperse fractions ({+-}1nm). Specifically, three primary tasks were performed to meet the overall objective. Task 1 involved the investigation of the effects of various operating parameters (such as temperature, pressure, ligand length and ligand type) on the efficiency of separation and fractionation of Ag nanoparticles. In addition, a thermodynamic interaction energy model was developed to predict the dispersibility of different sized nanoparticles in the gas expanded liquids at various conditions. Task 2 involved the extension of the experimental procedures identified in task 1 to the separation of other metal particles used in catalysis such as Au as well as other materials such as semiconductor particles (e.g. CdSe). Task 3 involved using the optimal conditions identified in tasks 1 and 2 to scale up the process to handle sample sizes of greater than 1 g. An experimental system was designed to allow nanoparticles of increasingly smaller sizes to be precipitated sequentially in a vertical series of high pressure vessels by

  13. Chemical template-assisted synthesis of monodisperse rattle-type Fe3O4@C hollow microspheres as drug carrier.

    Science.gov (United States)

    Cheng, Lin; Ruan, Weimin; Zou, Bingfang; Liu, Yuanyuan; Wang, Yongqiang

    2017-08-01

    A chemical template strategy was put forward to synthesize monodisperse rattle-type magnetic carbon (Fe3O4@C) hollow microspheres. During the synthesis procedure, monodisperse Fe2O3 microspheres were used as chemical template, which released Fe(3+) ions in acidic solution and initiated the in-situ polymerization of pyrrole into polypyrrole (PPy) shell. With the continual acidic etching of Fe2O3 microspheres, rattle-type Fe2O3@PPy microspheres were generated with the cavity appearing between the PPy shell and left Fe2O3 core, which were then transformed into Fe3O4@C hollow microspheres through calcination in nitrogen atmosphere. Compared with traditional physical template, the shell and cavity of rattle-type hollow microspheres were generated in one step using the chemical template method, which obviously saved the complex procedures including the coating and removal of middle shells. The experimental results exhibited that the rattle-type Fe3O4@C hollow microspheres with different parameters could be regulated through controlled synthesis of the intermediate Fe2O3@PPy product. Moreover, when the rattle-type Fe3O4@C hollow microspheres were investigated as drug carrier, they manifested sustained-release behaviour of doxorubicin, justifying their promising applications as carriers in drug delivery. The aim of the present study was first to synthesize rattle-type Fe3O4@C hollow microspheres through a simple synthesis method as a drug carrier. Here a chemical template synthesis of rattle-type hollow microspheres was developed, which saved the complex procedures including the coating and removal of middle shells in traditional physical template. Second, all the influence factors in the reaction processes were systematically investigated to obtain rattle-type Fe3O4@C hollow microspheres with controlled parameters. Third, the rattle-type Fe3O4@C hollow microspheres were studied as drug carriers and the influences of their structural parameters on drug loading and

  14. Facile synthesis of monodisperse functional magnetic dialdehyde starch nano-composite and used for highly effective recovery of Hg(II).

    Science.gov (United States)

    Wang, Yang; Zhang, Yun; Hou, Chen; Qi, Zhigang; He, Xinghua; Li, Yanfeng

    2015-12-01

    By covalently linking dialdehyde starch and amine functionalized Fe3O4 nanoparticle, and modifying with aminothiourea functional group, the novel monodisperse nano-composite has been successfully synthesized without any toxic crosslinking agent. The resulting nano-composite was characterized by means of the Fourier transform infrared spectra (FT-IR), transmission electron microscope (TEM), X-ray diffraction (XRD), elemental analysis and vibrating sample magnetometer (VSM). As the new kind of low-cost and environmentally friendly adsorbent with the excellent monodispersity in aqueous phase, the obtained nano-composite has shown not only the good adsorption capacity for Hg(II) on high initial concentration, but also the strong removal ability on low concentration. Moreover, the unique selectivity for Hg(II) among the mixed metal ions solution and good regeneration performance of nano-composite has also been demonstrated by batch experiments.

  15. STUDY ON THE FORMATION MECHANISM OF MONODISPERSE PARTICLES IN THE EMULSIFIER-FREE EMULSION POLYMERIZATION OF METHYL METHACRYLATE AND BUTYL ACRYLATE

    Institute of Scientific and Technical Information of China (English)

    Hong-quan Xie; Gui-ying Liao; Yu Gao

    2003-01-01

    The formation mechanism of monodisperse polymer latex particles in the emulsifier-free emulsion polymerization of methyl methacrylate and butyl acrylate with potassium persulfate as initiator was investigated. A multi-step formation mechanism for the monodisperse polymer particles was proposed. The nucleation mechanism is considered to be the coagulation of the precursor particles by homogeneous nucleation when the primary particles reach a critical size with high surface charge density and sufficient stability. It had been proved by a special experiment that the early latex particles formed by the coagulation were stable. The primary particles grow by absorbing monomers and radicals in the polymerization system and then become colloidally unstable again due to the understandable decrease of particle surface charge density, which leads to the aggregation of the growing particles and the formation of larger latex particles therefrom. After the nucleation period,the preferential aggregation of the smaller particles in the propagation process leads to the change of the particles towards a uniform size and narrower particle size distribution. The coexistence and competition of homogeneous nucleation,coagulation, propagation and aggregation result in the increase of the polydispersity index (U = D43/D10) in the first stage,then its decrease in the later stage because of the competition of propagation and aggregation, and the gradual formation of the monodisperse particles.

  16. Synthesis of Monodisperse Poly(glycidylmethacrylate-co-ethylene dimethacrylate) Beads and Their Application in Separation of Biopolymers

    Institute of Scientific and Technical Information of China (English)

    GONG, Bo-Lin(龚波林); KE, Cong-Yu(柯从玉); GENG, Xin-Du(耿信笃)

    2004-01-01

    The monodisperse poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads with macroporous in the range of 8.0-12.0 μm were prepared by a single-step swelling and polymerization method. The seed particles prepared by dispersion polymerization exhibited good absorption of the monomer phase. The pore size distribution of the beads was evaluated by gel permeation chromatography and mercury intrusion method. By using this media, a weak cation exchange (WCX) stationary phase for HPLC was synthesized by a new chemical modification method. The prepared resin has advantages of biopolymer separation, high column efficiency, low column backpressure, high protein mass recovery and good resolution for proteins. The measured bioactivity recovery for lysozyme was (96±5)%. The dynamic protein loading capacity of the synthesized WCX packings was 21.3 mg/g. Five proteins were completely separated in 8.0 min using the synthesized WCX stationary phase. The experimental results show that the obtained WCX resin has very weak hydrophobicity. The WCX resin was also used for the rapid separation and purification of lysozyme from egg white in 8 min with only one step . The purity and specific bioactivity of the purified lysozyme was found more than 92.0% and 70184 U/mg, respectively.

  17. Preparation of Immobilized Metal Affinity Chromatographic Packings Based on Monodisperse Hydrophilic Non-porous Beads and Their Application

    Institute of Scientific and Technical Information of China (English)

    BO Chun-Miao; GONG Bo-Lin; HU Wen-Zhi

    2008-01-01

    Three hydrophilic immobilized metal affinity chromatographic packings for HPLC have been synthesized by chemical modification of 3.0 μm monodisperse non-porous poly(glycidyl methacrylate-co-ethylenedimethacrylate)(PGMMEDMA)beads.The retention behavior of proteins on the metal ion chelated columns loaded with copper(Ⅱ),nickel(Ⅱ)and zin(Ⅱ)ion was studied.The effect of pH on the protein retention Was investigated on both the naked and metal ion chelated columns in the range from 4.0 to 9.0.Four proteins were quickly separated in 3.0 min with linear gradient elution at a flow rate of 3.0 mL/min by using the synthesized Ni2+ -IDA(iminodiacetic acid)packings.The separation time was shorter than other immobilized metal affinity chromatography reported in the literature.Purification of lysozyme from egg white and trypsin on the commercially available trypsin was performed on the naked-IDA and Cu2+ -IDA columns,respectively.The purities of the purified trypsin and lysozyme were more than 92%and 95%,respectively.

  18. A posteriori determination of the useful data range for small-angle scattering experiments on dilute monodisperse systems.

    Science.gov (United States)

    Konarev, Petr V; Svergun, Dmitri I

    2015-05-01

    Small-angle X-ray and neutron scattering (SAXS and SANS) experiments on solutions provide rapidly decaying scattering curves, often with a poor signal-to-noise ratio, especially at higher angles. On modern instruments, the noise is partially compensated for by oversampling, thanks to the fact that the angular increment in the data is small compared with that needed to describe adequately the local behaviour and features of the scattering curve. Given a (noisy) experimental data set, an important question arises as to which part of the data still contains useful information and should be taken into account for the interpretation and model building. Here, it is demonstrated that, for monodisperse systems, the useful experimental data range is defined by the number of meaningful Shannon channels that can be determined from the data set. An algorithm to determine this number and thus the data range is developed, and it is tested on a number of simulated data sets with various noise levels and with different degrees of oversampling, corresponding to typical SAXS/SANS experiments. The method is implemented in a computer program and examples of its application to analyse the experimental data recorded under various conditions are presented. The program can be employed to discard experimental data containing no useful information in automated pipelines, in modelling procedures, and for data deposition or publication. The software is freely accessible to academic users.

  19. Rapid synthesis of monodispersed highly porous spinel nickel cobaltite (NiCo2O4) electrode material for supercapacitors

    Science.gov (United States)

    Naveen, A. Nirmalesh; Selladurai, S.

    2015-06-01

    Monodispersed highly porous spinel nickel cobaltite electrode material was successfully synthesized in a short time using combustion technique. Single phase cubic nature of the spinel nickel cobaltite with average crystallite size of 24 nm was determined from X-ray diffraction study. Functional groups present in the compound were determined from FTIR study and it further confirms the spinel formation. FESEM images reveal the porous nature of the prepared material and uniform size distribution of the particles. Electrochemical evaluation was performed using Cyclic Voltammetry (CV) technique, Chronopotentiometry (CP) and Electrochemical Impedance Spectroscopy (EIS). Results reveal the typical pseudocapacitive behaviour of the material. Maximum capacitance of 754 F/g was calculated at the scan rate of 5 mV/s, high capacitance was due to the unique porous morphology of the electrode. Nyquist plot depicts the low resistance and good electrical conductivity of nickel cobaltite. It has been found that nickel cobaltite prepared by this typical method will be a potential electrode material for supercapcitor application.

  20. Upconversion Nanoparticles and Monodispersed Magnetic Polystyrene Microsphere Based Fluorescence Immunoassay for the Detection of Sulfaquinoxaline in Animal-Derived Foods.

    Science.gov (United States)

    Hu, Gaoshuang; Sheng, Wei; Zhang, Yan; Wang, Junping; Wu, Xuening; Wang, Shuo

    2016-05-18

    A novel fluorescence immunoassay for detecting sulfaquinoxaline (SQX) in animal-derived foods was developed using NaYF4:Yb/Tm upconversion nanoparticles (UCNPs) conjugated with antibodies as fluorescence signal probes, and monodisperse magnetic polystyrene microspheres (MMPMs) modified with coating antigen as immune-sensing capture probes for trapping and separating the signal probes. Based on a competitive immunoassay format, the detection limit of the proposed method for detecting SQX was 0.1 μg L(-1) in buffer and 0.5 μg kg(-1) in food samples. The recoveries of SQX in spiked samples ranged from 69.80 to 133.00%, with coefficients of variation of 0.24-25.06%. The extraction procedure was fast, simple, and environmentally friendly, requiring no organic solvents. In particular, milk samples can be analyzed directly after simple dilution. This method has appealing properties, such as sensitive fluorescence response, a simple and fast extraction procedure, and environmental friendliness, and could be applied to detecting SQX in animal-derived foods.

  1. A facile one-pot synthesis and enhanced formic acid oxidation of monodisperse Pd-Cu nanocatalysts.

    Science.gov (United States)

    Park, Kyu-Hwan; Lee, Young Wook; Kang, Shin Wook; Han, Sang Woo

    2011-06-06

    Highly monodisperse spherical 3 nm Pd-Cu alloy nanoparticles (NPs) were synthesized in high yield through the coreduction of [Pd(acac)(2)] (acac=acetylacetonate) and [Cu(acac)(2)] in nonhydrolytic solutions by using trioctylamine and oleic acid. The relative compositions of Pd and Cu could be tuned by controlling the molar ratios between the metal precursors in the raw solutions. The carbon-supported Pd-Cu NPs (Pd-Cu/C) were chemically dealloyed by acetic acid washing, which resulted in the formation of porous structures. The prepared Pd-Cu/C catalysts exhibited at least threefold enhancement of Pd mass activities compared with a commercial Pd/C catalyst toward formic acid oxidation in an acidic medium, and also showed outstanding electrocatalytic stabilities. The improved electrocatalytic properties of the Pd-Cu NPs are attributed to the presence of a large number of active sites on their surfaces owing to their small particle sizes and chemically dealloyed porous structures. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Monodisperse Pt atoms anchored on N-doped graphene as efficient catalysts for CO oxidation: A first-principles investigation

    KAUST Repository

    Liu, Xin

    2015-01-01

    We performed first-principles based calculations to investigate the electronic structure and the potential catalytic performance of Pt atoms monodispersed on N-doped graphene in CO oxidation. We showed that N-doping can introduce localized defect states in the vicinity of the Fermi level of graphene which will effectively stabilize the deposited Pt atoms. The binding energy of a single Pt atom onto a stable cluster of 3 pyridinic N (PtN3) is up to -4.47 eV, making the diffusion and aggregation of anchored Pt atoms difficult. Both the reaction thermodynamics and kinetics suggest that CO oxidation over PtN3 would proceed through the Langmuir-Hinshelwood mechanism. The reaction barriers for the formation and dissociation of the peroxide-like intermediate are determined to be as low as 0.01 and 0.08 eV, respectively, while that for the regeneration is only 0.15 eV, proving the potential high catalytic performance of PtN3 in CO oxidation, especially at low temperatures. The Pt-d states that are up-shifted by the Pt-N interaction account for the enhanced activation of O2 and the efficient formation and dissociation of the peroxide-like intermediate.

  3. Influence of Particle Size on Reaction Selectivity in Cyclohexene Hydrogenation and Dehydrogenation over Silica-Supported Monodisperse Pt Particles

    Energy Technology Data Exchange (ETDEWEB)

    Rioux, R. M.; Hsu, B. B.; Grass, M. E.; Song, H.; Somorjai, Gabor A.

    2008-07-11

    The role of particle size during the hydrogenation/dehydrogenation of cyclohexene (10 Torr C{sub 6}H{sub 10}, 200-600 Torr H{sub 2}, and 273-650 K) was studied over a series of monodisperse Pt/SBA-15 catalysts. The conversion of cyclohexene in the presence of excess H{sub 2} (H{sub 2}:C{sub 6}H{sub 10} ratio = 20-60) is characterized by three regimes: hydrogenation of cyclohexene to cyclohexane at low temperature (< 423 K), an intermediate temperature range in which both hydrogenation and dehydrogenation occur; and a high temperature regime in which the dehydrogenation of cyclohexene dominates (> 573 K). The rate of both reactions demonstrated maxima with temperature, regardless of Pt particle size. For the hydrogenation of cyclohexene, a non-Arrhenius temperature dependence (apparent negative activation energy) was observed. Hydrogenation is structure insensitive at low temperatures, and apparently structure sensitive in the non-Arrhenius regime; the origin of the particle-size dependent reactivity with temperature is attributed to a change in the coverage of reactive hydrogen. Small particles were more active for dehydrogenation and had lower apparent activation energies than large particles. The selectivity can be controlled by changing the particle size, which is attributed to the structure sensitivity of both reactions in the temperature regime where hydrogenation and dehydrogenation are catalyzed simultaneously.

  4. Synthesis and application of monodisperse oligo(oxyethylene)-grafted polystyrene resins for solid-phase organic synthesis.

    Science.gov (United States)

    Lumpi, Daniel; Braunshier, Christian; Horkel, Ernst; Hametner, Christian; Fröhlich, Johannes

    2014-07-14

    In a preliminary investigation by our group, we found that poly(styrene-oxyethylene) graft copolymers (PS-PEG), for example, TentaGel resins, are advantageous for gel-phase (13)C NMR spectroscopy. Because of the solution-like environment provided by the PS-PEG resins, good spectral quality of the attached moiety can be achieved, which is useful for nondestructive on-resin analysis. The general drawbacks of such resins are low loading capacities and the intense signal in the spectra resulting from the PEG linker (>50 units). Here, we describe the characterization of solvent-dependent swelling and reaction kinetics on a new type of resin for solid-phase organic synthesis (SPOS) that allows an accurate monitoring by gel-phase NMR without the above disadvantages. A series of polystyrene-oligo(oxyethylene) graft copolymers containing monodisperse PEG units (n = 2-12) was synthesized. A strong correlation between the linker (PEG) length and the line widths in the (13)C gel-phase spectra was observed, with a grafted PEG chain of 8 units giving similar results in terms of reactivity and gel-phase NMR monitoring to TentaGel resin. Multistep on-resin reaction sequences were performed to prove the applicability of the resins in solid-phase organic synthesis.

  5. Producing monodisperse drug-loaded polymer microspheres via cross-flow membrane emulsification: the effects of polymers and surfactants.

    Science.gov (United States)

    Meyer, Robert F; Rogers, W Benjamin; McClendon, Mark T; Crocker, John C

    2010-09-21

    Cross-flow membrane emulsification (XME) is a method for producing highly uniform droplets by forcing a fluid through a small orifice into a transverse flow of a second, immiscible fluid. We investigate the feasibility of using XME to produce monodisperse solid microspheres made of a hydrolyzable polymer and a hydrophobic drug, a model system for depot drug delivery applications. This entails the emulsification of a drug and polymer-loaded volatile solvent into water followed by evaporation of the solvent. We use a unique side-view visualization technique to observe the details of emulsion droplet production, providing direct information regarding droplet size, dripping frequency, wetting of the membrane surface by the two phases, neck thinning during droplet break off, and droplet deformation before and after break off. To probe the effects that dissolved polymers, surfactants, and dynamic interfacial tension may have on droplet production, we compare our results to a polymer and surfactant-free fluid system with closely matched physical properties. Comparing the two systems, we find little difference in the variation of particle size as a function of continuous phase flow rate. In contrast, at low dripping frequencies, dynamic interfacial tension causes the particle size to vary significantly with drip frequency, which is not seen in simple fluids. No effects due to shear thinning or fluid elasticity are detected. Overall, we find no significant impediments to the application of XME to forming highly uniform drug-loaded microspheres.

  6. CO ppb sensors based on monodispersed SnOx:Pd mixed nanoparticle layers: Insight into dual conductance response

    Science.gov (United States)

    Aruna, I.; Kruis, F. E.; Kundu, S.; Muhler, M.; Theissmann, R.; Spasova, M.

    2009-03-01

    This study reports the modifications in CO sensing of SnOx nanoparticle layers by utilizing monodispersed Pd nanoparticles. The distinct advantage of monosized particles and contaminant-free samples with open porosity in addition to size effects resulted in improved CO sensing with decrease in Pd nanoparticle size to 5 nm, decreasing the lowest detection levels of CO using SnOx-based sensor technology down to 10 ppb (parts per billion) in dry synthetic air. The homogeneously mixed nanoparticle layers also exhibit discrimination capability between CO and ethanol in dry air as a manifestation of the dual conductance response. Detailed x-ray photoelectron spectroscopy studies clearly reveal "Mars-van Krevelen" as the key mechanism responsible for the observed sensing in mixed nanoparticle layers. The interfacial/surface PdO formed upon pretreatment in air is continuously "consumed" and "reformed" upon exposure, respectively, to CO and synthetic air. In contrast to the case of ethanol exposure with n-type response, the Pd aided reduction of tin oxide surface in CO ambient leads to p-type response. The sensors of the present study have a wide range of promising applications from air quality control to food and fuel industries.

  7. Frequency domain photon migration measurements of dense monodisperse charged lattices and analysis using solutions of Ornstein Zernike equations.

    Science.gov (United States)

    Dali, Sarabjyot S; Sevick-Muraca, Eva M

    2012-11-15

    Isotropic scattering coefficient measurements were made of monodisperse polystyrene lattices of two different diameters of 144 nm and 223 nm and at volume fractions ranging from 0.15 to 0.22, using frequency domain photon migration measurements at wavelengths of 660, 685, 785 and 828 nm. The isotropic scattering coefficient measurements were shown to be sensitive to the changing ionic strength (0.5-4 mM, NaCl equiv.) of the dispersions exhibiting hindered scattering owing to structure at the lowest ionic strength values. Monte Carlo simulations and numerical solution of the Ornstein Zernike equations were used to compute isotropic scattering coefficients for comparison to measured values. The interaction potential was modeled as a hard sphere Yukawa potential and the Hypernetted Chain closure was used to solve the OZ equation. Effective particle charges were found after renormalization of the bare particle charge and used to predict the isotropic scattering coefficient. The model data were found to follow similar trends as experimental measurements. The refractive index of the particles has found to be an important factor for predicting experimental isotropic scattering coefficient values. Published by Elsevier Inc.

  8. Self-Templated Stepwise Synthesis of Monodispersed Nanoscale Metalated Covalent Organic Polymers for In Vivo Bioimaging and Photothermal Therapy.

    Science.gov (United States)

    Shi, Yanshu; Deng, Xiaoran; Bao, Shouxin; Liu, Bei; Liu, Bin; Ma, Ping'an; Cheng, Ziyong; Pang, Maolin; Lin, Jun

    2017-07-10

    Size- and shape-controlled growth of nanoscale microporous organic polymers (MOPs) is a big challenge scientists are confronted with; meanwhile, rendering these materials for in vivo biomedical applications is still scarce. In this study, a monodispersed nanometalated covalent organic polymer (MCOP, M=Fe, Gd) with sizes around 120 nm was prepared by a self-templated two-step solution-phase synthesis method. The metal ions (Fe(3+) , Gd(3+) ) played important roles in generating a small particle size and in the functionalization of the products during the reaction with p-phenylenediamine (Pa). The resultant Fe-Pa complex was used as a template for the subsequent formation of MCOP following the Schiff base reaction with 1,3,5-triformylphloroglucinol (Tp). A high tumor suppression efficiency for this Pa-based COP is reported for the first time. This study demonstrates the potential use of MCOP as a photothermal agent for photothermal therapy (PTT) and also provides an alternative route to fabricate nano-sized MCOPs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Sub-6 nm monodisperse hexagonal core/shell NaGdF4 nanocrystals with enhanced upconversion photoluminescence.

    Science.gov (United States)

    Liu, Jing; Chen, Guanying; Hao, Shuwei; Yang, Chunhui

    2017-01-07

    The ability to fabricate lanthanide-doped upconversion nanocrystals (UCNCs) with tailored size and emission profile has fuelled their uses in a broad spectrum of biological applications. Yet, limited success has been met in the preparation of sub-6 nm UCNCs with efficient upconversion photoluminescence (UCPL), which enable high contrast optical bioimaging with minimized adverse biological effects entailed by size-induced rapid clearance from the body. Here, we present a simple and reproducible approach to synthesize a set of monodispersed hexagonal-phase core NaGdF4:Yb/Ln (Ln = Er, Ho, Tm) of ∼3-4 nm and core/shell NaGdF4:Yb/Ln@NaGdF4 (Ln = Er, Ho, Tm) UCNCs of ∼5-6 nm. We show that the core/shell UCNCs can be up to ∼1000 times more efficient than the corresponding core UCNCs due to the effective suppression of surface-related quenching effects for the core. The observation of prolonged PL lifetime for the core/shell than that for the core UCNCs demonstrates the role of the inert shell layer for the protection of the core. The achievement of sub-6 nm NaGdF4 UCNCs with significantly improved luminescence efficiency constitutes a solid step towards high contrast UCPL optical imaging with secured biological safety.

  10. Selective hydrogenation of Dibenzo-18-crown-6 ether over highly active monodisperse Ru/γ-Al2O3 nanocatalyst

    Directory of Open Access Journals (Sweden)

    Y.R. Suryawanshi

    2015-03-01

    Full Text Available Ru/γ-Al2O3 nanocatalyst with different metal loading was synthesized by microwave irradiated sol-vothermal technique. Synthesized nanocatalyst (4-14 nm of metal particle sizewas then successfully implemented for the hydrogenation of Dibenzocrown-18-crown-6 ether (DB18C6 at 9 MPa, 393 K tem-perature and 3.5 h. It was observed that the metallic small nanoclusters produced at 4 wt% metal con-centration exhibited higher catalytic activity and resulted 96.7% conversion with 100% selectivity to-wards cis-syn-cis-dicyclohexano-18-crown-6 ether (CSC DCH18C6. © 2015 BCREC UNDIP. All rights reservedReceived: 18th July 2014; Revised: 10th September 2014; Accepted: 10th September 2014How to Cite: Suryawanshi, Y.R., Chakraborty, M., Jauhari, S., Mukhopadhyay, S., Shenoy, K.T., Sen, D. (2015. Selective Hydrogenation of Dibenzo-18-crown-6 ether over Highly Active Monodisperse Ru/γ-Al2O3 Nanocatalyst. Bulletin of Chemical Reaction Engineering & Catalysis, 10 (1: 23-29. (doi:10.9767/bcrec.10.1.7141.23-29Permalink/DOI: http://dx.doi.org/10.9767/bcrec.10.1.7141.23-29

  11. Interfacial Fast Release Layer in Monodisperse Poly (lactic-co-glycolic acid) Microspheres Accelerates the Drug Release.

    Science.gov (United States)

    Wu, Jun; Zhao, Xiaoli; Yeung, Kelvin W K; To, Michael K T

    2016-01-01

    Understanding microstructural evolutions of drug delivery devices during drug release process is essential for revealing the drug release mechanisms and controlling the drug release profiles. In this study, monodisperse poly (lactic-co-glycolic acid) microspheres in different diameters were fabricated by microfluidics in order to find out the relationships between the microstructural evolutions and the drug release profiles. It was found that poly (lactic-co-glycolic acid) microspheres underwent significant size expansion which took place from the periphery to the center, resulting in the formation of interfacial fast release layers. At the same time, inner pores were created and the diffusion rate was increased so that the early stage drug release was accelerated. Due to the different expansion rates, small poly (lactic-co-glycolic acid) microspheres tendered to follow homogeneous drug release while large poly (lactic-co-glycolic acid) microspheres tendered to follow heterogeneous drug release. This study suggests that the size expansion and the occurrence of interfacial fast release layer were important mechanisms for early stage drug release of poly (lactic-co-glycolic acid) microspheres.

  12. Monodispersed biocompatible Ag2S nanoparticles: Facile extracellular bio-fabrication using the gamma-proteobacterium, S. oneidensis

    Energy Technology Data Exchange (ETDEWEB)

    Suresh, Anil K [ORNL; Doktycz, Mitchel John [ORNL; Wang, Wei [ORNL; Moon, Ji Won [ORNL; Gu, Baohua [ORNL; Meyer III, Harry M [ORNL; Hensley, Dale K [ORNL; Retterer, Scott T [ORNL; Allison, David P [ORNL; Phelps, Tommy Joe [ORNL; Pelletier, Dale A [ORNL

    2011-01-01

    Interest in engineered metal and semiconductor nanocrystallites continues to grow due to their unique size and or shape dependent optoelectronic, physicochemical and biological properties. Therefore identifying novel non-hazardous nanoparticle synthesis routes that address hydrophilicity, size and shape control and production costs have become a priority. In the present illustration we report for the first time the efficient generation of extracellular Ag2S nanoparticles by the metal reducing bacterium, Shewanella oneidensis. The particles are nearly monodispersed with homogeneous shape distributions and are produced under ambient temperatures and pressures at high yield, 85 % theoretical maximum. UV-vis and Fourier transform infrared spectroscopy, dynamic light scattering, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy measurements confirmed the formation, optical properties, purity, and crystallinity of the as-synthesized particles. Further characterization revealed that the particles consist of spheres in the size range of 1-22 nm, with an average size of 9 3 nm and are capped by a detachable protein/peptide surface coat. Toxicity assessments of these silver sulfide nanoparticles on Gram-negative Escherichia coli and Shewanella oneidensis and Gram-positive Bacillus subtilis bacterial systems as well as eukaryotic; mouse lung epithelial (C 10) and macrophage (RAW-264.7) cells showed that the particles were non-inhibitory or non-cytotoxic to both these systems. Our results provide a facile, eco-friendly and economical route for the fabrication of technologically important semiconducting Ag2S nanoparticles which are dispersible and biocompatible; thus providing excellent potential for their uses in optical imaging and electronic devices, and solar cell applications.

  13. Templating gold surfaces with function: a self-assembled dendritic monolayer methodology based on monodisperse polyester scaffolds.

    Science.gov (United States)

    Öberg, Kim; Ropponen, Jarmo; Kelly, Jonathan; Löwenhielm, Peter; Berglin, Mattias; Malkoch, Michael

    2013-01-01

    The antibiotic resistance developed among several pathogenic bacterial strains has spurred interest in understanding bacterial adhesion down to a molecular level. Consequently, analytical methods that rely on bioactive and multivalent sensor surfaces are sought to detect and suppress infections. To deliver functional sensor surfaces with an optimized degree of molecular packaging, we explore a library of compact and monodisperse dendritic scaffolds based on the nontoxic 2,2-bis(methylol)propionic acid (bis-MPA). A self-assembled dendritic monolayer (SADM) methodology to gold surfaces capitalizes on the design of aqueous soluble dendritic structures that bear sulfur-containing core functionalities. The nature of sulfur (either disulfide or thiol), the size of the dendritic framework (generation 1-3), the distance between the sulfur and the dendritic wedge (4 or 14 Å), and the type of functional end group (hydroxyl or mannose) were key structural elements that were identified to affect the packaging densities assembled on the surfaces. Both surface plasmon resonance (SPR) and resonance-enhanced surface impedance (RESI) experiments revealed rapid formation of homogenously covered SADMs on gold surfaces. The array of dendritic structures enabled the fabrication of functional gold surfaces displaying molecular covering densities of 0.33-2.2 molecules·nm(-2) and functional availability of 0.95-5.5 groups·nm(-2). The cell scavenging ability of these sensor surfaces for Escherichia coli MS7fim+ bacteria revealed 2.5 times enhanced recognition for G3-mannosylated surfaces when compared to G3-hydroxylated SADM surfaces. This promising methodology delivers functional gold sensor surfaces and represents a facile route for probing surface interactions between multivalently presented motifs and cells in a controlled surface setting.

  14. Numerical simulations of flows through fixed networks of monodispersed and bi-dispersed spheres, for moderate Reynolds numbers; Simulations numeriques d'ecoulements a travers des reseaux fixes de spheres monodisperses et bidisperses, pour des nombres de Reynolds moderes

    Energy Technology Data Exchange (ETDEWEB)

    Massol, A.

    2004-02-15

    The application of statistically averaged two-fluid models for the simulation of complex indus- trial two-phase flows requires the development of adequate models for the drag force exerted on the inclusions and the interfacial heat exchange. This task becomes problematic at high volume fractions of the dispersed phase. The quality of the simulation strongly depends upon the inter- facial exchange terms, starting with the steady drag force. For example, an accurate modelling of the drag force is therefore a crucial point to simulate the expansion of dense fluidized beds. Most models used to study the exchange terms between particles and fluids are based on the interaction between an isolated particle and a surrounding gas. Those models are clearly not adequate in cases where the volume fraction of particles increases and particle-particle interactions become important. Studying such cases is a complex task because of the multiple possible configurations. While the interaction between an isolated sphere and a gas depends only on the particle size and the slip velocity between gas and particles, the interaction between a cloud of particles and a gas depends on many more parameters: size and velocity distribution of particles, relative position of particles. Even if the particles keep relative fixed positions, there is an infinite number of combinations to construct such an array. The objective of the present work is to perform steady and unsteady simulations of the flow in regular arrays of fixed particles in order to analyze the influence of the size and distributions of spheres on drag force and heat transfer (the array of spheres can be either monodispersed, either bi-dispersed). Several authors have studied the drag exerted on the spheres, but only for low Reynolds numbers and/or solid volume fractions close to the packed limit. Moreover some discrepancies are observed between the different studies. On top of that, all existing studies are limited to steady flows

  15. Production and characterization of monodisperse plutonium, uranium, and mixed uranium-plutonium particles for nuclear safeguard applications.

    Science.gov (United States)

    Ranebo, Y; Niagolova, N; Erdmann, N; Eriksson, M; Tamborini, G; Betti, M

    2010-05-15

    In order to prevent nuclear proliferation, the isotopic analysis of uranium and plutonium microparticles has strengthened the means in international safeguards for detecting undeclared nuclear activities. In order to ensure accuracy and precision in the analytical methodologies used, the instrumental techniques need to be calibrated. The objective of this study was to produce and characterize particles consisting of U, Pu, and mixed U-Pu, suitable for such reliability verifications. A TSI vibrating orifice aerosol generator in connection with a furnace system was used to produce micrometer sized, monodispersed particles from reference U and Pu materials in solution. The particle masses (in the range of 3-6 pg) and sizes (approximately 1.5 microm) were controlled by the experimental conditions and the parameters for the aerosol generator. Size distributions were obtained from scanning electron microscopy, and energy-dispersive X-ray analysis confirmed that the particle composition agreed with the starting material used. A secondary ion mass spectrometer (SIMS) was used to characterize the isotopic composition of the particles. Isobaric and polyatomic interference in the SIMS spectra was identified. In order to obtain accurate estimates of the interference, a batch of Pu particles were produced of mainly (242)Pu. These were used for SIMS analysis to characterize the relative ionization of Pu and U hydride ions and to determine the SIMS useful yields of U and Pu. It was found that U had a higher propensity to form the hydride than Pu. Useful yields were determined at a mass resolution of 450 for U-Pu particles: (1.71 +/- 0.15) % for Pu and (0.72 +/- 0.06) % for U. For Pu particles: (1.65 +/- 0.14) % for Pu. This gave a relative sensitivity factor between U and Pu (RSF(U:Pu)) of 2.4 +/- 0.2. However, the RSF(U:Pu) showed large fluctuations during the sputtering time for each analyses of the mixed U-Pu particles, in the range of 1.9-3.4.

  16. Charge carrier photogeneration and recombination in ladder-type poly(para-phenylene): Interplay between impurities and external electric field

    Science.gov (United States)

    Gulbinas, V.; Hertel, D.; Yartsev, A.; Sundström, V.

    2007-12-01

    Charge carrier generation and decay in m -LPPP polymer films were examined by means of femtosecond transient absorption spectroscopy in the time window of 100fs-15ns . Two modes of polaron formation with distinct behavior were identified, impurity induced in the absence of an external electric field and electric field induced in pristine film. While field induced charge generation is relatively slow, occurring throughout the excited state lifetime, the rate of impurity induced charge generation is much faster and depends on excitation wavelength; it occurs on the several hundred femtosecond time scale under excitation within the main absorption band, but excitation into the red wing of the absorption band results in charge generation within less than 100fs . Polaron decay through geminate electron-hole recombination occurs with widely distributed lifetimes, from ˜0.8ns to microseconds; the polarons characterized by the shortest decay time have a redshifted absorption spectrum (as compared to more long-lived polarons) and are attributed to tightly bound polaron pairs.

  17. One-pot synthesis and visible light photocatalytic activity of monodispersed AgIn{sub 5}S{sub 8} microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiangqing [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China); Wang, Lei; Wei, Dailong [School of Chemistry and Molecular Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China); Kang, Shizhao [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China); Mu, Jin, E-mail: mujin@sit.edu.cn [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China)

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Monodispersed AgIn{sub 5}S{sub 8} microspheres were prepared in a one-pot process. ► The process is environmental friendly. ► The AgIn{sub 5}S{sub 8} microspheres display high photocatalytic activity. -- Abstract: Monodispersed AgIn{sub 5}S{sub 8} microspheres were synthesized using a one-pot solution method and characterized with X-ray diffraction, UV–vis diffuse reflectance spectroscopy, scanning electron microscope, energy dispersive X-ray spectroscopy and N{sub 2} adsorption–desorption isotherm. The results indicated that the AgIn{sub 5}S{sub 8} microspheres were of cubic spinel structure and the mean diameter of about 0.5 μm. In addition, the visible light photocatalytic activity of AgIn{sub 5}S{sub 8} microspheres was also investigated at room temperature. The AgIn{sub 5}S{sub 8} microspheres showed very high photocatalytic activity for the degradation of methyl orange with a degradation efficiency of about 98% under visible light irradiation for 20 min.

  18. Application of monodispersive anion exchangers in sorption and separation of y3+ from Nd3+ and Sm3+ complexes with dcta

    Institute of Scientific and Technical Information of China (English)

    Halina Hubicka; Dorota Kolody(n)ska

    2008-01-01

    Rare earth complexes with trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (DCTA) of the Ln(dcta)- ype exhibited an unusual sequence of affinity on the polystyrene anion exchangers: pm3+>Nd3+>Sm3+>pr3+>Ce3+>Eu3+>Gd3+>La3+>Sc3+>Tb3+>Dy3+>Ho3+>y3+>Er3+>Tm3+>yb3+>Lu3+[1]. Taking into account the position of Y3+, Sm3+, and Nd3+ in this affinity series, for the monodispersive polystyrene anion exchangers, Lewafit MonoPlus M 500, Lewatit MonoPlus M 600, Lewatit MonoPlus MP 500, Lewatit MonoPlus MP 64,and for the heterodispersive anion exchanger, Lewatit MP 62, the weight (Dg,) and bed (Dv) distribution coefficients of these complexes and working ion exchange capacities (Cw) were determined. Based on these values, purifications of Y3+ from Nd3+ and y3+ from Sm3+ in the macro-micro component system on these anion exchangers were studied. The application potential of this method was highlighted for the separation of yz3+ in the presence of Nd3+ and Sm3+. With 1 L of monodispersive and strongly basic polystyrene gel anion exchanger Lewatit MonoPlus M 500 in the acetate form, it is possible to obtain approximately 79 g Y2O3 purified from Nd2O3 and 70 g Y2O3 purified from Sm2O3 in the same process condition.

  19. Liquid-in-gas droplet microfluidics; experimental characterization of droplet morphology, generation frequency, and monodispersity in a flow-focusing microfluidic device

    Science.gov (United States)

    Tirandazi, Pooyan; Hidrovo, Carlos H.

    2017-07-01

    Microfluidic techniques for production of uniform droplets usually rely on the use of two immiscible liquids (e.g. water-in-oil emulsions). It has been shown recently that a continuous gas flow instead of a second liquid carrier can be used as an alternative approach in droplet microfluidics. In this work we experimentally investigate the generation of liquid water droplets within air in flow-focusing configurations. Over a wide range of flow conditions we identify six distinct flow regimes inside the microchannel: Co-flowing, Threading, Plugging, Dripping, Multi-Satellite Formation, and Jetting. Flow regimes and their transitions are plotted and characterized based on the Weber number (We) of the system. We further investigate the impact of liquid microchannel size on the flow maps. Generation frequency, morphology, and monodispersity of the droplets are characterized in more detail in the Dripping regime. Generation frequency can be related to the product of the liquid and gas flow rates. However, droplet morphology (length and width) is more dependent on the gas flow rate. We demonstrate the production of monodisperse droplets (d lab-on-a-chip systems for a variety of applications in biochemical research and material synthesis.

  20. Biogenic green synthesis of monodispersed gum kondagogu (Cochlospermum gossypium) iron nanocomposite material and its application in germination and growth of mung bean (Vigna radiata) as a plant model.

    Science.gov (United States)

    Raju, Dugyala; Mehta, Urmil J; Beedu, Sashidhar Rao

    2016-06-01

    An eco-friendly green and one-pot synthesis of highly monodispersed iron (Fe) nanoparticles (NPs) by using a natural biopolymer, gum kondagogu (GK) as reducing and capping agent is proposed. The NPs synthesised were characterised by ultra-violet-visible spectroscopy, transmission electron microscopy, scanning electron microscopy and X-ray diffraction. As the concentration of gum and time increases, the intensity of NPs formation increased. The NPs were highly monodispersed with uniform circular shapes of 2-6 nm in size. The formed NPs were crystalline in nature which was confirmed by diffraction analysis. The conversion ratio of Fe ionic form to NPs was 21% which was quantified by inductively coupled plasma mass spectroscopy (ICP-MS). Fe is essential for plant growth and development. A study was conducted to examine the effect of these NPs on the growth of mung bean (Vigna radiata). The radical length and biomass was increased in seeds exposed to Fe NPs than the ions. The uptake of Fe NPs by the sprouts was also quantified by ICP-MS, in which Fe was more in mung bean seeds exposed to NPs. The α-amylase activity was increased in the seeds exposed to NPs. The observed increase in the biomass by Fe NPs and seed germination may facilitate its application in the agriculture as an important cost-effective method for plant growth.

  1. Monodisperse Pt Nanoparticles Assembled on Reduced Graphene Oxide: Highly Efficient and Reusable Catalyst for Methanol Oxidation and Dehydrocoupling of Dimethylamine-Borane (DMAB).

    Science.gov (United States)

    Yildiz, Yunus; Erken, Esma; Pamuk, Handan; Sert, Hakan; Sen, Fatih

    2016-06-01

    Herein, monodisperse platinum (0) nanocatalyst assembled on reduced graphene oxide (Pt(0)@RGO) was easily and reproducibly prepared by the double solvent reduction method at room temperature. Pt(0)@RGO was characterized by X-ray diffraction (XRD), X-ray photoelectron microscopy (XPS) and transmission electron microscopy (TEM) measurements that verify the formation of monodisperse Pt (0) nanoparticles on RGO. The catalytic and electrocatalytic performances of Pt(0) @ RGO in terms of activity, isolability and reusability were investigated for both methanol oxidation and the dehydrocoupling of dimethylamine-borane (DMAB) in which Pt(0)@RGO was found to be highly active and reusable heterogeneous catalyst even at room temperature. The prepared nanoparticles can also electrocatalyze methanol oxidation with very high electrochemical activities (5.64 A/cm2 at 0.58 V for methanol). The activation energy (Ea), activation enthalpy (ΔH#), and activation entropy (ΔS#) for DMAB dehydrogenation were calculated to be 59.33 kJ mol(-1), 56.79 kJ mol(-1) and -151.68 J mol(-1) K(-1), respectively. The exceptional stability of new Pt(0) @ RGO nanoparticles towards agglomeration, leaching and CO poisoning allow these particles to be recycled and reused in the catalysis of DMAB dehydrogenation and methanol oxidation. After four subsequent reaction and recovery cycles, Pt(0) @ RGO retained ≥ 75% activity towards the complete dehydrogenation of DMAB.

  2. Inter-laboratory comparison on the size and stability of monodisperse and bimodal synthetic reference particles for standardization of extracellular vesicle measurements

    Science.gov (United States)

    Nicolet, Anaïs; Meli, Felix; van der Pol, Edwin; Yuana, Yuana; Gollwitzer, Christian; Krumrey, Michael; Cizmar, Petr; Buhr, Egbert; Pétry, Jasmine; Sebaihi, Noham; de Boeck, Bert; Fokkema, Vincent; Bergmans, Rob; Nieuwland, Rienk

    2016-03-01

    In future, measurements of extracellular vesicles in body fluids could become a standard diagnostic tool in medicine. For this purpose, reliable and traceable methods, which can be easily applied in hospitals, have to be established. Within the European Metrological Research Project (EMRP) ‘Metrological characterization of micro-vesicles from body fluids as non-invasive diagnostic biomarkers’ (www.metves.eu), various nanoparticle reference materials were developed and characterized. We present results of an international comparison among four national metrology institutes and a university hospital. The size distributions of five monodisperse and two bimodal spherical particle samples with diameters ranging from 50 nm to 315 nm made out of silica and polystyrene were compared. Furthermore, the stability of the samples was verified over a period of 18 months. While monodisperse reference particle samples above a certain size level lead to good agreements of the size measurements among the different methods, small and bimodal samples show the limitations of current ‘clinical’ methods. All samples proved to be stable within the uncertainty of the applied methods.

  3. 单分散ZnO微球的合成及表征%Synthesis of monodispersed ZnO microspheres and characterizations

    Institute of Scientific and Technical Information of China (English)

    颜蔚; 安明; 王响; 董琪琪; 孙丽宁; 施利毅; 邓维

    2012-01-01

    采用简单的两步法合成了直径范围从50~200 nm的单分散的ZnO微球:在第一步反应中制备了ZnO纳米粒子的乙醇分散液;然后在第二步反应中加入适量的ZnO纳米粒子的乙醇分散液,从而合成出单分散的ZnO微球.通过改变第二步反应中所加入的ZnO纳米粒子的乙醇分散液的量,可以改变制备的单分散ZnO微球的直径.通过透射电子显微镜和X-射线衍射分析可以得知,ZnO微球是由ZnO纳米粒子聚集而成.不论ZnO微球的直径是多少,其多分散指数均小于1,并且当ZnO微球的直径为150 nm时,其多分散指数仅为0.16.%In this paper, monodispersed ZnO microspheres in sizes from 50 to 200 nm were synthesized with a developed two-step method. In the primary reaction, ethanol suspension of ZnO nanoparticles was prepared, and monodispersed ZnO microspheres were synthesized in the secondary reaction by adding the ZnO nanoparticles suspension into the reaction solution. Diameter of the ZnO microspheres could be controlled by varying the volume of QDs suspension added. The transmission microscopy images and X-ray diffraction patterns of the ZnO microspheres showed that no matter their diameters, the ZnO microspheres were formed by aggregation of well crystallized ZnO nanoparticles. The polydispersity indexes (PDI) of ZnO microspheres were detected. It is found that PDI values of the microspheres were all less than 1. 0, suggesting the monodispersi-ty of the ZnO microspheres. The PDI value was only 0. 16 when the diameter of the ZnO microspheres was 150 nm.

  4. PREPARATION OF MONODISPERSE POLYSTYRENE MICROSPHERES BY SHELL POROUS GLASS-SUSPENSION POLYMERIZATION%用多孔玻璃膜管-悬浮聚合法制备单分散性聚苯乙烯微球

    Institute of Scientific and Technical Information of China (English)

    范星河; 谢晓峰

    2001-01-01

    Monodisperse polystyrene microspheres are prepared by shell porous glass(SPG)-suspension polymerization. The influences of SPG on size and size dispersity of the microspheres are investigated. The properties of the microspheres are studied by GPC, TEM and SEM. The results indicate that the polystyrene microspheres possess definite monodispersibity and their particle size is in the range of 5~12μm.

  5. Monodispersed Silica Nanospheres Encapsulating Fe3O4 and LaF3:Eu3+ Nanoparticles for MRI Contrast Agent and Luminescent Imaging

    Science.gov (United States)

    Tian, Yang; Yu, Binbin; Yang, Hong-Yu; Liao, Ji

    2013-03-01

    Bifunctional nanospheres of silica encapsulating Fe3O4 and LaF3:Eu nanoparticles were synthesized in a reverse microemulsion solution. The nanospheres were perfectly monodispersed with a small diameter of 20 nm. The composition of the bifunctional nanospheres was confirmed by powder X-ray diffraction. Their magnetic and luminescent properties were measured at room temperature. The relaxation efficiency and T2-weighted images showed the high-performance for the product as a resonance imaging contrast agent. In addition, a qualitative cell uptake in human cervical cancer HeLa cells demonstrated that the SFLE nanospheres were efficiently up-taken into cytosol. Taken together, these findings suggest that the SiO2/Fe3O4-LaF3:Eu3+ nanospheres are good luminescence probes for bio-imaging.

  6. Synthesis and Characterization of Nearly Monodisperse Pt Nanoparticles for C1 to C3 Alcohol Oxidation and Dehydrogenation of Dimethylamine-borane (DMAB).

    Science.gov (United States)

    Erken, Esma; Yildiz, Yunus; Kilbaş, Benan; Sen, Fatih

    2016-06-01

    Highly efficient nearly monodisperse Pt NPs catalyze C1 to C3 alcohol oxidation with very high electrochemical activities and provides one of the highest catalytic activities (TOF = 21.50 h(-1)) in the dehydrogenation of DMAB at room temperature. The exceptional stability towards agglomeration, leaching and CO poisoning for the prepared catalyst allow these particles to be recycled and reused in the catalysis of both DMAB dehydrogenation and C1 to C3 alcohol oxidation. After four subsequent reaction and recovery cycles, catalyst retained ≥ 80% activity towards the complete dehydrogenation of DMAB. The prepared catalyst structures were determined by the X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM) respectively.

  7. 声化学法制备均匀分散的ZnO纳米晶%Sonochemical Synthesis of Monodispersed Nanocrystalline ZnO

    Institute of Scientific and Technical Information of China (English)

    何旭昭; 史丹; 程继鹏

    2009-01-01

    采用超声化学方法制备ZnO纳米颗粒,透射电子显微镜(TEM)测试结果显示,合成出的ZnO纳米颗粒尺寸均匀,形状规则.而X-射线衍射(XRD)结果表明,提高反应温度可以促进ZnO的生长.因而,对于合成单一分散的ZnO纳米晶而言,声化学方法是一种非常简便的方法.%reaction temperature. Sonochemical method is thought as a convenient one to synthesize monodispersed ZnO nanocrystallites.

  8. Monodisperse and inorganically capped Sn and Sn/SnO2 nanocrystals for high-performance Li-ion battery anodes.

    Science.gov (United States)

    Kravchyk, Kostiantyn; Protesescu, Loredana; Bodnarchuk, Maryna I; Krumeich, Frank; Yarema, Maksym; Walter, Marc; Guntlin, Christoph; Kovalenko, Maksym V

    2013-03-20

    We report a facile synthesis of highly monodisperse colloidal Sn and Sn/SnO2 nanocrystals with mean sizes tunable over the range 9-23 nm and size distributions below 10%. For testing the utility of Sn/SnO2 nanocrystals as an active anode material in Li-ion batteries, a simple ligand-exchange procedure using inorganic capping ligands was applied to facilitate electronic connectivity within the components of the nanocrystalline electrode. Electrochemical measurements demonstrated that 10 nm Sn/SnO2 nanocrystals enable high Li insertion/removal cycling stability, in striking contrast to commercial 100-150 nm powders of Sn and SnO2. In particular, reversible Li-storage capacities above 700 mA h g(-1) were obtained after 100 cycles of deep charging (0.005-2 V) at a relatively high current of 1000 mA h g(-1).

  9. UV-visible light-activated Ag-decorated, monodisperse TiO2 aggregates for treatment of the pharmaceutical oxytetracycline.

    Science.gov (United States)

    Han, Changseok; Likodimos, Vlassis; Khan, Javed Ali; Nadagouda, Mallikarjuna N; Andersen, Joel; Falaras, Polycarpos; Rosales-Lombardi, Pablo; Dionysiou, Dionysios D

    2014-10-01

    Noble metal Ag-decorated, monodisperse TiO2 aggregates were successfully synthesized by an ionic strength-assisted, simple sol-gel method and were used for the photocatalytic degradation of the antibiotic oxytetracycline (OTC) under both UV and visible light (UV-visible light) irradiation. The synthesized samples were characterized by X-ray diffraction analysis (XRD); UV-vis diffuse reflectance spectroscopy; environmental scanning electron microscopy (ESEM); transmission electron microscopy (TEM); high-resolution TEM (HR-TEM); micro-Raman, energy-dispersive X-ray spectroscopy (EDS); and inductively coupled plasma optical emission spectrometry (ICP-OES). The results showed that the uniformity of TiO2 aggregates was finely tuned by the sol-gel method, and Ag was well decorated on the monodisperse TiO2 aggregates. The absorption of the samples in the visible light region increased with increasing Ag loading that was proportional to the amount of Ag precursor added in the solution over the tested concentration range. The Brunauer, Emmett, and Teller (The BET) surface area slightly decreased with increasing Ag loading on the TiO2 aggregates. Ag-decorated TiO2 samples demonstrated enhanced photocatalytic activity for the degradation of OTC under UV-visible light illumination compared to that of pure TiO2. The sample containing 1.9 wt% Ag showed the highest photocatalytic activity for the degradation of OTC under both UV-visible light and visible light illumination. During the experiments, the detected Ag leaching for the best TiO2-Ag photocatalyst was much lower than the National Secondary Drinking Water Regulation for Ag limit (0.1 mg L(-1)) issued by the US Environmental Protection Agency.

  10. Synthesis of monodisperse MFe{sub 2}O{sub 4} (M = Fe and Zn) nanoparticles for polydiethylsiloxane-based ferrofluid with a solvothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei [State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Provincial Key Laboratory of Photovoltaics Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Laboratory of Nanophotonic Functional Materials and Devices, Institute of Optoelectronic Materials and Technology, South China Normal University, Guangzhou 510631 (China); Zhuang, Lin, E-mail: stszhl@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Provincial Key Laboratory of Photovoltaics Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Zhang, Yong [Laboratory of Nanophotonic Functional Materials and Devices, Institute of Optoelectronic Materials and Technology, South China Normal University, Guangzhou 510631 (China); Shen, Hui [State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Provincial Key Laboratory of Photovoltaics Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2015-09-15

    Highlights: • MFe{sub 2}O{sub 4} nanoparticles were synthesized through a facile solvothermal method. • The relationship between viscosity and temperature of the polydiethylsiloxane-based ferrofluid is discussed. • Fe{sub 3}O{sub 4} nanoparticles have a saturation magnetization of 73.06 emu/g at room temperature. - Abstract: Monodisperse MFe{sub 2}O{sub 4} (M = Fe, Zn) nanoparticles were successfully synthesized for the application of polydiethylsiloxane-based (PDES) ferrofluids (FFs) via a novel solvothermal method, with which 1-octanol and 1-octanamine act as binary solvent, oleic acid (OA) as the surfactant and metal acetylacetonate [M(acac){sub 3}](M = Fe and Zn) as the metal source. X-ray diffractometer confirms that the resultant nanoparticles are pure MFe{sub 2}O{sub 4} with a spinel structure. Infrared spectroscopy indicates that oleic acid is bound to the surface of MFe{sub 2}O{sub 4} through a covalent bond between carboxylate (COO{sup −}) and metal cations. The ratio of 1-octanol and 1-octanamine plays a key role in the formation of the sphere-shaped morphology. Transmission electron microscopy (TEM) images confirm that the Fe{sub 3}O{sub 4} particles are of 4–11 nm with good monodispersity and a narrow size distribution. The saturation magnetization of Fe{sub 3}O{sub 4} nanoparticles with sizes of 7 nm can reach up to 73.06 emu/g. Polydiethylsiloxane-based (PDES) FFs show relatively smaller changes of the viscosity with low temperatures (from −7 to 20 °C) than the polydimethylsiloxane-based (PDMS) FFs. For FFs applications, the relationship between viscosity and temperature is also discussed.

  11. Monodisperse magnetic hydroxyapatite/Fe{sub 3}O{sub 4} microspheres for removal of lead(II) from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Zhuang, Fuqiang [Faculty of Electrical Engineering and Computer Science, Ningbo University, Ningbo 315211 (China); Tan, Ruiqin, E-mail: tanruiqin@nbu.edu.cn [Faculty of Electrical Engineering and Computer Science, Ningbo University, Ningbo 315211 (China); Shen, Wenfeng; Zhang, Xianpeng; Xu, Wei; Song, Weijie [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2015-07-15

    Highlights: • Monodisperse HAp/Fe{sub 3}O{sub 4} microspheres were explored for the removal of lead(II). • The sorption capacity toward Pb{sup 2+} reached 440 mg/g at pH 3.0. • Pb{sup 2+}-loaded HAp/Fe{sub 3}O{sub 4} microspheres can be easily collected by magnetic separation. • The removal mechanism of Pb{sup 2+} was different at pH 2.0–6.0. - Abstract: Monodisperse magnetic hydroxyapatite (HAp)/Fe{sub 3}O{sub 4} microspheres were successfully synthesized and explored for the removal of lead(II) from aqueous solution. The mechanism of Pb{sup 2+} uptake was characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. The sorption capacity toward Pb{sup 2+} reached 440 mg/g at pH 3.0 and equilibrium was achieved within 1 h. The experimental data followed the Langmuir isotherm model (R{sup 2} = 0.9969) and the kinetic results accorded with the pseudo-second-order model (R{sup 2} = 0.9970). The sorption of Pb{sup 2+} on the surfaces of HAp/Fe{sub 3}O{sub 4} and the following ion exchange are the primary mechanism at pH 3.0–6.0. The dissolution–precipitation mechanism response to the removal of Pb{sup 2+} when pH varied from 3.0 to 2.0. The Pb{sup 2+}-loaded magnetic HAp/Fe{sub 3}O{sub 4} could be separated conveniently.

  12. 单分散介孔二氧化硅微球的制备%Synthesis of monodisperse mesoporous silica microsphere

    Institute of Scientific and Technical Information of China (English)

    钟立峰; 宁海金; 徐先进; 廖道发

    2012-01-01

    Modified Stober method was used to prepare monodisperse mesoporous silica microsphere by two-step reaction including hydrolysis and condensation of tetraethyl orthosilicate(TEOS)with ammonia as catalyst.Effects of the reaction parameters on the size and mono-disperse of the microsphere were discussed based on many characterization tests.Results showed: the microsphere size increased with the increment of ammonia and TEOS concentrations while decreased at higher temperature due to the evaporation of ammonia;effects of the reaction time on the particle distribution existed mainly in the initial stage,then got smooth gradually.The comparison of small angle X ray analysis suggested that peak intensity of silica microsphere increased and the overlapping peaks drifted rightward after calcination,indicating that the surfactant molecules were removed from the hole and the aperture shrank at the same time.In addition,the texture of the product was affected by reaction conditions to some extent.The mechanism study revealed the formation of silica microsphere was achieved through TEOS hydrolysis and polycondensation two steps successively.This is a simple,effective and repeatable method,which may be used for mass production,for the preparation of mono-dispersed mesoporous silica microspheres.%在Stober方法基础上制备了单分散二氧化硅微球,系统研究了反应条件对成球粒径以及单分散性的影响。通过多种测试手段,发现随着正硅酸乙酯和氨水浓度的提高,成球的粒径逐渐增大;而温度的提高会促使氨水挥发而使得成球的粒径降低;反应时间在反应初期对成球粒径的影响很大,然后逐渐趋于平缓。经对煅烧前后产物的小角X射线衍射对比分析,发现煅烧后产物的峰强度增加,并且重叠峰向右漂移,指示表面活性剂分子从孔中移除并发生了孔径收缩现象,同时发现不同反应条件对产物的织构性质有一定的影响。研究了相关的反应机

  13. Synthesis of magnetic cobalt ferrite nanoparticles with controlled morphology, monodispersity and composition: the influence of solvent, surfactant, reductant and synthetic conditions

    Science.gov (United States)

    Lu, Le T.; Dung, Ngo T.; Tung, Le D.; Thanh, Cao T.; Quy, Ong K.; Chuc, Nguyen V.; Maenosono, Shinya; Thanh, Nguyen T. K.

    2015-11-01

    In our present work, magnetic cobalt ferrite (CoFe2O4) nanoparticles have been successfully synthesised by thermal decomposition of Fe(iii) and Co(ii) acetylacetonate compounds in organic solvents in the presence of oleic acid (OA)/ oleylamine (OLA) as surfactants and 1,2-hexadecanediol (HDD) or octadecanol (OCD-ol) as an accelerating agent. As a result, CoFe2O4 nanoparticles of different shapes were tightly controlled in size (range of 4-30 nm) and monodispersity (standard deviation only at ca. 5%). Experimental parameters, such as reaction time, temperature, surfactant concentration, solvent, precursor ratio, and accelerating agent, in particular, the role of HDD, OCD-ol, and OA/OLA have been intensively investigated in detail to discover the best conditions for the synthesis of the above magnetic nanoparticles. The obtained nanoparticles have been successfully applied for producing oriented carbon nanotubes (CNTs), and they have potential to be used in biomedical applications.In our present work, magnetic cobalt ferrite (CoFe2O4) nanoparticles have been successfully synthesised by thermal decomposition of Fe(iii) and Co(ii) acetylacetonate compounds in organic solvents in the presence of oleic acid (OA)/ oleylamine (OLA) as surfactants and 1,2-hexadecanediol (HDD) or octadecanol (OCD-ol) as an accelerating agent. As a result, CoFe2O4 nanoparticles of different shapes were tightly controlled in size (range of 4-30 nm) and monodispersity (standard deviation only at ca. 5%). Experimental parameters, such as reaction time, temperature, surfactant concentration, solvent, precursor ratio, and accelerating agent, in particular, the role of HDD, OCD-ol, and OA/OLA have been intensively investigated in detail to discover the best conditions for the synthesis of the above magnetic nanoparticles. The obtained nanoparticles have been successfully applied for producing oriented carbon nanotubes (CNTs), and they have potential to be used in biomedical applications. Electronic

  14. Preparation and Characterization of Monodisperse Polystyrene Microspheres%单分散性聚苯乙烯微球的制备与表征

    Institute of Scientific and Technical Information of China (English)

    万纪强; 石志琪

    2012-01-01

    Appropriate amount of sodium styrene sulfonate is introduced into the system of styrene emulsion polymerization in copolymerization by using emulsifier-free emulsion polymerization. The polymerization process is divided into two stages, in the first stage the ratio of sodium styrene sulfonate and styrene is the key factor which determines latex diameter and the monodispersity. When the reaction achieves high conversion rate, the second stage's monomer mixture is added into the reactant. The ratio of the sodium styrene sulfonate and styrene in this stage determines the particle's final surface charge density. Through the above two stages by emulsifier-free emulsion polymerization, latex particle of particle size of 100~400nm, good monodispersity, high surface charge density with the core-shell structure is successfully prepared. On this foundation, the influence of the ratio of styrene and sodium styrene sulfonate in the first stage on latex particle diameter and the influence of latex particle diameter on the microsphere's surface charge density are discussed.%利用无皂乳液聚合[1,2],在苯乙烯的乳液聚合体系中引入适量的苯乙烯磺酸钠参与共聚合.聚合过程中分两阶段料,第一阶段中苯乙烯磺酸钠与苯乙烯的比例是决定乳胶粒粒径及单分散性的关键因素.当反应达到较高的转化率时,加入第二阶段单体混合物,此阶段中的苯乙烯磺酸钠与苯乙烯的比例决定了最终胶粒表面电荷密度.利用上述两阶段无皂乳液聚合法制备了粒径在100~400nm,单分散性较好,表面电荷密度较高并且具有核壳结构的乳胶粒.在此基础上,讨论了的第一阶段中苯乙烯和苯乙烯磺酸钠的比例对乳胶粒粒径的影响以及乳胶粒粒径对微球表面电荷密度的影响.

  15. Dispersed-nanoparticle loading synthesis for monodisperse Au-titania composite particles and their crystallization for highly active UV and visible photocatalysts.

    Science.gov (United States)

    Sakamoto, Takeshi; Nagao, Daisuke; Noba, Masahiro; Ishii, Haruyuki; Konno, Mikio

    2014-06-24

    Submicrometer-sized amorphous titania spheres incorporating Au nanoparticles (NPs) were prepared in a one-pot synthesis consisting of a sol-gel reaction of titanium(IV) isopropoxide in the presence of chloroauric acid and a successive reduction with sodium borohydride in a mixed solvent of ethanol/acetonitrile. The synthesis was allowed to prepare monodisperse titania spheres that homogeneously incorporated Au NPs with sizes of ca. 7 nm. The Au NP-loaded titania spheres underwent different crystallization processes, including 500 °C calcination in air, high-temperature hydrothermal treatment (HHT), and/or low-temperature hydrothermal treatment (LHT). Photocatalytic experiments were conducted with the Au NP-loaded crystalline titania spheres under irradiation of UV and visible light. A combined process of LHT at 80 °C followed by calcination at 500 °C could effectively crystallize titania spheres maintaining the dispersion state of Au NPs, which led to photocatalytic activity higher than that of commercial P25 under UV irradiation. Under visible light irradiation, the Au NP-titania spheres prepared with a crystallization process of LHT at 80 °C for 6 h showed photocatalytic activity much higher than a commercial product of visible light photocatalyst. Structure analysis of the visible light photocatalysts indicates the importance of prevention of the Au NPs aggregation in the crystallization processes for enhancement of photocatalytic activity.

  16. Synthesis of monodisperse spherical core-shell SiO2-SrAl2Si2 O8:Eu2+ phosphors by hydrothermal homogeneous precipitation method

    Directory of Open Access Journals (Sweden)

    Yidong Li, Liyuan Xiao, Yingliang Liu, Pengfei Ai and Xiaobo Chen

    2010-01-01

    Full Text Available Nanocrystalline SrAl2Si2 O8 :Eu2+ phosphor layers were coated on nonaggregated, monodisperse and spherical SiO2 particles using a hydrothermal homogeneous precipitation. After annealing at 1100 °C, core-shell SiO2@SrAl2 Si2 O8 :Eu2+ particles were obtained. They were characterized with x-ray diffraction (XRD, scanning electron microscopy, transmission electron microscopy and photoluminescence techniques. XRD analysis confirmed the formation of SiO2 @SrAl2 Si2 O8 :Eu2+ particles; it indicated that the SrAl2 Si2 O8 :Eu2+ shells on SiO2 particles consisted of hexagonal crystallites. The core-shell phosphors obtained are well-dispersed submicron spherical particles with a narrow size distribution. The thickness of the coated layer is approximately 20–40 nm. Under ultraviolet excitation (361 nm, the particles emit blue light at about 440 nm due to the Eu2+ ions in their shells.

  17. Cross-linked branching nanohybrid polymer electrolyte with monodispersed TiO2 nanoparticles for high performance lithium-ion batteries

    Science.gov (United States)

    Ma, Cheng; Zhang, Jinfang; Xu, Mingquan; Xia, Qingbing; Liu, Jiatu; Zhao, Shuai; Chen, Libao; Pan, Anqiang; Ivey, Douglas G.; Wei, Weifeng

    2016-06-01

    Nanohybrid polymer electrolytes (NHPE) with ceramic particles have attracted significant attention owing to their improvement in electrochemical performance. However, particle aggregation and weak nanoparticle/polymer matrix interaction restrict their further application in lithium-ion batteries (LIBs). We demonstrate a facile in-situ polymerization/crystallization method to synthesize a homogeneous TiO2-grafted NHPE with a cross-linked branching structure, comprised of ion-conducting poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and non-polar stearyl methacrylate (SMA). This technique is different from existing methods of blending functionalized ceramic particles into the polymer matrix. Highly monodispersed TiO2 nanocrystals enhance the effective interfacial interactions between particles and polymer matrix, which suppress the crystallization of ethylene oxide (EO) groups and facilitate forming continuously interconnected ion-conducting channels. Moreover, an increased dissociation degree of Li salt can also be achieved. The TiO2-grafted NHPE exhibits superior electrochemical properties with an ionic conductivity of 1.1 × 10-4 S cm-1 at 30 °C, a high lithium ion transference number and excellent interfacial compatibility with the lithium electrode. In particular, a lithium-ion battery based on TiO2-grafted NHPE demonstrates good C-rate performance, as well as excellent cycling stability with an initial discharge capacity of 153.5 mAh g-1 and a capacity retention of 96% after 300 cycles at 1 C (80 °C).

  18. Rapid synthesis of monodispersed highly porous spinel nickel cobaltite (NiCo{sub 2}O{sub 4}) electrode material for supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Naveen, A. Nirmalesh, E-mail: nirmalesh.naveen@gmail.com; Selladurai, S. [Ionics Laboratory, Department of Physics, Anna University, Chennai-600025 (India)

    2015-06-24

    Monodispersed highly porous spinel nickel cobaltite electrode material was successfully synthesized in a short time using combustion technique. Single phase cubic nature of the spinel nickel cobaltite with average crystallite size of 24 nm was determined from X-ray diffraction study. Functional groups present in the compound were determined from FTIR study and it further confirms the spinel formation. FESEM images reveal the porous nature of the prepared material and uniform size distribution of the particles. Electrochemical evaluation was performed using Cyclic Voltammetry (CV) technique, Chronopotentiometry (CP) and Electrochemical Impedance Spectroscopy (EIS). Results reveal the typical pseudocapacitive behaviour of the material. Maximum capacitance of 754 F/g was calculated at the scan rate of 5 mV/s, high capacitance was due to the unique porous morphology of the electrode. Nyquist plot depicts the low resistance and good electrical conductivity of nickel cobaltite. It has been found that nickel cobaltite prepared by this typical method will be a potential electrode material for supercapcitor application.

  19. Regulating Mid-infrared to Visible Fluorescence in Monodispersed Er3+-doped La2O2S (La2O2SO4) Nanocrystals by Phase Modulation

    Science.gov (United States)

    Pan, Qiwen; Yang, Dandan; Kang, Shiliang; Qiu, Jianrong; Dong, Guoping

    2016-11-01

    Rare earth doped mid-infrared (MIR) fluorescent sources have been widely investigated due to their various potential applications in the fields of communication, chemical detecting, medical surgery and so forth. However, with emission wavelength extended to MIR, multiphonon relaxation process that strongly quenched the MIR emission is one of the greatest challenges for such practical applications. In our design, we have described a controllable gas-aided annealing strategy to modulate the phase, crystal size, morphology and fluorescent performance of a material simultaneously. Uniform and monodispersed Er3+-doped La2O2S and La2O2SO4 nanocrystals with a similar lattice structure, crystallinity, diameter and morphology have been introduced to investigate the impact of multiphonon relaxation on luminescence performance. Detailed spectroscopic evolutions in the region of MIR, near-infrared (NIR), visible upconversion (UC) and their corresponding decay times provide insight investigation into the fluorescent mechanism caused by multiphonon relaxation. A possible energy transfer model has also been established. Our results present direct observation and mechanistic investigation of fluorescent evolution in multiphonon relaxation process, which is conductive to design MIR fluorescent materials in the future. To the best of our knowledge, it is the first investigation on MIR fluorescent performance of La2O2S nanocrystals, which may find various applications in many photoelectronic fields.

  20. Large-scale synthesis of monodisperse SiC nanoparticles with adjustable size, stoichiometric ratio and properties by fluidized bed chemical vapor deposition

    Science.gov (United States)

    Liu, Rongzheng; Liu, Malin; Chang, Jiaxing

    2017-02-01

    A facile fluidized bed chemical vapor deposition method was proposed for the synthesis of monodisperse SiC nanoparticles by using the single precursor of hexamethyldisilane (HMDS). SiC nanoparticles with average particle size from 10 to 200 nm were obtained by controlling the temperature and the gas ratio. An experimental chemical vapor deposition phase diagram of SiC in the HMDS-Ar-H2 system was obtained and three regions of SiC-Si, SiC and SiC-C can be distinguished. The BET surface area and the photoluminescence properties of the SiC nanoparticles can be adjusted by changing the nanoparticle size. For the SiC nanospheres with free carbon, a novel hierarchical structure with 5 8 nm SiC nanoparticles embedded into the graphite matrix was obtained. The advantages of fluidized bed technology for the preparation of SiC nanoparticles were proposed based on the features of homogenous reaction zone, narrow temperature distribution, ultra-short reactant residence time and mass production.

  1. Monodispersed FeCO3 nanorods anchored on reduced graphene oxide as mesoporous composite anode for high-performance lithium-ion batteries

    Science.gov (United States)

    Xu, Donghui; Liu, Weijian; Zhang, Congcong; Cai, Xin; Chen, Wenyan; Fang, Yueping; Yu, Xiaoyuan

    2017-10-01

    The development of advanced 1D/2D hierarchical nanocomposites for high-performance lithium-ion batteries is important and promising. Herein, monodispersed FeCO3 nanorods anchored on reduced graphene oxide (RGO) are prepared via a facile and efficient one-pot hydrothermal synthesis. The influence of RGO content on the morphology and electrochemical performances of the mesoporous FeCO3/reduced graphene oxide (FeCO3/RGO) composites are systematically studied. Optimized FeCO3/RGO composite shows good cycling stability. It delivers an initial discharge capacity of 1449 mAh·g-1 at the current density of 200 mA g-1 and maintained a capacity of 789 mAh·g-1 after 80 cycles. A moderate amount of RGO sheets can not only provide more conductive channels to improve the electrode conductivity, but also effectively buffer the large volume variation of FeCO3 during continuous charge/discharge process. The combination of FeCO3 nanorods with RGOs synergistically contribute to enhanced capacity and durability of the composite anode. It demonstrates that RGO anchored-FeCO3 nanorods should be an attractive candidate as anode material for high-performance lithium-ion batteries.

  2. Monodisperse REPO4 (RE = Yb, Gd, Y) hollow microspheres covered with nanothorns as affinity probes for selectively capturing and labeling phosphopeptides.

    Science.gov (United States)

    Cheng, Gong; Zhang, Ji-Lin; Liu, Yan-Lin; Sun, De-Hui; Ni, Jia-Zuan

    2012-02-13

    Rare-earth phosphate microspheres with unique structures were developed as affinity probes for the selective capture and tagging of phosphopeptides. Prickly REPO(4) (RE = Yb, Gd, Y) monodisperse microspheres, that have hollow structures, low densities, high specific surface areas, and large adsorptive capacities were prepared by an ion-exchange method. The elemental compositions and crystal structures of these affinity probes were confirmed by energy-dispersive spectroscopy (EDS), powder X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy. The morphologies of these compounds were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen-adsorption isotherms. The potential ability of these microspheres for selectively capturing and labeling target biological molecules was evaluated by using protein-digestion analysis and a real sample as well as by comparison with the widely used TiO(2) affinity microspheres. These results show that these porous rare-earth phosphate microspheres are highly promising probes for the rapid purification and recognition of phosphopeptides.

  3. High Ionic Conductivity of Composite Solid Polymer Electrolyte via In Situ Synthesis of Monodispersed SiO2 Nanospheres in Poly(ethylene oxide).

    Science.gov (United States)

    Lin, Dingchang; Liu, Wei; Liu, Yayuan; Lee, Hye Ryoung; Hsu, Po-Chun; Liu, Kai; Cui, Yi

    2016-01-13

    High ionic conductivity solid polymer electrolyte (SPE) has long been desired for the next generation high energy and safe rechargeable lithium batteries. Among all of the SPEs, composite polymer electrolyte (CPE) with ceramic fillers has garnered great interest due to the enhancement of ionic conductivity. However, the high degree of polymer crystallinity, agglomeration of ceramic fillers, and weak polymer-ceramic interaction limit the further improvement of ionic conductivity. Different from the existing methods of blending preformed ceramic particles with polymers, here we introduce an in situ synthesis of ceramic filler particles in polymer electrolyte. Much stronger chemical/mechanical interactions between monodispersed 12 nm diameter SiO2 nanospheres and poly(ethylene oxide) (PEO) chains were produced by in situ hydrolysis, which significantly suppresses the crystallization of PEO and thus facilitates polymer segmental motion for ionic conduction. In addition, an improved degree of LiClO4 dissociation can also be achieved. All of these lead to good ionic conductivity (1.2 × 10(-3) S cm(-1) at 60 °C, 4.4 × 10(-5) S cm(-1) at 30 °C). At the same time, largely extended electrochemical stability window up to 5.5 V can be observed. We further demonstrated all-solid-state lithium batteries showing excellent rate capability as well as good cycling performance.

  4. Production of nearly monodisperse Fe3O4 and Fe@Fe3O4 nanoparticles in aqueous medium and their surface modification for biomedical applications

    Science.gov (United States)

    Tegafaw, Tirusew; Xu, Wenlong; Lee, Sang Hyup; Chae, Kwon Seok; Chang, Yongmin; Lee, Gang Ho

    2017-02-01

    Iron (Fe)-based nanoparticles are extremely valuable in biomedical applications owing to their low toxicity and high magnetization values at room temperature. In this study, we synthesized nearly monodisperse iron oxide (Fe3O4) and Fe@Fe3O4 (core: Fe, shell: Fe3O4) nanoparticles in aqueous medium under argon flow and then, coated them with various biocompatible ligands and silica. In this study, eight types of surface-modified nanoparticles were investigated, namely, Fe3O4@PAA (PAA = polyacrylic acid; Mw of PAA = 5100 amu and 15,000 amu), Fe3O4@PAA-FA (FA = folic acid; Mw of PAA = 5100 amu and 15,000 amu), Fe3O4@PEI-fluorescein (PEI = polyethylenimine; Mw of PEI = 1300 amu), Fe@Fe3O4@PEI (Mw of PEI = 10,000 amu), Fe3O4@SiO2 and Fe@Fe3O4@SiO2 nanoparticles. We characterized the prepared surface-modified nanoparticles using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) absorption spectroscopy, a superconducting quantum interference device (SQUID), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy and confocal microscopy. Finally, we measured the cytotoxicity of the samples. The results indicate that the surface-modified nanoparticles are biocompatible and are potential candidates for various biomedical applications.

  5. Evaporative purification to produce highly monodisperse polymers: Application to polystyrene for n =3 -13 and quantification of Tg from oligomer to polymer

    Science.gov (United States)

    Zhu, S.; Chai, Y.; Forrest, J. A.

    2017-07-01

    We demonstrate the use of selective thermal evaporation to separate and purify small molecular weight polymers into highly monodisperse polymers over an extended range of polymerization index. By exploiting the calculated dependence of polymer vapor pressure on polymerization index N and temperature T , we can isolate individual components (N -mers) of an initially polydisperse mixture. To demonstrate this ability, we consider polystyrene samples of Mw=600 g/mol and Mw=890 g/mol with narrow molecular weight distributions, as well as a Mw=1200 g/mol sample with a broader distribution. In each case we are able to separate the sample into milligram quantities of many different components. Using this technique, we have been able to isolate N -mers from 3 to 13. We use differential scanning calorimetry to measure the Tg values of these components, and find that the components have the same Tg values independent of the Mw or polydispersity of the sample they originate from. We find that even initially narrow molecular weight distributions have many different components whose Tg values can differ by more than 50 K. Calculations suggest the isolated components have Mw/Mn values less than 1.001 and through a second iteration of the process could become as low as 1.000 003. The measured Tg values for the N -mers as well as large N polymers are well described by a simple relation derived from the Fox equation for the Tg of mixtures.

  6. Development of ultrafine multichannel microfluidic mixer for synthesis of bimetallic nanoclusters: catalytic application of highly monodisperse AuPd nanoclusters stabilized by poly(N-vinylpyrrolidone).

    Science.gov (United States)

    Hayashi, Naoto; Sakai, Yuka; Tsunoyama, Hironori; Nakajima, Atsushi

    2014-09-02

    On account of their novel properties, bimetallic nanoparticles and nanoclusters (NCs) are strong potential candidates for optical, magnetic, and catalytic functional materials. These properties depend on the chemical composition and size (number of constituent atoms) of the NCs. Control of size, structure, and composition is particularly important for fabricating highly functional materials based on bimetallic NCs. Size- and structure-controlled synthesis of two-element alloys can reveal their intrinsic electronic synergistic effects. However, because synergistic enhancement of activity is strongly affected by composition as well as by size and structure, controlled synthesis is a challenging task, particularly in catalytic applications. To investigate catalytic synergistic effects, we have synthesized highly monodisperse, sub-2 nm, solid-solution AuPd NCs stabilized with poly(N-vinylpyrrolidone) (AuPd:PVP) using a newly developed ultrafine microfluidic mixing device with 15 μm wide multiple lamination channels. The synergistic enhancement for catalytic aerobic oxidation of benzyl alcohol exhibited a volcano-shaped trend, with a maximum at 20-65 at. % Pd. From X-ray photoelectron spectroscopic measurements, we confirmed that the enhanced activity originates from the enhanced electron density at the Au sites, donated by Pd sites.

  7. Rapid Preparation of Monodisperse Nano-Silver Colloids Using Microwave Irradiation%微波法快速制备单分散纳米银溶胶

    Institute of Scientific and Technical Information of China (English)

    徐光年; 乔学亮; 邱小林; 陈建国

    2012-01-01

    不添加任何还原剂,在PVP保护下通过微波辐射[Ag(NH3)2]OH络合物水溶液激发自由电子还原Ag+形成纳米银溶胶.UV-Vis吸收光谱测试表明,胶态纳米银粒子的吸光度随微波辐射时间的延长而增加,但最大吸收波长基本不变.当Ag+/PVP质量比为1:8,微波辐射时间为5 min时,吸光度趋于稳定.TEM观测和图像分析结果表明,纳米银粒子的形貌为球形、单分散、平均粒径1.36 nm、标准偏差0.54 nm.%The Ag+ were reduced to elemental silver by free-electron from microwave radiation [Ag(NH3)2]OH complex aqueous solution without any reducing agent, and the nano-silver sol was formed under the protection of PVP. UV-Vis absorption spectra show that the absorbance of the colloidal silver nanoparticles increases with the radiation time, but the maximal absorption wavelength does not change. The absorbance keeps stable when the microwave radiation time is up to 5 min at the mass ratio of Ag7PVP=l:8. TEM observation and image analysis results show that the morphology of nano-silver particles are spherical and monodisperse, with an average diameter of 1.36 nm and the standard deviation of 0.54 nm.

  8. Self-assembly and graft polymerization route to Monodispersed Fe3O4@SiO2--polyaniline core-shell composite nanoparticles: physical properties.

    Science.gov (United States)

    Reddy, Kakarla Raghava; Lee, Kwang-Pill; Kim, Ju Young; Lee, Youngil

    2008-11-01

    This study describes the synthesis of monodispersed core-shell composites of silica-modified magnetic nanoparticles and conducting polyaniline by self-assembly and graft polymerization. Magnetic ferrite nanoparticles (Fe3O4) were prepared by coprecipitation of Fe+2 and Fe+3 ions in alkaline solution, and then silananized. The silanation of magnetic particles (Fe3O4@SiO2) was carried out using 3-bromopropyltrichlorosilane (BPTS) as the coupling agent. FT-IR spectra indicated the presence of Fe--O--Si chemical bonds in Fe3O4@SiO2. Core-shell type nanocomposites (Fe3O4@SiO2/PANI) were prepared by grafting polyaniline (PANI) on the surface of silanized magnetic particles through surface initiated in-situ chemical oxidative graft polymerization. The nanocomposites were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Fourier transform infrared (FTIR) spectra, UV-visible spectroscopy, photoluminescence (PL) spectra, electrical conductivity and magnetic characteristics. HRTEM images of the nanocomposites revealed that the silica-modified magnetic particles made up the core while PANI made up the shell. The XPS spectrum revealed the presence of silica in the composites, and the XRD results showed that the composites were more crystalline than pure PANI. PL spectra show that composites exhibit photoluminescent property. Conductivity of the composites (6.2 to 9.4 x 10(-2) S/cm) was higher than that of pristine PANI (3.7 x 10(-3) S/cm). The nanocomposites exhibited superparamagnetism. Formation mechanism of the core-shell structured nanocomposites and the effect of modified magnetic nanoparticles on the electro-magnetic properties of the Fe3O4@SiO2/PANI nanocomposites are also investigated. This method provides a new strategy for the generation of multi-functional nanocomposites that composed of other conducting polymers and metal nanoparticles.

  9. Improved crystallinity, spatial arrangement and monodispersity of submicron La0.7Ba0.3MnO3 powders: A citrate chelation approach

    Science.gov (United States)

    Rao, Ch. N.; Samatham, S. Shanmukharao; Ganesan, V.; Sathe, V. G.; Phase, D. M.; Kale, S. N.

    2012-11-01

    The perovskite manganite systems have been the materials of tremendous interest due to their strong correlation between structure, transport and magnetism. These materials in their single-crystal form show colossal magneto-resistance (CMR), but the applied fields are very high (˜1-5 T). The polycrystalline samples do show high low-field magneto-resistance (LFMR), but good amount of control over particle sizes and grain-boundary distribution is required, which is well known but less realized in practical approaches. In this context, we report on synthesis and manipulation of polycrystalline La0.7Ba0.3MnO3 (LBMO) submicron powders using citric acid chelation. The Citrate-gel route is used to synthesize poly-dispersed LBMO powders which are subjected to citrate chelation for a duration of 0 (LB0) to 4 h(LB4) . The samples show improved ordering in X-ray diffraction patterns. Raman spectroscopy scans indicate changed mode signatures due to the probable chelating process, which alters the surface morphology. X-ray photoelectron microscopy shows an evidence of fine citrate layer on the grain boundaries. Low temperature B-H curves exhibit fine hysteresis loops for all samples, while room temperature B-H curves shows paramagnetic response. Scanning electron microscopy images showed the formation of well arranged, connected, mono-dispersed grains of LB4 sample, as against polydispered LB0. The magneto-resistance (at H=100 kOe) is seen to enhance for LB4 at its transition temperature (75%, as compared to LB0, where it is 60%), which can be attributed to the well-controlled inter-grain tunneling phenomenon and thin insulating regions in between, created due to citrate chelation, which probably enhances the scattering phenomenon and its susceptibility to applied fields. As citric acid is known to chelate Mn ions, it probably chelates the smaller LB particulate structure and leaves behind citrate-connected submicron grains of LBMO, which are seen to be well engineered.

  10. Ti(IV) carrying polydopamine-coated, monodisperse-porous SiO2 microspheres with stable magnetic properties for highly selective enrichment of phosphopeptides.

    Science.gov (United States)

    Salimi, Kouroush; Usta, Duygu Deniz; Çelikbıçak, Ömür; Pinar, Asli; Salih, Bekir; Tuncel, Ali

    2017-05-01

    A marked decrease in the saturation magnetization by the formation of functional shells around the magnetic core is an important disadvantage of magnetic core-shell nanoparticles. Another drawback of Ti(IV)-functionalized immobilized metal affinity chromatography (IMAC) sorbents is the acidic character of the binding medium used for Ti(4+) attachment onto composite magnetic nanoparticles, which causes an additional decrease in the saturation magnetization owing to the chemical interaction between the acidic moiety and the magnetic core. An IMAC sorbent in the form of magnetic microspheres with superior and stable magnetic properties with respect to magnetic core-shell nanoparticles was designed for phosphopeptide enrichment. Magnetic, monodisperse-porous silica microspheres (MagSiO2) 6μm in size were synthesized by a new staged-shape template hydrolysis-condensation protocol. A porous-silica shell layer was generated around the microspheres to protect the magnetic core from the acidic medium during Ti(4+) attachment (MagSiO2@SiO2). The MagSiO2@SiO2 microspheres were coated with a polydopamine shell (MagSiO2@SiO2@PDA) and Ti(4+) was attached onto the composite microspheres (MagSiO2@SiO2@PDA@Ti(IV)). Formation of the PDA layer and Ti(4+) attachment did not cause any significant decrease in the saturation magnetization. The platform exhibited excellent performance for phosphopeptide enrichment from the digests of phosphorylated proteins. Selectivity was investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The detection limit for phosphopeptide enrichment by the MagSiO2@SiO2@PDA@Ti(IV) microspheres from the tryptic digests of β-casein was 50 fmol/mL. Usability of the proposed magnetic sorbent with complex biological samples was demonstrated by successful enrichment of four phosphopeptides from human serum. The proposed sorbent showed stable performance over five repeated uses. Copyright © 2017 Elsevier B.V. All rights

  11. Tailored synthesis of monodispersed nano/submicron porous silicon oxycarbide (SiOC) spheres with improved Li-storage performance as an anode material for Li-ion batteries

    Science.gov (United States)

    Shi, Huimin; Yuan, Anbao; Xu, Jiaqiang

    2017-10-01

    A spherical silicon oxycarbide (SiOC) material (monodispersed nano/submicron porous SiOC spheres) is successfully synthesized via a specially designed synthetic strategy involving pyrolysis of phenyltriethoxysilane derived pre-ceramic polymer spheres at 900 °C. In order to prevent sintering of the pre-ceramic polymer spheres upon heating, a given amount of hollow porous SiO2 nanobelts which are separately prepared from tetraethyl orthosilicate with CuO nanobelts as templates are introduced into the pre-ceramic polymer spheres before pyrolysis. This material is investigated as an anode for lithium-ion batteries in comparison with the large-size bulk SiOC material synthesized under the similar conditions but without hollow SiO2 nanobelts. The maximum reversible specific capacity of ca. 900 mAh g-1 is delivered at the current density of 100 mA g-1 and ca. 98% of the initial capacity is remained after 100 cycles at 100 mA g-1 for the SiOC spheres material, which are much superior to the bulk SiOC material. The improved lithium storage performance in terms of specific capacity and cyclability is attributed to its particular morphology of monodisperse nano/submicron porous spheres as well as its modified composition and microstructure. This SiOC material has higher Li-storage activity and better stability against volume expansion during repeated lithiation and delithiation cycling.

  12. Rose-like monodisperse bismuth subcarbonate hierarchical hollow microspheres: One-pot template-free fabrication and excellent visible light photocatalytic activity and photochemical stability for NO removal in indoor air

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Fan [College of Environmental and Biological Engineering, Chongqing Technology and Business University, Chongqing, 400067 (China); Department of Civil and Structural Engineering, Research Center for Environmental Technology and Management, The Hong Kong Polytechnic University, Hong Kong (China); Department of Environmental Engineering, Zhejiang University, Hangzhou 310027 (China); Lee, S.C., E-mail: ceslee@polyu.edu.hk [Department of Civil and Structural Engineering, Research Center for Environmental Technology and Management, The Hong Kong Polytechnic University, Hong Kong (China); Wu, Zhongbiao [Department of Environmental Engineering, Zhejiang University, Hangzhou 310027 (China); Huang, Yu [Department of Civil and Structural Engineering, Research Center for Environmental Technology and Management, The Hong Kong Polytechnic University, Hong Kong (China); Fu, Min [College of Environmental and Biological Engineering, Chongqing Technology and Business University, Chongqing, 400067 (China); Ho, Wing-Kei [Nano and Advanced Materials Institute Limited, Hosted by The Hong Kong University of Science and Technology, Hong Kong (China); Zou, Shichun [School of Marine Sciences, Sun Yat-Sen University, Guangzhou, 510275 (China); Wang, Bo [Department of Civil and Structural Engineering, Research Center for Environmental Technology and Management, The Hong Kong Polytechnic University, Hong Kong (China)

    2011-11-15

    Graphical abstract: Rose-like monodisperse hierarchical nitrogen doped (BiO){sub 2}CO{sub 3} hollow microspheres fabricated by a one-pot template-free method exhibit excellent visible light photocatalytic activity and photochemical stability in the removal of NO in indoor air. The special hierarchical microstructure, the high charge separation efficiency and two-band-gap structure in all contribute to the outstanding photocatalytic performance. Highlights: {yields} Rose-like monodisperse hierarchical (BiO){sub 2}CO{sub 3} hollow microspheres are fabricated. {yields} The (BiO){sub 2}CO{sub 3} microspheres are self-assembled of single-crystalline nanosheets. {yields} Nitrogen is in situ doped into the lattice of hierarchical (BiO){sub 2}CO{sub 3} microspheres. {yields} The (BiO){sub 2}CO{sub 3} microspheres exhibit outstanding visible light activity for NO removal. {yields} The (BiO){sub 2}CO{sub 3} microspheres also exhibit high photochemical stability. - Abstract: Rose-like monodisperse hierarchical (BiO){sub 2}CO{sub 3} hollow microspheres are fabricated by a one-pot template-free method for the first time based on hydrothermal treatment of ammonia bismuth citrate and urea in water. The microstructure and band structure of the as-prepared (BiO){sub 2}CO{sub 3} superstructure are characterized in detail by X-ray diffraction, Raman spectroscopy, Fourier transform-infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, N{sub 2} adsorption-desorption isotherms, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The monodisperse hierarchical (BiO){sub 2}CO{sub 3} microspheres are constructed by the self-assembly of single-crystalline nanosheets. The aggregation of nanosheets result in the formation of three dimensional hierarchical framework containing mesopores and macropores, which is favorable for efficient transport of reaction molecules and harvesting of photo-energy. The result reveals the existence of

  13. Cascade energy transfer versus charge separation in ladder-type oligo(p-phenylene)/ZnO hybrid structures for light-emitting applications

    Energy Technology Data Exchange (ETDEWEB)

    Bianchi, F.; Sadofev, S.; Schlesinger, R.; Koch, N.; Henneberger, F.; Blumstengel, S., E-mail: sylke.blumstengel@physik.hu-berlin.de [Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin (Germany); Kobin, B.; Hecht, S. [Institut für Chemie and IRIS Adlershof, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin (Germany)

    2014-12-08

    Usability of inorganic/organic semiconductor hybrid structures for light-emitting applications can be intrinsically limited by an unfavorable interfacial energy level alignment causing charge separation and nonradiative deactivation. Introducing cascaded energy transfer funneling away the excitation energy from the interface by transfer to a secondary acceptor molecule enables us to overcome this issue. We demonstrate a substantial recovery of the light output along with high inorganic-to-organic exciton conversion rates up to room temperature.

  14. Rose-like monodisperse bismuth subcarbonate hierarchical hollow microspheres: one-pot template-free fabrication and excellent visible light photocatalytic activity and photochemical stability for NO removal in indoor air.

    Science.gov (United States)

    Dong, Fan; Lee, S C; Wu, Zhongbiao; Huang, Yu; Fu, Min; Ho, Wing-Kei; Zou, Shichun; Wang, Bo

    2011-11-15

    Rose-like monodisperse hierarchical (BiO)(2)CO(3) hollow microspheres are fabricated by a one-pot template-free method for the first time based on hydrothermal treatment of ammonia bismuth citrate and urea in water. The microstructure and band structure of the as-prepared (BiO)(2)CO(3) superstructure are characterized in detail by X-ray diffraction, Raman spectroscopy, Fourier transform-infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, N(2) adsorption-desorption isotherms, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The monodisperse hierarchical (BiO)(2)CO(3) microspheres are constructed by the self-assembly of single-crystalline nanosheets. The aggregation of nanosheets result in the formation of three dimensional hierarchical framework containing mesopores and macropores, which is favorable for efficient transport of reaction molecules and harvesting of photo-energy. The result reveals the existence of special two-band-gap structure (3.25 and 2.0 eV) for (BiO)(2)CO(3). The band gap of 3.25 eV is intrinsic and the formation of smaller band gap of 2.0 eV can be ascribed to the in situ doped nitrogen in lattice. The performance of hierarchical (BiO)(2)CO(3) microspheres as efficient photocatalyst are further demonstrated in the removal of NO in indoor air under both visible light and UV irradiation. It is found that the hierarchical (BiO)(2)CO(3) microspheres not only exhibit excellent photocatalytic activity but also high photochemical stability during long term photocatalytic reaction. The special microstructure, the high charge separation efficiency due to the inductive effect, and two-band-gap structure in all contribute to the outstanding photocatalytic activities. The discovery of monodisperse hierarchical nitrogen doped (BiO)(2)CO(3) hollow structure is significant because of its potential applications in environmental pollution control, solar energy conversion, catalysis and other related

  15. PREPARATION OF MONODISPERSE CdS NANOCRYSTALS/PNIPAM HYDROGEL AND ITS THERMOSENSITIVE FLUORESCENCE%单分散CdS纳米晶/PNIPAM复合水凝胶的制备及其温敏荧光特性

    Institute of Scientific and Technical Information of China (English)

    宋秋生; 朱小飞; 杨洋

    2012-01-01

    In order to investigate the influence of polymer aggregate state and chemical environment on the fluorescent performance of nanocrystal, monodisperse CdS nanocrystal is prepared via liquid-solid-solution synthesis ( LSS ) strategy, and monodisperse CdS nanocrystals/poly(iV-isopropylacrylamide) ( PNIPAM ) complex hydrogel are prepared by radical polymerization. The microstructure and performance of the monodisperse CdS nanocrystal and the complexes hydrogel are characterized by high resolution transmission electron microscopy (HRTEM) ,X-ray diffraction (XRD) ,Fourier transformed infrared spectroscopy (FTIR) , differential scanning calorimetry (DSC) and photoluminescence (PL). As evidenced from the HRTEM photos and XRD patterns, CdS nanocrystals show well monodispersity, and their size is about 2. 8 nm. PL spectrum shows that CdS nanocrystal has a strong emitting peak around 533 nm and a weak emitting peak around 469 nm. DSC curves suggest that the complex hydrogel is thermosensitive,and LCST of which is higher than that ofPNIPAM hydrogel. The results of PL spectra and DSC curves indicate that the complex hydrogel shows well thermosensitive-fluorescent performance, the variation of the fluorescent intensity of the complex hydrogel is in good agreement with its phase transformation. With variation of environmental temperature from 20℃ to 45℃ , the complex hydrogel changes from swollen state to collapse state, and the chemical environment around CdS nanocrystal changes from hydrophilic to hydrophobic, quantum yield of CdS nanocrystal changes respectively. The lower the environmental temperature is kept, the lower fluorescent intensity of the complex hydrogel is observed,and the fluorescent intensity changes sharply around its LCST. Testing on PL intensity change of CdS/PNIPAM hydrogel as a function of cooling-heating cycles between 20t and 40t demonstrates that the thermosensitive-fluorescent performance of the CdS/PNIPAM hydrogel is reversible.%采用液体-固

  16. Controlled synthesis and magnetic properties of monodisperse Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4}/MWCNT nanocomposites via microwave-assisted polyol process

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huaqiang, E-mail: wuhuaq@mail.ahnu.edu.cn [College of Chemistry and Materials Science, Anhui Key Laboratory of Functional Molecular Solids, Anhui Normal University, Wuhu 241000 (China); Zhang, Ning; Mao, Li; Li, Tingting; Xia, Lingling [College of Chemistry and Materials Science, Anhui Key Laboratory of Functional Molecular Solids, Anhui Normal University, Wuhu 241000 (China)

    2013-03-25

    Highlights: ► Microwave-assisted polyol preparation of monodisperse Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4}/MWCNT nanocomposites. ► The composition can be controlled through adjusting the atomic ratios of nickel and zinc salts. ► Ms reaches maximum for x = 0.5. Hc is low and thus exhibits superparamagnetic. -- Abstract: Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4}/MWCNT nanocomposites (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1) with controllable composition have been successfully synthesized via microwave-assisted polyol process using triethylene glycol solution (TREG) as solvent. Experimental results demonstrated that monodisperse face-centered cubical Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} nanoparticles with average size (6 nm) had been attached on the MWCNTs. The composition of ferrite nanoparticles can be controlled through adjusting the atomic ratios of the nickel and zinc salts in the mixed nitrate solution. The magnetic properties of nanocomposites with different Zn contents were measured by vibrating sample magnetometer (VSM). The saturation magnetization (Ms) of Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4}/MWCNT nanocomposites gradually increases when the x is less than 0.5 while decreases when the x is larger than 0.5. Ms reached maximum value when the x is 0.5. The coercivity (Hc) of nanocomposites is low at room temperature, which exhibits characteristic of superparamagnetic.

  17. Factors determining the stability, size distribution, and cellular accumulation of small, monodisperse chitosan nanoparticles as candidate vectors for anticancer drug delivery: application to the passive encapsulation of [14C]-doxorubicin

    Directory of Open Access Journals (Sweden)

    Masarudin MJ

    2015-12-01

    Full Text Available Mas Jaffri Masarudin,1 Suzanne M Cutts,2 Benny J Evison,3 Don R Phillips,2 Paul J Pigram4 1Department of Cell and Molecular Biology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Malaysia; 2Department of Biochemistry, La Trobe University, Melbourne, Victoria, Australia; 3Department of Chemical Biology and Therapeutics, St Jude Children's Hospital, Memphis, TN, USA; 4Department of Physics, La Trobe University, Melbourne, Victoria, Australia Abstract: Development of parameters for the fabrication of nanosized vectors is pivotal for its successful administration in therapeutic applications. In this study, homogeneously distributed chitosan nanoparticles (CNPs with diameters as small as 62 nm and a polydispersity index (PDI of 0.15 were synthesized and purified using a simple, robust method that was highly reproducible. Nanoparticles were synthesized using modified ionic gelation of the chitosan polymer with sodium tripolyphosphate. Using this method, larger aggregates were mechanically isolated from single particles in the nanoparticle population by selective efficient centrifugation. The presence of disaggregated monodisperse nanoparticles was confirmed using atomic force microscopy. Factors such as anions, pH, and concentration were found to affect the size and stability of nanoparticles directly. The smallest nanoparticle population was ~62 nm in hydrodynamic size, with a low PDI of 0.15, indicating high particle homogeneity. CNPs were highly stable and retained their monodisperse morphology in serum-supplemented media in cell culture conditions for up to 72 hours, before slowly degrading over 6 days. Cell viability assays demonstrated that cells remained viable following a 72-hour exposure to 1 mg/mL CNPs, suggesting that the nanoparticles are well tolerated and highly suited for biomedical applications. Cellular uptake studies using fluorescein isothiocyanate-labeled CNPs showed that cancer cells

  18. 膜乳化法制备尺寸均-P(NIPAM-co-AAc)微球及其羧基分布%Distribution of Carboxyl Groups in Monodispersed Poly(N-Isopropylacylamide-co-Acrylic Acid) Microspheres Prepared by Membrane Emulsification

    Institute of Scientific and Technical Information of China (English)

    司天保; 秦佳; 王玉霞; 马光辉

    2011-01-01

    Temperature-/pH-responsive monodispersed poly(N-isopropyl acrylamide-co-acrylic acid) [P(NIPAM-co-AAc)] microspheres were prepared by Shirasu porous glass membrane emulsification at room temperature with N,N,N',N'-tetramethylethylenediamine as accelerator and cyclohexane/trichluromethane mixture as oil phase. The monodispersed P(NIPAM-co-AAc) microspheres with controllable diameter could be reproducibly obtained with cyclohexane-trichloromethane mixture (volumetric ratio 7:3) as oil phase and two stage stirring speeds (140 and and 170 r/min) under the membrane emulsification pressure of 2 kPa. Conductometric titration was used to determine the distribution of carboxyl groups in the microspheres. Four-step titration curves of all the P(NIPAM-co-AAc)microspheres with different acrylic acid contents were obtained. With the increase of AAc content, the amounts of both exterior carboxyl and embeded carboxyl groups increased gradually, but the percentage of exterior carboxyl groups increased firstly, then remained at a fixed value. The highest percentage of exterior carboxyl groups was obtained with 15%(ω) acrylic acid in the microspheres.%采用膜乳化法,以环己烷和氯仿混合溶液为油相,在室温下通过加入加速剂TEMED引发聚合反应,制备了一系列不同内烯酸含量的P(NIPAM-co-AAc)微球.结果表明,在压力2 kPa、环己烷/氯仿体积比7:3、第一和第二阶段过膜搅拌速度分别为140和170 r/min的条件下,可制备粒径均一、大小可控、重复性较好的P(NlPAM-co-AAc)微球.用电导滴定法测定微球中羧基分布,所有不同丙烯酸含量的P(NIPAM-co-AAc)微球电导滴定曲线均为4阶梯形状,随其含量增加,微球外层羧基含量和内层包埋的羧基含量均逐渐增加,但外层羧基占总羧基含量比例先增大然后趋于不变,丙烯酸含量为15%时达最大值.

  19. 单分散间苯二酚-甲醛气凝胶微球的制备工艺%Preparation of Monodisperse Resorcinol-formaldehyde Aerogel Microspheres

    Institute of Scientific and Technical Information of China (English)

    侯海乾; 王朝阳; 唐永建; 付志兵; 周莹

    2009-01-01

    采用T型微流体注射成型技术,以邻苯二甲酸二丁酯、液体石蜡和司班80为油相,间苯二酚/甲醛(RF)溶液为水相,经过溶胶-凝胶、溶剂交换、超临界干燥等过程制备了单分散RF气凝胶微球,并就制备过程中RF溶液与分散剂油相的选择、预聚时间、流速比、搅拌速率、固化温度等影响因素进行了初步讨论.当RF溶液质量分数为10%,60℃预聚1.5 h,间苯二酚与碳酸钠的物质的量之比为100,邻苯二甲酸二丁酯与液体石蜡的质量比为8:1,流速比控制在8~16,搅拌速率为65~90r/min,固化温度为35℃时,制备得到了RF乳液,其粒径分布系数小于2%.%Based on a novel T-shaped microfluidic device, monodisperse RF aerogel microspheres are prepared by using dibutyl phthalate,atoleine and span 80 as oil phase, RF solution as water phase, and by sol-gel, solvent exchanging and supercritical drying. The factors such as the choice of RF solution and oil, prepolymerization time, the flow rate ratio of oil to water phase, stirring rate and solidification temperature, which affect the process have been preliminarily discussed. When the polymerization reaction occur in the following conditions: RF solution is 10% ,prepolymerization time is 1. 5 hours at 60℃, the molar ratio of resorcinol to sodium carbonate is 100, the mass ratio of dibutyl phthalate to atoleine is 8,the flow rate ratio of oil to water phase is 8-16, stirring rate is 65~90r/min and solidification temperature is 35℃, the experiment has fabricated monodisperse RF aerogel microspheres, whose coefficient of variation (CV value) of all the RF droplets is below 2% .

  20. Synthesis of Monodisperse Silica Particles Grafted with Concentrated Ionic Liquid-Type Polymer Brushes by Surface-Initiated Atom Transfer Radical Polymerization for Use as a Solid State Polymer Electrolyte

    Directory of Open Access Journals (Sweden)

    Takashi Morinaga

    2016-04-01

    Full Text Available A polymerizable ionic liquid, N,N-diethyl-N-(2-methacryloylethyl-N-methylammonium bis(trifluoromethylsulfonylimide (DEMM-TFSI, was polymerized via copper-mediated atom transfer radical polymerization (ATRP. The polymerization proceeded in a living manner producing well-defined poly(DEMM-TFSI of target molecular weight up to about 400 K (including a polycation and an counter anion. The accurate molecular weight as determined by a GPC analysis combined with a light scattering measurement, and the molecular weight values obtained exhibited good agreement with the theoretical values calculated from the initial molar ratio of DEMM-TFSI and the monomer conversion. Surface-initiated ATRP on the surface of monodisperse silica particles (SiPs with various diameters was successfully performed, producing SiPs grafted with well-defined poly(DEMM-TFSI with a graft density as high as 0.15 chains/nm2. Since the composite film made from the silica-particle-decorated polymer brush and ionic liquid shows a relatively high ionic conductivity, we have evaluated the relationship between the grafted brush chain length and the ionic conductivity.

  1. 不同粒径单分散SiO2粒子的制备与表面改性%Preparation and Surface Modification of Monodispersed Silica Colloid Particles with Different Dimensions

    Institute of Scientific and Technical Information of China (English)

    刘文军; 罗鲲; 喻亮

    2012-01-01

    TEOS was employed to prepare SiO2 colloid particles in diameters of 290nm, 960nm, 1.3μm and 1.9 μm, respectively,by sol-gel and seed-mediated growth methods. The effect of KH570 treatment on the surface hydro-phobicity of the S1O2 colloid particles was investigated. The SiO2 colloid particles were characterized by particle size analysis, SEM and XRD, which indicate that the products are monodispersed spherical SiO2 particles. Measurements of contact angle, hydroxyl group number and lipophilic degree were also carried out to investigate the modification process, which reveal that the concentration of KH570 and modification time exert a significant effect on the hydro-phobicity of the as^modified S\\Ch colloid particles, where the addition of acetone into the KH570 ethanol solution is more beneficial than water for the surface modification, An ethanol solution containing 1% KH570 with addition of acetone and 6-hour reflux were determined as the optimized condition for the modification of SiO2 particles. The introduction of KH570 into the sol-gel process was able to prepare hydrophobic monodispersed SiO2 particles with a diameter of 1.9μm in one step.%以正硅酸乙酯为原料,采用溶胶-凝胶法及种子生长法制备出不同粒径(290nm、960nm、1.3μm和1.9μm)的SiO2胶体颗粒,并研究了KH570对SiO2胶体颗粒表面疏水性的影响.粒度分析、扫描电镜及X射线衍射分析结果表明,产物均为球形单分散SiO2胶体颗粒;而接触角、表面羟基数和亲油化度等测试结果显示,KH570浓度和改性时间对SiO2胶体表面性质影响显著,且丙酮作为助剂改性效果比水更好,最佳条件是以丙酮为助剂,使用1%KH570回流处理6h.此外,在存在KH570时进行溶胶-凝胶过程可一步制备出直径为1.9μm的单分散SiO2疏水颗粒.

  2. Hydrothermal synthesis of superparamagnetic and red luminescent bifunctional Fe3O4@Mn2+-doped NaYF4:Yb/Er core@shell monodisperse nanoparticles and their subsequent ligand exchange in water

    Science.gov (United States)

    Qin, Zhenli; Du, Sinan; Luo, Yang; Liao, Zhijian; Zuo, Fang; Luo, Jianbin; Liu, Dong

    2016-08-01

    We report the use of an efficient hydrothermal method to synthesize superparamagnetic and red luminescent bifunctional Fe3O4@Mn2+-doped NaYF4:Yb/Er nanoparticles (NPs) with core@shell structures via a seed-growth procedure. Oleic acid coated Fe3O4 (OA-Fe3O4) NPs were initially synthesized using a coprecipitation method. The as-synthesized OA-Fe3O4 NPs were then used as seeds, on which the red upconversion luminescent shell (Mn2+-doped NaYF4:Yb/Er) was formed. Furthermore, hydrophobic to hydrophilic surface modification of the Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs was achieved via a ligand exchange method where oleic acid was displaced by a PEG phosphate ligand [PEG = poly(ethylene glycol)]. These materials were characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, and vibrating sample magnetometry (VSM). The Fe3O4 cores were uniformly coated with a Mn2+-doped NaYF4:Yb/Er shell, and the bifunctional Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs were monodispersed. Furthermore, the Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs exhibited a saturated magnetization value of 6.2 emu/g and emitted red luminescence under a 980 nm laser. The obtained bifunctional Fe3O4@Mn2+-doped NaYF4:Yb/Er NPs may find potential applications in drug targeting, bioseparation, and diagnostic analysis. The synthetic method may be employed for the preparation of other bifunctional nanomaterials.

  3. Hydrothermal synthesis of monodisperse ZnxCd1-xS spheres and their photocatalytic properties%水热合成单分散球状ZnxCd1-xS及其光催化性质

    Institute of Scientific and Technical Information of China (English)

    贾志方; 王富民; 辛峰

    2011-01-01

    采用简单的水热合成路线制备高产量单分散球状ZnxCd1-xS,通过X射线衍射、扫描电镜以及紫外-可见漫反射对所得的产物进行表征.结果表明,所得产物呈现六方相纤锌矿结构,并且ZnxCd1-xS产物呈现出很好的均匀性与规则性.采用光催化降解罗丹明B反应来评价ZnxCd1-xS的光催化活性.其中,Zn0.4Cd0.6S具有最高的催化活性,并且在降解反应过程中表现出很高的稳定性.%Monodisperse ZnxCd1-xS spheres were successfully fabricated with a high yield by a facile hydrothermal route.The as-prepared samples were characterized by X-ray diffractometry,scanning electron microscopy and UV-vis diffusion reflectance spectroscopy.The results indicate that all the prepared samples have the same hexagonal wurtzite phase and exhibit good size uniformity and regularity.Degradation of rhodamine-B (RhB) was used to evaluate the photocatalytic activities of ZnxCd1-xS samples.Zn0.4Cd0.6S possessed the best photocatalytic activity and exhibited high stability during the reaction.

  4. Size-tunable and monodisperse Tm³⁺/Gd³⁺-doped hexagonal NaYbF₄ nanoparticles with engineered efficient near infrared-to-near infrared upconversion for in vivo imaging.

    Science.gov (United States)

    Damasco, Jossana A; Chen, Guanying; Shao, Wei; Ågren, Hans; Huang, Haoyuan; Song, Wentao; Lovell, Jonathan F; Prasad, Paras N

    2014-08-27

    Hexagonal NaYbF4:Tm(3+) upconversion nanoparticles hold promise for use in high contrast near-infrared-to-near-infrared (NIR-to-NIR) in vitro and in vivo bioimaging. However, significant hurdles remain in their preparation and control of their morphology and size, as well as in enhancement of their upconversion efficiency. Here, we describe a systematic approach to produce highly controlled hexagonal NaYbF4:Tm(3+) nanoparticles with superior upconversion. We found that doping appropriate concentrations of trivalent gadolinium (Gd(3+)) can convert NaYbF4:Tm(3+) 0.5% nanoparticles with cubic phase and irregular shape into highly monodisperse NaYbF4:Tm(3+) 0.5% nanoplates or nanospheres in a pure hexagonal-phase and of tunable size. The intensity and the lifetime of the upconverted NIR luminescence at 800 nm exhibit a direct dependence on the size distribution of the resulting nanoparticles, being ascribed to the varied surface-to-volume ratios determined by the different nanoparticle size. Epitaxial growth of a thin NaYF4 shell layer of ∼2 nm on the ∼22 nm core of hexagonal NaYbF4:Gd(3+) 30%/Tm(3+) 0.5% nanoparticles resulted in a dramatic 350 fold NIR upconversion efficiency enhancement, because of effective suppression of surface-related quenching mechanisms. In vivo NIR-to-NIR upconversion imaging was demonstrated using a dispersion of phospholipid-polyethylene glycol (DSPE-PEG)-coated core/shell nanoparticles in phosphate buffered saline.

  5. 高度单分散聚乙烯基倍半硅氧烷球形纳米粒子的制备及性能%Preparation and Properties of Highly Monodisperse Spherical Poly (vinylsilsesquioxane) Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    陈连喜; 李洁; 李曦; 翟鹏程; 张江涛; 张中明

    2013-01-01

    在水溶液中,以乙烯基三乙氧基硅烷(VTES)为前驱体,氨水(NH3·H2O)为催化剂,在表面活性剂十二烷基苯磺酸钠(SDBS)存在下,通过溶胶一凝胶法成功合成了具有不同粒径、高度单分散的聚乙烯基倍半硅氧烷(PVSQ)球形纳米粒子.研究结果表明,催化剂NH3·H2O与表面活性剂SDBS的用量对PVSQ的粒径和粒径分布影响很大,而前驱体VTES的用量对PVSQ的粒径无明显影响.通过场发射扫描电子显微镜(FESEM)、傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)及热重(TG)分析对产物的形貌、粒径和粒径分布、结构及热性能进行了表征.%In aqueous solution,highly monodisperse spherical poly (vinylsilsesquioxane) (PVSQ) particles with various sizes have been prepared successfully in the presence of surfactant sodium dodecyl benzene sulfonate(SDBS) using vinyl triethoxysilane (VTES) as precursor and ammonia hydroxide as catalyst by sol-gel method.The research results show that the amounts of catalyst(NH3· H2O) and surfactant(SDBS) have great effects on size and size distribution of PVSQ.However,the amount of precursor(VTES) has unobvious effect on size and size distribution of PVSQ.The shape,size and size distribution,structure,surface property and thermal behavior of the resulting products were analyzed and characterized by field emission scanning electron microscope(FESEM),Fourier transform infrared spectroscopy (FTIR),X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis(TGA),respectively.

  6. Synthesis of monodisperse spherical nanometer ZrO{sub 2} (Y{sub 2}O{sub 3}) powders via the coupling route of w/o emulsion with urea homogenous precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Ying [Department of Materials, College of Chemical and Environment Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China); Dong, Shijie, E-mail: dongsjsj@163.com [School of Mechanical Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China); Wang, Huihu [School of Mechanical Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China); Du, Kuanhe; Zhu, Qingbiao [Department of Materials, College of Chemical and Environment Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China); Luo, Ping [School of Mechanical Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China)

    2012-03-15

    Graphical abstract: In this paper, the weight loss and reaction evolution of ZrO{sub 2} precursor powders are determined by TG-DTA, and 600 Degree-Sign C is the most reasonable calcination temperature of precursor according to the TG-DTA. At the same time, we study the effect of reaction conditions upon the particle sizes, such as concentration of zirconium nitrate solution, reaction temperature and urea content. TEM micrographs of zirconia powders indicated that ZrO{sub 2} nano-powders prepared via the coupling route of w/o emulsion with homogenous precipitation possess spherical shape and excellent dispersing. Highlights: Black-Right-Pointing-Pointer The monodisperse spherical nanometer ZrO{sub 2} (Y{sub 2}O{sub 3}) powders have been prepared via the coupling route of w/o emulsion with urea homogenous precipitation. Black-Right-Pointing-Pointer The principle of the coupling route of emulsion with homogenous precipitation has been studied. Black-Right-Pointing-Pointer The concentration of zirconium nitrate, reaction temperature of water bath and the quantity of urea effect regularly on the average particle size of products. -- Abstract: Using xylol as the oil phase, span-80 as the surfactant, and an aqueous solution containing zirconium (3 mol% Y{sub 2}O{sub 3}) and urea as the water phase, tetragonal phase ZrO{sub 2} nano-powders have been prepared via the coupling route of w/o emulsion with urea homogenous precipitation. The effects of the zirconium concentration, the reaction temperature and the urea content on the average size of the products have been examined. The as-prepared ZrO{sub 2} powders and the precursor powders were characterized by TGA-DTA, XRD, TEM and BET. Experimental results indicate that ZrO{sub 2} powders prepared via the coupling route of w/o emulsion with urea homogenous precipitation possess some excellent characteristics, such as well-rounded spherical shape and excellent dispersing.

  7. Preparation, Characterization of Monodisperse Polysiloxane Microspheres and Its Application as Light Scattering Agents%单分散聚硅氧烷微球的制备表征及作为光散射剂的应用

    Institute of Scientific and Technical Information of China (English)

    马文石; 张冬桥; 段宇; 万兆荣; 王洪; 徐迎宾

    2012-01-01

    以乳液聚合法制备粒径分布均匀、球形度良好的聚硅氧烷微球。采用扫描电镜(SEM)、动态光散射(DLS)、红外光谱(FT-IR)、X射线衍射(XRD)、热重分析(TGA)和接触角等测试技术对微球的微观形貌、粒径大小及分布、聚集态结构、耐热性、疏水性等进行了表征。将平均粒径为1.5μm的聚硅氧烷微球作为光散射剂添加到光学级聚甲基丙烯酸甲酯(PMMA)树脂中,可制备出性能优良的光散射材料。当聚硅氧烷微球添加质量分数约0.6%时,光散射材料的透光率是86.1%,雾度是91.25%,拉伸强度达到最大值77.2 MPa,弯曲强度是87.2 MPa,简支梁缺口冲击强度是2.16 kJ/m2,悬臂梁缺口冲击强度是2.71 kJ/m2,综合性能良好。%Highly uniform and monodisperse polysiloxane microspheres were prepared by emulsion polymeration.The morphology,size distribution,and state of aggregation were characterized by SEM,dynamic light scattering(DLS),FT-IR and XRD.The thermodecomposition and hydrophobicity of these microspheres were investigated with TGA and water contact angle measurement.Light scattering material with excellent performance could be prepared by blending polysiloxane microspheres(the average size of 1.5 μm) with optical-grade polymethylmethacylate(PMMA).When the mass fraction of microspheres is about 0.6%,the transmittance of composite material is 86.1% and the haze is 91.25%,the tensile strength reaches its maximum,namely 77.2 MPa,the bending strength is 87.2 MPa,the charpy notched impact strength is 2.16 kJ/m^2,the Izod notched impact strength is 2.71 kJ/m^2.The comprehensive properties of the composite material are excellent.

  8. 单分散性纳米银凝胶制备及其抗菌性能研究%Study on preparation of monodispersity silver nanogel and its antimicrobial properties

    Institute of Scientific and Technical Information of China (English)

    范友华; 陈泽君; 申爱荣; 马芳

    2012-01-01

    以聚乙烯吡咯烷酮(K30)为稳定剂,硝酸银为银源,通过化学还原法,制备了单分散性稳定存在的纳米银凝胶,并运用透射电子显微镜(TEM)、紫外可见吸收光谱(UV-Vis)等对纳米银凝胶及室温下存放1年凝胶进行了表征.结果表明,纳米银凝胶在室温下放置1年后仍能稳定存在,纳米银颗粒无明显团聚,分散性好.以大肠杆菌为研究对象,纳米银凝胶原样品的质量分数为31.25×10-6,而保存1年后纳米银凝胶质量分数大于62.5×10-6时,有较好抑菌效果;该原样最低抗菌浓度(MIC)为31.25×10-6,而保存1年后纳米银凝胶的最低抗菌浓度为62.5×10-6,表明该纳米银凝胶具有较好的抗菌性能,且随着保存时间延长,该纳米银凝胶的抗菌性能有所下降.%Monodispersity silver nanogel was prepared via chemical reduction method using silver nitrate as silver source and Polyvinylpyrrolidone (PVP) as stabilizer. The silver nanogel and stored for one-year silver nanogel were characterized by transmission electron microscope, UV-Vis spectrum. The results reveal that the silver nanogel deposited for one-year under indoor temperature had good stability and good dispersibility, its silver grains had no envious agglomeration. Antibacterial nature tests were carried out with Escherichia coli. The results show that the silver nanogel had good antibacterial performance and the minimum inhibitory concentrations (MIC) of the original silver nanogel was 31.25 × 10-6, while the sample stored one- year, the MIC was 62.5 ×10-6. The results prove that the antibacterial performance of nanogel descend with the storing time extension.

  9. 单分散磁性纳米粒子固定化猪胰脂肪酶的研究%STUDY ON LIPASE IMMOBILIZATION ON MONODISPERSE MAGNETIC NANOPARTICLES

    Institute of Scientific and Technical Information of China (English)

    朱浩; 侯晨; 李彦锋

    2011-01-01

    A simple, effective, green and economic approach of lipase immobilization is provided in this article. Single-crystal,hydrophilic, biocompatible Fe3O4magnetic nanoparticles as good carriers were prepared via a solvothermal reduction method. Microsphere diameters were observed to be about 200 nm by transmission electron microscopy ( TEM ). Superior monodispersity was demonstrated, and saturation magnetization was found to be 83.7 emug-1 . The resulting products were modified directly with γ-aminopropyltriethoxysilane (APTS). Porcine pancreas lipase ( PPL) was covalently immobilized on the obtained particles using glutaraldehyde as a coupling reagent. The enzymatic activities of free and immobilized PPL were measured by titration of fatty acid which came from the hydrolysis of olive oil and the amount of protein was determined by the Bradford method using bovine serum albumin ( BSA) as a standard. The factors related with the activity of the immobilized lipase on prior carriers, such as the pH value of the immobilized reaction, the concentration of glutaraldehyde and the amount of enzyme were investigated. The immobilized lipase exhibited excellent thermal stability and reusability in comparison with free enzyme. High activity recovery (54. 8% ) of the immobilized lipase was achieved and the amount of protein was up to 120 mg/g. This immobilized lipase can be reused 10 times with the enzymatic activity remained above 90% .%借助溶热法制备了一种亲水及生物相容良好的Fe3O4磁性纳米粒子,用γ-氨丙基三乙氧基硅烷直接对所得磁性粒子表面改性,然后用戊二醛偶联法制得了固定化猪胰脂肪酶.表征研究显示,所得磁性粒子粒径约200 nm,具有良好的单分散性和磁响应性.考察了戊二醛浓度、给酶量和反应时间对脂肪酶固定化过程的影响,并通过游离酶与固定化酶的比较研究了所得固定化酶的性质.所得固定化猪胰脂肪酶呈现出优异的热稳定性

  10. Interface area transport of monodispersed spherical particulates

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chong H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-05

    We present an interface area transport model required in tracking of mass, momentum, and energy exchange between dispersed and background materials. The basic transport equation has been rigorously derived from the volume fraction evolution equation. Interface area changes due to mass transport and local compression/expansion are included. The model is then simplified for the case in which the dispersed phase is composed of spheres of locally uniform size. A procedure for calculating advective flux with interface reconstruction has been suggested.

  11. Preparation and Properties of Monodisperse SnO2 Hollow Micro/Nano Spheres%单分散SnO2中空微纳米球的制备和性质

    Institute of Scientific and Technical Information of China (English)

    蔡宏敏; 任素贞; 王萌; 贾翠英

    2013-01-01

      模板法是制备无机中空微纳米球的重要方法之一。本文以苯乙烯为单体,通过乳液聚合得到粒径约为620 nm的单分散聚苯乙烯(PS)微球。以磺化后的聚苯乙烯(PSS)微球为模板,利用阴阳离子静电吸附作用,将PSS与前驱体SnSO4中的Sn2+结合。通过Sn2+在乙醇-水介质中的水解作用得到核-壳复合结构,再经高温煅烧,得到SnO2中空微纳米球。实验对前驱体的浓度、表面活性剂的用量、反应时间及模板选择等方面做了研究,通过扫描电镜(SEM)、X射线衍射(XRD)、红外(IR)光谱、热重分析(TGA)、H2程序升温还原(H2-TPR)、Brunauer-Emmett-Tel er (BET)比表面积等技术深入探究SnO2中空微纳米球的结构,并对比中空SnO2与实心粒子的氧化还原特性。 BET和H2-TPR显示将SnO2制备成微纳米空心球后其比表面积增大,表面氧空位明显增多,氧化活性明显提高。从IR及XRD推断核-壳结构形成机理,进而优化出简单合理的实验方案,获得表面光滑、结构致密,包覆厚度可控的SnO2中空微纳米球。%Templating is one of the most important methods for preparation of inorganic hol ow micro/nano spheres. We prepared monodisperse polystyrene (PS) microspheres having a diameter of 620 nm by the emulsion polymerization of styrene. Sulfonated polystyrene (PSS) microspheres were used as a template, through electrostatic adsorption of anions and cations, for modification with Sn2 + from SnSO4 precursor. The core-shel composite structures thereby produced through Sn2+ hydrolysis in an ethanol-water medium were calcined at high temperature to remove PSS and to obtain SnO2 hol ow micro/nano spheres. We investigated the effects of precursor concentration, amount of surfactant, reaction time, and templates choice. Scanning electron microscopy (SEM), X-ray diffraction (XRD), infrared (IR) spectroscopy, thermogravimetric analysis (TGA), H2 temperature programmed

  12. Electric-Field-Induced Fluorescence Quenching in Polyfluorene, Ladder-Type Polymers, and MEH-PPV Evidence for Field Effects on Internal Conversion Rates in the Low Concentration Limit

    NARCIS (Netherlands)

    Moscatelli, Alberto; Livingston, Kathryn; So, Woong Young; Lee, Suk Jun; Scherf, Ullrich; Wildeman, Jurjen; Peteanu, Linda A.

    2010-01-01

    Electric field-induced fluorescence quenching has been measured for a series of conjugated polymers with applications in organic light-emitting diodes Electrofluorescence measurements on isolated chains in a glassy matrix at 77 K show that the quenching efficiency for poly[2-methoxy-5-(2-ethylhexylo

  13. Monodisperse Ru Nanoparticles in [Bmim]BF4:Preparation and Application in Benzene Selective Hydrogenation%离子液体[Bmim]BF4中单分散Ru纳米粒子的制备及选择加氢性能

    Institute of Scientific and Technical Information of China (English)

    魏珺芳; 王延吉; 励娟; 薛伟

    2011-01-01

    The monodisperse Ru nanoparticles were prepared by chemical reduction method in 1-butyl-3-methyl limidizaolium tetrafluoroborate ([BMim]BF4). The prepared Ru nanoparticles were characterized by XRD as hexagonal close packed structure and no diffraction peak from oxidation products. TEM analysis of these nanoparticles shows that the monodisperse Ru nanoparticles prepared by positive dripping method disperse in the ionic liquids with diameter less than 5 nm. The Ru nanoparticles prepared by reverse dripping method agglomerate with diameter more than 10 nm. FTIR results indicate that a physically absorbed layer of ionic liquid is evident on the surface of Ru nanoparticles. TG results indicate that the ionic liquid serves not only as a protective agent or stabilizing agent to inhibit the aggregation of Ru nanoparticles, but also a modification agent adsorbed on the Ru nanoparticles. Results of benzene selective hydrogenation show that benzene conversion is relatively high in the reaction system with water, however the selectivity of cyclohexene is low, only 14.5% at 27.3% benzene conversion in the same system.%采用化学还原法在离子液体1-丁基-3-甲基咪唑四氟硼酸盐([BMim]BF4)中制备了单分散纳米金属Ru粒子.采用X射线衍射(XRD)、透射电镜(TEM)、傅里叶红外光谱(FTTR)及热重(TG)对所制备样品的形貌和结构进行了表征.XRD表征结果显示:在[BMim]BF4中制备的Ru具有六方紧密堆积结构,无氧化物峰出现;TEM结果显示:采用正滴法制备的Ru纳米粒子为球形颗粒,呈现良好的单分散状态,粒径分布窄,为2~5 nm,而采用反滴法制备的Ru纳米粒子则发生了严重的团聚,团聚体粒径大于10 nm;FTIR表征表明:Ru纳米粒子表面存在[BMjm]BF4液体层,分析二者之间存在较强的物理吸附作用,[BMim]BF4在Ru纳米粒子的制备中起到了修饰剂和保护剂的双重作用,这一推论通过TG分析得到了进一步验证.将分散于[BMim]BF4的Ru纳

  14. 单分散、规则球形Au@SiO_2核-壳纳米粒的制备及光谱研究%Preparation and Spectrum Study of Monodispersed Regular Spherical Au@SiO_2 Core-Shell Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    姚祖福; 黄可龙; 于金刚; 郭军; 李艳华; 方东

    2009-01-01

    Using 3-mercaptopropyhrimethoxysilane as linker,single gold nanoparticle was successfully encapsulated by silicon oxide shell,and Au@SiO_2 core-sheU nanoparticles were prepared.The nanocomposites were spherical and monodispersal.The gold nanoparticle located at the center of silica nano-sphere.No congregating gold nanoparticles were embedded in one silica sphere.The morphologies of the samples were characterized by transmission electron microscopy(TEM).The chemical contents of the samples were analyzed using energy diffraction X-ray(EDX)spectroscopy.And their optical properties were studied.%采用3-巯基丙基三甲氧基硅烷作为联结剂,成功将单个金纳米粒子包在氧化硅壳中,制得Au@SiO_2核壳纳米粒子;该复合纳米粒子形貌呈球形、单分散性较好,金纳米粒子位于氧化硅球的中心.无团聚的金纳米粒子包覆在氧化硅壳中.采用透射电镜(TEM)对样品的形貌进行了表征,通过能量散射X-射线能谱(EDX)分析了目标物的化学成分,并对所得核壳纳米粒子的光谱性质进行了研究.

  15. Synthesis of a Novel Surfactant with Two Alkyl Tail-Chains (DDOBA) and Fabrication of Hydrophobic Gold Nanoparticles with High Monodispersity%新型双链表面活性剂DDOBA的合成与高单分散性憎水纳米金的制备

    Institute of Scientific and Technical Information of China (English)

    韩莹; 朱露; 沈明; 李恒恒

    2013-01-01

    3,4-Didodecyloxybenzylamine (DDOBA), a novel surfactant with two alkyl tail-chains, was designed and synthesized. DDOBA-capped hydrophobic gold nanoparticles were successful y fabricated using formic acid as a reducing agent in a DDOBA/n-butanol/n-heptane/formic acid/HAuCl4·4H2O water/oil (W/O) microemulsion system under microwave irradiation. DDOBA-stabilized gold nanoparticles were characterized by ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD). The experimental results showed that DDOBA not only participated in the formation of a stable W/O microemulsion system, but also became a good protecting agent for gold nanoparticles. Within an appropriate concentration range of components in the W/O microemulsion system, hydrophobic gold nanoparticles with high monodispersity can be obtained using this experimental method and automatical y form large areas of ordered monolayer built with DDOBA-capped gold nanoparticles at the air/water interface.%  自行设计合成了新颖的苄胺型双链表面活性剂3,4-双十二烷氧基苄胺(DDOBA)。利用DDOBA/正丁醇/正庚烷/甲酸/HAuCl4·4H2O自发形成的水/油(W/O)型微乳液作为微反应器,通过微波辐射下的甲酸还原法成功制备了DDOBA保护的憎水性金纳米粒子,并通过紫外-可见(UV-Vis)光谱、透射电镜(TEM)、高分辨透射电镜(HR-TEM)和X射线衍射(XRD)等方法进行了表征和分析。结果显示, DDOBA既可参与形成稳定的W/O型(油包水型)微乳液,又可作为金纳米粒子的良好保护剂。在合适的微乳液体系组成范围内,用本实验方法可以获得高单分散性的憎水性金纳米粒子,并能在空气/水界面上自动形成大面积短程有序的纳米金二维自组装膜。

  16. Preparation of Monodisperse Core-Shell Type Silver-coated Silica Composite-spheres and its Mechanism%单分散核-壳型银包覆二氧化硅微球的制备及复合机理研究

    Institute of Scientific and Technical Information of China (English)

    洪阳; 诸跃进

    2015-01-01

    The synthesis of bare silica is achieved based on Stober method and the synthesis of SiO2@Ag has been obtained by controlled-reduction of silver nitrate and ammonia in ethyl alcohol with PVP as a protective and reducing agent. The particles size, structure and composition analyses reveal that the resultant SiO2@Ag composite-spheres are monodisperse which is well-proportioned and stable with a mean silica core diameter of 255 nm and the silver shell nanoparticles diameter of 8 nm. The synthesis mechanism of the core-shell type composite-spheres is studied in terms of the impact on growth and morphology from these the main factors that are silver source solution, reaction temperature and pH of the reaction solution. The optimal synthesis conditions are finally obtained as follows: the optimum ion concentration is about 2.0 mmol·L-1, the main growth temperature is 40~50℃, and the best core-shell structure appears in pH=12.12.%基于Stober水解法制备得到纯二氧化硅微球,通过以PVP为保护剂和还原剂的可控还原法制备得到银包覆二氧化硅复合微球.该复合微球的单分散性好,且均匀而稳定,其中核的平均粒径在255 nm,壳层银纳米粒子粒径约为8 nm.根据银源溶液的浓度、反应温度以及反应液pH值等3个主要因素对复合微球的生长和形貌的重要影响,研究了该核-壳型复合微球的合成机理,得到最优合成条件:最佳离子浓度为2.0 mmol·L-1,主要生长温度为40~50℃,且最适酸碱度在pH=12.12处.该复合微球在光学和催化等诸多领域都有广泛的潜在应用前景.

  17. Dynamic dilution exponent in monodisperse entangled polymer solutions

    DEFF Research Database (Denmark)

    Shahid, T.; Huang, Qian; Oosterlinck, F.

    2017-01-01

    We study and model the linear viscoelastic properties of several entangled semi-dilute and concentrated solutions of linear chains of different molar masses and at different concentrations dissolved in their oligomers. We discuss the dilution effect of the oligomers on the entangled long chains...... of the long chain extremities. Then we discuss the influence of the polymer concentration on the terminal relaxation time of the solutions and how this can be modelled by the enhanced contour length fluctuation process (CR-CLF). We point out that this larger dilution effect is not only a function...... of concentration but also depends on the molar mass of the chains. While the proposed approach successfully explains the viscoelastic properties of a large number of semi-dilute solutions of polymers in their own oligomers, important discrepancies are found for semi-dilute entangled polymers in small...

  18. Porous TiO2 Assembled from Monodispersed Nanoparticles.

    Science.gov (United States)

    Liu, Xu; Duan, Weijie; Chen, Yan; Jiao, Shihui; Zhao, Yue; Kang, Yutang; Li, Lu; Fang, Zhenxing; Xu, Wei; Pang, Guangsheng

    2016-12-01

    Porous TiO2 were assembled by evaporating or refluxing TiO2 colloid, which was obtained by dispersing the TiO2 nanoparticles with a crystallite size (d XRD) of 3.2 nm into water or ethanol without any additives. Porous transparent bulk TiO2 was obtained by evaporating the TiO2-C2H5OH colloid at room temperature for 2 weeks, while porous TiO2 nanospheres were assembled by refluxing the TiO2-H2O colloid at 80 °C for 36 h. Both of the porous TiO2 architectures were pore-size-adjustable depending on the further treating temperature. Porous TiO2 nanospheres exhibited enhanced photocatalysis activity compared to the nanoparticles.

  19. Elongational viscosity of monodisperse and bidisperse polystyrene melts

    DEFF Research Database (Denmark)

    Nielsen, Jens Kromann; Rasmussen, Henrik Koblitz; Hassager, Ole

    2005-01-01

    polystyrene melt with a molecular weight of 390 kg/mole (PS390K). The measurements have all been preformed on a Filament Streching Rheometer (FSR) equipped with an oven: A cylindrical test sample is placed between two parallel, circular plates and stretched. A load cell measures the transmitted force...

  20. Cytotoxicity of monodispersed chitosan nanoparticles against the Caco-2 cells

    Energy Technology Data Exchange (ETDEWEB)

    Loh, Jing Wen [Laboratory for Drug Delivery, Pharmacy, Characterisation and Analysis, University of Western Australia (Australia); Saunders, Martin [Centre for Microscopy, Characterisation and Analysis, University of Western Australia (Australia); Lim, Lee-Yong, E-mail: lee.lim@uwa.edu.au [Laboratory for Drug Delivery, Pharmacy, Characterisation and Analysis, University of Western Australia (Australia); School of Biomedical, Biomolecular and Chemical Sciences, 35 Stirling Hwy, Crawley 6009 (Australia)

    2012-08-01

    Published toxicology data on chitosan nanoparticles (NP) often lack direct correlation to the in situ size and surface characteristics of the nanoparticles, and the repeated NP assaults as experienced in chronic use. The aim of this paper was to breach these gaps. Chitosan nanoparticles synthesized by spinning disc processing were characterised for size and zeta potential in HBSS and EMEM at pHs 6.0 and 7.4. Cytotoxicity against the Caco-2 cells was evaluated by measuring the changes in intracellular mitochondrial dehydrogenase activity, TEER and sodium fluorescein transport data and cell morphology. Cellular uptake of NP was observed under the confocal microscope. Contrary to established norms, the collective data suggest that the in vitro cytotoxicity of NP against the Caco-2 cells was less influenced by positive surface charges than by the particle size. Particle size was in turn determined by the pH of the medium in which the NP was dispersed, with the mean size ranging from 25 to 333 nm. At exposure concentration of 0.1%, NP of 25 ± 7 nm (zeta potential 5.3 ± 2.8 mV) was internalised by the Caco-2 cells, and the particles were observed to inflict extensive damage to the intracellular organelles. Concurrently, the transport of materials along the paracellular pathway was significantly facilitated. The Caco-2 cells were, however, capable of recovering from such assaults 5 days following NP removal, although a repeat NP exposure was observed to produce similar effects to the 1st exposure, with the cells exhibiting comparable resiliency to the 2nd assault. -- Highlights: ► Chitosan nanoparticles reduced mitochondrial dehydrogenase activity. ► Cellular uptake of chitosan nanoparticles was observed. ► Chitosan nanoparticles inflicted extensive damage to the cell morphology. ► The transport of materials along the paracellular pathway was facilitated.

  1. Monodisperse, Uniformly-Shaped Particles for Controlled Respiratory Vaccine Delivery

    Science.gov (United States)

    Fromen, Catherine Ann

    The majority of the world's most infectious diseases occur at the air-tissue interface called the mucosa, including HIV/AIDS, tuberculosis, measles, and bacterial or viral gut and respiratory infections. Despite this, vaccines have generally been developed for the systemic immune system and fail to provide protection at the mucosal site. Vaccine delivery directly to the lung mucosa could provide superior lung protection for many infectious diseases, such as TB or influenza, as well as systemic and therapeutic vaccines for diseases such as Dengue fever, asthma, or cancer. Specifically, precision engineered biomaterials are believed to offer tremendous opportunities for a new generation of vaccines. The goal of this approach is to leverage naturally occurring processes of the immune system to produce memory responses capable of rapidly destroy virulent pathogens without harmful exposure. Considerable knowledge of biomaterial properties and their interaction with the immune system of the lung is required for successful translation. The overall goal of this work was to fabricate and characterize nano- and microparticles using the Particle Replication In Non-wetting Templates (PRINT) fabrication technique and optimize them as pulmonary vaccine carriers. (Abstract shortened by ProQuest.).

  2. Monodisperse cobalt ferrite nanomagnets with uniform silica coatings.

    Science.gov (United States)

    Dai, Qiu; Lam, Michelle; Swanson, Sally; Yu, Rui-Hui Rachel; Milliron, Delia J; Topuria, Teya; Jubert, Pierre-Olivier; Nelson, Alshakim

    2010-11-16

    Ferro- and ferrimagnetic nanoparticles are difficult to manipulate in solution as a consequence of the formation of magnetically induced nanoparticle aggregates, which hamper the utility of these particles for applications ranging from data storage to bionanotechnology. Nonmagnetic shells that encapsulate these magnetic particles can reduce the interparticle magnetic interactions and improve the dispersibility of the nanoparticles in solution. A route to create uniform silica shells around individual cobalt ferrite nanoparticles--which uses poly(acrylic acid) to bind to the nanoparticle surface and inhibit nanoparticle aggregation prior to the addition of a silica precursor--was developed. In the absence of the poly(acrylic acid) the cobalt ferrite nanoparticles irreversibly aggregated during the silica shell formation. The thickness of the silica shell around the core-shell nanoparticles could be controlled in order to tune the interparticle magnetic coupling as well as inhibit magnetically induced nanoparticle aggregation. These ferrimagnetic core-silica shell structures form stable dispersion in polar solvents such as EtOH and water, which is critical for enabling technologies that require the assembly or derivatization of ferrimagnetic particles in solution.

  3. Two-Dimensional, High Flow, Precisely Controlled Monodisperse Drop Source

    Science.gov (United States)

    1993-03-15

    pro - duces a small effect on the undriven sheet. When the spatial perturbations are combined with temporal perturbations (the acous- tic drive), the...Industrial Park Road Medway MA 02053 Telephone 800-255-8823 Distributor of tubing and fittings Laser drilling of small nozzles 22. Mikros

  4. Microfluidic synthesis of monodisperse Cu nanoparticles in aqueous solution.

    Science.gov (United States)

    Ke, Te; Zeng, Xiao-Fei; Wang, Jie-Xin; Le, Yuan; Chu, Guang-Wen; Chen, Jian-Feng; Shao, Lei

    2011-06-01

    The continuous production of Cu nanoparticles with a particle size of 2-5 nm was conducted by sodium borohydride reduction of copper sulfate in aqueous solution in a tube-in-tube microchannel reactor (TMR), which consists of an inner tube and an outer tube with the reaction performed in the annular microchannel between these two tubes. The as-prepared Cu nanoparticles were compared with those obtained by a conventional batch synthesis process by using transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis spectroscopy. Due to the highly intensified micromixing effects in the TMR, Cu nanoparticles prepared by this route exhibits a smaller particle size, narrower size distribution and better stability in air. The TMR shows an excellent ability of preparing high-quality Cu nanoparticles in mild conditions. In addition, with the unique microchannel structure, the throughput capability of the TMR for the production of Cu nanoparticles is up to several liters per minute.

  5. Synthesis of mono-dispersed nanofluids using solution plasma

    Energy Technology Data Exchange (ETDEWEB)

    Heo, Yong Kang, E-mail: yk@rd.numse.nagoya-u.ac.jp [Graduate School of Materials Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); Bratescu, Maria Antoaneta, E-mail: maria@rd.numse.nagoya-u.ac.jp [Graduate School of Materials Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); Knowledge Hub Aichi, Yakusa-cho, Nagakute-ku, Toyota (Japan); Ueno, Tomonaga, E-mail: tomo@rd.numse.nagoya-u.ac.jp [Graduate School of Materials Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); Green Mobility Collaborative Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); CREST, Japan Science and Technology Agency, Goban-cho, Chiyoda-ku, Tokyo (Japan); Saito, Nagahiro, E-mail: hiro@rd.numse.nagoya-u.ac.jp [Graduate School of Materials Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); Knowledge Hub Aichi, Yakusa-cho, Nagakute-ku, Toyota (Japan); Green Mobility Collaborative Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan); CREST, Japan Science and Technology Agency, Goban-cho, Chiyoda-ku, Tokyo (Japan)

    2014-07-14

    Small-sized and well-dispersed gold nanoparticles (NPs) for nanofluidics have been synthesized by electrical discharge in liquid environment using termed solution plasma processing (SPP). Electrons and the hydrogen radicals are reducing the gold ions to the neutral form in plasma gas phase and liquid phase, respectively. The gold NPs have the smallest diameter of 4.9 nm when the solution temperature was kept at 20 °C. Nucleation and growth theory describe the evolution of the NP diameter right after the reduction reaction in function of the system temperature, NP surface energy, dispersion energy barrier, and nucleation rate. Negative charges on the NPs surface during and after SPP generate repulsive forces among the NPs avoiding their agglomeration in solution. Increasing the average energy in the SPP determines a decrease of the zeta potential and an increase of the NPs diameter. An important enhancement of the thermal conductivity of 9.4% was measured for the synthesized nanofluids containing NPs with the smallest size.

  6. Monodisperse Hollow Tricolor Pigment Particles for Electronic Paper

    Directory of Open Access Journals (Sweden)

    Meng Xianwei

    2009-01-01

    Full Text Available Abstract A general approach has been designed to blue, green, and red pigments by metal ions doping hollow TiO 2. The reaction involves initial formation of PS at TiO2 core–shell nanoparticles via a mixed-solvent method, and then mixing with metal ions solution containing PEG, followed calcining in the atmosphere. The as-prepared hollow pigments exhibit uniform size, bright color, and tunable density, which are fit for electronic paper display.

  7. Synthesis of mono-dispersed nanofluids using solution plasma.

    Science.gov (United States)

    Heo, Yong Kang; Bratescu, Maria Antoaneta; Ueno, Tomonaga; Saito, Nagahiro

    2014-07-14

    Small-sized and well-dispersed gold nanoparticles (NPs) for nanofluidics have been synthesized by electrical discharge in liquid environment using termed solution plasma processing (SPP). Electrons and the hydrogen radicals are reducing the gold ions to the neutral form in plasma gas phase and liquid phase, respectively. The gold NPs have the smallest diameter of 4.9 nm when the solution temperature was kept at 20 °C. Nucleation and growth theory describe the evolution of the NP diameter right after the reduction reaction in function of the system temperature, NP surface energy, dispersion energy barrier, and nucleation rate. Negative charges on the NPs surface during and after SPP generate repulsive forces among the NPs avoiding their agglomeration in solution. Increasing the average energy in the SPP determines a decrease of the zeta potential and an increase of the NPs diameter. An important enhancement of the thermal conductivity of 9.4% was measured for the synthesized nanofluids containing NPs with the smallest size.

  8. Elongational viscosity of monodisperse and bidisperse polystyrene melts

    DEFF Research Database (Denmark)

    Nielsen, Jens Kromann; Rasmussen, Henrik Koblitz; Hassager, Ole

    2005-01-01

    polystyrene melt with a molecular weight of 390 kg/mole (PS390K). The measurements have all been preformed on a Filament Streching Rheometer (FSR) equipped with an oven: A cylindrical test sample is placed between two parallel, circular plates and stretched. A load cell measures the transmitted force...

  9. Porous TiO2 Assembled from Monodispersed Nanoparticles

    OpenAIRE

    Liu, Xu; Duan, Weijie; Chen, Yan; Jiao, Shihui; Zhao, Yue; Kang, Yutang; Li, Lu; Fang, Zhenxing; Xu, Wei; Pang, Guangsheng

    2016-01-01

    Porous TiO2 were assembled by evaporating or refluxing TiO2 colloid, which was obtained by dispersing the TiO2 nanoparticles with a crystallite size (d XRD) of 3.2 nm into water or ethanol without any additives. Porous transparent bulk TiO2 was obtained by evaporating the TiO2-C2H5OH colloid at room temperature for 2 weeks, while porous TiO2 nanospheres were assembled by refluxing the TiO2-H2O colloid at 80 °C for 36 h. Both of the porous TiO2 architectures were pore-size-adjustable depending...

  10. Hydrothermal synthesis of superparamagnetic and red luminescent bifunctional Fe{sub 3}O{sub 4}@Mn{sup 2+}-doped NaYF{sub 4}:Yb/Er core@shell monodisperse nanoparticles and their subsequent ligand exchange in water

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Zhenli; Du, Sinan; Luo, Yang; Liao, Zhijian; Zuo, Fang, E-mail: polymerzf@swun.cn; Luo, Jianbin; Liu, Dong

    2016-08-15

    /Er shell, and the bifunctional Fe{sub 3}O{sub 4}@Mn{sup 2+}-doped NaYF{sub 4}:Yb/Er NPs were monodispersed. Furthermore, the Fe{sub 3}O{sub 4}@Mn{sup 2+}-doped NaYF{sub 4}:Yb/Er NPs exhibited a saturated magnetization value of 6.2 emu/g and emitted red luminescence under a 980 nm laser. The obtained bifunctional Fe{sub 3}O{sub 4}@Mn{sup 2+}-doped NaYF{sub 4}:Yb/Er NPs may find potential applications in drug targeting, bioseparation, and diagnostic analysis. The synthetic method may be employed for the preparation of other bifunctional nanomaterials.

  11. 共轴微反应器制备单分散聚N-异丙基丙烯酰胺/蒙脱石纳米复合微凝胶%Preparation of monodisperse poly(N-isopropylacrylamide)/clay nanocomposite hydrogel microspheres using coaxial microfluidic device

    Institute of Scientific and Technical Information of China (English)

    纪磊鹏; 张青红; 李耀刚; 王宏志

    2011-01-01

    A monodisperse nanocomposite poly ( N-isopropylacrylamide)/clay ( PNIPAm/Clay) microspheres is synthesized with coaxial microfluidic device using clay as cross-linker. The disperse phase contains the monomer ( N-isopropylacrylamide) ( NIPAm) , the initiator ( potassium peroxydisulfate) ( KPS ) , the cross-linker ( clay) and deionized water. The immiscible continuous phase is composed of soya-bean oil and the catalyst ( tetramethyl ethylene diamine) ( TEMED) . The monomer, NIPAm , has three distinctive absorbance peaks at 917 ,965 , 992 cm -1 ,indicating the vibration of the monomer's C -C double bond. However, these characteristic peaks disappear in the FF-IR spectra of PNIPAm/Clay and the Si-O characteristic peaks of clay,l 000 cm -1 ,appears in the FT-IR spectra of PNIPAm/Clay.The effects of changing tips, the flow rate of continuous phase and the content of the surfactant on the size of the microgels are studied. The results show that the microgels from 300 μn to 450 μm can be synthesized by changing the Lips of the dispersed phase injection tube;The size of the microgels between 315 and 435 μm with dispersion coefflcient below 5% can be adjusted by changing the flow rate of continuous phase;The diameter of the microgels decreases when the content of the surfactant( polyglycerol polyricinoleate) ( PGPR) in the continuous phase increases.%以蒙脱石(Clay)为交联剂,采用含有N,N,N'N'-四甲基乙二胺(TEMED)的豆油溶液为连续相,含有单体N-异丙基丙烯酞胺(NIPAm)、引发剂过硫酸钾(KPS)和分散有蒙脱石的水溶液为分散相,在共轴毛细管微反应器中制备了单分散聚N-异丙基丙烯酞胺/蒙脱石(PNIPAm/Clay)复合微凝胶.红外光谱分析表明:单体的C=C双键的红外特征峰917、965cm-1和992 cm-1在聚合后的微凝胶红外谱图中消失,而Clay的Si-O键特征峰1000 cm-1则出现在微凝胶的红外谱图中.研究了不同内径的管头、分散相的流速和表面活性剂的浓度对微

  12. Controllable Synthesis of Monodispersed Middle and Heavy Rare Earth Oxysulfide Nanoplates Based on the Principles of HSAB Theory%基于软硬酸碱理论的单分散中重稀土硫氧化物纳米板的可控合成

    Institute of Scientific and Technical Information of China (English)

    顾均; 丁祎; 柯俊; 张亚文; 严纯华

    2013-01-01

    Based on the theory of hard and soft acids and bases, trivalent ions of middle and heavy rare earths belong to very hard acids, which possess weak affinity towards S2- ions but strong affinity to O2- ions. So it is difficult to synthesize middle and heavy rare earth oxysulfide nano-materials through the thermolysis method in high-boiling-point organic solvent. In this article, monodispersed oxysulfide nanoplates of Y, Eu, Gd, Er and Yb were synthesized through this thermolysis method we developed. Both sodium-doped and undoped rare earth oxysulfide nanoplates could be prepared, and the doping of sodium ions could promote the crystallization of the nanoplates. Rare earth acetylacetonates were used as metal precursors and H2S gas as the sulfurizing reagent. The reactions were conducted in oleylamine at 280 °C for 1 hour. The thermogravimetric analysis of the precursor showed that the initial decomposition temperature of the rare earth acetylacetonates is about 200 'C, which is much lower than that of rare earth oleates. The transmission electron microscopy observation and energy dispersive X-ray analyses of the intermediate products during the synthesis of the nanoplates showed that rare earth oxide nanoplates formed firstly at about 220 °C, and these nanoplates transformed to oxysulfide nanoplates gradually during the temperature ramping period. Density functional theory calculation was used to compare the total free energy of the oxide and oxysulfide of different rare earth elements. According to this thermodynamical comparison, we concluded that, from light rare earths to heavy rare earths, higher chemical potential of sulfur is needed to obtain the oxysulfide rather than oxide. On one hand, H2S gas has higher sulphurizing power than sulfur. On the other hand, a comparatively low reaction temperature favors the dissolving of H2S in oleylamine. As a result, the chemical potential of sulfur in synthetic system could be effectively increased by using rare earth

  13. Study on the training scheme of the combination of engineering and engineering with ladder type-- based on mobile communication technology%工学结合阶梯式培养人才培养方案研究--基于移动通信技术专业

    Institute of Scientific and Technical Information of China (English)

    鄢长卿; 张晓峰

    2015-01-01

    高职学生培养应侧重于技能与职业素质。因为高职学生不同于普通本科高等院校的学生。他们高中阶段知识积累相对不足,对于理论的研究兴趣低。他们进入高职学习的目的明确,想要通过三年的时光,掌握一门技能,走入专业岗位。要实现这个目标就要采用新的培养模式,黑龙江农业工程职业学院也在不断探索与研究,实现培养模式的改革与创新。本文就黑龙江农业工程职业学院移动通信技术专业探索的“工学结合四阶梯进”人才培养模式进行了详细的阐述。%The cultivation of higher vocational students should focus on skills and professional quality. Because higher vocational students are different from the students of ordinary undergraduate colleges and universities.Their knowledge accumulation in high school is relatively insufficient,which is of low interest in theory..They enter the purpose of Higher Vocational Education explicitly,want to pass three years time,master a skill,walk into professional post.To achieve this goal,we should adopt the new cultivation mode,Heilongjiang Vocational College of Agricultural Engineering is also exploring and studying, the reform and innovation of the training mode..This paper expounds the talent training mode of "combining learning and learning with four steps and learning" in the mobile communication technology of Heilongjiang Vocational College of Agricultural Engineering..

  14. Inkjet Printing of Viscous Monodisperse Microdroplets by Laser-Induced Flow Focusing

    Science.gov (United States)

    Delrot, Paul; Modestino, Miguel A.; Gallaire, François; Psaltis, Demetri; Moser, Christophe

    2016-08-01

    The on-demand generation of viscous microdroplets to print functional or biological materials remains challenging using conventional inkjet-printing methods, mainly due to aggregation and clogging issues. In an effort to overcome these limitations, we implement a jetting method to print viscous microdroplets by laser-induced shockwaves. We experimentally investigate the dependence of the jetting regimes and the droplet size on the laser-pulse energy and on the inks' physical properties. The range of printable liquids with our device is significantly extended compared to conventional inkjet printers's performances. In addition, the laser-induced flow-focusing phenomenon allows us to controllably generate viscous microdroplets up to 210 mPa s with a diameter smaller than the nozzle from which they originated (200 μ m ). Inks containing proteins are printed without altering their functional properties, thus demonstrating that this jetting technique is potentially suitable for bioprinting.

  15. Contact electrification in aerosolized monodispersed silica microspheres quantified using laser based velocimetry

    DEFF Research Database (Denmark)

    Alois, Stefano; Merrison, Jonathan P.; Iversen, Jens Jacob

    2017-01-01

    The contact electrification of aerosolized micro particles has been studied using a novel technique involving laser velocimetry. This has allowed the simultaneous determination of size and electrical charge of individual silica microspheres (in the range 1 – 8 µm). Interestingly the particles...

  16. Covalent immobilization of lipases on monodisperse magnetic microspheres modified with PAMAM-dendrimer

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Weiwei [Lanzhou University, State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Institute of Biochemical Engineering and Environmental Technology (China); Zhang, Yimei [Suzhou Research Academy of North China Electric Power University (China); Hou, Chen; Pan, Duo; He, Jianjun; Zhu, Hao, E-mail: zhuhao07@lzu.edu.cn [Lanzhou University, State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Institute of Biochemical Engineering and Environmental Technology (China)

    2016-02-15

    This paper reported an immobilization of Candida rugosa lipase (CRL) onto PAMAM-dendrimer-grafted magnetic nanoparticles synthesized by a modified solvothermal reduction method. The dendritic magnetic nanoparticles were amply characterized by several instrumental measurements, and the CRL was covalently anchored on the three generation supports with glutaraldehyde as coupling reagent. The amount of immobilized enzyme was up to 150 mg/g support and the factors related with the enzyme activity were investigated. The immobilization of lipase improved their performance in wider ranges of pH and temperature. The immobilized lipase exhibited excellent thermal stability and reusability in comparison with free enzyme and can be reused 10 cycles with the enzymatic activity remained above 90 %. The properties of lipase improved obviously after being immobilized on the dendritic supports. The inactive immobilized lipase could be regenerated with glutaraldehyde and Cu{sup 2+}, respectively. This synthetic strategy was facile and eco-friendly for applications in lipase immobilization.

  17. Fast, microwave-assisted synthesis of monodisperse HfO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Roo, Jonathan De; Keukeleere, Katrien De; Feys, Jonas; Lommens, Petra [Ghent University, Sol-Gel Centre for Research on Inorganic Powders and Thin Films Synthesis (SCRiPTS) (Belgium); Hens, Zeger [Ghent University, Physics and Chemistry of Nanostructures (PCN) (Belgium); Driessche, Isabel Van, E-mail: Isabel.VanDriessche@ugent.be [Ghent University, Sol-Gel Centre for Research on Inorganic Powders and Thin Films Synthesis (SCRiPTS) (Belgium)

    2013-07-15

    A conventional solvothermal synthesis was compared to a microwave-assisted method for the synthesis of HfO{sub 2} nanoparticles. In a microwave, the reaction could be completed in 3 h, compared to 3 days in an autoclave. In the microwave synthesis, the ensemble of particles was found to have a better size dispersion and a smaller average size (4 nm). The reaction mechanism was investigated and proof for an ether elimination process was provided. Post-synthetic modification with dopamine or dodecanoic acid permitted the suspension of the synthesized particles in both polar and apolar solvents, which is an advantage for further processing.

  18. Synthesis of highly monodispersed Ga-soc-MOF hollow cubes, colloidosomes and nanocomposites

    KAUST Repository

    Cai, Xuechao

    2016-07-06

    Ga-soc-MOF hollow cubes with an average size of about 300 nm were prepared by a polyvinylpyrrolidone (PVP) assisted acid etching process. Colloidosomes with sizes of around 5-10 mu m composed of single-layer tetrakaidecahedron building blocks (BBs) were synthesized for the first time. Au@Ga-soc-MOF nanocomposites with excellent catalytic properties were obtained.

  19. A Continuous Time Random Walk Description of Monodisperse, Hard-Sphere Colloids below the Ordering Transition

    Science.gov (United States)

    Lechman, Jeremy; Pierce, Flint

    2012-02-01

    Diffusive transport is a ubiquitous process that is typically understood in terms of a classical random walk of non-interacting particles. Here we present the results for a model of hard-sphere colloids in a Newtonian incompressible solvent at various volume fractions below the ordering transition (˜50%). We numerically simulate the colloidal systems via Fast Lubrication Dynamics -- a Brownian Dynamics approach with corrected mean-field hydrodynamic interactions. Colloid-colloid interactions are also included so that we effectively solve a system of interacting Langevin equations. The results of the simulations are analyzed in terms of the diffusion coefficient as a function of time with the early and late time diffusion coefficients comparing well with experimental results. An interpretation of the full time dependent behavior of the diffusion coefficient and mean-squared displacement is given in terms of a continuous time random walk. Therefore, the deterministic, continuum diffusion equation which arises from the discrete, interacting random walkers is presented. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  20. Rational design of the gram-scale synthesis of nearly monodisperse semiconductor nanocrystals

    Directory of Open Access Journals (Sweden)

    Renard Olivier

    2011-01-01

    Full Text Available Abstract We address two aspects of general interest for the chemical synthesis of colloidal semiconductor nanocrystals: (1 the rational design of the synthesis protocol aiming at the optimization of the reaction parameters in a minimum number of experiments; (2 the transfer of the procedure to the gram scale, while maintaining a low size distribution and maximizing the reaction yield. Concerning the first point, the design-of-experiment (DOE method has been applied to the synthesis of colloidal CdSe nanocrystals. We demonstrate that 16 experiments, analyzed by means of a Taguchi L16 table, are sufficient to optimize the reaction parameters for controlling the mean size of the nanocrystals in a large range while keeping the size distribution narrow (5-10%. The DOE method strongly reduces the number of experiments necessary for the optimization as compared to trial-and-error approaches. Furthermore, the Taguchi table analysis reveals the degree of influence of each reaction parameter investigated (e.g., the nature and concentration of reagents, the solvent, the reaction temperature and indicates the interactions between them. On the basis of these results, the synthesis has been scaled up by a factor of 20. Using a 2-L batch reactor combined with a high-throughput peristaltic pump, different-sized samples of CdSe nanocrystals with yields of 2-3 g per synthesis have been produced without sacrificing the narrow size distribution. In a similar setup, the gram-scale synthesis of CdSe/CdS/ZnS core/shell/shell nanocrystals exhibiting a fluorescence quantum yield of 81% and excellent resistance of the photoluminescence in presence of a fluorescent quencher (aromatic thiol has been achieved. PACS: 81.20.Ka, 81.07.Bc, 78.67.Bf

  1. Polyurethanes with monodisperse rigid segments based on a diamine-diamide chain extender

    NARCIS (Netherlands)

    Biemond, G.J.E.; Braspenning, K.; Gaymans, R.J.

    2008-01-01

    Polyether(bisurethane-bisurea-bisamide)s (PEUUA) based on poly(tetramethylene oxide) (PTMO) were synthesized by chain extension of PTMO endcapped with a diisocyanate (DI), and a diamine-diamide extender. The prepolymers were PTMOs with molecular weights between 1270 and 2200 g mol-1, either endcappe

  2. Autoadhesion of High-Molecular-Weight Monodisperse Glassy Polystyrene at unexpected low temperatures

    DEFF Research Database (Denmark)

    Boiko, Yuri M.; Lyngaae-Jørgensen, Jørgen

    2004-01-01

    Healing of symmetric interfaces of amorphous anionically polymerized high- and ultra-high-molecular weight (HMW and UHMW, respectively) polystyrene (PS) in a range of the weight-average molecular weight M-w from 102.5 (M-w/M-n = 1.05) to 1110 kg/ mol (M-w/M-n = 1.15) was followed at a constant...

  3. Quantitative prediction of transient and steady-state elongational viscosity of nearly monodisperse polystyrene melts

    DEFF Research Database (Denmark)

    Wagner, Manfred H.; Kheirandish, Saeid; Hassager, Ole

    2005-01-01

    Elongational behavior of four narrow molar mass distribution polystyrene melts of masses 50 000, 100 000, 200 000, and 390 000, g/mol, respectively was investigated up to Hencky strains of 5. All melts show strain hardening behavior. For the two highest molar mass polystyrenes, strain hardening s...

  4. A constitutive analysis of the extensional flows of nearly monodisperse polyisoprene melts

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.

    2016-01-01

    Here two particular formulations [M.H. Wagner, S. Kheirandish, O. Hassager, Journal of Rheology 49 (6) (2005) 1317–1327; H.K. Rasmussen, Q. Huang, Rheologica Acta 53 (3) (2014) 199–208; G. Marrucci, G. Ianniruberto, Macromolecules 37 (10) (2004) 3934–3942] of the ‘interchain pressure’ [39......], incorporated into the molecular stress function method [M.H. Wagner, S. Kheirandish, O. Hassager, Journal of Rheology 49 (6) (2005) 1317–1327], are used to assess the extensional [J.K. Nielsen, O. Hassager, H.K Rasmussen, G.H. McKinley, Journal of Rheology 53 (6) (2009) 1327–1346; G. Liu, H. Sun, S. Rangou, K....... Ntetsikas, A. Avgeropoulos, S.-Q. Wang, Journal of Rheology 57 (1) (2013) 89–104] and shear viscosities [D. Auhl, J. Ramirez, A.E. Likhtman, P. Chambon, C. Fernyhough, Journal of Rheology 52 (3) (2008) 801–835] of narrow molecular weight distributed (NMMD) polyisoprene melts. These two formulations...

  5. Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres

    Indian Academy of Sciences (India)

    K C Barick; D Bahadur

    2006-11-01

    The assembly of superparamagnetic Fe3O4 nanoparticles on submicroscopic SiO2 spheres have been prepared by an in situ reaction using different molar ratios of Fe3+/Fe2+ (50–200%). It has been observed that morphology of the assembly and properties of these hybrid materials composed of SiO2 as core and Fe3O4 nanoparticles as shell depend on the molar ratio of Fe3+/Fe2+.

  6. Autoadhesion of High-Molecular-Weight Monodisperse Glassy Polystyrene at unexpected low temperatures

    DEFF Research Database (Denmark)

    Boiko, Yuri M.; Lyngaae-Jørgensen, Jørgen

    2004-01-01

    -bulk corresponding to a second-order phase transition temperature). To our knowledge, this is the first observation of such nature, which gives further evidence of the lowering of the T-g at polymeric surfaces and the persistence of this effect at early stages of healing of polymer-polymer interfaces.......Healing of symmetric interfaces of amorphous anionically polymerized high- and ultra-high-molecular weight (HMW and UHMW, respectively) polystyrene (PS) in a range of the weight-average molecular weight M-w from 102.5 (M-w/M-n = 1.05) to 1110 kg/ mol (M-w/M-n = 1.15) was followed at a constant...... healing temperature, T-h, well below the glass transition temperature of the polymer bulk [Tg-bulk = 105 - 106degreesC as measured by differential scanning calorimeter (DSC)]. The bonded interfaces were shear fractured in tension on an Instron tester at ambient temperature. Autoadhesion at symmetric HMW...

  7. Converting homogeneous to heterogeneous in electrophilic catalysis using monodisperse metal nanoparticles.

    Science.gov (United States)

    Witham, Cole A; Huang, Wenyu; Tsung, Chia-Kuang; Kuhn, John N; Somorjai, Gabor A; Toste, F Dean

    2010-01-01

    A continuing goal in catalysis is to unite the advantages of homogeneous and heterogeneous catalytic processes. To this end, nanoparticles represent a new frontier in heterogeneous catalysis, where this unification can also be supplemented by the ability to obtain new or divergent reactivity and selectivity. We report a novel method for applying heterogeneous catalysts to known homogeneous catalytic reactions through the design and synthesis of electrophilic platinum nanoparticles. These nanoparticles are selectively oxidized by the hypervalent iodine species PhICl(2), and catalyse a range of π-bond activation reactions previously only catalysed through homogeneous processes. Multiple experimental methods are used to unambiguously verify the heterogeneity of the catalytic process. The discovery of treatments for nanoparticles that induce the desired homogeneous catalytic activity should lead to the further development of reactions previously inaccessible in heterogeneous catalysis. Furthermore, a size and capping agent study revealed that Pt PAMAM dendrimer-capped nanoparticles demonstrate superior activity and recyclability compared with larger, polymer-capped analogues.

  8. Monodisperse gold nanoparticles formed on bacterial crystalline surface layers (S-layers) by electroless deposition

    Energy Technology Data Exchange (ETDEWEB)

    Dieluweit, S. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Pum, D. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Sleytr, U.B. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Kautek, W. [Department for Physical Chemistry, University of Vienna, Waehringer Strasse 42, A-1090 Vienna (Austria)]. E-mail: wolfgang.kautek@univie.ac.at

    2005-12-15

    The fabrication of patterned arrays of nanoparticles whose electronic, optical and magnetic properties will find technological applications, such as ultra-high-density memories, is currently one of the most important objectives of inorganic material research. In this study, the in situ electroless nucleation of ordered two-dimensional arrays of gold nanoparticles (5 nm in size) by using bacterial S-layers as molecular templates and their characterization by small spot X-ray photoelectron emission spectroscopy (XPS) is presented. This yielded the elemental composition of the nanoclusters, which consisted of almost entirely elemental gold, and possible side reactions on the cluster and protein surface. The preferential deposition of the gold nanoparticles on the S-layer suggests that topography and functional groups are important for superlattice formation.

  9. Rational design of the gram-scale synthesis of nearly monodisperse semiconductor nanocrystals

    Science.gov (United States)

    Protière, Myriam; Nerambourg, Nicolas; Renard, Olivier; Reiss, Peter

    2011-07-01

    We address two aspects of general interest for the chemical synthesis of colloidal semiconductor nanocrystals: (1) the rational design of the synthesis protocol aiming at the optimization of the reaction parameters in a minimum number of experiments; (2) the transfer of the procedure to the gram scale, while maintaining a low size distribution and maximizing the reaction yield. Concerning the first point, the design-of-experiment (DOE) method has been applied to the synthesis of colloidal CdSe nanocrystals. We demonstrate that 16 experiments, analyzed by means of a Taguchi L16 table, are sufficient to optimize the reaction parameters for controlling the mean size of the nanocrystals in a large range while keeping the size distribution narrow (5-10%). The DOE method strongly reduces the number of experiments necessary for the optimization as compared to trial-and-error approaches. Furthermore, the Taguchi table analysis reveals the degree of influence of each reaction parameter investigated (e.g., the nature and concentration of reagents, the solvent, the reaction temperature) and indicates the interactions between them. On the basis of these results, the synthesis has been scaled up by a factor of 20. Using a 2-L batch reactor combined with a high-throughput peristaltic pump, different-sized samples of CdSe nanocrystals with yields of 2-3 g per synthesis have been produced without sacrificing the narrow size distribution. In a similar setup, the gram-scale synthesis of CdSe/CdS/ZnS core/shell/shell nanocrystals exhibiting a fluorescence quantum yield of 81% and excellent resistance of the photoluminescence in presence of a fluorescent quencher (aromatic thiol) has been achieved. PACS: 81.20.Ka, 81.07.Bc, 78.67.Bf

  10. Green synthesis and antimicrobial activity of monodisperse silver nanoparticles synthesized using Ginkgo Biloba leaf extract

    Science.gov (United States)

    Ren, Yan-yu; Yang, Hui; Wang, Tao; Wang, Chuang

    2016-11-01

    Various parts of plants can be used as a raw material for the synthesis of nanoparticles, which is eco-friendly way and does not involve any harmful chemicals. In this project, Ginkgo biloba leaf, an abundantly available medicinal plant in China, was for the first time adopted as a reducing and stabilizing agent to synthesize smaller sized and stable silver nanoparticles (AgNPs). To improve the quality of AgNPs, the reduction was accelerated by changing the concentrations of initial Ag+ (0.02, 0.04, 0.06 and 0.08 mol/L) of the reaction mixture consisting of silver nitrate solution (AgNO3) and Ginkgo biloba leaf extract. At pH = 8 and lower AgNO3 concentration (0.02 mol/L), a colloid consisting of well-dispersed spherical nanoparticles was obtained. The synthesized nanocrystals were successfully characterized by UV-vis and XRD. TEM images revealed the size of the spherical AgNPs ranged between 10-16 nm. FTIR analysis revealed that biological macromolecules with groups of sbnd NH2, sbnd OH, and others were distributed on the surface of the nanoparticles. The biosynthesized AgNPs exhibited good antibacterial activities against gram-negative bacteria and gram-positive bacteria. Compared to traditional chemical methods, Ginkgo biloba leaf extract provides an easy green synthetical way. It is anticipated that the biosynthesized AgNPs can be used in areas such as cosmetics, foods and medical applications.

  11. A Study of Multiple Refractive Scattering of Monoenergetic X-Rays from Ensembles of Monodisperse Spheres

    CERN Document Server

    Khromova, Anastasiya

    2010-01-01

    A Monte Carlo program based on a three dimensional vector approach was developed to model multiple refractive scattering of X-ray photons in objects with a fine structure. A particular interest was paid to the investigation of lung tissue. Alveoli are low contrast and low absorbing structures. Hence, they are not visible in the conventional radiography which is based on the changes in the absorption arising from density differences and from variation in the thickness and composition of the object. Another possibility to image fine structure objects is to use the phase imaging techniques. As known, the phase change constant delta at low energies (15-30 keV) is 1000 times larger than the absorption constant beta. The Diffraction Enhance Imaging (DEI) technique is one of the recent phase sensitive techniques based on the use of an analyzer crystal placed between the sample and the detector.

  12. Size-driven magnetic transitions in monodisperse MnO nanocrystals

    OpenAIRE

    Lee, Yi-Cheng; Pakhomov, Alexandre B.; Krishnan, Kannan M.

    2010-01-01

    We report the observation of weak ferromagnetism up to TC≈250 K and a spin-glass-like behavior at temperatures below TSG≈30 K in nanoscale MnO particles. TSG is considerably lower and TC is much higher than the Néel temperature (TN=122 K) of bulk MnO. While the dominant low temperature behavior (below 30 K) may be attributed to the effects studied in this system before, such as uncompensated surface spins in antiferromagnetic particles, no manganese oxides have been observed with the Curie te...

  13. Separation of Gases Using Ultra-Thin Porous Layers of Monodisperse Nanoparticles

    Directory of Open Access Journals (Sweden)

    Bubenchikov Mikhail A

    2016-01-01

    Full Text Available The present paper deals with a numerical solution of the two-dimensional problem of helium and methane molecules motion through an ultra-thin layer of a porous material composed of spherical nanoparticles of the same size. The interaction potential “nanoparticle-molecule” is obtained by integrating paired molecular interactions over the nanoparticle volume. Using the method of classical molecular dynamics, permeability of a layer having the size of about 10−8 m is studied.

  14. Converting Homogeneous to Heterogeneous in Electrophilic Catalysis using Monodisperse Metal Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Witham, Cole A.; Huang, Wenyu; Tsung, Chia-Kuang; Kuhn, John N.; Somorjai, Gabor A.; Toste, F. Dean

    2009-10-15

    A continuing goal in catalysis is the transformation of processes from homogeneous to heterogeneous. To this end, nanoparticles represent a new frontier in heterogeneous catalysis, where this conversion is supplemented by the ability to obtain new or divergent reactivity and selectivity. We report a novel method for applying heterogeneous catalysts to known homogeneous catalytic reactions through the design and synthesis of electrophilic platinum nanoparticles. These nanoparticles are selectively oxidized by the hypervalent iodine species PhICl{sub 2}, and catalyze a range of {pi}-bond activation reactions previously only homogeneously catalyzed. Multiple experimental methods are utilized to unambiguously verify the heterogeneity of the catalytic process. The discovery of treatments for nanoparticles that induce the desired homogeneous catalytic activity should lead to the further development of reactions previously inaccessible in heterogeneous catalysis. Furthermore, our size and capping agent study revealed that Pt PAMAM dendrimer-capped nanoparticles demonstrate superior activity and recyclability compared to larger, polymer-capped analogues.

  15. Fabrication of monodisperse FePt rate at Au core-shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wei, D.H. [Institute of Physics, Academia Sinica, Taipei 115 (China); Hung, D.S. [Department of Information and Telecommunications Engineering, Ming Chuan University, Taipei 111 (China); Ho, C.S.; Wang, J.W. [Department of Chemical Engineering, Tunghai University, Taichung 407 (China); Yao, Y.D. [Department of Materials Engineering, Tatung University, Taipei 104 (China)

    2007-12-15

    Hydrophobic FePt rate at Au core-shell nanoparticles were chemically synthesized and with controllable surface-function properties. The enhanced optical property is due to the contribution of Au shell. The surface modification of FePt rate at Au nanoiparticles by using 11-mercaptoundecanoic acid (MUA) was hydrophilic through ligand exchange and with good biocompatibility for future multi-functional applications. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Hybrid composites of monodisperse pi-conjugated rodlike organic compounds and semiconductor quantum particles

    DEFF Research Database (Denmark)

    Hensel, V.; Godt, A.; Popovitz-Biro, R.

    2002-01-01

    Composite materials of quantum particles (Q-particles) arranged in layers within crystalline powders of pi-conjugated, rodlike dicarboxylic acids are reported. The synthesis of the composites, either as three-dimensional crystals or as thin films at the air-water interface, comprises a two...... analysis of the solids and grazing incidence X-ray diffraction analysis of the films on water. 2) Topotactic solid/gas reaction of these salts with H2S to convert the metal ions into Q-particles of CdS or PbS embedded in the organic matrix that consists of the acids 6(H) and 8(H). These hybrid materials...

  17. A New Monodisperse Reactive Resin with Active Groups on the Particle Surface

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A novel reactive resin as active support was synthesized by an improved method based on seed swelling and surface coating polymerization. The resin is monosized beads with inner nucleus of cross-linked polymer and surface layer of copolymer containing epoxy groups. The physico-chemical structures of beads were characterized.

  18. Study on Analyzing Monodisperse Uranium Oxide Particle by FT-TIMS

    Institute of Scientific and Technical Information of China (English)

    CHEN; Yan; WANG; Fan; ZHAO; Yong-gang; LI; Li-li; ZHANG; Yan; SHEN; Yan; CUI; Jian-yong; LIU; Yuang

    2012-01-01

    <正>Environmental sampling is the important one of IAEA safeguards technology, the aim of which is detecting the undeclared nuclear activities. Analyzing isotopic ratio of single uranium-bearing particle in swipe samples was a effective analytic technique in virtue of its ability of achieving the present or past information of nuclear facilities. For this purpose, a new method of Fission track (FT) technique combined with thermal ionization mass spectrometry (TIMS) was developed.

  19. Crystallisation and structural studies of monodisperse nylon oligomers and related polymers

    CERN Document Server

    Sikorski, P T

    2001-01-01

    Examination of the chain conformation for this phase shows that most of peptide units have backbone torsional angles around 60 deg away from the beta-conformation. When this liquid-crystalline phase was partially dried, it transformed into metastable phase, described in the literature as silk I. The properties of this silk I phase are discussed. of hydrogen-bonded sheet formed by these molecules can influence the way in which these sheets stack to form crystals. In addition, a study of the 9-amide molecule showed that a particular type of hydrogen-bonded sheet, a-sheet, is preferred for nylon 4 6. This discovery suggests that an amide unit is found in the fold in the chain-folded nylon 4 6 polymer crystals, to allow the a-sheets to be formed. It is not a consequence of a need to form a stress-free fold. In the regular adjacent re-entry chain-folded crystals, one amide unit must be removed from straight-stems in order for the a-sheets to be formed. For the 4-amide nylon 4 6 molecule changes in the unit cell on...

  20. Synthesis and characterization of monodisperse Eu3+doped gadolinium oxysulfide nanocrystals

    Institute of Scientific and Technical Information of China (English)

    J Cichos; M Karbowiak; D Hreniak; W Strk

    2016-01-01

    Gd2O2S:Eu3+nanoparticles were synthesized using two step process consisting of sulfuration of basic carbonates obtained by homogenous precipitation. Annealing of lanthanide nitrates at total concentration of 5×10–3 mol/L in a water solution containing relatively high, three molar concentration of urea ensured the optimal conditions for the reproducible preparation of uniform and small spherical particles. During sulfuration step elemental sulfur was mixed with precursor which eliminated necessity of using an auxiliary furnace and provided sulfur-reach reaction atmosphere. Such optimized protocol afforded synthesis of spherical and non-agglomerated nanoparticles with diameter smaller than 100 nm. The precursors morphology was maintained, but particles size was reduced by 15%–20%during sulfuration. The results indicated that higher emission intensity was observed for Gd2O2S:Eu3+(8%) oxysulfide sample synthesized using crystalline Gd(CO3)OH precursor, than for that obtained from amorphous Gd2(OH)2(CO3)2⋅H2O precursor, although some further efforts to improve morphology of the former are still required.

  1. Synthesis of Monodispersed Tantalum(V) oxide Nanospheres by an Ethylene Glycol Mediated Route

    Science.gov (United States)

    Tantalum(V) oxide (Ta2O5) nanospheres have been synthesized by a very simple ethylene glycol mediated route. The two-step process involves the formation of glycolate nanoparticles and their subsequent hydrolysis and calcination to generate the final Ta2O5 nanospheres. The synthes...

  2. Microbe-Assisted Synthesis and Luminescence Properties of Monodispersed Tb3+-Doped ZnS Nanocrystals

    Directory of Open Access Journals (Sweden)

    Zhanguo Liang

    2015-01-01

    Full Text Available Tb3+-doped zinc sulfide (ZnS:Tb3+ nanocrystals were synthesized by spray precipitation with sulfate-reducing bacterial (SRB culture at room temperature. The morphology of the SRB and ZnS:Tb3+ nanocrystals was examined by scanning electron microscopy, and the ZnS:Tb3+ nanocrystals were characterized by X-ray diffractometry and photoluminescence (PL spectroscopy. The PL mechanism of ZnS:Tb3+ nanocrystals was further analyzed, and the effects of Tb3+ ion concentration on the luminescence properties of ZnS:Tb3+ nanocrystals were studied. ZnS:Tb3+ nanocrystals showed a sphalerite phase, and the prepared ZnS:Tb3+ nanocrystals had high luminescence intensity under excitation at 369 nm. The main peak position of the absorption spectra positively blueshifted with increasing concentrations of Tb3+ dopant. Based on the strength of the peak of the excitation and emission spectra, we inferred that the optimum concentration of the Tb3+ dopant is 5 mol%. Four main emission peaks were obtained under excitation at 369 nm:489 nm (5D4→7F6, 545 nm (5D4→7F5, 594 nm (5D4→7F4, and 625 nm (5D4→7F3. Our findings suggest that nanocrystals have potential applications in photoelectronic devices and biomarkers.

  3. Monodisperse Co, Zn-Ferrite nanocrystals: Controlled synthesis, characterization and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sanjeev, E-mail: sanjeevkumar.dubey2@gmail.com [University of Petroleum and Energy Studies, Dehradun 248007 (India); Singh, Vaishali; Aggarwal, Saroj [School of Basic and Applied Sciences (India); Mandal, Uttam Kumar [University School of Chemical Technology, GGS Indraprastha University, Kashmere Gate, Delhi 110403 (India); Kotnala, R.K. [National Physical laboratory, New Delhi 110012 (India)

    2012-11-15

    Co{sub x}Zn{sub y}Fe{sub 3-x-y}O{sub 4} ferrite (x=1 to 0; y=0 to1) nanocrystals have been synthesized by reverse microemulsion method. The nanocrystals are then comprehensively characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Field emission transmission electron microscopy (FETEM), and magnetic properties were measured by using Vibrating sample magnetometer. X-ray analysis showed that all the crystals were cubic spinel. The lattice constant increased with the increase in Zn substitution. FETEM reveals that particle size varies in the range from 3 to 6 nm. As the concentration of Zn increases the magnetic behavior varies from ferromagnetic at y=0 and 0.2 to superparamagnetic to paramagnetic at y=1. The Curie temperature decreases with increasing concentration of Zn. - Highlights: Black-Right-Pointing-Pointer Reverse microemulsion route is a very facile route for synthesis of Co{sub x}Zn{sub y}Fe{sub 3-x-y}O{sub 4} ferrite and all particles synthesized by reverse microemulsion is in the range of 3-6 nm. Black-Right-Pointing-Pointer Presence of Zn changes the structural and magnetic properties of the Zn substituted CoFe{sub 2}O{sub 4}. Black-Right-Pointing-Pointer The lattice constant increases with the increase in Zn substitution. Black-Right-Pointing-Pointer The curie temperature decreases with Zn concentration appreciably. Black-Right-Pointing-Pointer Magnetic behavior varies from ferromagnetic at y=0, 0.2 to superparamagnetic to paramagnetic at y=1.

  4. Green synthesis of monodisperse silver nanoparticles using hydroxy propyl methyl cellulose

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Chunfa; Zhang, Xianglin, E-mail: hust_zxl@mail.hust.edu.cn; Cai, Hao

    2014-01-15

    Graphical abstract: -- Highlights: • Synthesis of silver nanoparticles using hydroxy propyl methyl cellulose is reported. • HPMC and glucose are used as capping agent and reducing agent respectively. • It is the first time to use HPMC for synthesis of silver nanoparticles. • The small, spherical and well-dispersed particle is observed in the range of 3–17 nm. • The green method can be extended to other noble metals. -- Abstract: A simple and environmentally friendly method for the synthesis of highly stable and small sized silver nanoparticles with narrow distribution from 3 nm to 17 nm is reported. Silver nitrate, hydroxy propyl methyl cellulose (HPMC) and glucose, were used as silver precursor, capping agents and reducing agents respectively. The formation of silver nanoparticles was observed by change of color from colorless to wine red. The silver nanoparticles were characterized by transmission electron microscopy (TEM), UV–visible spectroscopy (UV–vis), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). The results demonstrated that the obtained metallic nanoparticles were single crystalline silver nanoparticles capped with HPMC. The effects of the reaction time, reaction temperature and the concentration of silver ion and reducing agents on the particle size were investigated. A possible formation mechanism was proposed. The method may be extended to other noble metal for other technological applications such as additional medicinal, industrial applications.

  5. Partitioned EDGE devices for high throughput production of monodisperse emulsion droplets with two distinct sizes

    NARCIS (Netherlands)

    Sahin, S.; Schroën, C.G.P.H.

    2015-01-01

    We present a novel microfluidic EDGE (Edge based Droplet GEneration) device with regularly spaced micron-sized partitions, which is aimed at upscaling of o/w emulsion preparation. By this means, remarkably higher pressure stability was obtained, and two orders of magnitude higher droplet formation f

  6. Electrocrystallization of Monodisperse Nanocrystal Copper on Highly Oriented Pyrolytic Graphite Electrode

    Institute of Scientific and Technical Information of China (English)

    黄令; LEE,Eun-Sung; KIM,Kwang-Bum

    2005-01-01

    Mechanism of copper electrocrystallization on highly oriented pyrolytic graphite electrode from a solution of 1 mmol/L CuSO4 and 1.0 mol/L H2SO4 has been studied using cyclic voltammogram and chronoamperometry. The results show that in copper electrodeposition the charge-transfer step is fast and the rate of growth is controlled by the rate of mass transfer of copper ions to the growing centers. Reduction of Cu(Ⅱ) ions did not undergo underpotential deposition. The initial deposition kinetics of Cu electrocrystallization corresponds to a model including progressive nucleation and diffusion controlled growth. Copper nanocrystals with size of 75.6 nm and relative standard deviation of 9% can be obtained by modulation potential electrodeposition.

  7. Synthesis, characterization, and growth mechanism of α-Cr2O3 monodispersed particles

    CSIR Research Space (South Africa)

    Khamlich, S

    2011-06-01

    Full Text Available characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Raman spectroscopy for structural, surface morphological, chemical, and physical properties, as a function of deposition time. The XRD and Raman spectroscopy showed that aging had...

  8. Controllable Synthesis and Magnetic Properties of Monodisperse Fe3O4 Nanoparticles

    Science.gov (United States)

    Wang, Zhu-Liang; Ma, Hui; Wang, Fang; Li, Min; Zhang, Li-Guo; Xu, Xiao-Hong

    2016-10-01

    Not Available Supported by the National Natural Science Foundation of China under Grant Nos 51571135, 11274214 and 61434002, the Special Funds of Shanxi Scholars Program under Grant No IRT1156, Collaborative Innovation Center for Shanxi Advanced Permanent Materials and Technology, and the Special Funds of the Ministry of Education of China under Grant No 20121404130001.

  9. Controlled Microwave-Assisted Growth of Monodisperse of Silica Nanoparticles under Acid Catalysis (Postprint)

    Science.gov (United States)

    2012-11-26

    over conventional heating techniques because they deliver large amounts of controlled power quickly to small volumes of absorbing media, promoting...transition states, such as pentacoordinate and hexacoordinate silanes .25,38,39 Recently, a DFT study has postulated that the formation of stable silica

  10. Monodisperse nonionic isoprenoid-type hexahydrofarnesyl ethylene oxide surfactants: high throughput lyotropic liquid crystalline phase determination.

    Science.gov (United States)

    Fong, Celesta; Weerawardena, Asoka; Sagnella, Sharon M; Mulet, Xavier; Krodkiewska, Irena; Chong, Josephine; Drummond, Calum J

    2011-03-15

    The neat and lyotropic phase behavior of eight new ethylene oxide amphiphiles (EO = 1-8) with a hexahydrofarnesyl chain (3,7,11-trimethyldodecyl) and narrow polydispersity (>98.5% purity) is reported. Below five EO units the behavior of the neat surfactants show only a glass transition, Tg ∼ -90 °C. Above four EO units, crystallization (Tcrys) and crystal-isotropic liquid (Tm) transitions are also observed that increase with degree of ethoxylation of the surfactant headgroup. The lyotropic liquid crystalline phase behavior spans a complex spectrum of surfactant-water interfacial curvatures. Specifically, inverse phases are present below ambient temperatures for EO ethoxylation, with the crossover to normal phases occurring at HFarn(EO)(7-8) which exhibits normal hexagonal (H(I)) and cubic (Q(I)) phases at ambient temperatures. The toxicity of colloidal dispersions of these EO amphiphiles was assayed against normal breast epithelial (HMEpiC) and breast cancer (MCF7) cell lines. The IC50 of the EO amphiphiles was similar in both cell lines with moderate toxicity ranging from ca. <5 to 140 μM in an in vitro cell viability assay. Observations are qualitatively rationalized in terms of the molecular geometry of the surfactant. The physicochemical behavior of the HFarnesyl ethylene oxide amphiphiles is compared to other ethylene oxide surfactants.

  11. Piezochromic phenomena of nanometer voids formed by mono-dispersed nanometer powders compacting process.

    Directory of Open Access Journals (Sweden)

    Lihong Su

    Full Text Available Piezochromism describes a tendency of certain materials changing colors when they are subjected to various pressure levels. It occurs particularly in some polymers or inorganic materials, such as in palladium complexes. However, piezochromism is generally believed to work at high pressure range of 0.1-10 GPa. This research work focused on unique piezochromism responses of the nanometer voids formed by the 5-20 nm inorganic ISOH nanometer powders. It was discovered that microstructures of the nanometer voids could change color at very low pressures of only 0.002-0.01 GPa; its sensitivity to pressure was increased by tens of times. It is believed that the uniform microstructures of nanometer powders contributed to the material's high sensitivity of piezochromic phenomena. One factor which quantum optical change caused by nanometer voids affected the quantum confinement effect; another is surface Plasmon Resonance of great difference dielectric property between conductive ITO powder and insulation hydroxide.

  12. Isolation of monodisperse nanodisc-reconstituted membrane proteins using free flow electrophoresis

    DEFF Research Database (Denmark)

    Justesen, Bo Højen; Laursen, Tomas; Weber, Gerhard;

    2013-01-01

    Free flow electrophoresis is used for rapid and high-recovery isolation of homogeneous preparations of functionally active membrane proteins inserted into nanodiscs. The approach enables isolation of integral and membrane anchored proteins and is also applicable following introduction of, e...

  13. Silica-modified monodisperse hexagonal lanthanide nanocrystals: synthesis and biological properties.

    Science.gov (United States)

    Kostiv, U; Janoušková, O; Šlouf, M; Kotov, N; Engstová, H; Smolková, K; Ježek, P; Horák, D

    2015-11-21

    Oleic acid-stabilized hexagonal NaYF4:Yb(3+)/Er(3+) nanocrystals, emitting green and red luminescence, were prepared by the high-temperature co-precipitation of lanthanide chlorides. By varying the reaction time and the Ln(3+)/Na(+) ratio, the nanocrystal size can be controlled within the range 16-270 nm. The maximum upconversion quantum yield is achieved under 970 nm excitation. The reverse microemulsion technique using hydrolysis and condensation of tetraethoxysilane is a suitable method to coat the nanocrystal surface with a silica shell to make the particles dispersible and colloidally stable in aqueous media. During the subsequent functionalization, (3-aminopropyl)trimethoxysilane introduced amino groups onto the silica to enable future bioconjugation with the target molecules. All specimens were characterized by TEM microscopy, electron and X-ray diffraction, ATR FT-IR spectroscopy, and upconversion luminescence. Finally, in vitro cytotoxicity and intracellular nanoparticle uptake (using confocal microscopy) were determined with human cervical carcinoma HeLa and mRoGFP HeLa cells, respectively. From the investigated particles, amino-functionalized NaYF4:Yb(3+)/Er(3+) nanocrystals internalized into the cells most efficiently. The nanoparticles proved to be nontoxic at moderate concentrations, which is important when considering their prospective application in biolabeling and luminescence imaging of various cell types.

  14. Continuous synthesis of monodispersed silver nanoparticles using a homogeneous heating microwave reactor system.

    Science.gov (United States)

    Nishioka, Masateru; Miyakawa, Masato; Kataoka, Haruki; Koda, Hidekazu; Sato, Koichi; Suzuki, Toshishige M

    2011-06-01

    Continuous synthesis of silver nanoparticles based on a polyol process was conducted using a microwave-assisted flow reactor installed in a cylindrical resonance cavity. Silver nitrate (AgNO(3)) and poly(N-vinylpyrrolidone) (PVP) dissolved in ethylene glycol were used respectively as a silver metal precursor and as a capping agent of nanoparticles. Ethylene glycol worked as the solvent and simultaneously as the reductant. Silver nanoparticles of narrow size distributions were synthesized steadily for 5 h, maintaining almost constant yield (>93%) and quality. The reaction was achieved within 2.8 s of residence time, although nanoparticles were not formed under this flow rate by conventional heating. A narrower particle size distribution was realized by the increased flow rate of the reaction solution. Nanoparticles of 9.8 nm average size with a standard deviation of 0.9 nm were synthesized at the rate of 100 ml h(-l).

  15. Synthesis and characterization of monodisperse Eu-doped luminescent silica nanospheres for biological applications

    Science.gov (United States)

    Enrichi, Francesco; Riccò, Raffaele; Parma, Alvise; Riello, Pietro; Benedetti, Alvise

    2008-04-01

    Luminescent nanoparticles are gaining more and more interest for bio-sensing and bio-imaging applications. In particular it is desiderable to work with cheap and non toxic materials which could be easily functionalized in their surface. To these respects silica nanoparticles seem to be a very promising and interesting solution. The liquid synthesis of silica spheres can be obtained by condensation of tetraethylortosilicate (TEOS) in basic or acid environment. Several strategies have been developed to make them luminescent by the incorporation of organic or inorganic emission centres, but often requiring multiple processing steps and use of expensive or toxic molecules. Moreover, common dyes suffer disadvantages such as a broad spectral band, short fluorescent lifetime and photobleaching. In contrast, rare earths exhibit narrow emission bands, large Stokes shifts and long luminescence lifetimes. In this work we focus our attention on the synthesis and characterization of europium-doped silica spheres. Europium introduction in the spheres can be interesting for biological applications to increase the signal to noise ratio due to the long luminescence lifetime (possibility to perform time-delayed analysis) and to the good emission intensity. The obtained results are presented and discussed, giving suggestions for the optimization of their morphological and optical properties. The possibility of realizing good luminescent silica spheres by following the described procedure is shown and suggestions for future development are given. The cheap and easy synthesis of these luminescent particles, the stability in water, the easy surface functionalization and bio-compatibility makes them very attractive in biological imaging and other applications.

  16. Synthesis of highly monodispersed Ga-soc-MOF hollow cubes, colloidosomes and nanocomposites.

    Science.gov (United States)

    Cai, Xuechao; Deng, Xiaoran; Xie, Zhongxi; Bao, Shouxin; Shi, Yanshu; Lin, Jun; Pang, Maolin; Eddaoudi, Mohamed

    2016-08-02

    Ga-soc-MOF hollow cubes with an average size of about 300 nm were prepared by a polyvinylpyrrolidone (PVP) assisted acid etching process. Colloidosomes with sizes of around 5-10 μm composed of single-layer tetrakaidecahedron building blocks (BBs) were synthesized for the first time. Au@Ga-soc-MOF nanocomposites with excellent catalytic properties were obtained.

  17. Fabrication of monodisperse hollow silica spheres and effect on water vapor permeability of polyacrylate membrane.

    Science.gov (United States)

    Bao, Yan; Yang, Yongqiang; Ma, Jianzhong

    2013-10-01

    Polystyrene/silica core-shell spheres were fabricated using polystyrene as templates by hydrolysis and condensation of tetraethyl orthosilicate through a sol-gel process, in which polystyrene was synthesized by emulsion polymerization. Then, hollow silica spheres were obtained after selective removal of the organic polystyrene core from the polystyrene/silica core-shell spheres by tetrahydrofuran etching. The effect of hollow silica spheres on water vapor permeability, mechanical property, and water uptake of polyacrylate membrane were investigated. The microstructure analysis shows that the mean size and wall thickness of hollow silica spheres are 170 nm and 20 nm, respectively. The silica shells consist of amorphous silica seed assembly with a broad size distribution, which roughen the surfaces of hollow silica spheres greatly. The specific surface area of hollow silica spheres is bigger than that of polystyrene/silica core-shell spheres. Hollow silica spheres can significantly improve water vapor permeability of polyacrylate membrane, but lead to the reduction in mechanical property.

  18. Experimental study of monodisperse granular flow through an inclined rotating chute

    NARCIS (Netherlands)

    Shirsath, S.S.; Padding, J.T.; Deen, N.G.; Clercx, H.J.H.; Kuipers, J.A.M.

    2013-01-01

    In blast furnaces, particles like coke, sinter and pellets enter from a hopper and are distributed on the burden surface by a rotating chute. Such particulate flows suffer occasionally from particle segregation during transportation caused by differences in density or size. To get a more fundamental

  19. Numerical investigation of monodisperse granular flow through an inclined rotating chute

    NARCIS (Netherlands)

    Shirsath, Sushil S.; Padding, Johan T.; Kuipers, J.A.M. (Hans); Peeters, Tim W.J.; Clercx, Herman J.H.

    2014-01-01

    A discrete element model of spherical glass particles flowing down a rotating chute is validated against high quality experimental data. The simulations are performed in a corotating frame of reference, taking into account Coriolis and centrifugal forces. In view of future extensions aimed at segreg

  20. Monodisperse TiO2 Spheres with High Charge Density and Their Self-Assembly.

    Science.gov (United States)

    Xia, Hongbo; Wu, Suli; Su, Xin; Zhang, Shufen

    2017-01-03

    Titanium dioxide (TiO2 ) spheres are potential candidates to fabricate three-dimensional (3D) photonic crystals owing to their high refractive index and low absorption in the visible and near-infrared regions. Here, TiO2 spheres with both high surface charge density and uniform size, which are necessary for the self-assembly of TiO2 spheres, have been prepared by means of sol-gel methods in ethanol in the presence of thioglycolic acid as ligand. Thioglycolic acid, which contains two functional groups, not only acts as coordinating ligand for stabilizing and controlling the growth of TiO2 spheres but also endows the resulting TiO2 spheres with high charge density as based on ζ-potential analysis when the pH of the TiO2 aqueous dispersion was 6.5 or higher. The SEM images illustrate that the diameter of the prepared TiO2 spheres can be tuned from 100 to 300 nm by simply controlling the concentration of H2 O. FTIR spectra confirm that thioglycolic acid bonded to the surface of TiO2 spheres through carboxylic groups. As anticipated, the obtained TiO2 spheres could self-assemble to form a 3D opal photonic crystal structure by means of a simple gravity sedimentation method. Then the TiO2 spheres in the 3D opal photonic crystal structure were able to transform into a pure anatase phase by annealing at different temperatures.

  1. Pharmacokinetics of inhaled monodisperse beclomethasone as a function of particle size

    NARCIS (Netherlands)

    J.E. Esposito-Festen; P. Zanen (Pieter); H.A.W.M. Tiddens (Harm); J.-W.J. Lammers (Jan-Willem)

    2007-01-01

    textabstractAims: For optimal efficacy, antiasthma drugs should be delivered to the desired region in the airways. To date, the optimal particle size for steroids in adults is not known. The aim of the study was to evaluate the pulmonary bioavailability for inhaled beclomethasone dipropionate (BDP)

  2. Synthesis and Characterization of Monodisperse Metallodielectric SiO2@Pt@SiO2 Core-Shell-Shell Particles.

    Science.gov (United States)

    Petrov, Alexey; Lehmann, Hauke; Finsel, Maik; Klinke, Christian; Weller, Horst; Vossmeyer, Tobias

    2016-01-26

    Metallodielectric nanostructured core-shell-shell particles are particularly desirable for enabling novel types of optical components, including narrow-band absorbers, narrow-band photodetectors, and thermal emitters, as well as new types of sensors and catalysts. Here, we present a facile approach for the preparation of submicron SiO2@Pt@SiO2 core-shell-shell particles. As shown by transmission and scanning electron microscopy, the first steps of this approach allow for the deposition of closed and almost perfectly smooth platinum shells onto silica cores via a seeded growth mechanism. By choosing appropriate conditions, the shell thickness could be adjusted precisely, ranging from ∼3 to ∼32 nm. As determined by X-ray diffraction, the crystalline domain sizes of the polycrystalline metal shells were ∼4 nm, regardless of the shell thickness. The platinum content of the particles was determined by atomic absorption spectroscopy and for thin shells consistent with a dense metal layer of the TEM-measured thickness. In addition, we show that the roughness of the platinum shell strongly depends on the storage time of the gold seeds used to initiate reductive platinum deposition. Further, using polyvinylpyrrolidone as adhesion layer, it was possible to coat the metallic shells with very homogeneous and smooth insulating silica shells of well-controlled thicknesses between ∼2 and ∼43 nm. After depositing the particles onto silicon substrates equipped with interdigitated electrode structures, the metallic character of the SiO2@Pt particles and the insulating character of the SiO2 shells of the SiO2@Pt@SiO2 particles were successfully demonstrated by charge transport measurements at variable temperatures.

  3. Microencapsulation of chemotherapeutics into monodisperse and tunable biodegradable polymers via electrified liquid jets: control of size, shape, and drug release.

    Science.gov (United States)

    Fattahi, Pouria; Borhan, Ali; Abidian, Mohammad Reza

    2013-09-06

    This paper describes microencapsulation of antitumor agent 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU, Carmustine) into biodegradable polymer poly(lactic-co-glycolic) acid (PLGA) using an electrojetting technique. The resulting BCNU-loaded PLGA microcapsules have significantly higher drug encapsulation efficiency, more tunable drug loading capacity, and (3) narrower size distribution than those generated using other encapsulation methods.

  4. Highly uniform and monodisperse carbon nanospheres enriched with cobalt-nitrogen active sites as a potential oxygen reduction electrocatalyst

    Science.gov (United States)

    Wan, Xing; Wang, Hongjuan; Yu, Hao; Peng, Feng

    2017-04-01

    Uniform cobalt and nitrogen co-doped carbon nanospheres (CoN-CNS) with high specific surface area (865 m2 g-1) have been prepared by a simple but efficient method. The prepared CoN-CNS catalyst exhibits outstanding catalytic performance for the oxygen reduction reaction (ORR) in both alkaline and acidic electrolytes. In alkaline electrolyte, the prepared CoN-CNS has more positive half-wave potential and larger kinetic current density than commercial Pt/C. In acidic electrolyte, CoN-CNS also shows good ORR activity with high electron transfer number, its onset and half-wave potentials are all close to those of commercial carbon supported platinum catalyst (Pt/C). CoN-CNS catalyst shows more superior stability and higher methanol-tolerance than commercial Pt/C both in alkaline and in acidic electrolytes. The potassium thiocyanate-poisoning test further confirms that the cobalt-nitrogen active sites exist in CoN-CNS, which are dominating to endow high ORR catalytic activity in acidic electrolyte. This study develops a new method to prepare non-precious metal catalyst with excellent ORR performances for direct methanol fuel cells.

  5. Structure-property relations of poly(propylene oxide) block copolymers with monodisperse and polydisperse crystallisable segments

    NARCIS (Netherlands)

    Schuur, van der Martijn; Boer, de Jan; Gaymans, Reinoud J.

    2005-01-01

    Segmented block copolymers with poly(propylene oxide) and crystallisable segments were synthesized and their structure-property relations studied. As crystallisable segments, amide units based on poly(p-xylylene terephthalamide), were used. The length of the amide segment was varied and these segmen

  6. Excitation dependent multicolor emission and photoconductivity of Mn, Cu doped In2S3 monodisperse quantum dots

    Science.gov (United States)

    Ghosh, Sirshendu; Saha, Manas; Ashok, Vishal Dev; Chatterjee, Arijit; De, S. K.

    2016-04-01

    Indium sulphide (In2S3) quantum dots (QDs) of average size 6 ± 2 nm and hexagonal nanoplatelets of average size 37 ± 4 nm have been synthesized from indium myristate and indium diethyl dithiocarbamate precursors respectively. The absorbance and emission band was tuned with variation of nanocrytal size from very small in the strong confinement regime to very large in the weak confinement regime. The blue emission and its shifting with size has been explained with the donor-acceptor recombination process. The 3d element doping (Mn2+ and Cu2+) is found to be effective for formation of new emission bands at higher wavelengths. The characteristic peaks of Mn2+ and Cu2+ and the modification of In3+ peaks in the x-ray photoelectric spectrum (XPS) confirm the incorporation of Mn2+ and Cu2+ into the In2S3 matrix. The simulation of the electron paramagnetic resonance signal indicates the coexistence of isotropic and axial symmetry for In and S vacancies. Moreover, the majority of Mn2+ ions and sulphur vacancies (VS ) reside on the surface of nanocrystals. The quantum confinement effect leads to an enhancement of band gap up to 3.65 eV in QDs. The formation of Mn 3d levels between conduction band edge and shallow donor states is evidenced from a systematic variation of emission spectra with the excitation wavelength. In2S3 QDs have been established as efficient sensitizers to Mn and Cu emission centers. Fast and slow components of photoluminescence (PL) decay dynamics in Mn and Cu doped QDs are interpreted in terms of surface and bulk recombination processes. Fast and stable photodetctors with high photocurrent gain are fabricated with Mn and Cu doped QDs and are found to be faster than pure In2S3. The fastest response time in Cu doped QDs is an indication of the most suitable system for photodetector devices.

  7. Monodisperse nanoparticles from self-assembling amphiphilic cyclodextrins: modulable tools for the encapsulation and controlled release of pharmaceuticals.

    Science.gov (United States)

    Mendez-Ardoy, Alejandro; Gómez-García, Marta; Gèze, Annabelle; Putaux, Jean-Luc; Wouessidjewe, Denis; Ortiz Mellet, Carmen; Defaye, Jacques; García Fernández, José M; Benito, Juan M

    2012-07-01

    Selective chemical functionalization of cyclodextrins (CDs) is a readily amenable methodology to produce amphiphilic macromolecules endowed with modulable self-organizing capabilities. Herein, the synthesis of well-defined amphiphilic CD derivatives, with a "skirt-type" architecture, that incorporate long-chain fatty esters at the secondary hydroxyl rim and a variety of chemical functionalities (e. g. iodo, bromo, azido, cysteaminyl or isothiocyanato) at the primary hydroxyls rim is reported. Nanoprecipitation of the new CD facial amphiphiles, or binary mixtures of them, resulted in nanoparticles with average hydrodynamic diameters ranging from 100 to 240 nm that were stable in suspension for several months. The precise size, zeta potential and topology of the nanoparticles are intimately dependent on the functionalization pattern at the CD scaffold. Highly efficient molecular encapsulation capabilities of poorly bioavailable drugs such as diazepam (DZ) were demonstrated for certain derivatives, the drug release profile being dependent on the type of formulation (nanospheres or nanocapsules). The efficiency and versatility of the synthetic strategy, together with the possibility of exploiting the reactivity of the functional groups at the nanoparticle surface, offer excellent opportunities to further manipulate the carrier capabilities of this series of amphiphilic CDs from a bottom-up approach.

  8. Effect of Organic Capping Layers over Monodisperse Platinum Nanoparticles upon Activity for Ethylene Hydrogenation and Carbon Monoxide Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Kuhn, John N.; Tsung, Chia-Kuang; Huang, Wenyu; Somorjai, Gabor A.

    2009-03-24

    The influence of oleylamine (OA), trimethyl tetradecyl ammonium bromide (TTAB), and polyvinlypyrrolidone (PVP) capping agents upon the catalytic properties of Pt/silica catalysts was evaluated. Pt nanoparticles that were 1.5 nm in size were synthesized by the same procedure (ethylene glycol reduction under basic conditions) with the various capping agents added afterward for stabilization. Before examining catalytic properties for ethylene hydrogenation and CO oxidation, the Pt NPs were deposited onto mesoporous silica (SBA-15) supports and characterized by transmission electron microscopy (TEM), H{sub 2} chemisorption, and elemental analysis (ICP-MS). PVP- and TTAB-capped Pt yielded mass-normalized reaction rates that decreased with increasing pretreatment temperature, and this trend was attributed to the partial coverage of the Pt surface with decomposition products from the organic capping agent. Once normalized to the Pt surface area, similar intrinsic activities were obtained regardless of the pretreatment temperature, which indicated no influence on the nature of the active sites. Consequently, a chemical probe technique using intrinsic activity for ethylene hydrogenation was demonstrated as an acceptable method for estimating the metallic surface areas of Pt. Amine (OA) capping exhibited a detrimental influence on the catalytic properties as severe deactivation and low activity were observed for ethylene hydrogenation and CO oxidation, respectively. These results were consistent with amine groups being strong poisons for Pt surfaces, and revealed the need to consider the effects of capping agents on the catalytic properties.

  9. UV-vis light activated Ag decorated monodisperse TiO2 for treatment of pharmaceuticals in water

    Science.gov (United States)

    Recently, many researchers have made a lot of effort to utilize the visible light portion of the solar spectrum to activate TiO2 photocatalyst for environmental applications, such as water, air, and soil remediation. The deposition of noble metals on photocatalysts is of great in...

  10. Microchannel emulsification study on formulation and stability characterization of monodisperse oil-in-water emulsions encapsulating quercetin.

    Science.gov (United States)

    Khalid, Nauman; Kobayashi, Isao; Neves, Marcos A; Uemura, Kunihiko; Nakajima, Mitsutoshi; Nabetani, Hiroshi

    2016-12-01

    The study used microchannel emulsification (MCE) to encapsulate quercetin in food grade oil-in-water (O/W) emulsions. A silicon microchannel plate (Model WMS 1-2) comprised of 10,300 discrete 10×104μm microslots was connected to a circular microhole with an inner diameter of 10μm. 1% (w/w) Tween 20 was used as optimized emulsifier in Milli-Q water, while 0.4mgml(-1) quercetin in different oils served as a dispersed phase. The MCE was carried by injecting the dispersed phase at 2mlh(-1). Successful emulsification was conducted below the critical dispersed phase flux, with a Sauter mean diameter of 29μm and relative span factor below 0.25. The O/W emulsions remained stable in terms of droplet coalescence at 4 and 25°C for 30days. The encapsulation efficiency of quercetin in the O/W emulsions was 80% at 4°C and 70% at 25°C during the evaluated storage period.

  11. Investigation of luminescent dye-doped or rare-earth-doped monodisperse silica nanospheres for DNA microarray labelling

    Science.gov (United States)

    Enrichi, F.; Riccò, R.; Meneghello, A.; Pierobon, R.; Cretaio, E.; Marinello, F.; Schiavuta, P.; Parma, A.; Riello, P.; Benedetti, A.

    2010-10-01

    DNA microarray is a high-throughput technology used for detection and quantification of nucleic acid molecules and others of biological interest. The analysis is resulting by specific hybridization between probe sequences deposited in array and a target ss-DNA usually functionalized by a luminescent dye. These organic labels have well known disadvantages like photobleaching and limited sensitivity. Therefore in this work we investigate a different strategy, based on the use of inorganic silica nanospheres incorporating standard luminescent dyes or rare earth ions. The synthesis and characterization of these biomarkers is reported and their application to the DNA microarray technology in comparison to the use of standard molecular fluorophores or commercial quantum dots is discussed. We show that dye doped silica spheres provides a significant increase of the optical emission signal with respect to the use of free dyes, while rare earth doped silica spheres allow reducing or completely avoiding the background noise. These aspects, together with their cheap and easy synthesis, stability in water, easy surface functionalization and bio-compatibility makes them very promising for present and future applications in bio-labelling and bio-imaging.

  12. Luminescent dye-doped or rare-earth-doped monodisperse silica nanospheres as efficient labels in DNA microarrays

    Science.gov (United States)

    Enrichi, F.; Riccò, R.; Meneghello, A.; Pierobon, R.; Marinello, F.; Schiavuta, P.

    2009-08-01

    Luminescent nanoparticles are gaining more and more interest in bio-labeling and bio-imaging applications, like for example DNA microarray. This is a high-throughput technology used for detection and quantification of nucleic acid molecules and other ones of biological interest. The analysis is resulting by specific hybridization between probe sequences deposited in array and a target ss-DNA usually expressed by PCR and functionalized by a fluorescent dye. These organic labels have well known disadvantages like photobleaching and limited sensitivity. Quantum dots may be used as alternatives, but they present troubles like blinking, toxicity and excitation wavelengths out of the usual range of commercial instruments, lowering their efficiency. Therefore in this work we investigate a different strategy, based on the use of inorganic silica nanospheres incorporating standard luminescent dyes or rare earth doped nanocrystals. In the first case it is possible to obtain a high luminescence emission signal, due to the high number of dye molecules that can be accommodated into each nanoparticle, reduced photobleaching and environmental protection of the dye molecules thanks to the encapsulation in the silica matrix. In the second case, rare earths exhibit narrow emission bands (easy identification), large Stokes shifts (efficient discrimination of excitation and emission) and long luminescence lifetimes (possibility to perform time-delayed analysis) which can be efficiently used for the improvement of signal to noise ratio. The synthesis and characterization of good luminescent silica spheres either by organic dye-doping or by rare-earth-doping are investigated and reported. Moreover, their application in the DNA microarray technology in comparison to the use of standard molecular fluorophores or commercial quantum dots is discussed. The cheap and easy synthesis of these luminescent particles, the stability in water, the surface functionalization and bio-compatibility makes them very promising for present and future applications in bio-labeling and bio-imaging.

  13. A facile route to monodisperse MPd (M = Co or Cu) alloy nanoparticles and their catalysis for electrooxidation of formic acid

    Science.gov (United States)

    Ho, Sally Fae; Mendoza-Garcia, Adriana; Guo, Shaojun; He, Kai; Su, Dong; Liu, Sheng; Metin, Önder; Sun, Shouheng

    2014-05-01

    MPd (M = Co, or Cu) nanoparticles (NPs) were synthesized by borane-amine reduction of metal acetylacetonates. The size of the MPd NPs was controlled at 3.5 nm and their compositions were tuned by the molar ratios of the metal precursors. These MPd NPs were active catalysts for electrochemical oxidation of formic acid and the Cu30Pd70 NPs showed the highest mass activity at 1192.9 A gPd-1, much higher than 552.6 A gPd-1 obtained from the 3.5 nm Pd NPs. Our synthesis provides a facile route to MPd NPs, allowing further investigation of MPd NP catalysts for electrochemical oxidation and many other chemical reactions.MPd (M = Co, or Cu) nanoparticles (NPs) were synthesized by borane-amine reduction of metal acetylacetonates. The size of the MPd NPs was controlled at 3.5 nm and their compositions were tuned by the molar ratios of the metal precursors. These MPd NPs were active catalysts for electrochemical oxidation of formic acid and the Cu30Pd70 NPs showed the highest mass activity at 1192.9 A gPd-1, much higher than 552.6 A gPd-1 obtained from the 3.5 nm Pd NPs. Our synthesis provides a facile route to MPd NPs, allowing further investigation of MPd NP catalysts for electrochemical oxidation and many other chemical reactions. Electronic supplementary information (ESI) available: Detailed synthetic and electrochemical analysis procedures, and XRD of the NPs. See DOI: 10.1039/c4nr01107d

  14. Shape Evolution Synthesis of Monodisperse Spherical, Ellipsoidal, and Elongated Hematite (alpha-Fe2O3) Nanoparticles Using Ascorbic Acid

    NARCIS (Netherlands)

    Tan, W.F.; Yu, Y.T.; Wang, M.X.; Liu, F.; Koopal, L.K.

    2014-01-01

    Spherical, ellipsoidal, and elongated hematite particles have been obtained via a simple chemical precipitation reaction of FeCl3 and NaOH in the presence of ascorbic acid,(AA). The effects of pH, molar ratio of AA/Fe(III), and time on the formation and shape of the hematite particles were investiga

  15. Monodisperse raspberry-like multihollow polymer/Ag nanocomposite microspheres for rapid catalytic degradation of methylene blue.

    Science.gov (United States)

    Tian, Qiong; Yu, Xiaojing; Zhang, Lifeng; Yu, Demei

    2017-04-01

    Raspberry-like multihollow polymer microspheres were prepared by seeded swelling polymerization and decorated with silver nanoparticles (AgNPs) in the presence of polyvinylpyrrolidone (PVP) which acted as both reducing and stabilizing agent. Formation mechanism of the raspberry-like multihollow microsphere was discussed on the basis of water absorption of sulfonated groups in the seeded swelling polymerization. Effects of weight ratio of sodium 4-vinylbenzenesulfonate to styrene (NaSS/St) of the seed particles, the concentration of PVP and [Ag(NH3)2](+) ions on the properties of polymer/Ag nanocomposite microspheres were investigated by microscopic observation, nitrogen adsorption/desorption isotherms, UV-vis absorption spectra, X-ray diffraction patterns and thermogravimetric analysis. The results demonstrated that the raspberry-like multihollow microspheres were successfully fabricated by controlling over the NaSS/St of the seed particles in the seeded swelling polymerization by which the fabrication of hollow structure became simple and convenient. The spherical AgNPs were loaded on the polymer microsphere by in-situ chemical reduction due to the stabilization and reduction of PVP and the attraction between sulfonated groups and [Ag(NH3)2](+) ions. The raspberry-like multihollow polymer/Ag microspheres showed good catalytic activity and reusability in the degradation of methylene blue in the presence of NaBH4.

  16. Polyurethane triblock copolymers with mono-disperse hard segments. Influence of the hard segment length on thermal and thermomechanical properties

    NARCIS (Netherlands)

    Arun, Araichimani; Baack, Kasper K.J.; Gaymans, Reinoud J.

    2008-01-01

    Polyurethane triblock copolymers were synthesized by reacting 4,4-methylenebis(phenyl isocyanate) (MDI)-endcapped poly(tetramethylene oxide) (PTMO) with mono-amine-amide (MMA) units. Four different MMA units were used, i.e. no-amide (6m), mono-amide (6B), di-amide (6T6m) and tri-amide (6T6B), based

  17. Encapsulation of single cells into monodisperse droplets by fluorescence-activated droplet formation on a microfluidic chip.

    Science.gov (United States)

    Hu, Rui; Liu, Pian; Chen, Pu; Wu, Liang; Wang, Yao; Feng, Xiaojun; Liu, Bi-Feng

    2016-06-01

    Random compartmentalization of cells by common droplet formation methods, i.e., T-junction and flow-focusing, results in low occupancy of droplets by single cells. To resolve this issue, a fluorescence-activated droplet formation method was developed for the on-command generation of droplets and encapsulation of single cells. In this method, droplets containing one cell were generated by switching on/off a two-phase hydrodynamic gating valve upon optical detection of single cells. To evaluate the developed method, flow visualization experiments were conducted with fluorescein. Results indicated that picoliter droplets of uniform sizes (RSDdroplets contained one bead. Further application of the developed methods to the compartmentalization of individual HeLa cells indicated 82.5% occupancy of droplets by single cells, representing a 3 fold increase in comparison to random compartmentalization.

  18. Monodisperse Picoliter Droplets for Low-Bias and Contamination-Free Reactions in Single-Cell Whole Genome Amplification.

    Directory of Open Access Journals (Sweden)

    Yohei Nishikawa

    Full Text Available Whole genome amplification (WGA is essential for obtaining genome sequences from single bacterial cells because the quantity of template DNA contained in a single cell is very low. Multiple displacement amplification (MDA, using Phi29 DNA polymerase and random primers, is the most widely used method for single-cell WGA. However, single-cell MDA usually results in uneven genome coverage because of amplification bias, background amplification of contaminating DNA, and formation of chimeras by linking of non-contiguous chromosomal regions. Here, we present a novel MDA method, termed droplet MDA, that minimizes amplification bias and amplification of contaminants by using picoliter-sized droplets for compartmentalized WGA reactions. Extracted DNA fragments from a lysed cell in MDA mixture are divided into 105 droplets (67 pL within minutes via flow through simple microfluidic channels. Compartmentalized genome fragments can be individually amplified in these droplets without the risk of encounter with reagent-borne or environmental contaminants. Following quality assessment of WGA products from single Escherichia coli cells, we showed that droplet MDA minimized unexpected amplification and improved the percentage of genome recovery from 59% to 89%. Our results demonstrate that microfluidic-generated droplets show potential as an efficient tool for effective amplification of low-input DNA for single-cell genomics and greatly reduce the cost and labor investment required for determination of nearly complete genome sequences of uncultured bacteria from environmental samples.

  19. Probing hydrodesulfurization over bimetallic phosphides using monodisperse Ni2-xMxP nanoparticles encapsulated in mesoporous silica

    Science.gov (United States)

    Danforth, Samuel J.; Liyanage, D. Ruchira; Hitihami-Mudiyanselage, Asha; Ilic, Boris; Brock, Stephanie L.; Bussell, Mark E.

    2016-06-01

    Metal phosphide nanoparticles encapsulated in mesoporous silica provide a well-defined system for probing the fundamental chemistry of the hydrodesulfurization (HDS) reaction over this new class of hydrotreating catalysts. To investigate composition effects in bimetallic phosphides, the HDS of dibenzothiophene (DBT) was carried out over a series of Ni-rich Ni2-xMxP@mSiO2 (M = Co, Fe) nanocatalysts (x ≤ 0.50). The Ni2-xMxP nanoparticles (average diameters: 11-13 nm) were prepared by solution-phase arrested precipitation and encapsulated in mesoporous silica, characterized by a range of techniques (XRD, TEM, IR spectroscopy, BET surface area, CO chemisorption) and tested for DBT HDS activity and selectivity. The highest activity was observed for a Ni1.92Co0.08P@mSiO2 nanocatalyst, but the overall trend was a decrease in HDS activity with increasing Co or Fe content. In contrast, the highest turnover frequency (TOF) was observed for the most Co- and Fe-rich compositions based on sites titrated by CO chemisorption. IR spectral studies of adsorbed CO on the Ni2-xMxP@mSiO2 catalysts indicate that an increase in electron density occurs on Ni sites as the Co or Fe content is increased, which may be responsible for the increased TOFs of the catalytic sites. The Ni2-xMxP@mSiO2 nanocatalysts exhibit a strong preference for the direct desulfurization pathway (DDS) for DBT HDS that changes only slightly with increasing Co or Fe content.

  20. Influence of α-amylase template concentration on systematic entrapment of highly stable and monodispersed colloidal gold nanoparticles

    Science.gov (United States)

    Ananth, A. Nitthin; Ananth, A. Nimrodh; Jose, Sujin P.; Umapathy, S.; Mathavan, T.

    2016-01-01

    Nano gold / α-amylase colloidal dispersions of profound stability were made using simple procedure with a conventional reducing agent. The surface plasmon resonance of the gold nanocrystals was used to quantify the extent of the dispersion stability and functionalization. It is found that the reduced gold nanoparticles were trapped into the protein network without denaturation the structure of α-amylase protein. This kind of entrapment of particles into the protein network prevents clustering of individual gold nanoparticles (6.42 nm ± 0.92 nm) by acting as a natural spacer. Systematic entrapment was facilitated by the affinity of gold to the sulfur moieties (Au-S) in the protein structure.

  1. Ultra-small-angle neutron scattering: a tool to study packing of relatively monodisperse polymer spheres and their binary mixtures.

    Science.gov (United States)

    Reynolds, Philip A; McGillivray, Duncan J; Jackson, Andrew J; White, John W

    2009-07-01

    We measured ultra-small-angle neutron scattering (USANS) from polymethylmethacrylate spheres tamped down in air. Two slightly polydisperse pure sphere sizes (1.5 and 7.5 microm diameters) and five mixtures of these were used. All were loose packed (packing fractions of 0.3-0.6) with nongravitational forces (e.g., friction) important, preventing close packing. The USANS data are rich in information on powder packing. A modified Percus-Yevick fluid model was used to parametrize the data-adequately but not well. The modifications required the introduction of small voids, less than the sphere size, and a parameter reflecting substantial deviation from the Percus-Yevick prediction of the sphere-sphere correlation function. The mixed samples fitted less well, and two further modifying factors were necessary. These were local inhomogeneities, where the concentration of same-size spheres, both large and small, deviated from the mean packing, and a factor accounting for the presence within these "clusters" of self-avoidance of the large spheres (that is, large spheres coated with more small spheres than Percus-Yevick would predict). The overall deviations from the hard-sphere Percus-Yevick model that we find here suggest that fluid models of loose packed powders are unlikely to be successful but lay the ground work for future theoretical and computational works.

  2. Preparation of mono-dispersed silver nanoparticles assisted by chitosan-g-poly(ε-caprolactone) micelles and their antimicrobial application

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Chunhua [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Zhang, Huan [State Key Laboratory of Bioreactor Engineering, New World Biotechnology Institute, East China University of Science and Technology, Shanghai 200237 (China); Lang, Meidong, E-mail: mdlang@ecust.edu.cn [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2014-05-01

    Graphical abstract: - Highlights: • Chemical modification of chitosan were conducted after phthaloyl protection of amino groups. • Silver nanoparticles were prepared in the presence of chitosan-based copolymer micelles. • The optimal time scale and weight ratios of silver to micelles were monitored by UV–vis spectrometer. - Abstract: Amphiphilic chitosan-graft-poly(ε-caprolactone) (CS-g-PCLs) copolymers were synthesized by a homogeneous coupling method and characterized by {sup 1}H NMR, FTIR and ninhydrin assay. The graft copolymers were subsequently self-assembled into micelles, which were measured by DLS and TEM. The particle size of the micelles decreased as the segment grafting fraction was increased. Thereafter, silver nanoparticles were prepared in the presence of chitosan-based micelles under UV irradiation. The molar ratio and radiation time of silver to micelles were optimized with process monitored via UV–vis spectrophotometer. DLS and TEM were used to illustrate the particle structure and size while XRD patterns were applied to characterize the crystal structures of polymer-assisted silver nanoparticles. Films impregnated with silver nanoparticles were conducted with results of strong antimicrobial activities against Escherichia coli and Staphylococcus aureus as model Gram-negative and positive bacteria.

  3. Monodisperse antimony nanocrystals for high-rate Li-ion and Na-ion battery anodes: nano versus bulk.

    Science.gov (United States)

    He, Meng; Kravchyk, Kostiantyn; Walter, Marc; Kovalenko, Maksym V

    2014-03-12

    We report colloidal synthesis of antimony (Sb) nanocrystals with mean size tunable in the 10-20 nm range and with narrow size distributions of 7-11%. In comparison to microcrystalline Sb, 10 and 20 nm Sb nanocrystals exhibit enhanced rate-capability and higher cycling stability as anode materials in rechargeable Li-ion and Na-ion batteries. All three particle sizes of Sb possess high and similar Li-ion and Na-ion charge storage capacities of 580-640 mAh g(-1) at moderate charging/discharging current densities of 0.5-1C (1C-rate is 660 mA g(-1)). At all C-rates (0.5-20C, e.g. current densities of 0.33-13.2 Ag(1-)), capacities of 20 nm Sb particles are systematically better than for both 10 nm and bulk Sb. At 20C-rates, retention of charge storage capacities by 10 and 20 nm Sb nanocrystals can reach 78-85% of the low-rate value, indicating that rate capability of Sb nanostructures can be comparable to the best Li-ion intercalation anodes and is so far unprecedented for Na-ion storage.

  4. Microspheres: Microfluidic Generation of Monodisperse and Photoreconfigurable Microspheres for Floral Iridescence-Inspired Structural Colorization (Adv. Mater. 26/2016).

    Science.gov (United States)

    Yeo, Seon Ju; Park, Kyung Jin; Guo, Kai; Yoo, Pil J; Lee, Seungwoo

    2016-07-01

    Flowering plants have advanced their colorization strategies to divide incoming white light into spatially sequenced vivid colors, especially by using 2D grating diffractive motifs. On page 5268, P. J. Yoo, S. Lee, and co-workers conceive a new idea for a microfluidic approach to mimic this wonderful biological strategy and its practical application to the color encoding of colloidal particles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Modeling the Permittivity of Two-Phase Media Containing Monodisperse Spheres: Effects of Microstructure and Multiple Scattering

    OpenAIRE

    Doyle, Timothy E; Robinson, David A.; Scott B. Jones; Warnick, Keith H.; Carruth, Brent L.

    2007-01-01

    A numerical modeling approach was developed to predict the dielectric properties of heterogeneous particulate materials with arbitrary microstructures. To test the method, simulation and experimental data were acquired for the effective permittivities of various glass sphere suspensions. Both ordered lattices and random microstructures of up to 3600 spheres were modeled for volume fractions of 0.025–0.60. The electric fields in the suspensions were computed using an iterative multipole method...

  6. Size measurement uncertainties of near-monodisperse, near-spherical nanoparticles using transmission electron microscopy and particle-tracking analysis

    Science.gov (United States)

    De Temmerman, Pieter-Jan; Verleysen, Eveline; Lammertyn, Jeroen; Mast, Jan

    2014-10-01

    Particle-tracking analysis (PTA) in combination with systematic imaging, automatic image analysis, and automatic data processing is validated for size measurements. Transmission electron microscopy (TEM) in combination with a systematic selection procedure for unbiased random image collection, semiautomatic image analysis, and data processing is validated for size, shape, and surface topology measurements. PTA is investigated as an alternative for TEM for the determination of the particle size in the framework of the EC definition of nanomaterial. The intra-laboratory validation study assessing the precision and accuracy of the TEM and PTA methods consists of series of measurements on three gold reference materials with mean area-equivalent circular diameters of 8.9 nm (RM-8011), 27.6 nm (RM-8012), and 56.0 nm (RM-8013), and two polystyrene materials with modal hydrodynamic diameters of 102 nm (P1) and 202 nm (H1). By obtaining a high level of automation, PTA proves to give precise and non-biased results for the modal hydrodynamic diameter in size range between 30 and 200 nm, and TEM proves to give precise and non-biased results for the mean area-equivalent circular diameter in the size range between 8 and 200 nm of the investigated near-monomodal near-spherical materials. The expanded uncertainties of PTA are about 9 % and are determined mainly by the repeatability uncertainty. This uncertainty is two times higher than the expanded uncertainty of 4 % obtained by TEM for analyses on identical materials. For the investigated near-monomodal and near-spherical materials, PTA can be used as an alternative to TEM for measuring the particle size, with exception of 8.9 nm gold, because this material has a size below the detection limit of PTA.

  7. Highly monodisperse M III-based soc -MOFs (M = in and Ga) with cubic and truncated cubic morphologies

    KAUST Repository

    Pang, Maolin

    2012-08-15

    In this work, we carry out an investigation on shape-controlled growth of In III- and Ga III-based square-octahedral metal-organic frameworks (soc-MOFs). In particular, controllable crystal morphological evolution from simple cubes to complex octadecahedra has been achieved, and resultant highly uniform crystal building blocks promise new research opportunities for preparation of self-assembled MOF materials and related applications. © 2012 American Chemical Society.

  8. Preparing mono-dispersed liquid core PDMS microcapsules from thiol–ene–epoxy-tailored flow-focusing microfluidic devices

    DEFF Research Database (Denmark)

    Mazurek, Piotr Stanislaw; Daugaard, Anders Egede; Skolimowski, Maciej

    2015-01-01

    An applied dual-cure system based on thiol–ene and thiol–epoxy “click chemistry” reactions was proved to be an extremely effective and easy to use tool for preparing microfluidic chips, thereby allowing for precise control over material properties and providing the possibility of covalently bonding...

  9. Intramolecular Insertions into Unactivated C(sp³)-H Bonds by Oxidatively Generated β-Diketone-α-Gold Carbenes: Synthesis of Cyclopentanones.

    Science.gov (United States)

    Wang, Youliang; Zheng, Zhitong; Zhang, Liming

    2015-04-29

    Generation of reactive α-oxo gold carbene intermediates via gold-catalyzed oxidation of alkynes has become an increasing versatile strategy of replacing hazardous diazo carbonyl compounds with benign and readily available alkynes in the development of efficient synthetic methods. However, one of the hallmarks of metal carbene/carbenoid chemistry, i.e., insertion into an unactivated C(sp(3))-H bond, has not be realized. This study reveals for the first time that this highly valuable transformation can be readily realized intramolecularly by oxidatively generated β-diketone-α-gold carbenes using ynones as substrates. Substrate conformation control via the Thorpe-Ingold effect is the key design feature that enables generally good to excellent efficiencies, and synthetically versatile cyclopentanones including spiro-, bridged, and fused bicyclic ones can be readily accessed.

  10. In situ growth of monodispersed Fe3O4 nanoparticles on graphene for the removal of heavy metals and aromatic compounds.

    Science.gov (United States)

    Wu, Hai-Xia; Wu, Jia-Wei; Niu, Zhi-Gang; Shang, Xiu-Li; Jin, Jun

    2013-01-01

    We report on the efficient removal of heavy metal ions and aromatic compounds from simulated wastewater with a nanocomposite. The nanocomposite was obtained via thermal decomposition of the precursor Fe(acac)3 onto the surface of graphene, modified by diethylenetriamine pentaacetic anhydride through dopamine. It was found that the maximum adsorption capacity of the nanocomposite toward Cu(2+) and naphthalene was 207.9 and 72.2 mg g(-1) respectively, displaying a high efficiency for the removal of heavy metal ions as well as aromatic compounds at pH 7.0 and 293 K. The Langmuir for naphthalene and the Freundlich for the Cu(2+) adsorption isotherms were applicable for describing the removal processes. Furthermore, the nanocomposite was carefully examined by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectra, and UV-vis spectroscopy. This work provides a very efficient, fast and convenient approach to exploring a promising nanocomposite for water treatment.

  11. Controllable assembly of well-defined monodisperse Au nanoparticles on hierarchical ZnO microspheres for enhanced visible-light-driven photocatalytic and antibacterial activity

    Science.gov (United States)

    Wang, Yuan; Fang, Hua-Bin; Zheng, Yan-Zhen; Ye, Rongqin; Tao, Xia; Chen, Jian-Feng

    2015-11-01

    A high-efficiency visible-light-driven photocatalyst composed of homogeneously distributed Au nanoparticles (AuNPs) well-defined on hierarchical ZnO microspheres (ZMS) via a controllable layer-by-layer self-assembly technique is demonstrated. The gradual growth of the characteristic absorption bands of Au loaded on ZnO in the visible light region with an increasing number of assemblies indicates the enhancement of the light harvesting ability of the ZMS/Au composites as well as the reproducibility and controllability of the entire assembly process. Results on the photoelectrochemical performance characterized by EIS and transient photocurrent response spectra indicate that the ZMS/Au composites possess increased photoinduced charge separation and transfer efficiency compared to the pure ZMS film. As a result, the hybrid composites exhibited enhanced decomposition activity for methylene blue and salicylic acid as well as antibacterial activity in killing S. aureus and E. coli under visible light irradiation. It can be noted that well-distributed Au components even at a rather low Au/ZnO weight ratio of ~1.2% also exhibited extraordinary photocatalysis. Such a facile and controllable self-assembly approach may be viable for preparing high-performance visible-light-driven ZMS/Au photocatalysts in a simple and controllable way, and consequently, the technology may extend to other plasmon-enhanced heterostructures made of nanostructured semiconductors and noble metals for great potential application in environmental protection.A high-efficiency visible-light-driven photocatalyst composed of homogeneously distributed Au nanoparticles (AuNPs) well-defined on hierarchical ZnO microspheres (ZMS) via a controllable layer-by-layer self-assembly technique is demonstrated. The gradual growth of the characteristic absorption bands of Au loaded on ZnO in the visible light region with an increasing number of assemblies indicates the enhancement of the light harvesting ability of the ZMS/Au composites as well as the reproducibility and controllability of the entire assembly process. Results on the photoelectrochemical performance characterized by EIS and transient photocurrent response spectra indicate that the ZMS/Au composites possess increased photoinduced charge separation and transfer efficiency compared to the pure ZMS film. As a result, the hybrid composites exhibited enhanced decomposition activity for methylene blue and salicylic acid as well as antibacterial activity in killing S. aureus and E. coli under visible light irradiation. It can be noted that well-distributed Au components even at a rather low Au/ZnO weight ratio of ~1.2% also exhibited extraordinary photocatalysis. Such a facile and controllable self-assembly approach may be viable for preparing high-performance visible-light-driven ZMS/Au photocatalysts in a simple and controllable way, and consequently, the technology may extend to other plasmon-enhanced heterostructures made of nanostructured semiconductors and noble metals for great potential application in environmental protection. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06359k

  12. Release and pharmacokinetics of near-infrared labeled albumin from monodisperse poly(D,L-lactic-co-hydroxymethyl glycolic acid) microspheres after subcapsular renal injection

    NARCIS (Netherlands)

    Kazazi-Hyseni, F.; Van Vuuren, S. H.; Van Der Giezen, D. M.; Pieters, E. H.; Ramazani, F.; Rodriguez, S.; Veldhuis, G. J.; Goldschmeding, R.; Van Nostrum, C. F.; Hennink, W. E.; Kok, R. J.

    2015-01-01

    Subcapsular renal injection is a novel administration method for local delivery of therapeutics for the treatment of kidney related diseases. The aim of this study was to investigate the feasibility of polymeric microspheres for sustained release of protein therapeutics in the kidney and study the s

  13. Synthesis and controllable oxidation of monodisperse cobalt-doped wüstite nanoparticles and their core-shell stability and exchange-bias stabilization

    Science.gov (United States)

    Chen, Chih-Jung; Chiang, Ray-Kuang; Kamali, Saeed; Wang, Sue-Lein

    2015-08-01

    Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ~4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (HE), an enhanced coercivity field (HC), and a pronounced vertical shift, thus indicating the presence of a strong exchange bias coupling effect. More importantly, the onset temperature of HE was found to be higher than 200 K, which suggests that cobalt doping increases the Néel temperature (TN) of the CWT core. In general, the results show that the homogeneous dispersion of Co in iron precursors improves the stability of the final CWT nanoparticles. Moreover, the CoFe2O4 shells formed following oxidation increase the oxidation resistance of the CWT cores and enhance their anisotropy energy.Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ~4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (HE), an enhanced coercivity field (HC), and a pronounced vertical shift, thus indicating the presence of a strong exchange bias coupling effect. More importantly, the onset temperature of HE was found to be higher than 200 K, which suggests that cobalt doping increases the Néel temperature (TN) of the CWT core. In general, the results show that the homogeneous dispersion of Co in iron precursors improves the stability of the final CWT nanoparticles. Moreover, the CoFe2O4 shells formed following oxidation increase the oxidation resistance of the CWT cores and enhance their anisotropy energy. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02969d

  14. Electro-hydrodynamic generation of monodisperse nanoparticles in the sub-10 nm size range from strongly electrolytic salt solutions: governing parameters of scaling laws

    Energy Technology Data Exchange (ETDEWEB)

    Maisser, Anne, E-mail: a.maisser@tudelft.nl [Delft University of Technology (Netherlands); Attoui, Michel B. [LISA, UMR CNRS University Paris Est Creteil, University Paris-Diderot (France); Ganan-Calvo, Alfonso M. [Universidad de Sevilla, ESI (Spain); Szymanski, Wladyslaw W. [University of Vienna, Faculty of Physics (Austria)

    2013-01-15

    A charge reduced electro-hydrodynamic atomization (EHDA) device has been used to generate airborne salt clusters in the sub 10 nm size range. The focus of this study on that specific sub-micron range of electrospray droplets with relatively high electrical conductivities and permittivities aims to address the still existing controversy on the scaling laws of electrosprayed droplet diameters. In this study different concentrations of sodium chloride and potassium chloride-both show strong electrolytic behavior-have been electrosprayed from solutions in pure water, or from aqueous ammonium acetate buffer liquids of varying concentrations. The dry residue salt cluster diameter generated by the EHDA process have been measured using a differential mobility analyzer. The initial droplet diameter has been determined indirectly from the measured particle size following the steps of Chen et al. (J Aerosol Sci 26:963-977, 1995). Results have been compared to existing scaling laws valid for direct droplet measurements. They can be interpreted concisely on the basis of a realistic hypothesis on possible electrochemical effects taking place and affecting the droplet and thus nanoparticle formation in EHDA. The hypothesis developed in this work and the comparison with the experimental results are shown and discussed in the manuscript.

  15. Computer Modeling Assisted Design of Monodisperse PLGA Microspheres with Controlled Porosity Affords Zero Order Release of an Encapsulated Macromolecule for 3 Months

    NARCIS (Netherlands)

    Kazazi-Hyseni, Filis; Landin, Mariana; Lathuile, Audrey; Veldhuis, Gert J.; Rahimian, Sima; Hennink, Wim E.; Kok, Robbert Jan; van Nostrum, Cornelus F.

    2014-01-01

    Purpose The aim of this study was the development of poly(D,L-lactide-co-glycolide) (PLGA) microspheres with controlled porosity, to obtain microspheres that afford continuous release of a macromolecular model compound (blue dextran). Methods PLGA microspheres with a size of around 40 μm and narrow

  16. Controllable synthesis of monodisperse MnO nanoparticles%单分散MnO纳米粒子的可控制备

    Institute of Scientific and Technical Information of China (English)

    刘新杰; 张智军; 杨祖培

    2013-01-01

    研究了不同实验条件对MnO纳米粒子尺寸和形貌调控的影响.采用高温分解法以油酸锰为前驱体成功可控制备了3 nm、6 nm、10 nm、20 nm等多种粒径的MnO纳米粒子,并通过透射电子显微镜对其进行了表征.结果表明:反应温度、表面活性剂用量、溶剂用量等对纳米粒子的大小都有一定的影响.随着反应温度的升高,MnO纳米粒子的尺寸逐渐增加,而表面活性剂的用量增大则导致MnO纳米粒子的尺寸变小,增加溶剂用量有利于合成较大尺寸的MnO纳米粒子.此外,还分别用CTAB、DMSA、多巴胺等对MnO纳米粒子进行修饰,结果显示表面经亲水性处理后纳米粒子增加了水溶性,使其更好地用于生物成像和载药.%The morphology of manganese oxide (MnO) nanoparticles significantly affects their properties and various applications.In this paper,we report controllable synthesis and characterization of MnO nanoparticles (3 nm,6 nm,10 nm,20 nm) through the hightemperature decomposition approach.Our results showed that the reaction temperature,the amount of surfactants and solvent affect the size of the nanoparticles.MnO nanoparticles size increases with temperature and solvent content.However,increase of surfactants leads to decrease in the particle size.Finally,we modified the MnO nanoparticles with CTAB,DMSA and dopamine to render their aqueous solubility,which is essential for their biological applications.

  17. Green Synthesis and Characterization of Monodispersed Gold Nanoparticles: Toxicity Study, Delivery of Doxorubicin and Its Bio-Distribution in Mouse Model.

    Science.gov (United States)

    Mukherjee, Sudip; Sau, Samaresh; Madhuri, Durga; Bollu, Vishnu Sravan; Madhusudana, Kuncha; Sreedhar, Bojja; Banerjee, Rajkumar; Patra, Chitta Ranjan

    2016-01-01

    In the present article, we report the in vitro and in vivo delivery of doxorubicin using biosynthesized gold nanoparticles (b-Au-PP). Gold nanoparticles were synthesized by a simple, fast, efficient, environmentally friendly and economical green chemistry approach using an extract of Peltophorum pterocarpum (PP) leaves. Because the biosynthesized b-Au-PP was highly stable in various physiological buffers for several weeks and biocompatible in both in vitro and in vivo systems, we designed and developed a biosynthesized gold nanoparticle (b-Au-PP)-based drug-delivery system (DDS) using doxorubicin (Dox) (b-Au-PP-Dox). Both b-Au-PP and b-Au-PP-Dox were thoroughly characterized using several analytical tools. Administration of doxorubicin-loaded DDS (b-Au-PP-Dox) resulted in a significant inhibition of the proliferation of cancer cells (A549, B16F10) in vitro and of tumor growth in an in vivo model compared to doxorubicin alone. Furthermore, we found that the cellular uptake and release of Dox in the nanoconjugated form (b-Au-PP-Dox) were faster than the uptake and release of unconjugated Dox. The in vivo toxicity study did not show any significant changes in the hematology, serum clinical biochemistry or histopathology in the C57BL6/J female mice after consecutive intraperitoneal (IP) injections over a period of seven days. To the best of our knowledge, our study is the first to report the application of a biosynthesized gold nanoparticle-based DDS for cancer therapy in an animal model, in addition to a detailed in vivo toxicity study. Together, the results demonstrate that a biosynthesized gold nanoparticle-based drug-delivery system (b-Au-PP-Dox) could be used in the near future as an alternative cost-effective treatment strategy for cancer therapy.

  18. Monodisperse magnetite (Fe3O4) nanoparticles modified with water soluble polymers for the diagnosis of breast cancer by MRI method

    Science.gov (United States)

    Rezayan, Ali Hossein; Mousavi, Majid; Kheirjou, Somayyeh; Amoabediny, Ghasem; Ardestani, Mehdi Shafiee; Mohammadnejad, Javad

    2016-12-01

    In this study, magnetic nanoparticles (MNPs) were synthesized via co-precipitation method. To enhance the biocompatibility and colloidal stability of the synthesized nanoparticles, they were modified with carboxyl functionalized PEG via dopamine (DPA) linker. Both modified and unmodified Fe3O4 nanoparticles exhibited super paramagnetic behavior (particle size below 20 nm). The saturation magnetization (Ms) of PEGdiacid-modified Fe3O4 was 45 emu/g, which was less than the unmodified Fe3O4 nanoparticles (70 emu/g). This difference indicated that PEGdiacid polymer was immobilized on the surface of Fe3O4 nanoparticles successfully. To evaluate the efficiency of the resulting nanoparticles as contrast agents for magnetic resonance imaging (MRI), different concentration of MNPs and different value of echo time TE were investigated. The results showed that by increasing the concentration of the nanoparticles, transverse relaxation time (T2) decreased, which subsequently resulted in MR signal enhancement. T2-weighted MR images of the different concentration of MNPs in different value of echo time TE indicated that MR signal intensity increased with increase in TE value up to 66 and then remained constant. The cytotoxicity effect of the modified and unmodified nanoparticles was evaluated in three different concentrations (12, 60 and 312 mg l-1) on MDA-MB-231 cancer cells for 24 and 48 h. In both tested time (24 and 48 h) for all three samples, the modified nanoparticles had long life time than unmodified nanoparticles. Cellular uptake of modified MNPs was 80% and reduced to 9% by the unmodified MNPs.

  19. Photocatalytic hydrogen production using visible-light-responsive Ta 3N5 photocatalyst supported on monodisperse spherical SiO2 particulates

    KAUST Repository

    Liu, Xiaoming

    2014-01-01

    Fine nanoparticles of Ta3N5 (10-20 nm) were synthesized on the surfaces of SiO2 spheres with a diameter of ∼550 nm. A sol-gel method was used to modify the surface of SiO2 with Ta2O5 from TaCl5 dissolved in ethanol in the presence of citric acid and polyethylene glycol. The resulting oxide composites were treated in an NH3 flow at 1123 K to form core-shell structured Ta3N5/SiO2 sub-microspheres. The obtained samples were characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDX), transmission electron microscopy (TEM), and photocatalytic activity measurements for H 2 evolution from an aqueous methanol solution. The XRD results demonstrate the expected sequential formation of Ta2O5 layers, followed by Ta3N5 after nitridation on the Ta 2O5/SiO2 composite. SEM and TEM observations indicate that the obtained Ta3N5/SiO2 sub-microspheres have a uniform size distribution with high crystallinity and an obvious core-shell structure. The presence of support maintained the intrinsic photocatalytic activity of Ta3N5 nanoparticles, but it did drastically improve the dispersion of the photocatalysts in the solution. This study proposes the use of an inert support in photocatalytic reactors to improve ease of handling the powder photocatalyst for gas-phase photocatalysis and the suspension of the solution, controlling nature of light harvesting and degree of scattering of the photoreactor. © 2013 Elsevier Ltd. All rights reserved.

  20. Heterogeneous catalysts need not be so "heterogeneous": monodisperse Pt nanocrystals by combining shape-controlled synthesis and purification by colloidal recrystallization.

    Science.gov (United States)

    Kang, Yijin; Li, Meng; Cai, Yun; Cargnello, Matteo; Diaz, Rosa E; Gordon, Thomas R; Wieder, Noah L; Adzic, Radoslav R; Gorte, Raymond J; Stach, Eric A; Murray, Christopher B

    2013-02-20

    Well-defined surfaces of Pt have been extensively studied for various catalytic processes. However, industrial catalysts are mostly composed of fine particles (e.g., nanocrystals), due to the desire for a high surface to volume ratio. Therefore, it is very important to explore and understand the catalytic processes both at nanoscale and on extended surfaces. In this report, a general synthetic method is described to prepare Pt nanocrystals with various morphologies. The synthesized Pt nanocrystals are further purified by exploiting the "self-cleaning" effect which results from the "colloidal recrystallization" of Pt supercrystals. The resulting high-purity nanocrystals enable the direct comparison of the reactivity of the {111} and {100} facets for important catalytic reactions. With these high-purity Pt nanocrystals, we have made several observations: Pt octahedra show higher poisoning tolerance in the electrooxidation of formic acid than Pt cubes; the oxidation of CO on Pt nanocrystals is structure insensitive when the partial pressure ratio p(O2)/p(CO) is close to or less than 0.5, while it is structure sensitive in the O(2)-rich environment; Pt octahedra have a lower activation energy than Pt cubes when catalyzing the electron transfer reaction between hexacyanoferrate (III) and thiosulfate ions. Through electrocatalysis, gas-phase-catalysis of CO oxidation, and a liquid-phase-catalysis of electron transfer reaction, we demonstrate that high quality Pt nanocrystals which have {111} and {100} facets selectively expose are ideal model materials to study catalysis at nanoscale.

  1. Self-Assembly Kinetics of Colloidal Particles inside Monodispersed Micro-Droplet and Fabrication of Anisotropic Photonic Crystal Micro-Particles

    Directory of Open Access Journals (Sweden)

    Ming-Yu Zhang

    2016-09-01

    Full Text Available A new microfluidic approach to preparing anisotropic colloidal photonic crystal microparticles is developed and the self-assembly kinetics of colloidal nanoparticles is discussed. Based on the “coffee ring” effect in the self-assembly process of colloidal silica particle in strong solvent extraction environment, we successfully prepared anisotropic photonic crystal microparticles with different shapes and improved optical properties. The shapes and optical properties of photonic crystal microparticles can be controlled by adjusting the droplet size and extraction rate. We studied the self-assembly mechanism of colloidal silica particles in strong solvent extraction environment, which has potential applications in a variety of fields including optical communication technology, environmental response, photo-catalysis and chromic material.

  2. Large-scale synthesis of nearly monodisperse CdSe/CdS core/shell nanocrystals using air-stable reagents via successive ion layer adsorption and reaction.

    Science.gov (United States)

    Li, J Jack; Wang, Y Andrew; Guo, Wenzhuo; Keay, Joel C; Mishima, Tetsuya D; Johnson, Matthew B; Peng, Xiaogang

    2003-10-15

    Successive ion layer adsorption and reaction (SILAR) originally developed for the deposition of thin films on solid substrates from solution baths is introduced as a technique for the growth of high-quality core/shell nanocrystals of compound semiconductors. The growth of the shell was designed to grow one monolayer at a time by alternating injections of air-stable and inexpensive cationic and anionic precursors into the reaction mixture with core nanocrystals. The principles of SILAR were demonstrated by the CdSe/CdS core/shell model system using its shell-thickness-dependent optical spectra as the probes with CdO and elemental S as the precursors. For this reaction system, a relatively high temperature, about 220-240 degrees C, was found to be essential for SILAR to fully occur. The synthesis can be readily performed on a multigram scale. The size distribution of the core/shell nanocrystals was maintained even after five monolayers of CdS shell (equivalent to about 10 times volume increase for a 3.5 nm CdSe nanocrystal) were grown onto the core nanocrystals. The epitaxial growth of the core/shell structures was verified by optical spectroscopy, TEM, XRD, and XPS. The photoluminescence quantum yield (PL QY) of the as-prepared CdSe/CdS core/shell nanocrystals ranged from 20% to 40%, and the PL full-width at half-maximum (fwhm) was maintained between 23 and 26 nm, even for those nanocrystals for which the UV-vis and PL peaks red-shifted by about 50 nm from that of the core nanocrystals. Several types of brightening phenomena were observed, some of which can further boost the PL QY of the core/shell nanocrystals. The CdSe/CdS core/shell nanocrystals were found to be superior in comparison to the highly luminescent CdSe plain core nanocrystals. The SILAR technique reported here can also be used for the growth of complex colloidal semiconductor nanostructures, such as quantum shells and colloidal quantum wells.

  3. Synthesis and functionalization of monodisperse near-ultraviolet and visible excitable multifunctional Eu3+, Bi3+:REVO4 nanophosphors for bioimaging and biosensing applications

    Science.gov (United States)

    Escudero, Alberto; Carrillo-Carrión, Carolina; Zyuzin, Mikhail V.; Ashraf, Sumaira; Hartmann, Raimo; Núñez, Nuria O.; Ocaña, Manuel; Parak, Wolfgang J.

    2016-06-01

    Near-ultraviolet and visible excitable Eu- and Bi-doped NPs based on rare earth vanadates (REVO4, RE = Y, Gd) have been synthesized by a facile route from appropriate RE precursors, europium and bismuth nitrate, and sodium orthovanadate, by homogeneous precipitation in an ethylene glycol/water mixture at 120 °C. The NPs can be functionalized either by a one-pot synthesis with polyacrylic acid (PAA) or by a Layer-by-Layer approach with poly(allylamine hydrochloride) (PAH) and PAA. In the first case, the particle size can also be tuned by adjusting the amount of PAA. The Eu- Bi-doped REVO4 based nanophosphors show the typical red luminescence of Eu(iii), which can be excited through an energy transfer process from the vanadate anions, resulting in a much higher luminescence intensity in comparison to the direct excitation of the europium cations. The incorporation of Bi into the REVO4 structure shifts the original absorption band of the vanadate anions towards longer wavelengths, giving rise to nanophosphors with an excitation maximum at 342 nm, which can also be excited in the visible range. The suitability of such nanophosphors for bioimaging and biosensing applications, as well as their colloidal stability in different buffer media of biological interest, their cytotoxicity, their degradability at low pH, and their uptake by HeLa cells have been evaluated. Their suitability for bioimaging and biosensing applications is also demonstrated.Near-ultraviolet and visible excitable Eu- and Bi-doped NPs based on rare earth vanadates (REVO4, RE = Y, Gd) have been synthesized by a facile route from appropriate RE precursors, europium and bismuth nitrate, and sodium orthovanadate, by homogeneous precipitation in an ethylene glycol/water mixture at 120 °C. The NPs can be functionalized either by a one-pot synthesis with polyacrylic acid (PAA) or by a Layer-by-Layer approach with poly(allylamine hydrochloride) (PAH) and PAA. In the first case, the particle size can also be tuned by adjusting the amount of PAA. The Eu- Bi-doped REVO4 based nanophosphors show the typical red luminescence of Eu(iii), which can be excited through an energy transfer process from the vanadate anions, resulting in a much higher luminescence intensity in comparison to the direct excitation of the europium cations. The incorporation of Bi into the REVO4 structure shifts the original absorption band of the vanadate anions towards longer wavelengths, giving rise to nanophosphors with an excitation maximum at 342 nm, which can also be excited in the visible range. The suitability of such nanophosphors for bioimaging and biosensing applications, as well as their colloidal stability in different buffer media of biological interest, their cytotoxicity, their degradability at low pH, and their uptake by HeLa cells have been evaluated. Their suitability for bioimaging and biosensing applications is also demonstrated. Electronic supplementary information (ESI) available: Additional details of experiments and results (NP characterization, NPs' uptake and imaging). See DOI: 10.1039/c6nr03369e

  4. Synthesis of highly monodispersed teardrop-shaped core–shell SiO{sub 2}/TiO{sub 2} nanoparticles and their photocatalytic activities

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Lihong; Zhou, Yifeng, E-mail: yifengzhou@126.com; Nie, Wangyan; Song, Linyong; Chen, Pengpeng, E-mail: chenpp@ahu.edu.cn

    2015-10-01

    Graphical abstract: - Highlights: • Uniform chitosan coated magnetic mesoporous silica nanoparticles (CMMSNs) were successfully synthesized. • The CMMSNs were applied to highly efficient methylene blue (MB) dyes removal, and the saturated adsorption capacity of MB was 43.03 mg/g. • The MB adsorption kinetic and adsorption isotherm analysis were studied. • The CMMSNs had a saturation magnetization of 12.6 emu/g and could be easily separated by a magnet after dye adsorption. - Abstract: In this study, teardrop-shaped SiO{sub 2}/TiO{sub 2} nanoparticles (TST-NPs) with core–shell structure were fabricated from tetraethoxysilane (TEOS) and tetrabutyl titanate (TBT) by sol–gel method. And these nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and UV–vis spectroscopy. Photocatalytic activity of teardrop-shaped SiO{sub 2}/TiO{sub 2} nanoparticles after calcination (CST-NPs) was studied towards degradation of methylene blue under sunlight irradiation. The result showed that CST-NPs possessed good photocatalytic activity. The photocatalytic mechanism was also studied by adding different capture agent. Results showed that addition of 0.003 M of I{sup −} decreased the degradation of MB more than same amount of Ag{sup +}, indicating that the photogenerated holes may play a more essential role than photoinjected electrons in the oxidation of MB.

  5. Synthesis and application of a monodispersed acetate-acrylate emulsion%一种单分散醋-丙乳液的合成与应用研究

    Institute of Scientific and Technical Information of China (English)

    王建方; 毛明富; 龚雁; 倪忠斌; 陈明清

    2011-01-01

    A kind of vinyl acetate-acrylate emulsion was synthesized by pre-emulsified and semi-continuous seed emulsion polymeri-zation using vinyl acetate(Vac)and butyl acrylale(BA)as comonomer in the presence of glycidylmethacrylate(CMA)as functional monomer. The size,size distribution and morphologies of the emulsion particles were characterized by transmission electron micros-copy (TEM) and laser light scattering(LLS). It was found that the size of emulsion particles is about 120 nm and presented good mono-dispeisibility. Zeta potential and theological determination results showed that the emulsion particles have plenty negative charges,the surface Zeta potential was-57.2mV. Emulsion presented pseudoplastic fluid property which the storage time was above 9 months under room temperature. It means that the emulsion have good dispersion stability.%以醋酸乙烯酯(VAc)、丙烯酸正丁酯(BA)和甲基丙烯缩水甘油酯(GMA)为共聚单体,采用预乳化-半连续种子乳液聚合的方法,合成了一类改性醋丙乳液.用透射电子显微镜(TEM)、激光光散射(LLS)等测定了乳胶粒的粒径、粒径分布和粒子形态,发现其粒径在120 nm左右,并呈现较好的单分散特性;Zeta电位和流变测定结果显示:该乳胶粒子表面的Zeta电位为-57.2 mV,说明其带有较多的负电荷,乳液呈现出假塑性流体的特征,室温条件下该乳液储存时间可长达9个月以上,具有较好的分散稳定性.

  6. Facile synthesis of near-monodisperse Ag@Ni core-shell nanoparticles and their application for catalytic generation of hydrogen.

    Science.gov (United States)

    Guo, Huizhang; Chen, Yuanzhi; Chen, Xiaozhen; Wen, Ruitao; Yue, Guang-Hui; Peng, Dong-Liang

    2011-05-13

    Magnetically recyclable Ag-Ni core-shell nanoparticles have been fabricated via a simple one-pot synthetic route using oleylamine both as solvent and reducing agent and triphenylphosphine as a surfactant. As characterized by transmission electron microscopy (TEM), the as-synthesized Ag-Ni core-shell nanoparticles exhibit a very narrow size distribution with a typical size of 14.9 ± 1.2 nm and a tunable shell thickness. UV-vis absorption spectroscopy study shows that the formation of a Ni shell on Ag core can damp the surface plasmon resonance (SPR) of the Ag core and lead to a red-shifted SPR absorption peak. Magnetic measurement indicates that all the as-synthesized Ag-Ni core-shell nanoparticles are superparamagnetic at room temperature, and their blocking temperatures can be controlled by modulating the shell thickness. The as-synthesized Ag-Ni core-shell nanoparticles exhibit excellent catalytic properties for the generation of H(2) from dehydrogenation of sodium borohydride in aqueous solutions. The hydrogen generation rate of Ag-Ni core-shell nanoparticles is found to be much higher than that of Ag and Ni nanoparticles of a similar size, and the calculated activation energy for hydrogen generation is lower than that of many bimetallic catalysts. The strategy employed here can also be extended to other noble-magnetic metal systems.

  7. Preparation of Mono-dispersed LiFePO4 Spheres%单分散LiFePO4球的制备

    Institute of Scientific and Technical Information of China (English)

    王彬帅; 王军伟; 张静杰; 黄俊杰

    2010-01-01

    以Fe(NO3)3、LiCH3COO和NH4H2PO4为原料,葡萄糖为还原剂,通过水热反应辅以热处理过程制备了单分散的LiFePO4/C球.XRD结果表明得到了具有橄榄石结构的LiFePO4,SEM显示LiFePO4球的球茎在5μm左右.LiFePO4球的形成与葡萄糖的脱水缩聚碳化有关.

  8. Solvothermal synthesis of monodisperse LiFePO4 micro hollow spheres as high performance cathode material for lithium ion batteries.

    Science.gov (United States)

    Yang, Shiliu; Hu, Mingjun; Xi, Liujiang; Ma, Ruguang; Dong, Yucheng; Chung, C Y

    2013-09-25

    A microspherical, hollow LiFePO4 (LFP) cathode material with polycrystal structure was simply synthesized by a solvothermal method using spherical Li3PO4 as the self-sacrificed template and FeCl2·4H2O as the Fe(2+) source. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the LFP micro hollow spheres have a quite uniform size of ~1 μm consisting of aggregated nanoparticles. The influences of solvent and Fe(2+) source on the phase and morphology of the final product were chiefly investigated, and a direct ion exchange reaction between spherical Li3PO4 templates and Fe(2+) ions was firstly proposed on the basis of the X-ray powder diffraction (XRD) transformation of the products. The LFP nanoparticles in the micro hollow spheres could finely coat a uniform carbon layer ~3.5 nm by a glucose solution impregnating-drying-sintering process. The electrochemical measurements show that the carbon coated LFP materials could exhibit high charge-discharge capacities of 158, 144, 125, 101, and even 72 mAh g(-1) at 0.1, 1, 5, 20, and 50 C, respectively. It could also maintain 80% of the initial discharge capacity after cycling for 2000 times at 20 C.

  9. In-situ synthesis of monodisperse micro-nanospherical LiFePO4/carbon cathode composites for lithium-ion batteries

    Science.gov (United States)

    Gong, Hao; Xue, Hairong; Wang, Tao; He, Jianping

    2016-06-01

    The LiFePO4 is recognized as the promising cathode material, due to its high specific capacity, excellent, structural stability and environmental benignity. However, it is blamed for the low tap density and poor rate performance when served as the cathode materials for a long time. Here, the microspheric LiFePO4/C composites are successfully synthesized through a one-step in-situ solvothermal method combined with carbothermic reduction. These LiFePO4/C microspheres are assembled by LiFePO4 nanoparticles (∼100 nm) and uniformly coated by the carbon, which show a narrow diameter distribution of 4 μm. As a cathode material for lithium ion batteries, the LiFePO4/C composites can deliver an initiate charge capacity of 155 mAh g-1 and retain 90% of initial capacity after 200 cycles at 0.1 C. When cycled at high current densities up to 20 C, it shows a discharge capacity of ∼60 mAh g-1, exhibiting superior rate performance. The significantly improved electrochemical performance of LiFePO4/C composites material can be attributed to its special micro-nano hierarchical structure. Microspheric LiFePO4/C composites exhibit a high tap density about 1.3 g cm-3. What's more, the well-coated carbon insures the high electrical conductivity and the nano-sized LiFePO4/C particles shorten lithium ion transport, thus exhibiting the high specific capacity, high cycling stability and good rate performance.

  10. HOW TO FORMULATE A STABLE AND MONODISPERSE WATER-IN-OIL NANOEMULSION CONTAINING PUMPKIN SEED OIL: THE USE OF MULTIOBJECTIVE OPTIMIZATION

    Directory of Open Access Journals (Sweden)

    B. G. Nikolovski

    Full Text Available Abstract The multiobjective optimization method was applied in order to improve the droplet size distribution and stability of water-in-oil emulsions composed of sunflower and pumpkin seed oils as continuous phase, polyglycerol polyricinoleate as emulsifier, water as dispersed phase and sodium chloride as co-stabilizer (lipophobe. Three composition factors were varied based on the three level Box-Behnken design and three characteristics of the obtained emulsions were measured for each experimental run. The mean volume diameter of water droplets and the span of the droplet size distribution, both determined immediately upon preparation of the emulsion, as well as the stability index over a three-month period were interrelated by regression functions with the surfactant concentration, oil composition and the salt content in the water phase of the emulsion. Also, the fourth objective function based on a difference in the prices of pumpkin seed and sunflower oils was considered for optimization. The multiobjective optimum was calculated by using the minimal loss method with weight factors. Additionally, effects of the continuous phase composition and the salt content on the equilibrium interfacial tension of water-oil systems and the changes of the droplet size distribution over time were studied.

  11. Synthesis and controllable oxidation of monodisperse cobalt-doped wüstite nanoparticles and their core-shell stability and exchange-bias stabilization.

    Science.gov (United States)

    Chen, Chih-Jung; Chiang, Ray-Kuang; Kamali, Saeed; Wang, Sue-Lein

    2015-09-14

    Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ∼4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (H(E)), an enhanced coercivity field (H(C)), and a pronounced vertical shift, thus indicating the presence of a strong exchange bias coupling effect. More importantly, the onset temperature of H(E) was found to be higher than 200 K, which suggests that cobalt doping increases the Néel temperature (T(N)) of the CWT core. In general, the results show that the homogeneous dispersion of Co in iron precursors improves the stability of the final CWT nanoparticles. Moreover, the CoFe2O4 shells formed following oxidation increase the oxidation resistance of the CWT cores and enhance their anisotropy energy.

  12. Immunocapture of CD133-positive cells from human cancer cell lines by using monodisperse magnetic poly(glycidyl methacrylate) microspheres containing amino groups

    Energy Technology Data Exchange (ETDEWEB)

    Kuan, Wei-Chih [Department of Chemical Engineering, Systems Biology and Tissue Engineering Research Center, National Chung Cheng University, Minhisung 621, Taiwan (China); Horák, Daniel, E-mail: horak@imc.cas.cz [Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6 (Czech Republic); Plichta, Zdeněk [Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6 (Czech Republic); Lee, Wen-Chien [Department of Chemical Engineering, Systems Biology and Tissue Engineering Research Center, National Chung Cheng University, Minhisung 621, Taiwan (China)

    2014-01-01

    Magnetic poly(glycidyl methacrylate)-based macroporous microspheres with an average particle size of 4.2 μm were prepared using a modified multi-step swelling polymerization method and by introducing amino functionality on their surfaces. Antibody molecules were oxidized on their carbohydrate moieties and bound to the amino-containing magnetic microspheres via a site-directed procedure. CD133-positive cells could be effectively captured from human cancer cell lines (HepG2, HCT116, MCF7, and IMR-32) by using magnetic microspheres conjugated to an anti-human CD133 antibody. After further culture, the immunocaptured CD133-expressing cells from IMR-32 proliferated and gradually detached from the magnetic microspheres. Flow-cytometric analysis confirmed the enrichment of CD133-expressing cells by using the antibody-bound magnetic microspheres. Such microspheres suitable for immunocapture are very promising for cancer diagnosis because the CD133-expressing cells in cancer cell lines have been suggested to be cancer stem cells. - Highlights: • Multi-step swelling polymerization produced poly(glycidyl methacrylate) microspheres. • Anti-human CD133 antibodies were bound to the amino-containing magnetic microspheres. • CD133-positive cells were effectively captured from human cancer cell lines. • Immunocaptured CD133-expressing cells proliferated and were detached from microspheres. • Enrichment of CD133-expressing cells was confirmed by flow-cytometric analysis.

  13. General and Robust Strategies for Multifunctional Organic-Inorganic Nanocompositesvia Direct Growth of Monodisperse Nanocrystals Intimately and Permanently Connected with Polymers

    Science.gov (United States)

    2016-04-21

    amphiphilic copolymer brushes: Poly( ethylene oxide )-graft-polystyrene. J. Polym. Sci. Part A: Polym. Chem. 44, 4361-4371 (2006). 2. Mora-Pale, M., Meli, L...results are summarized as follows. Recent research has witnessed tremendous advances in isotropic nanomaterials synthesis , which has provided access...nanocrystals of both fundamental and practical interest.(12, 13) Current emerging synthesis approaches, including template-assisted synthesis ,(14-16

  14. Microwave-induced three-photon coherence of Rydberg atomic states

    Science.gov (United States)

    Kwak, Hyo Min; Jeong, Taek; Lee, Yoon-Seok; Moon, Han Seb

    2016-12-01

    We investigate the three-photon coherence (TPC) effects of the Rydberg state in a Doppler-broadened four-level ladder-type atomic system for the 5S1/2(F=3)-5P3/2(F‧=4)-50D5/2-51P3/2 transition of 85Rb atoms. Upon interaction of the Rydberg Rb atom of the ladder-type electromagnetically induced transparency (EIT) scheme with a resonant microwave (MW) field, we numerically analyze the spectral features of the Rydberg TPC from two viewpoints, Autler-Townes splitting (AT-splitting) of the Rydberg EIT and three-photon electromagnetically induced absorption (TPEIA). We determine the criterion to differentiate between AT-splitting of the Rydberg EIT and TPEIA in the Doppler-broadened ladder-type atomic system.

  15. A scheme for implementing quantum clock synchronization algorithm in cavity QED

    Institute of Scientific and Technical Information of China (English)

    Wu Qin-Qin; Kuang Le-Man

    2006-01-01

    In this paper, we propose a scheme for implementing the quantum clock synchronization (QCS) algorithm in cavity quantum electrodynamic (QED) formalism. Our method is based on three-level ladder-type atoms interacting with classical and quantized cavity fields. Atom-qubit realizations of three-qubit and four-qubit QCS algorithms are explicitly presented.

  16. Self-sustained Flow-acoustic Interactions in Airfoil Transitional Boundary Layers

    Science.gov (United States)

    2015-07-09

    all tested airfoils multiple tones were observed. Tracking the dominant tone at increasing flow speed produces the so-called ladder-type tonal...anecho c w nd tunne of Eco e Centra e de Lyon. Measurements of wa pressure, far- f e d acoust c pressure and ve oc ty f uctuat ons us ng the hot-w re

  17. Preparation of mono-disperse spherical silicon dioxide by ultrasonic hydrothermal method%超声水热法制备单分散球形二氧化硅及因素分析

    Institute of Scientific and Technical Information of China (English)

    申晓毅; 翟玉春; 刘岩

    2008-01-01

    引言单分散球形二氧化硅颗粒性能优良,在催化剂载体、化工、医药和固体填料领域应用广泛[1],对其开发具有重要的实际意义。Kolbe[2]发现在碱催化下,正硅酸乙酯在醇溶液中发生水解缩聚反应生成SiO2。Stober等[3-4]发现用氨水作正硅酸乙酯水解反应的催化剂可以控制SiO2粒子的粒径,生成颗粒细小的SiO2,

  18. 含酚基羧甲基纤维素的合成及单分散微胶囊的制备%Synthesis of carboxymethylcellulose with phenol moieties for preparation of monodisperse microcapsules

    Institute of Scientific and Technical Information of China (English)

    孔谦; 柯渔; 卢建波; 张奕; 薛巍

    2011-01-01

    为了实现可程序控制的活性物质的释放,制备了单分散的羧甲基纤维素(CMC)衍生物微胶囊.采用1-乙基-(3-二甲基氨基丙基)碳二亚胺(EDC)和N-羟基琥珀酰亚胺(NHS)作为偶合剂,在CMC的大分子链上引入酚基,合成了含酚基羧甲基纤维素(Ph-CMC).产物的紫外吸收光谱证实,在275 nm处出现苯环的特征吸收峰,根据吸光度值计算,每100个CMC结构单元中酚基数量为30~50个.Ph-CMC溶液具备牛顿流体的特征,且随着Ph-CMC相对分子质量或溶液浓度的增加,流体切应力及黏度呈上升趋势.采用自行研制的同轴汇聚微流体装置,以含辣根过氧化物酶的Ph-CMC水溶液为内流体,含双氧水和卵磷脂的液体石蜡为外流体,制备了半径为150~200 μm,且偏差系数≤3%的单分散Ph-CMC微胶囊.

  19. PREPARATION OF MONO-DISPERSED COLLOIDS OF P(ST-MMA-SPMAP) BY SOAP-FREE EMULSION COPOLYMERIZATION%无皂乳液聚合法制备P(St-MMA-SPMAP)单分散乳胶颗粒

    Institute of Scientific and Technical Information of China (English)

    杨凌露; 丛海林; 曹维孝

    2005-01-01

    利用无皂乳液聚合,分别用一步法和两步法合成了单分散的聚(苯乙烯-甲基丙烯酸甲酯-甲基丙烯酸丙基磺酸钾)(P(St-MMA-SPMAP))乳胶颗粒.在该聚合体系中,当水溶性磺酸基单体SPMAP的浓度小于17mmol/L时,为均相成核过程,能制备单分散的乳胶颗粒.其中,用两步法制备的乳胶颗粒相互之间无粘连.此外,还对一步法合成苯乙烯-甲基丙烯酸甲酯-甲基丙烯酸辛基磺酸钠(P(St-MMA-SOMAS))乳胶颗粒进行了初步研究.

  20. 不同溶剂中制备单分散量子点%The Synthesis and Characterization of Monodisperse CdSe Quantum Dots at Different Organic Solvents

    Institute of Scientific and Technical Information of China (English)

    贺蓉; 田红叶; 古宏晨

    2005-01-01

    选用比较缓和反应条件,用无毒、价廉、稳定性好的无机化合物作为反应前驱体制备半导体量子点材料.通过选择不同的反应溶剂,可以得到粒径大小不同从而发光波长可"调谐"的一系列CdSe量子点材料.用紫外吸收光谱(UV-Vis),荧光发射光谱(PL)跟踪了反应的过程,用X射线衍射(XRD)和透射电镜(TEM)对得到的量子点材料的结构进行了表征.对量子点材料在有机溶剂和水溶液中的转相进行了研究,为量子点与生物分子的连接,进而在生物标记方面的应用提供材料基础.该方法是对传统高温条件下有机金属化合物前驱体分解制备方法的补充,是一种环境友好的半导体量子点材料的制备方法.