表面電漿共振(surface plasmons reasnoance，SPR)之生物感測器其具有無需標定待測物(label free)與高靈敏度(high sensitivity)等優點，可即時量測分析生物分子間之作用情形然而在微小濃度下的小生物分子間作用時，傳統之SPR生物感測器的靈敏度能然顯得不足。因此，如何提升感測器之靈敏度，是目前主要的研究課題之一。本實驗室所提出的金屬奈米粒子強化之SPR生物感測器，藉由金屬奈米粒子的作用，已成功地將靈敏度提高10倍，達到100 fg/mm2表面生物分子覆蓋度之境界。而為了能夠更進一步提高靈敏度，因此了解表面電漿子(surface plasmons，SPs)與粒子電漿子(particle plasmons，PPs)之特性，其造成局域電磁場強化與感測器靈敏度間之關係是一重要的研究課題。 在本論文中，首先利用Maxwell-Garnett(MG)等效介電常數理論，來描述金之奈米粒子層的特性，然而此理論限制條件太多，故無法滿足研究上的需求。因此加以時堿有限差分法(finite-difference time-domain method，FDTD Method)輔助，藉由模擬計算各種奈米膜層結構下之電磁場分佈情況，以了解表電漿子與粒子電漿子間的交互作用。我們將這些效應分別以單獨奈米粒子電漿子、奈米粒子間耦合作用(interparticle coupling)及奈米粒子層和金屬膜間作用(gap mode)等三部分逐一分析。 Surface plasmon reasonance (SPR) biosensor has the advantages of label free and high sensitivity. However, the sensitivity is not good enough to analyze biomolecular interaction for small biomolecular in low concentration. Hence, the sensitivity improvement of biosensor is a very important works. We proposed a new metal nanostructure to increase the sensitivity. In the experimental result, we successfully demonstrate that the detection limit to reach can be achieved to 100pg/mm2 of the surface coverage of biomolecular. In order to approach the detection limit to 1fg/mm2, the characteristics of surface plasmons (SPs) and particle plasmons (PPs), such as local electro-magnetic (EM) field enhancement and sensing sensitivity improvement are needed to be studied. In this thesis, we use Maxwell-Garnett (MG) effective media theory to explain the gold-nanoparticle layer. The MG model can not completely match the experimental results. Hence, we use a finite-difference time-domain (FDTD) method to study nanoparticle effect more detail. The plasmon effects such as particle plasmon effect, interparticle coupling effect, and gap mode effect through different structures to enhance the EM field are simulated and studied.
