A rapid colorimetric detection method of trace Cr (VI) based on the redox etching of Agcore-Aushell nanoparticles at room temperature

► Agcore-Aushell nanoparticles are facilely synthesized via a two-step reaction. ► A sensor with Agcore-Aushell nanoparticles was designed for the detection of Cr (VI). ► The method for the detection of Cr (VI) can be performed in water with high sensitivity and selectivity.