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1.
Synthesis of nanostructured magnetic photocatalyst by colloidal approach and spray-drying technique 总被引:1,自引:0,他引:1
A.L. Costa B. Ballarin A. SpegniF. Casoli D. Gardini 《Journal of colloid and interface science》2012,388(1):31-39
Nanostructured particles with a magnetic core and a photocatalytic shell are very interesting systems for their properties to be magnetically separable (and so reusable) in photocatalytic water depuration implant. Here, a robust, low time-consuming, easily scale up method to produce Fe3O4/SiO2/TiO2 hierarchical nanostructures starting from commercial precursors (i.e. Fe3O4, SiO2) by employing a colloidal approach (i.e. heterocoagulation) coupled with the spray-drying technique is presented. In particular, a self-assembled layer-by-layer methodology based on the coagulation of dissimilar colloidal particles was applied. First, a passive layer of silica (SiO2, amorphous) was created on magnetite in order to avoid detrimental phenomena arising from the direct contact between magnetite and titania, then the deposition of titania onto silica-coated-magnetite was promoted. TiO2, SiO2 and Fe3O4 nanosols were characterized in terms of zeta potential, optimized and a self-assembled layer-by-layer approach was followed in order to promote the heterocoagulation of silica onto magnetite surface and of titania onto silica coated magnetite. Once optimized the colloidal route, the mixture was then spray-dried to obtain a granulated powder with nano-scale reactivity, easier to handle and re-disperse in comparison to starting nanopowders with the same surface properties. The nanostructured particles have been characterized by different techniques such as SEM, TEM, XDR and their magnetic properties have been investigated. Moreover, preliminary photocatalytic texts have been performed. 相似文献
2.
Polymer modifications of ultrafine monodispersed colloidal metal oxide particles, smaller than 80 nm in diameter, by the graft-polymerization of styrene to a hydrophilic macromer adsorbed on the surface were investigated. The polymerization in ethanolic silica and titania colloid solution, which had negatively larger ζ-potentials, ?30 and ?42 mV in neutral aqueous solution respectively, gave poly(styrene)–silica or titania composite, being of nonspherical shape. The modifications of colloidal particles, having lower surface energy, such as Al(OH)3 and CeO2–TiO2–SiO2 complex, led to the formation of spherical composites, ranging in size from 500 to 3000 nm, of scattered metal oxide or hydroxide particles. 相似文献
3.
Yong Yang Yuming Zhou Jianhua Ge Yongjuan Wang Yunxia Zhu 《Journal of solid state chemistry》2011,184(10):2617-2622
Optically active polyurethane/titania/silica (LPU/TiO2/SiO2) multilayered core–shell composite microspheres were prepared by the combination of titania deposition on the surface of silica spheres and subsequent polymer grafting. LPU/TiO2/SiO2 was characterized by FT-IR, UV–vis spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), SEM and TEM, and the infrared emissivity value (8–14 μm) was investigated in addition. The results indicated that titania and polyurethane had been successfully coated onto the surfaces of silica microspheres. LPU/TiO2/SiO2 exhibited clearly multilayered core–shell construction. The infrared emissivity values reduced along with the increase of covering layers thus proved that the interfacial interactions had direct influence on the infrared emissivity. Besides, LPU/TiO2/SiO2 multilayered microspheres based on the optically active polyurethane took advantages of the orderly secondary structure and strengthened interfacial synergistic actions. Consequently, it possessed the lowest infrared emissivity value. 相似文献
4.
Silica and core–shell structured titania/silica (TiO2/SiO2) nanoparticles with particles size ranging from tens to hundreds of nanometers were prepared and deposited onto cotton fabric
substrates by sol–gel process. The morphologies of the nanoparticles were characterized by field-emission scanning electron
microscope (FE-SEM). The photocatalytic decomposition properties as well as UV-blocking properties of the fabrics treated
with SiO2 and TiO2/SiO2 nanoparticles were investigated. 相似文献
5.
Won Young Jung Seung Hee Baek Seong Soo Park Gun-Dae Lee Euh Duck Jeong Hyun Gyu Kim Seong-Soo Hong 《Reaction Kinetics and Catalysis Letters》2007,91(2):233-240
The nanosized titania and TiO2/SiO2 particles were prepared by the microwave-hydrothermal method. The effect of physical properties TTIP/TEOS ratio and calcination
temperature has been investigated. The major phase of the pure TiO2 particle is of the anatase structure, and a rutile peak was observed above 800°C. In TiO2/SiO2 particles, however, no significant rutile phase was observed, although the calcination temperature was 900°C. No peaks for
the silica crystal phase were observed at either silica/titania ratio. The crystallite size of TiO2/SiO2 particles decreases as compared to pure TiO2 at high calcination temperatures. The TiO2/SiO2 particles show higher activity on the photocatalytic decomposition of orange II as compared to pure TiO2 particles. 相似文献
6.
Gun'ko VM Zarko VI Leboda R Marciniak M Janusz W Chibowski S 《Journal of colloid and interface science》2000,230(2):396-409
Fumed oxides, such as silica, alumina, titania, and mixed X/silicas (X=Al2O3 (AS), TiO2 (TS), CVD-TiO2, Al2O3/TiO2 (AST)), pristine or covered by carbon deposits formed due to pyrolysis of cyclohexene, were studied using nitrogen adsorption–desorption, photon correlation spectroscopy particle sizing, and electrophoresis. A significant influence of the nature of surface-active sites and structural features of oxides (individual silica, mixed fumed, or prepared using chemical vapor deposition (CVD)) on the pyrolysis of cyclohexene is observed with respect to the pore size distributions due to differences between primary particles in aggregates and on their outer surfaces in the filling of channels by pyrocarbon, resulting also in a decrease in fractal dimension. Structural characteristics and dependences of the particle size distribution and electrokinetic potential of X/SiO2 and C/X/SiO2 on the pH of aqueous suspensions suggest that the carbon deposit covers mainly acidic sites at the X/SiO2 interfaces and X phase patches possessing catalytic activity in pyrolysis, as the negative charge of particles is reduced by pyrocarbon grafting. 相似文献
7.
The influence of silica/titania and silica/zirconia nanoparticles on thermooxidative degradation of PMMA was studied by non-isothermal
thermogravimetry. Kinetic parameters describing the length of the oxidation induction periods were obtained from the treatment
of the dependence of oxidation onset temperature on heating rate. Using these parameters, the protection factors of nanoparticles
have been calculated. It was found that SiO2/TiO2 nanoparticles increase the thermooxidation stability of PMMA where the stabilizing effect, expressed as the protection factor,
depends on temperature only slightly. The stabilizing effect of SiO2/ZrO2 is much stronger than that of SiO2/TiO2 and decreases with increasing temperature. 相似文献
8.
Dong Hwan Ryu Seong Chul Kim Sang Man Koo Dong Pyo Kim 《Journal of Sol-Gel Science and Technology》2003,26(1-3):489-493
Titania coated silica nanoparticles were prepared through a sol-gel process using peptized TiO2 nano-sols. The TiO2 sols were obtained by peptization, the process of redispersing a coagulated colloid, and were coated on SiO2 particles by the control of the weight ratio of TiO2/SiO2 and the pH of the mixture in aqueous solution. At pH 4.5 the difference of zeta-potential between SiO2 and TiO2 maximized and then the TiO2-coated SiO2 particles with highest TiO2 contents (20%) were obtained without the self-aggregation of TiO2 sols. The morphologies of particles were characterized with field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) and the isoelectric points (IEP) of particles were measured by zeta potential. The nature of exposed titanium ions on the surface of titania-coated silica nanoparticles was elucidated by X-ray photoelectron spectroscopy (XPS). 相似文献
9.
Poly(styrene) (PST) coatings of monodispersed colloidal metal oxide particles by surface grafting to poly(N-vinyl-2-pyrrolidone) (ST–PVP) or quaternized poly(4-vinylpyridine) (ST-PVPy(Me)) macromer, having a vinylphenylene end group, were investigated. Radical polymerization of styrene (ST) in ethanolic silica colloid in the presence of ST-PVP successfully led to the formation of monodispersed PST/PVP copolymer/SiO2composites. The addition of divinylbenzene (DVB) to the reaction system gave SiO2 composites coated with crosslinked PST. Graft-polymerization of ST to ST-PVP also took place on TiO2, CeO2 and Al(OH)3 colloidal particles in ethanolic solution. However, ST-PVPy(Me) adsorbed on colloidal silica did not effectively graft PST. 相似文献
10.
Hongtao Cui Minmin Wang Wanzhong Ren Yan Liu Yunan Zhao 《Journal of Sol-Gel Science and Technology》2013,66(3):512-517
Silica monoliths embedded with high concentration of γ-Fe2O3 or TiO2 nanoparticles were prepared by a sol–gel procedure designed according to the inherent properties of oxide colloids. In the first step, highly dispersible oxide nanoparticles were produced using an in situ modification sol–gel strategy. Then, these particles were re-dispersed in silicon alkoxide-containing solution to form a stable colloidal solution. The hydrolysis and condensation reactions of alkoxide were catalyzed by an organic base (morpholine). Due to the large molecule size of morpholine, the electric double layer on the surface of colloidal particles was not compressed by the ionized morpholine molecules. The colloidal solution thus remained stable during the gelation process. Through this procedure, oxide nanoparticles could be immobilized homogeneously in the pores of a silica matrix, forming highly transparent and crack-free monoliths. 相似文献
11.
《Analytical letters》2012,45(13):2515-2523
Abstract Cellulose tris(3,5‐dimethylphenylcarbamate) (CDMPC) coated TiO2/SiO2 has been prepared by coating CDMPC on TiO2/SiO2 which consists of micrometer‐sized silica spheres as core and nanometer‐sized titania particles as surface coating. Eight basic indole ring derivative enantiomers were separated on this CDMPC coated CSP and symmetrical peaks were obtained using hexane as the mobile phase and various alcohols as modifiers. The influence of the mobile phase composition and structural variation of the solutes on the enantioseparation was investigated and discussed. 相似文献
12.
Poly(methylmethacrylate)/silica/titania films were prepared via a nonaqueous sol–gel route at ambient temperature, followed by spin-coating and multistep baking. The acrylic monomers used were methyl methacrylate (MMA) and 3-(trimethoxysilyl)propyl methacrylate (MSMA). Silicic acid and titanium(IV) chloride were used as the precursors of the inorganic component. FTIR results indicated the successful bonding between TiO2 and SiO2. TEM images suggested the silica/titania particles were well dispersed in the Poly(methyl methacrylate) (PMMA) matrix with the particles size smaller than 40 nm in our study. The refractive index and extinction coefficient were also studied. The refractive index of the hybrid increased with increasing the titania content, and the hybrid films showed high optical transparency in visible region. 相似文献
13.
Li Chen Haixia Shen Zhen Lu Cang Feng Su Chen Yanru Wang 《Colloid and polymer science》2007,285(13):1515-1520
TiO2–SiO2 composite nanoparticles were prepared by a sol–gel process. To obtain the assembly of TiO2–SiO2 composite nanoparticles, different molar ratios of Ti/Si were investigated. Polyurethane (PU)/(TiO2–SiO2) hybrid films were synthesized using the “grafting from” technique by incorporation of modified TiO2–SiO2 composite nanoparticles building blocks into PU matrix. Firstly, 3-aminopropyltriethysilane was employed to encapsulate TiO2–SiO2 composite nanoparticles’ surface. Secondly, the PU shell was tethered to the TiO2–SiO2 core surface via surface functionalized reaction. The particle size of TiO2–SiO2 composite sol was performed on dynamic light scattering, and the microstructure was characterized by X-ray diffraction and
Fourier transform infrared. Thermogravimetric analysis and transmission electron microscopy (TEM) employed to study the hybrid
films. The average particle size of the TiO2–SiO2 composite particles is about 38 nm when the molar ratio of Ti/Si reaches to1:1. The TEM image indicates that TiO2–SiO2 composite nanoparticles are well dispersed in the PU matrix. 相似文献
14.
Dongfang Zhang 《High Energy Chemistry》2012,46(2):133-138
Nanometer platinum-deposited titania particles were prepared through a soft chemical reduction method. The physico-chemical
properties of the obtained products are analyzed by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, and photoluminescence
spectra. The as-prepared metal-TiO2 nanohybrid was found to show excellent photocatalytic reactivity toward rhodamine-B decomposition. In the current case, chemical
reduction of hydrogen hexachloroplatinate by glucose results in the intercalation of metallic platinum into the titania matrix.
The deposited platinum atoms were featured by surface-plasmon resonance under visible-light excitation and electrons from
platinum nanoparticles would transfer to the conduction band of titania and accelerate the formation O2*− to degrade dye molecule. As a consequence, platinum deposition onto TiO2 surface is confirmed to yield a superior photocatalytic performance over the naked titania. 相似文献
15.
SiO2/TiO2 composite microspheres with microporous SiO2 core/mesoporous TiO2 shell structures were prepared by hydrolysis of titanium tetrabutylorthotitanate (TTBT) in the presence of microporous silica microspheres using hydroxypropyl cellulose (HPC) as a surface esterification agent and porous template, and then dried and calcined at different temperatures. The as-prepared products were characterized with differential thermal analysis and thermogravimetric (DTA/TG), scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption. The results showed that composite particles were about 1.8 μm in diameter, and had a spherical morphology and a narrow size distribution. Uniform mesoporous titania coatings on the surfaces of microporous silica microspheres could be obtained by adjusting the HPC concentration to an optimal concentration of about 3.2 mmol L−1. The anatase and rutile phase in the SiO2/TiO2 composite microspheres began to form at 700 and 900 °C, respectively. At 700 °C, the specific surface area and pore volume of the SiO2/TiO2 composite microspheres were 552 and 0.652 mL g−1, respectively. However, at 900 °C, the specific surface area and pore volume significantly decreased due to the phase transformation from anatase to rutile. 相似文献
16.
17.
The Critical Effect of Niobium Doping on the Formation of Mesostructured TiO2: Single‐Crystalline Ordered Mesoporous Nb‐TiO2 and Plate‐like Nb‐TiO2 with Ordered Mesoscale Dimples 下载免费PDF全文
Takamichi Matsuno Dr. Yoshiyuki Kuroda Prof.Dr. Atsushi Shimojima Prof.Dr. Hiroaki Wada Prof.Dr. Kazuyuki Kuroda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(37):13073-13079
Highly ordered mesoporous niobium‐doped TiO2 with a single‐crystalline framework was prepared by using silica colloidal crystals with ca. 30 nm in diameter as templates. The preparation of colloidal crystals composed of uniform silica nanoparticles is a key to obtain highly ordered mesoporous Nb‐doped TiO2. The XPS measurements of Nb‐doped TiO2 showed the presence of Nb5+ and correspondingly Ti3+. With the increase in the amount of doped Nb, the crystalline phase of the product was converted from rutile into anatase, and the lattice spacings of both rutile and anatase phases increased. Surprisingly, the increase in the amount of Nb led to the formation of plate‐like TiO2 with dimpled surfaces on one side, which was directly replicated from the surfaces of the colloidal silica crystals. 相似文献
18.
Three-dimensional photonic crystals made of close-packed polymethylmethacrylate (PMMA) spheres or air spheres in silica, titania and ceria matrices have been fabricated and characterized using SEM, XRD, Raman spectroscopy and UV–Vis transmittance measurements. The PMMA colloidal crystals (opals) were grown by self-assembly from aqueous suspensions of monodisperse PMMA spheres with diameters between 280 and 415 nm. SEM confirmed the PMMA spheres crystallized uniformly in a face-centred cubic (fcc) array, and UV–Vis measurements show that the colloidal crystals possess pseudo photonic band gaps in the visible and near-IR regions. Inverse opals were prepared by depositing silica (SiO2), titania (TiO2) or ceria (CeO2) in the voids of the PMMA colloidal crystals using sol-gel procedures, then calcining the resulting structure at 550 °C to remove the polymer template. The resulting macroporous materials showed fcc ordering of air spheres separated by thin frameworks of amorphous silica, nanocrystalline titania or nanocrystalline ceria particles, respectively. Optical measurements confirmed the photonic nature of the inverse opal arrays. UV–Vis data collected for the opals and inverse opals obeyed a modified Bragg’s law expression that considers both diffraction and refraction of light by the photonic crystal architectures. The versatility of the colloidal crystal template approach for the fabrication of macroporous oxide structures is demonstrated. 相似文献
19.
Cadmium hydroxide-deposited cadmium selenide nanoparticles were prepared by the addition of cadmium sulfate solution to cadmium selenide nanoparticles in a weak alkaline solution at room temperature. The photoluminescence measurements displayed that the luminescence intensity was greatly increased by the addition of cadmium ions due to the formation of cadmium hydroxide on the surfaces of the cadmium selenide nanoparticles. Then, CdSe/Cd(OH)2/SiO2 nanocomposite particles were synthesized using 3-mercatopropyl trimethoxysilane by Stöber method. After the formation of CdSe/Cd(OH)2/SiO2 nanocomposite particles, the emission ability was mostly stabilized. Additionally, the stabilization of the composite particles against dilution with the physiological saline was checked. The results showed that the photoluminescence stability was promoted after the deposition of silica on the surfaces of the CdSe/Cd(OH)2 nanoparticles. Comparison of the stability of CdSe/SiO2 nanoparticles with that of CdSe/Cd(OH)2/SiO2 ones showed that Cd(OH)2 shell could enhance the photoluminescence effectively. 相似文献
20.
Xiangfu Meng Zhongzhong Qian Haitao Wang Xiaowei Gao Shimin Zhang Mingshu Yang 《Journal of Sol-Gel Science and Technology》2008,46(2):195-200
In this study, SiO2/TiO2–organoclay hybrids with high adsorption capability and high photocatalytic activity were synthesized by immobilizing mixed
silica and titanium dioxide nanoparticles on organically modified clay via a hydrothermal sol–gel method. Addition of negatively
charged silica particles enhanced the uniform dispersion of titanium dioxide nanoparticles on organoclay layers by decreasing
the system tension, which resulted in high photocatalytic activity of SiO2/TiO2–organoclay hybrids. The high adsorption capability endowed by organically modified clay enriched the organic compounds around
the photoactive sites, and thus greatly improved the photodegradation efficiency. Combining the high adsorption capability
of organoclay with the high photocatalytic activity of TiO2 nanoparticles, SiO2/TiO2–organoclay hybrids were promising and cost-effective photocatalysts in removal of pollutants from wastewater. 相似文献