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標題: | 利用四極表面電漿共振增益現象開發高效能環境友善元件 exploiting the enhancement of quadrupole surface plasmon resonance to develop highly efficient eco-friendly devices |
作者: | Chang-Ching Shao 邵長卿 |
指導教授: | 陳學禮(Hsuen-Li Chen) |
關鍵字: | 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, quadrupole surface plasmon resonance,localized surface plasmon resonance,silver nanoparticle,colloidal lithograhy,ultravilolet photocatalyst,laser-induced photothermal effect,anatase-phase titania, |
出版年 : | 2014 |
學位: | 碩士 |
摘要: | 金屬奈米粒子由於特殊的侷域性表面電漿共振現象(localized surface plasmon resonance, LSPR),被廣泛的應用在各類環境友善光電能源元件上。在過去的研究中都以研究金屬奈米粒子的偶極LSPR為主,反觀四極極矩LSPR的應用非常少見。本論文將利用銀奈米粒子的四極極矩LSPR現象發展高效率的環境友善元件,提供一個快速簡易光催化分解環境中污染物的途徑。論文中將利用簡易的奈米球微影術搭配鍍膜以及雷射誘發快速熱退火技術來製作次波長尺寸的銀奈米結構,並探討銀奈米結構在紫外光波段四極極矩LSPR的特有性質,利用四極極矩LSPR在波長320-360 nm電場增強的現象、二氧化鈦吸收波段以及太陽光譜紫外光頻譜三個波段重疊的性質,將其應用於增益二氧化鈦光催化反應。在本論文的第一部份將利用聚苯乙烯(polystyrene, PS)球核—銀球殼結構製作出次波長尺寸銀奈米粒子,其在波長330 nm有顯著的四極表面電漿共振現象。在使用等效厚度只有僅僅8 nm的二氧化鈦粉末(P25)進行紫外光下光催化,將有表面電子轉移、電場增益效果及結構表面散射增加光徑等機制的增益,可提升3.8倍的光催化效率;而與沒有銀的結構比較,具有四極極矩特性的銀奈米粒子結構有明顯52%的效率增益。並與其他文獻偶極矩LSPR現象增益光催化結果相比,四極極矩LSPR波段較不易隨環境折射率改變而紅移,因此非常適合用於紫外光波段範圍的應用,此技術同時也適合應用於其他寬能隙的光電材料。
在本論文的第二部分將雷射誘發光熱效應的快速熱退火技術,以一次性步驟(one-step)同時得到大尺寸銀奈米粒子和銳鈦礦anatase相的結晶二氧化鈦複合結構。在論文中使用拉曼散射光譜和掃描式電子顯微鏡來分析在不同雷射快速熱退火參數下此種複合結構的形貌、結晶性質及奈米粒子的粒徑,並得到一最佳化的結構。而在後續的光催化實驗中,亦證實了此種複合結構可以提升光催化反應的速度。本論文提出了兩種特殊的二氧化鈦及銀奈米粒子複合結構,即使是使用非常少量的二氧化鈦,光催化結果都有很明顯增益。此兩項技術皆可應用於可撓曲的基材上,且其光催化反應皆非常快速,因此非常有潛力作為環境友善且高效能的綠能複合光電元件。 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. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/58157 |
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顯示於系所單位: | 材料科學與工程學系 |
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