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Sensors, Volume 3, Issue 10 (October 2003), Pages 404-503

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Research

Open AccessArticle Quartz Crystal Microbalance Coated with Sol-gel-derived Thin Films as Gas Sensor for NO Detection
Sensors 2003, 3(10), 404-414; doi:10.3390/s31000404
Received: 15 June 2003 / Accepted: 15 September 2003 / Published: 31 October 2003
Cited by 7 | PDF Full-text (880 KB)
Abstract
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). [...] Read more.
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. Full article
Open AccessArticle Morphology, Structure and Nonstoichiometry of ZnCr2O4 Nanophased Powder
Sensors 2003, 3(10), 415-423; doi:10.3390/s31000415
Received: 15 May 2003 / Accepted: 17 August 2003 / Published: 31 October 2003
Cited by 15 | PDF Full-text (1358 KB)
Abstract
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 [...] Read more.
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. Full article
Open AccessArticle A Novel Coated Graphite Rod Th(IV) Ion Selective Electrode Based On Thorium Oxinate Complex and Its Application
Sensors 2003, 3(10), 424-437; doi:10.3390/s31000424
Received: 13 July 2003 / Accepted: 14 September 2003 / Published: 31 October 2003
Cited by 11 | PDF Full-text (141 KB)
Abstract
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 [...] Read more.
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). Full article
Open AccessArticle Preparation of SnO2 Films with Thermally Stable Nanoparticles
Sensors 2003, 3(10), 438-442; doi:10.3390/s31000438
Received: 3 April 2003 / Accepted: 11 September 2003 / Published: 31 October 2003
Cited by 5 | PDF Full-text (777 KB)
Abstract 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. Full article
Open AccessArticle Determination of Dopamine in the Presence of Ascorbic Acid using Poly (Acridine red) Modified Glassy Carbon Electrode
Sensors 2003, 3(10), 443-450; doi:10.3390/s31000443
Received: 6 August 2003 / Accepted: 25 September 2003 / Published: 31 October 2003
Cited by 31 | PDF Full-text (231 KB)
Abstract
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 [...] Read more.
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. Full article
Open AccessArticle Semiconductor Metal Oxide Sensors in Water and Water Based Biological Systems
Sensors 2003, 3(10), 451-457; doi:10.3390/s31000451
Received: 1 May 2003 / Accepted: 15 September 2003 / Published: 31 October 2003
Cited by 4 | PDF Full-text (109 KB)
Abstract 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. Full article
Open AccessArticle Chemometric Classification of Herb – Orthosiphon stamineus According to Its Geographical Origin Using Virtual Chemical Sensor Based Upon Fast GC
Sensors 2003, 3(10), 458-471; doi:10.3390/s31000458
Received: 5 June 2003 / Accepted: 28 August 2003 / Published: 31 October 2003
Cited by 20 | PDF Full-text (703 KB)
Abstract
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. [...] Read more.
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. Full article
Open AccessArticle Impedance Spectroscopy Technique for DNA Hybridization
Sensors 2003, 3(10), 472-479; doi:10.3390/s31000472
Received: 4 August 2003 / Accepted: 15 September 2003 / Published: 31 October 2003
Cited by 27 | PDF Full-text (197 KB)
Abstract
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 [...] Read more.
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. Full article
Open AccessArticle Contribution of Structure and Morphology of Design Constituents to Performance Improvement of Multilayer Polaritonic Photodetector
Sensors 2003, 3(10), 480-490; doi:10.3390/s31000480
Received: 1 April 2003 / Accepted: 22 August 2003 / Published: 31 October 2003
Cited by 1 | PDF Full-text (750 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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. Full article
Open AccessArticle Sensors Auto-calibration Method - Using Programmable Interface Circuit Front-end
Sensors 2003, 3(10), 491-497; doi:10.3390/s31000491
Received: 22 June 2003 / Accepted: 9 September 2003 / Published: 31 October 2003
PDF Full-text (304 KB)
Abstract
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 [...] Read more.
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. Full article
Open AccessArticle Implementation of a Feedback I2-Controlled Constant Temperature Environment Temperature Meter
Sensors 2003, 3(10), 498-503; doi:10.3390/s31000498
Received: 29 March 2003 / Accepted: 29 August 2003 / Published: 31 October 2003
Cited by 9 | PDF Full-text (464 KB)
Abstract
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 [...] Read more.
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. Full article

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