Devarajan Supriya, Vimalan B, Sampath S
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India.
J Colloid Interface Sci. 2004 Oct 1;278(1):126-32. doi: 10.1016/j.jcis.2004.05.038.
Mercaptopropionic acid (MPA) capped Au-Ag alloy nanoparticles consisting of various mole fractions of gold and silver have been synthesized in aqueous medium using a citrate reduction method. UV-visible spectra confirm the formation of alloy phases and transmission electron microscopy (TEM) reveals a rather uniform distribution of several nanometer-sized particles. The particles could easily be phase-transferred into organic solvents, isolated, and redispersed in a variety of solvents such as benzene, chloroform, and dichloromethane. The phase transfer from aqueous medium to an organic solvent does not alter the particle size and distribution. It is also recognized that the surfactant, alkaline MPA, should be aged for about 3 days in order to observe the formation of silver and silver-rich phases of alloy nanoparticles. The reason for this observation is discussed in terms of the competitive interaction between the Na+ and -COOH/-SH groups and subsequent reduction of metal ions.
采用柠檬酸盐还原法在水相中合成了由不同摩尔分数的金和银组成的巯基丙酸（MPA）包覆的金-银合金纳米颗粒。紫外-可见光谱证实了合金相的形成，透射电子显微镜（TEM）显示了几种纳米尺寸颗粒相当均匀的分布。这些颗粒可以很容易地相转移到有机溶剂中，分离出来，并重新分散在多种溶剂中，如苯、氯仿和二氯甲烷。从水相介质到有机溶剂的相转移不会改变颗粒大小和分布。还认识到，表面活性剂碱性MPA应老化约3天，以便观察合金纳米颗粒银相和富银相的形成。从Na⁺与-COOH/-SH基团之间的竞争相互作用以及随后金属离子的还原方面讨论了这一观察结果的原因。
