Fabrication of transparent–colorless Nb2O5 nanocrystal layers and their photocatalytic evaluation using organosilane thin films

Photocatalytic Nb2O5 nanocrystal layers were successfully synthesized using NbOx nanosheets obtained from layered K4Nb6O17 crystals. First, idiomorphic K4Nb6O17 crystals were grown using the KCl flux method, and then a two-step process involving proton exchange and exfoliation was carried out in order to make the nanosheets. Next, the rectangular nanosheets were mixed with polyethylene glycol, water and ethanol to prepare a nanosheet paste, and the paste was then evenly spin-cast on silica glass. Upon heating, decomposition and evaporation of the solvents yielded transparent, colorless nanocrystal layers with good adhesion. During the heating process, some nanosheets rolled up into nanotubes; therefore, nanocrystal layers consisting of both nanosheets and nanotubes were fabricated. The nanocrystal layers exhibited photocatalytic activity for the photodegradation of organosilane thin films under UV light irradiation. The organosilane thin films were photocatalytically decomposed and that the surfaces were converted from hydrophobic to ultrahydrophilic. Furthermore, micropatterned nanocrystal layer was readily fabricated using hydrophobic/hydrophilic template.