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The SnO2-based family is a traditional but important gas-sensitive material. However, the requirement for high working temperature limits its practical application. Much work has been done to explore ways to improve its gas-sensing performance at room temperature (RT). For this report, SnO2, SnO, and SnO/SnO2 heterojunction was successfully synthesized by a facile hydrothermal combined with subsequent calcination. Pure SnO2 requires a high operating temperature (145 °C), while SnO/SnO2 heterojunction exhibits an excellent performance for sensing NO2 at RT. Moreover, SnO/SnO2 exhibits a fast response, of 32 s, to 50 ppm NO2 at RT (27 °C), which is much faster than that of SnO (139 s). The superior sensing properties of SnO/SnO2 heterojunction are attributed to the unique hierarchical structures, large number of adsorption sites, and enhanced electron transport. Our results show that SnO/SnO2 heterojunction can be used as a promising high-performance NO2 sensitive material at RT. [ABSTRACT FROM AUTHOR]

In this work poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with ethylene glycol (EG) and SnO or SnO2 nanoparticles are mixed in a controlled way to create hybrid composites in form of thin films via spin coating. The potential applicability of these composites as gas sensors and as thermoelectric materials is tested, while insights are achieved in the comprehension of the underlying physical mechanisms. The addition of SnO in the composite promotes an enhancement in the chemoresistive response upon ethanol gas exposure at room temperature. Based on the Seebeck coefficient and Hall effect measurements, improvement of the power factor (PF) is achieved by the controlled addition of SnO nanoparticles in the composite. These results promise well for progress in the use of hybrid composites in these areas paving the way for future improvement in research on hybrid electronics, involving improved scalability and energy saving. [ABSTRACT FROM AUTHOR]

Three types of SnO/SnO2 nanocomposites with different component ratios were synthesized using a simple hydrothermal process. Three samples, S1, S2, and S3, were produced by optimizing the occupied volume inside the Teflon flask, and are referred to as SnO2 rich, intermediate level, and SnO rich, respectively. In terms of degradation of malachite green under visible light, the photocatalytic activity of the S2 sample outperforms the other two samples and pure SnO by 30 %. It is attributed to the fact that the S2 sample has the most heterojunction between p‐type SnO and n‐type SnO2 of the three samples because the formation of p‐type SnO and n‐type SnO2 heterojunction in S2 prevents photogenerated electron‐hole recombination. By comparing S1 and S3 samples, we figured out that Sn2+ doped into the SnO2 lattice acts as an electron trap, slowing the recombination process and increasing photocatalytic activity. [ABSTRACT FROM AUTHOR]

All available thermodynamic properties and phase diagram data of the Sn-O system at 1 atm total pressure were critically evaluated and optimized to obtain a set of thermodynamic functions of all stable phases. The discrepancies among available experimental phase diagram data were resolved. In addition, new experiments were attempted to determine the melting temperature of SnO 2 using sealed Pt capsules. It was confirmed that the melting temperature of SnO 2 is higher than 1700 °C, which was taken into account in the present optimization. The Gibbs energies of the liquid solution of SnO-SnO 2 and all solid compounds were obtained. A new phase diagram at 1 atm total pressure was constructed from the optimized Gibbs energy functions of all phases. [ABSTRACT FROM AUTHOR]

Abstract Tin oxide (SnO x) is a promising oxide semiconductor due to the distinct properties of n-type SnO 2 and p-type SnO based on its stoichiometry. However, the stoichiometry control of SnO x remains challenging due to the thermodynamic instability of SnO. In the study, we focus on establishing the controllable stoichiometry of SnO x via atomic layer deposition (ALD) and subsequent treatment. The controllable synthesis of SnO 2 and SnO is investigated by multiple analyses involving the chemical composition, crystal structure, and band structure. The ALD SnO x is composed mostly of Sn4+ O bonds with intrinsic oxygen vacancies and is transformed into crystalline SnO 2 phase via post-annealing. The refractive index (~1.8) and optical bandgap energy (~3.6 eV) of ALD SnO x correspond to those of SnO 2. Post-deposition treatment with H 2 plasma enables the effective transformation of SnO 2 into SnO due to the easy penetration of H+ ion into the film and de-bonding of Sn O via ion bombardment. The transformed SnO exhibits a significant amount of Sn2+ O bonds with a refractive index of 2.8 and optical bandgap energy of ~2.9 eV. Specifically, the transformed SnO exhibits promise as an oxide semiconductor because it exhibits excellent stability with respect to re-oxidation into SnO 2 or further reduction into Sn metal. The present study advances practical applications that require a stable p-n junction through n-type SnO 2 and p-type SnO in various forms of device architectures. Highlights • Formation of SnO 2 and SnO was controlled by atomic layer deposition and post-process. • Chemical composition, crystal structure, and band structure of SnO x were analyzed. • As-deposited SnO x exhibits typical characteristics of SnO 2. • Post-deposition treatment with H 2 plasma effectively transforms SnO 2 into SnO. • Transformed SnO is stable against re-oxidation or reduction during post-process. [ABSTRACT FROM AUTHOR]

Abstract Cl-doped SnO photocatalysts were synthesized by mechanical alloying (MA) from SnCl 2 and NH 4 HCO 3. The effects of MA time on the structural characterization and photocatalytic activity of SnO powders were studied. Cl-doped SnO nanoparticles can be obtained by MA treatment after 1 h, but MA time considerably affected the crystalline size, microstrain, and photocatalytic properties of the samples. The crystalline size and specific surface area of the SnO samples gradually decreased and their microstrain increased with prolonged MA time. The peak intensity of the photoluminescence spectra of the Cl-doped SnO samples remarkably increased with prolonged MA time. Moreover, the MA samples had good photocatalytic properties. The photodegradation rate of methyl orange dye in 30 min over Cl-doped SnO nanoparticles obtained by MA for 2, 4, and 8 h was approximately 99%. Aging treatment of the SnO samples remarkably affected their phase composition, which can enhance the transformation of SnO to SnO 2. The SnO 2 transformation degree significantly increased with prolonged MA time through aging treatment, which also slightly deteriorated the degradation efficiency of the samples. [ABSTRACT FROM AUTHOR]

Abstract Atomic layer deposition (ALD) of SnO and SnO 2 thin films was successfully demonstrated over a wide temperature range of 70–300 °C using a divalent Sn-precursor, bis(N- ethoxy-2,2-dimethyl propanamido)tin (Sn(edpa) 2). The regulated growth of the SnO 2 and SnO films was realized by employing O 2 -plasma and H 2 O, respectively. Pure SnO 2 and SnO films were deposited with negligible C and N contents at all the growth temperatures, and the films exhibited polycrystalline and amorphous structures, respectively. The SnO 2 films presented a high transmittance of > 85% in the wavelength range of 400–700 nm and an indirect band gap of 3.6–4.0 eV; meanwhile, the SnO films exhibited a lower transmittance of > 60% and an indirect band gap of 2.9–3.0 eV. The SnO 2 films exhibited n-type semiconducting characteristics with carrier concentrations of 8.5 × 1016–1.2 × 1020 cm−3 and Hall mobilities of 2–26 cm2/V s. By employing an alternate ALD growth of SnO and SnO 2 films, SnO 2 /SnO multilayer structures were successfully fabricated at 120 °C. The in-situ quadrupole mass spectrometry analysis performed during ALD revealed that the oxidation of chemisorbed Sn-precursor occurs dominantly during the Sn(edpa) 2 /O 2 -plasma ALD process, resulting in the production of combustion by-products, whereas the Sn(edpa) 2 /H 2 O ALD process was governed by a ligand exchange reaction with the maintenance of the original oxidation state of Sn2+. [ABSTRACT FROM AUTHOR]

Abstract SnO microspheres were synthesized by a simple one-step ultrasonic reaction method. SnO materials were annealed at 150–250 °C to enhance their photocatalytic performance by adjusting their phase composition and lattice distortion. Effects of annealed temperature on the phase composition, microstructure and photocatalytic performance of SnO materials were investigated in detail. The results reveal that the annealing treatment considerably affected phase composition, absorption in the visible light zone, and the photocatalytic activity of the SnO materials. At increased temperature, SnO 2 content in the products gradually increased. At 250 °C, SnO materials were transformed to SnO 2. Correspondingly, the photocatalytic activity of the samples improved gradually with increasing temperature. The excellent photocatalytic efficiency of 98.3% within 40 min for the SnO microspheres annealed at 225 °C was achieved under the visible-light irradiation. The enhancement of the photocatalytic activity of this sample can be ascribed to lattice distortion of SnO combined with increased SnO 2 content. [ABSTRACT FROM AUTHOR]

It is urgent to solve the problems of the dramatic volume expansion and pulverization of SnO anodes during cycling process in battery systems. To address this issue, we design a hybrid structure of N-doped carbon fibers@SnO nanoflowers (NC@SnO) to overcome it in this work. The hybrid NC@SnO is synthesized through the hydrothermal growth of SnO nanoflowers on the surface of N-doped carbon fibers obtained by electrospinning. The NC is introduced not only to provide a support framework in guiding the growth of the SnO nanoflowers and prevent the flower-like structures from agglomeration, but also serve as a conductive network to accelerate electronic transmission along one-dimensional structure effectively. When the hybrid NC@SnO was served as anode, it exhibits a high discharge capacity of 750 mAh g at 1 A g after 100 cycles in Li-ion battery and 270 mAh g at 100 mA g for 100 cycles in Na-ion battery, respectively. [ABSTRACT FROM AUTHOR]

Photocatalysis is an effective method to control the environmental pollution. In this study, the SnO/GO composites were successfully prepared by ultrasound method to improve the photocatalytic activities of SnO. The physical and photophysical properties of the as-prepared SnO/GO samples were characterized by X-ray diffractometer, field emission on scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, UV-Vis diffuse reflectance spectroscopy, photoluminescence emission spectroscopy and Raman experiments. The photocatalytic activities of these composites were evaluated by decomposing organic pollutants under UV light irradiation. The degradation rate of the SnO/1.0 wt%GO photocatalyst is about 2 times that of the pure SnO. Then the pure SnO and the SnO/1.0 wt%GO photocatalysts were used in fluorocarbon resin (PEVE) coatings to sterilize the bacterial of the seawater. According to the results, the sterilization rate of the SnO/1.0GO/PEVE coating is about 2.5 times that of the pure PEVE coating. The high photocatalytic sterilization activity of the SnO/GO is attributed to its high electron-hole separation efficiency. This work provides a new approach to address marine biofouling problems. [ABSTRACT FROM AUTHOR]

Pechini method has been widely used in the synthesis of oxides, but the physicochemical process that happens during this one have not been discussed in detail, for example the resin conformation that is obtained in one of the stages of the process. Knowing the resin evolution and since the most important parameter of this one are modified, it could determinate the most appropriate conditions to conform thin films though the Pechini method. In this work the resin evolution of the tin system considering parameters like pH, viscosity, time and temperature of heating were studied. Infrared spectroscopy (FTIR) and viscosity measures in differents steps of the process were used. The IR spectroscopy results shows that as it advances the aging time of the resin, to a temperature between 80 and 100ºC and a pH of 6,5, Sn-O bonds are strengthen. Films were conformed with the resin obtained during the pechini process, it being defined a value of 110cP as the most appropriate to favor the homogeneity and adherence of this ones. The grain size film was of ∼110nm what indicates that the realized process allows to obtain bidimensional nano-structures.A pesar que el método de precursor polimérico, Pechini es ampliamente utilizado en la síntesis de óxidos, los procesos fisicoquímicos que ocurren durante el mismo no se han discutido en detalle; tal es el caso de la conformación de la resina que se obtiene en una de las etapas del proceso. Conociendo la evolución de esta resina, y como se modifican los parámetros más importantes de la misma, se podrían determinar las condiciones más adecuadas para conformar películas delgadas a través de este método. En este trabajo se estudio la evolución de la resina del sistema de estaño considerando parámetros como pH, viscosidad, tiempo y temperatura de calentamiento de la misma. Para este estudio se utilizó espectroscopía infrarroja (FTIR) y medidas de viscosidad de la resina en diferentes instantes del proceso. Los resultados de espectroscopía IR indican que a medida que avanza el tiempo de envejecimiento de la resina, a una temperatura entre 80 y 100ºC y un pH de ∼6,5, se fortalecen los enlaces Sn-O. Con esta resina se conformaron recubrimientos definiéndose un valor de 110cP como el más adecuado para favorecer la homogeneidad y adherencia de los mismos. El tamaño de grano en la película fue de ∼110nm lo que indica que el proceso realizado permite obtener nano-estructuras bidimensionales.

[Display omitted] • SnO 2 -SnO nanocomposites were prepared by simple electrodeposition method. • The deposition potential influences the composition, characteristics and the performances of SnO 2 photocatalyst. • SnO 2 -SnO-Sn nanocomposites were applied as immerged thin films in MB aqueous solution for photo catalysis degradation. • The presence of SnO phase in the nanocomposites enhances dye removal performance, while the Sn has a negative effect. In this paper, the effect of the deposition potential on characteristics, phase compositions and photocatalysis performances of SnO 2 nanostructures obtained by electrodeposition method was studied. A cyclic voltammetry was utilized to investigate the electrochemical behaviour of SnO 2 deposits. X-ray diffraction (XRD) analysis confirms the formation of a polycrystalline phase of rutil SnO 2 structures and a deterioration of SnO 2 crystallinity accompanied with the formation of SnO and Sn phases at a deposition potential of −1.3 and −1.5 V vs. SCE. Mott-Schottky plots confirm n -type conductivity of SnO 2 semiconductor and show high donor densities in the order of 1020 cm−3. The electrochemical impedance spectroscopy (EIS) measurements indicated a high separation of the photogenerated carriers for SnO 2 -SnO nanocomposite deposited at −1.3 V. From field emission scanning electron microscopy (FE-SEM) images, a porous and homogenous SnO 2 deposit with ultra-fine nanoparticles were observed. Optical transmittance spectra and Tauc plots display a variation of transmittance and gap energy with the deposition potential variation. The highest transmittance of 44 % with largest gap energy of 4.17 eV were obtained for SnO 2 nanostructures deposited at −1.1 V. Photodegradation of MB organic dye using SnO 2 catalyst was confirmed for all samples and reached a maximum efficiency of 49 % for the SnO2-SnO nanocomposite deposited at −1.3 V. [ABSTRACT FROM AUTHOR]

Abstract: Herein, we present a new approach to achieve well-defined SnO/SnO2 composites with in situ formation of p–n heterojunctions. The materials synthesized by a simple one-pot hydrothermal method were characterized in detail using powder X-ray diffraction (XRD), thermogravimetry (TGA), micro-Raman, X-ray photo electron spectroscopy (XPS), and ultra violet-diffused reflectance spectroscopy (UV-DRS). Analysis confirms the presence of mixed phases and the findings are consistent. The morphological evaluations were carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The investigations reveal the self-assembly of smaller nanoparticles into hierarchical structures resembling nanorods which aggregate further to form loose cube-like morphology finally transforming into dense micro-prisms. Selected area electron diffraction (SAED) establishes the phases of these nano- and microstructures. Synthesized materials also show improved electrical properties owing to the presence of SnO/SnO2 multiple p–n heterojunctions in the bulk. The advantage is reflected in the results of gas sensing studies that indicate enhanced hydrogen gas sensing response. Significant improvement in sensor response, selectivity and sensitivity could be achieved further with incorporation of Pd. A plausible mechanism of gas sensing on the material surface based on the formation of heterojunctions is discussed. [Copyright &y& Elsevier]

Abstract: The electronic structures of SnO, Sn2O3 and SnO2 layers adsorbed on the Rh(111) surface have been calculated by DFT. A drastic difference between densities of states of SnO and SnO2 in the energy range that corresponds to O 2s and Sn 4d states can be used for an unambiguous determination of the degree of the tin oxidation. In particular, the complex structure of the Sn 4d peak in photoemission spectra ultimately indicates the formation of SnO2 rather than SnO species in adsorbed layers. [Copyright &y& Elsevier]

Abstract: Spray pyrolysis is one of the most cost-effective methods to prepare SnO2 films due to its ability to deposit large uniform area, low fabrication cost, simplicity and low deposition temperature. Conventionally, scanning electron microscopy (SEM) and X-Ray Diffraction (XRD) are routinely used to investigate microstructure and crystal structure of the SnO2 films. In the present study, the SnO2 films were deposited by spray pyrolysis at 300, 400 and 500°C and the microstructure of the 500°C film was further examined by using transmission electron microscopy (TEM) and convergent beam electron diffraction (CBED). It was found that large grain-size vertically-aligned columnar SnO2 grains were formed after a few layers of small grain-size randomly oriented SnO2 grains. Moreover, CBED showed the presence of SnO nanodefects that had not been reported before and could not be detected by SEM or XRD. [Copyright &y& Elsevier]

Abstract: Structural changes of a variety of different SnO, SnO2 and GeO2 catalysts upon reduction in hydrogen were correlated with associated catalytic changes in methanol steam reforming. Studied systems include SnO, SnO2 and GeO2 thin film model catalysts prepared by vapour phase deposition and growth on polycrystalline NaCl surfaces and, for comparison, the corresponding pure oxide powder catalysts. Reduction of both the SnO2 thin film and powder at around 673K in 1bar hydrogen leads to a substantial reduction of the bulk structure and yields a mixture of SnO2 and metallic β-Sn. On the powder catalyst this transformation is fully reversible upon oxidation in 1bar O2 at 673K. Strongly reduced thin films, however, can only be re-transformed to SnO2 if the reduction temperature did not exceed 573K. For GeO2, the situation is more complex due to its polymorphism. Whereas the tetragonal phase is structurally stable during reduction, oxidation or catalytic reaction, a small part of the hexagonal phase is always transformed into the tetragonal at 673K independent of the gas phase used. SnO2 is highly active and CO2 selective in methanol steam reforming, but the initial high activity drops considerably upon reduction between 373 and 573K and almost complete catalyst deactivation is observed after reduction at 673K, which is associated with the parallel formation of β-Sn. In close correlation to the structural results, the catalytic activity and selectivity can be restored upon an oxidative catalyst regeneration at 673K. Tetragonal GeO2 exhibits only a small activity and no pronounced selectivity to either CO or CO2, at least after reduction. In its fully oxidized state release of surface/lattice oxygen results in a non-catalytic formation of CO2 by oxidation of CO originating from catalytic dehydrogenation. [Copyright &y& Elsevier]

Abstract: A highly sensitive and fast responding CO sensor was fabricated from a sheet-like SnO2. The SnO sheets were prepared by a room temperature reaction between SnCl2, hydrazine and NaOH, and they were subsequently oxidized into SnO2 sheets at high temperature (600°C). The morphology and size of the SnO2 sheets could be controlled during the formation of SnO, which influence the sensor response (R a/R g) and response time to a great extent. The sensor response of SnO nanosheets to 10ppm CO was enhanced up to 2.34, and the 90% sensor response time could be reduced to 6s, which are significantly higher and shorter than those of SnO2 powders (1.57 and 88s), respectively. The realization of both a high sensitivity and rapid response were explained in terms of rapid gas diffusion onto the entire sensing surface due to the less-agglomerated and very thin structure of SnO2 nanosheets and the catalytic effect of Pt. [Copyright &y& Elsevier]

Abstract: In this paper, single-crystalline SnO2 nanowires have been successfully prepared by a carbothermal reduction process employing SnO as the starting material and CuO as the catalyst. Their morphologies, purity and sizes of the products were characterized by transmission electron microscopy (TEM), selected area electron diffraction, X-ray diffraction, field emission scanning electron microscopy (FESEM) and Raman spectroscopy, respectively. The FESEM images reveal wire-like and rod-shaped nanowires of about 100–800μm in length and 30–200nm in the transverse dimensions. The three observed Raman peaks at 474, 634 and 774cm−1 indicate the typical rutile phase of the SnO2 which is in agreement with the X-ray diffraction results. The influence of some reaction parameters, including the temperature and the reaction duration, on the forming, morphology and particle size of SnO2 crystallize is discussed. [Copyright &y& Elsevier]

The EPR g factors gi (i=x, y, z) for Co2+ ions at both the substitutional (i.e. Sn4+) and interstitial sites of SnO2 lattice are calculated from the second-order perturbation formulas based on the cluster approach for g factors of 3d7 ions in rhombic octahedral clusters. The calculated results for Co2+ at the substitutional site are in line with the experimental values. For Co2+ at the interstitial site, the calculated gy and gz are close to the observed values, but the calculated gx is in disagreement with the observed one. The causes resulting in the disagreement are discussed. The defect structures of both Co2+ centers in SnO2 are also estimated from the calculations. [ABSTRACT FROM AUTHOR]

Abstract: Structural and electronic properties of tin oxides, SnO and SnO2, were studied using the full-potential linearized-augmented-plane-waves method within the local density and the generalized gradient approximations. Internal positional parameters, density of states and the electric-field gradient tensor at Sn sites were calculated. The results for the electronic and structural properties are compared to experimental measurements and with results obtained in different band-structure calculations. [Copyright &y& Elsevier]

Thick-film gas sensors are successfully fabricated using the nanostructure tin-oxide powder. In order to suppress the coarsening of the nanostructure tin-oxide particles during the adding process, the low-temperature catalyst adding (LTCA) method is proposed in this paper. LTCA is an adding method of noble Pd catalyst onto the nanostructure tin-oxide particles under the lower temperature below 300°C by excluding chloride. It turned out that the adding without particle coarsening is successfully carried out by means of LTCA. Applying LTCA to the fabrication of the thick film using nanostructure tin-oxide powder having a size smaller than 5 nm leads to an excellent performance with respect to the methane gas sensing. After aging at 400°C, a good sensitivity (R3500/R1000) of 0.66 is obtained for the sensor doped with 5 wt% of Pd catalyst. Also, the sensitivity of the sensor is so stable that the deviation of the electrical resistance is within 3% after 400 h of aging. [ABSTRACT FROM PUBLISHER]

Quantum-chemical modeling of electronic structure and interatomic interaction parameters has been performed for a series of fullerenelike cage molecules based on the isoelectronic TiO2, SnO2, and SnS2. The above characteristics are analyzed in relation to the type of atomic configuration, as well as the size and chemical composition of a nanostructure. [ABSTRACT FROM AUTHOR]

Quantum-chemical modeling of electronic structure and interatomic interaction parameters has been performed for a series of fullerenelike cage molecules based on the isoelectronic TiO2, SnO2, and SnS2. The above characteristics are analyzed in relation to the type of atomic configuration, as well as the size and chemical composition of a nanostructure. [ABSTRACT FROM AUTHOR]