共查询到20条相似文献,搜索用时 15 毫秒
1.
S. R. Meher Kuyyadi P. Biju Mahaveer K. Jain 《Journal of Sol-Gel Science and Technology》2009,52(2):228-234
Polycrystalline Mg x Zn1?x O (MZO) thin films on glass substrates were prepared by sol–gel method. All the films retained the hexagonal wurtzite structure of ZnO. The band gap values determined from transmission spectra were found to be smaller than the values obtained from Vegard’s law for the as-deposited MZO films. For the films with x = 0.1, 0.2 and 0.3, the band gap blue-shifted initially and then red-shifted with increase in the annealing temperature. The reason for this anomalous shift in the band gap is attributed to the proper substitution of Mg atoms into the Zn lattice sites after a certain critical annealing temperature. 相似文献
2.
The variation in the band gap of a (Gly)30 α-helix with position in the peptide sequence has been investigated using AM1 semiempirical molecular orbital (MO) theory within an extensive singles configuration interaction (CI) treatment. The dipole-charge interaction along the length of the helix results in the highest local electron affinity near the N-terminus and the lowest local ionization potential near the C-terminus. The calculations suggest that the band gap, measured as the difference between the local ionization potential and electron affinity, decreases from the C-terminus to the N-terminus for the model (Gly)30 α-helix in vacuo. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 79: 120–124, 2000 相似文献
3.
Manuel A. Aguirre 《Journal of mathematical chemistry》2000,27(1-2):1-12
In this paper we give a sense to the products $${{\left| x \right|^{(n - 2)/2} }} \cdot \frac{{\delta ^{(k - 1)} (x_0 + \left| x \right|)}} {{\left| x \right|^{(n - 2)/2} }}$$ and $\delta ^{(k - 1)} (x_0 - \left| x \right|) \cdot \delta ^{(k - 1)} (x_0 + \left| x \right|)$ . The first of them is a generalization of the product $${{\left| x \right|^{(n - 2)/2} }} \cdot \frac{{\delta (x_0 + \left| x \right|)}} {{\left| x \right|^{(n - 2)/2} }}{\text{ }}$$ given in [1, p. 158]. 相似文献
4.
《Tetrahedron letters》2014,55(50):6827-6830
A series of push–pull benzothiazoles were designed and synthesized by the Pd-catalyzed Sonogashira cross-coupling and [2+2] cycloaddition–retroelectrocyclization reactions. The photonic and electrochemical properties of these systems exhibit strong donor–acceptor interaction. The BTs 5–8 show strong intramolecular charge-transfer in the near-infrared (NIR) region. The absorption studies indicate systematic lowering of the optical HOMO–LUMO gap with increase in acceptor strength. The computational studies reveal that incorporation of strong acceptors TCNE and TCNQ results in substantial stabilization of the LUMO level compared to the HOMO level, leading to the low HOMO–LUMO gap and bathochromic shift of the absorption spectrum. The TCBD and DCNQ linked BTs 5–8 exhibit multi-step redox waves and improved thermal stability. 相似文献
5.
V. P. Gorelov V. B. Vykhodets T. E. Kurennykh V. B. Balakireva A. V. Kuz’min M. V. Ananiev 《Russian Journal of Electrochemistry》2013,49(9):915-918
The hydrogen content in CaZr1 ? x Sc x O3 ? x/2 (x = 0.00–0.20) and BaZr0.9Y0.1O3-α (for comparison) was studied by powder nuclear microanalysis. The samples were saturated with heavy water (D2O) vapors at 350 and 400°C in air. The chemical expansion of the CaZr0.95Sc0.05O3-α and BaZr0.95Y0.05O3-α samples at 700°C was measured at different water vapor pressures. A model was suggested to explain the lowered hydrogen content in oxides based on CaZrO3. 相似文献
6.
S. Anandan S. Muthukumaran M. Ashokkumar 《Journal of Sol-Gel Science and Technology》2014,70(1):133-141
Nd-doped and Nd, Cu co-doped ZnO nanoparticles (Zn0.96?xNd0.04CuxO, x = 0, 0.05, 0.1 and 0.15) were synthesized by sol–gel method. The structural and optical properties of the samples were investigated by X-ray diffraction (XRD) and UV–visible photo-spectrometer. The synthesized nanoparticles have different microstructure without changing a hexagonal wurtzite structure. CuO phase was noticed in XRD spectra at 38.73° after Cu = 5 % which was formed from remaining un-reacted Cu2+ ions. The average crystal size was gradually increased from Cu = 0 % (17 nm) to 15 % (17.6 nm) having lowest value (16.7 nm) at Cu = 5 %. The change in lattice parameters confirmed the substitution of Cu in Zn–Nd–O lattice. The observed constant c/a ratio revealed that there was no change in hexagonal wurtzite structure by Cu-doping. The energy dispersive X-ray spectra confirmed the presence of appropriate amount of Nd and Cu in Zn–O lattice. The optical absorption was increased gradually from Cu = 0–10 % and showed maximum at Cu = 10 % due to the presence of more nucleation centres and defect states. The defects related green band between 487 and 493 nm was due to the oxygen vacancies and intrinsic defects. The higher transmittance (≈ 90 %) noticed at Cu = 15 % leads to the industrial applications. The observed blue shift in energy gap from 3.49 eV (Cu = 0 %) to 3.65 eV (Cu = 10 %) and the red shift from Cu = 10 % (3.65 eV) to Cu = 15 % (3.61 eV) can be explained by the Burstein–Moss effect. Presence of chemical bonding was confirmed by Fourier transform infrared spectra. 相似文献
7.
N. V. Chezhina A. V. Fedorova S. M. Musatov 《Russian Journal of General Chemistry》2013,83(9):1645-1648
Calcium- and strontium-containing lanthanum orthoferrites have been studied using magnetic dilution method. It has been shown that the iron-atom clusters with competing ferro- and antiferromagnetic exchange interactions can exist. By using Mossbauer spectroscopy, Fe(IV) atoms have been found in the La1?0.33x Ca0.33x FexAl1?x O3 solid solutions and Fe(III) atoms in two different surroundings have been found in the La1?0.33x Sr0.33x Fe x Al1?x O3 solid solutions. The compositions of paramagnetic clusters stable at the infinite dilution have been proposed basing of the magnetic susceptibility and Mossbauer spectroscopy data. 相似文献
8.
H. Ohyama E. Simoen C. Claeys J. Vanhellemont K. Hayama J. Tokuyama Y. Takami H. Sunaga J. Poortmans M. Caymax 《Journal of Radioanalytical and Nuclear Chemistry》1999,239(2):351-355
Results are presented of an extended study on the induced lattice defects and their effects on the degradation of Si1−x
Ge
x
devices, subjected to a 20 MeV alpha-ray, 1 MeV electron, 1 MeV fast neutron, and 20 and 86 MeV proton irradiations. The
degradation of the electrical device performance increase with increasing fluence, while it decreases with increasing germanium
content. In the Si1−x
Ge
x
epitaxial layers, electron capture levels associated with an interstitial-substitutional boron complex are induced. The radiation
source dependence of performance degradation is attributed to the difference of mass and the probability of nuclear collision
for the formation of lattice defects. 相似文献
9.
In this paper, LiCr
x
Fe
x
Mn2−2x
O4 (x = 0, 0.05, 0.1) electrode materials were prepared by sol–gel technique and characterized by X-ray diffraction (XRD) and transmission
electron microscopy or high-resolution transmission electron microscopy techniques. XRD results reveal that the Cr–Fe-co-doped
LiCr
x
Fe
x
Mn2−2x
O4 materials are phase-pure spinels. The electrochemical properties of the LiMn2O4, LiCr0.05Fe0.05Mn1.9O4, and LiCr0.1Fe0.1Mn1.8O4 electrodes in 5 M LiNO3 aqueous electrolyte were investigated using cyclic voltammetry, AC impedance, and galvanostatic charge/discharge methods.
In the current range of 0.5–2 A g−1, the specific capacity of the LiCr0.05Fe0.05Mn1.9O4 electrode is close to that of the LiMn2O4 electrode, but the specific capacity of the LiCr0.1Fe0.1Mn1.8O4 electrode is obviously lower than that of the LiMn2O4 electrode. When the electrodes are charge/discharge-cycled at the high current rate of 2 A g−1, the LiCr0.05Fe0.05Mn1.9O4 electrode exhibits an initial specific capacity close to that of the LiMn2O4 electrode, but its cycling stability is obviously prior to that of the LiMn2O4 electrode. 相似文献
10.
New potassium-conducting solid electrolytes based on potassium monogallate in the K2?2x Ga2?x V x O4 system are synthesized and studied. It is found that an introduction of V5+ ions leads to a considerable increase in the KGaO2 conductivity due to the formation of vacancies in the potassium sublattice. The conductivity for optimal compositions is approximately 10?3 S cm?1 at 400°C and above 10?2 S cm?1 at 700°C. The results are compared with early obtained data for potassium monogallate dopped with four-charged cations. 相似文献
11.
12.
Pagliara S Galimberti G Mor S Montagnese M Ferrini G Grandi MS Galinetto P Parmigiani F 《Journal of the American Chemical Society》2011,133(16):6318-6322
As is well-known, the character of the π orbitals is of paramount importance for the chemical properties of the carbon allotropes and their derived compounds. While at equilibrium the nature of these orbitals is well understood, their photoinduced nonequilibrium behavior is under investigation. Here, we demonstrate that when a UV-laser pulse excites a carrier density larger than 10% of the π* density of state in graphite, a renormalization of the π-π* band gap takes place. This result has been achieved by detecting the transient reflectivity and the associated decay time of an infrared probe following the excitation of a UV pump pulse tuned across the π-π* absorption resonance. The pump photon energy at which both the transient reflectivity and the decay time are maximum is downshifted by 500 meV with respect to the relative absorption maximum at equilibrium. This finding is interpreted as a transient π-π* band gap shrinking of similar magnitude, near the M point of the Brillouin zone. 相似文献
13.
S. B. Artemkina N. G. Naumov A. V. Virovets V. E. Fedorov 《Russian Journal of Coordination Chemistry》2013,39(1):1-5
A solid solution Mo6 ? x Nb x I11 (x = 1.1–1.5) containing cluster cores {Mo5NbI8} is obtained by the high-temperature reaction of molybdenum, niobium, and iodine (550°C, 70 h, quartz ampule). According to the X-ray diffraction data, heating at 800°C in a molybdenum container results in the decomposition of the solution to Mo6I12 and Nb6I11. According to the X-ray structure analysis data, the compounds are isostructural to the high-spin modification Nb6I11 (space group Pccn). The presence of Nb atoms in the structure changes the structural type from the layered (Mo6I12) to framework structure, noticeably increases the metalmetal distances (2.661–2.716 Å, 2.695 Å) Mo6 octahedron with the retention of the distance from the metal (M) to the μ3-“capped” I atoms, and strongly elongates the M6-I-M6 bridges almost to the value observed in Nb6I11. 相似文献
14.
N. I. Sorokin 《Russian Journal of Electrochemistry》2006,42(1):106-108
Electrophysical properties of single-crystal Li2 + x Fe 2 ? 2x 2+ Fe x 3+ (MoO4)3 (x = 0.22) are studied at 25–400°C. It is found that the conduction is of electronic nature and the conductivity equals 5 × 10-2 S/cm at 300°C. The activation energy for the electron transport is 0.23 eV. The conductance in molybdate Li2.22Fe 1.56 2+ Fe 0.22 3+ (MoO4)3 is markedly anisotropic. 相似文献
15.
V. N. Krasil’nikov O. I. Gyrdasova I. V. Baklanova L. Yu. Buldakova M. Yu. Yanchenko R. F. Samigullina O. V. Koryakova 《Russian Journal of Inorganic Chemistry》2013,58(2):120-126
Quasi-one-dimensional (1D) solid solutions Ti1 ? x Fe x (OCH2CH2O)2 ? x/2 (0 < x ≤ 0.1) with the structure of anatase were prepared by heating the glycolate Ti1 ? x Fe x (OCH2CH2O)2 ? x/2 in an atmosphere of air at a temperature of >450°C. The conditions of formation and the properties of the new glycolate Ti3Fe2(OCH2CH2O)9 were described. It was found that the synthesized Ti1 ? x Fe x O2 ? 2x/2 solid solutions exhibit photocatalytic activity in the reaction of hydroquinone oxidation in an aqueous solution on irradiation with UV light. A correlation between the rate of oxidation of hydroquinone and the concentration of iron in the catalyst was established. A procedure for the preparation of titanium dioxide with the structure of anatase doped with iron and carbon (Ti1 ? x Fe x O(2 ? x/2) ? yCy) and also composites on its basis, which contain an excess amount of carbon, was proposed. 相似文献
16.
T. Yu. Vergentyev E. Yu. Koroleva A. G. Banshchikov N. S. Sokolov A. G. Chibisov 《Russian Journal of Electrochemistry》2013,49(8):783-787
The longitudinal conductivity of La1 ? x Sr x F3 ? x solid solution films (x = 0–0.24) with thicknesses of 40–260 nm grown on glass ceramics at temperatures from room temperature to 300°C and frequencies of 10?1–106 Hz was studied by impedance spectroscopy. The concentration dependence of film conductivity on the SrF2 content had a maximum near x = 0.05. An equivalent circuit was constructed on the basis of the impedance plots to describe migration processes. The DC conductivity was evaluated for all samples under study. The activation energies were estimated from the temperature dependences of the DC conductivities of the films. The resulting dependences of electrophysical parameters were compared with those for bulk materials in terms of the relaxation conductivity model. 相似文献
17.
Kuz'min A. V. Gorelov V. P. Sharova N. V. Balakireva V. B. 《Russian Journal of Electrochemistry》2003,39(5):454-460
Phase transitions in BaCe1 – x
Nd
x
O3– (x = 0–0.15) are studied on ceramic samples by dilatometry (at 370–1100 K) and by measuring electroconductivity (at 750–1220 K). Ion transport numbers are measured by an EMF method at 850–1240 K. All measurements are done in dry air (2 40 Pa). By treating the obtained temperature dependences of linear expansion with a difference method (difference between first-degree polynomial approximating the dependence and experimental points), the position and the sort of the phase transitions are determined. High-temperature phase transitions are confirmed by measuring the electroconductivity and ion transport numbers. Second-order phase transitions in pure BaCeO3 are discovered at 480 ± 10, 530 ± 10, 900 ± 10, 1030 ± 20, and 1170 ± 10 K and a first-order transition, at 665 ±10 K. Phase transitions at 900 and 1030 K are discovered for the first time ever. 相似文献
18.
A. A. Bel’mesov A. V. Levchenko T. A. Palankoev L. S. Leonova A. E. Ukshe A. I. Chikin N. G. Bukun 《Russian Journal of Electrochemistry》2013,49(8):831-835
Electrocatalysts based on platinized titania modified with ruthenia (0–9 mol %) were studied. The synthesized materials were investigated as working electrodes in potentiometric sensors sensitive to hydrogen and carbon monoxide. All electrocatalysts showed reproducible behavior at pure gas concentrations from 400 to 4000 ppm. In CO-H2 mixtures with comparable concentrations of both gases, the sensors were selective toward hydrogen at ≥0.05 mol % Ru, but not selective to hydrogen or CO at less than 0.05 mol % Ru in the substrate. 相似文献
19.
C. Lucas I. Eiroa M. R. Nunes P. A. Russo M. M. L. Ribeiro Carrott M. I. da Silva Pereira M. E. Melo Jorge 《Journal of Solid State Electrochemistry》2009,13(6):943-950
The electrochemical properties of Ca1 − x
Ce
x
MnO3 perovskite-type oxide electrode have been investigated by cyclic voltammetry in Na2SO4 aqueous solutions with pH 14. The structural and morphological characterizations have also been investigated and the information
used to interpret the electrochemical behavior. An estimation of the electrode’s capacitance and roughness factor has been
obtained by means of cyclic voltammetry. The specific capacitance and consequently the roughness factor values are affected
by the presence of Ce ions in the oxide. These findings are in agreement with the increase of the oxide-specific surface area
by the introduction of Ce ion. The open-circuit potential and the voltammetric patterns are dependent on the presence of Ce
ion in the electrodes and support that the surface electrochemistry of the perovskite oxide electrodes is governed by the
Mn4+–Mn3+ redox couple. 相似文献
20.
Hoel CA Amores JM Morán E Alario-Franco MA Gaillard JF Poeppelmeier KR 《Journal of the American Chemical Society》2010,132(46):16479-16487
The corundum-type In(2-2x)Zn(x)Sn(x)O(3) solid solution (cor-ZITO, x ≤ 0.7) was synthesized at 1000 °C under a high pressure of 70 kbar. cor-ZITO is a high-pressure polymorph of the transparent conducting oxide bixbyite-In(2-2x)Zn(x)Sn(x)O(3) (x ≤ 0.4). Analysis of the extended X-ray absorption fine structure suggests that significant face-sharing of Zn and Sn octahedra occurs, as expected for the corundum structure type. In contrast to the ideal corundum structure, however, Zn and Sn are displaced and form oxygen bonds with lengths that are similar to those observed in high-pressure ZnSnO(3). Powder X-ray diffraction patterns of cor-ZITO showed the expected unit cell contraction with increased cosubstitution, but no evidence for ilmenite-type ordering of the substituted Zn and Sn. A qualitative second harmonic generation measurement, for the solid solution x = 0.6 and using 1064 nm radiation, showed that Zn and Sn adopt a polar LiNbO(3)-type arrangement. 相似文献