High-Performance Biosensing Using Arrays of Plasmonic Nanotubes

Abstract

We show that aligned gold nanotube arrays capable of supporting plasmonic resonances can be used as high performance refractive index sensors in biomolecular binding reactions. A methodology to examine the sensing ability of the inside and outside walls of the nanotube structures is presented. The sensitivity of the plasmonic nanotubes is found to increase as the nanotube walls are exposed, and the sensing characteristic of the inside and outside walls is shown to be different. Finite element simulations showed good qualitative agreement with the observed behavior. Free standing gold nanotubes displayed bulk sensitivities in the region of 250 nm per refractive index unit and a signal-to-noise ratio better than 1000 upon protein binding which is highly competitive with state-of-the-art label-free sensors.

Surface plasmon and photonic mode propagation in gold nanotubes with varying wall thickness

“…1 The advantage of metallic nanotubes compared with nanowires, in terms of sensing capability, is their greater surface-area-to-volume ratio and evanescent surface plasmon mode propagation at the metalanalyte interface on both the inner and outer tube surfaces. 2 Sensing enhancement as a function of increased surfacearea-to-volume ratio has been observed previously when comparing solid gold nanospheres to gold nanoshells, with the latter showing a greater wavelength shift per unit change in surrounding refractive index. 3,4 The resonant properties of noble metal nanotubes, like nanoshells, can be tuned through control of inner diameter and wall thickness.…”

“…These simulations demonstrate that large 200-nm ID AuNTs support three different mode types that depend on excitation direction and polarization: (1) when excitation is incident at the AuNT end, which we refer to as end-on excitation, propagating SPP modes are excited along the length of the nanotube walls, analogous to that of planar metal films and IMI waveguides. 14 (2) In addition to the propagating SPP mode, a photonic mode is excited in the core of the nanotube. Similarly, for excitation normal to the nanotube long axis (which we refer to as normal excitation) and polarized parallel to the nanotube long axis, both a propagating SPP mode and a photonic mode are also supported.…”

Advanced AuNMs as nanomedicine’s central goals capable of active targeting in both imaging and therapy in biomolecules

“…There are many successful examples of SPR sensing as a medical diagnostic tool, which have been reported for biomarkers, pathogen detection and hormone analysis with high sensitivity. For example, McPhillips et al [75] employed aligned Au nanotube arrays to strengthen performance of refractive index sensors in biomolecular binding reactions. Generally, sandwich [76] and competitive or inhibition assay [77] are two major detection approaches in SPR biosensor.…”

CdS nanoparticles decorated anatase TiO 2 nanotubes with enhanced visible light photocatalytic activity

“…So far, they have been extensively used in a lot of fields, such as solar cells, lithium batteries, photodetectors, light waveguides, gas sensing, photocatalysis [1][2][3][4][5][6][7][8][9][10], and particularly used as photocatalysts in the degradation of organic pollutants in environment [11]. Among 1D TiO 2 nanostructures, TiO 2 nanotubes (TNTs) possess high specific surface area and nanotubular morphology, the nanotubular features of TiO 2 provide a large amount of channels for enhanced electron transfer, which is important during photocatalytic oxidation of organic compounds.…”