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Recently, combining long afterglow materials with organic fluorescent dyes, particularly carbon dots (CDs) to produce heterojunction and improve its luminescence and persistence properties became an important research direction. However, the precise role of these internal defects in the energy transfer process of CD@inorganic matrix composite fluorescent materials has not been thoroughly discussed. Establishing matching trap level to promote the energy transfer between the trap level and CDs level not only helps to enhance the afterglow performance, but also can explain the heterogeneous structure interaction between organic–inorganic fluorescent materials. Herein, ZLAGC@CDs luminescent composite is successfully synthesized via coating CDs on Zn1‐x(Li/Al)xGa2xO4:0.005Cr3+ (ZLAGC, x = 0–1), which exhibits a unique double emission at ≈430 nm (the defect luminescence of CDs) and 718 nm (the 2E→4A2 transition of Cr3+). After coating, the energy transfer from the defect level of CDs to the excited state of Cr3+ enhanced the NIR emission. The electron transfer between the defect level of CDs and the split deeper trap level of ZLAGC also improved the visible and near‐infrared (NIR) afterglow. The fluorescence and afterglow signals of ZLAGC@CDs are highly sensitive to solution pH under acidic conditions, indicating that the prepared fluorescent composite has potential application in acid microenvironment fluorescence detection. [ABSTRACT FROM AUTHOR]

With malate (Mal2−) as a new type of chelate, tetragonal (t-) and monoclinic (m-) structured LaVO4:Eu crystals (∼10–60 nm) were selectively crystallized as nanosquares and nanorods via a hydrothermal reaction at 200 °C for 24 h. The effects of the Mal2−:(La,Eu)3+ molar ratio, solution pH and Eu3+ content on the phase structure and crystal morphology were systematically investigated and elucidated. The competition between OH− and Mal2− toward rare earth ions was discussed to play a critical role in phase selection, and the t-phase can only be fabricated at pH ∼ 6–8 with the assistance of Mal2−. The optimal Eu3+ content for luminescence was determined to be ∼5 at% under the VO43− → Eu3+ energy transfer mechanism. Experimental comparison showed that t-(La0.95Eu0.05)VO4 (λex = 275 nm, λem = 620 nm) emits ∼5.3 times as strong as m-(La0.95Eu0.05)VO4 does (λex = 313 nm, λem = 616 nm), while theoretical analysis revealed that the 5D0 level of Eu3+ has a quantum efficiency of ∼80% for the former and ∼70% for the latter. Besides, the t- and m-(La0.95Eu0.05)VO4 nanocrystal phosphors were analyzed to have fluorescence lifetimes of ∼1.53 ± 0.01 and 2.28 ± 0.01 ms for their 620 and 616 nm red emissions, respectively. [ABSTRACT FROM AUTHOR]

Uniform spheres are highly desired for the fabrication of advanced ceramics and as phosphor for lighting and display. Green emitting (Y 0.95− x Gd x Tb 0.05 ) 2 O 3 phosphor spheres were successfully synthesized in this work via homogeneous precipitation, with particular emphases on size enlargement of the particles and the effects of particle size, Gd 3+ incorporation and calcination on photoluminescence. Ammonium nitrate (NH 4 NO 3 ) was originally used to effectively enlarge the precursor particles from ∼150 ± 10 to 590 ± 43 nm, whose effects were found to tend to saturate at NH 4 NO 3 :rare-earth = 1:1 molar ratio. Size enlargement up to ∼630 ± 57 nm has also been achieved via a self-seeded growth approach. The optimal Gd 3+ content for luminescence was determined to be 2 at% ( x = 0.02) for the phosphors, and the spin-allowed 7 F 6 → 7 D J Tb 3+ excitation at ∼278 nm successively lowers at a higher Gd 3+ content or calcination temperature owing to bandgap narrowing of the host lattice. Intensity of the 543 nm green emission steadily improves with increasing temperature of calcination or particle size, and the lifetime of the 543 nm emission, affected by particle size and calcination, falls in the range of ∼1.75–2.81 ms. The phosphors have similar color coordinates of around (0.32, 0.56), irrespective of the Gd content, particle size, and calcination temperature. [ABSTRACT FROM AUTHOR]

(Y,Gd,Tb)2O3monodispersed spheres have been calcined from the precursors synthesized via urea-based homogeneous precipitation. The resultant particles are polycrystalline, consisting of ∼40 nm grains. A facile particle size control from 162 nm to 110 nm can be achieved through varying the urea/cation molar ratio. Upon UV excitation at ∼275 nm, the phosphors exhibit green emission at ∼546 nm (5D4→7F5transition of Tb3+). The phosphors showed luminescent intensity clearly dependent on their particle size, and stronger emission was found for larger spheres mainly due to their smaller surface area. However, the oxides with various particle sizes exhibited similar lifetimes of ∼1.51ms. [ABSTRACT FROM PUBLISHER]

• (Ce,Tb)PO 4 monospheres were originally used for effective sensing of VC and MnO 4 −. • Analyte detection was achieved in wide concentration ranges. • The sensing system has favorable response rates. • Numerical expression was established for analyte concentration. (Ce 0.9 Tb 0.1)PO 4 monospheres (˜1.39 ± 0.11 μm) of negligible aggregation and high geometric uniformity were synthesized via microwave assisted homogeneous precipitation, whose luminescence responses toward MnO 4 − oxidant and vitamin C reductant were studied in detail. Through exciting Ce3+ with 275 nm UV light, strong and broad UV emission centered at ˜350 nm (FWHM ˜40 nm) and sharp green emission at ˜544 nm (FWHM ˜10 nm) were obtained, and efficient Ce3+ → Tb3+ energy transfer, with an efficiency of ˜65%, was observed. Interacting the monospheres with MnO 4 − (0–50 μM) effectively quenched the luminescence via Ce3+ oxidation, and treating the luminescence-quenched monospheres with VC (0–250 μM) sufficiently recovered the luminescence via Ce4+ reduction. Numerical expressions were also established to correlate the emission intensity with VC and MnO 4 − concentrations. Besides, the colloidal monospheres exhibited the favorable response time of ˜18 and 50 s for 25 μM of MnO 4 − and 150 μM of VC, respectively. [ABSTRACT FROM AUTHOR]