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The dual‐site synergistic effect in heterogeneous catalysis is quite interesting, and also complex because at least two substrate molecules are adsorbed or activated on the catalyst surface, which apparently needs two spatially separated and functionally independent active sites. It would become more difficult when the substrate molecules are large ones. The replacement of Al3+ in Al4B6O15 lattice with Co2+ leads to the formation of unsaturated Co2+ (4‐fold coordination) along with oxygen vacancies (Ov). The former one behaves as a medium‐strength Lewis acid site, and can adsorb and activate molecules with a nitro group (e. g., β‐nitrostyrene). The latter one can adsorb and activate oxygen species, which further activates the indole derivatives. Next, the spatially separated dual sites on the catalyst surface can synergistically and efficiently catalyze their Friedel‐Crafts alkylation reactions under mild conditions. The high durability can be proved by the as‐maintained high yields, that is, 98, 93, 96, 92 and 90 % for 5 runs, respectively. The reaction kinetics obey the second‐order characteristic. Annealing under hydrogen condition can further generate more surficial Ov, leading to an improvement to the catalytic activity. A simple and probably routine aliovalent doping endows such a complex synergistic catalysis involving two large substrate molecules, providing an inspired perspective of developing dual‐site catalysts. [ABSTRACT FROM AUTHOR]

Searching efficient red phosphors under near‐UV or blue light excitation is practically important to improve the current white light‐emitting diodes (WLEDs). Eu2+‐ and Mn4+‐based red phosphors have been extensively studied. Here we proposed that Eu3+ is also a promising activator when it resides on a noncentrosymmetric coordination site. We proved that Cd4GdO(BO3)3 is a good host, which has a significantly distorted coordination for Eu3+. A careful crystallographic study was performed on the solid solutions of Cd4Gd1‐xEuxO(BO3)3 (0≤x≤1) by Rietveld refinements. The as‐doped Eu3+ cations locate at the Gd3+ site and are well separated by CdO8, CdO6 and BO3 groups; thus, only a slight concentration quenching was observed at ≈80 atom % Eu3+. Most importantly, the parity‐forbidden law of 4f‐4f transitions for Eu3+ are severely depressed, thus the absorptions at ≈393 and ≈465 nm are remarkable. Cd4Gd0.2Eu0.8O(BO3)3 can be pumped by a 395 nm LED chip to give a bright red emission, and when mixed with other commercial blue and green phosphors, it can emit the proper white light (0.3657, 0.3613) with a suitable Ra≈87 and correlated colour temperature ≈4326 K. In‐situ photoluminescence study indicated the low thermal quenching of these borate phosphors, especially under 465 nm excitation. Our case proves the practicability to develop near‐UV excited red phosphors in rare‐earth‐containing borates. [ABSTRACT FROM AUTHOR]

Rare-earth borates are good candidates for optical applications. To date, however, the high-pressure/high-temperature technique has produced a large number of novel borates with optical properties that have rarely been investigated due to the severe problem of substantial defects. We targeted the high-pressure polymorph of β-GdB3O6 and synthesized three solid solutions of β-Gd0.75− xBi0.25Tb xB3O6 (0≤ x≤0.75), β-Gd0.75− yBi0.25Eu yB3O6 (0≤ y≤0.75), and β-Gd0.50− zBi0.25Tb0.25Eu zB3O6 (0≤ z≤0.05) by using typical solid-state reactions at 820 °C. Here, the function of Bi3+ is to stabilize the high-pressure phase by lowering the synthetic temperature and being the sensitizer to promote the green and red emissions of Tb3+ and Eu3+. The multiple energy transfer paths were investigated by using lifetime decay experiments and photoluminescent spectra, and both efficiency and mechanism were determined. Eventually, color-tunable and white emissions were achieved by rational doping of Bi3+, Tb3+, and Eu3+ into β-GdB3O6, that is, the CIE chromaticity coordinate for β-Gd0.44Bi0.25Tb0.30Eu0.01B3O6 is (0.318, 0.365) with a correlated color temperature of 6101 K. [ABSTRACT FROM AUTHOR]

Partial solid solutions of In1-xGaxBO3 (0 ≤ x ≤ 0.5) were synthesized by the solvothermal method, and they were characterized by powder X-ray diffraction, scanning and transmission electron microscopy, UV/Vis absorption spectroscopy, and N2 adsorption-desorption, in order to identify the phase purity and micromorphology. Nanocrystallites of InBO3 exhibit a particular anisotropic growth along the [110] direction, forming spindlelike morphology (with a diameter of ca. 20 nm and a length of ca. 200 nm). These nanocrystallites further aggregate into microspheres. With Ga3+ substitution, the anisotropic growth was depressed; the nanocrystallites thus exhibited a typical rodlike morphology. Metal borates are well-known optical materials; however, their photocatalytic properties have been rarely studied. Here, post-annealing under O2 flow at 350 °C improved the photocatalytic H2 evolution rate of InBO3 from 18.2(6) to 29.5(8) μmol h-1 g-1. A loading of Pt, RuOx, or NiOx as cocatalyst resulted in further enhancement of the H2 evolution rate, with an optimal value of 56.1(5) μmol h-1 g-1 under UV light. [ABSTRACT FROM AUTHOR]

Borates are well-known candidates for optical materials and, here, we are particularly interested in Ba6Bi9B79O138 (BBBO), which has an interesting layered-type structure and Bi3+-containing characteristics that has prompt us to explore its host-sensitized photoluminescence (PL). Solid solutions of BBBO: xTb3+ (0 ≤ x ≤ 1) were prepared and its host-sensitized photoluminescence was confirmed, which is a result of the efficient Bi3+-to-Tb3+ energy transfer. Furthermore, an evolution of the coordination environments of the Bi3+/Tb3+ sites was observed when increasing x. This evolution was found to correlate to the variation of the PL spectra. In particular, the value of the ratio of cyan/green [defined as I(5D4→7F6)/ I(5D4→7F5) of Tb3+] was about 0.28 when x < 0.4, and it increased to 0.71 at x = 0.9 and thereafter remained almost constant. Ba6(RE0.3- yBi yTb0.7)9B79O138 (RE = La or Y, 0 ≤ y ≤ 0.3) were also prepared for better understanding of the host-sensitization effect and in both series, Ba6(RE0.1Bi0.2Tb0.7)9B79O138 show the highest emission. [ABSTRACT FROM AUTHOR]

There are limited photoluminescence (PL) studies for rare earth borates with crystalline water molecules, which are usually supposed to have low PL efficiency because the vibrations of H2O or –OH may lead to emission quenching. We investigated the PL properties of Sm1−xEux[B9O13(OH)4]·H2O (x = 0–1.00) and their dehydrated products α-Sm1−xEuxB5O9. There is no quenching effect in those studied polyborates because the large borate ionic groups isolate the Eu3+ activators very well. Sm3+ and Eu3+ are basically separated luminescent activators. Comparatively, Sm3+ shows a very small emission intensity, which can be almost ignored, therefore our interest is focused on the Eu3+ luminescence. By TG-DSC and powder XRD experiments, we defined three weight-loss steps for Eu[B9O13(OH)4]·H2O and a re-crystallization process to α-EuB5O9, during which luminescent spectra of Eu3+ are recorded. It shows an interesting variety and therefore is a good medium to understand the coordination environment evolution of Eu3+, even for the intermediate amorphous phase. In fact, the coordination symmetry of Eu3+ in the amorphous state is the lowest. The high efficiency of the f–f transitions and large R/O value (3.8) imply this amorphous phase is potentially a good red-emitting UV-LED phosphor. Anhydrous α-EuB5O9 shows the highest luminescent efficiency excited by Eu3+ CT transition. In addition, α-Sm1−xEuxB5O9 was synthesized by a sol–gel method directly for the first time, and α-EuB5O9 shows superior PL properties due to its better crystallinity. A lot of hydrated polyborates with crystalline water molecules remain unexplored and our study shows their potential as good phosphors. [ABSTRACT FROM AUTHOR]

It is important to develop red phosphors which can be efficiently excited by near ultraviolet (NUV) irradiation, matching the wavelength of commercial LED chips. ZnLaB 5 O 10 possesses a significantly distorted coordination of La3+ and suitable for the Eu3+ incorporation, whose parity-forbidden law could be suppressed in such a coordination and be efficiently excited by f - f transitions in the NUV range. ZnLa 1- x Eu x B 5 O 10 (0 ≤ x ≤ 1.0) were prepared by high temperature solid state reactions. Excitation and emission spectra prove that the concentration saturation occurs at a high Eu3+ concentration (∼60 atm%). All the phosphors emit the bright red light with a high red-to-orange ratio (2.7–3.1) and CIE coordinate (0.64, 0.36). In-situ high temperature photoluminescence spectra of ZnLa 0.4 Eu 0.6 B 5 O 10 prove its high thermal stability, i.e. the emission intensity at 150 °C remains 90% of the value at room temperature, thus being a suitable candidate for NUV-LED pumped red phosphor. ZnLa 1- x Eu x B 5 O 10 (0 ≤ x ≤ 1.0) were prepared by solid state reactions and the photoluminescence property was investigated systematically. Eu3+ locates at a 10-fold coordination environment with C 1 symmetry, thus the f - f transition at 393 nm is substantially intense and the emission quenching occurs at a high Eu3+ concentration (>60 atm%). The optimal sample ZnLa 0.4 Eu 0.6 B 5 O 10 together with commercial blue and green phosphors were combined with the 390 nm LED chip to emit a warm white light. Image 1 • ZnLa 1- x Eu x B 5 O 10 (0 ≤ x ≤ 1.0) were prepared by typical solid state reactions. • The concentration saturation occurs at a high Eu3+ concentration (∼60 atm%). • All samples emit the bright red light with a high red-to-orange ratio (2.7–3.1). • The emission intensity of ZnLa 0.4 Eu 0.6 B 5 O 10 at 150 °C remains 90%. • ZnLa 0.4 Eu 0.6 B 5 O 10 phosphor can be efficiently pumped by a 395 nm LED chip. [ABSTRACT FROM AUTHOR]

Metal borates are well-known optical materials while their semiconducting behavior, i.e. photocatalytic property, was less studied. Inspired by the recent publications on gallium borates with good photocatalytic performances, we investigated photocatalytic water reduction activity of another gallium borate, PbGaBO 4 , comprising edge-sharing GaO 6 -chains. Both conventional and solution assisted solid state reaction methods were employed for the preparation. Phase purity and the crystallinity of both samples were identified by powder X-ray diffraction and scanning electron microscopy. The UV–Vis reflectance spectra suggested the wide bandgap characteristic (4.10 eV) and theoretical calculations pointed out that the 6s and 5p orbitals of Pb 2+ contribute to both the bottom of CB and the top of VB. However the ionic bonding of Pb O in PbGaBO 4 led to a slight hydrolysis during the photocatalysis process, which can be suppressed by loading cocatalysts of Pt and RuO x . In addition, such a surficial modification significantly improved the photocatalytic water reduction ability, with an optimal H 2 evolution rate of 41.9(9) μmol/h/g under UV-light irradiation. [ABSTRACT FROM AUTHOR]

Extensive studies on photoluminescence (PL) were devoted to the well-known “ RE BaB 9 O 16 ” family, while the structure remained unsolved until the recent work on the structure determination of its new analogue Ba 6 Bi 9 B 79 O 138 . Accordingly, a re-visit to “ RE BaB 9 O 16 ” with the new formula was rationally performed by the syntheses and Tb 3+ -PL study on Ba 6 La 9 B 79 O 138 ( BLBO ) and Ba 6 Y 9 B 79 O 138 ( BYBO ). Powder XRD patterns of Ba 6 ( RE 1− x Tb x ) 9 B 79 O 138 ( RE = La and Y, 0 ≤ x ≤ 1) show a linear shrinkage or expansion of the unit cell in BLBO : x Tb 3+ and BYBO : x Tb 3+ , respectively. The ratio of Tb 3+ cyan/green (C/G) emission was proposed to evaluate the evolution principle of the RE -site symmetry in both series of phosphors. The C/G value remains unchanged in BLBO : x Tb 3+ , while it is sensitive to the Tb 3+ -to-Y 3+ substitution in BYBO : x Tb 3+ . For example, C/G keeps almost constant (∼0.30) when 0.10 ≤ x ≤ 0.5; a dramatic increase of C/G (from 0.33 to 0.67) occurs in the range of 0.50 ≤ x ≤ 0.90, accompanied with a RE -site symmetry transition from centrosymmetric to noncentrosymmetric; the value of C/G remains unchanged thereafter. The Ce 3+ -to-Tb 3+ sensitization effect is applied in Ba 6 ( RE 0.3− y Ce y Tb 0.7 ) 9 B 79 O 138 ( RE = La or Y, 0 ≤ y ≤ 0.3), and the samples with y = 0.2 possess the strongest green emission. [ABSTRACT FROM AUTHOR]

We present a systematic investigation on the photocatalytic ability of an open-framework gallium borate, Ga-PKU-1. It was reported to be intrinsically active for water reduction or oxidation, however, acquiring sacrificial reagents. Here the loading of CoO x , RuO x , Pt, Au, NiO x and Ag as cocatalysts greatly enhanced the catalytic activity, which eventually lead to overall water splitting into stoichiometric H 2 (28.4 μmol/h/g) and O 2 (14.5 μmol/h/g) for 1 wt.% RuO x –1 wt.% Pt loaded Ga-PKU-1. After three cycles of photocatalytic water splitting experiments, it gave the constant H 2 evolution rate with no degradation of the catalyst. [ABSTRACT FROM AUTHOR]

Abstract: Three new borates MB12O14(OH)10 (M=Mn, Fe, Zn) have been synthesized by boric acid flux methods, which are isotypic to NiB12O14(OH)10. Single-crystal XRD was performed to determine the crystal structures in detail. They all crystallize in the monoclinic space group P21/c. The size of MO6 (M=Mg, Mn, Fe, Co, Ni, Zn) octahedron shows a good agreement with the Shannon effective ionic radii of M2+. Magnetic measurements indicate MnB12O14(OH)10 is antiferromagnetic without a long-range ordering down to 2K. The values of its magnetic superexchange constants were evaluated by DFT calculations, which explain the observed magnetic behavior. The UV–vis diffuse reflectance spectrum of ZnB12O14(OH)10 suggests a band gap ∼4.6eV. DFT calculations indicate it has a direct band gap 4.9eV. The optical band gap is contributed by charge transfers from the occupied O 2p to the unoccupied Zn 4s states. [Copyright &y& Elsevier]

The high-pressure polymorph of β-YB 3 O 6 was stabilized by doping Bi3+ under ambient pressure, thus solid solutions of β-Y 1- m Bi m B 3 O 6 (0.10 ≤ m ≤ 0.30), β-Y 0.80- x Bi 0.20 Tb x B 3 O 6 (0.05 ≤ x ≤ 0.80), and β-Y 0.80- y Bi 0.20 Eu y B 3 O 6 (0.05 ≤ y ≤ 0.80) were prepared simply by high temperature solid state reactions. The phase purity and the successful cationic substitutions were confirmed by powder X-ray diffraction, where the linear expansion of lattice parameters was observed due to the replacement of Y3+ by lager cations. The second function of Bi3+ was to behave as a photoluminescent activator giving the blue emission, as well as a sensitizer to Tb3+ and Eu3+, which emit green and red light, respectively. Bright and color-tunable emissions from blue to green (or blue to red) were achieved by manipulating the relative ratio between Bi3+ and Tb3+ (or Eu3+). In final, a white emission was observed for the triply-doped phosphor β-Y 0.49 Bi 0.20 Tb 0.30 Eu 0.01 B 3 O 6. Since the highly efficient energy transfers from Bi3+ to Tb3+ and from Bi3+ to Eu3+, color-tunable emissions from blue to green and from blue to red can be achieved in Bi3+/Tb3+ and Bi3+/Eu3+ co-doped β-YB 3 O 6 , which is originally a high-pressure polymorph and could be stabilized at ambient pressure due to the Bi3+ substitutions. Image 1 • The high-pressure phase β-YB 3 O 6 was stabilized at ambient pressure by doping Bi3+. • Bi3+ emits the blue light and the optimal doping concentration is 20 atom%. • Bi3+, Tb3+, Eu3+ co-doped and triply-doped β-YB 3 O 6 were prepared. • Highly efficient energy transfer from Bi3+ to Tb3+/Eu3+ was proved. • Bright color-tunable emissions from blue to green (or blue to red) were achieved. [ABSTRACT FROM AUTHOR]

Completed solid solutions of Y 1- x Eu x [B 6 O 9 (OH) 3 ] were prepared by boric acid flux method and the structure of Eu[B 6 O 9 (OH) 3 ] was determined by single crystal X-ray diffraction (XRD). The successful cationic doping was supported by the linear change of unit cell parameters obtained by Le Bail fitting on powder XRD. Thermal treatments on Y 1- x Eu x [B 6 O 9 (OH) 3 ] will lead to the dehydration, re-crystallization into TD-α-Y 1- x Eu x B 5 O 9 , and decomposition to α-Y 1- x Eu x B 3 O 6 eventually. For comparison, the sol-gel method was also applied to prepare SG-α-Y 1- x Eu x B 5 O 9. Rietveld refinements on powder XRD was applied to obtain the crystallographic data for α-YB 5 O 9. PL investigation indicated that the existence of hydroxyl groups weakened the Eu3+ charge transfer (CT) in Y 1- x Eu x [B 6 O 9 (OH) 3 ]. In α-Y 1- x Eu x B 5 O 9 , an intense CT absorption was detected and a bright right emission was observed. Moreover, both series of phosphors exhibited a right shift of CT maximum wavelength due to the expansion of unit cell and the delayed concentration at x = 0.6. Complete solid solutions of α-Y 1- x Eu x B 5 O 9 were prepared by either heating the precursors Y 1- x Eu x [B 6 O 9 (OH) 3 ] or direct sol-gel method, and the purity of the borates were verified by careful analyses on powder XRD. Detailed photoluminescence property investigation proved that α-Y 1- x Eu x B 5 O 9 are good red phosphors with a delayed concentration quenching at x = 0.6. Image 1 • Y 1- x Eu x [B 6 O 9 (OH) 3 ] (0 ≤ x ≤ 1) were prepared by boric acid flux method. • Heating Y 1- x Eu x [B 6 O 9 (OH) 3 ] at 670 °C led to the formation of TD-α-Y 1- x Eu x B 5 O 9. • Sol-gel method was also applied to synthesize SG-α-Y 1- x Eu x B 5 O 9. • The CT transition of Eu3+ in Y 1- x Eu x [B 6 O 9 (OH) 3 ] was weakened by hydroxyl groups. • α-Y 1- x Eu x B 5 O 9 have a bright red emission and a concentration quenching at x = 0.6. [ABSTRACT FROM AUTHOR]

Octahedron-based redox molecular sieves Cr-PKU-5 were synthesized by a two-step template annealing method and used as catalysts for the liquid-phase ammoximation of cyclohexanone. PKU-5 (Al 4 B 6 O 15 ) is a novel anhydrous aluminoborate, but difficult to be synthesized due to the severe demands of preparation procedures. Interestingly, Cr-stabilized PKU-5 can be facilely prepared with nano-scaled distribution and large BET surface area by annealing Cr-doped PKU-1 precursors at high temperature. Le Bail fitting of powder XRD patterns demonstrated large amounts of Cr 3+ has been incorporated into the framework of PKU-5. Much different with TS-1 redox molecular sieve, Cr-PKU-5 was favorable to produce ketazine in the liquid-phase ammoximation of ketone, rather than oxime. Based on the discussion about reaction pathway, a probable reaction mechanism was proposed to interpret the critical role of Cr-PKU-5 in such a complex multi-step reaction. [ABSTRACT FROM AUTHOR]

It is quite interesting to develop photocatalytic applications among borate materials, in addition to their applications in optics. The diversity in structural chemistry may provide suitable electronic structures, possessing low e − -h + recombination rate. With this rationale, polycrystalline Cd 12 Ge 17 B 8 O 58 was unraveled as a new efficient photocatalyst for H 2 evolution in pure water. The calculated electronic structure suggests different effective masses of e − and h + , facilitating the anisotropic migration of charges. Various cocatalysts (Ag, Au, Pd, Pt, CuO x , RuO x , NiO x ) were applied to significantly enhance the activity, and the optimal H 2 evolution rate in pure water achieved 163 μmol/h/g. [ABSTRACT FROM AUTHOR]

PKU-5 (Al 4 B 6 O 15 ) is potentially a solid acid catalyst, and it possesses an interesting open-framework composed of [AlO 6 ] and [B 2 O 5 ] groups. PKU-5 shows a high thermal stability, while no physical and chemical properties were investigated thus far, because of the difficulty in its synthesis. Cr-stabilized PKU-5 with the formula (Al 1− x Cr x ) 4 B 6 O 15 (0.08 ≤ x ≤ 0.14) can be easily prepared by annealing Cr-doped PKU-1 precursors. XRD and TEM experiments demonstrate Cr 3+ has been successively incorporated into the framework of PKU-5. NH 3 -TPD measurements indicate that the partial substitution of Al 3+ by Cr 3+ leads to a small change of acid sites in total amounts and distributions. Cr-PKU-5 shows a good catalytic activity for methanol dehydration from 300 to 450 °C. Other operation conditions, such as the Cr 3+ content, space velocity of methanol were also discussed in detail to evaluate its catalytic performance. [ABSTRACT FROM AUTHOR]

An aluminoborate (PKU-1) with octahedron-based framework was found to be a highly efficient solid acid catalyst for the rapid and convenient synthesis of α-aminonitriles from imines and TMSCN under mild reaction conditions. The catalytic active sites are related to the borate hydroxyl groups in the 18-ring structural channels. The borate hydroxyl groups play a critical role as Brønsted acid to protonate imine and activate TMSCN, thus providing the imine intermediate and producing CN anions, respectively. [ABSTRACT FROM AUTHOR]

A series of rare earth polyborate with the general formula LiCa RE 5 (BO 3) 6 (RE ​= ​Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y) were synthesized by high temperature solid state reactions. In literature, the Cd-analogues and LiCaTb 5 (BO 3) 6 were reported, here Rietveld refinements were performed on high quality powder X-ray diffraction data and the crystallographic parameters were obtained for the title compounds. Eu3+-luminescence in LiCa RE 5 (BO 3) 6 (RE ​= ​Gd, Y, Lu) were characterized. Eu3+ activators were doped into both the close-to-centrosymmetric and strongly-distorted coordination environments. Overall, bright orange-red emission can be observed with a slight increase of the red-to-orange (R / O) ratio with RE 3+ ionic radius increases. High quality powder samples of LiCa RE 5 (BO 3) 6 (RE ​= ​Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y) were synthesized by high temperature solid state reactions. Rietveld refinements on all samples confirmed the co-occupancy of Ca2+ and RE 3+ at M1 and M3 sites, and LiCa(RE 0.95 Eu 0.05) 5 (BO 3) 6 (RE ​= ​Gd, Y, Lu) exhibits a bright red-orange emission. Image 1 • LiCa RE 5 (BO 3) 6 were synthesized by high temperature solid state reactions. • High quality powder XRD data confirm the phase purity. • Structure details were obtained by careful Rietveld refinements. • Ca2+ co-occupy with the rare earth cations at M1 and M3 sites. • LiCa(RE 0.95 Eu 0.05) 5 (BO 3) 6 (RE ​= ​Gd, Y, Lu) gives a bright red-orange emission. [ABSTRACT FROM AUTHOR]

A strategy to utilize the nonlinear optical borate as the photoluminescent host is proposed in order to gain enhanced 4 f -4 f transitions because there exists a high probability of Eu3+ locating in a noncentrosymmetric coordination, serving as the near ultraviolet LED pumped red phosphor. With such a rationale, La 1- x Eu x B 4 O 6 (OH) 2 Cl have been prepared by boric acid flux method, which transfer to TD-α-La 1- x Eu x B 3 O 6 by high temperature annealing. In the meantime, HS-α-La 1- y Eu y B 3 O 6 (y ​= ​0, 0.075, 0.15, 0.3, 0.4) are synthesized directly by high temperature solid state reactions. The Eu3+-dependent cell volume is employed to obtain equation (1): V 1 ​= ​421.0(3)-26(1) y. Accordingly, the x values of TD-α-La 1- x Eu x B 3 O 6 can be deduced and the cell volume of La 1- x Eu x B 4 O 6 (OH) 2 Cl can be simulated into equation (2): V 2 ​= ​695.1(1)-37.9(8) x. In the following, all the x values for 11 samples of La 1- x Eu x B 4 O 6 (OH) 2 Cl are determined. The noncentrosymmetric coordination as well as the mix-coordination atoms lead to strong 4 f -4 f transitions of Eu3+, and only a slight concentration quenching effect is observed despite the existence of hydroxyl groups. Once combined with a 395 ​nm LED chip, it emits a bright pink light, and the thermal stability is satisfied according to the in-situ high temperature photoluminescent study. The noncentrosymmetric coordination as well as the mix-coordination atoms in La 1- x Eu x B 4 O 6 (OH) 2 Cl lead to strong 4 f -4 f transitions of Eu3+, and only a slight concentration quenching effect was observed despite the existence of hydroxyl groups, suggesting the potential as the NUV LED pumped red phosphor. Image 1 • La 1- x Eu x B 4 O 6 (OH) 2 Cl were prepared by boric acid flux method. • Eu3+-contents in La 1- x Eu x B 4 O 6 (OH) 2 Cl were determined by external standard method. • 4 f -4 f transitions of Eu3+ were enhanced due to the oxychloride coordination. • Once combined with a 395 ​nm LED chip, it emitted a bright pink light. • In-situ high temperature PL spectra proved its high thermal stability. [ABSTRACT FROM AUTHOR]

Ga4B2O9 is prepared by hydrothermal (HY), sol-gel (SG), and high-temperature solid state (HTSSR) reactions. [ABSTRACT FROM AUTHOR]