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White-emitting SrSc1-xLiTeO6:xDy3+ phosphors were conveniently synthesized by a conventional high-temperature solid-state synthesis process. The crystal structure, photoluminescence spectrum characteristics, fluorescence quenching phenomenon, fluorescence lifetime analysis and the thermal stability of SrSc1-xLiTeO6:xDy3+ phosphors were comprehensively illustrated. The Egap of the SrScLiTeO6 host was approximately 4.65 eV based on diffuse reflectance spectroscopy (DRS) analysis. Moreover, the SrSc0.94LiTeO6:0.06Dy3+ phosphor exhibits two principal emission bands: the narrow-band emission at 481 nm (4F9/2→6H15/2, magnetic dipole transition, blue light area) and 573 nm (4F9/2→6H13/2, electric dipole transition, yellow light area) under the excitation of 366 nm ultraviolet light, respectively. The values of τ are determined to be 0.558, 0.380, 0.307 and 0.254 ms for SrSc1-xLiTeO6:xDy3+ (x = 0.005, 0.01, 0.04, 0.08) samples, respectively. The value of ΔE for SrSc0.94LiTeO6:0.06Dy3+ phosphor is deduced to be 0.1969 eV, which indicates excellent thermal stability. In addition, the CIE coordinates are located in the white light-emitting area. The abovementioned results show that the SrSc1-xLiTeO6:xDy3+ can serve as a phosphor with potential application value for outdoor illumination.

New complexes of Dy (III) and Gd (III) with b-diketones containing unsaturated and aryl substituents were synthesized. Metal polymers based on synthesized complexes were obtained by the method of radical polymerization. The composition and structure of synthesized complexes and metal polymers are established. It is shown that during polymerization the coordination environment of the central ion remains unchanged. The spectral-luminescent cha­racteristics of the synthesized compounds were studied. The presence of water molecules in the immediate coordination environment causes a low intensity of emission of monomeric dysprosium complexes. In the luminescence spectra of metal polymers, there are bands magnetic dipole transition (4F9 → 6H15/2) and electric dipole transition (4F9 → 6H13/2). The close energies of the triplet level of the ligand and the resonant level of the dysprosium ion cause low emission characteristics of the synthesized dysprosium complexes.

A new series of narrow orange emitting phosphors in 1:2 B-site cation ordered Eu3+ doped triple Perovskite Ba3CaNb2O9 was prepared by the conventional solid-state route. Powder X-ray diffraction analysis of these phosphors confirms the formation of trigonal perovskite-type structure with the space group P-3m1 and Z = 3. The weak intensity superlattice reflections at low 2θ angles support the idea of 1:2 ordering on the B-site. UV–visible absorption spectra show strong absorption below 325 nm. These phosphors exhibit dominant narrow orange emission with fwhm ~ 4 nm due to allowed magnetic dipole transition, 5D0–7F1 under near-UV (394 nm), or charge transfer band (288 nm) excitations. The intensity for the CT band excitation (x = 0.2) is double that of the direct Eu3+ excitation at 394 nm inferring good host sensitization by way of energy transfer to Eu3+ ions. The ordering on the B-site cations aids a high concentration quenching in the Ba3CaNb2O9:Eu3+ phosphor at 20 mol%. The low asymmetric ratio values and high lifetimes corroborate the environment of Eu3+ ions in most symmetrical surrounding of the host. The CIE color co-ordinates of Ba3CaNb2O9:0.2Eu3+ phosphor are (0.57, 0.41) that are close to the Nichia Corporation developed Amber LED NSPAR70BS. The above results demonstrate that the Ba3CaNb2O9:0.2Eu3+ phosphor is a potential candidate for near-ultraviolet-based phosphor-converted white light-emitting diodes.

Nuclear excited states with T > 0 in sd even-even N=Z nuclei have been studied by using shell model. The calculations have employed the USDB Hamiltonian in order to predict the energy levels, the reduced electric quadrupole transition probabilities and reduced magnetic dipole transition probabilities. The study also include the average number of nucleons in each sd- active orbitals. The results compared with available experimental data. The comparison showed a good agreement between theoretical and experimental energy sates for most of the states studied in this work. On the other hand there was a difference between theoretical and experimental values of transition probabilities, but it can be said that it remained within the acceptable range of the difference.

In this work, the combustion method was adopted to compound Ca3Sr3(VO4)4: xDy3+ samples at 900 °C, and Eu3+ was co-doped into Ca3Sr3(VO4)4: Dy3+ samples to obtain better luminescent properties such as low correlation color temperature (CCT). The microstructure and photoluminescence characteristics of the prepared phosphors were explored with X-ray diffractometer (XRD), scanning electron microscope (SEM), and photoluminescence (PL) spectroscopy, respectively. The rhombohedral crystal structure was demonstrated by the results of XRD analysis, which were in agreement with the standard Ca3Sr3(VO4)4 phase. Under near-ultraviolet (NUV) excitation at 387 nm, the emission spectra of Ca3Sr3(VO4)4: xDy3+ samples consist of two characteristic emission peaks centered at 484 nm and 575 nm, corresponding to the magnetic dipole transition 4F9/2 → 6H15/2 (blue emission) and electron dipole transition 4F9/2 → 6H13/2 (yellow emission) of Dy3+ ions, respectively. In particular, the CCT values were lowered by the addition of Eu3+ ions. The above-mentioned conclusions demonstrate that Ca3Sr3(VO4)4: Dy3+, Eu3+ sample possesses a promising prospect for warm white light-emitting diodes (white LEDs) under NUV excitation.

We review electric dipole active magnetic resonance and nonreciprocal directional dichroism in magnetoelectric multiferroic materials in terahertz and millimeter wave regions. Owing to dynamical magnetoelectric coupling generated by the spin-dependent electric polarization, magnetic resonance, which usually occurs owing to magnetic dipole transition, can be induced by the oscillating electric fields of electromagnetic wave. This electric dipole active magnetic resonance can be useful for microscopic investigations of magnetic excitation in unconventional spin systems. The magnetoelectric coupling also induces the nonreciprocal directional dichroism, which provides a novel functionality to materials as an optical diode, in teraheltz and microwave absorption by magnetic resonance. As examples, we describe the results of the high field ESR measurements of the triangular lattice antiferromagnet $$\hbox {CuFeO}_{\mathrm{2}}$$ and the interacting quantum spin dimer systems $$\hbox {TlCuCl}_{\mathrm{3}}$$ and $$\hbox {KCuCl}_{\mathrm{3}}$$ .

Group theoretical predictions obtained from Raman and IR spectra emphasize the structures of B-site ordered double perovskites Ba2R2/3TeO6 (R = Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) with ubiquitous BO6 or B′O6 octahedral tilting are monoclinic (P21/n), which was further confirmed via the Rietveld refinement of XRD patterns. The wide band gaps of these compounds were consistent with their ability to absorb UV radiation and hence their potential to act as photoluminescent host materials. Photoluminescence spectra of Eu3+-activated Ba2Y2/3TeO6, irrespective of substitution at A- or B-sites, yielded a dominant magnetic dipole transition at 592 nm and a less intense electric dipole transition at 610 nm when excited at 276 nm suggested the preference of Eu3+ ions to occupy Y3+ sites. The thermal activation energy of the Ba2Y2/3TeO6:Eu3+ phosphor was 0.15 eV and its relative sensitivity in the temperature range 300–500 K was estimated to have a maximum of 0.18% K−1 at 300 K for FIR measurements, which is better than its decay lifetime counterpart. The red shift and the peak broadening of the high-energy Raman modes at elevated temperatures of Ba2Y2/3TeO6:Eu3+ are due to enhanced B-site octahedral distortions and are correlated with the thermal quenching of Eu3+ emission. Temperature-dependent lifetimes in the range 80–500 K imply intensification of non-radiative relaxation within the limit. Furthermore, the phosphorescence lifetime, color parameters, and JuddOfelt parameters are explained in detail. The multifunctional optical properties of this phosphor can thus be utilized for technological applications, such as solid-state lighting and ratiometric optical thermometry.

High pressure spectroscopy is of immense importance in understanding materials with respect to their high pressure phases, structural phase transitions, designing pressure sensors, etc. With this objective in mind, we have carried out time resolved photoluminescence and Raman spectroscopy on La2Hf2O7:Eu3+ (LHOE) nanoparticles (NPs) under applied high pressure. High pressure Raman spectra of the LHOE NPs suggest enhanced disordering at high pressure and shifting of the most intense F2g Raman band to higher wavenumber. High pressure excitation photoluminescence spectra of the LHOE NPs demonstrate that the O2− → Eu3+ charge transfer band quenches beyond 2.7 GPa whereas not many changes could be observed from the intra-configurational f–f excitation bands of Eu3+ ion. High pressure emission photoluminescence spectra of the LHOE NPs show gradual lowering of asymmetry ratio value, reduced Stark component in magnetic dipole transition, and the disappearance of the 5D0 → 7F0 transition of Eu3+ ion at high pressure. These observations suggest significant improvement in Eu3+ symmetry. These results are further corroborated with lifetime spectroscopy, which indicates high pressure induced tunneling of Eu3+ ion from La3+ to Hf4+ sites. These changes are visualized by beautiful color tunability of the LHOE NPs from red to orange to yellow and correlated color temperature from 1900 to 2600 K. This work demonstrates a new mode of designing optically tunable luminescent nanomaterials and understanding high pressure induced changes in photonic materials.

The local symmetry of a Eu3+ ion has a crucial effect on its luminescence properties. In this work, we show that the red/orange ratio in the emission of Eu3+-doped MgIn2P4O14 phosphors is tunable by adjusting the Eu3+ concentrations, due to the change in the local symmetry of metal ions. The substitution of Eu3+ for In3+ lowers the distortion in the lattice of monoclinic MgIn2P4O14, and an increase in Eu3+ doping concentration causes the metal ion sites to shift closer to an inverse center, leading to a reversal of the relative emission intensity of a magnetic dipole transition to an electric dipole transition. Meanwhile, the higher asymmetry of metal ion sites occupied by Eu3+ in MgIn2P4O14 makes the luminescence less thermally stable than that in Mg3In4P6O24.

Efficient excitation of a triplet (T1 ) state of a molecule has far-reaching effects on photochemical reaction and energy conversion systems. Because the optical transition from a ground singlet (S0 ) to a T1 state is spin-forbidden, a T1 state is generated via intersystem crossing (ISC) from an excited singlet (S1 ) state. Although the excitation efficiency of a T1 state can be increased by enhancing ISC utilizing a heavy atom effect, energy loss during S1 →T1 relaxation is inevitable. Here, a general approach to directly excite a T1 state from a ground S0 state via magnetic dipole transition, which is boosted by enhanced magnetic field induced by a dielectric metasurface, is proposed. As a dielectric metasurface, a hexagonal array of silicon (Si) nanodisks is employed; the nanodisk array induces a strongly enhanced magnetic field on the surface due to the toroidal dipole (TD) resonance. A proof-of-concept experiment is performed using ruthenium (Ru) complexes placed on a metasurface and demonstrates that the phosphorescence is 35-fold enhanced on a metasurface when the TD resonance is tuned to the wavelength of the direct S0 →T1 transition. These results indicate that photon energy necessary to excite the T1 state can be reduced by more than 400 meV compared to the process involving the ISC. By combining optical measurements with numerical simulations, the mechanism of the phosphorescence enhancement is quantitatively discussed.

The 1.14 µm inner-shell magnetic dipole transition in neutral thulium possesses very low blackbody radiation shift in comparison to other neutrals. Together with other features of Tm electronic structure it opens new perspectives for compact optical clocks almost free from hard-to-control systematic shifts.

We studied supramolecular chirality induced by circularly polarized light. Photoresponsive azopolymers form a helical intermolecular network. Furthermore, studies on photochemical materials using optical vortex light will also attract attention in the future. In contrast to circularly polarized light carrying spin angular momentum, an optical vortex with a spiral wave front and carrying orbital angular momentum may impart torque upon irradiated materials. In this review, we summarize a few examples, and then theoretically and computationally deduce the differences in spin angular momentum and orbital angular momentum depending on molecular orientation not on, but in, polymer films. UV-vis absorption and circular dichroism (CD) spectra are consequences of electric dipole transition and magnetic dipole transition, respectively. However, the basic effect of vortex light is postulated to originate from quadrupole transition. Therefore, we explored the simulated CD spectra of azo dyes with the aid of conventional density functional theory (DFT) calculations and preliminary theoretical discussions of the transition of CD. Either linearly or circularly polarized UV light causes the trans–cis photoisomerization of azo dyes, leading to anisotropic and/or helically organized methyl orange, respectively, which may be detectable by CD spectroscopy after some technical treatments. Our preliminary theoretical results may be useful for future experiments on the irradiation of UV light under vortex.

It is widely reported that rare-earth ions could be used to probe the phase structure by photoluminescence (PL) spectra after doping into ferroelectrics, while most reported results are qualitative. In this work, we show that PL spectra of Eu3+ ions could be used to do quantitative phase analyses of (Na1-x,Kx)0.5Bi0.497Eu0.003TiO3 (NKBT: Eu) ferroelectric ceramics with compositions near morphotropic phase boundary(MPB). The mechanism was elaborated based on the emission intensity ratios of the “hypersensitive” transition to the magnetic dipole transition with the Judd-Ofelt theory. The results were further confirmed by X-Ray Diffraction Rietveld refinements. This work shows a simple yet practical method for quantitative phase analyses for NKBT: Eu ceramics near MPB, and the method is expected to be applied in more ferroelectric material systems.

LiMgBO3 :Dy3+ , a low Zeff material was prepared using the solution combustion method and its luminescence properties were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermoluminescence (TL), photoluminescence (PL), Fourier transform infrared spectroscopy, and electron paramagnetic resonance (EPR) techniques. Reitvield refinement was also performed for the structural studies. The PL emission spectra for LiMgBO3 :Dy3+ consisted of two peaks at 478 due to the 4 F9/2 →6 H15/2 magnetic dipole transition and at 572 nm due to the hypersensitive 4 F9/2 →6 H13/2 electric dipole transition of Dy3+ , respectively. A TL study was carried out for both the γ-ray-irradiated sample and the C5+ irradiated samples and was found to show high sensitivity for both. Moreover the γ-ray-irradiated LiMgBO3 :Dy3+ sample showed linearity in the dose range 10 Gy to 1 kGy and C5+ -irradiated samples show linearity in the fluence range 2 × 1010 to 1 × 1011 ions/cm2 . In the present study, the initial rise method, various heating rate method, the whole glow curve method, glow curve convolution deconvolution function, and Chen's peak shape method were used to calculate kinetic parameters to understand the TL glow curve mechanism in detail. Finally, an EPR study was performed to examine the radicals responsible for the TL process.

Orange-red light emitting Eu3+ (5 at.%) doped GdxLa1−xPO4 (x = 1.0, 0.9, 0.7, 0.5, 0.3, 0.1, 0.0) phosphors with various concentrations were synthesized via chemical co-precipitation method at a calcination temperature of 1000 °C for 5 h was presented. The synthesized phosphors were characterized via XRD, PL, FT-IR, SEM and CIE respectively. The XRD analysis confirms that the prepared phosphors in a monazite monoclinic system with a space group P21/n(14). The PL spectra of (GdxLa1−x)PO4:0.05%Eu3+ phosphors were measured at 250 nm excitation wavelength. The most dominant emission peak of Eu3+ for 5D0 → 7F1 transition located at 597 nm, which is magnetic dipole transition, is responsible for emission of orange-red light. The SEM was carried out to understand the surface morphological feature and grain sizes. According to the experimental outcome, it was indicated that these phosphors have appropriate CIE, suitable color correlated temperature parameter, valuable life-time, and appreciable purity of color, which comparable with the reported rear-earth ions doped orange-red light phosphors. The results show that these orange-red emitting phosphors may have a potential application on the white light-emitting diode and other related electronic systems, which is observing the picture in orange-red color.

The xMg2+/ySm3+ ions co-doped CaTiO3:0.12Eu3+ red phosphors were synthesized by solid-state reaction method and their structure, crystalline morphology, luminescent properties, decay curves and quantum efficiency were investigated in detail. The XRD patterns show these phosphors have an orthorhombic perovskite structure when the sintering temperature was 1350 °C. From photoluminescence spectra, two excitation peaks were observed located at 397 nm (7F0 → 5L6) and 465 nm (7F0 → 5D2), and there are two prominent red emission peaks around 595 nm (5D0 → 7F1) and 616 nm (5D0 → 7F2) corresponding to the magnetic dipole transition and electric dipole transition of Eu3+ respectively. The luminescent properties were improved by adjusting Mg2+ and Sm3+ ions co-doping concentration and their optimal doping amount was found to be 7 mol% and 0.5 mol%. At this moment, their internal quantum efficiency was measured to be 52.4% and 47.5% respectively and decay times were 0.64 ms and 0.59 ms. According to concentration quench theory, the critical distance between activators in CaMTiO3:Eu3+ (M = Mg, Sm) were 15.27 A and 15.07 A. CaTiO3:Eu3+ phosphor’s thermal stability has been improved a lot due to Mg2+ introduction. When temperature increases from 248 to 388 K, the red emission intensity of CaMg0.07TiO3:0.12Eu3+ and CaMg0.07TiO3:0.12Eu3+,0.005Sm3+ phosphors have decayed only 12.1% and 15.9% respectively. These experimental results have indicated that the synthesized red phosphors can be used in solid state lighting devices.

Er3+ ions doped oxyhalide barium borate glasses were prepared by means of conventional melt quenching technique. In the studied glass system, besides the Er3+ doping, barium oxide was partially replaced by BaF2 and/or BaCl2. The amorphous nature of as-prepared glasses was confirmed by X-ray diffraction patterns. The effects of the compositional changes were investigated through spectroscopic techniques such as optical absorption, emission and decay lifetime. It was found that the luminescence and decay lifetime of Er3+: 4I13/2 → 4I15/2 transition are affected by both Er3+ doping and halide insertions. By applying the Judd-Ofelt (JO) theory, the JO intensity parameters (Ωt, t = 2, 4, and 6) were calculated, and the trend Ω2 > Ω4 > Ω6 was found, which is in accordance with previous studies. Optical properties such as electric and magnetic dipole transition probabilities, fluorescence branching ratios, integrated emission cross sections and radiative lifetimes were also obtained and discussed for many excited states of Er3+ ions. The lifetime of the 4I13/2 excited level was measured and compared with the calculated one.

CaTiO3:Eu3+ luminescent nanoparticles (NPs) and Ppy/CaTiO3:Eu3+ nanocomposites (NCs) are synthesized via combustion and solution casting techniques respectively and their structural and optical properties are investigated. The powder X-ray diffraction patterns of the as-formed products show single orthorhombic phase. The crystallite size measurement is assessed utilizing Scherrer's technique and observed to be in the range of 40–45 nm. The impact of Eu3+ ions on luminescence properties of the produced nanophosphors is examined the outcomes are given in detail. The phosphors displayed splendid red emission at 398 nm excitation. The emission peaks observed at 540, 593, 615, 653, 696 and 706 nm (5D0→7Fj = 0, 1, 2, 3, 4, 5) are assigned to Eu3+ ions transitions. The electronic transition equivalent to 5D0→7F2 (615 nm) is robust than the magnetic dipole transition 5D0→7F1 of Eu3+ ions (596 nm). The CIE chromaticity co-ordinates are ascertained from emanation spectra, the obtained values are very close to NTSC standard value of red emission. Hence, the present phosphors are exceedingly valuable for display applications. The obtained results demonstrate that Ppy-assisted solution casting is an effective methodology for the synthesis of rare-earth doped CaTiO3:Eu3+ nanocomposites (NCs).

Mie-resonant high-index dielectric nanoparticles and metasurfaces have been suggested as a viable platform for enhancing both electric and magnetic dipole transitions of fluorescent emitters. While the enhancement of the electric dipole transitions by such dielectric nanoparticles has been demonstrated experimentally, the case of magnetic-dipole transitions remains largely unexplored. Here, we study the enhancement of spontaneous emission of Eu3+ ions, featuring both electric and magnetic-dominated dipole transitions, by dielectric metasurfaces composed of Mie-resonant silicon nanocylinders. By coating the metasurfaces with a layer of an Eu3+ doped polymer, we observe an enhancement of the Eu3+ emission associated with the electric (at 610 nm) and magnetic-dominated (at 590 nm) dipole transitions. The enhancement factor depends systematically on the spectral proximity of the atomic transitions to the Mie resonances as well as their multipolar order, both controlled by the nanocylinder size. Importantly, the branching ratio of emission via the electric or magnetic transition channel can be modified by carefully designing the metasurface, where the magnetic dipole transition is enhanced more than the electric transition for cylinders with radii of about 130 nm. We confirm our observations by numerical simulations based on the reciprocity principle. Our results open new opportunities for bright nanoscale light sources based on magnetic transitions.

Doping of ceria with trivalent lanthanides and pentavalent ions is known to influence its catalytic activity, optical properties and ionic conductivity. In this study, (Nb,Eu)-codoped CeO2 has been synthesized by hydroxide precipitation to study the synergistic effect of (Nb, Eu) codoping on the defect evolution and optical properties of CeO2. Through X-ray diffraction, it was seen that Nb5+ has limited solubility in CeO2 which could be enhanced by codoping with Eu3+. From Rietveld refinement of the X-ray diffraction data, the ceria lattice seems to expand on Eu3+ doping which could be explained taking into account the formation of oxygen vacancies (OVs) in stoichiometric ratios. The observed lower than expected contraction in the Nb5+ doped samples is attributed to lattice expansion due to the creation of oxygen interstitials (OIs). PL studies in terms of the ratio of electric dipole transition (EDT) to magnetic dipole transition (MDT) intensities have shown that Eu3+ lacks inversion symmetry at Ce4+ which invokes the formation of OVs for charge compensation. Interestingly, Nb5+ co-doping restored the inversion symmetry around the Eu3+ site by eliminating the formed OVs. This is achieved by ion pair matching of the dopants. This work has great relevance in understanding the role of defects and co-doping in designing highly efficient catalysts, solid oxide fuel cells and doped phosphors.

Hyperfine structure (hfs) investigations were performed on singly ionized atomic iodine (I II) in the spectral region 12,000 - 24,000 cm−1, utilizing microwave discharge method in combination with high resolution Fourier Transform Spectroscopy (FTS). Electrodeless discharge lamps (EDL) were used to generate the iodine plasma. In the present work, 141 hyperfine spectral transitions are reported. Hfs measurements were carried out on 73 well resolved spectral lines and derived the magnetic dipole constant (A) and electric quadrupole constant (B) for 61 energy levels (29 even parity and 32 odd parity). Further, a magnetic dipole transition (14,366 cm−1) and a blended line (20,611 cm−1) have been observed.

We have synthesized novel inorganic–organic hybrid systems based on the interactions between calcium phosphate (CP) and tris(2,2,6,6-tetramethyl-3,5-heptanedionato)europium (III) (EuTH) complex to clarify the states of the EuTH molecules. We achieved the nucleation and crystal growth of electronically localized of EuTH molecules using two different synthetic processes (based on the timing of the addition EuTH before and after the CP nucleation stage). The coordination environment of the Eu3+ ion inside/on the hybrids was clearly changed, having the higher spatial symmetry states in the hybrid. The aspect ratios of the hybrid crystallites were 2.5–6.0, suggesting that the EuTH molecules selectively interacted with the a–plane of the CP nuclei to induce preferential crystal growth along with the uncovered c–plane. The segregated EuTH molecules on CP surfaces suppressed Ca2+ dissolution from the hybrids in phosphate buffer saline. In the excitation spectra of the hybrids, the 7F0 → 5L6 transition appeared as a result of the interaction between the EuTH and phosphate ions, suggesting that the phosphate ions affected the coordination environment. In the luminescence spectra of the hybrids, the luminescence intensity ratio of the magnetic dipole transition (5D0 → 7F1) to electric dipole transition (5D0 → 7F2) were higher than those of EuTH and the other Eu3+-doped inorganic systems. Thus, the higher spatial symmetry states of the Eu3+ ion in the hybrids resulted in greater luminescence intensities and quantum efficiencies, which would be affected by the phosphorus anti-quenching. In the future, CP hybrids with various organic complexes will be prepared, and these could be applied in the biomedical fields such as in bio-imaging and drug delivery systems.