Carbon dots as a sustainable alternative to plant extracts for the green synthesis of noble metal nanoparticles

Abstract

Biogenic synthesis of noble metal nanoparticles is an alluring alternative to other chemical methods employing conventional reducing and capping agents. Herein, a completely green protocol is projected for the synthesis of noble metal nanoparticles using the recent entry of the nanocarbon family, carbon nanodots (CDs). Spherical CDs of size less than 5 nm were synthesized from the leaves of two herbs, Plectranthus amboinicus and Leucas lavandulifolia via hydrothermal method. The luminescence exhibited by these CDs was influenced by temperature, pH and excitation wavelength. Silver nanoparticles (AgNPs) with size around 10–16 nm are achieved from Ag(I) solution within minutes in the absence of heat treatment and supporting reagents. Reduction of Au (III) in presence of CDs yielded metallic gold nanoparticles (AuNPs) in the size range 50–60 nm under mild heat treatment. The involvement of functional groups in CDs as reducing and stabilizing agents was confirmed by FT-IR analyses. Carbon dots derived from the extracts were found to excel corresponding extracts in their reducing ability, in terms of the time of production, stability, particle size, etc.