AUTHOR=Douman Samantha F. , De Eguilaz Miren Ruiz , Cumba Loanda R. , Beirne Stephen , Wallace Gordon G. , Yue Zhilian , Iwuoha Emmanuel I. , Forster Robert J. 

TITLE=Electrochemiluminescence at 3D Printed Titanium Electrodes

JOURNAL=Frontiers in Chemistry

VOLUME=Volume 9 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2021.662810

DOI=10.3389/fchem.2021.662810

ISSN=2296-2646

ABSTRACT=The fabrication and electrochemical properties of a 3D printed titanium electrode array are described.  The array comprises twenty-five round cylinders (0.015 cm radius, 0.3 cm high) that are evenly separated on a 0.48 cm x 0.48 cm square porous base (total geometric area of 1.32 cm2).  The electrochemically active surface area consists of fused titanium particles and exhibits a large roughness factor 17.  In acidic, oxygenated solution, the available potential window is from approximately -0.3 V to +1.2 V. The voltammetric response of ferrocyanide is quasi-reversible arising from slow heterogeneous electron transfer due to the presence of a native/oxidatively formed oxide.  Unlike other metal electrodes, both [Ru(bpy)3]1+ and [Ru(bpy)3]3+ can be created in aqueous solutions which enables electrochemiluminescence to be generated by an annihilation mechanism. Depositing a thin gold layer significantly increases the standard heterogeneous electron transfer rate constant, ko, by a factor of approximately 80 to a value of 8.0±0.4x10-3 cm s-1 and the voltammetry of ferrocyanide becomes reversible.  Both the native titanium and gold coated arrays generate electrochemiluminescence using tri-propyl amine as a co-reactant, but the intensity of the gold-coated array is between 30 (high scan rate) and 100-fold (slow scan rates) higher at the gold coated arrays.  Moreover, while the voltammetry of the luminophore is dominated by semi-infinite linear diffusion, the ECL response is significantly influenced by radial diffusion to the individual microcylinders of the array.