A sensitive nonenzymatic hydrogen peroxide sensor based on DNA–Cu complex electrodeposition onto glassy carbon electrode

In this paper, DNA–Cu²⁺ complex was electrodeposited onto the surface of glassy carbon (GC) electrode, which fabricated a DNA–Cu²⁺/GC electrode sensor to detect H₂O₂ with nonenzyme. Cyclic voltammogram of DNA–Cu²⁺/GC electrode showed a pair of well-defined redox peaks for Cu²⁺/Cu⁺. Moreover, the electrodeposited DNA–Cu²⁺ complex exhibited excellent electrocatalytic behavior and good stability for the detection of H₂O₂. The effects of Cu²⁺ concentration, electrodeposition time and determination conditions such as pH value, applied potential on the current response of the DNA–Cu²⁺/GC electrode toward H₂O₂ were optimized to obtain the maximal sensitivity. The linear range for the detection of H₂O₂ is 8.0 × 10⁻⁷ M to 4.5 × 10⁻³ M with a high sensitivity of −40.25 μA mM⁻¹, a low detection limit of 2.5 × 10⁻⁷ M and a fast response time of within 4 s. In addition, the sensor has good reproducibility and long-term stability and is interference free.     

Low-cost colorimetric sensor for the quantitative detection of gaseous hydrogen sulfide

A simple, rapid and low-cost method for differentiating a wide range of concentrations of gaseous hydrogen sulfide (H₂S) is described. A large dynamic range (50 ppb to 50 ppm) was successfully classified at ambient temperature using a colorimetric sensor array comprised of chemoresponsive dyes coupled to a commercially available 8-bit flatbed scanner. Principle component analysis of the composite magnitude and kinetics of color change for the array of dye spots over the entire dynamic range resulted in 100% classification. This was achieved by including chemoresponsive dyes which reacted specifically with H₂S at different detection thresholds.     

Pd/PVDF thin film hydrogen sensor system based on photopyroelectric purely-thermal-wave interference

A novel sensitive solid-state sensor system for trace hydrogen gas detection has been developed as a next generation device to earlier photopyroelectric (PPE) hydrogen sensors. The basic principle of the sensor is based on the technique of PPE purely-thermal-wave interferometry recently developed in this Laboratory. The active element of the sensor is a thin polyvinylidene fluoride (PVDF) pyroelectric film, sputter-coated with Pd on one surface and with a Ni–Al alloy electrode on the other surface. Unlike the conventional PPE hydrogen sensors, this new sensor produces a coherent differential PPE signal in a single detector, rather than using two detectors (one active, the other reference) and complicated electronics. The measurement results show that the signal noise level, the detectivity and the signal dynamic range are improved by more than one order of magnitude compared with the conventional single-beam method. The operating characteristics have been examined for three different thicknesses of Pd coating on the same thickness PVDF-film detector. The signal generating mechanism, attributed to the change of the optical absorptance of the Pd coating when exposed to hydrogen, and/or the shift in the Pd work function, is also discussed.     

A hydrogen peroxide biosensor based on direct electrochemistry of hemoglobin in Hb–Ag sol films

Hemoglobin (Hb) was used as a template to fabricate hemoglobin–silver (Hb–Ag) sol in which the hemoglobin showed direct electrochemistry on a glass carbon (GC) electrode. Ultraviolet–visible (UV–vis) spectra and reflectance absorption infrared (RAIR) spectra suggested that hemoglobin in Hb–Ag sol retained its native secondary structure. Scanning electron microscopy (SEM) demonstrated that the morphology of the Hb film was much different from the Hb–Ag sol film. The Hb–Ag film proved to exhibit a good electrocatalytic activity for the reduction of hydrogen peroxide. Based on this, a novel amperometric hydrogen peroxide biosensor was developed, which showed a sensitive response to the reduction of H₂O₂ without any electron mediator. Under optimum conditions, the biosensor responded linearly to H₂O₂ in the concentration range of 1 × 10⁻⁶ to 2.5 × 10⁻² M with detection limit of 1 × 10⁻⁷ M at 3σ. Moreover, the studied biosensor exhibited high sensibility, good reproducibility, and long-term stability.     

Micromachined catalytic combustible hydrogen gas sensor

An integrated catalytic combustion H₂ sensor has been fabricated by using MEMS technology. Both the sensing elements and the reference elements could be integrated into the suspended micro heaters connected in a suitable circuit such as a Wheatstone configuration with low power consumption. Two sensitive elements and two reference sensors were integrated together onto a single chip. The size of chip was 5.76 mm² and the catalytic combustion sensor showed high response to H₂ at operating voltage of 1 V. The response and recovery times to 1000 ppm H₂ were 0.36 s and 1.29 s, respectively.     

Exfoliated single-walled carbon nanotube-based hydrogen sensor

The paper presents a simple and inexpensive method for the preparation of an efficient hydrogen gas sensor based on exfoliated Pd-decorated single-walled carbon nanotubes (SWNTs). SWNTs were synthesized by catalytic chemical vapor deposition of methane using a fixed-bed catalytic reactor over hydrides of Mm_0.2Tb_0.8Co₂ obtained through hydrogen decrepitation technique. Purified and chemically treated SWNTs were functionalized with Pd, resulting in nanostructured Pd dispersion on the SWNT surface. Structural, morphological and vibrational characterizations were carried out using XRD, TEM, HRTEM, Raman spectroscopy and FTIR spectroscopy. Sensor devices were fabricated by spraying palladium-dispersed chemically treated SWNT dispersions on smooth glass substrates. Systematic investigations on the hydrogen sensing properties of Pd-SWNT were carried out. Pd-functionalization of the employed SWNT enabled increasing the device response towards hydrogen. Exfoliated SWNT achieved using gum arabic (GA) showed better response to hydrogen when compared to naive purified SWNT. The fabricated thin film sensors exhibited good reversible and reproducible response towards hydrogen at room temperature.     

Room temperature hydrogen gas sensor nanocomposite based on Pd-decorated multi-walled carbon nanotubes thin films

Multi-walled carbon nanotubes (MWCNTs) are successfully processed in the form of thin films (buckypapers), and their morphology and electrical behaviour are characterized. The MWCNTs are synthesized by the floating catalyst chemical vapour deposition process. The effects of a sequence of treatments applied for MWCNTs purification on the buckypapers electrical behaviour are also examined. Nanocomposite thin films constituted of pristine and purified MWCNTs and Pd nanoparticles are prepared in order to evaluate their viability as H₂ sensors at room temperature. For this purpose, the electrical resistance of the nanocomposite films in atmospheres with different H₂ concentrations, is determined. Scanning electron microscopy (SEM) images show that the buckypapers and the nanocomposite films are 2D structures constituted by randomly oriented MWCNTs. The buckypapers present a semiconductor-like electrical behaviour as determined by the standard four point method. Room temperature resistivity values of around 10⁻³ Ω m are assessed. Nanocomposite films show different electrical behaviour depending on the purification treatment applied to the MWCNTs employed. Furthermore, the electrical resistance of the nanocomposite films is found to increase when the measurements are performed in H₂ atmosphere. Values of H₂ sensitivity at room temperature of the nanocomposite films up to 2.15% are determined for H₂ average concentration higher than 350 ppm with short recovery time.     

基于AMR传感器的车辆检测算法

深入研究了各向异性磁阻(AMR)传感器的数据采集原理和特征波形向量提取方法,提出了一种基于AMR传感器的车辆检测算法:自适应状态机的车辆检测算法。该算法可以自适应地更新阈值和基线,利用状态机,达到对车辆的准确和高效的检测。可以用于检测道路交通车流量,也可以应用在大型停车场的车辆诱导系统。     

Characterization of carbon paste electrodes modified with manganese based perovskites-type oxides from the amperometric determination of hydrogen peroxide

This work proposes the amperometric determination of hydrogen peroxide reduction and oxidation as a tool for the characterization of La_1−xA_xMnO₃ perovskites dispersed in a graphite composite electrode (carbon paste electrode, CPE). The catalytic activity of perovskites towards the oxidation and reduction of hydrogen peroxide is highly dependent on the nature of the A cation and on the temperature and time of calcination employed during the synthesis. Therefore, the selection of the optimal synthesis conditions to obtain the best catalytic activity towards hydrogen peroxide can be performed from amperometric determinations.We also report the analytical application of the perovskite modified CPE through the quantification of hydrogen peroxide in two real samples. Some preliminary results about the usefulness of La_0.66Sr_0.33MnO₃–CPE to develop a glucose biosensor by incorporation of the enzyme glucose oxidase (GOx) within the electrode are also reported. The difference in sensitivity to glucose at CPE–GOx and CPE–La_0.66Sr_0.33MnO₃–GOx (11.9 μA mol⁻¹ L and 158.1 μA mol⁻¹ L, respectively), clearly demonstrate the advantages of the association of the biocatalytic activity of GOx and the catalytic activity of perovskites towards hydrogen peroxide oxidation/reduction, and opens the doors to the development of new sensors for other important bioanalytes.     

基于ANSYS的声表面波氢气传感器压电分析

设计了声表面波氢气传感器的结构,利用ANSYS软件建立了声表面波传感器的有限元模型,并对SAW氢气传感器进行了仿真,最后用数据处理软件Origin分析了敏感薄膜的材料参数对传感器输出的影响.传感器通人1 000× 10-6的氢气后,钯膜的厚度、密度、弹性模量等发生了相应改变,进而导致输出电压、频率等发生改变.分析表明:...     

基于稀疏分解残差的氢气传感器故障探测与辨识方法

针对传感器故障探测和诊断,提出了一种基于稀疏分解残差的氢气传感器故障探测和辨识方法.基于信号稀疏分解理论,对采集的传感器正常信号数据集,利用K奇异值分解(K-SVD)学习算法得到一超完备字典D;在字典上对非正常(故障)信号进行分解,根据稀疏分解的残差大小和范围完成对传感器故障的探测及辨识.实验结果表明:对氢气传感器的故障探测率和总辨识率分别达到98.75%和97.25%,可以有效地解决氢气传感器的故障探测和辨识.     

基于相敏检测技术的光纤氧传感器

采用相敏检测技术,实现了对弱荧光信号的检测。用于一种基于荧光猝灭原理的光纤氧传感器。传感器具有较强的抗干扰能力、较好的重复性和稳定性。     

基于微变电容式传感器的角度-振动测量方法

利用微变电容式MEMS传感器,设计了一种角度-振动量的检测方法。以RC串联回路直流充放电理论为基础,单片机系统为主体,实现振动量和角度偏移量的检测。经过适当的滤波算法对原始信号进行处理,可以有效地减小噪声的干扰,并快速而准确地分离出基波分量和高次谐波分量,进而得出较好的振动曲线和角度曲线。经实验验证：角度检测和振动检测可同时进行且互不干扰。     

Pt nanoparticle-supported multiwall carbon nanotube electrodes for amperometric hydrogen detection

Platinum nanoparticles (Pt NPs) were grown directly on multiwall carbon nanotubes (MWNTs) using a wet chemical reduction process. Gas permeable Pt NP-supported MWNT (Pt/MWNT) electrodes were then formed on microporous PTFE membranes through the vacuum-filtration of a Pt/MWNT solution. The potential use of these electrodes in amperometric hydrogen sensor applications was assessed. Various material analysis methods such as SEM, TEM and XRD were employed in order to characterize the morphologies and microstructures of the Pt/MWNT nanocomposites. The electrodes exhibited a nanoporous interwoven surface morphology as a result of Pt agglomerates attached to the MWNTs. From the XRD and TEM measurements, individual polygonal Pt NPs were confirmed to have polycrystalline face-centered cubic (fcc) structures and very small particle sizes of 2-7 nm. The electrode fabrication process was sequentially optimized by adjusting the MWNT content, H₂PtCl₆ concentration, NaBH₄ concentration, and the drying temperature. At optimized conditions, the Pt/MWNT electrode displayed a high sensitivity greater than 200 μA/ppm, a fairly good selectivity to interfering CO species, and an excellent linear response over the wide concentration range of 5-1000 ppm. Furthermore, the performances of the electrodes were found to be better than those of binary NP-supported MWNT systems (Pt-Pd/MWNT, Pt-Zn/MWNT, Pt-Ni/MWNT and Pt-ZnO/MWNT).     

基于四相检测技术的微电容传感器

一种基于四相检测技术的电荷转移式微电容传感器,具有很强的消除杂散电容影响的能力,适用于被检测对象电容值小于1pF的场合,分辨力达1fF,灵敏度高于1V/pF,并能输出4～20mA的电流。其优良的性能和低廉的价格,使得微电容传感器的广泛推广应用成为可能。     

Solvatochromic betaine dyes as optochemical sensor materials: detection of polar and non-polar vapors

Solvatochromic effects in the UV/VIS spectra of dyes can be applied to the monitoring of solvents in the gaseous phase. Within the class of solvatochromic dyes Reichhardt's betaine reveals an outstanding hypsochromic effect on protic solvents with a band shift of up to 350 nm. For vapor detection, the sensor behavior was optimized according to the linearity of the response signal, the sensitivity and a minimum influence of humidity by hydrophobizing siloxanes as additives. Furthermore, the dyes were immobilized under mild conditions by a sol–gel process which generates a high porosity for easy analyte access. The detection principle could be further extended to aprotic, polar solvents by embedding the dyes in protic matrices that form hydrogen bonds to the betaine oxygen. Then, the analyte disturbs the hydrogen bonds resulting in a bathochromic band shift resembling a back titration. Finally, the betaine phenol blue even allows the detection of halogenated hydrocarbons that lack a pronounced functionality but nonetheless a hyperchromic effect occurs during analyte exposition. Mechanistic aspects of these solvent absorption processes were traced by mass-sensitive measurements.     

基于微波传感器的生化溶液浓度检测

用同轴线设计了一种探针式的微波传感器,对几种有代表性的生化溶液：NaCl 溶液、葡萄糖溶液、蛋白胨溶液进行了浓度测量。实验结果显示：传感器反射系数在3900～3950MHz 的频段内随着 NaCl浓度的增大而减小,在3953～3975 MHz 的范围内随着葡萄糖浓度的增大而减小,蛋白胨的敏感区则在3850～3950 MHz 的频段内。实验结果表明：该传感器可以为生化溶液浓度的检测提供一种低成本、高效的解决办法。     

An electrochemical biosensor for determination of hydrogen peroxide using nanocomposite of poly(methylene blue) and FAD hybrid film

An electrochemical biosensor for determination of hydrogen peroxide (H₂O₂) has been developed by the hybrid film of poly(methylene blue) and FAD (PMB/FAD). The PMB/FAD hybrid film was performed in PBS (pH 7) containing methylene blue and FAD by cyclic voltammetry. Repeatedly scanning potential range of −0.6-1.1 V, FAD was immobilized on the electrode surface by electrostatic interaction while methylene blue was electropolymerized on electrode surface. This modified electrode was found surface confined and pH dependence. It showed good electrocatalytic reduction for H₂O₂, KBrO₃, KIO₃, and NaClO as well as electrocatalytic oxidation for NADH. At an applied potential of −0.45 V vs. Ag/AgCl, the sensor showed a rapid and linear response to H₂O₂ over the range from 0.1 μM to 960 μM, with a detection limit of 0.1 μM and a significant sensitivity of 1109 μA mM⁻¹ cm⁻² (S/N = 3). It presented excellent stability at room temperature, with a variation of response current less than 5% over 30 days.     

基于金纳米-植酸胶束混合组装的过氧化氢传感器的电化学研究

采用混合组装技术,利用植酸胶束(IP6micelles)的磷酸酯键络合辣根过氧化物酶(HRP)和金纳米粒子(GNPs),形成了具有生物亲和性的纳米复合材料,保持了辣根过氧化物酶的生物活性,并利用金纳米粒子的高电子密度、介电特性和催化性能,实现了HRP与玻碳电极(GCE)表面的直接电子转移。Nafion膜的滴加能提高电极的选择性和稳定性。实验过程中借助紫外-可见吸收光谱和透射电子显微镜进行表征,实验结果证明:GNPs的高导电和高催化性能,结合植酸胶束的优良生物相容性和对酶的高负载量的特点,使得吸附在其上的HRP保持活性,制备的生物传感器能对H2O2进行电催化还原。Nafion/HRP-IP6micelles-GNPs/GCE对H2O2的线性浓度范围为5×10-7～1.15×10-5mol/L(线性相关系数r=0.993,n=9),最低检测限为0.1μmol/L(信噪比S/N=3),米氏常数为0.002 4 mmol/L。     

基于气体传感器阵列的动态检测系统

描述了一个基于传感器阵列的气体检测系统,其阵列由6只气体传感器组成。系统采用较以往静态加热所不同的动态加热方式,重点介绍了该系统的硬件结构。通过分析系统的气体响应特性实验得出:该系统具有静态测试所不具备的许多优点,如,信号特征多、容易识别等。