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.