An azothiazole probe as a multianalyte colorimetric chemosensor for urea and biologically significant amines†

We report an azothiazole-based probe as a chemosensor for urea with a LOD of 45 μM. The underlying sensing principle is an instantaneous color change associated with the complex forming between the probe and ammonia, a hydrolysis product of urea catalyzed by the enzyme urease. In addition, the probe has a broad scope in sensing biologically significant amines such as arginine and lysine across a wide range of pH (4 to 8). Through extensive spectroscopic and computational studies in conjunction with control experiments, the importance of H-bonding in the sensing mechanism has been unraveled, revealing the stoichiometry, binding constant and LOD of these analytes with the probe. Indeed, the two individual amino acids can be distinguished by the spectral changes associated with UV-vis spectroscopy or by contrasting color diffusion under agarose gel conditions. Moreover, the probe shows a broad scope in detecting a range of aliphatic primary and secondary amines, including cyclic amines. The utility of the probe has also been demonstrated by using it for sensing urea in urine samples. These attributes make this probe a cost-effective, reusable and versatile chemosensor with ease of handling for sensing multianalytes by varying the conditions and detection modes.