Effects of the induced micro- and meso-porosity on the single site density and turn over frequency of Fe-N-C carbon electrodes for the oxygen reduction reaction

Fe-N-C have emerged as one of the best non-PGM alternatives to Pt/C catalysts for the electrochemical reduction of O2 in fuel cells. In this work, we explore the effect of steam and CO2 treatments at high temperatures on the nanometric porous structure of a commercial carbon black. Using those support materials, we synthesize different Fe-N-C catalysts to achieve a better understanding on the role of micro- and mesopores of the support towards catalytic site formation and site activity. Different time and temperature of treatments result in an almost linear increment of surface area and microporous volume, which allows better nitrogen functionalization. Site density evaluation, performed using a recently described NO-stripping technique, showed an increase in site density and TOF which correlates well with the morphology variation. The percentage of active iron increases from 2.65 % to 14.74 % in activated catalysts confirming a better access of electrolyte to the iron sites

Top-down synthesis of multifunctional iron oxide nanoparticles formacrophage labelling and manipulation

Multifunctional iron oxide (FeOx) magnetic nanoparticles (MNPs) are promising items for biomedical applications. They are studied as theranostic agents for cancer treatment, selective probes for bioanalytical assays, controllable carriers for drug delivery and biocompatible tools for cell sorting or tissue repair. Here we report a new method for the synthesis in water of FeOx–MNPs via a top-down physical technique consisting in Laser Ablation Synthesis in Solution (LASiS). LASiS is a green method that does not require chemicals or stabilizers, because nanoparticles are directly obtained in water as a stable colloidal system. A gamut of characterization techniques was used for investigating the structure of FeOx–MNPs that have a polycrystalline structure prevalently composed of magnetite (ca. 75%) and hematite (ca. 22%). The FeOx–MNPs exhibit very good magnetic properties if compared to what is usually reported for iron oxide nanoparticles, with saturation magnetization close to the bulk value (ca. 80 emu g1) and typical signatures of the coexistence of ferrimagnetic and antiferromagnetic phases in the same particle. The functionalization of FeOx–MNPs after the synthesis was possible with a variety of ligands. In particular, we succeeded in the functionalization of FeOx–MNPs with carboxylated phosphonates, fluorescent alkylamines, fluorescent isothiocyanates and bovine serum albumin. Our FeOx–MNPs showed excellent biocompatibility. Multifunctional FeOx–MNPs were exploited for macrophage cell labelling with fluorescent probes as well as for cell sorting and manipulation by external magnetic fields

Surface Engineering of Chemically Exfoliated MoS<inf>2</inf> in a "click": How to Generate Versatile Multifunctional Transition Metal Dichalcogenides-Based Platforms

Copyright © 2018 American Chemical Society. The interest for transition metal dichalcogenides (TMDs) as two-dimensional (2D) analogues of graphene is steadily growing along with the need of efficient and easy tunable protocols for their surface functionalization. This latter aspect holds a key role in the widespread application of TMDs in various technological fields and it represents the missing step to bridge the gap between the more popular C sp2-based networks and their inorganic counterparts. Although significant steps forward have already been made in the field of TMDs functionalization (particularly for MoS2), a rational approach to their surface engineering for the generation of 2D organic-inorganic hybrids capable to accommodate various molecules featured by orthogonal groups has not been reported yet. The paper paves the way toward a new frontier for "click" chemistry in material science. It describes the post-synthetic modification (PSM) of covalently decorated MoS2 nanosheets with phenylazido pendant arms and the successful application of CuAAC chemistry (copper-mediated azide-alkyne cycloaddition) towards the generation of highly homo- and hetero-decorated MoS2 platforms. This contribution goes beyond the proof of evidence of the chemical grafting of organic groups to the surface of exfoliated MoS2 flakes through covalent C-S bonds. It also demonstrates the versatility of the hybrid samples to undergo post-synthetic modifications thus imparting multimodality to these 2D materials. Several physico-chemical [SEM microscopy, fluorescence lifetime imaging (FLIM)], spectroscopic (IR, Raman, XPS, UV-vis), and analytical tools have been combined together for the hybrids' characterization as well as for the estimation of their functionalization loading

Ventilatory associated barotrauma in COVID-19 patients: A multicenter observational case control study (COVI-MIX-study)

Background: The risk of barotrauma associated with different types of ventilatory support is unclear in COVID-19 patients. The primary aim of this study was to evaluate the effect of the different respiratory support strategies on barotrauma occurrence; we also sought to determine the frequency of barotrauma and the clinical characteristics of the patients who experienced this complication. Methods: This multicentre retrospective case-control study from 1 March 2020 to 28 February 2021 included COVID-19 patients who experienced barotrauma during hospital stay. They were matched with controls in a 1:1 ratio for the same admission period in the same ward of treatment. Univariable and multivariable logistic regression (OR) were performed to explore which factors were associated with barotrauma and in-hospital death. Results: We included 200 cases and 200 controls. Invasive mechanical ventilation was used in 39.3% of patients in the barotrauma group, and in 20.1% of controls (p<0.001). Receiving non-invasive ventilation (C-PAP/PSV) instead of conventional oxygen therapy (COT) increased the risk of barotrauma (OR 5.04, 95% CI 2.30 - 11.08, p<0.001), similarly for invasive mechanical ventilation (OR 6.24, 95% CI 2.86-13.60, p<0.001). High Flow Nasal Oxygen (HFNO), compared with COT, did not significantly increase the risk of barotrauma. Barotrauma frequency occurred in 1.00% [95% CI 0.88-1.16] of patients; these were older (p=0.022) and more frequently immunosuppressed (p=0.013). Barotrauma was shown to be an independent risk for death (OR 5.32, 95% CI 2.82-10.03, p<0.001). Conclusions: C-PAP/PSV compared with COT or HFNO increased the risk of barotrauma; otherwise HFNO did not. Barotrauma was recorded in 1.00% of patients, affecting mainly patients with more severe COVID-19 disease. Barotrauma was independently associated with mortality. Trial registration: this case-control study was prospectively registered in clinicaltrial.gov as NCT04897152 (on 21 May 2021)

Enhanced reactivity of NiO/Pd(100) ultrathin films toward H-2: Experimental and theoretical evidence for the role of polar borders

NiO layers in the ultrathin regime exhibit an enhanced reactivity toward hydrogen with respect to the typical chemical inertness of bulk-like thicker samples. Such a behavior has been studied by means of photoemission (from both core and valence band levels) and quantum mechanical calculations. It is found that after H2 dosing in mild conditions (from PH2 = 6.5 7 10-7 Pa and T = 330 K) ultrathin films (thickness 646MLE, MLE = monolayer equivalent) quickly react forming metal nickel and water. The kinetic of the reaction has been followed in situ recording the intensity of the O 1s and Ni 2p photoemission spectra under different reaction conditions (PH2 ranging from 5 7 10-7 to 2 7 10-5 Pa and T from 330 up to 453 K), and a first-order dependence of the reaction rate on the PH2 and the activation energy of the rate determining step (0.16 \ub1 0.02 eV) have been determined. A 8 MLE thick film recovers the behavior of bulk-like NiO(100) surfaces, where more drastic reduction conditions are needed, and the kinetic implies an induction period followed by autocatalysis. The enhanced reactivity has been explained assuming the presence of NiO(100) islands exposing polar borders, whose existence was evidenced by previous scanning tunneling microscopy investigations. Such a scenario is confirmed by ab initio quantum mechanical calculations carried out employing polar and nonpolar terminated stepped surface epitaxially strained in order to account for the presence of the metal support which has not been explicitly included. Reported calculations indicate that the polar border can easily dissociate H2 without any activation barrier. The rate determining step of the reaction has been associated to the stage of the reaction where the previously formed hydroxyl groups react with a second hydrogen molecule (an Eley 12Rideal-like mechanism) to form metal Ni islands and water, which readily desorbs