Institute of Chemistry and Chemical Technology

The synthesis and precise structural characterization of highly ordered three-dimensional close-packed cage-type mesoporous silica is reported. The siliceous mesoporous material is proven to be commensurate with the face-centered-cubic Fm3m symmetry in high purity by a combination of experimental and simulated powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. The cage-type calcined samples were additionally characterized by nitrogen physisorption. The aqueous synthesis method to prepare large cage mesoporous silica with cubic Fm3m structure is based on the use of EO106PO70EO106 triblock copolymer (F127) at low HCl concentrations, with no additional salts or organic additives. Here, emphasis is put on the low HCl concentration regime, allowing the facile thermodynamic control of the silica−triblock copolymer mesophase self-assembly. Further, simple application of hydrothermal treatments at various temperatures ranging from 45 to 150 °C enables the tailoring of the mesopore diameters and apertures. The combination of experimental and simulated XRD patterns and TEM images is confirmed to be a very powerful means for the accurate elucidation of the structure of new mesoporous materials.

In this work, the X-ray diffraction structure modeling was employed for analysis of hexagonally ordered large-pore silicas, SBA-15, to determine their pore width independently of adsorption measurements. Nitrogen adsorption isotherms were used to evaluate the relative pressure of capillary condensation in cylindrical mesopores of these materials. This approach allowed us to extend the original Kruk-Jaroniec-Sayari (KJS) relation (Langmuir 1997, 13, 6267) between the pore width and capillary condensation pressure up to 10 nm instead of previously established range from 2 to 6.5 nm for a series of MCM-41 and to improve the KJS pore size analysis of large pore silicas.

A new method of full-profile refinement is developed on the basis of the minimization of the derivatives of the profile difference curve. The use of the derivatives instead of the absolute difference between the observed and calculated profile intensities allows refinement independently of the background. The procedure is tested on various powder diffraction data sets and is shown to be fully functional. Besides having the capability of powder diffraction structure analysis without modelling the background curve, the method is shown to allow the derivation of structure parameters of even higher quality than those obtained by Rietveld refinement in the presence of systematic errors in the model background function. The derivative difference minimization principles may be used in many different areas of powder diffraction and beyond.

Abstract SBA‐15 (2D hexagonal structure) and KIT‐6 (3D cubic structure) silica materials are used as templates for the synthesis of two different crystalline mesoporous WO 3 replicas usable as NO 2 gas sensors. High‐resolution transmission electron microscopy (HRTEM) studies reveal that single‐crystal hexagonal rings set up the atomic morphology of the WO 3 KIT‐6 replica, whereas the SBA‐15 replica is composed of randomly oriented nanoparticles. A model capable of explaining the KIT‐6 replica mesostructure is described. A small amount of chromium is added to the WO 3 matrix in order to enhance sensor response. It is demonstrated that chromium does not form clusters, but well‐distributed centers. Pure WO 3 KIT‐6 replica displays a higher response rate as well as a lower response time to NO 2 gas than the SBA‐15 replica. This behavior is explained by taking into account that the KIT‐6 replica has a higher surface area as demonstrated by Brunauer–Emmett–Teller analyses and its mesostructure is fully maintained after the screen‐printing step involved in sensors preparation. The presence of chromium in the material results in a shorter response time and improved sensor response to the lowest NO 2 concentrations tested. Electrical differences related to mesostructure are reduced as a result of additive introduction.

Colloidal silver has gained wide acceptance as an antimicrobial agent, and various substrates coated with nanosilver such as fabrics, plastics, and metal have been shown to develop antimicrobial properties. Here, a simple method to develop coating of colloidal silver on paper using ultrasonic radiation is presented, and the coatings are characterized using X-ray diffraction (XRD), high resolution scanning electron microscope (HRSEM), and thermogravimetry (TGA) measurements. Depending on the variables such as precursor concentrations and ultrasonication time, uniform coatings ranging from 90 to 150 nm in thickness have been achieved. Focused ion beam (FIB) cross section imaging measurements revealed that silver nanoparticles penetrated the paper surface to a depth of more than 1 μm, resulting in highly stable coatings. The coated paper demonstrated antibacterial activity against E. coli and S. aureus, suggesting its potential application as a food packing material for longer shelf life.

The structure of ordered mesoporous carbons (OMC) synthesized with sucrose, furfuryl alcohol or acenaphthene using the SBA-16 mesoporous silica template with cubic Imm structure has been investigated with X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N2 adsorption. This work shows that, in contrast to carbons prepared from sucrose by using SBA-15 silica as template, the impregnation of SBA-16 with sucrose failed to produce OMC with cubic Imm structure. However, when furfuryl alcohol and acenaphthene were used as carbon precursors, the cubic Imm structure was retained in the products. Thus, the latter carbon precursors were more suitable than sucrose for the formation of rigidly interconnected carbon bridges through narrow apertures of the cage-like siliceous SBA-16 mesostructure. In particular, the use of furfuryl alcohol as carbon precursor allowed us to control the degree of mesopore filling in SBA-16 and consequently, to synthesize hollow or fully filled cage-like silica–carbon mesostructures as was done in the case of channel-like SBA-15. In the case of acenaphthene only fully filled mesostructures were formed but with a much higher degree of graphitization. In the present work, we took advantage of the recent developments in the synthesis of SBA-16 with tailored diameter and entrance size of mesopores and made a step forward in the fabrication of OMC by using cage-like mesoporous silicas with narrow interconnections as templates.

This review discusses principal patterns that govern the processes of lignins' catalytic oxidation into vanillin (3-methoxy-4-hydroxybenzaldehyde) and syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde). It examines the influence of lignin and oxidant nature, temperature, mass transfer, and of other factors on the yield of the aldehydes and the process selectivity. The review reveals that properly organized processes of catalytic oxidation of various lignins are only insignificantly (10-15%) inferior to oxidation by nitrobenzene in terms of yield and selectivity in vanillin and syringaldehyde. Very high consumption of oxygen (and consequentially, of alkali) in the process-over 10 mol per mol of obtained vanillin-is highlighted as an unresolved and unexplored problem: scientific literature reveals almost no studies devoted to the possibilities of decreasing the consumption of oxygen and alkali. Different hypotheses about the mechanism of lignin oxidation into the aromatic aldehydes are discussed, and the mechanism comprising the steps of single-electron oxidation of phenolate anions, and ending with retroaldol reaction of a substituted coniferyl aldehyde was pointed out as the most convincing one. The possibility and development prospects of single-stage oxidative processing of wood into the aromatic aldehydes and cellulose are analyzed.

The Bochner-Martinelli integral representation for holomorphic functions or'sev eral complex variables (which has already become classical) appeared in the works of Martinelli and Bochner at the begin

The (5α,6α)-7,8-didehydro-4,5-epoxy-17-methylmorphinan-3,6-diol (morphine)molecule has been studied using the density functional theory and molecular docking methods and non covalent interactions. The conformational analysis of the molecule at the B3LYP/6−311++G** and HF/6−311++G** levels has been made. The comparison of the structural parameters computed using the B3LYP function with the experimental data has revealed their good agreement. The weak intermolecular interactions in the morphine structure have been analyzed using several techniques. The Hirshfeld surface study has been carried out to identify the diverse intermolecular interactions (mainly hydrogen bonds) and the … π stacking interactions. The analysis of the topological (AIM, ELF, LOL) and non covalent (RDG, IRI, DORI) interactions has revealed different categories of inter- and intramolecular contacts on the basis of the electron localization density and color scale indicator, respectively. The molecular docking study has been carried out to examine the possibility of biological application of the title conformer using the 1DLO (cancerous), 2BK3 (Parkinson), 3LN1 (inflammatory), 4HOE (microbial), and 5 K95 (schizophrenia) enzymes. The analysis has shown that the morphine structure can be used not only in analgesia, but also in the treatment of diseases. The investigated compound has shown good results with monoamine oxidase B (MOAB) at a score of −105.04 kcal/mol.

Abstract Different aspects concerning the process of direct methane conversion to oxygen-containing products developed during more than half a century have been considered in previous reviews [1–3]. In particular, Gesser et al. [13 paid most attention to the homogeneous stages in methane conversion, while Foster [2] and Pitchai and Klier [3] examined the effect of different catalysts on methanol and formaldehyde formation. At present the main product of the homogeneous methane oxidation process with oxygen is shown to be methanol formed according to a chain-branching mechanism. In the presence of homogeneous initiators [4] (benzene, 2,2,4- trimethylpentane, etc.) or heterogeneous catalysts [2,3,5,6], formaldehyde is formed together with CH30H. However, the yield of the desirable products is low and does not exceed 8–10%. Charged atomic oxygen forms are considered to take part in the process of catalytic methane oxidation.

In this work, we studied intermolecular aqueous clusters of biuret, an important urea derivative. FTIR showed an increase in the intensity of absorption bands when water molecules are introduced into the biuret. X-ray diffraction analysis showed that the introduction of water molecules into the biuret structure significantly increases the intensity of the bands on the diffraction patterns in the range from 14 to 65 2˚⊖. Aqueous biuret clusters have also been studied in the gas phase by theoretical methods: density functional theory and Atoms in Molecules (AIM) using the DFT level B3LYP/6–31 + G (d, p). The nature of molecular interactions between water and biuret through hydrogen bonds was also investigated using the electron localization function (ELF) and non-covalent reduced density gradient (NC-RDG). The thermodynamic and Non-linear optical properties of biuret-water clusters were performed also.

Adsorption complexes of palladium atoms on Fs, Fs+, Fs2+, and O2− centers of MgO(001) surface have been investigated with a gradient-corrected (Becke–Perdew) density functional method applied to embedded cluster models. This study presents the first application of a self-consistent hybrid quantum mechanical/molecular mechanical embedding approach where the defect-induced distortions are treated variationally and the environment is allowed to react on perturbations of a reference configuration describing the regular surface. The cluster models are embedded in an elastic polarizable environment which is described at the atomistic level using a shell model treatment of ionic polarizabilities. The frontier region that separates the quantum mechanical cluster and the classical environment is represented by pseudopotential centers without basis functions. Accounting in this way for the relaxation of the electronic structure of the adsorption complex results in energy corrections of 1.9 and 5.3 eV for electron affinities of the charged defects Fs+ and Fs2+, respectively, as compared to models with a bulk-terminated geometry. The relaxation increases the stability of the adsorption complex Pd/Fs by 0.4 eV and decreases the stability of the complex Pd/Fs2+ by 1.0 eV, but it only weakly affects the binding energy of Pd/Fs+. The calculations provide no indication that the metal species is oxidized, not even for the most electron deficient complex Pd/Fs2+. The binding energy of the complex Pd/O2− is calculated at −1.4 eV, that of the complex Pd/Fs2+ at −1.3 eV. The complexes Pd/Fs and Pd/Fs+ exhibit notably higher binding energies, −2.5 and −4.0 eV, respectively; in these complexes, a covalent polar adsorption bond is formed, accompanied by donation of electronic density to the Pd 5s orbital.

A detailed characterization of large-pore cagelike mesoporous SBA-16 silica materials with tailored pore dimensions is reported. The materials were synthesized in a EO106PO70EO106 (F127)−butanol−H2O system under mildly acidic conditions, and the pore diameters were tailored by varying the hydrothermal treatment temperature. Structural information was acquired by full-profile analysis of powder X-ray diffraction (XRD) patterns. High-resolution diffraction data were obtained for all the materials using synchrotron radiation as the X-ray source, enabling a comprehensive XRD modeling supplemented with the generation of electron density distribution maps. The structural parameters derived from the XRD modeling were compared with data obtained from nitrogen and argon physisorption experiments performed at −196 °C. An excellent agreement was found between the XRD modeling results and those obtained by a new nonlocal density functional theory (NLDFT) kernel developed for pore size analysis based on gas adsorption in spherical pores, while NLDFT analysis based on a cylindrical pore model was shown to systematically underestimate the pore dimensions by about 30% which exceeds previous expectations. Furthermore, the Barrett−Joyner−Halenda model was shown to give errors up to about 45% in the pore size range above 4 nm. The structure of the surfactant−silica hybrid materials was also analyzed by XRD, which shed more light on the structural changes accompanying the thermal surfactant removal process. The present study is expected to provide a reference source for the accurate characterization of large cagelike mesoporous silica materials, on the basis of a direct comparison of suitable data collected independently by gas physisorption and comprehensive XRD modeling.

Exceptional control of the phase behavior of highly ordered large pore mesostructured silica (with the choice of Fm3m, Im3m or p6mm symmetry) is achieved using a triblock copolymer (EO(106)PO(70)EO(106)) and butanol at low acid concentrations.

Essential oils are volatile oil-like liquids with a characteristic strong smell and taste. They are formed in plants and are then extracted. Essential oils have extremely strong physiological and pharmacological properties, which are used in the medicine, cosmetics, and food industries. In this study, the molecules caryophyllene oxide, β-pinene, 1,8-cineol, α-cubebene, and β-caryophyllene, which are the molecules with the highest contents in the essential oil of the plant mentioned in the title, were selected and theoretical calculations describing their interactions with water were performed. Because oil–water mixtures are very important in biology and industry and are ubiquitous in nature, quantum chemical calculations for binary mixtures of water with caryophyllene oxide, β-pinene, 1,8-cineol, α-cubebene, and β-caryophyllene were performed using the density functional theory (DFT)/B3LYP method with a basis of 6–31 G (d, p). Molecular structures, HOMO–LUMO energies, electronic properties, reactivity (ELF, LOL, and Fukui), and NCI-RDG and molecular electrostatic potential (MEP) on surfaces of the main components of Phlomis bruguieri Desf. essential oil were calculated and described.

Three new alkaline earth metal complexes, [Ca2(H2O)8(μ2-HTBA-O,O′)2(HTBA-O)2] (1), [Ca(H2O)5(HTBA-O)2]·2H2O (2), and [Sr(H2O)4(μ2-HTBA-O,S)2]n (3) (H2TBA = 2-thiobarbituric acid, C4H4N2O2S), were synthesized and characterized by FT-IR spectroscopy, TG-DSC, and single-crystal and powder X-ray diffraction analysis. The single-crystal X-ray diffraction data revealed that 1 and 2 are discrete structures, whereas 3 is a polymer. In 1 and 2, Ca2+ is seven-coordinate and forms a monocapped trigonal prism. In 1, the prisms are pairwise connected with the assistance of two [μ2-HTBA-O,O′]− ligands. In 3, Sr2+ is coordinated by four monodentate HTBA− via S or O donors and four waters, with the formation of a distorted square antiprism. The antiprisms are connected by μ2-O,S bridging HTBA−. Hydrogen bonding involving coordinated water and π–π interactions plays an important role in construction of the supramolecular 3-D structures in 1–3. Infrared spectroscopic data supported the structural data. The thermal stability of 1–3 decreases in the order 1 > 2 > 3. Dehydration of 1–3 was a multi-step process, followed by exothermic oxidative degradation of the 2-thiobarbiturate moiety between 290 and 800 °C.

Elimination of AuX(PR3)(X = halogen, R = Ph, tol) occurs readily in reactions between compounds containing C(sp)- or C(sp2)-X bonds and alkynyl or polyynyl gold(I) complexes; this reaction has been applied to the syntheses of complexes containing a variety of metal centres linked by C(n) chains (n up to 16).

The chemical and phase composition, morphology, and shell structure of narrow fractions of nonmagnetic and magnetic low-density nonperforated cenospheres separated from fly ash concentrates produced via the pulverized combustion of coal from the Kuznetsk Basin (Russia) have been studied. Narrow fractions of nonmagnetic cenospheres contain 2.6–3.5 wt % Fe2O3 and include globules with a uniform smooth or relief surface and shells with different degrees of porosity. For nonmagnetic cenospheres, the aluminum concentration increase leads to an increase in the mullite phase content and a decrease in the average sphere diameter, glass-crystalline shell thickness and porosity, and the crystalline quartz content. The quartz phase comprises two modifications with different lattice parameters. The narrow fractions of magnetic cenospheres contain 3–21 wt % Fe2O3 and include globules with thick porous shells covered by heterogeneous regions of ferrospinel on their outer surface. In magnetic cenospheres, an increase in the iron concentration leads to an increase in the ferrospinel phase content and crystallite size, accompanied by a decrease in the degree of substitution of magnesium and aluminum for iron.

Sorption recovery of toxic ions – chromium (VI) and manganese (II) – from aqueous solutions with different acidity (0.001–0.5 M HCl) was investigated on cation and anion exchangers synthesized with long-chained cross-linking agents (LCA). The initial concentrations of Cr(VI) and Mn(II) were 1 g/L and 5 g/L, respectively. It was shown that the resins with LCA possess high ionic permeability due to the elasticity of polymeric skeleton. High selectivity and good kinetic properties of these sorbents allowed to achieve quantitative (∼100%) recovery and separation of manganese (II) and chromium (VI) in counter-current columns, which results in the complete purification of solutions from toxicants (below the maximum permissible limits), whereas the valuable components (chromium and manganese) can be returned back to industrial process. Keywords: Sorption, Ion exchangers, Long-chained cross-linking agents, Chromium, Manganese

The model of structure and structural transformation of the mesostructured carbon material CMK-1 was established by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) investigations. The investigations showed that the enantiomeric carbon subframeworks formed within the pores of the MCM-48 mesoporous template used for the material synthesis displaced with respect to one another without significant distortions after the dissolution of the silica wall of the template. The model proposed agrees well with TEM images observed. The XRD structural modeling of CMK-1 done using the continuous density function technique allowed perfect fit of the calculated to the experimental powder diffraction pattern and provided geometric characteristics of the material texture. The structural characteristics obtained agreed fairly well with TEM analysis and with previously reported adsorption data.