Upconverting particles in near-infrared light-induced TiO2 photocatalysis: towards the optimal architecture of upconverter/photocatalyst systems

Preparation of highly active core–shell/hybrid materials based on up-converting particles combined with semiconductors for photocatalytic application usually requires sophisticated and multi-step synthesis procedures. We propose a new design of a highly efficient NIR-driven photocatalytic system composed of spatially separated thin films of upconverting NaYF4:Yb,Tm particles (UCPs), and TiO2. Several samples of UCPs were prepared in the form of thin films and suspensions, directly coated with a titania layer or mixed with P25. Photocatalytic and photoelectrochemical studies have shown that thin film samples achieved significantly higher photocatalytic activity than their suspended counterparts. Moreover, the sample consisting of spatially separated layers of UCPs and P25 presented a significant photocatalytic activity and generated the highest photocurrent intensity. Separating the photocatalyst and upconverter layers allows for an interchangeable photocatalytic system active in a wide range of light.