Urea biosensor utilizing graphene-MoS<inf>2</inf> and Kretschmann-based SPR

Abstract

In this paper, a Kretschmann-based surface plasmon resonance (SPR) biosensor based on a combination of two dimensional (2D) nanomaterial and graphene is presented. The Kretschmann configuration is well known as one of the most effectively used technique for plasmon excitation. It leads to improvement in the efficiency of an urea biosensor due to high adsorption. In this work, we investigated the effect of 2D materials such as molybdenum disulfide (MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) with a fine layer of graphene deposited on a plasmonic material, gold (Au), and a oxide material, aluminium oxide (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ), into the configuration. Simulation is based on finite-difference time-domain (FDTD) method for analysis. The performance of SPR biosensor can be monitored by analyzing the sensitivity and minimum reflectance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> ) of the SPR curves. The measurements are observed at 670 nm and 785 nm for urea detection. The molarity and refractive index (RI) is varied from 0.625 gm/dl to 10 gm/dl and RI of 1.335 to 1.347 for the sensing layer. The results show that there is 20% increase in the sensitivity of the urea biosensor with the addition of MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and graphene at optical wavelength of 670 nm. This indicates that the proposed SPR biosensor is capable of increasing the sensitivity of urea detection using an easy and label-free method.