Reversible Intercalation of Organic Solvents in Graphite and Its Hindrance by a Strongly Adsorbing Supramolecular Monolayer

Abstract

At elevated temperatures, the prototypical organic solvents used to study the self-assembly of supramolecular monolayers at liquid-solid interfaces alter a graphite substrate by intercalation. As a consequence, less strongly bound supramolecular monolayers become thermodynamically unstable, as probed by scanning tunneling microscopy. Complementary characterization by atomic force microscopy, confocal Raman spectroscopy and low energy electron microscopy consistently points to subsurface changes in the top few layers of the graphite substrate due to solvent intercalation. High-temperature annealing at 900 degrees C in the vacuum restores the adsorption properties of the graphite substrates, indicating a high activation energy for deintercalation. However, strongly adsorbing hydrogen-bonded monolayers of trimesic acid inhibit solvent intercalation and thus protect the graphite substrate. Mildly solvent-intercalated graphite may prove useful as an easily prepared graphitic material with further weakened adsorption properties. The solvents commonly used for self-assembly studies at liquid-solid interfaces alter graphite substrates at elevated temperatures by intercalation, rendering weakly bound supramolecular monolayers thermodynamically unstable. This solvent intercalation can be reversed by high-temperature vacuum annealing at 900 degrees C or prevented by strong and persistent adsorption of supramolecular monolayers of trimesic acid. imageAt elevated temperatures, the prototypical organic solvents used to study the self-assembly of supramolecular monolayers at liquid-solid interfaces alter a graphite substrate by intercalation. As a consequence, less strongly bound supramolecular monolayers become thermodynamically unstable, as probed by scanning tunneling microscopy. Complementary characterization by atomic force microscopy, confocal Raman spectroscopy and low energy electron microscopy consistently points to subsurface changes in the top few layers of the graphite substrate due to solvent intercalation. High-temperature annealing at 900 degrees C in the vacuum restores the adsorption properties of the graphite substrates, indicating a high activation energy for deintercalation. However, strongly adsorbing hydrogen-bonded monolayers of trimesic acid inhibit solvent intercalation and thus protect the graphite substrate. Mildly solvent-intercalated graphite may prove useful as an easily prepared graphitic material with further weakened adsorption properties. The solvents commonly used for self-assembly studies at liquid-solid interfaces alter graphite substrates at elevated temperatures by intercalation, rendering weakly bound supramolecular monolayers thermodynamically unstable. This solvent intercalation can be reversed by high-temperature vacuum annealing at 900 degrees C or prevented by strong and persistent adsorption of supramolecular monolayers of trimesic acid. image