Electric Dipole Transition Research Articles

A novel Dy[formula omitted] doped Zn2V2O7 nanoparticles: Photoluminescence and electrochemical studies for display and supercapacitor applications

A novel series of Dy3+-doped Zn2V2O7 (ZV) nanoparticles (NPs) spanning concentrations from 1 to 9 mol% was synthesized via Menthaspicata leaves extract-mediated solution combustion method. Upon Dy3+ doping, the diffraction pattern matches well with the monoclinic crystal structure with the C2/c(2/m) space group of ZV host matrix. Morphological analysis revealed a transition from irregularly shaped NPs to hexagonal shaped NPs with varying dopant concentration. The crystallite size estimated via Scherrer’s method correlated closely with transmission electron microscopy analysis. Determination of the optical band gap from Tauc’s plot using UV–Visible absorption indicated a tuning from 3.045 to 2.986 eV with increasing dopant concentration. Under 266 nm excitation, the peak at 489 and 586 nm corresponds to 4F9/2→6H15/2 (Magnetic dipole) and 4F9/2→6H13/2 (electric dipole) transition of Dy3+ ion. The dominance of the blue emission (MD) over the yellow emission (ED) of Dy3+ indicates the symmetric nature of the host. The sample exhibits 7 mol % as the optimal doping content. CIE coordinates distinctly falls within the blue region with increasing dopant concentration, with an average color-coordinated temperature of 19902 K, indicative of a cooler appearance. Moreover, cyclic voltammetry analysis provided valuable insights into redox reactions, electrode kinetics, and overall electrochemical behavior, while Electrochemical Impedance Spectroscopy (EIS) offered information on ion transport kinetics. Galvanostatic Charge–Discharge (GCD) analysis revealed super capacitance values ranging from 85.79 F/g to 143.92 F/g at 10 mV/s scan rate, with increasing dopant concentration, highlighting the material’s potential for applications in energy storage and display technology.

Interferometric Near-field Fano Spectroscopy of Single Halide Perovskite Nanoparticles.

Semiconducting halide perovskite nanoparticles support Mie-type resonances that confine light on the nanoscale in localized modes with well-defined spatial field profiles yet unknown near-field dynamics. We introduce an interferometric scattering-type near-field microscopy technique to probe the local electric field dynamics at the surface of a single MAPbI3 nanoparticle. The amplitude and phase of the coherent light scattering from such modes are probed in a broad spectral range and with high spatial resolution. In the spectral domain, we uncover a Fano resonance with a 2π phase jump. In the near-field dynamics, this Fano resonance gives rise to a destructive interference dip after a few femtoseconds. Mie theory suggests that the interference between electric quadrupole and magnetic dipole modes of the particle, with spectra affected by resonant interband absorption of MAPbI3, lies at the origin of this effect. Our results open up a new approach for probing local near-field dynamics of single nanoparticles.

Radiative decay rates for magnetic dipole (M1) and electric quadrupole (E2) transitions between low-lying levels within the 4f3 ground configuration of Pr III

Abstract A new set of theoretical radiative decay rates characterizing forbidden transitions in doubly charged praseodymium (Pr III) is reported in the present paper. More precisely, transition probabilities were computed for all magnetic dipole (M1) and electric quadrupole (E2) lines involving the lowest energy levels of the 4f$^3$ ground configuration located below 20000 cm$^{-1}$ since the levels above this limit are preferentially depopulated by allowed electric dipole (E1) transitions. The calculations were carried out using different computational strategies based firstly on the pseudo-relativistic Hartree-Fock (HFR) method and secondly on the fully relativistic Multiconfiguration Dirac-Hartree-Fock (MCDHF) method. The comparison between the results obtained by these independent approaches makes it possible to estimate their reliability. Comparisons with the few previously published data were also made. In addition, some astrophysical implications were deduced from the new atomic parameters computed in the present work, such as the possible presence of [Pr III] lines in the infrared spectra recorded by the {\it James Webb Space Telescope} ($JWST$) in the context of the investigation of kilonovae in their nebular phase, i.e. several days after neutron star mergers.

Exploring the influence of emissive centers in mono and dinuclear europium(III) complexes for advance lighting applications: Synthesis, characterization and computational modelling

The combination of 4,4,4-trifluoro-1-phenyl-1,3-butanedione (TFPB) and pyrazine (pyz) with Eu3+ ions results in the formation of two distinct types of complexes, characterized by general formulae [Eu(TFPB)3(L)2] (here, L is either H2O or pyrazine) and [(Eu(TFPB)3)2pyz]. The impact of surrounding environment on the photophysical properties of synthesized complexes was thoroughly examined. Photoluminescence (PL) analysis revealed the dominance of electric dipole (ED) transition (5D0→7F2) in these complexes. Theoretical calculations via Judd-Ofelt analysis were also performed. These complexes exhibit visible luminescence in both solid and solvated forms. Notably, the luminescence intensity of prepared dinuclear complex is found to be manifolds greater than its mononuclear analogues, affirming the contribution of both metal centers towards emission intensity. Furthermore, the absence of ligand centered emission in prepared complexes suggests the effective energy transfer from coordinated moieties to metal center. CIE color coordinates of prepared Eu(III) complexes, in both solid and solution media, exhibited intense red emission. DFT calculations were conducted to elucidate the distribution of electronic density in synthesized complexes. Additionally, a comprehensive analysis of these complexes, including IR, UV, NMR, thermogravimetry and cyclic voltammetry was conducted.

Enhancement of the Spin-Orbit Forbidden Transition Intensity in Nitric Oxide.

The magnetic field-induced modification of the electric-dipole forbidden transitions between the lowest rotational states of the 2Π1/2 and the 2Π3/2 substates of a 2Π diatomic radical is probed by model calculations for the ground electronic states of NO, OH and CH. Magnetic fields in the range of 0-12 T and more were considered and the intensities of the respective allowed rotational transitions for the given systems were calculated for comparison. In particular, NO shows enhanced field dependence of calculated intensities.

Inversion of circularly polarized luminescence by electric current flow during transition.

The development of chiral compounds exhibiting circularly polarized luminescence (CPL) has advanced remarkably in recent years. Designing CPL-active compounds requires an understanding of the electric transition dipole moment (μ) and the magnetic transition dipole moment (m) in the excited state. However, while the direction and magnitude of μ can, to some extent, be visually inferred from chemical structures, m remains elusive, posing challenges for direct predictions based on structural information. This study utilized binaphthol, a prominent chiral scaffold, and achieved CPL-sign inversion by strategically varying the substitution positions of phenylethynyl (PE) groups on the binaphthyl backbone, while maintaining consistent axial chirality. Theoretical investigation revealed that the substitution position of PE groups significantly affects the orientation of m in the excited state, leading to CPL-sign inversion. Furthermore, we propose that this CPL-sign inversion results from a reversal in the rotation of instantaneous current flow during the S1 → S0 transition, which in turn alters the orientation of m. The current flow can be predicted from the chemical structure, allowing anticipation of the properties of m and, consequently, the characteristics of CPL. This insight provides a new perspective in designing CPL-active compounds, particularly for C2-symmetric molecules where the S1 → S0 transition predominantly involves LUMO → HOMO transitions. If μ represents the directionality of electron movement during transitions, i.e., the "difference" in electron locations before and after transitions, then m could be represented as the "path" of electron movement based on the current flow during the transition.

Violet light excitable BaLiZn3(PO4)3: Eu orange-red-emitting phosphor towards white LED application

White light-emitting diode (WLED) has been widely used as solid-state lighting in recent years, with the advantages of energy saving, high luminous efficiency, and safety. Red phosphors are crucial to the color rendering index of WLED, and Eu3+-activated red phosphors can significantly improve the chromaticity performance of WLED. In this work, a series of new orange-red emitting BaLiZn3(PO4)3: Eu3+ phosphors were synthesized through high-temperature solid-state reaction method. The phase composition, crystal structure, morphology and photoluminescence properties of BaLiZn3(PO4)3: Eu3+ samples were investigated. The phosphors can be effectively excited by the violet light at 394 nm and emit orange-red lights corresponding to the electric dipole transition (5D0→7F1) at 594 nm. The optimal doping concentration of Eu3+ ions was about 5 mol%. The concentration quenching was caused by the electric dipole-dipole interaction between Eu3+ ions. Temperature-dependent PL spectra indicate that BaLiZn3(PO4)3: Eu3+ has excellent emission and color stability at high temperatures. The color coordinates were calculated and fall in the orange-red luminescent area. The color purity is about 98.3 %, and the correlated color temperature is 1710K. These results indicate that the new orange-red phosphor BaLiZn3(PO4)3: Eu3+ has potential application prospects in WLED.

Hard-scattering approach to strongly hindered electric dipole transitions between heavy quarkonia

The conventional wisdom in dealing with electromagnetic transition between heavy quarkonia is the multipole expansion, when the emitted photon has a typical energy of order quarkonium binding energy. Nevertheless, in the case when the energy carried by the photon is of order typical heavy quark momentum, the multipole expansion doctrine is expected to break down. In this work, we apply the “hard-scattering” approach originally developed to tackle the strongly hindered magnetic dipole (M1) transition [Y. Jia , ] to the strongly hindered electric dipole (E1) transition between heavy quarkonia. We derive the factorization formula for the strongly hindered E1 transition rates at the lowest order in velocity and αs in the context of the nonrelativistic QCD, and conduct a detailed numerical comparison with the standard predictions for various bottomonia and charmonia E1 transition processes. Published by the American Physical Society 2024

A novel red-emitting InScW3O12:Eu3+ phosphor with anti-thermal-quenching performance for high-power WLED applications

A series of red-emitting InScW3O12:Eu3+ (ISWO:Eu3+) phosphors with anti-thermal-quenching performance were successfully synthesized by conventional solid-state reaction. The phase structure and luminescent properties of ISWO:Eu3+ were systematically studied. The photoluminescence excitation (PLE) spectrum showed that ISWO:Eu3+ phosphor can be effectively matched with commercial ultraviolet (UV), violet and blue light chips. The main emission peak of the phosphor was located at 613 nm, which was attributed to the electric dipole transition 5D0 → 7F2. Under the optimal excitation, the prepared ISWO:0.08Eu3+ phosphor showed excellent anti-thermal-quenching performance, its photoluminescence (PL) intensity at 180 °C reached 157.4 % of initial intensity at room temperature. At 465 nm excitation, it also exhibited the anti-thermal-quenching property and the PL intensity remained 115.1 % at 150 °C of that at room temperature. In situ XRD analysis revealed that the lattice contraction resulting in an increase in structural rigidity as the temperature rising, which caused the change of Eu3+ local environment and improved the PL intensity. Finally, a series of warm white LED devices under varying power density conditions with stable output were prepared using the red ISWO:0.08Eu3+ phosphor, indicating that the ISWO:Eu3+ phosphor with excellent anti-thermal-quenching performance has potential application prospects in high-power white light-emitting diodes (WLEDs).

Eco-friendly synthesis of Nd³⁺-doped Eu₂O₃ nanoparticles for enhanced dye-sensitized solar cells utilizing oxalis Corniculata leaf extract

An environmentally friendly synthesis of Nd³⁺-doped Eu₂O₃ nanoparticles (NPs) was developed using Oxalis Corniculata leaf (OCL) extract to enhance the performance of dye-sensitized solar cells (DSSCs). The as-synthesized NPs were annealed at 600 °C to improve their crystallinity. X-ray diffraction and field-emission scanning electron microscopy revealed high crystallinity and a sub-100 nm spherical morphology. Annealing reduced the NP size from ∼85 nm to ∼45 nm and decreased the bandgap from 4.97 eV to 4.62 eV, enhancing low-energy photon absorption. Fourier-transform infrared spectroscopy showed changes in the chemical bonding environment, with a higher presence of dangling bonds in the as-prepared NPs compared to the 600 °C-annealed NPs, likely due to the OCL extract. Photoluminescence spectra confirmed strong red emission peaks at 580 nm and 612 nm, with a slight reduction in the full width at half maximum of the electric dipole transition after annealing. Integrating these NPs into TiO₂ matrices in DSSCs improved power conversion efficiency to 8.58%, outperforming both as-prepared NPs (6.88%) and bare TiO₂ cells (5.05%). This green synthesis approach offers a sustainable pathway for slightly enhancing performance of photovoltaic devices, with additional potential for UV-shielding applications when incorporated into PVA films.

Mie metasurfaces for enhancing photon outcoupling from single embedded quantum emitters

Abstract Solid-state quantum emitters (QE) can produce single photons required for quantum information processing. However, their emission properties often exhibit poor directivity and polarisation definition resulting in considerable loss of generated photons. Here we propose and numerically evaluate Mie metasurface designs for outcoupling photons from an embedded and randomly-positioned QE. These Mie metasurface designs can provide over one order of magnitude enhancement in photon outcoupling with only several percent of photons being lost. Importantly, the Mie metasurfaces provide the enhancement in photon outcoupling without the need for strict QE position alignment and without affecting the intrinsic QE emission rate (Purcell enhancement). Electric dipole modes are key for achieving the enhancement and they offer a path for selective outcoupling for photons emitted with specific polarisation, including the out-of-plane polarisation. Mie metasurfaces can provide an efficient, polarisation-selective and scalable platform for QEs.

Spectral characteristics and luminescence applications of Eu3+-activated fluorosilicate Na2MgGd2[SiO3]4F2

This work reports the luminescence spectra and application of novel Eu3+-doped Na2MgGd2[SiO3]4F2 phosphor. The X-ray powder diffraction confirmed the pure phase formation of the samples with the monoclinic space group P21/c (No:14). The phosphors demonstrated efficient red emission at 613 nm from the electric dipole transitions 5D0→7F2. The optimal doping concentration was found to be approximately 25 mol%. Na2MgGd2[SiO3]4F2:0.25Eu3+ exhibits a high quantum efficiency (QE) of 57 % with excellent thermal stability and pure chromaticity. Red- and the white light-emitting diode devices were packaged using InGaN chips and Na2MgGd2[SiO3]4F2:0.25Eu3+. The fabricated WLED has CIE coordinates of (x = 0.33, y = 0.34), which are very close to the white point in the National Television System Committee (x = 0.33, y = 0.33). The color rendering index (CRI, Ra) and correlated color temperature (CCT) of the WLED are 91 and 4400 K, respectively. The results show that as a red luminescent phosphor, it is a potential candidate for the preparation of near-UV/blue InGaN-based WLEDs.

Synthesis, Structural Features and Fluorescent Properties of Terbium Acylpyrazolone Complexes

AbstractThree 8‐coordinated terbium acylpyrazolone complexes [Tb(DMBPMP)3(H2O)2] (Tb1), [Tb(DMBMCPMP)3(H2O)2] (Tb2), and [Tb(DMBPTMP)3(H2O)2] (Tb3) with a distorted bicapped trigonal prismatic structure were synthesized (where, 3,5‐dimethylbenzoyl 1‐(phenyl = DMBPMP/m‐chlorophenyl = DMBMCPMP/p‐tolyl = DMBPTMP) 3‐methyl 5‐pyrazolone). The structures of the complexes were comprehensively analyzed using mass ESI, FTIR, UV–vis, powder XRD, and TG‐DTA methods. Single‐crystal analysis of Tb3·H2O confirmed an eight‐coordinate structure (TbO8) with a distorted bicapped trigonal prismatic geometry. In the on‐state emission spectrum, the 5D4 → 7F5 transition exhibits hypersensitivity in the green region of the visible spectrum (∼540–560 nm). The differences between electric dipole (ED) and magnetic dipole (MD) transitions indicate a small degree of asymmetry. The examination of solid‐state emission spectra included the assessment of intensity, G/B ratio, green color purity, and the antenna effect energy diagram.

The luminescent behaviors and J-O theory analysis of red phosphor Ca1-xGeO3:xEu3+

The luminescent material Eu3+-doped CaGeO3 has been synthesized using a high-temperature solid-state reaction technique. The crystal structure was analyzed using X-ray diffraction (XRD). The results showed that the samples belonged to the triclinic crystal system with the space group P1̅. The luminescent properties including photoluminescence excitation (PLE), Photoluminescence emission (PL) spectra, and lifetime, thermal stability, and diffuse reflectance spectroscopy (DRS) have been investigated. Under near-ultraviolet excitation at 390 nm, the phosphor emits red light with the highest intensity around 611 nm, which is dominated by the 5D0→7F2 electric dipole transitions. It indicates that Eu3+ is in the inversion center of the crystal. The concentration quenching occurs at about 6 % doping from the concentration-dependent luminescence behavior. The energy transfer mechanism was analyzed to be mainly the energy transfer between neighboring ions. The thermal stability was 82.16 % at 423 K. The chromaticity coordinates are in the red area and the color purity approaches 99 %. Furthermore, the J-O theoretical results are used to confirm the experimental result. It suggests that Ca1-xGeO3:xEu3+ is an effective red luminescent material for illumination and backlight display applications.

Enhancing Circularly Polarized Luminescence Dissymmetry Factor of Chiral Cylindrical Molecules to -0.56 through Intramolecular Short-Range Charge Transfer.

High-performance circularly polarized luminescent (CPL) materials have received wide attention recently by virtue of broad application in circularly polarized light-emitting diodes, 3D display, and encryption. Reaching both high luminescence efficiency and strong luminescence dissymmetry factor (glum) is still a challenging goal that requires continuous efforts. Herein, we performed a systematic theoretical investigation on the chiroptical properties of helical cylindrical molecules (-)-[4]cyclo-2,6-anthracene [(-)-[4]CA2,6] and (P)-[4]cyclo-2,8-chrysenylene [(P)-[4]CC2,8], and found that the unique and symmetric cylindrical structure could make the transition dipole moment components offset along the cylindrical surface but concentrated along the vertical central axis. This structural superiority contributes the collinear electric and magnetic transition dipole moment vectors and thus the large glum. Based on the results of decomposed transition dipole moment vectors to individual atoms, an effective strategy to enhance the glum through introducing intramolecular short-range charge transfer by embedding B,N atoms is proposed. The decreased electric transition dipole moment and well-kept magnetic transition dipole moment enable the glum of B,N-embedded designed molecules (-)-[4]CA2,6-4BN and (P)-[4]CC2,8-4BN up to -0.31 and -0.56, respectively. This molecular-insight investigation deepens the understanding of the structure-property relationship and provides efficient guidance for improving glum of CPL materials.

Blue to Red Emission Tunable Bi3+ co-doped YPO4:Eu3+: Host Emission and Phase Change.

Bi3+(0, 1, 3, 5, 7, 10, 12 and 15 at.%) co-doped YPO4:Eu3+ have been hydrothermally synthesized. Bi3+ (x ≥ 1 at.%) co-doping in YPO4:Eu3+ renders mixed crystalline phase of tetragonal to hexagonal. Pure tetragonal phase of Bi3+ co-doped YPO4:Eu3+ could be achieved upon annealing at 900°C. The luminescence intensity is improved significantly upon annealing at 900°C. This is due to the reduction of quenching pathways such as water molecules, dangling bonds, etc. The probability of magnetic dipole and electric dipole transitions is observed to be altered. As-prepared samples show near blue emission, while 900°C annealed samples exhibit red emission, which could be a potential candidate for display, sensing and biological labelling, etc.

Unveiling the Versatility of Coumarin-Integrated with Phenanthroline/Thiabendazole-Based EuIII Complexes for Smart LEDs, Vapoluminescence, and Bioimaging Applications.

Narrow band red-emitting phosphors based on organo-Eu(III) complexes prove their energetic features with surprising performance in smart red/white LEDs, sensing, and biological fields. In this report, a series of unique Eu(III) complexes have been synthesized with coumarin integrated with a class of phenanthroline(Phen)/thiabendazole(TBZ) based ancillary ligands and dibenzoyl methane (DBM)/2-theonyl trifluoroacetone (TTA) as an anionic ligand. The computational study reveals that the TBZ/Phen-based neutral ligands are superior energy harvesters to those other reported analogue neutral ligands. All the Eu-complexes demonstrated outstanding red emission due to electric dipole (ED) transition (5D0 → 7F2) in solid, solution, and thin film with high quantum yield (QY). Theoretical analysis (TD-DFT) and experimental findings describe that the energy transfer (ET) from the ligand's triplet level to the Eu(III) ion is completely occurring. The Eu(III) complexes can potentially be used to fabricate intense hybrid white and red LEDs. All of the fabricated red LEDs revealed high luminous efficiency of radiation (LER) values. The fabricated blue LED based hybrid white LEDs displayed remarkable performance with a low correlated color temperature (5634 K), high color rendering index 88%, and CIE values (x = 0.33; y = 0.342) for 3Eu. By interaction with acid-base vapors, Eu-complexes displayed effectively alterable on-off-on luminescence. Further, cellular imaging shows that Eu-complexes can be a potential biomarker for cancer cell lines.

Magneto-optical metasurfaces for high-Q perfect absorption with quasi-bound states in the continuum.

We present a novel, to the best of our knowledge, magneto-optical (MO) metasurface composed of a bismuth iron garnet (BIG) nanocube array, designed to achieve near-perfect absorption through quasi-bound states in the continuum (QBICs). This metasurface supports a stable QBIC mode induced by MO-induced permittivity terms that break the symmetry of the permittivity tensors, corresponding to a longitudinal electric dipole (ED) mode. By integrating graphene to introduce material loss, the absorption reaches 99.6% at a wavelength of 1512.3 nm with a Q factor of 9440, despite monolayer graphene's inherent absorption being only 2.3%. The inherent transverse ED background mode, with high reflection and low Q, helps decrease the radiative loss of the QBIC mode, allowing the structure to surpass the 50% absorption limit. This approach offers a simplified pathway for designing high-Q metasurface perfect absorbers, with potential applications in optical switches and modulators.

Full-Stokes polarization mid-wave infrared photodetector based on the polarization-converting metasurface

It is very challenging to achieve direct capture of the circular polarization due to the complex mechanism of the chiral materials. We numerically demonstrate a circular polarization photodetector composed of the silicon (Si) metasurfaces rotated 45° clockwise presenting as the phase delayer and the grating-coupled quantum well infrared photodetectors (QWIP) chip detecting the transverse magnetic (TM) mode. The circular dichroism and extinction ratio of the circular polarization (CP) photodetector are 0.25 and 20 dB at 4 μm operation wavelength, respectively. In addition, the linear dichroism (LD) and extinction ratios (ER) of the linear polarization device are 0.22 and 60 dB, respectively. The excellent LD performance is caused by the Fano resonance of the Si/SiO2 linear grating corresponding to the interference of the bright electric dipole mode and the dark electric quadrupole mode. The full Stokes pixel of the six-image-element technique can almost accurately obtain arbitrary polarized light at 4 μm operation wavelength. The errors of the degree of linear polarizations (Dolp) and the degree of circular polarizations (Docp) are less than −30 dB and −20 dB, respectively.

Inverse Faraday Effect in Ferrite–Garnet Films in the Near-Infrared Range

The magneto-optical Faraday effect is determined by the electric dipole and magnetic dipole transitions in a transparent magnetic material. At the same time, the inverse Faraday effect is still described by an expression that includes only electric dipole transitions. The magnetic dipole contribution to the inverse Faraday effect is considered theoretically, and the dependence of the inverse Faraday effect on the wavelength in the near-infrared range (where the magnetic dipole contribution becomes significant) is obtained by the example of a ferrite–garnet film. It is shown that, although both contributions to the inverse Faraday effect always take place for homogeneous films, only the magnetic-dipole inverse Faraday effect manifests itself for films with a periodic nanostructure upon excitation by a TE waveguide mode, which may be useful for its experimental observation.