Self-Assembled Large-Area Annular Cavity Arrays with Tunable Cylindrical Surface Plasmons for Sensing

Abstract

Surface plasmons that propagate along cylindrical metal/dielectric interfaces in annular apertures in metal films, called cylindrical surface plasmons (CSPs), exhibit attractive optical characteristics. However, it is challenging to fabricate these nanocoaxial structures. Here, we demonstrate a practical low-cost route to manufacture highly ordered, large-area annular cavity arrays (ACAs) that can support CSPs with great tunability. By employing a sol-gel coassembly method, reactive ion etching and metal sputtering techniques, regular, highly ordered ACAs in square-centimeter-scale with a gap width tunable in the range of several to hundreds of nanometers have been produced with good reproducibility. Ag ACAs with a gap width of 12 nm and a gap height of 635 nm are demonstrated. By finite-difference time-domain simulation, we confirm that the pronounced dips in the reflectance spectra of ACAs are attributable to CSP resonances excited in the annular gaps. By adjusting etching time and Ag film thickness, the CSP dips can be tuned to sweep the entire optical range of 360 to 1800 nm without changing sphere size, which makes them a promising candidate for forming integrated plasmonic sensing arrays. The high tunability of the CSP resonant frequencies together with strong electric field enhancement in the cavities make the ACAs promising candidates for surface plasmon sensors and SERS substrates, as, for example, they have been used in liquid refractive index (RI) sensing, demonstrating a sensitivity of 1505 nm/RIU and a figure of merit of 9. One of the CSP dips of ACAs with a certain geometry size is angle- (0-70 degrees) and polarization-independent and can be used as a narrow-band absorber. Furthermore, the nano annular cavity arrays can be used to construct solar cells, nanolasers and nanoparticle plasmonic tweezers.

Reproducible and Bendable SERS Substrates with Tailored Wettability Using Block Copolymers and Anodic Aluminum Oxide Templates

“…The detection limits of the hybrid substrates are found to be 10 −12 m , implying that the hybrid substrates can be utilized for practical biomolecular sensing applications. [ 37–39 ] The collected signal intensities of 100 individual points from different concentrations are plotted in the scatter diagram shown in Figure 4e. It is observed that even at dilute concentrations not only the intensity distributions are narrow (for concentrations 10 −8 , 10 −10 , and 10 −12 m , the RSD = 2%, 5%, and 4%, respectively) but also a good linear relationship is obtained (Figure 4f).…”

Dynamically Switchable Polarization-Independent Triple-Band Perfect Metamaterial Absorber Using a Phase-Change Material in the Mid-Infrared (MIR) Region

“…Thanks to Padilla et al, the perfect metamaterial absorber (PMA) was first proposed in 2008 in the field of electromagnetic waves, and thus PMAs has been developed rapidly [ 1 ]. In recent years, there has been a great need for perfect absorbers (PAs) in stealth [ 2 , 3 ], photovoltaics technology, sensors [ 4 , 5 ], and other opto-electronic devices [ 6 , 7 ]. High-resolution manufacturing technologies for nanostructures are becoming more common as they are updated, and PMAs are receiving more and more attention due to their multiple light control functions.…”

Tunable Plasmonic Resonances in the Hexagonal Nanoarrays of Annular Aperture for Biosensing

“…Recently, annular aperture arrays have drawn a wide research interest in the color filter [24,25], thresholdless nanolaser [26], and quarter-wave plates [27] in the visible range. However, there are few reports about annular aperture arrays for the application of biosensors [28].…”