Synthesis and evaluation of photocatalytic properties of Na–TiO2/Sr4All4O25:Eu,Dy phosphor composites

Sub-micron Sr4Al14O25:Eu,Dy phosphor particles were coated by a TiO2-sol precipitation procedure at 80 °C for 3 h. The effects of Na/H2O2 additives on TiO2 precipitation and stability of the composites over heat treatment conditions were evaluated. The distribution of TiO2 nanoclusters on the sub-micron phosphor support changed from sparse to dense clusters with increasing Na additive. X-ray diffraction and Raman spectroscopy analyses revealed that the anatase and rutile phases dominated in the Na–TiO2/phosphor nanocomposites at 300 °C. Heat treatment at 450 °C was detrimental to the stability of TiO2 anatase phase. Ultraviolet and visible light were utilized for photocatalytic decomposition of methylene blue and toluene volatile organic components in the vicinity of the Na–TiO2/phosphor composites. Optimum photocatalytic performances were obtained in TiO2/phosphor composites with low concentration precipitation additives (1% Na and 0.23 vol% H2O2) heat-treated at 300 °C. Anatase phases and Na+ existence in TiO2/Sr4Al14O25:Eu,Dy phosphor composites improved the light sensitization and overall photocatalytic efficiencies.