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排序方式: 共有840条查询结果,搜索用时 15 毫秒
1.
The refractive indices (n) of eight standard oils from Physikalisch Technische Bundesanstalt, Germany were determined with an accuracy of ±1×10−4 by using Abbe Refractometer. The measurements were performed at temperature 20°C in the spectral range 0.4–0.7 μm. The experimental data were fitted to the simple Cauchy dispersion formula and the results were found to be consistent within the limits of experimental error. In all cases, the refractive index decreased monotonically with increasing wavelength. The refractive indices (n) of these oils have been measured as a function of the temperature t (20°C up to 50°C) at λ=0.589 μm and were found to have linear temperature dependencies. The refractive indices of the studied oils and the uncertainty in their values are calculated at λ=0.589. The Lorentz–Lorenz (L–L) formula has been tested and it was found to be valid with a maximum deviation of 0.4% and was used to calculate the molecular polarizability θ. 相似文献
2.
CuPc molecules adsorbed on Au(1 1 0)-(1 × 2): growth morphology and evolution of valence band states
Fabrizio Evangelista A. RuoccoValdis Corradini M.P. DonzelloCarlo Mariani Maria Grazia Betti 《Surface science》2003,531(2):123-130
We present the growth morphology, the long-range ordering, and the evolution of the valence band electronic states of ultrathin films of copper phthalocyanine (CuPc) deposited on the Au(1 1 0)-(1 × 2) reconstructed surface, as a function of the organic molecule coverage. The low energy electron diffraction patterns present a (5 × 3) reconstruction from the early adsorption stages. High-resolution UV photoelectron spectroscopy data show the disappearance of the Au surface states related to the (1 × 2) reconstruction, and the presence of new electronic features related to the molecule-substrate interaction and to the CuPc molecular states. The CuPc highest occupied molecular orbital gradually emerges in the valence band, while the interface electronic states are quenched, upon increasing the coverage. 相似文献
3.
Fluorometric investigation of the interaction of bovine serum albumin with surfactants and 6-mercaptopurine 总被引:2,自引:0,他引:2
Hu YJ Liu Y Jiang W Zhao RM Qu SS 《Journal of photochemistry and photobiology. B, Biology》2005,80(3):235-242
Fluorescence quenching in solutions of bovine serum albumin has been investigated in the presence of 6-mercaptopurine and ionic surfactants. Spectroscopic analysis of the emission quenching at different temperatures revealed that the quenching mechanism of bovine serum albumin by 6-mercaptopurine was dynamic quenching mechanism. The Stern–Volmer quenching model has been successfully applied, and the activation energy of the interaction between 6-mercaptopurine and bovine serum albumin as much as 4.26 kJ mol−1 was calculated. The distance r between donor (bovine serum albumin) and acceptor (6-mercaptopurine) was obtained according to fluorescence resonance energy transfer (FRET). The result of synchronous fluorescence spectra shows that the conformation of bovine serum albumin has been changed at the present of 6-mercaptopurine. 相似文献
4.
A visible light promoted, photoredox catalysed, green one-pot approach for the alkylation of amine substrates with sp2 carbon has been developed. This eosin Y based organic transformations, can behave as an effective direct hydrogen-atom transfer catalyst for coupling reaction. The proposed strategy includes simple procedure which can make adduct product with sp2 carbon. This eosin Y based photocatalytic hydrogen-atom transfer strategy may hold great potential for diverse functionalization of a wide range of native CH bonds in an economical and sustainable manner. 相似文献
5.
《Arabian Journal of Chemistry》2020,13(11):8347-8360
FeN -co-doped TiO2 photocatalysts are prepared by sol–gel method using titanium tetraisopropoxide, urea and iron(II) acetylacetonate as precursors of titania, nitrogen and iron, respectively. The prepared samples are analysed from chemical-physical point of view by X-ray diffraction (XRD), Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS), specific surface area measurements and scanning electron microscopy (FESEM). UV–Vis DRS spectra evidence that the co-doping of TiO2 with N and Fe leads to the narrowing of the band gap value (2.7 eV) with respect to Fe-doped TiO2 (2.8 eV) and N-doped TiO2 (2.9–3 eV). XRD patterns show that photocatalysts are mainly in anatase phase and Fe and N ions are successfully incorporated into the TiO2 lattice. The average crystallite size of Fe-N co-doped TiO2 is slightly lower than the other samples and equal to about 7 nm and the specific surface area of the co-doped sample results to be 117 m2 g−1. Photocatalytic performances of all prepared samples are evaluated by analysing the degradation of Acid Orange 7 azo dye under visible light irradiation. Photocatalytic efficiency obtained using FeN co-doped TiO2 strongly increases compared to undoped TiO2, N-doped TiO2 and Fe-doped TiO2 photocatalysts. In detail, using the co-doped photocatalyst, dye discoloration and mineralization result equal to about 90 and 83% after 60 min of LEDs visible light irradiation, underlining the best performances of the FeN co-doped TiO2 photocatalyst both in terms of treatment time and electric energy consumption. 相似文献
6.
本文通过酶活性测定,荧光光谱和紫外光谱研究了外加Cu2+与烟草多酚氧化酶(简称PPO)的相互作用。结果表明,微量铜的加入能增加酶的活性,[Cu2+]/[PPO]为0.20左右时酶活性最大,[Cu2+]/[PPO]为0.91时,Cu2+开始表现出对PPO活性的抑制;Cu2+对PPO内源荧光的猝灭机制属于形成络合物所引起的静态猝灭,猝灭常数Ksv为8.0375×103L·mol-1;Cu2+的加入使PPO蛋白质分子构象发生变化,α-螺旋含量增加,多肽链及Trp和Tyr残基的芳杂环进一步向分子内收缩,疏水基团之间的疏水作用增强。 相似文献
7.
《Discrete Mathematics》2022,345(12):113074
It has previously been observed that the limiting gap distribution of the directions to visible points of planar quasicrystals may vanish near zero, that is, there exist planar quasicrystals with a positive limiting minimal normalised gap between the angles of visible points. The exact values of these limiting minimal normalised gaps have not been determined. In this paper we give explicit formulas for the densities of visible points for planar quasicrystals from several families, which include the Ammann–Beenker point set and the vertex sets of some rhombic Penrose tilings. Combining these results with a known characterisation of the limiting minimal gap in terms of a probability measure on an associated homogeneous space of quasicrystals, we give explicit values of the limiting minimal normalised gap between the angles of visible points for several families of planar quasicrystals, in particular, for the Ammann–Beenker point set and for the vertex sets of some rhombic Penrose tilings. We also compare our results with numerical observations. 相似文献
8.
XUE Zhixin YANG Guipeng CHEN Dianbao MA Xiaomei ZHANG Xiqin QUAN Zhenlan 《反应性高分子(英文版)》2006,15(1):35-39
Fullerenes (C60/C70) linked up to Ni-doped ZnS through the medium of an amphalic polymer polyvinyl pyrrolidone (PVP) to form a new kind of photocatalyst for hydrogen evolution from aqueous Na2S/Na2SO3 solution under visible light irradiation, the photocatalytic activities of this novel photocatalyst C60/C70-PVP-Zn0.999Ni0.001S are 3-5 fold higher compared with that of precurse catalyst Zn0.999Ni0.001S. This result could be attributed to Schottky barrier layer built between C60/C70 and Zn0.999Ni0.001S due to the electro-negativity of C60 and characteristic of being used as a multiple electron acceptor. C60 or C60/C70, its moiety, with its low energy first excited singlet state, is a good energy acceptor and in addition readily accepts multiple electrons, making it a potential electron accumulate as we know, which could protect the separation between electrons and holes against combination. This is an important reason for the marked increase of amount of H2 evolution during the photocatalytic process for the composite system C60/C70-PVP-Zn0.999Ni0.001S. 相似文献
9.
Joanna Szymańska-Cybulska Ewa Kamieńska-Piotrowicz 《Journal of solution chemistry》2006,35(12):1631-1643
The enthalpies of solution of Co(II) and Na(I) trifluoromethanesulfonates (triflates) in N,N-dimethylformamide (DMF)–methanol (MeOH) mixtures have been measured over the whole range of solvent composition. From these
data the enthalpies of transfer of Co(II) and triflate ions from methanol to the mixed solvent have been determined usingliterature
values of the enthalpies of transfer of the Na+ ion. The results have been analyzed by means of the theory of preferential solvation. The analysis revealed the preference
of DMF for solvating the Co(II) ion in the MeOH-rich region of solvent composition and the lack of preference of any component
in the DMF-rich region. Visible absorption spectra of the Co(II) ion in DMF–MeOH mixtures have been also measured in the whole
range of solvent composition and analyzed using the partial least-squares method. The mean composition of the solvation sphere
of the Co(II) ion versus solvent composition has been determined on the basis of both analyses. The results were found to be consistent with each
other and with those obtained previously from FT-IR spectra. 相似文献
10.
CuAl2O4 powder synthesis by sol-gel method and its photodegradation property under visible light irradiation 总被引:1,自引:0,他引:1
Jiang Yanyan Li Jinggang Sui Xiaotao Ning Guiling Wang Chengyu Gu Xiumei 《Journal of Sol-Gel Science and Technology》2007,42(1):41-45
Nanocrystalline spinel CuAl2O4 powders were prepared by sol-gel method from nitrate Cu(NO3)2·3H2O, Al(NO3)3·9H2O and complex C6H8O7·H2O. Sintering was carried out at 400, 500, 600, 700, 800°C respectively for 2 h in air. The XRD patterns started to appear
CuAl2O4 peaks after sintering of 500°C and consist of only CuAl2O4 peaks as spinel crystal after sintering of 700°C. The powders were analyzed by TEM and UV-vis diffuse reflectance spectrum
to be round, about 10–30 nm in size and Eg=1.77 eV. Photodegradation property of nanocrystalline CuAl2O4 powders was investigated by using methyl orange as model pollutant and mercury lamp (λ>400 nm) as energy source. The results
indicated that CuAl2O4 powders sintered at 700°C had the excellent visible photocatalytic property. Under the irradiation of visible light, methyl
orange could be degraded 97% in 120 min. 相似文献