Development of a novel AIE active piperazine appended chemosensor for solvent-regulated selective detection of IIB elements [Zn(ii), Cd(ii), Hg(ii)], Cl− and picric acid via varying emission colors to distinguish one another: environmental and biological applications

Abstract

Piperazine appended Schiff base chemosensor (HL) (Z)-2,4-dibromo-6-(4-(piperazin-1-yl)but-1-en-1-yl)phenol, developed by a simple condensation of 3,5-dibromosalicylaldehyde and 2-aminoethyl piperazine, is successfully utilized to recognize Zn(II) and Cl⁻ ions among several competitive cations and anions in 9 : 1 ethanol–water medium via turn on fluorescence. Interestingly, this chemosensor bears novel aggregation induced emission (AIE) properties in H₂O–ethanol mixtures up to a ratio of 9 : 1, and the results obtained from dynamic light scattering (DLS), scanning electron microscopy (SEM), UV, and fluorescence spectroscopic studies help to confirm the presence of this property. With the help of this AIE activity, this probe has been used for selective detection of Cd (II) and Hg(II) via turn-on and off fluorescence, respectively, in a near aqueous medium. At the same time, in AIE active medium, the chemosensor can recognize picric acid also via turn-off fluorescence. All the sensing phenomena have been spectroscopically handled. In the presence of adenosine triphosphate (ATP)/AgNO₃/Cl⁻, individual detection of the analyte is possible when four aforementioned analytes [Zn(II), Cd(II). Hg(II), Cl⁻] are present together in a solution. The moderately high host–guest binding constant values assure us about the chemosensor-analyte adduct formation, and the chemosensor-analyst binding mechanism is confirmed by IR and mass spectroscopy. The density functional theory (DFT) study gives the optimized structure of probe–analyte complexes. The on-site clear visual detection of the analytes in paper strips, along with AIE property, is shown by the investigated chemosensor. As a practical application, this chemosensor can notably track Zn(II) and Hg(II) in plant cells and HeLa cells, respectively. The detection of Hg(II) and Cd(II) is also possible in real water samples.