排序方式: 共有42条查询结果,搜索用时 31 毫秒
21.
The dynamic behaviour of chain conformations, hydrogen bonds and translational diffusion of aqueous poly(methacrylic acid) (PMA) solution as a function of polymer volume fraction Φp across dilute to concentrated regimes inclusive of the pure polymer amorphous state was studied by molecular dynamics simulations. The behaviour of the relaxation time (τ) of the backbone dihedral angle auto-correlation function (ACF) reveals slower relaxation at higher level of polymer concentration and the existence of a concentration-driven relaxation transition for the aqueous polymer solution which occurs in the polymer volume fraction range, specifically 54% < Φp < 82% for this system. The relaxation constant τ for backbone dihedral angle exhibits a linear variation with Φp, indicating a first-order kinetic transition. The intermittent ACF for decay of the H-bond correlation shows that H-bonds among water molecules relax faster than those of the PMA–PMA and PMA–water type. The relaxation rate of PMA–water H-bonds shows a decrease up to Φp = 72% and becomes faster at Φp = 82% due to the confining influence of neighbouring PMA chains. PMA–water and water–water H-bond dynamics show transitions around Φp = 72% PMA. With increase in Φp PMA diffusion coefficient decreases exponentially and water diffusion coefficient decreases linearly, in agreement with experimental observations using fluorescence and nuclear magnetic resonance (NMR) spectroscopic studies. 相似文献
22.
Chockalingam Karunakaran Jayaraman Jayabharathi Marimuthu Venkatesh Perumal Venugopal Thanikachalam Prasoon Kumar Thakur 《Journal of Physical Organic Chemistry》2013,26(5):386-406
Phenanthrimidazoles as hole transport materials have been synthesized, characterized, and applied as nondoping emitters in organic light emitting devices. The synthesized molecules possess high fluorescent quantum yield and thermal properties and display film forming abilities. The highest occupied molecular orbital (HOMO) energies of these materials are shallower than the reported tris(8‐hydroxyquinoline)aluminum (Alq3), which enables the hole transport ability of these phenanthrimidazoles. Taking advantage of the thermal stability and hole transporting ability, these compounds can be used as a functional layer between NPB [4,4‐bis(N‐(1‐naphthyl)‐N‐phenylamino)biphenyl] and Alq3 layers and show that these phenanthrimidazoles can be alternatively used as novel hole transport materials and to improve the device performances. Geometrical, optical, electrical, and electroluminescent properties of these molecules have been probed. Further, natural bond orbital, nonlinear optical materials (NLO), molecular electrostatic potential, and HOMO–lowest unoccupied molecular orbital (LMO) energy analysis have been made by density functional theory (DFT) method to support the experimental results. Hyperpolarizability analysis reveals that the synthesized phenanthrimidazoles possess NLO behavior. The chemical potential, hardness, and electrophilicity index of phenanthrimidazoles have also been computed by DFT method. Photoinduced electron transfer explains the enhancement of fluorescence by nanoparticulate ZnO, and the apparent binding constant has been obtained. Adsorption of the fluorophore on ZnO nanoparticle lowers the HOMO and LUMO energy levels of the fluorophore. The strong adsorption of the phenanthrimidazoles on the surface of ZnO nanocrystals is likely due to the chemical affinity of the nitrogen atom of the organic molecule to Zn(II) on the surface of nanocrystal. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
23.
Chockalingam Karunakaran Ramamoorthy Dhanalakshmi Paramasivam Gomathisankar 《Research on Chemical Intermediates》2010,36(4):361-371
Phenol gets adsorbed on Al2O3 and mineralizes under UV light in the presence of dissolved O2. The degradation exhibits first-order kinetics and its rate increases linearly with the light intensity and decreases with
pH. 2,4-Diphenoxycyclohexanone and 2,6-diphenoxycyclohex-3-ene-1-ol are the intermediates of the reaction. While particulate
TiO2, ZnO, ZnS, Fe2O3, CuO, CdO, and Nb2O5 individually photocatalyze the degradation, each semiconductor exhibits synergistic photocatalysis, an enhanced photodegradation,
when present along with Al2O3, indicating electron abstraction by illuminated semiconductors from the phenol adsorbed on Al2O3. 相似文献
24.
Arunachalam Chockalingam 《Operations Research Letters》2010,38(2):82-86
We present a transformation that helps price American options on assets that are modeled by a diffusion as well as a jump component. The presence of a jump component circumvents some shortcomings of the Black-Scholes model. The proposed transformation essentially transforms the arising free-boundary partial integro-differential equation (PIDE) into a sequence of fixed-boundary PIDEs which are much easier to solve. Finally, we provide numerical results illustrating convergence of the scheme and comparisons to other methods. 相似文献
25.
26.
27.
Ratinum Ulagi Perumal Kuselan Chockalingam Karunakaran 《Monatshefte für Chemie / Chemical Monthly》2001,132(7):799-804
Summary. The oxidation of fluoren-9-ols by 4-nitro-1-chlorobenzotriazole in aqueous acetic acid is a second order reaction with a
reaction constant of −1.4. The oxidation exhibits a kinetic deuterium isotope effect indicating the cleavage of the 9-C*H
bond in the rate-determining step. The title oxidation is compared with that by 1-chlorobenzotriazole.
Received October 23, 2000. Accepted (revised) January 22, 2001 相似文献
28.
29.
Manickam MC Annalakshmi S Pitchumani K Srinivasan C 《Organic & biomolecular chemistry》2005,3(6):1008-1012
Multiple recognition by cyclodextrin in a bimolecular reaction, namely bromination of styrene, methyl cinnamate, phenylacetylene and allylbenzene, has been studied. Bromohydrin is obtained as a major product along with dibromide in the bromination of styrene and methyl cinnamate. The percentage of bromohydrin decreases as the cavity size increases. With phenylacetylene, bromophenylacetylene and phenacyl bromide are obtained in addition to the dibromides. In the bromination of cyclodextrin complexes of allylbenzene, the product distribution is the same as in solution bromination. The observed results demonstrate the efficiency of cyclodextrin in stabilizing the open carbocationic intermediate and thus provide chemical evidence for the participation of cyclodextrin hydroxyl groups. 相似文献
30.
Thiruneelakandan Chockalingam Manohar Muthuraman Rajkumar Seenivasan Rajagopal 《Transition Metal Chemistry》2006,31(4):549-555
The electron transfer reaction of Cr(VI) with organic sulfides is facilitated by added pyridine bases 2,2′-bipyridine, 1,10-phenanthroline,
picolinic acid and pyridine 2,6-dicarboxylic acid. The added base forms a Cr(VI)-base adduct carrying positive charge which
acts as a more reactive oxidant compared to Cr(VI). UV–Visible spectrophotometric study provides evidence for the formation
of Cr(V) as the intermediate. The reactions in the absence and presence of pyridine bases follow the reactivity–selectivity
principle. 相似文献