MnFe2O4/SiO2/Ag磁性奈米複合粒子之製備及其在拉曼光譜分析之應用

Preparation and Application of MnFe2O4/SiO2/Ag Magnetic Nanocomposites in Surface Enhanced Raman Spectroscopy

本研究利用化學共沉法，合成出MnFe2O4磁性奈米粒子，再以溶膠──凝膠法將SiO2包覆於其表面上，製備出MnFe2O4/SiO2磁性奈米複合粒子，改善易氧化之問題；接著利用無電鍍法，在MnFe2O4/SiO2磁性奈米複合粒子表面鍍上銀奈米粒子，並以不同反應參數控制銀奈米粒子的粒徑及分佈，達到提高Ag奈米粒子包覆MnFe2O4/SiO2磁性奈米複合粒子之包覆量。利用X射線繞射儀 (XRD)、穿透式電子顯微鏡 (TEM)、X光能量散佈元素組成分析儀 (EDX)、超導量子干涉儀 (SQUID)分析奈米複合粒子之粒徑、形態與磁化量。分析結果顯示，MnFe2O4磁性奈米粒子其粒徑分佈為88.4 nm，飽和磁化量為46.4 emu/g，MnFe2O4/SiO2磁性複合粒子粒徑為116 nm，二氧化矽層厚度為14.2nm。以無電鍍條件加入0.1 M銀胺溶液2.4 mL、1 M葡萄糖0.48mL時，具有較佳的包覆率，其銀奈米粒子平均粒徑為23.2 nm。利用顯微拉曼光譜儀 (Microscopes Raman Spectrometer)測試奈米複合材料之表面增強拉曼散射效應 (SERS)，以rhodamine 6G (R6G)作為分子探針，從實驗結果得知，SERS隨著MnFe2O4/SiO2/Ag磁性奈米複合粒子之添加量、聚集及pH值增加而隨之提高，且較單純量測R6G分子的拉曼訊號更好。最佳檢測條件為pH=7與磁性濃縮，最低濃度可量測至0.01 ppm且表面增強拉曼散射因子 (AEF)達4.8×107，證實此系統有良好檢測效果。可重複回收使用，仍有相當增強效果。

In this study, magnetic plasmonic nanocomposites, multicore MnFe2O4/SiO2/Ag magnetic nanoparticles (MNPs) were successfully prepared using both co-precipitation and modification with SiO2 through a sol-gel method. Sliver nanoparticles are trained by electroless plating. The effect of parameters of electroless plating on the properties of nanocomposites has also been systematically investigated. The physical and magnetic properties of as-synthesized nanocomposites were characterized by Transmission Electron Microscope (TEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray Diffraction (XRD) and Superconducting Quantum Interference Device (SQUID) measurements. TEM images show that the size of MnFe2O4/SiO2 nanocomposites is 116 nm and each particle shows a thin SiO2 layer of 14.2 nm. The saturation magnetization of MnFe2O4 NPs is 46.4 emu/g. The MnFe2O4/SiO2/Ag nanocomposites were successively prepared under the addition of 2.4mL of 0.1 M Tollens' reagent and 0.48mL of 1 M glucose solution. From TEM images, silver nanoparticles were anchored homogeneously and tightly onto the silica layer of MnFe2O4/SiO2 nanocomposites. The average size is about 23.2 nm. MNPs coupled to silver nanoparticles by SiO2 layer were also applied to surface enhanced Raman spectroscopy and bactericidal tests. The measurement of spectra reveals that MnFe2O4/SiO2/Ag nanocomposites have a high sensitivity to rhodamine 6G molecules at a concentration of 0.01 ppm. The analytical enhancement factor (AEF) can reach 4.8×107.