Optimizing the Tin Selenide (SnSe) Allotrope/Gold-Based Surface Plasmon Resonance Sensors for Enhanced Sensitivity
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Optimizing the Tin Selenide (SnSe) Allotrope/Gold-Based Surface Plasmon Resonance Sensors for Enhanced Sensitivity Pericle Varasteanu 1,2 Received: 19 March 2020 / Accepted: 9 August 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The 2D material tin selenide monolayer (SnSe) has attracted a lot of attention due to its excellent optoelectronic properties. This study focuses on the investigation of the potential improvement of the response of surface plasmon resonance (SPR) sensors by coating the gold layer with SnSe allotrope (α, δ, ε) monolayers. Using an optimization algorithm along with the transfer matrix method (TMM), we determined the optimal thickness of the gold layer as a function of the number of monolayers added to significantly increase the sensor’s response in terms of reflectivity and phase. With respect to reflectivity, sensitivity increased by 20% in comparison with the optimal bare gold structure, whilst with respect to phase, sensitivity was approximately two orders of magnitude greater than the bare gold structure. Our results demonstrate that SPR sensors modified with SnSe monolayers could be used in diagnostic applications where both high sensitivity and small concentration of analyte are required. Keywords Tin selenide allotropes . Surface plasmons resonance . Enhanced sensitivity . Optimization
Introduction Sensors based on surface plasmon resonance (SPR) have attracted tremendous interest over the past two decades due to their high sensitivity, real-time monitoring of surface biomolecular interactions, and label-free detection capabilities. Their high sensitivity and specificity have led to various studies in chemistry and biology, such as detecting free cell DNA during the early stages of pregnancy [1], protein-antibody reactions [2], and single-molecule sensing [3]. Moreover, SPR sensors have been used for measuring the refractive index [4] or as temperature sensors in a liquid environment [5]. Their high sensitivity is attributed to the resonant energy transfer between the incidence radiation energy and the surface plasmon polaritons (SPP), propagating along the metal-dielectric interface. Even though the incidence light could not be coupled to the surface plasmons directly (due to the mismatch between the wavevectors), a prism in attenuated total refraction (ATR) was used to increase the incidence light
* Pericle Varasteanu [email protected] 1
National Institute for R&D in Microtechnology-IMT Bucharest, Voluntari, Romania
2
Faculty of Physics, University of Bucharest, 405 Atomistilor Street, 077125 Magurele, Romania
wavevector [6]. The change in the dielectric’s refractive index increases the SPP wavevector such that in order to restore the resonance condition, it is necessary to increase the incident radiation wavevector which can be achieved by increasing the incidence angle. In this way, the displacement of the incidence angle satisfying the resonant condition or the resonance angle is a measure of the dielectric’s refractive index ch
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