Direct Measurements of the Interaction between Pyrene and Graphite in Aqueous Media by Single Molecule Force Spectroscopy:  Understanding the π−π Interactions

Pyrene derivatives can absorb onto the surface of carbon nanotubes and graphite particles through π−π interactions to functionalize these inorganic building blocks with organic surface moieties. Using single molecule force spectroscopy, we have demonstrated the first direct measurement of the interaction between pyrene and a graphite surface. In particular, we have connected a pyrene molecule onto an AFM tip via a flexible poly(ethylene glycol) (PEG) chain to ensure the formation of a molecular bridge. The π−π interaction between pyrene and graphite is thus indicated to be ∼55 pN with no hysteresis between the desorption and adhesion forces.