Photochromic Properties of Porous Glass Modified with Molybdenum Oxide Groups

Porous glass plates were modified via their interaction with molybdenum(V) chloride, followed by a treatment with humid air at 473°C. The extent of the reaction is characterized on the basis of IR spectra of OH groups on the starting glass surface and grafted layer. The photochromism of the resulting plates is exhibited under their UV irradiation as a progressive blue coloration. The suggested photoreduction mechanism consists in splitting-off oxygen atoms from bridge bonds‒Mo‒O‒Mo‒, with transition of molybdenum atoms to the pentavalent state. The subsequent discoloration of the plates is provided by their heating in air at 473°C. The full reversibility of the photoreduction and oxidation processes is observed in their multiple repetitions.