Fe3O4-protected gold nanoparticles: New plasmonic-magnetic nanomaterial for Raman analysis of surfaces

The First Silver-Based Plasmonic Nanomaterial for Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy with Magnetic Properties

“…The measurements were carried out for films of (Fe 3 O 4 @Ag)@SiO 2 nanoparticles prepared with and without the application of a strong external magnetic field during evaporation of the solvent. As in the case of the previously formed magnetic–plasmonic materials for SHINERS measurements [ 16 , 17 ], the deviation from the mean value was significantly lower for films prepared when a magnetic field was used during the drying process. It is likely that the main reason for a certain nonreproducibility of the measured intensity of the SERS spectra of p-MBA, observed even in the case of measurements carried out on (Fe 3 O 4 @Ag)@SiO 2 layers prepared with the application of a strong external magnetic field during evaporation of the solvent, was a partial agglomeration of magnetic–plasmonic structures, the occurrence of which was facilitated by the magnetic properties of the nanomaterial used.…”

“…As already reported in some previous publications, the intensity of the Raman spectrum recorded in a single measurement using a more homogeneously deposited layer of magnetic–plasmonic nanostructures is significantly more reproducible [ 16 , 17 ]. Figure 7 shows a logarithm of the intensity of the strongest Raman band at 1587 cm − 1 in 50 subsequently measured Raman spectra of a Pt/p-MBA monolayer covered with (Fe 3 O 4 @Ag)@SiO 2 nanoparticles.…”

“…The magnetic–plasmonic systems produced were used to perform SERS and SHINERS measurements of a model surface, namely a monolayer of para-mercaptobenzoic acid on platinum (Pt/p-MBA). As described previously, Pt/p-MBA monolayers can be easily formed in a very repeatable way by soaking a flame-annealed platinum plate for about one day in a saturated aqueous solution of para-mercaptobenzoic acid [ 16 ]. Figure 5 shows the Raman spectra of a Pt/p-MBA monolayer before the deposition of the plasmonic nanoresonators, and of such monolayers covered with Ag, Fe 3 O 4 @Ag, and (Fe 3 O 4 @Ag)@SiO 2 nanomaterials.…”

“…In some cases, an interesting improvement of SERS nanoresonators is the introduction of strong magnetic properties in such structures, which makes it easy to manipulate SERS nanomaterials by means of a strong magnetic field. Such modification allows for simple concentration of nanostructures from their sol [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ], or their easy and homogeneous deposition on an analyzed surface [ 16 , 17 , 18 , 19 ] by means of the following simple wet deposition method: (i) the deposition of a layer of a sol of the SERS nanoresonators with magnetic properties followed by (ii) the evaporation of the solvent while the sample is placed in a strong magnetic field [ 16 , 17 , 18 ]. When placed in a strong magnetic field, the magnetic–plasmonic SERS nanoresonators are quickly ‘magnetically glued’ to the analyzed surface, and therefore they do not migrate to the boundary of the drying region.…”

“…There have already been two literature reports on magnetic nanomaterials for SHINERS measurements in the form of gold nanoparticles protected with Fe 3 O 4 (Au@Fe 3 O 4 ) [ 16 ] and in the form of silica-covered nanostructures composed of magnetic Fe 3 O 4 cores with gold nanostructures attached ((Fe 3 O 4 @Au)@SiO 2 ) [ 17 ]. In this contribution, we report on a modification of previously developed (Fe 3 O 4 @Au)@SiO 2 SHINERS nanoresonators using silver plasmonic nanostructures instead of gold ones.…”