共查询到20条相似文献,搜索用时 62 毫秒
1.
Gu S Kondo T Mine E Nagao D Kobayashi Y Konno M 《Journal of colloid and interface science》2004,279(1):281-283
Jingle bell-shaped hollow spheres were fabricated starting from multilayered particles composed of a silica core, a polystyrene inner shell, and a titania outer shell. Composite particles of silica core-polystyrene shell, synthesized by coating a 339-nm-sized silica core with a polystyrene shell of thickness 238 nm in emulsion polymerization, were used as core particles for a succeeding titania-coating. A sol-gel method was employed to form the titania outer shell with a thickness of 37 nm. The inner polystyrene shell in the multilayered particles was removed by immersing them in tetrahydrofuran. These successive procedures could produce jingle bell-shaped hollow spheres that contained a silica core in the titania shell. 相似文献
2.
Eiichi Mine Mitsuaki Hirose Masaki Kubo Yoshio Kobayashi Daisuke Nagao Mikio Konno 《Journal of Sol-Gel Science and Technology》2006,38(1):91-95
A previously proposed method for preparing monodispersed titania particles was extended to preparation of titania-coated silica spherical particles. The core silica particles with an average size of 264 nm were prepared with Stöber method. The titania-coating was performed in ethanol/acetonitrile solvent in the presence of silica particles by a sol-gel method with the use of titanium tetraisopropoxide (TTIP) and methylamine (MA) catalyst. Average size of the silica-titania particles decreased from 457 to 292 nm with an increase in concentration of silica particles. Coefficient of variation for the particle size was less than 5%. Colloidal crystals could be fabricated with a dip-coating technique and a sedimentation process, respectively. Measurements of reflectance revealed peaks based on the Bragg diffraction. Those peaks red-shifted with an increase in titania shell thickness because of a high refractive index of titania. Annealing at high temperature transformed crystal structure of titania shell from amorphous to anatase (500°C) and rutile (1000°C), which led to red-shift of reflection peak because of an increase in refractive index of titania due to the crystallization. 相似文献
3.
利用St觟ber方法合成了平均粒径在800 nm,球形度、单分散性良好的SiO2微球,再将其作为制备核壳结构SiO2@TiO2颗粒的内核。利用钛酸四丁酯水解反应,在SiO2内核上包覆制备了壳厚在30~100 nm的TiO2壳层,TiO2壳层厚度可根据水解反应中钛酸四丁酯的量调控。将制得的SiO2@TiO2核壳结构颗粒在550℃煅烧1 h,氧化钛壳层的晶型转变为锐钛矿相,晶型转变为锐钛矿相的TiO2更适合作为填料应用于近红外反射涂层。本文合成厚度可控SiO2@TiO2微球的方法是一种改进的溶胶凝胶方法,即在溶胶凝胶方法的基础上增加水热合成工艺。另外,本合成方法工艺简单,无表面活性剂或者耦合剂的引入。 相似文献
4.
The monodisperse hybrid silica particles (h-SiO(2)) were firstly prepared by a modified sol-gel process and the surface was modified in situ with double bonds, then abundant carboxyl moieties were introduced onto the surface of the silica core via thiol-ene click reaction. Afterward, the h-SiO(2)/TiO(2) core/shell microspheres were prepared by hydrolysis of titanium tetrabutoxide (TBOT) via sol-gel process in mixed ethanol/acetonitrile solvent, in which the activity of TBOT could be easily controlled. The carboxyl groups on the surface of silica particles promote the formation of a dense and smooth titania layer under well control, and the layer thickness of titania could be tuned from 12 to 100nm. The well-defined h-SiO(2)/TiO(2) core/shell structures have been confirmed by electron microscopy and X-ray photoelectron spectroscopy studies. After calcination at 500°C for 2h, the amorphous TiO(2) layer turned into anatase titania. These anatase titania-coated silica particles showed good photocatalytic performance in degradation of methyl orange aqueous solution under UV light. 相似文献
5.
Sakai H Kanda T Shibata H Ohkubo T Abe M 《Journal of the American Chemical Society》2006,128(15):4944-4945
Core/shell-type titania nanocapsules containing a single Ag nanoparticle were prepared. Ag nanoparticles were prepared using the reduction of silver nitrate with hydrazine in the presence of cetyltrimethylammonium bromide (CTAB) as protective agent. The sol-gel reaction of titanium tetraisopropoxide (TTIP) was used to prepare core/shell-type titania nanocapsules with CTAB-coated Ag nanoparticles as the core. TEM observations revealed that the size of the core (Ag particle) and the thickness of the shell (titania) of the core/shell particles obtained are about 10 nm and 5-10 nm, respectively. In addition, the nanocapsules were found to be dispersed in the medium as individual particles without aggregation. Moreover, titania coating caused the surface plasmon absorption of Ag nanoparticles to shift toward the longer wavelength side. 相似文献
6.
Song C Wang D Gu G Lin Y Yang J Chen L Fu X Hu Z 《Journal of colloid and interface science》2004,272(2):340-344
Silver-coated poly(methyl acrylic acid) (PSA) core-shell colloid particles were prepared by an in situ chemical reduction method. Crystalline silver/titania composite hollow spheres were obtained by coating the as-prepared PSA/silver particles with an amorphous titania layer and subsequently calcining in Ar atmosphere. SEM and TEM investigation indicated that the size of the as-prepared PSA/silver and PSA/silver/TiO(2) core-shell particles and silver/titania composite hollow particles was fairly uniform and the wall thickness of the hollow spheres was in the range of 40-80 nm. UV-vis absorption spectra were recorded to investigate their optical properties. 相似文献
7.
Zaicheng Sun Dong Ha Kim Markus Wolkenhauer Gabriela Gina Bumbu Wolfgang Knoll Jochen S Gutmann 《Chemphyschem》2006,7(2):370-378
High-density arrays of titania nanoparticles were prepared using a polystyrene-b-poly(ethylene oxide) block copolymer (PS-b-PEO) as a template and a titanium tetraisopropoxide based sol-gel precursor as titania source via a spin-coating method. The hydrophilic titania sol-gel precursor was selectively incorporated into hydrophilic PEO domains of PS-b-PEO and form titania nanoparticle arrays, due to a microphase separation between the PS block and the sol-gel/PEO phase. Field emission scanning electron microscopy (FESEM) and scanning probe microscopy (SPM) images showed that the uniformity and long-range order of the titania/PEO domains improved with increasing sol-gel precursor amount. Grazing incidence small-angle X-ray scattering (GISAXS) results indicate that the ordered structures exist over large length scales. Titania nanocrystal arrays of anatase modification were obtained by calcination at 600 degrees C for 4 h. After calcination, separated particles were observed for low and medium amounts of sol-gel precursors. Films with higher precursor amounts showed wormlike structures due to the aggregation between neighboring particles. Removal of the polymer matrix via UV treatment leads to highly ordered arrays of amorphous titania while retaining the domain size and interparticle distance initially present in the hybrid films. Photoluminescence (PL) properties were investigated for samples before and after calcination. The PL intensity increases with the increasing amount of sol-gel precursor. Bands at 412 nm were ascribed to self-trapped exitons and bands at 461 and 502 nm to oxygen vacancies, respectively. Uncalcined or UV-treated samples also showed PL properties similar to calcined samples, indicating that the local environment of the titanium atoms is similar to the environment of the crystalline anatase modification. 相似文献
8.
Rawolle M Niedermeier MA Kaune G Perlich J Lellig P Memesa M Cheng YJ Gutmann JS Müller-Buschbaum P 《Chemical Society reviews》2012,41(15):5131-5142
Nanostructured titania films are of growing interest due to their application in future photovoltaic technologies. Therefore, a lot of effort has been put into the controlled fabrication and tailoring of titania nanostructures. The controlled sol-gel synthesis of titania, in particular in combination with block copolymer templates, is very promising because of its high control on the nanostructure, easy application and cheap processing possibilities. This tutorial review gives a short overview of the structural control of titania films gained by using templated sol-gel chemistry and shows how this approach is extended by the addition of further functionality to the films. Different expansions of the sol-gel templating are possible by the fabrication of gradient samples, by the addition of a homopolymer, by the combination with micro-fluidics and also by the application of novel precursors for low-temperature processing. Moreover, hierarchically structured titania films can be fabricated via the subsequent application of several sol-gel steps or via the inclusion of colloidal templates in a one-step process. Integrated function in the block copolymer used in the sol-gel synthesis allows for the fabrication of an integrated blocking layer or an integrated hole-conductor. Both approaches grant a one-step fabrication of two components of a working solar cell, which make them very promising towards a cheap solar cell production route. Looking to the complete solar cell, the top contact is also of great importance as it influences the function of the whole solar cell. Thus, the mechanisms acting in the top contact formation are also reviewed. For all these aspects, characterization techniques that allow for a structural investigation of nanostructures inside the active layers are important. Therefore, the characterization techniques that are used in real space as well as in reciprocal space are explained shortly as well. 相似文献
9.
Recent progresses of molecular imprinting in metal oxide matrices were summarized. Application of the surface sol-gel process to mixtures of organic carboxylic acids and titanium alkoxide provides ultrathin layers of titania gel (10-20 nm thick), in which molecule-sized cavities are kept intact upon removal of the organic templates. The imprinted cavity reflects the structural and functional features of the template molecule, and the enantioselective imprinting of dipeptide isomers is observed. Robustness and flexibility of the ultrathin titania layer is demonstrated by the formation of interconnected titania hollow structures. Possible practical applications and unsolved problems of this technique are discussed. 相似文献
10.
Eu2O3 nanotubes have been successfully fabricated by an improved sol-gel template method within the nanochannels of porous anodic alumina templates. The morphology, structure, and composition of the nanotubes were characterized by means of X-ray diffraction techniques, scanning electron microscope, transmission electron microscopy, and selected-area electron diffraction. The results show that the Eu2O3 nanotubes are polycrystalline with a cubic structure. The outer diameter of nanotubes is 50-80 nm, and the thickness of the tube wall is about 5 nm. The mechanism of nanotube formation was discussed. 相似文献
11.
Submicrometer-sized titania hollow spheres have been synthesized by employing sulfonated polystyrene latex particles (averaged diameter: 200 nm) as a template in conjunction with the sol-gel method. Utilization of 0.20 mol/L titanium tetrabutoxide and 25 g/L latex led to the formation of anatase particles having shell thickness of about 15 nm and void diameter of about 150 nm. Photocatalytic activity of the titania hollow spheres was examined by focusing on its enhancement by electron scavengers in the photocatalytic decomposition of methylene blue (MB). The electron scavengers employed were inorganic oxidants such as ClO*3, BrO*3, IO*4, H2O2, and S2O2*8. Differences in electronegativity, atomic radius of the halogens, and the number of highly reactive radical and nonradical intermediates were proven to be important criteria for an electron scavenger to yield high efficiency in the MB photodecomposition. Based on the results, the effect of the oxidants used were found to be in the order of S2O2*8 > IO*4 > BrO*3 > H2O2 > ClO*3. 相似文献
12.
Hollow silica tubes with mesoporous wall structure were synthesized through the sol-gel reactions of tetraethoxysilane and n-octadecyltrimethoxysilane (TEOS/C18-TMS) on the surface of ammonium dl-tartrate crystals. Novel hollow carbon tubes with mesoporous walls and rectangular-shaped channels were fabricated using the silica tubes as templates. 相似文献
13.
Coaxial metal and magnetic alloy nanotubes in polycarbonate templates by electroless deposition 总被引:1,自引:0,他引:1
James F. Rohan Declan P. Casey Bernadette M. Ahern Fernando M.F. Rhen Saibal Roy David Fleming Simon E. Lawrence 《Electrochemistry communications》2008,10(9):1419-1422
We present a novel technique for the preparation of coaxial metal and magnetic alloy nanotubes, which is demonstrated for the coaxial nanotubes of Ni/Co and Ni/CoNiFe alloys deposited in activated polycarbonate templates using electroless plating. For each metal or alloy the tube wall thickness was controlled to be less than 100 nm. The process involved two consecutive deposition steps from hypophosphite and/or borane reducing agent based electroless plating solutions. We further characterise the magnetic properties of the ternary magnetic alloy films and coaxial nanotubes. The coaxial tubes show homogenous wall thickness and composition, which is delineated from the magnetic measurements. 相似文献
14.
三元添加剂水溶液体系制备CaCO3空心球 总被引:2,自引:0,他引:2
利用原位聚合方法, 通过加入一定量的引发剂使甲基丙烯酸原位聚合, 在三嵌段共聚物(P123)、聚甲基丙烯酸(PMAA)和十二烷基硫酸钠(SDS)的三元添加剂混合溶液体系中成功地制备了CaCO3空心球. 采用扫描电子显微镜(SEM)和X射线粉末衍射(XRD)对合成样品的形貌、结构进行了表征. 结果显示, 方解石CaCO3空心球直径约0.5-2 μm. 空心球壁由直径约25-35 nm的圆形粒子组成, 壁厚约100-300 nm. 利用核鄄壳机理解释了空心球结构的形成过程. 相似文献
15.
Mukesh Agrawal Andrij Pich Nikolaos E. Zafeiropoulos Manfred Stamm 《Colloid and polymer science》2008,286(5):593-601
Submicron hollow spheres are an interesting class of materials that receive significant attention nowadays. Closed and mechanically
robust homogeneous hollow titania microspheres with as much shell thickness as 130 nm were fabricated by coating polystyrene
beads with titania nanoparticles using sol–gel chemistry and subsequently removing the core either via heating or a chemical
dissolution process. The thickness of the titania shell deposited on polystyrene core was finely tuned between 100 and 130 nm
by varying the concentration of titania precursor, i.e., Ti(OEt)4 salt from 0.5 to 2 mM during the coating process. The obtained hybrid core–shell particles and hollow microspheres were characterized
by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray diffraction, and thermo-gravimetric
analysis. The approach employed is well suited to the preparation of titania-coated polystyrene hybrid particles and hollow
titania spheres, which can find their applications as novel building blocks with unique optical properties for fabrication
of advanced materials, catalyst, and drug delivery system. 相似文献
16.
17.
Metallic Ag nanoparticles-incorporating titania films were prepared using the sol-gel method. X-ray diffraction (XRD) patterns,
UV/Vis optical spectra and transmission electron microscopy (TEM) images were recorded to characterize the Ag/titania composite
films. Electrometer was used to estimate the resistance of Ag/titania composite film to understand the effect of the incorporation
of metallic Ag nanoparticles on the electrical properties of titania film. The results showed that metallic Ag nanoparticles
distributed randomly in titania film and most metallic Ag particles size was in the range of 5–15 nm. The agglomeration of
a small quantity of metallic Ag particles occurred and when the amount of Ag species was increased the agglomeration was enhanced.
The resistance of Ag/titania composite films decreased greatly compared with pure titania film. 相似文献
18.
Sol-gel synthesis of titania typically produces a mixture of brookite and anatase. Rietveld refinements were used to systematically track the brookite content and particle size as functions of synthetic variables. Results demonstrate that brookite content and anatase particle size decrease with decreasing Ti/H(2)O ratios. In syntheses at pH 3, the addition of HCl resulted in increased amorphous content compared to samples synthesized using HNO(3). Similar amorphous contents were observed for particles prepared at pH 6-9. Hydrothermal aging for 4 h at 200 degrees C of sol-gel products containing substantial amorphous titania resulted in higher brookite content than did hydrothermal aging of sol-gel products containing little to no amorphous titania. Finally, dialysis prior to hydrothermal aging appeared to inhibit phase transformation from brookite to anatase in aged materials. Results presented demonstrate that considerable control over the relative anatase and brookite contents can be achieved through control of synthetic variables. 相似文献
19.
A convenient method for the synthesis of very well defined porous silica glasses using ionic liquids as templates is presented. Depending on template concentration, these systems form a homologous series of mesoporous systems with diverse shapes, with the pores having constant thickness of about 2.4 nm. These nanostructures allow the analysis of the two-dimensional behavior of glasses, either from a liquid to be embedded in the pore or of the silica glass forming the wall. For the walls, the third reduced dimension can be varied in a systematic fashion. This approach is exemplified by analyzing the static glass structure of 2D-silica by WAXS. 相似文献
20.
Macroporous titania monoliths were prepared via sol-gel method using polymer foam as templates.The poly-mer foam polymerized via concentrated emulsion polymerization was immerged in a solution of titanium(IV)iso-propoxide in 2-propanol,which underwent a sol-gel process.The organic components were subsequently removedby calcination.The effects of various parameters,including the nature of the monomer,the volume fraction of dis-persed phase of the concentrated emulsion,and concentration of the sol-gel solution were investigated.The SEMmicrographs of the macroporous titania monoliths thus obtained showed that the porous structure of the final mate-rial was effectively controllable. 相似文献