Spectroscopic study of screening of interactions by a single layer graphene

Graphene supported on a substrate is used for electronic applications and it remains unknown whether the underlying substrate influences the performance of graphene. The conclusions based on the contact angle measurements remain inconclusive. In this study, we report the direct measurements of interfacial interactions by monitoring the shift of the sapphire OH vibrational peaks using interface sensitive sum frequency generation spectroscopy (SFG) in contact with liquids of different polarity. We compare this shift of the sapphire OH peak in contact with liquids of different polarity with and without the single-layer graphene in between. For polar liquids with strong hydrogen bonding interactions, we observe a lower shift for graphene-coated sapphire compared to those liquids in direct contact with a sapphire substrate, indicating screening of polar interactions by single-layer graphene. We also finds that liquids with aromatic groups show surprisingly low screening. We will discuss the differential screening ability of graphene layer for various polar and non-polar liquids. Our experimental results can aid in designing more efficient graphene-based technology.