Cytidine-stabilized gold nanocluster as a fluorescence turn-on and turn-off probe for dual functional detection of Ag+ and Hg2+

•Au NCs and AuAg NCs as fluorescent turn-on and turn-off probes were synthesized.•Au NCs recognize silver ions by fluorescence enhancement to form AuAg NCs.•AuAg NCs can be reused to detect Hg2+ based on fluorescence quenching.•The fluorescent nanoprobes are used to monitor environmental water samples.

In this study, we have developed a label-free, dual functional detection strategy for highly selective and sensitive determination of aqueous Ag+ and Hg2+ by using cytidine stabilized Au NCs and AuAg NCs as fluorescent turn-on and turn off probes, respectively. The Au NCs and AuAg NCs showed a remarkably rapid response and high selectivity for Ag+ and Hg2+ over other metal ions, and relevant detection limit of Ag+ and Hg2+ is ca. 10 nM and 30 nM, respectively. Importantly, the fluorescence enhanced Au NCs by doping Ag+ can be conveniently reusable for the detection of Hg2+ based on the corresponding fluorescence quenching. The sensing mechanism was based on the high-affinity metallophilic Hg2+–Ag+ interaction, which effectively quenched the fluorescence of AuAg NCs. Furthermore, these fluorescent nanoprobes could be readily applied to Ag+ and Hg2+ detection in environmental water samples, indicating their possibility to be utilized as a convenient, dual functional, rapid response, and label-free fluorescence sensor for related environmental and health monitoring.

Graphical abstractScheme for formation of cytidine-stabilized Au NCs and used as a fluorescent turn-on and turn-off probe for dual functional detection of Ag+ and Hg2+.Figure optionsDownload full-size imageDownload as PowerPoint slide