Detection of CO2 absorption in graphene using surface acoustic waves

CO
2
absorption mechanism in sheets of graphene layers prepared by thermal exfoliation of graphene oxide was investigated using surface acoustic waves. In this experiment, LiNbO
3
SAW delay-line device was spray coated with graphene flakes. The transmission at SAW frequencies was attenuated by more than 12.7 dB due to deposition of graphene. A maximum phase change ∼34 degrees was observed as the CO
2
pressure inside the chamber increased from 0.01 Torr to 700 Torr, which is at least 10 times than the phase shift observed on free surface of LiNbO
3
under similar conditions. Transient measurements on the graphene-coated sample indicate a phase change of 4 degree because of 0.43 mg/cm
³
of CO
2
absorption and subsequent full recovery after 20 min of CO
2
purging.