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Hirdyesh Mishra

Bio: Hirdyesh Mishra is an academic researcher from Banaras Hindu University. The author has contributed to research in topics: Molecular orbital & Density functional theory. The author has an hindex of 20, co-authored 65 publications receiving 1086 citations. Previous affiliations of Hirdyesh Mishra include University of Maryland, Baltimore County & Kumaun University.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the potential energy profile for intramolecular proton transfer in salicylic acid has been studied by ab initio molecular orbital calculations using the 6-31G** basis set at the restricted Hartree -Fock (RHF) and configuration interaction-single excitation (CIS) levels and also using the semi-empirical method AM1 at the RHF level as well as with single and pair doubles excitation configuration interaction spanning eight frontier orbitals (PECI ) 8).
Abstract: Energetics of the ground and excited state intramolecular proton transfer in salicylic acid have been studied by ab initio molecular orbital calculations using the 6-31G** basis set at the restricted Hartree -Fock (RHF) and configuration interaction-single excitation (CIS) levels and also using the semiempirical method AM1 at the RHF level as well as with single and pair doubles excitation configuration interaction spanning eight frontier orbitals (PECI ) 8). The ab initio potential energy profile for intramolecular proton transfer in the ground state reveals a single minimum corresponding to the primary form. In the first excited singlet state, however, there are two minima corresponding to the primary and tautomeric forms, separated by a barrier of 6 kcal/mol, thus accounting for dual emission in salicylic acid. Electron density changes with electronic excitation and tautomerism indicate no zwitterion formation. Changes in spectral characteristics with change in pH, due to protonation and deprotonation of salicylic acid, are also accounted for, qualitatively. Although the AM1 calculations suggest a substantial barrier for proton transfer in the ground as well as the first excited state of SA, it predicts the transition wavelength in near quantitative accord with the experimental results for salicylic acid and its protonated and deprotonated forms.

113 citations

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TL;DR: A systematic and significant improvement in the thermal and fluorescence properties of the complex is observed with an increase in the mole concentration of Phen and the maximum fluorescence is observed for Eu(DBM)(3)Phen(1·5), which is a new composition as compared with the usual composition reported.
Abstract: Tris (dibenzoylmethanido) (o-phenanthroline)-europium(III) complexes [Eu(DBM)3(Phen)x] have been synthesized, and their structural, thermal, and fluorescence properties have been investigated both as an independent complex and also after embedding it in poly(methyl methacrylate) (PMMA) polymer matrix. X-ray analysis reveals an unusual crystalline to amorphous transformation in structure of the Eu(DBM)3Phenx complexes when x exceeds 1.0 (mole %). Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) analysis depict the interaction between the Eu(DBM)3Phenx complex and the PMMA matrix. The fluorescence intensity of Eu3+ ion in the Eu(DBM)3Phen1·5 complex is an order of magnitude larger compared to the Eu(DBM)3·2H2O complex. In addition to the transition 5D0 → 7F2, which has a rise time of 83 μs, transitions from the 5D1 and 5D2 levels are also observed, along with several ligand field splittings in the Eu(DBM)3Phen1·5 complex. Appearance of a rise time (∼0.76 ns) in the ...

94 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that a linear quenching of fluorescence intensity and decay time of salicylic acid doped polyvinyl alcohol (PVA) film in the presence of moisture or water in the organic solvents can be useful as an optical sensor for determination of humidity in the range 5%-85% and water contents in these solvolents in the ranges 1%-60% with an accuracy of (0.2%).
Abstract: Photoluminescence of salicylic acid (SA) and its sodium salt in poly(vinyl alcohol) (PVA) film and its quenching by water/moisture has been studied by steady-state and time domain fluorescence measurements. The results suggest that salicylic acid is completely ionized and present as a monoanion in PVA film, having a molar extinction coefficient (max) of 3545 M -1 cm -1 , and its emission shows a large Stokes shifted (8300 cm -1 ) fluorescence band with a quantum yield (f) of 0.34 and a decay time (Uf) of 6.7 ns. This emission band is due to excited-state intramolecular proton transfer (ESIPT) and is found to be sensitive to moisture and water contents in organic solvents. The films dipped in organic solvents, viz. dioxane, ethanol, and acetonitrile, containing water shows Stern-Volmer type fluorescence quenching. It is shown that a linear quenching of fluorescence intensity and decay time of SA doped PVA film in the presence of moisture or water in the organic solvents can be useful as an optical sensor for determination of humidity in the range 5%-85% and water contents in these solvents in the range 1%-60% with an accuracy of (0.2%. The response time of the sensor film is about 2 min, and recovery time is less than 1 min.

94 citations

Journal ArticleDOI
TL;DR: The findings suggest that the distance dependence of metal-enhanced phenomena such as fluorescence, phosphorescence and delayed fluorescence is underpinned by the decay of the electric near-field, and depending on the actual silver silica sample embodiment, one can see either decreased or enhanced luminescence.
Abstract: Distance dependent singlet and triplet metal-enhanced emission of eosin from silica coated silver island films (SiFs) has been studied by steady-state and time resolved fluorescence techniques, along with theoretical finite difference time domain (FDTD) numerical simulations, to understand how the thickness of the dielectric coating surrounding silver nanoparticles fundamentally affects luminescence enhancement. Our findings suggest that the distance dependence of metal-enhanced phenomena such as fluorescence, phosphorescence and delayed fluorescence is underpinned by the decay of the electric near-field, and depending on the actual silver silica sample embodiment, one can see either decreased or enhanced luminescence. These results not only expand our current MEF thinking but also suggest that one may well be able to approximate plasmon-enhanced luminescence values.

76 citations

Journal ArticleDOI
TL;DR: Energy transfer is found to take place both from excited singlet as well as triplet states in salicylic acid monoanion and subsequent sensitization of Tb(3+) ion in polyvinyl alcohol (PVA).
Abstract: In the present work, excited state intramolecular proton transfer (ESIPT) in salicylic acid (SA) monoanion and subsequent sensitization of Tb(3+) ion in polyvinyl alcohol (PVA) have been studied. The study has been carried out both by steady state and time domain fluorescence measurement techniques at room temperature. It is found that the SA completely ionizes and exists as monoanion in PVA. It exhibits a large Stokes shifted blue emission (10 000 cm(-1)) due to ESIPT and shows a decay time of 6.85 ns. On the other hand, Tb(3+) ion shows a very weak green emission and a decay time of approximately 641 mus in PVA film. Upon incorporating Tb(3+) ion in SA doped PVA film, both intensity and decay time of SA decrease and sensitized emission from Tb(+3) ion along with 3.8 mus rise time is observed. Energy transfer is found to take place both from excited singlet as well as triplet states. A brief description of the properties of the present system from the viewpoint of luminescent solar collector material is addressed.

57 citations


Cited by
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28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

01 Jan 2016
TL;DR: The principles of fluorescence spectroscopy is universally compatible with any devices to read and is available in the digital library an online access to it is set as public so you can download it instantly.
Abstract: Thank you very much for downloading principles of fluorescence spectroscopy. As you may know, people have look hundreds times for their favorite novels like this principles of fluorescence spectroscopy, but end up in malicious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they cope with some harmful bugs inside their desktop computer. principles of fluorescence spectroscopy is available in our digital library an online access to it is set as public so you can download it instantly. Our digital library spans in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the principles of fluorescence spectroscopy is universally compatible with any devices to read.

2,960 citations

Journal ArticleDOI

2,877 citations

Journal ArticleDOI
TL;DR: This critical review will present the role of nanoparticles (NPs) in the directions that are vital to the new field of nanomedicine, including imaging and drug delivery, and review recent advances in major NP based biomedical applications.
Abstract: This critical review will present the role of nanoparticles (NPs) in the directions that are vital to the new field of nanomedicine, including imaging and drug delivery. We reflect on the physical properties that make NPs advantageous for in vivo efficacy, and review recent advances in major NP based biomedical applications. Critical questions of transport, uptake, and clearance will be discussed and illustrated through the success and opportunities of NP imaging and therapy on a photodynamic therapy (PDT) based NP system that has been developed in our lab over the past decade (540 references).

925 citations

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TL;DR: This critical review begins with a formulation of the fundamentals of lanthanide organic complex luminescence, and presents various current designed ideas, synthetic routes, luminescent behaviors and potentials of the latest advanced organic-inorganic hybrid materials.
Abstract: A great deal of research has been carried out on lanthanide organic complex-based organic-inorganic hybrid materials in the last decade. This critical review begins with a formulation of the fundamentals of lanthanide organic complex luminescence, and presents various current designed ideas, synthetic routes, luminescence behaviors and potentials of the latest advanced (a) sol-gel materials, (b) mesoporous materials, (c) titania materials, (d) ionic liquids and ionogels, (e) polymers, and (f) bifunctional magnetic-optical composites based on lanthanide organic complexes. Finally, challenges and opportunities for further improvement of organic-inorganic hybrid luminescent materials based on lanthanide organic complexes will be discussed.

658 citations