Replacing Metals with Oxides in Metal-Assisted Chemical Etching Enables Direct Fabrication of Silicon Nanowires by Solution Processing

Metal-assisted chemical etching (MACE) has emerged as an effective method to fabricate high aspect ratio nanostructures. This method requires a catalytic mask that is generally composed of a metal. Here, we challenge the general view that the catalyst needs to be a metal by introducing oxide-assisted chemical etching (OACE). We perform etching with metal oxides such as RuO2 and IrO2 by transposing materials used in electrocatalysis to nanofabrication. These oxides can be solution-processed as polymers exhibiting similar capabilities of metals for MACE. Nanopatterned oxides can be obtained by direct nanoimprint lithography or block-copolymer lithography from chemical solution on a large scale. High aspect ratio silicon nanostructures were obtained at the sub-20 nm scale exclusively by cost-effective solution processing by halving the number of fabrication steps compared to MACE. In general, OACE is expected to stimulate new fundamental research on chemical etching assisted by other materials, providing new possibilities for device fabrication

Block-Copolymers Enable Direct Reduction and Structuration of Noble Metal-Based Films

Noble metal nanostructured films are of great interest for various applications including electronics, photonics, catalysis, and photocatalysis. Yet, structuring and patterning noble metals, especially those of the platinum group, is challenging by conventional nanofabrication. Herein, an approach based on solution processing to obtain metal-based films (rhodium, ruthenium (Ru) or iridium in the presence of residual organic species) with nanostructuration at the 20 nm-scale is introduced. Compared to existing approaches, the dual functionality of block-copolymers acting both as structuring and as reducing agent under inert atmosphere is exploited. A set of in situ techniques has allowed for the capturing of the carbothermal reduction mechanism occurring at the hybrid organic/inorganic interface. Differently from previous literature, a two-step reduction mechanism is unveiled with the formation of a carbonyl intermediate. From a technological point of view, the materials can be solution-processed on a large scale by dip-coating as polymers and simultaneously structured and reduced into metals without requiring expensive equipment or treatments in reducing atmosphere. Importantly, the metal-based films can be patterned directly by block-copolymer lithography or by soft-nanoimprint lithography on various substrates. As proof-of-concept of application, the authors demonstrate that nanostructured Ru films can be used as efficient catalysts for H-2 generation into microfluidic reactors

Challenging claims in the study of migratory birds and climate change

Recent shifts in phenology in response to climate change are well established but often poorly understood. Many animals integrate climate change across a spatially and temporally dispersed annual life cycle, and effects are modulated by ecological interactions, evolutionary change and endogenous control mechanisms. Here we assess and discuss key statements emerging from the rapidly developing study of changing spring phenology in migratory birds. These well-studied organisms have been instrumental for understanding climate-change effects, but research is developing rapidly and there is a need to attack the big issues rather than risking affirmative science. Although we agree poorly on the support for most claims, agreement regarding the knowledge basis enables consensus regarding broad patterns and likely causes. Empirical data needed for disentangling mechanisms are still scarce, and consequences at a population level and on community composition remain unclear. With increasing knowledge, the overall support (‘consensus view’) for a claim increased and between-researcher variability in support (‘expert opinions') decreased, indicating the importance of assessing and communicating the knowledge basis. A proper integration across biological disciplines seems essential for the field's transition from affirming patterns to understanding mechanisms and making robust predictions regarding future consequences of shifting phenologies

High dose of dexamethasone protects against EAE-induced motor deficits but impairs learning/memory in C57BL/6 mice

Multiple sclerosis (MS) is an autoimmune and neuroinflammatory disease characterized by demyelination of the Central Nervous System. Immune cells activation and release of pro-inflammatory cytokines play a crucial role in the disease modulation, decisively contributing to the neurodegeneration observed in MS and the experimental autoimmune encephalomyelitis (EAE), the widely used MS animal model. Synthetic glucocorticoids, commonly used to treat the MS attacks, have controversial effects on neuroinflammation and cognition. We sought to verify the influence of dexamethasone (DEX) on the EAE progression and on EAE-induced cognitive deficits. In myelin oligodendrocyte glycoprotein peptide (MOG35-55)-induced EAE female mice, treated once with DEX (50 mg/kg) or not, on the day of immunization, DEX decreased EAE-induced motor clinical scores, infiltrating cells in the spinal cord and delayed serum corticosterone peak. At the asymptomatic phase (8-day post-immunization), DEX did not protected from the EAE-induced memory consolidation deficits, which were accompanied by increased glucocorticoid receptor (GR) activity and decreased EGR-1 expression in the hippocampus. Blunting hippocampal GR genomic activation with DnGR vectors prevented DEX effects on EAE-induced memory impairment. These data suggest that, although DEX improves clinical signs, it decreases cognitive and memory capacity by diminishing neuronal activity and potentiating some aspects of neuroinflammation in EAE

Detailed Clinical and Psychological Phenotype of the X-linked HNRNPH2-Related Neurodevelopmental Disorder

Objective: To expand the clinical phenotype of the X-linked HNRNPH2-related neurodevelopmental disorder in 33 individuals. Methods: Participants were diagnosed with pathogenic or likely pathogenic variants in HNRNPH2 using American College of Medical Genetics and Genomics/Association of Molecular Pathology criteria, largely identified via clinical exome sequencing. Genetic reports were reviewed. Clinical data were collected by retrospective chart review and caregiver report including standardized parent report measures. Results: We expand our clinical characterization of HNRNPH2-related disorders to include 33 individuals, aged 2-38 years, both females and males, with 11 different de novo missense variants, most within the nuclear localization signal. The major features of the phenotype include developmental delay/intellectual disability, severe language impairment, motor problems, growth, and musculoskeletal disturbances. Minor features include dysmorphic features, epilepsy, neuropsychiatric diagnoses such as autism spectrum disorder, and cortical visual impairment. Although rare, we report early stroke and premature death with this condition. Conclusions: The spectrum of X-linked HNRNPH2-related disorders continues to expand as the allelic spectrum and identification of affected males increases.Grant support for L. Boyle provided by TL1TR001875.info:eu-repo/semantics/publishedVersio

The origin of the high electrochemical activity of pseudo-amorphous iridium oxides

The origins of the superior catalytic activity of poorly crystallized Ir-based oxide material for the OER in acid is still under debate. Here, authors synthesize porous IrMo oxides to deconvolute the effect of Ir oxidation state from short-range ordering and show the latter to be a key factor

Nouvelles membranes de polybenzimidazoles sulfonés pour application en pile à combustible (étude des mécanismes de dégradation des assemblages membrane-électrodes)

Ce travail s'inscrit dans le contexte du développement des piles à combustible type PEMFC. La première partie de ce mémoire décrit la préparation de nouveaux polybenzimidazoles sulfonés, permettant l'obtention de membranes conductrices protoniques, selon deux voies : par sulfonation directe du polymère, par introduction d'un monomère fonctionnel lors de la synthèse. La sulfonation directe conduit à des polymères possédant des conductivités ioniques élevées et pouvant être utilisés comme polyélectrolytes dans un dispositif électrochimique de type PEMFC. La partie II concerne l'étude des mécanismes de dégradation des assemblages membrane-électrodes (AME). La caractérisation des AME pendant, et après, fonctionnement à potentiel élevé a permis de mettre en évidence la dissolution, puis migration, du catalyseur dans les ionomères perfluorosulfonés. La présence de Pt(II) dans l'ionomère conduit à la formation de radicaux peroxydes et est une des causes de la dégradation de l'électrolytehis work is related to the development of PEM fuel cells. The first part of the manuscript describes the preparation of new sulfonated polybenzimidazoles, allowing to obtain proton conducting membranes, using two different ways: direct sulfonation of the polymer backbone under mild conditions, introduction of a sulfonated monomer during polymer synthesis. Direct sulfonation lead to highly proton conducting polymers that can be used as polyelectrolyte in electrochemical devices like fuel cells. The second part describes the study that has been done to determine membrane-electrodes (MEA) degradation mechanisms during fuel cell operation. MEA characterisation during, and after, running at high potential allow us to evidence catalysts dissolution, and further migration, in the perfluorosulfonated ionomer. Pt(II) species present in the ionomer lead to radical formation and causes electrolyte degradationMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Hydrocarbon proton conducting polymers for fuel cell catalyst layers

Proton exchange membrane fuel cells (PEMFCs) employing proton conducting membranes are promising power sources for automotive applications. Perfluorosulfonic acid (PFSA) ionomer represents the state-of-the-art polymer used in both the membrane and catalyst layer to facilitate the transport of protons. However, PFSA ionomer is recognized as having significant drawbacks for largescale commercialization, which include the high cost of synthesis and use of fluorine-based chemistry. According to published research much effort has been directed to the synthesis and study of non-PFSA electrolyte membranes, commonly referred to as hydrocarbon membranes, which has led to optimism that the less expensive proton conducting membranes will be available in the not-so-distant future. Equally important however, is the replacement of PFSA ionomer in the catalyst layer, but in contrast to membranes, studies of catalyst layers that incorporate a hydrocarbon polyelectrolyte are relatively sparse and have not been reviewed in the open literature; despite the knowledge that hydrocarbon polyelectrolytes in the catalyst layer generally lead to a decrease in electrochemical fuel cell kinetics and mass transport. This review highlights the role of the solid polymer electrolyte in catalyst layers on pertinent parameters associated with fuel cell performance, and focuses on the effect of replacing perfluorosulfonic acid ionomer with hydrocarbon polyelectrolytes. Collectively, this review aims to provide a better understanding of factors that have hindered the transition from PFSA to non-PFSA based catalyst layers.Peer reviewed: YesNRC publication: Ye

pH-dependence on HER electrocatalytic activity of iron sulfide pyrite nanoparticles

Iron sulfide pyrite (FeS2) nanoparticles are investigated for the electrocatalysis of hydrogen evolution reaction (HER) at pH values ranging from 0.3 to 13. It is evidenced that HER can be performed at any pH, showing remarkable robustness and stability for more than 24 h. The catalytic mechanism for HER by pyrite nanoparticles changes over the pH range, with a pH-dependent behavior below pH 5 and a pH-independent behavior above pH 5. Keywords: Hydrogen evolution reaction, Pyrite, Iron sulfide, Electrocatalytic film