Structure and solid state properties of nano-graphite derived from nano-diamond

Abstract

According to theoretical predictions, nano-graphite has unique electronic features associated with the cooperation of non-bonding π-electronic state of edge origin (edge state) around the Fermi level (EF), which are entirely different from the electronic properties of ordinary bulk graphite. We investigate the structure and the electronic properties of nano-graphite obtained by heat-treatment-induced conversion from nano-sized diamond particles. The diamond-graphite conversion is completed around HTT of 1600°C, where nano-graphite particles are typically described in terms of polyhedrons with a hole inside and facets consisting of a stacking of 3-7 graphene planes with an in-plane size of ca.3 nm. The density of states at EF, is two orders of magnitudes larger than that of bulk graphite, suggesting an important contribution of the edge states to the electronic features. Intercalation compounds (GIC) with donor (K) and acceptor (Br, I) are prepared. The structure does not have a definite staging feature due to the finite size effect. Interestingly, iodine is found to form GIC, in contrast to bulk graphite that does not give I-GIC. The charge transfer rate becomes reduced in donor GICs in comparison with that of the bulk counterpart, whereas that in acceptor GICs has an opposite trend. The charge transfer makes the role of the edge state less important.