  Surface plasmon resonance (SPR) is generally observed by excitation of
surface plasmon polaritons on the metal (Au/Ag) surface. In order to utilize
the SPR phenomenon for sensing application, the metal surface is functionalized
with suitable ligands. Although such functionalization can enhance the specific
adsorption capability of the sensor however due to large thickness of the
ligands, the plasmonic field of the metal surface becomes less sensitive
towards the adsorption of analytes. In the next generation SPR based sensor,
graphene can be utilized not only as plasmonic material but also a suitable
ligand for attracting analytes through {\pi}-{\pi} interaction. In this
article, we present our theoretical simulation studies on the observation of
SPR phenomenon using graphene monolayer (MLG), bilayer graphene (BLG) and
in-plane twisted layers of BLG (T-BLG) as plasmonic materials deposited over
Zinc-Selenide substrate. The Kretschmann configuration under wavelength
interrogation setup was simulated and SPR wavelength for graphene systems/water
interface was estimated. The bio-sensing simulation was performed and the
sensing parameters viz. sensitivity, figure-of-merit (FOM) and plasmonic field
for different graphene systems were obtained. Interestingly, the excellent
sensing parameters were found in T-BLG system with relative in-plane twist
angle near to magic angle viz. 1o. The enhancement is due to strong coupling
between the layers twisted at the magic angle. This study demonstrates that the
monolayer, bilayer and twisted bilayer graphene can be employed as a standalone
layer system for not only generation of plasmonic fields but also enhanced
sensing due to its intrinsic pi-pi interactions with bio-analytes.
