Weighing graphene with QCM to monitor interfacial mass changes

In this Letter, we experimentally determined the mass density of graphene using quartz crystal microbalance (QCM) as a mechanical resonator. We developed a transfer printing technique to integrate large area single-layer graphene on QCM. By monitoring the resonant frequency of an oscillating quartz crystal loaded with graphene, we were able to measure the mass density of graphene as similar to 118 ng/cm(2), which is significantly larger than the ideal graphene (similar to 76 ng/cm(2)) mainly due to the presence of wrinkles and organic/inorganic residues on graphene sheets. High sensitivity of the quartz crystal resonator allowed us to determine the number of graphene layers in a particular sample. Additionally, we extended our technique to probe interfacial mass variation during adsorption of biomolecules on graphene surface and plasma-assisted oxidation of graphene. Published by AIP Publishing.