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.     

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.     

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...     

Kinetics of Aggregation and Relaxation in Micellar Surfactant Solutions

Theoretical results published in the last 17 years on the kinetics of aggregation and relaxation in micellar surfactant solutions have been reviewed. The results obtained by the analytical and direct numerical solution of the Becker–Döring kinetic equations and the Smoluchowski generalized equations, which describe different possible mechanisms of aggregation and relaxation on all time scales from ultrafast relaxation while reaching the quasi-equilibrium in the region of subcritical molecular aggregates to the last stage of slow relaxation of micelles to the final aggregated state, have been considered in detail. The droplet model and the model linear with respect to aggregation numbers have been used for the work of aggregation to describe the dynamics of the rearrangement of micellar systems consisting of only spherical, only cylindrical, and coexisting spherical and cylindrical aggregates, with the dynamics being both linear and nonlinear with respect to deviations from equilibrium. The results of molecular simulation of the rearrangement kinetics of micellar systems subjected to initial disturbance have been reviewed.     

The Stage of Ultrafast Relaxation in Micellar Surfactant Solutions

The Becker–Döring kinetic equations are employed to describe the stage of ultrafast relaxation in micellar surfactant solutions, which ends in the establishment of a quasi-equilibrium distribution in the premicellar region of aggregate sizes. This is performed by analyzing the spectrum of the eigenvalues of the matrix of kinetic coefficients of the linearized Becker–Döring difference equations, which describes the complete multistage relaxation in a micellar system. The first value of the spectrum ordered as an ascending series is equal to zero (infinite relaxation time), thereby corresponding to the law of conservation of the surfactant quantity. The second value is very small; it differs from the series of subsequent values by several orders of magnitude and determines the time of slow relaxation. The other eigenvalues describe the processes of fast relaxation and comprise the contributions from the relaxation processes in both micellar and premicellar regions of aggregate sizes. In the latter region of the spectrum, the contribution of the ultrafast relaxation can be numerically distinguished. The obtained result is confirmed by the analysis of the spectrum of relaxation times of premicellar aggregates, which are considered as a closed system. It is also shown that the spectrum of ultrafast relaxation times is mainly determined by the first diagonal elements of the matrix of the linearized Becker–Döring equations and can be described analytically.     

On the Chemical Processes Accompanying Silver Reduction from Solutions of Its Salts in Organic Media

Silver reduction from its nitrate has been studied in the media of DGEBA-based and aliphatic epoxy resins. It has been found that, under the experimental conditions that were employed, silver ions can be reduced without chemical interaction with the medium only due to photochemical processes. The reduction rate is determined by the rate of dissolution of the initial silver salt in an organic medium and the possibility of the formation of solvates by the system components. Refractometry has been proposed for use in monitoring the kinetics of silver nitrate dissolution in epoxy resins and the formation of silver nanoparticles. Stable dispersions of silver nanoparticles in epoxy resins have been obtained.     

Photochemical Synthesis of Anisotropic Silver Nanoparticles in Aqueous Solutions in the Presence of Sodium Citrate

The rapid one-step photochemical synthesis of anisotropic silver nanoparticles (ANPs) is reported. Silver ANPs were prepared from silver nitrate by a citrate route in aqueous solutions at room temperature under exposure to unfiltered light of a DRK 120 high-pressure mercury lamp. The silver ANPs form through one-electron reduction of the silver cation in its chelate complex with the production of sodium citrate photolysis. In the course of synthesis, small charged silver clusters and nanoparticles are formed first, which are then stabilized by citrate ions. Key factors that influence the synthesis of silver ANPs and their further transformation have been determined.     

银纳米粒子的一步合成与表征

在水和乙醇溶液中,以对巯基苯胺作为还原剂,利用一步法合成了银纳米微粒,并利用拉曼光谱仪考察了对巯基苯胺在银纳米微粒表面的自组装行为.结果表明,合成的银纳米微粒的形貌与介质的pH值密切相关;对巯基苯胺可在银纳米微粒表面自组装.     

Ag纳米颗粒的快速制备及其性能研究

以黄药子提取液为还原剂和表面活性剂,快速制备出Ag纳米颗粒。通过紫外-可见分光光度计(UV-Vis)、透射电子显微镜(TEM)和X-射线衍射(XRD)对Ag纳米颗粒的形貌、成分和微观结构进行表征、分析。结果表明,Ag纳米颗粒为类球形,粒径为20.6 nm。说明了黄药子提取液具有良好的还原性。以合成的Ag纳米颗粒作为催化剂可以在10 min内将4-硝基苯酚(4-NP)完全降解,4-NP降解的速率常数可以通过Ag纳米颗粒的添加量来调节,最大值为0.286 min~(-1),说明合成的Ag纳米颗粒具有良好的光催化活性。     

Synthesis of Protein A Conjugates with Silver Nanoparticles

The single-stage synthesis of the conjugates of protein A with silver nanoparticles is performed. The dependence of the dispersity of the prepared sols on the composition of reaction mixture is investigated by optical spectroscopy and transmission electron microscopy. The relative stability of the obtained preparations with respect to the coagulation by NaCl is estimated.     

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.     

银纳米粒子的合成及其在喷墨打印电路中的应用

银纳米粒子在光学、电磁学和生物相容性等方面所具有的独特优点,使其在一系列领域得到了广泛的应用。本文综述了银纳米粒子的合成方法,以及其作为喷墨打印材料在电路制备中的应用,并展望了其发展前景。     

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: Dependence of the Antimicrobial Activity on the Synthesis Conditions

Russian Journal of General Chemistry - Specific features of the synthesis of stable silver nanoparticles by chemical reduction with agents differing in the reducing ability were studied using...     

Study of Relaxation in Micellar Solution by the Numerical Experiment

A numerical simulation of the relaxation process of surfactant micellar solution to a new equilibrium state is performed using model analytical representations for the main characteristics of micellar aggregates. Relaxation stages of molecular aggregate size distribution in the typical regions of aggregation number variations predicted by the analytical theory in two-flux approximation are revealed. Good agreement between the predicted values of the relaxation times of micellar solution and those obtained in numerical simulation is disclosed within the domain of applicability of two-flux approximation. Numerical algorithm proposed in this work makes it possible to study the relaxation process of micellar solution even in the case when two-flux approximation becomes inapplicable. The realization of numerical algorithm can be considered as a kind of experiment for studying the relaxation process of a model micellar solution.     

The Charging of Micellar Nanoparticles in Electrospray Ionization

Charging of nanoparticles through electrospray has scarcely been explored. Spherical nanometer‐sized amphiphilic block copolymer nanoparticles with diameters ranging from ～65 to ～150 nm were electrosprayed and analysed by charge detection spectrometry. Herein, we explore the charging of these micellar nano‐objects by conducting a thorough study in different solvents, including pure water, and upon the addition of “supercharging” agents. The charge (z) of micellar nanoparticles electrosprayed from water solution is compared to the Rayleigh’s limiting charge (z_R) of a charged water droplet of the same dimensions. An average ratio (z/z_R) of 0.6–0.65 is observed for the micellar macro‐ions, supporting the charge residue mechanism, where the number of charges available to the micellar macro‐ion is limited by the number of charges on the nanodroplet, which is a function of the surface tension of the solvent. Also we show the possibility of increasing the charging of micellar nanoparticles in the negative mode by adding organic bases (in particular piperidine) to water/methanol solutions.     

Synthesis of Stable Silver Nanoparticles with Antimicrobial Activities in Room-temperature Ionic Liquids

Stable silver nanoparticles was successfully synthesized by chemical reduction of silver nitrate in an ionic liquid,1-n-butyl-3-methylimidazolium tetrafluoroborate([BMIM]·BF4) at room temperature.Results of UV-Vis diffuse reflectance spectroscopy show as-prepared Ag nanoparticles exhibit a typical emission peak at 400―430 nm.By varying the reaction temperature and the precursor concentration,the size and the shape of the silver nanoparticles could be easily controlled under mild conditions.Analyses of trans...     

Role of Dioctyl Sulfide in Micellar Preconcentration,Synthesis, and Coagulation of Gold Nanoparticles

Extraction preconcentration of gold(III) by mixed Triton N-42 plus dioctyl sulfide (DOS) micelles from acid sulfate-chloride solutions was studied. The distribution ratio increases from 200 to 1200 as the DOS concentration rises from 0 to 0.25 mol/L (positive synergetic effect). Analysis of extraction equilibria shows that mixed micelles are key contributors into gold(III) extraction compared to Triton N-42 micelles and DOS molecular species in n-decane. Introduction of DOS at the synthesis stage increases the rate constants for gold reduction by hydrazine and enhances the coagulation of nascent nanoparticle     

Synthesis of Silver and Gold Nanoparticles by a Novel Electrochemical Method

Spherical silver and gold nanoparticles with narrow size distributions were conveniently synthesized in aqueous solution by a novel electrochemical method. The technological keys to the electrochemical synthesis of monodispersed metallic nanoparticles lie in the choice of an ideal stabilizer for the metallic nanoclusters and the use of a rotating platinum cathode. Poly(N‐vinylpyrrolidone) (PVP) was chosen as the stabilizer for the silver and gold clusters. PVP not only protects metallic particles from agglomeration, but also promotes metal nucleation, which tends to produce small metal particles. Using a rotating platinum cathode effectively solves the technological difficulty of rapidly transferring the (electrochemically synthesized) metallic nanoparticles from the cathode vicinity to the bulk solution, avoiding the occurrence of flocculates in the vicinity of the cathode, and ensuring the monodispersity of the particles. The particle size and particle size distribution of the silver and gold nanoparticles were improved by adding sodium dodecyl benzene sulfonate (SDBS) to the electrolyte. The electrochemically synthesized nanoparticles were characterized by TEM and UV/Vis spectroscopy.