Gold nanoclusters Cys-Au NCs as selective fluorescent probes for “on–off–on” detection of Fe(3+) and ascorbic acid

Gold nanoclusters exhibit attractive properties owing to their excellent biocompatibility and strong photostability in the biomedical domain. In this research, cysteine-protected fluorescent gold nanoclusters (Cys-Au NCs) were synthesized via decomposing Au(i)–thiolate complexes for the detection of Fe(3+) and ascorbic acid in a bidirectional “on–off–on” mode. Meanwhile, the detailed characterization confirmed that the mean particle size of the prepared fluorescent probe was 2.43 nm and showed a fluorescence quantum yield of 3.31%. In addition, our results indicate that the fluorescence probe for ferric ions exhibited a broad detection scope ranging from 0.1 to 2000 μM and excellent selectivity. The as-prepared Cys-Au NCs/Fe(3+) was demonstrated to be an ultrasensitive and selective nanoprobe for the detection of ascorbic acid. This study indicated that the “on–off–on” fluorescent probes Cys-Au NCs held a promising application for the bidirectional detection of Fe(3+) and ascorbic acid. Furthermore, our novel “on–off–on” fluorescent probes provided insight into the rational design of thiolate-protected gold nanoclusters for biochemical analysis of high selectivity and sensitivity.