Toward the Control of Partial Covalent Modification of Glassy Carbon Surfaces

Abstract

The patterning of surfaces with control over the relative ratios of different components represents one of the goals in the creation of devices for biosensing and energy storage, since it could improve the stability and sensitivity of the response. Considering this, a general methodology for the creation of controlled mixed monolayers on glassy carbon (GC) surfaces was developed, using osmium bipyridyl complexes and anthraquinone as model redox probes, but potentially applicable to more complex systems. The work consisted in the electrochemical grafting on GC of a mixture of diamine linkers in different ratios and characterised by protecting groups which allowed orthogonal deprotection. After optimisation of the deprotection conditions, it was possible to selectively remove one of the protecting groups, couple a suitable osmium complex and cap the residual free amines. The removal of the second protecting group allowed the coupling of anthraquinone. The characterisation of the surfaces by cyclic voltammetry showed the variation of the surface coverage of the two redox centres in relation to the initial ratio of the linking amine in solution. It was then possible to build patterned surfaces where the osmium complex acted as mediator for Glucose dehydrogenase (GDH), covalently bonded to GC through an exposed cysteine residue to a maleimide moiety.