Deprotection induced modulation of excited state intramolecular proton transfer for selective detection of perborate and ammonia

Acetate protected Naphthalene Coupled Benzothiazole (NCB) has been designed and synthesized for selective detection of perborate (BO3-) and ammonia (NH3) based on modulation of excited-state intramolecular proton transfer (ESIPT) process by chemodosimetric deacetylation pathway. In presence of nucleophilic species like BO3- and NH3, acetyl group deprotection of NCB resulted ESIPT within the molecule exhibiting a significant enhancement of absorption and emission signals at 425 nm and 472 nm respectively. The emission enhancement of NCB has been observed by 31-folds and 14-folds in presence of BO3-. and NH3 respectively. The selectivity and fast sensitivity of NCB have been shown by the lower detection limit (1.32 mu M for BO3-, 1.74 mu M for NH3 in UV-vis study and 0.60 mu M for BO3- and 4.39 mu M for NH3 in fluorescence study) and fast response (rate constants: 12.36 s(-1) and 5.54 s(-1) for BO3- and NH3 respectively). Analytes induced deacetylation pathway of NCB followed by ESIPT has been clearly demonstrated by theoretical calculation. The test strips based on NCB with BO3- and NH3 are fabricated, which can act as a convenient and efficient test kits for both these analytes. In the practical applications, the sensor NCB can be utilized as low cost food spoilage indicator and soil analysis by fluorometric method.