A large-area (over
1 cm2) nanoparticle-in-ring array
(NPIRA) with strong Fano resonance is fabricated by a low-cost shadow
sphere lithography (SSL) method. Controlled narrow nanogaps of 8–20
nm are formed between the nanoparticles (NPs) and rings. Quadrupole
modes are excited in the nanogaps and interact with the dipole mode
of the NPs and ring, resulting in two Fano resonances. The two Fano
resonances are in the visible and near-infrared region, respectively,
and show a maximum refractive index sensitivity of 425 nm/RIU and
a figure of merit of 4.7–7.1 RIU–1. In addition,
the NPIRAs show enhanced Raman intensity due to the strong electric
fields confined in the nanogaps. The structure has great potential
for the dual plasmonic sensor applications, i.e., surface-enhanced
Raman scattering and refractive index sensing, and provides a robust
sensing performance for each.
By combining nanosphere lithography and glancing angle deposition, a morphological transition from disconnected patchy silver (Ag) coated nanosphere particles to a connected Ag nanohole sheet on close-packed nanosphere monolayers has been demonstrated, which significantly changes the optical property of the Ag nanostructure deposited. For different sized nanosphere monolayers, when the vapor incident angle was set to be 55°, the transmission spectra showed complicated features when the Ag deposition thickness was less than 60 nm. When the thickness was large enough (≥60 nm), a distinguished extraordinary optical transmission (EOT) peak was observed. The EOT peak wavelength position is independent of the Ag thickness deposited and is proportional to the nanosphere diameter. The obtained EOT peaks possess a high quality factor and have high transmission values compared to those reported in the literature for similar structures. The Monte Carlo growth simulations demonstrate the morphological transition from the patchy arrays to nanohole arrays while the electromagnetic numerical calculations confirm the change in the optical properties. Such a high quality EOT response could be used for constructing better sensors or developing other plasmonic applications.
The plasmonic property of Ag patchy particles fabricated using a colloid monolayer and oblique angle deposition shows significant variations due to the multidomain nature of the monolayer. A swinging oblique angle deposition method is proposed to create uniform patchy particles. Both numerical calculations and experiment show that when the swinging angle is larger than 90°, the resulting plasmonic patchy particles have similar morphology and demonstrate uniform optical response that does not depend on the monolayer domain orientation. These uniform patchy plasmonic particles have great potential for plasmonic-based applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.