Synthesis of core-shell NaYF4:Yb,Tm@TiO2-Acac micro- and nano-sized particles for efficient photocatalysis

Abstract

Micro- and nano-sized core-shell particles for efficient photocatalysis were successfully synthesized by a two step wet-chemical route. The core composed of up-converting (UC) NaYF4:Yb,Tm phase was prepared through EDTA assisted hydrothermal process, while the shell of anatase TiO2 –Acetylacetone (TiO2-Acac) charge-transfer complex was formed via a sol-gel method. During coating, the effect of polyvinylpyrrolidone (PVP) addition on the core and shell coupling was investigated. Two forms of core structures were obtained: hexagonal microprisms of beta-NaYF4:Yb,Tm and alpha-NaYF4:Yb,Tm nanospheres, both coated with TiO2-Acac nanocrystals.