Preparation of Nanoparticles and Their Applications of Photonic Crystals and Electromagnetic Interference Shielding Materials
Date Issued
2009
Date
2009
Author(s)
Huang, Chih-Kai
Abstract
In recent decades, the interests in nanomaterials and nanostructures have been growing rapidly as a result of their distinctive and fascinating properties as well as unique applications in diversified fields. Many researches have addressed on the design and controlled fabrication of nanostructured materials prepared from nanomaterials. In this dissertation, we focus on the preparation of nanomaterials (polymeric and silica microspheres as well as silver nanospheres and nanowires) and their corresponding applications to photonic crystals (PCs) nanostructures and electromagnetic interference (EMI) shielding materials.n the field of PCs nanostructures, we proposed a rapid and feasible method to fabricate two-dimensional (2-D) and three-dimensional (3-D) PCs structures using monodisperse polymeric microspheres as the templates. The approaches toward the creation of their corresponding inversed structures are also described. The inversed structures were prepared by subjecting an introduced silica source to a sol–gel process; programmed heating was then performed to remove the template without spoiling the inversed structures. Thus, 2-D and 3-D PCs and their corresponding highly-ordered inversed multilayer or monolayer structures were developed on the substrate. esides polymer microspheres, monodispersed silica microspheres could also be prepared and utilized to construct the PCs structures. In order to control the array of silica colloids, we also synthesized monodisperse SiO2 coated magnetic Fe3O4 (SiO2/Fe3O4) microspheres to fabricate magnetic PCs. The magnetic SiO2/Fe3O4 microspheres with a diameter of 700 nm were synthesized in the basic condition with ferric sulfate, ferrous sulfate, tartaric acid and tetraethyl orthosilicate (TEOS) in the reaction system. Monodisperse SiO2/Fe3O4 superparamagnetic microspheres have been successfully used to fabricate PCs under the existing magnetic field. The photonic bandgap of the 700nm SiO2/Fe3O4 magnetic PCs was observed at 1620nm.n addition, we also developed the following nanomaterials: silver-silica composites nanoparticles, silver nanoparticles (Ag NPs) and their applications of EMI shielding materials. The Ag NPs have been immobilized onto silica microspheres through the adsorption and subsequent reduction of Ag+ ions on the surfaces of the silica microspheres. The neat silica microspheres that acted as the core materials were prepared through sol–gel processing, then their surfaces were functionalized using 3-mercaptopropyl trimethoxysilane (MPTMS). The average particle size of the obtained Ag NPs on the silica microsphere was found to be controllable (ranging from 2.9 to 51.5nm) by adjusting the ratio of MPTMS/TEOS and the amount of AgNO3. The silver-silica composites microspheres exhibited an EMI shielding effectiveness (SE) of 32.5 dB at 761 MHz.o improve the EMI SE, we prepared a UV-curable silver nanowire paste comprising a UV-curable resin, photoinitiators, and Ag NPs (nanowires and nanospheres), which was obtained from the polyol process using silver nitrate as the Ag source, ethylene glycol as the solvent and reducing agent, and polyvinylpyrrolidone (PVP) as a polymeric stabilizer that guided the growth of the Ag nanowires. Various patterns of Ag NPs on glass substrates which was obtained using the UV-curable Ag pastes and lithography processes were examined for their use as EMI shielding materials. The electromagnetic wave SE of a pattern prepared using 28% Ag NPs reached 41.3 dB at 780.7 MHz. After sintering, its value increased to 73 dB at 413.8 MHz. The effects on the SE of varying the pattern shape and the content of Ag NPs are also discussed.
Subjects
Photonic crystals (PCs)
emulsion polymerization
sol-gel process
electromagnetic interference (EMI) shielding materials
polyol process
Type
thesis
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