Controllable Fe3O4/Au substrate for surface-enhanced infrared absorption spectroscopy

In this paper, the Fe3O4/Au nanocomposites were fabricated and employed as surface-enhanced infrared absorption (SEIRA) substrates. The superparamagnetic nature of Fe3O4/Au nanocomposites makes them suitable for controlled magnetic manipulation. The infrared absorption enhancements of Fe3O4/Au composite were improved as the magnetic field intensity increasing both for mercaptobenzoic acid and nitrobenzoic acid probe molecules. When the magnetic field intensities increase to 280mT, the infrared enhancement could raise up to 3.3 and 10.7 times for -SH and - NO2 groups, respectively. The enhancement is due to the synergy of localized surface plasmon resonance of Au and the magnetism of Fe3O4. Under the strong magnetic field, the superparamagnetic Fe3O4/Au nanoparticles are highly concentrated, leading to the increase number of SEIRA "active sites" and the surface density of Au nanoparticles. The synergistic effects of both Fe3O4 and Au nanoparticles make the composites an excellent SEIRA substrate. In addition, the Fe3O4/Au nanocomposites were also utilized to determine the thiol and thione tautomers in -SH based molecules. (C) 2015 AIP Publishing LLC.