Highly selective thiazole-appended “switch off” fluorogenic sensor with a detection level of nM for Cu2+: DFT calculations and practically applications

Several precedents demonstrate that fluorogenic sensors are promising candidates for the recognition and reasonable control of metal ions like Cu2+ in the environment because of real-time monitoring, abundant acquirable signals and its facile operation. Therefore, a new benzothiazole-based colorimetric and fluorogenic sensor, 4-(benzo[d]thiazol-2-yl)-2-(((4-(phenylamino)phenyl)imino)methyl)phenol (TAPOH), has been constructed as a sensing material for Cu2+ in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) and acetonitrile (ACN) (v:v, 3:7, pH:7) media. TAPOH could specifically recognize and rapidly respond to Cu2+ during 0.5 min. The emission intensity of the TAPOH quenched with the adding of Cu2+ (0–20.0 eqv), showing a fairly low LOD of 2.23 nM. The reaction mechanism of the TAPOH-Cu2+ was fully characterized through MALDI–TOF MS techniques and then supported by density functional theory (DFT) computations. The binding stoichiometry for TAPOH-Cu2+ was confirmed as 2:1 and the possible mechanism for TAPOH-Cu2+ was suggested depended on the chelation-enhanced fluorescence quenching (CHEQ) of the heavy atom effect of Cu2+. Additionally, the TAPOH coated silica plates were successfully utilized for the sensing of Cu2+. All outcomes demonstrated that TAPOH could conveniently be employed for tracking Cu2+ in solutions.