Facile fabrication of ZrO2 hollow porous microspheres with yeast as bio-templates

ZrO₂ hollow porous microspheres have been fabricated successfully using living yeast cells as bio-templates through a facile ageing process at lower crystallizing temperature. XRD, SEM, FT-IR and N₂ adsorption-desorption were used to characterize ZrO₂ hollow microspheres. The results showed that the inorganic-organic hybrid hollow microspheres were fabricated at 100 °C and ZrO₂ hollow microspheres with tetragonal phase and porous structure were obtained at 300 °C. The crystallization temperature of ZrO₂ decreased obviously due to the inducting of bio-molecules. The as-prepared hollow microspheres are approximately ellipsoid. The shells of these hollow microspheres are porous, which are composed of some nanoparticles with size of ∼20 nm. The formation mechanism of ZrO₂ hollow microspheres was proposed and discussed tentatively.     

以PSA-A乳胶粒为模板批量制备TiO2空心球

以表面富载马来酸羧基的聚(苯乙烯-丙烯酸酯)阴离子(PSA-A)乳胶粒为模板,硫酸钛为原料,水为分散介质,制备了PSA-A/钛水解产物核壳微球,然后在空气中适当温度下煅烧得到粒径约为450nm的TiO2空心球壳,用TG、SEM、TEM、IR和XRD对样品进行了分析表征,并研究了核壳结构形成的过程和各实验条件对陈化过程中体系pH值变化速率的影响.得出影响核壳结构的关键因素为体系的pH值变化速率,以此依据设计出钛盐浓度为1mol/L,乳胶粒浓度为230g/L的高浓度条件下批量制备TiO2空心球壳的新实验方案,最终产物保持良好的空心球结构.     

Hollow Multishelled Heterostructured Anatase/TiO2(B) with Superior Rate Capability and Cycling Performance

TiO₂ is a potential anode material for lithium‐ion batteries due to its high rate capability and high safety. Here, a controllable synthesis for hollow nanostructured TiO₂, with heterostructured shells of TiO₂(B) and anatase phases, is presented for the first time, by using a sequential templating approach. The hollow nanostructures can be easily controlled to produce core–shell and double‐shelled materials with different compositional ratios of anatase to TiO₂(B) by tuning the synthetic conditions. When used as the anode materials for lithium‐ion batteries, a specific discharge capacity of 215.4 mAh g^?1 for the double‐shelled anatase/TiO₂(B) hollow microspheres is achieved at a current rate of 1 C (335 mA g^?1) for the 100th cycle and shows high specific discharge capacities of 141.6 and 125.7 mAh g^?1 at the high rates of 10 and 20 C over 1000 cycles. These results are due to the unique stable hollow multishelled structure, which has a high specific surface area, as well as the interface between the heterostructured anatase/TiO₂(B) phases contributing a substantial number of lithium‐ion storage sites.     

Novel triethanolamine assisted sol-gel synthesis of N-doped TiO2 hollow spheres

A facile preparation of N-doped anatase TiO₂ hollow spheres in sub-micron size with good morphology was developed in this work. Polystyrene latexes in size of 470 nm were used as the templates to fabricate polystyrene/TiO₂ core-shell spheres in the sol-gel process. Here the ammonia/triethanolamine positive/negative catalyst pair was first employed to control the coating of TiO₂ onto the surface of the PS templates. And synchronously triethanolamine served also as the N source. The N-doped TiO₂ hollow spheres with good morphology were first obtained here after calcinations of the core-shell spheres. It was proved that the hollow spheres have distinct visible light response from 390 to 600 nm. The content of the N doping could be easily adjusted by changing the amount of triethanolamine added and the optical response of TiO₂ hollow spheres shifted more to the visible light as the content of the N doping increasing. The N doping could increase the separation efficiency of the photoinduced electron and hole, so the intensity of photoluminescence decreased obviously with increased content of the N doping.     

Photocatalytic properties of nanocrystalline TiO2 thin film with Ag additions

In the present study, nanocrystalline TiO₂/Ag composite thin films were prepared by a sol–gel spin coating technique. While, by introducing polystyrene (PS) microspheres, porous TiO₂/Ag films were obtained after calcining at a temperature of 500 °C. The as-prepared TiO₂ and TiO₂/Ag thin films were characterized by X-ray diffractometry, and scanning electron microscopy to reveal the structural and morphological differences. In addition, the photocatalytic properties of these films were investigated by degrading methylene blue under UV irradiation.After 500 °C calcination, the microstructure of PS-TiO₂ film without Ag addition exhibited a sponge-like microstructure while significant sintering effect was noticed with Ag additions and the films exhibited a porous microstructure. Meanwhile, coalescence of nanocrystalline anatase-phase TiO₂ can be observed with respect to the sharpening of XRD diffraction peaks. The photodegradation of porous TiO₂ doped with 1 mol% Ag exhibited the best photocatalytic efficiency where 72% methylene blue can be decomposed after UV exposure for 12 h.     

Sol-gel synthesis of silver/titanium dioxide (Ag/TiO2) core-shell nanowires for photocatalytic applications

Silver/titanium dioxide (Ag/TiO₂) core-shell nanowires were synthesized by direct coating of TiO₂ shells on the surface of silver nanowires (AgNWs) through a simple sol-gel process. TEM image and EDX elemental analysis had confirmed the presence of TiO₂ coating on the surface of AgNWs. The thickness of titanium dioxide coating was about 10 nm. These Ag/TiO₂ core-shell nanowires showed good photocatalytic activities in the decomposition of methylene blue as a model organic dye in aqueous solution under UV light irradiation. Ag/TiO₂ core-shell nanowires are potentially useful in photocatalytic applications.     

Synergistic effects of hollow structure and surface fluorination on the photocatalytic activity of titania

To study the synergistic effects of hollow structure and surface fluorination on the photoactivity of TiO₂, TiO₂ hollow microspheres were synthesized by a hydrolysis–precipitate method using sulfonated polystyrene (PS) as templates and tetrabutylorthotitanate (TBOT) as precursor, and then calcined at 500 °C for 2 h. The calcined samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N₂ sorption. Photocatalytic activity was evaluated using reactive brilliant red X3B, an anionic organic dye, as a model pollutant in water. The results show that the photocatalytic activity of TiO₂ hollow microspheres is significantly higher than that of TiO₂ nanoparticles prepared in the same experimental conditions. At pH 7 and 3, the apparent rate constants of the former exceed that of the latter by a factor of 3.38 and 3.15, respectively. After surface fluorination at pH 3, the photoactivity of hollow microspheres and nanoparticles further increases for another 1.61 and 2.19 times, respectively. The synergistic effect of surface fluorination and hollow structure can also be used to prepare other highly efficient photocatalyst.     

Preparation of helical TiO2/CMC microtubes and pure helical TiO2 microtubes

Helical TiO₂/CMC (carbon microcoils) microtubes and helical TiO₂ microtubes were obtained by making TiO₂ layer coatings on the surface of CMC templates using a sol-gel and chemical vapor deposition (CVD) processes. The preparation conditions, morphologies and some properties were examined. Uniform TiO₂ (anatase) layers were obtained on the CMC templates by a CVD process using vapor phase hydrolysis of titanium tetra-isopropoxide at 300°C followed by heat treatment in N₂ or by calcination in air at 500–;650°C. The helical TiO₂/CMC microtubes showed good photocatalytic activity. It was considered that the helical structure activated and enhanced the photocatalytic activity of TiO₂, probably caused by the generation of inductive microelectric current induced by the irradiation of UV light, resulting in the generation of micromagnetic fields around the tubes.     

Preparation of rutile (TiO<Subscript>2</Subscript>) nanostructured materials at low temperature from TiCl<Subscript>4</Subscript> aqueous solution

The synthesis of rutile (TiO₂) nanostructured materials at low temperature from TiCl₄ aqueous solution was described. TiO₂ coatings on polystyrene (PS) particles were prepared by layer-by-layer assembly technique. The samples were characterized by DTA-TG, SEM, XPS, TEM and XRD techniques. The experimental results showed that pure rutile-TiO₂ coatings with nanocrystal structure were synthesized at 100 °C. On the surface of PS particles, sphere-type TiO₂ coatings exhibited uniform shape and a narrow size distribution. The amount of TO₂ (wt%) and shell thickness of particles increased with the adding of coating layers. Hollow TiO₂ spheres were obtained by calcination at 450 °C. TiO₂/PS with 2 coating layers showed higher degradation rate. The photocatalytic activity of hollow TiO₂ spheres was higher than that of TiO₂/PS.     

Surface Modification of Sericite Using TiO2 Powders Prepared by Alkoxide Hydrolysis: Whiteness and SPF Indices of TiO2-Adsorbed Sericite

Titania (TiO₂) powders have been prepared from the 0.025-M titanium isopropoxide/ethanol solution and the 0.5-M distilled water/ethanol solution. The prepared TiO₂ powders showed an anatase phase and a rutile phase after heat treatment at 500°C for 2 h and 1000°C for 2 h, respectively. The heterocoagulation adsorption between TiO₂ powder and sericite surface in water was achieved in the range of pH 3.63.7 (where this pH range shows a maximum Zeta-potential difference for two powders). On the other hand, an anomalous transformation behavior appeared in the TiO₂-adsorbed sericite after heat treatment at 1000°C. The surface modification of sericite through the TiO₂-adsorption improved the whiteness as well as the SPF (Sun Protection Factor) indices.