氧化鋅奈米柱、奈米錐陣列及奈米複合材料之合成與特性研究

Abstract

近幾年來由於奈米材料具有包羅萬象的新穎物理及化學性質不斷的被發現，這些現象驅使著科學家對於合成具低維度結構的奈米材料，例如零維度的奈米粒子及一維度的奈米線感到相當濃厚的興趣。本論文研究主要致力於具低維度的氧化鋅奈米材料包含奈米柱、奈米錐陣列以及奈米複合材料合成和性質探討

本論文研究第一部分是探討在基板上直接成長出一維單晶氧化鋅奈米柱。利用一種新穎的兩步驟合成方法，我們已經可以在極為低溫90 oC的水溶液中長出高密度且平均直徑約45奈米的氧化鋅奈米柱。值得注意的是之所以在低溫下可以製備出氧化鋅奈米柱是因為藉由氧化鋅奈米結構基板的幫助，這裡所扮演作用如同是自身種子作用以利於控制氧化鋅奈米柱的成核種子及直徑大小。

本論文研究第二部分是利用一種溫和化學製程方法成長具高順向性排列及獨立式的氧化鋅奈米錐陣列。除此之外我們利用此種方法合成出一些極為新穎的氧化鋅奈米結構材料，例如”奈米錐/柱”陣列，奈米刷子，奈米筆及”奈米柱/板”陣列。利用x光繞射分析發現氧化鋅奈米錐是屬於六方柱wurtzite結構並且其成長軸方向完美順著基材方向成長。從高解析度穿透式電子顯微鏡中可知奈米錐是單晶構造。在室溫下量測奈米錐可發現在波長 378 nm左右有著高強度的紫外光發光。我們也針對氧化鋅奈米錐陣列作場發射性質的探討，從研究結果發現在電流密度約為0.1 □A/cm-1時，起始電場強度約為10.8 V/□m，並且當施加電場強度為19.5 V/□m 時電流密度可達1 mA/cm2。

本論文研究第三部分是我們利用一種奈米粒子表面改質方法以獲得高透明度及安定發光的氧化鋅/聚乙基醇丙烯酸甲酯奈米複合材料。利用一種簡單且溫和的溶膠-凝膠反應中加入3-(Trimethoxysilyl)propyl methacrylate (TPM)安定劑以製備TPM-modified的氧化鋅奈米粒子。當奈米粒子表面覆蓋安定劑時可明顯提升奈米粒子的安定性並且改善奈米粒子和有機基材之間的互溶性。從實驗結果可知利用安定劑改質的奈米粒所製備出的複合材料具較佳的分散性及較佳可操縱性光的學性質。我們亦利用紫外□可見光吸收光譜，粉末式x光繞射，穿透式電子顯微鏡及氫核磁共振光譜來對改質及非改質的氧化鋅奈米粒子作性質分析

Growing low-dimensional nanostructured materials, such as zero-dimensional nanoparticles, and one-dimensional nanorowires (nanorods), have attracted great interested due to their novel physical and chemical properties. This dissertation work concerns the synthesis and characteristics of low-dimensional ZnO nanostructures containing nanorods, well-aligned nanotips arrays, nanoparticles/Poly(hydroxyethyl methacrylate) nanohybrid Film.

In the first part of the dissertation, we discuss the synthesis of one-dimensional single crystal ZnO nanorods directly grown on the substrates. Employing a novel two steps procedure, the high density of ZnO nanorods with a diameter about 45 nm can be successfully grown on the substrate in aqueous solution at attractive low temperature in 90 oC. Notably, low-temperature growth of ZnO nanorods can be achieved via the help of ZnO nanostructured (ZnO nanoparticles/ITO) substrate, as self-seeding purpose, which can be used to be effectively control of the diameter and nuclei sites of ZnO nanorods.

In the second part of the dissertation, we have proposed highly aligned and free-standing ZnO nanotip arrays grown on the ZnO films by soft chemical method. In addition, the soft growing method also has been extended to synthesize a novel of fascinating ZnO nanostructures, such as nanotips/rod arrays, nanopaintbrushs, nanopencils, nanorods/nanoplate arrays. X-ray diffraction analysis shows that the ZnO nanotips are hexagonal wurtzite structure, and the c-axes of nanotips are perfectly along the substrate surface normal. HRTEM demonstrates the ZnO nanotip to be a single crystal. Room temperature photoluminescence of the ZnO nanotips has a strong UV emission band at 378 nm. The field emission of ZnO nanotip arrays shows a turn-on field of about 10.8 V/□m at a current density of 0.1 □A/cm-1 and emission current density up to about 1 mA/cm2 at a bias field of 19.5 V/□m.

In the last part of the dissertation, high transparent and stable luminescent ZnO/Poly(hydroxyethyl methacrylate) nanocomposites have been synthesized via a nanoparticle surface modified method. 3-(Trimethoxysilyl)propyl methacrylate (TPM) was used as the stabilizing agent in the simple, mild sol-gel route to prepare the TPM-modified ZnO nanoparticles. The existence of TPM agent on the nanoparticle surface effectively promotes the stability of colloidal ZnO nanoparticles and the compatibility between inorganic nanoparticles and organic matrix in solid nanohybrid. The resulting ZnO/PHEMA nanocomposites with TPM-modified nanoparticles have a better dispersibility and controllable luminescent properties. The characteristics of TPM-modified and unmodified ZnO nanoparticles have been studied by ultraviolet-visible (UV-vis) absorption spectroscopy, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and 1H NMR spectroscopy.