水溶液中电化学沉积GaSb相变存储薄膜

利用恒电位共沉积技术和热处理的方法成功制备了GaSb薄膜,探索了添加乙二醇溶剂对薄膜结晶性和形貌的影响. 采用循环伏安法初步研究了共沉积GaSb的机理,并用X-射线衍射技术（XRD）、扫描电子显微技术（SEM）和能谱分析（EDS）表征、观察样品. 研究表明,在沉积过程中,SbO⁺先还原成Sb单质,再诱导Ga³⁺发生共沉积;沉积电位对薄膜的结晶性、微观形貌和成分有显著影响;电解液加入乙二醇更利于在较正电位下直接沉积出GaSb,且有效地提高了薄膜的结晶度,改善了薄膜的微观形貌.     

Novel growth methods of optoelectronic crystals based on antimonides

This work contributes to the growth of bulk crystals where crystals are grown from a molten-solution zone (MSZ). Our original modifications ofTHM have been used for a crystallization of GaSb and of (Ga.In)Sb—the ternary Solid Solution (TSS). The crystallization process has been accelerated with a low frequency and low energy vibrational stirring (VS). Lately, the stirring has been combined with the magneto-hydrodynamical stirring (MHD-S) and applied on GaSb. The lattice parameter ‘a’ ofTSS crystals has been constant throughout the significant part of the ingot length. This approach has permitted the growth of these crystalline ingots with ‘a’ apriori chosen and calculated—having the deviation from its constancy less than 0.03% (0.2 pm) with a 75 mm length. Crystals can have a mosaic structure at this stage.     

锑化镓的光助微刻蚀及其表面氧化物的研究

用电化学和光电化学方法研究锑化镓表面的腐蚀以及锑化镓表面氧化膜的生成和溶解，锑化镓电极在一定电势下生成的氧化膜，用俄歇能谱证明，其主要成分为难溶的氧化锑，此氧化膜的存在抑制了锑化镓的进一步腐蚀，同时亦使锑化镓的半导体光电化学性能大为减弱，通过激光微刻蚀及电子显微镜的观察，在刻蚀剂中添加酒石酸，柠檬酸和氢氟酸等试剂，可使刻蚀形得改善，实验研究了锑化镓的平带电势的测定。     

Structure and Chemical Composition of Manganese-Doped GaSb Dislocations

Electron microscopic observations showed that the preparation of magnetic semiconductor GaSb〈Mn〉 by melt quenching is accompanied by discrete manganese precipitation on GaSb dislocations, this precipitation generating inclusions sized from a split micrometer to several micrometers. The chemical composition of microinclusions was determined by electron probe microanalysis. The superposition of the magnetic properties of compounds that are formed in the Mn–Sb system determines the magnetic properties of GaSb〈Mn〉.     

Copper solubility and distribution in doped GaSb single crystals

For the GaSb single crystals doped with copper (grown using the Czochralski method without encapsulant in flowing atmosphere of hydrogen) the distribution coefficient of copper in GaSb,k _eff=0.0021±0.0006 was found and the copper solubility in GaSb was discussed. The region of copper solubility in GaSb was analyzed on the thermodynamic basis using chemical phase diagram in the Sb?Ga?Cu system. Due to a rather low solubility of copper, its excessive amount in GaSb caused probably an increase of the dislocation density at the end of the GaSb single crystals.     

Trace gas detection with antimonide-based quantum-well diode lasers

Widely tunable GaInAsSb/AlGaAsSb quantum well (QW) lasers have been grown by molecular beam epitaxy on GaSb substrates. Their emission wavelength, from 2.0 to 2.5 microm, make them suitable for the detection of many gas species in the wavelength range which corresponds to an atmospheric transmission window. Using these devices an experimental setup for open path gas detection has been developed.     

Electroless Deposition of III–V Semiconductor Nanostructures from Ionic Liquids at Room Temperature

Group III–V semiconductor nanostructures are important materials in optoelectronic devices and are being researched in energy‐related fields. A simple approach for the synthesis of these semiconductors with well‐defined nanostructures is desired. Electroless deposition (galvanic displacement) is a fast and versatile technique for deposition of one material on another and depends on the redox potentials of the two materials. Herein we show that GaSb can be directly synthesized at room temperature by galvanic displacement of SbCl₃/ionic liquid on electrodeposited Ga, on Ga nanowires, and also on commercial Ga. In situ AFM revealed the galvanic displacement process of Sb on Ga and showed that the displacement process continues even after the formation of GaSb. The bandgap of the deposited GaSb was 0.9±0.1 eV compared to its usual bandgap of 0.7 eV. By changing the cation in the ionic liquid, the redox process could be varied leading to GaSb with different optical properties.     

聚-3,4-乙烯二氧噻吩导电聚合物纳米粒子的制备及性能

采用反向胶束合成法, 以二乙基磺基琥珀酸钠(AOT)形成的反胶束为模板制备了导电聚合物聚-3,4-乙烯二氧噻吩(PEDOT)纳米粒子. 用紫外-可见-近红外光谱、红外光谱、X射线光电子能谱、扫描电子显微镜及透射电镜等手段对PEDOT粒子进行了表征. 研究了纳米粒子的导电性能并采用石英微天平(QCM)对纳米粒子的气敏特性进行了分析, 对相应导电机理及气体敏感机理进行了讨论.     

Phase equilibria and electrical and magnetic properties of a eutectic in the GaSb-MnSb system

A set of physicochemical analysis methods showed that GaSb and MnSb form a eutectic at 41 mol % MnSb and T _melt = 632°C. The eutectic is of the platelet type and has metallic conduction. The eutectic GaSb + MnSb is a composite ferromagnetic with a Curie temperature of ～600 K. The behavior of the electrical resistance in a magnetic field is complex. At low magnetic fields up to 0.8 T, the resistance abruptly drops, and at high magnetic fields, it slowly increases. Such behavior occurs both at low temperatures (5 K) and at 300 K. The change of the trend in the resistance takes place at the magnetic field at which there is magnetization saturation in the magnetic field dependences. Such a dependence of the resistance on the magnetic field is explained by a change of the mechanism of scattering of charge carriers.     

Immobilization of silver nanoparticles obtained by electric discharge method on a track membrane surface

Composite poly(ethylene terephthalate) track membranes containing immobilized silver nanoparticles with the aim of using them for surface-enhanced Raman scattering spectroscopy have been obtained and studied. A dispersion of negatively charged silver nanoparticles has been synthesizes by the method of pulsed electrical discharge between silver electrodes immersed in distilled water. To ensure the electrostatic deposition of nanoparticles onto the track membrane surface, it has been modified with polyethyleneimine. The composition and morphology of the surface of the obtained composite membranes have been studied by X-ray photoelectron spectroscopy and scanning electron microscopy. Aggregation of nanoparticles on the surface has been analyzed. The coefficient of Raman-scattering enhancement has been determined by the example of rhodamine 6G molecules adsorbed on a membrane with immobilized silver nanoparticles.     

Copper nanoparticles synthesized by the polyol method and their oxidation in polar dispersion media. The influence of chloride and acetate ions

Copper nanoparticles have been synthesized from Cu(2+) acetate in the medium of dimethylformamide by the polyol method using hydrazine as a reductant and poly(vinylpyrrolidone) as a stabilizer. Optical spectroscopy has been employed to study the influence of chloride and acetate ions on the oxidation of copper nanoparticles by atmospheric oxygen in aqueous and dimethylformamide media, respectively. It has been established that the presence of ions of one of the aforementioned types in a colloidal solution significantly accelerates the oxidation of metal nanoparticles. In the case of acetate ions, copper oxide particles rapidly dissolve to form the corresponding salt. It has been shown that Cu nanoparticles can be repeatedly formed in such a solution by the addition of hydrazine.     

Simple nanoprecipitation method for size-restricted synthesis of aloevera nanoparticles: Characteristic analysis and its application as an adsorbent

The Nanoprecipitation method has been proved favorable to synthesize size-restricted Aloevera nanoparticles from the aloevera polysaccharide in a very simple and single step. Dropwise addition of 1% homogeneous aloevera solution (1 ?mL) to absolute alcohol (20 ?mL) resulted in the formation of 50–100 ?nm-sized Aloevera nanoparticles. The results showed that the amount of ethanol played a significant role in deciding the shape and size of nanoparticles. The synthesis of aloevera nanoparticles has been confirmed by SEM, FTIR, XRD, and BET studies. The effect of other precipitating mediums and surfactants has also been studied to analyze their effect on the size of nanoparticles. The nanoparticles are also found to be potential adsorbents of Reactive Blue H5G dye which showed an affinity for AVNP and the adsorption study indicated 95% adsorption of the dye in 4 ?h. This indicates its efficacy as an adsorbent for wastewater treatment.     

Synthesis, characterization and computational study of nitrogen-doped CeO2 nanoparticles with visible-light activity

Nitrogen-doped CeO2 nanoparticles were synthesized through a wet-chemical route. Nitrogen has been successfully incorporated into CeO2 nanoparticles and the nitrogen-doping level was also successfully controlled. The optical properties due to the different N-doping levels in CeO2 nanoparticles were characterized by UV-Vis diffuse reflectance spectroscopy (DRS), which showed a visible-light absorbance shift. The resulting nanoparticles show enhanced visible-light sensitivity and photocatalytic activity compared to undoped CeO2 nanoparticles. DFT calculations were performed to explore the effect of nitrogen doping versus oxygen vacancies. The calculations show that the change of the electronic structure upon N-doping CeO2 is quite different from that of N-doped TiO2, which has been studied extensively.     

Enhanced two-photon singlet oxygen generation by photosensitizer-doped conjugated polymer nanoparticles

We have prepared photosensitizer-doped conjugated polymer nanoparticles by using a reprecipitation method. The conjugated polymer, poly[9,9-dibromohexylfluorene-2,7-ylenethylene-alt-1,4-(2,5-dimethoxy)phenylene] (PFEMO), was used as the host matrix to disperse tetraphenylporphyrin (TPP). These TPP-doped PFEMO nanoparticles are stable and have a uniform size of ～50 nm. Efficient intraparticle energy transfer from PFEMO to TPP has been observed. The TPP emission of the nanoparticles was found to be enhanced by 21-fold by PFEMO under two-photon excitation. Enhanced two-photon excitation singlet oxygen generation efficiency in the TPP-doped PFEMO nanoparticles has been demonstrated. Our results suggest that these photosensitizer-doped conjugated polymer nanoparticles can act as novel photosensitizing agents for two-photon photodynamic therapy and related applications.     

Synthesis and characterization of high concentration block copolymer-mediated gold nanoparticles

The formation of high concentration gold nanoparticles at room temperature is reported in block copolymer-mediated synthesis where the nanoparticles have been synthesized from hydrogen tetrachloroaureate(III) hydrate (HAuCl(4)·3H(2)O) using block copolymer P85 (EO(26)PO(39)EO(26)) in aqueous solution. The formation of gold nanoparticles in these systems has been characterized using UV-visible spectroscopy and small-angle neutron scattering (SANS). We show that the presence of additional reductant (trisodium citrate) can enhance nanoparticle concentration by manyfold, which does not work in the absence of either of these (additional reductant and block copolymer). The stability of gold nanoparticles with increasing concentration has also been examined.     

Hydrotalcite and nanometric silica as finishing additives to enhance the thermal stability and flame retardancy of cotton

Suspensions of nanoparticles (namely, hydrotalcite and nanometric silica) have been employed during the finishing of cotton in order to improve its thermal stability and/or flame retardancy. The immersion approach has also been coupled to a surface pre-treatment of the textile by cold oxygen plasma in order to load a higher amount of nanoparticles onto fibres. The time of immersion and the resulting distribution of the nanoparticles onto the fibres, evaluated by scanning electron microscopy in combination with elemental analysis, have been thoroughly investigated. The present study has shown that the above parameters are functions of nanoparticle type. Pre-treatment by cold plasma has been found to be more effective than the immersion only. As far as the thermal stability and the combustion behaviour of treated cotton are concerned, the nanoparticles turned out to be able to delay the degradation in air, modifying mechanism and kinetics, and at the same time enhancing the flame retardancy of cotton by increasing the time to ignition and decreasing the heat release rate peak during the combustion. The joint effect of the two nanoparticles has also been evaluated and found more efficient than the effect of single species.     

New two-dimensional polymer-metal composites based on highly ordered ensembles of nanoparticles. Design and optical properties

A new method has been proposed for designing composite materials that represent highly ordered two-dimensional metal nanoparticles ensembles having variable geometric parameters and being embedded into the surface layer of a polymer matrix to a predetermined depth. The method is based on diblock copolymer micellar lithography and the effect of decreased glass-transition temperature of a polymer surface as compared with its bulk value. The possibility of independent variations in the depth of embedding of metal nanoparticles (by system annealing) and their size (by seeded growth) has resulted in the systematic study of the influence of the temperature and time of annealing on the kinetics of nanoparticle embedding into a polymer. For the first time, the plasmon-resonant properties of hexagonally ordered ensembles of gold nanoparticles located at a polymer-air interface have been experimentally studied. It has been established that the embedding of an ensemble of nanoparticles into a polymer is accompanied by a bathochromic shift of the maximum of its localized surface plasmon resonance due to a growth in the effective dielectric permittivity of the environment of the nanoparticles. An empirical equation has been proposed, which satisfactorily describes these experimental data.     

Preparation and characterization of Cr(CO)(4)dpp (chromium tetracarbonyl 2,3-bis(2'-pyridyl)pyrazine) adsorbed on silver nanoparticles

A transition metal carbonyl species, Cr(CO)(4)dpp, has been successfully attached to bare silver nanoparticles prepared by laser ablation of a metal foil in ethanol. Transmission electron microscopy (TEM) images have shown that at least a portion of the silver nanoparticles have been capped by the chromium species, and ligand shells corresponding to Cr(CO)(4)dpp multilayer adsorption onto the silver nanoparticles of 30-50 nm diameter have been observed. The detection of the strongest Raman-active nu(CO) band of Cr(CO)(4)dpp at 2004 cm(-1) revealed that the species has been adsorbed without decomposition. The time-of-flight secondary ion mass spectrometry (TOF-SIMS) signals recorded of the chromium-capped silver nanoparticles were also consistent with the nondecomposition adsorption process. Density functional calculations have been used to reproduce the Raman spectrum using Ag(7)(+) as a model surface. A large binding energy of about 122 kJ/mol has also been computed between silver and nitrogen atoms thus lending support to Cr(CO)(4)dpp being chemisorbed onto the silver surface.     

Role of silica coated magnetic nanoparticle on cell flocculation,lipid extraction and linoleic acid production from Chlorella pyrenoidosa

Abstract

In the present work, it has been observed that magnetic (Fe₃O₄) – silica core- shell nanoparticles helps in flocculation of Chlorella pyrenoidosa cells with simultaneous production of linoleic acid. The mean particle size in Dynamic light scattering (DLS) of the silica coated magnetic nanoparticle was estimated 444.7?nm. The characterization of nanoparticles was also performed by X-ray diffraction technique (XRD). Apart from flocculation, it has been observed that in presence of magnetic silica core- shell nanoparticles the amount of lipid obtained was four times than that of control. On the contrary, in presence of these nanoparticles, linoleic acid (18:2) has been produced in Chlorella pyrenoidosa cells almost by 80% whereas, it has been noticed only 8.73% in control. This is the first report where the linoleic acid has been obtained as major component of microalgal fatty acid methyl esters (FAME) having important application in nutraceuticals and pharmaceutical sectors.     

Understanding the role of surfactants on the preparation of ZnS nanocrystals

We have synthesized surface modified ZnS nanoparticles of size 2-3 nm using non-ionic surfactant-stabilized reverse emulsions. The non-ionic surfactants in the Span series, i.e. sorbitan monolaurate (Span 20) and sorbitan monooleate (Span 80) of hydrophilic-lipophilic balance (HLB) values of 8.6 and 4.3, respectively, have been used for the stabilization of emulsions. The role of these surfactants in controlling the size and properties of the ZnS nanoparticles has been discussed. The triethylamine (TEA) has been proved to be the effective surface modifying (capping) agent for the preparation of free-standing ZnS nanoparticles. The Span 20 with the higher HLB value of 8.6 has been found to be highly suitable in synthesizing TEA-capped ZnS nanoparticles of smaller size and higher photophysical characteristics compared to that of the Span 80 of lower HLB value of 4.3. A mechanism for the formation of TEA-capped ZnS nanoparticles from the surfactant-stabilized reverse emulsions has been proposed.