Visualization of latent fingerprints using an AIE-active unsymmetrical azine: 2-Naphthol-pyrrole acrylate conjugate and its fluorescent sensing of Cu2+ and S2− ions, smartphone and logic gate applications

Abstract

A novel, AIE-active unsymmetrical azine-based probe LH2 was designed and developed by simple condensation of ethyl-α-cyano-5-formyl-2-pyrroleacrylate and 1-(hydrazonomethyl)naphthalene-2-ol. The synthesized probe LH2 was characterized by NMR and mass spectrometric methods. Aggregation-induced emission (AIE) behavior of azine derivative, LH2 was examined in a DMSO-H2O mixture, where the compound displayed a weak emission in pure organic solvent DMSO, and the emission was found to be enhanced at 608 nm on increasing the water fraction owing to the occurrence of restriction of intramolecular rotation (RIR). The aggregation feature of LH2 was supported by DLS and FE-SEM studies. Further, the practical application of aggregates was established by imaging latent fingerprints (LFPs) over a TLC glass slide and other platofrms. In addition, the probe LH2 could selectively detect Cu2+ ions colorimetrically and fluorometrically in DMSO: H2O mixture over the other metal ions. More significantly, the naked eye-detectable color change of LH2 has been fruitfully integrated with an RGB color value app to make it suitable for easy on-site and real-time detection of Cu2+ ions. The LH2-Cu2+ ensemble displayed high selectivity towards S2− ion over other anions via displacement approach and such reversible On-Off-On emission characteristics were utilized for the construction of the IMPLICATION logic gate.