Photoinduced electron injection from Ru(dcbpy)2(NCS)2 to SnO2 and TiO2 nanocrystalline films

Photoinduced electron injection from the sensitizer Ru(dcbpy)2(NCS)2 (RuN3) into SnO2 and TiO2 nanocrystalline films occurs by two distinct channels on the femto- and picosecond time scales. The faster electron injection into the conduction band of the different semiconductors originates from the initially excited singlet state of RuN3, and occurs in competition with intersystem crossing. The rate of singlet electron injection is faster to TiO2 (1/55 fs-1) than to SnO2 (1/145 fs-1), in agreement with higher density of conduction band acceptor states in the former semiconductor. As a result of competition between the ultrafast processes, for TiO2 singlet, whereas for SnO2 triplet electron injection is dominant. Electron injection from the triplet state is nonexponential and can be fitted with time constants ranging from approximately 1 ps (2.5 ps for SnO2) to approximately 50 ps for both semiconductors. The major part of triplet injection is independent of the semiconductor and is most likely controlled by intramolecular dynamics in RuN3. The overall time scale and the yield of electron injection to the two semiconductors are very similar, suggesting that processes other than electron injection are responsible for the difference in efficiencies of solar cells made of these materials.     

Tin oxide (SnO2) nanoparticles/electrospun carbon nanofibers (CNFs) heterostructures: controlled fabrication and high capacitive behavior

Tin oxide (SnO(2))/carbon nanofibers (CNFs) heterostructures were fabricated by combining the versatility of the electrospinning technique and template-free solvent-thermal process. The results revealed that the SnO(2) nanostructures were successfully grown on the primary electrospun carbon nanofibers substrates. And, the coverage density of SnO(2) nanoparticles coating on the surface of the CNFs could be controlled by simply adjusting the mass ratio of CNFs to SnCl(4)·5H(2)O in the precursor during the solvent-thermal process for the fabrication of SnO(2)/CNFs heterostructures. The electrochemical performances of the SnO(2)/CNFs heterostructures as the electrode materials for supercapacitors were evaluated by cyclic voltammetry (CV) and galvanostatic charge-discharge measurement in 1 M H(2)SO(4) solution. At different scan rates, all the samples with different coverage densities of SnO(2) showed excellent capacitance behavior. And, the sample CS2 (the mass ratio of CNFs to SnCl(4)·5H(2)O reached 1:7) exhibited a maximum specific capacitance of 187 F/g at a scan rate of 20 mV/s. Moreover, after 1000 cycles, the specific capacitance retention of this sample was over 95%. The high capacitive behavior could be ascribed to the low resistance of SnO(2)/CNFs heterostructures and rapid transport of the electrolyte ions from bulk solution to the surface of SnO(2).     

Copper (II) adsorbed on SiO(2)/SnO(2) obtained by the sol-gel processing method: application as electrochemical sensor for ascorbic acid

With the objective of producing a material showing better conductive properties to be used as a support for electroactive species, a SiO(2)/SnO(2) mixed oxide was prepared. The procedure for SiO(2)/SnO(2) mixed oxide preparation using the sol-gel processing method, starting from tetraethylorthosilicate and SnI(4) as precursor reagents, is described. SiO(2)/SnO(2) with composition Sn=15.6 wt% and S(BET) = 525 m(2)g(-1), V(p)=0.28 mlg(-1), and D(p)= 1.5 nm, where S(BET), V(p) and D(p) are the specific surface area, the average pore volume, and the average pore diameter, respectively, was obtained. The X-ray photoelectron spectroscopy showed that the mixed oxide was thermally very stable for samples heat-treated at up to 1073 K. The Br?nsted acid sites, probed with pyridine molecules for samples heat-treated at various temperatures, were chemically stable up to 473 K. Segregation of SnO(2) crystalline phase was observed at 1473 K but no crystalline phase was verified for SiO(2) at this temperature. The porous SiO(2)/SnO(2) matrix was used as base for Cu(II) immobilization and an electrode was developed for application in electrochemical detection of vitamin C in tablets.     

Hydroxoverbindungen. 9. Barium-Oxohydroxostannat(II) Ba[SnO(OH)]2

Hydroxo Compounds. 9. Barium Oxohydroxostannate(II) Ba[SnO(OH)]₂ The pale yellow barium hydroxostannate(II), to which different stoichiometries have been assigned in the past, is now identified doubtlessly as Ba[SnO(OH)]₂. The compound crystallizes in the monoclinic space group P2₁ (a = 759.4(2) pm, b = 576.2(1) pm, c = 717.4(2) pm, β = 107.67(2)°, Z = 2, R = 0.038, 645 I_hkl) and exhibits a typical layer structure. Ba[SnO(OH)]₂ contains a new structural element in tin(II) chemistry, which is a one dimensional polyanion [SnO(OH)]^? with syndiotactical conformation. In the context with the structures of two Na-hydroxostannates(II) which were characterized recently, the polyanion can be looked at as an intermediate condensation product of a (topotactical ?) reaction to SnO which all known hydroxostannates(II) undergo.     

Incorporating Zn(2) SnO(4) Quantum Dots and Aggregates for Enhanced Performance in Dye-Sensitized ZnO Solar Cells

The performance of dye-sensitized ZnO solar cells was improved by a facile surface-treatment approach through chemical-bath deposition. After the surface treatment, the quantum dots of Zn(2) SnO(4) were deposited onto ZnO nanoparticles accompanied by the aggregations of Zn(2) SnO(4) nanoparticles. The ZnO film displayed a better resistance to acidic dye solution on account of the deposited Zn(2) SnO(4) nanoparticles. Meanwhile, the open-circuit photovoltage was greatly enhanced, which can be ascribed to the increased conduction-band edge of ZnO and inhibited interfacial charge recombination. Although the deposition of Zn(2) SnO(4) decreased the adsorption amounts of N719 dye, the aggregates of Zn(2) SnO(4) with a size of 350-450?nm acted as the effective light-scattering layer, thereby resulting in an improved short-circuit photocurrent. By co-sensitizing 10?μm-thick ZnO film with N719 and D131 dyes, a top efficiency of 4.38?% was achieved under the illumination of one sun (AM?1.5, 100?mW?cm(-2) ).     

Optical and photocatalytic properties of heavily F(-)-doped SnO2 nanocrystals by a novel single-source precursor approach

Heavily F-doped SnO(2) nanocrystals were successfully prepared by a novel synthetic approach involving low-temperature oxidation of a Sn(2+)-containing fluoride complex KSnF(3) as the single-source precursor with H(2)O(2). The F-doped SnO(2) powder was characterized by powder X-ray diffraction, TG-MS, BET surface area, diffuse reflectance spectroscopy, XPS, PL, FTIR spectroscopy, Raman spectroscopy, EPR spectroscopy, SEM, and TEM. Broadening of the diffracted peaks, signifying the low crystallite size of the products, was quite evident in the powder X-ray diffraction pattern of SnO(2) obtained from KSnF(3). It was indexed in a tetragonal unit cell with lattice constants a = 4.7106 (1) ? and c = 3.1970 (1) ?. Agglomeration of particles, with an average diameter of 5-7 nm, was observed in the TEM images whose spotwise EDX analysis indicated the presence of fluoride ions. In the core level high-resolution F 1s spectrum, the peak observed at 685.08 eV was fitted by the Gaussian profile yielding the fluoride ion concentration to be 21.23% in the SnO(2) lattice. Such a high fluoride ion concentration is reported for the first time in powders. SnO(2):F nanocrystals showed greater thermal stability up to 300 °C when heated in a thermobalance under flowing helium, after which generation of small quantities of HF was observed in the TG coupled mass spectrometry analysis. The band gap value, estimated from the Kubelka-Munk function, showed a large shift from 3.52 to 3.87 eV on fluoride ion doping, as observed in the diffuse reflectance spectrum. Such a large shift was corroborated to the overdoped situation due to the Moss-Burstein effect with an increase in the carrier concentration. In the photoluminescence (PL) spectrum, SnO(2):F nanocrystals exhibited a broad green emission arising from the singly ionized oxygen vacancies created due to higher dopant concentration. The evidence for singly ionized vacancies was arrived from the presence of a signal with a g value of 1.98 in the ESR spectrum of SnO(2):F at room temperature. The disordered nature of the rutile lattice and the enormous oxygen vacancies created due to fluoride ion doping were evident from the broad bands observed at 455, 588, and 874 cm(-1) in the room-temperature Raman spectrum of SnO(2):F. As the consequence of the oxygen vacancies, F-doped SnO(2) was examined for the function as a photocatalyst in the degradation of aqueous RhB dye solution under UV irradiation. A very high photocatalytic efficiency was observed for the F-doped SnO(2) nanocrystals as compared to pure SnO(2). The BET surface area of pure SnO(2) was quite high (207.81 m(2)/g) as compared to the F-doped SnO(2) nanocrystals (45.16 m(2)/g). Pore size analysis showed a mean pore diameter of 1.97 and 13.97 nm for the pure and doped samples. The increased photocatalytic efficiency was related to the very high concentration of oxygen vacancies in SnO(2) induced by F doping.     

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.     

Theoretical Study on the Structural and Electronic Properties of the Reduced SnO2 （110） Surface

The reduced SnO2(110) surface has been investigated by using first-principles method with a slab model. By examining the vacancy formation energy of three kinds of reduced SnO2(110) surfaces, the most energetically favorable defect surface is confirmed to be the surface with the coexistence of bridging and in-plane oxygen vacancies, which is different with the traditional model by only removing bridging oxygen. The results of band structure calculations indicate that the electronic structure of this defect surface is similar to the SnO surface.     

Density functional theory study on the structural and electronic properties of low index rutile surfaces for TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 composite systems

The present study is concerned with the structural and electronic properties of the TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 composite systems. Periodic quantum mechanical method with density functional theory at the B3LYP level has been carried out. Relaxed surface energies, structural characteristics and electronic properties of the (110), (010), (101) and (00) low-index rutile surfaces for TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 models are studied. For comparison purposes, the bare rutile TiO2 and SnO2 structures are also analyzed and compared with previous theoretical and experimental data. The calculated surface energy for both rutile TiO2 and SnO2 surfaces follows the sequence (110) < (010) < (101) < (001) and the energy increases as (010) < (101) < (110) < (001) and (010) approximately = (110) < (101) < (001) for SnO2/TiO2/SnO2 and TiO2/SnO2/TiO2 composite systems, respectively. SnO2/TiO2/SnO2 presents larger values of surface energy than the individual SnO2 and TiO2 metal oxides and the TiO2/SnO2/TiO2 system renders surface energy values of the same order that the TiO2 and lower than the SnO2. An analysis of the electronic structure of the TiO2/SnO2/TiO2 and SnO2/TiO2/SnO2 systems shows that the main characteristics of the upper part of the valence bands for all the studied surfaces are dominated by the external layers, i.e., by the TiO2 and the SnO2, respectively, and the topology of the lower part of the conduction bands looks like the core layers. There is an energy stabilization of both valence band top and conduction band bottom for (110) and (010) surfaces of the SnO2/TiO2/SnO2 composite system in relation to their core TiO2, whereas an opposite trend is found for the same surfaces of the TiO2/SnO2/TiO2 composite system in relation to the bare SnO2. The present theoretical results may explain the growth of TiO2@SnO2 bimorph composite nanotape.     

氧化锡表面的原子簇模型计算

Cluster models of SnO2(110) face and oxygen vacancies and oxygen adsorption on its surface have been calculated by EHMO method. The results show that a tin atom with a coordination number of four is the adsorption center, because the total energy of cluster model becomes lower when an oxygen atom adsorpts on the tin atom with a coordination number of four. The tin atom with this coordination number gains and loses electrons more easily than tin atoms with a coordination number of five. All tin atoms in the cluster of SnO2(110) face are Sn4+.     

PbS/RL~2(NCS)~2复合敏化SnO~2纳米多孔膜电极的光电化学研究

用光电化学方法和UV-vis吸收光谱研究了PbS和Rul~2(NCS)~2(L=2,2'--bipydine--4,4'-dicarboxylicacid)复合敏化SnO~2纳米晶多孔膜电极的光电化学行为.实验表明,复合敏化比用PbS或RuL~2(NCS)~2分别单独敏化的效果好,不仅使电极的光吸收拓展到可见光区,而且复合敏化显著提高了光电转换效率,并讨论了复合敏化电极的电荷传输机理。     

Direct formation of Ge-C bonds from GeO(2)

Germanium dioxide in the presence of 5% KOH reacted with dimethyl carbonate (DMC) at 250 degrees C to give (MeO)(4)Ge. The reaction of GeO(2) and DMC is similar to that reported for SiO(2); however, the rate of reaction for germanium is much higher than that of the corresponding silicon reaction. In a side-by-side experiment using SiO(2) and GeO(2) where the surface area of the silicon dioxide was 2 orders of magnitude higher than that of the GeO(2), the base-catalyzed reaction with DMC was about an order of magnitude higher for the germanium dioxide. When GeO(2) and 5% KOH were reacted with DMC at 350 degrees C, two products formed: (MeO)(4)Ge (70%) and MeGe(OMe)(3) (30%). Confirmation of the identity of MeGe(OMe)(3) was by GCMS, (1)H and (13)C NMR, and comparison to an authentic sample made by reaction of MeGeCl(3) with NaOMe. Experiments to determine the mechanism of the direct formation of Ge-C from GeO(2) ruled out participation from CO, H(2), or carbon. The KOH-catalyzed reaction of other metal oxides was explored including B(2)O(3), Ga(2)O(3), TiO(2), Sb(2)O(3), SnO(2), and SnO. Boron reacted to give unknown volatile products. Antimony reacted to give a solid which analyzed as Sb(OMe)(3). SnO reacted with DMC to give a mixture that included (MeO)(4)Sn and possibly Me(3)Sn(OMe).     

(Sn,Sb)O2-x基纳米结构厚膜材料气敏特性及机理

对采用水热合成技术所形成的纳米(Sn,Sb)O2 x晶粒结构、厚膜材料的气敏特性及其机理进行了研究,并采用XRD、TEM手段对纳米尺度的（Sn、Sb)O2 x晶粒的结构与表面效应及晶粒形态进行了表征.结果表明,当掺杂Sb5＋的浓度（摩尔分数xSb5＋)为（2.9～5.8)×10－6时,（Sn、Sb)O2 x纳米晶粒表面的电子缺陷浓度增大,增强了对气体的吸附能力,从而提高了对可燃性气体的灵敏度.同时可使晶粒保持短柱状的形态特征,对其灵敏度有一定的控制作用.     

Combined X-ray diffraction and diffuse reflectance analysis of nanocrystalline mixed Sn(II) and Sn(IV) oxide powders

Nanocrystalline mixtures of Sn(II) and Sn(IV) oxide powders, potential gas sensor materials, are synthesized via a simple precipitation route using SnCl(2) as the precursor. Materials are characterized by powder X-ray diffraction, thermogravimetric analysis, UV-visible diffuse reflectance spectroscopy (DRS), and Fourier transform infrared spectroscopy. The ratio of Sn(II)/Sn(IV) in powders precipitated at room temperature, as well as the identity of the primary Sn(II) product (SnO or Sn(6)O(4)(OH)(4)), can be varied by adjusting aging time and washing procedures. The identity of the initial Sn(II) product influences the subsequent phase composition and degree of disorder in the tetragonal SnO(2) phase obtained following sintering in air. Analysis of the DRS absorption edge and long-wavelength (Urbach) absorption tail is used to determine the SnO(2) optical band gap and extent of disorder. SnO(2) obtained by heating the SnO/SnO(2) mixture at 600 or 800 degrees C has a smaller optical band gap and a broader Urbach tail than the analogous sample obtained from heating Sn(6)O(4)(OH)(4), indicating a more disordered material.     

Novel 3-D superstructures made up of SnO(2)@C core-shell nanochains for energy storage applications

New 1-D SnO(2)@C core-shell nanochains built into 3-D superstructures are presented for the first time as anode materials for lithium-ion batteries. These novel SnO(2)@C core-shell nanochains exhibit desirable lithium storage properties.     

纳米SnO2@TiO2包覆催化剂的制备及表征

采用活性层包覆法在自制细SnO2胶体粒子表面包覆TiO2,制备出SnO2@TiO2包覆型复合催化剂,以其对有机磷农药DDVP的降解效果作为评价光催化活性的标准,对制备条件进行了优化,并用XRD、TEM和BET等手段对样品进行了表征,结果表明,SnO2胶体乙醇溶液含水量20％,钛酸丁酯质量分数为34.5％。灼烧温度680℃时制得TiO2含量56.45％的包覆样品SnO2@TiO2为纳米级粒子,且其光催化活性最佳。     

Comparisons of multilayer H2O adsorption onto the (110) surfaces of alpha-TiO2 and SnO2 as calculated with density functional theory

Mono- and bilayer adsorption of H2O molecules on TiO2 and SnO 2 (110) surfaces has been investigated using static planewave density functional theory (PW DFT) simulations. Potential energies and structures were calculated for the associative, mixed, and dissociative adsorption states. The DOS of the bare and hydrated surfaces has been used for the analysis of the difference between the H2O interaction with TiO2 and SnO 2 surfaces. The important role of the bridging oxygen in the H2O dissociation process is discussed. The influence of the second layer of H2O molecules on relaxation of the surface atoms was estimated.     

SnO2负载Au和M-Au(M=Pt,Pd)催化剂及其低温催化氧化CO性能

以SnO₂为载体, 采用沉积沉淀法(DP)、共沉淀法(CP)和浸渍法(IM)制备了金负载Au/SnO₂催化剂, 同时采用沉积沉淀法制备了M-Au/SnO₂(M=Pd, Pt)双金属负载催化剂. 通过X射线衍射(XRD)、BET比表面积测定、透射电镜(TEM)和X射线光电子能谱(XPS)等技术对样品进行表征, 并测定其对CO的催化活性. 结果表明: 与CP法和IM 法相比, DP法制备的Au/SnO₂-DP 催化剂, Au 颗粒(<5 nm)较小, 分布均匀; Au/SnO₂-DP 中的Au 是以金属态Au0存在, 而Au/SnO₂-CP 和Au/SnO₂-IM 中, 金以Au⁰和Au³⁺的混合价态存在, 在Au/SnO₂-DP和M-Au/SnO₂中的Au、Pt、Pd和SnO₂之间存在相互作用; Au/SnO₂-DP 催化性能明显优于Au/SnO₂-CP 和Au/SnO₂-IM. Au与Pt 和Pd的双金属复合催化剂催化活性明显提高. 不同方法制备Au/SnO₂催化活性的差别主要是由于Au颗粒大小和Au氧化态的不同而产生. 而M-Au/SnO₂活性提高, 可能是由于Au与Pt 和Pd之间的相互作用.     

Theoretical calculation of EPR g factors for Ni(3+) ion at the interstitial site of SnO(2) crystal

The EPR g factors g(x), g(y) and g(z) for Ni(3+) ion at the interstitial site in the rutile-type SnO(2) crystal are calculated from the second-order perturbation formulas of g factors based on the cluster approach for 3d(7) ion in rhombic symmetry. The calculated results are in agreement with the experimental values. The local lattice distortion induced by the impurity Ni(3+) at the interstitial site of SnO(2) is also estimated from the calculations. These results are discussed.     

A novel SnO(2)-based gas sensor

A novel 'two-terminal' semiconductor gas sensor was developed based on a heavily Sb-doped SnO(2) film prepared by cathodic sputtering. The sensor is heated at its operational temperature by the gas sensitive film itself. A device for detecting the leakage of flammable gases, some noxious or hazardous gases can be made in this way.