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The inverted classroom is a methodology that allows learning drivers to adapt efficiently, and in a multidisciplinary way, to the contents of the area we practice, to the objectives and to the abilities of the student, generating commitments from both the teacher and the student for their professional success. For the research, a quasiexperimental methodology was used with a student population of fifty young people of both sexes, with a control and experimental group, for whose execution four didactic procedures were carried out with their respective input-output evaluations. The analysis of variance (ANOVA) showed the permanent improvement in the learning of natural sciences with increasing trends (means) and decreasing trends (standard deviation); that is, better learning and the homogenization of the group. Studies on the subject have shown its effectiveness in learning processes and where positive reactions as well as reorientation of students are evident.

Oxyfluorotellurite glasses in the form of 60TeO2–(15–x)Li2O–25ZnO–xLiF, 65TeO2–(15–x)Li2O–20ZnO–xLiF (with x = 0, 5, 10, and 15 in mol %), and 65TeO2(20–x)Li2O–15ZnO–xLiF (x = 0, 5, 10, 15, and 20 in mol %) have been synthesized. The amorphous state of the samples was assessed using X-ray diffraction (XRD). Density, molar volume, and oxygen packing density (OPD) were measured. The thermal properties were analyzed from room temperature to 873 K using a differential scanning calorimeter (DSC). The structural and optical properties were investigated using Fourier-transform infrared (FTIR), Raman, and ultraviolet–visible (UV–Vis) spectroscopies. The results demonstrated that the OPD values decreased with increasing LiF content, and this decrease can be attributed to a decrease in the total oxygen number. The structural characterization revealed that the addition of LiF reinforces the vitreous network causing the formation of F–Te–O bonds within a more connected network. In addition, increasing the LiF content improved the glass’s thermal properties, with a decrease in the glass transition temperature and an increase in thermal stability, which facilitates the glass manufacturing process. However, this feature is dependent on ZnO concentration.

The subject of Phonology has always presented a complex learning curve. Most teachers consider it very difficult to teach the production of sounds, as well as their description to discriminate them. This, which is essential for the learning of phonology, does not receive the importance due to the cloister when this course is taught. The purpose of this research has been to demonstrate how the use of ICT positively influences the learning of phonology. The observed reality was interpreted from the positivist paradigm, using the hypothetical deductive method, with a quantitative approach, of an applied type, with an experimental design. Four treatments were applied which were evaluated with each pretest and posttest to 20 student-collaborators. These instruments were validated by seven experts. The normality test has been processed with Shapiro-Wilk (0.011). Intentional non-probabilistic sampling was used; Non-parametric statistics were used with the Wilcoxon signed rank tests, the Kruskal-Wallis test and the Bonferroni post hoc comparison tests with SPSS 26. It was shown that there are significant differences in the results of each treatment in terms of regarding the use of ICT in the learning of Phonology. The score obtained in treatment 4 was significantly better than treatment 1. Finally, there was a significant improvement between the pretest of treatment 1 (8.35) and the posttest of treatment 4 (18.40) with respect to the outstanding achievement level. on a vigesimal basis. Non-parametric statistics were used with the Wilcoxon signed rank tests, the Kruskal-Wallis test and the Bonferroni post hoc comparison tests with SPSS 26. It was shown that there are significant differences in the results of each treatment in terms of regarding the use of ICT in the learning of Phonology. The score obtained in treatment 4 was significantly better than treatment 1. Finally, there was a significant improvement between the pretest of treatment 1 (8.35) and the posttest of treatment 4 (18.40) with respect to the outstanding achievement level. on a vigesimal basis. Non-parametric statistics were used with the Wilcoxon signed rank tests, the Kruskal-Wallis test and the Bonferroni post hoc comparison tests with SPSS 26. It was shown that there are significant differences in the results of each treatment in terms of regarding the use of ICT in the learning of Phonology. The score obtained in treatment 4 was significantly better than treatment 1. Finally, there was a significant improvement between the pretest of treatment 1 (8.35) and the posttest of treatment 4 (18.40) with respect to the outstanding achievement level. on a vigesimal basis. It was shown that there are significant differences in the results of each treatment regarding the use of ICT in the learning of Phonology. The score obtained in treatment 4 was significantly better than treatment 1. Finally, there was a significant improvement between the pretest of treatment 1 (8.35) and the posttest of treatment 4 (18.40) with respect to the outstanding achievement level. on a vigesimal basis. It was shown that there are significant differences in the results of each treatment regarding the use of ICT in the learning of Phonology. The score obtained in treatment 4 was significantly better than treatment 1. Finally, there was a significant improvement between the pretest of treatment 1 (8.35) and the posttest of treatment 4 (18.40) with respect to the outstanding achievement level. on a vigesimal basis.

In recent years, infrared emitting luminescence nanothermometers have attracted significant attention because their potential for the development of new diagnosis and therapy procedures. Despite their promising applications, concerns have been...

Un método de adsorción utilizando la resina Dowex™Marathon™ WBA ha sido desarrollado con el fin de evaluar larecuperación de ácido cítrico producido por fermentación sumergida. Para determinar la viabilidad de este método de separación, la resina fue evaluada a diferentes condiciones de temperatura (30 – 70 °C) y pH (1.5 – 6.5). Los resultadosmostraron que a pH bajo, se mejora la adsorción de ácido cítrico, a través de la cual, se recupera el 85% del ácido y se obtiene una pureza del 92%. Esto representa una capacidad máxima de adsorción de 0.46 g de ácido cítrico por gramo de resina empleada.

This study aimed to evaluate the physical–chemical properties (particle size, zeta potential, encapsulation, and thermal stability), antioxidant properties, antibacterial properties and casein-flavonoid interaction studies of soluble complexes, called caseinates of red propolis. The caseinates of red propolis were successfully prepared using the spray-dryer technique, which presented two populations of nanometre and micrometre particles, and were able to encapsulate flavonoids and isoflavonoids from the red propolis extract as a soluble complex. SEM analysis demonstrated casein nanoparticles and fat globules combined with lipophilic compounds (terpenes) from red propolis extract. FTIR analysis proved the encapsulation of flavonoids into caseinates. The thermogravimetric assays demonstrated thermal stability of red propolis caseinates and DTA analysis observed the denaturation during the coagulation temperature. The fluorescence, antioxidant, Folin–Ciocalteu method and chromatographic assays have shown that flavonoids bind to the amino acid residues present in the casein protein matrix, demonstrating a reversible interaction between flavonoids and casein amino acids. Dissolution studies prove the formation of a casein-flavonoids soluble complex and can bring benefits and increase the process of absorption of flavonoids by biological membranes. Despite the interaction of flavonoids with casein amino acids, caseinates of red propolis demonstrated antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa. The caseinates of red propolis can be easily incorporated in foods such as cakes, pies, dairy and cocoa such as foods bio-preservatives. The caseinates of red propolis can be manufactured by the pharmaceutical and nutraceuticals industries as intermediary bioproduct in the powder form for supplements, capsules and oral emulsion systems for beverages as yogurts.

Este artigo investiga o processo de preservação arquitetônica a partir da aplicação de técnicas fotogramétricas para a documentação digital. Adotou-se, como objeto empírico, a Igreja Nossa Senhora Mãe dos Homens, localizada em Coqueiro Seco, no estado de Alagoas, Brasil. Datada de 1790, consiste em um dos exemplares da arquitetura religiosa mais antigo do estado, protegida pela União por meio do tombamento desde 2011 e com previsão de uma obra de restauro em suas estruturas. O objetivo deste artigo é documentar o estado anterior à intervenção na igreja, descrevendo o processo de documentação patrimonial e utilizando como recurso técnicas fotogramétricas mistas. Metodologicamente, foram realizadas pesquisas bibliográficas e documentais; levantamentos fotográficos da Igreja, seguindo os princípios da restituição fotogramétrica interativa e do Dense Stereo Matching (DSM); construção de modelos geométricos por meio do software PhotoModeler Scanner e vetorização das fachadas utilizando-se uma ferramenta CAD. Como resultados, registraram-se as fachadas principais do bem com a fotogrametria e disponibilizou-se a documentação produzida. Além disso, o artigo traz uma reflexão acerca das limitações das técnicas utilizadas, enfatizando a relevância do uso híbrido das tecnologias disponíveis para o registro e democratização do acesso à documentação da arquitetura de interesse cultural.

We report the microwave-assisted synthesis of binary doped optical-magnetic up/downconverting NaGdF4:RE and iron oxide/SiO2/NaGdF4:RE nanoparticles. The morphological characteristics were finely tuned from elongated rod-shaped to ovoidal nanoparticles. The (Yb, and Er) activated particles provided an excellent up/down conversion luminescence emission in the green and mid-infrared region under excitation of 980 nm, whereas the (Ce, and Eu) activated systems exhibited a strong red emission via the Gd3+ sublattice upon excitation in the UV region. The magnetic hysteresis at 300 K for β-NaGdF4:RE showed typical signatures of a paramagnetic system, whereas iron oxide/SiO2/β-NaGdF4:RE exhibited superparamagnetic behavior along with a Curie-like component. The luminescence quenching effects induced by the presence of iron oxide phase have been validated through comparing the emission/lifetime decay curves. In addition to the excellent optical and magnetic properties, these materials show remarkably high longitudal and transverse relaxivity values (for Fe and Gd) and thus are potential candidates for T1 and T2-weighted bioimaging.

Hexagonal LaF3:Yb3+/Ln3+ and tetragonal LaOF:Yb3+/Ln3+ (Ln = Ho, Tm, Er) have been successfully prepared via a two-step reaction, which includes a facile aqueous ligand free solution method and the following heat treatment of the as-prepared LaF3 precursor. The phase formation evolution from LaF3 to LaOF with different phase structures was characterized by X-ray diffraction (XRD), scanning electron microscopy, Fourier transform infrared, and Raman spectroscopy. At an annealing temperature of 500 °C pure hexagonal LaF3:Yb3+/Ln3+ (Ln = Ho, Tm, Er) nanoparticles with an average size of 32 nm were obtained and they showed a strong visible upconversion and a modest infrared emission upon 976 nm laser excitation. Further, using an annealing temperature of 900 °C, tetragonal LaOF:Yb3+/Ln3+ (Ln = Ho, Tm, Er) nanoparticles with a size of around 44 nm were obtained (obtained from XRD) and an expressive enhancement in the emission of the VIS and near-infrared regions was observed. These results envision applications that require efficient emissions such as fluorescent and thermal images, and LaF3 nanocrystals have recently been widely explored for applications in biological systems.

We demonstrate the feasibility of an unconventional excitation of Nd3+ at 1064 nm by a photon-avalanche-like mechanism, which involves an energy looping due to energy transfer among excited Nd3+ followed by resonant excited-state absorption.

Freeze- and spray-dried inclusion complexes (ICs) of chlorhexidine (CHX) in β-cyclodextrin were characterized by Fourier transform (FT)-Raman, 1H nuclear magnetic resonance (NMR), and photoacoustic spectroscopy. The active Raman modes of CHX were simulated using the density functional theory. By considering semiempirical calculations, it was observed that the guest penetrates on the wider rim of the host in a proportion of 1:2. We observe from the FT-Raman analysis that the drying method influences the CHX:β-cyclodextrin conformational adjustment by the rearrangement of hydrophilic biguanides of the guest. The photoacoustic spectroscopy results inferred that the freeze-drying method provided a better inclusion due to a lower interaction between phenyl groups and hexamethylene of CHX. The freeze-dried IC achieved a faster dissolution pattern. These ICs provided immediate drug dissolution profiles in an aqueous medium better than a pure drug. The release profiles of freeze- and spray-dried ICs were explained by Fickian diffusion. These data support further planning and development projects of novel immediate release systems based on CHX.

In recent years, an unconventional excitation of trivalent neodymium ions ( N d 3 + ) at 1064 nm, not resonant with ground-state transitions, has been investigated with the unprecedented demonstration of a photon-avalanche-like (PA-like) mechanism, in which the temperature increase plays a fundamental role. As a proof-of-concept, N d A l 3 ( B O 3 ) 4 particles were used. A consequence of the PA-like mechanism is the absorption enhancement of excitation photons providing light emission at a broad range covering the visible and near-infrared spectra. In the first study, the temperature increase was due to intrinsic nonradiative relaxations from the N d 3 + and the PA-like mechanism ensued at a given excitation power threshold ( P t h ). Subsequently, an external heating source was used to trigger the PA-like mechanism while keeping the excitation power below P t h at room temperature. Here, we demonstrate the switching on of the PA-like mechanism by an auxiliary beam at 808 nm, which is in resonance with the N d 3 + ground-state transition 4 I 9 / 2 → { 4 F 5 / 2 , 2 H 9 / 2 } . It comprises the first, to the best of our knowledge, demonstration of an optical switched PA, and the underlying physical mechanism is the additional heating of the particles due to the phonon emissions from the N d 3 + relaxation pathways when exciting at 808 nm. The present results have potential applications in controlled heating and remote temperature sensing.

In this work, we report a potential nanothermometer with high thermal sensitivity based on sodium niobate (NaNbO3) nanocrystals doped and co-doped with Tm3+ and Tm3+/Yb3+, respectively, synthesized by the Pechini (sol–gel) method. Under anti-Stokes excitation (1064 nm) it was investigated the fluorescence intensity ratio ( F I R = I 700 n m / I 660 n m ) of the 700 nm (3F2,3 → 3H6) and 660 nm (1G4 → 3F4) emissions, which are within the first biological window, as a function of temperature in the 300–493 K range. Relative thermal sensitivities constant with the temperature were obtained, with values of 1.60% K−1 and 1.86% K−1 for NaNbO3:1%Tm3+ and NaNbO3:1%Tm3+/1%Yb3+ samples, respectively, which is the highest value in the literature for Tm3+/Yb3+ co-doped system under 1064 nm excitation. The importance of the anti-Stokes excitation relies on the fact that emissions (up and downconversion) in general increase with the temperature, making possible obtaining fluorescence and thermal images with better resolutions. Additionally, as both excitation and emission are within the biological windows, these nanoparticles might be useful for biological applications.

Orthorhombic sodium niobate (NaNbO3) nanocrystals, transparent in the visible and near-infrared, were synthesized by using the Pechini's sol-gel method. Experiments were performed to measure the first hyperpolarizability of the nanoparticles by using a pulsed laser operating at 1064 nm. The hyper-Rayleigh scattering technique was used to analyze the second harmonic scattered light generated by the nanocrystals. By using the external reference method, with para-nitroaniline as the standard reference, we determined the NaNbO3 hyperpolarizability per nanoparticle volume (0.93 × 10−29 esu/nm3) for the first time, and show that the effective second-order susceptibility has the same order-of-magnitude as LiNbO3 and KNbO3 nanocrystals.

An extension of Drude–Lorentz model based on the fractional approach was used to investigate quantitative measurement of refractive index as a function of wavelength of Tellurite glasses. Tellurite glass samples were synthesized by conventional melt-quenching method with the composition of 65TeO2–15Li2O–20ZnO undoped and doped with different concentrations of Er2O3. Refractive index measurements were performed using the Brewster angle technique with polarized lasers at 442, 532, 594 and 633 nm as light source. From the Sellmeier’s coefficient it was possible to obtain the behavior of refractive index from 0.35 to 1.8 μm. The analytical solution obtained from the generalized Drude–Lorentz model was used to investigate the experimental data of refractive index behavior obtained by the two-pole Sellmeier’s equation showing that the mean polarizability increases with Er2O3 concentration and this behavior can be related to a collective fractal character of the material.

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.

Recently, mixed-former glasses have attracted a large attention due to the appropriate combinations of the chemical, physical and optical properties of each glass former. In this scenario, the optical properties of fluoroborate glasses doped with rare earth ions is of importance due to their good transparency window from ultra-violet to near-infrared region, good rare-earth solubility, long excited state lifetime of such ions, and high mechanical strength. In this work, we had studied the optical properties of the Tb3+ doped fluoroborate glasses, focusing on the concentration dependent behavior of luminescence dynamics of 5D3 and 5D4 exited states of this ion. The blue-to-green intensity ratio, lifetime of the emitting levels under various excitation wavelengths, cross-relaxation rate, ion-ion critical distance and emission gain bandwidth are calculated.

The use and applications of infrared emitting rare-earth luminescent nanoparticles as nanothermometers have attracted a great deal of attention during the last few years. Researchers have regarded rare-earth doped luminescent nanoparticles as appealing systems due to their reliability, sensitivity and versatility for minimally invasive thermal sensing in nanomedicine. The challenge of developing nanothermometers operating over 1000 nm with outstanding brightness and enhanced sensitivity is being constantly addressed. In this sense, this work explores the potential of Tm3+ emissions at around 1.23 and 1.47 μm, under excitation at 690 nm, for ratiometric thermometry in Tm3+ doped LaF3 nanoparticles. The temperature dependence of the 1.23 μm emission band, which cannot be observed in systems such as NaNbO3:Tm, was demonstrated to be very effective and presented a relative thermal sensitivity as high as 1.9% °C−1. The physical mechanisms behind the strong thermal dependences were explained in terms of multiphonon decays and cross-relaxations. As a proof of concept, the nanothermometers presented were capable of accessing the basic properties of tissues in an ex vivo experiment using thermal relaxation dynamics.

T m 3 + / H o 3 + -codoped low silica calcium aluminosilicate (LSCAS) glasses were prepared and characterized using optical absorption, luminescence decay, and thermal lens techniques. The emission band at 2.0 µm exhibited an enhancement when the Ho concentration was increased. The luminescence quantum efficiency values were determined for both 3 F 4 and 5 I 7 levels of T m 3 + and H o 3 + ions, respectively. The high decrease of the quantum efficiency of the 3 F 4 ( T m 3 + ) level for high H o 3 + concentration evidenced efficient energy transfer processes from T m 3 + to H o 3 + . The heat generated in the energy transfer processes were estimated via a thermal lens experiment, and a rate equation model was proposed to explain the obtained result. The experimental and estimated parameters with the proposed theoretical model are in good agreement. Finally, the results of this work suggest the T m 3 + / H o 3 + -codoped LSCAS is a promising material for applications using the emission around 2.0 µm that is of great interest for biomedical applications.

Supporting Information

Photon avalanche (PA) is a fascinating mechanism for exciting trivalent rare-earth ions (REI3+). It occurs when cross-relaxation mechanisms provide a non-zero population at a lower excited state. Then, photons that are nonresonant with ground-state transitions can be increasingly absorbed from this level. PA has been demonstrated with some REI3+-doped materials under specific excitation wavelengths and temperature regimes. Here the PA-like was observed on NdAl3(BO3)4 particles at some fixed temperature values (within 23 °C ≤ T ≤ 215 °C), while the excitation power was increased. In this study, the PA-like is associated to a cross-relaxation mechanism [4F3/2, 4I9/2] → [4I15/2, 4I15/2]. After multiphonon emissions, the population of Nd3+ ions at the 4I11/2 state doubles at every iteration, a process followed by a resonant excited-state absorption (4I11/2 → 4F3/2). In this case, the excitation power threshold decreased threefold. In a second round of experiments, we demonstrate for the first time the triggering the PA-like mechanism by increasing the temperature (27 °C ≤ T

Hexagonal LaF

El trauma, la osteomielitis, las resecciónes de tumores óseos y el tratamiento de las deformidades congénitas son las principales causas de deficiencia de hueso. En los escenarios clínicos referidos los injertos autólogos son el tratamiento de elección. No obstante, los sitios anatómicos para obtener injertos óseos son limitados, la procuración dolorosa y con riesgos de infección. Por lo anterior, se han explorado nuevos abordajes experimentales para la obtención de una cantidad suficiente de hueso autólogo útil para autotrasplante como la ingeniería tisular basada en el uso de factores de crecimiento y células madre pluri-potenciales. Nosotros desarrollamos un modelo experimental de formación de hueso heterotópico en los músculos rectos del abdomen en perros. Este modelo consiste en implantes envueltos en epiplón constituidos por esponjas de colágena, polvo de hueso desmineralizado, cloruro de cálcio, trombina y plasma rico en plaquetas como fuente de factores de crecimiento. Aunque este es un modelo eficiente para la formación de hueso heterotópico, no es adecuado para autotrasplante debido a que requiere al menos cuatro meses para la formación de hueso maduro. El objetivo de este trabajo fue acelerar la producción de hueso. Para lo anterior, primero se aislaron los constituyentes histológicos más representativos del hueso autólogo (tejido conectivo/inflamatorio periespicular, hueso maduro e inmaduro, tejido adiposo) y se purificó de estos el RNA total que fue utilizado a su vez para obtener la cinética de expresión genética de los principales factores de crecimiento y diferenciación por medio de RT-PCR. Posteriormente, los factores expresados en mayor cantidad y con mayor rapidez de síntesis fueron vi producidos en hojas de tabaco. Nuestros resultados mostraron que las proteínas morfogénicas óseas 2 y 7, y el factor de crecimiento transformante-1 fueron los factores principales, y su incorporación como proteínas recombinantes en las esponjas de colágena favorecieron la formación de hueso heterotópico en sólo un mes, lo cual es de mayor utilidad en autotrasplante.

The scientific community has, for a long time, been fascinated with lanthanide-doped dielectric nanocrystals. This is mainly due to the fact that their narrow band emissions, large Stokes and anti-Stokes shifts, long lifetimes, superior stability, low toxicity, feasibility to many excitation and emission wavelengths, weak fluorescence background, and, in several situations, large penetration depth give rise to a wide range of applications in optical and electronic devices. Additionally, since they have a unique 4f orbital configuration and biocompatibility, they are considered to be very promising in theranostics. In fact, many works report on the new perspectives on diagnosis, therapy, fluorescence imaging, and thermometry offered by lanthanide-doped nanoparticles. Recently, however, the attention has been placed on near-infrared imaging due to a deeper light penetration, absence of autofluorescence, high signal-to-noise ratio, and low tissue damage. This, in turn, is reflected in a huge demand for luminescence nanoparticles operating in spectral ranges known as biological windows. In this chapter, we report the main synthesis methods utilized for the production of lanthanide-doped dielectric nanoparticles, the recent progresses of their diagnostic and therapeutic applications, and the enhancement of their spectroscopic properties as achieved by different methods of surface functionalization and/or coating.

Er3+/Tm3+/Yb3+ tri-doped YNO phosphors were obtained by the solid-state reaction method. X-ray diffraction, Raman spectroscopy, and FE-SEM were employed for characterization of the materials, and no significant structural changes have been noticed. The materials exhibited red, green and blue (RGB) upconversion emissions under 980 nm excitation. The increase of the Tm3+ concentration reduced the blue and green UC emissions due to possible Tm3+-Tm3+ and Er3+-Tm3+ energy transfer processes, respectively. White UC emission with CIE color coordinates equal to x = 0.31 and y = 0.35 has been obtained in the YNO:0.5%Er3+2.0%Tm3+20%Yb3+ composition under 64.5 mW/cm2. The tri-doped systems presented color tunability behavior indicating that multicolor, such as white light, can be easily achieved by adjusting of the Tm3+ and Yb3+ contents.

BaBi2Nb2O9:Li+/Tm3+/Er3+/Yb3+ phosphors were successfully synthesized by the high-temperature solid-state method and up-conversion white-light emission has been achieved by tuning of the Tm3+ and Li+ contents. X-ray diffraction and room temperature photoluminescence were used, respectively, to investigate the structural and optical properties of the luminescent systems. Decay dynamics of 4F9/2 levels in BBN:Tm3+/Er3+/Yb3+ and BBN:Er3+/Yb3+ phosphors have been analyzed to study the energy-transfer mechanism between Er3+ and Tm3+ ions. The introduction of Li+ ions into the BBN:0.5%Tm3+0.05%Er3+8%Yb3+ has induced an adjustment of tristimulus values shifting the chromaticity color coordinates of the phosphor towards to the ideal white region (x = 0.31 and y = 0.34). Furthermore, the high color purity white-light coming from the BBN:2%Li+0.5%Tm3+0.05%Er3+8%Yb3+ composition was obtained under moderate power density establishing the BBN phase as a host matrix able to generate RGB with energy saving.

This work presents a spectroscopic investigation of tellurite glasses with the composition 65TeO2-15Li2O-20ZnO doped with different concentrations of Er2O3. Optical absorption and emission spectroscopy were performed at room temperature to determine emission properties of Er3+ in the visible and near-infrared regions. The samples presented intense green emission due to the H 11 / 2 2 → I 15 / 2 4 and S 3 / 2 4 → I 15 / 2 4 transitions. Emission intensities at 992 and 1550 nm exhibit a relative increase with increasing doping concentration. Luminescence decay curves for the S 3 / 2 4 → I 15 / 2 4 transition follows a non-exponential behavior, while the I 11 / 2 4 → I 15 / 2 4 and I 13 / 2 4 → I 15 / 2 4 transitions presented simple exponential behavior with high lifetime values. Under 975 nm excitation, upconversion luminescences in the green and red regions are observed, with a relative increase for red emission as function of doping concentration. The possible mechanisms considering multi-phonon relaxation, energy transfer and cross-relaxation processes were discussed for green and red emissions under excitations at 488 and 975 nm. The square dependence of green emission on the excitation power indicates two photons contribution to the upconversion emission. The full width at half-maximum values of emission at 1550 nm increased with increasing Er3+ concentration, showing the potential of the studied material as infrared amplifier.

Oxygen impurities played a pivotal role by affecting the optical and structural properties of Nd:YF3 phosphor, mainly when annealing procedure at high temperature is applied on it. In this work, it was demonstrated that luminescence decay, excitation and emission spectra of Nd:YF3 phosphor were greatly influenced by quenching sites and crystal bulk and surface defects induced by the presence of oxygen impurities incorporated into its structure. The excitation spectra presented a broad band from 200 to 550 nm, related to oxygen impurities, showing an alternative pathway to identify its presence. To overcome this recurrent problem, fluorine excess was used to reduce the oxygen contamination, allowing improvement of both crystallinity and luminescence efficiency of the Nd:YF3 phosphor. Despite this outstanding result, it was found that the fluorine content cannot be applied indiscriminately above of the stoichiometric proportion and its optimum quantity in excess was found to be at around 20%.

Advanced diagnostic procedures are required to satisfy the continuously increasing demands of modern biomedicine while also addressing the need for cost reduction in public health systems. The development of infrared luminescence-based techniques for in vivo imaging as reliable alternatives to traditional imaging enables applications with simpler and more cost-effective apparatus. To further improve the information provided by in vivo luminescence images, the design and fabrication of enhanced infrared-luminescent contrast agents is required. In this work, we demonstrate how simple dopant engineering can lead to infrared-emitting rare-earth-doped nanoparticles with tunable (0.1-1.5 ms) and medium-independent luminescence lifetimes. The combination of these tunable nanostructures with time-gated infrared imaging and time domain analysis is employed to obtain multiplexed in vivo images that are used for complex biodistribution studies.

Intense ultraviolet upconversion emission was produced in single Tm3+-doped OH--free low silica calcium aluminosilicate glasses. A new excitation route based upon multi-Stokes Raman emissions generated in an optical fiber pumped at 1.064 µm, and exploiting the absorption band around 1.2 µm by means of the 3H5 thulium excited state, was used. Furthermore, the other bands of the stimulated Raman scattering spectrum resonantly enhances all the upconversion processes, resulting in efficient ultraviolet (295 nm, 360 nm), blue (456 nm, 480 nm), red (650 nm, 667 nm), and near-infrared (800 nm) emissions. The population of the 1P0, 1D2, 1G4, 3F2 and 3H4 excited-state emitting levels was accomplished through stepwise multi-photon absorption. Results indicate competing cross-relaxation processes involving Tm3+ ion-pairs producing UV emission population quenching

Green emitting iron-oxide@NaGdF4:RE3+ (RE = 5%Ce, 5%Tb, 5%Dy) nanoparticles have been synthesized using microwave assisted solvothermal method. The Rietveld analysis of powder X-ray diffraction and high-resolution transmission electron microscopy provides an average crystallite size (∼20 nm) and the hexagonal crystal structure. Magnetic hysteresis loops at 300 K display superparamagnetic behavior along with paramagnetic feature for the reference NaGdF4:RE3+, further validated through magnetization versus temperature curves taken in an external magnetic field of 100 Oe. The photoluminescence investigation of the nanoparticles, suggest a down-converting energy transfer. The excitation spectra consist of a dominant broad band at around 254 nm due to Ce3+(4f–5d) along with f-f transitions due to Gd3+, Tb3+ and Dy3+ ions. The strong emission color lines due to characteristic transitions of Tb3+ (5D4 → 7FJ, J = 6–3), and Dy3+ (4F9/2–6H15/2, 6H13/2), were observed. The luminescence quenching in iron-oxide/NaGdF4:RE3+ through leakage path provided by iron-oxide to excite electrons has been confirmed and explained by comparing the time decay analysis.

The current status of the use of core-shell rare-earth-doped nanoparticles in biomedical applications is reviewed in detail. The different core-shell rare-earth-doped nanoparticles developed so far are described and the most relevant examples of their application in imaging, sensing, and therapy are summarized. In addition, the advantages and disadvantages they present are discussed. Finally, a critical opinion of their potential application in real life biomedicine is given, This work has been partially supported by the Ministerio de Economía y Competitividad de España (MINECO) (MAT2016-75362-C3-1-R), by the Instituto de Salud Carlos III (PI16/ 00812), by the Comunidad Autónoma de Madrid (B2017/ BMD-3867RENIM-CM), by the European Comission (NanoTBTech), and co-financed by European Structural and Investment Fund. This work has also been partially supported by COST action CM1403. L. L. P. thanks the Universidad Autónoma de Madrid for the “Formación de personal investi-gador (FPI-UAM)” program. P. R. S. thanks MINECO and the Fondo Social Europeo (FSE) for the “Promoción del talento y su Empleabilidad en I+D+i” statal program (BES-2014-069410). D. H. O. is grateful to the Instituto de Salud Carlos III for a Sara Borrell Fellowship (CD17/00210)

Forsterite (Mg2SiO4) is an easily dopable dielectric oxide with elevated transparency in the ultraviolet (UV), visible (Vis), and near-infrared (NIR) ranges. Despite its properties, the use of forsterite as a phosphor host has not been extensively studied. In this paper, Mg2SiO4 was used as a host for different combinations of Er3+, Eu3+, and Yb3+. The insertion of multiple dopants in the forsterite structure is presented for the first time. DC and UC photoluminescence were measured with excitation at 380, 976, and 1470 nm. Yb3+-doped forsterite showed an elevated UC emission at 480 nm (blue) due to the cooperative luminescence (CL) allowed by the host. Interestingly, the efficiency of the Er3+ UC and DC emissions involving the 4I11/2 level considerably increased in the presence of Eu3+. The Eu3+ ion serves as energy storage for Er3+ in the Mg2SiO4 crystal, presenting a behavior never reported in other hosts. Er3+/Eu3+/Yb3+ co-doped nanoparticles showed the highest DC emission among the samples under 976 nm excitation, indicating the insertion of Eu3+ as an alternative to improve Er3+/Yb3+-doped waveguide amplifiers. Moreover, the Er3+/Eu3+/Yb3+ co-doping resulted in efficient energy conversion from the NIR and UV to the Vis, the main spectral range for solar cell applications.

Luminescence-based thermometers have been widely investigated due to their exciting applications in science and technology. Rare-earth ions doped materials are among the potential candidates for such means, although their thermal sensitivity still needs improvement. This work aims to investigate the effect of the silver nanoparticles (SNPs) on the luminescence thermometry parameters of Er3+ ions doped zinc tellurite glasses. The formation of SNPs with an average diameter of about 12 nm was confirmed by transmission electron microscopy. The presence of SNPs intensifies the up-conversion luminescence of Er3+ ions observed at 537 nm, 557 nm, and 670 nm and the lifetime of 4S3/2 level from 25.1 µs to 38.8 µs. When co-doped with SNPs, the maximum absolute thermal sensitivity obtained for thermally coupled levels was 2.79 × 10−3 K−1 at 446 K, 44% higher than for Ag-free sample (1.94 × 10−3 K−1 at 446 K), suggesting the investigated materials for potential applications as the optical thermometer. These results are discussed in detail.

Rare earth ions doped transparent glasses are among promising solid-state materials for various optical applications. In this report, Eu3+ ions doped new fluoroborate glasses were prepared by conventional melt-quenching technique and their optical properties were characterized by absorption and luminescence spectroscopy as well as excited state lifetime measurements. The absorption spectra revealed the characteristic transitions between the 7F0 ground state and 7F1 first excited state to the upper-lying electronic states. The variation in the luminescence intensity of the radiative transitions occurring at 590 and 611 nm and the bi-exponential behavior of the fluorescence decay of the 5D0 level, with different trend for the amplitude of the decays, are discussed in terms of low and high symmetry sites depending on the EuF3 concentration and the possible energy transfer between ions at these sites.

Frequency upconversion luminescence in Yb 3+ /Tm 3+ co-doped 60P 2 O 5 ·15ZnO·5Al 2 O 3 ·10BaO·10PbO glass (PZABP) excited at 980 nm is reported. Pump power dependence, lifetime measurements, and the absorption spectra of the Tm 3+ ions in the visible to IR region are investigated as a function of sensitizer (Yb 3+ ) concentration. Blue light at 475 nm and red light at 660 nm generation was observed. Intensity saturation behavior is observed for the 475 nm ( 1 G 4 – 3 H 6 ), 650–664 nm ( 1 G 4 – 3 F 4 and/or 3 F 2,3 – 3 H 6 ) and 793 nm ( 3 H 4 – 3 H 6 ) upconversion emissions, when laser power was above ∼ 75 mW (∼1.9 kW/cm 2 ). The radiative lifetimes measured for the observed emissions were 270 μs (475 nm), 195 μs (650 nm), 177 μs (664 nm), 184 μs (793 nm) and 335 μs (1211 nm). The application of the Davis-Mott model detected a slight change of 6.6% in the value of the energy bandgap for the highest doping concentration in comparison with the undoped sample. Results indicate that the PZABP glass matrix herein reported is a promising contender as host for rare-earth doped based photonic devices.

Tm3+/Dy3+ co-doped LaF3 nanocrystals have been synthesized by the co-precipitation method and the luminescence properties under UV light excitation examined. Tunable light emission containing blue (450 nm), yellow (570 nm), and red (660 nm) light components was observed. The excitation spectrum was investigated and the optimum excitation UV wavelength determined. The excitation mechanism responsible for the generation of the multicolor emission indicated that Tm-Dy energy-transfer plays a major role in the process. Tuning of the overall white-light emission was accomplished via variation of the Tm and Dy active ions contents in the nano-powder samples. The CIE chromaticity coordinates show that the Tm3+/Dy3+ co-doped LaF3 may be an excellent candidate for white light emitting diode devices.

We report on the potential application of NIR–NIR two-photon excited fluorescence of Tm3+ doped sodium niobate (NaNbO3:Tm) nanoparticles with both emission (800 nm) and excitation (1.319 μm) operating respectively within first and second biological windows for high resolution and deeper penetration bio-images. Ex vivo tissue depth using 1.319 μm was achieved as high as twice in comparison with the already conventional 800 nm excitation. The spectral profile of Tm3+ upconversion luminescence was analyzed in detail in the biophysical temperature range. A twofold enhancement of the solely detected 800 nm upconversion emission was obtained in the 22–90 °C temperature interval. The population redistribution of the thermally coupled sub-levels was demonstrated useful for ratiometric nanothermometry. The outstanding penetration depth together with the fluorescence thermal sensitivity make the NaNbO3:Tm nanocrystal an excellent candidate as multifuncitional nanoprobe for high contrast and highly penetrating fluorescence imaging.

Syntheses of metal sulfide nanocrystals (NCs) by heat-up routes in the presence of thiols yield NC arrangements difficult to further functionalize and transfer to aqueous media. By means of different NMR techniques, and exemplified by Ag2S NCs, a metal-organic polymer formed during the synthesis acting as a ligand has been identified to be responsible for such aggregation. In this work, a new synthetic hot-injection strategy is presented to synthesize Ag2S NCs which are easily ligand exchangeable in water. Furthermore, the hot-injection route allows an extra NC treatment with Se to produce Ag2S/Ag2(S,Se) NCs with improved optical properties with respect to the Ag2S cores, and better resistance to oxidation, as demonstrated by X-ray absorption experiments.