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.
Highlights
Development of functional nanocomposites is a fast-growing branch of research in the advanced materials science
In this study we focused on the fabrication of surface-enhanced Raman scattering (SERS)-active and magneto-responsive Fe3O4/Ag nanocomposite, coated with a relatively thin layer of silica, as well as on demonstration of the applicability of the material as nanotags
Operating Principle This work aimed at addressing the issue of self-aggregation of silicacoated magnetic-plasmonic nanocomposites on the example of hybrid nanostructures composed of plasmonic AgNPs attached to a magnetic Fe3O4 core, embedded in a SiO2 shell
Summary
Development of functional nanocomposites is a fast-growing branch of research in the advanced materials science. These nanocomposites can exhibit multiple or improved optical, electronic, magnetic, or catalytic properties compared to their individual single-component counterparts. Such multiphase structures were found useful in light harvesting (Liu et al, 2014; Xu et al, 2015), photoelectrochemistry (Kolodziejak et al, 2017; Kwiatkowski et al, 2017), nanomedicine (Inamuddin and Mohammad, 2018), sensing (Wang et al, 2012; Yuan et al, 2013), nanolasers (Passarelli et al, 2016; Galanzha et al, 2017), etc. Nanocomposites exhibiting more than only plasmonic properties allow for the design of SERS-active materials showing multifunctionality (Han et al, 2013; Lai et al, 2013) and/or improved analytical performance: both in terms of limit of detection (LOD) (Du and Jing, 2011) and accuracy of the measurement (Frank et al, 2015)
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