One-step synthesis of Ag-Fe3O4 nanocomposites and their SERS properties

Noble metal and ferromagnetic oxides nanocomposites have attracted great interest because of their optical and magnetic properties. In this paper, we prepared Ag-Fe3O4 nanocomposites by a facile, one-step, and repeatable solvothermal method. The diameter of the as-synthesized nanocomposites was about 250 nm, and the composition of the products was tuned by varying the molar ratio of Ag/Fe. The saturated magnetization of the Ag-Fe3O4 nanocomposites at room temperature gradually decreased with increasing of Ag/Fe molar ratios. The saturated magnetization of the products was 30.6 emu g(-1) with the molar ratio of 1:1, which enables them to be easily concentrated from the solution by simply applying a small magnet. These nanocomposites have broad surface plasmon resonance absorption bands from 400 to 600 nm, which are overlapping with the excitation laser of 532 nm. The surface-enhanced Raman spectroscopy (SERS) properties of the nanocomposites were studied using Rhodamine 6G and crystal violet as the target molecules. The correlation of the product composition on SERS was then demonstrated by gradually increasing Ag/Fe molar ratios. So these efficiently and conveniently concentrated products have a great potential in the fields of the biomedical sensitive detection and assay.