Covalent grafting of organic layers on sputtered amorphous carbon: Surface preparation and coverage density

The covalent attachment of ester-, pyridine-, and ferrocene-functionalized organic layers to amorphous carbon surfaces, grown by graphite sputtering in Ar-H-2 mixtures, is reported. The surface modification is based on a low temperature (160 degrees C) liquid-phase process. Thermally assisted grafting of linear alkenes is investigated by means of X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and contact angle measurements. The beneficial role of surface oxygen removal by argon ion sputtering or thermal treatment prior to the ester grafting step is also discussed. Careful XPS data analysis provides a quantitative estimate of the density (0.2-4.3 x 10(11) cm(-2)) of attached molecules as a function of surface preparation. The large packing density has been confirmed by the voltammetric response of a ferrocene-functionalized carbon surface.