G. Zerbi , C. Mapelli, E. Meroni, C. Castiglioni
Dip. di Chimica Industriale e Ingegneria Chimica del Politecnico di
Milano,
P. Leonardo Da Vinci, 32 - 20133 Milano
A new interest in graphitic materials has grown recently due to the several possible techological applications. In particular, the synthesis of carbon nanotubes offers new possibilities for the development of nanodevices for applications in the field of electronics.
Vibrational spectroscopy is a powerful tool for the structural characterization of materials; moreover the understanding of the bands pattern in Raman and infrared spectra allows to obtain specific informations about charge mobility and pigreco electrons polarizability. These informations are very useful for obtaining structure/property correlations helpful in the search of new strategies for the development of new materials with improved characteristics.
For this reason we have carried out a systematic analysis of vibrational spectra of several "graphitic" compounds, ranging from molecular compounds properly synthetized, with different size and symmetry (poly-aromatic-hydrocarbons, PAH) to graphite (both highly crystalline graphite and disordered graphites).
This study has required the development of a common valence force field for all the compounds considered. Based on this force field vibrational frequencies have been predicted in a very satisfactory way and vibrational assignements have been done. This has allowed to discuss in a coherent way the relevant vibrational properties of this class of materials.
On this basis specific bands observed in the Raman spectra of disordered graphites have been ascribed to the presence of conjugated domains of few nanometers size.