Dipole Interaction Mechanism Research Articles

Multi-site occupancies and luminescence properties of cyan-emitting Ca9–xNaGd2/3(PO4)7:Eu2+ phosphors for white light-emitting diodes

Cyan-emitting Ca9NaGd2/3(PO4)7:Eu2+ phosphors were synthesized via high temperature solid-state route. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) were used to verify the phase and morphology of the Ca9NaGd2/3(PO4)7:Eu2+ (CNGP:Eu2+) phosphors. The as-obtained phosphor exhibits a broad excitation band of 250–420 nm, which is near the ultraviolet region. An intense asymmetric cyan emission at 496 nm corresponds to the 5d-4f transition of Eu2+. The multiple-site luminescent properties of Eu2+ ions in CNGP benefit from versatile structure of β-Ca3(PO4)2 compounds. The effective energy transfer distance is 5.46 nm (through the spectral overlap calculation), validating that the resonant energy migration type is via dipole–dipole interaction mechanism. Compared to the initial one at room temperature, the luminescent intensity of CNGP:Eu2+ phosphor can maintain 77% as it is heated up to 420 K. A white light-emitting diode (WLED) with excellent luminescent properties was successfully fabricated. Moreover, the CIE chromaticity coordinates of fabricated WLED driven by changing current just change slightly.

Electromagnetically induced grating in semiconductor quantum dot and metal nanoparticle hybrid system by considering nonlocality effects

The optical polarization from a hybrid system including a closely spaced spherical SQD (modeled as a three-level V-type system) and a metal nanoparticle which are considered classically and are connected by the dipole–dipole interaction mechanism is investigated. The interaction between the SQD and the MNP shows an interesting optical response. In the weak probe field regime and MNP nonlocality correction, the absorption spectrum of the hybrid system exhibits an EIT window with two absorption peaks and the plasmon-assisted quantum interference plays an important role in the position and amplitude of these peaks, which are intensely altered by including the nonlocal effects. The probe diffraction grating is created based on the excitons-induced transparency by applying a standing-wave coupling field. The results of this study are useful in numerous areas of all-optical communications.

Photoluminescence properties of Ca8Zn(SiO4)4Cl2: Ce3+, Mn2+ as a color-tunable phosphor for near-ultraviolet-pumped white light-emitting diodes

In this article, we firstly reported a novel color-tunable luminescence phosphors of Ca8Zn(SiO4)4Cl2: Ce3+, Mn2+. Ca8Zn(SiO4)4Cl2: Ce3+, Mn2+ phosphors could be efficiently excited by near-ultraviolet light to exhibit the blue and orange-red emission bands peaking at 411 and 600 nm corresponding to the 4f05d1-4f1 transition of Ce3+ and the 4T1(4G)-6A1(6S) transition of Mn2+, respectively. Utilizing the principle of energy transfer from Ce3+ to Mn2+ ions, our phosphors could be tuned the chromaticity coordinates from blue to orange-white and eventually to orange-red by appropriate adjusting the Mn2+ doping concentration. Based on the theoretical calculation, the energy transfer from Ce3+ to Mn2+ ions was demonstrated to be the dipole–dipole interaction mechanism with the maximum efficiency of 75.43%. Combining the 370 nm near-ultraviolet chip and the typical Ca8Zn(SiO4)4Cl2: 0.03Ce3+, 0.05Mn2+ phosphor finally produced the warm white light-emitting diode with high color rendering index of 86.6, demonstrating the potential of our phosphors for white light-emitting diode applications.

Photoluminescent properties and energy transfer mechanism of Tb3+-Ce3+ doped CaSi2O2N2 oxynitride phosphors

The Ce3+-Tb3+ doped CaSi2O2N2 phosphors are successfully obtained via conventional solid-state reaction at normal pressure. Broad absorption bands from Ce3+ are clearly observed in the excitation spectra of CaSi2O2N2:Tb3+, Ce3+. The emission spectra present a combination of Tb3+ and Ce3+ emission bands, and the emission intensity of Ce3+ is decreased along with the enhancement of the emission intensity of Tb3+. The energy transfer from Ce3+ to Tb3+ in the CaSi2O2N2 host is confirmed to be resonant type via a dipole–dipole interaction mechanism. It is also found that the luminescence intensity of the Tb3+-Ce3+ doped CaSi2O2N2 phosphors prepared in N2/H2 atmosphere is stronger than that prepared in pure N2.

Generation of bright white-light by energy-transfer strategy in Ca19Zn2(PO4)14:Ce3+, Tb3+, Mn2+ phosphors

Single-phase Ca19Zn2(PO4)14:Ce3+,Tb3+,Mn2+ phosphors have been prepared by a high temperature solid-state reaction method. X-ray diffraction (XRD), scanning electric microscopy (SEM), and photoluminescence (PL) spectra were utilized to characterize thephosphors. The optimal concentration of Ce3+ ions in Ca19Zn2(PO4)14:Ce3+ phosphors is found to be x = 0.05. The energy transfer process from Ce3+ to Tb3+ is determined to the dipole–dipole interaction mechanism. The emissive colors of Ca19Zn2(PO4)14:Ce3+,Tb3+,Mn2+ phosphors can be effectively realized by energy transfer strategy. The bright white-light emission are successfully observed by adjusting the individual concentrations of Ce3+, Tb3+ and Mn2+ ions in Ca19Zn2(PO4)14 phosphors excited by UV light. The obtained results suggest the presented Ca19Zn2(PO4)14:Ce3+,Tb3+,Mn2+ phosphors can be potentially a candidate for single-phase white-light phosphor for UV-pumped sources.

Investigation of luminescence properties and the energy transfer mechanism of LiSrBO3: Ce3+, Tb3+ phosphors

A series of LiSrBO3:Ce3+, Tb3+ phosphors have been prepared via a high-temperature solid-state reaction process. X-ray diffraction (XRD), scanning electric microscopy (SEM), photoluminescence (PL) spectra, and the diffuse reflection spectra were utilized to characterize the samples. The luminescence properties of LiSrBO3:Ce3+, Tb3+ phosphors have been discussed. The energy transfer process from Ce3+ to Tb3+ has been demonstrated to be a resonant type via the dipole–dipole interaction mechanism. The emissive colors of LiSrBO3:Ce3+, Tb3+ samples can be adjusted from blue to yellowish-green by the energy transfer of Ce3+ and Tb3+, respectively. The results suggest the present phosphors can be potentially applied as a candidate of green-light phosphor for UV-pumped W-LED.

Luminescence properties of M3(VO4)2:Eu3+(M = Ca, Sr, Ba) phosphors

In this paper, M3(VO4)2:Eu3+(M = Ca, Sr, Ba) phosphors have been synthesized by high-temperature solid-state method. The phase composition and luminescence properties of the synthesized phosphors were characterized by X-ray powder diffraction and photoluminescence (PL) spectra, respectively. The influences of fluxing agent and doped concentration of rare-earth ions on PL properties of the phosphor were investigated. The results indicated that the energy transfers between VO4 3− and Eu3+ in the host occurred mainly via a dipole–dipole interaction mechanism. The increase in cation radius (from Ca2+ to Ba2+) in the host causes the emission peak originated from 5D0 → 7F2 transition of Eu3+ shifting from 615 to 621 nm, as well as decreasing the fluorescence lifetimes of Eu3+ from 0.77 to 0.19 ms and changing the CIE chromaticity coordinates from the orange-red region to the white region. Moreover, the emission colors of Ba3−x (VO4)2:xEu3+ can be firstly adjusted from cyan region to white light region via controlling the concentration of Eu3+. Temperature-dependent luminescence spectra proved the good thermal stability of the as-prepared phosphor. This work shows the potential application of europium-doped samples in UV converted pc-WLEDs.

Tunable luminescence of Ce3+/Tb3+-codoped BaSrBO3F through energy transfer: Potential single-component blue-green-emitting phosphors

Single-component color-tunable BaSrBO3F: Ce3+, Tb3+ phosphors were firstly synthesized by the solid-state reactions. X-ray powder diffraction profiles, luminescent properties, CIE chromaticity variation, and energy transfer of the obtained phosphors were investigated in detail. Under near-ultraviolet irradiation, BaSrBO3F: Ce3+, Tb3+ not only exhibits a blue emission band attributed to the 4f05d1–4f1 transition of Ce3+, but also gives a series of sharp emission lines due to the 5D4–7FJ (J = 6, 5, 4, 3) transitions of Tb3+. By properly tuning the relative composition of Ce3+/Tb3+ through the principle of energy transfer, the varied emitted colors from blue through cyan (greenish-blue) and eventually to green were achieved. Moreover, the energy transfer from Ce3+ to Tb3+ ions in BSBF: Ce3+, Tb3+ phosphors was demonstrated via the dipole–dipole interaction mechanism, and the critical distance (RC) was calculated to be 18.51Å. These results suggest that our developed BaSrBO3F: Ce3+, Tb3+ phosphors have potential applications as single-component color-tunable phosphor-converted materials for near-ultraviolet light-emitting diodes.

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.

Preparation and luminescence properties of Sr7Zr(PO4)6:Dy3+ single-phase full-color phosphor

Novel single-phase white-light-emitting Sr7Zr(PO4)6:Dy3+ phosphors for light-emitting diode (LED) applications were synthesized by conventional solid-state reactions. The phases and luminescent properties of the obtained Sr7Zr(PO4)6:Dy3+ phosphors were characterized. The results show that the luminescence spectra excited by 350 nm consist of two characteristic blue and yellow bands, corresponding to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+, respectively. When x > 0.02, the concentration quenching effect occurred, and the critical transfer distance (Rc) was ~19.247 A. The energy transfer of the Dy3+ ions is the electric dipole–dipole interaction mechanism. The International Commission on Illumination chromaticity coordinates for Sr7−xZr(PO4)6:xDy3+ phosphors were located in the white region. The developed phosphor has great potential as a single-component white-light-emitting phosphor for UV-LEDs.

White light-emitting properties of NaGdF4nanotubes through Tb3+, Eu3+doping

White light-emitting NaGdF4 phosphor samples based on efficient energy transfer between Tb3+ and Eu3+ were synthesized via a conventional hydrothermal reaction process. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra and lifetime measurement were performed to characterize the samples. The energy transfer process between Tb3+ and Eu3+ was demonstrated to be a resonant type via a dipole–dipole interaction mechanism. Furthermore, for NaGdF4:Tb3+,Eu3+, white light emission can be realized in the single-phase NaGdF4 host by reasonably adjusting the relative doping concentrations of Tb3+ and Eu3+ under ultraviolet excitation. Due to their excellent PL properties and good CIE chromaticity coordinates, the as-prepared Tb3+, Eu3+ co-doped NaGdF4 nanocrystalline phosphors have potential application in field-emitting displays.

Luminescence properties and energy transfer of a novel bluish-green tunable NaBa4(BO3)3:Ce3+, Tb3+ phosphor

A series of single-phased emission tunable NaBa4(BO3)3:Ce3+, Tb3+ phosphors were synthesized by solid-state reaction. The crystal structure, photoluminescence properties, concentration quenching and energy transfer of NaBa4(BO3)3:Ce3+, Tb3+ were systematically investigated. The wavelength-tunable bluish-green light can be realized by coupling the emission bands centered at 425 and 543nm ascribed to the contribution from Ce3+ and Tb3+, respectively. The energy transfer from Ce3+ to Tb3+ in NaBa4(BO3)3 host was studied and demonstrated to be a resonant type via a dipole–dipole interaction mechanism. The energy transfer efficiency (Ce3+→Tb3+) obtained by decay curves was consistent with the result calculated by the emission intensity, which gradually increased from 0% to 84.5% by increasing the Tb3+ doping content from 0 to 0.45. The results indicate that the NaBa4(BO3)3:Ce3+, Tb3+ phosphors have potential applications as an ultraviolet-convertible phosphor due to its effective excitation in the ultraviolet rang.

Luminescence properties and energy transfer investigations of Sr3AlO4F:Ce3+, Tb3+ phosphor

Abstract Ce 3+ and Tb 3+ co-doped Sr 3 AlO 4 F phosphors were synthesized by the conventional high temperature solid-state method. X-ray diffraction (XRD) was used to characterize the phase structure. The luminescence spectra and decay lifetime curves of Ce 3+ have been measured to prove energy transfer (ET) from Ce 3+ to Tb 3+ . Under the excitation of near-ultraviolet light, Sr 3 AlO 4 F:Ce 3+ ,Tb 3+ phosphors exhibited blue emission corresponding to the f–d transition of Ce 3+ ions and green emission bands corresponding to the f–f transition of Tb 3+ ions, respectively. Effective energy transfer occurred from Ce 3+ to Tb 3+ in Sr 3 AlO 4 F host due to the observed spectra overlap between the emission spectrum of Ce 3+ ion and the excitation spectrum of Tb 3+ ion. The energy transfer efficiency from Ce 3+ ion to Tb 3+ ion was also calculated to be 51%. Furthermore, the energy transfer from Ce 3+ to Tb 3+ in Sr 3 AlO 4 F host was demonstrated to be resonant type via a dipole–dipole interaction mechanism. The present Ce 3+ and Tb 3+ co-doped Sr 3 AlO 4 F phosphor may have potential use in the technology of white light-emitting diodes.

Photoluminescence properties of Ce3+ and Ce3+–Eu2+ energy transfer in Ba1.3Ca0.7SiO4 phosphors

Ce3+ doped and Ce3+–Eu2+ co-doped Ba1.3Ca0.7SiO4 phosphors are synthesized by the conventional solid state reaction method. The Ce3+ activated sample exhibits five excitation bands peaking at 240, 257, 280, 327 and 362nm, which are attributed to the five energy levels due to 5d splitting, and has two intense blue emission bands peaking at 398 and 431nm by two sites. It is discussed that Ce3+ substituted coordinated number 10 and 12 of Ca sites in Ba1.3Ca0.7SiO4. It was found that the emission intensity of Ba1.3Ca0.7−xSiO4:xCe3+ phosphors increases clearly with increasing of Ce3+ concentration and reaches a maximum at 1mol%. The energy transfer between Ce3+ and Eu2+ ions is investigated with increasing Eu2+ ions at fixed Ce3+ concentration, the energy transfer is determined to be due to the dipole–dipole interaction mechanism.

Luminescence properties and energy transfer investigations of Sr3Gd(PO4)3:Ce3+,Tb3+ phosphors

Ce3+ and Tb3+ co-doped Sr3Gd(PO4)3 phosphors were synthesized by the solid-state method. The phase structure and luminescence properties of the phosphor samples were characterized by using powder X-ray diffraction (XRD), photoluminescence (PL) excitation and emission spectra, decay time, respectively. The obtained phosphor exhibits a strong excitation band between 200 and 400nm, matching well with the dominant emission band of a ultraviolet (UV) light-emitting-diode (LED) chip. Effective energy transfer occurred from Ce3+ to Tb3+ in Sr3Gd(PO4)3 hosts due to the spectra overlap between the PL emission spectrum of Ce3+ ion and the PL excitation spectrum of Tb3+ ion. The energy transfer from Ce3+ and Tb3+ in Sr3Gd(PO4)3 host was demonstrated to be resonant type via a dipole–dipole interaction mechanism with the energy transfer critical distance of 1.87nm. Furthermore, Sr3Gd(PO4)3:Ce3+,xTb3 can be systematically tuned to generate blue light to yellow–greenish light under UV excitation. It can serve as a potential color-tunable UV phosphor for white-light LED (w-LEDS) devices.

Color tuning of (K1−x,Nax)SrPO4:0.005Eu2+, yTb3+ blue-emitting phosphors via crystal field modulation and energy transfer

Two series of K1−xNaxSrPO4:0.005Eu2+ and K0.4Na0.6Sr0.995−yPO4:0.005Eu2+, yTb3+ phosphors are synthesized via a high-temperature solid-state reaction. Their emission color can be tuned from deep blue to blue–green by modulating the crystal field strength and energy transfer. Partial substitution of K+ with Na+ results in a contraction and distortion of the unit cell of the K1−xNaxSr0.995PO4:0.005Eu2+ host, tuning the emission from 426 to 498 nm. The red-shifted emission is attributed to an increased crystal field splitting for Eu2+ in a lowered symmetry crystal field. The tunable emission is further demonstrated in the cathodoluminescence spectra, which indicates that the luminescence distribution of the K1−xNaxSr0.995PO4:0.005Eu2+ phosphor is very homogenous. Additionally, utilizing the principle of energy transfer, the emission color can be further tuned by co-doping with Tb3+. The chromaticity coordinates for the co-doped phosphor, K0.4Na0.6Sr0.995−yPO4:0.005Eu2+, yTb3+, can be adjusted from (0.202, 0.406) for y = 0 to (0.232, 0.420) for y = 0.09. The energy transfer processes from the sensitizer (Eu2+) to the activator (Tb3+) are studied and demonstrated to have a resonance-type dipole–dipole interaction mechanism, with the critical distance of the energy transfer calculated to be 12.46 Å using a concentration quenching method.

Synthesis and luminescent properties of BaGd2O4:Dy3+, an novel scintillating phosphor

The BaGd2−xO4:xDy3+ (0 ≤ x ≤ 0.08) phosphors were synthesized at 1,300 °C in air by the solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction, photoluminescence excitation spectra, photoluminescence (PL) spectra, X-ray excited luminescence (XEL) spectra, and thermoluminescence (TL) spectra. It is found that the quenching concentration of Dy3+ ions in BaGd2O4 host is dependent on the selected excitation wavelength. The optimal PL intensity for the investigated BaGd2−xO4:xDy3+ phosphors is found to be x = 0.01, 0.02, and 0.04, upon excitation by 234, 277, and 350 nm ultraviolet light, respectively. The energy transfer among Dy3+ ions upon excitation by 350 nm is confirmed to be an electric dipole–dipole interaction mechanism based on the fitting of Huang’s rule. In addition, the intensive XEL from BaGd2O4:Dy3+ phosphor is observed by the naked eyes at room temperature, and TL properties of the investigated phosphors are analyzed and discussed. All the results imply that the investigated phosphors could be a promising scintillating phosphor.

Luminescence properties and energy transfer investigations of BaAl2B2O7:Ce3+,Tb3+ phosphors

Ce3+ and Tb3+ co-doped BaAl2B2O7 phosphors were synthesized by the solid-state method. X-ray diffraction (XRD) was used to characterize the phase structure. The photoluminescent properties of Ce3+ and Tb3+ co-doped BaAl2B2O7 phosphors were investigated by using the photoluminescence emission and excitation spectra. Under the excitation of near ultraviolet (n-UV) light, BaAl2B2O7:Ce3+,Tb3+ phosphors exhibited blue emission corresponding to the f–d transition of Ce3+ ions and green emission bands corresponding to the f–f transition of Tb3+ ions, respectively. Effective energy transfer occurred from Ce3+ to Tb3+ in BaAl2B2O7 host due to the observed spectra overlap between the emission spectrum of Ce3+ ion and the excitation spectrum of Tb3+ ion. The energy transfer efficiency from Ce3+ ion to Tb3+ ion was also calculated to be 71%. Furthermore, the concentration quenching and critical distance of BaAl2B2O7:Ce3+,Tb3+ phosphors were also discussed. The energy transfer from Ce3+ to Tb3+ in BaAl2B2O7 host was demonstrated to be resonant type via a dipole–dipole interaction mechanism with the energy transfer critical distance of 16.13Å.

Synthesis of BaSi2O2N2:Ce3+,Eu2+ Phosphors and Determination of their Luminescence Properties

BaSi2O2N2:Ce3+,Eu2+ phosphors were successfully synthesized via the solid‐state reaction method. Their luminescence properties were experimentally investigated and qualify them for further consideration as components in white light‐emitting diodes. In particular, BaSi2O2N2:Eu2+ phosphors have an efficient bluish–green emission band that peaks at 490 nm. Ce3+‐doped BaSi2O2N2 showed a bright emission band at 390 nm. A red shift tuning capability of emission bands was achieved by increasing the Eu2+ or Ce3+ contents. Measurements of the intensity of emission spectra suggested a concentration quenching effect for both Eu2+ and Ce3+. Analysis of the experimental results suggests that the enhancement of emission intensity in the produced codoped BaSi2O2N2:Ce3+,Eu2+ phosphors is due to resonance‐type energy transfer from Ce3+ to Eu2+ ions, which is predominantly governed by dipole–dipole interaction mechanism. The efficiency of energy transfer was calculated and the critical distance of energy transfer between Ce3+ and Eu2+ was determined as ∼25 Å.

Novel Approach for the Separation of Shape-Constrained Isomers with Alternating Copolymer-Grafted Silica in Reversed-Phase Liquid Chromatography

This paper describes a novel packing material for high selective reversed-phase high-performance liquid chromatography (RP-HPLC). The organic phase on silica is chemically designed in a way that the weak interaction sites are integrated with high orientation along the polymer main chain and high selectivity can be realized by multiple interactions with solutes. For the above purpose, we synthesized poly(octadecyl acrylate-alt-N-octadecylmaleimide)-grafted silica (Sil-poly(ODA-alt-OMI)) stationary phase. The alternating copolymerization was carried out from 3-marcaptopropyltrimethoxysilane (MPS)-modified silica via surface-initiated radical-chain transfer reaction. Elemental analysis, diffuse reflectance infrared Fourier transform (DRIFT),(1)H NMR, solid-state (13)C cross polarization magic angle spinning (CP/MAS) NMR, and suspended-state (1)H NMR were used to characterize the new organic phase. Aspects of shape selectivity was evaluated with Standard Reference Material (SRM 869b), Column Selectivity Test Mixture for Liquid Chromatography. Enhanced molecular shape selectivity was observed, that lead to the separation of SRM 1647e (16 polycyclic aromatic hydrocarbons, PAHs) in an isocratic elution. The effectiveness of this phase was also demonstrated by the separation of several beta-carotene and tocopherol isomers. The complete baseline separation of the tocopherol isomers was achieved using the Sil-poly(ODA-alt-OMI) phase. Chromatographic study revealed that Sil-poly(ODA-alt-OMI) has extremely high separation ability compared to monomeric and polymeric C(18) columns. Higher shape selectivity of the new RP material can be explained by a pi-pi and dipole-dipole interaction mechanism.