A metal-dielectric photonic crystal-based glucose sensor with sensitivity enhancement by using 2D materials

Metal-dielectric photonic crystals (MDPhCs) that support the excitation of Bloch-like surface waves (BLSWs) at the interface of an MDPhC and the adjacent medium (analyte) have emerged as a very promising alternative for sensing gaseous analytes with high sensitivity. In this paper we report on an extension of the concept for glucose sensing when the BLSW-based resonances in the Kretschmann configuration are accompanied by narrow dips and are characterized by ultra-high sensitivities. Moreover, one of the possible solutions to enhance the sensitivity represents an MDPhC with a 2D material overlayer, such as black phosphorus or molybdenum disulfide (MoS2). For an MDPhC comprising two bilayers of TiO2/Au with a termination layer of TiO2, we demonstrate that the BLSW-based resonances are resolved for TE waves when simulated glucose solutions are considered, and the glucose analyte refractive index (RI) is in a range of 1.32797-1.32867 at a wavelength of 1.55 um, corresponding to physiologically relevant glucose concentrations of 0-500 mg/dL. Using the wavelength interrogation, an RI sensitivity of 17.4 um/RI unit (RIU), a figure of merit (FOM) of 915 RIU-1, and a limit of detection (LOD) of 5.7x10-6 RIU were attained. The analysis extended to six monolayers of MoS2 on the MDPhC revealed that even if the angle of incidence is greater, the RI sensitivity is increased up to 20.2 um/RIU, representing an enhancement of more than 87% compared to the MDPhC alone, the FOM reached 808 RIU-1, and the LOD is as low as 5.0x10-6 RIU. This research is the demonstration of exceptional properties of the BLSW-based sensors employing MDPhCs whose sensitivity can be enhanced by using 2D materials. Such sensors are potentially well suited to a variety of biosensing applications.