European researchers claim to have harnessed the optical and electronic properties of graphene in the development of a sensitive and tuneable sensor capable of detecting nanoscale molecules such as proteins and drugs.
Developed by a team from Swiss research University EPFL (École Polytechnique Fédérale de Lausanne) and the Institute of Photonic Sciences in Barcelona, the device is claimed to have significant advantages over infrared absorption spectroscopy, the most commonly used molecule detection method.
This existing technique uses light to excite molecules, which can then be identified courtesy of their unique vibration signature. However, whilst it’s effective for larger molecules, the wavelength of an infrared photon (around 6,000 nanometres) means that it struggles to detect the vibration of nano-scale molecules.
In an effort to improve on this technique the team turned to graphene and began by creating a pattern of nanostructures on the surface of the graphene by bombarding it with electron beams and etching it with oxygen ions.
When exposed to light, electrons in these nanostructures began to oscillate, and this phenomenon concentrates light into tiny spots, which are comparable with the dimensions of the target molecules. According to the group, it is then possible to detect nanometric compounds in proximity to the surface.
The group claims that the process can also help 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.
Commenting on potential applications for the device, ICFO’s Prof Valerio Pruneri said: “the concept can be used in different application fields, ranging from gas leakage, toxic and explosive gas sensing, and contaminants in water to DNA and proteins.”
The results are described in an article appearing in the latest edition of the journal Science.