Hybrid nanoparticle–nanoline plasmonic cavities as SERS substrates with gap-controlled enhancements and resonances

Abstract

We present hybrid nanoline-nanoparticle plasmonic substrates which allow easily achievable sub-5 nm gaps and a possibility of large-area fabrication. These substrates--based on plasmonic nanocavities formed by arrays of plasmonic nanoparticle (NP) dimers lying inside periodic metal nanolines (NLs)--can be used as tunable surface enhanced Raman scattering (SERS) substrates due to the tunability of cavity modes in the gap regions. Theoretical studies were conducted, using finite difference time domain (FDTD) modeling, to understand the plasmon resonance tunability as a function of gaps in these hybrid plasmonic substrates. The gaps forming the nanocavities include those between nanolines and nanoparticles (NL-NP) and between two nanoparticles (NP-NP). Our analysis reveals that these gaps play a combined role in tuning the resonance wavelength and the magnitude of electromagnetic field enhancement. Moreover, distinct structure-dependent plasmon resonance peaks are present in addition to material-dependent resonance peaks characteristic to the metal involved. Replacing the spherical particle arrays inside the nanolines with nanorod arrays revealed the possibility of tuning the plasmon resonance in the near-infrared regime. This indicates that there is a possibility of tuning the plasmon resonance wavelength to any region of the visible or near-infrared spectrum by changing the size or shape of the particles assembled inside these plasmonic nanolines.

Glucose detection using SERS with multi-branched gold nanostructures in aqueous medium

“…23 The success of SERS is highly dependent on the interaction between adsorbed molecules and the surface of plasmonic nanostructures. In the last years, many studies have strived to optimize substrate structure and conguration to maximize enhancement factors such as new plasmonic materials [24][25][26] with different shapes and sizes 27,28 that support increased SERS enhancement. The SPR of a metal nanoparticle may be tuned throughout visible and near-infrared (NIR) wavelengths by varying the size and shape or the aspect ratio.…”

Rapid Large-Scale Assembly and Pattern Transfer of One-Dimensional Gold Nanorod Superstructures

“…The observed two-file Au NR assembly opens up new possibilities not only for assembling nanorods in a chainlike structure but also for controlling the spacing between nanorod chains. Such a control over nanorod spacing was shown in a recent theoretical finite difference time domain (FDTD) calculation 38 to be of great potential in amplifying plasmon coupling and enhancing nearinfrared tunability. While such patterns have been observed on spherical nanoparticles with chemically modified surfaces, 39 the gratings used in this work were not modified in any form.…”

Nanoline-gap controlled self assembly of plasmonic nanoparticles inside plasmonic nanolines

“…More specifically, these plasmonic substrates can be employed for surface enhanced Raman scattering (SERS), which allows the inherently weak Raman signals from trace amount of analytes to be sufficiently enhanced for efficient detection. Moreover, plasmonic nanostructures with sub-10 nm gaps lead to a very high electromagnetic (EM) enhancement of SERS signals due to the formation of highly localized electromagnetic hotspots and thus, can be employed as highly sensitive SERS-based chemical or biological sensors [6][7][8][9][10]. However, for employment as efficient SERS based sensors, these plasmonic substrates must have the capability to be fabricated controllably and reproducibly.…”