Covalent immobilization of graphene oxide on biomedical grade CoCr alloy by an improved multilayer system assembly via Silane/GO bonding

Improvements in durable lubrication together with minimized wear are essential for obtaining long-term, functioning metallic joint prostheses. To achieve this objective, CoCr surface was functionalized with Graphene Oxide (GO) and characterized by FTIR and XPS. CoCr alloy was subjected to alkalinization in order to generate high hydroxyl content on the surface. FTIR and XPS revealed reactive OH groups, enabling intermediate coupling via (3-aminopropyl) triethoxysilane (APTES), which was cured at 45 °C and 75 °C for 24 h and 30 min, respectively. FTIR revealed cross-linked films (Si–O–Si), inferring condensation and self-assembly of silane layers, while XPS revealed the presence of NH2, enabling chemical binding of GO. Silane-coated CoCr disks were immersed in GO solution at 60 °C for 12h and 24h, respectively. FTIR displayed CC band confirming the assembly of GO on silane-coated CoCr surfaces. XPS revealed three possible surface mechanisms: (1) reaction between primary amines of APTES and epoxy groups of GO; (2) free –OH groups in APTES and carboxyl groups in GO; and (3) reaction between APTES primary amines and –OH from carboxyl groups of GO. Overall, the multilayer system CoCr–OH–Si45-GO24h showed covalent functionalization of metal substrate with GO to a large extension of surface area among all the multilayer systems studied. •Cross-linking of self-assembled silane layers on CoCr surface was proved by FTIR.•Opening of epoxy ring through nucleophilic attack was proved by XPS on the surface.•GO and APTES on surface mainly react through epoxy and primary amine, respectively.•Additional reactive groups from GO and APTES might be involved in surface reaction.•Chemisorption of GO on CoCr surface was achieved through intermediate silane layers.