**4. Long afterglow phosphor-assisted photocatalysts**

Long afterglow phosphor-assisted novel photocatalysts become promising functional mate‐ rials due to their effective utilization of solar light in practical applications of environmental purification. In this section, the recent development on TiO2-based and Ag3PO4-based fluo‐ rescence photocatalyst composites with full-time active photocatalytic properties is reviewed.

The long afterglow phosphor (CaAl2O4:(Eu, Nd)) has a high luminescent brightness around 440 nm of wavelength, long afterglow time, good chemical stability, and low toxicity. The luminescent brightness around 440 nm can excite the visible-light-responsive nitrogen-doped titania (TiO2–xNy). Therefore, TiO2–xNy photocatalyst was expected to possess a novel photo‐ catalytic property after coupling with CaAl2O4:(Eu, Nd).

In our research [147–149], the degradation of continuous NO gas was achieved by TiO2–xNy surface-immobilized CaAl2O4:(Eu, Nd) microparticles (Fig. 9). The results show a persistent deNO*x* ability of the CaAl2O4:(Eu, Nd)/TiO2−xNy composite. In another work [149], the persistent fluorescence-assisted photocatalysts of Ag3PO4 composites have been synthesized to expand the application of Ag3PO4 on dye decomposition day and night. Sr4Al14O25:(Eu,Dy)/ Ag3PO4 composites exhibited excellent photocatalytic activities for the Rhodamine B (RhB) decomposition reaction in the dark without additional light sources (Fig. 9c).

**Figure 9.** (a) Composition and (b) the mechanism of the persistent fluorescence-assisted photocatalysts; (c) variation of RhB solution concentration against illumination time using Sr4Al14O25:(Eu,Dy)/Ag3PO4 composites. Reproduced with permission from ref. 148 © 2013 Elsevier B.V. & ref. 149 © 2013 RSC.
