Plasmonic Biosensing with Nano-Engineered Van der Waals Interfaces.

Observing a Goos-Hänchen (GH) shift of the incident light beam provides a simple and convenient method of detecting fast phase variations without the need for cumbersome direct phase measurements. Here, we show that few-monolayers-thick van der Waals structures (WS₂ , MoSe₂ and graphene) nano-engineered onto a plasmonic surface can enhance the phase variation sensitivity to analyte presence, leading to more than 3 orders of magnitude increase in the Goos-Hänchen shift (ca. 886 mm/RIU for a WS₂ /graphene/Au multilayer). The detection limit is evaluated to be as low as 0.1 aM (6.7 pg/mL) for bovine serum albumin protein with molecular weight of 67 kDa and 1 fM (24.4 ng/mL) for biotin (244 Da) molecules.