利用模板法製備氧化物奈米材料及其光性質之研究

Nanostructures of Al2O3 and TiO2 Prepared by Template Method and Their Optical Properties

王致傑(Chih-Chieh Wang)

指導教授 ： 彭宗平

國立清華大學/工學院/材料科學工程學系/博士(2008年)

https://doi.org/10.6843/NTHU.2008.00139

摘要

摘要
本論文主要是利用模板法來製備氧化鋁及二氧化鈦奈米材料。根據模板的種類，論文分為兩部分，第一部分是利用熱蒸鍍方式製備八羥奎林鎵鹽(Gaq3)的有機奈米線，將其當作模版，利用原子層鍍膜技術(Atomic Layer Deposition (ALD))將氧化鋁鍍於其上，之後利用甲苯或低溫加熱移除內層Gaq3，即可得到氧化鋁奈米管，此方法快速簡單，在文獻上係第一次被提出，並且所得的奈米管品質良好，具有高深寬比，表面均勻，且管徑能準確控制，為往後製備不同種類氧化物奈米管提供了更好的選擇。在奈米管成長的過程中，牽涉到有機奈米線本身氫氧官能基與氧化鋁起始物的反應，導致氧化鋁生成。再者，將表面鍍有氧化鋁的Gaq3奈米線，量測其PL，並於氧氣、水氣、空氣及氬氣下做穩定性測試，發現形成此種核殼結構的奈米線，其PL發光波長並沒有改變，推測氧化鋁的生成只是於奈米線表面產生化學反應，沒有牽涉到有機奈米線內部晶格的變化。而穩定性測試則顯示出氧化鋁的厚度越厚，所得到的穩定性越佳但發光的強度會降低。在不同氣氛測試之下在氬氣之下穩定性最佳，而水氣於分解過程中，只是扮演催化劑角色，氧氣則是提供分解有機奈米線最主要助劑。
第二部分則是利用聚苯乙烯奈米球陣列當作模板，製備出不同二氧化鈦奈米結構並探討其光催化性質。首先，四氯化鈦分別在異丙醇、乙醇、水中稀釋，由於此三種溶劑與奈米球表面張力的不同，可製備出不同種類奈米蜂巢。其中異丙醇與聚苯乙烯奈米球的作用力最佳，可以得到結構良好的奈米蜂巢狀結構。三者吸收光譜除了能帶的吸收之外，還有一缺陷所造成可見光吸收，量測其光催化效應，會較同濃度所製備出的薄膜佳。若將起始物取代為二氧化鈦奈米粒子，將粒子濃度有效控制，於高溫空氣中則可製備出二氧化鈦奈米線，其成長機制不同於一般V-L-S，為一應力析出過程。首先二氧化鈦奈米粒子會與矽基板反應生成鈦矽化物，之後鈦矽化物經由氧化而從二氧化矽中析出二氧化鈦奈米線。由於此種材料電子電洞再結合機率下降且能帶變寬，光催化活性會較奈米球有效提升。

關鍵字

二氧化鈦 ； 氧化鋁 ； 奈米材料 ； 原子層鍍膜技術 ； 奈米線 ； 奈米管

並列摘要

Abstract
In this study, alumina and titania nanostructures were prepared by template methods, where Tris-(8-hydroxyquinoline) gallium (Gaq3) organic nanowires and polystyrene (PS) nanosphere monolayer, respectively were used as the templates. The dissertation is divided into two parts. The growth mechanism, photoluminescence (PL) and photocatalysis of the nanostructures are discussed.
In the first part, Gaq3 nanowires prepared by thermal evaporation were used as the templates. Atomic layer deposition (ALD) was employed to coat Al2O3 on the Gaq3 nanowires. Toluene and low temperature heating were then used to remove Gaq3 nanowires, and therefore alumina nanotubes were formed. The wall and thickness of the nanotubes were very uniform and could be well controlled. The growth of Al2O3 by ALD on the nanowires involved reaction of hydroxyl group on the nanowires with the precursor of alumina. In addition, PL spectra and their stability of Gaq3-Al2O3 core-shell nanowires in different gases were examined. No difference of PL spectra of Gaq3 and Gaq3-Al2O3 core-shell nanowires could be observed. The core-shell nanowires showed the highest degradation rate in oxygen among all gases. On the other hand, water acted only as a catalyst to provide oxygen and argon was protective.
In the second part, TiO2 nanohoneycomb and nanowires were prepared by means of PS nanosphere monolayer. The nanohoneycombs were fabricated by titanium tetrachloride in different solvents, i.e., t-butanol, ethanol, and water. Because of higher affinity between t-butanol and polystyrene nanospheres, the nanohoneycomb prepared by t-butanol shows the better morphology. Besides the absorption due to the band gap of TiO2, the absorption in visible light was also obtained due to the defects of nanohoneycomb. Nanohoneycomb has better photocatalytic activity than that of thin film because of its higher surface area. Subsequently, as the precursor, titanium tetrachloride was replaced by TiO2 nanoparticles. In this case, TiO2 nanowires were formed. Different from V-L-S (vapor-liquid-solid) mechanism, the growth of the nanowires involved a precipitation process. In the beginning of the process, TiO2 nanoparticles reacted with silicon substrate to form titanium silicide. Titanium silicide was then oxidized to form TiO2 and SiO2. TiO2 nanowires were precipitated from the silica matrix to reduce the energy. Finally, the photocatalysis of the nanowires was also examined. They had higher activity for decomposition of rhodamine B than nanoparticles. It may be due to recombination of electrons and holes and the band gap widening.

並列關鍵字

TiO2 ； Al2O3 ； nanostructure ； ALD ； nanowire ； nanotube

參考文獻

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