European researchers have developed a sensor made from graphene to
detect molecules such as proteins and drugs. The sensor is
reconfigurable and highly sensitive, “exploiting the unique electronic
and optical properties of graphene for a practical application,” a
release stated.
Teams from the Swiss University
EPFL (école Polytechnique Fédérale de Lausanne) and the Institute of
Photonic Sciences in Barcelona used graphene to improve upon infrared
absorption spectroscopy for molecule detection. Traditionally, this
method uses light to excite molecules, which vibrate differently
depending on their nature, and the vibration creates a unique signature
that can be read in reflective light.
(Graphene's
higher level of field confinement enables highly sensitive vibrational
spectroscopy and refractive-index based sensing. Source: EPFL)
This
method isn’t effective for nanometrically-sized molecules, which are
often significantly smaller than the 6 micron wavelength of the infrared
photon used to detect the molecule. Researchers found that graphene is
able to focus the light on a specific spot to accurately “hear” the
vibration of a nanometric molecule.
An EPFL publication stated:
When
the light arrives, the electrons in graphene nanostructures begin to
oscillate. This phenomenon, known as “localized surface plasmon
resonance,” serves to concentrate light into tiny spots, which are
comparable with the dimensions of the target molecules. It is then
possible to detect nanometric structures.
Potential
applications for the sensor range from detecting gas leakage, sensing
toxic and explosive gas, measuring and detecting DNA and proteins as
well as contaminants in water, according to the reports.
Graphene
can be tuned to different frequencies by applying voltage — which is
not possible with current sensors, the release stated. As a result, the
process can also show the nature of the bonds that connect atoms in a
molecule by assessing the nuances between different vibrations.
When
graphene's electrons oscillate in different ways, it’s possible to
"read" all the vibrations of the molecule on its surface. "We tested
this method on proteins that we attached to the graphene. It gave us a
full picture of the molecule," said Hatice Altug, an associate professor
in the Bionanophotonic Systems Laboratory at EPFL.
Altug
said the graphene-based process could also work for polymers and many
other substances. The results of this study appeared in the journal
Science.
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