紙基與矽基之準三維微奈米複合結構於表面增強拉曼散射之定量分析與應用研究

Abstract

在本論文中，我們期望製作出低成本環境友善且具有高靈敏度之準三維(quasi-3D)微奈米複合結構作為表面增強拉曼散射基材，並探討所製作之拉曼增強基材的定量分析能力。在第一部分與第二部分的論文中，我們分別以雷射熱退火所誘發之光熱效應，使濺鍍於濾紙基材之金屬薄膜成為奈米粒子；以及利用硝酸銀與檸檬酸鈉還原出之銀奈米粒子懸浮液配合配位基(ligand)的方式形成液態面鏡(liquid mirror)，再將之轉置於濾紙基材，作為物理法以及化學還原法所製作之兩種表面增強拉曼散射試紙，並且將全氟辛基三氯矽烷蒸鍍於拉曼試紙，利用超疏水濃縮效應來達到濃縮待測物以及去除液態面鏡中配位基本身具有的背景拉曼訊號，使之成為良好的拉曼增強基材。在入射雷射光為633奈米的量測架構下，於4-胺基苯硫酚之拉曼訊號強度與濃度對數座標關係圖中，銀拉曼試紙能夠提供的線性分析區域範圍是10^-6~10^-11 M之間，而可以量測到的最低濃度為10^-12 M；另一方面，液態面鏡本身是非常緊密排列的銀奈米粒子陣列所構成，在液態時即能夠量測到10^-17 M之4-胺基苯硫酚的拉曼增強訊號，而液態面鏡轉置於濾紙後形成的試紙呈現的線性區域為10^-5~10^-11 M，最低濃度則是能夠量測到10^-13 M。並且，我們也探討了不同入射雷射光波長、不同金屬種類、不同奈米粒子形貌與不同倍率物鏡之光學量測架構對定量分析線性區域涵蓋範圍的影響。在這兩部分的實驗中，我們成功製作出具有準三維微奈米複合結構，並且具備了可撓性、拋棄式以及環境友善特性的拉曼增強試紙。 在第三部分的論文中我們以氫氧化鉀蝕刻未拋光之矽晶圓，利用其本身晶面特性形成微米大小的金字塔結構並濺鍍鎳與銅過渡金屬於其上，由於鎳與銅本身相較於金與銀是披覆性較好而較容易成膜的金屬，因此可以在較低的鍍膜厚度下形成緊密的奈米粒子結構。鍍膜厚度為20奈米之銅金字塔結構與鍍膜厚度為10奈米之鎳金字塔分別能夠量測到10^-10 M與10^-9 M之羅丹明的拉曼增強訊號，此量測結果已經超越既有文獻中以此二種金屬直接作為拉曼增強基材之最低偵測濃度極限值。並且，我們透過經由不同倍率的物鏡在拉曼試紙與金屬金字塔結構上量測待測物之拉曼訊號，發現這類電場增強熱點具有微米等級縱深分布的準三維結構，除了存在有效拉曼偵測體積範圍內之熱點數能夠較平面的拉曼基材為多，在載台離焦時待測物的訊號強度衰減速度較緩慢外，準三維拉曼基材適合以低倍率物鏡進行訊號量測，在戶外攜帶式的拉曼量測系統的應用上非常具有潛力。

In this thesis, we aimed for fabricating low-cost, highly sensitive quasi-three dimensional (quasi-3D) micro-and nanostructures as surface enhanced Raman scattering (SERS) substrates, and elaborate the ability to demonstrate quantitative detection of analyte molecules. In the first part and second part of this thesis, we prepared our SERS paper substrates from physical and chemical reduction methods, respectively. First, we adopted laser-induced photo-thermal effect to convert metal thin film into nanoparticles (NPs) on filter paper. Second, we used silver nitrite and sodium citrate to synthesize silver nanoparticles (AgNPs), and then fabricated liquid mirror via the addition of chemical ligand followed by transferring liquid mirror onto filter paper. Moreover, we used superhydrophobic treatment by coating perflurooctyltrichlorosilane onto the paper SERS substrates to further improve SERS detection sensitivity. The Raman background signal interference of the ligand in liquid mirror could be significantly reduced at the same time. By the excitation laser having a wavelength of 633 nm, the AgNPs SERS paper provided linear response of SERS intensity with the concentration of 4-aminothiophenol (4-ATP) from 10^-6 M to 10^-11 M in log/log plot, and the detection limit was 10^-12 M. On the other hand, liquid mirror was composed of extremely closely packed AgNPs array, the detection limit of 4-ATP could down to 10^-17 M at liquid state. After transferred onto filter paper, liquid mirror SERS paper provided linear response of SERS intensity with the concentration of 4-ATP from 10^-5 M to 10^-11 M, and the detection limit was 10^-13 M. Also, we discussed the influences of the wavelength of excitation laser, the kind of metal, the distribution of NPs in SERS substrates and the instrumental factors on the linear region of quantitative detection. We have fabricated deformable, disposable and eco-friendly SERS paper with quasi-3D micro-and nanostructures. In the third part of this thesis, anisotropic etching by potassium hydroxide was used to fabricate silicon pyramid, and then transition metal thin film was deposited onto these micro pyramids. Due to the better adhesion of nickel and copper to substrates compared to gold and silver, they were able to form relatively close NPs when the deposition thickness was thin. The detection limit of rhodamine 6G on copper pyramid SERS substrate was 10^-10 M and it was 10^-9 M on nickel pyramid when the deposition thicknesses were 20nm and 10nm, respectively. The detection limit is superior to other SERS substrates made from copper or nickel in previous researches. By the way of measuring the SERS signals of analyte via different objective lens, we found that if the hot-spots exhibited quasi-3D distribution, more hot-spots could reside in the probing volume of SERS signal over flat SERS substrates. The SERS intensity of analyte would decrease slowly when the stage of microscope was defocusing. Quasi-3D SERS paper and transition metal pyramid are suitable for measuring SERS signals via objective lens with low magnification. These quasi-3D substrates have the potential to be applied to low cost of portable Raman systems.