Graphene, the one-atom-thick carbon lattice that is the
subject of last year's Nobel Prize in Physics, has found
application in surface plasmon resonance (SPR)
biosensing.
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| Fig. 1 The N-Layer model for surface plasmon
resonance (SPR) biosensor: prism | Au (50 nm) | graphene
(L 0.34 nm) | sensing medium, where L is the number of
graphene layers, and z0 = 100 nm is the thickness of
biomolecule layer. |
Adding a few graphene layers onto the conventional gold-film
SPR biosensor will boost up its sensitivity dramatically. The
improved sensitivity comes from the graphene layer's increased
adsorption of biomolecules and the graphene layer's optical
modification to the SPR.
Surface plasmon resonance (SPR) biosensors are optical sensors,
which use surface plasmon polariton waves to probe the
interactions between biomolecules and the sensor surface. In
the conventional SPR biosensor configuration, a thin metallic
film is coated on one side of the prism, separating the sensing
medium and the prism. The metallic film is typically made from
noble metals, such as gold and silver, which support the
propagation of surface plasmon polariton at visible light
frequencies. But, gold is usually preferred because it has good
resistance to oxidation and corrosion in different
environments.
However, biomolecules adsorb poorly on gold. This drawback
limits the sensitivity of the conventional SPR biosensor.
An attractive way to improve the sensitivity of SPR biosensor
is to functionalize the gold film with biomolecular recognition
elements (BRE) in order to enhance the adsorption of
biomolecules on the gold surface.
Here, we propose to use graphene as the BRE, where a sheet of
graphene is coated on the gold surface in the conventional SPR
biosensor setup. Graphene-on-Au (111) has been proposed and
fabricated recently, which is shown to stably adsorb
biomolecules with carbon-based ring structures (e.g. ssDNA).
This special property of graphene enables a greater refractive
index change near the graphene | sensing medium interface than
that of the conventional SPR biosensor. Moreover, the coating
of the gold surface with graphene will also modify the
propagation constant of surface plasmon polariton (SPP);
thereby change the sensitivity to refractive index change.
For more detail, including an in-depth explanation of how the
proposed graphene-on-gold SPR biosensor functions, please see
the attached pdf.
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| Fig. 2 (a) The surface plasmon resonance curves
for the conventional biosensor (L = 0) (black thin
lines) and the monolayer graphene biosensor (L = 1)
(blue thick lines) for He-Ne laser light (λ0 = 633
nm): prism (1.723) | Au (50 nm, 0.1726 + i 3.4218)
| graphene (L × 0.34 nm, 3 + i 1.149106) | water
(1.33) before (dashed lines) and after (solid
lines) the adsorption of biomolecules, assuming the
same refractive index change n = 0.005. (b) The
sensitivity enhancement SRIL/SRI0 as a function of
the number of graphene layers L. |
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Associated files
available for download
View/download the file 'Graphene_SPR_sensor.pdf
.
SOURCE
