In Situ Imaging of Photocatalytic Activity at Titanium Dioxide Nanotubes Using Scanning Ion Conductance Microscopy

In this letter, in situ imaging of the photocatalytic activity of titanium dioxide (TiO₂) nanotubes for the degradation of an organic pollutant (i.e., Rhodamine B (RhB)) is realized with nanometer resolution using scanning ion conductance microscopy (SICM). Upon illumination, the separated electrons and holes at the nanotubes induce oxidation of RhB to produce the more positively charged Rhodamine 123 (Rh 123), which leads to increased ionic current through the capillary orifice and an elevated apparent altitude in the SICM image. Active sites with higher activity on the nanotubes exhibit a significant high spatial-resolution character. The successful imaging of the photocatalytic activity of TiO₂ nanotubes should provide an in situ approach for local investigation of the photocatalytic process at the catalyst.