Grafting of manganese phthalocyanine on nanocrystalline diamond films



Thin boron-doped nanocrystalline diamond (NCD) films have been prepared by microwave plasma enhanced chemical vapour deposition (MPCVD) and used as platforms for grafting of photosensitizer (manganese phthalocyanine, Mn-Pc). The surface of the as-grown films is H-terminated; in order to modify it and study the influence of the termination on the attachment of Mn-Pc the NCD films were subjected to O2 plasma or NH3/N2 plasma treatments. Contact angle measurements and XPS results showed a successful exchange of the surface termination with OH- or NH2-groups. Manganese phthalocyanine molecules were grafted on the NCD surfaces with different terminations, after which each sample was subsequently characterized by XPS and Raman spectroscopy. Finally, the NCD/Mn-Pc samples were used for the preparation of electrodes which were tested in an electrochemical cell with a Pt counter electrode and an Ag/AgCl reference electrode; phosphate buffered saline was used as electrolyte. The characteristics of the electrodes were measured by cyclic voltammetry (CV) and open circuit potential (OCP) in dark and under illumination with a light-emitting diode (LED) operating at 770 nm (a wavelength close to the absorption maximum of Mn-Pc). The first results indicated that after plasma modifications NCD surfaces are suited for Mn-Pc grafting.