BITS Faculty Publications
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Item Pyridinium-based schiff-base fluorescent chemosensor for sequential detection of al3+ ions and tnp: applications in cell imaging and latent fingerprint visualization(Wiley, 2024-12) Jha, Prabhat Nath; Khungar, BhartiA fluorescent pyridinium-based chemosensor (E)-1-(2-(3-hydroxy-4-((pyridin-2-ylimino) methyl) phenoxy) ethyl) pyridin-1-ium bromide (BzPySB) was synthesized and characterized using various spectroscopic techniques. The chemosensing potential of BzPySB was explored using UV-vis and fluorescence spectroscopy in the aqueous medium. The turn-on fluorescence behavior was observed for BzPySB in the presence of Al3+, while other metal ions were non-responsive. The B−H and Job′s plot confirmed the 1 : 1 stoichiometric ratio of the BzPySB and Al3+. The in situ generated complex BzPySB-Al3+ offered selectivity toward TNP via fluorescence turn-off phenomena with high Ksv and LOD values. The “off-on-off” sensing mechanism was elucidated through 1H NMR, mass spectrometry, and DFT calculations. The probe also detected Al3+ in plant and MCF-7 cells, highlighting its potential in biological systems. Moreover, BzPySB exhibited solid-state luminescent properties credited to weak π-π interaction, leading to its successful application in the visualization of latent fingerprints.Item A pyrazinium-based fluorescent chemosensor for the selective detection of 2,4,6-trinitrophenol in an aqueous medium(RSC, 2022) Khungar, BhartiSensing nitroaromatic explosives has gained significant attention due to both increased terrorist threats and a need for environmental protection. In this regard, a fluorescent chemosensor, 1-benzyl-3,5-di(thiophen-2-yl)pyrazin-1-ium bromide (BTPyz), was synthesized and characterized via spectroscopic methods. The photophysical properties were investigated using absorption and emission spectral analysis. As a fluorescent chemosensor, BTPyz exhibited a selective response towards 2,4,6-trinitrophenol (TNP) with a detection limit of 11.6 nM and quenching constant (KSV) of 3.8 × 104 M−1. The fluorescence quenching mechanism was attributed to ground-state charge-transfer complex formation and resonance energy transfer, as evident from Uv-visible, fluorescence and NMR spectroscopy, single-crystal XRD studies, and density functional theory calculations. BTPyz was also employed for the contact mode detection of TNP on paper strips. The detection of TNP in real water and soil samples demonstrated BTPyz to be a promising detection tool toward environmental specimensItem Detection of TNP and sulfite ions in an aqueous medium using a pyrazinium-based chemosensor(RSC, 2024) Khungar, BhartiA fluorescent pyrazinium-based 1-benzyl-3,5-diphenylpyrazin-1-ium bromide (BPPyz) chemosensor was synthesized and well-characterized. A significant reduction in blue emission of BPPyz was observed in the presence of TNP as compared to other nitroaromatic compounds, indicating high selectivity towards TNP. In the presence of sulfite ions, BPPyz showed fluorescence quenching and rapid naked-eye detection with a significant color change. The sensing mechanism was investigated through UV–visible studies, time-resolved fluorescence results, and density functional theory (DFT) calculations. The quenching constants (KSV) are 4.12 × 105 M−1 for TNP and 3.8 × 105 M−1 for sulfite with the detection limits of 9.5 nM and 46.17 nM for TNP and sulfite, respectively. The selectivity of BPPyz towards TNP was ascribed to the ground state charge transfer complex (GSC) formation and resonance energy transfer. Sulfite ion detection involved the formation of a GSC through hydrogen bonding with the pyrazinium proton.