Improved Surface Plasmon Effect in Ag-based SPR Biosensor with Graphene and WS2: An Approach Towards Low Cost Urine-Glucose Detection

Gold and silver are the two notable noble metals with wide implications in surface plasmon resonance (SPR) based sensors. Gold possesses a superior SPR phenomenon compared to silver, however, with extremely high costs. To resolve this problem, the current study proposes a new gold-free SPR biosensor design employing silver as the noble metal for efficient detection of blood glucose using urine as the biosample. The proposed design employs two types of 2D materials such as graphene and tungsten disulfide (WS2) to enhance the sensitivity of the silver-based SPR biosensor. An investigation for design of a low-cost biosensor for urine-glucose detection is done using the proposed configuration. The glucose concentration in the biosample ranges from 0 to 15 mg/dl (for normal persons) and 0.625 gm/dL, 1.25 gm/dL, 2.5 gm/dL, 5 gm/dL, and 10 gm/dL (for diabetic persons), with corresponding refractive indices of 1.335, 1.336, 1.337, 1.338, 1.341, and 1.347. The material's type, order, and thickness have been chosen through numerous case studies. It is worth noting that, with 4-layer graphene (0.34 nm) and 4-layer WS2 (0.8 nm), the proposed silver-based SPR biosensor shows improved sensitivity (288.86(o)/RIU) and figure of merit (88.89/RIU) than its gold-based counterpart (sensitivity 150(o)/RIU). Finally, this study is also compared with similar reported literatures. The proposed structure has potential to develop low-cost and efficient SPR-based biosensors (glucose sensors), with a substantial shift in resonance angle of SPR curves as shown in the present study.