Formaldehyde sensing of polymer films based on fluorescence and circularly polarized luminescence

Abstract

Formaldehyde (FA) is a common volatile organic compound widely present in furniture, the chemical industry, and building materials. Since excess FA poses significant threat to human health, developing simple and effective methods for its detection and removal is of crucial importance. However, most previously reported FA fluorescent probes rely on solution-based systems, requiring homogeneous dissolution of samples. In contrast, using solid substrates for FA sensing provides compelling advantages, including low cost, ease of use, and straightforward operation. In this work, by embedding an FA-probing molecule (FAP) into an EVA matrix, an FAP-EVA film capable of turn-on fluorescence sensing for FA was prepared. Subsequently, the FAP-EVA layer was combined with a cholesteric liquid crystal polymer network (CLCN) film to fabricate a composite system. This composite material responded to FA vapor and simultaneously emitted circularly polarized luminescence (CPL) with a high g_lum of up to 0.97. Furthermore, FAP was immobilized in a cholesteric liquid crystal elastomer (CLCE) film by a diffusion method, successfully preparing a single-layer FA detection film. In a fluorescent mode, a patterned CLCE film exhibited a vivid FA-sensing effect. This work not only provides effective FA-sensing approaches based on fluorescence and CPL, but also presents facile and practical methods for the preparation of vapor-responsive polymer films.