Graphene as a Polymer Composite Nano Material and SERS Substrate

Abstract

Graphene is one of the carbon allotropes, and forms a one-atom-thick (0.142 nm) planar sheet of sp2 hybrid carbon atoms with a honeycomb crystal structure. The graphene has demonstrated unprecedented properties such as high charge transport mobility, high transparency, and mechanical strength, and due to these extraordinary characteristics, graphene has been considered as a next-generation nanomaterial for nanoelectornics, nanosensor, and nanocomposites. In this thesis, two kinds of graphene applications have been investigated for polymer nanocomposite material and the surface-enhanced Raman scattering (SERS) substrate. As a first part, we fabricated a free-standing multilayered graphene and PEDOT composite films by using a spin-coating technique. Poly(3,4-ethylenedioxythiophene) (PEDOT)-based film has relatively high con-ductivity, flexibility and transmittance. However, the improvement for mechanical strength and conductivity is still required to be adopted for commerical applications. Graphene, a one-atom-thick planar sheet of sp2-bonded carbon atoms is considered as an ideal nanocomposite material for these purposes. In this study, we have developed PEDOT and graphene composite films, two layered graphene/PEDOT and three layered graphene/PEDOT/graphene. The conductivity of a 32 nm-thick PEDOT film was improved more than twice by graphene deposition, while the high transmittance of the composite film was maintained over 90%. The mechanical strength of the PEDOT and graphene composite film shows 6-fold enhancement over the pristine PEDOT film. Due to the contribution of graphene layer for enhancing the mechanical strength, a 44 nm-thick graphene/PEDOT/graphene could be obtained as a free standing film by delaminating the graphene layer from the glass substrate under a weak base solution. These results imply that the graphene not only improves the conductivity and mechanical strength of PEDOT, but also enables to produce a free-standing film which could find ...