In this paper we review the preparation and reaction properties of ordered SmRh surface alloys and SmOx/Rh(1 0 0) model catalyst which have been systematically investigated by low energy electron diffraction (LEED), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HREELS) and temperature desorption spectroscopy (TDS). The growth of Sm on Rh(1 0 0) at room temperature follows the Stranski-Krastanov mode. Thermal treatment of the Sm films on Rh(1 0 0) leads to the formation of ordered SmRh surface alloys. An “inverse” SmOx/Rh(1 0 0) model catalyst is produced under controlled oxidation of the SmRh surface alloy. CO adsorption on the SmRh alloy and SmOx/Rh(1 0 0) surfaces gives rise to five TDS characteristic features originating from different adsorption sites. Both the site blocking of SmOx and the electron transfer between SmOx and Rh substrate significantly affect the CO adsorption. Acetate decomposition on both Rh(1 0 0) and the SmOx/Rh(1 0 0) surfaces are found to undergo two competitive pathways that yields either (i) CO(a) and O(a) or (ii) CO2(g) and H2(g) at high temperature. The reactive desorption of acetic acid on SmOx/Rh(1 0 0) is dramatically different from that on Rh(1 0 0). A rapid decomposition of acetic acid to produce CO(g) and CO2(g) can be observed only on SmOx/Rh(1 0 0), where CO(g) becomes the predominant product at 225 K, indicating a strong promotional effect of SmOx in the selective decomposition of acetate. Finally, we briefly describe the future outlook of research on rare earth oxide/metal model catalysts. 相似文献
CdSe nanoparticles of improved stability against aggregation were synthesized by using amphiphilic block copolymer polyacrylonitrile-block-poly(ethylene glycol)-block-polyacrylonitrile (PAN-b-PEG-b-PAN, PEA). The products were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopic (HRTEM). The optical properties were characterized by UV-vis spectrophotometer and the room temperature photoluminescence (PL). The results revealed that the CdSe nanoparticles have been uniformly distributed throughout the copolymer with diameters of 6-7 nm and the produced novel hybrid nanocomposites displayed obviously quantum size effects and interesting fluorescence features. FTIR results provided the information on the interaction between the copolymer and the nanoparticles. The TGA revealed that the thermal property of the copolymer enhanced due to the interaction of the nanoparticles and the groups of the copolymer. 相似文献
A Weyl semimetal (WSM) features Weyl fermions in its bulk and topological surface states on surfaces, and is novel material hosting Weyl fermions, a kind of fundamental particles. The WSM was regarded as a three‐dimensional version of “graphene” under the illusion. In order to explore its promising photoelectric properties and applications in photonics and photoelectronics, here, we study the anisotropic linear and nonlinear optical responses of a WSM TaAs, which are determined by the relationship and balance between its topological surface states and Weyl nodes. We demonstrate that topological surface states which break the bulk symmetry are responsible for the anisotropy of the mobility, and the anisotropic nonlinear response shows saturable characteristic with extremely large saturable intensity. We also find that the mobility is anisotropic with the magnitude of 104 cm2V−1s−1 at room temperature and can be accelerated by the optical field. By analyzing the symmetry, the nonlinear response is mainly contributed by the fermions close to the Weyl nodes, and is related to the Pauli's blocking of fermions, electron‐electron interaction. This work experimentally discovers the anisotropic ultrahigh mobility of WSMs in the optical field and may start the field for the applications of WSMs in photonics and photoelectronics.
High-spin states of 160Lu have been studied through the 144Sm( 19F, 3n) reaction. The previously known πh11/2⊗υi13/2 yrast band is extended from Iπ = 21- to 25- and a four quasiparticle band with configuration πh11/2[523]7/2 -⊗υh9/2[521]3/2 -⊗ (υi13/2)2 is reported.
Received: 21 May 2001 / Accepted: 19 July 2001 相似文献