Finite element modeling of plasmonic resonances in photothermal gold nanoparticles embedded in cells.

The use of plasmonic nanoparticles in performing photothermal treatments in cancer cells requires a full knowledge about their optical properties. The surface plasmon resonance is easily foreseen and measurable in colloidal suspensions, however it can be strongly modified when located inside cells. Assessing the optical behavior of plasmonic nanoparticles in cells is essential for an efficient and controlled treatment. This requires the combination of experimental data and computational models to understand the mechanisms that cause the change in their optical response. In this work, we investigate the plasmonic response of Au nanospheres (AuNSs) internalized into cancer cells (MCF-7). Experimental data are compared to the simulations provided by a 3D model based on a finite element method. We demonstrate the impact of physical parameters such as the type of NS assembly, the surrounding medium and the interparticle gap, in the photothermal efficiency of AuNSs. Results open the avenue to predict, by numerical calculations, the optical properties of plasmonic nanoparticles inside cells to minimize treatment costs and times in photothermal therapies.

Cuarenta años: un canto a la transformación y la trayectoria de la Terapia Ocupacional / Forty years: An ode to the transformation and trajectory of Occupational Therapy / Quarenta anos: um canto à transformação e à trajetória da Terapia Ocupacional

La Revista Ocupación Humana ha sido un importante medio de divulgación del conocimiento en Terapia Ocupacional y en los estudios sobre ocupación humana. Su primera edición, emitida el 24 de octubre de 1984, significó un hito para Colombia y para Latinoamérica, al constituirse en referente para el ejercicio profesional y el desarrollo disciplinar. Inicialmente, se orientó a comprender las áreas del desempeño profesional, a socializar investigaciones, a promover la discusión y la proyección de la profesión en ciencia y tecnología, y a conocer y difundir la emergente participación en escenarios de incidencia comunitaria, social y política. Después de una pausa editorial de cinco años, en el año 2013, se retoma la publicación. Desde entonces, se ha trabajado en su fortalecimiento, visibilidad y apertura, proceso en el que se ha contado con la participación de colegas de Colombia y otros países hermanos. En este aniversario, el Comité Editorial desea que la revista siga consolidándose como medio fundamental para que las y los terapeutas ocupacionales sigan escuchándose, conociéndose, conectándose con los debates profesionales y fortaleciéndose como gremio. Por eso, celebra e invita a celebrar con un canto estos cuarenta años de retos y a dar la bienvenida a los que vendrán

The Revista Ocupación Humana has been an essential medium in disseminating knowledge in Occupational Therapy and studies on human occupation. Its first edition, released on 24 October 1984, marked a milestone for Colombia and Latin America, becoming a benchmark for professional practice and disciplinary development. Initially, it focused on understanding areas of professional performance, disseminating research, promoting discussion, and projecting the profession in science and technology, and understanding and spreading the emerging participation in community, social, and political-impact scenarios. After a five-year editorial break, in 2013, the publication resumed. Since then, work has been undertaken to strengthen its visibility and openness, with the participation of colleagues from Colombia and other sister countries. On this anniversary, the Editorial Board hopes that the magazine will continue to consolidate itself as a key means for occupational therapists to continue listening to each other, get to know each other, engage in professional debates, and strengthen themselves as a body. As such, it celebrates and invites you to celebrate these forty years of challenges and welcome those that will come.

A Revista Ocupación Humana tem sido um importante meio de divulgação do conhecimento em Terapia Ocupacional e em estudos sobre ocupação humana. Sua primeira edição, emitida em 24 de outubro de 1984, significou um marco para a Colômbia e para a América Latina, ao se constituir como referência para a prática profissional e o desenvolvimento disciplinar. Inicialmente, dedicou-se a compreender as áreas do desempenho profissional, a socializar pesquisas, a promover a discussão e a projeção da profissão em ciência e tecnologia, a conhecer e difundir a emergente participação em cenários de incidência comunitária, social e política. Após uma pausa editorial de cinco anos, em 2013, retomou-se a publicação. Desde então, tem-se trabalhado no seu fortalecimento, visibilidade e abertura, processo no qual se conta com a participação de colegas da Colômbia e de outros países irmãos. Neste aniversário, o Comitê Editorial deseja que a revista continue a se consolidar como meio fundamental para que as e os terapeutas ocupacionais continuem ouvindo-se, conhecendo-se, conectando-se com os debates profissionais e fortalecendo-se no coletivo. Por isso, celebra e convida a celebrar com um canto estes quarenta anos de desafios, bem como a dar as boas-vindas aos que virão.

Structural Defects on Graphene Generated by Deposition of CoO: Effect of Electronic Coupling of Graphene.

Understanding the interactions in hybrid systems based on graphene and functional oxides is crucial to the applicability of graphene in real devices. Here, we present a study of the structural defects occurring on graphene during the early stages of the growth of CoO, tailored by the electronic coupling between graphene and the substrate in which it is supported: as received pristine graphene on polycrystalline copper (coupled), cleaned in ultra-high vacuum conditions to remove oxygen contamination, and graphene transferred to SiO2/Si substrates (decoupled). The CoO growth was performed at room temperature by thermal evaporation of metallic Co under a molecular oxygen atmosphere, and the early stages of the growth were investigated. On the decoupled G/SiO2/Si samples, with an initial low crystalline quality of graphene, the formation of a CoO wetting layer is observed, identifying the Stranski-Krastanov growth mode. In contrast, on coupled G/Cu samples, the Volmer-Weber growth mechanism is observed. In both sets of samples, the oxidation of graphene is low during the early stages of growth, increasing for the larger coverages. Furthermore, structural defects are developed in the graphene lattice on both substrates during the growth of CoO, which is significantly higher on decoupled G/SiO2/Si samples mainly for higher CoO coverages. When approaching the full coverage on both substrates, the CoO islands coalesce to form a continuous CoO layer with strip-like structures with diameters ranging between 70 and 150 nm.

Tailoring the Lithium Concentration in Thin Lithium Ferrite Films Obtained by Dual Ion Beam Sputtering.

Thin films of lithium spinel ferrite, LiFe5O8, have attracted much scientific attention because of their potential for efficient excitation, the manipulation and propagation of spin currents due to their insulating character, high-saturation magnetization, and Curie temperature, as well as their ultra-low damping value. In addition, LiFe5O8 is currently one of the most interesting materials in terms of developing spintronic devices based on the ionic control of magnetism, for which it is crucial to control the lithium's atomic content. In this work, we demonstrate that dual ion beam sputtering is a suitable technique to tailor the lithium content of thin films of lithium ferrite (LFO) by using the different energies of the assisting ion beam formed by Ar+ and O2+ ions during the growth process. Without assistance, a disordered rock-salt LFO phase (i.e., LiFeO2) can be identified as the principal phase. Under beam assistance, highly out-of-plane-oriented (111) thin LFO films have been obtained on (0001) Al2O3 substrates with a disordered spinel structure as the main phase and with lithium concentrations higher and lower than the stoichiometric spinel phase, i.e., LiFe5O8. After post-annealing of the films at 1025 K, a highly ordered ferromagnetic spinel LFO phase was found when the lithium concentration was higher than the stoichiometric value. With lower lithium contents, the antiferromagnetic hematite (α-Fe2O3) phase emerged and coexisted in films with the ferromagnetic LixFe6-xO8. These results open up the possibility of controlling the properties of thin lithium ferrite-based films to enable their use in advanced spintronic devices.

Eco-Friendly Sol-Gel Coatings with Organic Corrosion Inhibitors for Lightweight AZ61 Alloy.

The latest advances in technology and materials science have catalyzed a transformative shift towards the adoption of environmentally conscious and lightweight materials across key sectors such as aeronautics, biomedical, and automotive industries. Noteworthy among these innovations are the magnesium-aluminum (Mg-Al) alloys employed in aeronautical applications, contributing to the overall reduction in aircraft weight and subsequently diminishing fuel consumption and mitigating atmospheric emissions. The present work delves into a study of the anti-corrosive properties inherent in various sol-gel coatings, leveraging a range of environmentally friendly corrosion inhibitors, specifically tailored for samples of the AZ61 alloy. Methodologically, the work involves the synthesis and application of sol-gel coatings on AZ61 alloy containing eco-friendly inhibitors: L-cysteine, N-acetyl-cysteine, curcumin and methylene blue. Subsequently, an accelerated corrosion test in a simulated saline environment is performed. Through microstructural and compositional analyses, the best inhibitors responses are achieved with inhibitors containing S, N heteroatoms and conjugated double bonds in their structure, probably due to the creation of a continuous MgCl2 layer. This research contributes to the ongoing discourse on protective eco-coatings, aligning with the broader paradigm shift towards sustainable and lightweight materials in key industries.

Ion-induced bias in Ag2S luminescent nanothermometers.

Luminescence nanothermometry allows measuring temperature remotely and in a minimally invasive way by using the luminescence signal provided by nanosized materials. This technology has allowed, for example, the determination of intracellular temperature and in vivo monitoring of thermal processes in animal models. However, in the biomedical context, this sensing technology is crippled by the presence of bias (cross-sensitivity) that reduces the reliability of the thermal readout. Bias occurs when the impact of environmental conditions different from temperature also modifies the luminescence of the nanothermometers. Several sources that cause loss of reliability have been identified, mostly related to spectral distortions due to interaction between photons and biological tissues. In this work, we unveil an unexpected source of bias induced by metal ions. Specifically, we demonstrate that the reliability of Ag2S nanothermometers is compromised during the monitoring of photothermal processes produced by iron oxide nanoparticles. The observed bias occurs due to the heat-induced release of iron ions, which interact with the surface of the Ag2S nanothermometers, enhancing their emission. The results herein reported raise a warning to the community working on luminescence nanothermometry, since they reveal that the possible sources of bias in complex biological environments, rich in molecules and ions, are more numerous than previously expected.

Biomineralization of magnetic nanoparticles in stem cells.

Iron is one of the most common metals in the human body, with an intrinsic metabolism including proteins involved in its transport, storage, and redox mechanisms. A less explored singularity is the presence of magnetic iron in the organism, especially in the brain. The capacity of human stem cells to biosynthesize magnetic nanoparticles was recently demonstrated, using iron released by the degradation of synthetic magnetic nanoparticles. To evidence a magnetic biomineralization in mammalian cells, it is required to address the biosynthesis of magnetic nanoparticles in cells supplied exclusively with non-magnetic iron salt precursors. Herein, mouse and human mesenchymal stem cells were incubated with ferric quinate for up to 36 days. By optimizing the concentration and culture time, and by measuring both total intracellular iron content and cellular magnetic signals, the biosynthesis of magnetic nanoparticles was found to occur from 14 days of continuous iron incubation and was correlated with important doses of intracellular iron. The local electronic structure and chemical environment of intracellular iron were further characterized by XAS spectroscopy at the Fe K-edge, showing a total conversion of Fe2+ to Fe3+ when using ferrous salts (ascorbate and sulfate), and a transformation towards ferrihydrite as well as a small proportion of a magnetic phase.

Evaluation of Low-Toxic Hybrid Sol-Gel Coatings with Organic pH-Sensitive Inhibitors for Corrosion Protection of AA2024 Aluminium Alloy.

Today's environmental needs require the reduction of the weight of vehicles, thus reducing fuel consumption and associated emissions. For this reason, the use of light alloys is being studied, which, due to their reactivity, must be protected before use. In this work, the effectiveness of a hybrid sol-gel coating doped with various organic environmentally friendly corrosion inhibitors applied to an AA2024 lightweight aluminium alloy is evaluated. Some of the inhibitors tested are pH indicators, acting as both corrosion inhibitors and optical sensors for the surface of the alloy. Samples are subjected to a corrosion test in a simulated saline environment and characterised before and after the test. The experimental results regarding their best inhibitor performance for their potential application in the transport industry are evaluated.

Generation of Defective Few-Layered Graphene Mesostructures by High-Energy Ball Milling and Their Combination with FeSiCuNbB Microwires for Reinforcing Microwave Absorbing Properties.

Defective few-layered graphene mesostructures (DFLGMs) are produced from graphite flakes by high-energy milling processes. We obtain an accurate control of the generated mesostructures, as well as of the amount and classification of the structural defects formed, providing a functional material for microwave absorption purposes. Working under far-field conditions, competitive values of minimum reflection loss coefficient (RLmin) = -21.76 dB and EAB = 4.77 dB are achieved when DFLGMs are immersed in paints at a low volume fraction (1.95%). One step forward is developed by combining them with the excellent absorption behavior that offers amorphous Fe73.5Si13.5B9Cu1Nb microwires (MWs), varying their filling contents, which are below 3%. We obtain a RLmin improvement of 47% (-53.08 dB) and an EAB enhancement of 137% (4 dB) compared to those obtained by MW-based paints. Furthermore, a fmin tunability is demonstrated, maintaining similar RLmin and EAB values, irrespective of an ideal matching thickness. In this scenario, the Maxwell-Garnet standard model is valid, and dielectric losses mainly come from multiple reflections, interfacial and dielectric polarizations, which greatly boost the microwave attenuation of MWs. The present concept can remarkably enhance not only the MW attenuation but can also apply to other microwave absorption architectures of technological interest by adding low quantities of DFLGMs.

The Thermoelectric Properties of Spongy PEDOT Films and 3D-Nanonetworks by Electropolymerization.

Recently, polymers have been attracted great attention because of their thermoelectric materials' excellent mechanical properties, specifically their cost-effectiveness and scalability at the industrial level. In this study, the electropolymerization conditions (applied potential and deposition time) of PEDOT films were investigated to improve their thermoelectric properties. The morphology and Raman spectroscopy of the PEDOT films were analyzed according to their applied potential and deposition time. The best thermoelectric properties were found in films grown at 1.3 V for 10 min, with an electrical conductivity of 158 ± 8 S/cm, a Seebeck coefficient of 33 ± 1 µV/K, and a power factor of 17 ± 2 µW/K·m2. This power factor value is three times higher than the value reported in the literature for electropolymerized PEDOT films in acetonitrile using lithium perchlorate as a counter-ion. The thermal conductivity was found to be (1.3 ± 0.3) × 10-1 W/m·K. The highest figure of merit obtained at room temperature was (3.9 ± 1.0) × 10-2 using lithium perchlorate as a counter-ion. In addition, three-dimensional (3D) PEDOT nanonetworks were electropolymerized inside 3D anodic aluminum oxide (3D AAO), obtaining lower values in their thermoelectric properties.

Digital Competencies for Nurses: Tools for Responding to Spiritual Care Needs.

Users show a growing interest in expanding the implementation of digital tools as a support of technical and management issues in healthcare. This medical care has focused on telemedicine but does not include the recognition of needs as an important part of patient-centred healthcare. Nurses interact with patients at critical times in their life journeys, including birth and death, which are historical events linked with religious beliefs. Furthermore, large migration flows have led to multicultural societies in which religion and spirituality are experienced in distinct ways by different people. Finally, most healthcare professionals lack the proper skills to handle the spiritual needs of their patients, especially for core and digital competences. This article shows the results of qualitative research applying as a research tool an open-ended questionnaire, which allows detecting the educational needs for nurses' interventions aimed at providing spiritual support to their patients using digital tools. The results obtained reveal that nurses need education and training on fundamental spiritual concepts and digital competencies to meet the multiple demands of their patients' spiritual needs. Finally, we present an open digital educational proposal for the development of competencies for nurses and other health professionals to provide spiritual care with the support of digital tools.

Providing Spiritual Care to In-Hospital Patients During COVID-19: A Preliminary European Fact-Finding Study.

Historically, there has be a close relationship between the nursing services and spiritual care provision to patients, arising due to the evolvement of many hospitals and nursing programmes from faith-based institutions and religious order nursing. With increasing secularism, these relationships are less entwined. Nonetheless, as nurses typically encounter patients at critical life events, such as receiving bad news or dying, nurses frequently understand the need and requirement for both spiritual support and religious for patients and families during these times. Yet there are uncertainties, and nurses can feel ill-equipped to deal with patients' spiritual needs. Little education or preparation is provided to these nurses, and they often report a lack of confidence within this area. The development of this confidence and the required competencies is important, especially so with increasingly multicultural societies with diverse spiritual and religious needs. In this manuscript, we discuss initial field work carried out in preparation for the development of an Erasmus Plus educational intervention, entitled from Cure to Care Digital Education and Spiritual Assistance in Healthcare. Referring specifically to post-COVID spirituality needs, this development will support nurses to respond to patients' spiritual needs in the hospital setting, using digital means. This preliminary study revealed that while nurses are actively supporting patients' spiritual needs, their education and training are limited, non-standardised and heterogeneous. Additionally, most spiritual support occurs within the context of a Judeo-Christian framework that may not be suitable for diverse faith and non-faith populations. Educational preparation for nurses to provide spiritual care is therefore urgently required.

Hybrid Sol-Gel Coatings Doped with Non-Toxic Corrosion Inhibitors for Corrosion Protection on AZ61 Magnesium Alloy.

Physiological human fluid is a natural corrosive environment and can lead to serious corrosion and mechanical damages to light Mg-Al alloys used in prosthetics for biomedical applications. In this work, organic-inorganic hybrid coatings doped with various environmentally friendly and non-toxic corrosion inhibitors have been prepared by the sol-gel process for the corrosion protection of AZ61 magnesium alloys. Effectiveness has been evaluated by pH measurements, optical microscopy, and SEM during a standard corrosion test in a Hanks' Balanced Salt Solution. The results showed that the addition of an inhibitor to the sol-gel coating can improve significantly the corrosion performance, being an excellent barrier for the L-cysteine-doped hybrid sol-gel films. The incorporation of TiO2 nanoparticles, 2-Aminopyridine and quinine organic molecules slowed down the corrosion rate of the Mg-Al alloy. Graphene oxide seemed to have the same response to corrosion as the hybrid sol-gel coating without inhibitors.

Massive Intracellular Remodeling of CuS Nanomaterials Produces Nontoxic Bioengineered Structures with Preserved Photothermal Potential.

Despite efforts in producing nanoparticles with tightly controlled designs and specific physicochemical properties, these can undergo massive nano-bio interactions and bioprocessing upon internalization into cells. These transformations can generate adverse biological outcomes and premature loss of functional efficacy. Hence, understanding the intracellular fate of nanoparticles is a necessary prerequisite for their introduction in medicine. Among nanomaterials devoted to theranostics is copper sulfide (CuS), which provides outstanding optical properties along with easy synthesis and low cost. Herein, we performed a long-term multiscale study on the bioprocessing of hollow CuS nanoparticles (CuS NPs) and rattle-like iron oxide nanoflowers@CuS core-shell hybrids (IONF@CuS NPs) when inside stem cells and cancer cells, cultured as spheroids. In the spheroids, both CuS NPs and IONF@CuS NPs are rapidly dismantled into smaller units (day 0 to 3), and hair-like nanostructures are generated (day 9 to 21). This bioprocessing triggers an adaptation of the cellular metabolism to the internalized metals without impacting cell viability, differentiation, or oxidative stress response. Throughout the remodeling, a loss of IONF-derived magnetism is observed, but, surprisingly, the CuS photothermal potential is preserved, as demonstrated by a full characterization of the photothermal conversion across the bioprocessing process. The maintained photothermal efficiency correlated well with synchrotron X-ray absorption spectroscopy measurements, evidencing a similar chemical phase for Cu but not for Fe over time. These findings evidence that the intracellular bioprocessing of CuS nanoparticles can reshape them into bioengineered nanostructures without reducing the photothermal function and therapeutic potential.

Assessing the parameters modulating optical losses of iron oxide nanoparticles under near infrared irradiation.

Heating mediated by iron oxide nanoparticles subjected to near infrared irradiation has recently gained lots of interest. The high optical loss values reported in combination with the optical technologies already existing in current clinical practices, have made optical heating mediated by iron oxide nanoparticles an attractive choice for treating internal or skin tumors. However, the identification of the relevant parameters and the influence of methodologies for quantifying the optical losses released by iron oxide nanoparticles are not fully clear. Here, we report on a systematic study of different intrinsic (size, shape, crystallinity, and iron oxidation state) and extrinsic (aggregation, concentration, intracellular environment and irradiation conditions) parameters involved in the photothermal conversion of iron oxide nanoparticles under near infrared irradiation. We have probed the temperature increments to determine the specific loss power of iron oxide nanoparticles with different sizes and shapes dispersed in colloidal suspensions or inside live breast cancer cells. Our results underline the relevance of crystal surface defects, aggregation, concentration, magnetite abundance, excitation wavelength and density power on the modulation of the photothermal conversion. Contrary to plasmonic or magnetic losses, no significant influence of nanoparticle size nor shape was observed on the optical losses released by the studied iron oxide nanoparticles. Interestingly, no significant differences of measured temperature increments and specific loss power values were either observed when nanoparticles were inside live cells or in colloidal dispersion. Our findings highlight the advantages of optical heat losses released by iron oxide nanoparticles for therapeutic applications.

Control of the Length of Fe73.5Si13.5Nb3Cu1B9 Microwires to Be Used for Magnetic and Microwave Absorbing Purposes.

A combination of high-energy ball milling, vacuum filtering, and sedimentation processes has been demonstrated to be a useful approach to reduce, in a controlled way, the length of as-cast Fe73.5Si13.5Nb3Cu1B9 amorphous magnetic microwires (MWs) and annealed material at 550 °C in nitrogen conditions. Homogeneous compositional microstructures with fairly narrow size distributions between 1300 and 11.7 µm are achieved, exhibiting tunable response as a soft magnetic material and as a microwave absorber. From the magnetic perspective, the soft magnetic character is increased with smaller length of the MWs, whereas the remanence has the opposite behavior mainly due to the structural defects and the loss of the shape anisotropy. From the microwave absorption perspective, a novel potential applicability is tested in these refined microstructures. This innovation consists of coatings based on commercial paints with a filling percentage of 0.55% of MWs with different lengths deposited on metallic sheets. Large attenuation values around -40 dB are obtained in narrow spectral windows located in the GHz range, and their position can be varied by combining different optimized lengths of MW. As an example of this powerful mechanism for absorbing microwaves at specific frequencies, MW lengths of 2 mm and 50 µm are chosen, where precise tailoring of the minimum reflection loss (RL) is obtained in a range between 8.85 and 13.25 GHz. To confirm these experimental results, an effective medium standard model proposed for electrical permittivity is used. Experimental and theoretical results are consistent and these novel composites are also proposed as a feasible candidate for designing frequency-selective microwave absorbers on demand, with low filling percentages and high absorption intensity values.

Transformation Cycle of Magnetosomes in Human Stem Cells: From Degradation to Biosynthesis of Magnetic Nanoparticles Anew.

The nanoparticles produced by magnetotactic bacteria, called magnetosomes, are made of a magnetite core with high levels of crystallinity surrounded by a lipid bilayer. This organized structure has been developed during the course of evolution of these organisms to adapt to their specific habitat and is assumed to resist degradation and to be able to withstand the demanding biological environment. Herein, we investigated magnetosomes' structural fate upon internalization in human stem cells using magnetic and photothermal measurements, electron microscopy, and X-ray absorption spectroscopy. All measurements first converge to the demonstration that intracellular magnetosomes can experience an important biodegradation, with up to 70% of their initial content degraded, which is associated with the progressive storage of the released iron in the ferritin protein. It correlates with an extensive magnetite to ferrihydrite phase transition. The ionic species delivered by this degradation could then be used by the cells to biosynthesize magnetic nanoparticles anew. In this case, cell magnetism first decreased with magnetosomes being dissolved, but then cells remagnetized entirely, evidencing the neo-synthesis of biogenic magnetic nanoparticles. Bacteria-made biogenic magnetosomes can thus be totally remodeled by human stem cells, into human cells-made magnetic nanoparticles.

Towards Blue Long-Lasting Luminescence of Eu/Nd-Doped Calcium-Aluminate Nanostructured Platelets via the Molten Salt Route.

Calcia-alumina binary compounds doped with rare earths and some transition metals cations show persistent luminescence from the visible to the infrared range. Specifically, the blue light can be obtained through the Eu2+ activator center in a potential host, such as dodecacalcium hepta-aluminate (Ca12Al14O33) and monocalcium aluminate (CaAl2O4). By doping with Nd3+, the persistent luminescence can be substantially prolonged; for this reason, the Eu/Nd pair is a potential choice for developing long-lasting blue luminescence. Herein, the phase evolution of the calcia-alumina system via molten salt synthesis is reported as a function of the synthesis temperature and the atmospheric environment. The fraction of CaAl2O4 phase increases when the temperature is higher. Synthesized microparticles of platelet-type morphology represent isolated nanostructured ceramic pieces. Under visible light, the particles are white. This indicates that the followed process solves the dark-gray coloring of phosphor when is synthesized in a reduced atmosphere at high temperature. As regards the synthesis mechanism, which is assisted by the molten flux, the dissolution-diffusion transport process is promoted at the surface of the alumina microparticles. In fact, the emission intensity can be modulated through the phase of the Eu-doped calcium-aluminate discrete platelets synthesized. Consequently, the photoluminescence intensity depends also on the oxidation state of the Eu ion. X-ray absorption near-edge structure and photoluminescence measurements corroborate the Eu reduction and the grain coarsening with the enhancement of the blue emission. The doped phosphors with Eu/Nd show a broad and strong absorption in the region of 320-400 nm and a broad emission band at around 440 nm when they are excited in this absorption range. From a broader perspective, our findings prove that the Ca12Al14O33 and CaAl2O4 phases open new opportunities for research into the design of blue long-lasting emitters for a wide range of fields from ceramic to optoelectronic materials.

Mn-Doping level dependence on the magnetic response of MnxFe3-xO4 ferrite nanoparticles.

Manganese/iron ferrite nanoparticles with different Mn2+/3+ doping grades have been prepared by a thermal decomposition optimized approach so as to ascertain the doping effect on magnetic properties and, especially, on the magnetic hyperthermia response. The oxidation state and interstitial position of Mn in the spinel structure is found to be critical. The particle size effect has also been studied by growing one of the prepared samples (from 10 to 15 nm in diameter) by a seed mediated growth mechanism. After analyzing the main structural and chemical parameters such as the Mn/Fe rate, crystalline structure, particle diameter, shape and organic coating, some Mn doping induced changes have been observed, such as the insertion of Mn2+ cations yielded more anisotropic shapes. Magnetic characterization, carried out by DC magnetometry (M(H), M(T)) and electron magnetic resonance (EMR) techniques, has shown interesting differences between samples with varying compositions. Lower Mn doping levels lead to larger saturation magnetization values, while an increase of the Mn content causes the decrease of the effective magnetic anisotropy constant at low T. The homogeneous magnetic response under applied magnetic fields, together with the great effect of nanoparticle size and shape in such a response, has been confirmed by the EMR analysis. Finally, a detailed magnetic hyperthermia analysis has demonstrated the large influence of NP size and shape on the magnetic hyperthermia response. The optimized Mn0.13Fe2.87O4_G sample with a diameter of 15 nm and slightly truncated octahedral shape is presented as an interesting candidate for future magnetic hyperthermia mediated biomedical treatments.

Transparent Sol-Gel Oxyfluoride Glass-Ceramics with High Crystalline Fraction and Study of RE Incorporation.

Transparent oxyfluoride glass-ceramic films and self-supported layers with composition 80SiO2-20LaF3 doped with Er3+ have been successfully synthesized by sol-gel process for the first time. Crack-free films and self-supported layer with a maximum thickness up to 1.4 µm were obtained after heat treatment at the low temperature of 550 °C for 1 min, resulting in a LaF3 crystal fraction of 18 wt%, as confirmed by quantitative Rietveld refinement. This is the highest value reported up to now for transparent oxyfluoride glass-ceramics prepared by sol-gel. This work provides a new synthesis strategy and opens the way to a wide range of potential applications of oxyfluoride glass-ceramics. The characterization by a wide range of techniques revealed the homogeneous precipitation of LaF3 nanocrystals into the glass matrix. X-ray absorption spectroscopy and electron paramagnetic resonance confirmed that the Er3+ ions are preferentially embedded in the low phonon-energy LaF3 nanocrystals. Moreover, photoluminescence (PL) measurements confirmed the incorporation of dopants in the LaF3 nanocrystals. The effective concentration of rare-earth ions in the LaF3 nanocrystals is also estimated by X-ray absorption spectroscopy.