Colorimetric detection of hydrogen peroxide and lactate based on the etching of the carbon based Au-Ag bimetallic nanocomposite synthesized by carbon dots as the reductant and stabilizer

•Carbon-based AuAg bimetallic nanocomposite was synthesized using carbon dots.•The as synthesized Au-Ag/C NC exhibits good optic response toward H2O2.•The SPR absorbance of Au-Ag declined and red-shifted with the color change.•A simple colorimetric and UV strategy for sensitive detection of H2O2 is proposed.•This colorimetric strategy can also be applied in detection of lactate by naked eye.

In this report, carbon-based gold core silver shell Au-Ag bimetallic nanocomposite (Au-Ag/C NC) was synthesized using carbon dots (C-dots) as the reductant and stabilizer by a facile green sequential reduction approach. The structure and morphology of the nanocomposite are characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The as synthesized Au-Ag/C NC exhibits good optic response toward hydrogen peroxide (H2O2) without adding any other chromogenic agents. The characteristic surface plasmon resonance (SPR) absorbance peak of Au-Ag/C NC declined and red-shifted with the solution color changing from reddish orange to light pink when adding H2O2 owing to the etching effect of H2O2 towards Ag. Thus, a simple colorimetric and UV strategy for sensitive detection of H2O2 is proposed. It provides the wide linear range for detection of H2O2 from 0.8-90 μM and 90-500 μM, and the detection limit was as low as 0.3 μM (S/N = 3). In addition, this colorimetric strategy can also be applied to directly distinguish and detect of lactate by naked eye and UV-Vis. The linear range of colorimetric sensing towards lactate was 0.1-22 μM and 22-220 μM, which was successfully applied in the analysis of lactate in human serum.

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