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Highly biocompatible and efficiently luminescent whiskers of the hydroxyapatite (Ca10(PO4)6(OH)2, HAp) doped with various concentrations (0‐5 at.%) of europium were prepared by hydrothermal synthesis and the Eu‐doped Hap‐coating layers onto the surface of titanium substrate were fabricated by the electrophoretic deposition (EPD) process for fluorescent probe application. The maximum doping concentration of Eu accommodating into the host lattice of HAp was detected as ~1.5 at.% and all the hydrothermally synthesized Eu‐doped HAp whiskers were found to have high crystallinity and orientation growth along the c‐axis by X‐ray diffraction (XRD) identification. The valence of the doped Eu was identified as trivalent and divalent coexistence at a concentration percentage of Eu3+: Eu2+ = 78%: 22% by X‐ray photoelectron spectroscopy (XPS) spectra. The replacement site of the doped Eu ions in the crystal structure of HAp host was clarified by Rietveld refinement. The whisker morphology of the hydrothermally synthesized particle was demonstrated by field‐emission scanning electron microscopy (FE‐SEM) observation and their component elements were analyzed by energy dispersive X‐ray (EDX) mapping. The photoluminescence (PL) emissions of the Eu‐doped HAp whiskers and fabricated their coating layers were both revealed mainly at ~615 nm (5D0 → 7F2) and ~697 nm (5D0 → 7F4), which is a wavelength that easily transmitting through living system for biological imaging. The PL emission are falling in the region of reddish orange and belonging to color temperature below 1500 K. Decay time and internal and external quantum efficiencies (QEs) were also measured to reveal them depending on the doping concentration of Eu. The hydrothermally prepared Eu‐doped HAp whiskers would be aimed at biomedical application, due to their promising fluorescent function of probe for in vivo imaging in medical diagnose by utilizing the superior biocompatibility of the HAp host and highly efficient luminescent property of the Eu activator. [ABSTRACT FROM AUTHOR]

Mn2+ doped γ-AlON is an interesting narrow-band green emitting phosphor which can be used in wide color gamut white LED backlights for liquid crystal displays (LCDs). However, the spin-forbidden transition of 3d5 in Mn2+ results in a quite low absorption efficiency, γ-AlON:Mn2+ thus has a small external quantum efficiency. Besides Eu2+,Ce3+ is another promising sensitizer and is expected to improve the emission of Mn2+ through a distinctive energy transfer process. In this work, a series of Ce3+–Mn2+ codoped γ-AlON phosphors were synthesized by gas pressure sintering at 1800 °C for 2 h under 0.5 MPa nitrogen gas pressure. The Rietveld refinement analysis shows that Al atoms occupy both 8a and 16d sites, while codoped Ce3+ and Mn2+ ions substitute the 8a Al atoms only in the tetrahedral sites. The 27Al solid state NMR spectrum further confirms the chemical shifts of AlO4 and AlO6 sites at 71.4 and 0 ppm, respectively. The measured PL, CL and decay times have evidenced that a brisk energy transfer occurs between the Ce3+ and Mn2+ ions. The energy transfer mechanism from Ce3+ to Mn2+ in γ-AlON is a quadrupole–quadrupole interaction and the critical distance is calculated to be 15.97 Å. Upon UV or blue light excitation, the codoped γ-AlON phosphor has higher luminescence intensity, quantum efficiency and thermal stability than the Mn2+-doped γ-AlON due to the energy transfer and low total concentration of Ce3+ and Mn2+ ions. Meanwhile, the absorption, internal quantum efficiency and external quantum efficiency are raised to 60.2%, 61.3% and 36.9% upon 310 nm excitation. [ABSTRACT FROM AUTHOR]

Ce3+ doped CaAlSiN 3 is a promising broadband orange phosphor that can be applied in white light-emitting diodes (wLEDs) solid state lighting for general illumination. However, its emission color and quantum efficiency are not good enough to achieve high color rendering properties and luminous efficacy of wLEDs. In this work, we proposed to realize the spectral tuning and property enhancement of CaAlSiN 3 :Ce3+ by bandgap engineering via the cationic substitution of Ca by Sr. The relationship between photoluminescence and local coordination structure as well as electronic structure were revealed. The substitution led to a blue-shift in emission maximum by 13 nm (from 595 to 582 nm) and a highest external quantum efficiency of 55% (enhanced by 10%). This broadband yellow phosphor enabled to produce wLEDs with a color rendering index of 83.3, luminous efficacy of 114.6 l m/W and a color temperature of 4604 K. With the substitution of Ca by Sr in broadband yellow phosphor CaAlSiN 3 :Ce3+, a blue-shift in the emission maximum (from 595 to 582 nm) was attained, while the quantum efficiency and thermal stability of the phosphor containing 40% Sr were increased by 10 and 7.2% due to the decreased crystal field splitting and increased bandgap of the host. Image 1 • The bandgap engineering was adopted to realize the spectral tuning of CaAlSiN 3 :Ce3+ via the substitution of Ca by Sr. • The relationship between local structure and luminescence properties in Sr x Ca 1-x AlSiN 3 :Ce3+ was comprehensively discussed. • With the substitution, a blue-shift in the emission maximum (from 595 to 582 nm) was attained. • The quantum efficiency and thermal stability of the sample containing 40% Sr were raised by 10 and 7.2%, respectively. • This broadband yellow phosphor enabled to produce wLEDs with a color rendering index of 83.3. [ABSTRACT FROM AUTHOR]

Investigating the phosphors doped with single activators in a single component to realize white-light emission is urgently desired for phosphor-converted white-light-emitting diodes. In this work, on the basis of the chemical unit cosubstitution strategy, the new borophosphate phosphors Ba 3 CaK(PO 4 ) 3- x (BO 3 ) x :0.02Eu 2+ with a mixed anion group were prepared. Coupling structure refinement and photoluminescence analyses, Ba 3 CaK(PO 4 ) 3- x (BO 3 ) x consists of five different cationic sites with different coordination environments, with Eu 2+ occupying the three sites for Ba 2+ . In the process of partial substituting (BO 3 ) 3- for (PO 4 ) 3- , because of the greatly distorted coordination field generated from the difference in the geometric configurations between the two anion groups, a red shift and broadening of the emission bands occurs, resulting in a color-adjustable emission from blue to white. A phosphor-converted light-emitting diode has been successfully fabricated with the incorporation of an as-prepared Ba 3 CaK(PO 4 ) 2.6 (BO 3 ) 0.4 :0.02Eu 2+ phosphor and a 405 nm near-ultraviolet chip, which exhibits Commission International de I'Eclairage chromaticity coordinates of (0.31, 0.37) and a correlated color temperature of 6295 K. As demonstrated in the present work, an approach adopted from phosphate to borophosphate is conducted to develop high-quality phosphors.

The borate Ba 3 InB 9 O 18 (BIBO) is a promising host material for phosphors. A series of Tb 3+ and Eu 3+ codoped Ba 3 InB 9 O 18 phosphors were synthesized. Based on the Rietveld method, structure refinement of the codoped BIBO phosphor was carried out. Then, the luminescence properties of BIBO:Tb 3+ , Eu 3+ phosphors were extensively investigated under ultraviolet (UV) and vacuum ultraviolet (VUV) excitation. The measured PL spectra and decay times evidenced that energy transfer occurs between the Tb 3+ and Eu 3+ ions. The energy-transfer mechanism from Tb 3+ to Eu 3+ in Ba 3 InB 9 O 18 is dominated by electric multipolar interactions, with the critical distance calculated to be 10.97 Å. The temperature sensitivity of the Tb 3+ and Eu 3+ codoped sample under VUV was also investigated at the low temperature range from 25 K to 298 K. The emission color could be tuned from green to the red region by adjusting the concentration of codoped ions. The results indicate that the BIBO-based phosphors are valuable candidates for applications in the display and lighting fields., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)