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981.
用第一性原理的密度泛函理论计算了PbTe(001)表面的几何结构和电子结构.计算结果表明:PbTe(001)表面不发生重构,但表面几层原子表现出明显的振荡弛豫现象,其中第一、第二层间距减小4.5%,第二、第三层间距增加2.0%,并且表面层原子出现褶皱.表面带隙在X 点,带隙变宽,在基本带隙中不引入新的表面态,而导带底和价带顶附近等多处出现新的表 面共振态;弛豫后费米面处态密度很低,所以表面结构很稳定.
关键词:
密度泛函理论
表面几何结构
表面电子结构
PbTe 相似文献
982.
Qiu-Juan Ma Xiao-Bing Zhang Zhi-Xiang Han Bo Huang Qin Jiang Guo-Li Shen 《International journal of environmental analytical chemistry》2013,93(1):74-86
A ratiometric fluorescent zinc probe 1 of carboxamidoquinoline with a carboxylic acid group was designed and synthesised. Probe 1 exhibits high selectivity for sensing Zn2+; about a 13-fold increase in fluorescence emission intensity and an 82?nm red-shift of fluorescence emission are observed upon binding Zn2+ in EtOH/H2O (1?:?1, V/V) solution. The ratiometric fluorescence response is attributed to the 1?:?1 complex formation between probe 1 and Zn2+ which has been utilised as the basis for the selective detection of Zn2+. The analytical performance characteristics of the proposed Zn2+-sensitive probe were investigated. The linear response range covers a concentration range of Zn2+ from 2.0?×?10?6 to 5.0?×?10?5?mol?L?1 and the detection limit is 2.7?×?10?7?mol?L?1. The determination of Zn2+ in both tap and river water samples shows satisfactory results. 相似文献
983.
ABSTRACTHerein, we develop a switchable peptide-equipped protein/cucurbit[7]uril (CB[7]) supramolecular assembly as novel targeted drug vector. Specifically, bovine serum albumin (BSA) is used to interact with CB[7], serving as the core of drug vector. Then, a peptide shield layer is formed on the surface of BSA/CB[7], yielding peptide-equipped supramolecular assembly (Pep@BSA@CB[7]). The equipped peptide shield layer is composed of switchable peptide probes consisting of a polycationic cell-penetrating peptide (CPP) motif, a polyanionic motif and a linking motif, and therefore provides a variety of desirable properties. First, the CPP motif displays excellent cell penetration ability and can facilitate internalisation of the drug vector. Secondly, the polyanionic motif performs intramolecular electrostatic interaction with CPP motif and thereby can reduce non-targeted delivery towards normal cells. Thirdly, the linking motif can be specifically cleaved by matrix metalloproteinases 2 that is up-regulated in tumour microenvironment, thus enabling precise cancer-targeting. As a consequent, Pep@BSA@CB[7] can serve as a promising drug vector that exhibits superior targeting ability and high uptake efficiency towards cancer cells, which may be of great potential in cancer-targeted treatment. 相似文献
984.
One-dimensional GdVO4:Ln3+ (Ln=Eu, Dy, Sm) nanofibers have been prepared by a combination method of sol-gel process and electrospinning technology. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL), quantum efficiency (QE), and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. The XRD, FT-IR, and TG-DTA results show that GdVO4:Ln3+ nanofibers samples crystallize at 700 °C. SEM images indicate that the as prepared precursor fibers are smooth. After being calcined at 700 °C for 4 h, the fibers still maintain their fiberlike morphology with rough surface. TEM image further manifests that the GdVO4:Ln3+ nanofibers consist of nanoparticles. Under ultraviolet excitation and low-voltage electron beam excitation, GdVO4:Ln3+ phosphors showed their strong characteristic emission due to an efficient energy transfer from vanadate groups to dopants. The optimum doping concentration of Ln3+ in the GdVO4 nanofibers also has been investigated. 相似文献
985.
986.
Linghao HeLu Yao Jing SunWei Wu Jie YangLifang Cai Rui Song Yongmei HaoZhi Ma Wei Huang 《Polymer Degradation and Stability》2011,96(7):1187-1193
The aim of this investigation is to obtain a polymer-based hybrid material with biodegradability, biocompatibility, and good mechanical properties and this object was realized via. in-situ introduction of the unmodified calcium carbonate (CaCO3) into a poly(l-lactic acid) (PLLA) matrix. As verified by the measurements from scanning electron microscopy (SEM), optical microscopy, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), the hybrid films which possesses a uniform dispersion of calcium carbonate CaCO3 in nano-meter scale, mechanically robustness and thermal stability could be fabricated by a mineralization-alike process. For example, the storage modulus increases from 441 MPa of neat PLLA to 1034 MPa of hybrid film containing 2% (w/w) CaCO3. In addition, the hybrid films display a significant improvement in its UV-exposure resistance. 相似文献
987.
Xu GC Zhang W Ma XM Chen YH Zhang L Cai HL Wang ZM Xiong RG Gao S 《Journal of the American Chemical Society》2011,133(38):14948-14951
A family of three-dimensional chiral metal-formate frameworks of [NH(4)][M(HCOO)(3)] (M = Mn, Fe, Co, Ni, and Zn) displays paraelectric to ferroelectric phase transitions between 191 and 254 K, triggered by disorder-order transitions of NH(4)(+) cations and their displacement within the framework channels, combined with spin-canted antiferromagnetic ordering within 8-30 K for the magnetic members, providing a new class of metal-organic frameworks showing the coexistence of magnetic and electric orderings. 相似文献
988.
Xie P Wang L Yang L Li E Ma J Huang Y Chen R 《The Journal of organic chemistry》2011,76(19):7699-7705
A novel domino annulation between sulfur ylides and salicyl N-thiophosphinyl imines was developed. The method allows the synthesis of a highly substituted trans-2,3-dihydrobenzofuran skeleton with high yield and excellent chemo- and stereoselectivity. 相似文献
989.
990.
The Pd(OAc)2/TFP-catalyzed cyclization reaction of 2,3-allenamides in the presence of propargylic carbonates provides an efficient route to β-allenyl furanimine derivatives. Preliminary mechanistic study showed that this reaction was probably initiated by Pd(0) species. 相似文献