One-step, size-controlled synthesis of gold nanoparticles at room temperature using plant tannin

Bayberry tannin (BT), a natural plant polyphenol, was used for one-step synthesis of gold nanoparticles (AuNPs) in aqueous solution at room temperature. During the synthetic process, BT simultaneously serves as a reducing agent and stabilizing agent, while no additional reagent (surfactant, template, and capping agent) or treatment (heat and photo-irradiation) is needed. The particle diameter and size distribution of BT-stabilized AuNPs (BT-AuNPs) can be facilely controlled by varying the concentration of BT, and the particle size of BT-AuNPs is as small as 1.8 ± 0.3 nm when the BT concentration was 800 mg L−1. Furthermore, this green approach for the auto-reduction synthesis of AuNPs can be completed in several minutes and exhibits high reproducibility, which shows great potential for practical applications.