Excited-state AIE material for differential recognition of toxic hair color ingredients: towards functional device applications

Abstract

We designed and synthesized an imino-linked dansyl-based molecule, DHNB, which exhibits interactions with the hair color ingredient p-phenylenediamine (PPD) and its oxidative trimer, Bandrowski's Base (BWB), over other analytes tested. Variable interactions, such as intra- and inter-molecular hydrogen bonding and environment-responsive conformational dynamics, were observed, leading to contrasting responses amongst the most responsive analytes. DHNB exhibits Excited State Intramolecular Proton Transfer (ESIPT)-assisted Aggregation-Induced Emission (AIE) in MeOH : H₂O (10 : 90), which is utilized for the detection of hair color ingredients. The presence of BWB quenches the fluorescence emission of DHNB in MeOH : H₂O (10 : 90) at 497 nm, whereas in the presence of PPD, the emission at 497 nm is quenched, with simultaneous appearance of a new blue shifted band at 402 nm. Importantly, the successful detection of PPD in a commercial hair color sample underscores the practical applicability of DHNB. Furthermore, variations in the charge transport properties of DHNB in MeOH : H₂O (10 : 90) and upon interaction with BWB/PPD were observed via current–voltage (I–V) measurements, suggesting its strong potential as an electrical sensor device.