Lithographically Patterned Electrodeposition of Gold, Silver, and Nickel Nanoring Arrays with Widely Tunable Near-Infrared Plasmonic Resonances

Abstract

A novel low-cost nanoring array fabrication method that combines the process of lithographically patterned nanoscale electrodeposition (LPNE) with colloidal lithography is described. Nanoring array fabrication was accomplished in three steps: (i) a thin (70 nm) sacrificial nickel or silver film was first vapor-deposited onto a plasma-etched packed colloidal monolayer; (ii) the polymer colloids were removed from the surface, a thin film of positive photoresist was applied, and a backside exposure of the photoresist was used to create a nanohole electrode array; (iii) this array of nanoscale cylindrical electrodes was then used for the electrodeposition of gold, silver, or nickel nanorings. Removal of the photoresist and sacrificial metal film yielded a nanoring array in which all of the nanoring dimensions were set independently: the inter-ring spacing was fixed by the colloidal radius, the radius of the nanorings was controlled by the plasma etching process, and the width of the nanorings was controlled by the electrodeposition process. A combination of scanning electron microscopy (SEM) measurements and Fourier transform near-infrared (FT-NIR) absorption spectroscopy were used to characterize the nanoring arrays. Nanoring arrays with radii from 200 to 400 nm exhibited a single strong NIR plasmonic resonance with an absorption maximum wavelength that varied linearly from 1.25 to 3.33 μm as predicted by a simple standing wave model linear antenna theory. This simple yet versatile nanoring array fabrication method was also used to electrodeposit concentric double gold nanoring arrays that exhibited multiple NIR plasmonic resonances.

Ultranarrow Band Absorbers Based on Surface Lattice Resonances in Nanostructured Metal Surfaces

“…Our results indicate that the most significant factor in determining the resonance wavelength is the periodicity, while other parameters such as metal thickness, width, and the size of the nanostructures provide slight modification in the resonance wavelength. 26 However, these geometrical parameters could significantly change the absorption intensity as discussed in Supporting Information. SLRs can be identified for the NBA resonance because periodic effect typically yields narrow band resonance depending on the lattice constant.…”

Top‐Up Fabrication of Gold Nanorings

“…The position of the extinction maximum is in accordance with published values of similar structures. [18] The formation of closed gold nanorings after 15 min of electroless plating are supported by the SEM images displayed in Figure 4. The gold nanorings have a thickness of approximately 60 nm, and their surface is rather rough.…”

The preparation and electrochemical characterization of urchin-like NiCo2O4 nanostructures

“…3g-j, a few microflakes are synthesized on the surface of the CC at the reaction time of 0.5 h. With the increase of the reaction time, the center area of the microflakes becomes gradually thin, and forms a hole at the reaction time of 2.5 h. They are called microring. Whose morphology is analogous to the porous NiCo 2 O 4 hexagonal ring-graphene hybrid [28], which is attributed to the chemical etching induced by the excessive amounts of NH 4 F [29,30]. With the help of NH 4 F, the nanowires will grow on microrings.…”