Synthesis of polyoxometalate-protected gold nanoparticles by a ligand-exchange method: Application to the electrocatalytic reduction of bromate

Gold nanoparticles (AuNPs) protected by an alkanethiol in nonaqueous solvent are converted to AuNPs with a surrounding layer of a polyoxometalate, AuNP-POM, by ligand exchange and liquid-liquid extraction into aqueous solution without changing the size of the metal core. With glassy carbon electrodes modified with PMo12-AuNP (PMo12=H3PMo12O40), the reduction of bromate was mediated by the first redox process of the Mo-VI centers; the reduction occurred at a lower overpotential and yielded a higher cathodic current than that observed with PMo12 alone as the mediator. This synergistic electrocatalysis, which approached a linear diffusion-controlled process, was used to demonstrate the feasibility of the determination of bromate. A detection limit of 3 KM (k = 3 criterion) was achieved by pulse voltammetry.