Efficient colorimetric detection of cyanide ions using hemicyanine-based polymeric probes with detection-induced self-assembly in water

The design and synthesis of hemicyanine-based water-soluble polymeric probes for colorimetric detection of CN− ions, which is accompanied by detection-induced self-assembly in aqueous media, is described. Random and block copolymers of N,N-dimethylacrylamide (DMA) and 3-vinylbenzaldehyde (VBA) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. After polymerization, the aldehyde groups of these copolymers were converted to hemicyanine groups by reaction with 1,2,3,3-tetramethyl-3H-indolium iodide, leading to the formation of hemicyanine-containing random and block copolymeric probes, RP and BP, respectively. These probes could efficiently detect CN− ions in aqueous media with a concomitant color change from yellow to colorless. Moreover, BP underwent morphological changes upon detection, with its molecular structure changing from unimers to micelles, indicating the occurrence of CN− detection-induced self-assembly. The general strategy presented in this work could be further extended to target-driven assemblies of block copolymer platforms for detection of other analytes.