Realization of high sensitive SERS substrates with one-pot fabrication of Ag–Fe3O4 nanocomposites

Ag–Fe3O4 nanocomposites were synthesized by the redox reaction between Ag2O and Fe(OH)2 in the absence of additional reductant at moderate temperature and atmospheric condition. The as-synthesized Ag–Fe3O4 nanocomposites are assembled into an orderly arrayed SERS substrate holding clean and reproducible properties with an applied external magnetic field. 4-mercaptobenzoic acid (4-MBA) is chosen as the probe molecule to test the enhancement factors (EF), uniformity and reproducibility of the SERS substrate. Experimental results indicate that the EF of 4-MBA on our proposed SERS substrate is up to 5.2 × 106 and the detection limit is down to ∼10−10 M. The SERS spectra of 4-MBA molecules ranging from 200 cm−1 to 2000 cm−1 were randomly collected from a number of positions on the substrate and six Ag–Fe3O4 nanocomposites substrates are measured with the same procedure. It is shown that the SERS substrate have the good uniformity and reproducibility with low standard deviation, indicating our proposed Ag–Fe3O4 nanocomposites with external magnetic field control abilities have potential applications in the fields of magnetic separation and SERS techniques.