Abstract
Near Infra-Red Surface Enhanced Raman Spectroscopy (NIR SERS) has gained huge attention in recent years as the conventional visible SERS suffers from overwhelming fluorescence background from the fluorophore resulting in the masking of Raman signals. In this paper, we propose a novel multi-layered SERS substrate- (Cu2O - Au) - Graphene – Au - for efficient NIR SERS applications. The proposed structure has a monolayer of Cu2O - Au core-shell particles on a Au substrate with 1 nm thick graphene spacer layer. Mie simulations are used to optimize the aspect ratios of core-shell particles to shift their plasmon resonances to NIR region using MieLab software. Further, Finite Difference Time Domain (FDTD) simulations using Lumerical software are used for the design of the multiparticle layered SERS substrate as MieLab software works only for single particle systems. Designed structure is shown to provide high field enhancement factor of the order of 108 at an excitation of 1064 nm thus ensuring the possibility of using the proposed structure as efficient NIR SERS substrate which could probably be used for various NIR sensing applications.
Highlights
Near Infra-Red Surface Enhanced Raman Spectroscopy (NIR SERS) has gained huge attention in recent years as the conventional visible SERS suffers from overwhelming fluorescence background from the fluorophore resulting in the masking of Raman signals
The aim of our present work is to model a novel and efficient near Infra-red (NIR) SERS substrate with large SERS field enhancement factor values at NIR excitation wavelength of 1064 nm
We propose a layered NIR SERS substrate with monolayer of Cu2O - Au core-shell particles on Au substrate separated by 1 nm thick graphene layer
Summary
Near Infra-Red Surface Enhanced Raman Spectroscopy (NIR SERS) has gained huge attention in recent years as the conventional visible SERS suffers from overwhelming fluorescence background from the fluorophore resulting in the masking of Raman signals. The proposed structure has a monolayer of Cu2O - Au core-shell particles on a Au substrate with 1 nm thick graphene spacer layer. Visible light excitation in SERS may result in photobleaching, plasmonic heating and in an overwhelming fluorescence background as most of the fluorophore analytes have strong emission within the visible region resulting in the masking of Raman signals[12]. These problems can be overcome by using larger wavelength excitations (NIR lasers)[13]. Mie calculations using MieLab software is used for the plasmon resonance study of single core-shell particle systems. Where Qsca, Qabs and Qext are the scattering, absorption and extinction efficiencies of particles, z is the size parameter
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