Estimation of the Electron Thermalization Length in Ionic Materials

We report estimations of the thermalization length and the diffusion coefficient of photogenerated carriers in the insulator LiYF₄ as a function of their initial energy. Combining modeling of electron–phonon interaction and the detailed analysis of the kinetic response of fluorescent center Ce³⁺ under vacuum ultraviolet excitation, the thermalization length is obtained as a function of the initial kinetic energy of the electron. This parameter is essential for the description of the carrier recombination in the case of nonideal plasma conditions, where electrons and holes are strongly correlated. This approach also demonstrates the effect of a complicated structure of electronic band on the thermalization process, which impacts the complex nonproportionality response of materials under ionizing radiation excitation

Quest to enhance up-conversion efficiency: a comparison of anhydrous vs. hydrous synthesis of NaGdF4: Yb3+ and Tm3+ nanoparticles

International audienceA major challenge in the field of up-converting (UC) nanomaterials is to enhance their efficiencies. The –OH defects on the surface of the nanoparticles are thought to be the main cause of luminescence quenching, but there are no comparative studies in the literature showing the impact of anhydrous vs. hydrous synthesis on up-conversion efficiency. In this article, we present the synthesis of up-converting NaGdF4: Yb+3, Tm+3 nanoparticles by two different methods: thermal decomposition of single source metal-organic anhydrous precursors [NaLn(TFA)4(diglyme)] (Ln = Gd, Tm, Yb; TFA = trifluoroacetate) and room temperature co-precipitation using hydrated inorganic salts Ln(NO3)3·5H2O (Ln = Gd, Tm, Yb), NaNO3 and NH4F in ethylene glycol. After a detailed study on the influence of solvents and the percentage of lanthanide dopant on the crystal phase of the up-converting nanoparticles (NPs) and their complete characterization, a comparative up-conversion study was carried out which revealed that the uniform nanospheres (av. size ∼13 nm) obtained from the anhydrous SSP had significantly higher up-conversion efficiency than agglomerated nanorods (∼197 nm in length and ∼95 nm in width) produced from hydrated inorganic salts. An enhanced up-conversion quantum yield of 1.8% for the anhydrous sample validates the anhydrous precursor approach as a strategy to obtain small but highly emitting up-converting particles without requiring a silica or undoped matrix surface passivation layer

Multi-color solar absorption as a synergetic UV up-conversion enhancement mechanism in LiYF 4 :Yb 3+ ,Tm 3+ nanocrystals

International audienceMotivated by the technologically important spectral conversion of sunlight for efficient photocatalysis, we present a detailed analysis of the multi-color excitation of LiYF 4 :Yb 3+ ,Tm 3+ nanocrystals leading to UV emission through upconversion. We demonstrate in particular that the combination of blue and IR light for generating upconversion UV emission is a linear mechanism that occurs at rather low density of excitation (a few mW/cm 2). This up-conversion efficiency is fully compatible with

Precursor-directed synthesis of upconverting LiYF4:Yb3+, Tm3+ nanoparticles and their composites designed for near infra-red driven photocatalysis

SSCI-VIDE+CDFA+BPU:SMR:SDAInternational audienceTitanium dioxide (TiO2) and graphitic carbon nitride (g-C3N4) are among the most promisingphotocatalysts due to their low cost, non-toxicity and high catalytic activity. However, thesephotocatalysts also have certain limitations in terms of low efficiency of visible light utilization and high recombination rate of the photo-generated electron-hole pairs. Coupling of these photocatalysts with lanthanide-based upconverting nanoparticles (UCNPs) can lead to utilization of near-infrared part of the solar spectrum and, therefore, enhance the photocatalytic efficiency many folds.1 In this context, upconverting nanomaterials LiYF4: Tm3+/Yb3+ have great potential as they show intense upconverted emissions in the deep-UV region,2 which would greatly facilitate efficiency of above photocatalysts. However, in comparison to the more thoroughly investigated NaLnF4-based systems, the studies on upconverting nanomaterials based on the LiYF4 host matrix remain in its nascent state.3 Here we describe bottom-up synthesis of a series of LiYF4 nanocrystals (NCs) co-doped with varying amount of Yb3+ and Tm3+ ions using new molecular precursors [Ln(TFA)3(monoglyme)] [Ln = Y, Tm, Yb] and [Li(TFA)(monoglyme)] (where TFA = trifluoroacetate, and monoglyme = dimethoxyethane). These precursors, synthesized in a simple one-pot reaction and characterized by spectroscopy, single crystal X-ray structures and thermogravimetric studies, are advantageous in terms of being anhydrous. The multicolour up-conversion fluorescence studies of the obtained LiYF4:Tm3+/Yb3+ NCs established them to be promising UC nanophosphors, which were further used to prepare composites with earlier-mentioned photocatalysts to realize near IR-driven photocatalysis.[1] a) S. Wu1, J. Lv, F. Wang, N. Duan, Q. Li, Z. Wang, Sci. Rep., 7, 14435-14746 (2018); b) Y. Chen, S. Mishra, G. Ledoux, E. Jeanneau, M. Daniel, J. Zhang, S. Daniele, Chem. Asian J. 9, 2415‒2421 (2014).[2] V. Mahalingam, F. Vetrone, R. Naccache, A. Speghini, J. A. Capobianco, Adv. Mater., 21, 4025–4028 (2009).[3] T. Cheng, R. Marin, A. Skripka, F. Vetrone, J. Am. Chem. Soc., 140, 12890−12899 (2018)

Iron deficiency diagnosed using hepcidin on critical care discharge is an independent risk factor for death and poor quality of life at one year: an observational prospective study on 1161 patients.

BACKGROUND: Iron deficiency is difficult to diagnose in critically ill patients, but may be frequent and may impair recovery. Measurement of hepcidin could help in the diagnosis of iron deficiency. We aim to assess if iron deficiency diagnosed using hepcidin is associated with poorer outcome one year after an intensive care unit stay. METHODS: We used the prospective FROG-ICU, multicentre (n = 28 ICUs), observational cohort study of critically ill survivors followed up one year after intensive care unit discharge. Iron deficiency was defined as hepcidin  0.8, measured in blood drawn at intensive care unit discharge. Main outcomes were one-year all-cause mortality and poor quality of life (defined as a Short Form 36 (SF-36) score below the median). RESULTS: Among the 2087 patients in the FROG-ICU cohort, 1570 were discharged alive and 1161 had a blood sample available at intensive care unit discharge and were included in the analysis. Using hepcidin, 429 (37%) patients had iron deficiency, compared to 72 (6%) using ferritin alone and 151 (13%) using the sTfR/log(ferritin) ratio. Iron deficiency diagnosed according to low hepcidin was an independent predictor of one-year mortality (OR 1.51 (1.10-2.08)) as was high sTfR/log ferritin ratio (OR = 1.95 (1.27-3.00)), but low ferritin was not. Severe ID, defined as hepcidin < 10 ng/l, was also an independent predictor of poor one-year physical recovery (1.58 (1.01-2.49)). CONCLUSIONS: Iron deficiency, diagnosed using hepcidin, is very frequent at intensive care unit discharge and is associated with increased one-year mortality and poorer physical recovery. Whether iron treatment may improve these outcomes remains to be investigated

Type-safe relaxing of schema consistency rules for flexible modelling in OODBMS

Programme 1 - Architectures paralleles, bases de donnees, reseaux et systemes distribues. Projet RodinSIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 14802 E, issue : a.1995 n.2638 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Differences in HADS and SF-36 scores 1 year after critical illness in COVID-19 patients.

Dear Editor, Long-term outcomes among coronavirus disease 2019 (COVID-19) survivors have been a cause for concern. Similarly, patients surviving critical illness from other conditions have shown anxiety, depression and altered quality of life, contributing to post-intensive care syndrome (PICS). Te specifc contribution of COVID-19 beyond the non-specifc contribution of critical illness, however, remains unknown. In this study, we matched and compared critically ill survivors admitted to the intensive care unit (ICU) for COVID-19 to critically ill patients admitted for pneumonia or acute respiratory distress syndrome unrelated to COVID-19. We explored hospital Anxiety and Depression Scale (HADS) and the Short Form (36) Health Survey (SF-36) scores 1 year after hospitalization. [...