Graphite intercalation by nitric acid: conduction ESR and theoretical studies Original Research Article

Results of an in situ conduction ESR (CESR) study of HNO3 molecules intercalation into narrow highly oriented pyrolytic graphite (HOPG) slab are presented. The changes in the graphite CESR signal line shape, intensity and line width and the stepwise changes both of intensity and line width of CESR signal from intercalated sample have been clearly detected during this reaction. Under the assumption that the graphite CESR signal evolution is caused by the advance of a boundary separating the intercalated and non-intercalated HOPG, the average probability value of spin reorientation during the collision of current carriers with this interface and the constant of two-dimensional diffusion of nitric acid molecules into HOPG were extracted from experimental data. Using the dependence of chemical potential on exposure time of graphite in HNO3 atmosphere offered by the authors for the experimental conditions, the stepwise evolution of CESR signal intensity from intercalated HOPG was calculated theoretically.