Electrochemical functionalization of epitaxial graphene

Abstract: In this work graphene has been functionalized with antibodies. Different functionalization methods of graphene already found in literature have been evaluated. An electrochemical functionalization process with subsequent immobilization of antibodies have been chosen for this thesis. The purpose of the thesis has been formulated in collaboration with Graphensic AB. From them a wish to implement an electrochemical cell has been brought up. If graphene could be functionalized it could be used as an electrode in an electrochemical cell to measure many different processes. Four graphene samples have been used, all of them manufactured by Graphensic AB. The graphene has been grown epitaxially on the silicon terminated surface of 4H-silicon carbide. The samples have been of a high quality, three of them were monolayers, monolayer compromising more than 95% of the surface, and one a bilayer, bilayer compromising more than 50 % of the surface. The functionalization could be divided into two steps. First the attachment of aryl radicals to the graphene surface. Then the attachment of antibodies to these aryls, both a primary antibody and a secondary. The attachment of aryl radicals were done in an electrochemical cell utilizing a diazonium salt. The decomposition of the diazonium salt into aryl radicals was driven electrochemically in the cell. The graphene samples were measured electrochemically between each functionalization step so that the changes could be evaluated. The impedance and the peak values of the cyclic voltammograms increased after the diazonium salt step. They then decreased again to values close to the initial value when attaching antibodies. The attachment of the secondary antibody slightly increased the peak values of the cyclic voltammogram. The secondary antibody contained a fluorescent molecule which was used to evaluate the functionalization. For two of the samples this showed that the functionalization most likely had been successful. For the other two it was hard to distinguish whether or not it had been successful.