An indolium inspired portable colorimetric sensor for cyanide recognition in environmental samples with smartphone integration

Cyanide is a highly hazardous and fast-acting blood agent widely used in various industries, making its monitoring crucial due to its severe impact on living organisms. Considering this, we had developed a novel indolium based low-cost and portable sensor for the colorimetric and fluorogenic detection of cyanide ions. The probe displayed a distinct visual color change and selectively exhibits a fluorogenic "turn-off" response to cyanide ions in pure aqueous medium. The chemodosimetric-approach-based detection of cyanide ions has been confirmed using ¹H NMR titration and DFT calculations. The presence of competing anions has minimal or no impact on the cyanide recognition process. The probe displayed an excellent detection limit as low as 3.78 nM with a response time of 5 s. The aqueous phase and optimum pH workability are some of the promising features of the developed probe. Additionally, a visual colorimetric strip based test was also developed using probe impregnated filter paper strips, which displayed a visual color change from red to colourless upon cyanide exposure. In addition to this, these test strips also showed excellent selectivity for cyanide ions, with no interference from fluoride or acetate ions. Furthermore, a smartphone-based protocol was developed to record the color change, demonstrating significant potential for cyanide detection without using sophisticated instrumentation. The formulation of the probe into an INHIBIT logic gate for facilitating cyanide recognition using electronic devices is one of the important applications.