Synthesis of nanosized TiO2 powder by sol gel method at low temperature

ABSTRACT

Nanotechnology is all about making products from very small constituents, components or subsystems to gain greatly enhanced material properties and functionality. Nanocrystalline anatase TiO₂ was prepared by a facile sol–gel route at a temperature of 50°C under mild conditions. Titanium tetraisopropoxide (TTIP) was used as a titanium precursor, and 2-propanol was used as a solvent. XRD, TEM, SEM, FT-IR and BET were applied to characterize the crystal phase. The Crystalline size of TiO₂ powder has been obtained with diameter < 30 nm for anatase at 500°C using an acid.     

氧化锡纳米晶的合成与生长

采用水热法制备了氧化锡纳米晶,通过X射线衍射仪(XRD)和高分辨透射电镜(HRTEM)对氧化锡纳米晶样品的晶体结构、晶粒形貌进行了表征,并研究了氧化锡纳米晶生长和位错的产生机制.结果表明:在退火温度低于500 ℃时,晶粒生长依靠着周围的非晶成分而长大,纳米晶内部无晶格缺陷;退火温度高于500 ℃时,晶粒通过相互粘结的方式而长大.晶粒之间的不完全取向粘结导致了缺陷与位错的产生.     

Cu替位与空位及Cu、S共掺SnO2的光磁性质研究

运用第一性原理,基于密度泛函理论,计算了Cu分别以替位和空位两种方式掺杂SnO2的电子结构和光电特性,并对两种掺杂方式做了一定的比较研究;磁性方面,主要研究了Cu、S共掺SnO2后的磁学性能.计算表明,两种方式掺杂,都使SnO2具有半金属特性,Cu原子将与周围的O原子发生强烈的交换作用,Cu原子对态密度的贡献主要在费米能级附近.相比之下,空位掺杂后的晶胞体积略大于替位掺杂后的SnO2,对光的能量损耗也比替位掺杂的低.对于Cu、S共掺的体系,计算表明:每个Cu原子的掺入将产生0.46μB的磁矩,而一个S原子将引入0.36μB的磁矩,Cu原子周围的O原子也对磁矩有一定的贡献.经过分析,发现体系的磁性来源主要是Cu-3d和S-3p,以及Cu-3 d与O-2 p间的强烈耦合作用.     

Stability of ruthenium nanoparticles synthesized by solvothermal method

One of the major obstacles to the synthesis of nanoparticles and nanocatalyst is the stability of particles. In the present study, polymer stabilized ruthenium nanoparticles were synthesized by solvothermal method using solutions of ruthenium chloride in ethylene glycol in presence of poly(N ‐vinyl‐2‐pyrrolidone) (PVP) as a stabilizing agent. Stability of nanoparticles was studied by varying different parameters e.g. PVP/RuCl₃ molar raio, RuCl₃ concentration, reaction temperature and time and expressed in terms of particle size and size distribution. Transmission electron microscope (TEM) analysis revealed the presence of metallic clusters with a uniform size of about 20‐65 nm. Dispersion destabilisation of colloidal nanoparticles was detected by Turbiscan. Polymer stabilized ruthenium nanoparticles were dispersed on γ‐alumina to prepare uniformly disperse Ru/γ‐Al₂O₃ catalyst by mechanical strirring and sonication. Inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), X‐Ray powder diffraction (XRD), Transmission electron microscopy (TEM) and Thermo gravimetric analysis (TGA) were used to characterize the supported catalyst. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and field emission properties of SnO2 nanowalls

SnO₂ nanowalls were synthesized on silicon substrate by the thermal chemical vapor transport method at a low temperature of around 650 °C under atmospheric pressure. The microstructure and morphology of the SnO₂ nanowalls were evaluated by using scanning electron microscopies and X‐ray diffraction. Room temperature photoluminescence spectra of the nanowalls showed a broad emission band centering at about 530 nm. Field emission measurements demonstrated that the nanowalls possessed good performance with a turn‐on field of ∼3.5 V/μm and a threshold field of ∼6.1 V/μm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

纳米SnO2的水热法合成及光催化性能研究

以SnCl2·2H2O为原料、酒石酸为络合剂,采用水热法制备了SnO2纳米颗粒,通过X射线衍射(XRD)、扫描电镜(SEM),紫外-可见(UV-Vis)光谱及荧光光谱(PL)等对样品的物相结构、微观形貌、光吸收性能等进行分析表征,以酸性红B模拟染料废水,考察了其光催化性能.结果表明:不同水热温度下所合成的样品均为四方晶系SnO2,空间群为P42/mnm,晶胞参数a=b=0.4738nm,c=0.3187 nm;160℃下所得样品具有优异的光催化性能,颗粒基本呈球形,尺寸约为13～23 nm.当催化剂用量为20 mg/50 mL,紫外光为光源,反应时间为50 min时,酸性红B的降解率可达97.1;,且降解反应属于一级反应动力学机理.     

水热法合成SnO2金红相纳米柱晶体

本文采用水热法,以SnCl4·5H2O为前驱物,NaOH为矿化剂,在180℃,填充度为68;,通过加入不同量的NaOH,调节溶液pH值分别为2、4、11,合成了三种具有不同形态的金红相SnO2纳米晶体.其中在较高浓度的酸或强碱环境下合成了具有清晰结构,长100nm、直径10nm的SnO2纳米柱体.     

Precipitation of Stoichiometric Hydroxyapatite by a Continuous Method

In this paper we present the precipitation of hydroxyapatite (HA), Ca₅(OH)(PO₄)₃, from highly concentrated CaCl₂ and K₂HPO₄ solutions, carried out by a continuous method in a MSMPR reactor. The procedure consists of adding the reagents in a ratio Ca to P equal to 1.67, maintaining a temperature of 85 °C, inert N2 atmosphere inside the reactor, and monitoring and adjusting automatically the pH by means of a pH‐stat system (pH = 9.0 ∓ 0.1). Under these conditions HA with a Ca to P ratio equal or close to the stoichiometric composition (Ca/P=1.667), with a high yield (up to 99%) and a high production rate (up to 1.17 g/l.min) is obtained at steady state. The CSD, morphology, crystallinity of the precipitates and impurities present fit the requirement for its biomedical applications.     

Microwave-assisted green synthesis of SnO2 nanoparticles and their optical and photocatalytic properties

Abstract

In this study, SnO₂ has been synthesized using Andrographis Paniculata (A. Paniculata) by microwave-assisted method. It is also characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). It exhibits the tetragonal structure with average crystallite size of 27?nm. The stretching vibration peak of Sn-O-Sn is 670?cm^?1. SEM reveals the formation of nanoparticles. The bandgap was estimated by the tauc’s relation as 3.52?eV from the UV-Visible (UV-Vis) spectra. Biosynthesized SnO₂ nanoparticles show excellent photocatalytic activity against Congo red dye under sunlight irradiation.     

水热法合成SnO2金红相纳米柱和亚微米晶体

本文采用水热法,以SnCl4·5H2O为前驱物,在180℃,填充度为68;,反应时间8h,强酸环境条件下合成了SnO2纳米金红相晶体,直径约为5～10nm,长30～100nm.加入一定量的NaOH,调节溶液pH值为强碱性(pH=11),同样条件下也合成了SnO2金红相纳米柱晶体,长200nm、直径10～20nm.提高水热反应的温度为430℃,矿化剂为3mol/L NaOH,反应时间24h,合成了亚微米金红相SnO2晶体,最大线度为300nm.     

Studies on optical properties of polycrystalline SnO2:Sb thin films prepared using SnCl2 precursor

Optical properties of spray deposited antimony (Sb) doped tin oxide (SnO₂) thin films, prepared from SnCl₂ precursor, have been studied as a function of antimony doping concentration. The doping concentration was varied from 0‐4 wt.% of Sb. All the films were deposited on microscope glass slides at the optimized substrate temperature of 400 °C. The films are polycrystalline in nature with tetragonal crystal structure. The doped films are degenerate and n‐type conducting. The sheet resistance of tin oxide films was found to decrease from 38.22 Ω/□ for undoped films to 2.17 Ω/□ for antimony doped films. The lowest sheet resistance was achieved for 2 wt.% of Sb doping. To the best of our knowledge, this sheet resistance value is the lowest reported so far, for Sb doped films prepared from SnCl₂ precursor. The transmittance and reflectance spectra for the as‐deposited films were recorded in the wavelength range of 300 to 2500 nm. The transmittance of the films was observed to increase from 42 % to 55 % (at 800 nm) on initial addition of Sb and then it is decreased for higher level of antimony doping. This paper investigates the variation of optical and electrical properties of the as‐deposited films with Sb doping. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of CaCO3 nanoparticles via citrate method and sequential preparation of CaO and Ca(OH)2 nanoparticles

Calcium carbonate nanoparticles were synthesized via so‐called sol–gel citrate method using calcium nitrate as precursor in presence of different concentration of citric acid, selected to be 0.0, 0.5, 1.25 and 2.5 times of the concentration of the precursor, on calcining at 600 °C for 5 h. Stable phase of the calcite is formed in presence of citric acid. The roles of organic additive concentration, calcination temperature and sonication on the particle size of the products were investigated. Calcium oxide nanoparticles were prepared by facial calcination of the resulted product at 900 °C for 5 h. Calcium hydroxide nanoparticles, however, were synthesized on sonication of the product for 20 min in water at room temperature. Samples were characterized by XRD and FT‐IR studies. Crystallite size of samples was calculated by XRD data and was measured by TEM analysis. The specific surface are (SSA) of samples was calculated by the XRD data and compared by the measured BET. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

SnO2/石墨分级纳米异质结构的合成及其电化学性能研究

以石墨为基底,五水合四氯化锡为锡源,氢氧化钠为沉淀剂,采用一步水热法合成了SnO2/石墨分级纳米异质结构.利用FESEM、XRD、EDS、Raman等对SnO2/石墨分级纳米异质结构进行了形貌、结构和成分表征.研究发现,结晶良好的SnO2纳米线首先组装成SnO2纳米棒,纳米棒进一步组装成直径约450 nm的花状结构,并...     

Structural and optical properties of TiO2:SnO2 thin films prepared by sol gel method

ABSTRACT

TiO₂:SnO₂ thin films were deposited on glass substrates, by using sol gel spin coating method with different ratio (3%, 5% and 7%) at 3200 rpm, to study their effect on different properties of TiO₂: SnO₂ thin films. The structural and optical properties of films have studied for different ratio. These deposited films have been characterized by various methods such as X-Ray Diffraction (XRD), Ultra Visible spectroscopy. The (XRD) can be used to identify crystal structure of as deposited films. The Transmission spectra have shown the transparent and opaque parts in the visible and UV wavelengths.     

Synthesis,structural and optical properties of well dispersed anatase TiO2 nanoparticles by non‐hydrothermal method

The formation of nanocrystalline TiO₂ particles has been investigated via a surfactant‐free synthetic non‐hydrothermal method. Titanium isopropoxide and toluene were used as the starting materials. At a low temperature of 250 °C for 6 h, the reaction mixture turned in to a white precipitate (TiO₂) as a result of the thermal decomposition of metal alkoxide. The obtained product was found to crystallize purely in the anatase phase with well defined morphology. The powder XRD study confirms that the average size of the particle is close to ∼15 nm. The TEM analysis indicates the sizes of the primary and secondary particles in the range between 8‐10 nm and 15‐20 nm respectively. The quantum size confinement of the crystallites is evident from the blue shift of the absorption edge in the UV‐Visible absorption spectrum. The luminescence property of the TiO₂ nanoparticles studied by the emission spectrum confirms the presence of defect levels caused by the oxygen vacancies. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determination of the Bone Mineral Crystallite Size and Lattice Strain from Diffraction Line Broadening

Diffraction line broadening observed for the biological apatite is ascribed to small crystallite dimensions and lattice imperfections. However, it is rather difficult to separate the individual contribution of each factor. Therefore in numerous works a total inverse width of a diffraction peak is only used as a size/strain parameter. Several authors determine the bioapatite crystallite size ignoring the lattice strain. As is shown in the present paper, this problem can be resolved for oriented specimens. The crystallite size and lattice strain were calculated by two independent methods: Fourier analysis and approximation with threefold convolution of X‐ray lines. The approach proposed can be useful in the investigations into structural aspects of the bone apatite and its synthetic analogues as the crystal size is related to surface defects and the lattice strain to lattice imperfections.     

Spray pyrolysis deposition of undoped SnO2 and In2O3 films and their structural properties

In this paper the results of structural analysis of the SnO₂ and In₂O₃ films deposited by spray pyrolysis are presented. The main goals of this analysis are summarizing the results obtained in this field, highlighting a correlation between parameters of film deposition and the material structure and formulating some general regularities, typical for metal oxides. Peculiarities and mechanisms of pyrosol deposition as well as advantages and disadvantages of this technology for deposition of the films with required parameters were also discussed. It is shown that this technology has great potential for controlling structural parameters of metal oxides such as thickness, the grain size, texturing, roughness, the grain faceting and the porosity.     

自掺杂SnO2微球的水热合成及其可见光催化性能

本研究采用水热法,以柠檬酸为螯合剂,通过控制n(Sn⁴⁺)/n(Sn²⁺)的数值,合成了由具有丰富氧空位的SnO₂纳米晶体组装成的微球。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶红外光谱(FT-IR)、X射线光电子能谱(XPS)及UV-Vis漫反射光谱对SnO₂纳米微球进行表征分析,结果表明:在酸性水热条件和柠檬酸的螯合作用下,二氧化锡纳米晶体聚集形成微球;在Sn⁴⁺/Sn²⁺摩尔比例为3:7时,其微球尺寸最小,整体分散性较好;同时适量二价锡离子的掺杂使得该样品氧空位浓度达到最佳,氧空位的存在将使得样品光吸收范围拓展至可见光,因而该样品显示出较强的可见光催化效率,在8 min内完全降解甲基橙。     

微波水热条件对氧化锌晶体的形态和粒度的影响

利用微波水热法，以氢氧化锌为前驱物，在反应温度不小于100℃的情况下，成功地制备出氧化锌微晶。研究了水热条件对氧化锌微晶的晶粒大小和形貌的影响。在水热环境下，当反应温度一达到100℃，氧化锌微粒就能快速形成和生长。反应温度在100℃时，延长反应时间(～4h)氧化锌微晶的形貌和晶粒大小均没有受到大的影响；然而，升高反应温度氧化锌微晶的晶粒大小会略微地减小。另一方面，当反应前溶液中的pH值从9增大到12时，氧化锌微晶的形态从不规则的片状颗粒改变到长柱状晶粒。另外，随着溶液中pH值的增加，氧化锌微晶的结晶性变好、粒度变大。合理地解释了反应温度、溶液中的pH值对制得的氧化锌微晶的形态、晶粒粒度的影响。     

离子掺杂对纳米二氧化钛粒径的影响

本研究以工业钛液和尿素为基本原料,采用普通均匀沉淀法制备出单分散的锐钛矿型的球形纳米TiO2,研究了La3+、Fe3+、Co2+、Al3+四种离子不同掺杂量对纳米TiO2粒子粒径的影响,并对其机理进行了分析.研究结果表明,离子掺杂可以显著细化纳米TiO2的粒径,且掺杂后的TiO2仍为锐钛矿型.没有发现掺杂离子的特征峰,可以认为离子掺杂属于替位掺杂.