“…As demonstrated in Figure 1 C, however, the fluorescence intensity of the APF phosphate buffer solution was greatly enhanced by applying a positive potential (0$ + 0.5 V QRE , where a silver wire was used as a quasi-reference electrode (QRE)). The onset of the increase in the fluorescence intensity at around + 0.35 V QRE can be easily correlated to the oxidation potential (E ox ) of aniline (+ 0.36 V QRE (+ 0.63 V NHE ; NHE = normal hydrogen electrode)), [9] which is much lower than that of fluorescein (+ 1.1 V NHE , Figure S4 in the Supporting Information), [10] thereby supporting the reaction scheme depicted in Figure 1 A. On the basis of these experimental results, we evaluated the photocatalytic activity of individual ETS-10 crystals by imaging the fluorescence generated by oxidized APF molecules during UV irradiation.…”