銀奈米粒子鑲嵌之聚苯乙烯球陣列於表面增強拉曼散射光譜之應用

Abstract

斷鍵-成核-長晶法為一項操作方便、省時、步驟簡易之獨特技術，不需經由繁複的分子修飾過程，即可快速合成出大量且具高均勻度之金屬奈米粒子鑲嵌於大多數的高分子基材上。本項研究中，銀奈米粒子可藉由斷鍵-成核-長晶法以原位還原方式鑲嵌於聚苯乙烯球表面，製作出大面積分佈之銀奈米粒子於三維結構二維聚苯乙烯球陣列。本研究中所選用之聚苯乙烯球為合成奈米粒子之基材，先以溶劑自然揮發的方式自組裝排列於一基板上，形成大面積之六方最密堆積陣列後，再以氧氣電漿活化聚苯乙烯球表面，之後浸入前驅物硝酸銀溶液中，經加熱反應後即可合成大量且均勻分佈的銀奈米粒子於聚苯乙烯球表面。本實驗發現，在氧氣電漿活化時間為30 s、硝酸銀濃度為20 mM、加熱反應時間為90分鐘下，即可得到密度約1328 N/μm2及尺寸約18 nm的銀奈米粒子分佈於聚苯乙烯球表面。此外，這些修飾於聚苯乙烯球表面之銀奈米粒子亦可被作為晶種，經由還原劑添加的步驟，還原溶液中既有的銀離子堆積在原有的晶種上，以形成較大尺寸之奈米粒子。隨著調控硝酸銀濃度、還原劑檸檬酸鈉濃度以及加熱反應時間，便可有效地控制銀奈米粒子的尺寸及密度。在硝酸銀濃度為3 mM、檸檬酸鈉濃度為15 mM及加熱反應40 min實驗條件下，可得到尺寸約為120 nm之銀奈米粒子於三維結構二維聚苯乙烯球陣列，本研究中將此銀奈米粒子鑲嵌之聚苯乙烯球陣列應用於表面增強拉曼散射光譜，發現隨著不同尺寸及密度變化下，可得到一系列拉曼訊號增強變化的趨勢。接著在變化趨勢中找到能得到最大訊號增強效果的奈米結構，將其檢測極低濃度的R6G分子，經由本研究重新定義之增強因子(Enhancement factor, EF)修正公式計算出此奈米結構的正確EF值，可達到約為109倍之極高增強倍率。

Break-seed-growth process is a robust and facile method to fabricate highly uniform and numerous metal nanoparticles decorating on polymer surfaces without the need of complicated molecule modification. In this study, monodispersed silver nanoparticles are in situ synthesized and decorated on the surface of polystyrene spheres by this break-seed-growth process. Highly ordered sphere arrays are first self-assembled with a hexagonal close-packed arrangement over a large area on a supporting substrate. Through O2 plasma treatments, uniform and large amounts of silver seed nanoparticles embedded into the activated polystyrene surface are obtained without adding any reducing agent and stabilizing molecule. A density of 1328 N/μm2 and size of 18 nm Ag nanoparticles are obtained under the condition of 30 s of O2 plasma, 20 mM of AgNO3 concentration and 90 min of metal ion solution incubation time. After the formation of silver seeds, the nanoparticle size subsequently becomes larger by adding reducing agents in the particle growth stage. The size and density of silver nanoparticles can be controlled by altering experimental conditions in our fabrication method and a trend of surface enhanced Raman signal on this nanoparticle array is obtained. The structure giving the highest Raman signal enhancement was utilized to detect an extremely low concentration of Rhodamine 6G, and a superiorly high enhancement factor of about 109 is achieved.