exploiting the enhancement of quadrupole surface plasmon resonance to develop highly efficient eco-friendly devices
Date Issued
2014
Date
2014
Author(s)
Shao, Chang-Ching
Abstract
Metallic nanoparticles (NPs) have been widely applied on eco-friendly, optoelectronic energy devices due to the unique localized surface plasmon resonance (LSPR) phenomenon. In previous studies, many efforts had been devoted in the dipole LSPR while the quadrupole LSPR did not reveal wide applications. In this thesis, highly efficient eco-friendly devices are developed by exploiting the quadrupole LSPR of Ag NPs, which provides a strategy for rapid and convenient photocatalytic degradation of environmental pollutants. This thesis focuses on the fabrication of Ag nanostructures in subwavelength scale by colloidal lithograhy with thin-film deposition and laser-induced photothermal effect. The quadrupole surface plasmon resonance phenomenon of Ag nanostructures in ultravilolet (UV) regime is discussed in detail, and the unique property of quadrupole LSPR phenomenon can be used to enhance the photocatalysis performance of TiO2. In the first part of this thesis, core-shell structures were fabricatred through Ag film coated on polystyrene. This structure could be used to enhance the photocatalysis performance of commercial TiO2 powders (P25), and the effective thickness of the coating powders is merely 8 nm. The core-shell nanostructure posssesses three mechanisms for enhancement: electron-transfer between metal-TiO2 interface, the electric field enhancement within near field and the increase of the optical path length by surface scattering of Ag nanostructures. And the rate of photocatalysis reaction was increased up to 3.8 times. The rate of structures with Ag core-shell structure would be even 52% faster than the one only with SiO2 core-shell structure. Moreover, compared to the dipole LSPR cases, the quadrupole LSPR does not perform an obvious wavelength-shift with surrounding refractive index change, and therefore it is more suitable for UV-regime applications as well as for other materials with wide bandgap.
In the second part of this thesis, one-step, rapid annealing method based on laser-induced photothermal effect was used to fabricate large-scaled Ag NPs and anatase-phase crystalized TiO2 composite structure simultaneously. Besides, Raman spectroscopy and scanning electron microscope (SEM) were used to analyze the morphology of the composite structure, crystalline of TiO2, and the size of Ag NPs. The optimized composite structure was demonstrated to improve the photocatalysis performance based on a series of experiments. Overall, two kinds of Ag-TiO2 composite structures are demonstrated in this thesis. These composite structures demonstrate a superior photocatalysis performance even with small amount of TiO2, and they can be fabricated on flexible substrates as well. Therefore, these composite structures are highly potential on the high-efficiency, eco-friendly optoelectronic devices in the future.
Subjects
四極表面電漿共振
侷域性表面電漿現象
銀奈米粒子
奈米球微影術
紫外光光催化
雷射快速熱退火
銳鈦礦二氧化鈦
Type
thesis
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