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

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Based on the reducing property of graphene dots, we developed a facile strategy to synthesize well-stable gra- phene 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 photo- electron 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 para- magnetic resonance (ESR) suggest that the catalyse-mimic activity of the GQD@AuNP like HRP and effectively catalyzed the decomposition of H2O2 intoOH 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 condi- tions, the proposed method allowed the detection of glucose in the range of 2.0×l0