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51.
Saeed Amir Aslanzadeh 《Chinese Journal of Physics (Taipei)》2018,56(5):1917-1924
Metal atom located on metal oxide (MMO) is a promising material with various applications such as hydrogen storage. As one of the metal oxides, niobium oxide (NbO) presents fascinating properties that make it a possibly applicable in MMOs. Here, we investigated the feasibility of transition metal-NbO hybrids as MMO materials for application in the hydrogen storage technology. In this respect, the hydrogen adsorption of transition metals (Fe, Ni, Cu, Pd, Ag, and Pt) decorated on the NbO nanocluster has been explored using density functional theory calculations. We found that the adsorption energy of the H2 molecule on the NbO adsorbent is remarkably increased by locating the transition metals on the NbO metal oxide. Our results reveal that the transition metals decorated on the NbO nanocluster can act as active sites for hydrogen adsorption. Among the studied transition metals, Pt shows the highest hydrogen capacity up to 6.52 wt%. 相似文献
52.
Taketoshi Matsumoto Patricia Nickut Kazuya Watanabe Tatsuya Tsukuda Katharina Al-Shamery 《Surface science》2007,601(22):5226-5231
Reduction of oxidized gold nanoclusters by exposures to foreign gases and irradiation of UV photons has been investigated using X-ray photoelectron spectroscopy. Gold nanoclusters with narrow size distributions protected by alkanethiolate ligands were deposited on a TiO2(1 1 0) surface with dip coating. Oxygen plasma etching was used for removal of alkanethiolate ligands and oxidization of gold clusters. The oxidized gold clusters were exposed to CO, C2H2, C2H4, H2, and hydrogen atoms. Although, C2H4 and H2 did not show any indications of reduction of oxidized gold clusters, CO, C2H2, and hydrogen atoms reduced the oxides on gold cluster surfaces. Among them, hydrogen atoms were most effective for reduction. Irradiation of UV photons around 400 nm could also reduce the oxidized gold clusters. The photochemical reduction mechanism was proposed as follows. The photo-reduction was initiated by electronic excitation of gold clusters and oxygen atoms activated reacted with carbon atoms at the surfaces of gold clusters. Carbon species were likely absorbed in gold clusters or remained at the boundaries between gold clusters when gold clusters agglomerated during oxygen plasma exposures. As the photochemical reduction progressed, carbon atoms segregated to the surfaces of gold clusters. 相似文献
53.
The atomic-scale structural changes in an α-Fe2O3 (hematite) (0 0 0 1) surface induced by sulfidation and subsequent oxidation processes were studied by X-ray photoemission spectroscopy, LEED, and X-ray standing wave (XSW) measurements. Annealing the α-Fe2O3(0 0 0 1) with a H2S partial pressure of 1 × 10−7 Torr produced iron sulfides on the surface as the sulfur atoms reacted with the substrate Fe ions. The oxidation state of the substrate Fe changed from 3+ to 2+ as a result of the sulfidation. The XSW measured distance of the sulfur atomic-layer from the unrelaxed substrate oxygen layer was 3.16 Å. The sulfide phase consisted of three surface domains identified by LEED. Formation of the two-dimensional FeS2 phase with structural parameters consistent with an outermost layer of (1 1 1) pyrite has been proposed. Atomic oxygen exposure oxidized the surface sulfide to a sulfate () and regenerated the α-Fe2O3(0 0 0 1) substrate, which was indicated by a (1 × 1) LEED pattern and the re-oxidization of Fe to 3+. 相似文献
54.
Piotr Matczak 《Molecular physics》2017,115(3):364-378
In this work, extensive quantum-chemical calculations have been carried out to identify and elucidate trends in the hydrogen-bonding (HB) interaction involving halogen acceptors covalently bonded to a group 14 atom. A series of 25 heterodimers composed of MH3X (where M = C?Pb and X = F?At) and HNC molecules have been selected as model complexes stabilised by the HB interaction occurring between the X atom of MH3X and the H atom of HNC. The interaction energy (Eint) between MH3X and HNC in the MH3X···HNC complexes falls in the range from ?2.7 to ?10.8 kcal/mol, indicating weak or medium strength of HB in these complexes. The strength of HB in the complexes remains consistent with the well-known HB weakening as X gets heavier. Regarding the effect of M on Eint, the gradual strengthening of HB is observed while descending group 14, but only from M = Si to M = Pb. The trends in Eint are compared with various HB-related parameters obtained from vibrational analysis, the natural bond orbital (NBO) method, the symmetry-adapted perturbation theory (SAPT) and the quantum theory of atoms in molecules (QTAIM). The parameters that present clear (possibly linear) relationships with Eint have been selected to characterise the effect of M and X on the HB interaction. 相似文献
55.
56.
Infrared reflection absorption spectroscopy that used buried metal layer substrates (BML-IRRAS) and density functional cluster calculations were employed to investigate the water related oxidation reactions of 2H + H2O/Si(1 0 0)-(2 × 1), 2D + H2O/Si(1 0 0)-(2 × 1), and H2O + H/Si(1 0 0)-(2 × 1). In addition to the oxygen inserted coupled monohydrides, which were previously reported in the former reaction system, we report several other oxidized Si hydride species in our BML-IRRAS experiments. Three new pairs of vibrational bands are identified between 900 and 1000 cm−1. These vibrational frequencies were calculated using Si9 and Si10 cluster models that included all possible structures from zero to five oxygen insertions into the top layer silicon atoms using a B3LYP gradient corrected density functional method with a polarized 6-31G** basis set for all atoms. The three pairs of vibrational modes are assigned to the scissoring modes of adjacent and isolated SiH2 with zero, one, and two oxygen atoms inserted into the Si back bonds. All the other newly observed vibrational peaks related to Si oxidation are also assigned in this study. The Si-O stretching bands observed in the reaction 2D + H2O/Si(1 0 0)-(2 × 1) show an isotope effect, which suggests that in the system 2H + H2O/Si(1 0 0)-(2 × 1) also, hydrogen atom tunneling plays an important role for the insertion of oxygen atoms into Si back bonds that form oxidized adjacent dihydrides. 相似文献
57.
乳腺癌组织中蛋白质与核酸分子氢键特征的研究 总被引:8,自引:0,他引:8
正常乳腺组织与乳腺癌组织的红外光谱之间存在明显而规律的差异,其中包括蛋白质与核酸等生物分子的氢键缔合方式和程度上的不同。光谱的变化主要表现在:(1)蛋白质的酰胺Ⅰ带,N-H基团和某些氨基酸残基上C-O(H)基团的振动谱带;(2)核酸分子中磷酸二酯的反对称伸缩振动谱带和配对的碱基N-H基团振动等谱带上。氢键是维系和促进蛋白质与核酸高级结构形成的重要作用力,癌变时氢键的变化与癌细胞的特殊生物学行为密切相关,因此有可能利用氢键的这些光谱特征作为乳腺癌诊断和预测癌变可能性的指标。 相似文献
58.
59.
金属氢的高压合成机理 总被引:3,自引:1,他引:3
从氢原子间及氢分子间的相互作用入手,提出了固体氢中氢分子在高压作用下解离为氢原子,并以氢原子相互结合成金属氢的微观转化过程的机理。用这样的转化机理,可以解释毛河光等关于固体氢的拉曼光谱频率随高压变化规律的实验结果。 相似文献
60.
催化动力学荧光法测定中草药对羟基自由基的清除率 总被引:11,自引:1,他引:11
苯甲酸具有很弱的荧光,在Co2+的催化下,过氧化氢能氧化苯甲酸发出强的荧光。中草药提取物可以清除溶液中的·OH, 使产物的生成量减少, 从而使溶液的荧光增加程度降低。据此原理建立了一种测定中草药对羟基自由基清除率的催化动力学荧光新体系。当中草药的浓度为4.0 mg(干重)·mL-1时,测得紫花地丁、苍术和赤芍对羟基自由基的清除率分别为60.8%,40.1%和94.3%。该方法与分光光度法测定结果相比无显著性差异。 相似文献