Periodic arrays of plasmonic crossed-bowtie nanostructures interspaced with plasmonic nanocrosses for highly sensitive LSPR based chemical and biological sensing.

Abhijit Das,Kamal Kumar,Anuj Dhawan

doi:10.1039/d0ra09012c

Abhijit Das, Kamal Kumar + Show 1 more

Open Access

https://doi.org/10.1039/d0ra09012c

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Abstract

In this paper, we present novel localized surface plasmon resonance (LSPR) sensors based on periodic arrays of gold crossed-bowtie nanostructures interspaced with gold nanocross pillars. Finite difference time domain (FDTD) numerical simulations were carried out to model bulk sensors as well as localized sensors based on the plasmonic nanostructures being proposed. The geometrical parameters of the plasmonic nanostructures are varied to obtain the best possible sensing performance in terms of sensitivity and figure of merit. A very high bulk sensitivity of 1753 nm per unit change in refractive index (nm RIU−1), with a figure of merit for bulk sensing (FOMbulk) of 3.65 RIU−1, is obtained for these plasmonic nanostructures. This value of bulk sensitivity is higher in comparison to previously proposed LSPR sensors based on plasmonic nanopillars and nanocrosses. Moreover, the optimized LSPR sensors being proposed in this paper provide maximum sensitivity of localized refractive index sensing of 70 nm/nm with a FOMlocalized of 0.33 nm−1. This sensitivity of localized refractive index sensing is the highest reported thus far in comparison with previously reported LSPR sensors. It is also demonstrated that the operating resonance wavelengths of these LSPR sensors can be controllably tuned for specific applications by changing the dimensions of the plasmonic nanostructures.

Highlights

Surface plasmons are collective oscillations of free electrons at metal–dielectric interfaces and can be excited in metallic thin lms or gratings as propagating plasmons or in metallic nanoparticles as localized surface plasmons
This value of bulk sensitivity is higher in comparison to previously proposed localized surface plasmon resonance (LSPR) sensors based on plasmonic nanopillars[17] and nanocrosses.[39]
In localized LSPR sensing, it is assumed that the plasmonic nanostructures are coated with a 2 nm thick layer of a biomolecule having a higher refractive index as compared to the solvent

Summary

Introduction

Surface plasmons are collective oscillations of free electrons at metal–dielectric interfaces and can be excited in metallic thin lms or gratings as propagating plasmons (surface plasmon polaritons) or in metallic nanoparticles as localized surface plasmons. In some of the structures proposed by us, values of FOMbulk > 6 RIUÀ1 have been achieved This value of bulk sensitivity is higher in comparison to previously proposed LSPR sensors based on plasmonic nanopillars[17] and nanocrosses.[39] the optimized LSPR sensors being proposed in this paper provide the maximum sensitivity of localized refractive index sensing of 70 nm/nm with a FOMlocalized of 0.33 nmÀ1. The plasmon resonance wavelengths of these LSPR sensors can be tunably varied for a wide spectral range (from 1100 nm to 2500 nm) by changing the geometrical parameters of the plasmonic nanostructures being proposed This can allow LSPR-based bulk and localized sensing to be carried out at desired wavelengths of interest

Structure and simulation details

Bulk LSPR sensing

Localized LSPR sensing

Conclusions