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研究生：	莊耕硯 Chuang, Geng-Yen
論文名稱：	CdSe/ZnS 奈米顆粒在中孔洞矽空心球-液晶的光學與非線性光學特性 Optical and non-linear optical properties of CdSe/ZnS quantum dots and mesoporous silica hollow spheres dispersed in nematic liquid crystal
指導教授：	羅光耀 Lo, Kuang-Yao
學位類別：	碩士 Master
系所名稱：	理學院 - 物理學系 Department of Physics
論文出版年：	2021
畢業學年度：	109
語文別：	英文
論文頁數：	77
中文關鍵詞：	量子點、無序層、中孔洞氧化矽空心球、向列型液晶、非線性光學
外文關鍵詞：	Quantum dots, Disorder layer(DOL), Mesoporous silica hollow sphere(MPSHS), Nematic liquid crystal, Non-linear optics
相關次數：	點閱：252 下載：0
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量子點是一種奈米材料，其光學性質會根據其顆粒大小不同而有所改變，因此具有許多應用，像是顯示器等光學元件。而當有膠體粒子加入到向列型液晶時(Colloids in NLC)，液晶分子的排列方式會因為這些顆粒球表面的錨定力影響而形變，形變會使系統增加額外的自由能。為了降低自由能，這些顆粒會傾向聚集，量子點也不例外。但是，聚集情況在不同的液晶態(nematic和isotropic態)也會有所差異。在此研究中，我們使用一種新穎材料-中孔洞矽空心球(mesoporous silica hollow sphere, 簡稱MPSHS)，由於其特殊的表面孔洞結構，在加到向列型液晶後，這些MPSHS周圍的液晶分子的排列方式是亂而無序的，我們將之稱為無序層(Disorder Layer, 簡稱DOL)，而這DOL就如同isotropic態的液晶。
本論文主要藉由提高MPSHS的濃度，在樣品內製造許多DOL的區域，再加入量子點，我們發現因為DOL越多，量子點之間的距離增加，更能均勻分布，整體系統的光學性質也跟著有所改變。另外，我們也從Second Harmonic Generation(SHG)的實驗中發現這些DOL 的存在會影響系統非線性光學的實驗結果。

Whenever the colloidal particles are introduced into nematic liquid crystal (NLC), the self-assembly of these particles is inevitable. However, the isotropic phase of NLC can be a better solvent for quantum dots (QDs) than that in the nematic. In this study, we introduce a new material, mesoporous silica hollow sphere (MPSHS). The uniqueness is that the orientation of NLC molecules around its porous surface is disordered, resulting in the disorder layer (DOL) when it was dispersing in NLC. The DOL can be analogous to the isotropic phase of NLC. Therefore, we can control the optical properties of the QDs/NLC system and space out the interparticle distance between QDs by adding various concentrations of MPSHS into it. In addition, the results from the second harmonic generation (SHG) measurement of this hybrid system of QDs and MPSHS reveal that the DOL has a significant impact on the non-linear optical effect.

Abstract (Chinese) I
Abstract (English) II
Acknowledgement III
Contents VI
Figure List VII
Table List XI
Chapter 1 Introduction 1
Chapter 2 Liquid Crystals and Colloids 3
1 Basic Properties of Liquid Crystals 3
1.1 Introduction 3
2 Physical Properties of Nematic Liquid Crystals 4
2.1 Order Parameter 4
2.2 Optical Anisotropy 5
2.3 Dielectric Anisotropy 6
2.4 Elastic Continuum Theory and Free Energy Density 8
3 Colloidal Particles in Liquid Crystal 9
3.1 Surface Anchoring 9
3.2 Topological Defects 10
3.3 Behavior of Silica Solid Sphere dispersed in NLC 11
3.4 Orientational Distortion under POM 11
Chapter 3 Semiconductor Nanocrystals 14
1 Fundamental Aspects 14
1.1 Introduction 14
1.2 Quantum Confinement Effect 14
1.3 Photoluminescence (PL) 18
2 Core/Shell Semiconductor Nanocrystals 18
2.1 Introduction 18
2.2 Classification of Core/Shell Systems 19
3 QDs in Anisotropic Media 21
3.1 QDs in anisotropic media 21
3.2 Energy Transfer 21
3.3 Förster Resonance Energy Transfer 22
Chapter 4 Theoretical Model 25
1 MPSHSs in Nematic Liquid Crystal 25
1.1 Morphology of MPSHSs 25
1.2 Postulate for Behavior of MPSHSs dispersed in NLC 26
1.3 Liquid Crystal Droplets 27
1.4 Confirmation of Anchoring Strength inside MPSHSs 28
2 QDs dispersed in NLC with MPSHSs 30
2.1 QDs dispersed in NLC 30
2.2 Prediction for QDs dispersed in NLC with MPSHSs 31
2.3 Quantitative model of DOL created by MPSHSs in NLC 31
3 Non-linear Optical Properties of QDs dispersed in NLC with MPSHSs 34
3.1 SHG 34
3.2 Multiple Scattering in disordered Materials 35
Chapter 5 Experimental Details 38
1 Experimental Section 38
1.1 Materials 38
1.2 LC cell fabrication 38
2 Measurements 40
2.1 Optical Imaging and Photoluminescence Microscopy 40
2.2 PL Measurements 40
2.3 SHG Measurements 41
2.4 Transmittance Measurements 42
Chapter 6 Results and Discussion 43
1 In-Plane Switching 43
1.1 SSS in IPS mode cell  43
1.2 Anchoring Strength inside MPSHSs 46
2 QDs dispersed in NLC with micro-sized Particles 49
2.1 QDs dispersed in NLC 49
2.2 QDs dispersed in NLC with MPSHSs and SSS 56
3 Non-linear optical properties of QDs dispersed in NLC with colloids 67
3.1 SHG results of QDs/LC 67
3.2 SHG results of QDs/LC with micro-sized Particles 68
3.3 Random Lasing Action in QDs/colloid-nanocomposites system 70
Chapter 7 Conclusion and Future Works 72
Reference 73
                                    

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2026-08-24公開

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