Understanding electrogenerated chemiluminescence at graphite screen-printed electrodes

Abstract

• The ECL response of screen-printed graphite electrodes is explained. • Carbon paste composition determines electrode wettability and electron transfer rates. • The ECL response of laser-induced HOPG SPE depends mainly on the paste binder. • ECL is highly sensitive to electrode microstructure and surface chemistry. • Image analysis of ECL using a smartphone facilitates the study of electrode activity. Screen printed graphite electrodes are widely used in electroanalysis, and increasingly in electrochemiluminescence (ECL) applications. However, their response is very dependent on graphite paste composition and electrode fabrication processes. This work studies the ECL of the tris(2,2′-bipyridyl)ruthenium (II)/tripropylamine (Ru(bpy) 3 2+ /TPrA) system at four graphite electrodes printed from three commonly found graphite pastes. Dropsens graphite electrodes are included in the study for completeness. Electrodes were also treated with a CO 2 laser in air (7.7–12.0 mJ cm −2 ) to remove surface binder impurities to form laser-induced-HOPG, a much more electrochemically active form of graphite. It has been found that the ECL intensity expressed by graphite electrodes depends on electrode kinetics but also very significantly on electrode wettability, both of which depend on paste composition, particularly carbon mix and polymer binder. The observed differences between as-printed and laser-activated electrodes were investigated using a combination of ECL generation techniques, scanning electron microscopy (SEM), contact angle measurements, thermal analysis and X-ray photoelectron spectroscopy (XPS). An affordable method to assess electrode quality using ECL and image capture with a mobile phone camera and open-source image analysis software is presented.