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Abstract The novel apatite-type phosphor Ca 9 Tb(PO 4) 5 (SiO 4)F 2 :Mn2+ (CTPSF:Mn2+) has been successfully synthesized and it demonstrated a potential for optical thermometry. The energy transfer process between Tb3+ and Mn2+ was of resonant type via a dipole-dipole mechanism based on the Inokuti–Hirayama theoretical model, and the energy transfer (ET) efficiency and ET rate were estimated. In view of the energy transfer behavior, a strategy, involving the use of Tb3+ and Mn2+ dual-emitting centers with different thermal quenching behavior, has been developed to achieve temperature sensitivity and good signal discrimination. The temperature dependence of the fluorescence intensity ratios (FIR) for the dual-emission bands peaking at 548 and 595 nm was studied in the range of 298–573 K under excitation of 377 nm ultraviolet light and the maximum relative sensitivity was approximately 1.92% K−1 at 423 K. It is expected that this preliminary study will provide an important advance in exploring novel ratiometric optical thermometry. Highlights • Novel apatite-type phosphor Ca 9 Tb(PO 4) 5 (SiO 4)F 2 was synthesized. • Energy transfer mechanism is estimated based on Inokuti–Hirayama model. • Non-contact thermometry was developed with a new inorganic material. • The maximum S r of the as-prepared phosphor was as high as 1.92% K−1. • This work provides an insight to design ratiometric optical thermometry. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) is one of the core reaction modules of important renewable energy technologies with applications in water splitting, metal-air (oxygen) cells and regenerative fuel cells. However, OER catalysts are forced to operate with a significant intrinsic overpotential and inefficient charge transfer due to the adsorption energy scaling balance between the reaction intermediates. It is critical to develop an understanding of structure-activity relationship of catalysts, determine the speed control steps and improve catalytic activity. In this work, cobalt pentlandite (Co , Ni , Fe) 9 S 8 (CNFS) electrocatalysts were successfully prepared by combining the earth-abundant transition metal elements Co, Ni and Fe into a single structure. Benefiting from the structure, nanoflower morphology, and the synergistic effect among the three elements, the optimized sample requires an overpotential of only 335 mV to drive a current density of 50 mA cm–2 under alkaline conditions. The experimental results establish a composition-structure-function relationship, and the density functional theory results further indicate that the Fe sites bind more moderately to the intermediates and the electron synergistic effect occurs dynamically during the OER cycle reaction. This work not only provides a very promising catalyst candidate for efficient OER processes but also highlights the superiority of the cobalt pentlandite structure in the rational design of efficient OER electrocatalysts. • We synthesized natural mineral structures of cobalt pentlandite (Co,Ni,Fe) 9 S 8 structured OER catalysts. • Synergistic effect among the Co, Ni and Fe accelerates charge transfer and results in superior catalytic activity. • DFT calculations illustrate that the cobalt pentlandite (Co,Ni,Fe) 9 S 8 have an active OER site at the interface Fe site. [ABSTRACT FROM AUTHOR]

Currently, the application potential of Cr3+ doped near-infrared (NIR) fluoride phosphors excited by blue light is promising. However, the development of near-infrared fluoride phosphors with wider emission bandwidth remains a challenge. Herein, we employed the hydrothermal method to prepare K 2 NaCrF 6 :Fe3+ phosphors. Upon excitation at 432 nm, the K 2 NaCrF 6 :xFe3+ phosphors exhibited broad near-infrared emission, with the main peak ranging from 752 nm to 780 nm. As the Fe3+ concentration increased, the luminescence intensity of the K 2 NaCrF 6 :xFe3+ phosphor decreased, accompanied by a redshift in the emission band and an increase in the full width of the emission spectrum half-peak. These changes can be attributed to the dipole-dipole interaction, specifically the energy transfer between Fe3+ and Cr3+, leading to the 4T 2 (4F) → 4A 2 (Cr3+) and 4T 1 (4G) → 6A 1 (6S) (Fe3+) transitions. • K 2 NaCrF 6 :Fe3+ phosphors display application potential for near-infrared (NIR) fluorescence when excited by blue light. • The developed phosphors exhibit a broad near-infrared emission bandwidth (752–780 nm) under 432 nm excitation. • Increasing Fe3+ concentration leads to redshift and broadening of the emission spectrum. • Luminescent changes are attributed to dipole-dipole interactions and efficient energy transfer. • Cr3+ and Fe3+ enables synchronous excitation processes, offering versatility for applications in spectroscopy. [ABSTRACT FROM AUTHOR]

It is urgent and crucial to develop highly efficient broadband Near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) which are applied in tiny solid-state NIR light sources. However, a lot of NIR phosphors suffer from low quantum yield and poor thermal stability in recent years. Hereon, the solid-state reaction synthesis process was used to create a new garnet Ca 2 GdZr 2 Ga 3 O 12 :Cr3+ (CGZG:Cr3+) phosphor, which can produce a broad range emission peak at (12,437 cm-1, 804 nm) with a full width at half maximum (FWHM) of (67567 cm−1, 148 nm). At 373 °C, thermal stability was determined to be 76%, an IQE of 75% and an EQE of 26% was observed. When driving current at 150 mA and 320 mA, the device achieved the output power of 473 mW and 968 mW. The results demonstrate CGZG:Cr3+ phosphor-convert NIR LEDs have great potential for applications in night-vision and biomedical imaging NIR spectroscopy technology. • The Ca 2 GdZr 2 Ga 3 O 12 :Cr3+ is found ultra-broadband near-infrared photoluminescence with peak at 804nm.and FWHM 148 nm. • The Ca 2 GdZr 2 Ga 3 O 12 :Cr3+ near-infrared phosphors with the very high outpower 968 mW@320 mA. • The Ca 2 GdZr 2 Ga 3 O 12 :xCr3+ is promising for use in night-vision and biomedical imaging NIR spectroscopy technology. [ABSTRACT FROM AUTHOR]

Samarium (III) doped fluorapatite phosphors La 6- x Ba 4 (SiO 4 ) 6 F 2 : x Sm 3+ (LBSF: Sm 3+ ) were synthesized for the first time, via the conventional high-temperature solid-state method in the air atmosphere. The samples were measured by X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy, i.e. emission and excitation spectra, as well as luminescence decay curves. The as-prepared samples can be excited in the range from 300–500 nm, centered at 404 nm. Photoluminescence measurements showed the emission spectra are composed of four sharp peaks characteristic of Sm 3+ ions, at about 565, 603, 650 and 711 nm. The critical concentration for quenching of Sm 3+ ions in the LBSF matrix is about 0.12 mol. According to the Dexter's theory, the mechanism of energy transfer between Sm 3+ ions was considered to be dipole-quadrupole (d-q) interactions, with the critical distance calculated by the concentration quenching method to 9.89 Å. Moreover, the temperature-dependent emission spectra showed that the as-prepared phosphors have good thermal stability, with an activation energy of about 0.161 eV. Finally, according to the CIE coordination, the phosphor exhibited reddish-orange emission. Thanks to the mentioned favorable structural and optical properties, the Sm 3+ -doped La 6 Ba 4 (SiO 4 ) 6 F 2 phosphors have a potential application character, for the near ultraviolet white light emitting diodes. [ABSTRACT FROM AUTHOR]

LED occupies a broad market due to its many advantages as a fourth-generation solid-state light source. However, single-component white LED generally has the disadvantages of high coloring temperature, low thermal stability, and low luminous efficiency. In order to solve these problems, Gd 5 Si 2 BO 13 :Dy3+,Eu3+ was prepared by a high temperature solid state method using a newer borate matrix based on Gd 5 Si 2 BO 13. A colour-tunable warm white phosphor was achieved by energy transfer between Dy3+ and Eu3+. The crystal structure, luminescence characteristics, thermal stability of luminescence, fluorescence lifetime and energy transfer mechanism were systematically studied, and the samples obtained had excellent luminescence performance. Its thermal stability of 150 °C luminescence was 83.77%. By adjusting the ratio of Eu3+, its color changes from cool white light to warm white light and finally moves to red light. Its corresponding color temperature can be adjusted to a range of 5475k∼2128 K. The packaging w-LED application test and the application test of colorless fluorescent anti-counterfeiting printing ink were carried out, and both showed excellent performance. This is the first time that Dy3+ and Eu3+ have been studied in Gd 5 Si 2 BO 13 , further understanding the newer substrate Gd 5 Si 2 BO 13 , and promoting the application of single-component warm white LED. Therefore, Gd 5 Si 2 BO 13 :Dy3+,Eu3+ have good market application prospects. [Display omitted] • Through the energy transfer between Dy3+ and Eu3+, Gd 5 Si 2 BO 13 :Dy3+/Eu3+ shows excellent Warm white light performance. • The phosphor showed good luminescence thermal stability, UV stability and wet resistance stability. • The color temperature of the sample was adjusted from 5475K to 2128K by adjusting the doping concentration of Eu3+. • The LED application test with Gd 5 Si 2 BO 13 :Dy3+,Eu3+ package shows good performance. [ABSTRACT FROM AUTHOR]

In this paper, K 3 ScF 6 :Er3+,Yb3+ up-conversion luminescent materials with cryolite structure were synthesized via solid-state method. The X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL) under the excitation of a 980 nm laser with different power density were used to investigate the phase structure, elemental composition, and up-conversion luminescence properties of K 3 ScF 6 :Er3+,Yb3+. The quenching concentrations of Yb3+ and Er3+ were confirmed to 0.15 and 0.05 (mol concentration) in this system, respectively. Upon 980 nm excitation, the K 3 ScF 6 :Er3+,Yb3+ showed a typical transition of Er3+ which contains two main bands in the visible region that green and red. According to the fitting result of the pump power dependence of up-conversion intensity, all the green and red up-conversion emission of K 3 ScF 6 :0.05Er3+,0.15 Yb3+ belong to the two-photon process. To better understand the origin of radiation and energy transfer mechanism of the red and green up-conversion, the possible mechanism and electron transition process were also discussed. Single-phase Er3+/Yb3+ co-doped K 3 ScF 6 with cryolite structure were synthesized. Image 1 • Single-phase Er3+/Yb3+ co-doped K 3 ScF 6 with cryolite structure was synthesized. • Structural and up-conversion properties of K 3 ScF 6 :Er3+, Yb3+ were studied. • Mechanism of up-conversion was analyzed. [ABSTRACT FROM AUTHOR]