Luminescence Centers Research Articles

Eu(III) functionalized ZnMOF based efficient dual-emission sensor integrated with self-calibrating logic gate for intelligent detection of epinephrine

The rapid detection of epinephrine (EPI) in serum holds immense importance in the early disease diagnosis and regular monitoring. On the basis of the coordination post-synthetic modification (PSM) strategy, a Eu3+ functionalized ZnMOF (Eu3+@ZnMOF) was fabricated by anchoring the Eu3+ ions within the microchannels of ZnMOF as secondary luminescent centers. Benefiting from two independent luminescent centers, the prepared Eu3+@ZnMOF shows great potential as a multi-signal self-calibrating luminescent sensor in visually and efficiently detecting serum EPI levels, with high reliability, fast response time, excellentrecycleability, and low detection limits of 17.8 ng/mL. Additionally, an intelligent sensing system was designed in accurately and reliably detecting serum EPI levels, based on the designed self-calibrating logic gates. Furthermore, the possible sensing mechanisms were elucidated through theoretical calculations as well as spectral overlaps. This work provides an effective and promising strategy for developing MOFs-based self-calibrating intelligent sensing platforms to detect bioactive molecules in bodily fluids.

Photoluminescence and afterglow of Tb3+ doped BaAl2O4

Tb3+ doped BaAl2O4 phosphors (0–9.0 mol%) were prepared through sol–gel combustion method. The crystal structure, morphology, chemical composition, photoluminescence (PL), afterglow and thermoluminescence (TL) glow curve of Tb3+ doped BaAl2O4 were investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, PL spectroscopy, afterglow spectroscopy, and TL dosimetry. Characterizations of the PL and afterglow spectra indicate that both Tb3+ doping species and oxygen vacancies act as the luminescence center of PL whereas only Tb3+ dopant works as the luminescence center of afterglow for Tb3+ doped BaAl2O4. The green afterglow of Tb3+ doped BaAl2O4 lasts for about 214 min at the optimal doping concentration of about 1.0 mol%. The profile of TL glow curve of Tb3+ doped BaAl2O4 heavily depends on the doping concentration, and the evolution of the TL glow curve with doping concentration reveals that doping BaAl2O4 with Tb3+ can significantly modify the distribution of carrier traps in the phosphor. The effects of Tb3+ doping on the PL, afterglow, and TL glow curve of Tb3+ doped BaAl2O4 are discussed in terms of the creation, recombination, and neutralization of defects in BaAl2O4. This work proves that doing with Tb3+ species is a general and robust strategy for endowing BaAl2O4 with highly efficient green afterglow. This “defect engineering” approach enables ultra-long afterglow for Tb3+ doped BaAl2O4 when defect centers in the phosphors are optimized.

Comparing thermoluminescence data on lanthanides in 36 compounds with predictions from vacuum referred binding energy diagrams

Thermoluminescence (TL) often involves the liberation of a charge carrier (an electron or a hole) from a charge carrier trapping centre into the conduction band (CB) or the valence band (VB) with subsequent recombination with a counter charge carrier at a luminescence centre. TL glow peak analysis can provide the energy ΔEt needed to liberate such charge carrier which then defines the location of the charge transition levels (CTL) of the carrier trapping centres below the CB-bottom or above the VB-top. The temperature at the maximum of the TL glow peak changes 3–4 K per 0.01 eV change in ΔEt thus providing an extremely sensitive probe of energy changes in CTLs. This work collects and reviews data on glow peaks due to electron or hole release from lanthanide dopants in 36 different inorganic compounds. To compare results from different literature sources, data were always re-analysed using the same method that is solely based on the temperature at the maximum of the glow peak. The changes in ΔEt along the lanthanides series provides insight at the sub 0.1 eV level on the changes in CTL energies. We will use a compound-dependent parameter to account for the nephelauxetic effect and a compound dependent parameter to account for lattice relaxation around the lanthanide. Together with information from lanthanide luminescence spectroscopy, the vacuum referred binding energy (VRBE) diagram will be constructed for each compound. The lanthanide electron or hole trap depth read from the VRBE scheme will be compared with that derived from the TL glow peak. Surprisingly good agreement will be demonstrated.

Planar technology fabrication of high-density luminescence structure based on NaYF4 microparticles

This study presents a technological capability of producing individual size-defined luminescent centers and high-density arrays of upconversion particles using monosize powder based on NaYF4 matrix doped with rare earth metals such as erbium and ytterbium. The integration of various techniques such as lithography, etching, and deposition has enabled the creation of cavity arrays, or trenches, with arbitrary shapes for localization of luminescent monodisperse microparticles with an average size of 1.65 μm.

Color Tunable Single-phase Cyclosilicate KBaScSi3O9: Eu2+/Tb3+/Sm3+ for n-UV pumped wLEDs

The exploration of stable/efficient phosphor for n-UV chip pumped white light-emitting diodes (wLEDs) remains an arduous task. Herein, a novel series of color tunable Eu2+/Tb3+/Sm3+ tridoped Sc-based cyclosilicate phosphors (KBaScSi3O9: Eu2+/Tb3+/Sm3+) have successfully designed and obtained via facile solid-state reaction based on comprehensive consideration of rigidly structural network of host, weak electron-phonon coupling strength and spectral adjustability of codopants via energy transfer (ET). The crystallographic occupancies of Eu, Tb and Sm primary in Ba/K, Ba and Ba sites in the monoclinic host, respectively were determined on the basis of the Rietveld refinements and crystal chemistry rules. The photoluminescence (PL) properties were systematically investigated in conjunction with structural analyses, implying that the ‘warm’ white light with excellent thermal stability is stemmed from combination of optimized blue (Eu2+), green (Tb3+) and red (Sm3+) emissions via Eu → Tb → Sm ET strategy. Interestingly, Tb ions play both roles of green light luminescent center and ET bridge to achieve cascade ET for connecting Eu/Sm ion pairs because of the adverse metal-metal charge transfer (MMCT) effect (Eu2+ + Sm3+ → Eu3+ + Sm2+). Furthermore, the phosphor-converted wLEDs (pc-wLEDs), by encapsulating the optimal KBS: 4%Eu/4%Tb/6%Sm with commercial n-UV LED chip, show high thermal stability with satisfactory electroluminescence (EL) performances. These results indicate the KBS: Eu/Tb/Sm phosphors are potential candidates for application in high power n-UV pumped pc-wLEDs.

Optical Information Transmission and Multimode Fluorescence Anticounterfeiting of Ca2-xMgxGe7O16:Mn2.

Multimode emission of Mn2+ for multimode fluorescence anticounterfeiting is achieved by cation site and interstitial occupancy in Ca2-xMgxGe7O16. The rings in Ca2-xMgxGe7O16 have a significant distortion for Mn2+ ions to enter the ring interstitials with a luminescence center at 665 nm, which is supported by XRD refinement results and first-principles calculations. The interstitial Mn2+ ion has good thermal stability with an activation energy of 0.36 eV. Surprisingly, these two luminescence centers, the cation site Mn and the interstitial Mn, have an obvious afterglow, and the disappearing afterglow will reappear by heating or irradiating with the 980 nm laser. The afterglow is significantly enhanced, as MnO2 is used as the manganese source, which is explained in detail by the thermal luminescence spectrum. Finally, Ca2-xMgxGe7O16:Mn2+ fully demonstrates its excellent prospects in fluorescent anticounterfeiting, information encryption, and optical information storage.

Advanced Synthesis and Characterization of CdO/CdS/ZnO Heterostructures for Solar Energy Applications.

This study introduces an innovative method for synthesizing Cadmium Oxide /Cadmium Sulfide/Zinc Oxide heterostructures (CdO/CdS/ZnO), emphasizing their potential application in solar energy. Utilizing a combination of electrochemical deposition and oxygen annealing, the research provides a thorough analysis of the heterostructures through scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) spectroscopy. The findings reveal a complex surface morphology and a composite structure with significant contributions from hexagonal CdS and cubic CdO phases. The study highlights the uniformity in the distribution of luminescent centers and the crystalline quality of the heterostructures, which is evident from the PL analysis. The redshift observed in the emission peak and the additional peaks in the excitation spectrum indicate intricate optical properties influenced by various factors, including quantum confinement and lattice strain. The research demonstrates these heterostructures' potential in enhancing solar cells' efficiency and applicability in optoelectronic devices. This comprehensive characterization and analysis pave the way for future optimization and application in efficient and sustainable solar energy solutions.

Local modification of the crystalline structure due to co-doping with RE3+ in cadmium metasilicate

Persistent emission is a well-known property of cadmium metasilicate (CdSiO3) doped and co-doped with rare earth ions due to the ease of choosing the desired luminescence colour, as well as the possibility of adjusting the emission colour and the luminescence duration. Experimental work has demonstrated that combinations of different rare earth ions can produce different emission spectra colours as well as modify the lifetime of emissions. Theoretical work demonstrated a preference of single dopants to substitute cadmium sites with a Cd-vacancy as a compensation mechanism. To help elucidate the luminescent mechanisms through structural modification and consequently modification of the crystal field generated in the material by the defective region, in this work, several configurations for combined defects were tested considering the distance and preferential configuration of all the defects that comprise the system, as well as the possibility of a high concentration of these defects. Results showed a preferential arrangement for the incorporation of a Cd-vacancy as a form of charge compensation. The arrangement forms an angle closer to 180° considering the Cd-vacancy as vertex and presents a distance of around 7 Å between rare earth ions. It was also identified that the formation of a single pair with two different RE3+ ions close to a cadmium vacancy are minimally energetically more favourable to be formed in relation to clusters of dopants and co-dopants. This indicates that at low doping concentrations, RE3+ dopant pairs will form separately, but by increasing the concentration it is possible to form a cluster of defects involving RE3+. This may explain the low concentrations of dopants in this matrix. The distortion caused in the local lattice by the presence of a RE3+ pair of different dopants is bigger than the distortion caused by a RE3+ pair of dopants of the same chemical species. Therefore, CdSiO3: RE13+, RE23+ has a crystal field that is different from the crystal field experienced by RE3+ as a single dopant and the presence of the co-dopant ion will modify the luminescence of the system even though the generating defect of the luminescent centre remains the same.

Multiemitting Ultralong Phosphorescent Carbonized Polymer Dots via Synergistic Enhancement Structure Design.

Advancing a metal-free room temperature phosphorescent (RTP) material that exhibits multicolor emission, remarkable RTP lifetime, and high quantum yield still faces the challenge of achieving intersystem crossing between singly and triplet excited states, as well as the rapid decay of triplet excited states due to nonradiative losses. In this study, a novel strategy is proposed to address these limitations by incorporating o-phenylenediamine, which generates multiple luminescent centers, and long-chain polyacrylic acid to synthesize carbonized polymer dots (CPDs). These CPDs are then embedded in a rigid B2O3 matrix, effectively limiting nonradiative losses through the synergistic effects of polymer cross-linking and the rigid matrix. The resulting CPD-based materials exhibit remarkable ultralong phosphorescence in shades of blue and lime green, with a visible lifetime of up to 49 s and a high phosphorescence quantum yield. Simultaneously, this study demonstrates the practical applicability of these excellent material properties in anti-counterfeiting and information encryption.

Dual substitution of host lattice ions to enhance the luminescence properties of Zn2TiO4:Cr3+ phosphor.

Near-infrared light sources have potential applications in many fields. Cr3+ is a good luminescence centre to prepare near-infrared phosphors. Improving the performance of existing near-infrared luminescent materials has indeed attracted great interest from researchers. The luminescence properties of Zn2TiO4:Cr3+ were improved by crystal field engineering strategies. Zn2+-Ti4+ was partially replaced using a Li+-Nb5+ ion pair based on the Zn2TiO4:Cr3+ phosphors. Luminescence Cr3+-activated luminescent materials are sensitive to changes in the local crystal structure and crystal field environment. Doping of Li+-Nb5+ increased the luminescence intensity up to 2.7 times that of the undoped sample. Also, the thermal stability of the phosphor was greatly increased by the replacement of Li+-Nb5+.

Overcoming Thermal Quenching in X‐ray Scintillators through Multi‐Excited State Switching

AbstractX‐ray scintillators have gained significant attention in medical diagnostics and industrial applications. Despite their widespread utility, scintillator development faces a significant hurdle when exposed to elevated temperatures, as it usually results in reduced scintillation efficiency and diminished luminescence output. Here we report a molecular design strategy based on a hybrid perovskite (TpyBiCl5) that overcomes thermal quenching through multi‐excited state switching. The structure of perovskite provides a platform to modulate the luminescence centers. The rigid framework constructed by this perovskite structure stabilized its triplet states, resulting in TpyBiCl5 exhibiting an approximately 12 times higher (45 % vs. 3.8 %) photoluminescence quantum yield of room temperature phosphorescence than that of its organic ligand (Tpy). Most importantly, the interactions between the components of this perovskite enable the mixing of different excited states, which has been revealed by experimental and theoretical investigations. The TpyBiCl5 scintillator exhibits a detection limit of 38.92 nGy s−1 at 213 K and a detection limit of 196.31 nGy s−1 at 353 K through scintillation mode switching between thermally activated delayed fluorescence and phosphorescence. This work opens up the possibility of solving the thermal quenching in X‐ray scintillators by tuning different excited states.

Overcoming Thermal Quenching in X-ray Scintillators through Multi-Excited State Switching.

X-ray scintillators have gained significant attention in medical diagnostics and industrial applications. Despite their widespread utility, scintillator development faces a significant hurdle when exposed to elevated temperatures, as it usually results in reduced scintillation efficiency and diminished luminescence output. Here we report a molecular design strategy based on a hybrid perovskite (TpyBiCl5) that overcomes thermal quenching through multi-excited state switching. The structure of perovskite provides a platform to modulate the luminescence centers. The rigid framework constructed by this perovskite structure stabilized its triplet states, resulting in TpyBiCl5 exhibiting an approximately 12 times higher (45 % vs. 3.8 %) photoluminescence quantum yield of room temperature phosphorescence than that of its organic ligand (Tpy). Most importantly, the interactions between the components of this perovskite enable the mixing of different excited states, which has been revealed by experimental and theoretical investigations. The TpyBiCl5 scintillator exhibits a detection limit of 38.92 nGy s-1 at 213 K and a detection limit of 196.31 nGy s-1 at 353 K through scintillation mode switching between thermally activated delayed fluorescence and phosphorescence. This work opens up the possibility of solving the thermal quenching in X-ray scintillators by tuning different excited states.

Enhanced upconversion luminescence of NaYF4:Er nanocrystals based on the synergy between whispering gallery mode excitation and förster resonant energy transfer

The upconversion luminescence at the visible band was excited by the high power density whispering gallery mode (WGM) on the surface of the microsphere. Under the WGM excitation, Er3+ of NaYF4:Er3+ directly absorbed three photons at 1525 nm, followed by the generation of upconversion luminescence. We used WS2 quantum dots (QDs) as donors and NaYF4:Er3+ upconversion nanoparticles (UCNPs) as acceptors to enhance upconversion luminescence by Förster resonant energy transfer (FRET). The physical mixture composed of monolayer WS2 and NaYF4:Er3+ nanoparticles was coated on SiO2 microsphere by immersion method. Excited by high power density WGM, three photons were absorbed by WS2-QDs based on the quantum size effect to generate excited electrons as donors and UCNPs as acceptors based on FRET, subsequently, the energy of the electrons were transferred to the luminescence center Er3+ to improve the upconversion luminescence efficiency. The mechanism model of upconversion luminescence enhancement based on FRET of WS2–NaYF4:Er3+ was proposed, and the enhancement effect was experimentally studied and demonstrated. To study the distance dependence of energy transfer between QD and UCNP pairs, we covered the surface of the silica microsphere with a controlled concentration of WS2 mixed with NaYF4:Er3+ nano-particles. When the mixed concentration of WS2-QDs was 0.15%, the upconversion luminescence reached the highest efficiency. The results showed that a twofold upconversion luminescence enhancement can be experimentally achieved. The proposed approach for enhancing the upconversion luminescence could benefit the improvement of imaging signal-to-noise ratio (SNR) using UCNPs for fluorescent labels in life sciences.

Study of NIR long afterglow luminescent materials are used in silicon solar cells to produce electricity under dark condition

It is well known that the silicon solar cells can realize effective photoelectric conversion only under sunlight irradiation, and that can not generate electricity under dark condition. Thus, the effective working (photoelectric conversion) time of silicon solar cells throughout the whole day is very limited. In this paper, the up-conversion NIR long afterglow luminescent materials, Zn3Ga2-x-y-zGe2O10:xCr3+,yYb3+,zEr3+, were successfully prepared through high temperature calcination method. The structure, morphology, elemental composition and optical property of the prepared samples were analyzed by a series of characterization methods. In addition, the mechanisms of afterglow luminescent of these materials and the energy transfer mechanisms of up-conversion luminescent between the luminescent center Cr3+ and sensitizer ions (Yb3+ and Er3+) are discussed, respectively. Finally, the prepared luminescent materials are fixed on glass sheets with reflective capacity, and then are integrated with silicon solar cells in the form of a cover plate. And then, under dark conditions, the current density-voltage (J-V) curves and current density-time (J-T) curves of these silicon solar cells were tested to explore the influences of doping proportions of Cr3+, Yb3+, Er3+, Yb3+-Er3+ pairs and the calcination temperatures of Zn3Ga2-xGe2O10:xCr3+ on the power generation of the silicon solar cells. The results show that the photovoltaic conversion instantaneous efficiency of silicon solar cell with Zn3Ga1.975Ge2O10:1.0Cr3+,1.0 Yb3+,0.5Er3+ reaches the maximum value of 2.549 % under dark condition. The average efficiency within 300 s is 0.238%. At the same time, the silicon solar cell can generate dark current for up to 8.0 h, whose maximum dark current density and open-circuit voltage of 4.88 μA/cm2 and 0.914 mV, respectively. It is hoped that this study can provide some new ideas for silicon solar cells to generate electricity without sunlight irradiation.

Portably and Visually Sensing Cytisine through Smartphone Scanning Based on a Post‐Modified Luminescence Center Strategy in Zinc‐Organic Frameworks

AbstractCytisine (CTS) is a useful medicine for treating nervous disorders and smoking addiction, and exploring a convenient method to detect CTS is of great significance for long‐term/home medication to avoid the risk of poisoning, but it is full of challenges. Here, a modified metal–organic framework sensor Tb@Zn‐TDA‐80 with dual emission centers was prepared using a post‐modified luminescence center strategy. The obtained Tb@Zn‐TDA‐80 can serve as a CTS sensor with high sensitivity and selectivity. To achieve portable detection, Tb@Zn‐TDA‐80 was further fabricated as a membrane sensor, M−Tb@Zn‐TDA‐80, which displayed an obvious CTS‐responsive color change by simply dropping a CTS solution onto its surface. Benefiting from this unique functionality, M−Tb@Zn‐TDA‐80 successfully realized the visual detection and quantitative monitoring of CTS in the range of 5.26–52.6 mM by simply scanning the color with a smartphone. The results of nuclear magnetic resonance spectroscopy and theoretical computation illustrated that the high sensing efficiency of Tb@Zn‐TDA‐80 for CTS was attributed to the N−H⋅⋅⋅π and π⋅⋅⋅π interactions between the ligand and CTS. And luminescence quenching may result from the intramolecular charge transfer. This study provides a convenient method for ensuring long‐term medication safety at home.

Portably and Visually Sensing Cytisine through Smartphone Scanning Based on a Post-Modified Luminescence Center Strategy in Zinc-Organic Frameworks.

Cytisine (CTS) is a useful medicine for treating nervous disorders and smoking addiction, and exploring a convenient method to detect CTS is of great significance for long-term/home medication to avoid the risk of poisoning, but it is full of challenges. Here, a modified metal-organic framework sensor Tb@Zn-TDA-80 with dual emission centers was prepared using a post-modified luminescence center strategy. The obtained Tb@Zn-TDA-80 can serve as a CTS sensor with high sensitivity and selectivity. To achieve portable detection, Tb@Zn-TDA-80 was further fabricated as a membrane sensor, M-Tb@Zn-TDA-80, which displayed an obvious CTS-responsive color change by simply dropping a CTS solution onto its surface. Benefiting from this unique functionality, M-Tb@Zn-TDA-80 successfully realized the visual detection and quantitative monitoring of CTS in the range of 5.26-52.6 mM by simply scanning the color with a smartphone. The results of nuclear magnetic resonance spectroscopy and theoretical computation illustrated that the high sensing efficiency of Tb@Zn-TDA-80 for CTS was attributed to the N-H⋅⋅⋅π and π⋅⋅⋅π interactions between the ligand and CTS. And luminescence quenching may result from the intramolecular charge transfer. This study provides a convenient method for ensuring long-term medication safety at home.

Luminescent manifestations of ytterbium ions in the crystal structure of silicate apatite

The manifestation of ytterbium ions in the microcrystals of the Sr2Y6.8YbSi6O26:Er0.2 solid solution with apatite structure was studied on the basis of low-temperature photoluminescence (PL) spectroscopy and spectral-kinetic measurement data. Intracenter down-conversion luminescence of Er3+ ions in the visible and IR ranges was detected. Up-conversion luminescence of Er3+ ions is observed upon IR excitation due to excitation of Yb3+ ions and subsequent energy transfer Yb3+ → Er3+. Overlapping bands at 412 and 430 nm with a Stokes shift of less than 0.3 eV are observed in the PL spectra at room temperature. These emission bands are assigned to the spin-allowed and spin-forbidden 4f135d → 4f14 transitions from the low-spin and high-spin exciting states of Yb2+ ion, respectively. The PL decay kinetics for transitions from the low-spin states is characterized by a dominant component τ = 0.39 ns. An alternative model of Yb3+ luminescence center associated with a charge transfer band does not explain the data of low-temperature (5K) PL spectroscopy. At T = 5 K, a new wide emission band with a maximum at 696 nm and a Stokes shift of 1.1 eV appears in the PL spectrum. Two options of this PL band nature are considered. The first is the luminescence of defects having a vacancy nature. The second possible option is the manifestation of anomalous luminescence of Yb2+ ions, which occupy a different crystallographic position in the apatite crystal structure.

Achieving broadband near-infrared luminescence in Cr3+-Activated Y2Mg2Al2Si2O12 phosphors via multi-site occupancy

Cr3+-activated near-infrared (NIR) phosphors are key for NIR phosphor-converted light emitting diodes (NIR pc-LED). While, the site occupancy of Cr3+ is one of the debates that have plagued researchers. Herein, Y2Mg2Al2Si2O12 (YMAS) with multiple cationic sites is chosen as host of Cr3+ to synthesize YMAS: xCr3+ phosphors. In YMAS, Cr3+ ions occupy simultaneously Al/SiO4 tetrahedral, Mg/AlO6 octahedral, and Y/MgO8 dodecahedral sites which form three luminescent centers named as Cr1, Cr2, and Cr3, respectively. Cr1 and Cr2 relate to an intermediate crystal field, with transitions of 2E→4A2 and 4T2→4A2 occurring simultaneously. As Cr3+ concentration increases, the 4T2→4A2 transition becomes more pronounced in Cr1 and Cr2, resulting in a red-shift and broadband emission. Cr3 consistently behaves a weak crystal field and exhibits the broad and long-wavelength emission. Wide-range NIR emission centering at 745 ​nm is realized in YMAS: 0.03Cr3+ phosphor. This phosphor has high internal quantum efficiency (IQE ​= ​86%) and satisfying luminescence thermal stability (I423 K ​= ​70.2%). Using this phosphor, NIR pc-LEDs with 56.6 ​mW@320 ​mA optical output power is packaged and applied. Present study not only demonstrates the Cr3+ multi-site occupancy in a certain oxide but also provides a reliable approach via choosing a host with diverse cationic sites and local environments for Cr3+ to achieve broadband NIR phosphors.

Fabrication and properties of novel multilayered Y3Al5O12/MgAl2O4 ceramics doped with rare-earth ions

Multilayer Y3Al5O12 (YAG)/MgAl2O4 (MAS) ceramics doped with europium and cerium ions exhibiting functionally graded properties was consolidated by the SPS method using during layer-by-layer formation powders approach. The optimal modes for YAG/MAS ceramics doped with rare earth ions preparation were obtained during the SPS process. It was observed that at the isothermal exposure stage at a temperature of 1450 °C shrinkage process stops. Introduction of CeO2, Eu2O3 into the YAG/MAS ceramics leads to a shift in the range of intense shrinkage to lower temperatures. Morphological, optical and luminescent properties have been studied in detail for fabricated YAG/MAS ceramics with different arrangement of the layers. The luminescent properties using time-resolved cathodoluminescence (CL) and steady state photoluminescence (PL) were investigated in detail. The spectral dynamics in nanosecond and millisecond time range was demonstrated after e-beam excitation. The PL efficiency of YAG/MAS ceramics and nature of luminescence centers were analyzed. The novel kind of YAG/MAS functional ceramics could be promising candidate for efficient luminescent converter.

Superior Quantum Efficiency Blue‐Emitting Phosphors with High Thermal Stability toward Multipurpose LED Applications

AbstractSince Bi3+‐activated phosphor are widely reported in phosphors‐converted light‐emitting diodes (pc‐LEDs), developing new‐high efficiency phosphors is imperative. Herein, superior internal quantum efficiency (IQE = 93.7%) and external quantum efficiency (EQE = 70.5%) are achieved with blue‐emitting gallate phosphor CaGdGaO4:Bi3+. Particularly, the photoluminescence excitation (PLE) spectrum ranges from 200 to 400 nm with two peaks at 337 and 368 nm, which match well with the 365 nm near ultraviolet (n‐UV) chip. The blue emission is attributed to two luminescence centers caused by Bi3+ occupying GdO6 and CaO6 sites. Furthermore, the thermal stability (@ 150 °C) enhanced from 73.2% to 80.1% when Ca2+ doping. A white LED (WLED) with high color rendering index (Ra) of 93.8 is prepared by as‐synthesized phosphors, indicating the potential application in WLED. The blue and red dual‐emitting phosphors are achieved by co‐doping Bi3+ and Eu3+. Finally, the rice planting experiment presents that the blue‐emitting can efficiently enhance the photosynthesis and seeding index of rice, which indicated these phosphors have significance in plant fill light.