Electrografting and Langmuir-Blodgett: Covalently Bound Nanometer-Thick Ordered Films on Graphite.

Abstract

We present two different molecular organizations obtained from octadecylamine (ODA) molecules on a highly oriented pyrolytic graphite (HOPG) surface: (i) self-organized physisorbed ODA molecules lying flat on the surface and (ii) a strongly electrografted compact crystalline monolayer of ODA molecules standing up on the surface. This new structure is obtained by combining the Langmuir-Blodgett transfer of an ODA Langmuir film onto HOPG with oxidative electrografting. The presence of an organic film on HOPG is characterized by attenuated total reflectance-infrared spectroscopy and Raman spectroscopy, while atomic force microscopy and scanning tunneling microscopy allow the observation of the two molecular organizations with adsorbed molecules lying flat on HOPG or strongly grafted in an upright position on the HOPG surface. Interestingly, the second molecular organization preserves a hexagonal symmetry and its lattice parameters are intermediate between those of ODA Langmuir films and that of the HOPG underlying surface. The functionalization of surfaces with organic films is a major issue in the design of sensors with biomedical applications or organic electronics and energy storage devices and these structures may find applications in these fields.