Figure 4.
(A, B) Simultaneous measurements of [H2O2] and pH. The pH and H2O2 concentrations were recorded when [H2O2] was added from 0 to 30, 60, 90, and 120 μM, and then, the pH was adjusted from 7.2 to (A) 8.2 and (B) 6.2. There is no pH change during standard addition of H2O2 and no significant [H2O2] change after pH adjustment. (C, D) Reversibility test of pH and H2O2 sensors in a SECM tip. (C) pH calibration after exposure to 100 μM of H2O2. (D) The H2O2 sensor signal changes, depending on the pH solution change.