Raman scattering study of rutile SnO2 nanobelts synthesized by thermal evaporation of Sn powders

Annealing Effects on SnO2 Thin Film for H2 Gas Sensing

Hydrogen (H₂) is attracting attention as a renewable energy source in various fields. However, H₂ has a potential danger that it can easily cause a backfire or explosion owing to minor external factors. Therefore, H₂ gas monitoring is significant, particularly near the lower explosive limit. Herein, tin dioxide (SnO₂) thin films were annealed at different times. The as-obtained thin films were used as sensing materials for H₂ gas. Here, the performance of the SnO₂ thin film sensor was studied to understand the effect of annealing and operating temperature conditions of gas sensors to further improve their performance. The gas sensing properties exhibited by the 3-h annealed SnO₂ thin film showed the highest response compared to the unannealed SnO₂ thin film by approximately 1.5 times. The as-deposited SnO₂ thin film showed a high response and fast response time to 5% H₂ gas at 300 °C of 257.34% and 3 s, respectively.

The strategy for organic dye and antibiotic photocatalytic removal for water remediation in an example of Co-SnO2 nanoparticles

A challenging problem to create an efficient photocatalyst suitable for industrial water remediation, aiming to remove cyclic organic compounds attracts increasing attention. The current study aimed to clarify a few "dark spots" in the field, namely to find out if it is possible to make an efficient photocatalyst activated with visible light by using a simple and cheap strategy and what are the key factor impacting its efficiency. In this work, a new procedure to obtain spherical nanoparticles with the same average size but different amounts of oxygen vacancies and defects and dopant concentrations was developed. The approach based on hydrothermal treatment was suggested to obtain rod-shaped nanoparticles. The systematic study of photocatalytic behavior on the example of oxytetracycline and methylene blue degradation under visible light of widely available LED lamp was performed. Based on chemical and computational experiments the main factor affecting the process efficiency was determined.

Exploring dopant effects in stannic oxide nanoparticles for CO2 electro-reduction to formate

The electrosynthesis of formate from CO₂ can mitigate environmental issues while providing an economically valuable product. Although stannic oxide is a good catalytic material for formate production, a metallic phase is formed under high reduction overpotentials, reducing its activity. Here, using a fluorine-doped tin oxide catalyst, a high Faradaic efficiency for formate (95% at 100 mA cm⁻²) and a maximum partial current density of 330 mA cm⁻² (at 400 mA cm⁻²) is achieved for the electroreduction of CO₂. Furthermore, the formate selectivity (≈90%) is nearly constant over 7 days of operation at a current density of 100 mA cm⁻². In-situ/operando spectroscopies reveal that the fluorine dopant plays a critical role in maintaining the high oxidation state of Sn, leading to enhanced durability at high current densities. First-principle calculation also suggests that the fluorine-doped tin oxide surface could provide a thermodynamically stable environment to form HCOO* intermediate than tin oxide surface. These findings suggest a simple and efficient approach for designing active and durable electrocatalysts for the electrosynthesis of formate from CO₂.

Though stannic oxides can catalyze CO₂ electroreduction to formate, the stability of these catalysts has been limited. Here, the authors demonstrate stable fluorine-doped SnO2 materials toward formate production at current densities of >300 mA/cm².

Al-Doped SnO₂ as Transparent Heater: Influence of Deposition Time

The research on transparent heater (Thf) films rapidly increases due to their unique photoelectric properties, leading to new generation of optoelectronic device. Here, we report a simple method to fabricate transparent heater based on Al-doped SnO2 (ASO) thin films. ASO films with 5 wt% Al as dopant were synthesized with various deposition times, namely, 5, 10 and 15 minutes using ultrasonic spray pyrolysis method. The correlation of deposition time on their structural characteristic, optical, electrical and thermal properties has been investigated. X-ray diffraction studies found that all samples exhibit tetragonal structure with preferred orientation along (110) plane. Meanwhile, the UV-Vis transmittance indicated that the sample having good optical transparency in visible light spectrum with the average transmittance up to 89.7%. The sheet resistance of ASO thin films was found to decrease as the deposition time increases to 10 minutes. Furthermore, Al-doped SnO2 based transparent heater prepared with 10 minutes deposition time presents the excellent thermal temperature up to 76.3 °C at the applied voltage of 20 volt. The above findings reveal that Al-doped SnO2 can be used as an alternative compound to substitute higher cost indium tin oxide as transparent heater. Keywords: aluminium, composite, spray pyrolysis, SnO2, transparent heater

SrO-layer insertion in Ruddlesden–Popper Sn-based perovskite enables efficient CO2 electroreduction towards formate

Tin (Sn)-based oxides have been proved to be promising catalysts for the electrochemical CO₂ reduction reaction (CO₂RR) to formate (HCOO⁻). However, their performance is limited by their reductive transformation into metallic derivatives during the cathodic reaction. This paper describes the catalytic chemistry of a Sr₂SnO₄ electrocatalyst with a Ruddlesden–Popper (RP) perovskite structure for the CO₂RR. The Sr₂SnO₄ electrocatalyst exhibits a faradaic efficiency of 83.7% for HCOO⁻ at −1.08 V vs. the reversible hydrogen electrode with stability for over 24 h. The insertion of the SrO-layer in the RP structure of Sr₂SnO₄ leads to a change in the filling status of the anti-bonding orbitals of the Sn active sites, which optimizes the binding energy of *OCHO and results in high selectivity for HCOO⁻. At the same time, the interlayer interaction between interfacial octahedral layers and the SrO-layers makes the crystalline structure stable during the CO₂RR. This study would provide fundamental guidelines for the exploration of perovskite-based electrocatalysts to achieve consistently high selectivity in the CO₂RR.

This paper describes how the insertion of a SrO-layer in Ruddlesden–Popper Sr₂SnO₄ perovskite electrocatalysts promotes CO₂ reduction towards formate via *OCHO intermediate. A faradaic efficiency of 83.7% and stability for over 24 h were obtained.

Current Applications of Gas Sensor Based on 2-D Nanomaterial: A Mini Review

Gas sensor, as one of the most important devices to detect noxious gases, provides a vital way to monitor the concentration and environmental information of gas in order to guarantee the safety of production. Therefore, researches on high sensitivity, high selectivity, and high stability have become hot issues. Since the discovery of the nanomaterial, it has been increasingly applied to the gas sensor for its distinguishing surface performances. However, 0-D and 1-D nanomaterials, with limited electronic confinement effect and surface effect, cannot reach the requirement for the production of gas sensors. This paper gives an introduction about the current researching progress and development trend of 2-D nanomaterials, analyzes the common forms of 2-D nanoscale structure, and summarizes the mechanism of gas sensing. Then, widely concerned factors including morphological properties and crystalline structure of 2-D nanomaterial, impact of doped metal on the sensibility of gas sensors, impact of symmetry, and working temperature on the selectivity of gas sensors have been demonstrated in detail. In all, the detailed analysis above has pointed out a way for the development of new 2-D nanomaterial and enhancing the sensibility of gas sensors.

2D SnO2 Nanosheets: Synthesis, Characterization, Structures, and Excellent Sensing Performance to Ethylene Glycol

Two dimensional (2D)SnO₂ nanosheets were synthesized by a substrate-free hydrothermal route using sodium stannate and sodium hydroxide in a mixed solvent of absolute ethanol and deionized water at a lower temperature of 130 °C. The characterization results of the morphology, microstructure, and surface properties of the as-prepared products demonstrated that SnO₂ nanosheets with a tetragonal rutile structure, were composed of oriented SnO₂ nanoparticles with a diameter of 6–12 nm. The X-ray diffraction (XRD) and high-resolution transmission electron microscope (FETEM) results demonstrated that the dominant exposed surface of the SnO₂ nanoparticles was (101), but not (110). The growth and formation was supposed to follow the oriented attachment mechanism. The SnO₂ nanosheets exhibited an excellent sensing response toward ethylene glycol at a lower optimal operating voltage of 3.4 V. The response to 400 ppm ethylene glycol reaches 395 at 3.4 V. Even under the low concentration of 5, 10, and 20 ppm, the sensor exhibited a high response of 6.9, 7.8, and 12.0 to ethylene glycol, respectively. The response of the SnO₂ nanosheets exhibited a linear dependence on the ethylene glycol concentration from 5 to 1000 ppm. The excellent sensing performance was attributed to the present SnO₂ nanoparticles with small size close to the Debye length, the larger specific surface, the high-energy exposed facets of the (101) surface, and the synergistic effects of the SnO₂ nanoparticles of the nanosheets.

The effect of annealing temperature on the structure and optical properties of well-aligned 1D SnO2nanowires synthesized using template-assisted deposition

We report the observations on the structural characterization and optical properties of SnO₂nanowires post-treated under different annealing temperatures (300, 400, 500 & 600 °C) for 1 h.

Synthesis and Electrochemical Performance of SnOx Quantum Dots@ UiO-66 Hybrid for Lithium Ion Battery Applications

A novel method that combines the dehydration of inorganic clusters in metal-organic frameworks (MOFs) with nonaqueous sol-gel chemistry and pyrolysis processes is developed to synthesize SnO_x quantum dots@Zr-MOFs (UIO-66) composites. The size of as-prepared SnO_x nanoparticles is approximately 4 nm. Moreover, SnO_x nanoparticles are uniformly anchored on the surface of the Zr-MOFs, which serves as a matrix to alleviate the agglomeration of SnO_x grains. This structure provides an accessible surrounding space to accommodate the volume change of SnO_x during the charge/discharge process. Cyclic voltammetry and galvanostatic charge/discharge were employed to examine the electrochemical properties of the ultrafine SnO_x@Zr-MOF (UIO-66) material. Benefiting from the advantages of the smaller size of SnO_x nanoparticles and the synergistic effect between SnO_x nanoparticles and the Zr-MOFs, the SnO_x@Zr-MOF composite exhibits enhanced electrochemical performance when compared to that of its SnO_x bulk counterpart. Specifically, the discharge-specific capacity of the SnO_x@Zr-MOF electrode can still remain at 994 mA h g^-1 at 50 mA g^-1 after 100 cycles. The columbic efficiencies can reach 99%.

Nanoscale insights into doping behavior, particle size and surface effects in trivalent metal doped SnO2

Despite considerable research, the location of an aliovalent dopant into SnO₂ nanoparticles is far to be clarified. The aim of the present study on trivalent lanthanide doped SnO₂ is to differentiate between substitutional versus interstitial and surface versus bulk doping, delineate the bulk and surface defects induced by doping and establish an intrinsic dopant distribution. We evidence for the first time a complex distribution of intrinsic nature composed of substitutional isolated, substitutional associates with defects as well as surface centers. Such multi-modal distribution is revealed for Eu and Sm, while Pr, Tb and Dy appear to be distributed mostly on the SnO₂ surface. Like the previously reported case of Eu, Sm displays a long-lived luminescence decaying in the hundreds of ms scale which is likely related to a selective interaction between the traps and the substitutional isolated center. Analyzing the time-gated luminescence, we conclude that the local lattice environment of the lattice Sn is not affected by the particle size, being remarkably similar in the ~2 and 20 nm particles. The photocatalytic measurements employed as a probe tool confirm the conclusions from the luminescence measurements concerning the nature of defects and the temperature induced migration of lanthanide dopants.

Metal oxide nanostructures: preparation, characterization and functional applications as chemical sensors

Preparation and characterization of different metal oxide (NiO, WO3, ZnO, SnO2 and Nb2O5) nanostructures for chemical sensing are presented. p-Type (NiO) and n-type (WO3, SnO2, ZnO and Nb2O5) metal oxide nanostructures were grown on alumina substrates using evaporation-condensation, thermal oxidation and hydrothermal techniques. Surface morphologies and crystal structures were investigated through scanning electron microscopy and Raman spectroscopy. Furthermore, different batches of sensors have been prepared, and their sensing performances towards carbon monoxide and nitrogen dioxide have been explored. Moreover, metal oxide nanowires have been integrated into an electronic nose and successfully applied to discriminate between drinking and contaminated water.

Nitrogen-doped-carbon-coated SnO2 nanoparticles derived from a SnO2@MOF composite as a lithium ion battery anode material

A facile method was developed to combine MOF-derived N-doped carbon with SnO₂ nanoparticles, which can cushion the volume change. The optimized SOC-3 composite achieved a reversible specific capacity of 1032 mA h g⁻¹ after 150 cycles at 100 mA g⁻¹.

Fabrication of SnO2 Asymmetric Membranes for High Performance Lithium Battery Anode

Alloy electrode material like tin dioxide (SnO2) possesses much higher specific capacity as compared to commercial graphite anode in lithium ion battery (783 vs 372 mAh g(-1)). However, the huge volume change (260%) of SnO2-based anode during the alloying and dealloying process can cause significant electrode pulverization and rapid capacity loss. Herein we report the synthesis of SnO2 asymmetric membranes via a unique combination of phase inversion and sol-gel chemistry to overcome this big challenge. The SnO2 asymmetric membrane electrode demonstrates a specific capacity of 500 mAh g(-1) based on the overall electrode mass at a current density of 280 mA g(-1) (∼0.5C) with >96% capacity retention after 400 cycles. When the current density is increased from 28 to 560 mA g(-1), its overall capacity is only reduced by 36%. Such an outstanding rate and cycling performance is attributed to the existence of networking porous structure in the membrane that can provide high electrical conductivity, multiple diffusion channels, and free volumes for electrode expansion. The carbonization temperature has a dramatic impact on the electrode performance. Membranes carbonized at 500 °C show an excellent cycling performance, whereas the capacity of the membrane carbonized at 800 °C decreases by 51% in 100 cycles. Such a drastic difference in cycle life is caused by the reduction of small SnO2 NPs (∼3.9 nm) into large metallic tin spheres (∼40 nm) at 800 °C. This is the first original report on using asymmetric membrane structure to stabilize an SnO2-based lithium ion battery anode with an excellent electrochemical performance.

Phase Engineering of 2D Tin Sulfides

Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations.

Insights from investigations of tin dioxide and its composites: electron-beam irradiation, fractal assessment, and mechanism

Tin dioxide (SnO2) is a unique strategic functional material with widespread technological applications, particularly in fields such as solar batteries, optoelectronic devices, and solid-state gas sensors owing to advances in its optical and electronic properties. In this review, we introduce the recent progress of tin dioxide and its composites, including the synthesis strategies, microstructural evolution, related formation mechanism, and performance evaluation of SnO2 quantum dots (QDs), thin films, and composites prepared by electron-beam irradiation, pulsed laser ablation, and SnO2 planted graphene strategies, highlighting contributions from our laboratory. First, we present the electron-beam irradiation strategies for the growth behavior of SnO2 nanocrystals. This method is a potentially powerful technique to achieve the nucleation and growth of SnO2 QDs. In addition, the fractal assessment strategies and gas sensing behavior of SnO2 thin films with interesting micro/nanostructures induced by pulsed delivery will be discussed experimentally and theoretically. Finally, we emphasize the fabrication process and formation mechanism of SnO2 QD planted graphene nanosheets. This review may provide a new insight that the versatile strategies for microstructural evolution and related performance of SnO2-based functional materials are of fundamental importance in the development of new materials.

Temperature and high pressure effects on the structural features of catalytic nanocomposites oxides by Raman spectroscopy

Structural characterizations of nanostructured oxides were studied by X-ray diffraction (XRD), Raman and infrared spectroscopy. The oxides catalysts namely, SnO2, ZrO2, CeO2, MnOx, Al2O3 and TiO2 were prepared by a nanocasting route and the effect of the temperature and pressure on the stability of the solids was evaluated. Raman spectra showed that ZrO2 and TiO2 exhibited phase transitions at moderate temperatures whereas CeO2, SnO2 and MnOx had an effective creation of defects in their structures upon annealing at elevated temperatures. The results suggested also that the effect of the temperature on the particles growth is related to the type of oxide. In this regard, phase transition by up to 600°C accelerated the sintering of ZrO2 and CeO2 grains compared to TiO2, SnO2 and MnOx counterparts. Under hydrostatic pressures lower than 10GPa, rutile TiO2 and tetragonal ZrO2 exhibited pressure induced phase transition whereas CeO2 and SnO2 were stable at pressures close to 15GPa. The experiments revealed that the nanostructured SnO2 oxide exhibited stable performance at relatively high temperatures without phase transition or sintering, being suitable to be used as catalysts in the range of temperature and pressure studied.

Influence of size and shape on the photocatalytic properties of SnO₂ nanocrystals

Tuning the functional properties of nanocrystals is an important issue in nanoscience. Here, we are able to tune the photocatalytic properties of SnO2 nanocrystals by controlling their size and shape. A structural analysis was carried out by using X-ray diffraction (XRD)/Rietveld and transmission electron microscopy (TEM). The results reveal that the number of oxygen-related defects varies upon changing the size and shape of the nanocrystals, which eventually influences their photocatalytic properties. Time-resolved spectroscopic studies of the carrier relaxation dynamics of the SnO2 nanocrystals further confirm that the electron-hole recombination process is controlled by oxygen/defect states, which can be tuned by changing the shape and size of the materials. The degradation of dyes (90%) in the presence of SnO2 nanoparticles under UV light is comparable to that (88%) in the presence of standard TiO2 Degussa P-25 (P25) powders. The photocatalytic activity of the nanoparticles is significantly higher than those of nanorods and nanospheres because the effective charge separation in the SnO2 nanoparticles is controlled by defect states leading to enhanced photocatalytic properties. The size- and shape-dependent photocatalytic properties of SnO2 nanocrystals make these materials interesting candidates for photocatalytic applications.

Luminescence studies on SnO2 and SnO2:Eu nanocrystals grown by laser assisted flow deposition

Eu³⁺ optically-activated transparent conductive tin oxide nanocrystals were produced by the innovative laser assisted flow deposition technique.

One-Dimensional Organic-Inorganic Nanocomposite Synthesized with Single-Walled Carbon Nanotube Templates

This study reports on single-walled carbon nanotubes (SWCNT) as templates for the preparation of 1D porous organic-inorganic hybrid composites. The in situ deposited SWCNT were sputter coated with Sn metal and thermally oxidized in air to form a SnO₂/SWCNT nanowire framework on SiO₂/Si substrate. Poly(acrylic acid) (PAA) was coated onto this scaffold through UV light-induced radical polymerization, which resulted in the final formation of hybrid composites. The structures of hybrid composites were investigated by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, and Raman spectroscopy. The results show that PAA was successfully coated and the structural advantage of nanowire was fairly maintained, which indicates that this framework is very stable for organic functionalization in solution. The simplicity of this method for the formation of porous organic-inorganic hybrid composites provides a potential application for nanoelectronic devices.

Hierarchical growth of SnO2 nanostructured films on FTO substrates: structural defects induced by Sn(II) self-doping and their effects on optical and photoelectrochemical properties

Direct hydrothermal growth of Sn(II)-doped SnO2 films on fluorine-doped tin oxide (FTO) substrates results in the formation of upstanding SnO2 nanosheet arrays covered by hierarchical SnO2 nanoflowers. The n-type semiconductor films show extended photoresponse in the visible spectrum arising from the coexistence of Sn(II) dopant ions and oxygen vacancies in these hierarchical SnO2 nanostructures, which leads to a narrowed bandgap. Photoluminescence spectroscopy revealed that the emission in the UV, blue and red spectral ranges is related to the evolution of Sn(II) dopants and oxygen vacancies with annealing temperature, whereas oxygen vacancies are mostly responsible for visible emission. The Sn(II)-doped SnO2 films show higher photocurrent when sensitized with narrow bandgap CdS nanoparticles, serving as efficient electron acceptors.

Selective detection of acetone and hydrogen sulfide for the diagnosis of diabetes and halitosis using SnO(2) nanofibers functionalized with reduced graphene oxide nanosheets

Sensitive detection of acetone and hydrogen sulfide levels in exhaled human breath, serving as breath markers for some diseases such as diabetes and halitosis, may offer useful information for early diagnosis of these diseases. Exhaled breath analyzers using semiconductor metal oxide (SMO) gas sensors have attracted much attention because they offer low cost fabrication, miniaturization, and integration into portable devices for noninvasive medical diagnosis. However, SMO gas sensors often display cross sensitivity to interfering species. Therefore, selective real-time detection of specific disease markers is a major challenge that must be overcome to ensure reliable breath analysis. In this work, we report on highly sensitive and selective acetone and hydrogen sulfide detection achieved by sensitizing electrospun SnO2 nanofibers with reduced graphene oxide (RGO) nanosheets. SnO2 nanofibers mixed with a small amount (0.01 wt %) of RGO nanosheets exhibited sensitive response to hydrogen sulfide (Rair/Rgas = 34 at 5 ppm) at 200 °C, whereas sensitive acetone detection (Rair/Rgas = 10 at 5 ppm) was achieved by increasing the RGO loading to 5 wt % and raising the operation temperature to 350 °C. The detection limit of these sensors is predicted to be as low as 1 ppm for hydrogen sulfide and 100 ppb for acetone, respectively. These concentrations are much lower than in the exhaled breath of healthy people. This demonstrates that optimization of the RGO loading and the operation temperature of RGO-SnO2 nanocomposite gas sensors enables highly sensitive and selective detection of breath markers for the diagnosis of diabetes and halitosis.

Morphological evolution of carbon nanofibers encapsulating SnCo alloys and its effect on growth of the solid electrolyte interphase layer

Two distinctive one-dimensional (1-D) carbon nanofibers (CNFs) encapsulating irregularly and homogeneously segregated SnCo nanoparticles were synthesized via electrospinning of polyvinylpyrrolidone (PVP) and polyacrylonitrile (PAN) polymers containing Sn-Co acetate precursors and subsequent calcination in reducing atmosphere. CNFs synthesized with PVP, which undergoes structural degradation of the polymer during carbonization processes, exhibited irregular segregation of heterogeneous alloy particles composed of SnCo, Co3Sn2, and SnO with a size distribution of 30-100 nm. Large and exposed multiphase SnCo particles in PVP-driven amorphous CNFs (SnCo/PVP-CNFs) kept decomposing liquid electrolyte and were partly detached from CNFs during cycling, leading to a capacity fading at the earlier cycles. The closer study of solid electrolyte interphase (SEI) layers formed on the CNFs reveals that the gradual growth of fiber radius due to continuous increment of SEI layer thickness led to capacity fading. In contrast, SnCo particles in PAN-driven CNFs (SnCo/PAN-CNFs) showed dramatically reduced crystallite sizes (<10 nm) of single phase SnCo nanoparticles which were entirely embedded in dense, semicrystalline, and highly conducting 1-D carbon matrix. The growth of SEI layer was limited and saturated during cycling. As a result, SnCo/PAN-CNFs showed much improved cyclability (97.9% capacity retention) and lower SEI layer thickness (86 nm) after 100 cycles compared to SnCo/PVP-CNFs (capacity retention, 71.9%; SEI layer thickness, 593 nm). This work verifies that the thermal behavior of carbon precursor is highly responsible for the growth mechanism of SEI layer accompanied with particles detachment and cyclability of alloy particle embedded CNFs.

Structural, chemical, optical, and electrical evolution of SnO(x) films deposited by reactive rf magnetron sputtering

In this paper, SnO(x) films were produced by reactive radio frequency magnetron sputtering under various oxygen partial pressure (P(O)) in conjunction with a thermal annealing at 200 °C afterwards. The obtained SnO(x) films were systematically studied by means of various techniques, including X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, spectroscopic ellipsometry, and Hall-effect measurement. The structural, chemical, and electrical evolution of the SnO(x) films was found to experience three stages: polycrystalline SnO phase dominated section with p-type conduction at P(O) ≤ 9.9%; amorphous SnO(2) phase dominated area at P(O) ≥ 12.3%, exhibiting n-type characteristics; and conductivity dilemma area in between the above mentioned sections, featuring the coexistence of SnO and SnO(2) phases with compatible and opposite contribution to the conductivity. The polycrystalline to amorphous film structure transition was ascribed to the enhanced crystallization temperature due to the perturbed structural disorder by incorporating Sn(4+) into the SnO matrix. The inversion from p-type to n-type conduction with P(O) variation is believed to result from the competition between the donor and acceptor generation process, i.e., the n-type behavior would be present if the donor effect is overwhelming, and vice versa. In addition, with increasing P(O), the refractive index decreased from 3.0 to 1.8 and the band gaps increased from 1.5 to 3.5 eV, respectively.

Graphene-supported SnO2 nanoparticles prepared by a solvothermal approach for an enhanced electrochemical performance in lithium-ion batteries

SnO2 nanoparticles were dispersed on graphene nanosheets through a solvothermal approach using ethylene glycol as the solvent. The uniform distribution of SnO2 nanoparticles on graphene nanosheets has been confirmed by scanning electron microscopy and transmission electron microscopy. The particle size of SnO2 was determined to be around 5 nm. The as-synthesized SnO2/graphene nanocomposite exhibited an enhanced electrochemical performance in lithium-ion batteries, compared with bare graphene nanosheets and bare SnO2 nanoparticles. The SnO2/graphene nanocomposite electrode delivered a reversible lithium storage capacity of 830 mAh g-1 and a stable cyclability up to 100 cycles. The excellent electrochemical properties of this graphene-supported nanocomposite could be attributed to the insertion of nanoparticles between graphene nanolayers and the optimized nanoparticles distribution on graphene nanosheets.

Field emission from in situ-grown vertically aligned SnO2 nanowire arrays

Vertically aligned SnO2 nanowire arrays have been in situ fabricated on a silicon substrate via thermal evaporation method in the presence of a Pt catalyst. The field emission properties of the SnO2 nanowire arrays have been investigated. Low turn-on fields of 1.6 to 2.8 V/μm were obtained at anode-cathode separations of 100 to 200 μm. The current density fluctuation was lower than 5% during a 120-min stability test measured at a fixed applied electric field of 5 V/μm. The favorable field-emission performance indicates that the fabricated SnO2 nanowire arrays are promising candidates as field emitters.