Erwin Maciak

A Study of a QCM Sensor Based on TiO2 Nanostructures for the Detection of NO2 and Explosives Vapours in Air

The paper deals with investigations concerning the construction of sensors based on a quartz crystal microbalance (QCM) containing a TiO2 nanostructures sensor layer. A chemical method of synthesizing these nanostructures is presented. The prepared prototype of the QCM sensing system, as well as the results of tests for detecting low NO2 concentrations in an atmosphere of synthetic air have been described. The constructed NO2 sensors operate at room temperature, which is a great advantage, because resistance sensors based on wide gap semiconductors often require much higher operation temperatures, sometimes as high as 500 °C. The sensors constructed by the authors can be used, among other applications, in medical and chemical diagnostics, and also for the purpose of detecting explosive vapours. Reactions of the sensor to nitroglycerine vapours are presented as an example of its application. The influence of humidity on the operation of the sensor was studied.

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.

A low temperature operated NO2 gas POF sensor based on conducting graft polymer

The paper presents the way that colour can serve solving the problem of calibration points indexing in a camera geometrical calibration process. We propose a technique in which indexes of calibration points in a black-and-white chessboard are represented as sets of colour regions in the neighbourhood of calibration points. We provide some general rules for designing a colour calibration chessboard and provide a method of calibration image analysis. We show that this approach leads to obtaining better results than in the case of widely used methods employing information about already indexed points to compute indexes. We also report constraints concerning the technique. Nowadays we are witnessing an increasing need for camera geometrical calibration systems. They are vital for such applications as 3D modelling, 3D reconstruction, assembly control systems, etc. Wherever possible, calibration objects placed in the scene are used in a camera geometrical calibration process. This approach significantly increases accuracy of calibration results and makes the calibration data extraction process easier and universal. There are many geometrical camera calibration techniques for a known calibration scene [1]. A great number of them use as an input calibration points which are localised and indexed in the scene. In this paper we propose the technique of calibration points indexing which uses a colour chessboard. The presented technique was developed by solving problems we encountered during experiments with our earlier methods of camera calibration scene analysis [2]-[3]. In particular, the proposed technique increases the number of indexed points points in case of local lack of calibration points detection. At the beginning of the paper we present a way of designing a chessboard pattern. Then we describe a calibration point indexing method, and finally we show experimental results. A black-and-white chessboard is widely used in order to obtain sub-pixel accuracy of calibration points localisation [1]. Calibration points are defined as corners of chessboard squares. Assuming the availability of rough localisation of these points, the points can be indexed. Noting that differences in distances between neighbouring points in calibration scene images differ slightly, one of the local searching methods can be employed (e.g. [2]). Methods of this type search for a calibration point to be indexed, using a window of a certain size. The position of the window is determined by a vector representing the distance between two previously indexed points in the same row or column. However, experiments show that this approach has its disadvantages, as described below. * E-mail: A.Nowakowski@ire.pw.edu.pl Firstly, there is a danger of omitting some points during indexing in case of local lack of calibration points detection in a neighbourhood (e.g. caused by the presence of non-homogeneous light in the calibration scene). A particularly unfavourable situation is when the local lack of detection effects in the appearance of separated regions of detected calibration points. It is worth saying that such situations are likely to happen for calibration points situated near image borders. Such points are very important for the analysis of optical nonlinearities, and a lack of them can significantly influence the accuracy of distortion modelling. Secondly, such methods may give wrong results in the case of optical distortion with strong nonlinearities when getting information about the neighbouring index is not an easy task. Beside this, the methods are very sensitive to a single false localisation of a calibration point. Such a single false localisation can even result in false indexing of a big set of calibration points. To avoid the above-mentioned problems, we propose using a black-and-white chessboard which contains the coded index of a calibration point in the form of colour squares situated in the nearest neighbourhood of each point. The index of a certain calibration point is determined by colours of four nearest neighbouring squares (Fig.1). An order of squares in such foursome is important. Because the size of a colour square is determined only by the possibility of correct colour detection, the size of a colour square can be smaller than the size of a black or white square. The larger size of a black or white square is determined by the requirements of the exact localisation step which follows the indexing of calibration points [3]. In this step, edge information is extracted from a blackand-white chessboard. This edge information needs larger Artur Nowakowski, Wladyslaw Skarbek Institute of Radioelectronics, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warszawa, A.Nowakowski@ire.pw.edu.pl Received February 10, 2009; accepted March 27, 2009; published March 31, 2009 http://www.photonics.pl/PLP

Surface plasmon resonance study of comb copolymers containing regioregular poly-3-hexylothiophene

The surface plasmon resonance (SPR) is very sensitive, and so is the optical technique used in chemical sensing. The angle of incident of light at which a resonant effect is observed, as well as the dip of a resonant are very sensitive to variations of the optical parameters of the medium on a surface-active plasmon metal layer. In this work a novel combcopolimer of regioregular poly-3-hexylothiophene (rr-P3HT) and is studied as a gas (NO2) sensing material. Gas sensing properties of this material is examined using SPR technique at room temperature.

Determination of the optical parameters of thin palladium layers and their application in optical hydrogen sensors

The paper presents the results and way of measuring the dispersion of the complex refractive index of thin palladium layers in an atmosphere containing hydrogen with a concentration below the threshold of explosion (<4%). The measurements were carried out making use of exciting the surface plasmon wave.

Study of blended conductive graft copolymer with graphite oxide thin films deposited using spin coating method for gas sensing and photovoltaic applications

This work presents an investigation on conductive graft comb copolymer like SILPEG CH9 with carbon materials like graphite oxide or reduced graphite oxide. Morphology and optical properties like sample roughness, graphite oxide particles distribution, optical transmittance were measured of obtained thin films deposited on glass substrate using spin coating method. The study showed that obtained thin films are repeatable, convenient to process, and their parameters can be easy changed by the spin rate regulation during the deposition. Given results shows the possibility of using such polymer blend in the implementation of organic photovoltaic cells and different optoelectronics applications.

Study of the impact of UV radiation on NO2 sensing properties of graft comb copolymers of poly(3-hexylthiophene) at room temperature

In this paper graft copolymer of poly(3-hexylthiophene) and poly(ethylene) glycol on the polymethylsiloxane core are investigated as a receptor material for resistance gas sensor. Sensor response to 5 ppm of NO2 and its recovery after the interaction with NO2 are studied at different conditions: room temperature (RT), RT with ultraviolet (UV) radiation and at elevated temperature (50 °C). Results shows that sensor regeneration occurred faster at RT with UV than at 50 °C in dark conditions. The sensor response at RT is also higher than at 50 °C. The mixed operation conditions, namely dark conditions for adsorption and UV for desorption, provides high sensor response (3590% for 5 ppm of NO2) and relatively good regeneration (250% deviation from base-line after 30 min). Thanks to this investigated graft copolymers are promising receptor materials for chemical NO2 sensors operating at RT.

Numerical and experimental determinations of temporal characteristics of the SAW sensor with a chemi-sensitive layer of WO3+Pd

The paper presents the results of numerical analyses of the surface acoustic wave (SAW) gas sensor based on WO3 layer with a catalytic nanolayer of Pd. The changes of SAW velocity vs. the surface electrical conductivity of the sensing layer is a essence of sensors of this kind. The conductivity of the porous sensoric layer which is deposited on a piezoelectric waveguide depends on the profile of concentration of gaseous molecules diffused inside the sensing layer. The Knudsen’s model of gas diffusion was used. Results of numerical analysis of the effect of the gaseous CH4 in air environment in the WO3 sensoric layer have been shown. The results of numerical analysis allow to select conditions of the SAW sensor, including the morphology of the sensor layer, its thickness and operating temperature. Some numerical results were verified by means of experimental studies.

Optical fiber coated with Nafion thin film for humidity sensing

It has developed a simple fiber optic sensor that is used to detection and measure concentration of water vapour in the air. The operating principle of the sensor is discussed in this work, and it was noticed that the wavelength positions of the reflectance peaks change with the concentration of H2O molecules. The sensor has been successfully used to monitor relative humidity of the air. The sensor utilizes a layered Fabry-Perot interferometric sensing structure. This structure was fabricated on the end of standard multi-mode fiber optic and includes Nafion® sensing film. The fiber optic hygrometer was tested for measurement of relative humidity in the range of 10-80% in air. SHT75 sensor (Sensirion Corp.) was used as reference sensor for control humidity level and temperature of gas mixture.

Combcopolimers of Regioregular Poly 3 Hexylothiophene Applied in Surface Plasmon Resonance Based NO 2 Sensor

In this work a novel combcopolimer of regioregular Poly 3-hexylothiophene (rr-P3HT) is applied as a gas (NO2) sensing material. Gas sensing properties of this material is examined using surface plasmon resonance technique at room temperature.