Design of Different Leaky MoS₂ Nanoresonators Focusing on Biosensing Application

Novel atomically thin layered two-dimensional transition metal-dichalcogenides (TMDCs) such as MoS₂ are a promising material for different for optoelectronic applications [1] as well as biosensing [2,3]. In recent reported works, MoS₂based field-effect transistor platform was demonstrated for sensing of protein and DNA molecules [4,5]. Stacked heterostructure of MoS₂ and graphene were also explored for detecting Rhodamine 6G (R6G) molecules [6] and DNA hybridization [7].<br/>In this work, we propose different metasurface designs with MoS₂ for biosensing applications. The reason of using MoS₂ is due to its high refractive index (n &gt; 4 [8]) contrast with air and low absorption (k &lt; 1 [8]) in the visible wavelength range both at monolayer and bulk thicknesses. Also, MoS₂ surface favours bonding with carboxyl (-COOH) group, which makes it compatible for biofunctionalization. We have explored designs with MoS₂split-nanorings and nanotriangles. Finite difference time domain (FDTD) simulations were performed to optimize the different design parameters such as, inner and outer diameter, pitch, and split gaps of nanorings and side length and gap between nanotriangles, height of MoS₂ to study the leaky resonances for biosensing applications. Simulations have been performed with polystyrene particles (100 nm diameter) distributed (Gaussian distribution) over the device surface and the resonance wavelength shift was calculated with respect to the number of particles. The size of polystyrene particles was chosen as 100 nm because, because it matches with the size of small virus such as, SARS-CoV-2 and Influenza (H1N1). Here, we have considered polystyrene particles as most of the bioanalytes have similar refractive index to the polystyrene [9].<br/>One of the best design parameters for split-nanorings resonators are: diameter: nanoring’s outer diameter- 200 nm, inner diameter- 100 nm, height of MoS₂ nanoring- 150 nm, split gap- 50 nm with gap between two adjacent nanorings- 200 nm, and sensitivity achieved 59.49 nm/decade. The best sensitivity achieved with MoS₂nanotriangles array is 305.31 nm/decade with 100 nm side length of 100 nm of equilateral triangle. In this study our primary goal is to introduce a symmetry breaking structure to leak out the resonance field to attain high detection sensitivity for small size bioanalytes detection. Attachment of target bioanalytes on the MoS₂ nanoresonators surface disturbs the resonance field and induces a red-shift at the resonance wavelength and detection sensitivity is obtained by calculating the slope of resonance shift curve with respect to the bioanalytes concentrations. We will present the design optimization and comparison between different MoS₂nanoresonators detection performances.