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61.
Yanchun?LiEmail author Liling?Sun Limin?Cao Jianhua?Zhao Haiyan?Wang Yun?Nan Zhenshan?Gao Wenkui?Wang 《中国科学G辑(英文版)》2003,46(1):47-51
Bulk single crystals β-FeSi2, as a new photoelectric and thermoelectric material, has been successfully grown using chemical vapor transport technique
by using iodine as transport agent in a sealed ampoule. The effects of crystal growth condition on quality and morphologies
of the single crystals were studied. Both needle-like and grain-like single crystals were gained. By changing substrate temperature,
tetrahedral high quality α-FeSi2 single crystals were also obtained. 相似文献
62.
Hua Lai Amurisana Bao Yuming Yang Yanchun Tao Hua Yang 《Journal of nanoparticle research》2008,10(8):1355-1360
Eu3+-doped (La, Ln) PO4 (Ln = Gd and Y) phosphors were prepared by a facile co-precipitation method. Their structures and luminescent properties
under UV excitation were investigated. Structural characterization of the nanostructured luminescence material was carried
out with X-ray powder diffraction analysis. Scanning electron microscopy was carried out to understand the surface morphological
features and grain sizes with 50–100 nm. It is found that (La, Gd) PO4:Eu3+ phosphors have the same crystal structure as LaPO4:Eu3+, which is monoclinic with a little different lattice parameters. In the case of (La, Y) PO4:Eu3+ phosphors, however, the gradual change from monoclinic to tetragonal structure of host lattice was observed, as the amount
of Y ion increased. From the photoluminescence spectra for (La, Ln) PO4:Eu3+ (Ln = Gd and Y), the emission transition 5D0 → 7F1 has been found to be more prominent over the normal red emission transition 5D0 → 7F2. Furthermore, the size influence on the products was discussed. It was observed that the spectral features possess sharp
and bright emission for potential applications on the monitors of the television and some other related electronic systems,
in observing the images in orange–red color. 相似文献
63.
Summary: A composite film composed of porous polyurethane (PU) and polystyrene (PS) microspheres with both superhydrophobicity and superoleophilicity has been prepared. In this film, the dual‐scale structure enhances both the hydrophobicity and oleophilicity of the surface material. The composite film with such an ‘intelligent’ wettability property can be utilized to separate oil and water systems efficiently.
64.
Xinzhen Du Weihua Lu Yarong Wang Yanchun Sun Hualin Deng Jinguo Hou 《Supramolecular chemistry》2013,25(3):209-214
Supramolecular inclusion of modified β-cyclodextrin (β-CD) with Triton X-100 (TX) and α-bromonaphthalene (BN) was studied by fluorescence and phosphorescence measurements. Major differences were observed in the magnitude of the apparent stability constants and quenching constants of the inclusion complexes. Methyl substitution on the rims of β-CD increased the binding of TX with β-CD but was unfavorable to the protection of the phenyl group of TX from fluorescence quenching and further accommodation of BN for steric considerations. According to the overall molecular size of β-CD, TX and BN, further inclusion of BN in the cavity of β-CD occupied by TX may force the flexible tert-octyl chain of TX to deform to a greater extent and close packing complexes were obtained. Phosphorescence of BN arising from intermolecular energy transfer between BN and the phenyl group of TX was observed when the phenyl group of TX was irradiated. In the case of heptakis(2,6-di-O-methyl)-β-CD, BN failed to penetrate into the cavity because of the steric hindrance of the methyl substituents at the rim of the β-CD cavity. 相似文献
65.
Zhennan Wu Dr. Yanchun Li Jiale Liu Prof. Zhongyuan Lu Prof. Hao Zhang Prof. Bai Yang 《Angewandte Chemie (International ed. in English)》2014,53(45):12196-12200
Metal nanoclusters (NCs) with diameter below 2 nm are promising catalysts in oxygen reduction reactions (ORR). However, the high surface energy of ultra‐small clusters leads to structural instability, shedding doubt on practical applications. Herein, we demonstrate a self‐assembly method to improve the durability of catalytic metal NCs, employing copper NCs capped by 1‐dodecanethiol (DT) to form free‐standing ribbons in colloidal solution. By tuning the cooperation between the dipolar attraction between Cu NCs and the van der Waals attraction between DT, the thickness of ribbons is adjusted to a single NC scale. Such free‐standing ribbons exhibit excellent catalytic activity and durability in ORR. 相似文献
66.
Sheng Chen Jianniao TianYixuan Jiang Yanchun ZhaoJuanni Zhang Shulin Zhao 《Analytica chimica acta》2013
In this paper, we report a simple, selective, sensitive and low-cost turn-on photoluminescent sensor for cysteine and homocysteine based on the fluorescence recovery of the CdTe/CdS quantum dots (QDs)–phenanthroline (Phen) system. In the presence of Phen, the fluorescence of QDs could be quenched effectively due to the formation of the non-fluorescent complexes between water-soluble thioglycolic acid (TGA)-capped QDs and Phen. Subsequently, upon addition of cysteine and homocysteine, the strong affinity of cysteine and homocysteine to QDs enables Phen to be dissociated from the surface of QDs and to form stable and luminescent complexes with cysteine and homocysteine in solution. Thus, the fluorescence of CdTe/CdS QDs was recovered gradually. A good linear relationship was obtained from 1.0 to 70.0 μM for cysteine and from 1.0 to 90.0 μM for homocysteine, respectively. The detection limits of cysteine and homocysteine were 0.78 and 0.67 μM, respectively. In addition, the method exhibited a high selectivity for cysteine and homocysteine over the other substances, such as amino acids, thiols, proteins, carbohydrates, etc. More importantly, the sensing system can not only achieve quantitative detection of cysteine and homocysteine but also could be applied in semiquantitative cysteine and homocysteine determination by digital visualization. Therefore, as a proof-of-concept, the proposed method has potential application for the selective detection of cysteine and homocysteine in biological fluids. 相似文献
67.
Crown ether-centered two-armed polymers, i.e., polystyrene-dibenzo-18-crown-6-polystyrene (PSCS) and poly(methyl methacrylate)-dibenzo-18-crown-6-poly(methyl methacrylate) (PMCM), were designed to self-assemble in a proposed manner directed by the specific affinity between the polar crown ether rings. When spin coated onto a silicon wafer surface, macroporous films were obtained. In contrast, the proposed assemblies were strongly adsorbed on a highly polar mica surface, looking like porous islands near the spin center. At areas far from the spin center, these islands slipped to form terrace islands under the huge shear by the centrifugal force. The formation of the porous islands and terrace islands provide further evidence to the proposed assembling of the two-armed polymers. 相似文献
68.
The surface morphology evolution of three thin polystyrene (PS)/polymethyl methacrylate (PMMA) blend films (<70 nm) on SiOx substrates upon annealing were investigated by atomic force microscopy (AFM) and some interesting phenomena were observed. All the spin-coated PS/PMMA blend films were not in thermodynamic equilibrium. For the 67.1 and the 27.2 nm PS/PMMA blend films, owing to the low mobility of the PMMA-rich phase layer at substrate surfaces and interfacial stabilization caused by long-range van der Waals forces of the substrates, the long-lived metastable surface morphologies (the foam-like and the bicontinuous morphologies) were first observed. For the two-dimensional ultrathin PS/PMMA blend film (16.3 nm), the discrete domains of the PS-rich phases upon the PMMA-rich phase layer formed and the secondary phase separation occurred after a longer annealing time. 相似文献
69.
Hongbo Li Yanchun Liang Ning Zhang Jinsong Guo Dong Xu Zhanshan Li 《Journal of Heuristics》2016,22(2):125-145
In this paper, we improved two classical degree-based variable ordering heuristics, \(\frac{\textit{Dom}}{\textit{Ddeg}}\) and \(\frac{\textit{Dom}}{\textit{Wdeg}}\). We propose a method using the summation of constraint tightness in degree-based heuristics. We also propose two methods to calculate dynamic constraint tightness for binary extensional constraints and non-binary intensional constraints respectively. Our work shows how constraint tightness can be practically used to guide search. We performed a number of experiments on some benchmark instances. The results have shown that, the new heuristics improve the classical ones by both computational time and search tree nodes and they are more efficient than some other successful heuristics on the instances where the classical heuristics work well. 相似文献
70.
Motion of integrated CdS nanoparticles by phase separation of block copolymer brushes 总被引:1,自引:0,他引:1
A new method of reversibly moving CdS nanoparticles in the perpendicular direction was developed on the basis of the phase separation of block copolymer brushes. Polystyrene-b-(poly(methyl methacrylate)-co-poly(cadmium dimethacrylate)) (PS-b-(PMMA-co-PCdMA)) brushes were grafted from the silicon wafer by surface-initiated atom transfer radical polymerization (ATRP). By exposing the polymer brushes to H2S gas, PS-b-(PMMA-co-PCdMA) brushes were converted to polystyrene-b-(poly(methyl methacrylate)-co-poly(methacrylic acid)(CdS)) (PS-b-(PMMA-co-PMAA(CdS))) brushes, in which CdS nanoparticles were chemically bonded by the carboxylic groups of PMAA segment. Alternating treatment of the PS-b-(PMMA-co-PMAA(CdS)) brushes by selective solvents for the outer block (a mixed solvent of acetone and ethanol) and the inner PS block (toluene) induced perpendicular phase separation of polymer brushes, which resulted in the reversible lifting and lowering of CdS nanoparticles in the perpendicular direction. The extent of movement can be adjusted by the relative thickness of two blocks of the polymer brushes. 相似文献