Intact Pattern Transfer of Conductive Exfoliated Graphite Nanoplatelet Composite Films to Polyelectrolyte Multilayer Platforms

Layer-by-layer (LBL) assembly of polyelectrolyte multilayers (PEM) has become a ubiquitous process for creating functional ultrathin films. Introduced by Decher, the simple deposition of two oppositely charged polyions can be performed on many types of surfaces giving them new functionality based on the type of polyelectrolytes utilized. Incorporating new functional materials such as nanoparticles, proteins, or medicine (therapeutic chemicals) to alter film properties has lead to changes in mechanical, surface wetting, antireflective, and luminescent properties and resulted in applications as biosensors or in drug delivery. Exfoliated graphite has been incorporated into PEM and other polymer composite films for its unique mechanical, thermal and electrical properties, which are comparable to carbon nanotubes. Multilayer graphite, large stacks of sp hybridized graphene sheets bound together by weak van der Waals interactions, is an ideal starting material because it is inexpensive and available in large quantities. To take advantage of these properties, oxidized graphite has been incorporated into PEM. Oxidized graphite is created by the acid treatment of graphite, which exfoliates the multilayered graphene sheets into platelets of only a few graphene layers thick, creates a negative charge so that they are stable in aqueous solutions, and renders the graphite nonconductive. LBL assembly with a positively charged polyelectrolyte allows for the formation of PEM. To make conductive films, the oxidized graphite must be reduced back to graphite, which is not cost-effective and can change the film morphology. To our knowledge no one has performed LBL assembly using exfoliated graphite that was not oxidized. Mass production of these films for electronic devices requires a patterned film on the substrate surface. Patterning a single layer of graphite does not result in a large enough surface coverage to surpass the