Rational Design of a Peptide‐Based Fluorescent Probe for Selective Recognition of Ag⁺ and Cu²⁺ Ions and Its Multifunctional Applications

Herein, a new large Stokes shift fluorescent probe DGCA based on dansyl group modified tripeptide molecule (Gly–Cys–Ala–NH 2 ) was successfully synthesized. DGCA acts as a promising probe for simultaneous detection of Ag + and Cu 2+ based on different response modes, which displayed fluorescence enhancement by Ag + and fluorescence quenching by Cu 2+ in 100% aqueous solution. In addition, DGCA exhibited high sensitivity recognition of Ag + and Cu 2+ , with the limits of detections (LODs) being 7.4 nM and 5.9 nM, respectively. Furthermore, the stoichiometry between DGCA and Ag + /Cu 2+ was 1:1 by means of fluorescence titration, Job's plot, electro‐spray ionization high‐resolution mass spectrometry (ESI‐HRMS) and theoretical calculation. The fluorescence changes of DGCA upon the addition of Ag + and Cu 2+ were applied as an ultrasensitive logic gate at the molecular level. Due to low toxicity and good permeability, DGCA was successfully used for bioimaging Ag + and Cu 2+ in living cells and zebrafish larvae. Moreover, it was also demonstrated that DGCA was suitable for the simultaneous detection of Ag + and Cu 2+ in real samples. More importantly, the smartphone App with RGB Color Picker was employed to analyze the concentration of Ag + and Cu 2+ with satisfactory results.