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Evolution of microstructures and optical properties of gadolinium oxide with oxygen flow rate and annealing temperature
摘要： In this study, the effects of oxygen flow rate and annealing temperature on Gd2O3 structures and optical properties were systematically analyzed. Gd2O3 films were deposited on both quartz and ZnS substrates by magnetron sputtering and then annealed under vacuum at 700, 800, and 900 (cid:1). Restructure and phase transformation from cubic to monoclinic occur at different temperatures depending on the oxygen flow rate. The optical band gap, which is more sensitive to the annealing temperature than oxygen flow rate changes from 5.32 to 5.65 eV. The refractive index is approximately 1.75 at 550 nm and is adjustable by the oxygen flow rate. The transmittance of the ZnS substrate with Gd2O3 film exceeds 80% and reaches 82% at the 7.5–9.5 μm range. When ZnS is coated on both sides, the transmittance is increased to approximately 90%. Our results indicate that Gd2O3 films are promising new candidates for anti-reflective coatings in the infrared region.
关键词： Rare earths,Infrared materials,Structures,Optical properties,Gadolinium oxide,Magnetron sputtering
更新于2025-09-23 15:23:52
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Comparative study of Sm3+ ions doped phosphate based oxide and oxy-fluoride glasses for solid state lighting applications
摘要： The physical and luminescent properties of Sm3+-doped oxide and oxy-fluoride phosphate glasses were investigated. The glass samples with chemical composition of 69P2O5-10BaO-10ZnO-10Gd2O3-1Sm2O3 and 69P2O5-10BaO-10ZnO-10GdF3-1Sm2O3 were prepared by conventional melt quenching technique. The prepared glass samples were characterized with density, molar volume, refractive index, FTIR, UV-Vis-NIR, photoluminescence, radio luminescence, decay time profile, and CIE diagram. The density and refractive index of the oxide glass have higher values as compared to the oxy-fluoride glass. The FTIR spectra show the reduction of O-H group in oxy-fluoride glass. The characteristic peaks of Sm3+ are observed at 360, 372, 402, 438, 419, 473, 944, 1077, 1227, 1373, 1474, 1529 and1585 nm in UV-VIS-NIR spectra. These peaks are related respectively to the transitions from ground state 6H5/2 to 4D3/2, 6P7/2, 6P3/2, 4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6F1/2 excited states. From photoluminescence and radio-luminescence it is observed that the oxy-fluoride glass samples show better emission intensity than the oxide glass. The Judd-Ofelt theory (J-O theory) was used to find J-O intensity ?λ (λ=2,4 and 6) parameters and radiative properties such as transition probability, stimulated emission cross section and branching ratios for titled glasses. The trend observed in the J-O parameters is ?4 >?2 >?6. The transition probability, emission cross section and branching ratio have the highest values for the 4G5/2→6H7/2 transition. The CIE coordinates of the prepared glass samples are positioned in the orange region and the CCT value is 3776.105 for oxide and oxyfluoride glass. The oxy-fluoride glass has shorter decay time as compared to the oxide glass and it is recorded to be 1.62 and 1.32 ms for oxide and oxy-fluoride respectively. According to the results obtained in this work, it is obvious that these glass samples can be good candidate materials for producing cool orange light.
关键词： Judd-Ofelt theory,Oxy-fluoride glass,Rare earths,Photoluminescence,CIE coordinates
更新于2025-09-23 15:23:52
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Effect of structural and Eu3+ amount in TiO2 semiconductor material on downconversion photoluminescence properties
摘要： The search for new materials for application in energy production and conversion has identified inorganic oxides doped with rare earth ions as promising candidates for the construction of photovoltaic devices for energy conversion. This work presents the synthesis of TiO2 powders doped with Eu3+, using propylene glycol in the reaction medium, changing the europium percentage at 0.2, 3 and 7 mol%, and heat-treated at 700, 750, 800 and 900 °C for 8 h. The results of X-ray diffraction showed the formation of TiO2 polymorphs (anatase and rutile), both belonging to the tetragonal system and also the formation of europium titanate. The Rietveld refinement showed the deformation of the network parameters and volume of the unit cell, as well as the percent composition of the phases. Raman spectroscopy corroborated the results of XRD. Photoluminescence results showed that the synthesized materials have intense emission in the red region with the most intense band positioned at 614 nm assigned to the 5D0 → 7F2 transition of Eu3+ mainly in the sample with 3 mol% of Eu3+ heat-treated at 700 °C. The life time results showed that the photoluminescence of the materials are dependent on the crystalline structure, the host matrix in which the Eu3+ is localized, and the amount of the dopant in the sample. According to the results obtained in this work, the materials have the interesting downconversion effect, being a great absorber of UV–vis energy and converting that energy to the visible region. Materials with these photoluminescence properties associated with the structural properties are very interesting for use in the improvement of solar cells.
关键词： Rare earths,Titanium dioxide,Photoluminescence,Downconversion
更新于2025-09-23 15:23:52
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Stable Singlet Biradicals of Rare-Earth-Fused Diporphyrin-Triple-Decker Complexes Having Low Energy Gaps and Multi-Redox States
摘要： Dinuclear rare-earth (TbIII, YIII) triple-decker complexes with a fused-diporphyrin (FP) and two tetraphenylporphyrin (TPP) ligands were synthesized in neutral, dianionic, and diprotonated forms. The neutral forms have large open shell biradical character, as determined from the temperature dependency of the magnetic susceptibility measurements and theoretical calculations. The coupling value (J = ?1.4 kcal mol?1, ?487 cm?1) of the radical centers in the neutral form of the YIII complex indicates weak pairing interactions. Theoretical calculations on the neutral form reveal a significant biradical character (y = 68%). Furthermore, the TbIII complex exhibits multi-redox states, having more than eight clear peaks in the voltammetry curves. The optical (3700 nm, 0.33 eV) and electrochemical measurements (3400 nm, 0.36 eV) indicate that the neutral form has very small HOMO?LUMO energy gap. Despite the large biradical character, the neutral complexes are thermally stable and do not decompose on heating at 120 ?C. These complexes with unique characteristics are promising candidates for use in molecular electronics, optics, and spintronics.
关键词： rare earths,redox chemistry,radicals,sandwich complexes,porphyrinoids
更新于2025-09-23 15:22:29
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Rare Earth Element || Optimisation of Parameters for Spectroscopic Analysis of Rare Earth Elements in Sediment Samples
摘要： The rapid demand for rare earth elements (REEs) in recent years due to increased use in various technological applications, agriculture, etc. has led to increased pollution and prevalence of REEs in the environment. Therefore, monitoring for REEs in the aquatic environment has become essential including the risk assessment to aquatic organisms. Since direct determination of REEs in sediment samples prove difficult at times, due to low concentrations available and complex matric effects, separation and enrichment steps are sometimes used. In this work, various REEs were determined employing wet acid digestion and lithium metaborate fusion in our optimised analytical technique. A com-parison of the two analytical techniques was also made. The results obtained from the optimised ICP-OES radial view technique were in 5% agreement with the ICP-MS results from the same samples. The accuracy of the method was checked with the geological ref-erence material GRE-03 and found to be in reasonable agreement. We demonstrated that there is a consistent relationship between the signals of the REEs and nebuliser gas flow rates, plasma power and pump speed. The detection limits for all the REEs ranged from 0.06 mg L-1 Yb to 2.5 mg L-1 Sm using the ICP-OES fusion technique.
关键词： spectroscopy optimization,rare earths elements,fusion digestion and sediment,lithium metaborate
更新于2025-09-23 15:21:21
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Modulating the photocatalytic activity of TiO2 (P25) with lanthanum and graphene oxide
摘要： The modulation and tuning of the photocatalytic activity of commercial titanium dioxide (TiO2) P25 nanoparticles is demonstrated through the incorporation of lanthanum (La) and/or graphene oxide (GO). These composite materials, which could have applications in commercial products, were prepared by a two-step hydrothermal method from the corresponding precursors. The effect of La (0.05 - 2 mol%) and GO (5 m%) content on the crystal structure, morphology and photocatalytic activity of TiO2 was investigated by XRS, SEM, EDS, TEM, UV-visible DRS, point of zero charge, photoluminescence and the decolorization of methylene blue. Lanthanum modified the recombination rate of the photogenerated electron-hole charges on TiO2 by inducing an increase in the structural defects, which resulted in a significant suppression, up to 90%, of the photocatalytic activity in the UVA light region. In contrast, the addition of GO enhanced the photocatalytic activity of TiO2. Materials with tuned intermediate photoactivity within the entire range from high to very low were prepared by dosing appropriate amounts of La and GO species. The strategy of combining La and GO represents a useful and simple method for tuning or for suppressing the photocatalytic activity of TiO2 under UVA light irradiation in materials and consumer products using TiO2.
关键词： lanthanides,rare earths,titanium dioxide,graphene oxide
更新于2025-09-23 15:21:21
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Temperature Dependent Spectroscopic Properties of Cu <sup>+</sup> and Dy <sup>3+</sup> Co-Doped Phosphate Glass: Band Gap Analysis and Cu Nanocluster-Enhanced Dy <sup>3+</sup> Luminescence
摘要： This paper reports on the effects of temperature on light absorption and emission in Cu + and Dy3 + co-doped phosphate glass, which is of interest for photonic applications. First, the temperature dependence of the absorption edge of the glass in connection with Cu + ions absorption was assessed. A thermally-induced red shift attributed to Cu + ion-lattice interactions was observed and analyzed through optical band gap determinations in the context of indirect-allowed transitions. Application of the Varshni model for the dependence of the energy gaps with temperature allowed to estimate the 0 K energy gap at 2.87 (? 0.01) eV. Furthermore, Dy3 + photoluminescence (PL) along with Cu nanoparticles (NPs) absorption was monitored in real-time during an isothermal treatment by the in situ concurrent PL and absorption microspectroscopy technique. Periods of enhancement and quenching of Dy3 + emission linked to bidirectional energy transfer processes involving non-plasmonic Cu clusters and plasmonic Cu NPs were revealed. The formation of Cu NPs was promoted by tin(II) used as reductant. It is the first time to the author’s knowledge that the 0 K energy gap is estimated for a highly Cu +-doped glass and that the enhancement of Dy3 + PL by Cu clusters is exposed.
关键词： rare earths,glasses,luminescence,copper,nanoparticles
更新于2025-09-23 15:19:57
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Effect of Sodium and Fluorine Co-Doping on the Properties of Fluorite-Like Rare-Earth Molybdates of Nd5Mo3O16 type
摘要： Fluorite-like oxyfluorides NaLn4Mo3O15F (Ln = La, Pr, Nd), which relate to the Nd5Mo3O16 structural type, were obtained by solid-phase synthesis in the air. Codoping of the Nd5Mo3O16+δ family with sodium and fluorine led to the appearance of a piezoelectric effect and a reversible phase transition in oxyfluorides, accompanied by a jump in the conductivity and an anomaly of the permittivity of the compounds. In contrast to Nd5Mo3O16+δ, which possess mixed oxide-ion/electronic interstitial conductivity, the NaLn4Mo3O15F compounds can have oxygen conductivity of vacancy type. The highest conductivity offered by these materials is 3.2×10–2 S/cm at 700 °C. NaLn4Mo3O15F compounds were found to be hygroscopic and can be considered as potential proton conductors.
关键词： rare earths,sodium,phase transitions,fluorine,solid-phase synthesis
更新于2025-09-19 17:15:36
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Luminescent properties of Dy3+/Eu3+ doped fluorescent glass for white LED based on oxyfluoride matrix
摘要： Rare earth ion-doped fluorescent glass has become a hotspot due to its characteristics. This work shows that the prepared Dy3+ and Dy3+/Eu3+ doped glasses have white light emission under ultraviolet excitation. There is a higher yellow light/blue light (Y/B) value, indicating an increase in the covalentity of Dy-O, and decrease in the symmetry with the increasing concentration of dopants (Dy3+). The correlated color temperature (CCT) can be effectively reduced by the red light emission of Eu3+, and the order of influence of excitation wavelength on CCT is 395 nm > 382 nm > 365 nm .The delay curve demonstrates that the energy transfer from Dy3+ to Eu3+. The glass has the characteristics of anti-blue light damage and wide tunable color temperature, which illustrates that it has potential application in the field of white LED.
关键词： correlation color temperature,rare earths,oxyfluoride glass,Y/B intensity ratio,energy transfer
更新于2025-09-16 10:30:52
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Controlled patterning of upconversion nanocrystals through capillary force
摘要： Lanthanide-doped upconversion nanoparticles (UCNPs) can absorb near-infrared photons and convert them into visible and ultraviolet emissions. These nanomaterials possess extraordinary optical performance and hold potential as active platforms for a variety of technological applications. The ability to fabricate highly ordered nanoparticle-based photonic elements over a large area is of fundamental significance for luminescence tuning. Despite all the efforts made, however, large-area spatial patterning of UCNPs into ordered arrays with high controllability remains a challenge. In this study, we report a high-throughput strategy to pattern optical nanomaterials through the use of polymer microspheres and templated assembly of UCNPs. This technique utilizes capillary force to drive hybrid clusters into the physical template, resulting in large-area, spatially ordered arrays of particles. The findings reported in this work may promote the development of novel nonlinear optical devices, such as solid-state laser arrays, high-density optical storage, and anti-counterfeiting labels.
关键词： self-assembly,rare earths,patterning,upconversion nanoparticles
更新于2025-09-16 10:30:52