Nanometer particles synthesis in reverse micelles: Influence of the size and the surface on the reactivity

In this paprr we are presenting the synthesss “in situ” of nanoparticles in reverse micelles. In the case of aggregates containing copper ions, it is possible to form metallic particles surrounded or not by an oxide layer. By mixing aggregates containing cadmium and sulphide ions, CdS particles are formed. The size and polydispersity of the particles are controlled. The photoelectron transfer reaction depends mainly on the surface composition. In the range of 1 to 5 nm, the efficiency in the electron transfer does not depend on the size of the particle. The reverse micelles are formed by using either sodium di(2-ethyl hexyl)sulfosuccinate, usually called {AOT} or mixed bivalent and sodium di(2-ethyl hexyl)sulfosuccinate {AOl/M(AOT)₂}.     

Studies of nanoparticulate cadmium sulfide in amphiphilic polymaleic acid octadecanol ester Langmuir-Blodgett films

The reversed micelles of CdS nanoparticles capped with oligomer–polymaleic acid octadecanol ester (PMAO) were synthesized by a colloid chemical method in an aqueous system. The chemical ratio of PMAO between the carboxylic group and the hydrocarbon chain was controlled to 1.5 : 1. The PMAO-capped CdS nanoparticles were transferred on to CaF₂ and Si substrates by the Langmuir–Blodgett (LB) technique. Surface pressure–area isotherms indicated that PMAO-capped CdS nanoparticles could form a stable monolayer on the water subphase. The measurement of FTIR and small angle X-ray diffraction showed that the reversed micelles of PMAO-capped CdS nanoparticles were formed with a uniform size and order in LB films. The photoluminescence properties of PMAO-capped CdS both in the solution and in the LB film indicated that the photoluminescence peaks of reversed micelles obviously changed as a result of the energy transfer from PMAO to CdS and the interaction between clusters.     

Time-dependent complexation of glucose-reduced gold nanoparticles with octadecylamine Langmuir monolayers

We report on the reduction of aqueous chloroaurate ions by glucose to form gold nanoparticles of uniform size. We further demonstrate the complexation of these particles with octadecylamine (ODA) monolayers at the air-water interface. Pressure-area (pi-A) isotherms as a function of time of complexation revealed a significant expansion of the monolayer. Surface pressure variation with time for constant areas after spreading of the monolayer was carried out to observe the kinetics of complexation of the colloidal particles at the interface. The kinetics of complexation of the particles at the interface was also monitored by Brewster angle microscopy (BAM) measurements. Langmuir-Blodgett films of the particles complexed with ODA were formed at a subphase pH of 9 onto different substrates. Quartz crystal microgravimetry (QCM) was used to quantify the amount of particles deposited per immersion cycle of the quartz crystal. The LB films were further characterized by UV-vis and transmission electron microscopy (TEM) measurements. TEM measurements indicate a close packed and equidistant arrangement of colloidal particles in the LB film, probably due to hydrogen-bonding interactions.     

CdS nanoparticles deposited on montmorillonite: preparation, characterization and application for photoreduction of carbon dioxide

CdS nanoparticles were precipitated by the reaction of cadmium acetate with sodium sulphide in the presence of cetyltrimethylammonium (CTA) and deposited on montmorillonite (MMT). The resulting CdS-MMT nanocomposite contained 6 wt.% of CdS and 30 wt.% of CTA. Band-gap energy of CdS was estimated at 2.63±0.09 eV using the Tauc plot. The size of CdS nanoparticles was calculated from the band-gap energy at 5 nm and from the micrographs of transmission electron microscopy (TEM) at 5 nm. Selected area electron diffraction (SAED) recognized the cubic structure of CdS (Hawleite). The dynamic light scattering (DLS) method confirmed that CdS nanoparticles were anchored on the surface of MMT particles. CTA was found to be intercalated into MMT and adsorbed on its external surface. CdS-MMT was used for the photoreduction of carbon dioxide dissolved in NaOH solutions. The yields of originating gas products can be arranged in the order: H(2) ? CH(4) > CO. Amounts of these products were 4-8 folds higher then those obtained with TiO(2) Evonic P25. Hydrogen reduced CO(2) to CO and CH(4).     

Preparation and electrorheological characteristic of CdS/Polystyrene composite particles

Cadmium sulfide/polystyrene (CdS/PS) hybrid particles were synthesized and their physical characteristics including electrorheology were examined. Monodisperse CdS/PS nanocomposite particles with diameters of 2 μm were obtained via dispersion polymerization. To form cadmium sulfide nanoparticles onto the PS surface, 2-(dimethylamino)ethyl methacrylate was used as a functional monomer for coordinating with Cd²⁺ ions. Finally, cadmium sulfide nanoparticles with size < 10 nm were formed with the release of S²⁻ ions from thioacetamide. The morphology of the as-prepared CdS/PS nanocomposite particles clearly showed that the CdS particles are present on the surface of the PS. The optical properties were also studied. In addition, their electrorheological characteristics were confirmed by using optical microscopy with applied electrical field. Recently, dielectric properties of CdS nanoparticles were already reported; however, electrorheological characteristics of CdS/PS nanocomposite particles were investigated for the first time.     

Characterization of CdS nanoparticles formed and aggregated in stearic acid Langmuir–Blodgett films by atomic force microscopy

Alternate films, which are composed of stearic acid and CdS nanoparticles were synthesized by exposing Langmuir–Blodgett (LB) films of cadmium stearate (CdSt₂) to H₂S gas at a pressure of 1 Torr. The changes of surface morphology of film with the increased reaction time were directly observed by atomic force microscopy for the first time. Before being exposed to H₂S, the surface of CdSt₂ LB film was homogeneous from microscale down to nanoscale, and it was observed that CdSt₂ molecules formed a well orderly rectangular herringbone lattice structure on the molecular scale. However, after being exposed to H₂S the ordered CdSt₂ molecules gradually changed into a disordered state, and eventually the LB film surface became rough with the apparent feature of bulk structures on the nanoscale. This change in the morphology can be attributed to the aggregation of buried CdS nanoparticles within LB films, which has been confirmed by a structured UV–visible absorption spectrum where the absorption edge is red-shifted about 0.7 eV with respect to bulk CdS. Finally, the aggregation mechanism of CdS in the LB film was analyzed.     

CdS纳米微粒在LB膜层隙聚集形态的AFM观察

用LB技术制备纳米微粒与超薄有机膜的复合膜是近年来值得注意的研究进展＊．利用该方法所制备出的材料既具有纳米粒子所特有的量子尺度效应，又具有LB股的分子层次有序、股厚可控以及易于组装等特点．它可用来制备结构可控的有机无机交替膜．而且，通过改变LB膜成膜材料和制备条件还可改变纳米粒子的光电特性．因此它在微电子学、光电子学、非线性光学及传感器等研究领域有着十分广阔的应用前景问．纳米微粒的聚集形态及LB膜在生成纳米微粒后的结构变化对材料的特性有着很大的影响．但采用一般的电镜技术或光谱分析手段均不能在实空间和…     

An X-ray spectroscopy study of CdS nanoparticles formed by the Langmuir–Blodgett technique on the surface of carbon nanotube arrays

The composition and electronic structure of cadmium sulfide (CdS) nanoparticles formed by the Langmuir–Blodgett (LB) technique on clean silicon wafers and the surface of vertically aligned carbon nanotube (CNT) arrays are studied by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The samples were annealed in a vacuum at 175 °C and 225 °C to remove the organic matrix of the LB film. From the analysis of the XPS data the increased concentration of sulfate groups on the surface of CdS nanoparticles formed on CNTs and the electron density transfer from CdS to CNTs are determined. An increase in the LB film annealing temperature causes an increase in the degree of crystallinity and the CdS crystallite size and a decrease in the photoluminescence intensity of a CdS–CNT hybrid.     

Semiconductor nanoparticle/polystyrene latex composite materials

Cadmium sulfide and cadmium selenide/cadmium sulfide core/shell nanoparticles stabilized with poly(cysteine acrylamide) have been bound to polystyrene (PS) latexes by three methods. First, anionic 5 nm diameter CdS particles were electrostatically attached to 130 nm surfactant-free cationic PS latexes to form stable dispersions when the amount of CdS particles was less than 10% of the amount required to form a monolayer on the surface of the PS particles or when the amount of CdS particles exceeded the amount required to form a monolayer on the PS particles. Transmission electron microscopy (TEM) showed nanoparticles on the surface of the latex particles. Fluorescence spectra showed unchanged emission from the nanoparticles. Second, anionic, surfactant-free PS latexes were synthesized in the presence of CdS and CdSe/CdS nanoparticles. TEM showed monodisperse latex particles with trapped nanoparticles. Third, surfactant-stabilized latexes were synthesized by copolymerization of styrene with vinylbenzyl(trimethyl)ammonium chloride electrostatically bound to the CdSe/CdS nanoparticle surface. Brownian motion of the submicroscopic composite particles in water was detected by fluorescence microscopy.     

Complex Langmuir-Blodgett films of SiO2 and ZnO nanoparticles with advantageous optical and photocatalytical properties

Multifunctional Langmuir-Blodgett (LB) films were fabricated on the surface of glass substrates using sol-gel derived ZnO and SiO2 particles. ZnO particles of 6 and 110 nm diameter were synthesized according to the methods of Meulenkamp and Seelig et al. (Meulenkamp, E. A. J. Phys. Chem. B 1998, 102, 5566; Seelig, E. W.; Tang, B.; Yamilov, A.; Cao, H.; Chang, R. P. H. Mater. Chem. Phys. 2003, 80, 257). Silica particles of 37 and 96 nm were prepared by the Stober method (Stober, W.; Fink, A.; Bohn, E. J. Colloid Interface Sci. 1968, 26, 62). Alternate deposition of monoparticulate Langmuir films of SiO2 and ZnO nanoparticles provided complex (six- and nine-layered) LB films with both antireflective and photocatalytic properties. The LB films were investigated with scanning electron microscopy (morphology and structure) and UV-vis spectroscopy (optical properties and stability). The photocatalytic activity was measured by immersing the UV-irradiated films into an aqueous solution of Methyl Orange and following the photodegradation of the dye by optical spectroscopy. Adding ZnO particles to the silica films slightly lowered the antireflection property but ensured strong photocatalytic activity. Both the photocatalytic activity and antireflection properties were proved to be sensitive to the sequence of the silica and ZnO layers, with optimum properties in the case of nine-layered films with a repeated (SiO2-ZnO-ZnO) structure.     

A low-temperature, soft chemistry method for the synthesis of zirconia nanoparticles in thermally evaporated fatty amine thin films

We demonstrate the synthesis of zirconia nanoparticles in a lipid matrix by a simple, low temperature beaker-based process. This is accomplished by electrostatic entrapment of ZrF6(2-) ions within thermally evaporated octadecylamine (ODA) thin films followed by the low-temperature in situ hydrolysis of the entrapped metal ion complexes. The zirconia particles thus formed were of the monoclinic phase and were fairly monodisperse with particles of average size 40 nm. The zirconia crystallites appeared to exhibit preferred orientation indicating epitaxial growth of the crystals within the lipid matrix. The formation of zirconia nanoparticles in the lipid matrix was investigated using quartz crystal microgravimetry (QCM), optical absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques.     

DNA分子在气液界面的组装相变特性及其LB膜结构研究

对十八胺与DNA在气液界面上组装及其相变过程进行了研究，利用AFM观察了不 同压力下转移的DNA复合LB膜结构。发现在低表面压时，DNA复合单分子膜表现为技 术发散的分形结构；随着压力的升高，DNA复合膜逐渐由紧密的网状排布结构变为 团聚的块状和团簇结构。表明通过调节膜压，可使膜内DNA分子的构象发生大的变 化，从而生成具有特定形态的二维纳米图案。这种具有特殊形态和结构的DNA LB膜 可望为合成新型生物纳米结构有序功能体系提供模板。     

Effect of sol-gel preparation method on particle morphology in pure and nanocomposite PZT thin films

Double-scale composite lead zirconate titanate Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films of 360 nm thickness were prepared by a modified composite sol-gel method. PZT films were deposited from both the pure sol and the composite suspension on Pt/Al₂O₃ substrates by the spin-coating method and were sintered at 650°C. The composite suspension formed after ultrasonic mixing of the PZT nanopowder and PZT sol at the powder/sol mass concentration 0.5 g mL⁻¹. PZT nanopowder (≈ 40–70 nm) was prepared using the conventional sol-gel method and calcination at 500°C. Pure PZT sol was prepared by a modified sol-gel method using a propan-1-ol/propane-1,2-diol mixture as a stabilizing solution. X-ray diffraction (XRD) analysis indicated that the thin films possess a single perovskite phase after their sintering at 650°C. The results of scanning electron microscope (SEM), energy-dispersive X-ray (EDX), atomic force microscopy (AFM), and transmission electron microscopy (TEM) analyses confirmed that the roughness of double-scale composite PZT films (≈ 17 nm) was significantly lower than that of PZT films prepared from pure sol (≈ 40 nm). The composite film consisted of nanosized PZT powder uniformly dispersed in the PZT matrix. In the surface micrograph of the film derived from sol, large round perovskite particles (≈ 100 nm) composed of small spherical individual nanoparticles (≈ 60 nm) were observed. The composite PZT film had a higher crystallinity degree and smoother surface morphology with necklace clusters of nanopowder particles in the sol-gel matrix compared to the pure PZT film. Microstructure of the composite PZT film can be characterized by a bimodal particle size distribution containing spherical perovskite particles from added PZT nanopowder and round perovskite particles from the sol-matrix, (≈ 30–50 nm and ≈ 100–120 nm), respectively. Effect of the PZT film preparation method on the morphology of pure and composite PZT thin films deposited on Pt/Al₂O₃ substrates was evaluated.     

酞菁铜化合物LB膜的制备及结构形态研究

利用LB技术研究了带有4个长碳氢链的酞菁铜化合物(CuC12Pc)的单分子膜及它与十八胺(ODA)、二十酸(AA)的混合LB膜的聚集结构形态. 结果表明这种酞菁铜化合物在气液界面上可以形成比较稳定有序的双层Langmuir膜, 且可以转移质量较好的多层LB膜. 利用原子力显微镜(AFM)研究了酞菁铜分子的聚集体结构, 发现CuC12Pc/AA混合膜表现为网状的聚集结构, 而CuC12Pc/ODA混合膜形成长岛颗粒状聚集, 并结合UV-Vis吸收光谱讨论了酞菁铜分子形成不同聚集结构的原因.     

Synthesis and characterization of CdS nanoparticles prepared by precipitation in the presence of span 20 as surfactant

Cadmium sulfide nanoparticles with average size of ≈16 nm have been synthesized using chemical precipitation reaction of CdCl₂ and Na₂S in the presence of nonionic surfactant stabilized reverse emulsions. Sorbian monolaurate (Span 20) is used for the stabilization of emulsions. The influence of Span 20 on controlling the size and properties of CdS nanoparticles were studied. The obtained CdS nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Energy-dispersive x-ray (EDX), and X-ray diffraction (XRD). The optical properties of CdS nanoparticles are investigated systematically by UV-visible absorption spectroscopy. The blue shift in the absorption region and increase in the bandgap to the larger value (2.77 eV) are attributed to the nanosize of the obtained particles.     

Tl2O3/聚-N-乙烯基咔唑复合纳米线的研究

Stable monolayers of electropolymerized poly-N-vinylcarbazole (EPVK) and arachidic acid(AA) are obtained on a subphase of alkaline Tl2O3 colloidal solutions. As revealed by the atomic force microscope, there is phase separation in the mixed LB monolayers. Transmission electron microscopic observations reveal that ordered arrays of composite Tl2O3/Epvk nanowires are formed in the mixed monolayers. Formation of the composite nanowire arrays is attributed to the ordered adsorption of Tl2O3 colloidal particles along the polycationic EPVK chains. The composite nanowire array is 3.2nm wide with a spacing of 2.7nm.The composite nanowire arrays can also be formed when pure EPVK is used. Composite LB multilayers of Tl2O3/EPVK nanowire arrays are prepared. The bilayer spacing is 5.54nm.The present study is of importance to the fabrication of inorganic semiconductor/functional polymer composite nanowires.     

Hybrid platinum nanoparticle ensemble for the electrocatalytic oxidation of H2O2: Toward nanostructured biosensor design

This paper reports the electrocatalysis of H₂O₂ oxidation by Langmuir–Blodgett (LB) thin films based on polymer-grafted platinum nanoparticles (PtNPs). 4-mercaptoaniline-functionalized PtNPs have been chemically modified to obtain poly(methacrylic acid)-grafted platinum nanoparticles (PMAA-PtNP) via surface-ATRP. These elementary bricks are used to form mixed LB films consisting of controlled mixtures of PMAA-PtNP and a redox-inactive fatty acid molecule to tune the PtNP surface density. Nanostructures are formed in which the number of layers and the number of particles in each layer may be varied. The nanostructure morphology strongly depends on the amount of PtNP. High Pt content leads to quite large nanoparticle domains whereas low content gives small domains with a finely divided nanostructure. The H₂O₂ oxidation current increases when the PMAA-PtNP surface density decreases. This result is discussed in terms of electrocatalyst accessibility modification related to the nanostructure of the films.     

Construction of inorganic nanoparticles by micro-nano-porous structure of cellulose matrix

In our previous work, the CdS nanoparticles/cellulose films exhibited significantly high photocatalytic H₂ production efficiency under visible light irradiation than the ordinary CdS photocatalyst. In present paper, the CdS nanoparticles were synthesized in situ in pores of the regenerated cellulose substrate and the porous structure of cellulose, formation of the CdS nanoparticles and interactions between CdS and cellulose matrix in the composite films were investigated deeply. The experimental results indicated that the micro-nano-porous structure of the cellulose matrix could be used easily to create inorganic nanoparticles, which supplied not only cavities for the formation of nanoparticles, but also a shell (semi-stiff cellulose molecules support the pore wall) to protect their nano-structure. When the cellulose films with porous structure at wet state were immersed into inorganic ions solution, the ions interacted immediately with the –OH groups of cellulose, and then transformed into inorganic composite via another treatment, finally inorganic nanoparticles formed during the dry. The pore size of the cellulose matrix decreased from 180 nm (at wet state) to about 18 nm (at dry state), leading to the formation of nanoparticles. The results revealed that the CdS nanoparticles with a mean particle diameter about 6 nm were dispersed well, and were immobilized tightly in the cellulose matrix, resulting in a portable photocatalyst with high efficiency for photocatalytic for H₂ evolution. This is simple and “green” pathway to prepare the organic–inorganic hybrid materials.     

硫化镉钠米微粒在聚合物网络中的组装

硫化镉钠米微粒在聚合物网络中的组装黄金满，杨毅，杨柏，刘式墉，沈家骢（吉林大学分子光谱与分子结构重点实验室、集成光电子国家重点实验室，长春，１３００２３）关键词组装，纳米微粒，离子交换，透射电子显微镜，电子衍射由于纳米半导体微粒的物理和化学性质介于分...     

Controlling the Structural and Electrical Properties of Diacid Oligo(Phenylene Ethynylene) Langmuir–Blodgett Films

The preparation, characterization and electrical properties of Langmuir–Blodgett (LB) films composed of a symmetrically substituted oligomeric phenylene ethynylene derivative, namely, 4,4′‐[1,4‐phenylenebis(ethyne‐2,1‐diyl)]dibenzoic acid (OPE2A), are described. Analysis of the surface pressure versus area per molecule isotherms and Brewster angle microscopy reveal that good‐quality Langmuir (L) films can be formed both on pure water and a basic subphase. Monolayer L films were transferred onto solid substrates with a transfer ratio of unity to obtain LB films. Both L and LB films prepared on or from a pure water subphase show a red shift in the UV/Vis spectrum of about 14 nm, in contrast to L and LB films prepared from a basic subphase, which show a hypsochromic shift of 15 nm. This result, together with X‐ray photoelectron spectroscopic and quartz crystal microbalance experiments, conclusively demonstrate formation of one‐layer LB films in which OPE2A molecules are chemisorbed onto gold substrates and consequently ? COO? Au junctions are formed. In LB films prepared on a basic subphase the other terminal acid group is also deprotonated and associates with an Na⁺ counterion. In contrast, LB films prepared from a pure water subphase preserve the protonated acid group, and lateral H‐bonds with neighbouring molecules give rise to a supramolecular structure. STM‐based conductance studies revealed that films prepared from a basic subphase are more conductive than the analogous films prepared from pure water, and the electrical conductance of the deprotonated films also coincides more closely with single‐molecule conductance measurements. This result was interpreted not only in terms of better electron transmission in ? COO? Au molecular junctions, but also in terms of the presence of lateral H‐bonds in the films formed from pure water, which lead to reduced conductance of the molecular junctions.