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Luminescent metal halides have attracted increasing attention because of their tunable emission and superior photoelectric properties. However, it is still challenging to achieve near‐infrared (NIR) emission from metal halides, which is important in applications such as food quality analysis and night vision. In this work, the broadband NIR emission is achieved by alloying Sn2+ into zero‐dimensional (0D) Cs2ZnBr4. The incorporating of Sn2+ cations enables the originally weakly luminescent Cs2ZnBr4 to exhibit an efficient broadband NIR emission. Upon photoexication, the optimized Sn2+ alloyed Cs2ZnBr4 (Cs2Zn0.875Sn0.125Br4) exhibits a highly efficient broadband NIR emission peaked around 700 nm, with a large Stokes shift of 323 nm, a full width at maximum of 177 nm, and a high quantum efficiency of around 41%. Spectroscopic and theoretical calculations unveil that the efficient NIR emission originates from the self‐trapping emission introduced by the Sn alloying. In addition to the high efficient broadband emission, the Sn2+ alloyed Cs2ZnBr4 also exhibits high thermal stability, retaining 78% of its initial intensity at 150 °C. The night vision application is demonstrated by using a light source fabricated by combining Sn2+ alloyed Cs2ZnBr4 phosphor with a 365 nm LED chip in the dark. [ABSTRACT FROM AUTHOR]

A series of Mn4+‐doped and Mn4+,K+‐co‐doped Ba2LaTaO6 (BLT) double‐perovskite phosphors was synthesized using a high‐temperature solid‐state reaction. The phase purity and luminescence properties were also studied. The optimum doping concentration of Mn4+ and K+ was obtained by investigating the photoluminescence excitation spectra and photoluminescence emission spectra. The comparison of BLT:Mn4+ phosphors with and without K+ ions shows that the photoluminescence intensity of K+‐doped phosphors was greatly enhanced. This is because there was a charge difference when Mn4+ ions were doped with Ta5+ ions in BLT. Mn4+–K+ ion pairs were formed after doping K+ ions, which hinders the nonradiative energy transfer between Mn4+ ions. Therefore, the luminescence intensity, quantum yield, and thermal stability of phosphors were enhanced. The electroluminescence spectra of BLT:Mn4+ and BLT:Mn4+,K+ were measured. The spectra showed that the light emitted from the phosphors corresponded well with chlorophyll a and phytochrome PR. The results show that the BLT:Mn4+,K+ phosphors had good luminescence properties and application prospects and are ideal materials for plant‐illuminated red phosphors. [ABSTRACT FROM AUTHOR]

An important challenge in the research and development of compact near‐infrared (NIR) light sources is the discovery of new efficient ultra‐broadband NIR luminescent materials to replace the conventional Cr3+‐doped compounds. Herein, this work reports a divalent europium‐doped Ba3GeO4Br2 phosphor that exhibits a high photoluminescence quantum yield of 48.8% and an ultra‐broad emission band ranging continuously from 500 to 1100 nm (full width at half maximum = 202 nm) under near‐ultraviolet or blue light excitation. A strategy of embedding alumina crucible in high purity graphite crucible is devised and deployed during solid‐state sintering to facilitate the conversion of Eu3+ into Eu2+. Theoretical calculations, structural refinement, and spectral analysis demonstrate that the visible to NIR emission in Ba3GeO4Br2:Eu2+ originates from the Eu2+ ions occupying the distorted Ba3O3Br4 polyhedra in the lattice. The as‐prepared phosphor‐converted light‐emitting diode device achieves an optical output power of 30.1 mW@100 mA (520–1100 nm) and a photoelectric efficiency of 22%@100 mA (350–1100 nm). Experiments on tissue penetration and NIR imaging illustrate its application in spectral detection and food quality testing appears promising. [ABSTRACT FROM AUTHOR]

In this paper, fluorescent and optical temperature sensing bi-functional Li+-doping NaLuF4:Ln (Ln = Yb3+, Tm3+/Er3+) nanocrystals were synthesized via a simple hydrothermal method using oleic acid as a capping ligand. The crystal phase, size, upconversion (UC) properties, and optical temperature sensing characteristics of the crystals can be easily modified by Li+ doping. The results reveal that additional Li+ can promote the transformation from the hexagonal phase to the cubic phase and reduce the size of the nanocrystals. In addition, NaLuF4:Ln (Ln = Yb3+, Tm3+, Li+) nanocrystals present efficient near infrared (NIR) emission, which is beneficial for in vivo biomedical applications due to the increased penetration depth and low radiation damage of NIR light in bio-tissues. More importantly, under 980 nm excitation, the temperature dependent UCL from the 2H11/2 and 4S3/2 levels of Er3+ ions in NaLuF4:Yb3+,Er3+,Li+ microcrystals was investigated systematically. The fluorescence intensity ratios (FIR) of the pairs of thermally coupled levels were studied as a function of temperature in the range of 298–523 K. The maximum sensor sensitivities were found to be about 0.0039 K−1 (523 K) by exploiting the UC emissions from the 2H11/2 and 4S3/2 levels. This suggests that the Li+-doped upconversion luminescence (UCL) materials are promising prototypes for application as multi-mode probes for use in bio-separation and optical thermometers. [ABSTRACT FROM AUTHOR]

Mono-dispersed Gd6O5F8:Yb3+/Er3+ micro-particles with different doping concentrations (Er3+: 0.1–1%) were synthesized by a facile hydrothermal route. The emission spectra, luminescent dynamic power-dependence and temperature sensing of up-conversion photoluminescence were investigated in detail. Under 980 nm excitation, the as-prepared samples exhibit intense red up-conversion and NIR emissions, which are influenced by the doping concentrations of Er3+ within Gd6O5F8. With increasing concentrations of Er3+ ions, the visible up-conversion emissions first increase and then decrease, but NIR down-conversion emissions display a distinct trend, in which one peak at 1010 nm is highly suppressed and another at 1530 nm is increased quickly. Furthermore, the 980 nm excited optical temperature sensing property of the synthesized sample is realized over a wide temperature range by monitoring the intensity of up-conversion luminescence. The study provides a novel strategy based on lanthanide oxy-fluoride micro-particles for multifunctional displays, lighting and temperature sensing in a single system. [ABSTRACT FROM AUTHOR]

To improve the visible light-induced catalytic activities of Ultrathin g-C 3 N 4 (UCN), a promising photocatalyst WO 3 /UCN (WU) was synthesized. Its visible light-driven photocatalysis performance was controllable by adjusting the theoretical mass ratio of WO 3 /UCN. We have calibrated the optimal preparation conditions to be: WO 3 /UCN ratio as 1:1, the stirring time of the UCN and sodium tungstate mixture as 9 h and the volume of concentrated hydrochloric acid as 6 mL which was poured into the mixture solution with an extra stirring time of 1.5 h. The optimal photocatalyst WU opt had porous and wrinkled configurations. Its light absorption edge was 524 nm while that of UCN was 465 nm. The band gap of WU opt was 2.13 eV, 0.3 eV less than that of UCN. Therefore, the recombination rate of photo-generated electron-hole pairs of WU opt reduced significantly. The removal rate of WU opt on RhB was 97.3%. By contrast, the removal rate of UCN was much lower (53.4%). WU opt retained a high RhB removal rate, it was 5.5% lower than the initial one after being reused for five cycles. The photodegradation mechanism was facilitated through the strong oxidation behaviors from the active free radicals ·O 2 - , ·OH and h + generated by WUopt under the visible light irradiation.

A series of Mn 4+ -doped and Mn 4+ ,K + -co-doped Ba 2 LaTaO 6 (BLT) double-perovskite phosphors was synthesized using a high-temperature solid-state reaction. The phase purity and luminescence properties were also studied. The optimum doping concentration of Mn 4+ and K + was obtained by investigating the photoluminescence excitation spectra and photoluminescence emission spectra. The comparison of BLT:Mn 4+ phosphors with and without K + ions shows that the photoluminescence intensity of K + -doped phosphors was greatly enhanced. This is because there was a charge difference when Mn 4+ ions were doped with Ta 5+ ions in BLT. Mn 4+ -K + ion pairs were formed after doping K + ions, which hinders the nonradiative energy transfer between Mn 4+ ions. Therefore, the luminescence intensity, quantum yield, and thermal stability of phosphors were enhanced. The electroluminescence spectra of BLT:Mn 4+ and BLT:Mn 4+ ,K + were measured. The spectra showed that the light emitted from the phosphors corresponded well with chlorophyll a and phytochrome P R . The results show that the BLT:Mn 4+ ,K + phosphors had good luminescence properties and application prospects and are ideal materials for plant-illuminated red phosphors., (© 2023 John Wiley & Sons Ltd.)

In this paper, fluorescent and optical temperature sensing bi-functional Li+-doping NaLuF4:Ln (Ln = Yb3+, Tm3+/Er3+) nanocrystals were synthesized via a simple hydrothermal method using oleic acid as a capping ligand. The crystal phase, size, upconversion (UC) properties, and optical temperature sensing characteristics of the crystals can be easily modified by Li+ doping. The results reveal that additional Li+ can promote the transformation from the hexagonal phase to the cubic phase and reduce the size of the nanocrystals. In addition, NaLuF4:Ln (Ln = Yb3+, Tm3+, Li+) nanocrystals present efficient near infrared (NIR) emission, which is beneficial for in vivo biomedical applications due to the increased penetration depth and low radiation damage of NIR light in bio-tissues. More importantly, under 980 nm excitation, the temperature dependent UCL from the 2H11/2 and 4S3/2 levels of Er3+ ions in NaLuF4:Yb3+,Er3+,Li+ microcrystals was investigated systematically. The fluorescence intensity ratios (FIR) of the pairs of thermally coupled levels were studied as a function of temperature in the range of 298-523 K. The maximum sensor sensitivities were found to be about 0.0039 K-1 (523 K) by exploiting the UC emissions from the 2H11/2 and 4S3/2 levels. This suggests that the Li+-doped upconversion luminescence (UCL) materials are promising prototypes for application as multi-mode probes for use in bio-separation and optical thermometers.

GdSr 2 AlO 5 :Yb 3+ /Er 3+ micro-particles were synthesized by a simple solid state method. The structure, morphology, size and upconversion luminescence features have been characterized. These results indicated that GdSr 2 AlO 5 has a contracted tetragonal cell and has irregular block shaped particles with sizes of about 5 μm. During upconversion, green ( 2 H 11/2 , 4 S 3/2 → 4 I 15/2 ) (527 nm, 549 nm) and red ( 4 F 9/2 → 4 I 15/2 ) (665 nm) emissions had been observed, both of which occurred via a two-photon population process. In addition, green UC emission characteristics were studied, and it was found that its temperature ranged from 293 K to 473 K and the sensitivity was 0.0054 K -1 at 473 K. This indicated that GdSr 2 AlO 5 :Yb 3+ /Er 3+ micro-particles may have potential application in high temperature environments for safety signs., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Mono-dispersed Gd 6 O 5 F 8 :Yb 3+ /Er 3+ micro-particles with different doping concentrations (Er 3+ : 0.1-1%) were synthesized by a facile hydrothermal route. The emission spectra, luminescent dynamic power-dependence and temperature sensing of up-conversion photoluminescence were investigated in detail. Under 980 nm excitation, the as-prepared samples exhibit intense red up-conversion and NIR emissions, which are influenced by the doping concentrations of Er 3+ within Gd 6 O 5 F 8 . With increasing concentrations of Er 3+ ions, the visible up-conversion emissions first increase and then decrease, but NIR down-conversion emissions display a distinct trend, in which one peak at 1010 nm is highly suppressed and another at 1530 nm is increased quickly. Furthermore, the 980 nm excited optical temperature sensing property of the synthesized sample is realized over a wide temperature range by monitoring the intensity of up-conversion luminescence. The study provides a novel strategy based on lanthanide oxy-fluoride micro-particles for multifunctional displays, lighting and temperature sensing in a single system.