Rational design of dual-functional peptide-based chemosensor for sequential detection of Ag+ (AgNPs) and S2− ions by fluorescent and colorimetric changes and its application in live cells, real water samples and test strips

Abstract

A novel bifunctional chemosensor L with excellent fluorescent group FITC labelled at tetrapeptide (CysProGlyHis-NH2) was designed and developed. L exhibited fluorescent quenching response and unique visual color change for Ag+ and AgNPs in aqueous solution. The stoichiometry between L and Ag+ was confirmed to be 1:1 based on fluorescent titration, Job's plot, ESI-HRMS and theoretical calculation studies. In particular, the limit of detection (LOD) of L for the detection of Ag+ and AgNPs were calculated as 3.35 nM and 4.57 nM, respectively. In addition, the L-Ag complex as a new relay chemosensor could be highly selective detection of S2−via obvious color and fluorescence changes, which could be monitored by the naked eye. The LOD for S2− was as low as to be 28.17 nM with high sensitivity. Furthermore, L indicated a rapid response (within 50 s), exciting circularity (more than 10 times) and wide pH response range (6 ∼ 12). Moreover, in view of excellent stability, low cytotoxicity and biocompatibility, we further successfully applied L for Ag+, AgNPs and S2− detection and imaging in living cells, real water samples and test strips.