bluuebunny/crossref_metadata_2025 huggingface dataset:
The Preparation of ZnGa2O4 Nano Crystals by Spray Coprecipitation and Its Gas Sensitive Characteristics
Authors: Jiao Zheng , Ye Gang , Chen Feng , Li Mingqiang , Liu Jinhuai
Published: October 2008

ZnGa2O4 nano crystals were prepared by an improved coprecipitation method, which we call ‘spray coprecipitation’. XRD results shows the resulting crystal size using the new method is under 10nm, whereas the powder prepared by ordinary coprecipitation is about 30nm. XRD results also shows ZnO peaks exists in ZnGa2O4 powder prepared by traditional coprecipitation, but disappears in ZnGa2O4 nano crystal prepared by spraying coprecipitation. SEM and TEM were used to analysis the structural characteristics of ZnGa2O4 nano crystals. The gas sensitive characteristics of ZnGa2O4 nano crystals are reported.
Mass Transfer in Amperometric Biosensors Based on Nanocomposite Thin Films of Redox Polymers and Oxidoreductases
Authors: Pishko Michael  V. , Revzin Alexander , Simonian Aleksandr L.
Published: October 2008

Mass transfer in nanocomposite hydrogel thin films consisting of alternating layers of an organometallic redox polymer (RP) and oxidoreductase enzymes was investigated. Multilayer nanostructures were fabricated on gold surfaces by the deposition of an anionic self-assembled monolayer of 11-mercaptoundecanoic acid, followed by the electrostatic binding of a cationic redox polymer, poly[vinylpyridine Os(bis-bipyridine)2Clco-allylamine], and an anionic oxidoreductase. Surface plasmon resonance spectroscopy, Fourier transform infrared external reflection spectroscopy (FTIR-ERS), ellipsometry and electrochemistry were employed to characterize the assembly of these nanocomposite films. Simultaneous SPR/electrochemistry enabled real time observation of the assembly of sensing components, changes in film structure with electrode potential, and the immediate, in situ electrochemical verification of substrate-dependent current upon the addition of enzyme to the multilayer structure. SPR and FTIR-ERS studies also showed no desorption of polymer or enzyme from the nanocomposite structure when stored in aqueous environment occurred over the period of three weeks, suggesting that decreasing in substrate sensitivity were due to loss of enzymatic activity rather than loss of film compounds from the nanostructure.
Room Temperature Ammonia and Humidity Sensing Using Highly Ordered Nanoporous Alumina Films
Authors: Dickey Elizabeth  C. , Varghese Oomman  K. , Ong Keat  G. , Gong Dawei , Paulose Maggie , Grimes Craig  A.
Published: October 2008

The effect of pore size and uniformity on the response of nanoporous alumina, formed on aluminum thick films through an anodization process, to ammonia and humidity at room temperature is reported. Pore sizes examined range from 13 nm to 48 nm, with pore size standard deviations ranging from 2.6 nm to 7.8 nm. The response of the material to ammonia and humidity is a strong function of pore size and operating frequency. At 5 kHz an alumina sensor with an average pore size of 13.6 nm, standard deviation 2.6 nm, exhibits a factor of two change in impedance magnitude as it is cycled between an ammonia and argon environment. At 5 kHz the same sensor exhibits a well-behaved change in impedance magnitude of 103 over 20% to 90% relative humidity. Cole-Cole plots of the 5 Hz to 13 MHz measured impedance spectra, modeled using equivalent circuits, are used to resolve the effects of adsorption and ion migration.
Nanoporous Platforms for Cellular Sensing and Delivery
Authors: Leoni Lara , Attiah Darlene , Desai Tejal  A.
Published: October 2008

In recent years, rapid advancements have been made in the biomedical applications of micro and nanotechnology. While the focus of such technology has primarily been on in vitro analytical and diagnostic tools, more recently, in vivo therapeutic and sensing applications have gained attention. This paper describes the creation of monodisperse nanoporous, biocompatible, silicon membranes as a platform for the delivery of cells. Studies described herein focus on the interaction of silicon based substrates with cells of interest in terms of viability, proliferation, and functionality. Such microfabricated nanoporous membranes can be used both in vitro for cell-based assays and in vivo for immunoisolation and drug delivery applications.
Multiparametric Porous Silicon Sensors
Authors: Baratto C. , Faglia G. , Sberveglieri G. , Gaburro Z. , Pancheri L. , Oton C. , Pavesi L.
Published: October 2008

We investigated the possibility of using several sensing parameters from porous silicon in order to improve gas selectivity. By fabricating porous silicon optical microcavities, three independent quantities can be measured, i.e. the electrical conductance, the photoluminescence intensity, and the wavelength of the optical resonance. We monitored the change of these three parameters as a function of NO2 (0.5-5 ppm), ethanol (300-15000 ppm) and relative humidity (0-100%). Preliminary results confirm that the examined species affect the parameters in a different way, both as a relative change and as dynamic.
Planar Amperometric Glucose Sensor Based on Glucose Oxidase Immobilized by Chitosan Film on Prussian Blue Layer
Authors: Zhu Jianzhong , Zhu Ziqiang , Lai Zongsheng , Wang Rong , Guo Xiaoming , Wu Xiaqin , Zhang Guoxiong , Zhang Zongrang , Wang Yiting , Chen Zongyou
Published: October 2008

A planar amperometric glucose microsensor based on glucose oxidase immobilized by chitosan film on Prussian Blue layer has been developed. The experimental results show that the optimum detection potential is 50 mV (versus Ag/AgCl) and the optimum pH is 6.5. Under the selective conditions the sensor exhibits excellent sensitivity of 98 nA/M and a linear range of 0.1-6.0 mM. The apparent Michanelis-Menten constant of the sensor is 21 mM. The response time is less than 60 seconds. No apparent change in the response to glucose was observed during one month. Foremost, the interference of ascorbic and uric acids can be avoided due to selective permeability of chitosan film and electrocatalysis of PB layer to H2O2. The sensor has been applied to detect glucose in human blood serum.
Asymptotic Regional Boundary Observer in Distributed Parameter Systems via Sensors Structures
Authors: Al-Saphory Raheam
Published: October 2008

The purpose of this paper is to study the concept of asymptotic regional observer in connection with the characterizations of sensors. We give various results related to different types of measurements, of domains and boundary conditions. Furthermore, we show that the measurements structures allow the existence of regional observer and we give a sufficient condition for such observer. We also show that, there exists a dynamical system for the considered system is not observer in the usual sense, but it may be regional boundary observer.
Natural Monocrystalline Pyrite as Sensor for Potentiometric Redox Titrations. Part I. Titrations with Permanganate
Authors: Antonijevic M. M. , Mihajlovic R. P. , Vukanovic B. V.
Published: October 2008

Results obtained in potentiometric titrations of Fe(II), Mn(II), Fe(CN)64-, C2O42- and As(III) with standard potassium permanganate solution, are presented. The titration end point (TEP) was detected with a universal electrode whose sensor is natural crystalline pyrite. The titrations of As(III) were carried out in HCl (1.2 M) and H2SO4 solutions (0.1- 4.5 M), whereas oxalate was determined in H2SO4 (0.1-4.5 M). Iron(II) and hexacyanoferrate(II) were titrated in H2SO4 and also in H3PO4 solutions (0.1-4.5 M). The titrations of Mn(II) were performed in H2P2O72- media at pH 4.0, 5.0, 6.0 and 7.0. The results obtained by using the pyrite electrode were compared with those obtained by the application of a Pt-electrode, and good agreement, reproducibility and accuracy were obtained. The potentials in the course of the titration and at the end-point (TEP) are rapidly established. The potential changes at the TEP ranged from 90 to 330 mV/0.1 mL, depending on the titrated system. The highest changes were observed in titrations of Fe(II) in H3PO4 (240-330 mV/0.1 mL). Reversed titrations were also performed and accurate and reproducible results were obtained.
Membranes of 5,10,15,20-Tetrakis(4-Methoxyphenyl) Porphyrinatocobalt (TMOPP-Co) (I) as MoO42- - Selective Sensors
Authors: Gupta Vinod  K. , Chandra S. , Chauhan D. K. , Mangla R.
Published: October 2008

Polyvinyl chloride (PVC) membrane electrodes based on porphyrin 5,10,15,20-tetrakis(4methoxyphenyl)porphyrinatocobalt (TMOPP-Co) (I) incorporating sodium tetra phenyl borate (NaTPB) as anion excluder and dibutyl phthalate (DBP), dioctyl phthalate (DOP), dibutyl butyl phosphonate (DBBP), tri-n-butyl phosphate (TBP), and 1-chloronaphthalene (CN) as plasticizing solvent mediators were prepared and tested for selective detection of molybdate ions. The membrane having anion excluder, NaTPB and DBP as plasticizer (membrane no. 2) proved to be best in terms of working concentration range 5.0×10-5 – 1.0×10-1M with a near – Nernstian slope of 32.0±1.0 mV/decade of activity over the pH range 5.4- 10.5. The response time of this sensor is 18s with a lifetime of about 4 months. The sensor can be used in non-aqueous medium with no significant change in the value of slope or working concentration range for the estimation of MoO42- in solutions having up to 25% (v/v) non-aqueous fraction.
γ-radiation Sensor Using Optical and Electrical Properties of Manganese Phthalocyanine (MnPc) Thick Film
Authors: Arshak A. , Zleetni S. , Arshak K.
Published: October 2008

Manganese phthaloyanine polymer thick films were fabricated using screenprinting techniques. The optical parameters were obtained from the analysis of the absorption spectra over a wavelength range of 385-900nm. The d.c. electrical measurements were carried out in a range of 0-30 volts. The effects of γ-radiation on the optical and the electrical properties were investigated for dosimetry applications. The optical energy band gaps of these films showed a decrease in their values with the increase in the radiation dose. The electronic transition has changed from direct allowed for the as-printed films (unexposed to γ-rays) to indirect allowed for the irradiated samples. Both the as-printed and irradiated Ag/MnPc/Ag devices demonstrated a Schottky conduction mechanism. Both the absorbance and the capacitance of the MnPc thick films displayed a highly consistent linear response to γ-ray exposure.
Conducting Polymers Functionalized with Phthalocyanine as Nitrogen Dioxide Sensors
Authors: Radhakrishnan S. , Deshpande S.  D.
Published: October 2008

The conducting polymers such as polyaniline, polypyrrole and polythiophene were functionalized with copper phthalocyanine using chemical oxidation method. The obtained polymers viz. PANI-CuPc, PPy-CuPc and PT-CuPc were studied as chemical sensors by their response characteristics after exposure to various chemical vapors such as methanol, ammonia and nitrogen dioxide. The results obtained showed that these polymers have moderate sensitivity towards the methanol as well as ammonia vapors whereas they show tremendous sensitivity towards nitrogen dioxide vapors. The sensitivity factor of as high as 50,000 was obtained for PT-CuPc polymers in nitrogen dioxide. In comparison to this, the sensitivity factors of about 100 and 40 were obtained, when these polymers were exposed to ammonia and methanol vapors. The very high selectivity towards the nitrogen dioxide was explained on the basis of charge transfer complex formed between, the phthalocyanine donor and nitrogen dioxide acceptor molecules. On the other hand, ammonia becomes a competing electron donor in CuPc containing conducting polymers. The very low response towards the methanol may be explained on the basis very little charge transfer / interaction between CuPc containing polymers and methanol. Thus, CuPc incorporated conducting polymers have much higher selectivity than their original homopolymer.
Chemical detection in liquid media with a refractometric sensor based on a multimode optical fibre
Authors: Cherif K. , Hleli S. , Abdelghani A. , Jaffrezic-Renault N. , Matejec V.
Published: October 2008

In this paper the physical basis for the design of an optical fibre sensor suited for aqueous medium and gas phase based on the excitation of an evanescent wave at the core/cladding interface is developed. The detection based on the refractive index changes (between 1.41 and 1.45) of the infinite dielectric medium which can be an electrolyte or a sol-gel polymer deposited on the uncladed part of the fibre. Refractive indices of absorbent and volatile compounds such as fuel and unleaded gas were determined. Using a xerogel sensing layer as optical cladding, toluene detection in water was performed. The observed sensitivity is linear and the detection limit is 1% (in volume) toluene in water.
Thin films of In2O3/SiO for Humidity Sensing Applications
Authors: Arshak K. , Twomey K.
Published: October 2008

This paper documents the manufacture and testing of a humidity sensor based on a combination of In2O3/SiO. A number of different sensor samples have been produced by thermal deposition and the effect of varying the vacuum pressure has also been investigated. The AC and DC conduction mechanisms have been investigated. From the AC conduction studies, the tunneling conduction mechanism has been observed at low frequencies and the hopping conduction mechanism, for the majority of sensor samples, has been observed at high frequencies. The DC conduction mechanisms have indicated the possibility of spacecharge-limited conduction. The sensor with the highest humidity sensitivity of 1.145%/RH% is 85%In2O3/15%SiO, which is produced at a vacuum pressure of 2×10-4 mbar.From the point of view of temperature stability, the 55%In2O3/45%SiO samples produced at a vacuum pressure of 2×10-4 mbar exhibit the lowest temperature sensitivity, 0.3%/oC.
Remote Query Resonant-Circuit Sensors for Monitoring of Bacteria Growth: Application to Food Quality Control
Authors: Ong Keat  Ghee , Bitler J.  Samuel , Grimes Craig  A. , Puckett Libby  G. , Bachas Leonidas  G.
Published: October 2008

This paper presents a technique for in-situ remote query monitoring of bacteria growth utilizing a printed thin or thick-film sensor comprised of an inductor-capacitor (LC) resonant circuit. The sensor, which is placed within the biological medium of interest and remotely detected using a loop antenna, measures the complex permittivity of the medium. Since bacteria growth increases the complex permittivity of a biological medium the LC sensor can be used to determine bacteria concentration. This paper presents results on monitoring of three different bacteria strains, Bacillus subtilis, Escherichia coli JM109, and Pseudomonas putida, demonstrating application of the sensor for monitoring bacteria growth in milk, meat, and beer. Due to its low unit cost and remote query detection, the sensor is potentially useful for commercial scale monitoring of food quality.
Polystyrene Based Silver Selective Electrodes
Authors: Gupta Vinod  Kumar , Antonijevic Milan  v , Chandra Sudeshna , Agarwal Shiva
Published: October 2008

Silver(I) selective sensors have been fabricated from polystyrene matrix membranes containing macrocycle, Me6(14) diene.2HClO4 as ionophore. Best performance was exhibited by the membrane having a composition macrocycle : Polystyrene in the ratio 15:1. This membrane worked well over a wide concentration range 5.0×10-6–1.0×10-1M of Ag+ with a near-Nernstian slope of 53.0 ± 1.0 mV per decade of Ag+ activity. The response time of the sensor is
Communication Buses and Protocols for Sensor Networks
Authors: Zhou Junwei , Mason Andrew
Published: October 2008

This paper overviews existing digital communication buses which are commonly used in sensor networks, discusses sensor network architectures, and introduces a new sensor bus for low power microsystem applications. The new intra-module multi-element microsystem (IM2) bus is nine-line interface with 8b serial data which implements several advanced features such as power management and plug-n-play while maintaining minimum hardware overhead at the sensor node. Finally, some issues in wireless sensor networking are discussed. The coverage of these issues provides a guideline for choosing the appropriate bus for different sensor network applications.
Optimal Energy Aware Clustering in Sensor Networks
Authors: Ghiasi Soheil , Srivastava Ankur , Yang Xiaojian , Sarrafzadeh Majid
Published: October 2008

Sensor networks is among the fastest growing technologies that have the potential of changing our lives drastically. These collaborative, dynamic and distributed computing and communicating systems will be self organizing. They will have capabilities of distributing a task among themselves for efficient computation. There are many challenges in implementation of such systems: energy dissipation and clustering being one of them. In order to maintain a certain degree of service quality and a reasonable system lifetime, energy needs to be optimized at every stage of system operation. Sensor node clustering is another very important optimization problem. Nodes that are clustered together will easily be able to communicate with each other. Considering energy as an optimization parameter while clustering is imperative. In this paper we study the theoretical aspects of the clustering problem in sensor networks with application to energy optimization. We illustrate an optimal algorithm for clustering the sensor nodes such that each cluster (which has a master) is balanced and the total distance between sensor nodes and master nodes is minimized. Balancing the clusters is needed for evenly distributing the load on all master nodes. Minimizing the total distance helps in reducing the communication overhead and hence the energy dissipation. This problem (which we call balanced k-clustering) is modeled as a mincost flow problem which can be solved optimally using existing techniques.
The Sensor Web: A Macro-Instrument for Coordinated Sensing
Authors: Delin Kevin  A.
Published: October 2008

The Sensor Web is a macro-instrument concept that allows for the spatiotemporal understanding of an environment through coordinated efforts between multiple numbers and types of sensing platforms, including both orbital and terrestrial and both fixed and mobile. Each of these platforms, or pods, communicates within their local neighborhood and thus distributes information to the instrument as a whole. Much as intelligence in the brain is a result of the myriad of connections between dendrites, it is anticipated that the Sensor Web will develop a macro-intelligence as a result of its distributed information with the pods reacting and adapting to their environment in a way that is much more than their individual sum. The sharing of data among individual pods will allow for a global perception and purpose of the instrument as a whole. The Sensor Web is to sensors what the Internet is to computers, with different platforms and operating systems communicating via a set of shared, robust protocols. This paper will outline the potential of the Sensor Web concept and describe the Jet Propulsion Laboratory (JPL) Sensor Webs Project (http://sensorwebs.jpl.nasa.gov/). In particular, various fielded Sensor Webs will be discussed.
The Development of Localized Algorithms in Wireless Sensor Networks
Authors: Qi Hairong , Kuruganti Phani  Teja , Xu Yingyue
Published: October 2008

Advances in sensor technology and wireless communications have made networked microsensors possible, where each sensor individually senses the environment but collaboratively achieves complex information gathering and dissemination tasks. These networked sensors, however, possess several characteristics that have challenged many aspects of traditional computer network design, such as the scalability issue caused by the sheer amount of sensor nodes, the infrastructureless network, and the stringent resource onboard the sensors. These new features call for a re-design of overall structure of applications and services. It has been widely accepted that practical localized algorithms is probably the best solution to wireless sensor networks. In this article, we discuss recent research results on localized algorithms design in supporting services and applications in sensor networks.
Wireless Magnetoelastic Resonance Sensors: A Critical Review
Authors: Grimes Craig  A. , Mungle Casey  S. , Zeng Kefeng , Jain Mahaveer  K. , Dreschel William 
																					 R. , Paulose Maggie , Ong Keat  G.
Published: October 2008

This paper presents a comprehensive review of magnetoelastic environmental sensor technology; topics include operating physics, sensor design, and illustrative applications. Magnetoelastic sensors are made of amorphous metallic glass ribbons or wires, with a characteristic resonant frequency inversely proportional to length. The remotely detected resonant frequency of a magnetoelastic sensor shifts in response to different physical parameters including stress, pressure, temperature, flow velocity, liquid viscosity, magnetic field, and mass loading. Coating the magnetoelastic sensor with a mass changing, chemically responsive layer enables realization of chemical sensors. Magnetoelastic sensors can be remotely interrogated by magnetic, acoustic, or optical means. The sensors can be characterized in the time domain, where the resonant frequency is determined through analysis of the sensor transient response, or in the frequency domain where the resonant frequency is determined from the frequency-amplitude spectrum of the sensor.
Mediated Electron Transfer at Redox Active Monolayers Part 2 : Analysis of the Chronoamperometric Response to a Potential Step Perturbation
Authors: Lyons Michael  E.G.
Published: October 2008

A theoretical model describing the transport and kinetic processes involved in heterogeneous redox catalysis of solution phase reactants at electrode surfaces coated with redox active monolayers is presented. We describe theoretically the time dependent chronoamperometric response expected for a redox active monolayer in the absence of a substrate in solution, and subsequently extend the analysis to consider the reaction of a solution phase substrate mediated by surface immobilized redox groups. This is accomplished via a Laplace transform based solution of the Fick diffusion equation for the substrate transport to the monolayer surface coupled with the development of a suitable flux matching condition at the monolayer/solution interface . The latter procedure enables the development of an analytical expression for the transient current response in terms of well established mathematical special functions. We have shown that kinetic information may be readily extracted from the developed expressions for the current response as a function of time. In the present paper we assume that the reaction between mediator and substrate is of a simple outer sphere bimolecular type.
Ethylene Detection Using Nanoporous PtTiO2 Coatings Applied to Magnetoelastic Thick Films
Authors: Zhang Rhong , Tejedor M. I. , Anderson Marc  A. , Paulose Maggie , Grimes Craig  A.
Published: October 2008

This paper reports on the use of nanoporous Pt-TiO2 thin films coated onto magnetoelastic sensors for the detection of ethylene, an important plant growth hormone. Five different metal oxide coatings, TiO2, TiO2+ZrO2, TiO2+TTCN(1,4,7-Trithiacyclononane)+Ag, SiO2+Fe, and TiO2+Pt, each having demonstrated photocatalytic activity in response to ethylene, were investigated for their ability to change mass or elasticity in response to changing ethylene concentration. Pt-TiO2 films were found to possess the highest sensitivities, and coupled with the magnetoelastic sensor platform capable of sensing ethylene levels of < 1 ppm.
A Hydrogen Ion-Selective Sensor Based on Non-Plasticised Methacrylic-acrylic Membranes
Authors: Heng Lee  v , Chern Loh  Han , Ahmad Musa
Published: October 2008

A methacrylic-acrylic polymer was synthesised for use as a non-plasticised membrane for hydrogen ion-selective sensor incorporating tridodecylamine as an ionophore. The copolymer consisted of methyl methacrylate and n-butyl acrylate monomers in a ratio of 2:8. Characterisation of the copolymer using FTNMR demonstrated that the amount of each monomer incorporated during solution polymerisation was found to be similar to the amount used in the feed before polymerisation. The glass transition temperature of the copolymer determined by differential scanning calorimetry was -30.9 ºC. Potentiometric measurements conducted showed a linear pH response range of 4.3 – 9.6 with the response slope of 56.7 mV/decade. The selectivity of the sensors towards hydrogen ions was similar to other plasticiser based membrane electrodes and the logarithmic selectivity coefficients for discrimination against interference cations is close to –9.7. However, the incorporation of a lipophilic anion as membrane additive is essential in ensuring optimum performance of the hydrogen ion sensor.
Gamma Radiation Dosimetry Using Tellurium Dioxide Thin Film Structures
Authors: Arshak Khalil , Korostynska Olga
Published: October 2008

Thin films of Tellurium dioxide (TeO2) were investigated for γ-radiation dosimetry purposes. Samples were fabricated using thin film vapour deposition technique. Thin films of TeO2 were exposed to a 60Co γ-radiation source at a dose rate of 6 Gy/min at room temperature. Absorption spectra for TeO2 films were recorded and the values of the optical band gap and energies of the localized states for as-deposited and γ-irradiated samples were calculated. It was found that the optical band gap values were decreased as the radiation dose was increased. Samples with electrical contacts having a planar structure showed a linear increase in current values with the increase in radiation dose up to a certain dose level. The observed changes in both the optical and the electrical properties suggest that TeO2 thin film may be considered as an effective material for room temperature real time γ-radiation dosimetry.
A First Step Towards a Microfabricated Thin-Film Sensor Array on the Basis of Chalcogenide Glass Materials
Authors: Kloock Joachim  P. , Mourzina Yulia  G. , Schubert Jürgen , Schöning Michael  J.
Published: October 2008

A first step towards a microfabricated potentiometric thin-film sensor array for the simultaneous detection of Pb2+, Cd2+ and Cu2+ has been realized. The sensitive layers used are on the basis of chalcogenide glass materials. These thin-film chalcogenide glass materials that consist of mixtures of Pb-Ag-As-I-S, Cd-Ag-As-I-S or Cu-Ag-As-Se have been prepared by pulsed laser deposition technique. The developed sensor array has been physically characterized by means of scanning electron microscopy and Rutherford backscattering spectrometry. The electrochemical sensor characterization has been performend by potentiometric measurements.
Study on the Characteristics of Ag Doped CuO-BaTiO3 CO2 Sensors
Authors: Jiao Zheng , Chen Feng , Su Run , Huang Xingjiu , Liu Wei , Liu Jinhuai
Published: October 2008

In this paper the characteristics of a CuO-BaTiO3 based CO2 gas sensor was investigated. The sensitivity of the CuO-BaTiO3 based CO2 sensor was influenced by doping various metal elements such as Au, Ag, Pt, Pd, Ce, Mg, Sr, La, Zn, Fe and Bi, which were added as a pure metal or in the form of metal oxides. It was found that Ag is the most suitable additive among all substances tested. The Ag-doped CO2 gas sensor has better sensitivity and lower operating temperature, with a detection concentration range of from 100 ppm to 10%. The sensor also shows good stability.
Benzene Sensing Using Thin Films of Titanium Dioxide Operating at Room Temperature
Authors: Mabrook Mohammed , Hawkins Peter
Published: October 2008

Benzene is a carcinogen with a maximum permitted exposure limit in the atmosphere of 16.25μg m-3 (5 ppb). There is a need for an inexpensive instrument for measuring benzene concentrations, particularly in urban areas. We have shown that thin films of titanium dioxide dispersed in poly(vinylidenfluoride) are sensitive to benzene at room temperature with possible applications in benzene monitors. In this paper, we present a detailed study into the direct current electrical characteristics of the films when exposed to benzene. The current I through the films increase linearly with applied voltage, V, at low applied voltages (V ≲0.6V) and at higher voltages, I α V5. The results are consistent with the films being p-type semiconductors and, at higher voltages, the conduction is dominated by a space charge limited process caused by negative traps with an average energy of 0.1 eV. The films are sensitive to benzene only at the higher voltages. The proposed mechanism is that benzene molecules on the surface of the films reduce the concentration of holes. The relative resistance of the films increases linearly (r = 0.92) with benzene concentrations (sensitivity of 0.042% ppm-1) and a detection limit of 10 ppm. The films have response times to increasing and decreasing concentrations of benzene of about 1 and 5 min respectively.
Dibenzocyclamnickel(II) as Ionophore in PVC-Matrix for Ni2+-Selective Sensor
Authors: Gupta Vinod K. , Prasad Rajendra , Kumar Azad
Published: October 2008

The tetramethyldibenzocyclam derivative, was synthesized and characterized and was used for fabrication of potentiometric sensor for Ni2+ metal ion. 5,7,8,14-tetramethyldibenzo[b,i]-1,4,8,11-tetrazacyclotetradecanenickel(II)chloride, ([Ni(Me4Bzo2[14]ane N4)]Cl2) (II) was obtained in good yield as orange red salt by Fe/HCl reduction of the corresponding tetraazaannulene complex [Ni(Me4Bzo2taa)], (I). Membrane having [Ni(Me4Bzo2[14]aneN4)]Cl2 (II) as electroactive material, sodium tetraphenylborate (NaTPB) as an anion discriminator, dibutyl butylphosphonate (DBBP) as plasticizer in PVC matrix in the percentage ratio 5.0:2.5:200:200 (II:NaTPB:DBBP:PVC)(w/w) exhibits a linear response to Ni2+ in the concentration range 7.0×10-6- 1.0×10-1M with a slope of 29.8±0.2 mV/decade of activity and a fast response time of 12s. The sensor works well in the pH range 2.0-7.6 and can be satisfactorily used in presence of 40% (v/v) methanol, ethanol or acetone. The sensor is highly selective for Ni2+ over a large number of mono-, biand trivalent cations. The sensor has been successfully used as indicator electrode in the potentiometric titration of Ni2+ against EDTA. These electrodes can be used to determine the concentration of Ni2+ in real samples.
Calixarene-Based Molecules for Cation Recognition
Authors: Ludwig Rainer , Dzung Nguyen Thi Kim
Published: October 2008

This review discusses molecular design principles of calixarene-type macrocycles for ion recognition and gives examples on the relationship between structure and selectivity, however without attempting to cover all the different approaches.
Sensor for Silver(I) Ion Based on Schiff-base-p-tertbutylcalix[4]arene
Authors: Mahajan R.  K. , Kaur Inderpreet , Sharma V. , Kumar M.
Published: October 2008

The preparation of polymer membrane selective to silver ion and its application to ion-selective electrode is reported here. PVC membrane contain silver-selective calix[4]arene derivative as ionophore. The membrane electrode is highly selective to silver ion and exhibit good linear response over a wide concentration range of 1.0×10-1 to 1.0×10-5M AgNO3 with Nernstian slope of 58.9 mV per decade. The detection limit of electrode is 6.31×10-6 M .The calix[4]arene based membrane electrode exhibit enhanced selectivities for silver ion over other cations; log KPotAg,Na = -2.35, log KPotAg,K= -2.65, log KPotAg,Mg = -4.57, log KPotAg,Ba = -4.10, log KPotAg,Cd = -3.42, log KPotAg,Pb = -3.45.Even the strongest interferent Hg2+ do not interfere to great extent, log KPotAg,Hg = -2.0.The electrode response is stable over wide pH range of 1.0-6.0. The response time of the sensor is 30 seconds and the membrane can be used for more than 6 months without observing any divergence. The sensor can also be applied as an indicator electrode for potentiometric titration of Ag+ ions with Cl-. It is possible to determine Ag(I) in the natural water spiked with silver with this electrode assembly.
Ion Selective PVC Membrane Electrode for the Determination of Methacycline Hydrochloride in Pharmaceutical Formulation
Authors: Aboul-Enein Hassan  Y. , Sun Xian  Xiang , Sun Cheng  Jun
Published: October 2008

A plastic membrane electrode for the determination of methacycline hydrochloride was fabricated based on the use of methacycline-tetraphenylborate as the electroactive substance, and dioctylphtalate as the plasticizing agent. It was found that the potential responses of the electrode were influenced by pH of the tested solution when pH>3. Under the condition of pH 2.6, the linear response range, slope (25ºC) and detection limit obtained were 3.0×10-2~6.0×10-6M, 52.9mv per decade and 3.4×10-6M ,respectively. The response time of the electrodes was
Reagents for Lithium Electrodes and Sensors for Blood Serum Analysis
Authors: Christian Gary  D.
Published: October 2008

The measurement of lithium in blood serum requires high selectivity since the blood contains about 140 mM sodium compared to the 0.5-1.5 mM lithium level in manic depressive patients under treatment with lithium salts. This review traces the development of optical and potentiometric methods for the selective measurement of lithium in the presence of sodium. Selectivities of over 1,000:1 are achievable with properly designed ionophores.
Mathematical Modelling of the Electrode Process of Azithromycin Using Cyclic Voltammetry at Hanging Mercury Drop Electrode
Authors: Shawabkeh Reyad  A. , Tutunji Maha F.
Published: October 2008

A theoretical treatment is presented to predict the kinetic behaviour of azithromycin at the surface of hanging mercury drop electrode using cyclic voltammetry. A model is developed to incorporate the occurrence of adsorption of the oxidized and reduced species of azithromycin at the surface of mercury drop electrode. An analytical solution was obtained using MATHEMATICA (V-3, Wolfram Research, Inc.) to predict the cyclic voltammetric profiles by calculating the currents resulting after applying variable potentials ranging –1.9 to –1.3 V versus Ag/AgCl. Simulation runs at different initial concentrations of azithromycin and different scan rates showed good agreement with experimental findings. However, this model should be modified to describe a multilayer adsorption with irreversible electrochemical reaction.
Study on pH Effect in Process of an Entero-gastric Fiber-optic Sensor Design
Authors: Guo-ping Chen , Rong-min Xia , Jun Gong , Wen-de Shou
Published: October 2008

The pH effect on design of a fiber optic sensor newly developed for monitoring entero-gastric reflux is investigated. The research has been carried out by utilizing the sensor to measure characteristic absorption of bilirubin standard solution (used as a calibrator) at different pH values from about 1 to 8. The results show explicitly that the estimation error according to the calibration curves with pH
Design of a Wireless Sensor Network for Long-term, In-Situ Monitoring of an Aqueous Environment
Authors: Yang Xiping , Ong Keat  G. , Dreschel William  R. , Zeng Kefeng , Mungle Casey  S. , Grimes Craig  A.
Published: October 2008

An aqueous sensor network is described consisting of an array of sensor nodes that can be randomly distributed throughout a lake or drinking water reservoir. The data of an individual node is transmitted to the host node via acoustic waves using intermediate nodes as relays. Each node of the sensor network is a data router, and contains sensors capable of measuring environmental parameters of interest. Depending upon the required application, each sensor node can be equipped with different types of physical, biological or chemical sensors, allowing long-term, wide area, in situ multi-parameter monitoring. In this work the aqueous sensor network is described, with application to pH measurement using magnetoelastic sensors. Beyond ensuring drinking water safety, possible applications for the aqueous sensor network include advanced industrial process control, monitoring of aquatic biological communities, and monitoring of waste-stream effluents.
Mediated Electron Transfer at Redox Active Monolayers. Part 3: Bimolecular Outer-Sphere, First Order Koutecky-Levich and Adduct Formation Mechanisms
Authors: Lyons Michael  E.G.
Published: October 2008

A number of theoretical models describing the transport and kinetic processes involved in heterogeneous redox catalysis of solution phase reactants at electrode surfaces coated with redox active monolayers (such as self assembled alkane thiols containing a ferrocene group) is presented. These models are : simple bimolecular outer-sphere, generalized Koutecky-Levich, and substrate binding/ adduct formation . For each model a general expression for the steady state reaction flux is derived. Simplified analytical expressions for the net reaction flux under steady state conditions, are derived for experimentally reasonable situations, and kinetic case diagrams are constructed outlining the relationships between the various approximate solutions. The theory developed enables simple diagnostic plots to be constructed which can be used to analyse experimental data.
Voltammetric Detection of Antioxidative Properties of Flavonoids Using Electrically Heated DNA Modified Carbon Paste Electrode
Authors: Korbut O. , Bučková M. , Labuda J. , Gründler P.
Published: October 2008

A simple electrochemical sensor consisting of electrically heated carbon paste electrode with the surface modified by dsDNA is used to characterize voltammetric behaviour and antioxidative activity of four selected flavonoids. Quercetin, rutin, catechin and epigallocatechin gallate accumulate within the DNA layer. A positive effect of the electrode temperature within the range of 20 to 38 ºC on the detection of a deep DNA degradation by a copper(II)/H2O2/ascorbic acid cleavage mixture as well as an antioxidative effect of flavonoids was evaluated.
A Wireless, Passive, Magnetically-soft Harmonic Sensor for Monitoring Sodium Hypochlorite Concentrations in Water
Authors: Ong Keat  G. , Paulose Maggie , Grimes Craig  A.
Published: October 2008

A wireless, passive, remote-query sensor for monitoring sodium hypochlorite (bleach) solutions is reported. The sensor is comprised of a magnetically-soft ferromagnetic ribbon, coated with a layer of polyurethane and alumina, having a large and nonlinear permeability that supports higher-order harmonics in response to a time varying magnetic field. The hypochlorite ions induce swelling in the coating, with the resultant stress altering the harmonic signature of the sensor from which the sodium hypochlorite concentration can be determined. The wireless, passive nature of the sensor platform enables long-term monitoring of bleach concentrations in the environment. The sensor platform can be extended to other chemical analytes of interest as desired.
Mediated Electron Transfer at Redox Active Monolayers. Part 4: Kinetics of Redox Enzymes Coupled With Electron Mediators
Authors: Lyons Michael  E.G.
Published: October 2008

A detailed kinetic analysis of the pertinent physical processes underlying the operation of enzyme electrodes immobilized within alkane thiol self assembled monolayers is developed. These electrodes utilize a soluble mediator, which partitions into the monolayer, regenerates the active catalytic form of the enzyme and is re-oxidized at the underlying support electrode surface giving rise to a current which reflects kinetic events at the enzyme surface. Both the enzyme/substrate and enzyme mediator kinetics have been quantified fully in terms of a ping-pong mechanism for the former and Michaelis-Menten kinetics for the latter. The effect of substrate and mediator diffusion in solution have also been specifically considered and the latter processes have been shown to result in a complex expression for the reaction flux. Four limiting kinetic cases have been enumerated and simple expressions for the reaction flux in each of these rate limiting situations have been developed. Kinetic case diagrams have been presented as an aid to mechanistic diagnosis. The complicating effects of diffusive loss of reduced mediator from the enzyme layer have also been examined and the relation between the observed flux corresponding to reduced mediator oxidation at the support electrode and the substrate reaction flux in the enzyme layer have been quantified in terms of an efficiency factor. Results extracted from recently published practical realizations of immobilized monolayer enzyme systems have been discussed in the context of the proposed model analysis.
Voltammetric Determination of Carcinogenic Nitrobiphenyls at a Hanging Mercury Drop Electrode
Authors: Štěpán Radek , Barek Jiří , Mejstřík Viktor , Zima Jiří
Published: October 2008

Differential pulse voltammetry (DPV) and adsorptive stripping voltammetry (AdSV) at a hanging mercury drop electrode (HMDE) was used for the determination of trace amounts of carcinogenic nitrobiphenyls, namely 2-nitrobiphenyl (2-NBP), 3-nitrobiphenyl (3-NBP) and 4-nitrobiphenyl (4-NBP) within the concentration range from 2.10-8 to 1.10-5 mol⋅L-1 for DPV and from 2.10-9 to 1.10-7 mol⋅L-1 for AdSV using a Britton-Robinson buffer – methanol (1:1) mixture with resulting pH 12 as a base electrolyte. The practical applicability of newly developed methods was verified using model samples of drinking and river water and liquid-liquid extraction for a preliminary separation and preconcentration.
Voltametric Behavior of Noradrenaline at 2-Mercaptoethanol Self-Assembled Monolayer Modified Gold Electrode and its Analytical Application
Authors: Zhang XiuHua , Wang ShengFu
Published: October 2008

2-Mercaptoethanol self-assembled monolayer (ME/Au SAMs) was prepared on a gold electrode. The ME/Au SAMs was characterized by using ATR-FTIR and dynamic contact angle measurements. The electrochemical behaviors of noradrenaline (NE) on the ME/Au SAMs were studied in BR buffer solution. The modified electrode accelerated electron transfer rate of the redox of NE and showed an excellent eletrocatalytic activity. The diffusion coefficient (D) of NE was obtained to be 4.3×10-8 cm2 s-1. The catalytic current increased linearly with the concentration of NE in the range of 2.0×10-6 -1.0×10-3 M by square wave voltammetry response. The modified electrode could eliminate the interference of ascorbic acid (AA) at 40-fold concentration of NE and could be satisfactorily used for the determination of NE in the drug injection.
A Sentinel Sensor Network for Hydrogen Sensing
Authors: Grimes Craig  A. , Ong Keat  G. , Varghese Oomman  K. , Yang Xiping , Mor G. , Paulose Maggie , Dickey Elizabeth  C. , Ruan Chuanmin , Pishko Michael  V. , Kendig James  W. , Mason Andrew  J.
Published: October 2008

A wireless sensor network is presented for in-situ monitoring of atmospheric hydrogen concentration. The hydrogen sensor network consists of multiple sensor nodes, equipped with titania nanotube hydrogen sensors, distributed throughout the area of interest; each node is both sensor, and data-relay station that enables extended wide area monitoring without a consequent increase of node power and thus node size. The hydrogen sensor is fabricated from a sheet of highly ordered titania nanotubes, made by anodization of a titanium thick film, to which platinum electrodes are connected. The electrical resistance of the hydrogen sensor varies from 245 Ω at 500 ppm hydrogen, to 10.23 kΩ at 0 ppm hydrogen (pure nitrogen environment). The measured resistance is converted to voltage, 0.049 V at 500 ppm to 2.046 V at 0 ppm, by interface circuitry. The microcontroller of the sensor node digitizes the voltage and transmits the digital information, using intermediate nodes as relays, to a host node that downloads measurement data to a computer for display. This paper describes the design and operation of the sensor network, the titania nanotube hydrogen sensors with an apparent low level resolution of approximately 0.05 ppm, and their integration in one widely useful device.
Influence of Methacrylic-Acrylic Copolymer Composition on Plasticiser-free Optode Films for pH Sensors
Authors: Heng Lee  Yook , Fang Teh  Huey , Chern Loh  Han , Ahmad Musa
Published: October 2008

In this work we have examined the use of plasticiser-free polymeric films incorporating a proton selective chromoionophore for optical pH sensor. Four types of methacrylic-acrylic copolymers containing different compositions of n-butyl acrylate (nBA) and methyl methacrylate (MMA) were synthesised for use as optical sensor films. The copolymers were mixed with appropriate amounts of chromoionophore (ETH5294) and a lipophilic salt before spin coated on glass slides to form films for the evaluation of pH response using spectrophotometry. Co-polymer films with high nBA content gave good response and the response time depended on the film thickness. A preliminary evaluation of the optical films of high nBA content with pHs from 2 - 14 showed distinguishable responses from pH 5 - 9. However, the adhesion of the pH sensitive film was good for copolymers with higher content of MMA but not for films with high nBA.
Amperometric Metronidazole Sensor Based on the Supermolecular Recognition by Metalloporphyrin Incorporated In Carbon Paste Electrode
Authors: Gong Fu-Chun , Zhang Xiao-Bing , Guo Can-Cheng , Shen Guo-Li , Yu Ru-Qin
Published: October 2008

An amperometric metronidazole (MTZ) sensor using a glycosylated metalloporphyrin as a recognition element, which was incorporated in a carbon paste electrode, is reported. For the preparation of a MTZ-sensitive active material, 5, 10, 15, 20-tetrakis [2-(2, 3, 4, 6-tetraacetyl-β-D-glucopyranosyl)-1-O-phenyl]porphyrin (T(oglu) PPH2) and its Mn(III) complex MnT(o-glu)PPCl were synthesized from the reaction of pyrrole with ortho-acetylglycosylated benzaldehyde by Lindsay’s method. The MnT(oglu) PPCl-modified electrode showed excellent selectivity toward MTZ with respect to a number of interferents and exhibited stable response. The calibration graph obtained with the proposed sensor was linear over the range of 2.9×10-3-5.8×10-8 M/L, with a detection limit of 5.8×10-8 M/L for MTZ. Cyclic voltammetric measurements indicated that MnT(oglu) PPCl included in graphite-epoxy resin matrices could efficiently mediate electron transfer from the base electrode to MTZ causing a decrease of reduction potential for MTZ detection. The sensor could be regenerated by simply polishing with an alumina paper, with an excellent reproducibility (RSD=1.6%). The experimental conditions such as pH and applied working potential were optimized. The prepared sensor is applied for the determination of MTZ in pharmaceutical preparations and the results agreed with the values obtained by the pharmacopoeia method.
Vinegar Classification Based on Feature Extraction and Selection From Tin Oxide Gas Sensor Array Data
Authors: Xiaobo Zou , Jiewen Zhao , Shouyi Wu , Xingyi Huang
Published: October 2008

Tin oxide gas sensor array based devices were often cited in publications dealing with food products. However, during the process of using a tin oxide gas sensor array to analysis and identify different gas, the most important and difficult was how to get useful parameters from the sensors and how to optimize the parameters. Which can make the sensor array can identify the gas rapidly and accuracy, and there was not a comfortable method. For this reason we developed a device which satisfied the gas sensor array act with the gas from vinegar. The parameters of the sensor act with gas were picked up after getting the whole acting process data. In order to assure whether the feature parameter was optimum or not, in this paper a new method called “distinguish index”(DI) has been proposed. Thus we can assure the feature parameter was useful in the later pattern recognition process. Principal component analysis (PCA) and artificial neural network (ANN) were used to combine the optimum feature parameters. Good separation among the gases with different vinegar is obtained using principal component analysis. The recognition probability of the ANN is 98 %. The new method can also be applied to other pattern recognition problems.