active sites distributed over the ETS-10 (Fig. 2.6) [14]. It was revealed that surface
treatment of ETS-10 with HF aqueous solution significantly increased not only the
adsorption and reaction efficiencies but also the heterogeneity of photocatalytic
activity among the crystals. The crystal defects serve as active sites during the
photocatalytic reaction in aqueous solution. The fluorescence intensity of fluorescein
increased gradually upon UV irradiation of phosphate buffer solutions containing
APF and ETS-10 powder. In the absence of ETS-10, the fluorescence intensity did
not increase at all, thus suggesting that fluorescein molecules might be generated by
the reaction of photoexcited ETS-10 and APF molecules. Meanwhile, a significant
increase in the fluorescence intensity was observed for HF-treated ETS-10 because
of the exposure of surface-active sites such as titanols and larger micropores by
partial dissolution of siliceous walls surrounding the titania wires (Fig. 2.7).
The Diffusion Distance of Radicals in a Single Particle Porous, cavitary, and
tubular structured photocatalysts with a high specific surface area have been
designed to improve the photocatalytic efficiency or achieve the selective transformation. These kinds of materials are supposed to have more active sites for the
Fig. 2.6 (a) Reaction scheme for the one-electron oxidation of the p-aminophenyl moiety, which
induces fluorescence in APF. ET ¼ electron transfer. (b) Cell configuration for in situ
spectroelectrochemical measurements under TIRFM. CE ¼ counter electrode, QRE ¼ quasi-reference electrode, WE ¼ working electrode. (c) Applied potential dependence of normalized fluorescence intensity (IFL) obtained for the phosphate buffer solutions in the absence (gray line) and
presence of APF (5 mm; solid line) or fluorescein (500 nm; dashed line). The images in (c) were
acquired at a bin time of 50 ms. Scale bars are 5 mm. (Reproduced from Ref. [14] by permission of
John Wiley & Sons Ltd)
24
2 In Situ Characterization of Photocatalytic Activity
treatment of ETS-10 with HF aqueous solution significantly increased not only the
adsorption and reaction efficiencies but also the heterogeneity of photocatalytic
activity among the crystals. The crystal defects serve as active sites during the
photocatalytic reaction in aqueous solution. The fluorescence intensity of fluorescein
increased gradually upon UV irradiation of phosphate buffer solutions containing
APF and ETS-10 powder. In the absence of ETS-10, the fluorescence intensity did
not increase at all, thus suggesting that fluorescein molecules might be generated by
the reaction of photoexcited ETS-10 and APF molecules. Meanwhile, a significant
increase in the fluorescence intensity was observed for HF-treated ETS-10 because
of the exposure of surface-active sites such as titanols and larger micropores by
partial dissolution of siliceous walls surrounding the titania wires (Fig. 2.7).
The Diffusion Distance of Radicals in a Single Particle Porous, cavitary, and
tubular structured photocatalysts with a high specific surface area have been
designed to improve the photocatalytic efficiency or achieve the selective transformation. These kinds of materials are supposed to have more active sites for the
Fig. 2.6 (a) Reaction scheme for the one-electron oxidation of the p-aminophenyl moiety, which
induces fluorescence in APF. ET ¼ electron transfer. (b) Cell configuration for in situ
spectroelectrochemical measurements under TIRFM. CE ¼ counter electrode, QRE ¼ quasi-reference electrode, WE ¼ working electrode. (c) Applied potential dependence of normalized fluorescence intensity (IFL) obtained for the phosphate buffer solutions in the absence (gray line) and
presence of APF (5 mm; solid line) or fluorescein (500 nm; dashed line). The images in (c) were
acquired at a bin time of 50 ms. Scale bars are 5 mm. (Reproduced from Ref. [14] by permission of
John Wiley & Sons Ltd)
24
2 In Situ Characterization of Photocatalytic Activity