Viscosity-sensitive and AIE-active bimodal fluorescent probe for the selective detection of OCl− and Cu2+: a dual sensing approach via DFT and biological studies using green gram seeds

Abstract

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 Cu²⁺. 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 H₂O–CH₃CN 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 Cu²⁺ at different emission wavelengths of 439 nm and 457 nm via 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 Cu²⁺ was proved by a low detection limit of 3.97 μM and a high binding constant of 1.66 × 10³ M⁻¹. The sensing mechanism of NCP towards OCl⁻ and Cu²⁺ was verified by UV-vis spectroscopy, fluorescence analysis, ¹H-NMR analysis, mass spectroscopy, DFT study and Job plot analysis. For practical applications, the binding of NCP with OCl⁻ and Cu²⁺ was determined using a dipstick method and a cell imaging study in a physiological medium using green gram seeds.