Ratiometric fluorescence detection of Cu2+ based on carbon dots/bovine serum albumin-Au nanoclusters.

A ratiometric fluorescence sensor for Cu2+ detection was developed by employing carbon dots (CDs) as the reference fluorophore, and bovine serum albumin (BSA)-Au nanoclusters (AuNCs) both as specific recognition element and as response signal. The CDs were prepared by heating an acetic acid solution of chitosan at 180°C. The proposed nanoprobe was prepared by simply mixing the CDs and BSA-AuNCs. Here, the CDs were associated with BSA-AuNCs to form CDs/BSA-AuNCs nanoprobes based on electrostatic interaction and hydrogen bonds. In the hybrid fluorescent CDs/BSA-AuNCs nanoprobe, the emission of BSA-AuNCs at 640 nm was quenched by Cu2+, whereas the emission of CDs at 424 nm was maintained. The fluorescence changes of I640/I424 had good linearity with Cu2+ concentration in the range 1.5-600 nM, and the detection limit of the nanoprobe was 0.5 nM for Cu2+ detection, almost 4 × 104 times lower than the maximum allowable amount of Cu2+ in drinking water. The proposed method for detecting Cu2+ also had high selectivity and feasibility.