超顺磁性Fe_3O_4/Au@Ag复合材料的合成及其SERS性能研究

Fabrication of Superparamagnetic Fe_3O_4/Au@Ag and Its SERS Performance

利用溶剂热法和种子生长法分别合成Fe3O4磁性纳米粒子和Au@Ag核壳纳米粒子,利用静电吸附方法成功将聚乙酰亚胺(PEI)修饰到Fe3O4表面并通过N—Ag共价键将Au@Ag核壳纳米粒子组装到Fe3O4表面,制备Fe3O4/Au@Ag复合材料.通过控制Au@Ag复合粒子的加入量,来调节Fe3O4/Au@Ag复合材料的表面增强拉曼(SERS)活性.以对巯基苯胺(p-ATP)为拉曼活性探针分子来考察该复合纳米材料的SERS性能,检测限可以低至2×10-9 mol/L.同时,将该复合材料应用于农药分子福美双的检测,检测限可以低至10-6 mol/L.这种功能性复合材料既具有良好的SERS活性,又具有Fe3O4磁性内核,可以通过外加磁场实现对待测分子的分离、富集,具有更广泛的应用前景.

In this paper, Fe3O4 nanoparticles were synthesized by solvothermal method and uniform silver-coated gold nanoparticles（Au@Ag NPs） were synthesized via seed growth through consecutive two-step reactions. Subsequently, Au@Ag NPs were assembled on the surface of Fe3O4 NPs functionalized with PEI due to the bond between-NH2 and Ag. We have regulated the SERS behavior of Fe3O4/Au@Ag NPs by adjusting the addition amount of Au@Ag. This Au@Ag NPs were characterized by Ultraviolet-visible（UV-vis） extinction spectroscopy. From the measurement of UV-vis spectra we can see that Au@Ag has a wide range of plasmon resonance from ca. 320 to 560 nm while one significant peak were observed at 530 nm for the Au NPs. This Fe3O4/Au@Ag NPs were systematically characterized by scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, vibrating sample magnetometer（VSM） and surface enhanced Raman spectroscopy（SERS）. The SEM and TEM observation showed the NPs are highly monodispersive. The magnetic hysteresis loops showed the saturation magnetization（Ms） values of Fe3O4 NPs and Fe3O4/Au@Ag NPs are about 83.6 emu·g^-1 and 57.1 emu·g^-1, respectively. p-Aminothiophenol（p-ATP） molecules were employed to explore surface-enhanced Raman Spectroscopy（SERS） performance of Fe3O4/Au@Ag and showed excellent sensitivity to 2×10^-9 mol/L. Simultaneously, Fe3O4@Au@Ag NPs were applied to the detection of thiram and showed sensitivity to 10^-6 mol/L. Using these nanoprobes, analyte molecules can be easily captured, magnetically concentrated, and analyzed by SERS. In addition, the Fe3O4/Au@Ag NPs can be recycled with magnet, which exhibited great practical potentials.