Synergy of CO 2 -response and aggregation induced emission in a small molecule: renewable liquid and solid CO 2 chemosensors with high sensitivity and visibility.

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 CO ₂ 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 CO ₂ , which controlled the molecular aggregation extent in water by CO ₂ . Combining with the well-known aggregate-induced emission effect, the highly selective CO ₂ chemosensor TPE-amidine-L was developed, which has the lowest CO ₂ detection limit of 24.6 ppm compared with other reported CO ₂ 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 CO ₂ sensing "tape" (TPE-amidine-S). The flexibility, adhesivity, CO ₂ sensitivity and reversibility of the "tape" is systematically investigated, showing great potential for "on-site" and "real-time" CO ₂ detection in practical applications.