Multi-stimuli responsive 1,8-naphthalimide-based optical materials for dynamic data encryption and real-time acid vapor sensing

Abstract

Recent studies have unveiled the opportunities hidden within boron complexes due to their stimuli-responsive emission and unique photo-physical properties. This paper presents a non-conjugated anhydride-based luminescent boron complex (1), which was investigated for its multi-stimuli responsive characteristics. Complex 1 exhibited excellent reversible sensing of acid vapors, such as HCl and TFA, in both solution and solid states, with detailed analyses conducted using fluorescence, ¹H NMR, and PXRD techniques. It also served as a fluorescence chemosensor for detecting trace amounts of water in DMSO, with color changes and fluorescence intensity shifts primarily attributed to aggregation-induced emission (AIE). The complex's water absorption capacity was evaluated under various environmental conditions to explore its practical applications. Theoretical insight also supported the complex's reversible acid/base-sensing and water-sensing behavior. 1 exhibited mechanochromic luminescence enhancement (MLE) with distinct color changes when ground into powder which is attributed to the disruption of non-covalent interactions. Furthermore, the complex exhibited data encryption and anticounterfeiting properties, exhibiting a different colour upon grinding and exposure to acid/base vapors, which can be potentially used for encoding or protection of sensitive information. Reversible data storage and real-time detection of acid vapors were successfully demonstrated utilizing a PMMA@1 composite film, fabricated with a PMMA polymer matrix.