| Summary: | 博士 === 國立交通大學 === 材料科學與工程系所 === 97 === Recently, environmental protection has gained attention as a result of industrial development and an increase in the emission of various kinds of exhaust gases. Noxious gases such as CO, CO2, SO2, and NO2 are presented in the atmosphere. They are highly toxic for the human body and also cause indirect harm to the environment. Traditional gas sensors that have been used thus far are expensive, heavy, and prone to delay; in order to overcome these problems, many studies have focused on developing gas sensors. In this study, three novel nanoporous gas sensors were synthesized by using the template replication method. P-type semiconducting sensors for example mesostructured carbon and mesostructured cobalt oxide were synthesized using a porous SiO2 template. Further, an n-type semiconducting porous ZnO sensor was synthesized using porous carbon as a template. The prepared mesostructured materials were highly ordered porous atructure with uniform particle sizes. Powder x-ray diffraction (XRD) spectra of the different mesostructured materials confirm the phase of these materials. The crystal structure and microstructure of the mesostructured materials were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The surface areas and pore-size distributions of the mesostructured materials were analyzed by N2 adsorption-desorption isotherms. Structural and morphological studies were carried out in order to investigate the influence of these materials on the sensing properties of sensors synthesized using mesostructured materials. All of the sensing materials have good sensitivity for low CO concentrations (10–100 ppm). Among the porous sensing materials, porous ZnO had a sensitivity of 51.7%. The sensing-mechanism of these novel gas sensors was reviewed. In order to reduce the power consumption in sensors, in this study, we have designed and developed a system for measuring energy consumption on the microscopic scale. Sensors were fabricated on silicon substrates using micro electromechanical systems (MEMS) technologies and compatible with integrated circuit (IC) process. The layers in the device include a micro-heater, an isolator, electrodes, and a sensing film. The sensing materials were aligned and immobilized between electrodes by using the dielectrophoresis process, which is known to be a convenient method for the manipulation of dielectric substances in a liquid. Experimental results showed that the regular aligned structure of these mesostructured materials provide number of active areas on the sensor; porous ZnO had a sensitivity of 60.0% and had a fast response time of 90 s. These mesostructured gas sensors have been developed in this study with high sensitivity, good response properties and good repeatability. Moreover, the preparation process of the mesostructured sensor was a simple method.
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