Synergy of CO2-response and aggregation induced emission in a small molecule: renewable liquid and solid CO2 chemosensors with high sensitivity and visibility

Abstract

A tetraphenylethylene (TPE) derivative (N,N-dimethyl-N′-(4-(1,2,2-triphenylvinyl)phenyl)acetimidamide, TPE-amidine) was designed and synthesized, and used to prepare visible CO₂ chemosensors, TPE-amidine-L (liquid) and TPE-amidine-S (solid). The hydrophilicity of TPE-amidine thoroughly changed because of the unique reversible reaction between the amidine group and CO₂, which controlled the molecular aggregation extent in water by CO₂. Combining with the well-known aggregate-induced emission effect, the highly selective CO₂ chemosensor TPE-amidine-L was developed, which has the lowest CO₂ detection limit of 24.6 ppm compared with other reported CO₂ chemosensors, and can be regenerated within 10 s by adding triethylamine. With the aim of being safer and more convenient to use, a polyacrylamide hydrogel containing TPE-amidine was prepared as a renewable CO₂ sensing “tape” (TPE-amidine-S). The flexibility, adhesivity, CO₂ sensitivity and reversibility of the “tape” is systematically investigated, showing great potential for “on-site” and “real-time” CO₂ detection in practical applications.