Viscosity-sensitive and AIE-active bimodal fluorescent probe for the selective detection of OCl and Cu: a dual sensing approach DFT and biological studies using green gram seeds.

A novel dual-mode viscosity-sensitive and AIE-active fluorescent chemosensor based on the naphthalene coupled pyrene (NCP) moiety was designed and synthesized for the selective detection of OCl and Cu. In non-viscous media, NCP exhibited weak fluorescence; however, with an increase in viscosity using various proportions of glycerol, the fluorescence intensity was enhanced to 461 nm with a 6-fold increase in fluorescence quantum yields, which could be utilized for the quantitative determination of viscosity. Interestingly, NCP exhibited novel AIE characteristics in terms of size and growth in HO-CHCN mixtures with high water contents and different volume percentage of water, which was investigated using fluorescence, DLS study and SEM analysis. Interestingly, this probe can also be effectively employed as a dual-mode fluorescent probe for light up fluorescent detection of OCl and Cu at different emission wavelengths of 439 nm and 457 nm chemodosimetric and chelation pathways, respectively. The fast-sensing ability of NCP towards OCl was shown by a low detection limit of 0.546 μM and the binding affinity of NCP with Cu was proved by a low detection limit of 3.97 μM and a high binding constant of 1.66 × 10 M. The sensing mechanism of NCP towards OCl and Cu was verified by UV-vis spectroscopy, fluorescence analysis, H-NMR analysis, mass spectroscopy, DFT study and Job plot analysis. For practical applications, the binding of NCP with OCl and Cu was determined using a dipstick method and a cell imaging study in a physiological medium using green gram seeds.