Facile Preparation of Graphene Dots Functionalized Au Nanoparticles and Their Application as Peroxidase Mimetics in Glucose Detection

Based on the reducing property of graphene dots, we developed a facile strategy to synthesize well-stable graphene dots functionalized Au nanoparticles (denoted as GQD@AuNP) by one-step process at low temperature without added protecting agent. The prepared GQD@AuNP were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectra. It was found that the as-prepared GQD@AuNP are spherical and monodisperse with an average diameter of ca. 10 nm. Graphene dots not only act as a mild reductant to reduce HAuCl4, but also as a capping agent to endow the GQD@AuNP with good stability in aqueous solvent and monodispersity and restrains the Au crystal growth, making the particles have narrow size distribution. Furthermore, the as-prepared GQD@AuNP showed an excellent intrinsic peroxidese-like activity, which could catalyze oxidization of 3,3',5,5'-tetramethylbiphenyl (TMB) by H2O2 to produce a colour variation. Using TMB as substrate, we systematically studied the effect of a series of conditions, such as temperature and pH, on the catalytic activity of the as-prepared GQD@AuNP. Results of electron paramagnetic resonance (ESR) suggest that the catalyse-mimic activity of the GQD@AuNP like HRP and effectively catalyzed the decomposition of H2O2 into (OH)-O-center dot radicals. On this basis, a highly sensitive and rapid colorimetric and visualization method was developed for glucose in blood samples, when combined with glucose oxidase (GOx). Under optimum conditions, the proposed method allowed the detection of glucose in the range of 2.0X10(-6) to 4.0X10(-5) mol.L-1 with detectable glucose as low as 3.0X10(-7) mol.L-1. Furthermore, another three sugars existing in the human serum, including maltose, fructose and lactose were detected by this method, which indicated the little disturbance by maltose and fructose, while no remarkable signals were observed for the lactose. This proposed method has been successfully applied to detect glucose in serum samples with good accuracy and precision.