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

Abstract

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 µM, 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.