The stable and reliable red phosphor with high-photon energy emission (620-650 nm) is critical for the fabrication of the phosphor-converted white light-emitting diode (WLED) with low correlated color temperature and high color rendering index. Mn ⁴⁺-activated phosphor is an emerging kind of red-emitting phosphor for WLED. Herein, the energy levels transition and photoluminescence characteristics of the Mn ⁴⁺ ion were introduced; then, the preparation, crystal structure and luminescent properties of as-far reported seven kinds of Mn ⁴⁺-doped oxyfluoride red phosphors (such as Na₂WO₂F₄:Mn ⁴⁺) containing d ⁰, d ¹⁰ or s ⁰ cations were reviewed. Currently, only in quite rare case of oxyfluoride, Mn ⁴⁺ was found to exhibit strong R-line emission, with local coordination remaining as either [MnF₆] or [MnO₆]. The studies on the chemical stability and quantum efficiency of Mn ⁴⁺-doped oxyfluoride phosphors are still insufficient. Finally, we prospected the future development of Mn ⁴⁺-doped oxyfluoride phosphor.

The sensitivity of optical temperature sensing based on the conventional rare-earth ion doped upconversion (UC) materials is limited by the energy gap between thermally coupled levels (TCLs) of rare-earth ions. Therefore, it is of great theoretical and technical interest to explore UC luminescent materials for optical temperature sensing with ultra-sensitive temperature characteristic. In this work, the UC luminescence properties and temperature sensing characteristics were studied for Er ³⁺ single-doped BiOCl excited by 1550 nm laser. Under near-infrared (NIR) excitation, BiOCl:Er ³⁺ exhibits strong red emission at 670 nm, weak green emissions at 525 and 542 nm, extremely weak violet emission at 406 nm, and near-infrared emission at 983 nm. Red and green emissions of the UC system exhibit strong temperature dependence, and in the temperature range of 300-563 K, the maximum absolute sensitivity (S_A) obtained by employing the non-thermally coupled levels (NTCLs, ⁴F_9/2/ ⁴S_3/2) is 95.3×10 ^-3K ^-1, which is 21 times more than that obtained by employing the thermally coupled levels (TCLs, ²H_11/2/ ⁴S_3/2), and the maximum relative sensitivity (S_R) is as high as 1.19% K ^-1. The results show that the intense red UC luminescence and temperature sensing with ultra-high sensitivity in BiOCl:Er ³⁺ under 1550 nm excitation may have potential application prospect in display and optical temperature sensing.

A series of tunable-luminescence MOF/CA, MOF/CA+RhB, MOF/CA+CV and MOF/CA+RhB+CV composite light-emitting materials were prepared by combining calcein (CA), rhodamine B (RhB), crystal violet (CV) with MOF using Cd as metal ion, isophthalic acid and benzimidazole as ligand by the one-step method at room temperature. The influence of the initial addition amount and ratio of dyes on the fluorescence properties of MOF/Dye composites was discussed. With the increase of CA amount, the characteristic fluorescence emission intensity of CA increased firstly and then decreased accompanied with red-shift. Although the position of the characteristic fluorescence emission wavelength of RhB or CV remained unchanged due to the unchanged addition amount, the characteristic fluorescence emission intensity of CA changed like CA. MOF/CA₃+RhB+CV composite with white light emission was further prepared by adjusting the molar ratio of dyes using MOF as a platform. Its chromaticity coordinate (0.335, 0.321) was close to the ideal white light coordinate (0.333, 0.333).

The sensitive detection of UV light is critical in industrial production and for personal protection, and the aim of this research is to develop novel UV detection materials. The uranyl unit generally exhibits relatively high UV absorption efficiency and strong fluorescence intensity. Hence in this work, a uranyl coordination polymer compound [(TEA)₂(UO₂)₅(PhPC)₆] (TEA = tetraethylammonium ion, PhPC = (2-carboxyethyl)phenylphosphinic acid, denoted as UPhPC-1) was successfully synthesized via the hydrothermal method. The structural analysis of UPhPC-1 based on the single crystal XRD data elucidates that there are three crystallographically unique uranyl centers. Two uranyl units are in the pentagonal bipyramidal geometry, while the third one is in the tetragonal bipyramidal geometry. All three uranyl units are connected by the ligands to form infinite uranyl layers in the [bc] plane, which are packed via hydrogen bonding networks and π-π interactions to yield the overall layered structure. The stability test results of UPhPC-1 demonstrate that the compound exhibits good thermal and hydrolytic stability with high radiation resistance. Moreover, results of the UV irradiation experiments show that the intrinsic luminescence of UPhPC-1 is highly sensitive to 365 nm UV irradiation with a low detection limit and a fast response rate. A negative correlation between the emission intensity and the UV irradiation dosage was then established. The electron paramagnetic resonance data analysis strongly supports the production of radicals in UPhPC-1 under UV radiation, which leads to the partial quenching of the uranyl fluorescence. Furthermore, the radicals in the quenched sample can be readily eliminated by heating, resulting in the recovery of the photoluminescence intensity of UPhPC-1. The current results suggest suitable application potential of UPhPC-1 in the field of quantitative UV detection.