Silver ions enhanced AuNCs fluorescence as a turn-off nanoprobe for ultrasensitive detection of iodide

Fluorescence nanoprobes are frequently employed to construct sensitive biosensors via turn-on and turn-off strategy. In this paper, a novel strategy for ultrasensitive detection of iodide was firstly constructed based on Ag⁺ regulated photoluminescence enhancement of gold nanoclusters (AuNCs) as a turn-off nanoplatform. In the presence of Ag⁺, the fluorescence (FL) intensity of AuNCs can be enhanced obviously. When adding iodide ions (I^-) in the Ag⁺-AuNCs, Ag⁺ can be pulled down from AuNCs and results in quenching of the fluorescent effectively owing to the combination between Ag⁺ and I^-. Compared with that of I^- directly reaction with AuNCs, the introducing of Ag⁺ shows improved quenching efficiency from 32% to 66% since I^- can react with Ag⁺ as well as AuNCs. Therefore, the platform could be applied to assay Ag⁺ and I^-, on the basis of the FL enhancement and the further FL quenching. The detection ranges and detection limits were 0.2-12μM and 0.06μM for Ag⁺, 0.001-6μM and 0.3nM for I^-, respectively. The new sensing method based on ion regulation to enhance the detection sensitivity can extend to the appliance of other fluorescent materials in biosensing and biomedical field.