不同形貌TiO2的水热合成及对苯酚的降解研究

采用水热合成法, 通过对溶液的pH值、反应物配比、陈化温度及陈化时间等条件的控制, 合成出不同晶型及形貌的TiO2纳米粒子. 结果表明, 溶液的pH＝11, n(钛酸丁酯):n(三乙醇胺)＝1:2, 陈化温度为150 ℃, 陈化时间为48 h时, 能得到较规则的、长径比约为4:1的棒状TiO2. 当溶液pH<10时, 得到球形的TiO2纳米粒子; 陈化时间为24 h时, 得到纺锤形TiO2纳米晶. 以上合成的纳米粒子均为锐钛矿型, 但当溶液的pH>12时, 则得到板钛矿型TiO2粒子. 以苯酚为降解模型, 考察了不同形貌TiO2的光催化活性.     

Novel dumbbell-like LaVO4:Eu3+ nanocrystals and effect of Ba2+ codoping on luminescence properties of LaVO4:Eu3+ nanocrystals

Journal of Sol-Gel Science and Technology - LaVO4:Eu3+ nanocrystals with different morphologies were synthesized via a simple hydrothermal method in a wide pH range. The as-synthesized samples were...     

Synthesis and Characterization of SnO2-TiO2 Nanocomposite with Rutile-phase via Hydrothermal Method at Low Temperature

With Ti(SO₄)₂, SnCl₄·5H₂O and urea as raw materials, SnO₂-TiO₂ nanocomposites were synthesized via low temperature hydrothermal method at 80―100 ℃ in aqueous solutions. The morphologies of the products were altered systematically by varying the Ti/Sn molar ratio of the reactants, and rutile-phase particles were obtained with an average diameter of about 52.2 nm at a molar ratio of Ti/Sn=7.5. The surface composition of the composite was revealed by X-ray photoelectron spectroscopy(XPS) and X-ray diffraction(XRD) to be solely TiO₂ with a rutile structure. This new composite material exhibits a high ultraviolet absorption capacity, and its photocatalytic activity for phenol oxidation is much lower than that of the commercial titania nanoparticles(P25).     

Preparation of hollow titania and strontium titanate spheres using sol–gel derived silica gel particles as templates

A facile approach, based on polyelectrolyte-mediated electrostatic adsorption of a water-soluble titanium complex on colloidal templates and hydrothermal treatment, is presented for the formation of hollow titania (TiO₂) and strontium titanate (SrTiO₃) spheres. Monodispersed silica gel particles were prepared by the sol?Cgel method and adopted as core templates. Deposition of a water-soluble titanium complex, titanium (IV) bis(ammoniumlactato)dihydroxide (TALH), on the silica gel particles was carried out via the layer-by-layer assembly technique. Hollow spheres were successfully formed from the core?Cshell particles. The silica gel particles used as core templates dissolved during hydrothermal treatment because of the particles?? undeveloped siloxane network. In addition, the hydrothermal treatment induced crystallization of the hollow shells. Therefore, the hydrothermal treatment played two roles; removal of the silica templates and crystallization of the hollow shells. When deionized water was used, hollow TiO₂ spheres were obtained. Hollow SrTiO₃ spheres could also be formed when an aqueous solution of Sr(OH)₂ was used. The approach presented here could be exploited as a novel and sustainable approach for the fabrication of a range of different inorganic hollow spheres.     

溶剂热法合成锐钛矿型二氧化钛纳米晶的形状演化规律

以钛酸四丁酯为前驱体,乙醇为溶剂,月桂酸和十二胺为共同稳定剂,采用溶剂热法制备了不同形状的锐钛矿型二氧化钛纳米晶。利用透射电子显微镜(TEM)、选区电子衍射(SAED)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱和热失重-差热分析(TG-DTA)等技术对纳米晶的结构、尺寸、形貌及形状进行了系统的表征,并探讨了月桂酸与十二胺不同配比时纳米晶的形状演化规律。结果表明:用溶剂热法在不同配比情况下获得的二氧化钛均为锐钛矿相;在月桂酸与十二胺总摩尔量不变的情况下,随着十二胺含量的增加,二氧化钛纳米晶的形状由球形逐渐演化为棒状,且结晶化程度在两者摩尔比为1:1时最好;月桂酸与十二胺稳定剂与纳米晶内核之间以桥接配位体的形式结合,且稳定剂在样品中的含量约为5%。     

Silica lite-1纳米晶的尺寸控制合成

全硅 Silicalite- 1沸石作为 MFI结构的 ZSM- 5分子筛家族中不含 Al的成员 ,不仅具有良好的热稳定性和特殊的十元环孔道结构 ,而且具有憎水和亲油等特性 [1,2 ] ,通常以四丙基铵根离子为模板剂在水热条件下进行合成 ,所得到的晶粒尺寸处于几微米至几十微米之间 [2～ 11] .如李军等 [3 ] 制得了晶粒在1 0μm左右的 Silicalite- 1膜 . Kath等 [4 ] 以硅酸铵为硅源、四丙基溴化铵为模板剂制备了粒径为 5 0μm的 Silicalite- 1 ;但以正硅酸乙酯为硅源、四丙基氢氧化铵为模板剂时 ,在乙醇的参与下合成了晶粒为0 .5 μm的超细 Silicalite- 1…     

阴离子氨基酸表面活性剂调控下水热合成羟基磷灰石纳米片

利用水热合成方法, 在含有氨基酸结构的阴离子表面活性剂N-酰基十二烷基肌氨酸钠(Sar-Na)的控制下, 合成具有较大长径比(aspect ratio)的片状纳米羟基磷灰石晶体. 采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)和傅立叶变换红外(FTIR)光谱表征, 并分析了合成产物的形貌、结构和组成. 结果表明, 在Sar-Na的调控下合成了长度0.5-1.0 μm、宽约30 nm的片状羟基磷灰石晶体, 其长径比约为20:1. 考察了表面活性剂Sar-Na的用量对羟基磷灰石形貌的影响. 随着Sar-Na的添加及用量的增加, 羟基磷灰石由椭圆形变为长片状, 并且片的两端逐渐变尖. 结果显示了Sar-Na对羟基磷灰石形貌的控制作用, 为合成具有较大长径比的羟基磷灰石纳米片提供了一个新的途径.     

Fabrication of Porous Titania Particles from Water-in-Oil Emulsions for the Applications of Photocatalyst

In this study, polystyrene nanospheres were synthesized by dispersion polymerization using batch-type reactor for the self-organization with precursor materials inside emulsion droplets. Mechanical homogenization was applied for the emulsification of the polymeric nanospheres and titanium diisopropoxide bis (acetylacetonate) to produce the macroporous titania particles by evaporation-driven self-assembly. Similarly, spherical titania crystallites could be synthesized via self-organization using triblock copolymer instead of polymeric latex beads after successive calcination. The morphologies of the porous particles were observed using electron microscope, and the crystallinity of the porous titania particles was analyzed by powder x-ray diffraction. As a demonstrative application, the macroporous titania microparticles with anatase phase were adopted as photocatalyst for the decomposition of Rhodamine B, and excellent catalytic performance was observed with higher rate constant compared to the result from commercial titania nanocolloid. Collectively, our macroporous titania microparticles were found to be safe catalytic materials for human body minimizing the skin toxicity since the size of the catalysts is in the micron-range.     

pH值对水热法制备的Bi4Ti3O12晶体光催化活性的影响

采用无助剂、非模板的水热法可控制备Bi4Ti3O12（BIT）晶体．通过调节反应物的pH值可以选择性地获得BIT纳米球、纳米带和纳米片．通过对不同pH值制备的样品的结构分析研究了这些不同形貌的形成机制．pH值为1制备的IT样品在可见光下光催化活性最高．基于不同pH值制备的BIT样品的形状、尺寸和局部结构振动分析了光催化活性不同的原因。     

二氧化钛纳米粒子和纳米管的合成、表征及对硝基苯的光催化性能研究

采用水热合成法, 通过改变反应条件, 控制反应参数, 成功地合成了粒径可控的球形TiO2纳米粒子和长径比、比表面积均比较大的纳米管. 用XRD, TEM, SAED和BET等手段对产物进行了表征. 为了测试产物的光催化性能, 以高浓度的硝基苯(NB)溶液为模拟水样, 进行了一系列提高降解效率的优化实验和光催化降解的对比实验. 通过对硝基苯溶液初始浓度、TiO2加入量和降解体系pH值等条件的考察, 得出硝基苯溶液的质量浓度为300 mg/L, TiO2的加入量为0.4 g/L, 体系的pH值为6~7时, 降解效果最好; 通过对比实验发现, 由于纳米管的大比表面积, 使得其光催化性能明显优于球形纳米粒子, 3 h后的降解率达到90%以上, 3.5 h左右硝基苯几乎被完全降解.     

GdF3∶Eu3+/NaGdF4∶Eu3+纳米晶的水热合成及发光性质

采用水热法,以聚乙二醇(400)为分散剂,以NaOH和HNO3溶液调节初始溶液pH值,合成GdF3∶Eu3+和NaGdF4∶Eu3+纳米晶。XRD和SEM结果表明:在酸性溶液(pH=3,5)、中性溶液(pH=7)和碱性溶液(pH=9)中,分别获得具有正交结构的GdF3∶Eu3+纳米晶,GdF3∶Eu3+和NaGdF4∶Eu3+混合晶,六方结构NaGdF4∶Eu3+棒状微米晶。根据Scherrer公式估算pH=3和pH=5时制备纳米晶的一次性粒径分别为49和28 nm。样品的发射光谱结果表明:特征发射峰来自于5D2、5D1、5D0到7FJ跃迁。在主晶相为GdF3样品中,主发射峰来自于Eu3+的5D0→7F1的磁偶极跃迁;晶相为NaGdF4样品的主发射峰来自于Eu3+的5D0→7F2电偶极跃迁。5D0→7F1和5D0→7F2跃迁发射相对强度比值显示:Eu3+在NaGdF4晶体中的格位对称性下降。激发光谱显示出Gd3+和Eu3+具有较好的能量传递。     

Synthesis of beltlike CdS nanocrystals via solvothermal route

CdS nanocrystals with a beltlike morphology were prepared via a low-temperature solvothermal route in ethylenediamine. The obtained nanocrystals were characterized by X-ray powder diffraction, transmission electron microscopic, ultraviolet-visible and fluorescence spectroscopy. In the mixed solvents of ethylenediamine and distilled water, CdS nanocrystals with various morphologies were obtained with the change of the volume ratio of the two constituents.     

Controlled Synthesis of Ultrathin Lanthanide Oxide Nanosheets and Their Promising pH‐Controlled Anticancer Drug Delivery

Various lanthanide oxides (Sm₂O₃ and Gd₂O₃) nanostructures were synthesized by a facile hydrothermal method. The loss of surfactants on the nanocrystals surface, followed by the resultant assembly is responsible for the formation of ultrathin nanosheets. Owing to strong surface effects, the different morphologies of the Sm₂O₃:5 % Eu and Gd₂O₃:5 % Eu nanocrystals present unique photoluminescence properties. As a proof‐of‐concept application, the as‐obtained Sm₂O₃ and Gd₂O₃ ultrathin nanosheets exhibit promising pH‐controlled anticancer drug‐delivery behavior.     

Preparation of titania-coated polystyrene particles in mixed solvents by ammonia catalysis

A mixed-solvent method was developed to coat polystyrene (PS) spheres with smooth, homogeneous shells of amorphous titania by ammonia catalysis. The TEM images showed that, in the presence of ammonia, the thickness of titania shells could be controlled in the range of 8-65 nm by varying the concentration of titanium tetrabutoxide (TBOT) in the ethanol/acetonitrile mixed solvents with an appropriate volume ratio. The diffusion-controlled mechanism of the mixed solvents and the catalysis mechanism of ammonia were investigated. After the calcination of core-shell particles for 2 h at 500 degrees C, spherical hollow titania shells could be obtained, and the surfaces of the particles remained quite smooth and homogeneous. The XRD analysis indicated that calcination promoted the transformation of amorphous titania into an anatase phase.     

Synthesis of CdSe, ZnSe, and ZnxCd1-xSe nanocrystals and their silica sheathed core/shell structures

Uniform ZnxCd1-xSe nanocrystals have been prepared at the artificially designed water-oil interface using Na2SeO3, Cd(NO3)2, and Zn(NO3)2 as precursors. The chemical composition and band gap of the ZnxCd1-xSe nanocrystals can be adjusted via different combinations of source material. The coating of a SiO2 shell could transform the hydrophobic particles into hydrophilic particles. An advantage of this method is that a water phase could be added to the oleic acid (OLEA) synthesis system, which could be extended to make the synthesis of various nanocrystals more simple and flexible.     

Controllable synthesis and up-conversion properties of tetragonal BaYF5:Yb/Ln (Ln=Er, Tm, and Ho) nanocrystals

The nanocrystals (NCs) of tetragonal barium yttrium fluoride (BaYF(5)) doped 1 mol% Ln(3+) (Ln=Er, Tm, Ho) and 20 mol% Yb(3+) with different morphologies and sizes have been successfully synthesized through a facile hydrothermal method. The influences of pH values of the initial solution and fluorine sources on the final structure and morphology of the products have been well investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the size, structure and morphology of these samples prepared at different conditions. And it is found that BaYF(5):Yb/Ln NCs prepared at pH value of 10 using NaBF(4) as F(-) source have a uniform spherical morphology with average diameter of 25 nm. Additionally, the up-conversion (UC) properties of Yb/Er, Yb/Tm, and Yb/Ho doped BaYF(5) nanoparticles were also discussed. Under 980 nm laser excitation, the BaYF(5):Yb/Er, BaYF(5):Yb/Tm, and BaYF(5):Yb/Ho NCs exhibit green, whitish blue, and yellow green UC luminescence, respectively. The luminescence mechanisms for the doped lanthanide ions were thoroughly analyzed.     

RHEOLOCY OF AQUEOUS DISPERSIONS OF ALUMINA,TITANIA AND MIXTURE OF ALUMINA AND TITANIA POWDERS

The electrophoretic mobility and rheology of alumina, titania and alumina / titania powder mixtures ( ratio of alumina : titania 1 : 2 and 2 : 1 ) were investigated in aqueous suspensions in the pH range 3 - 10. The results suggest that the electrophoretic mobility of the individual powders is independent of the particle concentration, but the electrokinetic behavior of the powder mixture depends upon the concentration of the individual constituents. The rheology of all the suspensions is charge related and while alumina and alumina / titania ( ratio 2 : 1 ) flocculate at pH 9.0 both titania and alumina / titania ( ratio 1 : 2 ) form low viscous dispersions. Similarly while later dispersions flocculate at pH 5.6, the former dispersions behave as Newtonian type fluids. Better correlation between the slip rheology and the electrokinetic behavior of suspensions containing both alumina and titania powders can be obtained provided the experimental results are evaluated based upon the total surface area of the individual powders but not the particle concentration.     

Architectural control syntheses of CdS and CdSe nanoflowers, branched nanowires, and nanotrees via a solvothermal approach in a mixed solution and their photocatalytic property

Wurtzite CdS and CdSe nanostructures with complex morphologies such as urchin-like CdS nanoflowers, branched nanowires, and fractal nanotrees can be produced via a facile solvothermal approach in a mixed solution made of diethylenetriamine (DETA) and deionized water (DIW). The morphologies of CdS and CdSe nanocrystals can be easily controlled via tuning the volume ratio of DETA and DIW. Urchin-like CdS nanoflowers made of CdS nanorods are in a form of highly ordered hierarchical structures, while the nanowires are branched nanowires, and the fractal CdS nanotrees are a buildup of branched nanopines. The results demonstrated that solvothermal reaction in a mixed amine/water can access a variety of complex morphologies of semiconductor materials. The photocatalytic activity of CdS particles with different morphologies has been tested by the degradation of acid fuchsine under both UV and visible light, showing that the as-prepared branched CdS nanowires exhibit high photocatalytic activity for degradation of acid fuchsine.     

Effects of Ti Addition on Alumina/Titania Composite Aerogels Synthesized by Sol–Gel Process and Supercritical Ethanol Drying

Alumina/titania composite aerogels with different titania contents were synthesized by the sol–gel process and supercritical ethanol drying. The structures and morphologies of synthesized aerogels were analyzed by X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry, and N₂ adsorption–desorption tests. Supercritical ethanol drying induced the crystallization of titania, which prompted the transformation of the structure from pseudoboehmite to γ‐Al₂O₃ . Reversely, alumina retarded the anatase‐to‐rutile transformation of titania. The content of titania significantly affected the structure and morphology of alumina/titania composite aerogels. A high content of titania (≥40%) resulted in the phase separation of titania particles, which grew to form the anatase phase octahedral particles with well‐developed facets. When the titania content was low, titania particles could be homogeneously dispersed in alumina particles to form spherical clusters with the poor crystallinity. Titania particles were in the anatase phase, and no rutile phase was formed until the temperature rose to 1000°C. In addition, titania addition resulted in a decrease in the specific surface area (SSA) of alumina aerogels because the SSA of titania was lower than that of alumina aerogels.     

表面活性剂辅助水热制备形貌结构可控的MoS2及其蒽加氢性能

随着原油资源重质化和劣质化的加剧以及对清洁燃料油品需求的不断增加,将重质油加工成清洁燃料成为现代炼厂面临的挑战.悬浮床加氢是重质油转化为清洁液体燃料的先进技术,其核心难题是高效加氢催化剂的开发.MoS2在石油化工领域油品加氢提质研究中表现出非常好的催化加氢性能.MoS2晶体结构中有两种面:沿S-Mo-S层间的剥离面,又称基面,化学性质稳定;沿Mo-S的断裂面,又称棱面,具有大量的不饱和键,化学性质不稳定,可做催化活性中心.由于MoS2结构和形貌对其物理化学性能有重要影响,所以通过合理设计和调控MoS2的结构和形貌可增加暴露的催化活性位,进而改善其催化性能.本文以七钼酸铵和硫代乙酰胺为原料,水合肼做还原剂,采用不同表面活性剂(包括PEG,PVP,P123,SDS,AOT和CTAB)辅助的水热合成法制备了结构及形貌可控的MoS2,并提出不同表面活性剂条件下MoS2催化剂的生长机理,进一步研究了重油模型化合物稠环芳烃蒽的催化加氢性能.结果表明,在不同表面活性剂辅助的条件下分别制得了由MoS2纳米片组装而成的球形、块状和花状的MoS2产物;通过改变表面活性剂种类可调变MoS2纳米片的长度、堆积层数、层间距以及最终产物的形貌.在PEG或PVP辅助下得到了球形MoS2产物,其中MoS2纳米片长<15 nm,堆积层数<6.在PEG辅助下制备的球形MoS2粒径约为250 nm,尺寸均一且分散性好.在PVP辅助下MoS2粒径在200–450 nm,粒径分布范围宽且有明显团聚.在P123或SDS辅助下得到了团聚较明显的块状微米级MoS2产物.在P123辅助下得到的MoS2纳米片长<15 nm,层数<6.在SDS辅助下制备的MoS2纳米片长>20 nm,堆积层数>8.在AOT或CTAB辅助下得到团聚比较严重的花状微米级MoS2产物,其中MoS2纳米片长>20 nm,堆积层数>8.另外,水热反应过程中,高温高压的环境促进了反应体系中游离的NH4+插入到MoS2层状结构中,导致MoS2纳米片层间距增大.基于此,本文提出了不同表面活性剂辅助的水热过程中不同结构和形貌MoS2产物的形成机理.对不同结构和形貌的MoS2样品进行了悬浮床蒽加氢催化性能评价.结果表明,PEG辅助制备的MoS2催化剂具有最高催化加氢活性.该MoS2催化剂中纳米片层短,堆积层数少,暴露了更多的加氢活性位.单分散的球形MoS2颗粒粒径小,分散性好,有利于加氢活性位的充分暴露,进而表现出较好的催化性能.本文所采用的表面活性剂辅助的水热法为可控合成不同结构和形貌的过渡金属硫化物提供了有效指导和借鉴.