Angle-independent structural colors from hollow silica nanospheres

다국어 초록 (Multilingual Abstract)

The colors present in the surroundings derive from the stimulation of cone cells in the human eye by electromagnetic radiation in the visible spectrum. And the color represented by light is generally represented by dyes, but there are structural colors represented by the interference of light from aligned structures in nature. In a perfectly aligned structure (photonic crystal structure), light is reflected by Bragg's law to give a color, but accordingly, different colors vary depending on the angle. On the other hand, an amorphous structure (photon glasses structure) is disorderly as a whole, but has a narrow region of aligned structures, and constructive interference between such narrow regions of aligned structures appears. Therefore, it has uniform scattering property in all directions and shows color independent of angle. In order to artificially prepare such a structure, multiple scattering of non-resonant wavelengths should be minimized. In addition, the form factor represented by the particles and the structure factor represented by the structure must be controlled. However, in general, when the red color is represented by the structure factor, it is difficult to all realize RGB colors because the color by the form factor is blue. For this reason, there is a part to be solved in order to all realize RGB color using the photon glass structure.
Hollow particles have a longer scattering cross section than regular particles, so the transport length is longer, resulting in less multi-scattering, resulting in a distinct color. And, the organic part can be easily doped with carbon, which serves to reduce multiple scattering. In addition, since the shell thickness can be easily adjusted, not only the refractive index can be adjusted, but also the distance between the particles can be easily adjusted when manufacturing the photon glass structure. Also, due to the advantages of excellent color and harmless to the human body it is possible to apply to color pigments. Finally, the light mass has the advantage that does not settling well compared to other particles even if left for a long time during the electric drive.
In this dissertation, to realize RGB, photonic glasses structures are prepared using hollow silica particles. And I describe them. In particular, the focus is on red color, which is difficult to implement in general. The first chapter introduces the basic description of photonic crystal structure and photon glass structure, how to make it, and the application field.
In the second chapter, I present the fabrication of a photon glass structure using two hollow silica particles with the same core size and different shell sizes. In particular, I describe a method of fabricating an inverse structure by refractive index matching a shell of a particle and a matrix and a method of implementing RGB color. And, I also describe a theoretical calculation method for the structure factor.
The third chapter describes how to introduce carbon into the shell part of the hollow silica particles, and the color implementation by the form factor of the particles suppressed by multi-scattering. I also demonstrate the potential of infrared reflective color pigments through the reflection of the infrared region of structural factors and the color implementation of particles in solvents and polymers.
The fourth chapter demonstrates to demonstrate the applicability of hollow silica particles to electrophoresis. Finally, I summarize for implementing RGB color using hollow silica particles and outline the challenges and outlook on photonic glasses for controlling light scattering using hollow particles.

목차 (Table of Contents)

• Chapter 1. Introduction 1
• 1.1 Introduction 1
• 1.2 Photonic crystal 10
• 1.2.1 1D photonic structures 15
• 1.2.2 2D photonic structures 18
• 1.2.3 3D photonic structures 22
• 1.3 Photonic glasses 26
• 1.3.1 Normal structures 31
• 1.3.2 Inverse structures 35
• 1.3.3 Application of photonic glasses 39
• 1.4 Contents of This Dissertation 42
• Chapter 2. Inverse Photonic glasses by Pacing Bi-disperse Hollow Mircospheres 43
• 2.1 Introduction 43
• 2.2 Experimental 48
• 2.2.1 Materials 48
• 2.2.2 Synthesis of PS particles 48
• 2.2.3 Preparation of hollow silica particles 49
• 2.2.4 Fabrication of inverse photonic glasses 49
• 2.2.5 Characterization 50
• 2.3 Results and Discussion 51
• 2.3.1 Synthesis of hollow silica particles 51
• 2.3.2 Disordered colloidal structures from binary hollow silica particles 57
• 2.3.3 Angle-independent colors from inverse photonic glasses 66
• 2.4 Summary 70
• Chapter 3. Solution-Processable Photonic Inks of Mie-Resonant Hollow Carbon-Silica Nanospheres 71
• 3.1 Introduction 71
• 3.2 Experimental 74
• 3.2.1 Materials 74
• 3.2.2 Preparation of hollow carbon-silica particles 74
• 3.2.3 Preparation of flat powder films of hollow carbon-silica particles 75
• 3.2.4 Fabrication of structurally colored composite film 75
• 3.2.5 Preparation of mixed solution of hollow carbon-silica nanospheres and PVDF-HFP 76
• 3.2.6 Preparation of PVDF color patterns 76
• 3.2.7 Characterization 76
• 3.2.8 Single-scattering calculations 77
• 3.3 Results and Discussion 79
• 3.3.1 Synthesis of hollow carbon-silica nanospheres 79
• 3.3.2 Structural colors from hollow carbon-silica nanospheres 86
• 3.3.3 Angle-independent colors in flexible composite film 101
• 3.3.4 Application of hollow carbon-silica particles 111
• 3.4 Summary 113
• Chapter 4. Electrical Manipulation of Reflective Colors in Photonic Glasses of Carbon Doped Hollow Silica Particles in Organic Media 114
• 4.1 Introduction 114
• 4.2 Experimental 117
• 4.2.1 Materials 117
• 4.2.2 Preparation of display test cell 117
• 4.2.3 Characterization 117
• 4.3 Results and Discussion 118
• 4.3.1 Preparation of Hollow carbon-silica particles 118
• 4.3.2 Electrical manipulation of hollow carbon-silica particles 123
• 4.4 Summary 128
• Chapter 5. Summary and Outlook 129
• References 134