Механизм термической ионизации уротропина на поверхности интерметаллида NaAu-=SUB=-x-=/SUB=-

Thermal ionization of methenamine (C6H12N4) on the surface of the NaAux intermetallic compound has been studied. It has been established that the processes of decomposition, desorption and ionization of adsorbed compounds, thermally stimulated on the surface, proceed due to the accumulation of energy at the degrees of freedom of the adsorption complex, including the adsorbed compound and a solid, by the mechanism of monomolecular decomposition reactions. In this case, the decomposition of the adsorption complex is accompanied by the desorption of ions that are not in thermal equilibrium with the solid. The uniformity of the temperature dependences of the ion current and their distribution over two groups allowed us to conclude that ions are desorbed from the surface, which correspond to the decays of individual adsorbed molecules, as well as the decays of dimers formed on the surface. The decay of methenamine molecules during thermal ionization occurs in the same way as their decay in vacuum during electron ionization, which indicates the preservation of the bulk structure of methenamine molecules during adsorption and a significant lifetime of the excited state of compounds on NaAux.

Kinetic and Thermodynamic Characteristics of Fluoride Ions Adsorption from Solution onto the Aluminum Oxide Nanolayer of a Bacterial Cellulose-Based Composite Material

The described research examined the adsorption of fluoride ions from solution immobilized onto an aluminum oxide-coated bacterial cellulose-based composite material in which aluminum oxide had been deposited using ALD technology. The kinetic regularities of the adsorption of fluoride ions from the solution as well as the mechanism of the processes were analyzed. The established equations show that the dynamics of adsorption correspond to first-order kinetics. Based on the Langmuir adsorption isotherms, we defined the adsorption equilibrium constants, parameter maximum adsorption, and change in Gibbs free energy. It is shown that, with increasing temperature, an increase in the reaction rate is constant, both forward and reverse. This testifies to the activated character of adsorption of the first fluoride on the surface of the sorbent based on bacterial cellulose modified with an alumina nanolayer. The activation energy of the desorption process is higher than the activation energy of the adsorption process, which characterizes the adsorption as ionic. The negative value of entropy indicates that in the course of sorption, an adsorption complex “aluminum-fluorine” is formed, where the system is more ordered than the initial system in which fluorine ions are in solution. The limiting stages of the process are revealed. The high sorption capacity of the resulting bacterial cellulose-based composite material obtained by means of biosynthesis through cultivation of the bacterium Komagataeibacter sucrofermentans B-11267 was demonstrated.

Catalytic Oxidation of Benzyl Alcohol to Benzaldehyde on Au8 and Au6Pd2 Clusters: A DFT Study on the Reaction Mechanism

Density functional theory calculations were performed to investigate the reaction mechanism of the aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by Au and Au–Pd clusters. Two consecutive reaction mechanisms were examined with Au8 and Au6Pd2 clusters: (1) the oxidation of benzyl alcohol with dissociated O atoms on metal clusters generating benzaldehyde and H2O; and (2) oxidation with adsorbed oxygen molecules generating benzaldehyde and H2O2. The calculations show that the aerobic oxidation of benzyl alcohol energetically prefers to proceed in the former mechanism, which agrees with the experimental observation. We demonstrate that the role of Au centers around the activation of molecular oxygen to peroxide-like species, which are capable of the H–abstraction of benzyl alcohol. The roles of Pd in the Au6Pd2 cluster are: (1) increasing the electron distribution to neighboring Au atoms, which facilitates the activation of O2; and (2) stabilizing the adsorption complex and transition states by the interaction between positively charged Pd atoms and the π-bond of benzyl alcohol, both of which are the origin of the lower energy barriers than those of Au8.

Interaction of N-acetylneyraminic acid with surface of silica with fructose in aqueous solution

Quantum chemical simulation of the adsorption of N acetylneuraminic acid (NANA) on the surface of silica with the participation of the fructose molecule by the method of density functional theory B3LYP, 6-31G (d, p) was done. The influence of the solvent was taken into account in the supermolecular and continuum approximations, and a cluster approach was used for the adsorption complexes. NANA adsorption of the hydrated silica surface was considered as a process of replacement of water molecules on the silica surface by adsorbate molecules. Two schemes of influence of fructose molecule on NANA adsorption are considered. According to the first scheme, the hydrated NANA molecule interacts with the hydrated silicon-fructose adsorption complex. According to the second scheme, the cluster of hydrated silica interacts with the hydrated NANA-fructose complex. The energy of intermolecular interaction according to the scheme 1 is -9.2 kJ / mol, which is significantly lower compared to the same value with the participation of glucose or sucrose (-20.5 and -86.2 kJ / mol). Scheme 2 proved to be a thermodynamically unfavorable process, as its energy effect is +6.9 kJ / mol, in contrast to similar processes for glucose (-21.8) and sucrose (-87.7 kJ / mol). This confirms the experimental fact of the interaction of substances in a mixture of NANA with carbohydrates in relation to the interaction with silica in comparison with the interaction of substances with silica separately.

Study of the mineral composition of some soils of the Syrian island: دراسة التركيب المعدني لبعض ترب الجزيرة السورية

The study was carried out with the aim of determining the mineral composition of the soil from the north-eastern region in Al-Hasakah governorate in Syria and its effect on some physical and chemical soil properties. Where five sections were excavated and three samples of dirt were taken from each section according to horizons, The results of the mineral composition study showed a group of primary metals and the highest percentage of calcite in the studied soils, Followed by quartz metal in terms of spread in the studied soils, but the potassium feldspar (Othoclaz) was less than calcite and quartz in the studied soils, while found only pyroxene in the soil of the fourth and fifth sectors where the rock basalt mother, while found Baligorskit metal and a small percentage in all types The clay minerals were found to be high in the fourth sector and less on the horizon A1 for the other sectors. There was no A0 in the horizon for the first two sectors (Al-Hasakah) and the second (Qamishli). Mica (often alkaline), kaolinite and chlorite were found to be lower in thickness than in all soil samples studied. The results of the physical study showed that most of the soils have a clay texture, with the lowest percentage of mud and hysteroscopic in the surface depth of Qamishli soil (Tal Maarouf) (41.00) and (5.06)%, respectively, in Tin Tin and Shakhala, in the third depth of the Malikiyah soil (Deir Tigris), and the bulk density values ​​ranged between (1.19-1.33) g / cm3, and the real density values ​​ranged from (2.62-2.75) g / cm3, and was accompanied by a variation in the values ​​of the total porosity, as its value ranged between (50.15--54.58)%. The chemical and fertility results showed that the degree of (pH) soil is moderate on the surface horizon of al-kamshli soil, reaching (7.71), and the average alkalinity becomes slightly more than (8.00), and the soil content of the exchanged cations ranged from medium to high, ranging between (32.24 and 45.32). m.m / 100g soil, and the calcium cation occupies the first place on the adsorption complex, followed by magnesium. The content of the studied soils from the organic matter in the first depth is considered low because its value ranges between (00.5 - 01.0)%. The total calcium carbonate percentage ranged between the lowest value (21.63%) in the Al-Malikiyah soil (Deir Djla), and the highest value (31.91%) in Qamishli (Tal Maouf). By studying the kinetics of potassium, it was found that the ARKe values ranged between (0.0092 and 0.183) (mol / liter) 1/2, where the highest value of ionic activity was recorded in Malikiyah soil (0.0183) (mol / liter) 1/2 and the lowest value of ionic activity was recorded in Qamishli soil. 0.0092 (mol / liter) 1/2. The values of K∆ for the studied soils ranged from (0.3595 - 0.885) centimole. Kg-1, where the values of the potassium voltage regulation values of the studied soils ranged between (33.751- 60.314) [cmol kg-1] / (M L-1) 0. 5]. That the values of the Capon modulus ranged between (0.867 - 1.713) liters to mol -1.

INFLUENCE OF FROST PENETRATION AND CRYOGENESIS ON SOIL PROPERTIES

Изучено влияние низких температур на изменение процессов ионного обмена в исследуемых почвах, изменение растворимости малорастворимых и труднорастворимых соединений. В качестве объекта были выбраны мерзлотно-таежные почвы, характерные для Якутии. Замораживание почвенных растворов сопровождается увеличением концентрации ионов в незамерзшей части, разрушением алюмосиликатов, изменением прочности связи воды с почвенно-поглощающим комплексом. Это проявляется в инфракрасных спектрах, дериватограммах, а эффект был зависим от продолжительности и кратности промораживания. Замерзание верхней части почвенного профиля при наличии многолетней мерзлоты приводит к развитию тиксотропии. Установлено, что интенсивность развития этих процессов отличается для почв разного гранулометрического и минералогического состава, гумусированности, для органических и минеральных горизонтов. Содержание катионов водорастворимых солей в замерзших и незамерзших почвенных растворах мерзлотно-таежных почв составляло соответственно К – 4,7±2,5 и 42,8±28,5 мг/л; Са – 0,2±0,1 и 3,2±1,4; Fе – 0,04±0,01 и 0,38±0,03 мг/л. Эти отличия были характерны для отдельных горизонтов почв. Замерзшая часть раствора менее минерализована, незамерзшая часть содержит большие концентрации элементов. Обсуждается роль многолетней мерзлоты в процессах почвообразования. Низкие температуры профиля и сниженная биологическая активность обуславливают специфику протекания реакций ионного обмена, изменение растворимости осадков, создание водоупора. Эти процессы способствуют аккумуляции веществ в надмерзлотном слое, возникновению новых градиентов и геохимических барьеров в почвенном профиле. Наблюдается локальное развитие почвообразования в слое, образующемся над вечной мерзлотой, при отсутствии промывного водного режима. Low temperatures lead to alterations of ion exchange processes in the soil, fallout solubility. As an object, permafrost-taiga soils characteristic of Yakutia were chosen. The soil solution freezing is provided with ion densification in unfrozen parts, alumosilicate damage, change of bond strengths between water and the soil adsorption complex, infrared spectra, thermograms. Freeze-up of the upper soil profile in the presence of permafrost causes tixotropy development. However, the rate of these processes development differs for the soils of different granulometric and mineralogical content, high humus content, for organic and mineral horizons. At this rate, the water-soluble cation content in frozen and unfrozen soil solutions of cryomorphic-taiga soils was К – 4,7±2,5 and 42,8±28,5 mg/l; Са – 0,2±0,1 and 3,2±1,4; Fе – 0,04±0,01 and 0,38±0,03 mg/l accordingly. These distinctions were typical for certain soil horizons. Frost penetration of the soils modified their thermograms and infrared spectra. The effect depended on the persistency and frequency of the frost penetration. The frozen part of the solution is less mineralized, the unfrozen part contains large concentrations of elements. The role of permafrost in soil formation is discussed. Low profile temperatures and reduced biological activity determine the specifics of the ion exchange reactions, changes in the solubility of precipitation, the creation of a water seal. These processes contribute to the accumulation of substances in the permafrost layer, the emergence of new gradients and geochemical barriers in the soil profile. There is a local development of soil formation in the layer formed over permafrost, in the absence of washing type of water regime.

О декорировании зигзагообразных краев наноленты эпитаксиального графена

A double-chain model of an epitaxial graphene nanoribbon, the zigzag edges of which are decorated with foreign adparticles, has been proposed. The substrate is assumed to be a metal. Analytical expressions for the Green’s functions of carbon adatoms and adparticles are obtained. The band spectrum for the free state is determined, and the approximation of the density of states is proposed. Analytical expressions for the occupation numbers in the mode of tight binding between the adsorption complex and the substrate are presented. A chain of carbon adatoms decorated with adparticles (epicarbyne) is considered.

DFT Study of Anthocyanidin and Anthocyanin Pigments for Dye Sensitized Solar Cells: Electron Injecting from the Excited States and Adsorption onto TiO2 (Anatase) Surface

We explored, the absorption spectra, excited states and electronic injection parameters of anthocyanidin and anthocyanin pigments using the level of theory (TD)CAM-B3LYP/6–31 + G(d,p). For all isolated dyes, the distribution pattern of HOMO and LUMO spread over the whole molecules, which lead an efficient electronic delocalization. The calculated LHEs are all near unity. Methoxy group in Peonidin molecule lead the largest oscillator strength and LHE. The presence of water lead a higher spontaneous electronic inject process, with ΔGinject average of −1.14 eV. The ΔGinject order is Peonidin<Delphinidin<Cyanin<Cyanidin. Similarly, the adsorption energies (Eads) onto anatase surface model were obtained from level of theory GGA(PBE)/DNP. Eads of anthocyanin-(TiO2)30 complex was calculated to be from 17 to 24 eV, indicating both, the strong interactions between the dyes and the anatase (TiO2) surface and stronger electronic coupling strengths of the anthocyanin-(TiO2)30 complex, which corresponded to higher observed η. The HOMO and LUMO shape showed the electrons delocalized predominantly on the anthocyanin structure while, the LUMO + 1 shape is localized into the (TiO2)30 surface. Therefore we expected a electronic injection from HOMO to LUMO + 1 in the anthocyanin-(TiO2)30 adsorption complex, after the light absorption.