排序方式: 共有97条查询结果,搜索用时 19 毫秒
51.
Zhengwen Yang 《Solid State Communications》2011,151(5):364-367
Inverse opal photonic crystals of Y b3+, Er3+ co-doped TiO2 (TiO2:Yb, Er) were prepared by a self-assembly technique in combination with a sol-gel method. Upconversion (UC) luminescence properties of the inverse opals were investigated. The results show that photonic bandgap has significant influence on the upconversion emission of the TiO2:Yb, Er inverse opal photonic crystals. Significant suppression of the upconversion emission was detected if the photonic bandgap overlapped with the Er3+ ions emission band. 相似文献
52.
53.
运用胶体化学法合成了尺寸可控的二氧化硅(SiO2)亚微米溶胶小球.透射电子显微镜(TEM)结果显示样品平均尺寸可从200nm变化至600nm,单分散性较高、平均标准偏差小于5%.通过自然沉积法,由溶胶SiO2小球自组织晶化制备了人工蛋白石晶体(opal晶体)结构.样品的剖面扫描电子显微镜(SEM)检测表明,样品为面心立方(fcc)结构.分析表明,较高的单分散性和缓慢的沉积过程是SiO2溶胶小球自组织晶化成三维有序结构的关键因素.反射谱中峰位在1320nm处的反射峰的出现,意味着样品在宏观尺度上的有序排列,
关键词:
亚微米二氧化硅溶胶小球
人工蛋白石晶体
方向带隙 相似文献
54.
G.A. Emelchenko A.N. Gruzintsev V.T. Volkov V.M. Masalov A.V. Bazhenov D.A. Fokin 《Photonics and Nanostructures》2007,5(2-3):96-100
The fabrication of the 2D periodic structures in ZnO thin films by magnetron sputtering on the opal matrices was developed. The microstructures were characterized by AFM and SEM. The spontaneous and stimulated emissions of the ZnO layers on opal were studied at N2 laser excitation (λ = 337 nm). The stimulated emission near 397 nm was observed at room temperature from ZnO–opal structure. The threshold of the electron–hole plasma recombination laser process was 300 kW/cm2 for this structure. This threshold is two orders of magnitude smaller of that one for the flat ZnO–SiO2 films owing to DFB resonator effect in 2D structure. 相似文献
55.
N. V. Gaponenko G. K. Malyarevich A. V. Mudryi O. B. Gusev M. V. Stepikhova M. Yu. Tsvetkov S. M. Kleshcheva M. I. Samoilovich A. P. Stupak 《Journal of Applied Spectroscopy》2007,74(5):687-691
We have studied the luminescence and luminescence excitation spectra of erbium in the 1.54 μm region in titanium oxide and
silicon oxide xerogels, formed in the mesoscopic pores of three-dimensional synthetic opals and two-dimensional porous aluminum
oxide structures. For erbium-doped titanium oxide films formed in opal, in contrast to analogous films on porous aluminum
oxide, in the luminescence excitation spectra we observe an intense broad band with a maximum in the ∼360 nm region. We discuss
the possible nature of this band.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 622–626, September–October, 2007. 相似文献
56.
A. Smallwood P. S. Thomas A. S. Ray P. Šimon 《Journal of Thermal Analysis and Calorimetry》2007,88(1):185-188
The dehydration of samples of a Coober Pedy, South Australian sedimentary
white opal, displaying play of colour, was investigated using TMA by heating
the samples of the specimen to a range of temperatures between room temperature
and 1000 at 200°C intervals followed by cooling to room temperature. Etched
fracture surfaces of the samples were then examined using SEM. The samples
showed the typical expansion at low temperature up to 210°C before contraction
was observed. The contraction of the opals was ascribed to both sintering,
supported by morphological change observed in the SEM micrographs, and dehydroxylation
of the silanol groups producing silicon-oxygen-silicon bridges resulting in
a more dense silica network. 相似文献
57.
Jaeyun Kim Sidi A. Bencherif Weiwei Aileen Li David J. Mooney 《Macromolecular rapid communications》2014,35(18):1578-1586
Three‐dimensional macroporous scaffolds have extensively been studied for cell‐based tissue engineering but their use is mostly limited to mechanical support for cell adhesion and growth on the surface of macropores. Here, a templated fabrication method is described to prepare cell‐friendly inverse opal‐like hydrogels (IOHs) allowing both cell encapsulation within the hydrogel matrix and cell seeding on the surface of macropores. Ionically crosslinked alginate microbeads and photocrosslinkable biocompatible polymers are used as a sacrificial template and as a matrix, respectively. The alginate microbeads are easily removed by a chelating agent, with minimal toxicity for the encapsulated cells during template removal. The outer surface of macropores in IOHs can also provide a space for cell adherence. The cells encapsulated or attached in IOHs are able to remain viable and to proliferate over time. The elastic modulus and cell‐adhesion properties of IOHs can be easily controlled and tuned. Finally, it is demonstrated that IOH can be used to co‐culture two distinct cell populations in different spatial positions. This cell‐friendly IOH system provides a 3D scaffold for organizing different cell types in a controllable microenvironment to investigate biological processes such as stem cell niches or tumor microenvironments.
58.
Qunling Fang Junlong Geng Bianhua Liu Daming Gao Dr. Fei Li Zhenyang Wang Dr. Guijian Guan Dr. Zhongping Zhang Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(43):11507-11514
This paper reports an inverted opal fluorescence chemosensor for the ultrasensitive detection of explosive nitroaromatic vapors through resonance‐energy‐transfer‐amplified fluorescence quenching. The inverted opal silica film with amino ligands was first fabricated by the acid–base interaction between 3‐aminopropyltriethoxysilane and surface sulfonic groups on polystyrene microsphere templates. The fluorescent dye was then chemically anchored onto the interconnected porous surface to form a hybrid monolayer of amino ligands and dye molecules. The amino ligands can efficiently capture vapor molecules of nitroaromatics such as 2,4,6‐trinitrotoluene (TNT) through the charge‐transfer complexing interaction between electron‐rich amino ligands and electron‐deficient aromatic rings. Meanwhile, the resultant TNT–amine complexes can strongly suppress the fluorescence emission of the chosen dye by the fluorescent resonance energy transfer (FRET) from the dye donor to the irradiative TNT–amino acceptor through intermolecular polar–polar resonance at spatial proximity. The quenching response of the highly ordered porous films with TNT is greatly amplified by at least 10‐fold that of the amorphous silica films, due to the interconnected porous structure and large surface‐to‐volume ratio. The inverted opal film with a stable fluorescence brightness and strong analyte affinity has lead to an ultrasensitive detection of several ppb of TNT vapor in air. 相似文献
59.
Brown L. D. Ray A. S. Thomas P. S. Guerbois J. P. 《Journal of Thermal Analysis and Calorimetry》2002,68(1):31-36
Naturally occurring opals from three different regions in Australia were studied for their thermal characteristics. All the
opals showed initial expansion followed by contraction in thermomechanical analysis (TMA) although the temperature at which
the change from expansion to contraction occurred depended on their provenance. Thermogravimetric analysis (TG) revealed different
rates and temperatures of dehydration for these opals. A general correlation between the temperature at which there was a
zero thermal expansion and that of the maximum rate of dehydration was observed. A dehydration–sintering mechanism is proposed
with the effect of sintering being more pronounced following total dehydration.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
60.
Fabrication of BaTiO3 Inverse Opal Photonic Crystal 总被引:1,自引:0,他引:1
AnXIANG JianPingGAO HongKuiCHEN JiuGaoYU RuiXianLIU 《中国化学快报》2004,15(2):228-230
The colloidal crystal template or opal with a closed-packed face centered cubic (fcc) lattice, was prepared from monodisperse polystyrene (PS) spheres by gravity sedimentation. The template was used for the generation of photonic crystal. The template provided void space for infiltration of liquid precursor composed of titanium butyloxide, barium acetate, ethanol, and acetic acid. The opal composite was hydrolyzed, dried, sintered by heating for completely removing PS spheres to form BaTiO3 photonic crystals with inverse opal structure. The PS spheres were replaced by air spheres, which interconnected each other through the windows on the BaTiO3 wall.So both the BaTiO3 wall and air void constitute continuous phases. 相似文献