Complex nano-assemblies of polymers and carbon nanotubes
Brendan Mc Carthya, Jonathan N. Colemana, Richard Czerwb, Alan B. Daltonc, Marc in het Panhuisa, Daniel Tekleabb, Hugh J. Byrnec, David L. Carrollb, and Werner J. Blau*, a
aMaterials Ireland Polymer Research Centre, Physics Department, Trinity College Dublin,
Dublin 2, Ireland bDepartment of Physics and Astronomy, Clemson University,
South Carolina, USA cFacility for Optical Characterisation and Spectroscopy, School of Physics, Dublin Institute of Technology, Kevin St., Dublin 2, Ireland
Since the discovery of carbon nanotubes in 1991, researchers have envisaged potential applications such as nanoscale electronic circuits, bioelectronic nanomaterials, and the construction of complex carbon-based nano-machines. Thus, the assembly of basic building blocks of complex nano-architectures, e.g. conjugated polymers and nanotubes, has been a driving goal of much of the nano-science community. Assemblies of proteins onto nanotubes have recently been suggested as a possible biosensor. A first step toward realizing this goal may be the attachment to, or modification by carbon nanotubes of structures such as polymers. This leads to the possibility of assembling individual polymer molecules onto carbon nanotubes with the net effect being the modification of the polymer's electronic properties and structure in a predictable way. To accomplish this, clearly, a more detailed understanding of the interactions between conjugated polymers and carbon nanotubes must be sought. In this work, we describe the assembly of the polymer, poly(m-phenylenevinylene-co-2,5-dioctyloxy-p-phenylenevinylene), (PmPV), into a coating around single walled carbon nanotubes, (SWNT). Using scanning tunneling microscopy, (STM), and scanning tunneling spectroscopy, (STS), we demonstrate that the low energy electronic structure of the assembled material is dominated by the one-dimensional nature of the nanotube as reflected in van Hove singularities. Further, we examine the modifications to electronic structure at higher energies using spectroscopy, which suggests that the polymer's electronic structure is altered by the introduction of nanotubes.