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[Display omitted] • The fluorescent probe DSD based on the dipeptide receptor was synthesized. • DSD exhibited fluorescent quenching for Cu2+ and recovered rapidly by adding CN−. • The detection limit of 2.4 nM for Cu2+ and 41.9 nM for CN−. • DSD was successfully applied for detecting and imaging Cu2+ and CN− in live cells. A novel fluorescent probe (DSD) was reasonably designed and synthesized with dansyl-labeled dipeptide (Dan-Ser-Asp-NH 2). DSD featured remarkably large Stokes shift (230 nm) and perfect water solubility, and exhibited high selectivity and rapid recognition toward Cu2+ via fluorescence quenching. The detection limit of DSD for Cu2+ was 2.4 nM, indicated that DSD has excellent sensitivity. In addition, the stoichiometry between DSD and Cu2+ were detected as 1:1 by fluorescence titration, Job's plot and ESI-HRMS data. As designed, DSD -Cu2+ system was able to sequentially detect CN− according to the displacement approach with fluorescence "off–on" response, and the detection limit for CN− was calculated to be 41.9 nM. Specifically, the response time of DSD with Cu2+ and CN− was less than 40 s, which rendered it suitable for real time detection in actual water samples. In addition, with the alternate addition of Cu2+ and CN−, the reversible cycles could be repeated for at least 10 times, indicated that DSD was a promising reversibility probe. DSD showed low toxicity and good biocompatibility, and was successfully applied to detect Cu2+ and CN− in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel peptide fluorescent probe DGGH was synthesized. • DGGH -Cu2+ system showed highly selective and "turn-on" response to S2−. • The detection limit of DGGH -Cu2+ for sensing S2− was calculated to be 13.7 nM. • DGGH -Cu2+ was successfully applied to monitor Cu2+ and S2− in real samples and living cells. We report a new fluorescent probe named DGGH with dansyl-labeled tripeptide (Dan-Gly-Gly-His-NH 2). DGGH showed obvious fluorescence quenching after the addition of Cu2+ ions and a 1:1 ensemble system (DGGH -Cu2+) was formed, the limit of detection was 37.9 nM. As expected, DGGH -Cu2+ ensemble system exhibited high selectivity and rapid response for S2− in 100% aqueous solutions, as a result of the addition of S2− immediately replaced Cu2+ from the DGGH -Cu2+ ensemble system. The limit of detection of the DGGH -Cu2+ ensemble for S2− was determined to be 13.7 nM. In addition, DGGH -Cu2+ has excellent detection performance within a wide pH range of 6 to 12, and its outstanding response time of less than 50s. Furthermore, we demonstrated the usability of the present approach for detecting Cu2+ and S2− in two water samples. What's more, DGGH was successfully applied to monitor Cu2+ and S2− in living LNcap cells based on good cells permeability and low toxicity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new fluorescent probe DAHK was synthesized based on copper peptide backbone. • DAHK could detect Cu2+ in 100 % aqueous medium with obvious fluorescence quenching. • DAHK-Cu2+ ensemble exhibited fluorescent "off–on" response with H 2 S. • DAHK was successfully used to selectively detect Cu2+ and H 2 S in living cells. • DAHK was successfully applied to sensitively detect Cu2+ and H 2 S in test strips. Copper ions (Cu2+) and hydrogen sulfide (H 2 S) detection is of great significance in environmental monitoring and disease screening. Herein, a novel fluorescent probe (DAHK) was rationally designed and easily synthesized based on a copper peptide backbone labelled a dansyl fluorophore. DAHK exhibited large Stokes shift (210 nm), high sensitivity (38.9 nM) and high selectivity response to Cu2+ ions based on obvious fluorescence quenching in HEPES buffer (10.0 mM, pH 7.4) solutions. In addition, the in situ formed DAHK -Cu2+ ensemble was successfully used as a secondary probe for rapidly and sequentially detected H 2 S via fluorescence "off–on" response, and without interference by a range of other anions. The limit of detection (LOD) for 47.3 nM was determined, which was a much lower value than WHO and EPA guidelines (H 2 S) for drinking water. The reversibility of interaction of DAHK with Cu2+ and H 2 S was monitored using fluorescence emission spectra. Cells imaging experiments exhibited that DAHK had good membrane permeability and excellent low toxicity. Moreover, DAHK was successfully made into fluorescent test strips for visual detection and rapid analysis based on the exciting stability and excellent water solubility. [ABSTRACT FROM AUTHOR]