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.

A visible-light-assisted Pd/TiO_(2)gas sensor with carbon nanotubes electrodes for trace formaldehyde detection

Owing to the ppb-level detection standard toward the toxic and harmful gas,the detection of trace gases has become an important subject in the field of indoor environment management.However,the traditional resistive gas sensors hardly meet the requirement due to the weak signal generated by trace gas molecules that are difficult to capture.Herein,a visible-light-assisted Pd/TiO_(2)gas sensor is proposed to endow the effective detection of trace formaldehyde(HCHO)gas without heating temperature.Benefiting from the enhanced photocatalytic properties of TiO_(2)by Pd decoration,the visible-light-assisted Pd/TiO_(2)gas sensor can detect the HCHO gas as low as80×10^(–9)at room temperature.The successful preparation of nanoscale TiO_(2)sensing layer is facilitated by the ultrathin carbon nanotube interdigital electrode in the gas sensor,which avoids the discontinuity of the sensing layer caused by the excessive thickness of the traditional metal electrode.In addition,the whole preparation process of the Pd/TiO_(2)gas sensor with carbon nanotube electrodes is compatible with mainstream CMOS fabrication technology,which is expected to realize the batch fabrication and micro-integrated application of gas sensors.It is expected that our work can provide a new strategy for the batch preparation of high-performance trace HCHO gas sensors and their future applications in portable electronic devices such as smartphones.

Effect of Tubular Chiralities and Diameters of Single Carbon Nanotubes on Gas Sensing Behavior: A DFT Analysis

Using density functional theory, the adsorption of CO, CO2, NO and CO2 gas molecules on different chiralities and diameters of single carbon nanotubes is investigated in terms of energetic, electronic properties and surface reactivity. We found that the adsorption of CO and CO2 gas molecules is dependent on the chiralities and diameters of CNTs and it is vice versa for NO and NO2 gas molecules. Also, the electronic character of CNTs is not affected by the adsorption of CO and CO2 gas molecules while it is strongly affected by NO and NO2 gas molecules. In addition, it is found that the dipole moments of zig-zag CNTs are always higher than the arm-chair CNTs. Therefore, we conclude that the zig-zag carbon nanotubes are more preferred as gas sensors than the arm-chair carbon nanotubes, especially for detecting NO and NO2 gas molecules.

Improvement in Sensitivity and Recovery of Single-Walled Carbon Nanotube-Based Gas Sensors

In this paper,an improvement in sensitivity and recovery of the single-walled carbon nanotube (SWNT)-based gas sensors was reported.The sensors were fabricated from SWNT powder by a screen-printing method,followed by annealing for 2 h in open-air at various temperatures.The Raman spectra of the SWNT bundles and the response to ammonia (NH_3) exposure of the sensors indicated that the annealing at a relevant temperature improved the sensor sensitivity.The sensor annealed at 200℃exhibited a high sensitivity in NH_3 detection.After 20 min of exposure to NH_3 at room temperature,the resistance of the sensor increased up to 12% in comparison with its initial value.By evacuating combined with maintaining the flux of carrier gas at 300 sccm,the sensor recovery was significantly speeded.The sensor resistance retrieved to its initial value after only 25 min degassing. These results would be considered in the development of the SWNT-based gas sensors.

High Response Gas Sensors for Formaldehyde Based on Er-doped In_2O_3 Nanotubes

Pure and Er-doped In 2O 3 nanotubes were systematically fabricated by using a single nozzle eletrospinning method followed by calcination.The as-synthesized nanotubes were characterized by scanning electron microscopy（SEM）,energy-dispersive X-ray（EDX） spectrometry and X-ray powder diffraction（XRD）.Compared with pure In 2O 3 nanotubes,Er-doped In 2O 3 nanotubes exhibit improved formaldehyde sensing properties at 260 ℃.The response of Er-doped In 2O 3 nanotubes to 20 ppm formaldehyde is about 12,which is 4 times larger than that of pure In 2O 3 nanotubes.The response and recovery times of Er-doped In 2O 3 nanotubes to 20 ppm formaldehyde are about 5 and 38 s,respectively.Furthermore,the response of Er-doped In 2O 3 nanotubes to 100 ppb formaldehyde is 2.19.

Excellent performance of gas sensor based on In_2O_3–Fe_2O_3 nanotubes

In2O3-Fe2O3 nanotubes are synthesized by an electrospinning method. The as-synthesized materials are characterized by scanning electron microscope and X-ray powder diffraction. The gas sensing results show that In2O3-Fe2O3 nanotubes exhibit excellent sensing properties to acetone and formaldehyde at different operating temperatures. The responses of gas sensors based on In2O3-Fe2O3 nanotubes to 100 ppm acetone and 100 ppm formaldehyde are 25 （240 ℃） and 15 （260℃）, and the response/recovery times are 3/7 s and 4/7 s, respectively. The responses of In2O3-Fe2O3 nanotubes to 1 ppm acetone （240 ℃） and formaldehyde （260 ℃） are 3.5 and 1.8, respectively. Moreover, the gas sensor based on In2O3-Fe2O3 nanotubes also possesses an excellent selectivity to acetone and formaldehyde.

Adsorption of CO, CO<SUB>2</SUB>, NO and NO<SUB>2</SUB>on Boron Nitride Nanotubes: DFT Study

The adsorption of CO, CO2, NO and CO2 gas molecules on different chiralities of single boron nitride nanotubes (BNNTs) is investigated, applying the density functional theory and using basis set 6 - 31 g (d,p). The energetic, electronic properties and surface reactivity have been discussed. We found that the best BNNT for adsorbing the CO, CO2, NO and NO2 gas molecules is (5,0) BNNT with adsorption energy of -0.27, -0.37 eV, -0.23 and -0.92 eV, respectively. Also, the electronic character of (5,0), (9,0), (5,5) and (6,6) BNNTs is found to be not affected by the adsorption of CO, CO2, NO and NO2 gas molecules. It is found that the dipole moments of zig-zag (5,0) and (9,0) BNNTs are always higher than the arm-chair (5,5) and (6,6) BNNTs. Also, it is noticed that the highest dipole moment is for (9,0) BNNT.

Toluene-sensing properties of In_2O_3 nanotubes synthesized by electrospinning

Abstract： The pristine In2O3 nanotubes were synthesized by electrospinning and subsequent calcination. Scanning electron microscope, X-ray powder diffraction and transmission electron micrograph were employed to analyze the morphology and crystal structure of the as-synthesized nanotubes. Gas-sensing properties of the as-synthesized In203 nanotubes were investigated by exposing the corresponding sensors to toluene, acetone, ethanol, formalde- hyde, ammonia and carbon monoxide at 340 ℃. The results show that the gas sensor possesses a good selectivity to toluene at 340 ℃. The response of the In2O3 nanotube gas sensor to 40 ppm is about 5.88. The response and recovery times are about 3 s and 17 s, respectively.

Photonic gas sensors exploiting directly the optical properties of hybrid carbon nanotube localized surface plasmon structures

Weinvestigate the modification of the optical properties of carbon nanotubes(CNTs)resulting from a chemical reaction triggered by the presence of a specific compound(gaseous carbon dioxide(CO_(2)))and show this mechanism has important consequences for chemical sensing.CNTs have attracted significant research interest because they can be functionalized for a particular chemical,yielding a specific physical response which suggests many potential applications in the fields of nanotechnology and sensing.So far,however,utilizing their optical properties for this purpose has proven to be challenging.We demonstrate the use of localized surface plasmons generated on a nanostructured thin film,resembling a large array of nano-wires,to detect changes in the optical properties of the CNTs.Chemical selectivity is demonstrated using CO_(2) in gaseous form at room temperature.The demonstrated methodology results additionally in a new,electrically passive,optical sensing configuration that opens up the possibilities of using CNTs as sensors in hazardous/explosive environments.

The study of adsorption gas sensor based carbon nanotube film

The study of gas sensitivity of multi-wall carbon nanotubes (MWNTs), which is deposited by low press chemical vapor deposition (LPCVD), is presented. The results show that the pure MWNTs are not sensitive to the gases measured, while the composite film consisting of the MWNTs and silicon dioxide is sensitive to the methane, the hydrogen and the acetylene. The MWNTs and silicon dioxide composite film have the capacitance characteristic because of the formation of Schottky junctions within the MWNTs. The chemistry adsorption of the gas measured on the surface of the MWNTs affects the space discharge area of the Schottky junction, so that the dielectric constant changes with the gas concentration. That is why the gas is sensed.

Synthesis and acetone gas sensing properties of α-Fe_2O_3 nanotubes

α-Fe2O3nanotubes was successfully prepared by single nozzle electrospinning method.Scanning electron microscope(SEM)was used to characterize the morphology of-Fe2O3nanotubes.The gas sensing properties of-Fe2O3nanotubes were investigated in detail.The results exhibit relatively good sensing properties to acetone at 240°C.The response and recovery times are about 3 and 5 s,respectively.The structure of nanotubes is beneficial to the gas sensing properties,which will enlarge the surface-to-volume ratio of α-Fe2O3and then be available for the transfer of gas,and thus improved the sensor performance consequentially.

Tunable Enhancement of a Graphene/Polyaniline/Poly(ethylene oxide) Composite Electrospun Nanofiber Gas Sensor

Electrospun nanofibers of a polyaniline(PANi)/(+)-camphor-10-sulfonic acid(HCSA)/poly(ethylene oxide)(PEO)composite doped with different variants of graphene oxide(GO)were fabricated and evaluated as chemiresistor gas sensors operating at room temperature.A new strategy for enhancing PANi/PEO gas sensor performance is demonstrated using GO dopants reduced via thermal(trGO)or chemical(crGO)routes.By varying the chemical reduction duration(6 h,crGO-6 or 24 h,crGO-24),tunable enhancement of sensor response was achieved.Upon exposure to short-chain aliphatic alcohol vapors,the partially reduced crGO-6 dopant exhibited higher response than GO and crGO-24,suggesting that the dopant enhances sensor performance via increased electrical conductivity over neat GO,and enhanced hydrogen bonding capability over the further-reduced crGO-24 variant.Sensor arrays consisting of PANi/PEO doped with trGO,crGO-6 or crGO-24 moieties successfully identified methanol,ethanol,and 1-propanol vapors using principal component analysis(PCA).

A Composite of Electrospun Nylon-6 Nanofibers and in-situ Polymerized Polypyrrole as an NH3 Gas Sensor

1 Results Electrospinning provides a simple and versatile method for preparing nanofibers with different morphology, such as porous fibers and nanotubes. It has been widely used for preparing nanomaterials with unique properties and potential applications in medicine, catalyst, photonics and sensors[1, 2]. In this study, uniform Nylon-6 nanofibers with diameter of ≈300 nm by electrospun from formic acid solution containing 15%wt Nylon-6. Polypyrrole (PPy) was then deposited on the nanofibers by in-situ ...

静电纺丝碳纳米管基复合材料在传感器中的应用研究进展

碳纳米管(CNTs)是一种具有特殊结构的一维量子材料,由于其优异的电学、热学、化学和力学性能,以及在储能和能量转换装置、传感器、储氢介质等许多领域的潜在应用,吸引了各界的广泛关注。本文综述了近年来国内外通过静电纺丝技术制备碳纳米管基复合材料传感器的研究现状,主要介绍了生物传感器、柔性应变/压力传感器、电化学传感器、湿度传感器、气体化学传感器的研究进展,并对其未来的发展前景进行了展望。

单壁碳纳米管气体传感器在GIS局部放电检测中的应用(英文)

This paper describes a realizable fabrication method to manufacture chemical gas sensors by using singlewalled carbon nanotubes(SWCNTs).The sensors were tested for the monitoring of SF_6 decomposition gas produced by partial discharge(PD) in GIS tank.The results showed a superior sensitivity,favorable reliability and good reproducibility. For further clarifying the relativity between sensor response and partial discharge activity,the discharge in GIS tank was monitored simultaneously through conventional pulse current method and a SWCNTs gas sensor,and the measurement results were put together for comparative analysis in this paper.The sensor response showed a great dependence on partial discharge characteristics.The sensor response increased nearly linearly with limits when the energy of discharge was persistently accumulated.Partial discharge power had a great influence on the response rate and the time delay.With the increase of partial discharge power,the response rate augmented almost in proportion while the time delay gradually becomes shorter with limits.The results were quite favorable to assess the partial discharge intensity and duration to some extent.Compared with pulse current method,the sensor was predominant to detect partial discharge exposed to constantly high levels of noise.It was capable of detecting partial discharge which was too weak to be detected with pulse current method.However,the sensor response didn't show much dependency on the apparent discharge of partial discharge.

静电纺碳纳米管电阻式柔性湿度传感器的制备及其性能

为制备灵敏度高的柔性湿度传感器,以更适合可穿戴使用场景,提出以聚对苯二甲酸乙二醇酯(PET)为柔性衬底,在其上制作叉指电极,然后以聚乙烯吡咯烷酮(PVP)和多壁碳纳米管(MWCNTs)为原料制备溶液,通过静电纺丝技术将MWCNTs/PVP沉积在柔性PET衬底上制成柔性湿度传感器。借助扫描电子显微镜对薄膜的微观结构进行表征和分析,并通过设计的实验装置对传感器的线性度、响应/恢复时间、重复性和稳定性进行测试。结果表明:该柔性湿度传感器的输出电阻值与相对湿度呈现良好的线性关系,线性相关系数为0.97,可检测的相对湿度范围为40%~90%,响应时间为20 s,恢复时间为5 s,在75%相对湿度下经40次重复测量,传感器表现出良好的重复性和稳定性。

碳纳米管/聚偏氟乙烯纳米纤维膜的制备及其压电性能

为提高聚偏氟乙烯(PVDF)的压电性能,采用静电纺丝法将碳纳米管(CNTs)引入到PVDF纳米纤维膜中制备CNTs/PVDF纳米纤维膜,并组装成三明治结构的柔性压电传感器,探究CNTs质量分数对CNTs/PVDF纳米纤维膜压电性能的影响。借助扫描电子显微镜、X射线衍射仪、傅里叶变换红外光谱仪、万能试验机以及数字示波器对纳米纤维的形貌、结构、力学性能及压电性能进行表征。结果表明:CNTs/PVDF纳米纤维膜具有良好的力学特性,CNTs的添加有利于晶体结构中β晶型的形成;当CNTs质量分数为5%时,CNTs/PVDF纳米纤维的晶体结构中β晶型含量最多,压电性能最强,此时柔性传感器的输出电压达到最大值7.5 V。

碳纳米管/聚氨酯复合薄膜的制备及其拉伸传感性能

采用静电纺丝制备聚氨酯纳米纤维薄膜作为可拉伸柔性基体,将碳纳米管(carbon nanotubes,CNTs)作为导电材料,利用真空浸渍和超声辅助将CNTs负载在聚氨酯纤维表面,形成的三维导电纤维薄膜用作拉伸传感器。利用扫描电子显微镜对复合材料进行形貌表征,利用傅里叶红外光谱仪和热量分析仪的测试来证明聚氨酯和碳纳米管之间存在强的相互作用力。研究浸渍时间对复合薄膜性能的影响发现,浸渍12h时,复合薄膜的灵敏性最大,肩峰最小。通过500圈循环测试,进一步证明了传感器的结构具有良好的稳定性,电阻具有可重复性。将传感器贴合在人体不同部位上,对人体活动进行了简单检测,证明传感器具有一定的实际应用价值。

Preparation and Ethanol Sensing Properties of ZnO Nanofibers

ZnO nanofibers with an average diameter of about 90 nm were prepared by an electrospinning method combined with a calcination process. The as-electrospun nanofibers before and after calcination were characterized by means of differential thermal analysis（DTA）, thermal gravimetric analysis（TGA）, X-ray diffraction（XRD） and scanning electron microscopy（SEM）. The fibers after calcination at 600 °C belong to the hexagonal wurtzite structure. The sensor based on ZnO nanofibers exhibited excellent ethanol sensing properties at 206 °C such as good linear dependence in the low concentration（1―100 μL/L）, high response, and good selectivity. Fast response（less than 2 s） and recovery（about 16 s） were also observed in our investigations.

复合纤维膜负载碳纳米管的制备及传感性能

文章模仿蛛网中包含不同结构的蛛丝,采用离心-静电纺丝法制备聚氨酯-聚对苯二甲酸乙二醇酯(PU-PET)复合纤维膜作为柔性基材,以多壁碳纳米管(MWCNTs)为导电介质,制备出兼具高弹性、高灵敏度的可拉伸复合纤维膜。不同纤维组成的复合纤维膜既能感知人体微小的动作变化,也可响应大幅度的肢体动作。经过一系列的性能测试表明,复合纤维膜断裂伸长率高、响应时间快、稳定性好、回复能力强、压力测试范围广,具有良好的抗氧化性能。这些优异的性能使得该复合纤维膜可以作为可穿戴器件监测人体不同部位的肢体动作,体现出分级响应能力。