Preparation of silver, gold and silver–gold bimetallic nanoparticles in w/o microemulsion containing TritonX-100

Silver, gold and silver–gold alloy nanoparticles were prepared in w/o microemulsion containing TritonX-100 and cyclohexane. Silver nitrate and tetrachloroauric(III) acid (HAuCl4) were taken as the metal precursors and sodium borohydride (NaBH4) was used as a reducing agent. The formation of Ag and Au nanoparticles was confirmed from the appearance of surface plasmon absorption maxima at 404 ± 2 and 525 ± 2 nm for Ag and Au nanoparticles, respectively. For bimetallic nanoparticles absorption peak was observed between the two maximas of corresponding metallic particles. The surface plasmon absorption maxima for bimetallic nanoparticles changes linearly with increasing Au mole ratio content in various alloy compositions. The transmission electron microscopy (TEM) showed formation of particles of 5–50 nm diameter. Dynamic light scattering (DLS) data gave narrow particle size distribution.