Porous Tin Dioxide Research Articles

Efficient one-pot synthesis of antimony-containing mesoporous tin dioxide nanostructures for gas-sensing applications

Currently, wide-bandgap metal oxide nanomaterials with attractive chemical and physical properties are intensively used for the fabrication of chemiresistive gas sensors and other catalytic devices. However, the low electrical conductance of sensors based on wide bandgap metal oxides is an issue that limits their application in small-scale systems to read out electrical signals and the manufacturing of portable sensing devices. In this regard, combining oxide nanostructures with other elements could be an effective strategy for enhancing their electrical and sensing performances. In this work, we attempted to improve the conductivity and sensitivity of porous tin dioxide to certain gases. Herein, we report a cost-effective and simple method for synthesizing antimony-containing mesoporous tin dioxide (Sb-SnO2) under ambient pressure and temperature. The X-ray diffraction, N2 sorption, transmission electron microscopy, energy-dispersive X-ray, and photoelectron spectroscopy analyses indicate that the prepared Sb-SnO2 material is a nanocrystalline powder with a large surface area. Meanwhile, the successful incorporation of Sb into the SnO2 framework results in increased electrical conductance by at least one order of magnitude or more compared to that of pure SnO2 and other doped SnO2 materials, respectively. The structure shows a very effective sensing response to volatile organic compounds and nitrogen dioxide. Hence, we developed an efficient method for synthesizing highly conductive oxide nanomaterials for use in chemical gas sensing devices.

Highly Sensitive, Selective and Stable NO2 Gas Sensor Based on Porous Influenced SnO2 Bilayer Thin Films

In this work, an attempt has been made to fabricate SnO2 porous films using automated nebulizer spray pyrolysis technique with the influence of a porogen. Pure tin dioxide and porous tin dioxide (SnO2/SnO2) thin films were prepared from a precursor solution composed of SnCl2·2H2O and polyethylene glycol as a porogen. The structural, morphological, optical and gas sensing performance of the prepared thin films were characterized. The inclusion of porogen significantly improved the sensing property of porous SnO2 bilayer thin films and it was confirmed by structural, morphological and gas sensing performance studies. The optimized spray process parameter was determined finally in this work as SnO2 precursor strength of 0.2 M for porous SnO2 layer. Under this condition, the increased lattice constant, lattice defect and increased pores diameter were achieved, which exhibited good gas sensitivity and selectivity towards NO2 gas at 250 ºC. The response and recovery time is decreased as 50%, the deduction limit is 0.9 ppm. In addition, during the five weeks test, the response level was observed nearly constant, which indicated that the SnO2 bilayer sensor has long-term stability.

Enhancement of Ammonia Gas Sensing by Tin Dioxide-Polyaniline Nanocomposite

Ammonia (NH3) gas is an important chemical in many industries. Employees working in such industrial areas may exposed to a certain concentration of NH3 which could cause various symptoms such as irritation of skin and eyes and problems in respiratory system. The development of new NH3 sensing material has attracted great attention. In this study, porous tin dioxide nanofibers (SnO2 NFs) were successfully fabricated by electrospinning. The SnO2 NFs was composited with polyaniline (PANI), conducting polymer. The tin dioxide nanofibers@polyaniline nanocomposite (SnO2 NFs@PANI) was examined and showed improving and desirable sensing for NH3 gas, which includes high sensitivity, quick response and fast recovery times at room temperature. HIGHLIGHTS Ammonia (NH3) gas has been used in many industries. For worker safety in those industrial area, a reliable NH3 gas sensor is necessary A new tin dioxide nanofibers@polyaniline nanocomposite (SnO2 NFs@PANI) had successfully developed for a selectively ammonia gas sensor Excellent analytical performance in team of stability, repeatability and widely response for NH3 concentration was achieved GRAPHICAL ABSTRACT

Preparation of cross-linked porous SnO2 nanosheets using three-dimensional reduced graphene oxide as a template and their gas sensing property

Semiconductor metal oxide nanostructures with large specific surface areas and high porosity will enhance their gas-sensing performance. Here, cross-linked porous tin dioxide nanosheets were obtained using three-dimensional reduced graphene oxide as a template followed by an annealing process. The as-synthesized porous SnO 2 nanosheets were composed of nanocrystals with a mean diameter of ca. 7.6 nm. The products were characterized using a range of techniques. The sensing property of the cross-linked porous SnO 2 nanosheets for toxic organic vapors, such as ethanol, acetone, isopropanol, benzene, methylbenzene, methanol, and formaldehyde, were studied. The sensor showed a high response of 37.9 for 100 ppm acetone, making it a promising candidate as a practical detector of volatile organic compounds. • A special cross-linked porous tin dioxide nanosheets were developed. • It involves a template solvothermal method and a subsequent annealing process. • The cross-linked porous SnO 2 nanosheets exhibit high sensing performance for VOCs. • High performance is due to cross-linked structure with small size nanocrystals.

Sensitive and Low-Power Metal Oxide Gas Sensors with a Low-Cost Microelectromechanical Heater.

In this study, a simple and cost-effective metal oxide semiconductor (MOS) gas sensor, which can be fabricated utilizing only two photolithography steps, was designed and developed through the planar microelectromechanical systems (MEMS) technique. Ball-milled porous tin dioxide nanoparticle clusters were precisely drop-coated onto the integrated microheater region and subsequently characterized using a helium ion microscope (HIM). The spatial suspension of the silicon nitride platform over the silicon substrate provides superior thermal isolation and thus dramatically reduces the power consumption of the microheater. The well-designed microheater exhibits excellent thermal uniformity, which was verified both computationally and experimentally. The as-fabricated sensors were tested for ethanol gas sensing at various operating temperatures with different concentrations. At the optimal work temperature of ∼400 °C, our gas sensors demonstrated a respectable sensitivity to 1 ppm ethanol, which is the lower detection limit to most commercial products. Moreover, stable performance over repetitive testing was observed. The innovative sensor developed here is a promising candidate for portable gas sensing devices and various other commercial applications.

Engineering of SnO2-Graphene Oxide Nanoheterojunctions for Selective Room-Temperature Chemical Sensing and Optoelectronic Devices.

The development of high-performing sensing materials, able to detect ppb-trace concentrations of volatile organic compounds (VOCs) at low temperatures, is required for the development of next-generation miniaturized wireless sensors. Here, we present the engineering of selective room-temperature (RT) chemical sensors, comprising highly porous tin dioxide (SnO2)–graphene oxide (GO) nanoheterojunction layouts. The optoelectronic and chemical properties of these highly porous (>90%) p–n heterojunctions were systematically investigated in terms of composition and morphologies. Optimized SnO2–GO layouts demonstrate significant potential as both visible–blind photodetectors and selective RT chemical sensors. Notably, a low GO content results in an excellent UV light responsivity (400 A W–1), with short rise and decay times, and RT high chemical sensitivity with selective detection of VOCs such as ethanol down to 100 ppb. In contrast, a high concentration of GO drastically decreases the RT response to ethanol and results in good selectivity to ethylbenzene. The feasibility of tuning the chemical selectivity of sensor response by engineering the relative amount of GO and SnO2 is a promising feature that may guide the future development of miniaturized solid-state gas sensors. Furthermore, the excellent optoelectronic properties of these SnO2–GO nanoheterojunctions may find applications in various other areas such as optoelectronic devices and (photo)electrocatalysis.

Fabrication of porous tin dioxide with enhanced gas-sensing performance toward NOx

A novel approach for preparing porous tin dioxide material by sol–gel hard template method was proposed in this study. The aerogel technology was used to synthesize the porous SnO2 and improve the porosity. The prepared material possesses excellent gas-sensing performance to NOx at room temperature, which has high sensitivity, excellent selectivity and fast response time. At room temperature, the maximum value toward 100 ppm NOx gas gets to 54%, and corresponding response time is only 19.5 s. The response time of the prepared sensor always remains within 26 s in NOx concentration ranging from 5 to 100 ppm. In the meantime, the response and response time for NOx at 5 ppm (the lowest detectable of the sensor) are 40% and 26 s, respectively. The prepared material can be used as a matrix material for gas-sensoring composites and has a very good development prospect in gas sensors’ field.

Cellulose Nanocrystal-Templated Tin Dioxide Thin Films for Gas Sensing.

Porous tin dioxide is an important low-cost semiconductor applied in electronics, gas sensors, and biosensors. Here, we present a versatile template-assisted synthesis of nanostructured tin dioxide thin films using cellulose nanocrystals (CNCs). We demonstrate that the structural features of CNC-templated tin dioxide films strongly depend on the precursor composition. The precursor properties were studied by using low-temperature nuclear magnetic resonance spectroscopy of tin tetrachloride in solution. We demonstrate that it is possible to optimize the precursor conditions to obtain homogeneous precursor mixtures and therefore highly porous thin films with pore dimensions in the range of 10-20 nm (ABET = 46-64 m2 g-1, measured on powder). Finally, by exploiting the high surface area of the material, we developed a resistive gas sensor based on CNC-templated tin dioxide. The sensor shows high sensitivity to carbon monoxide (CO) in ppm concentrations and low cross-sensitivity to humidity. Most importantly, the sensing kinetics are remarkably fast; both the response to the analyte gas and the signal decay after gas exposure occur within a few seconds, faster than in standard SnO2-based CO sensors. This is attributed to the high gas accessibility of the very thin porous film.

A rationally designed 3D interconnected porous tin dioxide cube with reserved space for volume expansion as an advanced anode of lithium-ion batteries

To work against the volume expansion (∼300%) of SnO2 during lithiation, here a sub-micro sized, interconnected, and porous SnO2 cube with rationally designed reserved space (∼375%) is synthesized via an artful topochemistry route (CaSn(OH)6-CaSnO3-SnO2). Owing to its microstructure, this novel material harvests enhanced lithium-storage performance.

Hierarchical structure assembled from in-situ carbon-coated porous tin dioxide nanosheets towards high lithium storage

Wide attention has been recently paid to the potential use of SnO2 material in lithium-ion batteries (LIBs) as a new high performance anode owe to its advantages such as high theoretical specific capacity and moderate working potential. However, the intrinsic problems such as pronounced volume change and low conductivity make the capacity decay quickly and rate capability behave badly, therefore severely hindering the practical application of SnO2 in LIBs. Two-dimensional materials with unique physicochemical properties have gained great attention in energy storage and conversion field, and considered as promising candidates for advanced anode materials of LIBs. Herein, we demonstrate a one-pot hydrothermal and subsequently carbonized approach to prepare a hierarchical structure assembled from in-situ carbon-coated porous tin dioxide (SnO2) nanosheets (SnO2@C NSs). By comparison with similar hierarchical structure assembled from pure SnO2 nanosheets indicates that the in-situ carbon coating significantly improves the electrochemical performances of SnO2@C NSs in terms of stability of structures and kinetics of electrochemical reactions. Consequently, the SnO2@C NSs demonstrates superior electrochemical performances, revealing high reversible capacity of 1077.6 and 730 mAh g−1 at 200 and 1000mAg−1 after 160 and 800cycles, respectively, as well as outstanding rate capabilities. Thus, the as-prepared SnO2@C NSs with excellent performances exhibits good potential to be a promising candidate of advanced anode materials for LIBs. Additionally, this paper may provide a new insight to synthesize fine porous SnO2 nanosheets/carbon composites.

Nano SnO2 in Flexible Carbon Spaces Protected by Rigid TiO2 for Efficient Reversible Lithium Storage

AbstractWe report a spatially‐confined strategy to improve the cycling stability of tin‐based anode materials, in which carbon acted as passenger particle is implanted in suit into the secondary structure of porous tin dioxide (SnO2), forming a spatial fault structure together with the SnO2 particles. Herein, the carbon (C) surrounding is endowed with the dual roles, which can not only prevent SnO2 and tin (Sn) nanoparticles aggregating for a better cycling stability, but also can improve the electron transport at the particle interface for high rate performance of the battery. Also, rigid titanium dioxide (TiO2) cavities are constructed for positive mechanical protections and releasing the mechanical stress to further improve the stability of the battery. Electrochemical tests reveal that such spatially‐confined architectures can enhance the cycling stability and improve the rate properties of tin‐based anode batteries remarkably. The discharge specific capacity of the spatial confined samples can be maintained 520 mAh g‐1 after 100 cycles at 0.2C and 320 mAh g‐1 at a high current rate of 1C.

Thermal calcination fabrication of porous tin dioxide for new flexible ultraviolet photodetectors

Porous tin dioxide (SnO2) have been successfully synthesized by using in-situ thermal calcination precursors at different calcination conditions, including different calcination temperature, different calcination times, and zone heating. The as-synthesized SnO2 samples were characterized by XRD, FESEM, TEM, UV–vis DRS and fluorescence spectrometry. Flexible photodetectors were then fabricated on PET (polyethylene terephthalate) substrate. The porous SnO2-based flexible ultraviolet photodetectors have high flexible, lightweight, low-cost and high stability. Especially, the flexible device exhibits linear photocurrent behaviors and good sensitivity to ultraviolet light at wavelengths of 254 nm and 365 nm. Our result should be useful for creating high efficiency optoelectronic devices.

Synthesis of mesoporous tin dioxide via sol-gel process assisted by resorcinol–formaldehyde gel

Tin dioxide is a useful n-type oxide semiconductor used in a variety of applications owing to its superior optical, electrical, and multifunctional properties. Here, we used a network of resorcinol–formaldehyde (RF) gel to synthesize mesoporous tin dioxide via a sol–gel process. The effects of various synthesis parameters on the morphology and mesoporosity of the obtained product were investigated, including aging time of the RF gel, tin-to-formaldehyde molar ratio, resorcinol-to-carbonate molar ratio, and the aging time of the tin/RF mixed gel. Our experimental results showed that the interaction between the network of the RF gel and tin-containing sol is a key factor that affected the structural strength of the porous network and the porosity of the final product. Through control of the interactions in the tin/RF mixed gel we obtained porous tin dioxide materials that could be effectively used to form large-surface area films with desirable mesoporous properties.

The formation of layers of porous crystalline tin dioxide from a composite on the basis of multiwalled carbon-nanotube arrays

A new method for the synthesis of porous crystalline tin-dioxide (SnO2) layers from composites on the basis of multiwalled carbon nanotubes (MWCNTs) and nonstoichiometric amorphous tin oxide (MWCNT/SnO x ) is proposed. An MWCN/SnO x composite layer produced by magnetron sputtering is annealed in air atmosphere at 500°C for 30 min. A homogeneous porous layer comprised of crystalline SnO2 spherical particles with a size of about 0.1 μm is obtained as a result. In the process of annealing, nearly all the amount of carbon is removed in the form of gaseous oxides (only a small amount remains in the upper part of the porous SnO2 layer). The structural defectiveness of nanotube walls, which increases because of the magnetron deposition of tin, plays a crucial role in the carbon oxidation and destruction of MWCNTs.

Design and fabrication of micro-nano fusion gas sensor based on two-beam micro-hotplatform

Micro-nano fusion gas sensors integrating two-beam micro-hotplatform with nanostructured porous film were fabricated in this study. The micro-hotplatform (MHP) was manufactured using standard micro-electro-mechanical systems technology in wafer runs. Based on a colloidal crystal template method, highly ordered porous tin dioxide films were in situ grown on the MHP. The as-fabricated sensors achieved the highest response at 250 °C with power consumption only 24 mW. Due to the low thermal capacity and ordered porous thin films of the sensor, the response time was about 2 s. The sensors are sensitive to ethanol in a large range from 0.1 to 250 ppm. The developed sensor here with high performance is an excellent candidate which can be incorporated into portable devices for alcohol detection such as breath analyzers.

Benefits and limitations of Pt nanoparticles supported on highly porous antimony-doped tin dioxide aerogel as alternative cathode material for proton-exchange membrane fuel cells

An electron-conducting metal-oxide substrate must fulfill three criteria to represent a viable alternative to conventional carbon blacks used as supports for Pt-based nanoparticles in proton-exchange membrane fuel cell (PEMFC): (i) be electron-conducting, (ii) be corrosion resistant and (iii) possess an opened porous structure compatible with facile ionomer insertion and efficient mass-transport properties. Using a sol-gel route, antimony-doped tin dioxide (Sb-doped SnO2, ATO) aerogels with such characteristics were synthesized: an optimal Sb content of 10at.% was found in terms of specific surface area and electrical conductivity. Pt nanoparticles were loaded onto 10at.% Sb-doped SnO2 (Pt/ATO), undoped SnO2 (Pt/SnO2) and Vulcan XC72 (Pt/C) via a modified polyol route, and their electrocatalytic activity for the oxygen reduction reaction (ORR) was evaluated. A 2-fold enhancement in ORR specific activity was measured on Pt/ATO over Pt/C. An accelerated stress test (AST) protocol, mimicking start-up/shutdown events in a PEMFC, was used to determine the long-term ORR performance of the Pt/ATO and the reference Pt/C electrocatalysts. The carbon support was not robust enough in these harsh conditions, as observed from the massive detachment of Pt nanoparticles from Vulcan XC72. On the contrary, the Pt nanoparticles did not detach from the ATO support. However, a core@shell structure with a Sb-poor surface covering a core featuring a Sb content close to the nominal formed during the AST. This core@shell structure restricted the capacity of the Pt nanoparticles to exchange electrons, as evidenced by the attenuated Pt surface oxide formation/reduction features, and led to decreased catalytic activity for the ORR.

Pt Nanoparticles Supported on Porous Antimony-Doped Tin Dioxide Aerogel As Cathode Material for Proton-Exchange Membrane Fuel Cells: Electrocatalytic Activity and Degradation Mechanism

Proton Exchange Membrane Fuel Cells (PEMFC) are high-efficiency energy converters that can be deployed for mobile, transport and stationary applications in an eco-friendly manner. Nevertheless, their large-scale development requires further improvements, specifically regarding their lifetime in operation1. In abnormal PEMFC operating conditions, e.g. start-up/shutdown events2 or localized fuel starvation3, the positive electrode may reach potentials of 1.5 V vs the reversible hydrogen electrode (RHE), which triggers extensive carbon support corrosion at the cathode side.To tackle this problem, one of the solution studied in the literature is to use (more robust) carbon-free catalyst supports based on metal oxides4-6. To represent viable alternatives to conventional carbon blacks, metal-oxide substrates must fulfill three criteria: be electron-conducting, resist corrosion and possess an opened porous structure compatible with facile ionomer insertion and efficient mass-transport properties.This study focuses on aerogel structures obtained using a sol-gel route, based on antimony-doped tin dioxide (ATO) with different doping levels (0, 5, 10 and 15 at.%). A Pt nanoparticles colloidal solution, obtained via a modified polyol route, was deposited on the ATO (Pt/ATO) featuring the best properties (10 at.% Sb-doped SnO2), and, for comparison, on Vulcan XC72 carbon (Pt/C) and on an undoped tin dioxide aerogel (Pt/SnO2). This strategy allowed the straightforward comparison of the Pt/ATO, Pt/C and Pt/SnO2 electrocatalysts in terms of catalytic activity for the oxygen reduction reaction (ORR) and durability. A 2-fold enhancement in specific activity for the ORR was measured on Pt/ATO over the reference Pt/C, suggesting strong metal support interactions between the Pt nanoparticles and the ATO support. An accelerated stress test (AST) protocol (5,000 or 10,000 potential cycles between 1.0 and 1.5 V vs RHE) enabled to determine the robustness of the Pt/ATO and the Pt/C electrocatalysts during model start-up/shut-down events. Figure 1 illustrates that Pt/C did not withstand operation in these conditions, as observed from the massive detachment of Pt nanoparticles from the carbon support following its corrosion. On the contrary, the Pt nanoparticles did not detach from the ATO support during ageing. However, evidences were provided that a core@shell structure with a Sb-poor surface covering a core with a Sb content close to the nominal forms during the AST. This core@shell structure restricts the capacity of the Pt nanoparticles to exchange electrons, as evidenced by the attenuated Pt surface oxide formation/reduction features, and the decreased catalytic activity for the ORR.

Three-Dimensionally Ordered Hierarchically Porous Tin Dioxide Inverse Opals and Immobilization of Palladium Nanoparticles for Catalytic Applications

A high surface area 3D ordered SnO2 inverted opal with walls composed of interconnected nanocrystals is reported using a facile approach with tin acetate precursors. The hierarchically porous structure exhibits porosity on multiple lengths scales (cm down to nm). The thickness of the IO wall structure comprising nanocrystals of the oxide can be tuned by multiple infilling of the precursor. Using highly monodisperse Pd nanoparticles, we show how the SnO2 IO can be functionalized with immobilized Pd NP assemblies. We show that the Pd NP size dispersion is controlled by utilizing weak ligand–metal interactions and strong metal-oxide interactions for the immobilization step. The resulting SnO2–Pd IOs were investigated X-ray photoelectron spectroscopy indicating electronic interactions between the Pd and SnO2 and alterations to NP surface chemistry. Pd NPs assembled with excellent dispersion on the ordered SnO2 IOs show superior catalytic performance for liquid phase chemical synthesis via Suzuki coupling reactions and allow easy removal of the catalyst substrate post reaction. Higher mass electrocatalytic activity is also demonstrated for formic acid oxidation, compared to commercial Pd/C catalysts, which is shown to be due to better access to the catalytically active sites on SnO2–Pd IOs. The high surface area interconnected phase-pure SnO2 IO, with programmable porosity forms a functional material for catalytic applications.

A Facile and Green Approach for the Controlled Synthesis of Porous SnO2 Nanospheres: Application as an Efficient Photocatalyst and an Excellent Gas Sensing Material

A facile and elegant methodology invoking the principles of Green Chemistry for the synthesis of porous tin dioxide nanospheres has been described. The low-temperature (∼50 °C) synthesis of SnO₂ nanoparticles and their self-assembly into organized, uniform, and monodispersed porous nanospheres with high surface area is facilitated by controlling the concentration of glucose, which acts as a stabilizing as well as structure-directing agent. A systematic control on the stannate to glucose molar concentration ratio determines the exact conditions to obtain monodispersed nanospheres, preferentially over random aggregation. Detailed characterization of the structure, morphology, and chemical composition reveals that the synthesized material, 50 nm SnO₂ porous nanospheres possess BET surface area of about 160 m²/g. Each porous nanosphere consists of a few hundred nanoparticles ∼2-3 nm in diameter with tetragonal cassiterite crystal structure. The SnO₂ nanospheres exhibit elevated photocatalytic activity toward methyl orange with good recyclability. Because of the high activity and stability of this photocatalyst, the material is ideal for applications in environmental remediation. Moreover, SnO₂ nanospheres display excellent gas sensing capabilities toward hydrogen. Surface modification of the nanospheres with Pd transforms this sensing material into a highly sensitive and selective room-temperature hydrogen sensor.

Novel hierarchically-packed tin dioxide sheets for fast adsorption of organic pollutant in aqueous solution

A unique porous tin dioxide (SnO2) sheet, which simultaneously possesses a porous exterior composed of nanoparticles and a hierarchical interior composed of nanoflakes, was reported for the first time. It was prepared via a facile solvothermal route combined with an annealing process. The as-prepared hierarchically-packed nanostructures were characterized by X-ray diffraction (XRD), field emission scanning electronic microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). The elemental mapping and the line scans were also performed in the high-angle annular dark-field (HAADF) mode on the same HRTEM. The novel SnO2 nanostructures were further employed to adsorb methylene blue which was used as the probe of organic pollutants in aqueous solution. The results show that the hierarchically-packed SnO2 sheets exhibit a fast adsorption rate to the absorbate. The removal efficiency reaches 98.5% in 5 min, which is significantly faster than that of commercial active carbon and some traditional nanostructures. As for the mechanism for such a fascinating adsorbing performance, a special adsorbate-depleted region formed inside the sheet is proposed, which is also supported by the study of the kinetic processes of gas adsorption and desorption. Moreover, the influence of pH, maximum adsorption capacity, and recyclability of the SnO2 sheets are also investigated. Our findings indicate that the novel hierarchically-packed SnO2 nanostructures could be a promising absorbent applied for rapid removal of organic pollutants in water.