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Large Blue Shift (large + blue_shift)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Nanostructures, Optical Properties, and Imaging Application of Lead-Sulfide Nanocomposite Coatings

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2004
Song Wei Lu
Lead-sulfide (PbS) nanocrystals were precipitated in nanocomposite coatings after a pre-photo-polymerization followed by a reaction with H2S gas at 25°C for 1 hr. PbS nanocrystalline size and optical absorption increased with decreasing UV energy for pre-photo-polymerization and increasing concentration. The absorption onset has a large blue shift from 0.41 eV of the corresponding bulk crystal, resulting from the quantum confinement effect. As a result, coating color changes significantly from deep brown to light yellow depending on coating processing conditions. Partially masking the coatings during pre-photo-polymerization gives rise to different colors, leading to imaging applications of PbS nanocomposite coatings. [source]

Hydrogen bonding interaction between 1,4-dioxane and water

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2010
Ajay Chaudhari
Abstract This work reports an interaction of 1,4-dioxane with one, two, and three water molecules using the density functional theory method at B3LYP/6-311++G* level. Different conformers were studied and the most stable conformer of 1,4-dioxane-(water)n (n = 1,3) complex has total energies ,384.1964038, ,460.6570694, and ,537.1032381 hartrees with one, two, and three water molecules, respectively. Corresponding binding energy (BE) for these three most stable structures is 6.23, 16.73, and 18.11 kcal/mol. The hydrogen bonding results in red shift in OO stretching and CC stretching modes of 1,4-dioxane for the most stable conformer of 1,4-dioxane with one, two, and three water molecules whereas there was a blue shift in CO symmetric stretching and CO asymmetric stretching modes of 1,4-dioxane. The hydrogen bonding results in large red shift in bending mode of water and large blue shift in symmetric stretching and asymmetric stretching mode of water. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source]

Highly conductive and optically transparent GZO films grown under metal-rich conditions by plasma assisted MBE

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 3-4 2010
H. Y. Liu
Abstract We demonstrate a critical effect of a metal-to-oxygen ratio on the electrical, optical, and structural properties of ZnO films heavily doped with Ga (carrier concentration in the range of 1020,1021 cm,3) grown by plasma-assisted molecular beam epitaxy. The as-grown layers prepared under the metal-rich conditions exhibited resistivities below 3 × 10,4 , cm and an optical transparency exceeding 90% in the visible spectral range as well as a large blue shift of the transmission/absorption edge attributed to the Burstein,Moss shift of the Fermi level deep into the conduction band, indicating high donor concentration. In contrast, the films grown under the oxygen-rich conditions required thermal activation and showed inferior properties. Furthermore, electrical measurements point to the nonuniform depth distribution of free carriers. An oxygen-pressure-dependent surface disordering is suggested to be responsible for the drastic effect of the metal-to-oxygen ratio on the film properties. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Proton Transfer in the Complex H3N,,,HCl Catalyzed by Encapsulation into a C60 Cage

CHEMPHYSCHEM, Issue 7 2009
Fang Ma Dr.
Abstract Caged up: In contrast to acid,base behavior in solution, single molecules of NH3 and HCl do not react to form the ion pair NH4+Cl, in isolation. Proton transfer occurs in the complex H3N,,,HCl inside the C60 cage, to form the ion pair NH4+Cl, under the catalytic action of C60 (see picture). We report proton transfer in the complex H3N,,,HCl to form the ion pair NH4+Cl,, which is favored inside the C60 cage according to quantum chemical calculations. The results show that the NH4+Cl,@C60 is stable with an interaction energy of ,2.78 kcal,mol,1. Compared with the complex H3N,,,HCl without proton transfer, it is found that the C60 cage plays the role of a catalyst for proton transfer. In NH4+Cl,@C60 a negative charge area in the C60 cage is near the cation NH4+ whereas a positive charge area is near the anion Cl,. Also, a confinement effect of the C60 cage is noticed, as the endohedral structure of NH4+Cl, is more compact than the structure of NH4+Cl, in the gas-phase complex. These findings indicate that the catalysis by the C60 cage comes from two effects: 1) electrostatic inducement between the C60 cage and endohedral molecules and 2) the confinement effect that compresses endohedral molecular structures inside the C60 cage. In the infrared spectrum, it is found that the confinement effect of the cage can cause large blue shifts of the N,H stretching vibrations in NH4+Cl,@C60 compared with those in the NH4+Cl,,,,H2O complex. [source]