Resonance-type Energy Transfer Research Articles

White light luminescence in Dy/Tm co-doped yttria stabilized zirconia single crystals

A series of high quality Dy2O3 and Tm2O3 co-doped yttria stabilized zirconia (YSZ) single crystals was synthesized. These crystals have a single cubic structure, and exhibit the characteristic of Dy3+ (blue and yellow emissions) and Tm3+ (blue emission) under excitation with NUV light. Importantly, the hue can be varied between blue and white by modifying the Tm3+/Dy3+ ratio. The photoluminescence and decay curves are consistent with the existence of resonance-type energy transfer from Tm3+ to Dy3+ ions via an electric multipole interaction mechanism. Maximum luminescence intensity is observed in YSZ doped with 0.50 mol% Tm2O3 and 0.75 mol% Dy2O3, and this sample has CIE coordinates (x = 0.33, y = 0.33) in accordance with those for white chromaticity. Thus, the outstanding luminescence properties of these single crystals suggest potential applications in white light emission devices.

Tunable multicolor and bright white emission in PEG modified β-NaGdF4 nanocrystals by systematic introduction of Ce3+ and Mn2+/Ln3.

In this paper, Mn2+/Ln3+-doped hexagonal phase (β-) NaGdF4:Ce (Ln = Tb, Dy, Eu) nanomaterials with subtly tuned multicolor output have been successfully synthesized by a typical simple hydrothermal method using polyethylene glycol (PEG) as a surface modifying agent. The crystal structures, morphology, luminescence performance, and energy transfer (ET) mechanism of the synthesized NaGdF4 nanoparticles (NPs) were investigated in detail. It is found that due to the effective ET between Ce3+ and Mn2+/Ln3+, the multicolor down-conversion (DC) emission phosphors can yield three major emission bands in the visible region including blue, green and red. Moreover, the white emission could be realized through manipulating the doping ratio of Ce3+, Dy3+ and Eu3+ with suitable concentration in β-NaGdF4 NPs through effective resonance-type ET under the irradiation of 273 nm. And the corresponding CIE1931 coordinates were calculated to be (0.31, 0.32), which is near the normative white emission (0.33, 0.33). All the multicolor tuning and white emission results evidently suggest that the present Ce3+ and Mn2+/Ln3+-doped β-NaGdF4 NPs are feasible phosphors for potential applications in white-light emitters, full-color displays and photonic devices.

A dual-emission Ca9MgLi(PO4)7: Ce3+, Mn2+ phosphor with energy transfer for plant-lighting

A series of multicolor-tunable Ca 9 MgLi(PO 4 ) 7 (CMLPO):Ce 3+ , Mn 2+ phosphors have been prepared by high-temperature solid-state reaction process under the reductive atmosphere and the luminescence properties have been explored. The photoluminescence excitation (PLE) spectra and emission (PL) spectra reveal that the bands are centered at 345 and 365 nm occupying the Ca3 site with respect to the CMLPO:Ce 3+ phosphors, while the bands located at 386 and 411 nm are ascribed to the emission of Ce 3+ ions occupying the eight-coordinated center (Ca1 and Ca2), according to the Van Uitert formula. In addition, an asymmetric broad band with the maximum at ~361 nm stemmed from the 5 d → 4 f transition can be observed, under 291 nm excitation. Also, the PL spectra display a broad band at ~650 nm, which is assigned to the 4 T 1 ( 4 G) → 6 A 1 ( 6 S) spin-forbidden transition of Mn 2+ for the CMLPO:Mn 2+ samples. Furthermore, the Ce 3+ can transfer a part of its energy to Mn 2+ and the energy transfer (ET) efficiency reaches as high as ~94.02%. Subsequently, the CMLPO:Ce 3+ , Mn 2+ phosphors present a series of colors by modulating the contents of Mn 2+ through an effective resonance-type ET and the dipole-quadrupole ( d - q) interaction governs the ET process. Importantly, the emission band of Mn 2+ distributed exactly in red and far-red regions, which can match well with the red light wavelength required for plant photosensitive pigments (P R , P FR ). In view of the aforementioned results, the as-prepared phosphors could open ideas for designing the plant growth LEDs. • The Ce 3+ can transfer a part of its energy to Mn 2+ and η T reaches as high as ~94.02%. • The emission band of Mn 2+ can match well with the wavelength required for PR and PFR. • The as-prepared phosphors could open ideas for designing the plant growth LEDs.

Energy transfer from Mn2+ to Nd3+ ions embedded in a nanostructured glass system with Zn1−xMnxTe nanocrystals

In this work, we study energy transfer (ET) processes between Mn2+ and Nd3+ ions in Nd2O3-doped P2O5–ZnO–Al2O3–BaO–PbO glass system, nanostructured with Zn1−xMnxTe diluted magnetic semiconductor nanocrystals (NCs), aiming nanotechnology applications. Transmission electronic microscopy (TEM), X-ray diffraction (XRD), optical absorption (OA), photoluminescence (PL), and lifetime measurements were performed for a complete characterization of the investigated materials. The TEM and XRD data confirm the formation of Zn1−xMnxTe NCs in the host glass system. The overlap between the Mn2+ ion emission band and the Nd3+ ion absorption bands suggests that an efficient resonant type energy transfer from Mn2+ to Nd3+ ions is expected. PL spectra show that the characteristic emission relative intensities of Nd3+ ions increase systematically with increasing Mn concentration. Indeed, the 4T1(4G) state lifetime of Mn2+ ions gradually decreases with rising Mn concentration. This result confirm the evidence on ET from Mn2+ ions to Nd3+ ions. In addition, the increase in the 4F3/2 state lifetime is an evidence of persistent luminescence due to the presence of Mn2+ ions.

Color-tunable luminescence and energy transfer properties of Dy3+/Tm3+ co-doped Sr9Mg1.5(PO4)7 phosphor for light-emitting diodes

A series of Sr9Mg1.5(PO4)7:Tm3+, Dy3+ phosphors were prepared by conventional sintering method. Rietveld refinement, X-ray diffraction patterns, PL/PLE spectra, lifetimes and thermal quenching spectra were measured and investigated in detail. All the prepared phosphors crystalized to single phase and consisted of micronized particles. When excited by 358 nm, the emission hue of Sr9Mg1.5(PO4)7:0.01 Tm3+, yDy3+ (0 ≤ y ≤ 0.20) turned from blue to white by modifying the Tm3+/Dy3+ ratio. The overlapped PL/PLE spectra and decreasing lifetimes of Sr9Mg1.5(PO4)7:Tm3+, yDy3+ indicated the energy transfer from Tm3+ to Dy3+. Moreover, the resonance type energy transfer from sensitizer (Tm3+) to activator (Dy3+), CIE chromaticity and energy transfer efficiency were confirmed and discussed, too. The energy transfer mechanism was determined as a resonant type via dipole-dipole mechanism with 53.05% energy transfer efficiency when the doping content y = 0.02. The CIE chromaticity coordinates of Sr9Mg1.5(PO4)7:0.01 Tm3+, 0.20Dy3+ was (0.3279, 0.3299) with 27.8% quantum efficiency. The sample also exhibited excellent thermal quenching performance with the remained 95% emission intensity at 150 °C compared with the original emission intensity at ambient temperature. The outstanding luminescence properties and excellent thermal stability suggested that Sr9Mg1.5(PO4)7:0.01 Tm3+, 0.20Dy3+ phosphor had a potential application in WLEDs.

Tri-chromatic Emission from a Single-phase Na5Y4(SiO4)4F:Eu2+,Tb3+,Eu3+ Phosphor for White-light-emitting Diodes

A series of single-phase Na5Y4(SiO4)4F:Eu2+,Tb3+,Eu3+ phosphors were successfully synthesized by high-temperature solid state reaction and their crystal structure and luminescence properties were investigated. The chromaticity coordinates of the as-prepared phosphors under 375 nm excitation can be tuned effectively, from the light blue (0.260, 0.213) to red (0.638, 0.337) and eventually to white (0.407, 0.373) via resonant type energy transfer and appropriate choice of color combination. Furthermore, the states occupation of the dopant ions and the energy transfer mechanisms Eu2+ → Tb3+ and Tb3+ → Eu3+ have been investigated and discussed, emphasizing on spectral content and thermal stability of Na5Y4(SiO4)4F:Eu2+,Tb3+,Eu3+ emission under 375 nm excitation. The results indicate that the Na5Y4(SiO4)4F:Eu2+,Tb3+,Eu3+ phosphors have a potential application in UV-based White LED devices.

Novel square plate-like NaGd(WO4)2:Tm3+,Dy3+ phosphors: Synthesis, characterization, tunable luminescence properties and energy transfer behaviors

A series of single-phase color-tunable NaGd(WO4)2(NGW):Tm3+,Dy3+ phosphors were prepared by a facile hydrothermal method. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectra, and fluorescence decay curves. The results show that all samples are tetragonal scheelite-type pure phase, taking on novel square plate morphology with the side length of 5–6 μm and the central thickness of 2.3 μm. Under the excitation of UV light, NGW:Tm3+ and NGW:Dy3+ exhibit the characteristic emissions of Tm3+ (blue) and Dy3+ (yellow), respectively. White light emission can be achieved by simply adjusting the doping concentration of Tm3+ and Dy3+ in NGW. The luminescence spectra and decay curves reveal the resonance-type energy transfer from Tm3+ to Dy3+ ions and the energy transfer mechanism has been proposed. In addition, the CIE chromaticity coordinates of NGW:Tm3+,Dy3+ can be tuned close to the standard white chromaticity (x = 0.33, y = 0.33). All the results indicate that the obtained products may be potentially applied in the area of UV-excited WLEDs.

Photoluminescence properties and efficient energy transfer of Ce3+/Eu2+ activated K2Ba7Si16O40 phosphors

Ce3+/Eu2+ activated K2Ba7Si16O40 phosphors have been synthesized via a high-temperature solid-state method with CO atmosphere. Under ultraviolet (UV) light pump, the photoluminescence (PL) spectra of K2Ba7Si16O40: Ce3+ is composed of a broadband from 300 nm to 500 nm ascribed to the spin-allowed 5d–4f transition of Ce3+ ions. The optimal concentration is 8% for Ce3+ single doped K2Ba7Si16O40 due to the ernergy dispersion between Ce3+ ions and the critical distance between Ce3+ ions is 15.05 Å. K2Ba7Si16O40: Eu2+ emits a broad green emission peaking at 498 nm. The spectral overlap between the emission of Ce3+ and the excitation of Eu2+ suggests the resonance-type energy transfer from Ce3+ to Eu2+, which is further demonstrated by the decay curves of K2Ba7Si16O40: 8 mol% Ce3+, m Eu2+. The critical distance between Ce3+ and Eu2+ ions is calculated to be 25.06 Å by Dexter’s theory. Furthermore, the energy transfer mechanism is dipole-dipole interaction. In addition, the thermal activation energy is calculated to be 0.26 eV. The CIE coordinates can be tuned from blue to green by increasing Eu2+ ions. All results suggest that K2Ba7Si16O40: Ce3+, Eu2+ is potentially useful for near-UV pumped white LEDs.

Ce 3+ Sensitized YPO 4 :Tb 3+ as Luminescent Probe for Selective Detection of Cu 2+ Ions

Poly (acrylic acid) (PAA) modified water dispersible Ce 3+ (5 at.%) sensitized YPO 4 doped with Tb 3+ (5 at.%) nanocrystals were prepared by polyol method. Structural characterization was thoroughly studied with X-ray diffraction (XRD). Transmission electron microscopy (TEM) image indicate the rod shape morphology of the synthesized material. Fourier transform infrared (FTIR) spectroscopy confirms the surface functionalization of these nanorods. The sample shows the occurrence of strong energy transfer from Ce 3+ ions to Tb 3+ ions. The emission from Tb 3+ ions (green colour) could be selectively quenched with the addition of Cu 2+ ions upto ~89% compared to many of the heavy metal ions. It is established from the investigation the sensing is through dynamic quenching via resonance type energy transfer. The limit of detection calculated using Stern-Volmer relation is found to be 19 μM (~ 1 ppm). This nanophosphor could be a potential luminescent probe for Cu 2+ ions sensing.

Photoluminescence properties and energy transfer of a color tunable phosphor: Dy3+ and Tm3+ co-activated SrCaAl2SiO7

A series of single-phased emission-tunable SrCaAl2SiO7:Dy3+, Tm3+ phosphors were successfully synthesized by solid-state reaction process. By controling the energy transfer, the emission colors could be tuned from blue to yellow, including the white light region. It was discovered that the energy is transferred from Tm3+ to Dy3+ by luminescence spectra and decay curves. The resonance-type energy transfer from Tm3+ to Dy3+ was demonstrated to be via the dipole–dipole mechanism. By changing the doping concentration of Dy3+ and Tm3+ in SrCaAl2SiO7, the sample with corresponding color coordinates close to the white color chromaticity coordinates (x=0.33, y=0.33) could be realized.

Tunable color of Ce3+/Tb3+-codoped Ba3Sr4(BO3)3F5 phosphors for near-UV-pumped LEDs

Single-component-tunable blue-to green-light-emitting phosphors Ba3Sr4(BO3)3F5: Ce3+, Tb3+, Na+ (BSBF: Ce3+, Tb3+, Na+) promising for near-UV-pumped light-emitting diodes (LEDs) were synthesized via high-temperature solid-state reactions, and their photoluminescence properties were systematically investigated. Upon the excitation of 360 nm, the BSBF: Ce3+, Tb3+, Na+ phosphors exhibited a broad blue emission band at 422 nm and a series of sharp emission lines at 490, 544, 585, and 623 nm, which originated from the 4f05d1–4f1 transition of Ce3+ ions, and 5D4–7FJ (J = 6, 5, 4, 3) transitions of Tb3+ ions, respectively. Through the resonance-type energy transfer, the varied emitted colors from blue through cyan and eventually to green were achieved by properly tuning the relative dopant composition of Ce3+/Tb3+. Moreover, the energy transfer from Ce3+ to Tb3+ in BSBF host matrix was demonstrated via the dipole–dipole interaction mechanism. Additionally, the critical distances (\( R_{\text{C}} \)) calculated by quenching concentration and spectral overlap method in such system were 2.166 and 1.940 nm, and the activation energy for thermal quenching (ΔE) was determined to be 0.117 eV. These results indicate that the developed color-tunable phosphors BSBF: Ce3+, Tb3+, Na+ are competitive as the promising single-component phosphor-converted materials for near-UV-pumped LEDs.

Ultrafast FRET at fiber tips: Potential applications in sensitive remote sensing of molecular interaction

Förster resonance energy transfer (FRET) strategy is well adopted in fiber-optics for efficient sensor design. However, resonance type energy transfer from one molecule (donor) to other (acceptor) should meet few key properties including donor to acceptor energy migration in non-radiative way, which is hard to conclude from simply emission quenching of the donor, rather needs careful investigation of excited state lifetime of the donor molecule. In the present study, we have shown that the evanescent field of an optical fiber can be coupled to covalently attached donor (dansyl) molecules at the fiber tip. By using picosecond resolved time correlated single photon counting (TCSPC) we have demonstrated that dansyl at the fiber tip transfers energy to a well known DNA-intercalating dye ethidium upon surface adsorption of DNA at the fiber tip. Our ultrafast detection scheme selectively distinguishes the probe (dansyl) emission from the intrinsic emission of the fiber. The validation of the energy transfer mechanism to be of resonance type (FRET), allows us to estimate the distance between the probe dansyl and the surface adsorbed DNA. We have also used the setup for the remote sensing of the dielectric constant (polarity) of an environment as the excited state lifetime of the probe dansyl heavily depends on the polarity of the immediate host environment. FRET signal from a used fiber tip immediately after adsorption of DNA reveals stepwise surface desorption of the biomolecule in saline solution. The reusability of the fiber tip for sensing has also been demonstrated.

Structural and luminescence properties of tunable white-emitting Sr0.5Ca0.5Al2O4:Eu2+, Dy3+for UV-excited white-LEDs

Tunable white-emitting Sr0.5Ca0.5Al2O4:Eu2+, Dy3+ phosphors were synthesized via solid-state reactions and evaluated as suitable candidates for white light emitting diodes in this study. The crystal structure of Sr0.5Ca0.5Al2O4:Eu2+, Dy3+ was refined and determined from X-ray diffraction (XRD) profiles via the Rietveld refinement method. The as-prepared phosphors exhibit a monoclinic structure with the P121/n1 space group. Under ultraviolet (UV) excitation, these phosphors display two emission bands, which peak at around 445 and 540 nm, corresponding to the 5d → 4f transition of Eu2+ ions. The photoluminescence results indicate that the Eu2+ ions tend to occupy three different crystallographic sites of the Ca2+ and Sr2+ ions in the Sr0.5Ca0.5Al2O4 structure. By the increment of Eu2+ ion concentration in Sr0.5Ca0.5Al2O4:Eu2+, Dy3+, the emission colors can be tuned from bluish white to warm white and eventually to yellowish white. Such color tuning has been achieved due to the resonance type energy transfer among the Eu2+ ions located at various crystallographic sites. The non-radiative energy transfer between Eu2+ ions is attributed to dipole–dipole interactions. The critical distances of the energy transfer are calculated to be 2.98 and 2.86 nm using concentration quenching and spectral overlap methods, respectively. The present research suggests that tunable white-emitting Sr0.5Ca0.5Al2O4:Eu2+, Dy3+ phosphors have the potentiality to be applied for UV excited white LEDs.

Optical properties and energy transfer of Eu2+/Ce3+ co-activated Na3Ca6(PO4)5 phosphor.

Ce(3+) /Eu(2+) co-doped Na3 Ca6 (PO4 )5 phosphors were prepared using a combustion-assisted synthesis method. X-Ray powder diffraction (XRD) analysis confirmed the formation of a Na3 Ca6 (PO4 )5 crystal phase. Na3 Ca6 (PO4 )5 :Eu(2+) phosphors have an efficient bluish-green emission band that peaks at 489 nm, whereas Ce(3+) -doped Na3 Ca6 (PO4 )5 showed a bright emission band at 391 nm. Analysis of the experimental results suggests that enhancement of the Eu(2+) emission intensity in co-doped Na3 Ca6 (PO4 )5 :Eu(2+) ,Ce(3+) phosphors is due to a resonance-type energy transfer from Ce(3+) to Eu(2+) ions, which is predominantly governed by an exchange interaction mechanism. These results indicate that Ce(3+) /Eu(2+) co-doped Na3 Ca6 (PO4 )5 is potentially useful as a highly efficient, bluish-green emitting, UV-convertible phosphor for white-light-emitting diodes.

A single-phased warm white-light-emitting phosphor BaMg2(PO4)2:Eu2+, Mn2+, Tb3+ for white light emitting diodes

A single-phase white-emitting phosphor BaMg2(PO4)2:Eu2+, Mn2+, Tb3+ is synthesized by a high temperature solid-state reaction. The luminescent properties and the efficient energy transfer from Eu2+ to Mn2+ and Tb3+ in BaMg2(PO4)2 are investigated. The chromaticity coordinates of BaMg2(PO4)2:Eu2+, Mn2+, Tb3+ can be tuned from (0.153, 0.056) (for BaMg2(PO4)2:Eu2+) to (0.666, 0.261) (for BaMg2(PO4)2:Mn2+), and eventually to (0.313, 0.562) (for BaMg2(PO4)2:Tb3+) by the effective resonance type energy transfer. The warm white light can be realized with the superior chromaticity coordinates of (0.346, 0.299) and low correlated color temperature (CCT=4464K) by coupling the emission bands peaking at 447, 544 and 663nm attributed to the contribution from Eu2+, Tb3+ and Mn2+, respectively.

Multicolor tunable luminescence and paramagnetic properties of NaGdF₄:Tb³⁺/Sm³⁺ multifunctional nanomaterials.

Tb(3+) and/or Sm(3+) doped NaGdF4 luminescent nanomaterials have been successfully synthesized by an SDS-assisted one-step hydrothermal method. The samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray energy dispersive spectrometer (EDS), photoluminescence (PL) spectra and a vibrating sample magnetometer (VSM). The results show that the synthesized samples are all pure β-NaGdF4. The as-prepared Tb(3+) or Sm(3+) doped samples show strong green and yellow emission, originating from the allowed (5)D3→(7)F(J) (J = 5, 4, 3, 2) and (5)D4→(7)F(J) (J = 6, 5, 4, 3) transitions of the Tb(3+) ions and the (4)G(5/2)→(6)H(5/2), (6)H(7/2), (6)H(9/2) transition of the Sm(3+) ions. Based on the excitation wavelengths, multiple (yellowish green, yellow, white) emissions are obtained by Sm(3+) ion co-activated NaGdF4:Tb(3+) phosphors. Moreover, an energy transfer from Tb(3+) to Sm(3+) is observed, which is justified through the luminescence spectra and the fluorescence decay curves. Furthermore, the resonance-type energy transfer from Tb(3+) to Sm(3+) is demonstrated to occur via the dipole-dipole mechanism. In addition, the obtained samples also exhibit paramagnetic properties at room temperature. It is obvious that these multifunctional Tb(3+), Sm(3+) co-doped β-NaGdF4 nanomaterials, with tunable multicolors and intrinsic paramagnetic properties, may have potential application in the fields of full-color displays, biological labels, bioseparation and magnetic resonance imaging.

Effect of Axial Ligand on the Binding Mode of M-Meso-Tetrakis(N-Methylpyridinium-4-Yl)Porphyrin to DNA and their Efficiency as an Acceptor in DNA-Mediated Energy Transfer

The binding modes of cationic porphyrins, namely M-meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (MTMPyP, where M=free base, Cu(II), Ni(II), Co(III), Mn(III), V(IV)=O and Ti(IV)=O), to native DNA were systematically investigated by polarized light spectroscopies. At low [porphyrin]/[DNA] ratio, planar porphyrins including TMPyP, CuTMPyP and NiTMPyP exhibited intercalative binding mode. In the intercalation pocket, the molecular plane of porphyrin is skewed to a large extent. As the mixing ratio was increased the coupling of the electric transition moments of the intercalated porphyrins was observed. Coupling can occur between the porphyrins when they are separated at least two DNA base. The porphyrins with axial ligands, namely VOTMPyP, TiOTMPyP, MnTMPyP and CoTMPyP bind to the exterior of the DNA at a low [porphyrin]/[DNA] ratio. The angle of one the two electric transitions of the porphyrin is in the range of 56°∼59°, while the other is in the range of 59°∼65°. Increasing the porphyrin density resulted in the appearance of an interaction between the bound porphyrins. All porphyrins were able to quench the fluorescence of intercalated ethidium. The mechanism behind the energy transfer is, at least in part, the Forster type resonance energy transfer (FRET). The minimum distance in base pairs between ethidium and porphyrin required to permit the excited ethidium to emit a photon was the longest for CoTMPyP being 17.6 base-pairs and was the shortest for CuTMPyP and NiTMPyP at 8.0 base-pairs. The variation in the distance was almost proportional to the extent of the spectral overlap, the common area under emission spectrum of ethidium and absorption spectrum of porphyrin, supporting the FRET mechanism, while the effect of the orientation factor which was considered by relative binding geometry was limited.

Blue–white–orange tunable luminescence from Ca6La2Na2(PO4)6F2:Eu2+, Mn2+ phosphors excited by UV light

New Eu2+ and/or Mn2+ activated Ca6La2Na2(PO4)6F2 phosphors were prepared and their photoluminescence properties upon ultraviolet excitation were investigated. Phosphor Ca6La2Na2(PO4)6F2:Eu2+,Mn2+ shows a broad blue emission band and an orange emission band, which originates from Eu2+ and Mn2+, respectively. The resonant type energy transfer from Eu2+ to Mn2+ was demonstrated, and the energy transfer efficiency was also calculated according to their PL decay curves. Tuning of the content of Mn2+ can generate the varied hues from blue to white and eventually to orange. Our results demonstrate that the phosphor is promising for producing UV-LED-based white LEDs.

Luminescence and energy transfer in Eu2+, Mn2+ co-doped Ca2SrNaLa(PO4)3F

A new compound Ca2SrNaLa(PO4)3F, isotypic with hexagonal Ca(Sr,Na,Ca)(Ca,Sr,Ce)3(PO4)3F, is reported. Its cell parameters have been determined from X-ray powder diffraction data. Crystallization occurs in the hexagonal space group P63 (No. 173) with a=9.515(1)Å, c=7.028(1)Å, and Z=2. Eu2+ and Mn2+ activated Ca2SrNaLa(PO4)3F phosphors have been prepared. The energy transfer of Eu2+ → Mn2+ has been investigated. The resonant type energy transfer from Eu2+ to Mn2+ has been demonstrated, and the energy transfer efficiency has also been calculated according to their PL decay curves. A color-tunable emission in Ca2SrNaLa(PO4)3F phosphors can be realized by Eu2+ → Mn2+ energy transfer. White light can be achieved in a single-phased Ca2SrNaLa(PO4)3F host by co-doping Eu2+ and Mn2+ with CIE (0.32,0.31). Our results demonstrate that the potential application of these phosphors in solid-state lighting and (or) other areas.

Luminescence spectroscopy and energy transfer in Eu2+/Mn2+-doped KCaPO4 phosphors

Eu2+/Mn2+-doped KCaPO4 phosphors were prepared by conventional solid-state reaction. X-ray powder diffraction (XRD), SEM, photoluminescence excitation, and emission spectra, and the luminescence decay curves were measured. Mn2+ singly doped KCaPO4 shows the weak origin-red luminescence band peaked at about 590 nm. The Eu2+/Mn2+ co-doped phosphors emit two distinctive luminescence bands: a blue one centered at 480 nm originating from Eu2+ ions and a broad red-emitting one peaked at 590 nm from Mn2+ ions. The luminescence intensity from Mn2+ ions can be greatly enhanced with the co-doping of Eu2+ ions. The efficient energy transfer from Eu2+ to Mn2+ was verified by the photoluminescence spectra together with the luminescence decay curves. The resonance-type energy transfer via a dipole–quadrupole interaction mechanism was supported by the decay lifetimes. The emission colors could be tuned by changing the Mn2+-doping concentration.