BITS Faculty Publications
Permanent URI for this communityhttp://localhost:4000/handle/123456789/1867
Browse
6 results
Search Results
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.Item N-Confused Porphyrin – A Unique “Turn-On” Chemosensor for CN− and F− ions and “Turn-Off” Sensor for ClO4− ions(Wiley, 2020-05) Grover, NitikaN-Confused meso-tetrakis(4-carbomethoxyphenyl)porphyrin (1) and its Ni(II) complex (1 a) have been synthesized and utilized for anion sensing studies, and the results are compared with N-confused meso-tetraphenylporphyrin (NCTPP). Anion susceptibilities of 1 and 1 a were investigated using spectroscopic, electrochemical, and DFT studies. Porphyrins 1 and 1 a were able to detect CN−, F−, and ClO4− ions selectively over the tested set of anions even at ppm level. Interestingly, the addition of ClO4− ions resulted in fluorescence quenching (turn off) whereas the addition of F− or CN− resulted in fluorescence enhancement (turn on). Notably, the TFA addition resulted in fluorescence quenching, whereas the fluorescence enhancement was observed while adding TBAOH. The higher association constant (Ka) values with anions, lower detection limit, and shifts in redox potentials are due to the electron-withdrawing effect of the −COOCH3 group at the para-position of the meso-phenyl ring. This electron-withdrawing nature is crucial for the higher affinity towards anions. The anion sensing description in this article may not only unveil the built-in nature of N-confused porphyrins, but may also provide a general proposal for the development of novel anion sensors based on porphyrinoids. The electron-deficient porphyrin framework, large polarisable π-system, and anion binding through the outer NH or a combination of the above factors serve as a foundation for N-confused porphyrin to act as an anion sensor.Item Detection of Hg2+ ions in aqueous medium using an indole-based fluorescent probe: Experimental and theoretical investigations(Elsiever, 2017-12) Sakhuja, Rajeev; Pant, Debi D.Mercury pollution is a widespread danger to human health and environment. Due to limitations associated with the existing Hg2+ chemosensors, development of new, efficient and selective chemosensors capable of sensing mercury ions in aqueous medium remains a demanding area of research. In this regard, an indole-based fluorescent probe has been synthesized and characterized by detailed spectroscopic analysis. The probe showed a high selectivity and sensitivity towards Hg2+ by giving significant fluorescence quenching over other tested cations in H2O/DMF (7:3, v/v) medium. The association constant (Ka) was 6.4 × 103 M− 1 between sensor and Hg2+. The detection limit of sensor to Hg2+ was found to be 0.143 μM (143 nM). The experimental results have been verified with Density Functional Theory.Item N-Glycoconjugates: Selective colorimetric chemosensors for aspartic acid and cysteine(Elsiever, 2021-10-05) Sah, Ajay KumarSelective recognition of naturally occurring amino acids have been explored using five glycopeptide-based receptors with the help of UV-visible and 1H NMR spectroscopy, while structures of two glycopeptides have been established via single crystal X-ray diffraction studies. The receptors containing alanine, valine, isoleucine and methionine moieties interact selectively with aspartic acid, while phenylalanine derivative with cysteine.