Reduced Self-Aggregation and Improved Stability of Silica-Coated Fe3O4/Ag SERS-Active Nanotags Functionalized With 2-Mercaptoethanesulfonate

Abstract

Nanocomposites combining magnetic and plasmonic properties are very attractive within the field of surface-enhanced Raman scattering (SERS) spectroscopy. Applications presented so far take advantage of not only the cooperation of both components but also synergy (enhanced properties), leading to multi-approach analysis. While many methods were proposed to synthesize such plasmonic-magnetic nanoparticles, the issue of their collective magnetic behavior, inducing irreversible self-aggregation, has not been addressed yet. Thus, here we present a simple and fast method to overcome this problem, employing 2-mercaptoethanesulfonate (MES) ions as both a SERS tag and primer molecules in the silica-coating process of the previously fabricated Fe3O4/Ag nanocomposite. The use of MES favored the formation of silica-coated nanomaterial comprised of well-dispersed small clusters of Fe3O4/Ag nanoparticles. Furthermore, adsorbed MES molecules provided a reliable SERS response, which was successfully detected after magnetic assembly of the Fe3O4/Ag@MES@SiO2 on the surface of the banknote. Improved chemical stability after coating with a silica layer was also found when the nanocomposite was exposed to suspension of yeast cells. This work reports on the application of 2-mercaptoethanesulfonate not only providing a photostable SERS signal due to a non-aromatic Raman reporter but also acting as a silica-coating primer and a factor responsible for a substantial reduction of the self-aggregation of the plasmonic-magnetic nanocomposite. Additionally, here obtained Fe3O4/Ag@MES@SiO2 SERS nanotags showed the potential as security labels for the authentication purposes, retaining its original SERS performance after deposition on the banknote.

Magnetic–Plasmonic Nanocomposites as Versatile Substrates for Surface–enhanced Raman Scattering (SERS) Spectroscopy

“…It was also emphasized that the presence of the SiO 2 shell led to a more homogeneous distribution of the MP nanocomposites, particularly under magnetic assembly conditions. [95] Furthermore, the SiO 2 shell not only protects MP nanocomposites from the external environment but also acts as a barrier that shields biological environments from potentially toxic nanocomposites. For example, when MP nanocomposites contain a plasmonic component like Ag, SiO 2 can serve as a barrier to prevent the release of Ag + ions, which could induce toxicity in various cell lines.…”

“…Subsequently, branched Ag nanoparticles were positioned on this supporting shell, enabling detection of cTnI at femtogram levels. [95] Copyright 2021 Frontiers. B) Synthesis route of Fe 3 O 4 @SiO 2 @Au/4-MPy composite microspheres: (a-b) TEM images, (c) bright-field TEM image and (d-h) corresponding elemental mapping of the composites.…”

Emerging integrated SERS-microfluidic devices for analysis of cancer-derived small extracellular vesicles

“…137 Surface modification such as polyethylene glycol (PEG coating) and 2-mercaptoethanesulfonate can be used to enhance electrostatic and steric repulsive forces between nanoparticles reducing the nanoparticle aggregation. 138,139 The sample pH and ionic content can also lead to surface charge neutralization and NP aggregation and should be considered in preparing the sample for microfluidic-SERS assays.…”

Raman Scattering-Based Biosensing: New Prospects and Opportunities

“…Bioconjugation of substrates containing carboxy or amino groups on the surface is carried out by covalent immobilization with the formation of an amide bond. For example, for silica-encapsulated SERS nanotag, thiol or amino-containing silanes with a bifunctional linker are used to bind to the receptor molecule [ 165 ]. In the absence of a stabilizing layer, both simple adsorption of bioreceptor molecules on the surface of the SERS substrate and covalent immobilization can be realized.…”