Aggregation-induced emission: New emerging fluorophores for environmental sensing

Abstract

PMMA films containing tetraphenylethylene (TPE) derivatives as red-emissive AIE fluorophores (AIEgen) were demonstrated to be sensitive to both volatile organic compounds (VOCs) and thermal stress. Notably, a novel AIE fluorophore (TPE_RED) was synthesized and used as the initiator to prepare red-emitting poly(methyl methacrylate) polymers (PMMA_TPE_RED1.5) via atom transfer radical polymerization (ATRP). The sensing performances of the spin-coated films (thickness of 2 μm) demonstrated significant vapochromism when exposed to VOCs characterized by high vapour pressure and favourable interaction with the polymer matrix. It was worth noting that PMMA_TPE_RED1.5 displayed substantial vapochromism already at concentration of CHCl3 vapours of 40 ppm, which is about four times smaller than those ever registered in our laboratory with the same apparatus. This threshold was even more decreased in the case of PMMA films containing the TPE_RED physically mixed or another TPE-based derivative already tested in literature, i.e., the barbituric acid-functionalized tetraphenylethene derivative (TPE-HPh-Bar). PMMA films containing TPE_RED AIEgen resulted also sensitive to temperature variations showing an evident thermochromic response close to the glass transition temperature of the polymer matrix.