Are Operando Measurements of Rechargeable Batteries Always Reliable? An Example of Beam Effect with a Mg Battery.

Operando and in situ techniques are becoming mandatory to study Li-ion, post Li-ion, and solid-state batteries. They are essential for monitoring the (electro)chemical and dynamic processes in the battery environment and for providing understanding at different spatial and temporal scales. While operando measurements are becoming more and more routine, scientists have to keep in mind that such experiments are not always harmless for the battery operation, especially when using synchrotron techniques. This is the case in the example described herein with Mg batteries. We show that the electrode reactivity in a InSb/organohaluminate electrolyte/Mg cell is strongly retarded during operando synchrotron X-ray absorption acquisition. Through comparison of ex situ, operando, and in situ data, we demonstrate that this effect occurred only on the samples' volumes exposed to the X-ray radiation. This study illustrates how incorrect conclusions might be drawn from operando measurements, especially when looking at new battery chemistries, and calls for extreme caution when designing and interpreting operando data.

Comparative uptake and impact of TiO2 nanoparticles in wheat and rapeseed.

Up to 2 million tons per year of titanium dioxide (TiO2) nanoparticles (NP) are produced worldwide. This extensive production is postulated to result in release into the environment with subsequent contamination of soils and plants; however, few studies have examined TiO2-NP uptake and impact on plants. In this study, wheat and rapeseed plantlets were exposed to 14 nm or 25 nm anatase TiO2-NP in hydroponics conditions, either through root or leaf exposure. Microparticle-induced x-ray emission (µPIXE) coupled with Rutherford backscattering spectroscopy (RBS) was used to quantify absorbed titanium (Ti). Micro x-ray fluorescence (µXRF) based on synchrotron radiation was used to evaluate Ti distribution in roots and leaves. Our results show that both TiO2-NP are accumulated in these plantlets upon root exposure and that Ti content is higher in rapeseed than wheat. Ti distribution in root cross sections depended on NP agglomeration state. NP are also accumulated in plantlets upon leaf exposure. Finally, it was found that TiO2-NP exposure induced increased root elongation but did not affect germination, evapotranspiration, and plant biomass. Taken together, these results confirm that TiO2-NP may be accumulated in plant crops but may only moderately impact plant development.

Cutting-edge spectroscopy techniques highlight toxicity mechanisms of copper oxide nanoparticles in the aquatic plant Myriophyllum spicatum.

Copper oxide nanoparticles (CuO-NPs) have been increasingly released in aquatic ecosystems over the past decades as they are used in many applications. Cu toxicity to different organisms has already been highlighted in the literature, however toxicity mechanisms of the nanoparticulate form remain unclear. Here, we investigated the effect, transfer and localization of CuO-NPs compared to Cu salt on the aquatic plant Myriophyllum spicatum, an ecotoxicological model species with a pivotal role in freshwater ecosystems, to establish a clear mode of action. Plants were exposed to 0.5 mg/L Cu salt, 5 and 70 mg/L CuO-NPs during 96 h and 10 days. Several morphological and physiological endpoints were measured. Cu salt was found more toxic than CuO-NPs to plants based on all the measured endpoints despite a similar internal Cu concentration demonstrated via Cu mapping by micro particle-induced X-ray emission (µPIXE) coupled to Rutherford backscattering spectroscopy (RBS). Biomacromolecule composition investigated by FTIR converged between 70 mg/L CuO-NPs and Cu salt treatments after 10 days. This demonstrates that the difference of toxicity comes from a sudden massive Cu2+ addition from Cu salt similar to an acute exposure, versus a progressive leaching of Cu2+ from CuO-NPs representing a chronic exposure. Understanding NP toxicity mechanisms can help in the future conception of safer by design NPs and thus diminishing their impact on both the environment and humans.

MIL-53 Metal-Organic Framework as a Flexible Cathode for Lithium-Oxygen Batteries.

Li-air batteries possess higher specific energies than the current Li-ion batteries. Major drawbacks of the air cathode include the sluggish kinetics of the oxygen reduction (OER), high overpotentials and pore clogging during discharge processes. Metal-Organic Frameworks (MOFs) appear as promising materials because of their high surface areas, tailorable pore sizes and catalytic centers. In this work, we propose to use, for the first time, aluminum terephthalate (well known as MIL-53) as a flexible air cathode for Li-O2 batteries. This compound was synthetized through hydrothermal and microwave-assisted routes, leading to different particle sizes with different aspect ratios. The electrochemical properties of both materials seem to be equivalent. Several behaviors are observed depending on the initial value of the first discharge capacity. When the first discharge capacity is higher, no OER occurs, leading to a fast decrease in the capacity during cycling. The nature and the morphology of the discharge products are investigated using ex situ analysis (XRD, SEM and XPS). For both MIL-53 materials, lithium peroxide Li2O2 is found as the main discharge product. A morphological evolution of the Li2O2 particles occurs upon cycling (stacked thin plates, toroids or pseudo-spheres).

Synthesis and catalytic properties of MIL-100(Fe), an iron(III) carboxylate with large pores.

The large-pore iron(III) carboxylate MIL-100(Fe) with a zeotype architecture has been isolated under hydrothermal conditions, its structure solved from synchrotron X-ray powder diffraction data, while Friedel-Crafts benzylation catalytic tests indicate a high activity and selectivity for MIL-100(Fe).

Intricate disorder in defect fluorite/pyrochlore: a concord of chemistry and crystallography.

Intuitively scientists accept that order can emerge from disorder and a significant amount of effort has been devoted over many years to demonstrate this. In metallic alloys and oxides, disorder at the atomic scale is the result of occupation at equivalent atomic positions by different atoms which leads to the material exhibiting a fully random or modulated scattering pattern. This arrangement has a substantial influence on the material's properties, for example ionic conductivity. However it is generally accepted that oxides, such as defect fluorite as used for nuclear waste immobilization matrices and fuel cells, are the result of disorder at the atomic scale. To investigate how order at the atomic scale induces disorder at a larger scale length, we have applied different techniques to study the atomic composition of a homogeneous La 2 Zr 2 O 7 pyrochlore, a textbook example of such a structure. Here we demonstrate that a pyrochlore, which is considered to be defect fluorite, is the result of intricate disorder due to a random distribution of fully ordered nano-domains. Our investigation provides new insight into the order disorder transformations in complex materials with regards to domain formation, resulting in a concord of chemistry with crystallography illustrating that order can induce disorder.

A new isoreticular class of metal-organic-frameworks with the MIL-88 topology.

We report here a new family of isoreticular MOFs, comprising three larger analogues of the nanoporous metallocarboxylate MIL-88; these solids were synthesized using a controlled SBU approach and the three crystal structures were solved using an original simulation-assisted structure determination method in direct space.

An EXAFS study of the formation of a nanoporous metal-organic framework: evidence for the retention of secondary building units during synthesis.

EXAFS data measured from amorphous intermediates and crystallisation solutions provides the first evidence that trimeric iron oxide secondary building units remain intact during crystallisation of the metal-organic framework MIL-89 from starting materials to products.

Mother-plant-mediated pumping of zinc into the developing seed.

Insufficient intake of zinc and iron from a cereal-based diet is one of the causes of 'hidden hunger' (micronutrient deficiency), which affects some two billion people(1,2). Identifying a limiting factor in the molecular mechanism of zinc loading into seeds is an important step towards determining the genetic basis for variation of grain micronutrient content and developing breeding strategies to improve this trait(3). Nutrients are translocated to developing seeds at a rate that is regulated by transport processes in source leaves, in the phloem vascular pathway, and at seed sinks. Nutrients are released from a symplasmic maternal seed domain into the seed apoplasm surrounding the endosperm and embryo by poorly understood membrane transport processes(4-6). Plants are unique among eukaryotes in having specific P1B-ATPase pumps for the cellular export of zinc(7). In Arabidopsis, we show that two zinc transporting P1B-ATPases actively export zinc from the mother plant to the filial tissues. Mutant plants that lack both zinc pumps accumulate zinc in the seed coat and consequently have vastly reduced amounts of zinc inside the seed. Blockage of zinc transport was observed at both high and low external zinc supplies. The phenotype was determined by the mother plant and is thus due to a lack of zinc pump activity in the seed coat and not in the filial tissues. The finding that P1B-ATPases are one of the limiting factors controlling the amount of zinc inside a seed is an important step towards combating nutritional zinc deficiency worldwide.

Investigation of acid sites in a zeotypic giant pores chromium(III) carboxylate.

A study of the zeotypic giant pores chromium(III) tricarboxylate Cr(III)3OF(x)(OH)(1-x)(H2O)2 x {C6H3-(CO2)3}2 x nH2O (MIL-100) has been performed. First, its thermal behavior, studied by X-ray thermodiffractometry and infrared spectroscopy, indicates that the departure of water occurs without any pore contraction and no loss in crystallinity, which confirms the robustness of the framework. In a second step, IR spectroscopy has shown the presence of three distinct types of hydroxy groups depending on the outgassing conditions; first, at high temperatures (573 K), only Cr-OH groups with a medium Brønsted acidity are present; at lower temperatures, two types of Cr-H2O terminal groups are observed; and at room temperature, their relatively high Brønsted acidity allows them to combine with H-bonded water molecules. Finally, a CO sorption study has revealed that at least three Lewis acid sites are present in MIL-100 and that fluorine atoms are located on a terminal position on the trimers of octahedra. A first result of grafting of methanol molecules acting as basic organic molecules on the chromium sites has also been shown, opening the way for a postsynthesis functionalization of MIL-100.

Synthesis of MIL-102, a chromium carboxylate metal-organic framework, with gas sorption analysis.

A new three-dimensional chromium(III) naphthalene tetracarboxylate, CrIII3O(H2O)2F{C10H4(CO2)4}1.5.6H2O (MIL-102), has been synthesized under hydrothermal conditions from an aqueous mixture of Cr(NO3)3.9H2O, naphthalene-1,4,5,8-tetracarboxylic acid, and HF. Its structure, solved ab initio from X-ray powder diffraction data, is built up from the connection of trimers of trivalent chromium octahedra and tetracarboxylate moieties. This creates a three-dimensional structure with an array of small one-dimensional channels filled with free water molecules, which interact through hydrogen bonds with terminal water molecules and oxygen atoms from the carboxylates. Thermogravimetric analysis and X-ray thermodiffractometry indicate that MIL-102 is stable up to approximately 300 degrees C and shows zeolitic behavior. Due to topological frustration effects, MIL-102 remains paramagnetic down to 5 K. Finally, MIL-102 exhibits a hydrogen storage capacity of approximately 1.0 wt % at 77 K when loaded at 3.5 MPa (35 bar). The hydrogen uptake is discussed in relation with the structural characteristics and the molecular simulation results. The adsorption behavior of MIL-102 at 304 K resembles that of small-pore zeolites, such as silicalite. Indeed, the isotherms of CO2, CH4, and N2 show a maximum uptake at 0.5 MPa, with no further significant adsorption up to 3 MPa. Crystal data for MIL-102: hexagonal space group P(-)6 (No. 169), a = 12.632(1) A, c = 9.622(1) A.

Very large swelling in hybrid frameworks: a combined computational and powder diffraction study.

Using a combination of simulations and powder diffraction, we report here the study of the very large swelling of a three-dimensional nanoporous iron(III) carboxylate (MIL-88) which exhibits almost a reversible doubling (approximately 85%) of its cell volume while fully retaining its open-framework topology. The crystal structure of the open form of MIL-88 has been successfully refined and indicates that atomic displacements larger than 4 angstroms are observed when water or various alcohols are adsorbed in the porous structure, revealing an unusually flexible crystallized framework. X-ray thermodiffractometry shows that only a displacive transition occurs during the swelling phenomenon, ruling out any bond breaking.