Photocatalytic activity of Ag-TiO2 nanoparticles encapsulated with titanium oxide layer.

The deposition of nanosized Ag on the TiO2 matrix was first prepared by the sonochemical reduction of silver precursor and the Ag-deposited TiO2 was subsequently encapsulated with titanium oxide layer through an ultrasonic-assisted sol-gel process. The resulting Ag-TiO2 nanocomposites (Ag-TiO2@TiOx) exhibited the lower PL spectra and higher photocatalytic activity as compared to pristine TiO2, indicating the increased separation efficiency of electron-hole pairs at the optimal thickness of TiOx. The excessive encapsulation of TiOx, however, induced the decrease of photocatalytic activity of Ag-TiO2@TiOx owing to the formation of amorphous titanium oxide with less photocatalytic activity. The annealed Ag-TiO2@TiOx at 500 degrees C for 2 hrs exhibited an enhanced photocatalytic activity as compared to non-annealed samples because of the partial transformation of amorphous TiOx into crystalline TiO2.