Synthesis Of Gold Magnetic Nanoparticles And Their Application In Rapid Detection Of Aflatoxin By Surface Enhanced Raman Spectroscopy

Surface enhanced Raman spectroscopy（SERS） is a fast, convenient, and highly sens itive detection technique and Raman substrate is a material which has surface enhanced Raman scattering effect. Therefore, to build highly sensitive Raman substrates is the key to improve SERS detection sensitivity and accuracy. In this work, the preparation of core-shell Fe₃O₄/Au magnetic nanoparticles and assembled Fe₃O₄/SiO₂/Au magnetic nanoparticles were systematically investigated. The physical and chemical properties of the two type nanoparticles were characterized by a variety of techniques（e.g., TEM, DLS, UV-vis, FTIR） and the application of the two type of magnetic nanoparticles as detection substrate for determination of aflatoxin B1 by surface-enhanced Raman spectroscopy was discussed. The work primarily covered following aspects:1. Synthesis and characterization of core-shell Fe₃O₄/Au magnetic nanoparticles.The Fe₃O₄/Au magnetic nanoparticles were prepared by thermal decomposition of ferric acetylacetonate. The optimal reaction conditions were determined and the magnetic nanoparticles were characterized by a variety of techniques such as TEM, DLS, EDX, UV-vis, FTIR and etc.2. Synthesis and characterization of assembled Fe₃O₄/SiO₂/Au magnetic nanoparticles.With Fe₃O₄ as an iron core, tetraethxoylsilane was first used to modify the surface of Fe₃O₄ to form Fe₃O₄/SiO₂ nanoparticles, followed by addition of 3-thiolpropyl-triethxoysilanes ilane and 3-aminopropyltriethxoysilane to introduce-NH2 and –SH to the surface of Fe₃O₄/SiO₂. Gold nanoparticles were prepared by the reduction of chloroauric acid with phenylsilane and the produced Au nanoparticles were assembled and attached to the surface of Fe₃O₄/SiO₂ via the interaction of-NH2 and –SH with Au nanoparticles to form Fe₃O₄/SiO₂/Au nanocomposite. The nanocomposite was characterized by a variety of techniques such as TEM, DLS, EDX, UV-vis and etc.3. The detection of Aflatoxin B1 by SERS using the two type of magnetic Au nanoparticles as detection substrate.Using core-shell Fe₃O₄/Au nanoparticles and assembled Fe₃O₄/SiO₂/Au nanoparticles as detection substrate for surface enhanced Raman spectroscopy, aflatoxin B1 was detected under Raman microscope. An external magnet was used to concentrate and aggregate the magnetic nanoparticles, leading to a significant increase of local concentration of gold magnetic nanoparticles and producing a detection sensitivity of 0.5 μg/m L for aflatoxin B1.