Multi-Stimuli-Responsive Amphiphilic Pyridinium Salt and Its Application in the Visualization of Level 3 Details in Latent Fingerprints.

Abstract

Organic luminescent materials that can simultaneously achieve multimode mechanochromism and its water-vapor-induced recovery are desirable for practical applications but rarely reported. Herein, an amphiphilic compound, 4-(9H-carbazol-9-yl)-1-(2-hydroxyethyl)pyridin-1-ium bromide (CPAB), was designed by integrating a lipophilic aromatic unit and hydrophilic end in the molecular architecture. Self-recovered mechanochromism from brown to cyan was observed upon mechanical grinding in air. Comprehensive research by X-ray diffraction, infrared spectroscopy, and single-crystal analysis revealed that the photoluminescence switch originated from the variation in intermolecular hydrogen bonds and molecular packing mode. The amphiphilic nature of CPAB allowed water molecules to enter the crystalline lattice, forming two polymorphs of the crystalline phase, namely CPAB-D and CPAB-W. The hydrosoluble CPAB exhibited excellent capability in probing the level 3 details of fingerprints because its lipophilic part could target the fatty acid residues of fingerprints, leading to strong aggregation-induced fluorescence. The research may inspire the design of latent fingerprint developers and application in forensics/anti-counterfeiting. This article is protected by copyright. All rights reserved.