Cu enhanced fluorescent Ag nanoclusters with tunable emission from red to yellow and the application for Ag sensing.

In this work, the water-soluble fluorescent Ag nanoclusters (DPA@Ag NCs) were first prepared based on D-Penicillamine (DPA) as a stabilizer, however, the fluorescence quantum yield (QY) of DPA@Ag NCs was very low, then Cu was employed to improve the fluorescence QY and the doped Ag nanoclusters with Cu (DPA@Ag/Cu NCs) were obtained. The study showed that the QY increased fourfold and the emission of nanoclusters changed from red to yellow after addition of Cu. The reasonfor change of fluorescent properties wasattributed to the change of self-assembly structures caused by adding Cu into reaction system, leading to the aggregation-induced emission enhancement (AIEE) effect and enhancing the band gap (Eg) between the HOMO and LUMO in nanoclusters. Subsequently, a fluorescent Ag sensor with high sensitivity and selectivity was established based on the DPA@Ag/Cu NCs as probes in aqueous solution. Experiments showed that the Ag could significantly quench the fluorescence of DPA@Ag/Cu NCs under experimental conditions, and there was a good linear relationship between the fluorescent intensity quenching value and Ag concentration in the range of 0.05-800 μM, and the limit of detection (LOD) was 0.03 μM (3σ/k). Meanwhile, most of common ions had no effect on the experimental results under the same conditions. In addition, the sensor was successfully applied on the detection of Ag in real water samples, and the recovery rate was 80.3-99.0%.