Tunable and enhanced SERS activity of magneto-plasmonic Ag–Fe3O4 nanocomposites with one pot synthesize method

Abstract

In this paper, we report the tunable and enhanced SERS activity of magneto-plasmonic Ag–Fe3O4 nanocomposites that are synthesized by a one pot method. Crystal violet (CV), rhodamine 6 G (R6G) and 4-mercaptobenzoic acid (4-MBA) molecules are used to investigate the SERS optical activity of Ag–Fe3O4 nanocomposites under different external magnetic fields (1500, 2000, 2500, 3500 and 5000 gauss). The experimental results demonstrate the enhanced Raman effects that can be obtained by increasing the magnitude of external magnetic field. This is because the electromagnetic hot spots located between the neighboring Ag–Fe3O4 nanocomposites can be tuned by utilizing the external magnetic field. The bigger density of the hot-spots and amplitude of the electric field in the hot-spot are responsible for the enhanced SERS effect. The detection limit of CV molecule can be at least down to 10−9 M. The spectra measurements of hemoglobin adsorbed on the Ag−Fe3O4 nanocomposites under different external magnetic fields are also performed to explore its bio-applications. Finite element method (FEM) is used to simulate the local electromagnetic field distribution in Ag–Fe3O4 nanocomposites, revealing the SERS enhanced mechanism is determined mainly by the near field enhanced electromagnetic field. Due to its tunable and enhanced properties, Ag–Fe3O4 nanocomposites are expected to be promising SERS substrates for chemical and biological sensing applications.