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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.

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.

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.

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.

12 p.-5 fig., Optical probes operating in the second near-infrared window (NIR-II, 1,000-1,700 nm), where tissues are highly transparent, have expanded the applicability of fluorescence in the biomedical field. NIR-II fluorescence enables deep-tissue imaging with micrometric resolution in animal models, but is limited by the low brightness of NIR-II probes, which prevents imaging at low excitation intensities and fluorophore concentrations. Here, we present a new generation of probes (Ag2S superdots) derived from chemically synthesized Ag2S dots, on which a protective shell is grown by femtosecond laser irradiation. This shell reduces the structural defects, causing an 80-fold enhancement of the quantum yield. PEGylated Ag2S superdots enable deep-tissue in vivo imaging at low excitation intensities (, Authors thank Dr A. Benayas (CICECO, U. Aveiro, Portugal), Prof G. Lifante and Prof J. García Sole (UAM) for helpful discussions. This work has been founded by Ministerio de Economı́a y Competitividad-MINECO (MAT2017-83111R and MAT2016-75362-C3-1-R) and the Comunidad de Madrid (B2017/BMD-3867 RENIM-CM) co-financed by European Structural and Investment Fund. D.M.-G. thanks UCM-Santander for a predoctoral contract (CT17/17-CT18/17). We thank the staff at the ICTS-National Centre for Electron Microscopy at the UCM for the help in the electron microscopy studies and C.M. at the beamline BL22-CLAESS of the Spanish synchrotron ALBA for his help in the XANES experiments. We also thank J.G.I at the Ultrafast Laser Laboratory at UCM for his help and fruitful discussion. Y.S. acknowledges the support from the China Scholarship Council (CSC File No. 201806870023). Additional funding was provided by the European Commission Horizon 2020 project NanoTBTech, the Fundación para la Investigación Biomédica del Hospital Universitario Ramón y Cajal project IMP18_38 (2018/0265). Ajoy K. Kar and Mark D. Mackenzie acknowledge support from the UK Engineering and Physical Sciences Research Council (Project CHAMP, EP/M015130/1). C. Jacinto thanks the financial support of the Brazilian agencies: CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) through the grants: Projeto Universal Nr. 431736/2018-9 and Scholarship in Research Productivity 1C under the Nr. 304967/20181; FINEP (Financiadora de Estudos e Projetos) through the grants INFRAPESQ-11 and INFRAPESQ-12; FAPEAL (Fundação de Amparo à Pesquisa do Estado de Alagoas) grant Nr. 1209/2016. H. D. A. Santos was supported by a graduate studentship from CNPq and by a sandwich doctoral program (PDSE-CAPES) developed at Universidad Autonoma de Madrid, Spain, Project Nr. 88881/2016-01.

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 hotinjection 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. Fil: Ruiz, Diego. Instituto Imdea Energia.; España Fil: Mizrahi, Martin Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Santos, Harrisson D. A.. Universidad Autónoma de Madrid; España. Universidade Federal de Alagoas; Brasil Fil: Jaque García, Daniel. Universidad Autónoma de Madrid; España Fil: Jones, Callum M. S.. Heriot Watt University; Reino Unido Fil: Marqués Hueso, José. Heriot Watt University; Reino Unido Fil: Jacinto, Carlos. Universidade Federal de Alagoas; Brasil Fil: Requejo, Felix Gregorio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Torres Pardo, Almudena. Universidad Complutense de Madrid; España Fil: González Calbet, José. Universidad Complutense de Madrid; España Fil: Juárez Hernández, Beatriz. Universidad Autónoma de Madrid; España. Instituto Imdea Energia.; España

Pr3+ and Yb3+ co-doped NaYF4 nanocrystals (NCs) were synthetized via a simple coprecipitation method and investigated their efficiency of near-infrared quantum cutting (down-converter) with possible application for photovoltaic solar cells. The effect of the Yb3+ concentration on the down-conversion and quantum cutting emissions was evaluated under ultraviolet/visible excitation. The Pr3+ emissions under excitation at 442 nm were observed in the range from 450 to 1550 nm. It was obtained that increasing the Yb3+ concentration all the Pr3+ emissions decrease, and it was associated to an efficient energy transfer process between Pr3+ and Yb3+ ions. In addition, the Yb3+ emission at 974 nm decreases with the Yb3+ concentration increasing, being the highest emission observed for the NC doped with 2 mol.% of Yb3+. The lifetime of the 3P0 state were measured and increasing the Yb3+ concentration the decay becomes faster leading to strong reduction of the lifetime from 18.6 (0 mol.% of Yb3+) to 2.2 μs (10 mol%Yb3+). A quantum cutting efficiency of 188% in NaYF4 co-doped with 0.5 mol.% of Pr3+ and 10 mol.% of Yb3+ was obtained, which is a relatively high value, close to the limit of 200%. Therefore, these investigated NCs, synthetized via a very simple and cheap coprecipitation route, have great potential for solar cells applications of silicon-based materials by down-converting the ultraviolet/visible part of the solar spectrum to ~1000 nm photons.

Phosphate glasses having composition 50P2O5–10B2O3–20ZnO–20PbO–xDy2O3 where x = 0.04, 0.18, 0.36, 1.10, 1.80, and 3.60 mol% were prepared by melt quenching technique. The FTIR spectra reveal the different structural groups of the phosphate glass induced by modifiers such as lead oxide and zinc oxide, which could be explained in terms of the distortion of PO4 tetrahedra and the network depolymerization process. The photoluminescence spectrum shows three prominent emission bands centered at 475, 586, and 675 nm corresponds to the 4F9/2 → 6HJ (J = 11/2, 13/2, 15/2) transitions, respectively, and the intensity ratio of yellow to blue emissions are enhanced as the concentration of Dy3+ ions increased up to 3.60 mol%. The 4F9/2 excited state's lifetime decreases by continuously increasing the amount of the trivalent lanthanide ion due to probable energy transfer between neighboring ions. The chromaticity diagram is studied as the rare-earth ion concentration, which gives the nearest condition to the white color at 0.36 mol% of the Dy3+ ions.

We report on the thermoelastic properties of Ni 2 MnGa shape-memory alloys across the martensitic to austenitic phase transition using the time-resolved pump–probe photothermal mirror technique. Quantitative information on the thermo-mechanical characteristics of the sample are obtained and compared to specific heat measurements and differential scanning calorimetry (DSC) analysis. The thermal diffusivity varied remarkably within the martensitic–austenitic transition range. Both the amplitude signal and the thermal diffusivity present, in addition to the strong martensite to austenite phase transition, a clear evidence of a subtle second-order type phase transition close to 80 ° C. This magnetic transition is also observed in the calorimetric analysis. The transformation temperatures suggest the non-stoichiometric composition of sample, which is also revealed by non-symmetrical shapes of DSC peaks. The possible variation of the local chemical composition could be a result of gallium loss during the sample preparation or local inhomogeneity in the martensitic transformation.

The green emissions of the trivalent erbium ions exhibit promising applications in photonics, such as the development of solid-state lasers, optical sensors, and light-emitting diodes (LED). In this work, the intensity of the emissions of two thermally coupled levels 2H11/2 and 4S3/2 excited states of Er3+ ions are studied in Er3+/Yb3+ co-doped tungsten sodium phosphate oxyfluoride glasses. The results demonstrate that an increase in the content of the PbF2 leads to an enhancement in the performance of these samples as optical sensors, and amplifies the relative thermal sensitivity from 0.82% K−1 to 1.15% K−1 for glass samples containing 10 mol% and 50 mol% of PbF2, respectively. Additionally, the effect of PbF2 is discussed in terms of the modifications of the site symmetries around Er3+ ions and changes in the energy gap between the thermally coupled levels, which implied in the improvement of the absolute thermal sensitivity at higher temperatures for high PbF2 contained sample.

In this work, we report a potential optical nanothermometer (NTh) based on Nd3+ doped TiO2 nanocrystals, operating within the biological windows. The Nd3+ emissions at around 900, 1060, and 1340 nm were used upon excitation at 808 nm. The fluorescence intensity ratio (FIR) corresponding to the emissions at 1060 nm and 1340 nm (FIR = I1060 nm/I1340 nm) was investigated as a function of the temperature in the range of 300−343 K. In addition, the effect of the Nd3+ ions concentration and influence of the crystalline phase on the luminescence and the relative thermal sensitivity were presented. As a result, it was found that TiO2 nanocrystals doped with 10 wt% of Nd3+ ions and associated with the brookite phase has the highest luminescence emission and relative thermal sensitivity compared to other samples investigated here and in previous literature. The maximum value obtained to the relative thermal sensitivity was 0.86 % K−1, which is high comparatively with other ones of Nd3+ doped systems, and minimum thermal resolution of ∼1 K. This information together with the biocompatibility of TiO2 nanocrystals, and excitation and emissions wavelengths lying within the biological windows, favor potential applications in fluorescence and thermal imaging of biological systems.

Pr2O3 doped 26.66B2O3–52.33PbO–16GeO2–4Bi2O3–1Pr2O3 (BPGBPr) glass was synthesized by melt quenching technique. X-ray diffraction confirmed the amorphous nature of the glass and the presence of different vibrational groups was identified by Raman spectroscopy. Differential thermal analysis indicated that the glass transition and crystallization temperature were ~354 °C and ~521 °C respectively, indicating good thermal stability. Visible and near infrared absorption spectra were measured and used to evaluate the Judd-Ofelt intensity parameters to calculate the radiative properties for the emission levels of Pr3+. Photoluminescence spectra were recorded in the visible and infrared regions at temperatures between 16 and 300 K. The spectroscopic results indicated that BPGBPr can be useful as a material for broadband optical amplifier in the region of ~1450 cm−1.

Nd 3+ ion doped LaF 3 dielectric nanoparticles have recently emerged as very attractive multifunctional nanoparticles capable of simultaneous sub-tissue heating and thermal sensing. Although they have been already used for selective photothermal treatment of cancer tumors in animal models, their real application as self-monitored photothermal agents require further optimization and development. Dynamic adjustment of the therapy parameters is mandatory for non-selective damage minimization. It would require real-time (sub-second) thermal sensing with a sub-degree thermal resolution. In this work we demonstrate that meeting this challenge is, indeed, possible by performing controlled thermal treatment on as-synthesized Nd 3+ doped LaF 3 nanoparticles. Temperature induced lattice ordering and defect re-combination have been concluded to induce, simultaneously, a line fluorescence narrowing, fluorescence brightness enhancement and a remarkable increment in thermal sensitivity. Ex-vivo experiments have demonstrated that, thanks to this multi-parameter optimization, Neodymium doped LaF 3 nanoparticles are capable of real time sub-tissue thermal reading with a temperature resolution as low as 0.7 °C.

The optical and structural properties of Nd:YF 3 phosphors, synthesized by precipitation reaction using ethylene glycol solvent, were investigated. The Y:F molar ratio of precursors, where NH 4 F was employed as the fluorine source, was varied to prevent oxygen contamination during nucleation of the particles and to improve the photoluminescence efficiency. Structural investigations were carried out by means of X-ray diffraction, Fourier transform infrared spectroscopy and energy dispersive X-ray techniques. Samples prepared using precursors in stoichiometric proportion presented orthorhombic YF 3 structure. The use of fluorine source in excess promoted formation of NH 4 Y 2 F 7 crystalline phase, which was decomposed into YF 3 after annealing at 400 °C for 1 h. Emission spectra of samples thermally treated enhanced by over 50 times compared with the as prepared. The results obtained show the role of fluorine excess associated with thermal annealing to obtain YF 3 with improved features.

Emission of visible and NIR frequency upconversion luminescence light mainly within the first biological window spectral region using excitation at 1319 nm in the second biological window in Tm3+/Er3+-codoped TeO2-based glass, is demonstrated. For Tm3+/Er3+-codoped tellurite glass samples, green(525, and 550 nm), red(660 nm) and NIR(980 nm) owing to erbium ions in addition to the main 800 nm signal originating from thulium ions is readily observed. Here, energy-transfer Tm3+[3F4]+Er3+[4I15/2]→Tm3+[3H6]+Er3+[4I9/2] producing the NIR emission, followed by excited-state absorption of 1.319 µm photons populating 2H11/2, 4S3/2, and 4F9/2 visible emitting levels. Erbium single-doped samples did not exhibited visible detectable emissions for excitation powers as high as 1.8 W of cw radiation at 1.319 µm. In Tm3+/Nd3+-codoped samples, energy-transfer from Tm3+ (3H6–3F4) to Nd3+ ions populates the 4F3/2 excited-state level producing NIR emission around 880 nm.

A highly transparent Sm3+ glass with composition B2O3–PbO–Bi2O3–GeO2 was obtained by the traditional melt quenching technique and characterized from structural and spectroscopic points of view. Analysis by X-ray diffraction and Raman spectroscopy confirmed the amorphous nature of the sample and revealed the expected low phonon energy. Differential thermal analysis was also carried out to obtain the glass transition and the crystallization temperatures, related to the thermal stability of the sample. Judd–Ofelt theory was applied to evaluate phenomenological intensity parameters Ωλ (λ=2, 4 and 6) from the optical absorption measurements. The transition probabilities, radiative lifetimes, branching ratio and stimulated emission cross-section were also calculated. Photoluminescence spectra recorded in the visible and infrared regions revealed intense green, orange, red and near infrared emission bands providing a new trace to develop tunable laser and optoelectronics devices.

The recent development of core/shell engineering of rare earth doped luminescent nanoparticles has ushered a new era in fluorescence thermal biosensing, allowing for the performance of minimally invasive experiments, not only in living cells but also in more challenging small animal models. Here, the potential use of active-core/active-shell Nd(3+)- and Yb(3+)-doped nanoparticles as subcutaneous thermal probes has been evaluated. These temperature nanoprobes operate in the infrared transparency window of biological tissues, enabling deep temperature sensing into animal bodies thanks to the temperature dependence of their emission spectra that leads to a ratiometric temperature readout. The ability of active-core/active-shell Nd(3+)- and Yb(3+)-doped nanoparticles for unveiling fundamental tissue properties in in vivo conditions was demonstrated by subcutaneous thermal relaxation monitoring through the injected core/shell nanoparticles. The reported results evidence the potential of infrared luminescence nanothermometry as a diagnosis tool at the small animal level.

Heavy metal oxide B2O3–PbO–Bi2O3–GeO2 transparent glass doped with Sm3+ was synthesized and implanted with Au+ using energy of 300 keV and fluence of 1 × 1016 cm−2. The annealing of the implanted glass at moderate temperature below the glass transition temperature induced the nucleation of gold nanoparticles, confirmed by the characteristic absorption band in the visible range and by transmission electron microscopy. Using Mies and Doyles theories for the surface plasmon resonance, the average size of the gold nanoparticles was about 4.6 nm, similar to the values observed by transmission electron microscopy. It was also observed the crystallization of a thin layer of the glass at the implanted surface after annealing, detected by X-ray diffraction and scanning electron microscope. Visible and near-infrared emission of Sm3+ was enhanced after annealing of the glass implanted with gold. Judd–Ofelt parameters and radiative parameters were calculated for the glass doped with Sm3+ with and without gold nanoparticles.

Photo-thermal therapies, based on the light-induced local heating of cancer tumors and tissues, are nowadays attracting an increasing attention due to their effectiveness, universality, and low cost. In order to avoid undesirable collateral damage in the healthy tissues surrounding the tumors, photo-thermal therapies should be achieved while monitoring tumor’s temperature in such a way that thermal therapy could be stopped before reaching the damage limit. Measuring tumor temperature is not an easy task at all and novel strategies should be adopted. In this work it is demonstrated how luminescent nanoparticles, in particular Neodymium doped LaF 3 nanoparticles, could be used as multi-functional agents capable of simultaneous heating and thermal sensing. Advantages and disadvantages of such nanoparticles are discussed and the future perspectives are briefly raised.

In this work, we study energy transfer (ET) processes between Mn2+ and Nd3+ ions in Nd2O3-doped P2O5–ZnO–Al2O3–BaO–PbO glass system, nanostructured with Zn1−xMnxTe diluted magnetic semiconductor nanocrystals (NCs), aiming nanotechnology applications. Transmission electronic microscopy (TEM), X-ray diffraction (XRD), optical absorption (OA), photoluminescence (PL), and lifetime measurements were performed for a complete characterization of the investigated materials. The TEM and XRD data confirm the formation of Zn1−xMnxTe NCs in the host glass system. The overlap between the Mn2+ ion emission band and the Nd3+ ion absorption bands suggests that an efficient resonant type energy transfer from Mn2+ to Nd3+ ions is expected. PL spectra show that the characteristic emission relative intensities of Nd3+ ions increase systematically with increasing Mn concentration. Indeed, the 4T1(4G) state lifetime of Mn2+ ions gradually decreases with rising Mn concentration. This result confirm the evidence on ET from Mn2+ ions to Nd3+ ions. In addition, the increase in the 4F3/2 state lifetime is an evidence of persistent luminescence due to the presence of Mn2+ ions.

We report the interaction between 5.0 wt.% and 20 wt.% Yb3+ doped phosphate glasses substrates with graphene single layer (1L) and bilayer (2L) by Raman spectroscopy. This interaction is studied in terms of shifting of the G, 2D and 2D’ bands of graphene, which is higher in 1L than in 2L graphene on the 20% Yb3+ substrate, in respect to the 5.0 wt.% substrate. Furthermore, changes in the full width at half maximum of the G, 2D and 2D’ bands, together with the I2D/IG ratio, for doped and undoped substrates, reveal this interaction. Additionally, when a single layer graphene is found on the surface of both substrates, some Raman peaks on the less doped sample are absent, whereas they are present on the more doped sample, indicating that the presence of Yb3+ ions increases the interaction between the substrate and the single layer graphene. The reported results give insights about graphene interaction with doped rare earth substrates.

In the present work, we exploited the capability of the trivalent thulium (Tm3+) ions doped sodium niobate (NaNbO3) nanocrystals as an optical nanothermometer with a giant relative thermal sensitivity (Sr) of up to 12%°C−1. Tm3+:NaNbO3 nanoparticles, under excitation at 1064 nm using a Q-switched and mode-locked Nd:YAG laser, provided emissions at multi-wavelengths from 460 nm to 840 nm through non-parametric transitions in Tm3+ ions, and parametric second-harmonic generation (SHG) at 532 nm (I532) of the excitation beam thanks to the large nonlinear response of the crystalline matrix. The proposed nanothermometer is based on the intensity ratio between the upconverted fluorescence at 695 nm (I695), associated with the 3F2,3 → 3H6 Tm3+ transitions, and I532. Due to the opposite behaviors of these two emissions with the temperature in the range of 20–80 °C, a super sensitive nanothermometer was demonstrated with a record of Sr ~12% oC−1 around 40–50 °C (the biological temperature regime). In addition, an efficient pump-induced self-heating system was reported and assigned to multiphonon relaxations in Tm3+ ions. These properties make this dual emitting system a nanoprobe for many potential applications, e.g., for studying dynamical biological and pump-induced self-monitored photothermal events. The combination of SHG in a wide spectral range (e.g., in complete first biological window) and emissions of lanthanide ions greatly increases the range of applications using this system, including as a multifunctional nanoprobe.

Tacrolimus (TAC) or FK506 is a macrolide lactone isolated from the bacterial fermentation of Streptomyces tsukubaensis which belongs to the group of calcineurin inhibitors. Its main mechanism of action is to act on the immune system. In addition, this drug has been widely explored for skin disorders. However, TAC shows high molecular weight, high hydrophobicity, and low water solubility that can limit its ability to effectively permeate through the skin. Hence, it becomes imperative to develop a percutaneous drug delivery system for increasing its permeation in relation to the conventional ointment and for reducing the dose and the adverse effects as erythema, itching, and burning. Therefore, the aim of this work was to investigate the stability of colloidal suspensions of TAC-loaded poly(ԑ-caprolactone) (PCL) nanoparticles that were stored at room temperature for 120 days. In that sense, pH, particle size, polydispersity index (PDI), zeta potential, and Raman spectroscopy were performed. Significant decrease of pH (p 0.05) during the time interval investigated. Zeta potential presented statistically significant difference (p

The inclusion complex of Nystatin (NYS) with β -cyclodextrin ( β -CD) can increase the solubility of the antibiotic in aqueous media. The complexes were obtained by freeze-drying (FD) and spray-drying (SD) methods. The spectroscopic techniques used to analyze the complexes were FT-Raman, photoacoustic spectroscopy (PAS), and 1H NMR. FT-Raman allowed the identification of the interactions of β -CD with NYS molecule through the vibrational modes assigned to tetraene, heptaene and C=O. PAS confirms that the main part of interaction from NYS is heptaene. The 1H NMR showed that the hydrogens inside the cavity of β -CD interact with NYS. These techniques confirmed the complex formation and that the drying method affects the form of complexation: by the FD method one molecule of β -CD is sufficient to form the complex with NYS. In contrast, the inclusion complex of NYS: β -CD by the SD method is formed by two molecules of β -CD. These results showed the effectiveness of these techniques in evaluating the inclusion complex and demonstrate that the drying method affects how this complexation occurs.

We report the effect of gold nanoparticles (AuNPs) and unwanted sodium citrate residues (UnR) left after deposition of AuNPs by drop-casting method on the Raman spectra of graphene sheets (GS). The AuNPs solution was deposited on three different substrates: 5.0 wt% Yb3+-doped (Q5) phosphate glass, silica glass (S1), and Si/SiO2-300 nm (S2) substrates. For Q5 substrate, a slight increase in intensity of the G peak was observed, mostly for thinner layers, which can be attributed to a weak SERS effect shielded by UnR. The combination of the following aspects: a blue shift of the G band position, a slight increase in the FWHM (Full Width at Half Maximum), and a slight increase of the Raman intensities of both G and 2D bands in other GS without UnR supports the argument of shielded SERS effect. On the other hand, the effects of UnR on the S1 and S2 substrates produce a decrease on the Raman intensities of G and 2D bands, opposite to the effect produced by the AuNPs; this result was found more intense for the S2 substrate in relation to S1. This is possibly caused by the greater amount of UnR accumulated on the Si/SiO2 substrate, due to its higher hydrophilicity in relation to other samples. Additional Raman measurements reveal that the Raman intensity of GS in all substrates is unaffected by the presence of a possible humidity on GS, revealing the effect of UnR. Hence, it is vital to understand how residues influence the salient features of GS/AuNPs.

Efficiency of solar devices is affected by several factors such as, devices surface reflection and the energy emitted in the ultraviolet and infrared regions, which are not harnessed by the cell, are among the main causes. To reduce these losses, we propose the use of rare-earth doped anti-reflection coatings. Erbium doped forsterite (Mg2SiO4:Er3+) thin films were synthesized in order to bind the anti-reflective property of forsterite films with the upconversion property of erbium ion. For the first time in literature, Mg2SiO4:Er3+ optical activity in the visible range with excitation at 1470 nm is presented. Single and double layers anti-reflective coating models, with forsterite as coating material, were simulated. The single layer model was compared to experimental data presenting elevated accordance. The coating application on silicon wafer leaded to a light absorption enhancement over 80% in the visible spectrum. The dopant influence on the films optical behavior was also studied indicating that despite the presence of erbium, the fosterite films preserved their anti-reflectivity. Moreover, the coatings were analyzed through chemical and mechanical resistance tests, indicating elevated scratch resistance (over 500 mN) and chemical stability at high humidity and corrosive environments. Mg2SiO4:Er3+ films revealed to be a promising anti-reflection coating for increasing commercial silicon-based solar cells efficiency.

We report a systematic investigation on the temperature dependence of fluorescence decay dynamics of infrared emitting colloidal Ag2S nanocrystals (NCs) with different surface coatings. The drastic lifetime reduction in the biological temperature range (20–50 °C) makes Ag2S NCs outstanding candidates for high sensitivity subcutaneous lifetime-based thermal sensing in the second biological window (1000–1400 nm). Indeed, the lifetime thermal sensitivity of Ag2S NCs has been found to be as large as 3–4% °C−1 at an operating wavelength of 1250 nm. Their application for lifetime-based luminescence nanothermometry has been demonstrated through simple ex vivo experiments specially designed to elucidate the magnitude of subcutaneous thermal gradients. Experimental data were found to be in excellent agreement with numerical simulations.

Glass samples in the form 80TeO2-(20-x)Na2O-xTiO2 with x = 0, 5, 10, 15 and 20 mol%, were fabricated by the melting quenching technique. The thermal behavior of samples was analyzed considering their crystallization kinetics mechanism and microstructural analysis. Differential Scanning Calorimetry (DSC) was performed at 20 ml/min argon flux and heating rates of 10, 13, 15 and 20 K/min, from ambient temperature to 873 K, and these data were analyzed using a non-isothermal model of phase transformation. The activation energy for crystallization and Avrami exponent were determined for each sample. We observed that the crystallization process depends on the role assumed by the TiO2, a modifier (5 mol%) or former network (10 and 15 mol%). The crystallization process changes from superficial to internal or three-dimensional crystallizations with increasing TiO2 content.

There is an urgent need to develop new diagnosis tools for real in vivo detection of first stages of ischemia for the early treatment of cardiovascular diseases and accidents. However, traditional approaches show low sensitivity and a limited penetration into tissues, so they are only applicable for the detection of surface lesions. Here, it is shown how the superior thermal sensing capabilities of near infrared-emitting quantum dots (NIR-QDs) can be efficiently used for in vivo detection of subcutaneous ischemic tissues. In particular, NIR-QDs make possible ischemia detection by high penetration transient thermometry studies in a murine ischemic hindlimb model. NIR-QDs nanothermometers are able to identify ischemic tissues by means of their faster thermal dynamics. In addition, they have shown to be capable of monitoring both the revascularization and damage recovery processes of ischemic tissues. This work demonstrates the applicability of fluorescence nanothermometry for ischemia detection and treatment, as well as a tool for early diagnosis of cardiovascular disease.

We report on Ytterbium and Neodymium codoped LaF3 core/shell nanoparticles capable of simultaneous heating and thermal sensing under single beam infrared laser excitation. Efficient light-to-heat conversion is produced at the Neodymium highly doped shell due to non-radiative de-excitations. Thermal sensing is provided by the temperature dependent Nd3+ → Yb3+ energy transfer processes taking place at the core/shell interface. The potential application of these core/shell multifunctional nanoparticles for controlled photothermal subcutaneous treatments is also demonstrated, This work was supported by the Spanish Ministerio de Economıa y Competitividad (MAT2013-47395-C4-1-R), by Brazilian Agencies: FINEP (Financiadora de Estudos e Projetos) through the Grant Nos. INFRAPESQ-11 and INFRAPESQ-12; CNPq (Conselho Nacional de Desenvolvimento Cientıfico e Tecnologico) Grants INCT NANO(BIO)SIMES and Project Universal No. 483238/2013-9; CAPES (Coordenadoria de Aperfeiçoamento de Pessoal de Ensino Superior) by means of the Project PVE No. A077/2013. Erving C. Ximendes is supported by a Ph.D. scholarship from CNPq and currently by the PVE A077/2013 Project by means of a Ph.D. sandwich program developed at the Universidad Autonoma de Madrid, Spain. Prof. Dr. Daniel Jaque is the PVE (Pesquisador Visitante Especial) of the Project No. A077/2013. Dr. K. U. Kumar is a post-doctoral fellow of this Project. Dr. Ueslen Rocha is supported by a Post Doctoral Fellowship grant PDE/CAPES at the Universidad Autonoma de Madrid-Spain through the Project No. 2108-14-3

In this work, we investigated the thermo-optical properties of highly Nd3+ doped YAG ceramics. The normalized lifetime thermal lens method was used to obtain the fluorescence quantum efficiency (η) versus Nd3+ concentration (N t) and to study the energy transfer microparameters C DD and C DA. The N t dependence of η was compared to the results of the previous literature. The C DA found is very similar to those of the previous literature, while the C DD is very different and higher than C DA, although the main dependence of η with N t is assigned to C DA. The figure of merit (η.N t versus N t) indicated a maximum around 3.8 at.% Nd2O3, which in addition to the very low ds/dT value, evidences the YAG ceramic as an excellent material for an ultra-high-power microchip laser system and for devices requiring minimum pump-induced local heating generation.