The detection of copper ions based on photothermal effect of cysteine modified Au nanorods

Abstract

The cysteine (CYS)-stimulated aggregation of Au nanorods (NRs) is used as an auxiliary reporting system for the optical detection of copper ions. CYS-Au NRs show end-to-end and side-by-side assembly at strong acidic and basic condition, and corresponding LSPR peaks shift to red or blue. However, Cu2+ can readily induce the end-to-end assembly of CYS-Au NRs based on the coordination between Cu2+ and CYS at weak acidic condition (pH 5). The assembly of Cu2+-CYS-Au make the decrease of LSPR peak at 800nm and appear a new peak at 1050nm, which reduce their photothermal conversion efficiency under 808nm laser irradiation. The different photothermal conversion efficiency has relation with the temperature change of Au NRs solution. So, a new nanosensor for detecting Cu2+ is developed based on the varied photothermal effect. Different from colorimetric detection for Cu2+, the sensor of photothermal effect is more sensitive to low concentration of Cu2+. It shows high sensitivity and selectivity. Here, the detection limit for Cu2+ is 5nM.