Peptide-based fluorescent and colorimetric dual-functional probe for visual detection of Cu2+, Hg2+and S2-in 100% aqueous media, living cells and paper test strips

In this study, a novel peptide-based fluorescent and colorimetric dual-functional probe (FAHK) was designed and synthesized by simulating the structure of copper peptide. FAHK exhibited high selectivity and rapid response to Cu2+ and Hg2+ with two non-fluorescence ensembles FAHK-Cu2+ and FAHK-Hg2+ formation by the 2:1 coordination mode, and the limits of detection for Cu2+ and Hg2+ were 37.1 nM and 20.8 nM, respectively. FAHK showed a naked eye colorimetric response for Cu2+ and Hg2+ in an aqueous solutions under visible light. As two new promising cascade probes, FAHK-Cu2+ and FAHK-Hg2+ ensemble were used for sequential selective recognition of S2- according to the displacement approach with fluorescence "turn-on" response and colorimetric change, and the limit of detection were 0.27 mu M (FAHK-Cu2+ ensemble) and 0.12 mu M (FAHK-Hg2+ ensemble) for S2-, which were well below the safety level the H2S standard in drinking waters (14.8 mu M, WHO guidelines). What' more, in view of low toxicity and biocompatibility, the potential application of FAHK in biological systems was demonstrated via living cells imaging. More importantly, FAHK could also be made into the paper test strips for visual detection of Cu2+, Hg2+ and S2- with the naked eye under 365 nm UV light and visible light, which suggested that better portability and operation simplicity that is favourable for on-site analysis.