PHOTOEMISSION-STUDY ON THE SNO2/P A-SICX-H INTERFACE

Ultraviolet and X-ray photoemission spectroscopies (UPS and XPS) have been employed to SnO2 and its interface with P-type a-SiCx:H. The HeI valence band spectra of SnO2 show that the valence band maximum (VBM) shifts from 4.7 eV to 3.6 eV below the Fermi level (E(F)), and the valence band tail (VBT) extends up to the E(F), as a consequence of H-plasma treatments. The work function difference between SnO2 and P a-SiCx:H is found to decrease from 0.98 eV to 0.15 eV, owing to the increase of the work function of the treated SnO2. The reduction of SnO2 to metallic Sn is also observed by XPS profiling, and it is found that this leads to a wider interfacial region between the treated SnO2 and the successive growth of P a-SiCx:H.

Size-controlled synthesis and characterization of quantum-size SnO2 nanocrystallites by a solvothermal route

By using ethylenediamine as both an alkali and ligand, quantum size SnO2, nanocrystallites were synthesized with a solvothermal route. The transmission electron micrographs (TEM) were employed to characterize the morphologies of the products. The crystal sizes of the as-synthesized SnO2 were ranged form 2.5 to 3.6 nm. The crystal structure and optical properties of the products were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, optical absorption spectra, photoluminescence and Raman spectra.

One-step synthesis of graphene/SnO2 nanocomposites and its application in electrochemical supercapacitors

A one-step method was developed to fabricate conductive graphene/SnO2 (GS) nanocomposites in acidic solution. Graphite oxides were reduced by SnCl2 to graphene sheets in the presence of HCl and urea. The reducing process was accompanied by generation of SnO2 nanoparticles. The structure and composition of GS nanocomposites were confirmed by means of transmission electron microscopy, x-ray photoelectron and Raman spectroscopy. Moreover, the ultracapacitor characteristics of GS nanocomposites were studied by cyclic voltammograms (CVs) and electrical impedance spectroscopy (EIS). The CVs of GS nanocomposites are nearly rectangular in shape and the specific capacitance degrades slightly as the voltage scan rate is increased. The EIS of GS nanocomposites presents a phase angle close to p/2 at low frequency, indicating a good capacitive behavior.

Direct electrochemistry of glucose oxidase and biosensing for glucose based on carbon nanotubes@SnO2-Au composite

Multiwalled carbon nanotubes@SnO2-Au (MWCNTs@SnO2-Au) composite was synthesized by a chemical route. The structure and composition of the MWCNTs@SnO2-Au composite were confirmed by means of transmission electron microscopy, X-ray photoelectron and Raman spectroscopy. Due to the good electrocatalytic property of MWCNTs@SnO2-Au composite, a glucose biosensor was constructed by absorbing glucose oxidase (GOD) on the hybrid material. A direct electron transfer process is observed at the MWCNTs@SnO2-Au/GOD-modified glassy carbon electrode. The glucose biosensor has a linear range from 4.0 to 24.0 mM, which is suitable for glucose determination by real samples. It should be worthwhile noting that, from 4.0 to 12.0 mM, the cathodic peak currents of the biosensor decrease linearly with increasing the glucose concentrations in human blood. Meanwhile, the resulting biosensor can also prevent the effects of interfering species.

Hydrothermal synthesis of Fe and Mn doped SnO2 and its magnetic structures

The dilute magnetic semiconductor of Sn1-x-yMnxFeyO2 (0 <= x <= 0.10, 0 <= y <= 0.10) Were syhthesized with the hydrothermal method using SnCl4, Mn(CH3COO)(2) center dot 4H(2)O and FeCl3 center dot 6H(2)O as the raw materials. The structure, morphologies and magnetic properties of the sample were characterized via X-ray powder diffractometer(XRD), transmission electron microscopy(TEM), Raman spectrum and superconducting and quantum interference device(SQUIT), and Mossbeaur spectrum. No secondary phase was found in the XRD spectrum. The morphology of the samples is affected by the kind or the mount of transition metal. The local vibrating model-of Mn Positioned SnO2 sites was found in Raman spectrum. The measured magnetic results indicate that when x = 0.10, y = 0, the sample exhibits strong magnetization in low-temperature (5 K), but the magnetization decrease rapidly at room. temperature; In contrast, when x = 0, y = 0.1, the sample's magnetization and coercivity are both small, but being temperature independent. Mossbeaur spectra indicates that part of the Fe is ferromagnetic coupled, and the simulating results indicate that the ferromagnetic character is intrinsic.

IrO2/SnO2 electrodes: prepared by sol-gel process and their electrocatalytic for pyrocatechol

IrO2/SnO2 (10%:90%, molar ratio) electrodes (ITEs) were prepared by the sol-gel method as an alternative to the electrode-position and thermal decomposition process. The electrodes were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), cyclic voltammetry (CV) and electrochemical impedance spectra (EIS). From the results of XRD, oxide films prepared at low temperature were in amorphous state, while hydrous IrO2 crystal and cassiterite phase SnO2 were formed at 300 degreesC or even to 500 degreesC. The highly porous structure was confirmed by AFM. The electrochemical experiments demonstrated that the sol-gel method made the ITEs having a fast electron transfer process with good stability and the optimal preparation temperature was 400 degreesC for the highest electroactivity. Furthermore, the electrocatalysis of pyrocatechol on the electrodes was investigated. A quasi-reversible process occurred and a linear range over three orders magnitude (1 x 10(-2) - 10 mM) was obtained by differential pulse voltammetry (DPV). Meanwhile the detection limit of pyrocatechol was 5 x 10(-3) mM. This study indicated that the sol-gel method was an appropriate route to prepare the IrO2/SnO2 electrodes for the electrocatalytic of pyrocatechol.

TiO2-SnO2复合凝胶的水-乙醇蒸汽吸附动力学研究

中国科学院山西煤炭化学研究所

TiO2-SnO2复合凝胶的结构表征及其吸附与催化性能研究

中国科学院山西煤炭化学研究所

Nanocrystalline SnO2 synthesised by means of hydrothermal precipitation

Nanocrystalline SnO2 with different particle sizes has been prepared by means of hydrothermal precipitation. The resulting SnO2 nanometer size powders, which are basically spherical in shape according to TEM, are tetragonal in structure with space group P4/mnm. Calculation shows that the crystallite size of SnO2 increases with increase of the calcination temperature, but that the average crystal lattice distortion rate decreases with increase of crystallite size. The smaller the particle, the bigger the crystal lattice distortion and the slower the crystal growth rate. Weight loss analysis indicates the prepared SnO2 is very slightly impure.

A novel method for preparing ordered SnO2/TiO2 alternate nanoparticulate films

A novel method using LB films as precursors to prepare pure inorganic ordered film with periodic structure was developed. Surfactant-stabilized SnO2 nanoparticulate organosols and TiO2 nanoparticulate organosols were prepared and used as spreading solutions. Using LB technique, the good film-forming ability of the surfactant-stabilized SnO2 nanoparticles and TiO2 nanoparticles was confirmed by the determination of the pi -A isotherms. The surfactant-stabilized SnO2 and TiO2 nanoparticulate monolayers were fabricated on the water surface and then were transferred to solid substrates (CaF2, quartz, silicon, and so on) alternately, layer-by-layer. Then the as-deposited alternate LB film was treated at different temperatures. The as-deposited alternate LB film and the treated film were characterized by Fourier transform infrared spectroscopy, UV visible spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results indicate that our method was successful. The as-deposited alternate LB film formed a periodic structure with a long spacing of 6.5 nm that was composed of SnO2 nanoparticles, TiO2 nanoparticles, and arachidic acid. The treated film composed of SnO2 nanoparticles and TiO2 nanoparticles formed a pure inorganic periodic structure with an ordered distance of 5.4 nm. (C) 2001 Academic Press.

Preparation of SnO2 thin films with extremely preferred orientation along (101) plane by LB deposition technique

SnO2 thin films with extremely preferred orientation along (101) plane were made by LB technique and characterized by FTIR,, UV-visible, X-ray diffraction, X-ray photoelectron spectroscopy and SEM.