Synthesis Of Polypyrrole Nanowire Arrays Based On Anodic Aluminum Oxide (aao) Templates And Studies Of Their Gas Sensing Properties

The fabrication of ordered array nano structures is important for obtaining scaled-up functional devices such as sensors devices. Anodic aluminum oxide (AAO) templates have high ordered nanochannel array structures, easy preparation technology and industrial production. It is one of the promising strategies to use AAO templates to prepare ordered array nano structures.In this paper, polypyrrole (PPy) nanowire arrays were synthesized in AAO templates by elecctrochemical method. The PPy nanowire arrays sensor was fabricated by semiconductor technology and was used to detecte ammonia. In addition, this paper had a study on the vapor of volatile organic compounds (VOCs), such as acetone, m-xylene, by PPy nanowires arrays. A preliminary research on detecting the o-dichlorobenzene in n-hexane by arrays was also studiedIn the first chapter, we introduced the development of the conducting polymers, their conductive mechanism and their applications. We presented the discovery of the material of PPy, its synthesis methods and its applications, sensors for example. Moreover, we generalized the harm of volatile organic compounds and detecting ways.Chapter 2 mainly studied the preparation of AAO templates. The highly ordered AAO templates with hexagonal pore structures were fabricated by two-step anodization under constant temperature. Meanwhile, we studied the fabrication of highly ordered PPy nanowire arrays in AAO template by electrochemical method under constant potential in different solvent. One sides of AAO was deposited a thin layer of Au and it was used to working electrode. The morphology and structure of PPy nanowire synthesized in distilled water were analyzed by a field emmission scanning electron microscope (SEM), FT-IR spectrum, and X-ray Photoelectron Spectroscopy. The crystallinity was examined by X-ray Diffraction.In chapter 3, the gas sensor based on vertically aligned polypyrrole nanowire arrays was fabricated and investigated. The fastness of the device was improved by deposited Au. In ambient atmosphere, we have investigated the response of the sensor to low concentrations of ammonia. Ammonia exhibited some electron rich and PPy doped with ClO4ˉwhich carries many electron holes. When ammonia was absorbed on the nanowires, it can donate electrons to the initially oxidized PPy and change the resistance of PPy. Our results indicated that PPy nanowire arrays had high sensitivity, relatively short response time and recovery time for ammonia. The reciprocal of response degree has a linear relationship with the reciprocal of gas concentration (1.5 ppm-77 ppm). The possible mechanism of the response was also discussed.In chapter 4, we had a preliminary study on the detection of volatile organic compounds based on the arrays structure of PPy nanowire such as acetone, m-xylene. According to the change of capacitance signal, we detect the o-dichlorobenzene in n-hexane by PPy nanowires arrays preliminary.At the end of this paper, a short conclusion for the work and the goal of future research were made.