Fabrication of Novel Electrochemical Biosensor Based on Graphene Nanohybrid to Detect H 2 O 2 Released from Living Cells with Ultrahigh Performance.

In this paper, a new class of metal-free nanocarbon catalyst-nitrogen (N) and sulfur (S) codoped graphene quantum dot/graphene (NS-GQD/G) hybrid nanosheets-was designed and synthesized for sensitive detection of hydrogen peroxide (H2 O2 ). NS-GQD/G was prepared through two steps. First, graphene quantum dots (GQDs) were self-assembled on graphene nanoplatelets via hydrothermal treatment to constitute hybrid nanosheets, followed by a thermal annealing procedure using the hybrid nanosheets and thiourea to form the NS-GQD/G hybrid nanosheets. This hybrid material possessed high specific surface area, numerous doping sites and edges, and high electrical conductivity, which leads to ultrahigh performance toward H2 O2 electrocatalysis reduction. Under the optimal experimental conditions, the proposed H2 O2 sensor displayed an extended linear response in the range from 0.4 μM to 33 mM with a low detection limit of 26 nM (S/N = 3). In addition to desirable selectivity, ideal reproducibility, and long-time stability, this H2 O2 sensor exhibited desirable performance in detecting H2 O2 in the human serum samples and that released from Raw 264.7 cells. Therefore, the novel NS-GQD/G nanocomposite was a promising metal-free material in the fields of electrochemical sensing and bioanalysis.