OICC Press International Journal of Nano Dimension 2228-5059 17 2 (April 2026) 2026 06 22 Increased sensitivity in planar waveguide plasmonic nanobiosensores based on two-dimensional graphene-MoS2 multilayers 10.57647/ijnd.2026.1704.05 EN Shabnam Andalibi Miandoab Department of Electrical Engineering, Ta.C., Islamic Azad University, Tabriz, Iran Nazlar Ghasemzadeh Department of Biomedical Engineering, Ta.C., Islamic Azad University, Tabriz, Iran Pedram Asmand Debaglou Department of Biomedical Engineering, Ta.C., Islamic Azad University, Tabriz, Iran Journal Article 2026 06 22 This paper investigates biosensors based on plasmonic nanostructures. A plasmonic sensor using planar optical waveguide consisting of graphene and metal oxide layers has been designed and simulated for   detecting biomolecules such as DNA. Plasmonics, branch of photonics, underpins many biophotonic applications, especially biosensing. Proposed biosensor relies on surface plasmon resonance in hybrid graphene/MoS2 structure, enabling high-sensitivity detection. Sensing mechanism analyzes transmission spectrum of an electromagnetic wave launched into waveguide, which varies with refractive index changes of biomolecules near surface. Performance has been evaluated at 633 nm and for different light incidence angles. Effects of number and arrangement of graphene and MoS2 layers on resonance angle, sensitivity, full width at half maximum (FWHM), and figure of merit (FOM) have been studied. Results show that a single graphene layer with a single MoS2 layer yields optimal performance, with sensitivity of 193 deg/RIU and FOM of 16.6 RIU-¹. Minimum FWHM of 11.62° and transmission intensity Tmin of 0.02 have been obtained. Increasing layer numbers due to optical absorption and plasmonic damping leads to higher optical losses, broader resonance curve, and reduced FOM. Electromagnetic field distribution and sensor characteristics have been analyzed via resonance angle shifts, identifying optimal structure with highest sensitivity and FOM.