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.