Synthesis and ethanol sensing properties of Fe-doped SnO2 nanofibers

Fe-doped SnO₂ nanofibers are synthesized through an electrospinning method and characterized by scanning electron microscopy and transmission electron microscopy. The sensor fabricated from these nanofibers exhibits high sensitivity and rapid response/recovery to ethanol at 300 °C. The sensitivity is up to 15.3 when the sensor is exposed to 100 ppm ethanol, and the response and recovery time is about 1 and 3 s, respectively. The linear dependence of the sensitivity on the ethanol concentration is observed in the range of 10-300 ppm. These results demonstrate that Fe-doped SnO₂ nanofibers can be used as the sensing material for fabricating high performance ethanol sensors.     

One-pot synthesis of intestine-like SnO2/TiO2 hollow nanostructures

In the present study the intestine-like binary SnO₂/TiO₂ hollow nanostructures are one-pot synthesized in aqueous phase at room temperature via a colloid seeded deposition process in which the intestine-like hollow SnO₂ spheres and Ti(SO₄)₂ are used as colloid seeds and Ti-source, respectively. The novel core (SnO₂ hollow sphere)-shell (TiO₂) nanostructures possess a large surface area of 122 m²/g (calcined at 350 °C) and a high exposure of TiO₂ surface. The structural change of TiO₂ shell at different temperatures was investigated by means of X-ray diffraction and Raman spectroscopy. It was observed that the rutile TiO₂ could form even at room temperature due to the presence of SnO₂ core and the unique core-shell interaction.     

Synthesis of SnO2/Pd composite films by PVD route for a liquid petroleum gas sensor

Synthesis of SnO₂/Pd composite films was carried out by depositing antimony doped SnO₂ films by magnetron sputtering technique and evaporating a thin layer of palladium on the top of it. This bi-layer structure was subjected to rapid thermal annealing for the incorporation of Pd in SnO₂. The films thus obtained were characterized by measuring electrical, optical and microstructural properties. Liquid petroleum gas-sensing properties were also investigated.     

Production of SnO2 nano-particles by hydrogel thermal decomposition method

SnO₂ is an important functional material having a wide range of applications in gas sensors and optoelectronic devices. There is a great interest for finding new cost-effective and straight-forward methods for production of these particles. In this research, hydrogel thermal decomposition method (HTDM) is used for production of high purity SnO₂ nano-particles. Cost effective reactants and green routs of production are the advantages of polysaccharide based hydrogel as starting material for this method. Visual observations indicated that there is very little tendency for agglomeration in the SnO₂ nano-particles produced by this method which can be considered as an advantage for this method over other methods for production of SnO₂ nano-particles. SnO₂ nano-particles are also characterized by X-ray diffraction (XRD) in terms of purity and the sizes. It is found that high purity SnO₂ nano-particles in the size range of 25-36 nm can be produced by HTDM.     

Template-free fabrication of SnO2 hollow spheres with photoluminescence from Sni

SnO₂ hollow spheres with interstitial Sn²⁺ defect were fabricated by the hydrothermal method without any surfactant or polymer, whose shell is constructed by two layers of tetragonal prism nanorod arrays. The growth mechanism of the hollow spheres was investigated and attributed to the nucleation and arrangement of SnO₂ tetragonal prism nanorods on the surface of the hydrothermal reaction formed NO bubbles in the aqueous solution. After illumination by 275 nm wavelength light, narrow peak emissions centered at about 587-626 nm have been found in the photoluminescence spectrum, which have been ascribed to the interstitial Sn²⁺ defect in the SnO₂ hollow spheres.     

In-situ preparation of TiO2/SnO2 nanocrystalline sol for photocatalysis

A novel preparation method to synthesize TiO₂/SnO₂ nanocrystalline sol under mild conditions was presented. Ti(OC₄H₉)₄ used as a precursor was hydrolyzed in the rutile SnO₂ nanocrystalline sol, and in-situ formed TiO₂/SnO₂ nanocrystalline sol. The crystal structure, morphology and photocatalysis performance of samples were investigated. The results show that the additional rutile SnO₂ nano grains serve as heterogeneous crystal nucleus and exhibite the inducing effect on TiO₂ grains growth, thus leading to the changes in crystalline phase and particle morphology. In addition, the photoluminescence (PL) spectra analysis indicates that TiO₂/SnO₂ composite structure induces a better charge separation, and thus the photocatalytic activity of TiO₂/SnO₂ sol is increased significantly compared with TiO₂ sol.     

A novel templating process for fabricating SnO2 hollow hemispherical arrays by pulsed laser deposition

Well ordered monolayer arrays of hollow SnO₂ shell were fabricated by combining colloidal templating and pulsed laser deposition methods. With increasing the thickness of SnO₂ hollow films, their half-spherical morphologies gradually develop to a bell-shaped one. While the surface of SnO₂ thin films is fairly flat, the surface of hollow SnO₂ shells consists of protruding crystals, indicating morphological dependency on the presence of substrate. Because of the low population of contiguous hollow SnO₂ shells, arrays of hollow SnO₂ showed higher dc electrical resistance than those of thin films.     

Ultraviolet photodetectors made from SnO2 nanowires

SnO₂ nanowires can be synthesized on alumina substrates and formed into an ultraviolet (UV) photodetector. The photoelectric current of the SnO₂ nanowires exhibited a rapid photo-response as a UV lamp was switched on and off. The ratio of UV-exposed current to dark current has been investigated. The SnO₂ nanowires were synthesized by a vapor-liquid-solid process at a temperature of 900 °C. It was found that the nanowires were around 70-100 nm in diameter and several hundred microns in length. High-resolution transmission electron microscopy (HRTEM) image indicated that the nanowires grew along the [200] axis as a single crystallinity. Cathodoluminescence (CL), thin-film X-ray diffractometry, and X-ray photoelectron spectroscopy (XPS) were used to characterize the as-synthesized nanowires.     

Influence of aqueous hexamethylenetetramine on the morphology of self-assembled SnO2 nanocrystals

The present report details the effects of synthesis time, concentrations of hexamethylenetetramine (HMTA) and precursor tin (II) chloride solutions on the self-assembly of SnO₂ nanocrystals. High-resolution electron microscopy images revealed that the structures were made of randomly attached SnO₂ nanocrystals with sizes in between ∼2 and 5 nm. X-ray photoelectron spectroscopy (XPS) showed that the Sn3d region was characterized by the spin-orbit splitting of the Sn3d_5/2 ground state at ∼487.6 eV and by the Sn3d_3/2 excited state at ∼496.1 eV, which was attributed to the Sn⁺⁴ oxidation state of the SnO₂ samples. We also found that the self-assembly could be achieved only with aqueous tin (II) chloride solution, and not with aqueous stannic (IV) chloride solution. A plausible growth mechanism is proposed in order to analyze the distinctive self-assembly of SnO₂ nanocrystals in the presence of aqueous HMTA solution.     

Photocatalytic performance of very thin TiO2/SnO2 stacked-film prepared by magnetron sputtering

TiO₂/SnO₂ stacked-layers are synthesized by reactive sputter deposition on the glass substrate. Very thin TiO₂/SnO₂ bilayer-photocatalysts exhibited a very high photocatalytic activity for a degradation of gaseous acetaldehyde. Both the control of an electronic structure of TiO₂ overlayer in the near-surface region and the interfacial separation of photogenerated electrons/holes in the TiO₂/SnO₂ stacked-layer are keys to improve the photocatalytic performance.     

Silicon doped SnO2 films for liquid petroleum gas sensor

Silicon doped SnO₂ films were synthesized by sputtering SnO₂ layer onto glass substrates with appropriate amount of silicon sputtered onto them. The bilayer structures were subjected to rapid thermal annealing for the incorporation of Si in SnO₂ matrix. The films thus obtained were characterized by measuring optical and microstructural properties. Liquid petroleum gas (LPG) sensing properties were also investigated. FTIR and Raman studies were also carried out on these films, both, before and after LPG exposure.     

Self-construction of SnO2 cubes based on aggration of nanorods

The SnO₂ cubes with the rutile structure have been successfully synthesized without using any catalyst. Their morphology and microstructure were studied by field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), and elected area electron diffraction (SAED). It is revealed that the SnO₂ nanocubes exhibit high crystalline quality. The size of the nanocubes ranges from 100 nm to 300 nm. The side surfaces of nanocubes are {110} planes, while their cube axes are [001] direction. The growth mechanism of SnO₂ nanocubes was discussed and we suggested vapor-solid process should dominate the growth. These SnO₂ nanostructures represent an important example of spontaneous organization.     

Synthesis and characterization of flower-like MoS2 microspheres by a facile hydrothermal route

Flower-like MoS₂ microspheres with high purity were successfully synthesized via a facile hydrothermal route by adding sodium silicate as an additive. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). XRD patterns showed that the MoS₂ microspheres had good crystallinity with well-stacked layered structure. TEM and SEM images showed that the MoS₂ microspheres had uniform sizes with mean diameter about 480 nm and were constructed with MoS₂ sheets with thickness of several nanometers. It was found that the possible precursor H₄SiMo₁₂O₄₀ obtained by sodium silicate reacting with sodium molybdate played a crucial role in the formation of the flower-like MoS₂ microspheres in our experiment. A possible formation mechanism of MoS₂ microspheres was preliminarily presented.     

In situ synthesis of SnO2/graphene nanocomposite and their application as anode material for lithium ion battery

SnO₂/graphene nanocomposite was prepared via an in situ chemical synthesis method. The nanocomposite was characterized by X-ray diffraction, filed emission scanning electron microscope and transmission electron microscope, which revealed that tiny SnO₂ nanoparticles could be homogeneously distributed on the graphene matrix. The electrochemical performance of the SnO₂/graphene nanocomposite as anode material was measured by galvanostatic charge/discharge cycling. The SnO₂/graphene nanocomposite showed a reversible capacity of 665 mAh/g after 50 cycles and an excellent cycling performance for lithium ion battery, which was ascribed to the three-dimensional architecture of SnO₂/graphene nanocomposite. These results suggest that SnO₂/graphene nanocomposite would be a promising anode material for lithium ion battery.     

Template-free synthesis of SnO2 nanostructural hollow spheres covered by nanorods

In the present work, SnO₂ nanostructural hollow spheres have been successfully synthesized in the absence of template by a simple synthetic route, and their surfaces were covered by nanorods. The synthesized nanostructural hollow spheres covered by nanorods were further characterized by XRD, SEM and TEM measurements. The diameter of SnO₂ hollow spheres and the thickness of shells are found to be ca. 150-200 and 20-30 nm, respectively. The size of the nanorod is found to be ca. 5 nm, and the length up to tens of nanometers. Based on a series of experimental results, an oxidizing-aggregating-Ostwald ripening model has been proposed for the formation of SnO₂ nanostructural hollow spheres.     

SiO2/TiO2 multilayer films grown on cotton fibers surface at low temperature by a novel two-step process

A novel two-step process was developed to synthesize and deposit SiO₂/TiO₂ multilayer films onto the cotton fibers. In the first step, SiO₂ particles on cotton fiber surface were synthesized via tetraethoxysilane hydrolysis in the presence of cotton fibers, in order to protect the fibers against photo-catalytic decomposition by TiO₂ nanoparticles. In the second step, the growth of TiO₂ nanoparticles into the modified cotton fiber surface was carried out via a sol-gel method at the temperature as low as 100 °C. The as-obtained SiO₂/TiO₂ multilayer films coated on cotton fibers were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy and X-ray diffraction, respectively.     

Synthesis of WS2 nanosheets by a novel mechanical activation method

WS₂ nanosheets were synthesized by a novel mechanical activation method, in which a ball-milled mixture of WO₃ and S was adopted as reagent and then annealed at 600 °C for 2 h in an atmosphere of Ar. The final products were characterized by XRD, SEM and TEM. It was found that the nanosheets were obtained with thickness of only about 10 nm, through the exfoliation from the sulfurized outer layers of tungsten trioxide. The ball milling played a crucial role in the mechanical activation of reagents and promoted direct production of WS₂ without any intermediate products. The effect of temperature was also discussed.     

An investigation of super-hydrophilic properties of TiO2/SnO2 nano composite thin films

A sol-gel dip coating technique was used to fabricate TiO₂/SnO₂ nano composite thin films on soda-lime glass. The solutions of SnO₂ and TiO₂ were mixed with different molar ratios of SnO₂:TiO₂ as 0, 3, 4, 6, 8, 9, 10.5, 13, 15, 19.5, 25 and 28 mol.% then the films were prepared by dip coating of the glasses. The effects of SnO₂ concentration, number of coating cycles and annealing temperature on the hydrophilicity of films were studied using contact angle measurement. The films were characterized by means of scanning electron microscopy, X-ray diffraction and atomic force microscopy measurements. The nano composite thin films fabricated with 8 mol.% of SnO₂, four dip coating cycles and annealing temperature of 500 °C showed super-hydrophilicity.     

Preparation and properties of Ti/SnO2-Sb2O5 electrodes by electrodeposition

Sb and Sn coatings were deposited on Ti substrate by the method of cathode deposition, and the Ti/SnO₂-Sb₂O₅ electrodes were obtained by annealing at different temperatures for 3 h. Ti/SnO₂-Sb₂O₅ coating was characterized using technique such as X-ray diffraction (XRD), and scanning electron microscopy (SEM). Ti/SnO₂-Sb₂O₅ electrode calcined at 550 °C exhibits the best catalytic capacity. Ti/SnO₂-Sb₂O₅ electrode obtained by electrodeposition had longer service life and faster degradation capacity compared with that obtained by dip-coating. Accelerated service life tests were carried out in 0.5 mol L^− 1 H₂SO₄ solution with the current density of 100 mA cm^− 2. Service life of Ti/SnO₂-Sb₂O₅ electrode prepared in present study was 15 h, and it was only 0.14 h for Ti/SnO₂-Sb₂O₅ electrode obtained by dip-coating.     

Large scale F-doped SnO2 coating on glass by spray pyrolysis

Large scale F-doped SnO₂ coating was carried out on a glass production line by a cheap in-house spray pyrolysis coater. The coater was installed on glass annealing lehr which has a width of ∼2 m. The solution for film formation consisted of SnCl₄·5H₂O and NH₄F dissolved in a solvent. The solution was sprayed by pressure spray nozzles downward to underneath hot glass sheet. The coating was done for 150 s where the glass temperature was in a range of 430-450 °C. The total length of the coated glass was ∼10 m. It was found by sheet resistance measurement that the coating started non-uniformly and then it covered the entire width of glass when spraying time approached 150 s. The lowest sheet resistance of the coated glass was 0.8 kΩ/□ where the film thickness was ∼80 nm which corresponds to film resistivity of ∼6.4 × 10^− 3 Ω-cm.