Scientific studies on photocatalysis started about three decades ago. Titanium dioxide (TiO ₂ ), which is one of the most basic materials in our daily life, has emerged as an excellent photocatalyst material for environmental purification. In this short account, we will briefly discuss some fundamental studies on TiO ₂ photocatalysis, summarize the present commercialization of TiO ₂ -based products, and highlight several points for the future development of TiO ₂ photocatalysis. .

Single-phased, high-color-rendering index (CRI) white-light phosphors are emerging as potential phosphor-converted white-light-emitting diodes (WLEDs) and as an alternative to blends of tricolor phosphors. However, it is a challenge to create a high CRI white light from a single-doped activator. Here, we present a high CRI (Ra = 91) white-light phosphor, Sr₅(PO₄)_3-x(BO₃)_xCl:Eu²⁺, composed of Sr₅(PO₄)₃Cl as the beginning member and Sr₅(BO₃)₃Cl as the end member. This work utilized the solid-solution method, and tunable Eu²⁺ emission was achieved. Color-tunable Eu²⁺ emissions in response to structural variation were observed in Sr₅(PO₄)_3-x(BO₃)_xCl solid solutions. This was further confirmed using X-ray Rietveld refinement, electron paramagnetic resonance spectroscopy, and in the photoluminescence spectra. The color-tunable emissions included the white light that originated from the combination of the blue emission of Sr₅(PO₄)₃Cl:Eu²⁺ and an induced Eu²⁺ yellow emission at approximately 550 nm in the solid solution. Importantly, the white-light phosphors showed a greater R9 = 90.2 under excitation at 365 nm. This result has rarely been reported in the literature and is greater than that of (R9 = 14.3) commercial Y₃A_l5O₁₂:Ce³⁺-based WLEDs. These findings demonstrate the great potential of Sr₅(PO₄)_3-x(BO₃)_xCl:0.04Eu²⁺ as a white-light phosphor for near-UV phosphor-converted WLEDs. These results also provide a shortcut for developing a high CRI white-light phosphor from a single Eu²⁺-doped compound.