Magnetic iron oxide cores with attached gold nanostructures coated with a layer of silica: An easily, homogeneously deposited new nanomaterial for surface-enhanced Raman scattering measurements

Abstract

Nanostructures made of magnetic cores (Fe3O4) with many smaller plasmonic (Au) nanostructures attached were covered with a very thin layer of silica. The first example of the application of this type of material for surface-enhanced Raman scattering (SERS) measurements is presented. (Fe3O4@Au)@SiO2 nanoparticles turned out to be very efficient substrates for SERS measurements. Moreover, due to the nanomaterial’s strong magnetic properties, it can be easily manipulated using a magnetic field, and it is therefore possible to form homogeneous layers (with no significant ‘coffee-ring’ effect) of (Fe3O4@Au)@SiO2 nanoparticles using a very simple procedure: depositing a drop of a sol of such nanoparticles and evaporating the solvent after placing the sample in a strong magnetic field. Synthesised (Fe3O4@Au)@SiO2 nanostructures have been used for the SERS detection of penicillin G in milk. Good quality SERS spectra of penicillin G were obtained even at a concentration of penicillin G in milk of 1 nmol/l – this means that the SERS detection of penicillin G in milk is possible at a concentration lower than the maximum residue limit of penicillin G in milk established by the European Commission..