Synthesis and Gas-sensing Performance of Nanosized SnO_2

Nanosized tin dioxide particles were prepared by sol-gel dialytic processes with tin(Ⅳ) chloride and alcohol as start materials. The nanoparticles of tin dioxide were charactered by thermogravimetry and differential thermal analysis(TG-DTA), X-ray diffraction(XRD), transmission electron microscopy (TEM) and BET. The results show that the average diameter of tin dioxide particles dried at 353 K was about 2 nm. Even if the tin dioxide particles were calcined at 873 K, the average diameter of particles was less than 10 nm. The removal of Cl- was solved by using this kind of method. The mechanism of the formation of tin dioxide nanosized particles was proposed and analyzed in this paper. We also measured the sensitivity of the sensor based on the tin oxide powder calcined at 673 K to NH 3, alcohol, acetone, hexane and CO. The gas-sensing performance results indicate that this sensor has a higher sensitivity to alcohol and acetone, and selectivity for NH 3, hexane and CO at an operating temperature of 343 K.

Ag3PO4 Microcrystals Synthesized by Room-Temperature Solid State Reaction:Enhanced Photocatalytic Activity and Photoelectronchemistry Performance

Ag3PO4 microcrystals with highly enhanced visible light photocatalytic activity are prepared by a facile and simple solid state reaction at room temperature. The composition, morphology and optical properties of the asprepared Ag3PO4 microcrystMs are characterized by x-ray diffraction, scanning electron microscopy and UV-vis diffuse reflectance spectra. The photocatalytie properties of Ag3PO4 are investigated by the degradation of both methylene blue and methyl orange dyes under visible light irradiation. The as-prepared Ag3PO4 microcrystals possess high photocatalytic oxygen production with the rate of 673μmolh-1g-1. Moreover, the as-prepared Ag3PO4 microcrystals show an enhanced photoelectrochemistry performance under irradiation of visible light.

Preparation and gas-sensing performance of SnO2/NiO composite oxide synthesized by microwave-assisted liquid phase deposition

We synthesized SnO2/NiO composite oxides by microwave-assisted liquid phase deposition to improve their surface physico-chemical properties and gas-sensing selectivity,and we investigated how the molar ratio of Ni^2+to Sn^4+and the microwave power affected their gas-sensing performance.The microstructure,surface physico-chemical states,and morphology of the samples were characterized by X-ray diffraction,X-ray photoelectron spectroscopy,and scanning electron microscopy,respectively.Nitrogen adsorption-desorption isotherms were used to characterize the specific surface areas of the samples.Our results showed that microwave-assisted liquid phase deposition increased the surface-adsorbed oxygen content and the specific surface area of the SnO2/NiO composite oxide from about 22to 120m2/g.When the molar ratio of Ni^2+to Sn^4+was 0.1,the gas response to 1000ppm ethanol gas reached 84.7at a lower working voltage of 3.5V.However,the optimum working voltages for methanol and acetone gas were 4.5and 4.0V,respectively.Thus,a new method was found to improve the selectivity of the gas sensor.Moreover,at a working voltage of 4.0V,the gas response of a SnO2/NiO gas sensor synthesized by microwave-assisted liquid phase deposition with the optimum radiation power of 450W to 1000ppm acetone gas was 49.7,twice that of a sensor synthesized by traditional liquid phase deposition.

Strategies and challenges for enhancing performance of MXene-based gas sensors:a review

With the advantages of metal conductivity,large specific surface area,and rich surface functional groups,two-dimensional(2D)MXenes have shown great potential in the field of gas sensing.However,gas sensors fabricated with pristine MXenes generally suffer from several problems such as low sensitivity,poor selectivity,significant baseresistance drift,and poor environment stability.Therefore,many efforts have been devoted to overcoming these problems.In this review,we review the progress on MXenebased gas sensors and summarize several efficient strategies(including structural design,surface modification,inorganic Schottky j unction/heterojunction sensitization,polymer addition,and metal-ion intercalation)to promote the gassensing performance.In addition,the major challenges and future development directions of MXene-based gas sensors are also outlined in the present review.

SnO_(2)nanostructured materials used as gas sensors for the detection of hazardous and flammable gases:A review

SnO_(2)has been extensively used in the detection of various gases.As a gas sensing material,SnO_(2)has excellent physical-chemical properties,high reliability,and short adsorption-desorption time.The application of the traditional SnO_(2)gas sensor is limited due to its higher work-temperature,low gas response,and poor selectivity.Nanomaterials can significantly impact gas-sensitive properties due to the quantum size,surface,and small size effects of nanomaterials.By applying nanotechnology to the preparation of SnO_(2),the SnO_(2)nanomaterial-based sensors could show better performance,which greatly expands the application of SnO_(2)gas sensors.In this review,the preparation method of the SnO_(2)nanostructure,the types of gas detected,and the improvements of SnO_(2)gas-sensing performances via elemental modification are introduced as well as the future development of SnO_(2)is discussed.

Solvothermal Synthesis of α-Fe2O3 Porous Nanobelts and Their Enhanced Acetone-sensing Properties

Porous α-Fe2O3 nanobelts have been prepared via a solvothermal route and subsequent calcination. The as-prepared nanostructure was characterized by XRD, FESEM, TEM, N2 adsorption-desorption isotherms, etc. The α-Fe2O3 nanobelts presented obvious porous structures with the length of ca. 1~2μm, width of ca. 200~350 nm and thickness of ca. 30~60 nm. It was found that the assistance of inorganic additives played an important role in the shape control of α-Fe2O3 nanostructure. The gas-sensing performance of the fabricated sensor based on α-Fe2O3 nanobelts sample was also investigated, and the response towards 1000 ppm acetone can reach 24.4. In addition, the gas-sensing conductive mechanism of the sensor was also proposed.

Two-dimensional transition metal MXene-based gas sensors:A review

As an emerging star in the family of two-dimensional(2D)materials,2D transition metal carbides,carbonitrides and nitrides,collectively referred to as MXenes,have large specific surface area,rich active sites,metallic conductivity and adjustable surface chemical properties.These features make MXenes promising candidates for gas-sensing materials.For the past few years,MXene-based sensors have drawn increasing attention due to their enhanced sensor performance.Based on this,this review systematically represents the structure,synthesis methods and properties of MXenes,and summarizes their applications in gas sensors.Firstly,the types,structure,main synthesis methods and properties of MXenes are introduced in a comprehensive way.Next,the corresponding design principle and working mechanism of MXene-based gas sensor are clarified.Subsequently,the sensing performances of pristine MXenes and the MXene-based nanocomposite are discussed.Finally,some future opportunities and challenges of MXene-based sensors are pointed out.