非接触点胶打印用ZnO-SnO_(2)复合气敏墨水的制备及气敏性能研究

非接触点胶打印是一种新型、高精度、无模板、低成本的成膜技术,墨水的理化性质是决定打印薄膜质量的关键,对微电子器件性能有着重要影响。本文采用聚乙二醇400(PEG400)作为分散剂取代传统的高分子量分散剂,以乙二醇和丙三醇为溶剂、ZnO-SnO_(2)复合气敏材料为功能相制备高性能气敏墨水,并利用非接触点胶技术在基于微电子机械系统(MEMS)的微热板上打印ZnO-SnO_(2)复合气敏薄膜。根据墨水的黏度及悬浮稳定性,分析了PEG400含量和固含量对墨水理化性质的影响,通过SEM观察薄膜的微观形貌,研究结果表明,当固含量为15%(质量分数,下同)、PEG400含量为6%时,复合气敏墨水具备可打印性及低温烧结成膜特性,制备的复合气敏薄膜厚度均匀,表面平整,边缘规整,对丙酮气体有良好的响应。

Fabrication of a novel electrochemical sensor based on MnFe_(2)O_(4)/graphene modified glassy carbon electrode for the sensitive detection of bisphenol A

Manganese ferrite(MnFe_(2)O_(4))has the advantages of simple preparation,high resistivity,and high crystal symmetry.Herein,we have developed an electrochemical sensor utilizing graphene and MnFe_(2)O_(4) nanocomposites modified glassy carbon electrode(GCE),which is very efficient and sensitive to detect bisphenol A(BPA).MnFe_(2)O_(4)/graphene(GR)was synthesized by immobilizing the MnFe_(2)O_(4) microspheres on the graphene nanosheets via a simple one-pot solvothermal method.The morphology and structure of the MnFe_(2)O_(4)/GR nanocomposite have been characterized through scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).In addition,electrochemical properties of the modified materials are comparably explored by means of cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS)and differential pulse voltammetry(DPV).Under the optimal conditions,the proposed electrochemical sensor for the detection of BPA has a linear range of 0.8-400μmol/L and a detection limit of 0.0235μmol/L(S/N=3)with high sensitivity,good selectivity and high stability.In addition,the proposed sensor was used to measure the content of BPA in real water samples with a recovery rate of 97.94%-104.56%.At present,the synthesis of MnFe_(2)O_(4)/GR provides more opportunities for the electrochemical detection of BPA in practical applications.

Double enzyme mimetic activities of multifunctional Ag nanoparticle-decorated Co_(3)V_(2)O_(8)hollow hexagonal prismatic pencils for application in colorimetric sensors and disinfection

Since the catalytic activity of most nanozymes is still far lower than the corresponding natural enzymes,there is urgent need to discover novel highly efficient enzyme-like materials.In this work,Co_(3)V_(2)O_(8)with hollow hexagonal prismatic pencil structures were prepared as novel artificial enzyme mimics.They were then decorated by photo-depositing Ag nanoparticles(Ag NPs)on the surface to further improve its catalytic activities.The Ag NPs decorated Co_(3)V_(2)O_(8)(ACVPs)showed both excellent oxidase-and peroxidase-like catalytic activities.They can oxidize the colorless 3,3’,5,5’-tetramethylbenzidine rapidly to induce a blue change.The enhanced enzyme mimetic activities can be attributed to the surface plasma resonance(SPR)effect of Ag NPs as well as the synergistic catalytic effect between Ag NPs and Co_(3)V_(2)O_(8),accelerating electron transfer and promoting the catalytic process.ACVPs were applied in constructing a colorimetric sensor,validating the occurrence of the Fenton reaction,and disinfection,presenting favorable catalytic performance.The enzyme-like catalytic mechanism was studied,indicating the chief role of⋅O_(2)-radicals in the catalytic process.This work not only discovers a novel functional material with double enzyme mimetic activity but also provides a new insight into exploiting artificial enzyme mimics with highly efficient catalytic ability.

Low-temperature NO_2 sensors based on polythiophene/WO_3 organic-inorganic hybrids

Polythiophene （PTP） was prepared by a chemical oxidative polymerization and nanosized WO3 was prepared by a colloidal chemical method. The organic-inorganic PTP/WO3 hybrids with different mass fractions of PTP were obtained by a simple mechanically mixing the prepared PTP and WO3. The as-prepared PTP/WO3 hybrids have a higher thermal stability than the pure PTP. The gas sensing measurements demonstrate that the PTP/WO3 hybrid sensors exhibit higher response for detecting NO2 at low temperature than the pure PTP and WO3 sensor. The sensing mechanism is suggested to be related to the existence of p-n heterojunctions in the PTP/WO3 hybrids. The response of the PTP/WO3 hybrids is markedly influenced by the PTP mass fraction. The 20% PTP/WO3 hybrid shows high response and good selectivity to NO2 at low temperature （〈90℃）. Therefore, the PTP/WO3 hybrids can be expected to be potentially used as gas sensor material for detecting NO2 at low temperature.

基于共溅射ZnO/SnO_(2)异质结薄膜的气体传感器研究

采用射频磁控共溅射法在叉指电极上制备了ZnO/SnO_(2)n-n异质结复合薄膜,系统测试了其气敏特性,并分析了其气敏机理。结果表明,与ZnO薄膜和SnO_(2)薄膜气体传感器相比,ZnO/SnO_(2)异质结薄膜气体传感器具有更低的工作温度、更高的灵敏度以及更快的响应和恢复速度。ZnO/SnO_(2)异质结薄膜气体传感器对乙醇具有较好的选择性,最低检测体积分数为1×10^(-6),最佳工作温度为250℃;对1×10^(-4)乙醇气体的灵敏度可达18.4,响应时间和恢复时间分别为10 s和19 s。

Highly Responsive and Selective Ethanol Gas Sensor Based on Co3O4-Modified SnO2 Nanofibers

SnO2 nanofibers were synthesized by electrospinning and modified with Co3O4 via impregnation in this work. Chemical composition and morphology of the nanofibers were system- atically characterized, and their gas sensing properties were investigated. Results showed that Co3O4 modification significantly enhanced the sensing performance of SnO2 nanofibers to ethanol gas. For a sample with 1.2 mol% Co3O4, the response to 100 ppm ethanol was 38.0 at 300 ℃, about 6.7 times larger than that of SnO2 nanofibers. In addition, the response/recovery time was also greatly reduced. A power-law dependence of the sensor response on the ethanol concentration as well as excellent ethanol selectivity was observed for the Co3O4/SnO2 sensor. The enhanced ethanol sensing performance may be attributed to the formation of p-n heterojunctions between the two oxides.

基于SiO_(2)纳米颗粒的无标记化学发光氯霉素适体传感器

经由食物链长期摄入氯霉素残留物会给人体带来各种危害和疾病。因此,建立快速、准确且高灵敏的食品中氯霉素检测方法具有重要意义。采用溶胶-凝胶法制备了表面氨基化的SiO_(2)纳米颗粒,并用X射线衍射、透射电镜和红外光谱对其进行了表征。然后,利用酰胺键和碱基互补配对作用在SiO_(2)纳米颗粒表面依次组装互补DNA链和氯霉素适配体,成功构建了无标记化学发光氯霉素适配体传感器。该传感器制备简便,其中的氯霉素适配体既可作为生物识别元件,又可与苯甲酰甲醛反应产生化学发光信号,无需标记信号分子。该传感器的氯霉素检出限为3.26×10^(-9) mol·L^(-1),且选择性较好。将该传感器应用于实际样品中进行加标,回收率在94.67%~103.00%之间,表明该适体传感器可用于食品中氯霉素的检测。

Strategy and Future Prospects to Develop Room-Temperature-Recoverable NO2 Gas Sensor Based on Two-Dimensional Molybdenum Disulfide

Nitrogen dioxide(NO2),a hazardous gas with acidic nature,is continuously being liberated in the atmosphere due to human activity.The NO2 sensors based on traditional materials have limitations of high-temperature requirements,slow recovery,and performance degradation under harsh environmental conditions.These limitations of traditional materials are forcing the scientific community to discover future alternative NO2 sensitive materials.Molybdenum disulfide(MoS2)has emerged as a potential candidate for developing next-generation NO2 gas sensors.MoS2 has a large surface area for NO2 molecules adsorption with controllable morphologies,facile integration with other materials and compatibility with internet of things(IoT)devices.The aim of this review is to provide a detailed overview of the fabrication of MoS2 chemiresistance sensors in terms of devices(resistor and transistor),layer thickness,morphology control,defect tailoring,heterostructure,metal nanoparticle doping,and through light illumination.Moreover,the experimental and theoretical aspects used in designing MoS2-based NO2 sensors are also discussed extensively.Finally,the review concludes the challenges and future perspectives to further enhance the gas-sensing performance of MoS2.Understanding and addressing these issues are expected to yield the development of highly reliable and industry standard chemiresistance NO2 gas sensors for environmental monitoring.

基于p-n异质结CuO/TiO_(2)复合物高效的载流子分离能力构建超灵敏AFP光电化学分析

将TiO_(2)纳米粒子与Cu(pta)MOFs复合,通过高温煅烧策略制得CuO/TiO_(2)复合物.在最优实验条件下,基于复合物对可见光更强的吸收利用效率,CuO/TiO_(2)修饰的ITO电极展现出显著的光电化学(PEC)响应信号,其光电流值(59.4μA)分别是单组分TiO_(2)和CuO粒子的15.5和7.4倍.线性扫描伏安法(LSV)测试结果证实CuO/TiO_(2)/ITO电极比CuO和TiO_(2)材料具有更大的LSV响应强度.这可归因于获得的薄片层状CuO粒子及其兼有的多孔隙特征促进了光的多重散射/反射效应,同时CuO/TiO_(2)复合材料具有的典型p-n异质结构(能级带隙匹配)大幅促进了光生电荷载流子(e^(-)/h^(+))的分离与转移.选用戊二醛(GA)作为交联手臂分子,通过温和的醛胺反应将壳聚糖(CS)和anti-AFP抗体组装于CuO/TiO_(2)/ITO电极表面,再用牛血清蛋白(BSA)封闭活性位点,构建出PEC传感平台(BSA/anti-AFP/GA-CS/CuO/TiO_(2)/ITO),实现了对不同浓度甲胎蛋白(AFP)的高灵敏检测(检出限达到2.63×10^(-4) ng/mL).制备的传感电极同时展示出良好的稳定性和选择性.

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.

Recent progress on gas sensors based on graphene-like 2D/2D nanocomposites

Two-dimensional(2D)nanomaterials have demonstrated great potential in the field of flexible gas sensing due to their inherent high specific surface areas,unique electronic properties and flexibility property.However,numerous challenges including sensitivity,selectivity,response time,recovery time,and stability have to be addressed before their practical application in gas detection field.Development of graphene-like 2D/2D nanocomposites as an efficient strategy to achieve high-performance 2D gas sensor has been reported recently.This review aims to discuss the latest advancements in the 2D/2D nanocomposites for gas sensors.We first elaborate the gas-sensing mechanisms and the collective benefits of 2D/2D hybridization as sensor materials.Then,we systematically present the current gas-sensing applications based on different categories of 2D/2D nanocomposites.Finally,we conclude the future prospect of 2D/2D nanocomposites in gas sensing applications.

Hydrogen Gas Sensor Based on Nanocrystalline SnO_2 Thin Film Grown on Bare Si Substrates

In this paper, high-quality nanocrystalline SnO_2 thin film was grown on bare Si(100) substrates by a sol–gel method. A metal–semiconductor–metal gas sensor was fabricated using nanocrystalline SnO_2 thin film and palladium(Pd)metal. The contact between Pd and nanocrystalline SnO_2 film is tunable. Ohmic barrier contact was formed without addition of glycerin, while Schottky contact formed by adding glycerin. Two kinds of sensor devices with Schottky contact were fabricated(Device 1: 8 h, 500 °C; Device 2: 10 h, 400 °C). The room temperature sensitivity for hydrogen(H_2) was120 and 95 % in 1000 ppm H_2, and the low power consumption was 65 and 86 l W for two devices, respectively. At higher temperature of 125 °C, the sensitivity was increased to 195 and 160 %, respectively. The sensing measurements were repeatable at various temperatures(room temperature, 75, 125 °C) for over 50 min. It was found that Device 1 has better sensitivity than Device 2 due to its better crystallinity. These findings indicate that the sensors fabricated on bare Si by adding glycerin to the sol solution have strong ability to detect H_2 gas under different concentrations and temperatures.

One-step Growth of Hierarchical Nanotreelike TiO2 on ITO without Template and Its Application in Gas Sensor

In this work,a distinctive hierarchical tree-like rutile TiO2 architecture growing directly on the conductive surface of indium tin oxide(ITO)conductive glass substrates was successfully prepared via a facile one-step hydrothermal process,where titanium butoxide used as Ti source and HCl as an acidic medium solution.The as-obtained products were characterized by X-ray diffraction(XRD),field emission scanning electron microscopy(FE-SEM),transmission electron microscopy(TEM),selected area electron diffraction(SAED)and applied in gas sensor.The characterization of FE-SEM indicates that the morphology of the products can be controlled by regulating solution acidity,the amount of titanium butoxide,reaction time,addition agents,and so on.The gas sensing test shows that the sensor fabricated with 3D nanotree-like rutile TiO2 has higher gas response towards CH3 COCH3 gas than those with 1 D rod-like TiO2 or common TiO2 precipitate,indicating that the 3D nanotree-like architectures may be promising gas sensitive materials.

H_2S Sensing Characteristics of Thin Film SnO_2 Sensor with N_2 Treatment

<正>SnO_2 thin film sensors were fabricated by a thermal evaporation method.The sensors were heated for thermal oxidation.For high porosity,SnO_2 thin film sensors were treated in a N_2 atmosphere.The sensors that were treated with O_2 after being treated with N_2 showed 70 % sensitivity for 1×10~ -6) of H_2S,which is higher than the sensors that were only treated with O_2.The Ni metal,as a catalyst,was evaporated on the thin film Sn on the Al_2O_3 substrate.The sensor was heated to grow the Sn nanowire in a tube furnace with N_2 flow.Sn nanowire was heated for oxidation.The sensitivity of SnO_2 nanowire sensor was measured for 500×10~ -9) of H_2S.The selectivity of the SnO_2 nanowire sensor was compared with the thin film and the thick film SnO_2.Each sensor was measured for H_2S,CO,and NH_3 in this study.

Enhancement of H_2 Sensing Properties of In_2O_3-based Gas Sensor by Chemical Modification with SiO_2

The sensitivity and selectivity to H_2 of a new In_2O_3-based gas sensor were improvedsignificantly by surface chemical modification. A dense layer of SiO_2 near the surface of the porousIn_2O_3 bead was formed by chemical vapor deposition(CVD)of diethoxydimethysilane(DEMS).The dense layer functioned as a molecular sieve, thereby the diffusion of gases with large moleculardiameters,except for H_2, was effectively controlled, resulting in a prominent selectivity and highsensitivity for H_2. The working mechanism of the sensor was also presented.

A NOVEL RESISTIVE HUMIDITY SENSOR BASED ON SODIUM POLYSTYRENESULFONATE/TiO_2 NANOCOMPOSITES

A resistive humidity sensor was prepared based on sodium polystyrenesulfonate (NaPSS)/TiO2 nanocomposites, and its electrical response to humidity was examined. The sensor exhibits better linearity, smaller hysteresis (< 4% RH) and quicker response (absorption: less than 2 s; desorption: less than 20 s) in comparison with sensor composed of NaPSS. The effect of concentration of NaPSS and TiO2 on humidity response of sensors was discussed.

A Fiber Optic Sensor for 2,4-dichlorophenol Analysis based on Optical Composite Oxygen-sensitive Film

A novel fiber optic sensor based on optical composite oxygen-sensitive film was developed for determination of 2,4-dichlorophenol(DCP).The optical composite oxygen-sensitive film consists of tris(2,2’-bipyridyl)dichloro ruthenium(II)hexahydrate(Ru(bpy)3Cl2)as the fluorescence indicator and iron(III)tetrasulfophthalocyanine(Fe(III)PcTs)as bionic enzyme.A lock-in amplifier was used for detecting the lifetime of the composite oxygen-sensitive film by measuring the phase delay of the sensor head.The different variables affecting the sensor performance were evaluated and optimized.Under the optimal conditions(i e,pH 6.0,25℃,Fe(III)PcTs concentration of 5.0×10^-5 mol/L),the linear detection range,detection limit and response time of the fiber optic sensor are 3.0×10^-7-9.0×10^-5 mol/L,4.8×10^-8 mol/L(S/N=3),and 220 s,respectively.The sensor displays high selectivity,good repeatability and stability,which have good potentials in analyzing DCP concentration in practical water samples.

A new algorithm for wireless sensor network based on NS-2

Considering wireless sensor network characteristics,this paper uses network simulator,version2(NS-2)algorithm to improve Ad hoc on-demand distance vector(AODV)routing algorithm,so that it can be applied to wireless sensor networks.After studying AODV routing protocol,a new algorithm called Must is brought up.This paper introduces the background and algorithm theory of Must,and discusses the details about how to implement Must algorithm.At last,using network simulator(NS-2),the performance of Must is evaluated and compared with that of AODV.Simulation results show that the network using Must algorithm has perfect performance.

Gas sensors based on TiO_(2) nanostructured materials for the detection of hazardous gases: A review

Hazardous gases have been strongly associated with being a detriment to human life within the environment The development of a reliable gas sensor with high response and selectivity is of great signifcance for detecting different hazardous gases.TiO_(2) nanomaterials are promising candidates with great potential and excellent per-formance in gas sensor applications,such as hydrogen,acetone,ammonia,and ethanol detection.This review begins with a detailed discussion of the di ferent dimensional morphologies of TiO_(2),whitch affect the gas sensing performance of TiO_(2) sensors.The diverse morphologies of TiO_(2) can easily be tuned by regulating the manufacturing conditions.Meanwhile,they exhibit unique characteristics for detecting gases,including large specific suface area,superior elecron tr ansport rates,extraordinary pemmeability,and active reaction sites,which offer new opportunities to improve the gas sensing properties.In addition,a variety of efforts have been made to functional TiO_(2) nanomaterials to further enhance sensing properties,including TiO_(2)-based composites and light-assisted gas sensors.The enhanced gas sensing mechanisms of multi-component composite nano-materials based on TiO_(2) include loaded noble metals,doped elements,constructed heterojunctions,and com-pounded with other functional materials.Finally,several studies have been summarized to demonstate the compar ative sensing properties of TiO_(2)-based gas sensors.

Fire monitoring in coal mines using wireless underground sensor network and interval type-2 fuzzy logic controller

From the view of underground coal mining safety system, it is extremely important to continuous monitoring of coal mines for the prompt detection of fires or related problems inspite of its uncertainty and imprecise characteristics. Therefore, evaluation and inferring the data perfectly to prevent fire related accidental risk in underground coal mining (UMC) system are very necessary. In the present article, we have proposed a novel type-2 fuzzy logic system (T2FLS) for the prediction of fire intensity and its risk assessment for risk reduction in an underground coal mine. Recently, for the observation of underground coal mines, wireless underground sensor network (WUSN) are being concerned frequently. To implement this technique IT2FLS, main functional components are sensor nodes which are installed in coal mines to accumulate different imprecise environmental data like, temperature, relative humidity, different gas concentrations etc. and these are sent to a base station which is connected to the ground observation system through network. In the present context, a WUSN based fire monitoring system is developed using fuzzy logic approach to enhance the consistency in decision making system to improve the risk chances of fire during coal mining. We have taken Mamdani IT2FLS as fuzzy model on coal mine monitoring data to consider real-time decision making (DM). It is predicted from the simulated results that the recommended system is highly acceptable and amenable in the case of fire hazard safety with compared to the wired and off-line monitoring system for UMC. Legitimacy of the suggested model is prepared using statistical analysis and multiple linear regression analysis.