含奈米銀粒子之溫敏性樹枝狀高分子微胞調控表面增強拉曼效應

Abstract

本研究成功開發具有刺激應答型的表面增強拉曼散射基板(surface-enhanced Raman scat-tering substrates, SERS substrates)，因分子結構具有溫度敏感性的性質，可藉由溫度的調控來改變分子的親疏水性，進而影響微胞的表面型態，同時使得還原於微胞上的銀奈銀粒子彼此間的距離變小，產生了增強的熱點效應(hot-spots resonance effects)，將可有效的提升拉曼訊號之偵測靈敏度，應用於快速檢測多種化合物。 實驗先利用具有反應選擇性的雙官能基單體 IDD，和結構單元交替反應，以收斂法先製備出一系列以長烷鏈段為末端基團的poly(urethane/malonamide)規則樹枝狀分子，並導入具有溫度敏感性的嵌段共聚物進行修飾，使不同代數之規則樹枝狀分子具有溫度敏感性的性質。由於雙親性的特性，分子會自組裝形成以疏水之C18長碳鏈為核，親水鏈段為殼的微胞結構。之後，以高分子鏈上之醚基與羰基作為成核點，利用還原反應生成奈米銀粒子而製備出具有溫敏性的SERS微胞基板。 探討以不同代數之數樹枝狀高分子製備出的微胞基板於高低溫下對SERS效應的影響，藉由拉曼光譜的分析並輔以TEM圖像的說明，推論高代數的微胞基板能還原較多的奈米銀粒子，故有較好的拉曼訊號放大能力；在高溫時，由於熱能造成的相轉換，誘發更強的熱點效應，使SERS效應比室溫下來的顯著。此外，利用該SERS基板對不同待測物進行最低檢測濃度(Limitation of detection, LOD)檢測，輔以微胞基板及不同待測物之表面張力分析，說明熱刺激誘發熱點效應對表面增強拉曼散射具有重要的影響。證實了本系統之SERS基板在高溫下，除了能放大微量待測物的拉曼訊號以利檢測，亦可應用於多種化合物分子之快速偵測及分析。

A series of thermo-sensitive dendritic-polymer micelles have been developed for sur-face-enhanced Raman scattering (SERS) substrates featuring with silver nanoparticles (AgNPs) of tunable spatial distribution which could effectively improve sensitivity of SERS signals with rapid de-tection of small molecules. Different generations of amphiphilic poly(urea/malonamide) dendrons with thermo-sensitive property were synthesized by post-modified diblock copolymers through the addition reactions. In aqueous solution, amphiphilic dendrons self-assembled into core-corona micelles with the alkyl chains as core and the poly(oxyethylene) block as corona. AgNPs were subsequently immo-bilized on dendritic-like micelle templates through in-situ reduction reaction of AgNO3 in aqueous dispersion to form thermo-sensitive SERS substrates. We explore the influence of different generation and temperature to the SERS effect. Results show that the higher generation of the micellar substrates the much stronger Raman signals will be detected owning to the more nucleation places for the silver nanoparticles on the micelles through observation of the Raman spectrums and TEM images. Fur-thermore, at high temperature, the even more pronounced hot spots effects will be induced which causing the enhanced amplication of signals than ones at room temperature. We assume that ther-mo-enhanced hot spot resonance effects will affect SERS behaviors much effectively, which can overcome the affinity effect between substrates and analytes as verified through analysis of limitation of detection (LOD) and surface tension for differenr analytes. Such substrates possess great potential to apply in the rapid and label-free SERS detection.