Colorimetric detection of Cr6+ ions based on surface plasma resonance using the catalytic etching of gold nano-double cone @ silver nanorods

Hexavalent chromium ion (Cr 6+ ) is highly toxic to human health and environment. Herein, high-performance detection of Cr 6+ is of great import. In this study, a rapid and sensitive multicolor colorimetric method for detection of Cr 6+ in aqueous solution was established on the basis of Cr 6+ etching of gold nano-double cone@silver nanorods (Au NDC@Ag NRs). Au NDC@Ag NRs was synthesized by a modified seed-mediated growth method. The catalytic etching induced by Cr 6+ changed the morphology of Au NDC@Ag NRs, leading to the attenuation of surface plasma resonance (SPR) and the redshift of absorption spectra . Meanwhile, Au NDC@Ag NRs exhibits obvious color changes from orange to pink, to purple, and finally becomes colorless with the increasing concentrations of Cr 6+ . With such a design, naked-eye detection of Cr 6+ was realized with high sensitivity. The proposed multicolor sensing method showed a good linearity between the redshift change of absorption peak (△λ) and the concentrations of Cr 6+ in the range from 2.5 to 40 μM. The limit of detection (LOD) was calculated as 1.69 μM in aqueous solution. In addition, successful detection of Cr 6+ in tap water and Yangtze River water, indicating the real applications of Au NDC@Ag NRs probe in monitoring Cr 6+ in environment.