Electrochemically reduced graphene oxide on gold nanoparticles modified with a polyoxomolybdate film. Highly sensitive non-enzymatic electrochemical detection of H2O2.

Gold nanoparticles (AuNPs) were prepared via the chloroauric acid reduction using Keggin-type anions (PMo12O403−). The layer of AuNPs was deposited on the glassy carbon electrode (GC) and conditioned using repetitive potential cycling between 0.3 and −0.4 V vs. SCE in the buffer solution at pH = 6. The changes in the polyoxometalate structure upon cycling are studied using Raman spectra. Graphene oxide(GO) was drop-cast on a thin layer of AuNPs on a GC electrode. Then, GO was reduced by scanning the electrode potential between −0.4 and −1.2 V vs. Ag/AgCl. The resulting layer of the electrochemically reduced graphene oxide (ERGO) on AuNPs shows non-enzymatic sensitivity to hydrogen peroxide. The sensitivity of the ERGO/AuNPs/GC/electrode to H2O2 equals 741 mA mM−1 cm−2 (limit of detection is equal to 56 nM) for the H2O2 concentration lower than 0.1 mM, and 381.5 mikroA mikroM−1 cm−2 at the higher concentration of H2O2. The electrocatalytic activity of the bare AuNPs layer and the activity of ERGO deposited directly on the GC electrode are significantly lower, which pointing to a synergistic effect between ERGO and AuNPs. The electrodes are characterized using Raman spectra. The mechanism of the ERGO-AuNPs synergistic electrocatalysis is proposed.