One-step synthesis of monodisperse Au–Ag alloy nanoparticles in a microreaction system

Monodisperse Au–Ag alloy nanoparticles were synthesized by a one-step rapid injection method in a capillary microreaction system with a short residence time (less than 3   min). Au–Ag alloy NPs possessed homogenous composition that revealed a linear relationship with surface plasmon resonance absorption peak. The optimal size distribution of Au–Ag alloy NPs with a standard deviation of 6% could be obtained from decreasing the molar ratio of Au 3+ :Ag + from 1:10 to 1:20 or enhancing the synthesis temperature from 140 to 160   °C. Transmission electron micrographs showed as-obtained Au–Ag alloy nanoparticles were sphere-like with the smallest average size of only 2.7   nm.