Physicists have found that graphene could be ideal for manufacturing plasmonic devices capable of detecting explosive materials based on the analysis of a single molecule.
Scientists have long been fascinated by the potential applications of a quasiparticle called the plasmon. In the case of a solid body, plasmons are the oscillations of free electrons and harnessing their effects could bring about a breakthrough in high-accuracy electronics and optics according to a study recently published in Physical Review B.
Of special interest are the effects arising from the surface interactions of electromagnetic waves with plasmons – usually in the context of metals or semimetals, as they have a higher free electron density. One possibility opened up by plasmonic effects is subwavelength light focusing, which increases the sensitivity of plasmonic devices to a point where they can distinguish a single molecule.
Such measurements are beyond what any conventional (classical) optical devices can achieve. Unfortunately, plasmons in metals tend to lose energy quickly due to resistance, and for this reason they are not self-sustained. To tackle this issue scientists are turning to composite materials with a predefined microstructure, including graphene.
Researchers at the Laboratory of Nanostructure Spectroscopy headed by Professor Yurii Lozovik have developed a quantum model that predicts plasmonic behaviour in graphene, describing the operation of a surface-plasmon-emitting diode (SPED) and the nanoplasmonic counterpart of the laser – known as the spaser – whose construction involves a graphene layer. Both devices would operate within the infrared region of the spectrum and could be used across a number of applications, such as detecting explosive materials or toxic chemicals.
“The graphene spaser could be used to design compact spectral measurement devices capable of detecting even a single molecule of a substance, which is essential for many potential applications. Such sensors could detect organic molecules based on their characteristic vibrational transitions ('fingerprints'), as the light emitted/absorbed falls into the medium infrared region, which is exactly where the graphene-based spaser operates,” said Alexander Dorofeenko, one of the study’s authors.