在生物化學領域上，對於具有掌性分子之辨認、分離、轉換是極為重要的研究課題，一般來說通常會使用圓二色圖譜、螢光檢測圓二色圖譜或旋光拉曼來進行分析，但是由於旋光與掌性分子間尺寸的不匹配導致其響應非常微弱，所以如何增強旋光與掌性分子間的作用力是一個熱門的研究領域。

在此研究中，我們結合理論計算及光學實驗探討電漿奈米結構的光學特性，利用電漿奈米結構提高光與分子間的作用並增益光學掌性。而近年來，電漿奈米結構亦常被使用在光學捕捉技術上，由於表面電漿共振具濃縮電場在近場、大幅提高電場梯度的特性，可以捕捉較傳統光學捕捉尺寸更小的粒子。所以我們希望使用電漿奈米結構達到近場增益同時結構扮演電漿光學鑷子角色來捕捉待測掌性分子進行旋光拉曼分析，使偵測靈敏度大幅提高，以達到超低濃度掌性分子分析。

在實驗上，我們先做電漿奈米圓洞的分析，分為兩實驗同時進行。首先我們先將圓洞裡鋪滿拉曼分子，入射雷射光激發圓洞從圓洞並量測奈米圓洞的穿透光得到分子的拉曼光譜，接著利用模擬計算進一步證明拉曼訊號強度和近場增益及穿透增益的關係。另一實驗，使用奈米洞結構進行光學捕捉直徑為 20 nm 的聚苯乙烯奈米球，長時間穩定地將聚苯乙烯球捕捉在洞中且具有高度再現性。
接著我們利用時域有限差分法模擬計算，找出具最強光學掌性增益的奈米橢圓結構尺寸，並計算在水溶液中對於聚苯乙烯球的光學捕捉力。

未來，我們希望可以進一步做掌性分子在橢圓洞中的拉曼旋光分析，最後結合光學捕捉，將掌性分子利用化學修飾在聚苯乙烯球表面上，並用線性偏振光激發奈米橢圓結構，同時間產生圓偏振近場光及捕捉住聚苯乙烯球，在水溶液中進行掌性分子的拉曼旋光分析。

Chiral molecules show slightly different absorbance of left- and right-handed circularly polarized light (CPL). Such circular dichroism (CD) effect can be used for the characterization of molecular chirality. Unfortunately, CD is usually very weak due
to the mismatch between the pitch of CPL helix and the size of molecular chiral domain.

Plasmonic nanostructures can concentrate optical fields at nanometer scale and provide stiff optical potential to enhance optical chirality and improve CD signals. Plasmonic elliptical nanoholes can create the concentrated chiral optical near field
based on localized surface plasmonic resonance (LSPR). The optical near field generated in nanohole can also provide trapping force to isolate, immobilize and manipulate the target nanoparticles. By controlling the polarization of the incident light, the chirality of the optical near field can be easily switched. Since the optical near field in the hole is circularly polarized, the Raman scattering also reveal the chirality of the
target due to the Raman optical activity (ROA).

This work is divided into two parts. First, we design and fabricate plasmonic circular nanoholes which are pave with R6G molecules. By measuring the Raman scattering spectrum of R6G molecules in single nanohole, we can then obtain the information between Raman intensity, near field enhancement and transmission enhancement. In second part, we use single nanohole to trap 20 nm polystyrene sphere
with high reproducibility in stable state.

In the further, combine optical trapping with plasmonic elliptical nanoholes, we are able to obtain ROA analysis by linearly polarized light in solution.

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