An optical fiber chemical sensor for mercury ions based on a porphyrin dimer

The synthesis of a novel fluoroionophore, 5-p-[[4-(10',15',20'-triphenyl-5'-porphinato) phenyloxyl]-1-butyloxyl]phenyl-10,15,20-triphenylporphine (DTPP), and its application for preparation of a Hg(II)-sensitive optical fiber chemical sensor are described. The response of the sensor is based on the fluorescence quenching of DTPP by coordination with Hg(II). The porphyrin dimer-based sensor shows a linear response toward Hg(II) in the concentration range 5.2 x 10(-7)-3.1 x 10(-4) mol x L(-1), with a working pH range from 2.4 to 8.0. The sensor shows excellent selectivity for Hg(II) over transition metal cations including Cd(II), Co(II), Cu(II), Ni(II), Pb(II), Zn(II), and Fe(III). As a sensing agent, the porphyrin dimer shows obviously better fluorescence response characteristics toward Hg(II) compared to porphyrin monomer or metalloporphyrin. The effect of the composition of the sensor membrane was studied, and the experimental conditions were optimized. The sensor has been used for determination of Hg(II) in water samples.     

Diffractive optical chemical sensor based on light absorption

A new type of chemical sensor based on light absorption is proposed. An array of zones alternatively containing the pH indicator thymolphthalein is formed in a gelatin film. By changing the sample solution from acidic to alkaline, a blue stripe appears in the gelatin film. This acts as a transmission grating and diffracts the introduced laser beam. Theory predicts that this method, which is based on light absorption/beam diffraction, is as sensitive as or more sensitive than fluorometry.     

Development of a specific and highly sensitive optical chemical sensor for determination of Hg(II) based on a new synthesized ionophore

A novel optode for determination of Hg(II) ions is developed based on immobilization of a recently synthesized ionophore, 7-(1H-imidazol-1-ylmethyl)-5,6,7,8,9,10-hexahydro-2H-1,13,4,7,10 benzodioxatriaza cyclopentadecine-3,11(4H,12H)-dione, in a PVC membrane. Dioctyl sebacate was used as a plasticizer, sodium tetraphenylborate as an anionic additive and ETH5294 as a chromoionophore. The response of the optode was based on the complexation of Hg(II) with the ionophore in the membrane phase, resulting an ion exchange process between Hg(II) in the sample solution and H⁺ in the membrane. The effects of pH and amounts of the ionophore, chromoionophore, ionic additive and type of plasticizer on the optode response were investigated. The selectivity of the optode was studied in the present of several cations. The optode has a linear response to Hg(II) in the range of 7.2 × 10^? 13–4.7 × 10^? 4 mol L^? 1 with detection limit of 0.18 pmol L^? 1. The optode was successfully applied to the determination of Hg(II) in real samples.     

Electrochemical sensor for ranitidine determination based on carbon paste electrode modified with oxovanadium (IV) salen complex

The preparation and electrochemical characterization of a carbon paste electrode modified with the N,N-ethylene-bis(salicyllideneiminato)oxovanadium (IV) complex ([VO(salen)]) as well as its application for ranitidine determination are described. The electrochemical behavior of the modified electrode for the electroreduction of ranitidine was investigated using cyclic voltammetry, and analytical curves were obtained for ranitidine using linear sweep voltammetry (LSV) under optimized conditions. The best voltammetric response was obtained for an electrode composition of 20% (m/m) [VO(salen)] in the paste, 0.10 mol L^? 1 of KCl solution (pH 5.5 adjusted with HCl) as supporting electrolyte and scan rate of 25 mV s^? 1. A sensitive linear voltammetric response for ranitidine was obtained in the concentration range from 9.9 × 10^? 5 to 1.0 × 10^? 3 mol L^? 1, with a detection limit of 6.6 × 10^? 5 mol L^? 1 using linear sweep voltammetry. These results demonstrated the viability of this modified electrode as a sensor for determination, quality control and routine analysis of ranitidine in pharmaceutical formulations.     

Photocatalytic sensor for chemical oxygen demand determination based on oxygen electrode

The construction and performance evaluation of a novel Chemical Oxygen Demand (COD) sensor is described. The sensor measures, using an oxygen electrode, a decrease of dissolved oxygen of a given sample resulting from photocatalytic oxidation of the organic compounds therein. As the photocatalyst, titanium dioxide (TiO2) fine particles adsorbed on a translucent poly(tetrafluoroethylene) (PTFE) membrane was used. The oxygen electrode with the membrane attached on its tip was used as the sensor probe. The operation characteristics of the sensor are demonstrated using an artificial wastewater and real water samples from lakes in Japan. This method is considered to be reliable, in that the observed parameter is close to the theoretical definition of chemical oxygen demand (COD), the amount of oxygen consumed for oxidation of organic compounds.     

An optical gas sensor based on ellipsometric readout

A gas sensor system based on ellipsometric readout is presented. It includes a gas chamber and a compact ellipsometer operated in off- mode. Small, low-cost optical components are used to demonstrate that this advanced methodology can be implemented in simplified instrumentation. The off- ellipsometric sensing principle and transducer mechanisms of the sensing layers, as well as the instrumentation, are described. The application of the sensor system is exampled with experimental results on low-concentration alcoholic gases (methanol, ethanol, and 2-propanol) using porous silicon as a sensing layer. Optimization of the optics of the sensor system, improvement of sensitivity or alteration of selectivity by modification of sensing layers, and multisensing by using several ellipsometric units in parallel are discussed.     

A selective optical sensor for beryllium determination based on incorporating of 1,8-dihydroxyanthrone in a poly (vinyl chloride) membrane

A new optical sensor was fabricated for determination of beryllium ions. The optode membrane was prepared by incorporation of 1,8-dihydroxyanthrone and sodium tetraphenylborate (NaTPB) in a plasticized poly (vinyl chloride) membrane containing ortho-nitrophenyl octyl ether (o-NPOE) as a plasticizer. Color of the sensing membrane in contact with Be(2+) ions at pH 10.5, was changed from orange to red. The different variables affecting uptake efficiency were evaluated and optimized. Under the optimum conditions (i.e. 28.0% PVC, 60.0% o-NPOE, 8.0% 1,8-dihydroxyanthrone, 4.0% NaTPB and response time of 6 min), the proposed sensor displayed a linear range of 0.1-5 μg mL(-1) with a detection limit of 0.03 μg mL(-1). Also the precision (RSD%) was better than 2.9% for 7 replicate determinations of 1 μg mL(-1) Be in various membranes. The selectivity of the probe was studied for some cations and anions. Experimental results showed that the sensor was high selective in the presence of ethylenediaminetetraacetic acid (EDTA) as a masking agent and could be used as an effective tool in analyzing the beryllium content of water samples.     

An optical chemical sensor using a fluorophor- embedded Langmuir-Blodgett film

An optical sensor with a Langmuir-Blodgett (LB) film was developed for simultaneous recognition of amino acids in an aqueous solution. Anthroyloxy- stearate-containing stearate LB films and perylene-containing arachidate LB films were deposited on a quartz glass. The fluorescence of these LB films in an aqueous solution was quenched in response to amino acids. Amino acids were classified into five groups by the pattern of fluorescence quenching of anthroyloxy stearate and perylene LB films.     

La(0.7)Sr(0.3)MnO3 nanoparticles based ultra-high sensitive ammonia chemical sensor

A facile, reliable, reproducible and ultra-high sensitive aqueous ammonia chemical sensor has been fabricated based on the utilization of La(0.7)Sr(0.3)MnO3 nanoparticles (LSMO NPs), as efficient electron mediators, and reported in this paper. The LSMO NPs were prepared by hydrothermal protocol followed by the annealing process and characterized in detail in terms of their mophological, structural and compositional properties. The I-V technique based aqueous ammonia sensor exhibits an ultra-high sensitivity of 494.68 +/- 0.01 microA cm(-2)mM(-1) and very low-detection limit of 0.2 microM with a response time less than 10 s. To the best of our knowledge, this is the first report in which LSMO is used as an efficient electron mediator for the fabrication of aqueous ammonia chemical sensor. Moreover, by comparing the literature, it is confirmed that the fabricated sensor exhibits highest sensitivity towards the detection of aqueous ammonia. This LSMO nanomaterial based research broadens the range of efficient electron mediators utilized for the fabrication of ultra-high sensitive chemical sensors.     

Heptadentate Schiff-base based PVC membrane sensor for Fe(III) ion determination in water samples

Tests performed using heptadentate Schiff's base ((tris(3-(thiophenal)propyl)amine (TTA)) toward Fe(III) ions indicated that it could be used as an Fe(III) selective ionophore to be used in a plasticized polymeric membrane sensor. The resulting sensors were found to produce a linear response range of five orders of magnitude with a slope of 19.8 ± 0.3 mV decade^− 1 with a detection limit is 8.3 × 10^− 9 mol L^− 1. The sensor could be used in a pH window of 2.4-4.3 and the response time of the sensor was below 10 s, in addition to its very good Fe(III) selectivity over many mono-,di- and trivalent transition and heavy metal ions. The life time of the electrode was found to be at least 10 weeks.     

基于光流传感器的视频稳像技术

针对平台运动导致的视频抖动问题,提出了一种基于光流传感器的视频稳像技术。该方案首先通过对一般光流传感器的改进,使其具有旋转运动下输出准确运动矢量的能力,然后利用光流传感器获得相邻两帧图像之间的运动矢量,并通过坐标变换计算出主相机的实时平移和旋转信息;其次,对原视频图像序列进行运动补偿,以获得稳定的图像序列,最终实现了视频稳像。实验结果表明,稳像后的图像序列与未稳像之前相比峰值信噪比提高了11.86 dB。该方案在视频抖动较大的情况下,能够明显减小图像序列的抖动现象,具有稳像效果好的特点,满足视频稳像的性能要求,对提高平台抗扰能力有着较高的实用性。     

Novel optical distance sensor based on MSM technology

This paper describes a novel distance-sensor concept based on photodiodes in metal-semiconductor-metal technology (MSM). MSM photodiodes can be operated as electrooptical mixers functioning similar to the so-called photonic mixing device (PMD). This paper employs the correlation techniques previously used with the PMD to the MSM. First, experimental results obtained with the MSM inserted into the authors' standard laboratory setup are provided. Additionally, different configurations well suited for mixer operation of the MSM are pointed out. Throughout this paper, similarities between the PMD and MSM are pointed out, as well as key differences.     

Conductometric chemical sensor based on individual CuO nanowires

CuO nanowires with high crystalline quality are synthesized via a simple thermal oxidation method. Charge conduction on individual nanowires under a transverse electric field exhibits an intrinsic p-type semiconducting behavior. Variations in signal transducer in different chemical gas environments are measured on individual CuO nanowire field effect transistors. They demonstrate good performance to both NO(2) and ethanol gasses. In particular, the nanowire chemical sensor reveals a reverse response to ethanol vapor under temperature variation. Experimental results and first-principles calculations indicate that ethanol is oxidized in air at high temperature, resulting in the production of CO(2) and H(2)O. The strong H(2)O adsorption leads to the reversal behavior, due to the electron transfer from H(2)O molecules to the CuO surface.     

溶胶—凝胶法制备基于荧光猝灭原理的光纤氧传感器在线监测水中溶解氧

利用氧分子对金属钌化合物的荧光具有猝灭作用的特性,构造出基于荧光猝灭原理的光纤氧传感器。就用于水中溶解氧在线监测的光纤光谱仪的搭建、传感器探头的设制及传感膜的制作过程进行探索,并对传感器的响应性能进行考察。结果表明以联吡啶钌等作为荧光指示剂以溶胶-凝胶法制备的传感膜对溶解氧的响应具有良好的可逆性,稳定性,较快的响应时间和较长的使用寿命。与标准法相对照,用本仪器系统测定了不同盐度的人工海水中的溶解氧浓度,两种方法在不同浓度水平下的溶解氧测定值均无显著性差异。本法的日内和日间RSD在1.7％～5.0％之间。     

An optical fibre sensor for dynamic deformation measurements based on the intensity modulation of a low-coherence source

Abstract

An optical fibre sensing technique for the measurement of dynamic deformations using a Michelson interferometer is reported. The method applied to interferometers with an initial path unbalance of around 1 cm is based on the rf intensity modulation of a low-coherence source. A large measurement range of 1 cm is intrinsic to the method and with an adequate demodulation process sensitivity better than 10 μm is obtained. This novel approach allows for measuring dynamic deformations with a bandwidth up to 100 Hz.     

Monolithically integrated optical displacement sensor based on triangulation and optical beam deflection

A monolithically integrated optical displacement sensor based on triangulation and optical beam deflection is reported. This sensor is simple and consists of only a laser diode, a polyimide waveguide, and a split detector (a pair of photodiodes) upon a GaAs substrate. The resultant prototype device is extremely small (750 mum x 800 mum). Experiments have shown that this sensor can measure the displacement of a mirror with resolution of better than 4 nm. Additionally, we have experimentally demonstrated both axial and lateral displacement measurements when we used a cylindrical micromirror (diameter, 125 mum) as a movable external object.     

一种基于脱氧核酶的铅离子电致化学发光传感器

本文设计了一种基于脱氧核酶(DNAzyme)检测Pb2+的电致化学发光(Electrocheluminescent,ECL)传感器。将对Pb2+特异性识别的DNAzyme通过金-巯键固定于金电极表面,并与标记有二氧化硅包埋的钌联吡啶(Ru-SNPs)的底物DNA链发生杂交,形成双链DNA(ds-DNA)传感器。Pb2+不存在时,由于Ru-SNPs靠近电极表面,产生强的ECL信号。当Pb2+存在时,DNAzyme催化底物链断裂,Ru-SNPs远离电极表面,导致ECL信号下降。实验结果表明ECL强度与Pb2+浓度在0.2-1.0 nmol/L范围内呈良好的线性关系,检测限可达0.04 nmol/L,其他二价金属离子对其基本无干扰。     

Fiber-optic temperature sensor used for oil well based on semiconductor optical absorption

This paper describes an optical-fiber sensor developed for temperature measurement under offshore oil well conditions. The sensor exploits the displacement of the optical absorption edge occurring in semiconductors under the influence of temperature variation as a result of temperature-induced energy shifting of conduction band extrema. The structure of the sensor and the measurement principle are described. The common-path reference measurement and node type error compensation technologies are developed. And, the detailed theoretical analysis indicates that the proposed sensor system can effectively improve measurement errors caused by light fluctuation, difference and variation of the detector responsiveness, circuit magnification times, and so on. It proves that this sensor system can be applied under long-term formidable conditions with fairly good measurement stability.     

An acoustic sensor system for determination of macroscopic surfaceroughness

In this paper, an alternative technique for the measurement of roughness of road surfaces is proposed. This noncontact method is based on the scattering of acoustic waves from the road surface and measuring the normalized Fourier spectrum of the scattered wave in the specular direction. Surfaces prepared with different size aggregates ranging from 2.36 mm to 25 mm were analyzed. The roughness parameter of a surface increases linearly with increasing aggregate size. The proposed method can possibly be extended to perform in situ surface roughness measurements from a moving vehicle     

Smart chemical taste sensor for determination and prediction of taste qualities based on a two-phase optimized radial basis function network

A novel, smart, chemical taste sensor that realistically mimics the behavior of the human gustatory system is described. The taste sensor consists of an array of electrochemical sensors that represent the gustatory receptors on the human tongue, and a two-phase optimized radial basis function network (RBFN) to represent the human brain, which comprehensively analyzes the gustatory stimulation and judges the overall taste. In the illustrated model, eight electrodes were fabricated to determine the eight major taste-causing substances, Na+, K+, Cl-, H+, sucrose, glucose, glutamate, and caffeine. The detected signals were fed to a two-phase RBFN optimized by the implementation of a basis optimization algorithm and weight decay term for appropriate data processing. The first phase of the two-phase RBFN quantifies the amount of taste-causing substances in food samples from the responses of the electrodes. These results are then fed to the second phase, which correlates the amount of substances with the overall taste. The final output is scored on a scale of 1-5 for each of the five basic tastes sensed by the human gustatory system, which are saltiness, sourness, sweetness, bitterness, and umami. The constructed network estimated the intensity of the basic tastes of 30 drink varieties with an average relative error of 7.0% compared to the human scores. The network could also estimate the variance in the human sensory perception. Moreover, the sensor successfully predicted the interactions of tastes such as suppression of bitterness by sweetness and enhancement of umami by saltiness, which are illusions sensed by the human gustatory system. With these abilities, the novel taste sensor can be considered as a quantitative yet humanlike sensor with a great potential for practical applications.