Tunable mid-infrared graphene sensor detects nanoscale molecules
The device is claimed to have advantages compared with infrared absorption spectroscopy, the most commonly used molecule detection method.
The European researchers claim to have harnessed the optical and electronic properties of graphene to create a tunable sensor capable of detecting nanoscale molecules such as proteins and drugs.
The researchers used graphene to improve on a well-known molecule-detection method: infrared absorption spectroscopy, which has important limitations when applied to molecules at the nano-scale. The wavelength of the infrared photon directed at a molecule is around 6 microns (6000 nm), while the target measures only a few nanometres, making it challenging to detect the vibration of such a small molecule.
If given the correct geometry, graphene is capable of focusing light on a precise spot on its surface and ‘hearing’ the vibration of a nanometric molecule that is attached to it. In the study , researchers first pattern nanostructures on the graphene surface by bombarding it with electron beams and etching it with oxygen ions. When the light arrives, the electrons in graphene nanostructures begin to oscillate. The phenomenon concentrates light into tiny spots, which are comparable with the dimensions of the target molecules making it possible to detect nanometric compounds in proximity to the surface.
In addition to identifying the presence of nanometric molecules, the process can also reveal the nature of the bonds connecting the atoms that make up the molecule. Graphene is able to pick up the sound given off by each of the strings because it is able to identify a whole range of frequencies. Researchers ‘tuned’ the graphene to different frequencies by applying voltage, which is not possible with current sensors. Making graphene’s electrons oscillate in different ways makes it possible to ‘read’ all the vibrations of the molecule on its surface.
Potential applications for the sensor range from gas leakage, toxic and explosive gas sensing as well as measuring and detecting DNA and proteins as well as contaminants in water.
The results are described in an article appearing in the journal Science.
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