Tunable Synthesis of Predominant Semi-Ionic and Covalent Fluorine Bonding States on a Graphene Surface

In this study, fluorinated graphene (FG) was synthesized via a hydrothermal reaction. Graphene oxides (GOs) with different oxygen bonding states and oxygen contents (GO(F), GO(P), and GO(HU)) were used as starting materials. GO(F) and GO(P) are commercial-type GOs from Grapheneall. GO(HU) was prepared using a modified Hummers method. The synthesized FGs from GO(F), GO(P), and GO(HU) are denoted as FG(F), FG(P), and FG(HU), respectively. The F atoms were bound to the graphene surface with predominantly semi-ionic or covalent bonding depending on the GO oxygen state. FG(F) and FG(HU) exhibited less extensive fluorination than FG(P) despite the same or higher oxygen contents compared with that in FG(P). This difference was attributed to the difference in the C=O content of GOs because the C=O bonds in GO primarily produce covalent C–F bonds. Thus, FG(F) and FG(HU) mainly exhibited semi-ionic C–F bonds. The doped F atoms were used to tune the electronic properties and surface chemistry of graphene. The fluorination reaction also improved the extent of reduction of GO.

Prone Position Ventilation for Pediatric Acute Respiratory Distress Syndrome with Extracorporeal Membrane Oxygenation: A Propensity Score-Matched Retrospective Multicenter Cohort Study

Background: Extracorporeal membrane oxygen (ECMO) has used for rescuing severe pediatric acute respiratory distress syndrome (PARDS) for half a century. Prone position ventilation (PPV) has been suggested according to the surviving sepsis campaign (SSC) guideline in children in 2020. We aimed to compare the outcomes and effect of PARDS patients with ECMO+PPV and ECMO only.Design: Retrospective Multicenter pair-matched StudySetting: In the present study, propensity score matching was conducted and the outcomes of severe PARDS patients were analyzed. The effect of PPV was compared as well. The efficiency of PPV included PaO2, Oxygen Index (OI), PaO2/FiO2, compliance of respiratory system and resistance of airway. The primary outcome was hospital mortality. Secondary outcomes included ECMO running time, PICU time, hospital days and mechanical ventilation time of survivors. Patients: 137 PARDS patients with criteria of ECMO from 11 hospitals in 5 years.Interventions: No interventions.Measurements and Main Results: Among 137 patients, 93 patients received ECMO+PPV at the same time and 44 patients didn’t. After matching, we got 34 pairs. For the survivors receiving ECMO+PPV, the PaO2, OI and PaO2/FiO2 increased significantly during the PPV period (P<0.01) and sustained for 4 hours at least. However, the hospital mortality of both groups showed no significant difference (50.0 vs. 55.9%, P=0.808). Conclusions: By far, there has been no ECMO+PPV efficiency study in PARDS patients. This study found that PPV was associated with improved oxygen state during ECMO. However, PPV was not associated with survival rate with PARDS patients on ECMO. Clinical Trial Registration: This study was registered at http://www.chictr.org.cn/index.aspx (chiCTR.gov; Identifier: ChiCTR1800019555). Registered 18 November 2018. Name of the registry: Extracorporeal membrane oxygenation in critical ill children with severe acute respiratory distress syndrome - A multicenter study.Take Home Message:1. Our study investigated prone position ventilation (PPV) could improve the oxygen state during ECMO for patients with severe PARDS.2. The results indicated PPV had no influence on the mortality of PARDS with ECMO.

Full Energy Range Resonant Inelastic X-Ray Scattering of O2 and CO2: Direct Comparison with Oxygen Redox State in Batteries

The varying oxygen state plays key roles in the performance and stability of various electrochemical systems. However, the nature of the non-divalent state remains elusive with speculations under active debates. A direct comparison between these unconventional states on their full oxygen spectroscopic profile is critical but remains missing. Here, high-efficiency full energy range O-K mapping of resonant inelastic x-ray scattering (mRIXS) was collected from O₂ (O⁰) and CO₂ (O^2-) gas molecules. The results are compared directly with Li₂O₂ (O^1-) and more importantly, the oxidized oxygen (O^n-, 0-n-2) state in representative Na-ion and Li-ion battery electrodes. All the mRIXS features of O₂ and CO₂ are interpreted, and we focus on the contrasts of two characteristic features among all oxidized oxygen species, especially on the striking 523.7 eV emission feature. The full mRIXS profile reveals that oxygen redox states in batteries have distinct distributions along the excitation energy compared with Li₂O₂ and O₂. This work provides not only the first full range mRIXS results of O₂ and CO₂, but also the direct comparison of four different oxygen states, i.e., O^2-, O^1-, O^n-(0-n-2), and O⁰. Our results indicate that the nature of the oxidized oxygen state in oxide electrodes is beyond a simple molecular configuration of either peroxide or O₂.

Full Energy Range Resonant Inelastic X-Ray Scattering of O2 and CO2: Direct Comparison with Oxygen Redox State in Batteries

The varying oxygen state plays key roles in the performance and stability of various electrochemical systems. However, the nature of the non-divalent state remains elusive with speculations under active debates. A direct comparison between these unconventional states on their full oxygen spectroscopic profile is critical but remains missing. Here, high-efficiency full energy range O-K mapping of resonant inelastic x-ray scattering (mRIXS) was collected from O₂ (O⁰) and CO₂ (O^2-) gas molecules. The results are compared directly with Li₂O₂ (O^1-) and more importantly, the oxidized oxygen (O^n-, 0-n-2) state in representative Na-ion and Li-ion battery electrodes. All the mRIXS features of O₂ and CO₂ are interpreted, and we focus on the contrasts of two characteristic features among all oxidized oxygen species, especially on the striking 523.7 eV emission feature. The full mRIXS profile reveals that oxygen redox states in batteries have distinct distributions along the excitation energy compared with Li₂O₂ and O₂. This work provides not only the first full range mRIXS results of O₂ and CO₂, but also the direct comparison of four different oxygen states, i.e., O^2-, O^1-, O^n-(0-n-2), and O⁰. Our results indicate that the nature of the oxidized oxygen state in oxide electrodes is beyond a simple molecular configuration of either peroxide or O₂.

Early Earth and the rise of complex life

The history of life on Earth progressed in parallel with the evolving oxygen state of the atmosphere and oceans, but the details of that relationship remain poorly known and debated. There is, however, general agreement that the first appreciable and persistent accumulation of oxygen in the oceans and atmosphere occurred around 2.3 to 2.4 billion years ago. Following this Great Oxidation Event, biospheric oxygen remained at relatively stable intermediate levels for more than a billion years. Much current research focuses on the transition from the intermediate conditions of this middle chapter in Earth history to the more oxygenated periods that followed — often emphasizing whether increasing and perhaps episodic oxygenation drove fundamental steps in the evolution of complex life and, if so, when. These relationships among early organisms and their environments are the thematic threads that stitch together the papers in this collection. Expert authors bring a mix of methods and opinions to their leading-edge reviews of the earliest proliferation and ecological impacts of eukaryotic life, the subsequent emergence and ecological divergence of animals, and the corresponding causes and consequences of environmental change.