Achieving highly-efficient H2S gas sensor by flower-like SnO_(2)–SnO/porous GaN heterojunction

A flower-like SnO_(2)–SnO/porous Ga N(FSS/PGaN) heterojunction was fabricated for the first time via a facile spraying process, and the whole process also involved hydrothermal preparation of FSS and electrochemical wet etching of GaN,and SnO_(2)–SnO composites with p–n junctions were loaded onto PGaN surface directly applied to H_(2)S sensor. Meanwhile,the excellent transport capability of heterojunction between FSS and PGaN facilitates electron transfer, that is, a response time as short as 65 s and a release time up to 27 s can be achieved merely at 150℃ under 50 ppm H_(2)S concentration, which has laid a reasonable theoretical and experimental foundation for the subsequent PGaN-based heterojunction gas sensor.The lowering working temperature and high sensitivity(23.5 at 200 ppm H2S) are attributed to the structure of PGaN itself and the heterojunction between SnO_(2)–SnO and PGaN. In addition, the as-obtained sensor showed ultra-high test stability.The simple design strategy of FSS/PGaN-based H_(2)S sensor highlights its potential in various applications.

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.

SnO_(2)/Co_(3)O_(4)nanofibers using double jets electrospinning as low operating temperature gas sensor

SnO_(2)/Co_(3)O_(4)nanofibers(NFs)are synthesized by using a homopolar electrospinning system with double jets of positive polarity electric fields.The morphology and structure of SnO_(2)/Co_(3)O_(4)hetero-nanofibers are characterized by using field emission scanning electron microscope(FE-SEM),transmission electron microscope(TEM),x-ray diffraction(XRD),and x-ray photoelectron spectrometer(XPS).The analyses of SnO_(2)/Co_(3)O_(4)NFs by EDS and HRTEM show that the cobalt and tin exist on one nanofiber,which is related to the homopolar electrospinning and the crystallization during sintering.As a typical n-type semiconductor,Sn O_(2)has the disadvantages of high optimal operating temperature and poor reproducibility.Comparing with Sn O_(2),the optimal operating temperature of SnO_(2)/Co_(3)O_(4)NFs is reduced from 350℃to 250℃,which may be related to the catalysis of Co_(2)O_(2).The response of SnO_(2)/Co_(3)O_(4)to 100-ppm ethanol at 250℃is 50.9,9 times higher than that of pure Sn O_(2),which may be attributed to the p–n heterojunction between the n-type Sn O_(2)crystalline grain and the p-type Co_(2)O_(2)crystalline grain.The nanoscale p–n heterojunction promotes the electron migration and forms an interface barrier.The synergy effects between Sn O_(2)and Co_(2)O_(2),the crystalline grain p–n heterojunction,the existence of nanofibers and the large specific surface area all jointly contribute to the improved gas sensing performance.

High-sensitivity formaldehyde gas sensor based on Ce-doped urchin-like SnO_(2) nanowires derived from calcination of Sn-MOFs

Metal-organic frameworks(MOFs)have attracted widespread attention due to their regular structures,multiple material centers,and various ligands.They are always considered as one kind of ideal templates for developing highly sensitive and selective gas sensors.In this study,the advantages of MOFs with the high specific surface area(71.9891 m^(2)·g^(-1))and uniform morphology were fully utilized,and urchin-like SnO_(2) nanowires were obtained by the hydrothermal method followed by the calcination using Sn-MOFs consisting of the ligand of C_(9)H_(6)O_(6)(H_(3)BTC)and Sn/Ce center ions as sacrificial templates.This unique urchin-like nanowire structure facilitated gas diffusion and adsorption,resulting in superior gas sensitivity.A series of Ce-doped SnO_(2) nanowires with different doping ratios were synthesized,and their gas sensing properties towards formaldehyde were studied.The resulted Ce-SnO_(2) was revealed to have high sensitivity(201.2 at 250℃),rapid response(4 s),long-term stability,and good repeatability for formaldehyde sensing,and the gas sensing mechanism of Ce-SnO_(2) exposed to formaldehyde was also systematically discussed.

The electric field effect on the sensitivity of tin oxide gas sensors on nanostructured substrates at low temperature

A novel low-temperature SnO_(2) gas sensor was prepared and studied on silicon nanostructures formed by femtosecond laser irradiation.By applying a bias voltage on the silicon substrate to alter the charge distribution on the surface of the SnO_(2),carbon monoxide(CO),and ammonia(NH_(3))gas can be distinguished by the same sensor at room temperature.The experimental results are explained with a mechanism that the sensor works at low temperature because of adsorption of gas molecules that trap electrons to the surface of the SnO_(2).

Synthesis of porous flower-like SnO_(2)/CdSnO_(3) microstructures with excellent sensing performances for volatile organic compounds

Porous flower-like SnO_(2)/CdSnO_(3) microstructures self-assembled by uniform nanosheets were synthesized using a hydrothermal process followed by calcination,and the sensing performance was measured when a gas sensor,based on such microstructures,was exposed to various volatile organic compound(VOC)gases.The response value was found to reach as high as 100.1 when the SnO_(2)/CdSnO_(3) sensor was used to detect 100 ppm formaldehyde gas,much larger than those of other tested VOC gases,indicating the high gas sensitivity possessed by this sensor especially in the detection of formaldehyde gas.Meanwhile,the response/recovery process was fast with the response time and recovery time of only 13 and 21 s,respectively.The excellent gas sensing performance derive from the advantages of SnO_(2)/CdSnO_(3),such as abundant n-n heterojunctions built at the interface,high available specific surface area,abundant porosity,large pore size,and rich reactive oxygen species,as well as joint effects arising from SnO_(2) and CdSnO_(3),suggesting that such porous flower-like SnO_(2)/CdSnO_(3) microstructures composed of nanosheets have a high potential for developing gas sensors.

Preparation of{200}crystal faced SnO_(2) nanorods with extremely high gas sensitivity at lower temperature

Demand for simple and effective gas sensing sensors is growing rapidly due to the growing threat of triethylamine(TEA).Semiconductor tin oxide(SnO_(2))is one of the most widely used sensing materials for metal oxide gas sensors.In recent years,a lot of binary ternary compound researches have been carried out.In this paper,five different SnO_(2) samples were synthesized by simple synthesis method to understand the internal relationship and obtain different gas sensing characteristics.Based on the low temperature nitrogen adsorption tests and the atomic arrangement model,it can be inferred that different exposed surfaces play a key role in TEA sensing properties.In addition,the TEA sensing activity relationship of SnO_(2) exposed crystal faces is proposed as listed:(200)>(101)>(110).

Sulfur dioxide gas sensing at room temperature based on tin selenium/tin dioxide hybrid prepared via hydrothermal and surface oxidation treatment

In this paper,a novel SnSe/SnO_(2) nanoparticles(NPs) composite has been successfully fabricated through hydrothermal method and surface oxidation treatment.The as-prepared sample was characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM).A series of morphological and structural characteristics confirm that the SnSe/SnO_(2) NPs composite shows a core-shell structure with a SnO_(2) shell with thickness of 6 nm.The prepared SnO_(2) NPs and SnSe/SnO_(2) NPs composite were applied as gas-sensing materials,and their gas-sensing properties were investigated at room temperature systematically.Experimental results show that the response value of the SnSe/SnO_(2) composite sensor toward 100×10^(-6) SO_(2) is 15.15%,which is 1.32 times higher than that of pristine SnSe(11.43%).And the SnSe/SnO_(2) composite sensor also has a detection limit as low as 74×10^(-9) and an ultra-fast response speed.The enhanced gas-sensing performance is attributed to the formation of p-n heterojunction between SnSe and SnO_(2) and the appropriate SnO_(2) shell thickness.

Ultrasensitive methyl salicylate gas sensing determined by Pd-doped SnO_(2)

Efficient chemicalwarfare agents(CWAs)detection is required to protect people from the cWAs in war and terrorism.In this work,a Pd-doped SnO_(2)nanoparticles-based gas sensor was developed to detect a nerve agent simulant named methyl salicylate.The sensing measurements of methyl salicylate under different Pd doping amounts found that the 0.5 at.%Pd-doped SnO_(2)exhibited a significant improvement in the detection of methyl salicylate at the ppb(1ppb=10-9)level,and the response value to 160 ppb methyl salicylate is 0.72 at 250℃.Compared with the pure SnO_(2),the response value is increased by 4.5 times,which could be attributed to the influence of the noble metal Pd on the oxygen state and its catalytic effect.In addition,the 0.5at.%Pd-doped SnO_(2)sensor still has an obvious response to 16ppb methyl salicylate with a response value of 0.13,indicating the lower detection limit of the sensor.

Improved triethylamine sensing properties of fish-scale-like porous SnO_(2) 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 SnO 2 nanomaterials assembled from ultrathin nanosheets with thick-ness of 16.8 nm were synthesized by a facile hydrothermal route.Then Ag nanoparticles were decorated on the surface of SnO_(2) nanosheets via one-step method to improve their gas-sensing performances.The sensing properties of pristine SnO_(2) and Ag/SnO_(2) nanosheets were investigated intensively.After deco-rating with Ag nanoparticles,the characteristics of SnO_(2) based sensor for triethylamine detection were significantly improved.Especially,the Ag/SnO_(2) 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/SnO_(2) sensors were attributed to the sensitizing actions of Ag nanoparticles as well as the unique hierarchical porous architecture.

Hydrothermal synthesis of hierarchical SnO_(2)nanomaterials for high-efficiency detection of pesticide residue

Acephate pesticide contamination in agricultural production has caused serious human health problems.Metal oxide semiconductor(MOS)gas sensor can be used as a portable and promising alternative tool for efficiently detection of acephate.In this study,hierarchical assembled SnO_(2)nanosphere,SnO_(2)hollow nanosphere and SnO_2 nanoflower were synthesized respectively as high efficiency sensing materials to build rapid and selective acephate pesticide residues sensors.The morphologies of different SnO_(2)3 D nanostructures were characterized by various material characterization technology.The sensitive performance test results of the 3 D SnO_(2)nanomaterials towards acephate show that hollow nanosphere SnO_(2)based sensor displayed preferable sensitivity,selectivity,and rapid response(9 s)properties toward acephate at the optimal working temperature(300℃).This SnO_(2)hollow nanosphere based gas sensor represents a useful tool for simple and highly effective monitoring of acephate pesticide residues in food and environment.According to the characterization results,particularly Brunauer-Emmett-Teller(BET)and Ultraviolet-Visible Spectroscopy(UV-vis),the obvious and fast response can be attributed to the mesoporous hollow nanosphere structure and appropriate band gap of SnO_2 hollow nanosphere.