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Organic-inorganic hybrid metal halides have recently attracted attention in the global research field for their bright light emission, tunable photoluminescence wavelength, and convenient synthesis method. This study reports the detailed properties of (C 10 H 16 N) 2 MnBr 4 , which emits bright green light with a high photoluminescence quantum yield. Results of powder X-ray diffraction, photoluminescence, thermogravimetric analysis, and Raman spectra show the phase transition of (C 10 H 16 N) 2 MnBr 4 at 430 K. This phase transition was identified as the solid to liquid state of (C 10 H 16 N) 2 MnBr 4 . Moreover, the pressure- and temperature-induced relationship between structural and optical properties in (C 10 H 16 N) 2 MnBr 4 can be identified. This investigation provides deep insights into the luminescent properties of metal halide crystals and promotes further research.

Near-infrared (NIR) phosphors are fascinating materials that have numerous applications in diverse fields. In this study, a series of La 3 Ga 5 GeO 14 :Cr 3+ phosphors, which was incorporated with Sn 4+ , Ba 2+ , and Sc 3+ , was successfully synthesized using solid-state reaction to explore every cationic site comprehensively. The crystal structures were well resolved by combining synchrotron X-ray diffraction and neutron powder diffraction through joint Rietveld refinements. The trapping of free electrons induced by charge unbalances and lattice vacancies changes the magnetic properties, which was well explained by a Dyson curve in electron paramagnetic resonance. Temperature and pressure-dependent photoluminescence spectra reveal various luminescent properties between strong and weak fields in different dopant centers. The phosphor-converted NIR light-emitting diode (pc-NIR LED) package demonstrates a superior broadband emission that covers the near-infrared (NIR) region of 650-1050 nm. This study can provide researchers with new insight into the control mechanism of multiple-cation-site phosphors and reveal a potential phosphor candidate for practical NIR LED application.

Two types of infrared fluoride phosphors, Cr 3+ -doped K 3 AlF 6 and K 3 GaF 6 , were developed in this research. The K 3 Al 1- x F 6 : x Cr 3+ and K 3 Ga 1- y F 6 : y Cr 3+ fluoride phosphors were proven to be pure phase via X-ray diffraction refinement, which demonstrated that the procedure can be applied to large-scale production. Electron paramagnetic resonance measurements indicated that Cr 3+ ions in cubic with respect to noncubic are coupled better with K 3 GaF 6 than with K 3 AlF 6 . The main differences between these two phosphors, the site symmetry and pressure behavior of the spectra, were obtained in temperature- and pressure-dependent spectra. According to the calculation results, Cr 3+ in fluorine coordination at ambient pressure indicates an intermediate crystal field. For the phosphor-converted light-emitting diodes (LEDs) fabricated from these two phosphors, the spectral range is from 650 to 1000 nm, which resulted in a radiant flux of 7-8 mW with an input power of 1.05 W. The research reveals detailed luminous properties, which will lead to a new way of studying Cr 3+ -doped fluoride phosphors and their application in LEDs.

In this paper, we report a simple, rapid, and stable method for the continuous synthesis of highly stable Cs 4 PbBr 6 perovskite microcrystals (MCs) using a microfluidic system. To demonstrate the potential application of Cs 4 PbBr 6 MCs, the sample was fabricated with K 2 SiF 6 :Mn 4+ phosphor onto InGaN blue chips as white-light-emitting diodes (LEDs). Our white-LED device achieved a high National Television Standards Committee value of 119% for backlight display, which indicated that the Cs 4 PbBr 6 MC is a promising material for future applications.

Photodynamic therapy (PDT) is a promising antitumor treatment that is based on photosensitizers. This therapy kills cancer cells by generating reactive oxygen species (ROS) after irradiation with specific laser wavelengths. Being a potential photosensitizer, graphitic carbon nitride (g-C 3 N 4 ) quantum dots (QDs) are noncytotoxic. Although the use of g-C 3 N 4 QDs is challenged by the limited tissue penetration of UV light, g-C 3 N 4 QDs display excellent ultraviolet (UV) light-triggered cytotoxicity. The g-C 3 N 4 QDs were synthesized using a solid-phase hydrothermal method. The well-distributed hydrophilic g-C 3 N 4 can be combined with NaYF 4 :Yb 3+ /Tm 3+ upconversion nanoparticles via the positive ligand poly(l-lysine) to produce the final nanocomposite, NaYF 4 :Yb/Tm-PLL@g-C 3 N 4 . Upconversion nanoparticles can transfer IR light into UV light and promote g-C 3 N 4 to release blue-to-green visible light to generate different images. Moreover, g-C 3 N 4 is a promising photosensitizer in PDT because g-C 3 N 4 can transfer oxygen into toxic ROS. The singlet oxygen formed by g-C 3 N 4 displays great potential for use in the treatment of cancer.

Red Ca0.99Al(1-4δ/3-x)Si(1+δ+x)N(3-x)C(x):Eu(2+)0.01 (δ = 0.345; x = 0-0.2) nitride phosphors exhibit a blue-shifted emission with increased eye sensitivity function and excellent thermal stability. The variations in the photoluminescence in the Ca0.99Al(1-4δ/3-x)Si(1+δ+x)N(3-x)C(x):Eu(2+)0.01 (δ = 0.345; x = 0-0.2) system are thoroughly investigated. The enhanced emission energy and the improved thermal stability with increasing x are dominated by the second-sphere shrinkage effect via the substitution of small Si(4+) for large Al(3+) with simultaneous charge compensation. Related proofs of the second-sphere shrinkage effect control for photoluminescence are confirmed via high-resolution neutron powder diffraction, EXAFS, and (29)Si solid-state NMR techniques.

This study investigated the photoluminescent properties of Tb(3+)-Yb(3+)-, Ce(3+)-Tb(3+)-Yb(3+)-, and Eu(2+)-Yb(3+)-doped KSrPO4. The samples were prepared by a solid-state reaction with various doping concentrations. Emission at near-infrared range was focused on the application of luminescent solar concentrator for solar cells. Quantum cutting (QC) energy transfer was confirmed by the lifetimes of the donor. Near-infrared QC involved emission of Yb(3+) ions was achieved by excitation of Ce(3+), Tb(3+), and Eu(2+) ions, where the energy transfer processes occurred from Ce(3+) to Tb(3+) to Yb(3+), Tb(3+) to Yb(3+), and Eu(2+) to Yb(3+), respectively. In addition, the concentration quenching effect of Yb(3+) ions was avoided by low doping concentrations. The overall quantum efficiencies were calculated, and the maximum efficiency reaches 139%. The energy diagrams for divalent and trivalent rare-earth ions in KSrPO4 host lattice were analyzed. Results of this study demonstrate that heat-stable phosphate phosphors are promising candidates for increasing the efficiency of silicon-based solar cells.

Novel single-phased white light-emitting KCaY(PO(4))(2):Eu(2+),Mn(2+) phosphors for light-emitting diode (LED) applications were synthesized by conventional solid-state reaction. The emission hue could be controlled by tuning the Eu(2+)/Mn(2+) ratio via the energy transfer; the the emission hue of KCaY(PO(4))(2):Eu(2+),Mn(2+) varied from blue (0.1853, 0.2627) to white-light (0.3350, 0.3203) and eventually to purple (0.3919, 0.2867). The mechanism of energy transfer from a sensitizer Eu(2+) to an activator Mn(2+) in KCaY(PO(4))(2):Eu(2+),Mn(2+) phosphors was demonstrated to be an electric dipole-quadrupole interaction. Combining a NUV 405-nm chip and a white-emitting KCaY(PO(4))(2):1%Eu(2+),4%Mn(2+) phosphor produced a white-light NUV LED, demonstrating CIE chromaticity coordinates of (0.314, 0.329) and a color temperature of 6507 K.