Covalent organic frameworks are a family of porous crystalline structures gaining attention due to their promising applications. However, despite significant efforts, the synthesis and understanding of uniform and specific morphologies remain a challenge. Herein, we report the first self-templated synthesis of hollow spherical boronate ester-linked COFs-polymers. A time-dependent investigation reveals the formation of hollow spheres driven by an inside-out Ostwald ripening mechanism, exclusively for COF-10 in the presence of a catechol-poly(N-isopropylacrylamide) (catechol-PNIPAm) polymer. The synthesized hollow spheres show a hydrodynamic radius of 300 nm, an oriented crystallinity, and continuous hexagonal pore channels throughout the membrane, associated with a high surface area (~800 m2·g-1). Interestingly, the hollow sphere cavity enables the encapsulation of a fluorogenic, thiol-responsive dye while the porous membrane regulates the size-selective penetration of thiols. Only thiols of appropriate size can access the encapsulated dye, thereby triggering fluorescence restoration.

While nanoscale kappa-carbide precipitation is a well-established strengthening mechanism in low-density steels, the unexpected enhancement of austenite strength observed with Mo addition, despite its known inhibitory effect on kappa-carbide formation, has remained unclear. In this study, we identify a novel and controllable short-range ordering (SRO) structure mediated by the Mo element in Fe-28Mn-9Al-1.2C-5Mo (wt.%) steel, accompanied by the surrounding C atoms occupying at octahedral interstices within the face-centered cubic lattice. Theoretical calculations indicate that the localized ordering of C atoms originates from the strong Mo-C interaction at first-nearest-neighbor sites. Meanwhile, this chemical SRO behavior markedly increases the nanohardness and intrinsic strength of the austenite matrix. These findings demonstrate that Mo not only alters the precipitation behavior of kappa-carbide but also induces SRO structure formation, providing a new pathway to tune the mechanical properties of low-density steels through atomic-scale structural design.

Mylonitic crustal rocks are often observed to contain micro-scale porosity, which in many instances can be found within regions of monomineralic quartz. This work documents micro-porosity that decorates quartz-rich shear bands of the Ikaria granite (Greece). Using scanning (SEM) and transmission (TEM) electron microscopy, we describe typical features of sub-micron, angular pores which commonly occur along grain boundaries in quartz mylonites. On grain boundary surfaces, we first observe that the pore-neighbour distance increases with pore size, suggesting pores to have coalesced over micrometric distances. Electron Backscatter Diffraction (EBSD) and high-angular resolution EBSD mapping, combined with focused ion beam cross-sectioning, confirm that faceted pores also decorate substructures, including some with high lattice distortions, presumably related to very high geometrically necessary dislocation densities (>= 1015 m(-2)). TEM observations do not confirm such high dislocation densities, but instead suggest that lattice curvature results from a residual elastic bending. TEM observations further reveal nanometric layers of amorphous silica, which embeds pores and wets grain boundaries as well as strain-induced intragrain boundaries. As indicated by SEM observations of a silica film on broken surfaces, amorphous silica is an intrinsic feature of pure quartz shear bands, here attributed to stress-induced mechanical amorphization.

This study describes the microstructural evolution of a 3 mol% yttria-stabilized zirconia during densification, comparing Conventional Sintering (CS) and Two-Step Sintering (TSS). Monitoring the microstructural evolution revealed a reduction in grain size and less phase partitioning with TSS than with CS, which is related to a more homogeneous yttria distribution with TSS. Diffusion lengths for both CS and TSS were estimated using Fick's laws. Since the sintered materials spend more time at high temperature in CS than in TSS, the cation diffusion lengths are longer for CS, which is consistent with the yttria distribution observed in the microstructures. Similar values of flexural strength and toughness were obtained for both TSS and CS materials. However, hydrothermal ageing tests revealed a clear improvement in the Low Temperature Degradation of the TSS sample. This difference is attributed to the diffusion-sensitive nature of hydrothermal ageing, unlike the diffusion-less martensitic phase change mechanism governing toughness.

Upon illumination, photocatalysts generate charge carriers for redox reactions, but their efficiency is often limited by carrier recombination and poor minority-carrier diffusion, despite many existing junction engineering strategies. Here we exploit the insulator-metal transition in VO2 to produce a material that promotes efficient charge separation and enhances the photocatalytic conversion of methane through the spontaneous formation of junctions. We find that the photocatalytic activity peaks at the critical temperature of the transition, which we attribute to coexisting insulating and metallic domains with non-integer dimensional boundaries and sizes smaller than the minority-carrier diffusion length. Increasing the charge-separating interface length by decreasing the film thickness improves the photocatalytic activity and C-C coupling between alkoxy intermediates, leading to a propane selectivity of 100%. Moreover, electrically triggering the phase transition at lower temperatures further boosts methane conversion via field-assisted carrier activation. Overall, the metal-insulator transition provides an effective alternative to complex nanoscale junction engineering in photocatalysis.

Electroactive composites combining ceramic nanoparticles with fluorinated polymers present great potential for applications in flexible electronics, sensors, and energy harvesting. However, the poor interfacial compatibility between the two constituents often limits their performance. In this study, barium titanate (BTO) nanoparticles were functionalized with six different dopamine-based coupling agents and then incorporated into a P(VDF-co-TrFE) 55/45 matrix. The objective was to assess the impact of the chemical structure of the coupling agents on the morphology and electroactive performance of the resulting composites. Microscopic analyses revealed that all coupling agents promote better dispersion of BTO nanoparticles within the polymer matrix. Furthermore, dielectric and ferroelectric measurements highlighted the crucial influence of the coupling agents' dipole moment. Dopamine-based coupling agents integrating high dipoles such as nitro and sulfanyl groups significantly enhance the dielectric constant and remnant polarization of the composites. These results emphasize the importance of selecting coupling agents with appropriate molecular properties to optimize the electroactive performance of ceramic/polymer composites.

This study presents the development of a solid symmetric supercapacitor using porous structured Fe-Cr-O oxide layers as both anode and cathode. The porous structures were obtained through a simple and efficient anodization method of stainless steel substrate. Further, an oxide layer containing Fe and Cr species was formed on the porous stainless steel mesh via a low-cost thermal oxidation process in an uncontrolled atmosphere. The prepared porous Fe-Cr-O structures delivered areal capacities of 172.66 and 155.77 mC & sdot;cm-2 from cyclic voltammetry (CV) and galvanic charge-discharge (GCD) measurements, respectively, and retained 96.5% of their capacity after 10,000 cycles. Additionally, a solid-state symmetric supercapacitor assembled employing Fe-Cr-O electrodes and a gelatinous PVA/KOH polymer electrolyte exhibited an operating voltage of 2 V and a capacity of 31.33 mC.cm-2 at a scan rate of 5 mV s-1, with 84.03% retention after 2000 cycles. The recorded energy density was 2.39 mWh cm-2 and the power density was 2669 mW cm-2. These performances reinforce the potential of porous Fe-Cr-O structures as electrode materials for the next generation of high-energy-density solid-state energy storage systems.

A promising way to address environmental problems caused by plastic waste is through its upcycling into renewable energy and resources.With annual production reaching millions of tons,one of the most widely single-use daily plastics,polyethylene terephthalate(PET),has recently been investigated in terms of chemical recycling to reduce its environmental impact and generate renewable fuels.This study intro-duces an innovative electrochemical method for the specific conversion of PET hydrolysate into high-value compounds utilizing CoCuOx@MXene/NF catalyst.Our findings revealed that the electrocatalyst was capable of facilitating the conversion of water into hydrogen(H2),while simultaneously oxidizing ethylene glycol(EG),obtained from PET plastic waste hydrolysis,into formate with a high selectivity and lower initial potential compared to water oxidation.Notably,the exceptional performance was attributed to the synergistic interfacial electronic coupling effect between CoCuOx and MXene,which results in a low overpotential(1.24 V@10 mA cm-2)and a high yield of formate product(87.6％).In addi-tion,the electrolyzer could be operated using solar energy panel for upcycling of PET to formic acid and hydrogen fuels by using CoCuOx@MXene catalyst.

The dehydration of antigorite is an important reaction in subduction zones with implications on both geochemical and geophysical processes. In this experimental study we focus on the onset of antigorite dehydration and investigate various chemical and physical parameters as possible drivers for the fluid release. We performed hydrostatic and co-axial Griggs experiments on antigorite serpentinites with variable chemical composition and microstructures at high-pressure and high-temperature conditions across the antigorite dehydration (1.5 GPa, 620–670 °C). For these conditions, our thermodynamic models predict the formation of olivine from magnetite decomposition and partial dehydration of antigorite. Detailed analyses of the run products reveal limited magnetite decomposition. Antigorite dehydration is restricted to samples that have been deformed. Nano-sized olivine and orthopyroxene formed locally in oblique dehydration bands and exhibit neither a clear crystallographic preferred orientation nor a topotactic relation with precursor antigorite. We argue that limited local dehydration in our experiments is related to strain and variations in reaction kinetics. Systematic investigation excludes mineralogical and chemical heterogeneities, and temperature gradients as reaction driving potentials. The structural relation of the dehydration bands suggests deformation-related dehydration, which is supported by numerical simulations that couple reaction kinetics with mechanical work rate and self-consistently predict dehydration bands. In this scenario, strain concentration due to applied axial stress locally increases the internal energy of antigorite to reach the activation energy of the dehydration reaction, enabling dehydration. This study highlights the importance of coupled mechanical and chemical processes and provides a mechanistic framework for deformation-induced dehydration of antigorite.

Poly(ethylene terephthalate) (PET), a common single-use plastic, significantly contributes to CO2 emissions when discarded or incinerated. In this study, we have employed an innovative approach by combining electrochemical PET hydrolysate oxidation and CO2 reduction reaction (CO2RR) to simultaneously produce formate in a single electrochemical cell. Utilizing simple electrochemical methods, a porous 3D carbon felt (CF) electrode was anodically oxidized to produce activated carbon felt (aCF). The latter was used as a support for the electrochemical deposition of bismuth oxide carbonate (Bi2O2CO3) and nickel cobalt phosphate (NiCoPOx) for CO2RR and anodic PET hydrolysate oxidation, respectively. In situ Raman analysis indicated that MOOH (M = Ni, Co) intermediates acted as active sites for PET hydrolysate oxidation, with the ability to regenerate into lower-valence nickel species post-reaction. Both electrodes exhibited Faradaic efficiencies (FEs) exceeding 90% in their respective half-cell reactions. When implemented in a two-electrolyzer setup, a combined FE of up to 158% for both reactions was recorded at a remarkably low cell voltage of 1.8 V. This research highlights the use of non-noble metals to transform PET plastic waste and CO2 into valuable fuels.

Colloidal 2D PbX (X = S, Se, Te) nanocrystals are innovative materials pushing the boundaries of quantum confinement by combining crystal thicknesses down to a monolayer with additional confinement in the lateral dimension. These flat PbSe quantum dots (fQDs) exhibit telecommunication band photoluminescence (1.43-0.83 eV), which is highly interesting for fiber optic information processing. With scanning tunneling microscopy/spectroscopy (STM/STS), we probe single-layer-defined fQD populations down to one monolayer, showing an in-gap state free QD-like density of states in excellent agreement with theoretical tight-binding (TB) calculations. Cryogenic ensemble spectra match STS/STM and TB calculations and exhibit the contribution of mono-, bi-, and trilayers to the photoluminescence. Comparing the electronic band gaps with the optical ones, we derive exciton binding energies as high as 600 meV for PbSe monolayers. Our results allow for a target-oriented synthesis of a new class of QDs with record binding energies and precisely tailored optical properties at technologically relevant wavelengths.

Expression of concern for ‘Phytic acid-doped poly-N-phenylglycine potato peels for removal of anionic dyes: investigation of adsorption parameters’ by Kahina Bouhadjra et al., New J. Chem., 2022, 46, 5111–5120, https://doi.org/10.1039/D1NJ04713B.

Summary: Deciphering the fossil record of cyanobacteria is crucial to understand their role in the chemical and biological evolution of the early Earth. They profoundly modified the redox conditions of early ecosystems more than 2.4 Ga ago, the age of the Great Oxidation Event (GOE), and provided the ancestor of the chloroplast by endosymbiosis, leading the diversification of photosynthetic eukaryotes. Here, we analyze the morphology, ultrastructure, chemical composition, and metals distribution of Polysphaeroides filiformis from the 1040–1006 Ma Mbuji-Mayi Supergroup (DR Congo). We evidence trilaminar and bilayered ultrastructures for the sheath and the cell wall, respectively, and the preservation of Ni-tetrapyrrole moieties derived from chlorophyll in intracellular inclusions. This approach allows an unambiguous interpretation of P. filiformis as a branched and multiseriate photosynthetic cyanobacterium belonging to the family of Stigonemataceae. It also provides a possible minimum age for the emergence of multiseriate true branching nitrogen-fixing and probably heterocytous cyanobacteria.

Dihydroxybenzenes, including catechol, resorcinol and hydroquinone, have significant commercial value for a variety of applications such as adhesives, resins, pharmaceuticals, coatings etc. However, selective production of required isomers by phenol hydroxylation represents a considerable challenge. Here, we report a new approach for the synthesis of dihydroxybenzenes by their isomerization using a bifunctional Pt/ZSM-5 catalyst. The catalyst successfully facilitates the transformation of catechol and hydroquinone to each other with a selectivity of up to 74 % and yields up to 50 %. The investigation of the mechanism suggests that isomerization proceeds via a carbonaceous deposit (coke) formed by intermediate quinone condensation with subsequent hydrogenolysis to isomers. The proposed mechanism shows the way for the design of the efficient process for isomerization of dihydroxybenzenes.

Silicified peritidal carbonates of the Tonian Draken Formation, Spitsbergen, contain highly diverse and well-preserved microfossil assemblages dominated by filamentous microbial mats, but also including diverse benthic and/or allochthonous (possibly planktonic) microorganisms. Here, we characterize eight morphospecies in focused ion beam (FIB) ultrathin sections using transmission electron microscopy (TEM) and X-ray absorption near-edge structure (XANES) spectromicroscopy. Raman and XANES spectroscopies show the highly aromatic molecular structure of preserved organic matter. Despite this apparently poor molecular preservation, nano-quartz crystallization allowed for the preservation of various ultrastructures distinguished in TEM. In some filamentous microfossils (Siphonophycus) as well as in all cyanobacterial coccoids, extracellular polysaccharide sheaths appear as bands of dispersed organic nanoparticles. Synodophycus microfossils, made up of pluricellular colonies of coccoids, contain organic walls similar to the F-layers of pleurocapsalean cyanobacteria. In some fossils, internal content occurs as particulate organic matter, forming dense networks throughout ghosts of the intracellular space (e.g., in Salome svalbardensis filaments), or scarce granules (in some Chroococcales). In some chroococcalean microfossils (Gloeodiniopsis mikros, and also possibly Polybessurus), we find layered internal contents that are more continuous than nanoparticulate bands defining the sheaths, and with a shape that can be contracted, folded, or invaginated. We interpret these internal layers as the remains of cell envelope substructures and/or photosynthetic membranes thickened by additional cellular material. Some Myxococccoides show a thick (up to ~ 0.9 μm) wall ultrastructure displaying organic pillars that is best reconciled with a eukaryotic affinity. Finally, a large spheroid with ruptured wall, of uncertain affinity, displays a bi-layered envelope. Altogether, our nanoscale investigations provide unprecedented insights into the taphonomy and taxonomy of this well-preserved assemblage, which can help to assess the nature of organic microstructures in older rocks.

Carbon dioxide is an abundant carbon resource for chemical and fuel synthesis. Formic acid, vital for hydrogen storage, has numerous applications. Covalent organic frameworks are a unique class of materials composed of interconnected organic building blocks through covalent bonds. They possess porosity and functional groups, making them suitable for creating supported metallic catalysts. In this study, we present a strategy that utilizes covalent organic frameworks with diverse structures and chemical compositions to enhance carbon dioxide hydrogenation to formic acid at low temperatures. This enhancement arises from both high density of single-atom ruthenium sites and their intrinsic activity. Operando X-ray absorption and catalytic tests demonstrate that the concentration of nitrogen functional groups affects the intrinsic single-site ruthenium activity, whereas the impact of oxygen-containing groups is minor. Catalyst stability is attributed to the ability of single atoms to resist reduction to metallic state. This strategy has broad applicability for various covalent organic framework-supported single-atom catalysts.

Magnetostrictive thin films, exhibit significant utility as functionalization materials for Surface acoustic wave sensors designed for magnetic field measurements. This research investigates the influence of annealing under vacuum and magnetic field at various temperatures on the magnetic properties of the FeCo/TbCo2 thin film and therefore on the sensitivity of shear and Rayleigh acoustic waveguides functionalized with these magnetic layers. The observed effects include a reduction in magnetic anisotropy field and an increase in magnetostriction. XPS and TEM coupled with EDS microanalysis provide insights into the variations in the properties of the nanostructured magnetic film. To safeguard the magnetic film, a thin layer of SiO2 is deposited on top, serving as a protective shield. The inclusion of this layer amplifies sensitivity to applied magnetic fields for modes with shear polarization while reducing sensitivity for Rayleigh mode. In ST-cut Quartz, the shear waves become waveguided upon the incorporation of magnetic thin films, with further enhancement achieved by introducing a SiO2 layer. Rayleigh waves are evanescent modes, the penetration depth is in the order of wavelength, and the addition of SiO2 decrease the wave confinement and therefore the sensitivity. The findings are supported by a theoretical model and experimentally validated results. This research investigates the influence of vacuum and magnetic field annealing at various temperatures over a 4 h duration on the magnetic properties of the FeCo/TbCo2 thin film and therefore on the sensitivity of acoustic shear and Rayleigh wave magnetic field sensors functionalized with these magnetic layers. image