Fluorescent litmus film for detecting acid vapors: free-standing and robust AIE sensing film fabricated by photopolymerization of self-assembled hierarchical triphenylamine-based gelators

In response to human damage caused by harmful vapors emitted throughout the industry, the detection of toxic vapors such as acid vapors is urgently required. Recognizing acid vapor leaks is particularly difficult due to their characteristics such as colorlessness, high diffusion coefficient, and high toxicity. Therefore, there is a great demand for the development of a detection litmus film with excellent resistance to acids as well as visualization of acid vapor leaks with a fast response and recovery rate. To meet these requirements, a programmed fluorophore (TPA-3MA) gelator was newly synthesized by chemically connecting a light-emissive triphenylamine (TPA) core and photopolymerizable methacrylate-functionalized flexible alkyl chains. Fluorescent litmus film with high mechanical stability is fabricated by the gelation of TPA-3MA (2 wt%) in hexyl methacrylate (HMA) monomer solvent and the subsequent photopolymerization. The free-standing and robust litmus film consisting of self-assembled TPA-3MA nanofibers shows excellent acid detection performance with long-term stability. This study may provide a versatile platform for the development of security labels and chemical sensors.