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

A ratiometric fluorescence sensor for Cu 2+ 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 Cu 2+ , whereas the emission of CDs at 424 nm was maintained. The fluorescence changes of I 640 / I 424 had good linearity with Cu 2+ concentration in the range 1.5–600 nM, and the detection limit of the nanoprobe was 0.5 nM for Cu 2+ detection, almost 4 × 10 4 times lower than the maximum allowable amount of Cu 2+ in drinking water. The proposed method for detecting Cu 2+ also had high selectivity and feasibility.