Functionalization of graphite, glassy carbon, and polymer surfaces with highly oxidized sulfur species by plasma treatments

Abstract

SO 2 and SO 2+H 2O plasma treatments have been performed on highly oriented pyrolytic graphite, glassy carbon and several polymers in order to functionalize their surface with sulfur in different oxidation states. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy measurements prove that highly oxidized sulfur species (SO 3, SO 3H, SO 4, and SO 4H) as well as covalently bound sulfur and low oxidized sulphur species (SO and SO 2) are formed and chemisorbed at the surface by plasma treatment. The oxidation state of the adsorbed sulfur species depends on the bias potential applied to the sample. The greater the bias, the lower the oxidation state. The same behavior as a function of the plasma parameters is found for all substrates. The maximal coverage of the surface with sulfur functionalities has been estimated to be about one monolayer. The modifications of the surface topography have also been measured with atomic force microscopy. © 2002 American Institute of Physics.