Abstract
We investigate both numerically and experimentally the optical properties and biosensing of gold elliptical nanoring (ENR) arrays with various aspect ratios. The gold ENR exhibits a strong localized surface plasmon bonding mode in near-infrared region, whose peak wavelength is red-shifted as increasing the aspect ratio under longitudinal and transverse polarizations. Furthermore, the disk- and hole-like optical properties for longitudinal and transverse modes are observed, which cause different behaviors in field intensity enhancement. For biomolecule sensing, we find that both modes show increased surface sensitivities when enlarging the aspect ratio of gold ENR.
Highlights
Noble metal nanoparticles have unique optical properties arising from the excitation of localized surface plasmon resonance (LSPR) which produces a large local field enhancement
We investigate both numerically and experimentally the optical properties and biosensing of gold elliptical nanoring (ENR) arrays with various aspect ratios
The gold ENR exhibits a strong localized surface plasmon bonding mode in near-infrared region, whose peak wavelength is red-shifted as increasing the aspect ratio under longitudinal and transverse polarizations
Summary
Noble metal nanoparticles have unique optical properties arising from the excitation of localized surface plasmon resonance (LSPR) which produces a large local field enhancement. Elliptical nanoring (ENR) is a hybrid nanoparticle geometry that offers the highly tunable plasmon resonances essentially arising from plasmon hybridization between an oval-shaped nanodisk and an elliptical nanohole This hybridization results in two plasmonic modes which are the low-energy symmetric bonding mode and the high-energy asymmetric antibonding mode respectively [13,14]. Compared with the transverse bonding mode, we find that the longitudinal bonding mode shows the larger wavelength shift for gold ENR with the higher aspect ratio when applied to very local changes of refractive index as induced by the presence of few molecules These results are important for the design of nanostructure-based LSPR biosensors for detecting biological interactions, such as antibody-antigen, biotin-streptavidin, and toxinreceptor interactions
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