氧化鋅奈米結構於有機溶液相中的製備

Synthesis of Zinc Oxide nanostructures in organic solvent

何聖彥(Sheng-Yen He)

指導教授 ： 段興宇

國立清華大學/工學院/化學工程學系/碩士(2010年)

摘要

於本篇的研究，我們致力於使用新型的合成方法，在超臨界有機溶劑的環境下，合成出新穎的氧化鋅奈米材料結構。其子領域可以分為，(1)一維氧化鋅奈米材料的合成與形狀控制、(2)孔洞氧化鋅奈米線的合成、(3)利用塞流式反應器合成新穎的氧化鋅奈米材料。實驗部份我們選擇前驅物為醋酸鋅-油胺的錯合物，並於超臨界流體相態的己烷中進行反應。
有關一維氧化鋅奈米材料的合成與形狀控制。我們使用半批式反應器為基礎，並利用調整反應溫度、前驅物注入流速這兩種動力學的控制方法，成功的調整一維奈米氧化鋅結構的長寬比。其形狀從低溫高流速條件下為接近圓形的顆粒變成高溫低流速條件下為高長寬比的奈米線結構，並證明其生長方向為[0001]。本研究利用了動力學的方式說明了氧化鋅晶體的生長行為，並以最後反應完的氧化鋅產物XRD圖做為輔助的驗證與說明。我們使用HRTEM幫助了解氧化鋅的晶體結構。我們利用FTIR與H-NMR光譜儀器的鑑定，互相比較反應前與反應後之溶液的光譜圖，證明出醋酸鋅在超臨界有機溶劑環境中的化學反應機制，其結果與在低溫時的化學反應機制相同。最後我們討論不同長寬比氧化鋅產物的光學性質，於我們的研究，當產物的長寬比變大，氧化鋅於UV區的激發波長越往藍移。
有關孔洞氧化鋅奈米線的研究。我們使用半批式反應器作為基礎，前驅物先在超臨界己烷中反應分解，之後再降至室溫中靜置反應，合成出高品質、超高長寬比的孔洞氧化鋅奈米線。奈米線在電子顯微鏡下觀察發現其具有孔洞性，而每根的奈米線是由顆粒大小為數個奈米的氧化鋅顆粒所聚集而成。我們發現在室溫下將反應時間拉長，奈米線可以生長至超級長的長度，其長度可以超過80μm。並利用在室溫下不同的反應時間的SEM圖，討論奈米線成長初期的成長行為。並以EDS分析鋅、氧原子於奈米線的分布情形以及原子比例。
我們使用塞流式反應器當做基礎，合成出更多新穎型態的氧化鋅結構，並做了初步的SEM鑑定，發現塞流式反應器其合成方法的潛力。

關鍵字

氧化鋅

並列摘要

In this research, we proposed a novel method for the synthesis of zinc oxide (ZnO) nanostructures under supercritical organic solvent. This thesis is categorized into three topics: (1) synthesis and shape control of one-dimensional zinc oxide nanostructures. (2) synthesis of porous zinc oxide nanowires. (3) plug-flow synthesis of novel zinc oxide nanostructures. Zinc acetate-oleylamine (Zn(Ac)2–OLA) complex was chosen as the precursor, and the precursor was then thermal decomposed in the supercritical hexane upon injection.
(1) Synthesis and shape control of one-dimensional zinc oxide nanostructures. In a semi-batch reactor, the aspect ratio of zinc oxide nanostructures was successfully tuned by kinetically control of the reaction temperature and injection rate. The shape changed from sphere-like nanocrystals with low aspect ratio to high aspect ratio nanowires when the reaction conditions was changed from low reaction temperature with high injection rate to high reaction temperature with low injection rate. In this study, we used the kinetic approach to describe the growth behavior of zinc oxide nanocrystal. X-ray diffraction (XRD) characterization was applied for further identification of the zinc oxide nanostructure. High-resolution transmission electron microscope (HR-TEM) imaging was used for better understanding of the crystal structure of zinc oxide. The mechanism of the chemical reaction was indentified using Fourier-transform infrared (FTIR) and nuclear magnetic resonance (H-NMR) spectroscope by comparing the spectra of the residue solution before and after the reaction. Result showed that the mechanism is the same with the literature at low temperature reaction. Finally, we discussed the optical properties of zinc oxide products with different aspect ratio. Blue shift of the excitation wavelength peak in the UV region was observed correspond to the increase of aspect ratio.
(2) Synthesis of porous zinc oxide nanowires. The precursor, i.e. Zn(Ac)2 – OLA complex was first thermally decomposed under supercritical hexane. The reactor was then allowed to cool to room temperature and kept still for reaction. The high quality and ultra-long porous zinc oxide nanowires were obtained. From HR-TEM images, we realized that these nanowires were seemed to be formed by the assembly of nanosized-ZnO particles. We found that when the reaction time was lengthened, ultra-long nanowires were formed, with length exceeding 80μm. SEM images of the product under different reaction time were used to discuss the growth of the nanowire. Zinc and oxygen atoms distribution in a porous nanowire was characterized by energy dispersive spectroscopy (EDS).
(3) Plug-flow synthesis of novel zinc oxide nanostructures. Plug-flow reactor was used as a basis for synthesis of more novel types of zinc oxide nanostructures. SEM images showed that plug-flow reactor have synthesis potential.

並列關鍵字

Zinc oxide ； ZnO

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