A glassy carbon electrode modified with graphene quantum dots and silver nanoparticles for simultaneous determination of guanine and adenine

A glassy carbon electrode (GCE) was modified with graphene quantum dots (GQDs) carrying silver nanoparticles. The modified GCE displays excellent performance in the electrochemical oxidation of guanine and adenine in showing lower anodic peak overpotentials (of 0.625 and 0.929 V, respectively) and increased anodic peak currents. The effective surface area of the modified GCE is about 21.5 times larger than that of the bare GCE. The electron transfer coefficient (alpha) and the electron transfer number (n) were calculated to be 2 and 0.60 for guanine, and 2 and 0.64 for adenine, respectively. Linear relationships between peak current and the concentrations were obtained in the range from 0.015 to 430 mu M (for guanine) and 0.015 to 390 mu M (for adenine). The detection limits are 10 nM and 12 nM (at a signal-to-noise ratio of 3), respectively. The modified GCE can well distinguish between guanine and adenine in mixed solutions, has fast response, a low detection limit, good reproducibility, and high stability.