Non-enzymatic hydrogen peroxide sensor based on graphene quantum dots-chitosan/methylene blue hybrid nanostructures

•A selective and sensitive non-enzymatic electrochemical biosensor based on GQDs-CS/MB nanocomposites was developed for the detection of hydrogen peroxide.•The fabricated sensor has good selectivity, fast amperometric sensing, wide linear range low detection limit, excellent stability as well as biocompatibility and good reproducibility.•GQDs-CS/MB/GCE successfully analyzed H2O2 in food and water samples without any interference from coexisting material.•Our proposed sensor may be used as a promising platform to design and construct a low-cost portable kit for the detection of H2O2 in the future.

Graphene quantum dots (GQDs) functionalized with chitosan (GQDs-CS) were used for the first time as a suitable nanostructured sensing film for efficient immobilization of methylene blue (MB) through amino-hydroxyl reaction to prepare a novel non-enzymatic hydrogen peroxide sensor using a glassy carbon electrode (GCE). The synthesized hybrid nanostructures were characterized by X-ray diffraction, field emission scanning electron microscopy, cyclic voltammetry, FT-IR, UV-vis, photoluminescence, and energy dispersive X-ray spectroscopy techniques. Cyclic voltammograms showed that the GQDs-CS/MB/GCE exhibited a significant electrocatalytic activity for the reduction of H2O2. The calculated kcat is 4.45 × 104 cm3mol−1s−1. The calibration graph for H2O2 constructed by amperometry (−0.6 V vs. SCE) at the modified electrode showed two different linear ranges (1.0 × 10−6-2.9 × 10−3 M and 2.9-11.78 mM) with a sensitivity of 10.115 μA/mM for the lower linear range and a calculated detection limit of 0.7 μM (S/N = 3). The response time of the sensor for H2O2 detection was 3s. The electrochemical response of GQDs-CS/MB/GCE is not influenced by potential interferents (ascorbic and uric acids, dopamine, caffeine, glucose, and various inorganic salts). This modified electrode exhibited suitability for the non-enzymatic H2O2 sensing in food and water samples.

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