利用自組裝之團連共聚合物製作有序排列之奈米金顆粒薄膜

Abstract

本研究成功的研製出條紋狀以及球狀排列的奈米金顆粒薄膜，利用團聯共聚合物可自我組裝成各種結構的特性，不僅可規則地排列，也可輕易的控制排列的間距，顆粒的大小，實驗材料亦由本實驗室所合成，包括PS-b-PMMA (polystyrene-b-polymethylmethacrylate)以及PS-b-P2VP (polystyrene-b-poly2-vinylpyridine)，其中條紋狀金顆粒薄膜是利用PS-b-PMMA共聚合物本身自組裝的機制，控制比例使其產生一柱狀排列的微結構，並簡易地在任何一種基材上旋轉塗佈，加熱處理使其達到熱力學上平衡的狀態後，利用反應離子蝕刻技術(RIE)進而製作出具有序微結構之條紋狀高分子模板，使其裸露於空氣界面，再使用蒸鍍的方式將金選擇性地排列於PS相；球狀結構之金顆粒薄膜則是利用PS-b-P2VP在溶液狀態下所產生的微胞結構，並利用浸漬塗佈的方式，製作出一具六角狀堆積的球狀金鹽顆粒薄膜，此方法的關鍵是在還原的步驟，不同於一般文獻的還原方式，為使還原後的金顆粒仍具有大範圍的排列性，本研究先將薄膜製作，再利用聯胺蒸氣進行原位(in-situ)還原。 在結構鑑定部分，利用AFM可觀察到在條紋狀高分子模版上蒸鍍金前後的變化，利用TEM的量測，可觀察到在球狀結構的單層膜上進行聯胺蒸氣還原前後，金顆粒的產生與聚集的現象，亦觀察到隨著還原時間更長或是P2VP鏈段長度更長時，將會導致微胞之間金顆粒的聚集以及原本有序二維結構的破壞。在光學性質的量測部分，利用紫外/可見光光譜確實觀察到條紋狀結構的金顆粒吸收將隨著所蒸鍍的膜厚，而有增加的趨勢；球狀結構的薄膜在還原後亦有金顆粒表面電漿共振之吸收訊號，更直接地印證金顆粒的存在。

The aim of this study was focusing on making a two-dimensional ordered structure with gold nanoparticles. Traditional top-down patterning methods like photolithography and e-beam lithography had shown to be time-consuming and expensive processes. In this study, a bottom-up method to fabricate an ordered nanodot with gold nanoparticles was proposed by using an amphiphilic block copolymer self-assembled into well-defined two/three dimensional structures. A stripe-like and a spherical nano-structure containing gold nanoparticles can be made by using block copolymer such as PS-PMMA and PS-P2VP that were also synthesized in our Lab. The fabrication process of stripe-like structure involved two steps. The first step involves spin coating the copolymer on a substrate, then thermal annealing it into ordered structure by self-assembly. The second step was to apply gold nanoparticles selectively on PS domain to form highly ordered gold nanoparticles array. The fabrication process of a spherical structure was made by PS-P2VP which formed micelles in toluene. The nanodot array of micelle monolayer containing gold salts was made by dip-coating. The block copolymer micelles containing gold salts were used as nanoscale reactors for the in-situ synthesis of gold by chemical treatment of the film sample with hydrazine vapor. A stripe-like and a spherical nanostructure containing gold nanoparticles were both observed either by AFM or by TEM. AFM was used successfully to evaluate the uniformity of stripe-like nanostructure coated on a silicon wafer before and after gold evaporation. TEM measurement of a spherical nanostructure showed that a monolayer of gold salts was reduced to one or a couple of gold nanoparticles inside the core volume of P2VP domain by nucleation and growth mechanism upon hydrazine vapor exposure. UV-vis spectrometer also show a characteristic surface plasmon absortion peak which demonstrate the effectiveness of the method in reducing gold salts.