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.

基于双通道检测技术的非分光红外CO_(2)传感器设计与研究

针对传统红外气体传感器气室与信号处理模块分离存在体积大、灵敏度差的问题,基于非分光红外双通道检测技术,设计了一种小体积、高精度的红外CO_(2)传感器。首先,对反射型气室进行光线追迹仿真,保证热释电探测器受到的红外辐射和气体吸收光路长度满足要求。同时,设计了可靠的光源驱动电路、带通放大电路;对传感器的温度漂移特性进行讨论,建立温度补偿算法模型。在温湿度箱中标定红外CO_(2)传感器参数,通过拟合曲线得到常数a和n,以及温度补偿系数β。经过实验测试表明,该红外CO_(2)传感器测量误差小于真值的±5%。

Room-Temperature Gas Sensors Under Photoactivation:From Metal Oxides to 2D Materials

Room-temperature gas sensors have aroused great attention in current gas sensor technology because of deemed demand of cheap,low power consumption and portable sensors for rapidly growing Internet of things applications.As an important approach,light illumination has been exploited for room-temperature operation with improving gas sensor's attributes including sensitivity,speed and selectivity.This review provides an overview of the utilization of photoactivated nanomaterials in gas sensing field.First,recent advances in gas sensing of some exciting different nanostructures and hybrids of metal oxide semiconductors under light illumination are highlighted.Later,excellent gas sensing performance of emerging two-dimensional materialsbased sensors under light illumination is discussed in details with proposed gas sensing mechanism.Originated impressive features from the interaction of photons with sensing materials are elucidated in the context of modulating sensing characteristics.Finally,the review concludes with key and constructive insights into current and future perspectives in the light-activated nanomaterials for optoelectronic gas sensor applications.

Zinc Oxide Nanostructure Thick Films as H₂S Gas Sensors at Room Temperature

The ZnO nanostructures have been synthesized and studied as the sensing element for the detection of H2S. The ZnO nanostructures were synthesized by hydrothermal method followed by sonication for different interval of time i.e. 30, 60, 90 and 120 min. By using screen printing method, thick films of synthesized ZnO nanostructure were deposited on glass substrate. Gas sensing properties of ZnO nanostructure thick films were studied for low concentration H2S gas at room temperature. The effects of morphology of synthesized ZnO nanostructure on gas sensing properties were studied and discussed. ZnO nanostructure synthesized by this method can be used as a promising material for semiconductor gas sensor to detect poisonous gas like H2S at room temperature with high sensitivity and selectivity.

In-situ fabrication of ZnO nanoparticles sensors based on gas-sensing electrode for ppb-level H_(2)S detection at room temperature

The zinc oxide(ZnO)nanoparticles(NPs)sensors were prepared in-situ on the gas-sensing electrodes by a one-step simple sol-gel method for the detection of hydrogen sulfide(H_(2)S)gas.The sphere-like ZnO NPs were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),x-ray diffraction(XRD),energy dispersive x-ray analysis(EDX),and their H_(2)S sensing performance were measured at room temperature.Testing results indicate that the ZnO NPs exhibit excellent response to H_(2)S gas at room temperature.The response value of the optimal sample to750 ppb H_(2)S is 73.3%,the detection limit reaches to 30 ppb,and the response value is 7.5%.Furthermore,the effects of the calcining time and thickness of the film on the gas-sensing performance were investigated.Both calcining time and film thickness show a negative correlation with the H_(2)S sensing performance.The corresponding reaction mechanism of H_(2)S detection was also discussed.

红外CO_(2)传感器温湿度补偿方法研究

为提高非色散红外(NDIR)CO_(2)传感器测量精度,基于原理分析了温度、湿度对测量精度的影响;进行了实验对比与验证,提出了基于贝叶斯优化的XGBoost(Bayesian-XGBoost)补偿模型。实验结果表明:在测试样本中,模型补偿后的均方根误差(RMSE)为20.98×10^(-6),平均绝对误差(MAE)为13.29×10^(-6),绝对误差小于±60×10^(-6);与反向传播神经网络(BPNN)、传统XGBoost模型相比,所提的模型精度更高。将算法模型嵌入传感器中并进行测试,补偿后传感器输出值绝对误差小于±110×10^(-6),测量精度得到了较好提升。

非色散红外CO_(2)气体传感器的抗温湿度干扰设计

为了抑制环境温湿度对非色散红外(NDIR)CO_(2)气体传感器测量精度的严重干扰,从硬件补偿的角度出发,为其设计了低湿控制模块与恒温控制模块。采用由聚偏氟乙烯(PVDF)疏水滤膜与3A分子筛构造的气体干燥管过滤CO_(2)气体中的水份实现气室降湿,同时采用增量式比例-积分-微分(PID)算法调节包裹在光学气室外的加热片的功率,达到恒温效果。研究分析了温湿度对气体浓度测量精度的影响,对低湿恒温抗干扰设计进行了测试和验证。实验结果表明,基于气体干燥管的低湿控制模块能够将CO_(2)气体的湿度降低到8%左右,而恒温控制模块能够将气室温度稳定在40℃。在复杂温湿度环境下,0~2000×10^(-6)气体浓度范围内,具有抗温湿度干扰设计的CO_(2)气体传感器的浓度测量平均相对误差为8.38%,显著减小了检测系统的温湿度漂移,研究结果对于研制高性能的NDIR气体传感器有参考价值。

Room temperature NO2-sensing properties of hexagonal tungsten oxide nanorods

Hexagonal WO_3 nanorods were synthesized through a facile hydrothermal method. The nanorods properties were investigated by scanning electron microscope（SEM）, transmission electron microscope（TEM）, energy dispersive spectroscopy（EDS）, and x-ray diffraction（XRD）. The NO_2-sensing performances in terms of sensor response, response/recovery times and repeatability at room temperature were optimized by varying the heat treatment temperature of WO_3 nanorods. The optimized NO_2sensor（400-℃-annealed WO_3 nanorods） showed an ultra-high sensor response of 3.2 and short response time of 1 s to 5-ppm NO_2. In addition, the 400-℃-annealed sample exhibited more stable repeatability.Furthermore, dynamic responses measurements of annealed samples showed that all the annealed WO_3 nanorods sensors presented p-type behaviors. We suppose the p-type behavior of the WO_3 nanorods sensor to be that an inversion layer is formed in the space charge layer when the sensor is exposed to NO_2 at room temperature.Therefore, the 400-℃-annealed WO_3 nanorods sensor is one of the most energy conservation candidates to detect NO_2 at room temperature.

Kinetics study of CO_(2) absorption in potassium carbonate solution promoted by diethylenetriamine

In this work,characterization and kinetics of CO2 absorption in potassium carbonate(K_(2)CO_(3))solution promoted by diethylenetriamine(DETA)were investigated.Kinetics measurements were performed using a stirred cell reactor in the temperature range of 303.15–323.15 K and total concentration up to 2.5 kmol m3.The density,viscosity,physical solubility,CO_(2) diffusivity and absorption rate of CO_(2) in the solution were determined.The reaction kinetics between CO_(2) and K2CO3þDETA solution were examined.Pseudo-first order kinetic constants were also predicted by zwitterion mechanism.It was revealed that the addition of small amounts of DETA to K_(2)CO_(3) results in a significant enhancement in CO_(2) absorption rate.The reaction order and activation energy were found to be 1.6 and 35.6 kJ mol1,respectively.In terms of reaction rate constant,DETA showed a better performance compared to the other promoters such as MEA,EAE,proline,arginine,taurine,histidine and alanine.

SF_6/N_2混合气体纯度检测系统的研究（英文）

为了快速、准确地检测出SF_6/N_2混合气体各组分浓度,考虑微量空气的渗入对其影响,给出了一种恒温控制下基于微流量热导传感器的SF6/N2浓度检测方法,并结合电化学传感器的微量O_2浓度检测原理,设计出了应用于现场分析的混合气体各组分浓度检测的整体方案,并对其进行了实验验证。实验结果表明:在传感器有效测试浓度范围内,此系统检测精度高(全量程平均测量误差±1%以内)、响应速度快、重复性好、性能稳定。

SnO-SnO_(2) modified two-dimensional MXene Ti3C2Tx for acetone gas sensor working at room temperature

Acetone,as widely used reagents in industry and laboratories,are extremely harmful to the human.So the detection of acetone gas concentrations and leaks in special environments at room temperature is essential.Herein,the nanocomposite combining SnO-SnO_(2)(p-n junction)and Ti_(3)C_(2)T_(x) MXene was successfully synthesized by a one-step hydrothermal method.Because of the existence of a small amount of oxygen during the hydrothermal conditions,part of the p-type SnO was oxidized to n-type SnO_(2),forming in-situ p-n junctions on the surface of Sn O.The hamburger-like SnO-SnO_(2)/Ti_(3)C_(2)T_(x) sensor exhibited improved acetone gas sensing response of 12.1(R_(g)/R_(a))at room temperature,which were nearly 11 and 4 times higher than those of pristine Ti_(3)C_(2)T_(x) and pristine SnO-SnO_(2),respectively.Moreover,it expressed a short recovery time(9 s)and outstanding reproducibility.Because of the different work functions,the Schottky barrier was formed between the SnO and the Ti_(3)C_(2)T_(x) nanosheets,acting as a hole accumulation layer(HALs)between Ti_(3)C_(2)T_(x) and tin oxides.Herein,the sensing mechanism based on the formation of hetero-junctions and high conductivity of the metallic phase of Ti_(3)C_(2)T_(x) MXene in SnO-SnO_(2)/Ti_(3)C_(2)T_(x) sensors was discussed in detail.

双通道非分光红外CO_(2)气体传感器设计与测试

针对目前非分光红外(NDIR)CO_(2)传感器灵敏度差、量程小的问题,设计并实现了一种微型双通道NDIR CO_(2)气体传感器。该红外传感器主要由双通道热释电探测器、信号读出与处理电路、温度传感器与光路气室构成。建立了温度、CO_(2)浓度与探测器输出值之间的关系模型,实现了传感器的温度补偿功能。测试结果表明,所设计传感器能够实现在0~40℃温度范围内,0%~5%气体浓度的测量,且在0%~2%浓度下测量误差值小于0.1%,在2%~5%浓度下测量误差值小于0.25%。

Ti3C2Tx/PEDOT:PSS hybrid materials for room-temperature methanol sensor

It is essential to develop a methanol gas sensor with high selectivity and low working temperature for human health and environmental monitoring.In this work,a blend of PEDOT:PSS and Ti3C2Tx with the mass ratio of 4:1 is used to fabricate a methanol gas sensor.It possesses a high response ratio of the largest response and the second largest response(5.54)and an enhanced response compared to pure PEDOT:PSS and pure Ti3C2Tx tested at room temperature.These findings may pave the way towards design of the MXenes based high-performance gas-sensing materials in the future.

恒温NDIR二氧化碳气体传感器研究

环境温度变化会影响CO_(2)对红外光的吸收效率,为提高非色散红外(NDIR)CO_(2)气体传感器的测量精度,设计了一种基于增量式PID算法的恒温CO_(2)气体传感器系统。首先利用ANSYS FLUENT软件对恒温控制下的采样气室内部热分布进行模拟仿真,验证了恒温控制的可行性,然后设计了基于PI加热片的恒温控制系统。实验结果表明,在0~2000 ppm气体浓度范围内,本文提出的CO_(2)气体传感器在恒温40℃时的测量误差小于±60 ppm,该结果对于研制高性能气体传感器有一定参考价值。

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.

Preparation of two-dimensional molybdenum disulfide for NO2 detection at room temperature

In this work,the two-dimensional MoS2 film was prepared by sulfuring the molybdenum atomic layer on SiO2/Si substrate.The reaction temperature,heating rate,holding time and carrier gas flow rate were inve stigated compre hensively.The quality of MoS2 film was characterized by optical microscopy,atomic fo rce microscopy,Raman and photoluminescence spectro scopy.The characte rization results showed that the optimum synthesis parameters were heating rate of 25℃/min,reaction temperature of 750℃,holding time of 30 min and carrier gas velocity of 100 sccm.The MoS2 gas sensor was fabricated and its gas sensing performance was tested.The test results indicated that the sensor had a good response to both reducing gas(NH3)and oxidizing gas(NO2)at room temperature.The sensitivity to 100 ppm of NO2 was 31.3%,and the response/recovery times were 4 s and 5 s,respectively.In addition,the limit of detection could be as low as 1 ppm.This work helps us to develop low power and integrable room temperature NO2 sensors.

Hollow Fe_(2)O_(3)/Co_(3)O_(4)microcubes derived from metal-organic framework for enhanced sensing performance towards acetone

In this work,hollow Fe_(2)O_(3)/Co_(3)O_(4)microcubes have been successfully synthesized through a hydrothermal method followed by an annealing process using metal-organic framework of Prussian blue as a soft template.The morphologies,microstructures,surface area and element compositions have been carefully characterized by a series of techniques.Meanwhile,compared with that of pure Fe_(2)O_(3)and Co_(3)O_(4),the gas sensor based on the hollow microcubes exhibits enhanced sensing performances towards acetone,e.g.,a higher response of 21.2 and a shorter response time of 5 s towards 20 ppm acetone at a relatively low working temperature of 200℃.Moreover,the hollow microcubes-based gas sensor still shows perfect long-term stability,excellent repeatability and the ability of sub-ppm level detection,which provides a possibility for its application in real life.The enhanced gas sensing performances can be attributed to the hollow structure with a high surface area and the formed p-n heterojunctions within the microcubes.