Redox properties of 8AQ were investigated by cyclic voltammetry and chronoamperometry, both combined with UV-Vis spectroscopic measurements. The measurements were performed using 0.5 mM 8AQ dissolved in 0.1 M NaH2PO4 adjusted to pH 3 at ambient temperature. The spectroelectrochemical experiments were carried out using a quartz photoelectrochemical cell with a 1 mm optical path length. A three-electrode configuration with Ag|AgCl|0.3 M NaCl as the reference, a platinum wire as the counter, and platinum gauze working electrode were used in the cell. The absorption spectra were acquired using an Ocean Optics Flame-T spectrophotometer.