Poly(ionic liquid) as an efficient carrier of hydrophobic small-molecule probes for ion detections in pure aqueous environments

Expanding the availability of hydrophobic small-molecule probes in pure aqueous environments is an important issue likely to significantly impact their application prospects in sensing detections. The present work demonstrates for the first time that poly(ionic liquid) (PIL) can serve as a superior carrier, which not only enables hydrophobic small-molecule probes to readily disperse in pure water and but helps maximize their sensing performances. As a proof-of-concept, a hydrophobic rhodamine derivative carried by PIL, P(RhBHSA-co-META), was designed and applied for the colorimetric determination of Cu 2+ and further for CN − in fully aqueous solutions. Due to the positively charged nature of polymeric backbone, the P(RhBHSA-co-META) was highly water-soluble and could avoid non-specific bonding. Moreover, the strong inter- and intra-chain electrostatic repulsions made the P(RhBHSA-co-META) possible to be fully free and highly stretched in water, facilitating the accessibility of receptor binding sites. Excellent sensing performance of P(RhBHSA-co-META) toward Cu 2+ was achieved in terms of high sensitivity, ultrafast color/absorption response, and excellent anti-disturbance ability. Furthermore, the pre-formed P(RhBHSA-co-META)–Cu 2+ complex was also verified to be highly efficient for colorimetric determination of CN − , exhibiting high sensitivity and selectivity. This study provides a simple, effective, and extendable approach for designing water-soluble chemosensors for ion detections and other sensing applications.