Fluorescence turn-on strategy based on silver nanoclusters-Cu2+ system for trace detection of quinolones

Herein, utilizing fluorescent Ag nanoclusters (Ag NCs) capped by polyethyleneimine (PEI) with different molecular weights, we constructed a novel Ag NCs-Cu2+ sensing system based on fluorescence turn-on strategy for trace detection of quinolones, including nalidixic acid, cinoxacin, ciprofloxacin/ofloxacin, and moxifloxacin; these were the representatives of four generations of quinolone antibacterial drugs. The fluorescence of Ag NCs could be efficiently quenched by Cu2+, while with the addition of quinolones, the fluorescence of this system recovered rapidly. This protocol exhibited excellent sensitivities to these five quinolones. For instance, the linear ranges were from 1 to 100 nM for nalidixic acid with limit of detection (LOD) 0.47 nM, from 1 to 80 nM for cinoxacin with LOD 0.43 nM, from 0.1 to 120 nM for ciprofloxacin with LOD 38 pM, from 0.1 to 80 nM for ofloxacin with LOD 49 pM, and from 0.1 to 120 nM for moxifloxacin with LOD 48 pM, respectively, revealing that this approach showed low detection limits and wide linear ranges. Benefiting from the high sensitivity, the satisfactory recoveries were obtained for trace detection of quinolones in real samples, such as tablets, human urine and serum.