“…During the last few years, a number of colorimetric anion sensors have been developed using urea, thiourea, amide and pyrrole based binding units. Most of the receptors sense different anions such as fluoride, acetate, nitrate, dihydrogen phosphate and hydroxyl group [6][7][8][9][10][11][12]. Cyanide is one of the most toxic anion, harmful to the environment.…”