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71.
Sebastian Heeg Nick Clark Antonios Oikonomou Aravind Vijayaraghavan Stephanie Reich 《固体物理学:研究快报》2014,8(9):785-789
We report plasmon‐enhanced Raman scattering of the order of 103 by a metallic carbon nanotube partially suspended inside a near‐field cavity. The tube is part of a small bundle, and is interfaced with an Au nanodisc dimer using a recently developed assembly scheme based on dielectrophoretic deposition. Spatially resolved Raman measurements with two excitation wavelengths and two orthogonal polarizations confirm that the enhancement arises from a 65 nm long suspended tube segment. We show that the orientation of the tube inside the cavity can be as effective for generating enhancement as placing the nanotube precisely in a plasmonic hotspot. Position and shape of the G‐peak show that the suspended part of the tube is free of strain and doped with a Fermi energy shift ≤40 meV. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
72.
Experimental densities (ρ), viscosities (η), and speeds of sound (u) of the binary mixtures of n-dodecane with an alkan-1-ol (hexan-1-ol, heptan-1-ol, octan-1-ol) or an alkan-2-ol (hexan-2-ol, heptan-2-ol and octan-2-ol) were measured over the whole mixture composition range at T = 298.15 K. From these data, the excess molar volume ( $ V_{\text{m}}^{\text{E}} $ V m E ), deviations in viscosity (Δη), and excess isentropic compressibility ( $ \kappa_{S}^{\text{E}} $ κ S E ) have been calculated. The results were fitted by means of the Redlich–Kister equation, in order to estimate the binary coefficients and standard errors. Differences among these binary systems are ascribed to the different association abilities of the alkan-1-ols and alkan-2-ols. Experimental data on the constituted binaries were analyzed using McAllister’s multi-body interaction model, the Jouyban–Acree model, the Prigogine–Flory–Patterson theory, and the Bloomfield and Dewan model. The experimental and calculated quantities are used to study the nature of mixing behavior among the mixtures. 相似文献
73.
A simple and convenient one-pot synthesis of aryl alkyl ethers by the alkoxylation of aryl halides with alcohol in the presence of Triton B as a base is described. The procedure is applicable for a variety of aryl and heteroaryl halides, and yields are very good. The use of a nonmetallic base and solvent-free conditions are important features of the reaction. 相似文献
74.
Phytochemical analysis of the leaves of Garcinia travancorica, a hitherto uninvestigated endemic species to the Western Ghats of south India, resulted in isolation and characterisation of the polyisoprenylated benzophenones 7-epi-nemorosone (1) and garcinol (2) along with biflavonoids GB-1a (3), GB-1 (4), GB-2 (5), morelloflavone (6) and morelloflavone-7″-O-β-d-glycoside or fukugiside (7). The compounds were identified using various spectroscopic techniques, mainly through NMR and MS. The methanol extract and the biflavonoids 3, 4, 5 and 7 showed potential in vitro antioxidant activities. The IC50 value of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of compound 7 was 8.34 ± 2.12 μg/mL, comparable to that of standard ascorbic acid (3.2 ± 0.50 μg/mL). In the superoxide radical scavenging assay, compound 7 gave IC50 value of 6.95 ± 1.33 μg/mL close to standard ascorbic acid with IC50 value of 5.8 ± 0.25 μg/mL. Validated HPTLC estimation revealed G. travancorica as a rich source of morelloflavone-7″-O-β-d-glycoside (7.12% dry wt. leaves). 相似文献
75.
J.S. Yadav B.V. Subba Reddy S. Aravind G.G.K.S. Narayana Kumar C. Madhavi A.C. Kunwar 《Tetrahedron》2008,64(13):3025-3031
Three-component coupling of carbonyl compounds, homoallylic alcohols, and nitriles has been achieved using 20 mol % of phosphomolybdic acid (PMA) at ambient temperature via the Prins-Ritter sequence to furnish 4-amidotetrahydropyrans in high yields with all cis selectivity. Spirocyclic-4-amidotetrahydropyrans are obtained using cyclic ketones. 相似文献
76.
Datta K Roy DK Mukherjee AK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(2):425-429
Charge transfer complexes of 1:1 stoichiometry have been found to form between vitamin B(6) (pyridoxine hydrochloride) and a series of electron acceptors including p-chloranil. Since vitamin B(6) is soluble in water while the electron acceptors are insoluble in water but soluble in ethanol, the medium chosen for study is water-ethanol mixture. From the trends in the CT absorption bands the vertical ionization potential of vitamin B(6) has been determined to be 8.12 eV. The enthalpy and entropy of formation of the complex between p-chloranil and vitamin B(6) have been determined by estimating the formation constant (K) spectroscopically at four different temperatures in 75% ethanol-water mixture. Again, the magnitude of K has been found to decrease noticeably with decrease in dielectric constant of the medium (as the percentage of ethanol in the aqueous-ethanol mixture is increased). A plausible explanation for this has been given in terms of hydrolysis of pyridoxine hydrochloride. 相似文献
77.
The dielectric properties in the vicinity of the isotropic-smectic-C* phase transition in ferroelectric liquid crystals are discussed. The temperature and frequency dependence of the complex dielectric permittivity in both the phases of the transition are calculated. The theoretical phase diagram of the dielectric permittivity is studied. 相似文献
78.
Singanaboina Rajaram Udugu Ramulu Seema Aravind Katragadda Suresh Babu 《Helvetica chimica acta》2015,98(5):650-656
An efficient and highly stereoselective synthesis of stagonolide E ( 1 ) starting from the readily available hexane‐1,6‐diol ( 8 ) was accomplished, employing MacMillan α‐hydroxylation, Horner? Wadsworth? Emmons olefination, (Z)‐selective Still? Gennari olefination, and Yamaguchi lactonization as key steps. 相似文献
79.
Copper‐Exchanged Tungstophosphoric Acid: An Efficient and Reusable Heteropoly Acid for the Synthesis of 2,3,4,5‐Tetrahydro‐4‐methylidenefuran Derivatives 下载免费PDF全文
Copper‐exchanged tungstophosphoric acid (Cu‐TPA) is found to catalyze efficiently the coupling of propargyl alcohol (prop‐2‐yn‐1‐ol) with (arylmethylidene)malononitriles to afford the corresponding 2,3,4,5‐tetrahydro‐4‐methylidenefuran derivatives in good yields and with high selectivity. The catalyst is recycled and reused for three‐to‐four subsequent runs with a minimal decrease of activity. 相似文献
80.
Propane σ‐Complexes on PdO(101): Spectroscopic Evidence of the Selective Coordination and Activation of Primary CH Bonds 下载免费PDF全文
Feng Zhang Li Pan Juhee Choi Vikram Mehar John T. Diulus Prof. Aravind Asthagiri Prof. Jason F. Weaver 《Angewandte Chemie (International ed. in English)》2015,54(47):13907-13911
Achieving selective C? H bond cleavage is critical for developing catalytic processes that transform small alkanes to value‐added products. The present study clarifies the molecular‐level origin for an exceptionally strong preference for propane to dissociate on the crystalline PdO(101) surface via primary C? H bond cleavage. Using reflection absorption infrared spectroscopy (RAIRS) and density functional theory (DFT) calculations, we show that adsorbed propane σ‐complexes preferentially adopt geometries on PdO(101) in which only primary C? H bonds datively interact with the surface Pd atoms at low propane coverages and are thus activated under typical catalytic reaction conditions. We show that a propane molecule achieves maximum stability on PdO(101) by adopting a bidentate geometry in which a H? Pd dative bond forms at each CH3 group. These results demonstrate that structural registry between the molecule and surface can strongly influence the selectivity of a metal oxide surface in activating alkane C? H bonds. 相似文献