The effect of SiO2 on TiO2 up-conversion photoluminescence film

In order to increase the photoelectric conversion efficiency of silicon solar cell, the up-conversion film has been tried to enhance the response of the solar cells to the infrared band. Yb³⁺, Er³⁺ co-doped SiO₂/TiO₂ composite films with different Ti/Si molar ratio were deposited on the glass substrate with sol–gel method and spin-coating technique. The effect of different molar ratio of Ti/Si on the film’s morphology and optical properties was investigated. The morphology, the absorption spectra and photoluminescence (PL) spectra of the film were tested and analyzed. After the film was annealed at 900 °C, the XRD diffraction pattern indicated that rare earths ions have evenly dispersed into the matrix lattice. The FT-IR showed that Si ions entered into the lattice of titanium dioxide, and the Ti–O–Si bonds came into being. When the film pumped with a laser of 980 nm, there were a dominant red emission and several weak green peaks. In addition, with the increase of the mole ratio of Si/Ti, the intensity of the film’s up-conversion luminescence increases at first and then decreases. When the molar ratio of Si/Ti is 1/8, the sample had the highest intensity of up-conversion luminescence.     

Synthesis and characterisation of alumina fibres using organic/inorganic composite sol

Abstract

The polyvinyl butyral–Al(NO₃)₃ composite sols and alumina fibres were synthesised by the sol–gel process in an aqueous solution using the polyvinyl butyral (PVB) and Al(NO₃)₃.9H₂O (AN). The viscosity of PVB–AN composite sol increased with increasing AN content and aging time when it was laid at room temperature. The addition of AN leads to the formation of new weak peak and the deviation of diffraction angle to higher degrees according to the X-ray diffraction patterns (XRD). The exothermic peak of PVB disappeared and a weak endothermic peak was observed in differential scanning calorimetry curves of composite powders. The XRD pattern of fibres sintered at 1200°C showed the formation of α-alumina and the fibres showed smooth surface and uniform diameter.     

Synthesis of the uniform hollow spherical Sr2SiO4:Eu2+ phosphors via an h-BN protective method

The uniform hollow spherical Sr₂SiO₄:Eu²⁺ green emitting phosphors have been successfully synthesized using hollow silica spheres as templates by an h-BN protective method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results directly confirmed the existence of the hollow spherical structure with a narrow size distribution and a shell thickness of 15–25 nm. The h-BN protective film, observed by high resolution TEM, plays an important role in the formation of the hollow spherical morphology and the improvement of photoluminescence properties. Comparing with the Sr₂SiO₄:Eu²⁺ micron-phosphor prepared by the traditional solid state reaction method, the hollow spherical phosphor with nano-sized grains exhibits stronger green emission under ultraviolet–blue light excitation. This could be attributed to the elimination of surface defects by the h-BN coating. This research gives an economic and convenient way to synthesize uniform spherical phosphors with high quantum efficiency.     

Preparation and Characterization of Buoyant Nitrogen-doped TiO2 Composites Supported by Fly Ash Cenospheres for Photocatalytic Applications

Fly ash cenospheres(FACs) coated with nitrogen-doped TiO2(N-TiO2) composites were prepared by the sole gel method for use as photocatalysts.The photocatalytic activity and kinetics of the composites produced at different calcination temperatures and with different nitrogen doping contents were studied under visible light irradiation by monitoring the environmental degradation of methylene blue(MB).The MB degradation ratio of N-TiO2/FAC(25%,450℃) was 10% higher than that of N-TiO2 and 40% higher than that of TiO2/FAC.These N-TiO2/FAC composites floated in water and could be recovered after the photocatalytic reaction by phase separation.     

CdS/ZnO复合颗粒的制备与电致发光性能

以sol-gel法制备了ZnO前驱体,并通过水热反应得到了CdS/ZnO复合颗粒.采用红外光谱(IR)、X射线衍射(XRD)、扫描电镜(SEM)表征其结构、组成及形貌,并对其电致发光(EL)特性进行表征.结果表明CdS纳米晶生长在ZnO基体上;EL谱表明没有煅烧的CdS/ZnO复合颗粒表现为CdS的激子发射,发光强度较纯CdS有了明显的提高;而煅烧后的CdS/ZnO复合颗粒则表现为ZnO的缺陷发射,发光谱的半高宽较纯ZnO有所减小.     

Preparation and characterization of V/TiO2 nanocatalyst with magnetic nucleus of iron

A magnetic composite containing V/TiO₂ was prepared by combination of sol–gel and wetness impregnation methods. The effects of synthesis temperature, different weight percents of Fe supported on TiO₂, vanadium loading and the heating rate of calcination on the structure and morphology of nanocatalyst were investigated. The optimum conditions for synthesized catalyst were 40 wt.% of Fe, 15 wt.% of V and synthesis temperature equal to 30 °C. Characterization of catalyst is carried out using XRD, TGA, DSC, SEM, FTIR and N₂ physisorption measurements. The magnetic character of nanocatalyst was measured using VSM, which showed the typical paramagnetic behavior of sample at room temperature with a saturation magnetization value equal to 8.283 emu/g. The nanocatalyst has a particle size about 56 nm and can easily be separated from medium by a magnet.     

Preparation of uniform Silicalite-1 microspheres with large secondary pore architecture using monodisperse porous polystyrene particles as template

A new method was developed for preparation of silicalite-1 microspheres with uniform diameter about 2.5 μm using monodispersed micron-sized poly- styrene-co-divinylbenzene (PSD) porous particles as template. In this method, the PSD particles were impregnated first with tetraethoxysilane (TEOS) and then with tetrapropylammonium hydroxide (TPAOH). After crystallization and calcination, the silicalite-1 microspheres, possessing a regularly spherical morphology similar to the original silicalite-1, were successfully synthesized. More importantly, the silicalite-1 microspheres have large secondary pores in the range of 40 to 120 nm and high pore volume up to 0.7 cm³g^− 1. All these would facilitate the applications of microspheres in catalysis avoiding diffusion limitation.     

溶胶—凝胶法制备TiO2／Pt／glass纳米薄膜及其光电催化性能

本文采用Ｓｏｌ－ｇｅｌ法制备了ＴｉＯ２／Ｐｔ／ｇｌａｓｓ纳米光催化薄膜，并进行了结构和乐电催化性能的测试。薄膜对染料溶液的光电催化降解结果表明，当输入正向偏压后，ＴｉＯ２／Ｐｔ／ｇｌａｓｓ薄膜的光催化性能有一定提高，且随着偏压增大而增强。同时，薄膜的中间层Ｐｔ及光源强度对薄膜的光电催化活性也有较大影响。     

Preparation and properties of sliver and nitrogen co-doped TiO2 photocatalyst

TiO₂ photocatalysts co-doped with different content of Ag and N were prepared by sol–gel method combined with microwave chemical method. The samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), ultraviolet–visible diffuse reflectance spectrum (UV–vis) and photo-luminescence emission spectrum (PL). The photocatalytic activity was investigated by photocatalytic degradation of methylene blue (MB) under irradiation of fluorescent lamp. The results indicate that Ag and N co-doping can restrain the increase of grain size, broaden the absorption spectrum to visible light region, and inhibit the recombination of the photo-generated electron–hole pairs. Moreover, the photocatalytic activity of Ag–N–TiO₂ in MB degradation is remarkable improved. The degradation rate of the sample with Ag:TiO₂ = 0.05 at%, N:TiO₂ = 18.50 wt% in 5 h is 93.44%, which is much higher than that of Degussa P25 (39.40%).     

Facile synthesis of luminescent TiO2 nanorods using an anionic surfactant: Their photosensitization and photocatalytic efficiency

Mixed phase (rutile/anatase) TiO₂ nanorods have been synthesized using an anionic surfactant template. Nanorod synthesis has been achieved using mild reaction conditions and without using any rod-shaped template. The shape and crystallinity of the TiO₂ nanomaterials can be modulated by careful control of the surfactant concentration. The novelty of the present work is that the anatase/rutile mixed phase nanorods were formed without using the well-known layer by layer assembly method or the hydrothermal method. These mixed phase TiO₂ nanorods are highly luminescent, can be easily sensitized by fluorescent dyes, show significant dye adsorption ability and function as efficient photocatalysts.     

Preparation of polymer-blended quinine nanocomposite particles by spray drying and assessment of their instrumental bitterness-masking effect using a taste sensor

Abstract

Context: The development of taste-masking technologies for foods and drugs is essential because it would enable people to consume and receive healthy and therapeutic effect without distress.

Objective: In the current study, in order to develop a novel method to prepare nanocomposite particles (microparticles containing bitter nanoparticles) in only one step, by using spray drying, a two-solution mixing nozzle-equipped spray dryer that we previously reported was used. The nanocomposite particles with or without poorly water-soluble polymers prepared using our spray-drying technique were characterized.

Methods: (1) The organic solution containing quinine, a model of bitter compound and poorly water-soluble polymers and (2) sugar alcohol (mannitol) aqueous solution were separately flown in tubes and two solutions were spray dried through two-solution type spray nozzle to prepare polymer-blended quinine nanocomposite particles. Mean diameters of nanoparticles, taste-masking effect and dissolution rate of quinine were evaluated.

Results: The results of taste masking by taste sensor suggested that the polymer (Eudragit EPO, Eudragit S100 or Ethyl cellulose)-blended quinine nanocomposite particles exhibited marked masking of instrumental quinine bitterness compared with the quinine nanocomposite particles alone. Quinine nanocomposite formulations altered the quinine dissolution rate, indicating that they can control intestinal absorption of quinine.

Conclusion: These results suggest that polymer-blended quinine composite particles prepared using our spray-drying technique are useful for masking bitter tastes in the field of food and pharmaceutical industry.     

Na0.5Li0.5CoO2 nanopowders: Facile synthesis,characterization and their application for the removal of methylene blue dye from aqueous solution

In this paper, delafossite-type Na_0.5Li_0.5CoO₂ nanoparticles (NPs) with an average particle size of 50 nm were successfully synthesized by sol–gel method. Prepared NPs were characterized by differential thermal analysis, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and scanning tunneling microscopy. The nanoparticles showed the excellent adsorption properties towards methylene blue dye (MBD) as a reactive dye. The kinetics of removal of MBD in aqueous solutions was studied in a series of experiments which were varied in the amount of NPs, contact time, pH, and temperature. The experimental data were fitted very well in the pseudo-second order kinetic model and the Freundlich adsorption isotherm model. 92% of dye was successfully removed in 10 min using 0.02 g Na_0.5Li_0.5CoO₂ NPs in a pH = 11. Thermodynamic study indicates that the adsorption of MBD is feasible, and spontaneous in nature.     

SiO2-PMMA无机-有机复合材料的制备与结构研究

应用溶胶－凝胶技术,采用预掺杂的方法,制备了SiO2-PMMA无机－有机复合材料（ORMOSILS）。应用红外光谱分析、广角X射线衍射、扫描电子显微镜分析、差示扫描分析和热失重分析,对SiO2-PMMA无机－有机复合材料（ORMOSILS）的显微结构进行了研究。结果表明：这种方法制备的SiO2-PMMA无机－有机复合材料（ORMOSILS）,有机物均匀分布在无机物基体中,非晶基体SiO2短程有序畴的大小与一般非晶玻璃短程有序畴的大小基本一致等结论。     

新型喷雾干燥法制备LiFePO_4/C复合材料及其性能研究

通过新型喷雾干燥技术及热处理制备出具有球形二次形貌结构的纳米LiFePO4/C复合材料。首先合成了纳米FePO4颗粒(约20nm),并与Li2CO3和一定量的蔗糖均匀混合,对材料前驱体进行碳包覆,通过喷雾干燥获得了前驱体二次颗粒;经过热处理获得了由一次颗粒组成的二次颗粒。详细研究了碳含量对一次颗粒粒径及复合材料性能及形貌的影响,发现当LiFePO4/C复合材料中碳含量为5.3%(质量分数),样品拥有良好的形貌结构和最佳的性能,0.1,1和5C下的比容量分别为162,145和116mAh/g。     

The preparation of zinc silicate/ZnO particles and their use as an efficient UV absorber

The formation of zinc silicate/ZnO particles synthesized by a two-step method and their incorporation into PMMA is presented. In the first step a segmented-flow tubular reactor was used for the continuous room-temperature preparation of a zinc silicate/Zn(OH)₂ gel that was thermally treated after rinsing and drying in the second step. The same preparation procedure was also employed for the synthesis of pure ZnO and pure zinc silicate particles. It was found that the presence of the zinc silicate phase significantly influenced the final particle size, decreased the degree of crystallization and reduced the particles’ UV absorption capabilities. The reduced photocatalytic activity of the zinc silicate/ZnO particles indicated that the majority of ZnO crystallites were formed inside the zinc silicate matrix. The nanocomposite prepared from zinc silicate/ZnO particles (0.04 wt.%) and PMMA showed high UV shielding and at the same time sufficient transmittance in the visible-light region.     

Fe／SiO2复合微颗粒的微结构及电磁特性研究

采用机械球磨法制备了Fe／SiO2复合微米量级颗粒粉体。用X射线衍射、扫描电镜和透射电镜研究样品结构形貌；测量了不同成分配比下的磁滞回线；测试了在2～18GHz频段下的电磁性能参数。结果表明，微米量级铁颗粒的饱和磁化强度比纳米量级的铁颗粒显著增大．在2～18GHz频段内，复合微米颗粒的相对介电常数的实部稳定，虚部很小；磁导率虚部在0．7～1．2之间。该微米复合颗粒作为微波吸收材料，具有良好的应用潜力。     

双子表面活性剂为模板纳米二氧化钛的制备及光催化活性

以脱氢松香为原料,通过化学合成的方法制备出一种新颖的双子表面活性剂,采用FT-IR及1 HNMR对其结构进行确证;以酞酸四正丁酯（TNB）为起始原料,通过加入自制的双子表面活性剂,采用水热合成法制备了平均粒径为8.81nm的锐钛矿型纳米二氧化钛颗粒;利用FT-IR、TEM、XRD对纳米二氧化钛进行表征;以紫外光为光源,罗丹明B（RhB）为模型污染物考察了纳米二氧化钛的光催化活性,结果表明其催化活性优于未加表面活性剂制备的纳米二氧化钛,且在紫外光下反应3h,RhB的降解率为99.7%,基本完全降解。     

ZnO/SiO2复合薄膜的制备及其阻隔性能研究

目的为了进一步提高氧化锌(ZnO)沉积复合薄膜对氧气的阻隔能力,探索其应用于食品和药品包装材料的可行性。方法采用射频磁控溅射技术(RF),以ZnO和二氧化硅(SiO2)为靶材,在PET塑料表面同时沉积,制备ZnO/SiO2复合薄膜包装材料,并详细分析SiO2的引入对ZnO沉积膜微观结构和阻隔能力的影响,优化ZnO/SiO2的制备工艺。结果SiO2的引入,使ZnO纳米颗粒的形状由片状燕麦变成了球形,当功率密度比PSiO2/PZnO为0.67,氩气流量为20 mL/min,沉积时间为20 min,工作气压为0.5 Pa时,ZnO/SiO2复合薄膜的氧气透过率降低为0.462 mL/(m^2·d),水蒸气透过率有所增加,为0.367 g/(m^2·d)。结论引入合适比例的SiO2,可有效提升ZnO沉积层对氧气渗入的阻隔能力,但SiO2引入量过高时,会加剧纳米裂纹,对复合薄膜的阻隔能力不利。     

Preparation of TiO2/NiO composite particles and their applications in dye-sensitized solar cells

This study investigates the applicability of n-type TiO₂ and p-type NiO on the FTO-glass (Fluorine doped tin oxide, SnO₂:F) substrate of the working electrode in a dye-sensitized solar cell (DSSC). The working electrode was designed and fabricated by depositing a film of TiO₂/NiO composite particles, which were prepared by mixing the Ni powder with TiO₂ particles using dry mixing method, on a FTO-glass substrate using a spin coating process. The working electrode was then immersed in the solution of N-719 (Ruthenium) dye at a temperature of 70 °C for 6 h. Moreover, a thin film of platinum (Pt) was deposited on the FTO-glass substrate of the counter electrode using an E-beam evaporator. Finally, the DSSC was assembled, and the short-circuit photocurrent, the open-circuit photovoltage and the power conversion efficiency of DSSC were measured using an I–V measurement system. This study also examined the effects of the mass ratio of TiO₂ to Ni and the number of coating of TiO₂ particles (or TiO₂/NiO composite particles) colloid on the power conversion efficiency of the DSSC. Most importantly, this study shows that the power conversion efficiency of the DSSC with TiO₂/NiO composite particles (3.80%) substantially exceeds that of the conventional DSSC (3.27%) due to the effects of the NiO barrier and the n–p junction.     

Ge/SiO2和Ge/ZnO/SiO2薄膜的磁控溅射制备及电学性能

采用射频磁控溅射方法以石英玻璃为衬底分别沉积制备出了Ge/SiO2和Ge/ZnO/SiO2薄膜。X射线衍射表明薄膜展示了明显的ZnO衍射峰和较弱的Ge衍射峰;傅里叶变换红外光谱曲线证明薄膜均具有各自的特征吸收峰;扫描电镜结果显示薄膜为颗粒状团簇结构,并且加入ZnO中间层可以有效的改善Ge层的质量。同时,对所得薄膜材料的电流-电压性能进行了研究,结果发现,Ge/SiO2薄膜的I-V曲线拟合后为斜线,相当于电阻;ZnO/SiO2薄膜为直线,可以认为是绝缘体;Ge/ZnO/SiO2薄膜在-10～10V之间电流电压呈线性关系,其电阻比Ge/SiO2薄膜小,当电压值超过15V之后,电流急剧增加而迅速使薄膜击穿,薄膜导通。