Green principles can be applied to exploit greener nano-synthesis with the intention of producing risk-free nanoscale gold particles and to obtain phytochemically-derived reducing agents for the generation and stabilization of gold nanoparticles under nontoxic conditions, reduce the complexity of current methodologies and enhance their efficiency.

Researchers at the Norwegian University of Science and Technology (NTNU) have recently developed a new environmentally friendly route for synthesizing gold nanoparticles (AuNPs) in one step at room temperature. The product is highly stable, non-toxic, biocompatible, water-soluble, monodispersed and size-controllable. The gold particles are made in just a few minutes by simply adding sodium hydroxide to the reaction mixture. The chemical acts as an initiator for the reduction of HAuCl4 in aqueous solution in the presence of polyvinylpyrrolidone without the use of any reducing agent. To control the size of the AuNPs, the researchers simply adjust the PVP/HAuCl4 ratio. The PVP-stabilized AuNPs demonstrate remarkable in vitro stability in a wide range of ionic strength (0–30 M), temperature (4–100 °C), pH (4.4–13.5), various buffer solutions and physiological conditions. The generation of PVP-stabilized AuNPs has been found to be non-toxic as assessed through MTT (3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assays. Also, the production strategy features several green concepts: the choice of friendly solvent, the selection of friendly benign and non-toxic reducing and capping agents, the one-step reaction at room temperature and a reaction time of just a few minutes.