Multilayer Substrate‐Mediated Tuning Resonance of Plasmon and SERS EF of Nanostructured Silver

Abstract

A thin-film of dielectric on a reflecting surface constituting a multilayer substrate modulates light intensity due to the interference effect. A nanostructure consisting of randomly oriented silver particles of different shapes, sizes, and interparticle spacings supports multiple plasmon resonances and is observed to have a broad extinction spectrum that spans the entire visible region. Combining the two systems by fabricating the nanostructure on the thin-dielectric film of the multilayer substrate yields a new composite structure which is observed to modulate both the extinction spectrum and the SERS EF (surface enhanced Raman scattering enhancement factor) of the nanostructure as the thickness of the thin-film dielectric is varied. The frequency and intensity of the visible extinction spectrum vary dramatically with the dielectric thickness and in the intermediate thickness range the spectrum has no visible band. The SERS EF determined for the composite structure as a function of the thin-film dielectric thickness varies by several orders of magnitude. Strong correlation between the magnitude of the SERS EF and the extinction intensity is observed over the entire dielectric thickness range indicating that the extinction spectrum corresponds to the excitation of the plasmon resonances of the nanostructure. A significant finding which has potential applications is that the composite structure has synergic effect to boost SERS EF of the nanostructure by an order of magnitude or more compared to the same nanostructure on an unlayered substrate.

Solution processed nanomanufacturing of SERS substrates with random Ag nanoholes exhibiting uniformly high enhancement factors

“…Our observations are also consistent with the interference-enhanced SERS signals reported in the literature for graphene, ITO nanoparticles and Ag nanoparticles. [46][47][48] 3.5 Electrical activation for relatively uniform SERS While enhancement factors up to 10 8 to 10 9 have been achieved in highly aggregated systems 49 as well as in controlled nanoparticle aggregation systems 50 due to the presence of 'hotspots' at specic locations, issues relating to substrate reproducibility and uniformity oen remain unattended. 51 Although the Ag lms with random holes show high SERS signals, smaller Ag nanocrystals present in the voids lead to a standard deviation of 9.49% of the enhancement factor as seen previously in Fig.…”

Metal island film-based structures for sensing using spectrophotometry and ellipsometry

“…The near field enhancement is largest for very small particles and inter-particle distances, which are typically few nanometers in the case of MIF. Strong coupling between SPR of metal nanoparticles and propagating surface plasmon of a nearby metal film (polariton), enhances this electric near field largely [11][12][13]. This work compares the sensitivity of MIF-based plasmonic structures, consisting of a single MIF layer or including a compact ML nearby MIF, to the quantity of dielectric material surrounding the metal nanoparticles.…”

Colored porous silicon as support for plasmonic nanoparticles

“…For SERS the amplification of the LSP resonances in the presence of these films is assumed to raise the detection sensitivity, and variations of the enhancement factor by several orders of magnitude, in dependence on the layer thickness, were already reported. 6 Porous silicon (PSi) formation represents a specific approach to realize a dielectric spacing layer between plasmonic particles and a semiconductor support. Recently, improved SERS activity could be reported for PSi templates, built by electrochemical preparation in HF containing solutions and subsequent deposition of Au-nanoparticles (Au-NPs).…”