Development of high sensitive gas sensors by using hetero junction of noble metal nanostructures and tin oxide microstructures

本研究旨在利用贵金属纳米结构和氧化锡微结构的异质结来开发高灵敏度的半导体气敏元件。由混合表面活性剂体系合成的贵金属纳米结构和氧化锡微结构，由于其独特的结构和物理化学性质，成为开发高灵敏半导体气敏传感器的有力候选者。本研究的主要目的是构建贵金属纳米结构/tm-cMde-narmparticles/氧化锡微粒的分级结构。对于氧化锡纳米颗粒的合成，发现含有纳米尺寸的氧化锡颗粒的氧化锡溶胶通过水热处理由氯化锡通过使用碳酸氢铵水解得到的氧化锡凝胶来合成。而在氧化锡微粒的合成中，平均粒径为1-2 μ m的球形SnO_2微粒 关于我们 以SnCl_4和混合表面活性剂为前驱体，经水热处理和500℃煅烧，成功地合成了三聚体。此外，还发现SnCl_2代替SnCl_2可以得到高收率的球形SnO_2微粒。为了得到高收率的球形SnO_2微粒，需要优化合成工艺，特别是水热温度和处理时间。这种球形SnO_2微粒的形成机理可能是基于氯化锡在混合表面活性剂组成的粘性介质中的水解过程以及前驱体的煅烧过程。类似的球形微粒可以在没有表面活性剂的情况下合成，但是它们的表面与在表面活性剂存在下合成的那些相比是相当粗糙的。使用这些球形微粒制备的半导体气敏元件对氢气表现出高灵敏度，其灵敏度比市售氧化锡高4倍。

In this study, it was aimed at developing highly sensitive semiconductor gas sensors by using hetero junction of noble metal nanostructures and tin oxide microstructures. Noble metal nanostructures and tin oxide microstructures which were reported to be synthesized from mixed surfactant system are strong candidates for developing highly sensitive semiconductor gas sensors because of their unique structures and physicochemical properties. The main purpose of this study is construction of hierarchical structures of noble-metal-nanostructures/tm-cMde-narmparticles/tinoxide-micropartices. As for the synthesis of tin oxide nanoparticles, it was found that the tin oxide sols containing nanosized tin oxide particles were synthesized by the hydrothermal treatment of tin oxide gels derived from hydrolysis of tin chloride by using ammonium hydrogen carbonate. On the other hand, as for the synthesis of tin oxide microparticles, the spherical microparticles of SnO_2 in average diameter of 1-2 urn … More were synthesized successfully by hydrothermal treatment of their precursor consisting of SnCl_4 and mixed surfactants, followed by calcinations at 500℃. Furthermore, it was found that the SnCl_2 gives highly yield for the synthesis of spherical SnO_2 microparticles instead of SnCk It was also found that synthesis processes should be optimized especially for hydrothermal temperatures and treatment time in order to obtain high yield spherical SnO_2 microparticles. The mechanism of the formation of such spherical SnO_2 microparticles can be based on the hydrolysis process of tin chloride in viscous media consisting mixed surfactants as well as calcination process of the precursor. Similar spherical microparticles can be synthesized in the absence of surfactants, but their surface is fairly rough in contrast to those synthesized in the presence of surfactants. The semiconductor gas sensors prepared by using these spherical microparticles showed highly sensitivity to hydrogen gas and their sensitivity was 4 time higher than that of commercially available tin oxides Less