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One of the types of gas sensors used for detection and identification of toxic-air pollutant is an electro-catalytic gas sensor. The electro-catalytic sensors are working in cyclic voltammetry mode, enable detection of various gases. Their response are in the form of I-V curves which contain information about the type and the concentration of measured volatile compound. However, additional analysis is required to provide the efficient recognition of the target gas. Multivariate data analysis and pattern recognition methods are proven to be useful tool for such application, but further investigations on the improvement of the sensor’s responses processing are required. In this article the method for extraction of the parameters from the electro-catalytic sensor responses is presented. Extracted features enable the significant reduction of data dimension without the loss of the efficiency of recognition of four volatile air-pollutant, namely nitrogen dioxide, ammonia, hydrogen sulfide and sulfur dioxide.

Many types of yttria-stabilized zirconia (YSZ) based gas sensors have been explored extensively in recent years. Great attention have been directed to mixed-potential-type gas sensors. It is due to growing concerns with environmental issues. Not without a significance is the fact of very attractive performance of this type of sensor allowing to detect low concentration of pollutant gases. In this paper two types of YSZ based mixed-potential planar sensors were investigated, with platinum electrode painted using commercial paste and with spin coated platinum layer. Both types had second electrode in the form of porous gold. Measurements were performed at 400 °C in synthetic air and different concentrations of SO2. Gas flow was set to 100 cm3min-1 and the concentration of 50 ppm SO2 was tested. During this measurements the sensor was sintered in-situ at increasing temperatures. Sensor with 100 nm spin-coated platinum layer sintered at 700 °C was shown to exhibit two times smaller response than sensor with 5 μm porous electrode, while consisting of over 20 times smaller amount of Pt. The influence of sintering temperature on electrical conductivity of platinum films was also examined. Moreover, the platinum microstructure was investigated using SEM microscopy.

A periodic temperature modulation using sinusoidal heater voltage was applied to a commercial SnO2 semiconductor gas sensor. Resulting resistance response of the sensor was analyzed using a feature extraction method based on Fast Fourier Transformation (FFT). The amplitudes of the higher harmonics of the FFT from the dynamic nonlinear responses of measured gas were further utilized as an input for Artificial Neuron Network (ANN). Determination of the concentration of chlorine was performed. Moreover, this work evaluates the sensor performance upon sinusoidal temperature modulation.

Gas analyzers based on gas sensors are the devices which enable recognition of various kinds of volatile compounds. They have continuously been developed and investigated for over three decades, however there are still limitations which slow down the implementation of those devices in many applications. For example, the main drawbacks are the lack of selectivity, sensitivity and long term stability of those devices caused by the drift of utilized sensors. This implies the necessity of investigations not only in the field of development of gas sensors construction, but also the development of measurement procedures or methods of analysis of sensor responses which compensate the limitations of sensors devices. One of the fields of investigations covers the dynamic measurements of sensors or sensor-arrays response with the utilization of flow modulation techniques. Different gas delivery patterns enable the possibility of extraction of unique features which improves the stability and selectivity of gas detecting systems. In this article three utilized flow modulation techniques are presented, together with the proposition of the evaluation method of their usefulness and robustness in environmental pollutants detecting systems. The results of dynamic measurements of an commercially available TGS sensor array in the presence of nitrogen dioxide and ammonia are shown.

In this work, 3D polypyrrole (PPy) structures as material for glucose detection is proposed. Polypyrrole was electrochemically polymerized on platinum screen-printed electrode from an aqueous solution of lithium perchlorate and pyrrole. The growth mechanism of such PPy structures was studied by ex-situ scanning electron microscopy. Preliminary studies show that studied here PPy film is a good candidate as a sensing material for glucose biosensor. It exhibits very high sensitivity (28.5 mA·mM-1·cm-2) and can work without any additional dopants, mediators or enzymes. It was also shown that glucose detection depends on the PPy morphology. The same PPy material was immobilized with the glucose oxidase enzyme. Such material exhibited higher signal response, however it lost its stability very fast.

Recent increasing demand for new eco-friendly materials and for low cost fabrication process for use in optical sensors field, raise concern about alternative materials for this application. We have designed two glass-ceramics compositions from the quaternary ROAl2O3- SiO2-B2O3(R=Ba) alkali-earth aluminum silicate system, labeled B72 and B69, with high refractive index (>1.6), large values of Abbe number (94.0 and 53.0, respectively), and free of lead and arsenic. We present an analysis and discussion of experimental optical properties, thermal and thermo-chemical stability along with important properties such as transition temperature (Tg), onset of crystallization (Tx) as well transport properties as ionic conductivity behavior in the quaternary glass-ceramic system containing boron for use as optical sensors. Complex Impedance Spectra (Bode Plot) and Potentiodynamic Polarization curves (Tafel plots) measurements were carried out in the temperature range of 600 to 850°C. The most probable conductivity mechanism is a thermally activated process of mobile ions overcoming a potential barrier (EA), according to the Arrhenius regime. Here we report that charge transfer is caused by the flux of electrons, in the region of elevated temperatures (>700°C), and is affected by immiscibility of crystals, nucleation and growth type, that causes phase separation. We found conductivity (σ) values from 10-9 to 10-5 S/cm at temperatures between 700 and 850°C. Our results highlight a need for research on ion mobility in the glassy network above the transition range, and the effect cause by metastable immiscibility in the alkaline-earth glasses are exposed. The two glass compositions B72 and B69 can be tailored by proper use as glassy optical sensor.

Results of impedance measurements of humidity sensors with epoxy resins containig quarternary ammonium salts are presented in this paper. The humidity sensitive membranes were prepared from polyethyleneimine (PEI). PEI was cross-linked using 1,4-butanediol diglycidyl ether (BDDGE) and glycidyl trimethyl ammonium chloride (GTMAC) was added as a humidity sensitive epoxy monomer.

Electrocatalytic sensors belong to a relatively new group of solid state electrochemical gas sensors. Its working principle is based on electric current acquisition, while voltage ramp is applied to the sensor. The current-voltage plot has unique shape, which depends on surrounding gas type and its concentration. Response of the electrocatalytic gas sensor contains significantly more information in comparison with typical amperometric or potentiometric one. Methods of sensors response analysis, which was employed so far, did not fully utilize this feature. Moreover, shape of sensor response, in case of some gases or mixtures, is hard to be interpreted with traditional techniques. In this work more advanced methods to analyze electrocatalytic gas sensor response, which are based on explorative and confirmative techniques as well as artificial neural network, are presented.

The effect of humidity influence on characteristics of a ceramic sensor with a porous dielectric Al2O3 layer is presented. Influence of chosen electrolytic process parameters on electrical properties of the sensor is shown. The experimental data of two groups of sensors are interpreted using two, known from literature, electric equivalent circuits.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In the paper the results of temperature investigations of polymer humidity sensor based on polyethyleneimine is presented. Sensor was prepared by chemical modification of polyethyleneimine and vacuum sputtering of gold electrodes on thick polymer film. The high thickness of the film limit the dynamic properties of the sensor. Electrical properties of the sensor were examined by impedance spectroscopy. The results allow structure optimization and improvement of dynamic properties of the sensor.

The simple electrochemical cell Au INASICONI Au which is sensitive to NO2 and SO2 atmosphere due to voltage excitationwas investigated. The shape of current! voltage characteristic is strongly dependent on specific gas concentration and revealspecific peaks. Selection of sweep polarization of the sensor is very important.Keywords: gas sensor, solid state electrolytes 1. INTRODUCTION Gas sensors play an important role in process control, pollution control and monitoring, hazardous materials detection andwarning. Interest in electrochemical sensors with solid electrolytes has increased since the successful application of thezirconia oxide Lambda sensor that measures oxygen. The advantages of using solid electrolytes for electrochemical sensorsinclude the possibilities of high temperature application and miniaturisation. Typically electrochemical sensors based onsolid electrolytes work either in potentiometric or amperomentic mode. Most of them are not in large scale production(except Lambda probe) mainly due to its low selectivity.In recent years a new principle of solid state electrochemical gas sensors based on the kinetics of controlled chemicalreaction of a gas with electroactive species of a solid electrolyte is under development [1], [2], [3]. In this kind of sensorperiodic voltage (or current) is applied to the solid state electrochemical cell and the current response (or voltage) ismeasured. The current