金-聚苯乙烯核殼奈米粒子之合成及其於乙型交感神經受體致效劑之光學感測應用

Abstract

本研究主要利用水甲苯液液兩相法(water-toluene liquid-liquid two-phase method)合成機能性高分子表面修飾之小金屬奈米粒子(nanoparticles, NPs)。有別於兩相法中廣泛使用之小分子量短碳鏈烷基硫醇，在此特別導入聚苯乙烯高分子硫醇化合物(thiol terminated polystyrene, PS-SH)，成功單步驟合成甲苯溶劑中分散性及懸浮性良好之金-聚苯乙烯核殼奈米粒子(Au-PS core-shell NPs)。合成所得之金-聚苯乙烯核殼奈米粒子，由於尺寸高度一致，展現出與理論相符之完美表面電漿共振(surface plasma resonance, SPR)特性。以直徑5 nm金奈米粒子，1.5 nm聚苯乙烯高分子殼層為例，其紫外光-可見光(UV-visible)吸收光譜於530 nm呈單一吸收峰，顯示其極具乙型交感神經受體致效劑(β-adrenergic agonist)光學感測應用之潛力。 乙型交感神經受體致效劑(俗稱瘦肉精)，除了用於治療人類氣喘疾病或作為減肥藥物(如：克羅特羅，clenbuterol)外，亦被添加於動物飼料中來提高生產效益(如：萊克多巴胺，ractopamine)。然而殘留的瘦肉精會污染肉品及其相關製品，對人類健康造成嚴重危害。因此開發一種以奈米粒子為主體之新穎先進感測技術，作為有效且快速檢測瘦肉精成為一重要且刻不容緩的研究主題。其感測原理主要利用聚苯乙烯高分子殼層與乙型交感神經受體致效劑分子皆具有苯環基團，藉由苯環上穩定環形π電子流，使兩分子間產生π ‒ π作用力而相互吸引，造成金-聚苯乙烯核殼奈米粒子產生團聚，進而改變表面電漿共振之吸收峰位置。以萊克多巴胺為例，在金-聚苯乙烯核殼奈米粒子溶液中，加入10 ppm萊克多巴胺瞬間，立即產生目視可辨之溶液顏色變化，紫外光-可見光吸收光譜呈紅位移，粒徑分析尺寸大幅增加5倍，清楚證明金-聚苯乙烯核殼奈米粒子已產生團聚。此利用奈米粒子進行光學感測之概念不僅提供了一個極具潛力之瘦肉精快篩技術，更加深對高分子表面修飾金奈米粒子之製造與表面電漿共振性質之理解。

In this work, the water-toluene liquid-liquid two-phase method was mainly applied for synthesizing the functional polymer-coated tiny metallic nanoparticles. In contrast to the commonly used smaller molecules of short-chain alkanethiols for the two-phase method, a very large molecule, namely thiol terminated polystyrene (PS-SH), was specially introduced for the successful one-step synthesis of well-dispersed and suspended gold-polystyrene core-shell nanoparticles (Au-PS core-shell NPs) in toluene. The obtained Au-PS core-shell NPs exhibit perfect surface plasma resonance (SPR) as theoretically predicted mainly due to the high size uniformity. In the case of 5 nm Au core diameter and 1.5 nm PS shell thickness, a very strong SPR peak at 530 nm was observed in the UV-visible absorption spectrum, indicating its great potential in optically detecting β-adrenergic agonists. β-adrenergic agonists have been widely used, not only as medicines for human asthma disease or losing weight (such as clenbuterol) but also as animal feed additives for improving production benefits (for example ractopamine). Residues of the beta agonists can be left behind resulting in contamination of meat as well as other food products from animal origin and thus poses serious risks to human health. Development of completely new and advanced nanoparticle-based sensing technique for effectively and easily determining the residual β-adrenergic agonists obviously becomes an important and urgent research topic. The sensing principle is based on the intermolecular forces between pi-electron clouds of phenyl groups in PS as well as β-adrenergic agonists. This interaction immediately leads significant aggregation of the well-dispersed Au-PS core-shell NPs and consequently induces an obvious red shift in the SPR spectra. For instance, with the presence of 10 ppm ractopamine, the color of the solution containing Au-PS core-shell NPs drastically changes from red to purple. An obvious red shift was recorded in the UV-visible spectra and the size analysis also showed a 5-times increase, evidently indicating the aggregation of the nanoparticles. We believe that the present nanoparticle-based sensing concept not only provides a promising approach for quickly screening the β-adrenergic agonists, but a bettering understanding in manufacturing such polymer coated metal nanoparticles and the corresponding SPR properties.