Preparation of plasma poly(1-isoquinolinecarbonitrile) thin film and its ultrafast nonlinear optical property

How to get a uniform, defect-free, and reproducible conjugated polymer thin films is now becoming the main fabrication problem for the practical application of these materials as the fast switches and modulators in opto-electronic devices. In this research, a novel plasma-polymerized 1-isoquinolinecarbonitrile (PPIQCN) thin film was prepared by plasma polymerization under different glow discharge conditions. The effect of the discharge power on the chemical structure and surface compositions of the deposited PPIQCN films was investigated by Fourier transform infrared (FTIR), UV-Visible absorption spectra and X-ray photoelectron spectroscopy (XPS). The results show that a high retention of the aromatic ring structure of the starting monomer in the deposited plasma films is obtained when a low discharge power of 10 W was used during film formation. In the case of higher discharge power of 30 W, more severe monomer molecular fragmentation can be observed, which results in a decrease in the effective conjugation length of PPIQCN film. The morphology characterized by atomic force microscopy (AFM) indicates that a fine, homogenous PPIQCN film could be obtained under a relatively low discharge power. A femtosecond time-resolved optical Kerr effect technique at a wavelength of 820 nm has been applied to investigate the third-order nonlinearity of the plasma PPIQCN film. For the first time, a non-resonant optical Kerr effect and ultrafast response of the PPIQCN film was observed.     

A surface acoustic wave humidity sensor with high sensitivity based on electrospun MWCNT/Nafion nanofiber films

Humidity detection has been widely used in a variety of fields. A humidity sensor with high sensitivity is reported in this paper. A surface acoustic wave resonator (SAWR) with high resonance frequency was fabricated as a basic sensitive component. Various nanotechnologies were used to improve the sensor's performance. A multi-walled carbon nanotube/Nafion (MWCNT/Nafion) composite material was prepared as humidity-sensitive films, deposited on the surface of an SAWR by the electrospinning method. The electrospun MWCNT/Nafion nanofiber films showed a three-dimensional (3D) porous structure, which was profitable for improving the sensor's performance. The new nano-water-channel model of Nafion was also applied in the humidity sensing process. Compared to other research, the present sensor showed excellent sensitivity (above 400 kHz/% relative humidity (RH) in the range from 10% RH to 80% RH), good linearity (R(2) > 0.98) and a short response time (～3 s@63%).     

Construction of Dual-Channel Water Transport in Mesoporous Silica Low Humidity Sensors to Achieve High Sensitivity

In this paper, strong hydrophilic poly(ionic liquid)s (PILs) are selectively grafted on different positions (mesoporous channels and outer surface) of mesoporous silica via thiol-ene click chemical reaction. The purposes of selective grafting are on the one hand, to explore the differences of adsorption and transportation of water molecules in mesoporous channels and on the outer surface, and on the other hand, to combine the two approaches (intra-pore grafting and external surface grafting) to reasonably design SiO₂@PILs low humidity sensing film with synergetic function to achieve high sensitivity. The results of low relativehumidity （RH） sensing test show that the sensing performance of humidity sensor based on mesoporous silica grafted with PILs in the channels is better than that of humidity sensor based on mesoporous silica grafted with PILs on the outer surface. Compared with water molecules transport single channel, the construction of dual-channel water transport significantly improves the sensitivity of the low humidity sensor, and the response of the sensor is up to 4112% in the range of 7–33% RH. Moreover, the existence of micropores and the formation of dual-channel water transport affect the adsorption/desorption behaviors of the sensor under different humidity ranges, especially below 11% RH.     

Preparation and fuel cell performance of catalyst layers using sulfonated polyimide ionomers

Sulfonated polyimide (SPI-8) ionomers were used as binders in the catalyst layers, and their fuel cell performance was evaluated. SPI-8 ionomers functioned well in the anode with only minor overpotential even at low humidity (50% relative humidity (RH)). In contrast, the cathode performance was significantly dependent on the content and molecular weight of the ionomers and humidity of the supplied gases. Higher molecular weight of the ionomer caused larger potential drop at high current density at 80 and 100% RH since oxygen supply and/or water discharge became insufficient due to higher water uptake (swelling) of the ionomer. Similar results were obtained at higher ionomer content, because of the increase of thickness in the catalyst layer. The mass transport was improved with decreasing humidity, however, proton conductivity became lower. While the maximum values of j(@0.70?V) for all membrane electrode assemblies (MEAs) were ca. 0.35 A/cm(2), each electrode could have the different appropriate operating conditions. The results suggest that the parameters such as oxygen supply, proton conductivity, and water uptake and discharge need to be carefully optimized in the catalyst layers for achieving reasonable cathode performance with hydrocarbon ionomers.     

Investigation of deposition rate and structure of pulse DC plasma polymers

In this study, hydrophobic plasma polymer films were prepared from perfluorohexane with saturated linear structure and octafluorotoluene with a cyclic unsaturated structure. Hydrophilic plasma polymer film was prepared from acrylic acid with an unsaturated linear structure. The film deposition rates were compared through in-situ laser interferometer measurement and correlated them with the precursor structure and the deposition parameters. The chemical structure and the surface energy of the films were also investigated with FTIR and contact angle measurement. The results showed that the deposition rate increased with the discharge power. Otherwise, the deposition rate relied on the structure of the precursors to a large extent. The deposition rate of octafluorotoluene is 7 times the deposition rate of perfluorohexane and 5 times the deposition rate of acrylic acid at the same deposition parameters. So a high deposition rate could be obtained for the precursors with cyclic and unsaturated structures. For the pulse discharge of acrylic acid, there existed a maximum deposition rate for a certain pulse frequency. But it was found that the pulse frequency had greater effects on the structure of the plasma films than on the deposition rate. As the pulse frequency decreased, more CHO and O---C=O groups were found in the deposited film of acrylic acid. And the pulse discharge at low power could keep more aromatic ring in octafluorotoluene plasma film than continuous discharge at high power. This explained the phenomenon that the surface energy of octafluorotoluene plasma film deposited by the low power pulse discharge was lower than that of the film deposited by the high power continuous discharge and showed to be more hydrophobic.     

Humidity sensing behaviour of polyaniline/magnesium chromate (MgCrO<Subscript><Emphasis Type="Bold">4</Emphasis></Subscript>) composite

‘In situ’ polymerization of polyaniline (PANI) was carried out in the presence of magnesium chromate (MgCrO ₄ ) to synthesize PANI/ceramic (MgCrO ₄ ) composite. These prepared composites were characterized by XRD, FTIR and SEM, which confirm the presence of MgCrO ₄ in polyaniline matrix. The temperature dependent conductivity measurement shows the thermally activated exponential behaviour of PANI / MgCrO ₄ composites. The decrease in electrical resistance was observed when the polymer composites were exposed to the broad range of relative humidity (ranging between 20 and 95% RH). This decrease is due to increase in surface electrical conductivity resulting from moisture absorption and due to capillary condensation of water causing change in conductivity within the sensing materials. PANI / MgCrO ₄ composites are found to be sensitive to low humidity ranging from 20 to 50 % RH.     

Pulsed laser deposited ZnO films and their humidity sensing behavior

The present paper describes an opto-electronic humidity sensor based on thin film of zinc oxide prepared by pulsed laser deposition method. Being optical in nature it gives electromagnetic disturbance-free monitoring. The sensing element is a right-angled isosceles prism with its base coated with ZnO thin film. Films have been characterized by XRD, SEM, and optical transmission. Film grown with substrate at room temperature is amorphous whereas that grown at elevated temperature is single crystalline with grain size 38.52 nm. Film deposited at room temperature is sensitive to humidity over a wide range i.e. 5–90RH% while that deposited at elevated temperature is found to be insensitive to humidity. The sensor shows better sensitivity for higher range of humidity. The response and recovery time of the sensor element have also been evaluated. This sensor configuration can be used for on-line applications and in-situ monitoring.     

Localized material growth by a dielectric barrier discharge

In this paper, we have reported a localized material growth method by dielectric barrier discharge (DBD) in a mixture of acetylene and argon. We found that, in the discharge, plasma polymerization takes place and the material growth rate is much higher along the discharge filaments than it is in other locations. Three layers of material, which correspond to three modes of discharge, are observed after the plasma polymerization. One layer is homogeneous, which corresponds to a glow-like discharge. The second layer is made of small and dense columns, which can be seen only under microscope, and this layer of material's growth corresponds to a corona-like discharge. The third layer is made of a few bigger columns, which can be seen visually, and they are grown along patterned discharge streamers. By scanning electron microscope (SEM), we see that the bigger columns are made of small ball-like material with the diameter of approximately 0.1 μm. A Fourrier transfer infra-red (FTIR) spectrum of the deposited material is also shown to confirm the polymerization.     

High-sensitivity sensor of low relative humidity based on overlay on side-polished fibers

A low relative humidity (RH) sensor based on overlay on side-polished fiber is presented. The evanescent field from a single-mode optical fiber is coupled to a TiO/sub 2/ waveguide overlay. The transmission response exhibits sharp resonances whose central wavelengths are linearly shifted with RH. This behavior is due to the porous columnar nanostructure of the TiO/sub 2/ film. The water is adsorbed in the pores of the nanostructure changing the refractive index of the layer and causing a shift of the wavelength resonances. The response of the sensor is determined by the shape and size of the pores. The optical fiber evanescent field sensor developed has a linear response and high sensitivity (0.5 nm/% RH) for low RH (RH/spl sim/0%-15%) at 26.1/spl deg/C/spl plusmn/0.6/spl deg/C. The lack of hysteresis in the adsorption-desorption cycle has been checked. The development of a sensor with tailored response is envisaged using properly techniques to control the porosity of the material.     

Synthesis,characterization and weight percent effect on humidity sensing properties of Polypyrrole/AlCeO3 (PPy/ACO) nanocomposites

Polypyrrole (PPy)/aluminum cerium oxide (ACO) nanocomposites with different weight percentages of the ACO nanoparticles in the matrix of PPy have been synthesized successfully. The addition of fillers in the conducting polymer makes significant changes in their electrical, chemical, mechanical and gas sensing properties. The exact amount of filler is one of the essential parameters to get the desired properties in the host polymer. So, the optimization of the percent weight of filler in the host conducting polymer is very much crucial. The structural and morphological studies were done by XRD, FTIR, SEM, and TEM. These experimental studies reveal that nanoparticles of Aluminum cerium oxide are dispersed uniformly in the PPy chains. The humidity sensing properties for different weight percent of nanocomposites were studied by using impedance analyzer in the frequency range from 100?Hz to 5?MHz and at relative humidity (% RH) variation from 30% RH to 90% RH. The graphs of impedance versus frequency for all nanocomposites showed a slightly linear dependence at all the frequencies over the entire humidity range. The complex impedance (cole-cole) graphs and the corresponding equivalent circuits were studied to understand the conduction phenomenon in nanocomposites. The conduction in pure PPy shows the contribution from grain and grain boundaries while all the nanocomposites show contribution only from grains. The lower weight percent nanocomposites exhibit better response compared to higher weight percent.     

Optical fibre Fabry–Perot relative humidity sensor based on HCPCF and chitosan film

Abstract

An optical fibre Fabry–Perot interferometer (FPI) sensor for relative humidity (RH) measurement is proposed. The FPI is formed by splicing a short section of hollow-core photonic crystal fibre(HCPCF) to single mode fibre and covering a chitosan film at the end of HCPCF. The refractive index of chitosan and film thickness will change with ambient RH, leading to the change in the reflected interference spectrum of FPI. RH response of the FPI sensor is analysed theoretically and demonstrated experimentally. It shows nonlinear response to RH values from 35 to 95%RH. The interference fringe shifts to shorter wavelength as RH increases with a maximum sensitivity of 0.28 nm/%RH at high RH level. And the fringe contrast also decreases as RH increases with an available maximum sensitivity of 0.5 dB/%RH. The sensor shows good stability and fast response time less than 1 min. With its advantages of compact structure, good performance, simple and safe fabrication, the proposed optical fibre FPI sensor has great potential for RH sensing.     

Agarose-Gel Based Guided-Mode Resonance Humidity Sensor

A photonic relative-humidity (RH) sensor employing the guided-mode resonance effect is designed, fabricated, and characterized. An agarose-gel transduction layer is integrated with a periodic silicon-nitride film to form a sensitive optical resonance structure. As the agarose-gel humidifies, the resonance wavelength shifts. Comparison with rigorous diffraction models allows quantification of the gel's refractive index and the attendant relative humidity. For the example sensor structure treated, the resonance wavelength shifts by ~9 nm on relative-humidity change from 20% RH to 80% RH     

Development and characterization of PET/Fish Gelatin–nanoclay composite/LDPE laminate

A three‐layer laminate film was developed with the following structure: polyethylene terephthalate (PET)/fish gelatin (FG)–nanoclay composite/low‐density polyethylene (LDPE). The FG–nanoclay composite material functioned as the oxygen barrier layer and demonstrated comparable oxygen barrier properties when compared with a similar laminate utilizing ethylene vinyl alcohol as the barrier layer at a relative humidity (RH) of up to 50%. The introduction of nanometer‐sized filler clay into the FG matrix lowered the oxygen permeability (OP) because of the tortuosity effect of the clay particles. In addition, the FG–nanoclay composite film exhibited bond strengths similar to both LDPE and PET. The hydrophilic nature of FG significantly increases OP under high (>50%) RH conditions. However, this new FG laminate film could be a possible alternative for packaging designers desiring a more sustainable packaging material for low‐RH (<50%) applications. Copyright © 2009 John Wiley & Sons, Ltd.     

多壁碳纳米管湿度传感器频率特性(英文)

为了研究测试频率对传感器性能的影响,改善多壁碳纳米管(multi-walled carbon nanotubes,MWCNTs)湿度传感器检测方法并提高传感器检测精度,对传感器频率特性进行了分析.在玻璃衬底上利用蒸镀和光刻技术制作了叉指电极,在电极表面涂敷了MWCNTs-SiO2敏感薄膜,最后通过烧结完成传感器制作.利用饱和盐溶液法产生相应湿度值,并使用RCL自动测试仪对传感器进行测试,测试频率选择在1 kHz到500 kHz之间.对传感器频率特性进行了实验与理论分析,结果表明,该传感器电容值对环境湿度敏感,并且其敏感特性受传感器检测频率的影响.使用毛细凝聚理论以及电解质物理理论对上述实验现象进行了合理的解释.传感器静态电容以及对湿度的灵敏度均随着测试频率的增加明显降低,测试频率为500 kHz时传感器灵敏度仅为测试频率1 kHz时的0.24倍.     

Ag-polyaniline nanocomposite cladded planar optical waveguide based humidity sensor

The paper reports synthesis of Ag-polyaniline nanocomposite and its evaluation as an active optical cladding on a planar optical waveguide (POW) as a humidity sensor with variable concentration of the composite. The nanocomposite is dispersed in acetonitrile, and spin coated on the planar waveguide to form a clad. The system shows response to humidity, when tested in the range of 20–92% relative humidity (RH). A prism film coupling is used to characterize the cladded waveguide. The maximum sensitivity is seen for 47% concentration of the nanocomposite in acetonitrile. The response and recovery of the sensor are 8 and 55 s respectively. The low hysteresis is exhibited by the sensor. The sensor has repeatability and reproducibility. Material characterization is done using Scanning Electron Micrograph (SEM), X-Ray Diffraction (XRD), Ultraviolet Spectroscopy (UV) and Fourier Transform Infrared Spectroscopy (FTIR).     

一种基于碳黑/聚四乙烯吡啶纳米复合物的新型湿度传感器

以4-羟-2,2,6,6-四甲基哌啶氮氧自由基(TEMPO)为引发剂,通过本体聚合方法制备聚四乙烯吡啶(P4VP)接枝纳米碳黑(CB)复合材料,以溴丁烷和1,4-二溴丁烷分别与之进行季胺化和交联季胺化反应,制得了新型电阻型湿敏材料.测试了该类纳米复合湿敏材料的温度响应特性,发现其在低湿环境下也具有较好的导电性,而且材料的导电行为同时存在离子导电和电子导电两种机理.通过改变碳黑与聚合物的相对比例,使聚合物产生季胺化以及交联季胺化反应等,可以调控两种导电机理的复合材料在电响应中所起的作用,从而改变其湿敏响应特性,制备可以全程响应的电阻型湿度传感器.     

溅射条件对湿敏薄膜特性的影响

本文介绍了RF溅射制备湿度敏感膜技术,讨论了衬底温度、工作气体及压力、放电电压及时间对湿敏膜感湿特性的影响。实验结果表明,只要认真控制上述工艺条件便可以制成感湿特性良好的湿度敏感膜。     

Device optimization of CO2 gas sensor using planar technology

A planar type Li+ ion based potentiometric CO2 micro gas sensor of size 2 x 3 mm has been fabricated on alumina substrate by combining thin and thick film technology. The heater, electrodes and electrolyte were deposited by thin film deposition technique and the sensing and reference electrodes were printed by silk screen printing technology. The optimal thickness and sintering temperature of electrolyte are 1.2 microm and 775 degrees C. The sensor with Li2CO3 and 20 mol% BaCO3 not only exhibits a good Nernstian behavior but also consistent results over a long time at 450 degrees C in dry as well as 70% RH humidity condition between 160-5000 ppm CO2 concentrations. The spreading effect of the sensing and reference materials was controlled by the addition of Al2O3:B2O3 (1:2 mol%) glass.     

Mesoporous thin-film on highly-sensitive resonant chemical sensor for relative humidity and CO2 detection

Distributed sensing of gas-phase chemicals is a promising application for mesoporous materials when combined with highly sensitive miniaturized gas sensors. We present a direct application of a mesoporous silica thin film on a highly sensitive miniaturized resonant chemical sensor with a mass sensitivity at the zeptogram scale for relative humidity and CO(2) detection. Using mesoporous silica thin-film, we report one of the lowest volume resolutions and a sensitive detection of 5.1 × 10(-4)% RH/Hz to water vapor in N(2), which is 70 times higher than a device with a nontemplated silica layer. In addition, a mesoporous thin-film that is functionalized with an amino-group is directly applied on the resonant sensor, which exhibits a volume sensitivity of 1.6 × 10(-4)%/Hz and a volume resolution of 1.82 × 10(-4)% to CO(2) in N(2).