Designing Efficient Localized Surface Plasmon Resonance-Based
Sensing Platforms: Optimization of Sensor Response by Controlling
the Edge Length of Gold Nanoprisms
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Abstract
Over the past few years, the unique localized surface
plasmon resonance
properties of plasmonic nanostructures have been used to design label-free
biosensors. In this article, we demonstrate that it is the difference
in edge length of gold nanoprisms that significantly influences their
bulk refractive index sensitivity and local sensing efficiency. Nanoprisms
with edge lengths in the range of 28–51 nm were synthesized
by the chemical-reduction method and sensing platforms were fabricated
by chemisorption of these nanoprisms onto silanized glass substrates.
The plasmonic nanosensors fabricated from 28 nm edge length nanoprisms
exhibited the largest sensitivity to change in bulk refractive index
with a value of 647 nm/RIU. The refractive index sensitivity decreased
with increasing edge length, with nanoprisms of 51 nm edge length,
displaying a sensitivity of 384 nm/RIU. In contrast, we found that
the biosensing efficiency of sensing platforms modified with biotin
increased with increasing edge length, with sensing platforms fabricated
from 51 nm edge length nanoprisms displaying the highest local sensing
efficiency. The lowest concentration of streptavidin that could be
measured reliably with this edge length nanoprism was 1.0 pM and the
limit of detection was 0.5 pM, which is much lower than found with
gold bipyramids, nanostars, and nanorods. In addition, the electromagnetic-field
decay length of the sensing platforms was substantially influenced
by the edge-length of the nanoprisms