Azobenzene–Hemicyanine Conjugated Polymeric Chemosensor for the Rapid and Selective Detection of Cyanide in Pure Aqueous Media

Abstract

ABSTRACTA water‐soluble polymeric probe was designed and synthesized that can be used for the colorimetric selective detection of cyanide ions in pure aqueous media. In particular, P1, a water‐soluble random terpolymer (P1) of N,N′‐dimethylacrylamide, 2‐((E)‐4‐((E)‐(4‐((2‐(acryloyloxy)ethyl)(methyl)amino)phenyl)diazenyl)styryl)‐1,3,3‐trimethyl‐3H‐indol‐1‐ium (M1), and N‐(4‐benzoylphenyl)acrylamide was synthesized via traditional free‐radical polymerization. Upon the addition of CN− ions to a P1 solution, a macroscopically detectable color change of the solution from brick red to light yellow took place, which was associated with a low limit of analyte detection (1.23 μM). Notably, P1 exhibited excellent selectivity toward CN− over other anions and biothiols, which may be present in the medium. Such highly selective colorimetric response to CN− by P1 originated from the nucleophilic attack of CN− anions onto the electron‐deficient polarized CN bonds of P1's indolium moieties, resulting in the perturbation of the intramolecular charge transfer process occurring within the probe via destruction of the polymer's extended π‐conjugation. P1 was also immobilized on a quartz slide by spin coating and then exposed to ultraviolet light. The resulting polymeric film displayed a rapid response to CN− consisting in a distinct color change, extending the scope of the usefulness of P1 as a cyanide‐ion probe beyond the solution phase. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 124–131