Novel Sb-SnO2 Electrode with Ti3+ Self-Doped Urchin-Like Rutile TiO2 Nanoclusters as the Interlayer for the Effective Degradation of Dye Pollutants

Stable and efficient SnO₂ electrodes are very promising for effectively degrading refractory organic pollutants in wastewater treatment. In this regard, we firstly prepared Ti³⁺ self-doped urchin-like rutile TiO₂ nanoclusters (TiO_2-x NCs) on a Ti mesh substrate by hydrothermal and electroreduction to serve as an interlayer for the deposition of Sb-SnO₂ . The TiO_2-x NCs/Sb-SnO₂ anode exhibited a high oxygen evolution potential (2.63 V vs. SCE) and strong ⋅OH generation ability for the enhanced amount of absorbed oxygen species. Thus, the degradation results demonstrated its good rhodamine B (RhB), methylene blue (MB), alizarin yellow R (AYR), and methyl orange (MO) removal performance, with the rate constant increased 5.0, 1.9, 1.9, and 4.7 times, respectively, compared to the control Sb-SnO₂ electrode. RhB and AYR degradation mechanisms are also proposed based on the results of high-performance liquid chromatography coupled with mass spectrometry and quenching experiments. More importantly, this unique rutile interlayer prolonged the anode lifetime sixfold, given its good lattice match with SnO₂ and the three-dimensional concave-convex structure. Consequently, this work paves a new way for designing the crystal form and structure of the interlayers to obtain efficient and stable SnO₂ electrodes for addressing dye wastewater problems.

Spectromicroscopy Studies of Silicon Nanowires Array Covered by Tin Oxide Layers

The composition and atomic and electronic structure of a silicon nanowire (SiNW) array coated with tin oxide are studied at the spectromicroscopic level. SiNWs are covered from top to down with a wide bandgap tin oxide layer using a metal-organic chemical vapor deposition technique. Results obtained via scanning electron microscopy and X-ray diffraction showed that tin-oxide nanocrystals, 20 nm in size, form a continuous and highly developed surface with a complex phase composition responsible for the observed electronic structure transformation. The "one spot" combination, containing a chemically sensitive morphology and spectroscopic data, is examined via photoemission electron microscopy in the X-ray absorption near-edge structure spectroscopy (XANES) mode. The observed spectromicroscopy results showed that the entire SiNW surface is covered with a tin(IV) oxide layer and traces of tin(II) oxide and metallic tin phases. The deviation from stoichiometric SnO₂ leads to the formation of the density of states sub-band in the atop tin oxide layer bandgap close to the bottom of the SnO₂ conduction band. These observations open up the possibility of the precise surface electronic structures estimation using photo-electron microscopy in XANES mode.

Room Temperature Humidity Tolerant Xylene Sensor Using a Sn-SnO2 Nanocomposite

Xylene is one of the representative indoor pollutants, even in ppb levels, that affect human health directly. Due to the non-polar and less reactive nature of xylene, its room temperature detection is challenging. This work demonstrates a metallic tin-doped Sn-SnO₂ nanocomposite under controlled pH conditions via a simple solvothermal route. The Sn nanoparticles are uniformly distributed inside the SnO₂ nanospheres of ∼70 nm with a high specific surface area of 118.8 m²/g. The surface of the Sn-SnO₂ nanocomposite exhibits strong affinity toward benzene, toluene, ethylbenzene, and xylene (BTEX) compared to other polar volatile organic compounds (VOCs) such as ethanol, acetone, isopropyl alcohol, formaldehyde, and chloroform tested in this study. The sensor's response is highest for xylene among BTEX molecules. Under ambient room temperature conditions, the sensor exhibits a linear response to xylene in the 1-100 ppm range with a sensitivity of ∼255% at 60 ppm within ∼1.5 s and recovers in ∼40 s. The sensor is hardly affected by humidity variations (40-70%), leading to enhanced reliability and repeatability under dynamic environmental conditions. The meso and microporous nanosphere morphology act as a nanocontainer for non-polar VOCs to diffuse inside the nanostructures, providing easy accessibility. The metallic Sn increases the affinity for less reactive xylene at room temperature. Thus, the nanocatalytic Sn-SnO₂ nanocomposite is an active gas/VOC sensing material and provides an effective solution for sensing major indoor pollutants under humid conditions.

Synthesis, Structural and Sensor Properties of Nanosized Mixed Oxides Based on In2O3 Particles

The paper considers the relationship between the structure and properties of nanostructured conductometric sensors based on binary mixtures of semiconductor oxides designed to detect reducing gases in the environment. The sensor effect in such systems is determined by the chemisorption of molecules on the surface of catalytically active particles and the transfer of chemisorbed products to electron-rich nanoparticles, where these products react with the analyzed gas. In this regard, the role is evaluated of the method of synthesizing the composites, the catalytic activity of metal oxides (CeO₂, SnO₂, ZnO), and the type of conductivity of metal oxides (Co₃O₄, ZrO₂) in the sensor process. The effect of oxygen vacancies present in the composites on the performance characteristics is also considered. Particular attention is paid to the influence of the synthesis procedure for preparing sensitive layers based on CeO₂-In₂O₃ on the structure of the resulting composites, as well as their conductive and sensor properties.

Nano-Confined Tin Oxide in Carbon Nanotube Electrodes via Electrostatic Spray Deposition for Lithium-Ion Batteries

The development of novel materials is essential for the next generation of electric vehicles and portable devices. Tin oxide (SnO2), with its relatively high theoretical capacity, has been considered as a promising anode material for applications in energy storage devices. However, the SnO2 anode material suffers from poor conductivity and huge volume expansion during charge/discharge cycles. In this study, we evaluated an approach to control the conductivity and volume change of SnO2 through a controllable and effective method by confining different percentages of SnO2 nanoparticles into carbon nanotubes (CNTs). The binder-free confined SnO2 in CNT composite was deposited via an electrostatic spray deposition technique. The morphology of the synthesized and deposited composite was evaluated by scanning electron microscopy and high-resolution transmission electron spectroscopy. The binder-free 20% confined SnO2 in CNT anode delivered a high reversible capacity of 770.6 mAh g-1. The specific capacity of the anode increased to 1069.7 mAh g-1 after 200 cycles, owing to the electrochemical milling effect. The delivered specific capacity after 200 cycles shows that developed novel anode material is suitable for lithium-ion batteries (LIBs).

Atmospheric Pressure Solvothermal Synthesis of Nanoscale SnO2 and Its Application in Microextrusion Printing of a Thick-Film Chemosensor Material for Effective Ethanol Detection

The atmospheric pressure solvothermal (APS) synthesis of nanocrystalline SnO₂ (average size of coherent scattering regions (CSR)-7.5 ± 0.6 nm) using tin acetylacetonate as a precursor was studied. The resulting nanopowder was used as a functional ink component in microextrusion printing of a tin dioxide thick film on the surface of a Pt/Al₂O₃/Pt chip. Synchronous thermal analysis shows that the resulting semiproduct is transformed completely into tin dioxide nanopowder at 400 °C within 1 h. The SnO₂ powder and the resulting film were shown to have a cassiterite-type structure according to X-ray diffraction analysis, and IR spectroscopy was used to establish the set of functional groups in the material composition. The microstructural features of the tin dioxide powder were analyzed using scanning (SEM) and transmission (TEM) electron microscopy: the average size of the oxide powder particles was 8.2 ± 0.7 nm. Various atomic force microscopy (AFM) techniques were employed to investigate the topography of the oxide film and to build maps of surface capacitance and potential distribution. The temperature dependence of the electrical conductivity of the printed SnO₂ film was studied using impedance spectroscopy. The chemosensory properties of the formed material when detecting H₂, CO, NH₃, C₆H₆, C₃H₆O and C₂H₅OH, including at varying humidity, were also examined. It was demonstrated that the obtained SnO₂ film has an increased sensitivity (the sensory response value was 1.4-63.5) and selectivity for detection of 4-100 ppm C₂H₅OH at an operating temperature of 200 °C.

A Tin Oxide-Coated Copper Foam Hybridized with a Gas Diffusion Electrode for Efficient CO2 Reduction to Formate with a Current Density Exceeding 1 A cm-2

The electrochemical CO₂ reduction reaction (CO₂ RR) is a promising strategy for closing the carbon cycle. Increasing the current density (  J) for CO₂ RR products is a critical requirement for the social implementation of this technology. Herein, nanoscale tin-oxide-modified copper-oxide foam is hybridized with a carbon-based gas-diffusion electrode (GDE). Using the resultant electrode, the J_formate is increased to -1152 mA cm^-2 at -1.2 V versus RHE in 1 m KOH, which is the highest value for CO₂ -to-formate electrolysis. The formate faradaic efficiency (FE_formate ) reaches ≈99% at -0.6 V versus RHE. The achievement of ultra-high-rate formate production is attributable to the following factors: i) homogeneously-modified Sn atoms suppressing H₂ evolution and ii) the hydrophobic carbon nanoparticles on GDEs penetrating the macroporous structure of the foam causing the increase in the thickness of triple-phase interface. Additionally, the FE_formate remains at ≈70% under a high J of -1.0 A cm^-2 for more than 20 h.

Tin Oxide Based Hybrid Nanostructures for Efficient Gas Sensing

Tin oxide as a semiconductor metal oxide has revealed great potential in the field of gas sensing due to its porous structure and reduced size. Especially for tin oxide and its composites, inherent properties such as high surface areas and their unique semiconducting properties with tunable band gaps make them compelling for sensing applications. In combination with the general benefits of metal oxide nanomaterials, the incorporation of metal oxides into metal oxide nanoparticles is a new approach that has dramatically improved the sensing performance of these materials due to the synergistic effects. This review aims to comprehend the sensing mechanisms and the synergistic effects of tin oxide and its composites in achieving high selectivity, high sensitivity and rapid response speed which will be addressed with a full summary. The review further vehemently highlights the advances in tin oxide and its composites in the gas sensing field. Further, the structural components, structural features and surface chemistry involved in the gas sensing are also explained. In addition, this review discusses the SnO2 metal oxide and its composites and unravels the complications in achieving high selectivity, high sensitivity and rapid response speed. The review begins with the gas sensing mechanisms, which are followed by the synthesis methods. Further key results and discussions of previous studies on tin metal oxide and its composites are also discussed. Moreover, achievements in recent research on tin oxide and its composites for sensor applications are then comprehensively compiled. Finally, the challenges and scope for future developments are discussed.

Low-Voltage-Driven SnO2-Based H2S Microsensor with Optimized Micro-Heater for Portable Gas Sensor Applications

To realize portable gas sensor applications, it is necessary to develop hydrogen sulfide (H2S) microsensors capable of operating at lower voltages with high response, good selectivity and stability, and fast response and recovery times. A gas sensor with a high operating voltage (>5 V) is not suitable for portable applications because it demands additional circuitry, such as a charge pump circuit (supply voltage of common circuits is approximately 1.8−5 V). Among H2S microsensor components, that is, the substrate, sensing area, electrode, and micro-heater, the proper design of the micro-heater is particularly important, owing to the role of thermal energy in ensuring the efficient detection of H2S. This study proposes and develops tin (IV)-oxide (SnO2)-based H2S microsensors with different geometrically designed embedded micro-heaters. The proposed micro-heaters affect the operating temperature of the H2S sensors, and the micro-heater with a rectangular mesh pattern exhibits superior heating performance at a relatively low operating voltage (3−4 V) compared to those with line (5−7 V) and rectangular patterns (3−5 V). Moreover, utilizing a micro-heater with a rectangular mesh pattern, the fabricated SnO2-based H2S microsensor was driven at a low operating voltage and offered good detection capability at a low H2S concentration (0−10 ppm), with a quick response (<51 s) and recovery time (<101 s).

F-doping-Enhanced Carrier Transport in the SnO2/Perovskite Interface for High-Performance Perovskite Solar Cells

SnO₂ is widely used as the electron transport layer (ETL) in n-i-p perovskite solar cells. However, the deep-level defects at the interface between SnO₂ and the perovskite film will lead to energy loss, reducing the open-circuit voltage. Therefore, the interface optimization is essential to raise the efficiency and enhance the stability of perovskite solar cells. In this work, we introduce NH₄F into the SnO₂ electron transport layers, and the optimized SnO₂ films reduce the interface defect density, improve the charge extraction, and reveal a better energy-level arrangement. Compared to the conventional SnO₂ perovskite solar cell, the average V_oc is improved by 70 mV with the champion efficiency up to 22.12%. Moreover, the unencapsulated F-doped SnO₂ perovskite solar cells show better thermal stability (maintained 86.2%) and humidity stability (maintained 80.8%) after 35 days.

Easy Diameter Tuning of Silicon Nanowires with Low-Cost SnO2-Catalyzed Growth for Lithium-Ion Batteries

Silicon nanowires are appealing structures to enhance the capacity of anodes in lithium-ion batteries. However, to attain industrial relevance, their synthesis requires a reduced cost. An important part of the cost is devoted to the silicon growth catalyst, usually gold. Here, we replace gold with tin, introduced as low-cost tin oxide nanoparticles, to produce a graphite-silicon nanowire composite as a long-standing anode active material. It is equally important to control the silicon size, as this determines the rate of decay of the anode performance. In this work, we demonstrate how to control the silicon nanowire diameter from 10 to 40 nm by optimizing growth parameters such as the tin loading and the atmosphere in the growth reactor. The best composites, with a rich content of Si close to 30% wt., show a remarkably high initial Coulombic efficiency of 82% for SiNWs 37 nm in diameter.

Nanosensor Based on Thermal Gradient and Machine Learning for the Detection of Methanol Adulteration in Alcoholic Beverages and Methanol Poisoning

Methanol, naturally present in small quantities in the distillation of alcoholic beverages, can lead to serious health problems. When it exceeds a certain concentration, it causes blindness, organ failure, and even death if not recognized in time. Analytical techniques such as chromatography are used to detect dangerous concentrations of methanol, which are very accurate but also expensive, cumbersome, and time-consuming. Therefore, a gas sensor that is inexpensive and portable and capable of distinguishing methanol from ethanol would be very useful. Here, we present a resistive gas sensor, based on tin oxide nanowires, that works in a thermal gradient. By combining responses at various temperatures and using machine learning algorithms (PCA, SVM, LDA), the device can distinguish methanol from ethanol in a wide range of concentrations (1–100 ppm) in both dry air and under different humidity conditions (25–75% RH). The proposed sensor, which is small and inexpensive, demonstrates the ability to distinguish methanol from ethanol at different concentrations and could be developed both to detect the adulteration of alcoholic beverages and to quickly recognize methanol poisoning.

Surface Morphology of Textured Transparent Conductive Oxide Thin Film Seen by Various Probes: Visible Light, X-rays, Electron Scattering and Contact Probe

Fluorine-doped tin oxide thin films (SnO₂:F) are widely used as transparent conductive oxide electrodes in thin-film solar cells because of their appropriate electrical and optical properties. The surface morphology of these films influences their optical properties and therefore plays an important role in the overall efficiencies of the solar cells in which they are implemented. At rough surfaces light is diffusely scattered, extending the optical path of light inside the active layer of the solar cell, which in term improves light absorption and solar cell conversion efficiency. In this work, we investigated the surface morphology of undoped and doped SnO₂ thin films and their influence on the optical properties of the films. We have compared and analysed the results obtained by several complementary methods for thin-film surface morphology investigation: atomic force microscopy (AFM), transmission electron microscopy (TEM), and grazing-incidence small-angle X-ray scattering (GISAXS). Based on the AFM and TEM results we propose a theoretical model that reproduces well the GISAXS scattering patterns.

Research Progress of p-Type Oxide Thin-Film Transistors

The development of transparent electronics has advanced metal–oxide–semiconductor Thin-Film transistor (TFT) technology. In the field of flat-panel displays, as basic units, TFTs play an important role in achieving high speed, brightness, and screen contrast ratio to display information by controlling liquid crystal pixel dots. Oxide TFTs have gradually replaced silicon-based TFTs owing to their field-effect mobility, stability, and responsiveness. In the market, n-type oxide TFTs have been widely used, and their preparation methods have been gradually refined; however, p-Type oxide TFTs with the same properties are difficult to obtain. Fabricating p-Type oxide TFTs with the same performance as n-type oxide TFTs can ensure more energy-efficient complementary electronics and better transparent display applications. This paper summarizes the basic understanding of the structure and performance of the p-Type oxide TFTs, expounding the research progress and challenges of oxide transistors. The microstructures of the three types of p-Type oxides and significant efforts to improve the performance of oxide TFTs are highlighted. Finally, the latest progress and prospects of oxide TFTs based on p-Type oxide semiconductors and other p-Type semiconductor electronic devices are discussed.

Highly Stable SnO2-Based Quantum-Dot Light-Emitting Diodes with the Conventional Device Structure

ZnO-based electron-transporting layers (ETLs) have been universally used in quantum-dot light-emitting diodes (QLEDs) for high performance. The active surface chemistry of ZnO nanoparticles (NPs), however, leads to QLEDs with positive aging and unacceptably poor shelf stability. SnO₂ is a promising candidate for ETLs with less reactivity, but NP agglomeration in nonionic solvents makes the conventional device structure abandoned, resulting in QLEDs with extremely low operational lifetimes. The large barrier for electron injection also limits the electroluminescence efficiency. Here, we report one solution to all the above-mentioned problems. Owing to the strong HO-SnO₂ coordination and the steric effect provided by the hydrocarbon groups, tetramethylammonium hydroxide can stabilize SnO₂ NPs in alcohol, while its intrinsic dipole induces a favorable electronic-level shift for charge injection. The SnO₂-based devices, with the conventional structure, exhibit not only the most efficient electroluminescence among ZnO-free QLEDs but also an operational lifetime (T₉₅) over 3200 h at 1000 cd m^-2, which is comparable with that of state-of-the-art ZnO-based devices. More importantly, the superior shelf stability means that the TMAH-SnO₂ NPs are promising to enable QLEDs with real stability.

Understanding the "Anti-Catalyst" Effect with Added CoOx Water Oxidation Catalyst in Dye-Sensitized Photoelectrolysis Cells: Carbon Impurities in Nanostructured SnO2 Are the Culprit

In 2017, we reported a dye-sensitized, photoelectrolysis cell consisting of fluorine-doped tin oxide (FTO)-coated glass covered by SnO₂ nanoparticles coated with N,N'-bis(phosphonomethyl)-3,4,9,10-perylenediimide (PMPDI) dye and then a photoelectrochemically deposited CoO_x water oxidation catalyst (WOCatalyst), FTO/nano-SnO₂/PMPDI/CoO_x. This system employed nanostructured SnO₂ stabilized by a polyethyleneglycol bisphenol A epichlorohydrin (PEG-BAE) copolymer and other C-containing additives based on a literature synthesis to achieve a higher surface area and thus greater PMPDI dye absorption and resultant light collection. Surprisingly, the addition of the well-established WOCatalyst CoO_x resulted in a decrease in the photocurrent, an unexpected "anti-catalyst" effect. Two primary questions addressed in the present study are (1) what is the source of this "anti-catalyst" effect? and (2) are the findings of broader interest? Reflection on the synthesis of nano-SnO₂ stabilized by PEG-BAE, and the large, ca. 10:1 ratio of C to Sn in synthesis, led to the hypothesis that even the annealing step at 450 °C in of the FTO/SnO₂ anode precursors was unlikely to remove all the carbon initially present. Indeed, residual carbon impurities are shown to be the culprit in the presently observed "anti-catalyst" effect. The implication and anticipated broader impact of the results of answering the two abovementioned questions are also presented and discussed along with a section entitled "Perspective and Suggestions for the Field Going Forward."

Black Phosphorus Quantum Dot-Engineered Tin Oxide Electron Transport Layer for Highly Stable Perovskite Solar Cells with Negligible Hysteresis

An effective combination of smart materials plays an important role in charge transfer and separation for high photoelectric conversion efficiency (PCE) and stable solar cells. Black phosphorus quantum dots (BPQDs) have been revealed as a direct band gap semiconductor with ultrahigh conductivity, which have been explored in the present work as an additive component to a precursor solution of SnO₂ nanoparticles that can effectively improve the performance of SnO₂ electron transport layer (ETL)-based perovskite solar cells. Such a device can yield a high PCE of 21% with the SnO₂/BPQDs mixed ETL, which is higher than those of perovskite solar cells based on SnO₂ single layer (18.2%), BPQDs/SnO₂ bilayer (19.5%), and SnO₂/BPQDs bilayer (20.5%) samples. The mixed samples still possess good stability of more than 90% efficiency after 1000 h under AM 1.5G lamp irradiation and negligible hysteresis. It is found that the strong interaction of BPQDs with SnO₂ can not only modify the defects inherent to the SnO₂ layer but also inhibit the oxidation of BPQDs. This work provides a promising functional material for SnO₂ ETL-based perovskite solar cells and proves that the BPQD-based modification strategy is useful for designing other solar cells with high performance.

Industrially Compatible Fabrication Process of Perovskite-Based Mini-Modules Coupling Sequential Slot-Die Coating and Chemical Bath Deposition

To upscale the emerging perovskite photovoltaic technology to larger-size modules, industrially relevant deposition techniques need to be developed. In this work, the deposition of tin oxide used as an electron extraction layer is established using chemical bath deposition (CBD), a low-cost and solution-based fabrication process. Applying this simple low-temperature deposition method, highly homogeneous SnO₂ films are obtained in a reproducible manner. Moreover, the perovskite layer is prepared by sequentially slot-die coating on top of the n-type contact. The symbiosis of these two industrially relevant deposition techniques allows for the growth of high-quality dense perovskite layers with large grains. The uniformity of the perovskite film is further confirmed by scanning electron microscopy (SEM)/scanning transmission electron microscopy (STEM) analysis coupled with energy dispersive X-ray spectroscopy (EDX) and cathodoluminescence measurements allowing us to probe the elemental composition at the nanoscale. Perovskite solar cells fabricated from CBD SnO₂ and slot-die-coated perovskite show power conversion efficiencies up to 19.2%. Furthermore, mini-modules with an aperture area of 40 cm² demonstrate efficiencies of 17% (18.1% on active area).

Electron Transport Assisted by Transparent Conductive Oxide Elements in Perovskite Solar Cells

Fluorine and indium elements in F-doped SnO₂ (FTO) and Sn-doped In₂ O₃ (ITO), respectively, significantly contribute toward enhancing the electrical conductivity of these transparent conductive oxides. In this study, fluorine was combined with indium to modify the SnO₂ electron transport layer (ETL) through InF₃ . Consequently, the modified perovskite solar cells (PSCs) showe the favorable alignment of energy levels, improved absorption and utilization of light, enhanced interfacial charge extraction, and suppressed interfacial charge recombination. After InF₃ modification, the open circuit voltage (V_oc ) and fill factor (FF) of the PSC were significantly improved, and the photoelectric conversion efficiency (PCE) reached 21.39 %, far exceeding that of the control PSC (19.62 %).

Tin Oxide Electron Transport Layers for Air-/Solution-Processed Conventional Organic Solar Cells

Commercialization of organic solar cells (OSC) is imminent. Interlayers between the photoactive film and the electrodes are critical for high device efficiency and stability. Here, the applicability of SnO₂ nanoparticles (SnO₂ NPs) as the electron transport layer (ETL) in conventional OSCs is evaluated. A commercial SnO₂ NPs solution in butanol is mixed with ethanol (EtOH) as a processing co-solvent to improve film formation for spin and slot-die coating deposition procedures. When processed with 200% v/v EtOH, the SnO₂ NPs film presents uniform film quality and low photoactive layer degradation. The optimized SnO₂ NPs ink is coated, in air, on top of two polymer:fullerene-based systems and a nonfullerene system, to form an efficient ETL film. In every case, addition of SnO₂ NPs film significantly enhances photovoltaic performance, from 3.4 and 3.7% without the ETL to 6.0 and 5.7% when coated on top of PBDB-T:PC₆₁BM and PPDT2FBT:PC₆₁BM, respectively, and from 3.7 to 7.1% when applied on top of the PTQ10:IDIC system. Flexible, all slot-die-coated devices, in air, are also fabricated and tested, demonstrating the versatility of the SnO₂ NPs ink for efficient ETL formation on top of organic photoactive layers, processed under ambient condition, ideal for practical large-scale production of OSCs.

Hydrothermal Synthesis of Hierarchical SnO2 Nanostructures for Improved Formaldehyde Gas Sensing

The indoor environment of buildings affects people’s daily life. Indoor harmful gases include volatile organic gas and greenhouse gas. Therefore, the detection of harmful gas by gas sensors is a key method for developing green buildings. The reasonable design of SnO₂-sensing materials with excellent structures is an ideal choice for gas sensors. In this study, three types of hierarchical SnO₂ microspheres assembled with one-dimensional nanorods, including urchin-like microspheres (SN-1), flower-like microspheres (SN-2), and hydrangea-like microspheres (SN-3), are prepared by a simple hydrothermal method and further applied as gas-sensing materials for an indoor formaldehyde (HCHO) gas-sensing test. The SN-1 sample-based gas sensor demonstrates improved HCHO gas-sensing performance, especially demonstrating greater sensor responses and faster response/recovery speeds than SN-2- and SN-3-based gas sensors. The improved HCHO gas-sensing properties could be mainly attributed to the structural difference of smaller nanorods. These results further indicate the uniqueness of the structure of the SN-1 sample and its suitability as HCHO- sensing material.

Characterization of Ti/SnO2 Interface by X-ray Photoelectron Spectroscopy

The Ti/SnO₂ interface has been investigated in situ via the technique of x-ray photoelectron spectroscopy. Thin films (in the range from 0.3 to 1.1 nm) of titanium were deposited on SnO₂ substrates via the e-beam technique. The deposition was carried out at two different substrate temperatures, namely room temperature and 200 °C. The photoelectron spectra of tin and titanium in the samples were found to exhibit significant differences upon comparison with the corresponding elemental and the oxide spectra. These changes result from chemical interaction between SnO₂ and the titanium overlayer at the interface. The SnO₂ was observed to be reduced to elemental tin while the titanium overlayer was observed to become oxidized. Complete reduction of SnO₂ to elemental tin did not occur even for the lowest thickness of the titanium overlayer. The interfaces in both the types of the samples were observed to consist of elemental Sn, SnO₂, elemental titanium, TiO₂, and Ti-suboxide. The relative percentages of the constituents at the interface have been estimated by curve fitting the spectral data with the corresponding elemental and the oxide spectra. In the 200 °C samples, thermal diffusion of the titanium overlayer was observed. This resulted in the complete oxidation of the titanium overlayer to TiO₂ upto a thickness of 0.9 nm of the overlayer. Elemental titanium resulting from the unreacted overlayer was observed to be more in the room temperature samples. The room temperature samples showed variation around 20% for the Ti-suboxide while an increasing trend was observed in the 200 °C samples.

Understanding the Origin of the Hysteresis of High-Performance Solution Processed Polycrystalline SnO2 Thin-Film Transistors and Applications to Circuits

Crystalline tin oxide has been investigated for industrial applications since the 1970s. Recently, the amorphous phase of tin oxide has been used in thin film transistors (TFTs) and has demonstrated high performance. For large area electronics, TFTs are well suited, but they are subject to various instabilities due to operating conditions, such as positive or negative bias stress PBS (NBS). Another instability is hysteresis, which can be detrimental in operating circuits. Understanding its origin can help fabricating more reliable TFTs. Here, we report an investigation on the origin of the hysteresis of solution-processed polycrystalline SnO₂ TFTs. We examined the effect of the carrier concentration in the SnO₂ channel region on the hysteresis by varying the curing temperature of the thin film from 200 to 350 °C. Stressing the TFTs characterized further the origin of the hysteresis, and holes trapped in the dielectric are understood to be the main source of the hysteresis. With TFTs showing the smallest hysteresis, we could fabricate inverters and ring oscillators.

Hydrophilic and Conductive Carbon Nanotube Fibers for High-Performance Lithium-Ion Batteries

Carbon nanotube fiber (CNTF) is a highly conductive and porous platform to grow active materials of lithium-ion batteries (LIB). Here, we prepared SnO₂@CNTF based on sulfonic acid-functionalized CNTF to be used in LIB anodes without binder, conductive agent, and current collector. The SnO₂ nanoparticles were grown on the CNTF in an aqueous system without a hydrothermal method. The functionalized CNTF exhibited higher conductivity and effective water infiltration compared to the raw CNTF. Due to the enhanced water infiltration, the functionalized CNTF became SnO₂@CNTF with an ideal core-shell structure coated with a thin SnO₂ layer. The specific capacity and rate capability of SnO₂@-functionalized CNTF were superior to those of SnO₂@raw CNTF. Since the SnO₂@CNTF-based anode was free of a binder, conductive agent, and current collector, the specific capacity of the anode studied in this work was higher than that of conventional anodes.

One-Step Synthesis of SnO2/Carbon Nanotube Nanonests Composites by Direct Current Arc-Discharge Plasma and Its Application in Lithium-Ion Batteries

Tin dioxide (SnO₂)-based materials, as anode materials for lithium-ion batteries (LIBs), have been attracting growing research attention due to the high theoretical specific capacity. However, the complex synthesis process of chemical methods and the pollution of chemical reagents limit its commercialization. The new material synthesis method is of great significance for expanding the application of SnO₂-based materials. In this study, the SnO₂/carbon nanotube nanonests (SnO₂/CNT NNs) composites are synthesized in one step by direct current (DC) arc-discharge plasma; compared with conventional methods, the plasma synthesis achieves a uniform load of SnO₂ nanoparticles on the surfaces of CNTs while constructing the CNTs conductive network. The SnO₂/CNT NNs composites are applied in LIBs, it can be found that the nanonest-like CNT conductive structure provides adequate room for the volume expansion and also helps to transfer the electrons. Electrochemical measurements suggests that the SnO₂/CNT NNscomposites achieve high capacity, and still have high electrochemical stability and coulombic efficiency under high current density, which proves the reliability of the synthesis method. This method is expected to be industrialized and also provides new ideas for the preparation of other nanocomposites.