Construction\nof a Long-Range Quantitative Fluorescence\nSensor for Multiple Amine Vapors by π···π\nAggregates of Carborane

The\nexploitation of small molecules as fluorescence sensors\nrepresents\na minimalistic solution toward the sensing of hazardous volatile organic\ncompounds (VOCs). Compared with the conventional aggregation-induced\nemitting sensors, the carborane (Cb)-based sensors have exhibited\nmultiple advantages and improved quantitative fluorescence (QF) sensing\nabilities toward the gaseous VOCs. However, in the current Cb-based\nsensors, the localization of a single responsive site toward VOCs\nremains less focused, which results in a bias in the trace detection\nand short-range testing windows. In this work, we synthesized two\npyrene-alkynylated carboranes (<b>Py-1</b> and <b>Py-2</b>) and investigated their photophysical properties in different cases.\nWe found that <b>Py-1</b> and <b>Py-2</b> in the films\nwere consistently self-assembled through π···π\naggregation of pyrenylethynyl moieties. Theoretical modeling showed\nthat the highly emissive π···π aggregates\nwere thermodynamically stable and their responsive sites toward VOCs\nwere localized on the electron-poor phenyl or fluorenyl groups. As\na result, the <b>Py-1</b> and <b>Py-2</b> films showed\nremarkable emission-off sensibilities toward NEt<sub>3</sub> vapors\nvia a major route of photoinduced electron transfer. The optimized\nQF sensor <b>Py-2</b> showed linear emission-off response toward\nthree types of static amine vapors in long concentration ranges (1.78–90\ng/m<sup>3</sup> at most), and the limit of detection could be lowered\nto 99 mg/m<sup>3</sup> in the in situ sensing.