Stable Silver Nanoparticles in Aqueous Dispersions Obtained from Micellar Solutions

Two methods for obtaining aqueous dispersions of silver nanoparticles, stable during several months, from their reverse micellar solutions in an organic solvent: (i) centrifugation of a two-phase system formed by micellar solution and water and (ii) mixing of micellar solution with water, followed by settling.     

Photochemical Synthesis of Silver Nanoparticles on the Surface of Polystyrene Globules

Silver nanoparticles were deposited photochemically under the action of monochromatic (254 nm) and unfiltered light on the surface of 100- to 1410-nm polystyrene globules. The kinetic relationships of the photodeposition, as influenced by the concentration of silver ions in the photolyte and the size of polystyrene globules, were determined. An electron microscopic examination showed that the photoreduction mainly occurs on the surface of the polymer globules, and the size of the forming nanoparticles does not exceed 60 nm. The silver nanoparticles are characterized by a narrow size distribution.     

Synthesis and Stabilization of Bismuth Nanoparticles in Aqueous Solutions

Russian Journal of Physical Chemistry A - A technique is developed for the low-temperature synthesis of bismuth nanoparticles in aqueous solutions. UV–Vis spectroscopy, X-ray analysis and...     

Silver Nanoparticles by PAMAM-Assisted Photochemical Reduction of Ag(+)

The photochemical synthesis of Ag(0) nanoparticles in the presence of amino- and carboxylate-terminated PAMAM dendrimers is reported. The formation of Ag(0) nanoparticles was followed spectrophotometrically and by transmission electron microscopy (TEM). According to TEM investigations Ag(0) nanoparticles with the average size of about 7 nm in diameter were produced. Based on the present investigation a possible mechanism for the Ag(0) nanoparticles formation is proposed. Copyright 2000 Academic Press.     

Relaxation of Physicochemical Processes during the Chemical Synthesis of Silver Nanoparticles in Reverse Micellar Solutions

Russian Journal of Physical Chemistry A - The kinetics of optical properties is studied experimentally on an OT Aerosol (dioctyl sulfosuccinate sodium salt)/isooctane/Qr (quercetin)/Ag+) reverse...     

Synthesis of Copper Nanoparticles Using Hydrazine in Micellar Solutions of Sodium Dodecyl Sulfate

Moscow University Chemistry Bulletin - The influence of the synthesis conditions and composition of the reaction medium on the size and morphology of copper nanoparticles is studied for the...     

Liquid Crystals in Aqueous Solutions of Sodium Naphthenates

The phase diagram of the sodium naphthenates (SN)/water system was determined between -5 and 95 degrees C. Oil, isotropic water solution, and birefringent gel phases were observed. The appearance of the oil phase was caused by the hydrolysis of SN. After the system was allowed to stand for 3 weeks, a lamellar liquid crystal (LLC) phase separated from the rest of the system at 25 degrees C. This phase was always observed together with other phases. This phase behavior is attributed to different partition coefficient values of the individual constituents of sodium naphthenates between the phases. The partition coefficient difference also caused the appearance of a clear LLC and a turbid gel phase. Under the influence of agitation, the LLC phase with isotropic water solution transformed to giant vesicles; however the equilibrium state of the LLC is of parallel stacked layer structure. Macroscopic dislocations of the liquid crystal were observed, and they were anchored to the interface of the isotropic solution and the liquid crystal phases. These dislocations are similar to screw-type dislocations. The solubilization curve of toluene by SN is analogous to that of hydrophobic materials by a hydrotrope. Copyright 2001 Academic Press.     

Kinetics and Mechanism of Silver Dissolution in Aqueous Sodium Nitrate

Russian Journal of Physical Chemistry A - The kinetics of the electrochemical oxidation–reduction of silver in aqueous solutions of sodium nitrate was studied by potentiometry. The effect of...     

甲烷氧化菌素介导一步法合成合成纳米银

以硝酸银为前体物,甲烷氧化菌素(Mb)将Ag(Ⅰ)还原Ag(0),并形成纳米银粒子(AgNPs),同时Mb吸附在形成的AgNPs表面,起到保护剂作用避免AgNPs聚集沉淀.采用紫外-可见光谱、荧光光谱、红外光谱、透射电镜和X射线电子能谱等对合成的AgNPs粒子过程、Mb合成AgNPs官能团、AgNPs形貌和AgNPs结构及价态等进行了分析.结果表明Mb可以一步法合成AgNPs离子.     

聚丙烯酰胺存在下微波高压合成银纳米粒子及其光谱特性

以聚丙烯酰胺为还原剂和稳定剂 ,采用微波高压液相合成法制备了黄色银纳米粒子。用吸收光谱和共振散射光谱研究了其制备条件的影响。在 4 2 1.6nm处产生最大吸收峰 ,在 4 70nm处产生一个最强共振散射峰。实验表明 :该法制备的银纳米粒子粒径均匀 ,平均粒径为 6 6nm ,其稳定性和分散性较好 ,合成方法简便、快捷。     

单分散性银纳米粒子的可控制备

以卤化银或氧化银作为前驱体,室温下以水为溶剂,在较高溶液浓度下,利用化学还原法制备了单分散性银纳米粒子,并通过改变前驱体的种类,实现了粒径可控制备。采取扫描电子显微镜（SEM）、紫外-可见光谱仪（UV-Vis）、X射线-粉末衍射仪（XRD）、X射线-光电子能谱仪（XPS）等对所制备的银纳米粒子的形貌及成分进行了表征。结果显示,所制备的银纳米粒子具有较高的单分散性,粒径在40~150 nm之间,具有面心立方多晶结构。该方法制备的银纳米粒子可用于喷墨打印RFID天线。     

硫酸氢钠催化合成柠檬酸三丁酯

以柠檬酸和正丁醇为原料 ,硫酸氢钠为催化剂合成了柠檬酸三丁酯 ,考察了影响产品收率的各种因素 ,确定了最佳反应条件为 :0 .1mol柠檬酸 ,醇酸摩尔比 4 .5 ,3.5g催化剂 ,反应时间 2h ,收率达 95 .6 %以上 .研究结果表明 ,硫酸氢钠是合成柠檬酸三丁酯的优良催化剂     

Optical Properties and Sizes of Silver Nanoparticles in Micellar Solutions

Sizes of silver nanoparticles prepared by the reduction of silver ions in reverse micelles with solvated electron (radiation-chemical synthesis) and natural pigment quercetin (biochemical synthesis) were determined. The sizes were measured by the dynamic light-scattering technique. Histograms of the micelle size distributions were compared with the absorption spectra of the corresponding solutions of nanoparticles. It was shown that the employed synthesis procedures made it possible to obtain metal particles with the sizes of the order of several nanometers; the changes of optical density in the maximum of nanoparticle absorption band correlated with the changes of the particle content in solution. The results obtained were compared with the data available for silver nanoparticles prepared by the radiation-chemical synthesis in aqueous solution in the presence of stabilizer and by the chemical synthesis in reverse micelles with traditional reducing agents.     

Photocatalysis of the Release of Molecular Hydrogen from Aqueous Solutions of Sodium Sulfite by Composite CdS/Ni Nanoparticles

The photocatalytic reduction of Ni²⁺ cations at the surface of CdS nanoparticles was investigated. It was found that the CdS/Ni nanocomposite formed as a result of the reaction exhibits photocatalytic activity in the release of molecular hydrogen from aqueous solutions of sodium sulfite. The kinetic relationships of the process are studied, and a mechanism for the studied reactions is proposed.     

纳米银形状控制合成与聚合物纳米银复合材料

纳米银(Ag NPs)由于其独特的物理、化学和生物学特性备受研究人员的关注.纳米银应用性能除了受到粒子尺寸、分布、纯度等因素影响,还与纳米银的形状密切相关.纳米银的形状对纳米银的抗菌性能、光学性能以及聚合物纳米银复合材料的综合性能都会产生重要影响.纳米银的形状控制合成可以进一步发挥聚合物纳米银复合材料的性能潜力.因此,不断发展纳米银新的合成方法,研究纳米银形状控制的机理就显得尤为重要.本文综述了纳米银合成方法和不同形状纳米银的最新研究进展,合成方法重点介绍了辐射法、激光烧蚀法、电化学法、光化学法和生物合成法,评述了这些方法的优缺点;同时从模板法、动力学、热力学以及氧化刻蚀4个方面介绍了纳米银形状控制的机理.介绍了聚合物纳米银复合材料的研究进展.     

聚氧乙烯类表面活性剂体系中银纳米颗粒的合成

将AgNO3水溶液与非离子表面活性剂AEO 7按一定比例混合,即可形成六方液晶.体系中的Ag＋被表面活性剂分子AEO 7还原成Ag,形成Ag的纳米颗粒.在这一过程中,非离子表面活性剂液晶既是还原剂,又是反应介质和稳定剂.在合成过程中,聚氧乙烯类表面活性剂的乙氧基形成了氢过氧化物,从而具有了将Ag＋还原成单质Ag的能力. Ag纳米颗粒生长到一定时间不再继续变大,这表明颗粒的长大是靠自身的生长,并不发生颗粒聚集.控制液晶体系中反应物的浓度、含量以及反应时间可得到不同大小的Ag纳米颗粒.所形成的Ag纳米颗粒的平均粒径一般小于10 nm.     

Freezing and Hydrate Formation in Aqueous Sodium Perchlorate Solutions

The determination of the phase diagram of the binary system sodium perchlorate – water is reported. Beside the eutectic point, two polymorph crystal structures of sodium perchlorate dihydrate were determined. The two crystal structures are discussed, compared to each other and to other known sodiumhalide dihydrate crystal structures. The two polymorphs of the perchlorate dihydrate represent the two variants of connected octahedra in the layer structure found for sodium halide dihydrates.     

Hydration and Ion Pairing in Aqueous Sodium Oxalate Solutions

Dielectric spectra have been measured for aqueous sodium oxalate solutions up to the saturation concentration (0.04≤c [mmol L^?1]≤0.25) at 25 °C over the approximate frequency range 0.2≤ν [GHz]≤20. The spectra exhibit a process at about 1 GHz associated with the presence of ion pairs, in addition to the dominant solvent relaxation process at about 18 GHz. Detailed analysis of the solvent dispersion amplitude indicates that the oxalate ion is highly hydrated but that its solvation sheath is “fragile”, decreasing quickly with increasing solute concentration. The NaOx(aq)^? ion pair is shown to be of the double‐solvent‐separated (2SIP) type, with an infinite dilution association constant K_A=1.04±0.02. Analysis of the ion‐pair relaxation time as a function of solute concentration gave rate constants for the formation (k₁₂=(7.3±0.4)10⁹ L mol^?1 s^?1) and dissociation (k₂₁=(6.7±0.5)10⁸ s^?1) of the ion pair. These values are reasonably close to the diffusion‐controlled values predicted by the Eigen theory, consistent with a 2SIP structure for the ion pair.     

Micelle and Solvent Relaxation in Aqueous Sodium Dodecylsulfate Solutions

Dielectric spectra have been measured for aqueous sodium dodecylsulfate (SDS) solutions up to 0.1 mol L^?1 at 25 °C over the frequency range 0.005≤ν GHz^?1≤89. The spectra exhibit two relaxation processes at approximately 0.03 GHz and 0.2 GHz associated with the presence of micelles in addition to the dominant solvent relaxation process at approximately 18 GHz and a small contribution at approximately 1.8 GHz due to H₂O molecules hydrating the micelles. Detailed analysis reveals that the micelles bind 20 water molecules per SDS unit, but not as strongly as trimethylalkylammonium halide surfactants do. The relaxation times and amplitudes of both micelle relaxation processes can be simultaneously analysed with the theory of Grosse, yielding the effective volume of a SDS unit in the micelle and the lateral diffusion coefficient of the bound counterions. The findings of this investigation fully corroborate recent molecular dynamics simulations on structure and dynamics of SDS micelles.