基于Nafion-结晶紫传感膜的光纤湿度传感器研究

通过研究基于荧光和可见光吸收的两种湿度传感方法,从数种湿度分子探针中优选出结晶紫为分子识别器,包埋于Nafion溶胶中,制备成基于可见光吸收原理的光纤化学湿度传感膜。该传感膜与电荷耦合二极管阵列检测器等构成的光纤湿度传感器,于640 nm波长处对30%～100%范围内的相对湿度(relative humidity, RH)具有较快的响应时间(＜2 min)、较高的灵敏度(≤5%RH)、选择性和良好的可逆性(RSD≤2.6%)。     

一种新型高灵敏度光学微环湿度传感器

提出了以聚酰亚胺（PI）为感湿材料的三耦合点单微环新型湿度传感器。外界湿度变化使得聚酰亚胺SOI微环谐振特性发生变化,最终通过谐振波长的漂移量确定湿度值。讨论了不同部位感湿时系统的传感特性,并且选择了最佳湿敏元件。数值模拟结果表明：与传统的单微环传感器相比,新型传感器具有较高灵敏度和测量范围,Through端口的自由频谱范围可提高3倍。三耦合点单微环谐振器整体结构可作为最佳湿敏元件,该传感器在10%RH~80%RH相对湿度范围内,灵敏度可达到0.98 nm/%RH,该结构为制备高灵敏度可集成微型湿度传感器件提供了一定的理论依据。     

Humidity sensor based on localized surface plasmon resonance of multilayer thin films of gold nanoparticles linked with myoglobin

Layer-by-layer self-assembled multilayer thin films of gold nanoparticles (GNPs) linked with myoglobin (Mb) show substantial sensitivity to humidity at room temperature according to measurements of localized surface plasmon resonance (LSPR) absorption that relies on the interparticle interaction present in the film. The sensor response is reversible, with response and recovery times as low as 5 s. The sensing mechanism is as follows: as the ambient humidity changes, Mb molecules change their size, making the GNP-to-GNP spacing and thereby the interparticle interaction change; the change in the interparticle interaction causes a change in the LSPR absorption of the multilayer thin film. We found that the LSPR band of the multilayer thin film was almost insensitive to both the surrounding refractive index and the adlayer thickness, rendering the multilayer-film-based humidity sensor highly immune to ambient disturbances.     

Humidity sensitive properties of K-doped mesoporous silica SBA-15

Humidity sensors based on K-doped mesoporous silica SBA-15 were prepared and characterized by XRD, SEM, TEM and N₂ adsorption-desorption isotherms. The humidity sensing test results show that KCl doping improves the sensing characteristic of humidity sensors. The optimal result is obtained via sample 50 wt% KCl-doped SBA-15, which exhibits an excellent linearity in the whole humidity range of 11%-95%. It also shows satisfactory reversibility and fast responses to the environmental moisture. The investigation of the humidity sensitive characteristics of the K-doped SBA-15 sensor shows that this material could have good prospects of application in humidity sensor.     

串联双微环湿度传感器光谱特性研究

提出了一种基于串联双微环谐振器的新型聚酰亚胺(Polyimide,PI)湿度传感器,采用传输矩阵法和耦合模的理论计算微环谐振器的传递函数,并对比了传统单微环与串联不同半径的双微环的输出光谱特性。外界湿度变化使得聚酰亚胺SOI波导吸收水汽后折射率发生变化,从而引起微环输出光谱发生漂移,通过探测光谱漂移量来测湿度值,得到了串联双微环传感器的灵敏度和测量范围,并且分析了感湿部位不同时谐振器输出光谱特性。理论结果表明：串联不同半径的微环谐振器的自由光谱范围（FSR）要比单微环有所提高,而且串联双微环谐振器整体感湿比单个微环单独感湿的传感性能更优良,可作为最佳的湿敏元件。与传统的单微环传感器相比,串联不同半径的微环结构可提高系统的测量范围和灵敏度,半径为30和50 μm的串联微环谐振器的FSR可达到0.15 μm,传感器测量湿度范围为10%RH～80%RH,灵敏度可达到0.001 7 μm·(%RH)-1。因此串联不同半径的双微环谐振器为制备成本低、结构简单、高灵敏度、可集成的微型湿度传感器件提供一定理论基础。     

一种适用于湿度传感的表面等离子微环传感器

提出了一种适用于湿度传感的表面等离子微环传感器。该传感器纵向上采用表面等离子多层波导结构,横向上采用U型微环结构,以聚酰亚胺(polyimide,PI)为感湿材料。根据传输矩阵法推导表面等离子微环传感器结构的传递函数,外界环境的相对湿度变化引起聚酰亚胺的折射率变化,从而多层波导结构的有效折射率发生改变,导致传感器的输出光谱发生漂移。重点分析讨论了多层波导结构的传输特性以及感湿部位折射率的变化对输出光谱的影响。根据计算和仿真得出：当U型波导的两个耦合点间的距离为微环周长的整数倍时,传感器的输出光谱水平漂移量较大,自由光谱范围(FSR)加倍,达到128 nm,当外界环境相对湿度从10%RH变化到100%RH时,漂移量Δλ_m在0.005～0.038 μm之间变化,相比于其他湿度传感器,灵敏度提高了10～50倍,高达0.0005 μm/%RH,并且传输稳定。结果表明：设计的表面等离子微环传感器,灵敏度较好,性能稳定,可以应用于湿度测量,并且实现了在高灵敏度感湿的同时兼顾大范围的滤波选频,为微型光学器件的制备提供了理论基础。     

光纤布拉格光栅嵌入SMS光纤结构的湿度传感器

提出了一种基于光纤布拉格光栅嵌入单模-多模纤芯-单模(single-mode-multimode fiber core-single mode, SMS)光纤结构的湿度传感器。当环境湿度变化时,SMS光纤结构的干涉光谱会发生漂移,而光纤布拉格光栅对湿度不敏感,其纤芯基模保持不变。因此利用SMS光纤结构对环境湿度的敏感性去调制光纤布拉格光栅纤芯基模,通过检测光纤布拉格光栅纤芯基模的反射能量变化就可以实现湿度测量。数值模拟了SMS光纤结构的内部光场分布规律,理论计算了不同环境折射率时,多模纤芯的长度、直径对SMS光纤结构输出能量耦合系数的影响。理论模拟表明,随着环境折射率变化,SMS光纤结构中传输的纤芯基模的输出能量耦合系数会发生变化。同时制作了传感器样品并对其进行了传感实验研究,实验结果表明多模纤芯长35 mm、纤芯直径为85 μm的传感器在45%～95%RH湿度变化范围内,湿度灵敏度为0.06 dBm·(%RH)-1。在20～80 ℃温度范围内,传感器的温度灵敏度为0.008 nm·℃-1,温度所带来的湿度测量误差为0.047%RH·℃-1。传感器具有制作简单、灵敏度高、反射式能量检测等优点,在湿度测量领域有一定的应用价值。     

衰减全反射型电压传感器的理论和实验研究

提出了一种新型反射型聚合物波导电压传感器理论,并且进行了实验研究。这种电压传感器采用棱镜波导耦合结构,在棱镜下底面依次镀有金属膜一聚合物一金属膜三层结构。通过两层金属膜对极化聚合物加电压,利用聚合物材料电光效应和导模共振吸收峰对聚合物折射率的敏感特性,通过反射光强的测量来确定作用电压的变化值。实验中的测试电压范围是从-140V至 140V,得到的线性度值为0．991,电压测量的分辨力为0．1V,电压测量灵敏度系数为0．0011V^-1。实验表明这种电压传感器具有良好的线性和较高的灵敏度。     

光纤光栅型温湿度传感器的设计与实现

针对目前温湿度测量过程中电量传感器长期稳定性和互换性差的不足,以光纤光栅为基础,以改性PI薄膜为湿敏涂层,研制出了一种新型非电量温湿度传感器.详细阐述了其测量原理、制作工艺及其主要参量的优化确定,对其测量范围、测量精度、湿滞特性等主要特征参量进行了试验测定.测试结果表明:该传感器可在20～80℃、10%～90%测量范围内实现精度为±0.2℃和±5%的实时测量,且具有响应时间短(≤15 s)和长期稳定性好等优点.     

Humidity sensing under aggressive conditions using nafion conductors

A sensor capable of detecting moisture in a chlorine-air environment has been assembled from Nafion and platinum. Nafion acts as the solid electrolyte while platinum chemically deposited on the Nafion is the electrode material. Thermogravimetric analysis suggests that Nafion is stable up to 473 K. A Frequency Response Analyser (FRA) was used to calibrate the sensor in terms of impedance as a function of relative humidity. The frequency range was 10⁻² to 10⁷ Hz and an amplitude of 100 mV was applied. Impedance measurements show that only a bulk process occurs and when relative humidity is high, diffusion of moisture into and out of the platinum/Nafion composite becomes significant. This is reflected in the form of a spike at about 45° to the real axis. The sensor detects chlorine in air without loosing its chemical and physical stability. Conductivity increases as a function of temperature and reaches its peak at 433 K. The response time of the sensor is governed by temperature, thickness of the Nafion film and the amount of platinum on the surface. In practice the sensor can be operated with a frequency controller. Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000.     

Humidity sensing properties of Pd-doped ZnO nanotetrapods

Pd²⁺-doped ZnO nanotetrapods were prepared and studied for the humidity detection application. The humidity sensors developed were featured by combination of a quartz crystal microbalance (QCM) as a transducer and Pd²⁺-doped ZnO nanotetrapods as a sensing element. The ZnO nanotetrapods were synthesized by evaporating highly pure zinc pellets (99.999%) at 900 °C in air and PdCl₂ was doped on by traditional solution mixing process. Then the mixed solution distributed onto the electrode surfaces of the quartz crystal at room temperature. Pd²⁺-doped ZnO nanotetrapods were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results indicated that the response of the sensors varied with the different dosage PdCl₂. Linear regression algorithm was used for evincing the highly linear behavior of the Pd²⁺-doped ZnO nanotetrapods sensor. In this humidity sensing system, the Pd²⁺-doped ZnO nanotetrapods sensing material coated on the gold electrode of QCM showed good sensitivity (∼74.24324 Hz/%RH (relative humidity)), reproducibility, linearity (R² = −0.98834), short response and recovery time (less than 5 s).     

Humidity sensing properties of different single-walled carbon nanotube composite films fabricated by layer-by-layer self-assembly technique

Poly(diallyldimethylammonium chloride)/single-walled carbon nanotube (PDDA/SWNT) multilayered thin films were prepared on quartz crystal microbalance by layer-by-layer self-assembly technique, and their sensing properties to humidity were studied. The SWNTs were characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The composite films were observed by field-emission scanning electron microscope. Two types of SWNT humidity sensors were fabricated using SWNTs and carboxyl (COOH) modified SWNTs as sensitive material, respectively. The results showed that the sensitivity of the PDDA/SWNT?CCOOH humidity sensor was 20.23?% higher than that of the PDDA/SWNT sensor. In contrast, the latter had a much superior hysteresis property, and the reason to cause this phenomenon was discussed.     

基于银/二氧化钛复合膜的表面等离子共振气体传感器

表面等离子体共振是一种免标记的传感技术,当介质周围的介电常数发生改变时,则SPR谐振光谱特性也会随之改变.因此表面等离子体共振传感技术已广泛应用于生物化学和环境监测等领域.由于二氧化钛(TiO2)覆盖层不仅可以保护金属层,还能调谐SPR谐振的光谱强度和谐振波长于近红外波段,应用于1550 nm的光纤传感,其氧化还原反应...     

Nanocrystalline SnO2–TiO2 thin film deposited on base of equilateral prism as an opto-electronic humidity sensor

Present paper reports the synthesis of SnO₂–TiO₂ nanocomposite, its characterization and performance as opto-electronic humidity sensor. Nanocrystalline SnO₂–TiO₂ film was deposited on the base of an equilateral prism using a photo resist spinner and the as prepared film was annealed at 200 °C for 2 h. The crystal structure of the prepared film was investigated using X-ray diffraction (XRD). Minimum crystallite size of the material was found 7 nm. Surface morphology of the film was investigated by Scanning electron microscope (SEM LEO-0430, Cambridge). SEM image shows that the film is porous. Differential scanning calorimetry (DSC) of as synthesized material shows two exothermic peaks at about 40 and 110 °C, respectively which are due to the evaporation of chemical impurities and water. Further the prepared film was investigated through the exposure of humidity and relative humidity (%RH) was measured directly in terms of modulation in the intensity of light recorded on a digital power meter. The maximum sensitivity of sensor was found 4.14 μW/%RH, which is quite significant for sensor fabrication purposes.     

Humidity Sensing Using Gelatin and Cobalt Chloride Coating on Indium Tin Oxide-Coated Long-Period Grating

Abstract

In this article, humidity sensing using gelatin and cobalt chloride on indium tin oxide coated long-period gratings was proposed and demonstrated. First, a thin overlay of indium tin oxide was deposited on a long-period grating by using a simple dip coating methodology. Similarly, a combination of gelatin and cobalt chloride was deposited onto the indium tin oxide layer. A field emission scanning electron microscope provided detailed evidence of the attachment of amalgamation on long-period gratings. The designed sensor showed a significant shift in the resonance wavelength when the relative humidity varied from 40% to 95%, with a sensitivity of 0.12 nm/% relative humidity and an accuracy of 98.45%.     

Fiber-optic humidity sensor based on an air-gap long period fiber grating

In this paper, we propose a novel high-sensitivity fiber-optic humidity sensor based on a calcium chloride thin film to be coated on an air-gap long-period grating fabricated (AG-LPG) by combining the fiber side-polishing and fiber etching methods. When the surrounding refractive index of the air-gap long-period grating is changed by a change in humidity, the grating resonant wavelength is considered varied. Experimental results indicate that humidity can be detected by this sensing mechanism and has a high sensitivity of about 1.36 nm/1%RH.     

Graphene oxide thin film coated quartz crystal microbalance for humidity detection

In this paper, we demonstrated that chemically derived graphene oxide (GO) thin film as a humidity sensitive coating deposited on quartz crystal microbalances (QCMs) for humidity detection. By exposing GO thin film coated QCMs to various relative humidity (RH) environments at room temperature, the humidity sensing characteristics of the QCMs such as sensitivity and linearity, response and recovery, humidity hysteresis were investigated. The experiment results show that GO thin film coated QCMs exhibit an excellent humidity sensing performance. Moreover, the possible humidity sensing mechanism of GO thin film coated QCMs was also investigated by monitoring the crystal's motional resistance change. It is suggested that the frequency response of the QCMs is dependent on water molecules adsorbed/desorbed masses on GO thin film in the low RH range, and on both water molecules adsorbed/desorbed masses on GO thin film and variations in interlayer expansion stress of GO thin film derived from swelling effect in the high RH range.     

光纤SPR湿敏传感器及其共振光谱特性研究

提出并研制了基于光纤SPR传感探针的新型湿敏传感器。首先研究了光纤SPR传感探针对环境湿度变化的敏感特性,在此基础上提出在光纤SPR传感探针表面增覆不同厚度且具有水分子吸附功能的PVA薄膜来实现环境相对湿度的监测。研究结果表明,增覆双层PVA薄膜的光纤SPR传感探针在高湿区具有较好监测效果,其共振强度对应的相对湿度测量灵敏度达到1.59%/%RH,较光纤SPR探针呈现显著提高。而增覆单层PVA薄膜的光纤SPR传感探针在高湿区共振波长对应的相对湿度监测灵敏度达到2.411nm/%RH。此外所提出的新型光纤SPR湿敏探针在PVA薄膜失效后经过特殊工艺处理仍可重复镀膜使用。     

Bimetallic Silver-Gold Film Waveguide Surface Plasmon Resonance Sensor

It is desirable that a surface plasmon resonance (SPR) sensor is highly sensitive to binding interactions within the sensing region, generate evanescent fields with long penetration depths, and utilize a metal film that is very stable even in extreme environmental conditions. In this study, we present the first example of a wavelength-modulated waveguide SPR sensor with a bimetallic silver-gold film for surface plasmon excitation. The underlying silver yields better evanescent field enhancement of the sensing surface, while the overlying gold ensures that the stability of the metallic film is not compromised. It is shown experimentally that in terms of dλ/dn, the bimetallic film waveguide SPR configuration has a sensitivity of 1232 nm/RIU, greater than two times improvement from the 594 nm/RIU achievable with single gold film waveguide SPR sensor. The higher sensitivity, compact nature, and better evanescent field enhancement of this configuration provides the potential to biosensing applications.     

Use of polyethylene glycol coatings for optical fibre humidity sensing

Humidity induced change in the refractive index and thickness of the polyethylene glycol (PEG) coatings are in situ investigated for a range from 10 to 95%, using an optical waveguide spectroscopic technique. It is experimentally demonstrated that, upon humidity change, the optical and swelling characteristics of the PEG coatings can be employed to build a plastic fibre optic humidity sensor. The sensing mechanism is based on the humidity induced change in the refractive index of the PEG film, which is directly coated onto a polished segment of a plastic optical fibre with dip-coating method. It is observed that PEG, which is a highly hydrophilic material, shows no monotonic linear response to humidity but gives different characteristics for various ranges of humidity levels both in index of refraction and in thickness. It undergoes a physical phase change from a semi-crystalline structure to a gel one at around 80% relative humidity. At this phase change point, a drastic decrease occurs in the index of refraction as well as a drastic increase in the swelling of the PEG film. In addition, PEG coatings are hydrogenated in a vacuum chamber. It is observed that the hydrogen has a preventing effect on the humidity induced phase change in PEG coatings. Finally, the possibility of using PEG coatings in construction of a real plastic fibre optic humidity sensor is discussed.