Urea-Based Polyphenol Receptor Demonstrate Colorimetric and Fluorometric Detection of Cyanide in Real-life Applications

Abstract

A strategy for rationalizing a new optical sensor for the selective and sensitive recognition of toxic cyanide (CN−) in an aqueous medium is presented. Two urea-based receptors, NPH and NPN, demonstrate advantageous optical sensing capabilities in the visible spectral range, characterized by a redshift and increased fluorescence upon binding to the analyte. The limit of detection (LOD), determined using UV-visible and fluorescence titration experiments, was found to be 0.28 µΜ and 1.36 µΜ, respectively. These values are significantly lower than the maximum concentration set by the World Health Organization (WHO) guideline for cyanide in drinking water, which is 1.9 μmol L−1. A plausible mechanistic study reveals hydrogen bonding interactions followed by deprotonation enhance the extent of intramolecular charge transfer (ICT). This paper explores the practical applications of this system for screening paper strips, testing real-life water samples, and analysing food samples, emphasizing its potential as a cyanide detection chemo-sensor. A DPPH free radical scavenging study also demonstrated that NPH exhibits good antioxidant properties.