Pd/CeO 2 has attracted great attention owing to its unique activity for methane catalytic oxidation; however, the active sites for CH 4 catalytic oxidation still remain elusive, which affects the comprehensive understanding of the catalytic mechanism. In this work, the structures of PdO x nanoparticles (NPs) loaded on octahedrons, cubes, and rods of nanocrystal CeO 2 supports were systematically studied by Cs-corrected HRTEM/STEM, XPS, and Raman spectroscopy. Our results indicate that the Pd species on CeO 2 supports are morphology-dependent: PdO NPs (Pd 2+ ) on octahedrons, PdO x (x = 1−2) clusters (1−2 nm) on cubes, and dispersed Pd 4+ ions on the CeO 2 rods. Additionally, the chemical states of Pd can be tuned in oxidizing/reducing atmospheres via interactions between Pd and CeO 2 . Detailed studies reveal that the Pd 2+ species are the active centers for the catalytic oxidation of methane. The activity of Pd 0 could be ascribed to Pd 2+ produced through the gradual oxidation of Pd 0 during the CH 4 oxidation. Further, Pd 4+ in the CeO 2 lattice is inactive for CH 4 oxidation. In situ Fourier transform infrared spectroscopy results suggest that the mechanism of CH 4 oxidation reaction on PdO x /CeO 2 follows the Mars−van Krevelen mechanism, and adsorbed CO can be produced in CH 4 decomposition over Pd 2+ in the absence of gas-phase oxygen. As revealed by density functional theory calculations, the incomplete coordination of Pd 2+ ions and adjacent oxygen atoms has excellent activity in cracking the C−H bond of CH 4 , which leads to high methane oxidation ability.

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Nanobiohybrids, synthesized by integrating functional nanomaterials with living systems, have emerged as an exciting branch of research at the interface of materials engineering and biological science. Nanobiohybrids use synthetic nanomaterials to impart organisms with emergent properties outside their scope of evolution. Consequently, they endow new or augmented properties that are either innate or exogenous, such as enhanced tolerance against stress, programmed metabolism and proliferation, artificial photosynthesis, or conductivity. Advances in new materials design and processing technologies made it possible to tailor the physicochemical properties of the nanomaterials coupled with the biological systems. To date, many different types of nanomaterials have been integrated with various biological systems from simple biomolecules to complex multicellular organisms. Here, we provide a critical overview of recent developments of nanobiohybrids that enable new or augmented biological functions that show promise in high-tech applications across many disciplines, including energy harvesting, biocatalysis, biosensing, medicine, and robotics.

Artificial cells or cell mimics have drawn significant attention in cell biology and material science in the last decade and its development will provide a powerful toolbox for studying the origin of life and pave the way for novel biomedical applications. Artificial cells and their subcompartments are typically constructed from a semi-permeable membrane composed of liposomes, polymersomes, hydrogels, or simply aqueous droplets enclosing bioactive molecules to perform cellular-mimicking activities such as compartmentalization, communication, metabolism, or reproduction. Despite the rapid progress, concerns regarding their physical stability (e.g. thermal or mechanical) and tunability in membrane permeability have significantly hindered artificial cells systems in real-life applications. In addition, developing a facile and versatile system that can mimic multiple cellular tasks is advantageous. Here, we report an ultra-stable, multi-functional and stimulus-responsive artificial cell system. Constructed from Metal-phenolic Network (MPN) membranes enclosing enzyme-containing This article is protected by copyright. All rights reserved. 2 Metal-organic Frameworks (MOFs) as organelles, the bionic cell system can mimic multiple cellular tasks including molecular transport regulation, cell metabolism, communication, programmed degradation, and significantly extends its stability range across various chemical and physical conditions. We hope the development of such responsive cell mimics will have significant potentials for studying cellular reactions and have future applications in biosensing and drug delivery.

Dynamics of runaway electrons in magnetic fields are governed by the competition of three dominant physics: parallel electric field acceleration, Coulomb collision, and synchrotron radiation. Examination of the energy and pitch-angle flows reveals that the presence of local vortex structure and global circulation is crucial to the saturation of primary runaway electrons. Models for the vortex structure, which has an O-point to X-point connection, and the bump of runaway electron distribution in energy space have been developed and compared against the simulation data. Identification of these velocity-space structures opens a new venue to reexamine the conventional understanding of runaway electron dynamics in magnetic fields.