Porous SnO2 Research Articles

Thermal shock-stabilized metal catalysts on oxide hemitubes: Toward ultrasensitive chemiresistors

To achieve powerful gas sensors oxide semiconductor chemiresistors, the uniform functionalization of nanocatalysts on the desired metal oxides is considered as a key strategy. However, still, it is challenging to achieve the nanocatalysts decoration on desired oxides without deterioration of target materials. In this study, thermal-shock (rapid joule-heating method) was applied to uniformly decorate Pt nanoparticles (NPs) on the surface of carbon nanofibers (CNFs) to achieve the uniform distribution of Pt NPs on one-dimensional structures. And then, SnO2 was physically deposited on the Pt NPs loaded CNFs and continuous heat-treatment was conducted to transfer the Pt NPs to desired SnO2 porous hemitubes. Thanks to the well-distributed Pt NPs on porous SnO2 hollow structures, the Pt laoded SnO2 hemitubes showed an exceptional sensitivity (Rair/Rgas = 1500 at 5 ppm) in H2S. Also, it showed high selectivity for H2S and high stability even under continuous gas exposure, confirming its potential as an effective H2S sensor.

Investigation on structural and optical properties of porous SnO2 nanomaterial fabricated by direct liquid injection chemical vapour deposition technique

In the present study, Cassiterite SnO2 thin film synthesized by direct liquid injection chemical vapour deposition method. The surface morphology of the nanomaterial exhibited the rope-like structures with nanospheroid. Peak broadening in the prepared material is analyzed by Scherrer, modified Scherrer, Williamson-Hall, Size-strain and Halder-Wagner methods for investigation of crystallite size and intrinsic strain. The optical properties of the nanomaterial such as bandgap (Eg), absorption coefficient (α), skin depth (δ), optical density (Dopt), extinction coefficient (k), refractive index (n), and dielectric constants (εi and εr) are analyzed by using the UV–Visible transmittance and reflectance spectrum of the prepared SnO2 nanomaterial. The optical band gap of SnO2 based thin film was calculated by the Tauc plot and found to be 3.8 eV.

Advanced Electrodegradation of Doxorubicin in Water Using a 3-D Ti/SnO2 Anode

This study investigated the application of an advanced electrooxidation process with three-dimensional tin oxide deposited onto a titanium plate anode, named 3-D Ti/SnO2, for the degradation and mineralization of one of the most important emerging contaminants with cytostatic properties, doxorubicin (DOX). The anode was synthesized using a commercial Ti plate, with corrosion control in acidic medium, used as a substrate for SnO2 deposition by the spin-coating method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses revealed that porous SnO2 was obtained, and the rutile phase of TiO2 was identified as an intermediary substrate onto the Ti plate. The results of CV analysis allowed us to determine the optimal operating conditions for the electrooxidation process conducted under a constant potential regime, controlled by the electron transfer or the diffusion mechanisms, involving hydroxyl radicals. The determination of UV–VIS spectra, total organic carbon (TOC), and chemical oxygen demand (COD) allowed us to identify the degradation mechanism and pathway of DOX onto the 3-D Ti/SnO2 anode. The effective degradation and mineralization of DOX contained in water by the electrooxidation process with this new 3-D dimensionally stable anode (DSA) was demonstrated in this study.

Selective photoactive gas detection of CO and HCHO using highly porous SnO2 and SnO2@TiO2 heterostructure

Herein, a controlled porous structure for photoactive gas sensors was fabricated using the gas-flow thermal evaporation and atomic layer deposition method. To control the porosity of the SnO2 matrix, Ar was introduced to the chamber to adjust the pressure from 0.1 to 1 Torr during thermal evaporation. Furthermore, nanoscale TiO2 layers were conformally deposited on the surface of porous SnO2 by atomic layer deposition as a selective active layer for HCHO. As a result, the sensor deposited at a pressure of 0.2 Torr showed high sensitivity and a relatively fast response than other deposition pressures owing to the optimized porosity and better electron transport. The nanoporous structure of SnO2 showed a high response rate of 56.7% when exposed to CO with a concentration of 50 ppm and a low detection limit of 1 ppm. The introduction of a TiO2 layer on the nanoporous SnO2 allowed selective response to HCHO with a response rate of 20% at 10 ppm when the oxidation level of the target gas was well aligned with the state of reactive oxygen of materials under UV irradiation. Furthermore, the sensing capabilities of the SnO2 and SnO2@TiO2 heterostructures, such as the response rate and response time, were assessed at different deposition pressures. Our results clearly show that the matching of energy levels between the redox energy of the target gas and the conduction band of the materials plays an important role in selectively detecting the target gas in photoactive gas sensors; therefore, we propose a rational design rule to enhance the selectivity for various target gases.

Ga-doped 3D ordered porous SnO2 with an ultrasmall pore size for enhanced formaldehyde sensitivity

Pure and Ga-doped 3 D ordered porous SnO2 (3DOPS) and SnO2 nanoparticles (NPs) were prepared. The 3DOPS/3% Ga-based sensor exhibits an improved response (61/50 ppm) to formaldehyde (HCHO), and the response is 3 times higher than pure 3DOPS (21/50 ppm) at low temperature (220 °C). However, the response of SnO2 NPs/3% Ga (10/50 ppm) is only 1.25 times that of the pure SnO2 NPs (8/50 ppm). Regardless of the SnO2 morphology, doping with Ga can improve its response. However, after the 3 D ordered porous structure of SnO2 doped with Ga element, its response is improved more obviously than that of the particle structure of SnO2. This may be attributed to the combined effect of the construction of the three-dimensional ordered porous structure and the doping elements.

Sponge-like loose and porous SnO2 microspheres with rich oxygen vacancies and their enhanced room-temperature gas-sensing performance.

Structure and surface modification of semiconductor materials are of great importance in gas sensors. In this study, a facile citric acid-assisted solvothermal method via a precise calcination process was leveraged to synthesize sponge-like loose and porous SnO2 microspheres with rich oxygen vacancies (denoted as LP-SnO2-Ov). When this material was used in a gas sensor, it exhibited an extremely high response to 10 ppm hydrogen sulfide gas at room temperature (Ra/Rg = 9688), which was 54 times higher than that of commercial SnO2. Furthermore, the response time of LP-SnO2-Ov was 5 s, while the recovery time was 177 s. Moreover, it displayed such high selectivity and stability for hydrogen sulfide gas that its properties remained almost unchanged after 1 month. This method paves a new way to fabricate materials possessing a sponge-like loose and porous structure with oxygen vacancies, which is promising for many other scientific fields such as lithium-ion batteries and photocatalysis.

Insights into the solvothermal reaction for synthesizing tin(iv) oxide porous spheres.

The solvothermal synthesis of SnO2 porous spheres was optimized by varying the reactants, solvents, additives, reaction temperature and reaction time. The products of these trials were characterized by X-ray diffraction, electron microscopy and X-ray fluorescence spectroscopy. SnO2 possessing a highly ordered spherical structure based on the aggregation of nanometer-sized primary particles was obtained using a simple one-pot solvothermal approach. These spheres were porous with a high specific surface area of more than 200 m2 g−1. The electrical conductivity of this material equaled or exceeded that of commercially available SnO2. SnO2-based spherical porous composites including various elements were easily synthesized by incorporating additional materials in the precursor solution.

Biotemplate-Inherited Porous Sno2 Monotubes with Oxygen Vacancies for Ultra-High Response and Fast Detection of Nitric Oxide at Low Temperature

Biotemplate-Inherited Porous Sno2 Monotubes with Oxygen Vacancies for Ultra-High Response and Fast Detection of Nitric Oxide at Low Temperature

Enhanced ppb-level formaldehyde sensing performance over Pt deposited SnO2 nanospheres

Formaldehyde is one of the most serious threats to human health in modern interior decoration. Thereby, online detection of indoor formaldehyde concentration has become an urgent problem. In this work, the Pt deposited porous SnO2 nanospheres were synthesized as the formaldehyde sensing materials, which were prepared by hydrothermal and chemical reduction methods. The diameter of as-synthesized Pt-SnO2 were centered in the range of 30–50 nm, with the dominant pore size of ~10 nm and the specific surface area of 89.79 m2 g−1, which provided a raft of passages and active sites for gas molecules to diffuse and interact mutually. Moreover, the experimental results demonstrated that the 1 wt.% Pt-SnO2 exhibited higher response (16.03), high-speed response time (9 s) and outstanding selectivity with exposure to low-concentration formaldehyde compared with original SnO2. The porous structures and catalytic effect of Pt nanoparticles were jointly responsible for the enhancement of SnO2 on sensing performance towards formaldehyde.

Improved arc erosion resistance of Ag/SnO2 composites fabricated by Ag melt-infiltration in the SnO2 skeleton

The typical Ag-SnO2 contact materials in which SnO2 dispersing in the Ag matrix suffer a poor arc erosion resistance because the individual SnO2 particles segregate and form a SnO2-rich layer under repeated arcing. Here, we introduce an architectured Ag/SnO2 composites in which individual SnO2 particles are bonding into a skeleton, fabricated by a novel method: (i) creating a porous SnO2 matrix by sintering SnO2 powders with NaCl space-holders, (ii) then infiltrated by Ag melt in the air. 95% relative density is achieved for the Ag/SnO2 composites. The microstructure evolution during the sintering and infiltration are investigated. 10,000 times make-and-break operations are conducted to evaluate the arc erosion resistance of the architectured composite, the temperature rise of the prepared Ag-60vol.%SnO2 composite decreases ∼90% compared with the particle dispersed composites. The microstructure of the arc-erased layer is analyzed and reveals that the SnO2 skeleton effectively suppresses the formation of the SnO2-rich layer, providing good arc erosion resistance and the potential for long lifetime contacts.

Ultrafast response and high-sensitivity acetone gas sensor based on porous hollow Ru-doped SnO2 nanotubes

Ru-doped porous hollow SnO2 nanotubes were prepared by simple electrospinning method, and their crystal structures, morphologies, and formation mechanism of porous hollow nanotubes were fully elucidated. The sensor based on the porous hollow Ru-doped SnO2 nanotubes shows an excellent sensing response of ~340 with ultrafast response time of 0.58 s at 250 ℃ to 100 ppm acetone. Moreover, the sensor exhibits good stability and excellent selectivity. Finally, the mechanism of the enhanced gas sensing properties was explained as the comprehensive effects of the larger specific surface area resulted from the hollow porous nanotubes structure, the ultra-fine SnO2 grain size, and the catalyst of RuO2. This research suggests the Ru-doped SnO2 nanotubes have the potential to be used as highly reliable and high-performance sensing layer for acetone gas sensors.

Improve the Formaldehyde Gas-Sensing Performance of 3D Porous SnO2 by Controlling the Calcination Time and the Amount of Holmium Doped

Improve the Formaldehyde Gas-Sensing Performance of 3D Porous SnO2 by Controlling the Calcination Time and the Amount of Holmium Doped

MOF-based nanoscale Pt catalyst decorated SnO2 porous nanofibers for acetone gas detection

Gas sensors fabricated by metal oxide semiconductors (SMOs) exhibited promising prospect for acetone detection due to their high sensitivity, small sizes, simple operation, facile fabrication and low cost. However, the current SMOs still face diverse challenges involving high power consumption, low response, poor anti-interfering ability and weak repeatability. In this work, in order to meet the ever-increasing requirements for acetone detection, Pt nanoparticles (NPs) were embedded into ZIF-8 templates then loaded on porous SnO2 nanofibers (NFs) via electrospinning and subsequent annealing process with a control of heating rate. The gas sensing characteristics of pristine SnO2, SnO2-ZnO, and Pt-ZnO-SnO2 porous NFs were investigated. The Pt-ZnO-SnO2 porous NFs displayed an ultrahigh response (Ra/Rg = 104.26–100 ppm at 170 °C), high selectivity and low detection limit (200 ppb) to acetone during dynamic measurements. In this study, the advanced sensing behavior can be ascribed to the multi-heterojunctions construction at the interface of SnO2-ZnO, ZnO/PtO2 and SnO2/PtO2, the increasement of oxygen vacancies, as well as the electronic and chemical sensitization of Pt NPs. The well-dispersed and ultrasmall-sized Pt NPs (~3 nm) functionalized on porous SnO2 NFs also play an essential role in fabricating high-performance acetone sensors.

Promotion on Formaldehyde Sensing of 3D Porous SnO2 by Eu Doping

The formaldehyde sensor with excellent performance has a wide range of applications in industrial production and the monitoring of many household products. Eu-doped 3D porous SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with a pore size of 120 nm were synthesized as a base material for high-performance formaldehyde sensors. The gas sensitivity test results show that the sensitivity of 3.6% Eu-doped 3D porous SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with a pore size of 120 nm to 20 ppm formaldehyde is 24 at an operating temperature of 230 °C, which is 1.8 times that of pure 3D porous SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with the same aperture. Moreover, the formaldehyde sensor made of 3.6% Eu-doped 3D porous SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with a pore size of 120 nm has good selectivity, with a selectivity coefficient of 5.5 for formaldehyde, good repeatability, and low detection limit (0.5 ppm/1.7). These excellent gas sensitivity characteristics are mainly attributed to the 3D porous SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with a loose and nano-scale porous morphology, more oxygen vacancies and Eu doping. Therefore, the gas-sensing of the metal oxide semiconductor material can be further improved by doping.

Highly Porous SnO2/TiO2 Heterojunction Thin-Film Photocatalyst Using Gas-Flow Thermal Evaporation and Atomic Layer Deposition

Highly porous heterojunction films of SnO2/TiO2 were prepared using gas-flow thermal evaporation followed by atomic layer deposition (ALD). Highly porous SnO2 was fabricated by introducing an inert gas, Ar, during thermal evaporation. To build heterogeneous structures, the TiO2 layers were conformally deposited on porous SnO2 with a range of 10 to 100 cycles by means of ALD. The photocatalytic properties for different TiO2 thicknesses on the porous SnO2 were compared using the degradation of methylene blue (MB) under UV irradiation. The comparisons showed that the SnO2/TiO2-50 heterostructures had the highest photocatalytic efficiency. It removed 99% of the MB concentration, and the decomposition rate constant (K) was 0.013 min−1, which was approximately ten times that of the porous SnO2. On the other hand, SnO2/TiO2-100 exhibited a lower photocatalytic efficiency despite having a TiO2 layer thicker than SnO2/TiO2-50. After 100 cycles of TiO2 ALD deposition, the structure was transferred from the heterojunction to the core–sell structure covered with TiO2 on the porous SnO2, which was confirmed by TEM analysis. Since the electrons photogenerated by light irradiation were separated into SnO2 and produced reactive oxygen, O2−, the heterojunction structure, in which SnO2 was exposed to the surface, contributed to the high performance of the photocatalyst.

Influence of calcination temperature on the gas-sensing performance of 3D porous SnO2 to formaldehyde

Porous SnO2 has received widespread attention because of its special structure. We successfully prepared 3 D porous SnO2 using carbon spheres as a template. Scanning electron microscopy (SEM) morphology characterization results show that with the increase of the calcination temperature (400 °C, 450 °C, 500 °C, 550 °C, 600 °C), the morphology of the 3 D porous SnO2 surface has changed. And when the calcination temperature is 500 °C, the pore distribution on the sample surface is more uniform. The results of nitrogen adsorption showed that the sample obtained when the calcination temperature was 500 °C had the largest specific surface area (62.02 m2/g). Different samples were tested for gas sensitivity, and we found that as the calcination temperature increased, the sensitivity of the samples to formaldehyde first increased and then decreased. The sensitivity of 3 D porous SnO2 calcined at 500 °C to 50 ppm formaldehyde is up to 27. The minimum concentration of formaldehyde is 0.5 ppm (sensitivity value is 2). Moreover, 3 D porous SnO2 calcined at 500 °C has a fast response time (2 s), low working temperature (230 °C), good selectivity (the selection coefficient for formaldehyde is 6.74) and linearity. These excellent performances are mainly due to the uniform 3 D porous structure, large specific surface area and more oxygen vacancies on the surface, which make it a promising formaldehyde sensor material.

Metal-organic framework-derived porous SnO2 nanosheets with grain sizes comparable to Debye length for formaldehyde detection with high response and low detection limit

The development of metal oxide semiconductors-based gas sensors that can simultaneously achieve high response and low detection limit towards formaldehyde (HCHO) remains a great challenge so far. In this work, we present the formation of porous SnO2 nanosheets via direct calcination of a Sn-based metal-organic framework that was prepared via a facile wet chemistry method with deionized water as solvent at 80 °C. The porous SnO2 nanosheets are found to be constructed by the interconnection of ultrafine nanoparticles with sizes of 4–9 nm, which is comparable to the Debye length of SnO2. The gas sensor based on the porous SnO2 nanosheets demonstrate a broad detection range towards HCHO (0.05–500 ppm), a low operating temperature (140 °C), very high response (540.8 to 50 ppm HCHO), extremely low detection limit (0.31 ppb), ideal selectivity, and outstanding reproducibility and durability. The excellent HCHO-sensing performance of the SnO2 sensor could be attributed to the high specific surface area (125.92 m2/g) of the porous SnO2 nanosheets, the ultrafine sizes of the SnO2 nanoparticles, and the presence of abundant of mesopores within the nanosheets. The porous SnO2 nanosheets with excellent HCHO-sensing characteristics may find widespread applications in fabricating gas sensors for detecting ppb-level HCHO.

Photo-characterization of Organic Dye-Sensitized Tin Oxide Films

Objectives: To develop organic dye sensitized film electrodes from highly porous tin oxide (SnO2) thin films prepared at room temperature using the SILAR technique. Methods/Analysis: SnO2 films were fabricated by the successive ionic layer adsorption and reaction (SILAR) technique at room temperature and its sensitization was done using the organic dye Rose Bengal (RB). The effect of sensitization on the as-grown and annealed film electrodes was investigated. Findings : Crystalline films with cauliflower-like morphology exhibit a large inherent adsorptive surface area and exhibit steady transmittance of 60-80% in the visible region. As-grown SnO2 films possess higher porosity and lower refractive index than that of the annealed films. SnO2 films have a resistivity in the range of 10-2-10-3 ΩcmΩcm. The dye adsorbed SnO2 film electrodes have much higher absorbance and cover a broad visible region compared to the bare SnO2 film electrodes. RB sensitization leads to an accelerated improvement in absorbed photon energy through the visible region of the spectrum extending from 2 to 3.75 eV. Novelty: Contrary to the sophisticated methods of preparation in the reported literature, highly porous crystalline SnO2 thin films were prepared at room temperature, using glacial acetic acid and hydrogen peroxide by a cost-effective simple wet chemical method. Work demonstrates that SnO2 films sensitized with RB act as an excellent dye-sensitized electrode, which can absorb almost half the visible spectrum (400-600 nm) of solar radiations. We believe that this is the unique report of surface modification of wet chemically prepared SnO2 electrodes by the photo-sensitizer RB. Keywords Photo­characterization, rose bengal, sensitization, thin films, tin oxide electrodes

Multilayer porous Pd-doped SnO2 thin film: Preparation and H2 sensing performance

Porous pure and Pd-doped SnO2 films are prepared using sol-gel synthesis with polystyrene (PS) microspheres as the template. Different characterizations are performed to analyze the microstructure and morphology of the films. The sensing performance of the films at various temperatures and hydrogen concentrations is investigated. Results show that high concentration of PS template significantly influences the continuity of films and the H2 sensing performance. The porous SnO2 film with 0.1 wt% PS microspheres exhibits the best performance. At 225 °C, the response magnitude of the porous 1 mol% Pd-doped SnO2 thin film to 1000 ppm H2 is 93.18, which is approximately 10.58 times of the pure sample.

Improved triethylamine sensing properties of fish-scale-like porous SnO2 nanosheets by decorating with Ag nanoparticles

Three dimensional (3D) porous nanostructures assembled by low-dimensional nanomaterials are widely applied in gas sensor according to porous structure which can facilitate the transport of gas molecules. In this work, fish-scale-like porous SnO2 nanomaterials assembled from ultrathin nanosheets with thickness of 16.8 nm were synthesized by a facile hydrothermal route. Then Ag nanoparticles were decorated on the surface of SnO2 nanosheets via one-step method to improve their gas-sensing performances. The sensing properties of pristine SnO2 and Ag/SnO2 nanosheets were investigated intensively. After decorating with Ag nanoparticles, the characteristics of SnO2 based sensor for triethylamine detection were significantly improved. Especially, the Ag/SnO2 based sensor with Ag content of 2 at% exhibited the highest triethylamine sensing sensitivity at optimum work temperature of 170 °C. The improved sensing properties of Ag/SnO2 sensors were attributed to the sensitizing actions of Ag nanoparticles as well as the unique hierarchical porous architecture.