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.

The effect of surface structure on the photoluminescence of SnO2 nanoparticles in hydrosols and organosols

In this paper, we report the optical properties of SnO2 semiconductor nanoparticles in hydrosols and those of SnO2 semiconductor nanoparticles in organosols in which the surfaces of the particles are coated by a layer of organic surfactant molecules. The photoluminescence spectra of SnO2 semiconductor nanoparticles in the hydrosols and organosols in different conditions were measured and discussed. We conclude that the surface structure of the SnO2 semiconductor nanoparticles affects their optical properties strongly. The oxygen deficiencies on the surface of SnO2 semiconductor nanoparticles play an important role in the optical properties. The surface modification of the particles effectively removes the surface defects of the particles and enhances the intensity of luminescence.

Particulate multilayers prepared from surfactant-stabilized SnO2 nanoparticles

Surfactant-stabilized SnO2 nanoparticulate organosol was prepared. The organosol mixed with arachidic acid was spread on water surfaces in a Langmuir-Blodgett (LB) balance. Surface pressure versus surface area isotherms were determined. The surfactant-stabilized SnO2 nanoparticulate monolayers were transferred, layer-by-layer by the LB technique, to solid substrates. Then the multilayers were characterized by Fourier transform IR spectroscopy, UV-visible spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The results indicate that the multilayer is composed of SnO2 nanoparticles and arachidic acid. It forms a Z-type periodic structure with a long spacing of 7.48 nm, i.e. a kind of three-dimensional superlattice. (C) 1999 Elsevier Science S.A. All rights reserved.

Study on the self-packing of SnO2 nanoparticles at the air-hydrosol interface and its composite LB films with arachidic acid

SnO2 nanoparticles were found to self-pack at the air-hydrosol interface and form a nanoparticulate film. The self-packed films were observed under a Brewster angle microscope, and investigated by recording the time evolution of surface pressure and pi-A isotherms. The results show that SnO2 nanoparticles take 3 h to form a complete film at the air-hydrosol interface. Composite monolayers of SnO2 and arachidic acid were obtained by spreading arachidic acid onto a fresh hydrosol surface. Composite Y-type LB films were transferred from the air-hydrosol interface onto substrates, and characterized by FTIR, UV-vis, X-ray diffraction spectroscopy and TEM techniques. The results show that the composite films have good structure, with SnO2 nanoparticles uniformly and compactly distributed in the arachidate matrix. (C) 1998 Elsevier Science S.A. All rights reserved.

Study of Multiple Films of Copper Phthalocyanine Embedded SnO2 Ultrafine Particles

Multiple films of copper phthalocyanine derivative embedded SnO2 ultrafine particles were studied, The results indicated that there is interaction between CuPc and SnO2, and structure of CuPc is destroyed to some extent. Gas sensitivity measurements show that conductance of LB films after embedding increases about one order of magnitude, stability of gas-sensing also increases.

Study on Ordered Assembly of SnO2 Nonoparticles-Arachidic Acid Composite LB Films

The hydrosol of SnO2 nanoparticles (NP) have been prepared by colloid chemistry method. The composite LB monolayer and multilayer of SnO2 NP-AA have been obtained by LB technique at the gas-liquid interface of the hydrosol subphase. The structures of the monolayer and multilayer were characterized by IR, UV-Vis, small angle X-ray diffraction spectroscopy and TEM technique, The results indicate that the coverage of SnO2 NP at the composite monolayer's surface is high and the sites of SnO2 NP are similar. The multilayer has good periodic structure.

Study on the Films Forming Process of Nanosized SnO2 Colloid Particles at the Gas-Liquid Interface

The hydrosol of SnO2 nanoparticles are prepared by the method of colloid chemistry. The free piling up process of nanosized SnO2 colloid particles are investigated at the gas-liquid interface by LB and Brewster Angle Microscopy techniques. The result indicates that solid state monolayer and multilayer of SnO2 nanoparticles can be formed at the gas-liquid interface only by aging the sol in air or compressing it without amphiphiles surfactant.

PREPARATION AND MICROSTRUCTURAL CHARACTERIZATION OF SURFACE-MODIFIED NANOSIZED SNO2 PARTICLES

Nanosized stannic oxide particles modified with a layer of DBS were successfully prepared through the colloidal chemical method and their microstructures were characterized. FTIR and XPS were used for the determination of the main components. It can be proved that the nanosized SnO2 particles were capped by DBS. The sizes of particle were determined by TEM and XRD. By the investigation of XPS, we can conclude that there are a lot of oxygen vacancies in the surface of the nanoparticulates. Based on this conclusion, the ESR signal of the sample can be explained.

STUDY ON THE NON-STIOCHIOMETRIC SNO2-X NANOCRYSTALLINE MATERIAL BY XRD, XPS AND ESR

Nonstiochiometric SnO2-x nanocrystalline material were successfully prepared through Sol-Gel process using anhydrous stannic chloride and iso-propyl alcohol. TEM observation shows that the mean diameter of the powder sintered at 700 degrees C for 2 hours is about 20 nm. By the investigation of XRD and ESR, we can conclude that the sample sintered at 300 degrees C for 2 hours was amorphous and it grew into nanocrystalline with the oxygen vacancies and defects when sintered at 700 degrees C for 2 hours. Using these conclusion, the ESR signals and the difference between the two SnO2-x samples are explained.