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

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, Cu 2+ can readily induce the end-to-end assembly of CYS-Au NRs based on the coordination between Cu 2+ and CYS at weak acidic condition (pH 5). The assembly of Cu 2+ -CYS-Au make the decrease of LSPR peak at 800   nm and appear a new peak at 1050   nm, which reduce their photothermal conversion efficiency under 808   nm laser irradiation. The different photothermal conversion efficiency has relation with the temperature change of Au NRs solution. So, a new nanosensor for detecting Cu 2+ is developed based on the varied photothermal effect. Different from colorimetric detection for Cu 2+ , the sensor of photothermal effect is more sensitive to low concentration of Cu 2+ . It shows high sensitivity and selectivity. Here, the detection limit for Cu 2+ is 5   nM.