Preparation and SERS Performance of Magnetic Ag@Fe3O4@C Supported Gold Nanoparticles

An Ag@Fe3O4@C-Au microspheres has been developed which including the synthesis of Ag@Fe3O4 by one-step via a versatile solvothermal reaction, an interlayer of carbon shell coating around the Ag@Fe3O4 with glucose as carbon source, the surfuce of Ag@Fe3O4@C modified by PEI via amidation reaction, and the coating Au nanoparticles on the surface of Ag@Fe3O4@C. The enhancement effect in the Raman active was investigated by using 4-mercaptobenzoic acid (4MBA) molecules as a probe molecule. In addition, we have regulated the SERS behavior of Ag@Fe3O4@C-Au core-shell microspheres by adjusting the additional amount of Au nanoparticles (NPs). The magnetic hysteresis loops showed the saturation magnetization (Ms) values of Ag@Fe3O4@C-Au-40 are about 411 A.g(-1) and the SERS effect of 4MBA on different microspheres is Ag@Fe3O4@C-Au-40 > Ag@Fe3O4@C-Au-10 > Ag@Fe3O4@C-Au-60 > Ag@Fe3O4@C nanospheres, which was identified by Finite Difference Time Domain (FDTD). Furthermore, the low concentrations of 4MBA (1x10(-9) mol.L-1 in the solution can be detected by Ag@Fe3O4@C-Au-40 microspheres. In addition, the Ag@Fe3O4@C-Au microspheres can be recycled with magnet.