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Eu3+ co-doped Sr3Gd(PO4)3:Dy3+ phosphors: luminescence properties and color-tunable white-light emission for NUV-WLEDs
摘要： A series of Dy3+ and Eu3+ co-doped Sr3Gd(PO4)3 phosphors were synthesized by a high-temperature solid-state method. The crystal structure, optical band gap energy, luminescence properties, concentration quenching, energy transfer process and thermal stability were investigated. All the phosphors are pure eulytite-type Sr3Gd(PO4)3 in structure. Under different wavelengths’ excitation, the Sr3Gd(PO4)3:Dy3+, Eu3+ phosphors exhibit different emission intensities for Eu3+ and Dy3+. The color and correlated color temperature (CCT) can be tuned from cool white to warm white by adjusting excitation wavelengths and the doping concentration of Eu3+. Under the 351-nm excitation, the optimal Sr3Gd(PO4)3:0.03Dy3+, 0.085Eu3+ phosphor displays a warm white emission with CIE coordinate of (0.3987, 0.3613), CCT of 3409?K, internal quantum efficiency of 44.8% and activation energy of 0.1883?eV. These results suggest that single-phased white-emitting phosphors Sr3Gd(PO4)3:Dy3+, Eu3+ can be used in the near-ultraviolet light-emitting diodes.
关键词： Optical materials and properties,Luminescence,Energy transfer,Phosphors
更新于2025-09-19 17:13:59
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Magnetic nanocomposite with fluorescence enhancement effect based on amino acid coated-Fe3O4 functionalized with quantum dots
摘要： Multifunctional nanoparticles with magnetic and fluorescent properties have high potential in different areas. A very attractive feature of these nanoparticles is that they can be controlled by an external magnetic field and monitored by fluorescence. For biological applications, the magnetic nanoparticles (MNPs) must be biocompatible and dispersible in water, which requires surface modification. This paper describes the synthesis of Fe3O4 MNPs modified with three amino acids (AA): L-Tryptophan (Trp), L-Phenylalanine (Phe) and L-Tyrosine (Tyr) by a co-precipitation method in a one-step reaction without the use of a spacer agent. The potential of AA as a robust anchor was assessed by binding mercaptopropionic acid (MPA)-coated CdTe quantum dots (QDs) to Fe3O4@AA nanoparticles, leading to a hybrid nanostructure with excellent fluorescent and magnetic properties. In particular, the Fe3O4@Trp@QDs nanocomposite showed a fluorescence enhancement effect due to F?rster resonance energy transfer (FRET) from Trp as energy donor to CdTe@QDs as acceptor. The nanomaterials were characterized by high-resolution transmission electron microscopy (TEM), X-Ray diffraction (XRD), zeta potential, thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), Fourier-transform infrared (FT-IR), UV-visible, and fluorescence spectroscopy. The nanocomposite also presents high stability and good dispersibility in water. This nanomaterial may be potentially used in different biomedical and environmental applications.
关键词： amino acid as anchor,fluorescent enhancement,energy transfer,stability and dispersibility in water,Magnetic and fluorescent nanocomposite,Fe3O4-amino acid-CdTe QD
更新于2025-09-19 17:13:59
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Photo-physical studies of ultrasmall upconversion nanoparticles embedded organometallic complexes: Probing a dual mode optical sensor for hydrogen peroxide
摘要： Here, we report an upconversion nanoparticles (UCNPs) embedded organomettalic complex for detection of hydrogen peroxide (H2O2). The structural as well as the optical properties of the hybrid nanoparticles (HNPs) have been studies to confirm the interaction as well as energy transfer mechanism. The structural characterization confirm the weak interacting force between the UCNPs and the organic complex in HNPs. The optical studies reveal that, HNPs show characteristic optical behaviour of both the phases i.e. it gives an intense downconverted red emission under UV excitation, due to the presence of organic part (Eu3t ion) as well as an efficient blue upconverted emission from inorganic part (Tm3t ion) under NIR excitation. The energy transfer between the inorganic (Tm3t ion) and the organic (Eu3t ion) material has been observed, which confirms the effective attachment of both the phases in HNPs. The upconversion and downconversion emission properties, have been have successfully utilized for dual mode H2O2 detection.
关键词： Hydrogen peroxide sensor,Lanthanides,Hybrid nanoparticles,Energy transfer
更新于2025-09-19 17:13:59
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Highly efficient near-UV-excitable Ca2YHf2Al3O12:Ce3+,Tb3+ green-emitting garnet phosphors with potential application in high color rendering warm-white LEDs
摘要： Inorganic phosphors with broadband near-ultraviolet (near-UV) excitation and efficient visible emissions are highly important for fabricating high-performance near-UV-pumped white light-emitting diodes (LEDs). Herein, we reported on novel efficient near-UV-excitable Ce3+/Tb3+ ions co-activated Ca2YHf2Al3O12 (CYHA) green-emitting garnet phosphors, which were successfully prepared through a high-temperature solid-state reaction process. X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental mapping, photoluminescence, CIE color coordinates, internal and external quantum efficiency, and temperature-dependent emission spectra were used to characterize the samples. Interestingly, due to the efficient energy transfer from Ce3+ to Tb3+ ions in CYHA, the CYHA:Ce3+,Tb3+ samples presented a wide excitation band in the 370-470 nm region peaking around 408 nm owing to the 4f-5d transition of Ce3+ ions, and under 408 nm excitation they showed intense characteristic sharp green emissions around 543 nm corresponding to the 5D4→7F0-6 transitions of Tb3+ ions. The energy transfer mechanism from Ce3+ to Tb3+ ions was ascribed to the quadruple-quadruple interaction, and the energy transfer efficiency reached as high as 93.2%. Notably, the composition-optimized CYHA:0.03Ce3+,0.6Tb3+ sample exhibited high internal quantum efficiency (IQE) of 78.5% and external quantum efficiency (EQE) of 56%, which were much higher than those of the Tb3+ singly-activated CYHA:0.6Tb3+ sample (IQE = 8%, EQE = 2.2%). Finally, a prototype white LED device was made by combining a 400 nm near-UV-emitting LED chip with the phosphor blend of the as-prepared CYHA:0.03Ce3+,0.6Tb3+ green phosphors, commercial BaMgAl10O17:Eu2+ blue phosphors and commercial CaAlSiN3:Eu2+ red phosphors, which emitted bright warm-white light with good CIE chromaticity coordinates of (0.391, 0.356), low correlated color temperature of 3528 K and high color rendering index of 92.3 under 120 mA driven current. This work opens up new opportunities for the development of efficient color converters toward near-UV-pumped warm-white LEDs with high color rendering index.
关键词： white LEDs,green-emitting garnet phosphors,Ce3+/Tb3+ co-activated,near-UV-excitable,energy transfer
更新于2025-09-19 17:13:59
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Nonradiative Energy Transfer in a??Colloidal Quantum Dot Nanoclustera??Dyea?? Hybrid Nanostructures: Computer Experiment
摘要： A computer model of nonradiative electronic excitation energy transfer from nanoclusters of colloidal quantum dots of cadmium selenide to the meso-tetra(3-pyridyl)porphyrin molecule in hybrid nanostructures nanocluster–dye has been constructed and analyzed. The model uses the experimental luminescence and absorption spectra of quantum dots and the dye, takes into account heterogeneity of the properties of quantum dots in nanoclusters and the different location of the dye in the hybrid structure. It has been shown that, in the ideal case, due to such energy transfer, the intensity of the luminescent signal of the dye can be increased by five orders of magnitude. However, this value is significantly reduced due to nonluminescent particles, the presence of a protective ligand shell, a large size distribution of the particles, and the non-optimal geometric structure of the hybrid system.
关键词： porphyrin dye,colloidal quantum dots,F?rster resonance energy transfer,hybrid systems,cadmium selenide,computer simulation
更新于2025-09-19 17:13:59
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A Projective Method for the Calculation of Excited State Electronic Coupling: Isolating Charge Transfer/Recombination Processes in Organic Photovoltaics
摘要： Electronic coupling between excited states is a vital parameter required in order to describe the ultrafast energy and charge transfer processes that occur in photo-responsive organic materials. In such systems short-range Coulombic, exchange, overlap, and configuration interaction effects must all be accounted for. Although a number of methods are available, the evaluation of the coupling between arbitrary excited states remains challenging. In this contribution, a flexible and scalable method for the calculation of short-range electronic coupling between excited states is developed. Excitation- or charge-localized states are projected onto the adiabatic states of a dimeric molecular system using an efficient wavefunction overlap algorithm. In addition to correctly treating Coulombic, exchange and overlap interactions, the inclusion of multistate interactions is inherent in the procedure. The method is then used to disentangle excitation energy transfer, charge-transfer, and charge recombination processes in donor acceptor systems relevant to organic photovoltaics, with a view towards the development of material design principles. Calculations were performed within single-excitation frameworks, but the scheme has the potential to be extended to multireference/higher-order excitation quantum-chemical methods.
关键词： excitation energy transfer,excited states,electronic coupling,charge transfer,organic photovoltaics
更新于2025-09-16 10:30:52
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Radiology, Lasers, Nanoparticles and Prosthetics || 11. Neutron radiotherapy
摘要： Neutrons like protons are hadrons, however neutrons are uncharged. They are more difficult to produce, and because they are neutral, accelerators and magnets cannot be used for tuning their energy or steering the beam. Neutron irradiation requires a neutron source and a radiological shielding environment that are very different to those for charged particles. Among the various external radiation treatments of cancer, neutron radiation therapy is presently not often prescribed.
关键词： fast neutrons,RBE,Boron Neutron Capture Therapy,BNCT,linear energy transfer,Neutron radiotherapy,LET,relative biological effectiveness
更新于2025-09-16 10:30:52
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Synthesis, energy transfer mechanism, and tunable emissions of novel Na3La(VO4)2:Re3+ (Re3+ = Dy3+, Eu3+, and Sm3+) vanadate phosphors for near-UV-excited white LEDs
摘要： In this study, novel Eu3+-, Dy3+-, and Sm3+-activated Na3La(VO4)2 phosphors were synthesized using a solid state reaction method. X-ray diffraction analysis results indicated that the Na3La(VO4)2 phosphors had an orthorhombic crystal structure with the Pbc21 space group. There were two different La(1)O8 and La(2)O8 polyhedra with high asymmetry in the crystal structure. Scanning electron microscopy revealed that the product had a sheet morphology with an irregular particle size. Further, the luminescence properties, including the excitation and emission spectra, and luminescence decay curve, were investigated using a fluorescence spectrometer. The results showed that the Na3La(VO4)2 compound was an excellent host for activating the luminescence of Eu3+ (614 nm), Dy3+ (575 nm), and Sm3+ (647 nm) ions. Further, Dy3+/Eu3+ co-doped Na3La(VO4)2 phosphors were exploited, and the energy transfer from Dy3+ to Eu3+ was demonstrated in detail by the photoluminescence excitation, photoluminescence spectra, and luminescent decay curves. The results showed that the energy transfer efficiency from Dy3+ to Eu3+ was highly efficient, and the energy transfer mechanism was dipole–dipole interactions. Finally, tunable emissions from the yellow region of CIE (0.3925, 0.4243) to the red region of CIE (0.6345, 0.3354) could be realized by rationally controlling the Dy3+/Eu3+ concentration ratio. These phosphors may be promising materials for the development of solid-state lighting and display systems.
关键词： Vanadate phosphor,White LED,Energy transfer,Lighting and display,Near ultraviolet excitation,Tunable emissions
更新于2025-09-16 10:30:52
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Photophysics and electroluminescence of red quantum dots diluted in a thermally activated delayed fluorescence host
摘要： A feasible, universal, and low-cost strategy for quantum dot light-emitting devices (QLEDs) was provided to significantly enhance the electroluminescent performances. The emissive layer consists of organic host materials and quantum dots (QDs), and then the efficient energy transfer process remarkably promotes the device performances. It is confirmed that a highly efficient QLED can be realized by a host–guest system without common hole transport layers. The red device based on the thermally activated delayed fluorescence host and QD guest achieved a peak external quantum efficiency of 7.4%. Further, by simply modifying PEDOT:PSS with poly(4-styrenesulfonic acid), the work-function can be easily elevated, accompanied with the boosted external quantum efficiency to 11.9%. It is believed that such performances originate simultaneously from reduced interfacial fluorescence quenching, elevated work-function and efficient F?rster resonance energy transfer in the host–guest system.
关键词： external quantum efficiency,electroluminescent performances,quantum dot light-emitting devices,QLEDs,thermally activated delayed fluorescence,F?rster resonance energy transfer,host–guest system
更新于2025-09-16 10:30:52
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Preparation of CdTe superparticles for white light-emitting diodes without F?rster resonance energy transfer
摘要： Due to many unique and excellent optical properties, quantum dots (QDs) have been seen as one of the most promising color conversion materials in light-emitting diodes (LEDs). However, the F¨orster resonance energy transfer (FRET) among di?erent colored QDs always causes a signi?cant red-shift of the ?uorescence emission, impeding the fabrication of LEDs with predicted photoluminescence (PL) emission spectra. In this work, we take advantage of CdTe superparticles (SPs), which are assembled by CdTe QDs, as the color conversion materials for the fabrication of WLEDs. Because of their submicron size, the distance between QDs with di?erent emissions can be large enough to avoid the FRET process. More importantly, this method provides us with an opportunity to precisely design and regulate the PL emission spectra of LEDs. By easily overlapping the individual PL spectra of CdTe SPs with di?erent emissions, the certain ratio of their usage for fabricating LEDs with desired PL emission spectra is identi?ed. According to this idea, a WLED with a color rendering index (CRI) of 81, luminous e?cacy of 27 lm W(cid:1)1, and color coordinate at (0.33, 0.34) with the color temperature of 5742 K is achieved.
关键词： F¨orster resonance energy transfer,white light-emitting diodes,quantum dots,color conversion materials,CdTe superparticles
更新于2025-09-16 10:30:52