AIE-Based Benzothiophene Derivatives as Efficient Latent Fingerprint Detectors

In this work, a series of benzothiophene compounds containing a cyanoacrylate motif was designed and synthesised. A complete physicochemical characterisation was then performed. Optical and electrochemical properties, as well as aggregation-induced emission, were investigated. The analysis was supplemented with theoretical DFT calculations of band gaps, HOMO levels, and LUMO levels. The aggregation-induced emission of the compounds was studied in various mixtures of MeCN, DMF, THF, DMSO, etc. (good solvents) and alcohols, water, and hexane (poor solvents), at varying water contents ranging from 0% to 90%. It was demonstrated that the differences in the physicochemical properties of the obtained compounds due to the length of the alkyl chain in the ester group were not significant for their solutions in good solvents. The opposite situation is observed for the AIE phenomenon (aggregation-enhanced emission), where the length of the alkyl chain in the ester group significantly affected the results. The investigated derivatives were tested for their potential use in latent fingerprint visualisation and material marking.