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A pseudo-octahedral coordination structure of Mn4+ has been innovatively designed, which has realized the maximum red shift and the widest full width at half-maximum (FWHM) of Mn4+ emission so far, not only extending the emission wavelength of Mn4+ to the near-infrared (NIR) region, but also effectively broadening its bandwidth. In the Ba3Ca4(BO3)3(SiO4)Cl:Mn4+ (BCBSC:Mn4+) phosphor, the [Mn/Ca1O9] polyhedron contains one [Mn/Ca1O6] octahedron, which constitutes the pseudo-octahedral coordination structure of Mn4+. The BCBSC:Mn4+ phosphor can be excited at 362 nm and 470 nm and exhibits a broadband NIR emission centered at ∼756 nm with a super-wide range from 650 nm to 1100 nm. The FWHM can reach ∼90 nm. In addition, the internal quantum efficiency (IQE) of the BCBSC:0.01Mn4+ phosphor is 69.7%. The unique luminescence characteristics of BCBSC:Mn4+ phosphors are explored using experimental data and first principles calculation. The significant redshift, the abnormal broadband emission, and the high luminous efficiency are closely related to the special highly distorted [Mn/Ca1O6] pseudo-octahedral coordination environment. The results contribute to comprehending the mechanism of the broadband NIR emission of Mn4+ activated phosphors and broaden the research ideas of developing high-performance Mn4+ doped phosphors for NIR phosphor-converted light-emission diode applications. [ABSTRACT FROM AUTHOR]

In this work, we prepared a new orange-red phosphor Li2La1−xTiTaO7:xSm3+ (abbreviated as LLTT:Sm3+) for white light-emitting diodes (w-LEDs). Its crystal structure, microstructure, photoluminescence characteristics, luminescence lifetime and thermal quenching properties were studied in depth. The LLTT:Sm3+ phosphor shows four intense emission peaks at 563, 597, 643, and 706 nm when excited at 407 nm. Thermal quenching is caused by the dipole–quadrupole (d–q) interaction of Sm3+ ions, and the optimum doping concentration of Sm3+ is x = 0.05. Meanwhile, the LLTT:0.05Sm3+ phosphor has a high overall quantum yield (QY = 59.65%) and almost no thermal quenching. The emission intensity at 423 K is 101.5% of the initial value at 298 K, while the CIE chromaticity coordinates barely change as the temperature rises. The fabricated white LED device exhibits excellent CRI and CCT values of 90.4 and 5043 K, respectively. These findings demonstrate that the LLTT:Sm3+ phosphor has promise in w-LED applications. [ABSTRACT FROM AUTHOR]

Cr3+-activated phosphors with high quantum efficiency show excellent promise in the field of near-infrared (NIR) phosphor converted light-emitting diodes (pc-LEDs). Here, we design an annealing program for Cr3+-doped phosphors containing variable valence elements that cannot be prepared in a reducing atmosphere to enhance their luminescence efficiency and thermal stability. A novel phosphor, Li2Mg3SnO6:Cr3+, developed by this annealing design, containing variable valence element Sn, exhibits higher quantum efficiency and better thermal stability than the one prepared by the conventional solid-state reaction. The Li2Mg3SnO6:0.03Cr3+ sample exhibits broadband NIR emission with a full width at half-maximum (FWHM) of 201 nm. After annealing, the internal quantum efficiency (IQE) and external quantum efficiency (EQE) of the Li2Mg3SnO6:0.03Cr3+ sample are enhanced from 48.5% to 84.7% and from 22.7% to 32.6%, respectively, and the thermal quenching temperature at which the luminescence intensity of the phosphor reduces to half of its initial value is promoted from ∼400 K to ∼425 K. The luminescence intensity of the optimized Li2Mg3SnO6:0.03Cr3+ sample at 425 K (∼152 °C) remains 49.2% of its initial intensity at 300 K. A NIR pc-LED is fabricated by combining the optimized Li2Mg3SnO6:0.03Cr3+ sample with a blue LED (455 nm blue chip), and the NIR radiant fluxes of 3.676 mW (at 10 mA) and 29.21 mW (at 100 mA), as well as a maximum NIR photoelectric efficiency of 14.2%, are obtained. The results show that this novel phosphor has great application potential in NIR pc-LEDs, and the annealing design exhibits huge potential for improving the optical properties of Cr3+-activated phosphors. [ABSTRACT FROM AUTHOR]

Phosphors have attracted significant interest as potential optical temperature sensors in recent years. In our work, a new blue-light stimulated KSr6Sc(SiO4)4:Eu2+ phosphor with decorative kröhnkite-like octahedral tetrahedral chains was successfully synthesized. Multiple site occupancy occurred in KSr6Sc(SiO4)4:Eu2+ and induced a yellow-orange emission band with a peak at 571 nm and an FWHM of 91 nm. Gaussian fitting and time-resolved photoluminescence mapping were combined to analyze the occupation of Eu2+ in five Sr2+ sites. In the meantime, the site occupation preference, energy transfer process, and thermal quenching mechanism of Eu2+ emission centers have been comprehensively examined. Under 450 nm excitation, the optimal sample possesses an acceptable quantum efficiency (EQE = 17.3%) and a high sensitivity between luminescence properties and temperature variation ranging from 200 to 475 K. The optimal sample's relative sensor sensitivity achieves a maximum value of 3.53% K−1 at 475 K. The phosphor KSr6Sc(SiO4)4:0.07Eu2+ presents the potentiality as an optical thermometer. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) emitting LED devices have broad applications. Using a visible light LED chip to excite Cr3+-activated phosphors to obtain NIR light has attracted extensive attention. In this study, a near-infrared luminescent material, Cr3+-doped Sc1−xTaO4, was synthesized by the element substitution method. It demonstrated a long emission wavelength (940 nm) and wide full width at half maximum (FWHM) (186 nm). The morphology, structure and photoluminescence of the samples were investigated using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy techniques. Moreover, the relationship between the NIR emission properties of Cr3+ and the substituted ions in the crystal matrix was studied. Based on this material, we fabricated near-infrared LED devices, which exhibited good near-infrared luminescence properties. [ABSTRACT FROM AUTHOR]

γ-phase copper(I) iodide (abbreviated to CuI hereafter) with different morphologies is realized through a one-step redox process from I-containing ionic liquid (IL) or poly(ionic liquid)s (PILs) precursors at room temperature. The phase composition, morphology, and electronic states of the synthesized CuI samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The resulting CuI products exhibit three different types of morphologies, namely nanocrystals, with an average size of 0.8 ± 0.2 μm, nanoplates, with a thickness of 35.8 ± 0.9 nm, and nanoflowers, with petals with a thickness of 12.2 ± 0.8 nm. Moreover, the as-synthesized CuI samples exhibit gradually diminishing bandgaps and improved photocatalysis performance for the photodegradation of rhodamine B (RhB) under visible light irradiation as the thickness decreases. XPS measurements confirm that IL/PILs coupled to the CuI surface, resulting in a further charge transfer between Cu and I. These results conclusively prove that IL/PILs serve as both the reducing agents and assemble as orientation templates in the formation of the CuI nanostructures, and also successfully mediate the functional properties of the samples by changing the surface electronic structures. [ABSTRACT FROM AUTHOR]

A new vanadate SrMn2(VO4)2(H2O)2 was synthesized and characterized by single-crystal X-ray analysis. It crystallizes in the monoclinic system with space group C2/m, and exhibits a quasi-one-dimensional (1D) structure. The Mn2+ ions form infinite linear-chains along the b-axis through edge-sharing oxygen atoms and further the linear-chains are connected by VO4 polyhedra into a layer in the ab-plane with Sr2+ ions residing in the space between the layers. Magnetic measurement results show that SrMn2(VO4)2(H2O)2 possesses two spin-canted antiferromagnetic orderings at ∼45 K and ∼7 K. The first ordering at ∼45 K possibly corresponds to a small deviation of spins from a strictly antiparallel arrangement. As the temperature decreases, further spin rotations occur leading to a steadier noncollinear antiferromagnetic phase, leading to the second ordering at ∼7 K. Also, a field-induced transition is observed at a critical field (0.4 T) below ∼7 K. [ABSTRACT FROM AUTHOR]

A new vanadate SrMn2(VO4)2(H2O)2 was synthesized and characterized by single-crystal X-ray analysis. It crystallizes in the monoclinic system with space group C2/m, and exhibits a quasi-one-dimensional (1D) structure. The Mn2+ ions form infinite linear-chains along the b-axis through edge-sharing oxygen atoms and further the linear-chains are connected by VO4 polyhedra into a layer in the ab-plane with Sr2+ ions residing in the space between the layers. Magnetic measurement results show that SrMn2(VO4)2(H2O)2 possesses two spin-canted antiferromagnetic orderings at ∼45 K and ∼7 K. The first ordering at ∼45 K possibly corresponds to a small deviation of spins from a strictly antiparallel arrangement. As the temperature decreases, further spin rotations occur leading to a steadier noncollinear antiferromagnetic phase, leading to the second ordering at ∼7 K. Also, a field-induced transition is observed at a critical field (0.4 T) below ∼7 K. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) long-lasting phosphorescence (LLP) phosphors have potential applications in biological and military fields. However, the properties of these phosphors are insufficient to satisfy the demands. Herein, we report a series of novel LLP phosphors Zn1.98−xLi0.02P2O7:xYb3+ with strong NIR LLP. By investigating the O–Yb3+ charge transfer (CT) band and host thoroughly, it can be confirmed that distinct photoluminescence (PL) of the two can be realized by selecting an appropriate excitation. For NIR emission, considering that the emission of Yb3+ originates from the characteristic 4f–4f transition between 4F5/2 and 4F7/2 levels and the difference between these two levels is too small to be excited by UV light, it is practicable to use the energy transfer of the host rather than that of the O–Yb3+ CT band as its energy level does not match with that of Yb3+. LLP is different from PL of the O–Yb3+ CT band, host or Yb3+, and it is strongly dependent on the appropriate depths of the traps; therefore, the selection and regulation of the traps are crucial. Considering the practicability and the demand of NIR LLP materials, we focus on how to excite Yb3+ and obtain LLP. [ABSTRACT FROM AUTHOR]

A novel dichromic luminescence probe SrO:Eu3+,Bi3+ for temperature sensing is achieved. The detailed luminescence properties, e.g., the excitation emission spectra, energy transfer efficiency, luminescence decay lifetimes and temperature dependent luminescence are comprehensively studied. The two dominant emissions 5D0→7F2 transition of Eu3+ and the 3P1→1S0 transition of Bi3+ display adjustable spectrum area. The interaction effect between Eu3+ and Bi3+ are proposed. The dichromic emissions are specifically responding to temperature with high sensitivity at ultra-wide range from 30 to 400 °C. Spatial and temporal temperature images on an aircraft surface have been successfully realized under excitation of commercial 365 nm light emitting diode (LED) by painting the SrO:Bi3+,Eu3+ phosphor on a plane model. Finally, the thermal quenching mechanism revealed by Arrhenius theory is employed to interpret the temperature sensitive luminescence behaviour. [ABSTRACT FROM AUTHOR]

A novel dichromic luminescence probe SrO:Eu3+,Bi3+ for temperature sensing is achieved. The detailed luminescence properties, e.g., the excitation emission spectra, energy transfer efficiency, luminescence decay lifetimes and temperature dependent luminescence are comprehensively studied. The two dominant emissions 5D0→7F2 transition of Eu3+ and the 3P1→1S0 transition of Bi3+ display adjustable spectrum area. The interaction effect between Eu3+ and Bi3+ are proposed. The dichromic emissions are specifically responding to temperature with high sensitivity at ultra-wide range from 30 to 400 °C. Spatial and temporal temperature images on an aircraft surface have been successfully realized under excitation of commercial 365 nm light emitting diode (LED) by painting the SrO:Bi3+,Eu3+ phosphor on a plane model. Finally, the thermal quenching mechanism revealed by Arrhenius theory is employed to interpret the temperature sensitive luminescence behaviour. [ABSTRACT FROM AUTHOR]

Cu5(VO4)2(OH)4 (turanite) is a layered compound, exhibiting a copper(ii) oxide layer in the [0 1 1] plane composed of edge-sharing CuO6 octahedra. Each Cu–O layer is further separated by VO4 tetrahedra. Closer scrutiny found that the copper(ii) oxide layer in the compound represents a totally new geometrically-frustrated lattice, a 1/6 depleted triangular lattice. More specifically, the spin network in the [0 1 1] plane is formed by the alternate ranking of triangular and honeycomb strips. Magnetic measurements show that the Cu5(VO4)2(OH)4 behaves as a spin-1/2 ferrimagnet with a Tc = ∼4.5 K. It exhibits an unusual 1/5 magnetization plateau arising from the competition between antiferromagnetic and ferromagnetic interactions caused by the strong frustration. The possible spin-arrangements are also suggested. [ABSTRACT FROM AUTHOR]

Adjusting and controlling an ion’s chemical state has always been a focus of researchers’ attention. Herein, an intense long-lasting phosphorescence of Eu2+ is obtained without any sacrificial reductant. The remarkable self-reducing process and the unique luminescence properties stem from a variation of the topological structure of the BO3 triangle. [ABSTRACT FROM AUTHOR]

A series of single-phase Ca9Sc(PO4)7:Eu2+,Tb3+,Mn2+ phosphors for UV excitations were synthesized by a high-temperature solid-state reaction. Energy transfer from Eu2+→ Tb3+ and Eu2+→ Mn2+ in a Ca9Sc(PO4)7 sample is a feasible route to realize color-tunable emission because Ca9Sc(PO4)7 single-doped Eu2+/Tb3+/Mn2+ emit blue, green and red light, respectively. Most of the white light region in the CIE chromaticity diagram has been realized in Ca9Sc(PO4)7:Eu2+,Tb3+,Mn2+ phosphors. Warm white light including the points of (0.337, 0.331), (0.353, 0.355) and (0.358, 0.327) close to day light (0.33, 0.33) with CCT of 5285 K, 4719 K and 4333 K is obtained, respectively. [ABSTRACT FROM AUTHOR]

A novel copper compound, Cu13(VO4)4(OH)10F4, featuring two types of two-dimensional extended kagome-like and triangular lattices, exhibits long-range antiferromagnetic ordering at ∼3 K, a strong spin-frustration effect with f = 21 and a spin-flop transition at 5 T. [ABSTRACT FROM AUTHOR]

A novel single-composition Ca4(PO4)2O:Ce3+,Eu2+ phosphor emitting white light was synthesized by conventional solid-state reaction for light-emitting diode applications. X-ray diffraction, photoluminescence spectra, and luminescence decay spectra were used to characterize the samples. Energy transfer from Ce3+ to Eu2+ ions was observed in the co-doped samples, and the transfer mechanism in the Ca4(PO4)2O:Ce3+,Eu2+ phosphors was dipole–dipole interaction. The emission hue of Ca4(PO4)2O:Ce3+,Eu2+ was found to vary from blue (0.165, 0.188) to white (0.332, 0.300) and eventually to orange (0.519, 0.366) by precisely controlling the ratio of Ce3+ to Eu2+. The combination of a 380 nm near-ultraviolet chip with a Ca4(PO4)2O:0.02Ce3+,0.012Eu2+ phosphor produced a diode emitting white light with ultra-wideband emission and a correlated color temperature of 4124 K. Overall, results indicated that the prepared samples may be potentially applied in white-light-emitting diodes. [ABSTRACT FROM AUTHOR]

Systematic explorations of new phases in the LnIII–VV–SeIV–O systems by hydrothermal syntheses led to four new quaternary compounds, namely, Nd2(VV2O4)(SeO3)4·H2O (1), Ln(VVO2)(SeO3)2(Ln = Eu 2, Gd 3, Tb 4). The structure of Nd2(VV2O4)(SeO3)4·H2O features a 3D framework composed of the 2D layers of [N d(SeO3)]+bridged by the infinite [VO2(SeO3)]−chains with the lattice water molecules located at the 6-membered ring tunnels formed. The structure of Ln(VVO2)(SeO3)2(Ln = Eu, Gd, Tb) also features a 3D framework composed of 2D layers of [Ln(SeO3)]+bridged by the infinite [(VO2)(SeO3)]−double chains. The 1D vanadium oxide selenite chain of 1differs significantly from those in compounds 2–4in terms of the coordination modes of the selenite groups and the connectivities between neighbouring VO6octahedra. Luminescent and magnetic properties of these compounds were also measured. [ABSTRACT FROM AUTHOR]

Correction for ‘Developing near-infrared long-lasting phosphorescence of Yb3+ through a medium: insights into energy transfer in the novel material Zn1.98Li0.02P2O7:Yb3+’ by Huimin Li et al., Dalton Trans., 2018, 47, 9814–9823. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) long-lasting phosphorescence (LLP) phosphors have potential applications in biological and military fields. However, the properties of these phosphors are insufficient to satisfy the demands. Herein, we report a series of novel LLP phosphors Zn1.98−xLi0.02P2O7:xYb3+ with strong NIR LLP. By investigating the O–Yb3+ charge transfer (CT) band and host thoroughly, it can be confirmed that distinct photoluminescence (PL) of the two can be realized by selecting an appropriate excitation. For NIR emission, considering that the emission of Yb3+ originates from the characteristic 4f–4f transition between 4F5/2 and 4F7/2 levels and the difference between these two levels is too small to be excited by UV light, it is practicable to use the energy transfer of the host rather than that of the O–Yb3+ CT band as its energy level does not match with that of Yb3+. LLP is different from PL of the O–Yb3+ CT band, host or Yb3+, and it is strongly dependent on the appropriate depths of the traps; therefore, the selection and regulation of the traps are crucial. Considering the practicability and the demand of NIR LLP materials, we focus on how to excite Yb3+ and obtain LLP. [ABSTRACT FROM AUTHOR]

Correction for ‘Developing near-infrared long-lasting phosphorescence of Yb3+ through a medium: insights into energy transfer in the novel material Zn1.98Li0.02P2O7:Yb3+’ by Huimin Li et al., Dalton Trans., 2018, 47, 9814–9823. [ABSTRACT FROM AUTHOR]