SnO Crystals Research Articles

Aqueous synthesis of nanosheet assembled tin oxide particles and their N 2 adsorption characteristics

Tin oxide particles were synthesized in aqueous solutions. They consisted of nanosheets of tin oxide crystals. The sheets were about 50–100 nm in size and 5–10 nm thickness. X-ray diffraction analysis revealed that the particles were crystals of SnO 2 and SnO. The particles had Brunauer–Emmett–Teller (BET) surface area of 85 m 2/g estimated with N 2 adsorption characteristics. Barrett–Joyner–Halenda (BJH) analysis indicated that mesopores of 3.9 nm in size contributed to the increase surface area.

Matrix-Mediated Formation of Hierarchically Structured SnO Crystals As Intermediates between Single Crystals and Polycrystalline Aggregates

Crystalline SnO grown in a Sn 6O 4(OH) 4 matrix exhibited hierarchical architectures, such as stepped bipyramids, stacked meshes, and rosettes, which were not categorized into the classical assortment of crystal morphologies. The complex architectures consisting of small building units were found to be produced through stacking and/or branching growth accompanied with a decrease in the unit size and degradation of the crystallographic symmetry in their assembly. This particular morphological evolution is presumed to be achieved by increasing the driving force of crystallization in the presence of abundant precursor species supplied from the matrix.

Surface characterization and catalytic activity of sulfated tin oxide catalyst

Abstract The effect of sulfate content and calcination temperature on the structure, acidity and catalytic activity of tin oxide was investigated. Sulfated tin oxide samples were characterized by thermal analysis (DTA and TGA), powder X-ray diffraction (XRD) and N 2 adsorption at −196 °C. The surface acidity was measured by Potentiometric titration, DSC-TGA and FT-IR techniques. The catalytic performance was evaluated on the esterification of acetic acid with amyl alcohol in the vapor phase between 150 and 250 °C. XRD measurements show that the sulfating of SnO 2 tends to hinder the crystallization of SnO 2 and inhibits crystal growth. It was found that the surface acidity increases with the increase of thermal treatment up to 550 °C, while the further increase of calcination temperature beyond 750 °C leads to a decrease of acid sites and acid sites strength. The addition of sulfate to SnO 2 brings about an increase of the specific surface area, whereas the calcination temperature exhibits a reverse trend. The formation of amyl acetate increases with increase of surface acidities. Lewis and Bronsted acid sites appears to be needed for catalytic activity in amyl acetate formation, both are maximum when the sulfate content and calcination temperature are 30 wt.% and 550 °C, respectively.

S-Nitrosylation-induced Conformational Change in Blackfin Tuna Myoglobin

S-nitrosylation is a post-translational protein modification that can alter the function of a variety of proteins. Despite the growing wealth of information that this modification may have important functional consequences, little is known about the structure of the moiety or its effect on protein tertiary structure. Here we report high-resolution x-ray crystal structures of S-nitrosylated and unmodified blackfin tuna myoglobin, which demonstrate that in vitro S-nitrosylation of this protein at the surface-exposed Cys-10 directly causes a reversible conformational change by "wedging" apart a helix and loop. Furthermore, we have demonstrated in solution and in a single crystal that reduction of the S-nitrosylated myoglobin with dithionite results in NO cleavage from the sulfur of Cys-10 and rebinding to the reduced heme iron, showing the reversibility of both the modification and the conformational changes. Finally, we report the 0.95-A structure of ferrous nitrosyl myoglobin, which provides an accurate structural view of the NO coordination geometry in the context of a globin heme pocket.

Microwave-assisted hydrothermal synthesis of nanocrystalline SnO powders

Tin oxide (SnO) powders were obtained by the microwave-assisted hydrothermal synthesis technique using SnCl 2·2H 2O as a precursor. By changing the hydrothermal processing time, temperature, the type of mineralizing agent (NaOH, KOH or NH 4OH) and its concentration, SnO crystals having different sizes and morphologies could be achieved. The powders were characterized by X-ray diffraction (X-ray), Field Emission Scanning Electron Microscopy (FE-SEM), High Resolution Transmission Electron Microscopy (HR-TEM) and Selected Area Electron Diffraction (SAED). The results showed that plate-like form is the characteristic morphology of growth and the TEM analyses indicate the growth direction as (200).

The Optical and Electrical Properties of Antimony-Doped Tin Oxide Transparent Conducting Thin Films Prepared by Sol-Gel Dip-Coating Technique

Antimony-doped tin oxide (ATO) transparent conducting thin films were prepared by sol-gel dip-coating technique in the alcohol solution of metal salts of tin (II) chloride dehydrate and antimony tri-chloride. Usual glass slides (25×76×1mm3) were used as the substrates. As-prepared thin films were dried at temperature of 343K and annealed at temperatures of 673~823K. Their optical properties were analyzed by Hitachi U-3310 spectrophotometer. The good optical transmission of the ATO thin films has been obtained as high as 80%-90% in visible region by the optimization of deposition conditions, but decreased substantially in IR region. From the X-ray diffraction (XRD) measurements, it showed that ATO films had the similar structures with the pure tin oxide films, i.e. tetragonal rutile structure, despite of some rhombic SnO crystals. We analyzed the transmittance in the visible region depending on the vary Sb doped level, temperature, and dip-coating times. The sheet resistance of the investigated thin films was determined by four-probe method, showing that it was about 85-1009/□, which decreased with the increase of antimony doped concentration.

Methane-assisted combustion synthesis of nanocomposite tin dioxide materials

Combustion synthesis of tin dioxide (SnO 2) was studied using a new synthesis approach where the combustion environment was augmented to control the temperature and flow conditions using methane as a supplemental fuel. The experiments were carried out at atmospheric pressure using a multi-element diffusion flame burner with a gas-phase precursor for SnO 2 and solid-phase precursor for metal additives. In the methane-assisted (MA) system, the inert carrier gas was replaced with methane as the transport gas for the SnO 2 and metal additive precursors. Two additive precursors were investigated: gold acetate and aluminum acetate. Particle morphology, primary particle size, crystallinity, phase, molecular and elemental composition were studied using transmission electron microscopy, X-ray diffraction, and energy-dispersive spectroscopy. Particle imaging velocimetry and thermocouple measurements provided velocity and temperature data for the synthesis environment experienced by particles. The MA system provided conditions for rapid sintering of particles into large faceted single crystals of SnO 2 ( d p = 46 nm) compared to methane unassisted system ( d p = 19 nm), thus offering a degree of control over grain size. Additionally, large aspect ratio (2.6 ± 0.9) single crystal SnO 2 particles were produced using the MA system. Gold-doped SnO 2 produced using the MA system yielded gold particles encapsulated in a layer of SnO 2. The characteristic reaction-, coagulation- and sintering-times were investigated for nanoparticle formation in the two systems using simplified models. The analysis provided qualitative justification for the trends observed in particle morphology. The modification of characteristic times in this study demonstrates a route for controlling size and morphology of single or multicomponent systems.

Selective Preparation of SnO2 and SnO Crystals with Controlled Morphologies in an Aqueous Solution System

The oxidation state of tin oxide crystals grown in an aqueous solution of Sn(II) was successfully controlled. Rutile-type SnO2 and tetragonal SnO were selectively produced under acidic conditions below pH 3.3 and alkaline conditions above pH 13.1, respectively. The nanostructures, including the grain size and shape, and the mesoscopic assembled states of the crystals were changed with the concentration of the Sn(II) species and a subtle variation of the pH. This versatile fabrication process for functional oxides is based on the difference in the stability of Sn(II) and Sn(IV) depending on the pH in an aqueous solution system.

All-solid-state rechargeable lithium batteries using SnX-P2X5 (X = S and O) amorphous negative electrodes

SnS-P2S5 and SnO-P2O5 amorphous materials were prepared by a mechanical milling technique. The SnO-P2O5 milled materials worked as a reversible electrode with higher capacity than SnO crystal in rechargeable lithium cells with conventional liquid electrolytes. All-solid-state cells with a SnX-P2X5 (X = S and O) amorphous electrode and the Li2S-P2S5 glass-ceramic electrolyte were charged and discharged at room temperature. The sulfide electrodes exhibited better charge-discharge performance than the oxide electrodes, suggesting that SnS-P2S5 electrodes are more compatible with Li2S-P2S5 sulfide solid electrolytes. All-solid state batteries 80SnS·20P2S5/LiCoO2 showed a charge-discharge plateau of about 3.4 V and high reversible capacity of over 400 mAh/g, even after 50 cycles. The SnX (X = S and O)-based amorphous materials are promising negative electrode materials with high capacity for rechargeable lithium batteries using not only liquid electrolytes but solid electrolytes.

Luminescence properties of Li + doped nanosized SnO 2:Eu

The influence of lithium doping on the crystallization behavior, morphology, and enhancement in photoluminescence intensity of SnO 2:Eu was investigated. In order to attain high homogeneous and pure samples, the Pechini type sol–gel method was adopted for the synthesis at low temperature (500 °C). The structure and morphology were characterized by using X-ray diffraction (XRD) and transmission electron microscope (TEM). The results indicate that the Li + doping could accelerate the crystallization of SnO 2 and the particle size of the phosphors is below 100 nm. In particularly, the incorporation of Li + ions into SnO 2 lattice could induce a remarkable increase of photoluminescence intensity.

High-pressure EXAFS and XRD investigation of unit cell parameters of SnO

This study combining x-ray diffraction and x-ray absorption spectroscopy reveals the variation of the lattice parameters a and c and the atomic position parameter z(Sn) of tetragonal stannous oxide SnO under pressure up to 10 GPa. The observed strong elastic anisotropy of the SnO crystal can be attributed to its layered structure. The axial ratio c/a decreases from 1.27 to 1.16 whereas the position parameter z(Sn) increases from 0.237 to 0.269.

Synthesis and acidic properties of the SiO 2/SnO 2 mixed oxides obtained by the sol–gel process. Evaluation of immobilized copper hexacyanoferrate as an electrochemical probe

SiO 2/SnO 2 mixed oxides were prepared by the sol–gel processing method using SnI 4 as the tin oxide precursor reagent. Solids with Sn compositions (in wt.%) of 4.1, 12.9 and 18.4 and presenting specific surface areas (determined by the BET method) of 492, 658 and 712 m 2 g −1, respectively, were obtained. Transmission microscopic images showed nanosized SnO 2 particles with average dimensions of (5.3±0.5) nm for samples having 12.9 wt.% Sn and (7.0±0.7) nm for samples having 18.4 wt.% Sn. For the sample presenting 4 wt.% of Sn the crystallites were poorly defined, barely being observed. The amorphous SnO 2 particles started to crystallize at different temperatures, i.e., 1273, 1173 and 1073 K for samples with 4.1, 12.9 and 18.4 wt.% of Sn, respectively. The X-ray diffraction patterns showed that only cassiterite crystallites were present in every case and, even at a temperature of 1473 K, the SiO 2 remained as an amorphous matrix. The Lewis and Brønsted acid sites were thermally stable up to a temperature of 523 K for all the compositions, as probed using pyridine molecules. The infrared spectra showed that Si–O–Sn bonds are formed at the interface between SiO 2 and SnO 2 particles. These bonds are the ones mainly responsible for the low mobility of the oxide particles, avoiding crystallization of SnO 2. Copper hexacyanoferrate was prepared in situ on the SiO 2/SnO 2 surface and cyclic voltammetry tests were carried out by sweeping the potential between 0.2 and 1.0 V. The midpoint potential corresponding to the redox process: SnOH 2 +/{KCu[Fe(CN) 6} −⇄SnOH 2 +/{Cu[Fe(CN) 6} −+K ++e − was observed at about 0.7 V. The electrochemical impedance spectroscopic data showed a charge transfer resistance of 17.8 Ω. This low value favors the oxidation–reduction process in the pores of the material.

Pore size control of mesoporous SnO 2 prepared by using stearic acid

Mesoporous SnO 2 with controlled pore size was prepared by calcination of the precursors containing stearic acid (STA). The vaporization of STA promoted the crystallization of SnO 2 at low temperature. Crystallization accompanied with the vaporization of STA at low temperature allowed SnO 2 crystallites to aggregate loosely to form mesopores. The SnO 2 consisted of the aggregates of crystallites, and the mesopores were located at intercrystallites. The pore size and crystallite size of the mesoporous SnO 2 increased with increasing calcination temperature ( T c). The specific surface area decreased with increasing T c, while the pore volume showed little change in the range of T c. The crystal growth of SnO 2 during calcination at high T c provided large mesopores at interparticles.

Theoretical study of oxygen-deficientSnO2(110)surfaces

Theoretical consideration of recently proposed ordered stoichiometric and oxygen-deficient (110) surfaces of ${\mathrm{SnO}}_{2}$ crystal with $1\ifmmode\times\else\texttimes\fi{}1,$ $1\ifmmode\times\else\texttimes\fi{}2,$ $2\ifmmode\times\else\texttimes\fi{}1,$ and $1\ifmmode\times\else\texttimes\fi{}4$ symmetries have been done. We use a first-principles density-functional method and plane-wave basis, combined with pseudopotentials to calculate surface electronic structures, surface geometries, and energetics. Calculated surface formation energies suggest that stability of the oxygen-deficient surfaces decrease with increasing oxygen deficiency. At oxygen-deficient $1\ifmmode\times\else\texttimes\fi{}2$ and $1\ifmmode\times\else\texttimes\fi{}4$ surfaces tin atoms similar to those in SnO crystal were found to appear. In all cases, the highest occupied orbitals were considerably localized at the sites of surface oxygen vacancies. The $2\ifmmode\times\else\texttimes\fi{}1$ added row surface structures were found to be relatively stable and associated with the decrease of the band gap due to jagged surface. Also, ultraviolet optical absorption coefficients for different surface structures were determined by using the electric dipole approximation with a scissor correction.

Process of crystallization in thin amorphous tin oxide film

Amorphous tin oxide films deposited on carbon substrates have been studied by high-resolution transmission electron microscopy. As-deposited film was composed of a mixture of microcrystallites of SnO, SnO 2 and SnO 3 with size of 2 nm. Crystallization took place above 450°C. SnO crystals appeared between 450°C and 500°C, whereas SnO 2 crystals appeared above 550°C. The appearance of β-tin crystals with the reduction of tin oxide has been verified using the heating stage of the electron microscope. A drop of liquid tin was recognized upon heating above 500°C. The difference in crystallization upon applying an electron beam, synchrotron radiation and heating in vacuum has been summarized and discussed with respect to the problem of the excitation of crystallites.

Effect of SR irradiation on crystallization of amorphous tin oxide film

In order to see the effect of SR irradiation on crystal growth, crystallization of tin oxide films has been performed in vacuum under SR irradiation. A thin amorphous tin oxide film 50 nm thick was prepared on the carbon substrate by vacuum evaporation of SnO 2 power. A SnO crystal appeared between 450–500°C upon vacuum heating, with a preferred orientation of (0 0 1). By SR irradiation using a cylindrical mirror for 20 s, the SnO crystal appeared with the preferred orientation of (1 1 1). The crystal with the crystallographic shear structure was grown by SR irradiation. This growth under a SR beam is discussed in terms of SR beam excitation of lone-pair electrons seen in the SnO crystal structure.

Characterization of indium tin oxide film and practical ITO film by electron microscopy

In order to clarify the structure of indium oxide film containing tin and tin oxides, various In 2O 3 based films prepared by vacuum evaporation were studied using high-resolution electron microscope (HREM). Indium tin oxide (ITO) film was composed of In 2O 3 and SnO. SnO crystal also contained (110) or (101) crystallographic shear (CS) structures that indicate excess amounts of tin. The CS structure was also found in a commercial ITO film having the resistivity of 2×10 −4 Ω cm.

Electronic structure of tin oxides

Electronic structure of tin oxides M. Meyer a, 1, G. Onida b, M. Palummo b, L. Reining a a CNRS-CEA, Laboratoire des Solides lrradi~s, Ecole Polytechnique, 91128 Palaiseau, France b Dipartimento di Fisica, Universit~ di Roma Tor Vergata , 1-00173 Roma, Italy Stannic oxide SnO 2 is a technologically important material which is frequently obtained by the oxidation of SnO. The tin oxides both have a tetragonal structure which differ essentially by the insertion of an oxygen plane between two tin planes in the layered SnO crystal. In order to well understand this structural evolution, it is crucial to have a precise description of the atomic and electronic structure of the two oxides. Preliminary results of calculations performed within Density Functional Theory in the Local Density Approximation (DFT-LDA) have already shown the relation existing between the electronic and geometric configurations of the two oxides [1]. The gap calculated for SnO2 was in good agreement with the experimental value [2], but the calculations did not reproduce with a very good accuracy the experimental structure of SnO [1]. We present an ab-init io (DFT-LDA) study of the electronic structure of SnO, in comparison with SnO2. The charge density distribution of each oxide is analysed with a special emphasis on low-charge-density contributions. Particular problems in the calculation of the equilibrium structure due to the pseudopotential of tin are put into evidence. We discuss the origin of these problems, and a possible solution. © 1999 Elsevier Science B.V. All fights reserved.

Rare earth ion doped semiconducting films by spray pyrolysis

A simple spray pyrolysis technique has been employed for the preparation of thin films of crystalline semiconductors ZnO and SnO 2. Furthermore, these materials could be doped with rare earth elements (Pr, Ce, Nd, Tb, Sm). The main parameters (substrate temperature, spraying time and doping material type) affecting the structural and optical properties of these films have been studied. Ultra-violet and visible spectroscopy, interference shearing microscopy, atomic force microscopy, X-ray diffraction and scanning electron microscopy were used for the investigation of the deposited layers. The films consist of aligned crystals of ZnO and SnO 2, with nm dimensions. Films with optical transmission T > 85% and structural uniformity in terms of average roughness < 10 nm have been obtained.

Comparative study of laser ablation techniques for fabricating nanocrystalline SnO 2 thin films for sensors

The microstructure and sensing properties of SnO 2 thin films prepared by using SnO 2 and Sn targets at different substrate temperatures with and without post annealing were investigated systematically. It is found that nanocrystalline SnO 2 films with grain size of 4.0–5.2 nm can be achieved by two methods: (1) by crystallization of amorphous SnO 2 films at 400 °C; and (2) by oxidation of Sn films at 400 °C. The nanocrystalline SnO 2 films prepared with these methods exhibit much higher C 2H 5OH gas sensitivity in comparison with SnO 2 films prepared using SnO 2 and Sn targets at higher substrate temperatures with grain sizes of several tens of nm upon exposure to air containing 2000 ppm C 2H 5OH.