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Abstract: The site and local structure of activator Eu2+ in phosphor Ca10−x (PO4)6Cl2:xEu2+ is investigated by experiment measurements, first-principle calculations and XAFS simulations. From first-principle calculations, the “local” structure [bond length L(M–O)≤R(M 2+)+R(O2−)] of host shows a significant deformation (expansion) when Ca2+ is substituted by Eu2+, and Eu2+ should prefer 6h site to 4f site in the host. The d→f emission of Eu2+ at 4f site should show a longer wavelength than that of Eu2+ at 6h site. The XAFS measurement and simulations suggest that the Eu2+ in our Ca9.9(PO4)6Cl2:0.1Eu2+ sample mainly locates at 6h site. In the emission spectrum, two emission profiles of Ca9.9(PO4)6Cl2:0.1Eu2+ sample are obtained and assigned. The major one (2.71eV≈456nm) should be the emission of Eu2+ at 6h site. The minor one (2.61eV≈465nm) should be that of Eu2+ at 4f site. [Copyright &y& Elsevier]

Nanosheet BiOI materials were synthesized using the precipitation-hydrothermal method. Subsequently, nanoparticle AgI/BiOI nanosheet composites were fabricated using an ion-exchange method and a controlled amount of BiOI. The phase composition, optical morphology, and absorption properties of the samples were determined using XRD, SEM, XPS, TEM, HRTEM, BET, and UV–Vis diffuse reflectance. Organic dyes, such as methyl orange (MO) and Coomassie brilliant blue R-250 (CBB), were used to check the composites' photocatalytic performance undergoing photodegradation in visible light. The prepared composites had high purity, and the AgI nanoparticles were evenly loaded on the flower-like BiOI nanosheets, both absorbing the visible light. The 50% AgI NP/BiOI NS compound demonstrated the best visible photocatalytic activity and degraded rate of 96.9% and 97% of the MO and CBB dye, respectively, under visible light for 30 ​min. The photocatalytic activity of sole BiOI or AgI was poor, whereas the composites were much better. The composite with 50% AgI exhibited the best photocatalytic activity because of the formation of a heterojunction, which promotes the separation of photogenerated carriers, making AgI stable under visible-light irradiation. AgI nanoparticle/BiOI nanosheet composites were successfully fabricated. The kinetic photocatalytic degradation was controlled by a pseudo-first-order kinetic model. Visible-light-driven photocatalytic performance of composites was enhanced and optimized. The 50% AgI NP/BiOI NS composite showed the highest photocatalytic activity. [Display omitted] • AgI nanoparticle/BiOI nanosheet composites were successfully fabricated via the hydrothermal method of precipitation and the ion-exchange method. • The kinetic photocatalytic degradation was controlled by a pseudo-first-order kinetic model. • Visible-light-driven photocatalytic performance of composites was enhanced and optimized by adjusting the component ratio. • Under Xe lamp irradation as visible light source, the 50% AgI NP/BiOI NS composite showed the highest photocatalytic activity in the degradation of MO and CBB dye in water. [ABSTRACT FROM AUTHOR]