Grzegorz Jasinski

Properties of a polyethyleneimine-based sensor for measuring medium and high relative humidity

In this paper a method of preparing polyethyleneimine films, which improves the water resistance of polymer humidity sensors, is proposed. The polyethyleneimine was cross-linked at elevated temperature using 1,4-butanediol diglycidyl ether, both being dissolved in dimethylsulfoxide. The optimum composition of polymer and optimum reaction temperature were obtained. Resistive-type sensors have been prepared by dip coating. The sensor preserves excellent durability in high humidities or even after immersion in water. The electrical properties of the sensors were investigated by impedance spectroscopy.

Properties of a lithium solid electrolyte gas sensor based on reaction kinetics

Principle of operation, construction and properties of a gas sensor based on lithium ion-conductor solid electrolyte (Lisicon) are presented. The sensor has been prepared using thick film technology. Its working principle is based on electric current acquisition, while a voltage ramp is applied to the sensor. The current–voltage plot has a unique shape, which depends on the surrounding gas type and its concentration. Results of measurements conducted in mixtures of high purity gases—nitrogen dioxide, sulfur dioxide, carbon dioxide and synthetic air of controlled concentration—over a wide range of temperatures are presented and discussed.

POTENTIOMETRIC OXYGEN SENSOR WITH SOLID STATE REFERENCE ELECTRODE

The concentration or the partial pressure of oxygen in an environment can be determined using different measuring principles. For high temperature measurements of oxygen, ceramic-based sensors are the most practical. They are simple in construction, exploration and maintenance. A typical oxygen potentiometric sensor consists of an oxygen ion conducting solid electrolyte and two electrodes deposited on the two sides of the electrolyte. In this paper different structures of potentiometric oxygen sensors with a solid state reference electrode were fabricated and investigated. The fabricated structures consisted of oxygen ion conducting solid electrolyte from yttria stabilized zirconia, a sensing platinum electrode and nickel-nickel oxide reference electrode. The mixture of nickel-nickel oxide was selected as the reference electrode because it provides reliable electrochemical potential in contact with oxygen conducting electrolyte. To avoid oxidation of nickel the reference electrode is sealed from ambient and the mixture of nickel-nickel oxide was formed electrochemically from nickel oxide after sealing. The effectiveness of the sealing quality and the effectiveness of nickel–nickel oxide mixture formation was investigated by impedance spectroscopy.

Determination of toxic gases based on the responses of a single electrocatalytic sensor and pattern recognition techniques

A response from an electrocatalytic gas sensor contains fingerprint information about the type of gas and its concentration. As a result, a single gas sensor can be used for the determination of different gases. However, information about the type of gas and its concentration is hidden in the unique shape of the current–voltage response and it is quite difficult to explore. One of the ways to get precise information about the measured gas is to use multivariate data analysis and pattern recognition techniques. In this paper we present the results of an investigation based on a combination of the cyclic voltammetry measurement technique and chemometric analysis methods such as principal components analysis, linear discriminant analysis and the k-nearest neighbors algorithm classifier for distinguishing different types of toxic gases. The responses of the single electrocatalytic gas sensor to 20 ppm of ammonia, nitrogen dioxide, sulfur dioxide and various concentrations of hydrogen sulfide in balance with synthetic air have been measured and analyzed. The reduction of measurement points in the data set used for multivariate analysis was evaluated.

The influence of the choice of the cross-linking agent on the electrical properties of polyethyleneimine-based humidity sensors

The results of impedance measurements of thin film polymer humidity sensors are presented in this paper. The sensors were made of chemically modified polyethyleneimine, spread on alumina substrate with comb type gold electrodes. Electrical properties of the sensors are strongly dependent on relative humidity (RH). The influence of the selected cross-linking agents on the properties, measuring range, and technology of preparation of the sensors is discussed.

Electrical properties of polymer humidity sensor based on polyethyleneimine

In the paper the amperometric properties of polymer humidity sensor based on polythyleneimine are presented. Usually properties of this sensor are examined by means of impedance spectroscopy. The new approach is proposed. It is shown that the current flow in the investigated sensor is a result of the electrode reaction at the anode. The quasi-static diffusion current is a linear function (in the log-lin scale) of relative humidity, so this sensor can be used as an amperometric. An equivalent circuit, containing the elements representing diffusion effect, has been proposed. The shape of impedance plots show diffusion related process.

Electrocatalytic nitrogen dioxide sensor

Construction and properties of electrocatalytic gas sensor based on samarium-doped ceria solid electrolyte are described. Electrocatalytic sensors form a new group of gas sensor, which employ kinetics of controlled chemical reaction. Measurements in mixtures of synthetic air and nitrogen dioxide are shown. Current-voltage response has unique shape, which depends on NO2 concentration. Influence of voltage sweep rate and temperature on sensor characteristics is reported. The constructed sensor can be used for nitrogen dioxide monitoring.

Low cost electrochemical sensor module for measurement of gas concentration

This paper describes a low cost electrochemical sensor module for gas concentration measurement. A module is universal and can be used for many types of electrochemical gas sensors. Device is based on AVR ATmega8 microcontroller. As signal processing circuit a specialized integrated circuit LMP91000 is used. The proposed equipment will be used as a component of electronic nose system employed for classifying and distinguishing different levels of air contamination.

Gas sampling system for matrix of semiconductor gas sensors

Semiconductor gas sensors are popular commercial sensors applied in numerous gas detection systems. They are reliable, small, rugged and inexpensive. However, there are a few problem limiting the wider use of such sensors. Semiconductor gas sensor usually exhibits a low selectivity, low repeatability, drift of response, strong temperature and moisture influence on sensor properties. Sample flow rate is one of the parameters that influence sensors response what should be considered in the measurement system. This paper describes low cost module for controlling measured gas flow rate. The proposed equipment will be used as a component of electronic nose system employed for classifying and distinguishing different levels of contamination in air.

Investigations of a new humidity sensor with polymer film

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.