Titanium is a very hard metal which makes it an ideal electrode material for use in harsh electrochemical environments. The ability to combine 3D printing with deposition of another metal opens up the possibility of designing complex, 3D electrode structures with interesting electrochemical properties such as plasmonically enhanced electrochemiluminescence (ECL).
In this article we report on the fabrication and characterisation of a novel 3D titanium electrode array using sintered laser melting. The electrodes are characterised with high resolution scanning electron microscopy (SEM) and HR-SEM. The microstructure of the titanium is found to be granular with a rough surface which is significantly larger than that observed for polished gold electrodes. This roughness is thought to be due to the amorphous nature of the titanium. The ECL response obtained from the titanium array is sigmoidal and exhibits strong scan rate dependence. This is consistent with the 3D structure of the titanium electrode array giving rise to enhanced mass transport of both the luminophore and co-reactant over that expected from semi-infinite linear diffusion.
The cyclic voltammograms for the oxidation and reduction of [Ru(bpy)3]2+ shown in Figure 4 demonstrate that the 3D titanium electrode array can be used to both oxidise and reduce this ruthenium complex in an aqueous solution. The currents and peak potentials observed for the first step of oxidation are well fitted to the Cottrell equation using a diffusion coefficient, ko, estimated from the SEM images of the titanium array. The currents and peak potentials observed at the second oxidation step are less satisfactorily modelled using the Cottrell equation. This may be due to the fact that the oxidation is followed by a reduction and the reaction may not proceed according to the classical thermodynamic calculations.