Pressure-induced Co2+ photoluminescence quenching in MgAl2O4

This work investigates the electronic structure and photoluminescence (PL) of Co2+-doped gAl2O4 and their pressure dependence by time-resolved spectroscopy. The variations of the visible absorption band and its associated emission at 663 nm (τ = 130 ns at ambient conditions) with pressure/temperature can be explained on the basis of a configurational energy model. It provides an interpretation for both the electronic structure and the excited-state phenomena yielding photoluminescence emission and the subsequent quenching. We show that there is an excited-state crossover (ESCO) [4T1(P)↔2E(G)] at ambient pressure, which is responsible for the evolution of the emission spectrum from a broadband emission between 300 K and 100 K to a narrow-line emission at lower temperatures. Contrary to expectations from the Tanabe-Sugano diagram, instead of enhancing ESCO phenomena, pressure reduces PL and even suppresses it (PL quenching) above 6 GPa. We explain such variations in terms of pressure-induced nonradiative relaxation to lower excited states: 2E(G)→4T1(F). The variation of PL intensity and its associated lifetime with pressure supports the proposed interpretation.Financial support from the Spanish Ministerio de Economia y Competitividad (Project No. MAT2011-28868-C02-01) and MALTA INGENIO-CONSOLIDER 2010 (Ref. CDS2007-0045) is acknowledged. L.N. thanks the University of Cantabria for a postdoctoral fellowship grant

Understanding the Efficiency of Mn4+ Phosphors: Study of the Spinel Mg2Ti1-xMnxO4

We present a spectroscopic study of Mn-doped Mg2TiO4 as a function of pressure and temperature to check its viability as a red-emitting phosphor. The synthesis following a solid-state reaction route yields not only the formation of Mn4+ but also small traces of Mn3+. Although we show that Mn4+ photoluminescence is not appreciably affected by the presence of Mn3+, its local structure at the substituted Ti4+ host site causes a reduction of the Mn4+ pumping efficiency yielding a drastic quantum-yield reduction at room temperature. By combining Raman and time-resolved emission and excitation spectroscopies, we propose a model for explaining the puzzling nonradiative and inefficient pumping processes attained in this material. In addition, we unveil a structural phase transition above 14 GPa that worsens their photoluminescence capabilities. The decrease of emission intensity and lifetime with increasing temperature following different thermally activated de-excitation pathways is mostly related to relatively small activation energies and the electric−dipole transition mechanism associated with coupling to odd-parity vibrational modes. A thorough model based on the configurational energy level diagram to the A1g normal mode fairly accounts for the observed excitation and emissionthe quantum yieldof this material

Development of an accurate method for dispersion and quantification of carbon nanotubes in biological media

Understanding the biological effects triggered by nanomaterials is crucial, not only in nanomedicine but also in toxicology. The dose-response relation is relevant in biological tests due to its use for determining appropriate dosages for drugs and toxicity limits. Carbon nanotubes can trigger numerous unusual biological effects, many of which could have unique applications in biotechnology and medicine. However, their resuspension in saline solutions and the accurate determination of their concentration after dispersion in biological media are major handicaps to identify the magnitude of the response of organisms as a function of this exposure. This difficulty has led to inconsistent results and misinterpretations of their in vivo behavior, limiting their potential use in nanomedicine. The lack of a suitable protocol that allows comparing different studies of the content of carbon nanotubes and their adequate resuspension in culture cell media gives rise to this study. Here, we describe a methodology to functionalize, resuspend and determine the carbon nanotube concentration in biocompatible media based on UV-Vis spectroscopy. This method allows us to accurately estimate the concentration of these resuspended carbon nanotubes, after removing bundles and micrometric aggregates, which can be used as a calibration standard, for dosage-dependent studies in biological systems. This method can also be extended to any other nanomaterial to properly quantify the actual concentration.This work has been funded by the Instituto de Salud Carlos III (ISCiii) (ref. PI16/00496, PI19/00349, DTS19/00033); co-funded by ERDF/ESF, “Investing in your future”; the Spanish MINECO (project ref. PGC2018-101464-B-I00) and MICINN NanoBioApp Network (MINECO-17-MAT2016-81955-REDT). Authors also thank the networks Raman4Clinics (BM1401). CRL thanks the MINECO for the Juan de la Cierva Formación grant (ref. FJCI-2015-25306) and LGL the ISCiii for the Sara Borrell grant (ref. CD17/00105). The authors want to also thank the IDIVAL for financial support (refs. NVAL18/07, INNVAL18/28) and technical support

Upconversion and Optical Nanothermometry in LaGdO3: Er3+ Nanocrystals in the RT-900 K Range

This work has been supported by the Spanish Ministerio de Economía, Industria y Competitividad (Projects Nos. MAT2015-69508-P and PGC2018-101464-B-I00), the European Research Council (Ref. NCLas H2020-EU829161), and BSH Electrodomésticos España, S.A

Engineering Sub-Cellular Targeting Strategies to Enhance Safe Cytosolic Silica Particle Dissolution in Cells

Mesoporous silica particles (MSP) are major candidates for drug delivery systems due to their versatile, safe, and controllable nature. Understanding their intracellular route and biodegradation process is a challenge, especially when considering their use in neuronal repair. Here, we characterize the spatiotemporal intracellular destination and degradation pathways of MSP upon endocytosis by HeLa cells and NSC-34 motor neurons using confocal and electron microscopy imaging together with inductively-coupled plasma optical emission spectroscopy analysis. We demonstrate how MSP are captured by receptor-mediated endocytosis and are temporarily stored in endo-lysosomes before being finally exocytosed. We also illustrate how particles are often re-endocytosed after undergoing surface erosion extracellularly. On the other hand, silica particles engineered to target the cytosol with a carbon nanotube coating, are safely dissolved intracellularly in a time scale of hours. These studies provide fundamental clues for programming the sub-cellular fate of MSP and reveal critical aspects to improve delivery strategies and to favor MSP safe elimination. We also demonstrate how the cytosol is significantly more corrosive than lysosomes for MSP and show how their biodegradation is fully biocompatible, thus, validating their use as nanocarriers for nervous system cells, including motor neurons.This research was funded by ISCIII Projects ref. PI16/00496, PI19/00349, DTS19/00033, co-funded by ERDF/ESF, "Investing in Your Future"; and MICINN Projects ref. CTM2017-84050-R, NanoBioApp Network (MINECO-17-MAT2016-81955-REDT), COST action Nano2Clinic CA17140, Xunta de Galicia (Centro Singular de Investigación de Galicia-Accreditation 2016-2019 and EM2014/035), European Union FEDER Funds (European Regional Development Fund-ERDF) and IDIVAL for INNVAL 17/11, INNVAL18/28, INNVAL19/18 and the technical support

Pressure effects on Jahn-Teller distortion in perovskites: The roles of local and bulk compressibilities

The interplay between the Jahn-Teller (JT) effect and octahedron tilting in transition-metal perovskites is investigated as a function of pressure. Our focus is on its effects on the exchange and electron-phonon interactions, both having a strong influence on materials properties. We demonstrate that the JT distortion in Cu2+ and Mn3+ is reduced upon compression and is eventually suppressed at pressures above 20 GPa. X-ray diffraction and x-ray absorption measurements in A2CuCl4 layer perovskites (A: Rb, CnH2n+1NH3; n = 1–3) show that, although pressure slightly reduces the long Cu-Cl distance in comparison to the Cu-Cu distance in the layer, the JT distortion is stable in the 0–20 GPa range. The difference between lattice (βC 0 = 0.14 GPa−1) and local CuCl6 (β0 = 0.016 GPa−1) compressibilities, together with the high stability of the JT distortion, lead to CuCl6 tilts upon compression. The evolution of the elongated CuCl6 octahedron in A2CuCl4, as well as MnF6 in CsMnF4 and MnO6 in LaMnO3 and DyMnO3, toward a nearly regular octahedron takes place above 20 GPa, in agreement with experimental results and a model analysis based on the JT energy derived from optical absorption spectroscopy: EJT = 0.25–0.45 eV/Cu2+, EJT = 0.45 eV/Mn3+ (CsMnF4), and EJT = 0.25 eV/Mn3+ (LaMnO3). The proposed model clarifies controversial results about pressure-induced JT quenching in Cu2+ and Mn3+ systems, providing an efficient complementary means to predict pressure behavior in perovskites containing JT transition-metal ions.Financial support from the Spanish Ministerio de Ciencia e Innovacion (Grant No. MAT2008-06873-C02-01/MAT) ´ is acknowledged. X-ray absorption and diffraction experiments were done at D11/LURE (Project PS203-01), and ID09A/ESRF (HS2159), respectively. The MALTA Consolider Ingenio 2010 program (CSD2007-00045) is also acknowledged

Adsorptive capture of ionic and non-ionic pollutants using a versatile hybrid amphiphilic-nanomica

A versatile, functional nanomaterial for the removal of ionic and non-ionic pollutants is presented in this work. For that purpose, the high charge mica Na-4-Mica was exchanged with the cationic surfactant (C16H33NH(CH3)2)+. The intercalation of the tertiary amine in the swellable nano-clay provides the optimal hydrophilic/hydrophobic nature in the bidimensional galleries of the nanomaterial responsible for the dual functionality. The organo-mica, made by functionalization with C16H33NH3+, was also synthesized for comparison purposes. Both samples were characterized by X-ray diffraction techniques and transmission electron microscopy. Then, the samples were exposed to a saturated atmosphere of cyclohexylamine for two days, and the adsorption capacity was evaluated by thermogravimetric measurements. Eu3+ cations served as a proof of concept for the adsorption of ionic pollutants in an aqueous solution. Optical measurements were used to identify the adsorption mechanism of Eu3+ cations, since Eu3+ emissions, including the relative intensity of different f–f transitions and the luminescence lifetime, can be used as an ideal spectroscopic probe to characterize the local environment. Finally, the stability of the amphiphilic hybrid nanomaterial after the adsorption was also tested.We would like to thank IDIVAL for financial support, project number INNVAL19/1

Composición de nanofilamentos para el tratamiento de tumores

Composición de nanofilamentos para el tratamiento de tumores. La presente invención se refiere a composiciones que comprenden nanofilamentos y al menos un excipiente para su empleo en el tratamiento antitumoral, donde los nanofilamentos, que actúan como agentes neoplásicos, están funcionalizados con suero procedente de sangre humana. Asimismo, se contempla el procedimiento de obtención de dichas composiciones.Solicitud: 201400254 (27.03.2014)Nº Pub. de Solicitud: ES2478793A1 (22.07.2014)Nº de Patente: ES2478793B2 (23.01.2015

Effect of TiO2 and ZnO nanoparticles on the performance of dielectric nanofluids based on vegetable esters during their aging

Over the last few decades the insulating performance of transformer oils has been broadly studied under the point of view of nanotechnology, which tries to improve the insulating and heat dissipation performance of transformer oils by suspending nanoparticles. Many authors have analyzed the thermal and dielectric behavior of vegetable oil based-nanofluids, however, very few works have studied the evolution of these liquids during thermal aging and their stability. In this paper has been evaluated the performance of aged vegetable oil based-nanofluids, which have been subjected to accelerated thermal aging at 150 °C. Nanoparticles of TiO2 and ZnO have been dispersed in a commercial natural ester. Breakdown voltage, resistivity, dissipation factor and acidity of nanofluid samples have been measured according to standard methods, as well as stability. Moreover, it has been analyzed the degradation of Kraft paper through the degree of polymerization (DP). The results have showed that although nanoparticles improve breakdown voltage, they increase the ageing of insulation liquids and dielectric paper.This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 823969.The authors of this research wish to thank the Ministry of Economy for its financial support for the National Research Project: Improvement of Insulation Systems of Transformers through Dielectric Nanofluids (DPI2015-71219-C2 1-R)