Random alloy of Au-Ag bimetallic nanoparticles at room temperature—facile synthesis and vibrational properties

The synthesis of nanometric alloys, or nanoalloys, is gaining interest in nanoscience due to their new and attractive physical properties. Furthermore, they improve the efficiency and performance of the diverse nanotechnological applications in comparison with the nanostructures composed of only one material. This study presents a novel synthesis method that facilitates the production of Au-Ag random bimetallic nanoalloys with uniform shape at room temperature, using the reducing and stabilizing properties of low-toxicity molecules, such as sucrose, ascorbic acid, and rongalite. The images taken with a transmission electron microscope (TEM) showed spherical bimetallic nanoparticles between 7 and 12 nm. The presence of Au and Ag in the nanostructures was confirmed by EDS. The optical absorption analysis showed a band centered at 480 nm, associated with surface plasmon resonance in Au-Ag nanoalloys. A Raman band was observed around 98 cm⁻¹ after the nanoparticles were synthesized. Additionally, the behavior of the radial breathing modes (RBM) of mixed bimetallic nanoalloys of Au_20-nAg_n (con n = 0–20) clusters was analyzed. The analysis was performed with the density functional theory (DFT) at Becke level, three-parameter, Lee-Yang-Parr (B3LYP) in combination with basis set Los Alamos Laboratory 2 double ζ (LANL2DZ). The predicted vibrational modes associated with RBM are located around 90–100 cm⁻¹ approximately. This shows a good tendency and correlation with the Raman band detected experimentally at low wave numbers.