Ratiometric fluorescence detection of Cd2+based on N, S co-doped carbon quantum dots/Au nanoclusters

A new enhanced fluorescent (FL) ratio probe for Cd2+ detection was developed. The gold nanoclusters (AuNCs) with red FL were used as internal reference FL molecules, and the nitrogen and sulfur co-doped carbon quantum dots (N,S-CDs) with blue FL were used as analysis signal molecules. The FRET effect between AuNCs and N,S-CDs result in the FL quenching. The added Cd2+ interacts with AuNCs to form complexes, and interacts with the oxygen atoms in the hydroxyl and carboxyl groups of N,S-CDs to form a stable complex that made N,S-CDs/ AuNCs aggregate and resulted in the FL enhancement. The FL intensities of N,S-CDs (F435) and AuNCs (F630) increased to different degrees after Cd2+ added. The ratio of FL intensity F435/F630 exhibited a good linear relationship with Cd2+ concentration in the range of 0-2.1 mu M, and the detection limit in tap water was calculated to be 62 nM. The reliability of the prepared FL ratio probe was also demonstrated in actual water samples.