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Coprecipitation with rare‐earth nitrate, ammonium sulfate, and ammonium hydroxide produced hydroxide‐type amorphous precursors incorporating sulfate and carbonate anions, from which [(Gd1−xLax)0.99Tb0.01]2O2SO4 and [(Gd1−xLax)0.99Tb0.01]2O2S (x = 0, 0.15, 0.3, 0.5, 0.65, 0.8, and 1) were obtained as two series of nanophosphors by calcination at 950°C in air and hydrogen, respectively. The detailed characterization by X‐ray diffractometer, scanning electron microscopy/transmission electron microscopy, Brunauer–Emmett–Teller, and particle sizing confirmed that solid solutions were directly formed and that the products have small crystallite size, unimodal size distribution, and high specific surface area, revealing the advantages of the synthesis method. Photoluminescence study revealed that La3+ admixture may significantly improve the 545 nm main emission of Tb3+ for both the phosphor series. Furthermore, the 545 nm main emission of [(Gd1−xLax)0.99Tb0.01]2O2SO4 was identified to have an excellent thermal stability, which retained over 90% of its room‐temperature intensity at 150°C (no quenching for Gd2O2SO4:Tb3+). The two series of phosphors were comparatively studied for their excitation and luminescence performances, as a function of temperature and La3+ content, and the results were rationalized by considering bandgap, crystal structure, UV absorption, and the character of chemical bonds. [ABSTRACT FROM AUTHOR]

Recently, study on Cr3+‐doped zinc gallate and zinc gallogermanate persistent phosphors has become a hot topic in persistent luminescence and bio imaging areas, because of their near infrared (NIR) emission and long afterglow. However, regulation of efficient traps and improvement of persistent luminescence through bottom‐up design are the key challenge. Here, we recommend a new paradigm of chemical unit co‐substitution with [Mg2+‐Ge4+] substituting for [Ga3+‐Ga3+] in ZnGa2O4, which contributes to the opposite charged and distorted octahedral defects of MgGa′ and GeGa· in pair around the CrN2 ions. The formed defect clusters of MgGa′‐CrN2‐GeGa·, which are closely related to the trap depth, can be accurately regulated through varying the doping content of Mg2+/Ge4+ in the resulting spinel solid solutions of ZnGa2−x(Mg/Ge)xO4:Cr3+ (x = 0–1.25). Moreover, the defect clusters cannot only store and recharge visible and UV radiations that contributes to the long lasting NIR persistent luminescence but also can enhance the NIR emission intensity at ~695 nm. The persistent luminescence induced by UV light excitation exhibits an improvement at a deeper trap depth, but it follows an opposite law through visible light excitation. The prepared nanoparticles have the advantages of intense NIR emission, long lasting afterglow, and excellent rechargeability for visible/UV radiations, so they are the potential nanoprobes for long‐term bio imaging in living animals. [ABSTRACT FROM AUTHOR]

The sulfate-type layered hydroxides of (Gd1− xTb x)2( OH)5( SO4)0.5· nH2O ( x = 0.06-0.10) have been directly crystallized via hydrothermal reaction at 120°C and pH ~10.0, without the need of conventional anion exchange. The primary crystallites were found to be thin platelets having lateral sizes of ~450-1000 nm and thicknesses of ~65-85 nm. Combined analysis by DTA/ TG, FTIR, and XRD revealed that the layered compounds convert into cubic (Gd1− xTb x)2O3 solid-solutions through dehydration, dehydroxylation, and desulfuration up to ~1200°C and via a (Gd1− xTb x)2O2.5( SO4)0.5 intermediate phase. Optical spectroscopies found that the layered compounds and the derived oxides have their strongest 4 f8→4 f75 d1 transition excitations at ~248 and 305 nm and optimal Tb3+ contents of 9 at.% ( x = 0.09) and 8 at.%, respectively. Both the types of materials exhibit the strongest emission at ~544 nm (the 5D4→7F5 transition of Tb3+), but the oxide has an emission intensity ~3 times that of the hydroxide. Fluorescence lifetime of the 544 nm green emission was found to decrease from 2.45 to 2.15 ms along with increasing Tb3+ content for the oxide, and smaller values of ~1.55 ms were derived for the layered hydroxides. [ABSTRACT FROM AUTHOR]

A novel Y3− x Si6 N11: x Ce3+ yellow phosphor was synthesized using the carbothermal reduction and nitridition method at 1550°C for 16 h in this letter. Photoluminescence spectra indicated that the phosphor showed broad excitation spectrum and had strong absorption in range of 350-450 nm. It also gave a broad emission band (Full width at half maximum = 153 nm) centered at 575 nm under 425-nm excitation. With increasing Ce3+ concentration, the strongest emission intensity was obtained at 5 mol% Ce3+ doping amount and a systematic redshift was observed as the Ce3+ concentration increased. The results indicate that this novel yellow phosphor is a promising candidate for using in blue-chip-excited white light-emitting diodes ( LEDs). [ABSTRACT FROM AUTHOR]