Browsing by Author "Romi Dwivedi"

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A dihydrazone based “turn–on” fluorescent probe for selective determination of Al3+ ions in aqueous ethanol
(Elsevier B.V., 2017) Divya Pratap Singh; Romi Dwivedi; Ashish Kumar Singh; Biplob Koch; Priya Singh; Vinod Prasad Singh
An efficient and highly selective dihydrazone based fluorescent probe N′,N′–bis((2–hydroxynaphthalen–1–yl)methylene)malonohydrazide (H2nmh), has been synthesized for selective detection of Al3+ ions and characterized by different physico–chemical and spectroscopic techniques. The probe shows an enhanced fluorescence in the presence of Al3+ ions in ethanol–water (2:3 v/v) solution which is not observed in the presence of other cations (Na+, K+, Mg2+, Ca2+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+ and Hg2+). The binding modes of H2nmh with Al3+ were studied by UV–vis, fluorescence and 1H NMR titrations. The probe act as dibasic hexa–dentate ligand and interacts with two Al3+ ions with a binding constant KB = 5.74 × 109 M−1 and detection limit 5.78 × 10−8 M. Detailed insights of probe–metal interaction mechanism were studied by mean of density functional theory (DFT) as well as time dependent–DFT calculation. MTT assay on live MCF–7 cells has been performed to evaluate the cytotoxicity of the probe which suggests viability of the probe to MCF–7 cells even at higher concentration (100 μM) with no serious cytotoxicity in cells. Live cell imaging study clearly indicates that the accumulation of Al3+ in the cytoplasm of cells can be detected by H2nmh. © 2016 Elsevier B.V.
Aroyl hydrazone with large Stokes shift as a fluorescent probe for detection of Cu2+ in pure aqueous medium and in vivo studies
(Elsevier B.V., 2020) Romi Dwivedi; Saumya Singh; Brijesh Singh Chauhan; S. Srikrishna; Anoop Kumar Panday; Lokman H. Choudhury; Vinod Prasad Singh
An aroyl hydrazone based fluorescent probe, hpsh, has been developed for the selective detection of Cu2+ ions in pure aqueous medium by static fluorescence quenching. The fluorescence quenching of hpsh in the presence of Cu2+ takes place as a result of ground state complex formation through intramolecular charge transfer (ICT). Addition of Cu2+ ions changes the color of the solution from colorless to yellow-green which is clearly visible by naked eye. Large Stokes shift of hpsh prevents the self-quenching of the probe in absence of metal ions. The observed stoichiometry between Cu2+ and probe has been found as 1:2 (M: L). MTT assay of hpsh on fruit flies confirms that the probe is non-toxic and biocompatible. The plausible in vivo bioimaging application of the probe to detect Cu2+ in Drosophila gut tissues as well as in adult fruit fly has been investigated with excellent results. © 2020 Elsevier B.V.
Intracellular application and logic gate behavior of a ‘turn off-on-off’ type probe for selective detection of Al3+ and F− ions in pure aqueous medium
(Elsevier B.V., 2018) Romi Dwivedi; Divya Pratap Singh; Brijesh Singh Chauhan; S. Srikrishna; Anoop Kumar Panday; Lokman H. Choudhury; Vinod Prasad Singh
A new Schiff base tcph, derived from 2-thiophene carboxylic acid hydrazide, has been synthesized and characterized by various spectroscopic techniques. The molecular structure of the compound has also been determined by X-ray crystallography. The tcph acts as a selective Al3+ and F− induced OFF-ON-OFF type of probe in aqueous media. The 1:1 binding stoichiometry between probe and Al3+ has been established from Job's plot and further supported by ESI–MS studies. The limit of detection of Al3+ ions is determined by 3σ methods, which is found to be 1.35 × 10−9 M. The coordination environment for the tcph-Al3+ complex is delineated by NMR titration and DFT calculations. Detailed insights of probe–metal interaction mechanism have been studied by density functional theory (DFT) as well as time dependent–DFT calculations. MTT assay of the probe on live SiHa cells suggests no serious cytotoxicity in cells even at higher concentration. The probe tcph and its tcph-Al3+ complex have also been successfully applied to detect Al3+ and F− ions in living cells (SiHa cells), respectively. © 2017 Elsevier B.V.
Logic gate behavior and intracellular application of a fluorescent molecular switch for the detection of Fe3+ and cascade sensing of F- in pure aqueous media
(Royal Society of Chemistry, 2019) Romi Dwivedi; Divya P. Singh; Saumya Singh; Ashish K. Singh; Brijesh S. Chauhan; S. Srikrishna; Vinod P. Singh
The nature and coordination sites of the Schiff base 3,3′-(1E,1′E)-(1,3-phenylenebis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)dinaphthalen-2-ol (APHN) were tuned by its selective reduction to design a highly efficient fluorescent probe, 3,3′-(pyridine-2,6-diylbis(azanediyl))bis(methylene)dinaphthalen-2-ol (RAPHN). The structures of APHN, RAPHN, and the RAPHN-Fe3+ complex were satisfactorily modeled from the results of density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. RAPHN worked in pure aqueous medium as a turn on-off-on probe of Fe3+ and F-. The fluorescence nature of the probe in the presence and absence of Fe3+/F- was regulated by a set of mechanisms including -CHN isomerization and LMCT. A 2:1 (M:L) binding stoichiometry was established from a fluorescence Job's plot and further substantiated from HR-MS studies. The limits of detection of RAPHN for Fe3+ and RAPHN-Fe3+ for F- were found to be 2.49 × 10-7 M and 1.09 × 10-7 M, respectively. The RAPHN probe caused no cytotoxicity in gut tissue of Drosophila even at high concentrations. The probe displayed excellent bioimaging applications for detection of Fe3+ and F- in gut tissue of Drosophila. A combinatorial logic gate was constructed for the proper understanding of the working principle of RAPHN. © 2019 The Royal Society of Chemistry.