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Carbon dots (CDs) have aroused widespread interest in the construction of room-temperature phosphorescent (RTP) materials. However, it is a great challenge to obtain simultaneous multicolor long-wavelength RTP emission and excellent stability in CD-based RTP materials. Herein, a novel and universal "CDs-in-YOHF" strategy is proposed to generate multicolor and long-wavelength RTP by confining various CDs in the Y(OH)

Recently, near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) have attracted considerable interest in the research field worldwide. As the key material, broadband NIR phosphors have become a research hotspot. Herein, a series of Cr3+-doped BaZrGe3O9 phosphors were successfully designed via nonequivalent substitution. The phosphors exhibited a broadband emission extending from 700 nm to 1200 nm (FWHM = 159 nm) with a maximum of ∼830 nm in the first biological window. To optimize the luminescence properties, the relationships between the doping concentration and crystal structure, luminescence spectra, decay curves were discussed. More importantly, the crystal field parameters Dq, B and Huang–Rhys factor were calculated, and the results may provide insight into factors determining and modifying the luminescence properties of the materials. The persistent luminescence of Cr3+ could also be realized, and the luminescence mechanism was proposed. Moreover, a pc-LED prototype was fabricated by combining the BaZrGe3O9:Cr3+ phosphor with a blue LED chip, and the potential application for broadband NIR pc-LEDs was discussed.

In this work, we have investigated the near-infrared (NIR) photoluminescence, upconversion (UC), and long-lasting phosphorescence properties of Nd3+/Yb3+-doped Ca2SnO4 phosphors. Two-photon NIR qua...

A series of Ce3+ and Dy3+ doped LiY9(SiO4)6O2 phosphors was prepared by conventional high temperature solid state reaction method. The dominant emission of Dy3+ originates from the 4F9/2 → 6H13/2 (yellow emission) electric dipole transition while that of Ce3+ locates in the blue region. The concentration quenching for Dy3+ emission was investigated by luminescence spectra and decay curves, the main mechanism responsible for the energy transfer between Dy3+ ions was determined by the Inokuti-Hirayama model. Energy transfer from Ce3+ to Dy3+ as well as the temperature sensing property was studied in detail. Thanks to the different thermal responses between Ce3+ and Dy3+ in the host, the highest sensing sensitivity was calculated to be 0.43% K−1. The results demonstrate that LiY9(SiO4)6O2: Ce3+, Dy3+ may be a potential candidate for a luminescent ratiometric thermometer.

A series of novel near-infrared (NIR) long persistent phosphors of Zn1.2Al1.6Ge0.2O4: Cr3+, Yb3+ was synthesized by a solid state method. The crystal structure of Zn1.2Al1.6Ge0.2O4 was identified. Yb3+ ions were effective codopants for improving the NIR persistent luminescence intensity even after 100 h of decay. The persistent luminescence decay curves and the thermo-luminescence spectra were analyzed. Results indicated that the increase in efficient electron trap concentration induced by doping Yb3+ ions was a major factor in the improvement of the NIR persistent luminescence. Moreover, short-wave infrared (SWIR = 900–1700 nm) emission of Yb3+ was be excited by UV and visible light through charge transfer transition of O2-–Yb3+ and energy transfer from Cr3+ to Yb3+, respectively.

We present novel near-infrared (NIR) Cr3+-doped non-gallate super-long-persistence phosphors (Zn1+xAl2-2xGexO4:Cr3+) by Germanium substitution in the original ZnAl2O4:Cr3+. Unlike the negligible NIR persistent luminescence of ZnAl2O4:Cr3+ upon UV or visible light excitation, the Ge substituted phosphors feature strong and super-long-persistent luminescence at approximately 650–750 nm for more than 120 h. The relation between the Ge substitution and the defect trapping states is investigated systematically. The experimental results combined with the first-principles calculations reveal that GeZn○○ and GeAl○ in the spinel structure would introduce shallow and deep defect states in the band gap to serve as new efficient traps, which are mainly responsible for the strong and super-long-persistent luminescence upon UV or visible light excitation. The present advanced phosphors is an alternative candidate for applications in biomedical imaging and night-vision surveillance.

Atomically thin layers of transition metal dichalcogenides (TMDs) have recently drawn great attention. However, doping strategies and controlled synthesis for wafer-scale TMDs are still in their early stages, greatly hindering the construction of devices and further basic studies. In this work, we develop the fast deposition of wafer-scale layered lanthanide ion Yb/Er co-doped WSe2 using pulsed laser deposition. WSe2 nanosheets were chosen as the host, while Yb3+ and Er3+ ions served as the sensitizer and activator, respectively. The obtained Yb/Er co-doped WSe2 layers exhibit good uniformity and high crystallinity with highly textured features. Under the excitation of a diode laser at 980 nm, down-conversion emission is observed at around 1540 nm, assigned to the emission transition between the 4I13/2 and 4I15/2 states of Er3+. Considering the significance of 1540 nm luminescence in the application of photonic technologies, this observation in the WSe2:Yb/Er nanosheets down to the monolayer provides a new opportunity for developing photonic devices at the 2D limit. Our work not only offers a general method to prepare wafer-scale lanthanide doped TMDs, but also to widely modulate the luminescence of atomically layered TMDs by introducing lanthanide ions.

Large-scale synthesis of two-dimensional (2D) materials is one of the significant issues for fabricating layered materials into practical devices. As one of the typical III-VI semiconductors, InSe has attracted much attention due to its outstanding electrical transport property, attractive quantum physics characteristics, and dramatic photoresponse when it is reduced to atomic scale. However, scalable synthesis of single phase 2D InSe has not yet been achieved so far, greatly hindering further fundamental studies and device applications. Here, we demonstrate the direct growth of wafer-scale layered InSe nanosheets by pulsed laser deposition (PLD). The obtained InSe layers exhibit good uniformity, high crystallinity with macro texture feature, and stoichiometric growth by in situ precise control. The characterization of optical properties indicates that PLD grown InSe nanosheets have a wide range tunable band gap (1.26-2.20 eV) among the large-scale 2D crystals. The device demonstration of field-effect transistor shows the n-type channel feature with high mobility of 10 cm

Ce 3+ , Yb 3+ and Tb 3+ singly doped and Ce 3+ -Yb 3+ , Tb 3+ -Yb 3+ codoped Ca 3 (BO 3 ) 2 phosphors were prepared by a solid state reaction method. The photoluminescence excitation and emission spectra at room temperature were investigated. The emissions of Yb 3+ ion are at around 1000 nm, matching well with the optimal response of Si-based solar cells. When codoped with Ce 3+ or Tb 3+ ion, the absorption is greatly broadened in the ultraviolet-visible region. Energy transfer from Ce 3+ /Tb 3+ to Yb 3+ was investigated, the cooperative energy transfer process is proposed.

Yb 3+ and Tb 3+ singly doped and Tb 3+ –Yb 3+ co-doped Ca 5 (BO 3 ) 3 F phosphors were prepared by a solid state reaction method. The luminescence emission and excitation spectra as well as the luminescence decay curves were investigated. The emission bands of Yb 3+ ion are located around 1000 nm, matching well with the optimal response of Si-based solar cells. Tb 3+ can be a sensitizer for Yb 3+ in the host. The energy transfer from Tb 3+ to Yb 3+ was investigated, the energy transfer mechanism was proposed as cooperative energy transfer. Tb 3+ concentration dependent quantum efficiency was calculated and the maximum efficiency approached 115.5%.

The near-infrared (NIR) luminescence materials have attracted great attention on account of their potential applications in optical imaging field. In this paper, a series of Cr3+ and Nd3+ doped GdY2Al3Ga2O12 phosphors with luminescence in the biological windows were synthesized using a solid-state reaction method. The crystal field parameters, concentration dependent photoluminescence and persistent luminescence properties of Cr3+ were discussed in detail. Nd3+ ions exhibit perfect NIR to NIR Stokes luminescence in the host. The influence of Nd3+ doping concentration was studied by emission spectra and decay curves. Taking the advantages of both Cr3+ and Nd3+, dual mode phosphors with NIR persistent luminescence and NIR to NIR Stokes luminescence were designed and achieved. Based on the energy transfer process, persistent luminescence and thermo-luminescence curves, the luminescence mechanism was proposed.

Atomically thin layers of transition metal dichalcogenides (TMDs) have recently drawn great attention. However, doping strategies and controlled synthesis for wafer-scale TMDs are still in their early stages, greatly hindering the construction of devices and further basic studies. In this work, we develop the fast deposition of wafer-scale layered lanthanide ion Yb/Er co-doped WSe2 using pulsed laser deposition. WSe2 nanosheets were chosen as the host, while Yb3+ and Er3+ ions served as the sensitizer and activator, respectively. The obtained Yb/Er co-doped WSe2 layers exhibit good uniformity and high crystallinity with highly textured features. Under the excitation of a diode laser at 980 nm, down-conversion emission is observed at around 1540 nm, assigned to the emission transition between the 4I13/2 and 4I15/2 states of Er3+. Considering the significance of 1540 nm luminescence in the application of photonic technologies, this observation in the WSe2:Yb/Er nanosheets down to the monolayer provides a new opportunity for developing photonic devices at the 2D limit. Our work not only offers a general method to prepare wafer-scale lanthanide doped TMDs, but also to widely modulate the luminescence of atomically layered TMDs by introducing lanthanide ions.

The phosphors of Ca3Ga2Ge3O12 (CGGG) co-doped with Nd3+ and Cr3+ ions were synthesized using conventional solid-state reaction techniques. Steady-state and time-resolved near-infrared (NIR) photoluminescence (PL) and long-lasting phosphorescence (LLP) properties are investigated in the Nd3+-doped CGGG samples. An increase in NIR luminescence traps can be realized in Nd3+/Cr3+ co-doped samples. Energy transfer from Cr3+ to Nd3+ with an efficiency of up to 57.5% is evident for Ca3−xNdxGa1.99Cr0.01Ge3O12 at x = 0.09. A cross relaxation scheme related to 4T2–4A2 of Cr3+ and 4I9/2–4F3/2 transitions of Nd3+ is discussed. We have presented the luminescence mechanism involving the competing processes of NIR PL and LLP, which is in accordance with our measurements. The results show that the NIR persistent luminescence of CGGG co-doped with Nd3+ and Cr3+ is more efficient compared to the single Nd3+ ion doped CGGG.

Near-infrared (NIR) quantum cutting (QC) from the Tm3+: 1G4 state essentially occurs via a three-step cascade radiation (case 1) and two-step cross-relaxations (case 2) by varying the Tm3+ content (x) from 0.0005 to 0.05 in La2–xTmxBaZnO5. In case 1, with the Tm3+ content x < 0.005, the energy of the 1G4 excited state is down-converted to three NIR photons emitted at approximately 1200, 1480, and 1800 nm, with 3H4 and 3F4 acting as intermediate levels, while in case 2, with the Tm3+ content x ≥ 0.005, the energy will be triply cut into approximately 1800 nm photon emissions. The three-photon NIR QC phenomena are investigated in terms of the static and dynamic photoluminescence. Based on the dependence of cross-relaxation and concentration quenching on Tm3+ density, a rate-equation model was built to describe the energy transfer (ET) dynamics of Tm3+. The calculation of internal quantum yield (QY) was developed by considering nonradiative processes, and the maximum QY for photon emission at 1800 nm was 198...

Near-infrared-to-near-infrared (NIR-to-NIR) anti-Stokes luminescence from Crsup3+/supsingly doped Casub3/subGasub2/subGesub3/subOsub12/sub(CGGG) occurs under the excitation of an 808 nm diode laser. The anti-Stokes processes vary from one photon to two photon, depending on the Crsup3+/supcontent (x) in Casub3/subGasub2-x/subCrsubx/subGesub3/subOsub12/sub. The results suggest that phonon-assisted anti-Stokes excitation and cooperative energy transfer are involved in the observed upconversion (UC) processes of CGGG:Crsup3+/sup. The relevant Crsup3+/sup-doping-concentration-dependent NIR-to-NIR anti-Stokes luminescent mechanism, either one-photon or two-photon UC, is investigated. Such an observation on modulating the UC process via varying the doping concentration is helpful in broadening the understanding of UC phenomena.

The BaCaBO3F wide band gap host and the charge-compensated phosphors BaCaBO3F:Ln3+ (Ln = Ce, Tb, Gd) and BaCaBO3F:Ce3+,Tb3+ have been synthesized by a solid-state reaction method at high temperature. Their spectroscopic properties in the vacuum ultraviolet (VUV)–vis range have been investigated. The band gap of the host lattice is estimated at 7.8 eV, which is considerably higher than the value found from its diffuse reflectance spectrum. The 5d crystal field level locations, Stokes shift, and Huang–Rhys factor have been determined from the VUV excitation and near-UV emission spectra of BaCaBO3F:Ce3+. The 5d1 decay lifetime is 29 ns at x ∼ 0.005. Concentration quenching occurs for Ba1–2xCexNaxCaBO3F with maximum intensity at x ∼ 0.035 and with critical distance Rc = 17.7 A. An unusual broad, intense band in the excitation spectrum of BaCaBO3F:Gd3+ is assigned to a near-defect exciton. Very weak emission from 5D3, and intense green emission from 5D4, has been assigned for BaCaBO3F:Tb3+. In the VUV region, ...

The VUV-UV spectroscopic properties of Ce3+ in Ba2Mg(BO3)(2), Ba2Ca(BO3)(2) and Sr2Mg(BO3)(2) were compared, and the relation between the energy of the 4f -> 5d transition of Ce3+ and the coordination environments of substituted alkaline earth ions was discussed. The chromaticity coordinates of Ce3+ activated X(2)Z(BO3)(2) (X=Ba, Sr; Z=Ca, Mg) phosphors were changeable from blue to whitish and further to green range by varying the doping concentration of Ce3+ or the types of substituted alkaline earth ions upon 172 nm excitation.

Phosphors of Eu3+ activated Ba2Mg(BO3)2 were prepared by a high-temperature solid-state reaction technique. The phase purity was characterized by powder X-ray diffraction (XRD). The luminescence properties in the VUV–vis range as well as the decay curves have been investigated. The results demonstrate that the band near 176 nm in the VUV excitation spectra can be ascribed to host-related absorption. The charge-transfer bands (CTBs) of O2− → Eu3+ in Ba2Mg(BO3)2:Eu3+ are at about 231 nm. The emission intensity of the 5D0→7F1 transition (594 nm) is dominant upon excitations at 172 nm or 231 nm (CTB), while that of 5D0→7F2 transition (613 nm) is dominant when excitations are at 395 nm (the 7F0→5L6 transition of Eu3+) or at other f–f transitions.

This report presents the luminescence properties of Ce 3+ and Pr 3+ activated Sr 2 Mg(BO 3 ) 2 under VUV–UV and X-ray excitation. The five excitation bands of crystal field split 5d states are observed at about 46 729, 44 643, 41 667, 38 314 and 29 762 cm −1 (i.e. 214, 224, 240, 261 and 336 nm) for Ce 3+ in the host lattice. The doublet Ce 3+ 5d→4f emission bands were found at about 25 840 and 24 096 cm −1 (387 and 415 nm). The influence of doping concentration and temperature on the emission characteristics and the decay time of Ce 3+ in Sr 2 Mg(BO 3 ) 2 were investigated. For Pr 3+ doped samples, the lowest 5d excitation band was observed at about 42017 cm −1 (238 nm), a dominant band at around 35714 cm −1 (280 nm) and two shoulder bands were seen in the emission spectra. The excitation and emission spectra of Ce 3+ and Pr 3+ were compared and discussed. The X-ray excited luminescence studies show that the light yields are ∼3200±230 and ∼1400±100 photons/MeV of absorbed X-ray energy for the samples Sr 1.86 Ce 0.07 Na 0.07 Mg(BO 3 ) 2 and Sr 1.82 Pr 0.09 Na 0.09 Mg(BO 3 ) 2 at RT, respectively.

The spectroscopic properties of Na 3 Gd(PO 4 ) 2 and Na 3 Gd(PO 4 ) 2 :Ce 3+ phosphors in the VUV–UV spectral range were investigated. Five excitation bands of Ce 3+ ions at Gd 3+ sites are observed at wavelengths of 205, 246, 260, 292, and 321 nm. Doublet Ce 3+ 5d → 4f emission bands are observed at 341 and 365 nm with a decay constant τ 1/ e around 26 ns. The X-ray excited luminescence of Na 3 Gd 0.99 Ce 0.01 (PO 4 ) 2 at room temperature shows a photon yield of ∼17,000 photons/MeV of absorbed X-ray energy.

A series of samples with nominal chemical formulas La 2-x Ce x CaB 10 O 19 and La 2 Ca 1-2x Ce x Na x B 10 O 19 were prepared by a solid state reaction route at high temperature. Their luminescence properties were investigated by the steady state excitation and emission spectra in the VUV-vis range, the luminescence decays, and the time-resolved emission spectra (TRES). The results demonstrate that Ce 3+ ions occupy two lattice sites in all samples. The lowest 5d absorption bands for two sites are at about 272 (La 3+ site) and 312 nm (Ca 2+ site), respectively. The emission for Ce 3+ in the La 3+ site shows a shorter decay time of 12 ns, and the doublet emission bands have maxima at about 291 and 310 nm. The emission for the Ce 3+ in Ca 2+ site has a longer lifetime of 26 ns with band maxima at about 329 and 355 nm. Efficient energy transfer between both sites occurs in the samples.

A series of phosphors Ca3La3(1-x)Tb3x(BO3)5 were synthesized by using a high-temperature solid-state reaction technique, and their VUV-vis luminescence properties were investigated. Strong host-related absorption is observed in the VUV region, and the f–d transitions of Tb3+ in the host lattice are assigned and discussed. The influence of both the doping concentration and the temperature on the spectroscopic properties that include the relative emission intensity and the decay time is investigated.

The phosphors, fluorapatites M5(PO4)3F (M=Ca, Sr, Ba) activated with Dy3+ ions, were prepared by a high‐temperature solid‐state reaction technique. The VUV‐UV excitation spectra and emission spectra under VUV/UV excitation were measured. The phosphors show broad and strong absorption near 172 nm and intensive emission with the chromaticity coordinates entering the white light region. Hence, the phosphors may be considered as suitable candidates for Hg‐free lamps.

The spectroscopic properties of Ce 3+ , Pr 3+ and Tb 3+ activated SrB 4 O 7 in VUV–vis range were investigated. The split 5d levels for Ce 3+ in the host lattice are discussed and an environmental factor F c is used to explain the crystal field splitting (CFS). The photon cascade emission (PCE) process was observed in Pr 3+ doped SrB 4 O 7 , and the quantum efficiency of PCE is estimated. An empirical relationship between the lowest spin-allowed f–d transition energy [ W fd( n ) ] and n -value for 4f n -series Ln 3+ (Ln = Ce, Pr, Tb) ions in SrB 4 O 7 is proposed.

Fluoro-apatite M5(PO4)3 F( M= Ca, Sr, Ba) phosphors activated with Ce 3+ ions were prepared by a solid state reaction technique at high temperature. The excitation spectra in the VUV (vacuum ultraviolet)–UV range and the emission spectra in the UV–vis range together with decay time spectra are investigated and discussed. X-ray excited emission spectra were measured and light yields are calculated. The results revealed that Ca(II) sites are preferentially occupied at low doping concentration, and then Ca(I) sites are dominant with the increasing of concentration for Ce 3+ in Ca5(PO4)3F. In contrast, Ce 3+ ions mainly occupied the Sr(II)/Ba(II) sites in Sr5(PO4)3 Fa nd Ba5(PO4)3F even at higher doping concentration. The low light output seems to suggest that the materials are not suitable x-ray or gamma-ray phosphors. (Some figures in this article are in colour only in the electronic version)

The phosphors NaGdFPO{sub 4}:Ln {sup 3+} and GdPO{sub 4}:Ln {sup 3+} (for Ln{sup 3+}=Ce{sup 3+} and Tb{sup 3+}) were prepared by solid-state reaction technique, the VUV-vis spectroscopic properties of the phosphors were investigated, and we vividly compare the luminescence of Ce{sup 3+} and Tb{sup 3+} in the hosts. For phosphors GdPO{sub 4}:Ln {sup 3+}, the band near 155 nm in VUV excitation spectrum is assumed to be the host-related absorption, and for NaGdFPO{sub 4}:Ln {sup 3+} the absorption is moved to longer wavelength, near 170 nm, showing the P-O bond covalency increased after fluoridation. The f-d transitions of Ce{sup 3+} and Tb{sup 3+} in the host lattices are assigned and corroborated, and it was found that the 5d states are with lower energy in NaGdFPO{sub 4}:Ln {sup 3+} than those in GdPO{sub 4}:Ln {sup 3+}. For fluoridation of GdPO{sub 4}:Ln {sup 3+} to NaGdFPO{sub 4}:Ln {sup 3+}, the energy change of Ln {sup 3+} (Ln=Ce, Tb) 5d states is consistent with that of host-related absorption.

The spectroscopic properties of Ba2Mg(BO3)2:Ce3+ and Ba2Mg(BO3)2:Eu2+ in vacuum-ultraviolet-vis range were investigated. The 5d crystal-field splitting components and the barycenter of Ce3+, the lowest 5d levels, the emission and the Stokes shifts of Eu2+ and Ce3+ in the host lattices, as well as the host-related absorption are identified and discussed in terms of the crystal structure of the host lattice.

The near-infrared (NIR) luminescence properties of Cr3+ activated Ca3Ga2Ge3O12 (CGGG) are studied under ultraviolet and visible light excitation. Three types of Cr3+ centers associated with 4T2–4A2 transition resulting in the emissions located at 650–1100 nm are identified in all Cr3+-doped samples. Thanks to the occupancy of three nonequivalent sites in CGGG, NIR luminescence is observed peaking at about 749, 803, and 907 nm, respectively. The influence of crystal field on site occupancy is studied, the relation between site occupancy and the NIR luminescence is addressed, and the energy transfer process among Cr3+ sites and the decay behaviors for Cr3+ in different sites are evaluated. It is found that a superior NIR/persistent luminescence comes from the traps that Cr3+ enters the Ga3+ site. The results are of benefit to investigate Cr3+-activated persistent phosphors.

Near-infrared-to-near-infrared (NIR-to-NIR) anti-Stokes luminescence from Cr3+ singly doped Ca3Ga2Ge3O12 (CGGG) occurs under the excitation of an 808 nm diode laser. The anti-Stokes processes vary from one photon to two photon, depending on the Cr3+ content (x) in Ca3Ga2−xCrxGe3O12. The results suggest that phonon-assisted anti-Stokes excitation and cooperative energy transfer are involved in the observed upconversion (UC) processes of CGGG:Cr3+. The relevant Cr3+-doping-concentration-dependent NIR-to-NIR anti-Stokes luminescent mechanism, either one-photon or two-photon UC, is investigated. Such an observation on modulating the UC process via varying the doping concentration is helpful in broadening the understanding of UC phenomena.

We have studied the structural and near-infrared (NIR) luminescent properties of KY3F10 phosphors, singly doped with Nd3+ serving as both sensitizer and activator. With a single laser diode at the wavelength of 808 nm as a pump source, simultaneous NIR-to-NIR upconversion (UC) and down-shifting (DS) emissions are effectively achieved, due to the specific energy levels of Nd3+ dopant and the low phonon energy of the host. The luminescence mechanism related to energy transfer is discussed. The luminescence can be modulated through controlling the population of Nd3+:4F3/2 state in our experiment. Interestingly, both UC and DS emissions of the material fall within the dual biological window, suggesting that the prepared phosphors have potential applications in the bioimaging field.

In order to develop a suitable green phosphor for plasma display panels (PDPs), samples Ca 5-2x Tb x Na x (PO 4 ) 3 F for x = 0.20, 0.35, 0.50, 0.65, 0.80, and 0.95 were prepared by a solid-state reaction technique at high temperature. The vacuum ultraviolet (VUV, wavelength λ 50,000 cm -1 )-vis spectroscopic properties and decay characteristic were investigated. Because the phosphor Ca 5-2x Tb x Na x (PO 4 ) 3 F for x = 0.95 shows broad and strong absorption in the vacuum ultraviolet (VUV) range, exhibits higher intensive emission under 147/172 nm excitation, and has a shorter decay time (τ ∼ 2.19 ms) in comparison with the commercial green PDP phosphor Zn 2 SiO 4 /Mn 2+ , it is considered to be a promising green phosphor in PDPs.

The phosphors of ${\mathrm{Ce}}^{3+}$ activated ${\mathrm{Ba}}_{2}\mathrm{Ca}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ with chemical formulas ${\mathrm{Ba}}_{2(1\ensuremath{-}x)}{\mathrm{Ce}}_{x}{\mathrm{Na}}_{x}\mathrm{Ca}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ and ${\mathrm{Ba}}_{2}{\mathrm{Ca}}_{1\ensuremath{-}2x}{\mathrm{Ce}}_{x}{\mathrm{Na}}_{x}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ were prepared. The luminescence properties have been investigated under vacuum ultraviolet UV and x-ray excitation. Though the point defects ${\mathrm{Ce}}_{{\mathrm{Ba}}^{\mathbf{∙}}}$ and ${\mathrm{Na}}_{{\mathrm{Ba}}^{\ensuremath{'}}}$ are expected to occur in samples ${\mathrm{Ba}}_{2(1\ensuremath{-}x)}{\mathrm{Ce}}_{x}{\mathrm{Na}}_{x}\mathrm{Ca}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$, and ${\mathrm{Ce}}_{{\mathrm{Ca}}^{\mathbf{∙}}}$ and ${\mathrm{Na}}_{{\mathrm{Ca}}^{\ensuremath{'}}}$ are expected to appear in samples ${\mathrm{Ba}}_{2}{\mathrm{Ca}}_{1\ensuremath{-}2x}{\mathrm{Ce}}_{x}{\mathrm{Na}}_{x}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ according to the formulas of the compounds, however, two types of ${\mathrm{Ce}}^{3+}$ centers were found in all samples due to the occupancy of both ${\mathrm{Ba}}^{2+}$ and ${\mathrm{Ca}}^{2+}$ sites. So the influence of doping concentration on the preferential site occupancy was studied, and it was found that ${\mathrm{Ce}}^{3+}$ ions always preferentially enter ${\mathrm{Ba}}^{2+}$ sites at low doping concentration for both samples ${\mathrm{Ba}}_{2(1\ensuremath{-}x)}{\mathrm{Ce}}_{x}{\mathrm{Na}}_{x}\mathrm{Ca}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ and ${\mathrm{Ba}}_{2}{\mathrm{Ca}}_{1\ensuremath{-}2x}{\mathrm{Ce}}_{x}{\mathrm{Na}}_{x}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$. In addition, the $5d$ energy levels and decay behaviors for ${\mathrm{Ce}}^{3+}$ in ${\mathrm{Ba}}^{2+}$ and ${\mathrm{Ca}}^{2+}$ sites, the concentration quenching, and the x-ray excited photon output were evaluated to clearly reveal the luminescence features.

Strong tunable photoluminescence (PL) from silicon oxynitride materials have been demonstrated by modulating the oxygen content. The increase of oxygen content in the films from 8% to 61% results in red, orange-yellow and white switching PL. The change in PL characteristics of these films is ascribed to the variation of defect luminescent centers as well as the evolution of dominant phase structures changing from silicon nitride to silicon oxynitride and silicon oxide. The intense PL intensity is suggested from the nanoseconds recombination lifetime as well as the alleviation of internal stress in silicon oxynitride.

Eu(3+)-activated La2CaB10O19 phosphors with nominal chemical formulae La(2-x)Eu(x)CaB10O19 and La2Ca(1-2x)Eu(x)Na(x)B10O19 were prepared. The luminescence properties under VUV-UV excitation were investigated. Luminescence spectra reveal Eu(3+) ions occupy both Ca(2+) and La(3+) sites in all samples. The O(2-)→ Eu(3+) charge transfer bands (CTBs) and the (5)D0→(7)F0 emissions of Eu(3+) at Ca (2+) site and La(3+) site are identified, respectively. The schematic energy levels for Eu(3+) in two sites were achieved. Luminescence decays of the (5)D0→(7)F0 transitions were measured for both sites.

The luminescence properties of Ce3+ activated Ba2Ca(BO3)2 with K+ as a charge compensator have been investigated and compared with those with Na+-compensating. Energy transfer of Ce3+ in Ba2+ (i.e. Ce(1)3+) and Ca2+ (i.e. Ce(2)3+) sites has been proven by VUV–UV excitation and emission spectra, luminescence decays and time-resolved emission spectra. In addition, by combining Ba2Ca(BO3)2 : Ce3+ phosphors with near-ultraviolet (n-UV) InGaN chips, the fabricated light-emitting diodes (LEDs) show intense bluish-green emission, and the phosphors exhibit good thermal stability.

The orthophosphate phosphors, Ba3La(PO4)3 activated with Dy3+ and Gd3+-Dy3+ ions, were prepared by a solid reaction technique at high temperature. Their spectroscopic properties were investigated in the vacuum ultraviolet (VUV)-visible range. We found that the introducing of Gd3+ greatly enhances the Dy3+ luminescence under 172 nm VUV excitation. The measurements on excitation spectra, emission spectra, and luminescence decay curves revealed that the energy transfer between Gd3+ and Dy3+ becomes more and more efficient with the increasing Gd3+ contents.

The phosphors Ba3Gd(BO3)3:Ce3+ were prepared by a solid-state reaction technique at high temperature. The vacuum ultraviolet-ultraviolet and visible spectroscopic properties of the phosphors together with decay time curves are investigated and discussed. The spectroscopic properties are explained by occupancy of Ce3+ at two different Gd sites in the host lattice. The x-ray excited emission spectra of Ba3Gd(BO3)3:Ce3+ were studied and the number of photons emitted per unit of absorbed x-ray energy was calculated. The yield is rather poor and Ba3Gd(BO3)3:Ce3+ appears not a suitable x-ray phosphor.