以雙水相系統萃取分離不同尺寸的銀奈米粒子

Abstract

本研究之目的是利用雙水相系統(aqueous two-phase systems，ATPS)，萃取分離不同大小之銀奈米粒子。我們選用聚乙二醇(PEG)加磷酸氫二鉀(K2HPO4)來製備雙水相系統，藉由改變PEG分子量、PEG和K2HPO4的重量百分比濃度，以及添加尿素分子(Urea)，尋找出理想的雙水相系統，並以批式萃取法分離不同尺寸的奈米粒子。 經過最佳化的實驗之後，選用PEG (M.W. 6000) 15%(w/w)，K2HPO4 10%(w/w)雙水相系統，來分離表面修飾上有機分子(11-mercaptoundecanoic acid，MUA) 之銀奈米粒子。發現，較大顆粒的銀奈米粒子傾向分佈於上層相，而較小顆粒銀奈米粒子於下層相分佈較多。我們認為MUA分子與雙水相系統中PEG分子之間的疏水性作用力(hydrophobic interaction)，影響銀奈米粒子在兩相中的分佈。 最後使用批式萃取的方法連續萃取三次。第一次萃取，上層相銀奈米粒子平均大小顆粒為11.5±1.9nm，下層相銀奈米粒子平均大小顆粒為10.5±1.8nm；第二次萃取，上層相銀奈米粒子平均大小顆粒為13.0±1.9nm，下層相銀奈米粒子平均大小顆粒為11.0±2.1nm；第三次萃取，上層相銀奈米粒子平均大小顆粒為 ii 13.1±2.1nm，下層相銀奈米粒子平均大小顆粒為11.1±2.4nm。經由實驗結果證明，利用銀奈米粒子大小尺寸，在雙水相系統兩相中的分佈不同，以批式萃取方法，可分離不同尺寸的銀奈米粒子。

The purpose of this study is size-separation of silver nanoparticles (AgNPs) using aqueous two-phase systems (ATPS). Polyethylene glycol (PEG) and K2HPO4 were selected to formulate the ATPS. By modifying the ATPS compositions, we could manipulate the partition coefficients of different size AgNPs in the two aqueous phases. The parameters modified in our study included the molecular weight of PEG, the salt concentration, the polymer concentration and the urea addition to the system. The optimum ATPS was 15% (w/w) PEG (M.W.6000) with 10% (w/w) K2HPO4. This solvent system was applied to extract the AgNPs in which the surface was modified by 11-mercaptoundecanoic acid (MUA). The size distributions of AgNPs in both phases were measured by Scanning Electron Microscopy. The partition of AgNPs with larger size was favored to enter the upper phase, i.e. PEG-rich phase, while the smaller AgNPs would exist in the bottom phase, i.e. K2HPO4-rich iv phase. Hydrophobic interaction between the MUA and PEG molecules was considered the major force on the AgNPs partitioning. Three-step batch extractions were then performed to examine the separation efficiency. The average sizes of AgNPs in the first step extraction were 11.5 ± 1.9 nm in the upper phase and 10.5 ± 1.8 nm in the bottom phase. The AgNPs sizes in the second extraction were 13.0 ± 1.9 nm in the upper phase and 11.0 ± 2.1 nm in the bottom phase. The sizes in the last extraction were 13.1 ± 2.1 nm in the upper phase and 11.1 ± 2.4 nm in the bottom phase. The results showed the partition of AgNPs was size-dependent; therefore the size separation of AgNPs could be successfully performed using ATPS extractions.