Development of simple imine based probe for selective fluorescent cyanide sensing with red-emission in solid and solution phases

Abstract

In the present work, an easy to make imine based receptor (3,3′(((5-(tert-butyl)-2-hydroxy-1,3-phenylene)bis(methanylylidene))bis(azanylylidene))bis(2-aminomaleonitrile)) (CNA) has been synthesized in good yield and characterized by spectral methods. CNA showed rapid, selective and sensitive naked-eye dual channel response (colorimetric and fluorogenic) towards cyanide ion. The receptor exhibited instantaneous colour change upon addition of cyanide ion based on deprotonation of phenolic –OH moiety in neat DMSO, 30% aq. DMSO and solid media. Interestingly, CNA showed red-emission (640 nm < λem < 677 nm) upon treatment with cyanide ion in all these media. Limit of detection of CNA for cyanide ion was determined to be 0.5 μM, which is much lower than the permissible limit of cyanide in drinking water as recommended by the World Health Organization. The fabricated cotton swabs and test strips demonstrated excellent selectivity towards cyanide ion in aqueous solution. Further, CNA is suitable for dual channel detection of cyanide ion in food materials. Furthermore, the observable colour change of the probe upon binding with cyanide ion has successfully been integrated with a smartphone Colour Picker app to estimate cyanide ions.