M. Urbańczyk

Thin palladium film as a sensor of hydrogen gas dissolved in transformer oil

A sensor for the detection of hydrogen gas dissolved in the transformer oil is proposed. The absorption of hydrogen in thin palladium film causes changes in the electrical and optical properties of the film. The proposed structure can be simultaneously used as a resistance and optical sensor. The sensor has been tested for different hydrogen concentration and in different temperatures. The hydrogen concentration was varied from 200 to 1500 ppm (in the transformer oil) and the oil temperature was changed from 20 to 120 °C. The sensor exhibits good sensitivity for low hydrogen concentration and the long-term stability of parameters in the transformer oil up to 90 °C. The sensitivity and the reaction time of the sensor strongly depend on the operation temperature. It should be possible to use such a sensor structure for the continuous monitoring of electric power systems.

Examination of thin films of phthalocyanines in plasmon system for application in NO2 sensors

Surface plasmon resonance spectroscopy is an optical technique that is capable of monitoring chemical and physical processes. It is sensitive to small changes of dielectric properties near a metal surface, and has been used to characterize a number of different types of films. This work analyzes the possibility of using the surface plasmon resonance phenomena for gas detection. We present examinations of thin films of phthalocyanines in plasmon systems from the point of view of their application in NO 2 sensors.

Investigation of sensor properties of copper phthalocyanine with the use of surface acoustic waves

Abstract This paper deals with an investigation into the interaction of a thin copper phthalocyanine (CuPc) layer about 1.3 μm thick with organic compound vapours, such as acetone, benzene, chloroform, trichloroethylene and diethyl ether. For this purpose a surface acoustic wave (SAW) device has been utilized in a dual delay-line oscillator system. The changes of physical properties of the CuPc layer are recorded as a change in differential frequency Δf, i.e., in the difference between the two oscillator frequencies. The acoustic waveguides are fabricated on the y-cut of the LiNbO3 piezoelectric substrate. The operating frequency of the implemented transducers is about 38 MHz. For the investigated CuPc layer various sensitivities and various response and regeneration speeds have been observed, according to the concentration of the organic compound vapour used. The greatest sensitivity (≈0.1 Hz ppm−1) is obtained for trichloroethylene.

Acoustoelectric Effect in Hydrogen Surface Acoustic Wave Sensors with Phthalocyanine-Palladium Sensing Bi-layers

Hydrogen has a role as an important chemical commodity that will continue to increase with the developments of the hydrogen economy. With a lower explosive limit of 4.73% by volume fast and accurate sensors are needed. Our recent work has shown that bilayers of phthalocyanine-palladium structures can be optimized to construct effective SAW sensors for hydrogen. In a bilayer sensing film structure, we can use the much stronger acoustoelectric effect in the SAW sensor response as the main detection mechanism more effectively than with a single sensing layer. This effect can be many times greater than the mass effect which can be dominant in nonconductive polymer films and simple metal and dielectric films typically employed in SAW gas sensors. The “work point” of such a structure must be shifted to the high sensitivity region, where small variations in conductivity (under the influence of gas molecules) cause remarkable changes in the wave velocity (see Figure 1). Thus, to take full advantage of the high sensitivity offered by the SAW sensor, the conductivity of sensing film must be tailored to a particular range.

Surface acoustic wave hydrogen sensor with a multilayer structure: preliminary results

Preliminary results concerning a hydrogen sensor based on a multilayer structure in a Surface Acoustic Wave dual-delay line system are presented. The sensor material consists of two layers performed in two different vapor deposition processes. The first one is a 720 nm CuPc layer, the other one -- a 20 nm thin palladium film. This structure was formed in a one of the dual-delay line system on a LiNbO3 Y-cut Z-propagation substrate. In such a multilayer structure can detect hydrogen in a medium concentration range (from 0.25% to 3% in nitrogen), even at room temperature. The sensor has a very good sensitivity, stability and is entirely reversible. The response and recovery times are very short (approximately 200 s - 800 s), which is very important from the practical point of view.

The Application of Surface Acoustic Waves in Surface Semiconductor Investigations and Gas Sensors

© 2013 Urbanczyk and Pustelny, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Application of Surface Acoustic Waves in Surface Semiconductor Investigations and Gas Sensors

Optical hydrogen sensitivity of Pd-metal oxide composite films prepared on fiber optics

The paper presents an optical-fiber hydrogen sensor. The sensor utilises a layered Fabry-Perot interferometer and includes gasochromic metal oxides (V2O5, Nb2O5, CeO2). The structure contains at the end a multi-mode optical fiber as the sensing element. The sensor permits to detect and to measure the concentration of hydrogen in a gaseous medium. A comparison of the properties of selected gasochromic metal oxides in the interferometric sensor structures has been presented.

Detection of hydrogen by means of a thin-film interferometer Fabry-Perot applying a-WO3 layers

The paper presents a layered sensing structure that permits to detect and to measure the concentration of hydrogen in a gaseous medium. This metal-dielectric-metal structure is a layered Fabry-Perot interferometer. The resonant cavity is made of WO3. The choice of just this material was dictated by its chemochromatic properties, i.e. the change of the optical properties due to the absorption of atomic hydrogen. In result of the absorption of H+ and e- the purely dielectric layer becomes a lost layer, displaying attenuation. The catalysis of molecular hydrogen to atomic hydrogen occurs in the palladium layer, which is also one of the mirrors of the interferometer. The measurement of the hydrogen concentration consists in the scanning of the angular variation of the interference peak position due to the absorption of hydrogen. The change of the peak position results from the change of the optical parameters of the Pd and WO3 layers.

Sensor properties of copper phthalocyanine in layer structures of a surface acoustic wave (SAW) type

Among the new methods of gas detection are those based on the use of a Surface Acoustic Waves in a layer structures. In such structures a chemically active layer can be a macromolecular compound--for instance: Copper Phthalocyanine (CuPc). In this paper are shown the results of the interaction investigations of a selected gas group with a CuPc layer. A linear dependence has been observed between the concentration of NO2 molecules in the air and the output signal of the device.