bluuebunny/crossref_metadata_2025 huggingface dataset:
H2S Detection Sensing Characteristic of CuO/SnO2 Sensor
Authors: Liu Jinhuai , Huang Xingjiu , Ye Gang , Liu Wei , Jiao Zheng , Chao Wnaglian , Zhou Zhongbai , Yu Zenglian
Published: October 2008

Among the various metal oxide additives tested, the complex of CuO is outstanding in promoting the sensing propoerties of an SnO2 sensor for H2S in air. The SnO2 sensors loaded with 5 wt. % CuO is extremely sensitive to H2S at 200 C° and below, while it is almost unsensitive to many other gases. The response to H2S is rather slow but the recovery is very rapid. Tha added CuO particles interact electronically with the surface of SnO2 (p-n junctions) to make the sensor highly resistive, while the interaction is disconnected when CuO is sulfurized to CuS in the H2S containing atmosphere, leading to a drastic decrease in electrical resistance. The H2S sensing properties, particularly the rate of response of CuO/SnO2 sensors are influenced by the CuO loadings andoperating temperature as well as the thickness of Cuo loading film.
Towards a Capacitive Enzyme Sensor for Direct Determination of Organophosphorus Pesticides: Fundamental Studies and Aspects of Development
Authors: Schöning Michael  J. , Arzdorf Michael , Mulchandani Priti , Chen Wilfred , Mulchandani Ashok
Published: October 2008

The realisation of a miniaturised potentiometric enzyme biosensor is presented. The biosensor chip utilises the enzyme organophosphorus hydrolase (OPH) for the direct determination of pesticides. The transducer structure of the sensors chip consists of a pH-sensitive capacitive electrolyte-insulator-semiconductor (EIS) structure that reacts towards pH changes caused by the OPH-catalised hydrolysis of the organophosphate compounds. The biosensor is operated versus a conventional Ag/AgCl reference electrode. Measurements were performed in the capacitance/voltage (C/V) and the constant capacitance (ConCap) mode for the two different pesticides paraoxon and parathion. For the development of this new type of biosensor, different immobilisation strategies, influence of buffer composition and concentration, transducer material, detection limit, long-term stability and selectivity have been studied.
DNA Electrochemical Behaviors, Recognition and Sensing by Combining with PCR Technique
Authors: Ye Yongkang , Ju Huangxian
Published: October 2008

The electrochemical studies on the behaviors and recognition of DNA have attracted cosiderable attention. DNA biosensors based on a nucleic acid hybridization process are rapidly being developed towards the goal of rapid and inexpensive diagnosis of genetic andinfectious deseases. This brief review focuses on the current state of the DNA electrochemical sensors with emphasis on recent advances, challanges and trends. The works on DNA electrochemical behaviors, recognition and detection in our group in the last three years are also introduced.
An influence of polyHEMA gate layer on properties of ChemFETs
Authors: Dawgul Marek , Pijanowska Dorota  G. , Krzyskow Alfred , Kruk Jerzy , Torbicz Wladyslaw
Published: October 2008

A complex deposition procedure of the hydrogel layer of modified poly(2-hydroxyethyl methacrylate) (polyHEMA) covalently linked to the silicon nitride surface and covering only the gate area of the ISFET, was optimized for photolithographic technology, using standard silicon wafers of 3” diameter. The influence of hydrogel composition and layer thickness on the sensors’ parameters was investigated. It was shown, that ISFETs covered with more than 100 μm thick polyHEMA layers in restricted pH-range could be practically insensitive to pH. Regarding mechanical stability of ion-selective sensors, a polyHEMA layer of ca. 20 μm thickness was found to be the best suitable for further manufacturing of durable ion selective sensors (Chemically modified Field-Effect Transistors – ChemFETs). The weak buffering properties of the thin polyHEMA layers had no disadvantageous influence on the sensors’ function.
Comparison of Urea Determination in Biological Samples by EnFETs Based on pH and pNH4 Detection
Authors: Bijanowska Dorota  G. , Dawgul Marek , Torbicz Wladyslaw
Published: October 2008

In this paper urea biosensors based on detection of pH and ammonium ions are presented. As transducers pH-sensitive ion-selective field effect transistors (ISFETs) and chemically modified FETs (ChemFETs) snsitive to ammonium ions were used.Results concerning urea determination by the bisensors in blood plasma and in dialysate show that the biosensors can be applied for urea monitoring in the effluent dialysate. However in the case of pNH4 based EnFETs a special pre-treatment (dilution with tris/HCl buffer) of the samples is necessary.
A New Laccase Biosensor For Polyphenols Determination
Authors: Gomes S. A.S.S. , Rebelo M. J.F.
Published: October 2008

The relevance of polyphenols in human health is a well known fact. Prompted by that, a very intensive research has been directed to get a method to detect them, wich will improve the current ones. Laccase (p-diphenol:dioxygen oxidoreductase EC 1.10.3.2) is a multi-copper oxidase, wich couples catalytic oxidation of phenolic substrates with four electron reduction of dioxygen to water [1]. A maximum catalytic response in oxigenated electrolyte was observed between 4.5 and 5.5 [2], while for pH > 6.9 the laccase was found to be inactive [3]. We prepared a biosensor with laccase immobilised on a polyether sulphone membrane, at pH 4.5, wich was applied at Universal Sensors base electrode. Reduction of the product of oxidation of several polyphenols, catalysed by laccase, was done at a potential for wich the polyphenol of interest was found to respond. Reduction of catechol was found to occur at a potential of -200mV, wich is often referred to in the literature for polyphenolic biosensors. However other polyphenols did not respond at that potential. It was observed that (+)- catechin produced a very large cathodic current when +100mV were applied to the laccase biosensor, both in aqueous acetate and 12% ethanol acetate buffer, whereas caffeic acid responded at -50mV. Other polyphenols tested were gallic acid, malvidin, quercetin, rutin, trans-resveratrol
Various Structures Based on Nickel Oxide Thick Films as Gamma Radiation Sensors
Authors: Arshak Khalil , Korostynska Olga , Fahim Farah
Published: October 2008

Thick films Nickel oxide (NiO) in the form of pn-junctions and planar structures with interdigitated electrodes were investigated for γ-radiation dosimetry purposes. Samples were fabricated using the thick film screen-printing technique. All devices were exposed to a disc-type 137Cs source with an activity of 370 kBq. They showed an increase in the values of current with the increase in radiation dose up to a certain level. Performance parameters of the devices, such as sensitivity to γ-radiation exposure and working dose region, were found to be highly dependant on the composition of the materials used.
New Method of Vapour Discrimination Using the Thickness Shear Mode (TSM) Resonator
Authors: Holloway A. F. , Nabok A. , Thompson M. , Ray A. K. , Crowther D. , Siddiqi J.
Published: October 2008

The Impedance analysis technique complimented with curve fitting software was used to monitor changes in film properties of Thickness Shear Mode (TSM) resonator on vapour exposure. The approach demonstrates how sensor selectivity can be achieved through unique changes in film viscosity caused by organic vapour adsorption.
Characterization of All Solid State Hydrogen Ion Selective Electrode Based on PVC-SR Hybrid Membranes
Authors: Piao Ming-Hua , Yoon Jang-Hee , Jeon Gerok , Shim Yoon-Bo
Published: October 2008

Hydrogen ion selective membranes formulated with 3140 RTV silicone rubber (SR) in PVC were studied to extend the life time of solid state ion sensors through improved membrane adhesion. All solid state hydrogen ion selective electrodes were prepared by incorporation of tridodecyl amine (TDDA) as an ionophore, potassium tetrakis[3.5-bis(p-chlorophenyl)borate (KTpClPB) as a lipophilic additive, bis(2-ethylhexyl)adipate (DOA) as a plasticizer. Their linear dynamic range was pH 2.0-11.0 and showed the near Nernstian slope of 55.1±0.2 mV/pH (r=0.999). The ifluences from alkali and alkaline earth metal ions were studied for the response of the final ISE membrane composition. Impedance spectroscopic data showed that the resistance was increased by increasing SR content in PVC. Brewster Angle Microscopy (BAM) image showed clear differences according to the SR compositions in PVC. Life time of the all solid state membrane electrode was extended to about 2 months by preparing the membrane with PVC and SR. The standard reference material from NIST (2181 HEPES Free acid and 2182 NaHEPESate) was tested for the ISE and it gave good result.
Flow-velocity Microsensors Based on Semiconductor Fieldeffect Structures
Authors: Poghossian Arshak , Yoshinobu Tatsuo , Schöning Michael J.
Published: October 2008

A time-of-flight-type flow-velocity sensor employing the in-situ electrochemically generation of ion-tracers is developed. The sensor consists of an ion generator and two downstream-placed pH-sensitive Ta2O5-gate ISFETs (ion-sensitive field-effect transistor) that detect generated H+- or OH--ions. The results of the developed flow-velocity sensor under different modes of ion generation are presented and discussed. By applying this ISFET-array, the time of flight, and consequently, the flow velocity can be accurately evaluated using the shift of the response curve of the respective ISFETs in the array along the time scale. A good linearity between the measured flow velocity with the ISFET-array and the delivered flow rate of the pump is observed. In addition, a possibility of flowvelocity measurements by means of a LAPS (light-addressable potentiometric sensor) is firstly demonstrated.
A poly(pyrrole-Cobalt(II)deuteroporphyrin) electrode for the potentiometric determination of nitrite
Authors: Cosnier Serge , Gondran Chantal , Wessel Rudolf , Montforts Franz-Peter , Wedel Michael
Published: October 2008

The electrochemical properties of a new Co(II) deuteroporphyrin substituted by two electropolymerizable pyrrole groups has been investigated in organic solvent. This functionalization has allowed the preparation of the first example of a cobalt deuteroporphyrin film by oxidative electropolymerization. The resulting conducting polypyrrole film exhibits the regular electroactivity of cobalt deuteroporphyrin. Compared to conventional cobalt porphyrin electrochemistry, the replacement of porphyrin macrocycle by deuteroporphyrin ring results in markedly more negative potential values for the metalcentered oxidation and reduction processes. The influence of NO2- as axial ligand on the reductive behavior of the electropolymerized cobalt (II) deuteroporphyrin is examined. The recognition properties of the film illustrated by the potentiometric shift of the Co(II)/(I) reduction were exploited for the determination of NO2- in the concentration range 2 10-6- 2.5 10-4 M.
A Porphyrin Based Potentiometric Sensor for Zn2+ Determination
Authors: Gupta V. K. , Chauhan D. K. , Saini V. K. , Agarwal Shiva , Antonijevic M. M. , Lang H.
Published: October 2008

PVC based membranes of disodium salt of porphyrin 3,7,12,17-tetramethyl-8, 13-divinyl 2,18-porphine dipropionic acid (I) as ionophore with sodium tetra phenyl borate (NaTPB) as anion excluder and dibutyl phthalate (DBP), dioctyl phthalate (DOP), dibutyl butyl phosphonate (DBBP), tris(2- ethyl hexyl)phosphate (TEP), tri-n-butylphosphate (TBP) and 1- chloronaphthalene (CN) as plasticizing solvent mediators were prepared and constructed for determination of Zn(II). The PVC based membrane of (I) with DBBP as plasticizer and having anion excluder, NaTPB in the ratio PVC: I: NaTPB: DBBP (150: 10: 2: 200) gave the best results in terms of working concentration range (1.3×10-5-1.0 ×10-1M) with a Nernstian slope (30.0 mV/decade of activity). The useful pH range of the sensor is 3.0 –7.4, beyond which a drift in potential was observed. The response time of the sensor is 10s and the lifetime was about 2 months during which it could be used without any measurable divergence. It had good stability and reproducibility. The membrane worked satisfactorily in non-aqueous medium up to 40% (v/v) non-aqueous content. The selectivity coefficient values indicate that the electrode is highly selective for Zn2+ over a number of other cations except Na+ and Cd2+. Although Na+ and Cd2+ are likely to cause some interference, they would not interfere if present at the concentrations < 1 ×10-5 and < 5 ×10-5 M, respectively. The electrode has been used as an indicator electrode to determine the end point in the potentiometric titration of Zn2+ with EDTA.
Development of a Surface Acoustic Wave Sensor for In-Situ Monitoring of Volatile Organic Compounds
Authors: Ho Clifford  K. , Lindgren Eric  R. , Rawlinson K.  Scott , McGrath Lucas  K. , Wright Jerome  L.
Published: October 2008

This paper describes the development of a surface-acoustic-wave (SAW) sensor that is designed to be operated continuously and in situ to detect volatile organic compounds. A ruggedized stainless-steel package that encases the SAW device and integrated circuit board allows the sensor to be deployed in a variety of media including air, soil, and even water. Polymers were optimized and chosen based on their response to chlorinated aliphatic hydrocarbons (e.g., trichloroethylene), which are common groundwater contaminants. Initial testing indicates that a running-average data-logging algorithm can reduce the noise and increase the sensitivity of the in-situ sensor.
The Influence of the Enzyme Membrane Thickness on the Response of Amperometric Biosensors
Authors: Baronas Romas , Ivanauskas Feliksas , Kulys Juozas
Published: October 2008

A mathematical model of amperometric biosensors has been developed. The model is based on non-stationary diffusion equations containing a non-linear term related to Michaelis-Menten kinetics of the enzymatic reaction. Using digital simulation, the influence of the thickness of enzyme membrane on the biosensor response was investigated. The digital simulation of the biosensor operation showed the non-monotonous change of the maximal biosensor current versus the membrane thickness at the various maximal enzymatic rates. Digital simulation was carried out using the finite difference technique. Results of the numerical simulation was compared with known analytical solutions. This paper presents a framework for selection of the membrane thickness, ensuring the sufficiently stable sensitivity of a biosensor in a required range of the maximal enzymatic rate.
Experimental Determination of Bending Resonances of Millimeter Size PVF2 Cantilevers
Authors: Mukherjee Niloy , Shukla Amit , Roseman Rodney  D. , Thompson David  F.
Published: October 2008

The polymer piezoelectric polvinylidene fluoride has found widespread use in sensors and actuators. The bending mode of piezoelectricity offers very high sensitivities and low mechanical input impedance, but has not been studied in as much detail for sensor applications. We report the dynamic electromechanical properties of millimeter size cantilevers made from electroded films of PVF2. All devices tested had a single polymer layer. Several resonances are found below 1 kHz and the experimentally observed resonance frequency dependence on cantilever thickness and length are seen to agree well with published models which take the properties of the electrodes into account. It is found that bending resonances are also modulated by the width of the cantilever. Therefore, though the length and thickness control the resonance frequency most strongly, the actual realized value can be fine-tuned by changing cantilever width and the electrode material and its thickness. Further, all resonances display high piezoelectric coupling coefficients (keff), ranging between 0.2 - 0.35. The data presented here will be extremely useful in the design of sensors and actuators for a number of applications, since the combination of millimeter size scales and high piezoelectric sensitivities in the low audio range can be realized with this marriage of polymeric materials and cantilever geometries. Such an array of sensors can be used in cochlear implant applications, and when integrated with a resonance interrogation circuit can be used for the detection of low frequency vibrations of large structures. If appropriate mass/elasticity sensitive layers are coated on the electrodes, such a sensor can be used for the detection of a wide range of chemicals and biochemicals.
Measurement of Nitric Oxide Production in Biological Systems by Using Griess Reaction Assay
Authors: Sun Jie , Zhang Xueji , Broderick Mark , Fein Harry
Published: October 2008

A review of using Griess Reaction method to determine nitric oxide production in biological systems.
The NO2 sensing ITO thin films prepared by ultrasonic spray pyrolysis
Authors: Jiao Zheng , Wu Minghong , Qin Zheng , Lu Minghua , Gu Jianzhong
Published: October 2008

In this paper ITO thin films were deposited on alumina substrates by ultrasonic spray pyrolysis. The NO2 sensing properties of ITO thin films were investigated. The results show ITO thin films have good sensitivity to nitrogen dioxide.
On the Electrooxidation and Amperometric Detection of NO Gas at the Pt/Nafion® Electrode
Authors: Ho Kuo-Chuan , Hung Wen-Tung , Yang Jin-Cherng
Published: October 2008

The electrochemical oxidation of nitric oxide (NO) gas at the Pt/Nafion® electrode has been studied at a concentration of 500 ppm. The electrooxidation of NO taking place over a wide potential range can be described by a transcendental equation, from which the half-wave potential of the reaction can be determined. For NO oxidation with appreciable overpotentials but negligible mass-transfer effects, the Tafel kinetics applies. The obtained charge transfer coefficient (a) and the exchange current density (io) are 0.77 and 14 mA/cm2, respectively. An amperometric NO gas sensor based on the Pt/Nafion® electrode has been fabricated and tested over the NO concentration range from 0 to 500 ppm. The Pt/Nafion® electrode was used as an anode at a fixed potential, preferably 1.15 V (vs. Ag/AgCl/sat. KCl), which assures current limitation by diffusion only. The sensitivity of the electrochemical sensor was found to be 1.86 mA/ppm/cm2. The potential interference by other gases, such as nitrogen dioxide (NO2) and carbon monoxide (CO), was also studied in the range 0-500 ppm. Both sensitivity for NO and selectivity of NO over NO2/CO show significant enhancement upon using a cyclic voltammetric (CV) activation, or cleaning procedure.
The Electrochemical Detremination of Nitric Oxide in Seawater Media with Microelectrodes
Authors: Zhang Zhengbin , Xing Lei , Jiang Liqing , Wang Yongchen , Ren Chunyan , Cai Wei-Jun
Published: October 2008

The electrochemical determination of nitric oxide in seawater with microelectrodes is reported in this paper. Two electrodes, ISO-NOPMC microsensor and modified platinum microelectrode, are evaluated for their performance in seawater. The peak current is found to be linear with the NO concentration in the range 1×10-6-1.2×10-5 mol/l for both microelectrodes. The detection limit of ISO-NOPMC microsensor is 1.4×10-8 mol/l. Two methods for calibration of NO sensor, saturated NO solutions and decomposition of S-nitroso-acetyl-DL-penicillamine (SNAP), are discussed and compared. In addition, we examined the performance degradation of these microelectrodes in seawater due to complexation with seawater components.
Real Time Microelectrode Measurement of Nitric Oxide in Kidney Tubular Fluid in vivo
Authors: Levine David  Z. , Iacovitti Michelle
Published: October 2008

In this review we summarize our experience using a microelectrode to measure nitric oxide concentrations [NO] in living rat kidney tubules. In the anaesthetized living rat, the abdomen can be opened, and the kidney can be placed in a cup such that one can puncture a surface single tubular segment, 1-2 mm long, connected to one of 30,000 filtering glomeruli. The tubular segment can be viewed with a stereo microscope and punctured using sophisticated micromanipulators. The segment, ranging in diameter from about 15 - 35 um contains freely flowing RBC-free fluid, electrolytes, O2, pCO2 and NO gas concentrations, and a host of other known and unknown substances. After a “pre” puncture with a 7-10 um beveled glass pipette, intratubular [NO] can be directly determined by inserting, into the tubular lumen, the tip of a specially modified amperometric integrated electrode (WPI P/N ISO-NOP007). We review our in vivo experience with this electrode, emphasizing optimal practice to ensure appropriate calibration, stability, and selectivity for in vivo use. The electrode is highly selective for NO, and, despite fragility, with appropriate precautions, it can provide reproducible and highly sensitive NO measurements in the 40-1000 nM range.
The Utility of the Nitric Oxide Electrochemical Sensor in Biomedical Research
Authors: Hurst Roger D. , Clark John B.
Published: October 2008

In recent years World Precision Instruments Inc. (WPI) produced for commercial use a selective and sensitive electrochemical sensor for the detection of the important biological free radical nitric oxide (NO). Though many kinds of NO sensors are now commercially available WPI offers a range of sensors of variable size and applicability for the detection of NO in vivo and in in vitro biomedical samples. This article overviews the working characteristics of the sensors and their utility for biomedical research.
Strategies of Miniaturised Reference Electrodes Integrated in a Silicon Based “one chip” pH Sensor
Authors: Simonis Anette , Lüth Hans , Wang Joseph , Schöning J.
Published: October 2008

Different types of Ag/AgCl reference electrodes have been realised by means of thin- and thick-film technique. For inner electrolyte, KCl-containing membranes have been deposited and different coatings have been used to protect the reference electrode from a fast leaching out of KCl. The stability of the potential of the reference electrodes without KClcontaining membranes in 3 M KCl was about 7 hours for thin-film electrodes and up to 90 hours for thick-film electrodes. The reference electrodes with membrane were stable for more than two months. The thick-film reference electrode was integrated with a thin-film pH sensor onto one chip and the system pH sensor/reference electrode was investigated by means of capacitance/voltage (C/V) and constant capacitance (ConCap) mode.
Monitoring of Milk Quality With Disposable Taste Sensor
Authors: Sim Maxsim  Yap Mee , Shya Teo  Jau , Ahmad Mohd  Noor , Shakaff Ali  Yeon Md , Othman Abdul  Rahman , Hitam Muhammad  Suzuri
Published: October 2008

A disposable screen-printed multi channel taste sensor composed of several types of lipid as transducers and a computer as data analyzer could detect taste in a manner similar to human gustatory sensation. The disposable taste sensor was used to measure the electrical potential resulted from the interaction between lipid membranes and taste substances. In the present study, two types of packaged commercial milk, the ultra high temperature (UHT) and the pasteurized milk were tested. It was found that the disposable taste sensor is capable to discriminate reliably between fresh and spoiled milk and to follow the deterioration of the milk quality when it is stored at room temperature based on a pattern recognition principle namely Principle Component Analysis (PCA). This research could provide a new monitoring method ideally for simple and cheap decentralized testing for controlling the quality of milk, which may be of great use in the dairy industries.
A Novel Hydrogen Peroxide Sensor via the Direct Electrochemistry of Horseradish Peroxidase Immobilized on Colloidal Gold Modified Screen-printed Electrode
Authors: Xu Xiaoxing , Liu Songqin , Ju Huangxian
Published: October 2008

The direct electrochemistry of horseradish peroxidase (HRP) immobilized on a colloidal gold modified screen-printed carbon electrode (HRP-Au-SPCE) and its application as a disposable sensor were studied. The immobilized HRP displayed a couple of stable and well-defined redox peaks with a formal potential of –0.338 V (vs. SCE) and a heterogeneous electron transfer rate constant of (0.75±0.04) s-1 in 0.1 M pH 7.0 PBS. It showed a highly thermal stability, fast amperometric response and an electrocatalytic activity to the reduction of hydrogen peroxide (H2O2) without the aid of an electron mediator. The biosensor exhibited high sensitivity, good reproducibility, and long-term stability for the determination of H2O2 with a linear range from 0.8 μM to 1.0 mM and a detection limit of 0. 4 μM at 3σ. The variation coefficients are 2.7 % and 2.3 % for over 10 successive assays at the H2O2 concentrations of 8.0 and 20 μM, respectively. The K M app for H2O2 sensor was determined to be 1.3 mM.
Detecting Pesticide Residue by Using Modulating Temperature Over a Single SnO2-Based Gas Sensor
Authors: Huang Xingjiu , Liu Jinhuai , Pi Zongxin , Yu Zengliang
Published: October 2008

A new rapid detecting method (called dynamic measurements ) was reported to detect and distinguish the presence of two pesticide gases in the ambient atmosphere. The method employed only a single SnO2-based gas sensor in a rectangular temperature mode to perform the qualitative analysis of a binary gas mixture (acephate and trichlorphon) in air. Polar plots was used for quantitative analysis which the feature extraction was performed by FFT. Experimental results showed that high selectivity of the sensor achieved in the range of 250~3000C and modulating frequency 20mHz, one can easily observe the qualitative difference among the response to pure acephate and trichlorphon gases of the same concentration and to the mixture, and the concentration of pesticide gases can be obtained based on the changes of polar plots.
Flow injection amperometric determination of persulfate in cosmetic products using a Prussian Blue film-modified electrode
Authors: Oliveira Marcelo  F. De , Saczk Adelir  A. , Neto Jose  A. Gomes , Roldan Paulo  S. , Stradiotto Nelson  R.
Published: October 2008

A flow-injection system with a glassy carbon disk electrode modified with Prussian Blue film is proposed for the determination of persulfate in commercial samples of hair bleaching boosters by amperometry. The detection was obtained by chronoamperometric technique and the sample is injected into the electrochemical cell in a wall jet configuration. Potassium chloride at concentration of 0.1 mol L-1 acted as sample carrier at a flow rate of 4.0 mL min-1 and supporting-electrolyte. For 0.025 V (vs. Ag/AgCl) applied voltage, the proposed system handles ca. 160 samples per hour (1.0 10-4 - 1.0 10-3 mol L-1 of persulfate), consuming about 200 μL sample and 11 mg KCl per determination. Typical linear correlations between electrocatalytic current and persulfate concentration was ca. 0.9998. The detection limit is 9.0 10-5 mol L-1 and the calculated amperometric sensibility 3.6 103 μA L mol-1. Relative standard deviation (n =12) of a 1.0 10-4 mol L-1 sample is about 2.2%. The method was applied to persulfate determination in commercial hair-bleaching samples and results are in agreement with those obtained by titrimetry at 95% confidence level and good recoveries (95 - 112%) of spiked samples were found.
Chemical Sensors – from Molecules, Complex Mixtures to Cells – Supramolecular Imprinting Strategies
Authors: Dickert Franz L. , Lieberzeit Peter  A. , Hayden Oliver , Gazda-Miarecka Sylvia , Halikias Konstantin , Mann Karl  Jürgen , Palfinger Christian
Published: October 2008

Methods of modern chemistry are a powerful tool in generating functional materials suitable as chemically sensitive layers to be combined with a variety of transducer principles. Molecular pits in polymers are formed by molecular imprinting, by suitable double-imprinting e.g. PAHs can be detected down to the sub-μg/l level. The resulting selectivity patterns depend both on the polymerization temperature and the template/mononomer composition. Organic contaminants in water can be either directly assessed in liquid phase or separated from the matrix by a porous Teflon membrane. Thus the detection limits can be reduced to the ppm-level due to the a much lower noise level in gaseous phase. Even complex processes such as engine oil degradation can be followed by suitably imprinted polymers. Pits on the nm- to μm scale are reached by surface templating polymers with microorganisms. The resulting layers show reversible, antibody-like interactions and thus are optimal sensor layers. The successful on-line detection of tobacco mosaic viruses (TMV) can be achieved by these surface imprinted layers.
PVC Based Selective Sensors for Ni2+ Ions Using Carboxylated and Methylated Porphine
Authors: Singh L. P. , Bhatnagar J. M.
Published: October 2008

Poly vinylchloride (PVC) based membranes of 4,4',4'',4'''-21H,23H-porphine–5,10,15,20 –tetrayl) tetrakis (benzoic acid) (TBAP) and 2,3,7,8,12,13,17,18-octamethyl - 21H, 23H-porphine (OMP) were prepared using dibutyl phthalate (DBP), dioctylphthalate (DOP), dibutyl(butyl)phosphonate (DBBP) and 1-chloronaphthalene (CN) as plastcizing solvent mediators and sodium tetraphenylborate (NaTPB) as an anion excluder for Ni2+ selective sensors. TBAP based membrane exhibits linearity over a wide concentration range 2.0x10-6–1.0x10-1M (0.12 – 5.8x103ppm) with a slope of 29.6 mV/decade of activity while OMP based membrane showed linear potential response in the concentration range 1.0x10-5 –1.0x 10-1M (0.60 – 5.8x103ppm) with a Nernstian slope of 29.0 mV/decade of activity. The electrode assembly works between pH 2.0 – 7.0, exhibits a fast response time of 10-15s and performed satisfactorily over a period of six months with good reproducibility. Excellent selectivity of the order of 10-3 over a number of cations and quantitative determination of Ni2+ in effluents discharged from electroplating industry demonstrates the utility of the proposed sensor. The electrode assembly was also used as an indicator electrode in the potentiometric titration of Ni2+ with EDTA.
Quartz Crystal Microbalance Coated with Sol-gel-derived Thin Films as Gas Sensor for NO Detection
Authors: Zhang J. , Hu J.  Q. , Zhu F.  R. , Gong H. , O’Shea S.  J.
Published: October 2008

This paper presents the possibilities and properties of Indium tin oxide (ITO)-covered quartz crystal as a NOx toxic gas-sensor. The starting sol-gel solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol (0-20% by weight). The ITO thin films were deposited on the gold electrodes of quartz crystal by spin-coating technique and subsequently followed a standard photolithography to pattern the derived films to ensure all sensors with the same sensing areas. All heat treatment processes were controlled below 500°C in order to avoid the piezoelectric characteristics degradation of quartz crystal (Quartz will lose its piezoelectricity at ~573°C due to the phase change from α to β). The electrical and structural properties of ITO thin films were characterized with Hall analysis system, TG/DTA, XRD, XPS, SEM and etc. The gas sensor had featured with ITO thin films of ~100nm as the receptor to sense the toxic gas NO and quartz crystal with frequency of 10MHz as the transducer to transfer the surface reactions (mass loading, etc) into the frequency shift. A homemade setup had been employed to measure the sensor response under the static mode. The experimental results had indicated that the ITO-coated QCM had a good sensitivity for NO gas, ~12Hz/100ppm within 5mins. These results prove that the ITO-covered quartz crystals are usable as a gas sensor and as an analytical device.
Morphology, Structure and Nonstoichiometry of ZnCr2O4 Nanophased Powder
Authors: Mancic L. , Marinkovic Z. , Vulic P. , Moral C. , Milosevic O.
Published: October 2008

It is well established that gas/humidity-sensing properties of spinels are markedly influenced by their stoichiometry and microstructure. In this work nucleation and spinel phase development in the Zn-Cr-O system were investigated from the viewpoint of structural and morphological phenomena occurred during nanophased particle synthesis through aerosol reaction. The aerosol was generated from nitrates precursor solution using ultrasonic atomizer operated at 1.7 MHz. The influence of different decomposition schedules on the particle chemical content and morphology was determined by adjusting the processing parameters (aerosol droplet density 3.9x106 droplets/cm3, droplet velocity 0.035m/s, max. temperature 900oC and residence times 3, 6 and 9s). A composite particle structure comprised of primary crystallites sized from 22 to 44nm is revealed by SEM and TEM analysis. XRD structural analysis (crystallite size, microstrains, unit cell and ionic occupancies) is performed in accordance with procedure based on Koalariet-Xfit program. A certain degree of non-stochiometry is characteristic for all powders. Homogenous distribution of the constituting elements and Zn/Cr ratio of about 0.68 are proved by EDAX mapping analysis in 470nm sized as-prepared particles. After additional treatment at 1000oC octahedral crystals form with the (111) surface dominat. Evaluated spinel non-stochiometry (Zn/Cr=0.58) is a result of the ZnO dissolving (1.9%wt) in the stoichiometric ZnCr2O4. Determination of the way by which the ZnO is incorporated into the spinel lattice is performed according to the procedure based on calculation of both formation and attachment energies.
A Novel Coated Graphite Rod Th(IV) Ion Selective Electrode Based On Thorium Oxinate Complex and Its Application
Authors: Arida Hassan  A. , Ahmed Mona  A. , El-Saied Abeer  M.
Published: October 2008

Preparation, characterization, and application of a novel coated graphite rod thorium selective electrode based on thorium 8-hydroxyquinolate [thorium oxinate, Th(C9H6NO)4.2H2O] complex ionophore as a sensing material, dioctylphthalate (DOP) as a solvent mediator, and PVC as a matrix have been developed. The coated graphite rod electrode exhibits a linear Nernstian response over the concentration range 5x10-6 - 1x10-1 mol l-1 of Th(IV) ions, with a calibration slope of 15.5 ± 0.5 mV/concentration decade and a detection limit of 1.6x10-6 mol l-1. It has a fast response time and can be used for a period of two months without any divergence in potentials. The proposed electrode reveals a good selectivity for Th(IV) cation over a varity of other cations and could be used in the pH range of (3 - 5). The sensor was successfully applied in the determination of thorium in real (monazite sand) sample. The average recovery obtained is ranging from 97.0 to 93.4% with standard deviation of 1.5% (n=8).
Preparation of SnO2 Films with Thermally Stable Nanoparticles
Authors: Adamyan Arsen  Z. , Adamian Zaven N. , Aroutiounian Vladimir  M.
Published: October 2008

Different regimes of preparations of nano-sized particles of SnO2 are considered. The films technology ensuring weak dependence of grains size on films calcinations temperature is offered.
Determination of Dopamine in the Presence of Ascorbic Acid using Poly (Acridine red) Modified Glassy Carbon Electrode
Authors: Zhang Yuzhong , Jin Guiying , Wang Yanling , Yang Zhousheng
Published: October 2008

Poly (acridine red) modified glassy carbon electrode was used for the detection of dopamine in the presence of ascorbic acid in a pH 7.4 phosphate buffer solutions (PBS) by cyclic voltammetry and differential pulse voltammetry. The major difficulty of the overlapped oxidation potential of ascorbic acid could be overcome through the distinct attractive ability of poly (acridine red) film to cationic dopamine and anionic ascorbic acid. The results showed that the dopamine anodic peak current and the concentration of dopamine had a linear relationship in the range of 1.0×10-7 ~ 1.0×10-4 mol dm-3. The detection limit (S/N=3) obtained by differential pulse voltammetry was 1.0×10-9 mol dm-3. The relative standard deviation of 10 successive scans was 2.07 % for 1.0×10-6 mol dm-3 DA. Ascorbic acid had hardly interference with the determination of dopamine. The proposed method exhibits good recovery and reproducibility.
Semiconductor Metal Oxide Sensors in Water and Water Based Biological Systems
Authors: Chibirova Fatima  Kh. , Avetisov Alexander  K. , Kazakov Serge  A. , Obvintseva Ludmila  A. , Strobkova Marina  V.
Published: October 2008

The results of implementation of In2O3-based semiconductor sensors for oxygen concentration evaluation in water and the LB-nutrient media (15.5 g/l Luria Broth Base, Miller (Sigma, Lot-1900) and NaCl) without bacteria and with E.coli bacteria before and after UV-irradiation are presented.
Chemometric Classification of Herb – Orthosiphon stamineus According to Its Geographical Origin Using Virtual Chemical Sensor Based Upon Fast GC
Authors: Sim Chew  Oon , Ahmad Mohd  Noor , Ismail Zhari , Othman Abdul  Rahman , Noor Nor  Amin Mohd , Zaihidee Ezrinda  Mohd
Published: October 2008

An analytical method using Electronic Nose (E-nose) instrument for analysis of volatile organic compound from Orthosiphon stamineus raw samples have been developed. This instrument is a new chemical sensor based on Fast Gas Chromatography and Surface Acoustics Wave (SAW) detector. Chromatographic fingerprint obtained from the headspace analysis of O. stamineus samples were used as a guideline for optimum selection of an array of sensor. Qualitative analysis was carried out based on the responses of each sensor array in order to distinguish the geographical origin of the cultivated sample. The results of the analysis showed variances of volatile chemical compound of the samples even though it is from the same species. However, similarities of main components from all five samples were observed. Usage of pattern recognition chemometric approaches such as Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA) and Cluster Analysis (CA) for processing instrumental data provided good classification of O. stamineus samples according to its geographical origin.
Impedance Spectroscopy Technique for DNA Hybridization
Authors: Hleli S. , Abdelghani A. , Tlili A.
Published: October 2008

The development of biosensors for detection and identification of DNA sequences by hybridization may reduce assay time and allow direct quantitation of the target. This article describes the use of impedance spectroscopy technique for digoxigeninthiol- labeled ssDNA probe immobilization, anti-digoxigenin binding and targeted DNA hybridization. The analysis of the impedance spectra in terms of equivalents circuits of the gold/electrolyte interface and gold/digoxigenin-thiol-labeled/electrolyte interface is discussed. The DNA hybridization shows a variation in the impedance spectra.
Contribution of Structure and Morphology of Design Constituents to Performance Improvement of Multilayer Polaritonic Photodetector
Authors: Dmitruk N. L. , Mayeva O. I. , Mamykin S. V. , Mamontova I. B. , Yastrubchak O. B.
Published: October 2008

This paper is devoted to estimate contribution of structure and morphology of the individual design constituents to performance improvement of multilayer polaritonic photodetector (optochemical sensor). Surface plasmon resonance (SPR) in the surface barrier heterostructure (SBH) with the corrugated interface is used as the basic principle underlying the device operation. The demonstration of correlation of the contribution with the enhanced SBH features was performed through the adequate characterization tool.
Sensors Auto-calibration Method - Using Programmable Interface Circuit Front-end
Authors: Kouider M. , Nadi M. , Kourtiche D.
Published: October 2008

In this paper we present a standard auto-calibration method of sensors. The purpose is to correct the accumulated errors at the sensor output. A universal conditioning circuit is used with the sensor, and the transfer function of the measurement chain is periodically corrected according to the progressive correction method. References physical inputs are used to allow the adjustment of the measurement and to calculate the calibration coefficients. Test results obtained using this method present a considerable enhancement of the measurement accuracy and a good handling of cross-sensitivity problem.
Implementation of a Feedback I2-Controlled Constant Temperature Environment Temperature Meter
Authors: Palma Lígia  S. , Oliveira Amauri , Costa Alexandre  S. , Andrade Antônio  Q. , Almeida Cleber  V. R. , Zurita Marcos  E. P. V. , Freire Raimundo  C. S.
Published: October 2008

A feedback thermo-resistive sensor-based measurement scheme was proposed to estimate physical quantities like solar radiation (H), fluid velocity (U) and environment temperature (Ta). It was implemented as an environment temperature meter, using PI controller. Controller implementation was done digitally using FPGA. Practical results are presented.
Iodide Selective Electrodes Based on Bis(2-mercaptobenzothiazolato) Mercury(II) and Bis(4-chlorothiophenolato) Mercury(II) Carriers
Authors: Amini Mohammad K. , Ghaedi Mehrorang , Rafi Ali , Habibi Mohammad. H. , Zohory Morteza M.
Published: October 2008

New iodide-selective electrodes based on bis(2-mercaptobenzothiazolato) mercury(II) [Hg(MBT)2] and bis(4-chlorothiophenolato) mercury(II) [Hg(CTP)2] carriers are described. The electrodes were prepared by incorporating the ionophores into plasticized PVC membranes, which were directly coated on the surface of graphite disk electrodes. The electrodes displayed high selectivity for iodide with respect to a number of inorganic and organic anions. The influence of the membrane composition and pH, and the effect of lipophilic cationic and anionic additives on the response properties of the electrodes were investigated. The electrodes exhibited near-Nernstian slopes of -57.6 ± 0.8 and -58.4 ± 1.4 mV/decade of iodide concentration over the range 1 × 10-6 – 1 × 10-1 M, with detection limits of ~4 × 10-7 and 6 × 10-7 M for the electrodes based on [Hg(MBT)2] and [Hg(CTP)2], respectively. They have relatively fast response times (≤ 10 s), satisfactory reproducibility, and life times of at least two months. The potentiometric responses of the electrodes are independent of pH of the test solution over the range 3.5 – 11.5.
Voltammetric Determination of Prochlorperazine and Ethopropazine Using a Gold Electrode Modified with Decanethiol SAM
Authors: Yang Yuxia , Peng Yan , Zhao Faqiong , Zeng Baizhao
Published: October 2008

The voltammetric behavior of prochlorperazine and ethopropazine at a decanethiol (DEC) self-assembled monolayer (SAM) modified gold electrode (DEC/Au) has been studied. It was observed that prochlorperazine exhibited an anodic peak at about 0.60 V (vs SCE), while ethopropazine exhibited two anodic peaks at about 0.49 V and 0.58 V on DEC/Au in pH 10 sodium carbonate buffer. This was due to their different electrochemical oxidation mechanisms. In this case, the oxidation of prochlorperazine and ethopropazine included one 2e step and two 1e steps, respectively. In the presence of some reductants such as ascorbic acid, the oxidation products of them can catalyze the oxidation of the reductants and thus make the peaks grow. In addition, it was found that the SAM structure became not so compact when prochlorperazine and ethopropazine were present, resulting from their permeating in the SAM. Various conditions were optimized for their determination. Under the selected conditions (i.e. 0.080 M pH 10 sodium carbonate buffer; scan rate: 100 mV/s; accumulation potential: –0.4 V or 0 V; accumulation time: 60 s), the peak currents were linear to prochlorperazine concentration in the ranges of 0.1~2.0 μM and 5.0~50 μM, and linear with ethopropazine in the ranges of 10 nM~0.1 μM and 0.5~20 μM. The RSD was 4.28% for 8 successive measurements of 1.0 μM prochlorperazine. The influence of some coexistents was examined.
Catalytic Oxidation of Thiourea at Alumina Modified Pt Electrode
Authors: Nematollahi Davood , Rafiee Mohammad
Published: October 2008

Catalytic oxidation of thiourea has been studied at alumina modified Pt electrode using cyclic voltammetry. The results indicate the suitability of alumina modified Pt electrode for voltammetric determination of thiourea. The catalytic peak currents are linearly dependent on the thiourea concentration in the range 2.5 x 10-5 – 7.0 x 10-3 M. The usefulness of the method was tested in determination of thiourea in real samples. Moreover, in this work the heterogeneous electron transfer rate constants of thiourea at the surface of modified and unmodified Pt electrodes were estimated by comparing the experimental cyclic voltammetric responses with the digital simulated results.
Semiconductor Sensors Application for Definition of Factor of Ozone Heterogeneous Destruction on Teflon Surface
Authors: Obvintseva Ludmila A. , Chibirova Fatima Kh. , Kazakov Serge A. , Avetisov Alexander K. , Strobkova Marina V. , Finogenova Nataliya V.
Published: October 2008

In our paper we present the results of our research, which was carried out by means of semiconductor sensor techniques (SCS), which allowed evaluating heterogeneous death-rate of ozone (γ) Teflon surface. When ozone concentration is near to Ambient Air Standard value, γ is assessed to be equal to 6,57*10-7. High technique response provide possibility to determine ozone contents in the air media and the percentage of ozone, decomposed on the communication surfaces and on the surfaces of installation in the low concentration range (1–100 ppb).
Direct Electrochemistry of Glucose Oxidase at a Gold Electrode Modified with Single-Wall Carbon Nanotubes
Authors: Liang Wang , Zhuobin Yuan
Published: October 2008

The direct electrochemistry of glucose oxidase (GOD) was accomplished at a gold electrode modified with single-wall carbon nanotubes (SWNTs). A pair of welldefined redox peaks was obtained for GOD with the reduction peak potential at –0.465 V and a peak potential separation of 23 mV at pH 7.0. Both FT-IR spectra and the dependence of the reduction peak current on the scan rate revealed that GOD adsorbed onto the SWNT surfaces. The redox wave corresponds to the redox center of the flavin adenine dinucleotide(FAD) of the GOD adsorbate. The electron transfer rate of GOD redox reaction was greatly enhanced at the SWNT-modified electrode. The peak potential was shown to be pH dependent. Verified by spectral methods, the specific enzyme activity of GOD adsorbates at the SWNTs appears to be retained.
A Disposable Sensor For Assessing Artocarpus heterophyllus L. (Jackfruit) Maturity
Authors: Sim Maxsim , Ahmad Mohd , Shakaff Ali , Ju Chang , Cheen Chang
Published: October 2008

The purpose of this work was an attempt to monitor the ripeness process and to investigate the different maturity stages of jackfruit by chemometric treatment of the data obtained from the disposable sensor. Response of the sensor strip fabricated using screenprinting technology was analyzed using Principal Component Analysis (PCA) and the classification model constructed by means of Canonical Discriminant Analysis (CDA) enable unknown maturity stages of jackfruit to be identified. Results generated from the combination of the two classification principles show the capability and the performance of the sensor strip towards jackfruit analysis.
Publisher’s Notice: New Leadership of Sensors
Authors: Lin Shu-Kun
Published: October 2008

After three years service as the Editor-in-Chief of Sensors, Prof. Dr. Milan M. Antonijevic resigned from this position at the end of 2003.[...]