Cu²⁺-mediated fluorescence switching of gold nanoclusters for the selective detection of clioquinol

It is of great significance to sense clioquinol (CQ) in a simple and fast way because of its potential application in the treatment of neurodegenerative diseases. In this contribution, we proposed a Cu²⁺-mediated fluorescence switchable strategy to detect CQ by taking bovine serum albumin (BSA) protected gold nanoclusters (AuNCs) as probes. It was found that the strong red fluorescence of BSA-protected AuNCs at 610 nm could be effectively quenched by Cu²⁺ (off state) and reversibly recovered by CQ (on state) owing to the specific coordination of CQ and Cu²⁺. Under the optimal conditions, there was a good linear relationship between the off–on efficiency (E_off–on) and the amount of CQ in the range of 1–12 μM (R² = 0.9902), with a detection limit of 0.63 μM (3σ). The “turn off–on” mode and the fast and unique complexation of CQ and Cu²⁺ endow AuNCs with high specificity for CQ sensing. The proposed strategy is label-free, fast and selective, which is applicable to the analysis of CQ in cream with satisfactory results.