3d Levels Research Articles

Luminescence and scintillation properties of fast Ce,Mg:Lu2YGaxAl5-xO12 ceramic scintillators fabricated from co-precipitated powders

Ce,Mg:Lu2YGaxAl5-xO12 (x = 1.5, 2, 2.5, 3) ceramic scintillators were fabricated by oxygen sintering combined with air annealing using nano-powders synthesized by the co-precipitation method. The Ce3+ 5d1 → 4f (2F5/2, 2F7/2) luminescence band was blue shifted with increasing Ga content due to the decrease in the crystal field splitting of the 5d levels. At room temperature (RT), the decrease of photoluminescence decay time and scintillation decay time was observed with increasing Ga content. At 662 keV γ-rays, the sample Ga2 exhibited high light yield (LY) of 28,700 photons/MeV, fast scintillation decay times of 17.7 ns (17 %) + 45.7 ns (83 %), and good time resolution of ∼220 ps. At RT, the decrease of LY value for the samples Ga2.5 and Ga3 could be attributed to the larger thermal ionization of the excited Ce3+ centers.

Growth, spectroscopy and Dy3+→Tb3+ energy transfer of TbAl3(BO3)4 and Dy3+:TbAl3(BO3)4 crystals

TbAl3(BO3)4 and Dy3+:TbAl3(BO3)4 crystals were grown by the top-seeded solution method and the polarized optical spectra of the crystals were investigated at room temperature. Peak absorption cross-sections for the 6H15/2 → 4I15/2 transition of Dy3+ in the Dy3+:TbAl3(BO3)4 crystal are 1.2 × 10−21 cm2 at 453 nm and 0.6 × 10−21 cm2 at 452.4 nm for σ and π polarizations, respectively. Under excitation at 453 nm, a strong green fluorescence of Tb3+ around 541 nm was observed in the Dy3+:TbAl3(BO3)4 crystal due to the efficient energy transfer from Dy3+ to Tb3+ ions. Peak emission cross-sections for the 5D4→7F5 transition of Tb3+ in the Dy3+:TbAl3(BO3)4 crystal are 2.8 × 10−21 and 1.5 × 10−21 cm2 at 541 nm for σ and π polarizations, respectively. Fluorescence lifetime of the 5D4 level of Tb3+ is 1.4 ms and the efficiency of energy transfer from Dy3+ to Tb3+ ions is about 92% in the Dy3+:TbAl3(BO3)4 crystal. The results show that a commercial high-power 450 nm diode laser may be used as the pumping source for Dy3+/Tb3+ co-doped crystal to realize Tb3+ visible laser.

Growth and spectroscopic properties of Ca3(Ta,Ga)5O12:Pr3+ single crystal as a promising new laser material in the visible domain

Structurally disordered Pr3+-doped Ca3(Ta,Ga)5O12 - Pr:CTGG single crystal was grown by the Czochralski technique for the first time and its spectroscopic properties were investigated. Modified Judd-Ofelt analysis was applied to determine spectroscopic and laser emission characteristics. Based on low-temperature absorption and emission spectra, the partial energy levels of Pr3+ ions have been obtained and a multicenter structure of the optical spectra was highlighted. The electron-phonon interactions were also observed in the emission spectra corresponding to the 3P0 → 3H4 transition under different excitation wavelengths. The fluorescence decays of the 3P0 and 1D2 levels were measured. The emission cross-sections corresponding to the 3P0 → 3H4 (486.5 nm) and 3P0 → 3F2 (652.7 nm) transitions were found to be σem = 19 × 10−20 cm2 and σem = 15 × 10−20 cm2, respectively. The values for other parameters that may predict the possibility of achieving efficient laser emission, especially at 486.5 nm, such as quantum efficiency (ⴄ = 50 %), gain bandwidth (σem× Δλeff, = 32.2 × 10−26 cm3), and optical gain (σem× τmeas = 12.86 × 10−25 cm2 s) were determined. The obtained results indicate that the Pr:CTGG crystal has a high potential for obtaining efficient laser emission in the blue domain.

Pr3+-doped YPO4 nanocrystal embedded into an optical fiber.

Optical fiber with YPO4:Pr3+ nanocrystals (NCs) is presented for the first time using the glass powder-NCs doping method. The method's advantage is separate preparation of NCs and glass to preserve luminescent and optical properties of NCs once they are incorporated into optical fiber. The YPO4:Pr3+ nanocrystals were synthesized by the co-precipitation and hydrothermal methods, optimized for size (< 100nm), shape, Pr3+ ions concentration (0.2mol%), and emission lifetime. The core glass was selected from the non-silica P2O5-containing system with refractive index (n = 1.788) close to the NCs (no = 1.657, ne = 1.838). Optical fiber was drawn by modified powder-in-tube method after pre-sintering of glass powder-YPO4:Pr3+ (wt 3%) mixture to form optical fiber preform. Luminescent properties of YPO4:Pr3+ and optical fiber showed their excellent agreement, including sharp Pr3+ emission at 600nm (1D2-3H4) and 1D2 level lifetime (τ = 156 ± 5µs) under 488nm excitation. The distribution of the YPO4:Pr3+ NCs in optical fiber were analyzed by TEM-EDS in the core region (FIB-SEM-prepared). The successful usage of glass powder-NCs doping method was discussed in the aspect of promising properties of the first YPO4:Pr3+ doped optical fiber as a new way to develop active materials for lasing applications, among others.

Structure and Luminescent Properties of Niobium-Modified ZnO-B2O3:Eu3+ Glass.

The effect of the addition of Nb2O5 (up to 5 mol%) on the structure and luminescent properties of ZnO-B2O3 glass doped with 0.5 mol% (1.32 × 1022) Eu2O3 was investigated by applying infrared (IR), Raman and photoluminescence (PL) spectroscopy. Through differential thermal analysis and density measurements, various physical properties such as molar volume, oxygen packing density and glass transition temperature were determined. IR and Raman spectra revealed that niobium ions enter into the base zinc borate glass structure as NbO4 tetrahedra and NbO6 octahedra. A strong red emission from the 5D0 level of Eu3+ ions was registered under near UV (392 nm) excitation using the 7F0 → 5L6 transition of Eu3+. The integrated fluorescence intensity ratio R (5D0 → 7F2/5D0 → 7F1) was calculated to estimate the degree of asymmetry around the active ion, suggesting a location of Eu3+ in non-centrosymmetric sites. The higher Eu3+ luminescence emission observed in zinc borate glasses containing 1-5 mol% Nb2O5 compared to the Nb2O5-free zinc borate glass evidences that Nb2O5 is an appropriate component for modifying the host glass structure and improving the emission intensity.

Optical characteristics and energy transfer analysis of Dy3+-Pr3+ ions doped in CeF3 crystal

The Dy,Pr:CeF3 single crystal was successfully grown and its optical characteristics were investigated systematically. The analysis of energy transfer process between Dy3+ and Pr3+ in CeF3 crystal was also carried out. The XRD study shows the crystal belongs to the hexagonal crystal system and its lattice parameters are a = 7.1252 Å and c = 7.2775 Å. The maximum phonon energy of the crystal was speculated to be 377.1 cm−1 by Raman spectrum. The absorption coefficient at 442 nm of Dy,Pr:CeF3 crystal is 0.89 cm−1. The radiative lifetime of Dy:4F9/2 level is 2.08 ms and the one of Pr:3P0 level is 145.25 μs in Dy,Pr:CeF3 crystal obtained by J-O theory calculation. The maximum emission cross-section of Dy: 4F9/2 → 6H13/2 transition is calculated to be ∼0.15 × 10−20 cm2 in the crystal. The fluorescence lifetimes of Dy:4F9/2, Pr:3P0 and Pr:1D2 levels are estimated to be ∼1.25 ms, ∼17.91 μs and ∼112.37 μs, respectively. The results show that Dy,Pr:CeF3 crystal not only owns a larger absorption coefficient at 442 nm than Dy:CeF3 crystal, but also holds the much longer lifetime of Pr:3P0 level than Pr:CeF3 crystal because of the energy transfer in Dy3+-Pr3+.

Colour-tunable features in thermally stable Tb3+/Eu3+ co-doped telluro tungstate glasses for photonic applications

The melt quenching procedure has been followed to synthesize transparent Tb3+ singly activated and Tb3+/Eu3+ co-activated TeO2–WO3–K2O–ZnO–Bi2O3 (TWKZBi) glasses. The structural characteristics of the prepared TWKZBi glass samples were examined through x-ray diffraction. The existence of functional units corresponding to the different vibrations has been examined via Raman spectroscopy. The photoluminescent characteristics and energy transfer (ET) analysis in the Tb3+/Eu3+ co-activated TWKZBi glasses were investigated in depth. Several emission peaks have been observed in Tb3+ doped TWKZBi glasses under n-UV and blue excitations and the maximum luminescent intensity has been detected for 2.0 mol% of Tb3+ doped TWKZBi glass sample. The emission spectra of co-doped Tb3+ and Eu3+ ions in the TWKZBi glasses have been studied, and the maximum ET efficiency is found to be 32.82% under n-UV excitation. The ET from sensitizer (Tb3+) to activator (Eu3+) ions happen through dipole–dipole interaction, as confirmed by Dexter’s and Reisfeld’s approximation. The colour-tunable emission in the prepared glass samples can be achieved via varying the content of activator ions. The decay profiles for the 5D4 level of Tb3+ ions diminish with varying the concentration of Eu3+ ions, confirming the ET from Tb3+ to Eu3+ ions. Furthermore, temperature-dependent photoluminescence studies show that the Tb3+/Eu3+ co-doped TWKZBi glasses have good thermal stability. All the aforementioned results reveal the suitability of the Tb3+/Eu3+ co-activated TWKZBi glass samples for photonic applications.

A Bifunctional Luminescent Whitening and Sensing Material Based on Photoluminescence and Mechanoluminescence.

A bifunctional luminescent whitening and luminescent sensing composite material, BaMgAl12O17:Eu2+/polydimethylsiloxane (BAM/PDMS), that utilizes natural sunlight and mechanical energy is presented. By increasing the Eu2+ content, the photoluminescence (PL) excitation spectrum of the material shows a maximum redshift of 23 nm due to 5d level splitting of Eu2+, resulting in more spectral overlap with sunlight and an excellent PL whitening effect. Meanwhile, the self-recoverable mechanoluminescence (ML) of the material can be easily excited under mechanical stimuli due to contact electrification, exhibiting a unique stress sensing effect. Based on the unique features of PL whitening and ML sensing, the material is applied to model cars through a spray process, and the results demonstrate that the bifunctional BAM/PDMS material shows promising applications in automobile decoration.

Highly Sensitive, Multiparametric Thermal History Phosphor Based on An Eu(BTC) Architecture

AbstractThe capacity to discern the highest temperature that an object is subjected to is a crucial diagnostic tool. Consequently, the pursuit of materials that enable the luminescence‐based investigation of the thermal history of an object with high sensitivity is of great importance from the functional applications standpoint. This study aims to present a multiparametric thermal history phosphor based on the luminescent coordination polymer [Eu(BTC)(H2O)6] [Eu(BTC)‐1, where H3BTC = 1,3,5‐benzenetricarboxylic acid]. The progressive dehydration that Eu(BTC)‐1 undergoes as a function of temperature increase in the 343–425 K range results in significant alterations in both the shape of the Eu3+ ions emission spectrum and the depopulation kinetics of their 5D0 level. Based on this occurrence, a thermal history phosphor with an unprecedentedly high relative sensitivity of 11.3% K−1 in ratiometric mode, and 1.8% K−1 in lifetime‐based mode, is developed. The outcomes of this research are expected to stimulate a wide interest in the exploitation of (porous) coordination polymer‐type materials for the development of thermal history phosphors.

Luminescence properties and Judd-Ofelt analysis of Tb3+ doped Sr2YTaO6 double perovskite phosphors for white LED applications.

A series of Tb3+-doped Sr2YTaO6 double perovskite phosphors (SYT:Tb3+) were synthesized using a conventional solid-state reaction method. A strong green emission was observed in the SYT:Tb3+ phosphors, and the optimal doping concentration of Tb3+ was confirmed to be 5 mol%. The electric dipole-dipole interaction was ascribed to be the main mechanism for the luminescence concentration quenching. Analysis of the concentration-dependent fluorescence decay confirmed that the self-generated quenching model holds for the dynamic process of Tb3+ decays in SYT. Furthermore, the internal quantum efficiencies, non-radiative transition rates, and energy transfer rates of the 5D4 level for the SYT:Tb3+ samples were estimated, respectively. The luminescence thermal stability of the sample was also evaluated based on the Arrhenius model. The chromaticity shift of the SYT:5 mol% Tb3+ phosphor was examined to be 0.013 when the sample temperature was increased from 303 to 483 K, thus indicating excellent chromaticity shifting resistance under high temperature conditions. Moreover, the Judd-Ofelt parameters were calculated from the emission spectra of SYT:Tb3+ to be Ω2 = 0.29 × 10-20, Ω4 = 0.45 × 10-20, and Ω6 = 0.72 × 10-20 cm2, respectively. The fluorescence branching ratios and radiative transition rates for the 5D4 level were calculated based on the obtained Judd-Ofelt parameters. Finally, a white light-emitting diode (LED) prototype was assembled using a 310 nm LED chip combined with a prepared green SYT:Tb3+ phosphor and two other commercial blue and red phosphors. The obtained warm white light exhibits good chromaticity coordinates (0.32, 0.32) and a high color rendering index of 96.1. Based on the above results, it can be known that the prepared SYT:Tb3+ phosphors have a potential application as green emitting phosphors in white LEDs.

Mapping the distribution of electronic states within the 5D4 and 7F6 levels of Tb3+ complexes with optical spectroscopy.

The Tb(III) ion has the most intense luminescence of the trivalent lanthanide(III) ions. In contrast to Eu(III), where the two levels only include a single state, the high number of electronic states in the ground (7F6) and emitting (5D4) levels makes detailed interpretations of the electronic structure-the crystal field-difficult. Here, luminescence emission and excitation spectra of Tb(III) complexes with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA, [Tb(DOTA)(H2O)]-), ethylenediaminetetraacetic acid (EDTA, [Tb(EDTA)(H2O)3]-) and diethylenetriaminepentaacetic acid (DTPA, [Tb(DTPA)(H2O)]2-) as well as the Tb(III) aqua ion ([Tb(H2O)9]3+) were recorded at room temperature and in frozen solution. Using these data the electronic structure of the 5D4 multiplets of Tb(III) was mapped by considering the transitions to the singly degenerate 7F0 state. A detailed spectroscopic investigation was performed and it was found that the 5D4 multiplet could accurately be described as a single band for [Tb(H2O)9]3+, [Tb(DOTA)(H2O)]- and [Tb(EDTA)(H2O)3]-. In contrast, for [Tb(DTPA)(H2O)]2- two bands were needed. These results demonstrated the ability of describing the electronic structure of the emitting 5D4 multiplet using emission spectra. This offers an avenue for investigating the relationship between molecular structure and luminescent properties in detailed photophysical studies of Tb(III) ion complexes.

3D Breast Cancer Model on Silk Fibroin-Integrated Microfluidic Chips.

To imitate in vivo environment of cells, microfluidics offer controllable fashions at micro-scale and enable regulate flow-related parameters precisely, leveraging the current state of 3D systems to 4D level through the inclusion of flow and shear stress. In particular, integrating silk fibroin as an adhering layer with microfluidic chips enables to form more comprehensive and biocompatible network between cells since silk fibroin holds outstanding mechanical and biological properties such as easy processability, biocompatibility, controllable biodegradation, and versatile functionalization. In this chapter, we describe design and fabrication of a microfluidic chip, with silk fibroin-covered microchannels for the formation of 3D structures, such as MCF-7 (human breast cancer) cell spheroids as a model system. All the steps performed here are characterized by surface-sensitive tools and standard tissue culture methods. Overall, this strategy can be easily integrated into various high-tech application areas such as drug delivery systems, regenerative medicine, and tissue engineering in near future.

Luminescence and Excited State Dynamics of Tb1-XEuxAl3(BO3)4 (x=0.01-0.20)

The room temperature luminescence spectra and emission decay curves of undoped and Eu3+-doped TbAl3(BO3)4 crystals, grown using the flux growth technique, are presented and discussed. The experimental results show that excitation of the Tb3+ excited states gives rise to 5D0 emission from the Eu3+ ion, and therefore non-radiative energy transfer involving the two ions is operative. Analysis of the experimental data indicates that the excitation of the Tb3+ donor ion gives rise to fast energy migration in the 5D4 level of the Tb3+ subset of cations, followed by the energy transfer process populating the 5D0 level of Eu3+. Upon increasing the Eu3+ acceptor concentration, the mainly green emission intensity and the decay time of the 5D4 level decrease, whilst the red emission of 5D0 becomes dominant. The experimental data are interpreted on the basis of the trigonal huntite-type structure of the double borate crystals under investigation.

Theoretical Analysis of Anomalous Emission of Eu2+ in Crystals By First-Principles Calculation

The 5d-4f transition energies of lanthanides are very versatile, especially the 4f65d1-4f75d0 transition energy of Eu2+ has high luminescence efficiency and is used in various luminescent materials such as phosphors like SrxCa1-xAlSiN3: Eu2+, scintillators, and solid-state lasers, etc. However, there are materials that do not undergo pure 5d-4f transitions, showing the so-called anomalous luminescence instead. The anomalous luminescence is caused by the formation of excitons due to the overlap of the 5d level of Eu2+ with the conduction band and the transition of electrons from the conduction band to the 4f level, resulting in a shift to a lower energy than the general 5d-4f transition energy. A more detailed analysis of this phenomenon is important for the development of novel luminescent materials using Eu2+.In this study, we aimed to theoretically analyze the anomalous luminescence based on first-principles electronic structure calculations. The model clusters of Eu2+-doped crystals consisting of Eu2+ at the substitution site and the surrounding ions were created. Then molecular orbital calculations were performed by the relativistic discrete-variational Xα (DV-Xα) method and subsequently multiplet calculations were performed by the relativistic discrete-variational multi-electron (DVME) method. These first-principles calculations were carried out for Eu2+-doped crystals that show anomalous luminescence and those that do not show anomalous luminescence, and the electronic states of these materials were compared in detail.

Sema4D as a biomarker for Predicting rheumatoid arthritis disease activity.

The semaphorins are membrane or secreted proteins first identified in neural development. Semaphorin 4D (Sema4D) is the first family member found to have immune properties. We evaluated the potential of Sema4D as a marker for rheumatoid arthritis (RA) disease activity, singly and in combination with other known biomarkers including rheumatoid factor (RF) and C-reactive protein (CRP). Three hundred and eleven RA patients were enrolled. The patients were divided into three groups based on their disease activity in 28 joints (DAS28): mild, moderate, and severe. The healthy group included 40 healthy individuals. SerumSema4D was measured by quantitative ELISA and the specificity and sensitivity of biomarkers were evaluated by generating a receiver operating characteristic (ROC) curve to analyze their diagnostic accuracy. Serum Sema4D levels in the moderate and severe RA groups were elevated significantly above those of the controls (P < 0.01), while levels in the mild RA and control groups did not differ significantly (P > 0.05). The Sema4D cutoff threshold was 15.7ng/ml when the DAS28 was applied as a reference. Compared to the erythrocyte sedimentation rate (ESR and CRP, Sema4D had the highest specificity (96.8%) and area under the curve (0.80) for diagnosing RA activity. The highest specificity (100%) for the biomarker combinations was obtained when Sema4D was combined with CRP and anti-CCP, the combination of the Sema4D combined with ESR and anti-CCP had the highest sensitivity (99.35%). According to this result, a new model for jointly calculating RA activity of Sema4D,anti-CCP and CRP was constructed. Meanwhile another model is established by using the method of multivariate analysis.Model comparison results showed the the multiple regression algorithm method fitted the patients' disease activity better. The serum Sema 4D level effectively reflects moderate to severe RA activity. Sema4D levels can be used together with conventional RA biomarkers to increase the diagnostic power of RA activity. The multiple regression algorithm method is promising in disease activity calculation.

Establishing the Congruity amongst 2D:4D Ratio, Sex, and Socio-Behavioural Traits in Medical Students of Enugu State University of Science and Technology (ESUT)

The second-to-fourth digit (2D:4D) ratio is a sexually dimorphic trait that has previously been reported to be associated with socio-behavioral characteristics. This study examined the relationship amongst 2D:4D ratio, sex, and socio-behavioral characteristics among undergraduate medical students at Enugu State University of Science and Technology. A quantitative descriptive cross-sectional study design was adopted and a sample size of 120 was calculated using the Taro-Yamane formula. Convenience sampling method was utilized and the majority exhibited positive socio-behavioral characteristics such as emotional control and stress management abilities. There was a significant difference in the personality traits (conscientiousness and openness) between the male and female population at P&lt;0.050. However, there were no significant differences between the left and right digit ratio among the male and female population as P&gt;0.050 in each case. Also, there was no significant difference in the level of executive functions (emotional control, inhibition control, and stress intolerance) among the male and female populations as P&gt;0.050 in each case. There was a significant negative correlation between the right-hand 2D:4D digit ratio and level of conscientiousness among the population with (r=-0.196) at P&lt;0.050. However, no significant association was found between personality traits and executive functions. There was no significant difference between the participants’ digit ratio and gender. However, the male right-hand 2D:4D digit ratio was significantly associated with conscientiousness among the population. Additionally, no significant correlation was found between the participant’s digit ratios and their executive functions (emotional control, inhibition control, and stress tolerance).

Atomic structure calculations, and electron impact ionization cross-sections of W LXI

The present study provides a wide range of calculations of atomic structure data for the tungsten ion W LXI, that belongs to the silicon isoelectronic sequence. The fully relativistic Multi-configuration Dira-Hartree–Fock (MCDHF) method including configuration interaction (CI) is applied to the current ion. Calculated results of energy levels, oscillator strengths, and radiative rates of W LXI are presented. A set of two configuration state lists including the configurations of 3s23p2, 3s3p3, 3s23p3d, and 3p4 at different angular momenta (J) and parity (P) are considered in the configuration interaction calculations of level energies and oscillator strengths. To increase the accuracy of the results, the electronic correlations from higher orbitals, i.e., 7l orbitals are included in the calculations. Quantum electrodynamics effects such as vacuum polarization and self-energy are recalled in the CI calculations. Many more transitions in the soft x-ray region (between 20 and 200 angstroms) have been identified. The flexible atomic code package has been used to compute the electron impact ionization cross-sections of 3s23p2 3P0,1, 1D2 levels in silicon-like tungsten. The cross-sections of the transitions from the ground level in W LXI to the first levels in the 61st ionization of tungsten have been computed using FAC code. The total ionization cross-sections of the 3s23p2 at electron energy range from 5–35 keV are evaluated as well.

Color‐tunable luminescence and energy transfer of Eu3+/Tb3+ co‐doped borophosphate glass for anti‐counterfeiting

AbstractEu3+/Tb3+ co‐doped borophosphate glass was synthesized by a melt‐quenching method for the luminescence color‐tunable performance. Under the excitation of 373 nm, the Tb3+‐doped glass exhibited a very strong green emission at 544 nm, corresponding to the electron transition 5D4→7F5 of Tb3+. The emission intensity and lifetime of 5D4 level of Tb3+ dropped with the increase of Eu3+ co‐doping, whereas the emission intensity and lifetime of Eu3+ at 615 nm increased, confirming the existence of energy transfer from Tb3+ to Eu3+. Additionally, the color‐tunable luminescence of the borophosphate glass was also realized from green region to orange‐red region through shifting the Eu3+/Tb3+ ion concentration and the excitation light. There was little difference in emission intensity of Eu3+/Tb3+ co‐doped borophosphate glass under working temperature between 303 and 483 K, manifesting excellent thermal stability. This study indicated that the Eu3+/Tb3+ co‐doped borophosphate glass could become a promising candidate for the applications of anti‐counterfeiting technology.

First-principles study of luminescence and electronic properties of Ce-doped Y2SiO5.

The transition of energy from the 4f to the 5d state is a fundamental element driving various applications, such as phosphors and optoelectronic devices. The positioning of the 4f ground states and the 5d excited states significantly influences this energy shift. In our research, we delve into the placement of these states utilizing a hybrid density functional theory (DFT) combined with spin-orbit coupling (SOC) via the supercell method. Additionally, we scrutinize the transition energy, applying the constrained density functional theory (cDFT) approach in conjunction with the ΔSCF method. Our study illustrates that the synergy of cDFT and SOC generates a discrepancy of about 2% for Ce1 and 4% for Ce2 when comparing the calculated results to experimental data. Moreover, We have determined the positions of the 4f ground states to be 2.73eV above the Valence Band Maximum (VBM) for Ce1 and 2.70eV for Ce2. We also note a tight correlation between the 5d levels identified in the experimental data and the theoretical outcomes derived from wave function calculations at the CASPT2 accuracy level.

Optical properties, Judd-Ofelt analysis and energy transfer processes of Eu3+ doped ZnS quantum dots

Quantum dots (QDs) of ZnS doped with different Eu3+ ion concentrations were synthesized using a chemical method. The X-ray diffraction (XRD) pattern showed that the prepared QDs were crystallized in the Zincblende phase and their size was estimated to be approximately 3 nm. The XRD pattern and XPS spectrum analysis showed that Eu3+ ions replaced Zn2+ ions in the crystal lattice. For the first time, the optical properties of Eu3+ doped ZnS QDs were studied using photoluminescence excitation (PLE), photoluminescence (PL) spectra, and Judd-Ofelt (J-O) theory. Ωλ (λ = 2, 4, 6) parameters were calculated from the PLE spectra of the samples. The luminescence quantum efficiency and properties of the ligand field of the material were calculated and compared with those of other lattice hosts. The energy transfer (ET) processes from the ZnS host to Eu3+ ion and between Eu3+ ions were also discussed in detail. The ET process from the ZnS host to the Eu3+ ion occurred through the exchange interaction. The dominant interaction between Eu3+ ions in the ET process is the dipole-dipole mechanism, which is determined by fitting the decay curve of the 5D0 level to the Inokuti-Hirayama model.