塊式共聚高分子媒介超音波合成金枝狀奈米環 及表面增強拉曼散射感測應用

Abstract

本論文探討(1)如何利用塊式共聚高分子，輔以超音波震盪法，合成新穎之Au枝狀奈米環結構，以及(2)形貌依存之表面電漿共振(Surface plasmon resonance, SPR)與表面增強拉曼散射(Surface enhanced Raman scattering, SERS)效應於孔雀石綠(Malachite green)分子之感測應用。 金屬枝狀奈米環結構由於具有特殊之表面及中空幾何構型，故無論是孤立存在或是堆疊成膜，均能提供較實心結構更高之比表面積與化學反應性。此外，有別於其它形貌之尺寸依存SPR與SERS特性，使其具有極高之基礎研究與感測應用價值。在合成策略方面，塊式高分子在化學合成中經常具有多重機能，諸如作為軟性模板、結構導向劑、介面活性劑、或還原劑之用。而超音波震盪由於能在液態介質中有效地傳遞能量，使合成溶液產生聲化學反應，故被廣泛應用於合成奈米金屬結構。本研究利用PEO-PPO-PEO三段式塊式高分子(Pluronic P84)之軟模板、離子還原及成長引導特性，配合超音波震盪，有效促使塊式共聚高分子溶液中奈米金屬的自組裝與融合，成功製備Au枝狀奈米環結構。此製程具有節省材料、成本低廉、低汙染、無需硬式模板與基板、以及低生物毒害等優點。合成所得之Au枝狀奈米環結構，展現突出SERS特性，成功感測有毒物質孔雀石綠，最低濃度偵測值達0.5 ppb，低於歐盟檢測標準(2 ppb)，顯示其感測應用的可行性與潛力。

This thesis describes two main subjects: (I) the block-copolymer mediated ultrasonic synthesis of novel Au branched nanorings and (II) the morphology dependent Surface plasma resonance (SPR) and the application of surface enhanced Raman scattering (SERS) in detecting malachite green molecules. Compared to the structures with a dense solid morphology with smooth surface, the branched surface and ringed morphology presented in the prepared novel gold branched nanorings can effectively provide larger specific surface area and higher chemical activity even when they are casted into films or bulk. In addition, the distinct nanostructures provide unusual morphology-dependent SPR and SERS properties completely differing from other metallic ones are interesting and valuable for fundamental researches and sensing applications. Regarding the synthesis strategy, block-copolymers frequently perform multiple functions in the chemical reactions, for instance, acting as soft templates, shape directing agents, surfactants, and reductants. Ultrasonic irradiation via liquid media is known as a facile and effective treatment for providing energy and thus activating or enhancing sonochemical syntheses of metallic nanostructures. In this work, by coupling the designating features of the block-copolymer (Pluronic P84) and ultrasonic irradiation, the Au branched nanorings were successfully synthesized. The present facile process is material-economized, pollution-limited, non-toxic, low-cost and hard-template- and substrate-free. In addition, the SERS raised from the casted films of the Au branched nanorings is successfully applied to trace a very low concentration (0.5 ppb) of toxic malachite green molecules. The extraordinary SERS sensing ability well satisfy the measurement requirement of an acceptable maximum level of 2 ppb published by European commission, indicating the great potential on practical applications.