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排序方式: 共有247条查询结果,搜索用时 156 毫秒
101.
Karthikeyan Gopalakrishnan Anbalagan Krishnamoorthy Elango Kuppanagounder P. 《Transition Metal Chemistry》2002,27(1):52-57
The photoreduction of trans-[Co(NH3)4Cl2]+, trans-[Co(en)2Cl2]+, [Co(dien)Cl3], [Co(trien)Cl2]+, and [Co(tetren)Cl]2+, ions has been studied using a low pressure Hg vapour lamp as light source (254 nm) in aqueous–organic solvents [0–30% (v/v) MeOH or 1,4-dioxane]. Quantum yields for CoII production by redox decomposition have been determined in all the cases, and increase considerably with the increase in concentration of MeOH or 1,4-dioxane in the binary solvent mixtures under investigation. A plot of log(quantum yield) versus the Grunwald–Winstein Parameter, Y, which is a measure of solvent ionizing power, shows that a different blend of general and specific solvent interacts with the solute. This kind of specific solvent interaction on the reactant/excited state has been analysed using multiple regression: viz. Krygowski–Fawcett and Kamlet–Taft equations. Reasons for the difference in reactivity with chelation are also discussed. 相似文献
102.
Spectral characteristics of 2-(4'N,N-dimethylaminophenyl)benzimidazole have been studied as a function of surfactant concentration and as a function of acid concentration in three surfactants. Dual fluorescence is observed in all the micelles. Fluorescence intensities of the local emission (B band) and twisted intramolecular charge transfer (A band, TICT) increase by an 17-30% and 38 to 64% respectively. When dissolved in micelles lifetimes of both the states also increase in the presence of micelles. The increase in the fluorescence intensities is attributed to the decrease in the non-radiative decay constant. cmc of the surfactants can be determined from the variation in the fluorescence intensity and the lifetime data. The equilibrium constants are determined for the prototropic reactions of the fluorophore in all the micelles in S0 and S1 states and the values obtained are discussed. Copyright 1999 Academic Press. 相似文献
103.
A. K. M. Sharif M. Alamgir K. R. Krishnamoorthy A. I. Mustafa 《Journal of Radioanalytical and Nuclear Chemistry》1993,170(2):299-307
Determination of arsenic, chromium, mercury, selenium and zinc in several commonly consumed tropical marine fishes have been carried out by neutron activation followed by radiochemical separation to remove the interfering activities of sodium, potassium, bromine, and phosphorus, etc., in order to establish the baseline data and to measure the levels of contamination, if any. The results of this study positively indicate that the marine fishes of Bangladesh have concentrations much below the permissible levels for these toxic elements. A radiochemical scheme for the separation of seven trace elements in biological material is also presented in this paper. 相似文献
104.
Turek AM Krishnamoorthy G Sears DF Garcia I Dmitrenko O Saltiel J 《The journal of physical chemistry. A》2005,109(2):293-303
all-trans-1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence in solution consists of emissions from the S1 (2(1)A(g)) and S2 (1(1)B(u)) states of the s-trans,s-trans conformer (s-t-DPH) and emission from the S1 state of the s-cis,s-trans conformer (s-c-DPH). The contribution of s-c-DPH fluorescence increases upon excitation at longer wavelengths, and both minor emissions, s-c-DPH and 1(1)B(u) s-t-DPH fluorescence, contribute more at higher temperatures (Ts). Resolution of a spectrothermal matrix of DPH fluorescence spectra by principal component analysis with self-modeling (PCA-SM) is hampered by T-dependent changes in the spectra of the individual components. We avoided differential polarizability-dependent spectral shifts by measuring the spectra in n-alkanes (Cn, C8 to C16 with n even) at T values selected to keep the index of refraction constant, hence under isopolarizability conditions. Compensation of the spectra for T-induced broadening allowed resolution of the spectral matrix into its three components. The optimum van't Hoff plot gives Delta H = 2.83 kcal/mol for s-c-DPH/s-t-DPH equilibration, somewhat smaller than the 3.4 kcal/mol calculated value, and the optimum Boltzmann distribution law plot gives Delta E(ab) = 4.09 kcal/mol for 1(1)B(u)/2(1)A(g) equilibration. The 1(1)B(u) fluorescence spectrum bears mirror-image symmetry with the DPH absorption spectrum, and the energy gap, 1431 cm(-1), is consistent with the 1615 cm(-1) difference between the lowest energy bands in the 1(1)B(u) and 2(1)A(g) fluorescence spectra. The results give V(ab) = 198 +/- 12 cm(-1) for the vibronic matrix coupling element between the 2(1)A(g) and 1(1)B(u) states. Fluorescence quantum yields and lifetimes under isopolarizability conditions reveal an increase in the effective radiative rate constant of s-t-DPH with increasing T. 相似文献
105.
Mukhopadhyay S Maitra U Ira I Krishnamoorthy G Schmidt J Talmon Y 《Journal of the American Chemical Society》2004,126(48):15905-15914
Tripodal cholamide 1 is a supergelator of aqueous fluids. A variety of physical techniques, including cryo-transmission electron microscopy (TEM), circular dichroism (CD), steady-state fluorescence, time-resolved fluorescence, and dynamic light-scattering, were employed to understand the structure and dynamics of the gel. Fluorescent probes [ANS (8-anilinonaphthalene-1-sulfonic acid) and pyrene] reported two critical aggregation concentrations (CAC(1) and CAC(2)) of 1 in predominantly aqueous media, with the minimum gel concentration (MGC) being close to CAC(2). Fluorescence lifetime measurements with pyrene revealed ineffective quenching of pyrene fluorescence by oxygen, possibly caused by slower Brownian diffusion due to the enhanced viscosity in the gel phase. The study of the gelation kinetics by monitoring the ultrafast dynamics of ANS revealed a progressive increase in the aggregate size and the microviscosity of the aqueous pool encompassed by the self-assembled fibrillar network (SAFIN) during the gelation. The striking difference between microviscosity and bulk (macroscopic) viscosity of the gel is also discussed. 相似文献
106.
Avinash P. Jadhav Ambarish Kumar Singh Ashakiran Maibam Sailaja Krishnamurty Kothandam Krishnamoorthy Jayaraj Nithyanandhan 《Photochemistry and photobiology》2023,99(2):529-537
In dye-sensitized solar cell, modulating the electronic properties of the sensitizer by varying the donor, π-spacer, acceptor and anchoring groups help optimizing the structure of the dye for better device performance. Here, a donor–acceptor–donor-based unsymmetrical thiosquaraine sensitizer ( SQ5S ) has been designed and synthesized. Photophysical, electrochemical, theoretical and photovoltaic characterizations of SQ5S dye have been compared with its oxygen analog, SQ5 . The incorporation of the sulfur atom in the acceptor unit of SQ5S dye showed an intense peak at 688 nm, which was 38 nm of red-shifted and showed the panchromatic light harvesting response with the onset of 850 nm compared with SQ5 dye. The LUMO and HOMO energy levels are well aligned with the conduction band of TiO2 and the redox potential of electrolyte for the charge injection and the dye-regeneration processes, respectively. Photovoltaic efficiency of 1.51% (VOC 610 mV, JSC 3.07 mA cm−2, ff 81%) has been achieved for SQ5S dye, whereas SQ5 showed the device performance of 5.43% (VOC 723 mV, JSC 9.3 mA cm−2, ff 80%). The decreased device performance for the dye SQ5S has been attributed to the favorable intersystem crossing process associated with the photoexcited SQ5S that reduces the driving force for the charge injection process. 相似文献
107.
The theoretical prediction of the association of a flexible ligand with a protein receptor requires efficient sampling of
the conformational space of the ligand. Several docking methodologies are currently available. We propose a new docking technique
that performs well at low computational cost. The method uses mutually orthogonal Latin squares to efficiently sample the
docking space. A variant of the mean field technique is used to analyze this sample to arrive at the optimum. The method has
been previously applied to explore the conformational space of peptides and identify structures with low values for the potential
energy. Here we extend this method to simultaneously identify both the low energy conformation as well as a ‘high-scoring’
docking mode. Application of the method to 56 protein–peptide complexes, in which the length of the peptide ligand ranges
from three to seven residues, and comparisons with Autodock 3.05, showed that the method works well.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
108.
This paper presents a total Lagrangian formulation of a plate/shell element for geometrically nonlinear analysis with the assumption of moderately large deflections but small rotations. Mallet and Marcal's nonlinear stiffness matrices [N1] and [N2] are derived explicitly by the procedure suggested by Rajasekaran and Murray for a four-node parallelogram isoparametric element with bilinear interpolation functions and an orthotropic constitutive relationship. The performance of the element based on this simplified formulation has been tested through a number of examples. It is concluded that this element offers potential for geometrically nonlinear analysis of large-scale practical structures. 相似文献
109.
Gangireddy Sujeevan Reddy Suresh Babu Nallapati P.S.V.K. Sri Saranya B. Sridhar Varadaraj Bhat Giliyaru Raghu Chandrashekhar Hariharapura G. Gautham Shenoy Manojit Pal 《Tetrahedron letters》2018,59(52):4587-4592
Propargylamine (secondary) has been explored as a building block in synthesizing indoles via an ultrasound assisted Pd/Cu-catalyzed coupling-cyclization method. Indoles containing a pyrazole moiety at C-2 attached via the –CH2NH– linker (designed as potential anti-tubercular agents) were synthesized first and then generality/scope of the methodology was expanded by synthesizing other indoles. Unexpected formation of imine side products in first cases helped in synthesizing related (pyrazole)imines via a Cu catalyzed ultrasound assisted aerobic oxidation of precursor amines. 相似文献
110.
Dr. Krishnamoorthy Sathiyan Dr. Ronen Bar-Ziv Dr. Vered Marks Prof. Dr. Dan Meyerstein Dr. Tomer Zidki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(64):15936-15943
Photocatalytic hydrogen production is proposed as a sustainable energy source. Simultaneous reduction and oxidation of water is a complex multistep reaction with high overpotential. Photocatalytic processes involving semiconductors transfer electrons from the valence band to the conduction band. Sacrificial substrates that react with the photochemically formed holes in the valence band are often used to study the mechanism of H2 production, as they scavenge the holes and hinder charge carrier recombination (electron-hole pairs). Here, we show that the desired sacrificial agent is one forming a radical that is a fairly strong reducing agent, and whose oxidized form is not a good electron acceptor that might suppress the hydrogen evolution reaction (HER). In an acidic medium, methanol was found to fulfill both these requirements better than ethanol and propan-2-ol in the TiO2-(M0-NPs) (M=Au or Pt) system, whereas in an alkaline medium, the alcohols exhibit a reverse order of activity. Moreover, we report that CH2(OH)2 is by far the most efficient sacrificial agent in a nontrivial mechanism in acidic media. Our study provides general guidelines for choosing an appropriate sacrificial substrate and helps to explain the variance in the performance of alcohol scavenger-based photocatalytic systems. 相似文献