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A new series of inorganic–organic hybrid perovskite materials were prepared by microwave-assisted grafting reactions. Simple carboxylic acids, acetic acid, and propionic acid, as well as hydroxyaromatic carboxylic acids, 3,5-dihydroxy benzoic acid (DBA), 5-hydroxyisophthalic acid (HPA), 4-hydroxybenzoic acid (HBA), and 4-hydroxy-4-biphenyl carboxylic acid (HBCA), were reacted with the Dion–Jacobson double-layered perovskite, HLaNb2O7, and its alcoxy derivatives. Grafting was found to not occur with simple carboxylic acids, while those molecules with hydroxyls were all attached to the perovskite interlayers. Reactivity of the hydroxyaromatic carboxylic acids varied with the different layered perovskite hosts where reactions with HLaNb2O7 did not occur, and those with n-propoxy-LaNb2O7 were limited; the greatest extent of reactivity was seen with n-decoxy-LaNb2O7. This is attributed to the larger interlayer spacing available for the insertion of the various hydroxyaromatic carboxylic acid compounds. The loading exhibited by the grafting species was less than that seen with well-known long-chain alkoxy grafting groups. It is expected that the width of the molecules contributes to this where, due to the benzyl groups, the interlayer volume of the grafted moieties occupies a larger horizontal fraction, therefore minimizing the loading to the below half. X-ray powder diffraction and transmission electron microscopy studies found that grafting of the n-decoxy-LaNb2O7 intermediates with the series of hydroxyaromatics resulted in a reduction in crystallinity along with a disruption of the layer structure. Raman data on the series show little variation in local structure except for HBCA, where there appears to be a lengthening of the Nb-O apical linkage and a possible reduction in the distortion of inner-layer NbO6 octahedra. The optical properties of the hydroxyaromatic carboxylic acid grafted perovskites were also investigated using diffuse-reflectance UV-Vis spectroscopy. The band gaps of DBA, HPA, and HBA were found to be similar to the parent (Eg ≈ 3.4 eV), while the HBCA was significantly less by ca. 0.6 eV. This difference is attributed to electron withdrawal from the perovskite block to the HBCA ligand, leading to a lower band gap for the HBCA compound. The methods described herein allow for the formation of a new series of inorganic–organic hybrid materials where the products are of interest as precursors to more complex architectures as well as models for band gap modification of metal oxide photocatalysts.

The lignin biosynthetic pathway has been studied for more than a century but has undergone major revisions over the past decade. Significant progress has been made in cloning new genes by genetic and combined bioinformatics and biochemistry approaches. In vitro enzymatic assays and detailed analyses of mutants and transgenic plants altered in the expression of lignin biosynthesis genes have provided a solid basis for redrawing the monolignol biosynthetic pathway, and structural analyses have shown that plant cell walls can tolerate large variations in lignin content and structure. In some cases, the potential value for agriculture of transgenic plants with modified lignin structure has been demonstrated. This review presents a current picture of monolignol biosynthesis, polymerization, and lignin structure.

The mechanical performance of bamboo is highly dependent on its structural arrangement and the properties of biomacromolecules within the cell wall. The relationship between carbohydrates topochemistry and gradient micromechanics of multilayered fiber along the diametric direction was visualized by combined microscopic techniques. Along the radius of bamboo culms, the concentration of xylan within the fiber sheath increased, while that of cellulose and lignin decreased gradually. At cellular level, although the consecutive broad layer (Bl) of fiber revealed a relatively uniform cellulose orientation and concentration, the outer Bl with higher lignification level has higher elastic modulus (19.59–20.31 GPa) than that of the inner Bl close to the lumen area (17.07–19.99 GPa). Comparatively, the cell corner displayed the highest lignification level, while its hardness and modulus were lower than that of fiber Bl, indicating the cellulose skeleton is the prerequisite of cell wall mechanics. The obtained cytological information is helpful to understand the origin of the anisotropic mechanical properties of bamboo.

Never-dried sulfite wood pulp was beaten and subsequently microfibrillated before being submitted to periodate oxidation for various times. The oxidation progress, which was followed by ¹³C solid-state NMR spectroscopy in conjunction with degree of oxidation (DO) measurements together with ultrastructural observations, revealed that the cellulose crystallinity and microfibrillar integrity were kept intact until a DO of 0.3/0.4, indicating that at that level, the cellulose microfibrils had been oxidized exclusively at their surface. Beyond this DO value, the sample crystallinity started to deteriorate, as the oxidation progressed toward the core of the microfibrils. Remarkably, throughout the oxidation, the created carbonyl moieties were never observed, as they were readily recombined into hemiacetals by cyclization either within the same anhydro glucose unit (AGU) or with the adjacent un-oxidized AGUs of the same cellulose chain. At DO below 0.3/0.4, hemiacetal coupling with adjacent cellulose chains was also considered, but it appeared unlikely in view of the interchain distance imposed by the crystalline lattice. The oxidized samples were subjected to a reductive amination with benzylamine in order to convert their hydrophilic surfaces into hydrophobic ones. Despite the ease of this derivatization, the analysis of the ¹³C solid-state NMR spectra of the aminated products showed that, below a DO of 0.3, only half of the hemiacetal moieties could be converted into secondary amine products, whereas the other half remained untouched, likely for steric reasons.

Thermal behaviour of fibrous tremolite from Maryland, USA has been investigated in situ up to breakdown temperature. Tremolite can be found both as primary constituent and as contaminant in Asbestos Containing Materials (ACMs). The products of breakdown are subcalcic diopside and calcium-rich clinoenstatite in a 2:1 ratio, traces of hematite plus minor silica-rich amorphous material. Thermal expansion follows a regular trend up to 723 K before the onset of Fe 2+ oxidation/OH – deprotonation which is completed at 1023 K. At 923 K the Fe 3+ migration starts towards M (1) and the corresponding counter-migration of Mg to M (2) and M (3). At T close to structure breakdown, M (2) shows a significant site-scattering reduction possibly consistent with the occurrence of minor vacancies. In fully oxidised tremolite, Fe 3+ is allocated prevalently at M (1) and subordinately at M (3). As it is well-known that M (1), along with M (2), is the most exposed octahedral site at the surface of amphiboles, most of the Fe 3+ is available for participating in the Fenton-like reactivity of oxidised tremolite, potentially making it dangerous for human health. This point should be properly taken into account in the evaluation of the safety of thermally decomposed tremolite-containing ACMs, in particular in the case of accidentally incomplete treatments.

The reaction of Fe(NO3)3⋅9 H2O with KOH under hydroflux conditions at about 200 °C produces red crystals of K2−xFe4O7−x(OH)x in a quantitative yield. In the crystal structure, edge‐sharing [FeO6] octahedra form ∞2[ Fe2O6] honeycomb nets. Pillars consisting of pairs of vertex‐sharing [FeO4] tetrahedra link the honeycomb layers and form columnar halls in which the potassium ions are located. The trigonal (P3‾ 1m) and the hexagonal (P63/mcm) polytypes of K2−xFe4O7−x(OH)x show oriented intergrowth. The sub‐stoichiometric potassium content (x≈0.3) is compensated by hydroxide ions. K2−xFe4O7−x(OH)x is an antiferromagnet above 2 K and its magnetic structure was determined by neutron powder diffraction. Under ambient conditions, K2−xFe4O7−x(OH)x hydrolyzes and K2CO3 ⋅ H2O forms gradually on the surface of the K2−xFe4O7−x(OH)x crystals. Upon annealing at air at about 500 °C, the potassium atoms in the columnar halls start to order into a superstructure. The thermal decomposition of K2−xFe4O7−x(OH)x proceeds via a topotactic transformation into K1+x′Fe11O17, adopting the rhombohedral β’’ or the hexagonal β‐aluminate‐type structure, before γ‐Fe2O3 is formed above 950 °C, which then converts into thermodynamically stable α‐Fe2O3. Call to order: Reaction of Fe(III) nitrate in approximately 40 m potassium hydroxide leads to oxo‐hydroxoferrate(III) K2−xFe4O7−x(OH)x. This compound shows an unusual vacancy ordering and decomposes topotactically into β’’ or β‐aluminate‐type K1+x′Fe11O17.

Understanding and controlling supramolecular template effect assembly via a photochemical reaction in different solid and solution phases is one of the main topics in photochemistry. Here, an interesting case of phase-mediated controllable intramolecular/intermolecular photochemical [2+2] cycloadditions assisted by supramolecular templates was demonstrated. Direct irradiation of the complexes in solution yields intramolecular photoproducts exclusively, whereas exposure of the solid powder sample under the same conditions yields intermolecular dinuclear species quantitatively. The nature of the phase and supramolecular interaction affects the geometrical arrangements of the metallacycles, leading to different cycloaddition products under photoirradiation. The crystal structures of different products were investigated by single-crystal X-ray diffraction, nuclear magnetic resonance (NMR) spectrometry, and electrospray ionization mass spectrometry (ESI-MS).

The xylem of Cactaceae is a complex system with different types of cells whose main function is to conduct and store water, mostly during the development of primary xylem, which has vessel elements and wide-band tracheids. The anatomy of primary xylem of Cactaceae has been widely studied, but little is known about its chemical composition. The aim of this study was to determine the structural chemical composition of the primary xylem of Cactaceae and to compare it with the anatomy in the group. Seeds from eight cacti species were used, representing the Pereskioideae, Opuntioideae, and Cactoideae subfamilies. Seeds were germinated and grown for 8 months. Subsequently, only the stem of the seedling was selected, dried, milled, and processed following the TAPPI T-222 om-02 norm; lignin was quantified using the Klason method and cellulose with the Kurshner-Höffer method. Using Fourier transform infrared spectroscopy, the percentage of syringyl and guaiacyl in lignin was calculated. Seedlings of each species were fixed, sectioned, and stained for their anatomical description and fluorescence microscopy analysis for the topochemistry of the primary xylem. The results showed that there were significant differences between species ( < 0.05), except in the hemicelluloses. Through a principal component analysis, it was found that the amount of extractive-free stem and hot water-soluble extractives were the variables that separated the species, followed by cellulose and hemicelluloses since the seedlings developed mainly parenchyma cells and the conductive tissue showed vessel elements and wide-band tracheids, both with annular and helical thickenings in secondary walls. The type of lignin with the highest percentage was guaiacyl-type, which is accumulated mainly in the vessels, providing rigidity. Whereas in the wide-band tracheids from metaxylem, syringyl lignin accumulated in the secondary walls S2 and S3, which permits an efficient flow of water and gives the plant the ability to endure difficult conditions during seedling development. Only one species can be considered to have paedomorphosis since the conductive elements had a similar chemistry in primary and secondary xylem.

—The raw-material base and the manufacture of zirconium, niobium, and rare-earth products in Russia are briefly reviewed. The prospects for their manufacture on the basis of the integrated processing of eudialyte are shown. The main methods of the acidic processing of this mineral are considered. The results of studying the kinetics of decomposition of eudialyte with hydrochloric and sulfuric acids are given. It is established that the process of acidic decomposition of eudialyte can be described with a high degree of accuracy by the formal equation d (1 – α)/ d τ = – k (1 – α) 2 for the conversion rate, from which the activation energies of the processes are determined (79.69 and 48.90 kJ/mol for HCl and H 2 SO 4 , respectively). Based on the topochemical kinetic equations describing various types, mechanisms, and geometric models of solid-phase reactions, the experimental data are mathematically processed. It is established that the mechanism of acidic decomposition of eudialyte is most accurately described by the equation (1 – 2α/3 – 1 –α) 2/3 = k GB τ) for the Ginstling–Brounschtein diffusion-controlled process.

Ionic liquids (ILs) as designer solvents have been applied in biomass pretreatment to increase cellulose accessibility and therefore improve the enzymatic hydrolysis. We investigated the characterization of the micromorphology and the topochemistry of poplar wood during 1-ethyl-3-methylimidazolium acetate pretreatment with mild conditions (90 °C for 20 and 40 min) by multiple microscopic techniques (FE-SEM, CLSM, and CRM). Chemical composition analysis, XRD, cellulase adsorption isotherm, and enzymatic hydrolysis were also performed to monitor the variation of substrate properties. Our results indicated that the biomass conversion was greatly enhanced (from 20.57% to 73.64%) due to the cell wall deconstruction and lignin dissolution (29.83% lignin was removed after incubation for 40 min), rather than the decrystallization or crystallinity transformation of substrates. The mild ILs pretreatment, with less energy input, can not only enhance enzymatic hydrolysis, but also provide a potential approach as the first step in improving the sequential pretreatment effectiveness in integrated methods. This study provides new insights on understanding the ILs pretreatment with low temperature and short duration, which is critical for developing individual and/or combined pretreatment technologies with reduced energy consumption.