Detection of CO Concentration by Using SnO2 SPR Apparatus and Common-Path Heterodyne Interferometer
A conception by using integration of chemical microsensors and surface plasmon resonance (SPR) is proposed to sense carbon monoxide (CO). The research is based on the common-path heterodyne interferometer which contains nondestructive, high-sensitivity, a
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Abstract A conception by using integration of chemical microsensors and surface plasmon resonance (SPR) is proposed to sense carbon monoxide (CO). The research is based on the common-path heterodyne interferometer which contains nondestructive, high-sensitivity, and high accuracy optical sensing system and combines the tin dioxide which is chemical stability to sense CO as analyte of SPR. Under this configuration, the method can measure tiny phase differences for SnO2 with different CO concentration. The minimum resolution of gas concentration is verified with a best value of 0.0207 ppm occurring in pH 9. Keywords SPR • SnO2 • Carbon monoxide
1 Introduction Carbon monoxide (CO) gas sensing is an important technique applied to detect CO concentrations in domestic and industrial environments and especially in the underground rapid transit system. Several methods had been proposed for the purpose. Recently, an attractive approach has been proposed by integrating surface plasmon resonance (SPR) apparatus and chemical sensing film. The applied sensing materials can significantly determine the sensitivity and selectivity of detected combustible, toxic, and pollutant gases. Metal oxide compounds, such as SnO2 and SnO2-TiO2, have been utilized as sensing materials for detection of carbon monoxide [1]. The tin dioxide (SnO2) has become a primary choice due to its high sensitivity, good stability,
K.-M. Chen (*) • C.-H. Shen Department of Mechatronics Engineering, National Changhua University of Education, Changhua 50007, Taiwan e-mail: [email protected] J.-H. Chen Department of Photonics, Feng Chia University, Taichung 40724, Taiwan J. Juang and Y.-C. Huang (eds.), Intelligent Technologies and Engineering Systems, Lecture Notes in Electrical Engineering 234, DOI 10.1007/978-1-4614-6747-2_97, # Springer Science+Business Media New York 2013
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Fig. 1 The schematic diagram of the experiment
and low cost. Over two decades, the phenomena of SPR have been widely applied for detection of biomedical and chemical reactions because of its high-sensitivity, labelfree, real-time response. In these applications, the refractive index variations of analyte coated on golden film are concerned. Several SPR techniques are implemented by measuring the intensity, wavelength, and phase of reflected detection light [2]. However, the environment vibrations and light source intensity stability can influence the measurement results. Accordingly, in this research, we propose a new method for carbon monoxide gas sensing by combing a common-path heterodyne interferometer [3] and SPR apparatus coated with a film of tin dioxide. In order to show the feasibility of the method, different pH values of prepared SnO2 were investigated to obtain an optimal condition. Relations between carbon monoxide concentration and the phase differences were obtained. The experimental results show that pH value of 9 gives a highest sensitivity and best measurement resolution in CO concentration (Fig. 1).
2 Principle of Sensing Mechan
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