Microwave-irradiated green synthesis of gold nanoparticles for catalytic and anti-bacterial activity

Abstract

Background: Herein, we report a green, microwave irradiated synthesis of gold nanoparticles by using a simple, low cost and ecofriendly technique. The green technique has been developed for the synthesis of gold nanoparticles (AuNPs) from HAuCl4 using papaya leaf extract. The papaya leaf extract served both as a reductant and a stabilizer. Method: The synthesized AuNPs had been characterized by UV-Visible spectrophotometer, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Zeta potential and Transmission electron microscopy (TEM) techniques. Results: The results indicated that the synthesized nanoparticles were crystalline, stable, well dispersed and spherical in shape and had an average diameter of 15 ± 2 nm. The AuNPs showed excellent catalytic activity for the reduction of p-nitrophenol (4-NP) to p-aminophenol (4-AP) in the presence of NaBH4. The effects of concentration of NaBH4, catalyst dose and temperature on the formation of nanoparticles were studied. The activation energy was found to be 28.15 ± 1.14 kJ/mol. Conclusions: The papaya leaf extract capped AuNPs are highly stable, and have showed effective catalytic activity in the reduction of 4-NP to 4-AP and antimicrobial activity on both gram-positive and gram-negative bacteria.