Study On Preparation Of Ag, Au And Au-ag Alloy Nanosized Structures Through Chemical Reduction Method

Nanomaterials have been the hot spot of research in the 21th century. Due to the special physicochemical properties, metal nanomaterials have attracted much attention in the past decades. Among them, noble metal nanomaterials, which possess promising potential application prospect in electronics, optics, catalysis, sensing, biolabeling and optoelectronics, have become important research area both at home and abroad. Precise control of anisotropic crystal growth by capping agents is the key to these excellent works. On the other hand, attempts have been made to develop facile, reliable and cost-effective synthetic strategies in order to enhance efficiency and realize mass production. Chemical reduction method is demonstrated to be a promising way for the synthesis of noble metal nanopartilces (NPs).In this paper, noble metal Ag, Au and Au-Ag alloy nanomaterials with different morphologies and sizes were prepared by chemical reduction method in organic and aqueous systems. And their properties have been characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM), high-resolution tranmission electron micorscopy(HR-TEM), selected-area electron diffraction(SAED), ultraviolet-visiable spectrophotometer (UV-Vis) and so on.Firstly, a new micro-emulsion system composed of organic solvents, span 80 as surfactant and silver nitrate aqueous solution as the precursor, was conducted to prepare Ag nanomaterials. The effects of reaction parameters, including solvents composition, the concentrations and ratios of silver nitrate and the reducing agent, were investigated. In addition, the reaction temperatures were also considered. Based on the results of experiments discussed, the reaction conditions for preparing monodisperse Ag NPs in the system of cyclohexanol-cyclohexanone were optimized as follows: tha adding amount of cyclohexanol was 18 ml, cyclohexanone 12 ml, Span 80 3 ml, 2,2'-Methylenebis(6-tert-butyl-4-methylphenol) 0.09g, AgNO3 solution (0.058 M) 0.3 ml, reaction temperature was 80°C, and the reaction time was 4 h.In sodium carboxymethyl cellulose(CMC) aqueous solution system, Ag and Au nanomaterials were prepared with CMC employed as both stabilizer and reducing agent. Based on the size, morphology and optical properties of the obtained nanopartilces, the effects of concentrations and ratios of CMC and AgNO3, temperature and reaction time were discussed. Finally, the optimum condition of preparing monodisperse silver nanoparticles in CMC system was aquired as follows: the adding amount of deioned water was 20 ml, CMC 0.012 g, NaOH aqueous solution(0.1 M) 0.5 ml, AgNO3 solution (0.2 M) 0.1 ml, reaction temperature was 80°C, and the reaction time was 4 h.It has not been reported about the method of preparing noble metal nanomaterials with inorganic phosphate as capping agent. Ag, Au and Au-Ag alloy nanomaterials were first prepared in the phosphate-stablized system. In sodium tripolyphosphate (STPP) aqueous system, silver nanomaterials with different morphologies and sizes were obtained. Through adjustments of reaction conditions, a large number of silver nanorods have been successfully synthesized. Based on the characterization results, a possible formation mechanism has been discussed. It suggests that the preferential direction for the growth of silver nanorods is along with the plane (111). It is therefore reasonable to speculate that the linear structure of STPP and the fairly slow reaction rate are both the key factors in the formation of rod-shaped silver nanoparticles. In addition, Au and Au-Ag alloy nanoparticles with narrow size distribution were also obtained in the STPP system.Polyacrylate acid sodium (PAAS), a polymer with excellent biocompatibility, was used as the capping agent to produce silver nanoplates for the first time. A large number of triangle silver nanoplates were first prepared. The effects of reaction parameters, including the concentration of PASS, concentration and ratio of glucose and AgNO3, reaction temperature, were discussed. The results showed that triangle, pentagon and hexagon silver nanoplates were prepared.