Reduced state carbon dots as both reductant and stabilizer for the synthesis of gold nanoparticles

The reduced state carbon dot (r-CD) is a new kind of carbon dot (CD) prepared by using sodium borohydride. Herein, we find that the r-CDs can directly reduce chloroauric acid to form gold nanoparticles (AuNPs) without adding other reducers or stabilizers. At the same time, we deduced that the hydroxyl groups (-OH) on the surfaces of r-CDs can act as both reducer and stabilizer for the synthesis of AuNPs. The AuNPs possess intrinsic catalytic activity, but compared with the AuNPs synthesized by citrate reduction, the AuNPs we prepared exhibit less excellent catalytic activity in the reduction of 4-nitrophenol (4-NP) with sodium borohydride. Conversely, for catalyzing oxidation of the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2, the AuNPs we prepared show much higher catalytic activity than the AuNPs synthesized by citrate reduction. This work may open up a new route for the applications of CDs.