超细均分散稀土化合物胶体粒子制备

利用尿素分解法制得轻、中、重稀土化合物的超细均分散胶体粒子,详细探讨了浓度、pH值、陈化温度、陈化时间及共存阴离子等因素对制备过程的影响,获得了各种粒子的最佳制备条件.     

在简化实验条件下制备均匀球状Fe3O4胶体粒子

所谓均匀胶体粒子是指不但组成、形状相同,而且粒子尺寸分布十分狭窄的胶体粒子。均匀胶体粒子在研究胶体界面双电层的电特性、吸附特性以及絮凝稳定性等方面具有重要的理论意义。由于均匀胶体性质的重现性,才能够真正定量化地对溶胶体系进行研究。尤其对于     

均匀球形α-Fe_2O_3胶体粒子的形成机理

在有关均匀胶体粒子的研究中,人们大多关注的是均匀胶体粒子的制备方法和实验条件的控制,其中包括溶液的组成,陈化温度和时间以及起决定作用的特殊阴离子.然而涉及其形成机理的分析很少,因为均匀胶体粒子的形成是个微观过程:成核、成长、相转变和微粒子的聚集等过程瞬息完成,难于捕捉到各个过程发生的具体时机.Sugimoto和Matijevic将含一定比例的FeSO_4,KOH和KNO_3溶液经85℃陈化制备均匀球状Fe_3O_4的实验中发现,陈化液中最初生成的Fe(OH)_2在硝酸根离子作用下经相转化生成Fe_3O_4微粒子,     

均匀Fe~3O~4胶体粒子形成机理II. 低温Mossbauer谱研究

在液氮温度下, 测定了均匀Fe~3O~4胶体粒子制备过程中陈化时间为1小时内的不同时间所得样品的Mossbauer谱。结果表明, γ-FeOOH为Fe~3O~4均匀胶粒形成过程的中间产物, 并提出均匀Fe~3O~4胶粒的形成机理。     

均匀Fe3O4胶体粒子形成过程的Mossbauer研究

应用经过改进的实验方法制得均匀球状Fe3O4胶体粒子, 通过对多种Fe3O4粒子的Mossbauer测量并结合发析, 我们发现, 在制备过程中, 反应浓度、加液次序以及陈化时间的不同对所生成的Fe3O4晶体的基本骨架与结构影响极小, 而随着陈化时间的不断增加, Fe3O4粒子的组成将逐渐接近化学计量, 以这些实验结果及文献报道为基础, 本文讨论了均匀Fe3O4胶体粒子的形成机理。     

均匀Fe~3O~4胶体粒子形成机理II. 低温Mossbauer谱研究

在液氮温度下, 测定了均匀Fe~3O~4胶体粒子制备过程中陈化时间为1小时内的不同时间所得样品的Mossbauer谱。结果表明, γ-FeOOH为Fe~3O~4均匀胶粒形成过程的中间产物, 并提出均匀Fe~3O~4胶粒的形成机理。     

均匀Fe3O4胶体粒子形成过程的Mossbauer研究

应用经过改进的实验方法制得均匀球状Fe3O4胶体粒子, 通过对多种Fe3O4粒子的Mossbauer测量并结合发析, 我们发现, 在制备过程中, 反应浓度、加液次序以及陈化时间的不同对所生成的Fe3O4晶体的基本骨架与结构影响极小, 而随着陈化时间的不断增加, Fe3O4粒子的组成将逐渐接近化学计量, 以这些实验结果及文献报道为基础, 本文讨论了均匀Fe3O4胶体粒子的形成机理。     

均匀Fe_3O_4胶体粒子形成过程的Mssbauer研究

应用经过改进的实验方法制得均匀球状Fe_3O_4胶体粒子,通过对多种Fe_3O_4粒子的Mossbauer测量并结合化学分析,我们发现,在制备过程中,反应浓度、加液次序以及陈化时间的不同,对所生成的Fe_3O_4晶体的基本骨架与结构影响极小,而随着陈化时间的不断增加,Fe_3O_4粒子的组成将逐渐接近化学计量.以这些实验结果及文献报道为基础,本文讨论了均匀Fe_3O_4胶体粒子的形成机理.     

均匀Fe_3O_4胶体粒子形成机理 Ⅱ.低温Mssbauer谱研究

在液氮温度下,测定了均匀Fe_3O_4胶体粒子制备过程中陈化时间为1小时内的不同时间所得样品的Μssbauer谱,结果表明,γ-FeOOH为Fe_3O_4均匀胶粒形成过程的中间产物,并提出均匀Fe_3O_4胶粒的形成机理为:     

TiO2纳米膜表面结构形态特征

采用反胶束法制备TiO2纳米溶胶,用浸渍提拉法在不同的条件下制备了三种TiO2多孔纳米薄膜,并利用AFM、SEM、XRD等方法对膜表面结构物理化学特性进行表征.结果表明三种膜基本上由粒径约为59 nm的纳米粒子以不同的方式堆积而成,溶胶刚生成时浸提一次,干燥、焙烧得到膜上纳米粒子分布均匀,所生成的二次粒子粒径最小,二次粒子形成的二次表面粗糙度最小,浸提10次得到膜上纳米粒子间存在较丰富缝隙结构,二次粒子粒径及其形成的表面粗糙度较大,而溶胶制备好陈化6 h后浸提得到的膜上二次粒子粒径最大,表面粗糙度最高.由分形理论估算得到三种膜的分形维数分别是2.22、2.20和2.27. XRD测试表明,膜上TiO2为锐钛矿晶相.这些结果表明,采用不同制备步骤得到的膜,其表面结构形态存在较大的差异.     

SnO2纳米粒子-花生酸LB膜有序组合体的研究

采用胶体化学法制备了稳定的SnO2纳米粒子（nanoparticleNP）水溶胶，用膜天平和原位布儒斯特角显微镜（BAM）考察了经典成膜材料花生酸（AA）在此水溶胶气-液界面的成膜性，并用LB膜技术在不同基底上制得了单层和多层AA-Sno2NP复合LB膜，通过TEM、小角X-ray、IR和UV-VIS光谱，进一步考察了该有序组装体的结构和周期性，以及组装作中Sno2纳米粒子的形貌、粒度分布和表面聚集状态.结果表明，用这种方法能够制得粒度分布均匀、农致密的Sno2纳米粒子复合LB膜，并且多层复合膜具有良好的周期性.     

CO oxidation on nanostructured SnO(x)/Pt(111) surfaces: unique properties of reduced SnO(x)

We have investigated surface CO oxidation on "inverse catalysts" composed of SnO(x) nanostructures supported on Pt(111) using X-ray photoelectron spectroscopy (XPS), low-energy ion scattering spectroscopy (LEISS) and temperature-programmed desorption (TPD). Nanostructures of SnO(x) were prepared by depositing Sn on Pt(111) pre-covered by NO(2) layers at low temperatures. XPS data show that the SnO(x) nanoparticles are highly reduced with Sn(II)O being the dominant oxide species, but the relative concentration of Sn(II) in the SnO(x) nanoparticles decreases with increasing Sn coverage. We find that the most active SnO(x)/Pt(111) surface for CO oxidation has smallest SnO(x) coverage. Increasing the surface coverage of SnO(x) reduces CO oxidation activity and eventually suppresses it altogether. The study suggests that reduced Sn(II)O, rather than Sn(IV)O(2), is responsible for surface CO oxidation. The occurrence of a non-CO oxidation reaction path involving reduced Sn(II)O species at higher SnO(x) coverages accounts for the decreased CO oxidation activity. From these results, we conclude that the efficacy of CO oxidation is strongly dependent on the availability of reduced tin oxide sites at the Pt-SnO(x) interface, as well as unique chemical properties of the SnO(x) nanoparticles.     

119Sn Mössbauer spectroscopy of Sn–O nanoparticles prepared by levitation-jet aerosol synthesis

Sn–O nanoparticles were prepared by levitation-jet aerosol synthesis and found to exhibit ferromagnetic behavior. X-ray powder diffraction analysis and ¹¹⁹Sn Mössbauer spectroscopy confirmed these nanoparticles consist of β-Sn, SnO and SnO₂ phases. The maximum specific magnetization was observed for nanoparticles containing the SnO/SnO₂ interface.     

Preparation of Ru-doped SnO2-supported Pt catalysts and their electrocatalytic properties for methanol oxidation

Ru-doped SnO2 nanoparticles were prepared by chemical precipitation and calcinations at 823 K. Due to high stability in diluted acidic solution, Ru-doped SnO2 nanoparticles were selected as the catalyst support and second catalyst for methanol electrooxidation. The micrograph, elemental composition, and structure of the Ru-doped SnO2 nanoparticles were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, respectively. The electrocatalytic properties of the Ru-doped SnO2-supported Pt catalyst (Pt/Ru-doped SnO2) for methanol oxidation have been investigated by cyclic voltammetry. Under the same loading mass of Pt, the Pt/Ru-doped SnO2 catalyst shows better electrocatalytic performance than the Pt/SnO2 catalyst and the best atomic ratio of Ru to Sn in Ru-doped SnO2 is 1/75. Additionally, the Pt/Ru-doped SnO2 catalyst possesses good long-term cycle stability.     

SnO2-TiO2薄膜载体对Au-Pt纳米颗粒电化学性能的影响

采用真空镀膜法在玻碳(GC)电极表面修饰SnO2-TiO2薄膜, 在SnO2-TiO2/GC复合电极表面组装Au-Pt双金属纳米颗粒, 制得Au-Pt/SnO2-TiO2/GC复合电极. 通过循环伏安法(CV)研究了SnO2-TiO2薄膜载体对Au-Pt双金属纳米颗粒电化学性能的影响; 采用扫描电镜(SEM)及X射线光电子能谱(XPS)对Au-Pt在SnO2-TiO2薄膜沉积的形貌及结构进行了表征. 研究结果表明, 10 nm的Au-Pt双金属纳米颗粒均匀地组装于SnO2-TiO2薄膜表面; SnO2-TiO2薄膜载体改善了复合电极抗CO中毒能力; Au-Pt双金属合金的形成提高了Pt 对甲醇氧化的电催化能力, SnO2-TiO2薄膜载体又使Pt纳米粒子d空轨道增多, 提高了Au-Pt双金属纳米颗粒的稳定性和催化性能.     

Biogenic synthesis of tubular SnO2 with hierarchical intertextures by an aqueous technique involving glycoprotein

Tetragonal SnO2 with hierarchical interwoven structures was prepared by a convenient soaking technique followed by a calcination treatment over 823 K. On the basis of the biomaterial eggshell membrane (ESM) being immersed in aqueous Sn colloid medium and a calcination treatment in succession, SnO2 nanocrystallites with a size of about 5 nm were formed, assembled into tubular fibers, and further intertwisted to construct hollow interconnective fibrous meshworks. With the biomaterial ESM serving as the physical substrate, chemical revulsant, and capping agent, the formation and assembly of hierarchical SnO2 nanomaterials should be under the control of glycoprotein contained in the ESM fiber mantle and directed by the interactions between the glycoprotein macromolecules (containing carboxyl, hydroxyl, and amino groups, etc.) and Sn colloid ingredients of the Sn impregnant. The unique hierarchical SnO2 nanomaterials of structural particularity and complexity are expected to find potential applications in gas sensors, photocatalysts, and dye-sensitized solar cells, etc.     

Size-controllable synthesis of monodispersed SnO2 nanoparticles and application in electrocatalysts

Size-controllable tin oxide nanoparticles are prepared by heating ethylene glycol solutions containing SnCl(2) at atmospheric pressure. The particles were characterized by means of transmission electron microscopic (TEM), X-ray diffraction (XRD) studies. TEM micrographs show that the obtained material are spherical nanoparticles, the size and size distribution of which depends on the initial experimental conditions of pH value, reaction time, water concentration, and tin precursor concentration. The XRD pattern result shows that the obtained powder is SnO(2) with tetragonal crystalline structure. On the basis of UV/vis and FTIR characterization, the formation mechanism of SnO(2) nanoparticles is deduced. Moreover, the SnO(2) nanoparticles were employed to synthesize carbon-supported PtSnO(2) catalyst, and it exhibits surprisingly high promoting catalytic activity for ethanol electrooxidation.     

Morphological and photoelectrochemical characterization of core-shell nanoparticle films for dye-sensitized solar cells: Zn-O type shell on SnO2 and TiO2 cores

Core-shell type nanoparticles with SnO2 and TiO2 cores and zinc oxide shells were prepared and characterized by surface sensitive techniques. The influence of the structure of the ZnO shell and the morphology ofnanoparticle films on the performance was evaluated. X-ray absorption near-edge structure and extended X-ray absorption fine structure studies show the presence of thin ZnO-like shells around the nanoparticles at low Zn levels. In the case of SnO2 cores, ZnO nanocrystals are formed at high Zn/Sn ratios (ca. 0.5). Scanning electron microscopy studies show that Zn modification of SnO2 nanoparticles changes the film morphology from a compact mesoporous structure to a less dense macroporous structure. In contrast, Zn modification of TiO2 nanoparticles has no apparent influence on film morphology. For SnO2 cores, adding ZnO improves the solar cell efficiency by increasing light scattering and dye uptake and decreasing recombination. In contrast, adding a ZnO shell to the TiO2 core decreases the cell efficiency, largely owing to a loss of photocurrent resulting from slow electron transport associated with the buildup of the ZnO surface layer.     

SnO_2/中空洋葱状碳纳米复合材料的制备及电化学性能

以炭黑为原料,硝酸铁为催化剂前驱体,氮气气氛下1000℃高温炭化制备了直径为40nm的中空洋葱状碳纳米颗粒(OC).用SnCl2/乙醇溶液浸渍,空气中350℃氧化得到SnO2/OC复合材料.进一步对该复合材料进行酸处理制备OC包覆的SnO2电极材料.采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和热失重分析(TGA)对OC和SnO2/OC复合材料进行表征;利用恒电流充放电和循环伏安(CV)方法对复合材料作为锂离子电池负极材料的电化学性能进行表征.结果表明:酸处理后的复合材料的循环性能得到明显改善,50次循环后可逆容量保持为446mAh·g-1,OC起到了缓冲SnO2膨胀和阻止团聚的作用.     

Effects of Cr2O3 modification on the performance of SnO2 electrodes in DSSCs

In this paper, we demonstrate that Cr(2)O(3), a visible absorbing insulator, can be used as an efficient blocking layer material for the anode of dye-sensitized solar cells (DSSCs). We prepared SnO(2) electrodes surface-modified with Cr(2)O(3) with various Cr/Sn ratios and studied the effect of the modification on the performance of DSSCs. DSSCs with Cr/Sn ratios 0.02, 0.05, and 0.10 showed increased overall photon-to-electricity conversion efficiency from that of pure SnO(2). Especially, the DSSC with the Cr/Sn ratio 0.02 showed a remarkably large increase by 55%. The electrode materials were analyzed by powder X-ray diffraction, transmission electron microscopy, N(2) adsorption studies, and UV-Vis diffuse reflectance spectroscopy. The Cr-containing species appears to be Cr(2)O(3) nanoparticles, spread evenly on the SnO(2) nanoparticles and filling the gap space between SnO(2) particles. The electrochemical properties of the electrodes were characterized by Mott-Schottky plots and electrochemical impedance spectroscopy. As the Cr-content increases, the flat-band potential is negatively shifted. The impedance spectroscopy data show that Cr/Sn = 0.02 and 0.05 samples have lower charge transport resistance at the electrode, which can be explained by the rise of the conduction level due to the charge transfer from the more basic Cr(2)O(3) nanoparticles to SnO(2) nanoparticles. These observations corroborate with the trends of the short-circuit current and the open-circuit voltage of the DSSCs.