Synthesis of functional SiO2-coated graphene oxide nanosheets decorated with Ag nanoparticles for H2O2 and glucose detection

In this paper, we report on the first preparation of well-defined SiO2-coated graphene oxide (GO) nanosheets (SiO2/GO) without prior GO functionalization by combining sonication with sol–gel technique. The functional SiO2/GO nanocomposites (F-SiO2/GO) obtained by surface functionalization with NH2 group were subsequently employed as a support for loading Ag nanoparticles (AgNPs) to synthesize AgNP-decorated F-SiO2/GO nanosheets (AgNP/F-SiO2/GO) by two different routes: (1) direct adsorption of preformed, negatively charged AgNPs; (2) in situ chemical reduction of silver salts. The morphologies of these nanocomposites were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It is found that the resultant AgNP/F-SiO2/GO exhibits remarkable catalytic performance for H2O2 reduction. This H2O2 sensor has a fast amperometric response time of less than 2 s. The linear range is estimated to be from 1 × 10−4 M to 0.26 M (r = 0.998) and the detection limit is estimated to be 4 × 10−6 M at a signal-to-noise ratio of 3, respectively. We also fabricated a glucose biosensor by immobilizing glucose oxidase (GOD) into AgNP/F-SiO2/GO nanocomposite-modified glassy carbon electrode (GCE) for glucose detection. Our study demonstrates that the resultant glucose biosensor can be used for the glucose detection in human blood serum.

► Well-defined SiO2-coated graphene oxide nanosheets are prepared. ► F-SiO2/GO nanosheets are obtained by surface functionalization with NH2 group. ► F-SiO2/GO nanosheets decorated with Ag nanoparticles by two different routes. ► They show remarkable catalytic performance toward H2O2 reduction. ► They can be used for glucose detection in human blood serum.