In most cases, the photoexcited molecule forms a layer (either single or multi-layers) on the WE. In our system, we suggest a different mechanism for photocurrent generation that originates from a photo-dissociation reaction of the PA and an electrochemical reaction between the formed ions in the excited state and the electrodes. To support this mechanism, i.e., to exclude the direct electron transfer mechanism from the excited PA (ROH * ) to the electrode without the involvement of the ESPT process, we turned to another common PA, which is 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS), and its non-photoacid methylated analog, 8-methoxypyrene-1,3,6-trisulfonic acid (MPTS) (Figure and). We did not use the HPTS PA in the previous experiments due to its propensity to undergo bleaching upon prolonged exposure to light. In common with the 2N6S PA, HPTS also exhibits a predominate 405 nm ROH peak in the absorption spectrum, corresponding to the ground state form, and a predominant 530 nm RO -peak in the emission spectrum, corresponding to the excited state form (Figure ), which is due to the ESPT process. In contrast, methylation of HPTS, (MPTS) exhibits only the ROCH3 405 nm peak in the absorption spectrum, and the 450 nm peak in the emission spectrum (Figure ). Since MPTS is not dissociated upon irradiation, any photocurrent generation would be possible only via a direct electron transfer mechanism. Thus, we followed the CA of HPTS and MPTS in dark/light irradiation (at λex=405 nm) intervals with a similar applied positive potential of +0.5V on the WE as is shown above (Figure ). As shown in the figure, a maximal photocurrent production of 0.06 µA/cm 2 was obtained for HPTS following light irradiation, which decayed to the baseline level in dark, while no photocurrent production was detected for MPTS. In line with the CA results, the CV measurements also show that the CV response of MPTS is identical in both dark and light conditions, whereas HPTS shows a photocurrent generation upon light irradiation with +0.5V being the onset of the photocurrent (Figure ). These results support our hypothesis that the photocurrent production from PAs derives from electrochemical reactions of the photo-dissociated ions in the excited state and not from a direct electron transfer to the electrode.