Two-Dimensional Transition Metal Dichalcogenide Enhanced Phase Sensitive Plasmonic Biosensors: Theoretical Insight

Atomically thin transition metal dichalcogenide nanomaterials have shown superior optical and electronic properties in the two-dimensional (2D) scale. They are considered as promising alternative materials to graphene. Here, we have precisely engineered a plasmonic sensing substrate with four types of two-dimensional transition metal dichalcogenide nanomaterial to achieve significant phase sensitivity improvement. Phase modulation is currently the most sensitive interrogation method among all the plasmonic detection approaches. The tuning of the substrate thickness in an atomic scale with a step less than 1 nm allows the efficient modulation of phase signals. More importantly, the optical absorption rate for each of these nanomaterials is different and can be tuned by changing the number of 2D layers, where perfect absorption and interrogation of the plasmonic signal can be obtained. Through systematically optimizing the parameters of the transition metal dichalcogenide structured plasmonic substrate, we can balance the optical absorption efficiencies and the electron losses at the plasmonic resonance condition. All of the calculations were based on the transfer matrix method and Fresnel equations. A very low minimum reflectivity of 3.2560 x 10(-8) was demonstrated with an excitation wavelength of 1024 nm, showing a complete transfer (similar to 100%) of the light energy into the plasmon resonance energy. The ultradark singularity at the resonance dip leads to an ultrahigh plasmonic sensitivity of 1.1 x 10(7) deg/RIU, which is 3 orders of magnitude higher than those with bare metallic sensing substrates used in commercial plasmonic sensors. The resolution is also improved by at least 3 orders of magnitude compared with conventional substrates.