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In an effort to obtain a novel cyan‐emitting phosphor, the [K1‐xRbx]3GdSi2O7: yCe3+ materials (x = 0, 0.1, 0.2, 0.3, 0.4, y = 0, 0.005, 0.01, 0.02, 0.03, 0.04) are synthesized via a solid‐state reaction pathway, and their crystal structure and luminescence behaviors are studied systematically. The chemical substitution of Rb+ in the K+ sites can enlarge the K3GdSi2O7 host lattice and help to the blue‐shifting of emission band of Ce3+ ions due to the decreased crystal field splitting effect. It is also confirmed that the Ce3+ ions tend to enter [Gd1O6] and [Gd2O6] polyhedrons simultaneously. Consequently, the [K0.7Rb0.3]3GdSi2O7: Ce3+ phosphor yields a broadband cyan emission centered at 492 nm with the full width at half maximum (FWHM) of ∼115 nm upon 365 nm excitation. The optimal concentration of Ce3+ dopant is determined to be 0.01, and the concentration quenching effect can be attributed to the dipole−dipole interactions. The white light emitting diode (WLED) device fabricated by employing the discovered [K0.7Rb0.3]3GdSi2O7: 0.01Ce3+ phosphor displays a high color rendering index (Ra = 91.7) and a low correlated color temperature (CCT = 3749 K). This work may promote the development of cyan phosphors for near ultraviolet‐converted WLEDs with high performance. [ABSTRACT FROM AUTHOR]

Lanthanide-doped fluoride nanoparticles (NPs) showcase adjustable X-ray-excited persistent luminescence (XEPL), holding significant promise for applications in three-dimensional (3D) imaging through the creation of flexible X-ray detectors. However, a dangerous high X-ray irradiation dose rate and complicated heating procedure are required to generate efficient XEPL for high-resolution 3D imaging, which is attributed to a lack of strategies to significantly enhance the XEPL intensity. Here we report that the XEPL intensity of a series of lanthanide activators (Dy, Pr, Er, Tm, Gd, Tb) is greatly improved by constructing dual heterogeneous interfaces in a double-shell nanostructure. Mechanistic studies indicate that the employed core@shell@shell structure could not only passivate the surface quenchers to lower the non-radiative relaxation possibility, but also reduce the interfacial Frenkel defect formation energy leading to increase the trap concentration. By employing a NPs containing flexible film as the scintillation screen, the inside 3D electrical structure of a watch was clearly achieved based on the delayed XEPL imaging and 3D reconstruction procedure. We foresee that these findings will promote the development of advanced X-ray activated persistent fluoride NPs and offer opportunities for safer and more efficient X-ray imaging techniques in a number of scientific and practical areas.High-resolution X-ray imaging requires a high radiation dose. Here, the authors achieve low-dose 3D imaging by increasing the XEPL intensity using a double-shell nanostructure with two heterogeneous interfaces. [ABSTRACT FROM AUTHOR]

White-light diodes (WLEDs) are widely used in high-brightness applications owing to their outstanding advantages. However, current methods for preparing commercial WLEDs significantly deteriorate their optical properties and limit their use in high-power applications. To address this, inorganic materials, such as phosphor-in-glass (PiG), have been recently investigated as practical alternatives. In this study, a series of high-efficiency white-emitting PiG samples were prepared by mixing silicate glass powders with different particle size distributions and different concentrations of Y3Al5O12:Ce3+ (YAG:Ce3+) phosphors. The microstructure, transmittance, and photoluminescence properties of PiG were investigated. When the glass powder with the particle size ranges of 75–150 and 30–48 μm were mixed, at a ratio of 94 : 6, a silicate glass with a thickness of 0.8 mm and a maximum transmittance of 75% in the visible range was obtained. Under excitation with a 450 nm blue-light laser diode, PiG produced white light with a total luminescence efficiency of 194.64 lm W−1 and a total luminous flux of 623.9 lm. These results demonstrate that the optical performance of PiG can be effectively adjusted by adjusting the particle size distribution of silicate glass powder and the mixing concentration of the YAG:Ce3+ phosphor, thereby providing a tuning pathway for smart white-light devices. [ABSTRACT FROM AUTHOR]

External manipulation of emission colour is of significance for scientific research and applications, however, the general stimulus-responsive colour modulation method requires both stringent control of microstructures and continously adjustment of particular stimuli conditions. Here, we introduce pathways to manipulate the kinetics of time evolution of both intensity and spectral characteristics of X-ray excited afterglow (XEA) by regioselective doping of lanthanide activators in core-shell nanostructures. Our work reported here reveals the following phenomena: 1. The XEA intensities of multiple lanthanide activators are significantly enhanced via incorporating interstitial Na+ ions inside the nanocrystal structure. 2. The XEA intensities of activators exhibit diverse decay rates in the core and the shell and can largely be tuned separately, which enables us to realize a series of core@shell NPs featuring distinct time-dependent afterglow colour evolution. 3. A core/multi-shell NP structure can be designed to simultaneously generate afterglow, upconversion and downshifting to realize multimode time-dependent multicolour evolutions. These findings can promote the development of superior XEA and plentiful spectral manipulation, opening up a broad range of applications ranging from multiplexed biosensing, to high-capacity information encryption, to multidimensional displays and to multifunctional optoelectronic devices. X-ray activated afterglow nanomaterials are desirable components for advanced optoelectronic applications. Here, the authors present pathways to modulate the stimulus-responsive color emissions in lanthanide-doped fluoride core-shell nanoparticles. [ABSTRACT FROM AUTHOR]

A series of Rb1−yKyNa3(Li3SiO4)4:Eu2+(0 ≤ y ≤ 1) phosphors were successfully synthesized through a high-temperature solid-state reaction. The introduction of K+ into the RbNa3(Li3SiO4)4:Eu2+ phosphor to partially or completely replace Rb+ allows the emission spectrum to be modulated from blue (λ = 473 nm, FWHM = 22.5 nm) to a narrow cyan band (λ = 485 nm, FWHM = 21.1 nm). As the K+ ion content increases, the space group of the phosphor evolves from I4/M to I41/A. The complete replacement of Rb+ by K+ results in the KNa3(Li3SiO4)4:Eu2+ cyan phosphor, which shows excellent thermal stability (the comprehensive emission loss is only 8% at 150 °C) and can be used to fill the cyan light gap in white LED devices. By adding the KNa3(Li3SiO4)4:Eu2+ cyan phosphor in packaging with yellow and red phosphors, the color rendering index is increased from 90.2 to 97.1 and the correlated color temperature improved to 3658 K. These results indicate that the cyan phosphor has important application value in full-spectrum white LEDs. [ABSTRACT FROM AUTHOR]

Phosphor is an important part of the new generation of light-emitting diodes (LEDs), which requires high luminous intensity and high-temperature resistance. In this study, a series of excellent (Ba1−x−yCax)AlSi5O2N7:yEu2+ phosphors was developed, which were synthesized by a high-temperature solid-state reaction in a reducing atmosphere. In addition, the crystallinity and luminescence intensity of the samples could be enhanced by some amount of Ca2+ substitution. The luminescence intensity was the highest when the Eu2+ concentration reached 0.06. Furthermore, the thermal stability of the luminescence was studied in detail. The results were satisfactory, showing that the luminescence intensity of the (Ba1−xCax)AlSi5O2N7:Eu2+ phosphors exhibited unique negative-thermal-quenching characteristics both at high (273–473 K) and low (4–273 K) temperatures. And the phosphor combined with UV LED chip and red phosphor Sr2Si5N8:Eu2+ can achieve a CRI of 90.4 in white LED application which indicated the (Ba1−xCax)AlSi5O2N7:Eu2+ phosphor has potential in LED applications. [ABSTRACT FROM AUTHOR]

Ultrathin two-dimensional (2D) materials have drawn great attention in recent years due to their promising applications in biomedicine and atomically optoelectronic devices. In this work, we have fabricated a 2D In2Se3 nanosheet doped with Nd3+ ions via the two-step method of solid phase synthesis and liquid exfoliation. Owing to the special inner 4f-4f energy level transitions, lanthanide ions can emit photons with almost the same energy in different environments. Here, a stable near-infrared luminescence from Nd3+-doped 2D In2Se3 nanosheets has been realized, which includes emission bands around 910, 1057, and 1324 nm. The doping of Nd3+ ions extends the emission region of In2Se3 nanosheets. Moreover, the photoluminescence mechanism of Nd3+ ions was investigated through a series of optical measurements. This work not only provides a reliable method to fabricate lanthanide ion-doped 2D materials but also possesses a great significance for luminescence study of lanthanide ions in the 2D matrix. [ABSTRACT FROM AUTHOR]

For achieving well-performing optical thermometry, a new type of dual-mode optical thermometer is explored based on the valley-to-peak ratio (VPR) and fluorescence lifetime of Eu3+ emissions in the ZrO2:Eu3+ nanocrystals with sizes down to 10 nm. In the VPR strategy, the intensity ratio between the valley (600 nm) generated by the emission band overlap and the 606 nm peak (5D0→7F2), which is highly temperature sensitive, is employed, giving the maximum relative sensing sensitivity (Sr) of 1.8% K−1 at 293 K and good anti-interference performance. Meanwhile, the 606 nm emission exhibits a temperature-dependent decay lifetime with the highest Sr of 0.33% K−1 at 573 K, which is due to the promoted nonradiative relaxation with temperature. These results provide useful information for constructing high-performance dual-mode optical thermometers, which may further stimulate the development of photosensitive nanomaterials for frontier applications. [ABSTRACT FROM AUTHOR]

Cation doping strategy has been extensively employed to enhance the charge carrier mobility and improve the stability of halide perovskites; however, the fundamental understanding of the inherent doping mechanism is still a challenge. Herein, based on a unique four-precursor synthetic strategy and density functional theory (DFT) calculation results, we verify that excessive chloride ion concentration benefits the formation of the bond [Pb⋯Cl] vacancy pair as well as the subsequent incorporation of the [Mn⋯Cl] ion pair synchronously. As a result, high Cl− ion concentration greatly promotes the incorporation of the Mn2+ ions into the CsPbCl3 crystal lattice. The particle size reduction of the CsPbCl3 perovskite with the incorporation of the Mn2+ ions is attributed to the increased surface electron charge density, which inhibits the diffusion of the negatively charged Cl− ions to the nuclei surface. These deep insights into the inherent Mn2+ doping mechanism could guide the realization of novel ion-doped perovskites with new optoelectronic performances. [ABSTRACT FROM AUTHOR]

Bi can exist in a variety of chemical states (with varying ionic charges) and the microstructure of the glass surrounding the ions can be engineered to manipulate the chemical state. In this work, efficient enhancement of Ho3+ emission is observed with the change in local glass environment around Bi by adding Al2O3 to multi-component germanosilicate glass. In this multi-component glass, Al3+ can form tetrahedral AlO4 by accepting the non-bridging oxygen (NBO) and then, the addition of the AlO4-tetrahedron to the glass network facilitates the diffusion of alkali metals. Hence, Al2O3 decreases the Ba2+-rich domain and is conducive to the existence of Bi ions that are at low valence state. Moreover, the emission spectra indicate high efficiency energy transfer (ET) derived from NIR emission centers (Bi0/Bi+) located in close proximity to the Ho3+ ions. These results indicate that the optimized fluorescence of Ho3+ for optical fiber laser can be achieved by adjusting the local structure of the host glass. [ABSTRACT FROM AUTHOR]

A series of novel Ce3+ and/or Sm3+ activated Y4SiAlO8N (YSAON) phosphors are successfully synthesized by a conventional solid-state reaction method. The formation of monophasic YSAON is confirmed by X-ray powder diffraction (XRD) analysis. The crystal structure of YSAON is solved by XRD refinement data. DFT calculations indicate that Y4SiAlO8N has an indirect band gap of 3.819 eV. Based on the analysis of crystal structure and lifetime curves, four emission sites of YSAON:0.02Ce3+ are identified, which are Y1 (413 nm, 448 nm), Y2 (428 nm, 469 nm), Y3 (619 nm, 698 nm) and Y4 (512 nm, 569 nm), respectively. The concentration quenching of Ce3+ in YSAON is investigated in detail and it is confirmed to be due to dipole–dipole interactions. Photoluminescence excitation (PLE) and photoluminescence (PL) spectral measurements showed that the Ce3+ and Sm3+ co-doped phosphor could be efficiently excited by near-UV light, and exhibited four emission bands peaked at 485 nm, 565 nm, 605 nm and 650 nm, respectively. The CIE chromaticity coordinates of the obtained white light can be tuned by adjusting the content of Ce3+ and Sm3+ ions. Therefore, we anticipate that these materials can be used in near-UV chip pumped white LEDs. [ABSTRACT FROM AUTHOR]

A series of Sr1.98−xBaxSi(O,N)4: 0.02Eu2+ (0 ≤x≤ 0.5) phosphors were synthesized by a conventional solid state reaction method. The Sr–N and Si–N bonds could be observed in FT-IR spectra. The XRD refinement results indicated that N3− would substitute for O22− and form Si–NO3 tetrahedrons during the process of forming the Sr1.98Si(O,N)4: Eu2+ (SSON: Eu2+) substitutional solid solution. The lattice constants of Sr1.98−xBaxSi(O,N)4: 0.02Eu2+ (SBSON) were increased due to the longer bond length of Ba–O. Compared with Sr2SiO4: Eu2+, the SSON: Eu2+ showed a remarkable red-shift, which is due to the nephelauxetic effect and the strong crystal field splitting originating from the stronger covalent bonding effect of the Eu–N bond. The SSON: Eu2+ presented a β phase structure before the introduction of Ba2+, whereas the α′-SBSON phase was obtained by the substitution of Ba2+ for Sr2+. Ba2+ doping led to an obvious blue-shift under 375 nm and 460 nm excitation. The 5d orbital of Ba2+ is coupled with the 5d orbital of Eu2+ on the higher energy level position in the host crystal. Under 375 nm excitation, the PL intensity gradually increased with the increase of the Ba2+ content. Under 460 nm excitation, the PL intensity gradually declined with the increase of Ba2+ content. The thermostability of α′-SBSON: Eu2+ was significantly improved compared with β-SSO: Eu2+ and β-SSON: Eu2+. On the basis of their adjustable emission wavelength, enhanced PL intensity and excellent thermostability in SBSON: Eu2+, we anticipate that these materials can be used as green or red phosphors in white light emitting diodes. [ABSTRACT FROM AUTHOR]

An emission-tunable, Eu2+-activated, Ba2Ca(PO4)2:Eu2+ phosphor was synthesized by a conventional solid-state reaction. X-ray powder diffraction (XRD) and FT-IR spectroscopic analysis confirmed the phase formation. Electron paramagnetic resonance (EPR) analysis indicated there are three different crystallographic Ba2+ sites, namely, Ba(1), Ba(2) and Ba(3), occupied by the Eu2+ ions. The excitation and emission spectra, concentration dependence of the emission intensity and decay curves of the phosphor were investigated. The results showed that with increasing Eu2+ concentration, the emission peak wavelength redshifted from 457 to 500 nm, and the color hue can be tuned from a greenish blue to a yellowish green. A white LED was fabricated using a near ultraviolet (n-UV) 410 nm chip pumped with a blend of phosphors consisting of greenish blue-emitting Ba1.97Ca(PO4)2:0.03Eu2+ and red-emitting Ca3.97(PO4)2O:0.07Eu2+. When the applied current was 350 mA, the white LED had Commission International de l'Eclairage color coordinates of (0.3249, 0.3421) at a white light (correlated color temperature = 6020 K) and an excellent color rendering index of 93. [ABSTRACT FROM AUTHOR]