Pillararene for fluorescence detection of n-alkane vapours

Abstract

It remains a challenge to detect n-alkanes, which contain only C–C and C–H groups. Herein pillararene sensors are developed toward n-alkane vapours. Fluorescence properties involving aggregation-induced emission have been innovatively demonstrated for pillar[5]arene compounds, including dimethoxypillar[5]arene (DMP[5]), difunctionalized (DBP[5] and DAP[5]) and perfunctionalized pillar[5]arene compounds (DEOP[5] and EOP[5]). The longer-wavelength emission at around 450 nm endows pillar[5]arene films with the ability to respond visually to various VOC (volatile organic compound) gases. DMP[5] and DEOP[5] films display fluorescent responses to nitrobenzene with high sensitivities (140 and 50 ppb). Notably, the luminescence of a transparent difunctionalized DBP[5] film displays both significant enhancements in fluorescence intensity and reduction in transparency toward n-alkane vapours (hexane, pentane and heptane) owing to host–guest interactions. The film sensors exhibit good recyclability in VOC sensing. The results highlight an innovative strategy to develop responsive sensors toward alkane vapours that are difficult to detect.