Enhancing or not: What dominates the response signal of phenolic compounds on electro-activated glassy carbon electrode?

Abstract

Electro-activation has been an important surface modification strategy to enhance the signal of analytes on glassy carbon electrodes (GCE). However, its unique effects on certain analytes remain to be further explored. Hence, due to the electro-active hydroxyl groups (–OH), phenolic compounds were selected as the analyte to reveal it to some extent. Except for the improved electrocatalytic activity of electro-activated GCE (e-GCE) which was attributable to the improved charge transfer ability and optimized surface properties (eg. surface area, surface roughness, and active sites), the oxygen-containing functional groups on the e-GCE surface were also identified as being of significant importance for enhanced response of phenolic compounds. After electro-activation, the newly generated CO constituted 12.81 % of the C1s spectra and 51.75 % of the O1s spectra, effectively facilitating the formation of donor–acceptor complexes between the analytes and the electrodes, thereby enhancing the adsorption of phenolic compounds. Furthermore, it was found that the structure of phenolic compounds had a remarkable impact on the response signal. The increase in the number of –OH groups involved in the electron transfer process, the increase in the number of aromatic rings, and the enhancement of the electronegativity of substituents all contributed positively to the response signal of phenolic compounds. At last, based on the great adsorption of catechol, a sensor for catechol with a sensitivity 12-fold higher than prior has been established. These results provide insights for the subsequent fabrication of green sensors for more electro-active molecules.