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

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 mu M and 90-500 mu M, and the detection limit was as low as 0.3 mu M (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 mu M and 22-220 mu M, which was successfully applied in the analysis of lactate in human serum. (C) 2016 Elsevier B.V. All rights reserved.