Synthesis and study of gold nanoparticles stabilized by bioflavonoids

A new procedure for the preparation of biocompatible gold nanoparticles using bioflavonoids: rutin, quercetin, and luteolin as reducing agents and stabilizers was proposed. On varying the bioflavonoid concentration, nanoparticles of different size are formed. By the combined use of spectroscopy and atomic force microscopy, the nanoparticle size was estimated (40–50 nm). Uniform and highly dispersed gold nanoparticles were obtained at Au: rutin ratios of 1: 1, 2: 1, and 4: 1 and Au: quercetin ratios of 2: 1 and 4: 1. The nanoparticle yield remains almost constant as the Au: rutin ratio varies over a broad range from 1: 1 to 12: 1. It was suggested that complete reduction of Au^III to Au⁰ with a large excess of Au is accompanied by extensive oxidation of bioflavonoid involving an intermediate oxidant formed in the system due to the high oxidative capacity of Au^III. For elucidating the catalytic role of bioflavonoids in the formation of gold nanoparticles, quantum chemical modeling of the process was performed.