A series of Tb3+, Pr3+ and Dy3+ monodoped CaTa4O11(CTO) persistent luminescence (PersL) phosphors have been successfully synthesized using the molten salt method with KCl flux. The PersL color is green and orange for Tb3+ and Pr3+ or Dy3+ doped samples, respectively. The trap depth of Tb3+, Pr3+ and Dy3+ monodoped CTO is 0.33, 0.31 and 0.30 eV, respectively. The PersL time of 3 mol% Tb3+, 1 mol% Pr3+ and 1 mol% Dy3+ monodoped samples is 52.20, 35.00 and 59.46 s, respectively. Tb3+, Pr3+ and Dy3+ monodoped CTO phosphors can be used in luminescence displays and anti-counterfeit labels under commercial 254 nm UV light.
Low phonon tantalate-based phosphors with a layer structure are considered to have excellent upconversion luminescence (UCL) intensity, which could be reduced due to the existence of impure phase defects and inappropriate doped rare earth ions. To improve their UCL performance, we have prepared single-phase CaTa4O11:Er3+/Yb3+ samples by a molten salt synthesis (MSS) using KCl as the reaction medium and compared its UCL properties with counterparts made by a conventional solid-state reaction (SSR) in this study. We have demonstrated that the MSS samples have a much higher UCL intensity under 980 nm laser excitation than the SSR ones due to accurate replacement of Ca2+ sites by Er3+/Yb3+ in high-purity single-phase MSS samples. We have further enhanced the green UCL intensity of the MSS samples by 1.57 times via acid picking (AP). Under 980 nm laser excitation at a high powder density of 61.3 W/cm2, the green UCL intensity of the MSS-AP samples can reach 3.72 times that of the SSR-AP samples. For potential luminescence thermometry applications, the maximum absolute sensitivity (SA) of the MSS-AP samples reaches 0.01316 K–1 at 501 K based on the luminescence intensity ratio. This study shows that CaTa4O11:Er3+/Yb3+ phosphors prepared by the MSS method are single-phase samples with excellent pure green UCL as a suitable temperature sensing material.
Hanghang Zhou,Ying Luo,Jun Xu,Lidan Deng,Zheng Wang,Hong He
Graphical The well-defined CaTaO 2 N single crystals with uniform particle size were successfully synthesized through a one-pot NaCl-assisted nitridation procedure. The performance of photocatalytic CO 2 reduction to CO by H 2 O under visible light was enhanced due to the high crystallinity of CaTaO 2 N and the modification with core-shell structured Ni−Ag bicomponent cocatalyst. Cubic-like CaTaO 2 N photocatalysts with high crystallinity and uniform particle size were successfully prepared by the flux-assisted nitridation method. The growth of CaTaO 2 N single crystals under different synthesis conditions was systematically investigated to understand the effects of the crystallinity and optical property on photocatalytic performance of CO 2 reduction. Moreover, the modification of CaTaO 2 N single crystals with core-shell Ni−Ag bicomponent cocatalyst by two-step decoration process gave a 2.4 times higher amount of CO evolution than the deposition of sole Ag cocatalyst, because of the synergistic effects of bicomponent cocatalyst on the interfacial electron transfer and surface catalytic process. This study provides a valuable way to construct high-crystalline photocatalysts with effective bicomponent cocatalyst for visible-light-driven CO 2 reduction with H 2 O.
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