Light inspires one-atom-thick material to recognize gas molecules
Oxygen is an important gas, the amount of which has to be monitored in many fields of human activity, such as energy production, transport and medicine. For that purpose the sensors are used that transform the oxygen concentration in the surrounding environment to electric current and subsequently to bit-sequence. The newest gas sensors are based on thin film materials and the sensors that comprise merely one atomic layer are under the development. In a recently published article in the top class journal of applied physics Applied Physics Letters, the scientists at the Institute of Physics of the University of Tartu showed that the electrical conductivity of the one-atom-thick carbon material, i.e. graphene, becomes sensitive to oxygen level due to ultraviolet light.
Although the high gas sensitivity of graphene was demonstrated already in 2007, it was carried out in a very sterile environment of inert gases. In ambient atmosphere, where the gas sensors should really function, it is much more complicated. It becomes clear from the study of the scientists of the University of Tartu that in ambient atmosphere, the surface of graphene is totally passivated as so many oxygen and water molecules have been bound on its surface that there is no room left. Light, in particular ultraviolet light activates the surface of the sensor.
Of course, oxygen is not the only gas present in ambient atmosphere that could be detected by the nanosensor made of graphene. There are many more other useful, dangerous or toxic gases that need to be monitored and light could be a useful means for detecting those also. The research group of the Institute of Physics now studies the application of this principle in case of other gases under the large-scale project of the European Union “Graphene Flagship”, with the purpose to design and develop with their industrial partners from the European Union a graphene-based sensor node for environmental monitoring.
"The studies of graphene as a material with superb properties is a very good example on how quickly it is possible go from basic studies to practical applications – the researchers of this two-dimensional material were awarded with the Nobel Prize of Physics only in 2010. Recently initiated basic studies by the physicists and material scientists of the University of Tartu on the international level have created an opportunity to transfer recent scientific results into a new type of sensor in cooperation with enterprises. I hope that in near future we are able to find cooperation partners in Estonia, with whom we can use graphene in high-tech products," said Marco Kirm, the Vice Rector for Research of the University of Tartu.
A. Berholts, T. Kahro, A. Floren, H. Alles, R. Jaaniso. Photo-activated oxygen sensitivity of graphene at room temperature. Appl. Phys. Lett. 105, 163111 (2014). http://dx.doi.org/10.1063/1.4899276.