Colorimetric sensing of chromium(VI) ions in aqueous solution based on the leaching of protein-stabled gold nanoparticles

Herein, we developed a simple, sensitive and non-aggregation-based method for the selective colorimetric detection of chromium(VI) ions (Cr(VI)) in an aqueous solution. In the presence of hydrobromic acid (HBr), bovine serum albumin stable gold nanoparticles (BSA-Au NPs) were gradually dissolved by Cr(VI) in the etching process of gold. The leaching of the BSA-Au NPs results in a rapid and remarkable damping of the surface plasmon resonance (SPR) and hence induces a visible color change. This colorimetric strategy based on the etching process of gold provided a highly sensitive and selective detection method toward Cr(VI). Under optimal conditions, the amount-dependent colorimetric response was linearly correlated with Cr(VI) concentrations ranging from 0.15 μM to 50.0 μM, with a detection limit down to 120 nM measured as 3δ. Moreover, the developed cost-effective probe was successfully applied to real river samples, which demonstrated its potential for field applications.