Self-Organized Conductive Gratings of Au Nanostripe Dimers Enable Tunable Plasmonic Activity

Abstract

Plasmonic metasurfaces based on quasi-one-dimensional (1D) nanostripe arrays are homogeneously prepared over large-area substrates (cm 2 ), exploiting a novel self-organized nanofabrication method. Glass templates are nanopatterned by ion beam-induced anisotropic nanoscale wrinkling, enabling the maskless confinement of quasi-1D arrays of out-of-plane tilted gold nanostripes, behaving as transparent wire-grid polarizer nanoelectrodes. These templates enable the dichroic excitation of localized surface plasmon resonances, easily tunable over a broadband spectrum from the visible to the near-and mid-infrared, by tailoring the nanostripes' shape and/or changing the illumination conditions. The controlled self-organized method allows the engineering of the nanoantennas' morphology in the form of Au-SiO 2 -Au nanostripe dimers, which show hybridized plasmonic resonances with enhanced tunability. Under this condition, superior near-field amplification is achievable for the excitation of the hybridized magnetic dipole mode, as pointed out by numerical simulations. The high efficiency of these plasmonic nanoantennas, combined with the controlled tuning of the resonant response, opens a variety of applications for these cost-effective templates, ranging from biosensing and optical spectroscopies to high-resolution molecular imaging and nonlinear optics.Appl. Sci. 2020, 10, 1301 2 of 10 ranges, such as Surface Enhanced Raman Scattering (SERS) [17][18][19][20][21] and Surface Enhanced Infrared Absorption (SEIRA) spectroscopy [11,[22][23][24]. Despite the high degree of control provided by the lithographic methods, the reduced patterned areas, limited at the micrometric scale, and/or the multi-step, time-consuming processes strongly hinder the effective application of optimized plasmonic metasurfaces in cost-effective optoelectronic, biosensing and/or diagnostic devices [25,26]. On the other hand, self-assembled nanofabrication methods [27][28][29] allow the large-area functionalization of surfaces, but are generally characterized by low homogeneity and the limited possibility of tailoring the nanostructure's shape.Here, large-area (cm 2 ) highly ordered plasmonic templates are prepared by a novel maskless self-organized nanofabrication method. A nanoscale wrinkling instability in glasses induces quasi-1D nanopatterned templates, which enable the confinement of out-of-plane tilted plasmonic nanostripes and/or nanostripe dimers [30]. The method allows the easy tailoring of the nanostripes' morphology, and thus the tuning of their localized plasmon resonances across the visible (VIS) and near-infrared (IR) spectrum. Most interestingly, our technique enables the engineering of Au-SiO 2 -Au nanostrip dimers supporting hybridized plasmon resonances [31]. A strong sub-radiant near-field confinement can therefore be achieved by exciting the hybridized magnetic dipole mode, with the additional possibility to tune its resonance over a broadband VIS and near-IR spectrum. The possibility to effectively tailor the nanoscale morphology-t...

Surface-enhanced photoluminescence and Raman spectroscopy of single molecule confined in coupled Au bowtie nanoantenna

“…Recently, a variety of new types of plasmon nanoantennas such as nanocube, nanorod, nanostar, bowtie nanoantenna and honeycomb nanoantenna with resonance wavelength in the range from visible to near-infrared spectroscopy have been designed to improve electromagnetic field [22][23][24][25], which can widely extend the applicability in surface science, photothermal conversion, optoelectronic device and biosensing [26][27][28][29][30][31]. In the above plasmonic structure, the novel bowtie nanoantenna, composed of two metallic triangular plates, in particular is one of the most promising candidates for surface-enhanced photoluminescence spectroscopy since it can simultaneously enhance and confine electric field at sharp tips and tiny gaps.…”