| 초록 |
The photocatalytic effects of nanocrystalline TiO2 coated upconversion phosphor NaYF4: (Gd3+, Si4+) were investigated in this study. Upconversion phosphor powders of NaYF4: (Gd3+, Si4+) were prepared by combustion method and coated with TiO2-sol. The diffuse reflectance spectrum of the upconversion phosphor showed wide absorption bands ranging from 200 nm to 400 nm in the ultra violet region and 700 nm to 1000 nm in the near infrared region. Photocatalytic reactivity was examined with 254 nm fluorescent lamp for the ultra violet photocatalysis whilst irradiations of 150 W xenon lamp of λ＞760nm were used in the near infrared photocatalysis. The photocatalytic reactivity of these systems showed enhanced methylene blue (MB) degradation efficiency with increase in Si+4 ions in the host matrix. The enhanced photocatalytic activity is attributed to the multi-phase photocatalyst composites of NaYSiO3/TiO2 and NaYF4:Gd,Si/TiO2 which existed due to limited solubility of Si+4 in NaYF4 host. |
