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This contribution exhibits the luminescence properties of BaHfO 3 : Tb3+ perovskite ceramics. The main objective is to know the effect on the luminescent properties of the trivalent Terbium ion (Tb3+), when it is introduced into a crystalline structure of high symmetry such as perovskite, where it can occupy any of two sites available in the lattice. The synthesis of these nanocrystal powders was conducted by hydrothermal route. X-ray diffraction pattern showed crystallized cubic perovskite type structure with space group Pm -3m. Luminescence spectra showed emission peaks which are associated to the 5D 4 →7F J (J = 2, 3, 4, 5, 6) typical transitions of trivalent terbium ion. Photoluminescence features were obtained as a function of Tb3+ doping concentration, being the sample doped with Tb3+ (5 at.%) the one presented the highest intensity peak emission. Also, some characteristics of the decay time, surface morphology, crystallite size and chemical composition of the studied powders, are shown. • Trivalent rare earth ions can present intense emissions in highly symmetrical cristal structures. • The hydrothermal technique allows obtaining nanostructured crystalline materials in short times. • The BaHfO3:Tb compound, has the highest luminescent emission with Tb (5% at.). [ABSTRACT FROM AUTHOR]

Near-infrared emission from phosphors Y 2 O 3 doped with Er3+, Li+ and Yb3+ ions under continuous excitation at 523 nm is reported. The downshifting emissions from 950 to 1090 nm correspond to transitions 4I 11/2 → 4I 15/2 of Er3+ ions and 2F 5/2 → 2F 7/2 of Yb3+ ions; the emissions from 1500 to 1600 nm correspond to transitions 4I 13/2 → 4I 15/2 of Er3+. The role of Yb3+ ions in phosphors of Y 2 O 3 doped with 4 at.% of Er, 2 at.% of Li and 2 at.% of Yb was to enhance the 950–1090 nm emissions around 3.5 times in comparison with Yb3+ free samples, through an energy transfer from the erbium 4I 11/2 level to the ytterbium 2F 5/2 level. Li+ plays an important role in such energy transfer process. With addition of Li+ an erbium 4I 13/2 and ytterbium 2F 5/2 level decay time increasing is also observed. A peak intensity increase in XRD patterns of the sample tri-doped revealed that the incorporation of lithium increases the phosphor crystallinity. FT-IR and SIMS studies confirmed that Li+ ions are incorporated into the Y 2 O 3 host. According to the optical and structural properties of these phosphors, they could be used to increase the photon absorption in photovoltaic systems. • Er3+, Li+ and Yb3+ doped Y 2 O 3 powders were synthesized by evaporation method. • Yb3+ luminescence is achieved through Er3+ to Yb3+ energy transfer. • Incorporation of Li+ increases the phosphor crystallinity. • Li+ ions are incorporated into the Yttria host according to XPS, SIMS and FTIR studies. • Incorporation of Li+ induces an erbium 4I 13/2 level decay time lengthening. [ABSTRACT FROM AUTHOR]

Zinc phosphate glasses, activated with Ag m n + clusters and Sm3+, were prepared by the conventional melt-quenching method. The X-ray diffraction patterns revealed that the samples remain amorphous for Ag and Sm3+ contents up to 3.0 and 1.0 mol%, respectively. The Raman and FTIR spectra showed that the main vibrational modes are associated with P–O bonds. The absorption coefficient spectrum of the Ag singly doped glass sample displayed a broad band centered at 318 nm, related to Ag m n + clusters, whereas those co-doped with Sm3+ showed, in addition to the Ag m n + cluster absorption, the well-known Sm3+ absorptions at 343, 360, 374, 401, 415, 438, 465 and 477 nm. The photoluminescence excitation spectrum of the Ag singly doped glass sample exhibited a broadband from 3 to 6 eV (207–413 nm), assigned to superposition of the Ag+: 4 d10 → 4d95s and Ag m n + cluster: S 0 → S 1 transitions, being the excitation into the Ag m n + clusters attractive for W-LEDs applications. The photoluminescence emission spectra of the Ag singly doped glass sample, upon Ag m n + cluster excitations at 340, 350 and 360 nm, displayed cold white light tonality, with (0.279, 0.300) CIE1931 chromaticity coordinates of 9453 K and bluish-white light tonality with (0.264, 0.276) and (0.259, 0.270) CIE1931 chromaticity coordinates and correlated color temperature values of 12901 and 14201 K, respectively. The global emission of the Ag and Sm3+ co-doped glass samples was, upon 340, 350 and 360 nm excitations, gradually tuned from the bluish and cold white region to the warm white one, as the Sm3+ content was increased, with correlated color temperatures in the 14201-2691 K range. The Sm.3+ emission bands, under excitations at 340 and 350 nm, were attained at expense of radiative and non-radiative energy transfer from the Ag m n + clusters, as revealed respectively by the sinks mounted on the Ag m n + cluster emission bands and the emission decay profile shortening in presence of Sm3+. Analysis of the Ag m n + cluster emission intensity and decay profiles, with the Dexter and Burstein models, showed that Ag m n + cluster cross-relaxation and/or non-radiative energy transfer to Sm3+ might be dominated by an electric quadrupole-quadrupole interaction. • Tunable white light emission in the zinc phosphate glass system activated with Ag and Sm3+. • Sensibilization of Sm3+ by radiative and non-radiative energy transfer from Ag m n + clusters. • Detailed description of the energy transfer pathways from Ag m n + clusters to Sm3+. [ABSTRACT FROM AUTHOR]

Hexagonal ZnO nanocolumns were synthesized by chemical bath deposition on previously deposited ZnO nanoseeds on Corning glass substrates, at deposition temperatures from 300 to 550 °C in steps of 50 °C, by ultrasonic spray pyrolysis technique. The ZnO nanoseeds were previously suspended in the spraying solution, with and without ultrasonic dispersion. Scanning Electron Microscopy study of surface morphology was carried out revealing the formation of hexagonal ZnO nanocolumns; the smaller diameters were obtained for ZnO seed layers deposited at substrate temperature between 400 and 450 °C. The best vertical alignment was observed on nanocolumns grown from ultrasonic-dispersed ZnO nanoseeds deposited at 400 °C. Raman spectroscopy was used to evaluate the crystal quality of the ZnO nanocolumns, a relationship was determined between nanocolumns stress with a shift to lower wavenumbers of E 2 H mode, the ZnO seeds deposition temperature and the nanocolumn diameters. Intrinsic defects of ZnO nanocolumns were studied with photo and cathodoluminescence spectroscopy. Also, photoluminescence life time measurements were carried out. Samples grown from ultrasonically dispersed ZnO seeds generated nanocolumns with greater stoichiometry and purity. • ZnO NCs were successfully grown by combination of USP and chemical bath techniques. • Seed layer is essential to a favorable morphology of ZnO nanocolumns. • Ultrasonically dispersed seeds favor a better alignment of the ZnO NCs. • ZnO seeds deposition temperature impact in nanocolumns diameters. • ZnO NCs with high surface exposure area have strong visible PL emission. [ABSTRACT FROM AUTHOR]

In this paper, luminescent properties of Europium trivalent ion in the matrix with unbalanced charge of barium hafnate under UV radiation, with special emphasis on the 5D 0 → 7F 0 transition are reported. The synthesis was conducted by the hydrothermal route at 200 °C with a reaction time of 90 min using chlorides as raw materials. In order to determinate the luminescent quenching concentration, the samples were doped with different amounts of Europium trivalent ions being the sample doped with 1 and 3% at of Eu3+ which shows the highest luminescent emission. X-ray diffraction analysis showed that the material crystallize in the cubic perovskite structure with space group Pm-3m. The Energy Dispersive Spectroscopy (EDS) shows there are not elements other those that Ba, Hf, O and Eu in the synthesized material. Photoluminescent emission spectra show peaks of emission associated with the 5D 0 → 7F J (J = 0,1,2,3,4) transitions, characteristics of europium ion. The 5D 0 → 7F 0 transition centered at 580 nm showed an unusual great intensity when it was excited with the wavelength associated with the charge transfer band (272 nm). Finally the decay time was measured in the 5D 0 → 7F J (J = 0,1,2,3,4) transitions using the sample doped with Eu3+ (3% at). • Powders of Eu doped BaHfO 3 were synthesized. • Effect of Eu dopant concentration was studied. • UV radiation effect in BaHfO 3 :Eu was discussed. • Decay time of 5D 0.→ 7F 0 transition was measured [ABSTRACT FROM AUTHOR]

Up-conversion emission from HfO 2 nanoparticles, as a host lattice, doped with Er 3+ and Yb 3+ ions and codoped with alkaline cations Li + and Na + obtained. The HfO 2 nanoparticles, about 80 nm in diameter, were synthesized by the hydrothermal method at 200 °C for 1.3 h, and an additional heat treatment at 1000 °C was necessary to ensure the dopants incorporation into the host lattice. These nanoparticles were studied by means of XRD, Raman Spectroscopy, SEM, EDS, PL, CL, and up-conversion luminescence. First, the doping was performed with Er 3+ ions in different percentages. The photoluminescence and cathodoluminescence studies showed an inefficient emission, and only at 7 at % Er 3+ ions, the sample presented emissions at 522, 545, and 656 nm corresponding to the transitions of the Er 3+ ions. So, codoping was carried out, and HfO 2 : Er 3+ /Yb 3+ generated an efficient conversion process. The atom percentage of Yb 3+ ions was fixed (7 at % Yb 3+ ), and the Er 3+ content was varied, showing the highest emission intensity at 3 at % Er 3+ ions. Subsequently, the up-conversion emission intensity was optimized by varying the percentage of Yb 3+ ions and keeping the Er 3+ ion content fixed (3 at %). Adding cations such as Na + and Li + in different percentages, a notable improvement of the up-conversion emission intensities in the HfO 2 : Er 3+ /Yb 3+ nanoparticles was obtained. The up-conversion emission bands observed were located at ∼523 and 544 nm, corresponding to the electronic transitions 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 , respectively. While the bands at ∼652 and 673 nm correspond to the transition 4 F 9/2 → 4 I 15/2 , respectively. The excitation of these materials with infrared radiation (980 nm) produced noticeable emission bands in the red spectral range, whereas excitation with accelerated electrons (CL) generated prominent bands in the green region., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Nanoscale particles described by Mie resonance in the UV-vis-NIR region are in high demand for optical applications. Controlling the shape and size of these particles is essential, as it results in the ability to control the wavelength of the Mie resonance peak. In this work, we study the extensive scattering properties of gadolinium niobate particles with complex bar- and cube-like shapes in the UV-vis-NIR region. We perform our experimental analysis by characterizing the morphology and extinction spectra, and our theoretical study by implementing a Mie scattering model for a distribution of spherical particles. We can accurately model the size distribution and extinction spectra of complex shaped particles and isolate the contribution of aggregates to the extinction spectra. We can separate the contributions of dipoles, quadrupoles, and octupoles to the Mie resonances for their respective electric and magnetic parts. Our results show that we can tune the broad Mie resonance peak in the extinction spectra by the nanoscale properties of our system. This behavior can aid in the design of lasing and luminescence-enhanced systems. These dielectric gadolinium niobate submicron particles are excellent candidates for light manipulation on the nanoscale., (Creative Commons Attribution license.)

Currently, there is a growing interest in the development of multi-colored materials based on the combination of two or more systems (organic or inorganic) as a strategy to take advantage of their combined physical or chemical properties. These multi-colored materials have found potential applications as sensors, amplifiers, and optical fibers. In this work, the physical characteristics of poly(methyl methacrylate) (PMMA) doped with Terbium(III)-tris-(2,2,6,6-tetramethyl-3,5-heptanedionate) (Tb(tmhd) 3 ) at 1.57-1.58 mmol and Rhodamine B (RhB) at different concentrations were analyzed. The emission obtained from these samples (multichromophoric samples) varied as function of RhB concentration due to an efficient energy transfer process (33-65%). The role of PMMA as inert matrix that assists in the recombination process was confirmed by FTIR and Raman spectra analysis. Moreover, an improvement in thermal resistance of the materials was observed due to the presence of the dopants during the polymerization process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019. Published by Elsevier B.V.)

Ceramic powders of Sr1-1.5xYbxTiO3 (x = 0.0, 0.0125, 0.025, 0.05 and 0.075) solid solutions were synthesized by the polymeric complex method. The crystal structure, microstructure and optical properties of the powders annealed at 800 °C for 1 h were investigated by X-ray diffraction, scanning electron microscopy, and diffuse reflectance and photoluminescence spectroscopy, respectively. All the solid solutions exhibit a cubic perovskite-like structure. The reflectance spectra show a broadband below 400 nm ascribed to the ligand-to-metal charge transfer (LMCT) O2- → Ti4+ fundamental state. The Yb3+ (λem = 980 nm) excitation spectra show a broadband being also compatible with the LMCT O2- → Ti4+ state, indicating the energy transfer from the host to the Yb3+. The sample with x = 0.025 presents the highest emission intensity upon near UV excitation, which is further enhanced when the powder is treated under an oxygen-rich atmosphere. The luminescence quenching of Yb3+ is explained as due to defects associated with O2- and Sr2+ vacancies. Finally, it is shown that the solid solutions may downshift photons from UV to wavelengths where a crystalline-silicon photovoltaic solar cell has a higher spectral responsivity.

The spray pyrolysis technique has been extensively used to synthesize materials for a wide variety of applications such as micro and sub-micrometer dimension MOSFET´s for integrated circuits technology, light emitting devices for displays, and solid-state lighting, planar waveguides and other multilayer structure devices for photonics. This technique is an atmospheric pressure chemical synthesis of materials, in which a precursor solution of chemical compounds in the proper solvent is sprayed and converted into powders or films through a pyrolysis process. The most common ways to generate the aerosol for the spraying process are by pneumatic and ultrasonic systems. The synthesis parameters are usually optimized for the materials optical, structural, electric and mechanical characteristics required. There are several reviews of the research efforts in which spray pyrolysis and the processes involved have been described in detail. This review is intended to focus on research work developed with this technique in relation to high- K dielectric and luminescent materials in the form of coatings and powders as well as multiple layered structures.

There is little information concerning the use of rare earths as dopants of Al2O3. This paper presents the preparation method and the results of studying the thermoluminescence characteristics of Al2O3:Eu exposed to ultraviolet light. Phosphor powder was obtained by the evaporation method. Optimum dopant concentration was 10% at an evaporation temperature of 700 degrees C. The powder obtained was submitted to thermal treatments at high temperatures in order to stabilise the traps. Diffraction patterns showed amorphous powder up to 500 degrees C; as the temperature was raised crystalline phases of Al2O3 appeared. The photoluminescence spectrum induced by 250 nm UV light exhibited four well defined peaks characteristic of the Eu3+ ion. The glow curve exhibited two peaks at 180 and 350 degrees C. The sensitivity of Al2O3:Eu was 10 times lower than Al2O3:C. The thermoluminescence response was linear from 2.4 to 3000 microJ.cm(-2) of spectral irradiance, and the fading 2% in a month. From these results it can be concluded that Al2O3:Eu has potential as an UV dosemeter.