金屬奈米粒子陣列在表面增強拉曼散射與光電生化感測器上之應用

Abstract

表面增強拉曼散射技術因為能有效偵測低濃度的分子，因此許多研究都致力於研究不同的金屬奈米結構，希望能再大幅提升其偵測的靈敏度，甚至達到單分子的偵測能力。但製作特殊結構通常費時又耗成本，且測量的再現性低。在本篇論文第一部分中，我們透過三維時域有限差分(three dimensional finite-difference time-domain, 3D FDTD)模擬討論在不同覆蓋面積以及不同直徑的金奈米粒子局部電場以及預期的表面拉曼增強效果並透過實驗加以印證，比較熱點個數及熱點強度對拉曼訊號的影響。在本篇論文第二部分，我們將利用晶種成長法(seed-mediated growth)製作金屬奈米棒狀粒子，並使用高分子先將金的奈米球接在矽基板上，再利用具有適當官能基的高分子，兩端各抓住金奈米棒及金奈米球，使得在金奈米球上方再形成金奈米棒層。利用橢圓儀量測的方法，觀察金奈米球與金奈米棒之間是否有出現耦合的現象，並同時利用建構光學多層膜模型來進行分析，考慮各層的光學常數及厚度，依照正確的順序建立，再藉由多次最小方差法最佳化，調整未知的光學常數或厚度參數，將此金屬奈米粒子層的光學常數求出。並進一步利用金奈米棒的高靈敏度，製作生物分子感測器，並透過橢圓儀對薄膜量測的高敏感度，希望得到偵測低濃度生物分子的光電生化感測器。

Surface-enhanced Raman scattering technique can detect molecules of low concentrations, so many groups are dedicated to study different metallic nanostructures and hope to improve the sensitivity even to single-molecule level. However, it is time-consuming and high-cost to manufacture the special structure and the detection usually performs poor repeatability. In the first part of this thesis, we use the FDTD method to simulate the localized electronic field and expected surface enhanced Raman scattering effect of gold nanospheres under different area coverage and diameters. Besides, we use design experiment to prove the results from related simulations, which compares the effect of hot spots’ numbers and intensity on the SERS signal. In the second part of this thesis, we use seed-mediated growth method to synthesize the gold nanorods. And we first place the gold nanospheres on the silicon substrate by binding agent. Then, we use polymer with appropriate end functional group to form nanorods layers on top the gold nanospheres layer. By ellipseometric measurement, we can observe the electromagnetic coupling between the gold nanospheres and the nanorods. We construct the multilayer optical thin film model to fit the optical constant. Furthermore, we take advantages of the high-sensitivity of gold nanorods to produce the bio-sensor and detect the molecules by ellipsometric measurement, and hope to obtain an optoelectronic bio-sensor with high sensitivity.