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1.
Nanocrystalline tin dioxide modified by Pd and Pt clusters or by bimetallic PdPt nanoparticles was synthesized. Distribution of the modifers on the SnO2 surface was studied by high-resolution transmission electron microscopy and energy dispersive X-ray microanalysis with element distribution mapping. It was shown that the Pd/Pt ratio in bimetallic particles varies over a broad range and does not depend on the particle diameter. The effect of platinum metals on the reducibility of nanocrystalline SnO2 by hydrogen was determined. The sensing properties of the resulting materials towards 6.7 ppm CO in air were estimated in situ by electrical conductivity measurements. The sensor response of SnO2 modified with bimetallic PdPt particles was a superposition of the signals of samples with Pt and Pd clusters.  相似文献   

2.
New hybrid materials based on nanocrystalline tin dioxide and two types of surface-immobilized polymer organosilicon structures with hydrocarbon substitutes were synthesized for gas sensors application. The sensing responses of pure SnO2 and hybrid samples were determined in the presence of NO2 (ppb range), CO (ppm range) and different humidity (RH = 15 – 95 %). Also the influence of water presence on sensor signal towards NO2 and CO was analyzed. Strong influence of nature of hydrocarbon substitutes on sensor response value towards NO2 and H2O was discovered.  相似文献   

3.
The sensor properties of nanostructured films of SnO2, In2O3, and their combinations for detecting CO in air in the temperature range of 330–520°C were investigated. It was found that SnO2 films show the least sensitivity to CO. Sensitivity grows as the concentration of In2O3 in SnO2 increases, and it reaches its maximum value in pure In2O3. At the same time, the maximum of sensitivity to CO in air shifts towards low temperatures. Sensor response time was found to be about 1 s for the studied SnO2 and In2O3 films, and about 0.5 s for the composite film. The mechanism of sensor sensitivity for the studied metal oxide films in detecting CO in air is discussed.  相似文献   

4.
SnO2/Pd nanocomposites were synthesized via sol-gel method followed by variable processing procedures. The materials are sensitive to CO gas in the concentration range 2-100 ppm at room operating temperature. It was shown that modification of nanocrystalline tin dioxide by Pd changes the temperature dependence of sensor response, decreasing the temperature of maximal signal. To understand the mechanism of room temperature CO sensitivity, a number of SnO2/Pd materials were characterized by XRD, TEM, BET, XPS and TPR techniques. From the results of FTIR, impedance and sensing measurements under variable ambient conditions it was concluded that improvement in CO sensitivity for Pd-modified SnO2 is due to alteration of CO oxidation pathway. The reaction of CO with surface OH-groups at room temperature was proposed, the latter being more reactive than oxygen species due to the possible chain character of the reactions. It was proposed that Pd additive may initiate chain processes at room temperature.  相似文献   

5.
Double-layer structures based on gas-sensitive semiconducting metal oxides and silicalite-1 were tested in detection of carbon monoxide in humid air. Pure tin dioxide and that modified with antimony and palladium served as materials of the sensitive layer. Upon deposition of a silicalite-1 layer on SnO2 and SnO2/PdOx, the signal for CO in dry air at room measurement temperature (T = 25°C) grows, but an increase in the air humidity results in that the sensor sensitivity fully disappears. Raising the measurement temperature to 100°C makes weaker the adverse effect of the humidity. The double-layer structure containing the SnO2(Sb)/PdOx nanocomposite is characterized by the most stable sensor signal that is independent of the air humidity within the range RH = 4?65%.  相似文献   

6.
Synthesis of Sn(IV) and La(III) based nanocomposites has been effectuated. According to the data obtained by XRD and TPR-H2 methods, it is supposed that La in nanocompites is located in amorphous La2Sn2O7 segregation. The effect of La(III) on the adsorption properties of SnO2 surface and concentration of chemisorbed oxygen was determined. Sensor properties of obtained materials towards 10 ppm of CO in air were studied by in situ DC conductance measurements. It is shown that La introduction allows to increase sensor response of SnO2 during CO detection in air.  相似文献   

7.
Hierarchical porous tin dioxide has been successfully prepared through a fast one-pot template-free synthesis route. The boiling of the mixture of alcohol and glycerol can be utilized to generate nanopores in the SnO2 monolith. Polycrystalline hierarchical SnO2 with well proportioned composition has also been obtained in the pore walls of tin dioxide.  相似文献   

8.
SnO2/B2O3 samples were produced by a reaction between SnCl4, H3BO3, and (NH2)2CO in a boiling aqueous solution. The Sn: B molar ratio in these samples was 1: 1, 1: 2, and 1: 3. The phase composition and degree of crystallinity of these materials was studied. The surface acidity of the samples was analyzed by the method based on a temperature-programmed reaction of dehydration of 2-methyl-3-butyn-2-ol. Thermal transformations of SnO2/B2O3 samples were examined by means of differential-thermal analysis.  相似文献   

9.
The dependence of the impedance of low-temperature sensors for carbon dioxide based on the solid-state electrochemical cells Na0.5WO3/Na5GdSi4O12/SnO2(Sb2O4) on the concentration of carbon dioxide in the air was studied. The reversible change in the sensor resistance was shown to be due to adsorption processes at intergrain boundaries of the solid electrolyte. The composition of the products of the electrochemical processes occurring in the sensors was established. Electronic Publication  相似文献   

10.
The influence of the dispersity and structural and phase state of oxide materials based on Fe2O3 and SnO2 on the gas-sensitive properties of these materials used as sensitive layers in chemical sensors was considered. It was found that high-dispersity Fe2O3-SnO2 (Fe: Sn = 9: 1) ceramic layers possessed high sensitivity to ethanol vapor in both dry and humid atmosphere and low sensitivity to CO and CH4. The maximum response to ethanol vapor in humid atmosphere was characteristic of layers with structures of substitution-interstitial solid solutions of Sn4+ in α-Fe2O3.  相似文献   

11.
It is suggested that, for the operation of platinum catalysts based on tin dioxide in air hydrogen fuel cells, hydrogen spillover (migration) leading to a change in the electron and proton contributions of the catalyst conductivity is of crucial importance. The hydrogen adsorption, dissociation, and migration in the platinum-tin dioxide-hydrogen system surface have been modeled by the density functional theory method within the generalized gradient approximation (GGA) under periodic conditions using a projector-augmented plane-wave (PAW) basis set with a pseudopotential. It has been demonstrated that the adsorption energy of a hydrogen molecule onto a platinum cluster increases from 1.6 to 2.4 eV as the distance to the SnO2 substrate decreases. The calculated Pt-H bond length for adsorbed structures is 1.58–1.78 Å. The computer modeling has demonstrated that: (1) the hydrogen adsorption energy on clusters is higher than on the perfect platinum surface; (2) dissociative chemisorption onto Pt n clusters can occur without a barrier and depends on the adsorption site and the cluster structure; (3) the adsorption energy of hydrogen onto the SnO2 surface is higher than the adsorption energy onto the platinum cluster surface: (4) multiple H2 dissociation on the tin dioxide surface occurs with a barrier; (5) the dissociation adsorption of hydrogen molecules onto the platinum cluster surface followed by atom migration (spillover) is energetically favorable.  相似文献   

12.
To expand the range of precursors used in the sol–gel technology for applying nanostructured SnO2 thin films promising as components of semiconductor chemical gas sensors, the efficiency of using tin acetylacetonate solutions with various precursor concentrations was demonstrated. It was determined that finely divided SnO2 with a crystallite size of 3–4 nm (cassiterite) can be obtained by hydrolysis by atmospheric moisture in the course of solvent evaporation at room temperature. Using tin acetylacetonate solutions with various precursor concentrations for applying SnO2 thin films by dip coating to the surface of rough ceramic Al2O3-based substrates with platinum interdigital electrodes and a microheater resulted in significant differences in microstructure, continuity, thickness, and porosity of the produced coatings. In a lower-concentration (0.13 mol/L) tin acetylacetonate solution, a multilayer dense continuous SnO2 coating was applied, whereas in a higher-concentration (0.25 mol/L) solution, the formed layer comprised aggregated nanoparticles 30–60 nm in size and had much more defects and higher porosity. The sensitivity of the obtained thin-film nanostructures to the most practically important gaseous analytes: CO, H2, CH4, CO2, and NO2. The produced two-dimensional nanomaterials were shown to be promising for detecting carbon monoxide at 200–300°C in dry air.  相似文献   

13.
Specimens of tin dioxide with modifying Sb and Pt additives are synthesized. Their physicochemical properties (specific surface area, porosity, and conductivity), chemisorption and catalytic activity in the model reaction of CO oxidation are studied. A considerable chemisorption of CO on SnO2 and SnO2-SbO x is observed at 150–180°C. The oxidation of CO in the flow of gases starts in the same temperature range. An addition of platinum leads to a significant increase in the rate of CO oxidation, the reaction starts at 80°C. It is proposed that the process proceeds at the SnO2/Pt interface.  相似文献   

14.
Dopants in nanocrystalline tin dioxide   总被引:3,自引:0,他引:3  
The review surveys studies aimed at constructing new materials for gas sensors based on nanocrystalline tin dioxide. The influence of doping with various impurities (Pt, Pd, Ru, Rh, Cu, Ni, or Fe) on the composition, microstructure, and electrophysical and sensor properties of nanocrystalline SnO2 was discussed. The conditions for the preparation of powders and thick and thin SnO2 films by the wet chemical method and aerosol pyrolysis of organometallic compounds are reported. The mechanism of interaction of pure and doped nanocrystalline SnO2 with a gas phase was analyzed based on the data from Mossbauer, Auger electron, and X-ray photoelectron spectroscopy and the results of in situ Raman spectroscopy, XANES, and conductivity measurements.  相似文献   

15.
Electrical properties of synthesized nanostructured materials based on nanocrystalline tin dioxide modified with copper iodide and polychlorotrifl uoroethylene were studied. It was shown that the complex dielectric permittivity in the microwave range and the low-frequency electrical conductivity of the polymeric composites depend on the copper iodide concentration on the surface of tin dioxide and reach the maximum values at a volume fraction of CuI of about 0.5. The percolation thresholds were determined for the three-component system. Their values increase from 0.04 to 0.05 vol. fraction as the content of copper iodide in the CuI/SnO2 system is raised from 0.04 to 0.6 vol. fraction.  相似文献   

16.
This paper presents the results of our XPS (X-ray photoelectron spectroscopy) and XANES (X-ray absorption near edge structure) studies of tin oxide nanolayers obtained by magnetron spraying of the metal and its further oxidation in air at different temperatures. It was shown that at 240°C (annealing temperature), tin monoxide was dominant in the surface layer of the samples. When the temperature was increased to 450°C, the phase composition corresponded to tin dioxide. Increased sorption ability was found for the samples oxidized at 450°C. The band structure model of SnO x nanolayers obtained by superposition of the XANES and XPS data revealed cross transitions with energy ~3.7 eV in the presence of the SnO and SnO2 phases. Surface doping of nanolayers with palladium gave the Pd, PdO, and PdO2 components, among which PdO was most intense. Alternate treatments with O2 and H2 gases led to the disappearance of palladium dioxide and the reduction of PdO to the Pd metal. After the volume doping of nanoplayers with palladium, the surface layer contained PdO and PdO2; the latter was represented by two types of particles with different sizes.  相似文献   

17.
Nanostructure luminescent ZnO and SnO2 materials are prepared by a two-step solid-state method based on the solution preparation of the macromolecular precursors ZnCl2·Chitosan and SnCl2·Chitosan having different ratios (1:1, 1:5 and 1:10), their pyrolysis under air at 800 °C. The pyrolytic ZnO and SnO2 nanomaterials show a dependence of the particle size, morphology and luminescent properties with the ratio [metal/polymer] in the MCl2·Chitosan precursors. Thus, ZnO semiconductor materials exhibit luminescence spectra with several emission at 440 nm corresponds to a radiative transition of an electron from the shallow donor level of oxygen vacancies, and the zinc interstitial, to the valence band. On the other hand, the photoluminescence spectrum of the nanostructured SnO2 shows an intense blue luminescence at a wavelength of 420 nm which may be attributed to oxygen-related defects that have been introduced during the growth process of the nanoparticles. Additionally, whereas SnO2 was successfully incorporated into SiO2 structure (SnO2//SiO2) by pyrolysis of solid-state mixtures of the precursors SnCl2·Chitosan in the presence of SiO2, the same reaction carried out with ZnCl2·Chitosan precursors led to a mixture of Zn2SiO4 and SiO2. Thus, this new methodology yields nanostructured semiconductor materials, ZnO and SnO2, suitable for optoelectronic and sensor solid-state devices.  相似文献   

18.
The Sb doped tin dioxide electrode (Sb-doped SnO2) inter-layer was prepared using electroposition layer-by-layer onto a titanium plate, and the Sb-doped SnO2 surface catalytic layer (Ti/SnO2-Sb) was prepared using thermo-decomposition method. Accelerated service life tests were carried out in 0.5 M H2SO4 solution and 1.0 M NaOH solution, respectively. The deactivation mechanism of the electrodes is studied using oxygen evolution reaction (OER) as the reaction mode. Cyclic voltammetry test showed that the electrodes after accelerated life tests had no catalytic-oxidizing activity upon phenol. Electrochemical impedance spectroscopy (EIS) analysis exhibited that the membrane resistance of the deactivated electrode increases obviously in 0.5 M H2SO4 solution and 1.0 M NaOH solution, with the values of 1231 and 90.6 Ω, respectively. The structure, morphology and the content of the fresh and deactivated electrode were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray detector (EDX). This suggested that the Ti content on the electrode surface increases after deactivation, and TiO2 membrane with poor conductivity is grown on the electrode surface.  相似文献   

19.
A nanocomposite consisting of a few layers of graphene (FLG) and tin dioxide (SnO2) was prepared by ultrasound-assisted synthesis. The uniform SnO2 nanoparticles (NPs) on the FLG were characterized by X-ray diffraction in terms of lattice and phase structure. The functional groups present in the composite were analyzed by FTIR. Electron microscopy (HR-TEM and FE-SEM) was used to study the morphology. The effect of the fraction of FLG present in the nanocomposite was investigated. Sensitivity, selectivity and reproducibility towards resistive sensing of liquid propane gas (LPG) was characterized by the I-V method. The sensor with 1% of FLG on SnO2 operated at a typical voltage of 1 V performs best in giving a rapid and sensitive response even at 27 °C. This proves that the operating temperature of such sensors can be drastically decreased which is in contrast to conventional metal oxide LPG sensors.
Graphical abstract Schematic of a room temperature gas sensor for liquefied petroleum gas (LPG). It is based on the use of a few-layered graphene (1 wt%)/SnO2 nanocomposite that was deposited on an interdigitated electrode (IDEs). A sensing mechanism for LPG detection has been established.
  相似文献   

20.
In this work, tin(II) oxalate was studied as a novel chloride-free starting material for the preparation of a stable Sn-containing precursor solution. This precursor was applied for the chemical solution deposition (CSD) of transparent conducting coatings of SnO2 on Si/SiO2 substrates. An influence of synthesis parameters, such as pH, complexing agent to metal ion ratio on the stability of the citrato peroxo Sn(IV) precursor has been investigated in this study. Insights into the precursor chemistry and its thermal decomposition based on TG-DSC analysis are also presented. The obtained SnO2 films were characterized by high temperature X-ray diffraction (HT-XRD) and scanning electron microscopy (SEM) to evaluate phase purity and film thickness, respectively.  相似文献   

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