金觸媒修飾鋅摻雜二氧化錫奈米棒簇之合成及其低溫氣體感測應用

Abstract

本研究主要探討新穎鋅摻雜二氧化錫奈米結構之合成、金奈米粒子表面修飾、及其於一氧化碳氣體感測應用。藉由水熱法合成參數之調控，以及金奈米粒子修飾技術之選擇，成功合成高氣感靈敏度金奈米粒子觸媒表面修飾之鋅摻雜二氧化錫棒簇結構(Nanorod clusters)。 在鋅摻雜二氧化錫奈米棒簇結構設計與合成方面，調控鋅錫離子比例，除了可以從缺陷化學的角度來最佳化氣感靈敏度之外，亦能有效改變奈米棒簇之形貌與尺寸。透過電子顯微鏡觀察，此奈米棒簇結構具有大量且複雜之海膽狀階層式三維立體結構，比表面積極高，有利於氣體之擴散及吸脫附反應，奈米棒直徑約為20~30 nm，接近氣感材料之理想尺寸。為了強化奈米棒簇之氣體感測效能，利用單步驟及雙步驟合成法，成功獲得金奈米粒子修飾之鋅摻雜二氧化錫奈米棒簇結構。並發現合成材料回收方法(加熱乾燥或離心)，亦將造成金奈米粒子沉積數量及分散性之差異。 一氧化碳感測結果發現，離心法之金奈米粒子均勻分散在二氧化錫奈米棒簇結構上，感測效果在本研究中最為顯著，其靈敏度、響應速率最佳，且工作溫度相對較低。此優異特性主要可歸因於離心法在相對低溫下，可有效地將金奈米粒子良好散布於鋅摻雜二氧化錫奈米棒之上，使感測材料可以在較低工作溫度下，促進大量氣體分子解離。由以上成果可知金奈米粒子修飾之鋅摻雜二氧化錫奈米棒簇結構是一非常具有潛力之低溫型氣體感測材料。

In the thesis, we mainly described the synthesis of novel Zn-doped SnO2 nanostructures, the surface decoration with tiny Au nanoparticles (NPs), and the CO gas sensing applications. With precisely controlled hydrothermal processes and unique Au decoration techniques, a series of highly CO-sensitive catalytic Au NPs decorated Zn-doped SnO2 nanorod clusters were successfully synthesized. Regarding the structural design and syntheis, doping of Zn into the SnO2 lattices is evidenced as a workable strategy not only for optimizing the CO sensitivity from the view point of defect chemistry, but for effectively varying the morphology and size of the prepared SnO2 nanorod clusters. From the observation using electron microscopes, the formed Zn-doped SnO2 nanorod clusters possess excellent urchin-like hierarchical nanostructures with an extremely high surface to volume ratio, which providing a great amount of channels for gas diffusion and large area for gas absorption. In addition, the diameter of each single nanorod is very close to the expected ideal size of nanosensors. For further enhancing the sensing performance, Au NPs synthesized by a one-step or two-step method successfully decorate the Zn-doped SnO2 nanorod clusters. It was also foud that differnt sample collecting techniques (a boiling or centrifugal method) would lead significant difference in the amount and dispersion of the Au NPs. From the analyses of CO sensing performance, remarkable response and recovery features with a highest sensitivity was found at a relatively low working tempeature for the Au NPs decorated Zn-doped SnO2 nanorod clusters prepared by a two-step hydrothermal method and collected by centrifugation. The structural investigations clearly evidence that the well-despersed Au NPs play as a very critical role for providing a great amount of catalytic sites for targeting gas. The present results conclude that the Au NPs decorated Zn-doped SnO2 nanorod cluster is one of the most promising nanomaterials for fabricating advanced low-temperature gas sensors.