Types Of Chemical Bonds Research Articles

Polymeric seed layer as a simple approach for nanostructuring of Ga-doped ZnO films for flexible piezoelectric energy harvesting

RF sputtering is used for the growth of Ga-doped ZnO (GZO) piezoelectric film (420 nm) on conjugated polymer PEDOT:PSS deposited on a flexible substrate. The PEDOT:PSS serves as an amorphous seed sublayer for nanostructured GZO growth and as a bottom electrode in a simple energy harvesting element. Dendrite type structure of the piezoelectric film is obtained and it is organized in a single-directional nanoporous manner, which increased the specific surface area of the material and facilitates piezoelectric voltage generation. As a result, the open-circuit voltage reached maximum 398 mV for the nanostructured GZO film on polymer electrode versus 231 mV for the film grown on the metal electrode at low frequency (up to 50 Hz) and weak mechanical loading (max. 40 g). X-ray diffraction spectrum of the GZO nanostructured film is similar to that of ZnO wurtzite structure. FTIR study shows that the Ga doping doesn't affect the wurtzite structure of the host material and does not cause modification of the chemical bond types. The output electrical power was calculated to be 2.05 μW and 3.34 μW, corresponding to non-structured and structured GZO films, respectively. This result is competitive with the recent reports for lead-free piezoelectric energy harvesting using conventional microfabrication technologies.

Fuels, power and chemical periodicity.

The insatiable-and ever-growing-demand of both the developed and the developing countries for power continues to be met largely by the carbonaceous fuels comprising coal, and the hydrocarbons natural gas and liquid petroleum. We review the properties of the chemical elements, overlaid with trends in the periodic table, which can help explain the historical-and present-dominance of hydrocarbons as fuels for power generation. However, the continued use of hydrocarbons as fuel/power sources to meet our economic and social needs is now recognized as a major driver of dangerous global environmental changes, including climate change, acid deposition, urban smog and the release of many toxic materials. This has resulted in an unprecedented interest in and focus on alternative, renewable or sustainable energy sources. A major area of interest to emerge is in hydrogen energy as a sustainable vector for our future energy needs. In that vision, the issue of hydrogen storage is now a key challenge in support of hydrogen-fuelled transportation using fuel cells. The chemistry of hydrogen is itself beautifully diverse through a variety of different types of chemical interactions and bonds forming compounds with most other elements in the periodic table. In terms of their hydrogen storage and production properties, we outline various relationships among hydride compounds and materials of the chemical elements to provide some qualitative and quantitative insights. These encompass thermodynamic and polarizing strength properties to provide such background information. We provide an overview of the fundamental nature of hydrides particularly in relation to the key operating parameters of hydrogen gravimetric storage density and the desorption/operating temperature at which the requisite amount of hydrogen is released for use in the fuel cell. While we await the global transition to a completely renewable and sustainable future, it is also necessary to seek CO2 mitigation technologies applied to the use of fossil fuels. We review recent advances in the strategy of using hydrocarbon fossil fuels themselves as compounds for the high capacity storage and production of hydrogen without any CO2 emissions. Based on these advances, the world may end up with a hydrogen economy completely different from the one it had expected to develop; remarkably, with 'Green hydrogen' being derived directly from the hydrogen-stripping of fossil fuels. This article is part of the theme issue 'Mendeleev and the periodic table'.

A revisit of the bond valence model makes it universal.

The use of simple, intuitive equations to correlate the geometry of crystal structures with electron descriptors of chemical bonds and material structural stability is a great advantage of the Bond Valence Model (BVM), which is based on Pauling's principles of bond order (BO) conservation and exponential BO/bond length relationship. However, the high potential of BVM to be used as an important analytical tool was overlooked in recent inorganic chemistry due to its empirical character and serious restrictions for its application. Recent quantum chemistry data (BOs and electron densities at the bond critical points, ρc) enable us to establish the validity of the BVM to any type of chemical bonds, as well as a direct BO/ρc relationship. Such a BVM revisit overcomes most of the limitations anticipated previously for the model and thus makes it universal. This Perspective highlights the advance in model development, in particular its application to compounds with metal-metal bonds, which allows us to establish (i) a linear correlation between BOs and stretching force constants used as a measure of the bond strength and (ii) a quantitative description of the steric/electrostatic effects in cluster compounds enabling us to understand their nature and the influence of such effects on structural stability. Thus, using interatomic distances, the simple Pauling equation and empirical constants, it is possible to calculate effective BOs and predict stretching force constants and electron densities at the bond critical points in any complex compound, all of this at zero cost!

Elemental carbon in the sp1 hybridization

Hybridizations of carbon atoms are textbook examples of different types of chemical bonds. Likewise, the elemental phases of carbon, graphite and diamond are well known as materials in pure sp2 or sp3 hybridizations. However, what is much less known is the elemental carbon phase in the sp1 (or sp) hybridization. The phase is called carbyne and still somewhat elusive, although many reports on successful syntheses have been given. Carbyne is assumed to consist of densely packed linear chains of carbon atoms and appears to be a rather unstable material. Individual chains of carbon atoms are perfectly one-dimensional structures and show many highly interesting physical properties of classical 1D materials. This article first gives an overview of the relation between the differently hybridized elemental phases of carbon and then focuses on the structure and the properties of individual sp1 chains of carbon atoms. A brief survey of the synthesis of individual carbon chains as well as bulk carbyne is given at the end of the article.

CHERENKOV RADIATION OF THE RELATIVISTIC ELECTRON BUNCH IN ION DIELECTRIC MEDIA

The process of wakefields excitation by the relativistic electron bunch in dielectric media with ion type of chemical bond is studied. The spatio-temporal structure of the excited wakefield in ion dielectric waveguide is obtained and investigated. It is shown that the excited wakefield in the infrared and longer wavelength ranges consists of the field of longitudinal optical phonons and Cherenkov radiation as a set of eigen electromagnetic waves of the dielectric waveguide.

Deposition of Films from a Mixture of Hexamethylcyclotrisilazane Vapor and Argon in Inductively Coupled Plasma

In an inductively coupled high-frequency discharge plasma, SiCxNy:H films are obtained from a mixture of hexamethylcyclotrisilazane vapor and argon at substrate temperatures of 100 to 400°C and a discharge power of 200 W. The simplest plasma components (nitrogen, cyan, silicon atoms, CH free radicals, and C2 dimers) are determined. Some physicochemical properties of the films, including the growth rate, types of chemical bonds, refractive index, transparency interval, and contact angle, are studied. The synthesized films have a polymer-like structure.

Structure and Optical Properties of Chalcogenide Glassy Semiconductors of the As–Ge–Se System

The types of structural elements and chemical bonds forming an amorphous matrix of chalcogenide glassy semiconductors of the As–Ge–Se system and changes occurring in them depending on the chemical composition are determined using a method for studying the Raman and transmission spectra and density measurements. It is shown that a transition from the elastic to isostatic state and then to the stressed-rigid state occurs in the system under study with increasing arsenic and germanium contents. The observed changes in the Raman spectra and the features of the dependences of optical and other parameters on the chemical composition are explained within the chemical-ordering model, taking into account the existence of local states near the allowed band boundaries.

Mass Spectrometry of Chalcogenide Glass and Carbon Nitrides

Based on the mass spectrometric study of chalcogenide and fullerene-chalcogenide glass (CG), as well as amorphous and crystalline carbon nitrides with general formula CnNm, which are similar to CG, are considered according to the type of chemical bond, their vapor composition, and the effect of the initial specimens of the synthesized materials, including those containing metal components, fullerenes, and binary and ternary chemical compounds, as well as other structural units (SUs) and structural motifs.

The Study of Regularities of Changing Melting Enthalpy of Intermetallides of Magnesium–Lantanoids Systems Rich in Magnesium

Providing a reasonable forecast of the required properties of intermetallic compounds (hereinafter also referred as intermetallides or IM) is an important scientific and commercial problem, which may be solved by focusing scientific researches and permanent generation of knowledge in this field. To date, researches in chemistry and physics of IM have been developing empirically for a simple reason, due to the complexity of describing the relationship between the crystal structure and chemical bonds, and, therefore, between all the properties of IM. IM is mainly characterized by metal type of chemical bond, as well as specific metallic properties. At the same time, among IM, there are also salt-like compounds with ionic bond, i.e. valency compounds formed from elements of different chemical nature, being stoichiometric compounds. The examples of such compounds are compounds with intermediate bond type, i.e. ionmetal and covalently-metal, as well as covalent bond types (e.g., NaAu). In the series of compounds of Mg with elements of the IV subgroup, along with decreasing the difference in the electrochemical characteristics of the components, the change in the IM properties is observed, from those peculiar to ionic compounds (for example, Mg2Si, Mg2Ge) to the properties typical of metals (Mg2Pb), etc. Due to the fact that lanthanides form the largest group of elements of the periodic system occurring in nature, and Mg is a relatively active chemical element in terms of IM formation (for example, it forms three IM with cadmium - Mg3Cd, MgCd and MgCd3), its oxides in slag provide decreasing average silicon content and increasing the stability of the silicon content in iron, being an important process indicator in the course of physicochemical reactions occurring in a blast furnace (for example, in the process of iron production). The presence of Si impurity (along with O, Au, Ti, V, Zr) produces the greatest effect on efficiency of solar cells, etc. [1–3]. Based on the foregoing, it is very important to study the state function, i.e. enthalpy of magnesium-lanthanide systems, rich in magnesium, and, based on the results of computer simulation, taking into account molecular dynamics method and other similar studies [4–8], to model regularities of changes in melting enthalpy of IM of the mentioned systems. The issue of modeling the pattern of change in melting enthalpy of IM of magnesium-lanthanide (Mg-Ln) magnesium-rich systems is considered based on systematic analyzing melting enthalpy of IM of Mg-Ln magnesium-rich system, including Mg2Ln, Mg3Ln and equimolar compound MgLn, implemented using semi-empirical method developed by N.S. Poluektov.

Modification of Ti6Al4V Titanium Alloy Surface Layer in the Ozone Atmosphere.

The paper reports the results of a study on the Ti6Al4V titanium alloy involving the XPS (X-ray photoelectron spectroscopy) photoelectron spectroscopy method. The position of bands in the viewing spectrum serves as a basis for the qualitative identification of atoms forming the surface layer, while their intensity is used to calculate the aggregate concentration of these atoms in the analyzed layer. High-resolution spectra are used to determine the type of chemical bonds based on characteristic numerical values of the chemical shift. The paper also presents the 3D results of surface roughness measurements obtained from optical profiling, as well as the results of energy state measurements of the Ti6Al4V titanium alloy surface layer after ozone treatment. It was shown that the ozone treatment of the Ti6Al4V titanium alloy removes carbon and increases concentrations of Ti and V ions at higher oxidation states at the expense of metal atoms and lower valence ions. The modification of the surface layer in ozone atmosphere caused a 30% increase in the Ti element concentration in the surface layer compared to the samples prior to ozone treatment. The carbon removal rate from the Ti6Al4V titanium alloy samples amounted to 35%, and a 13% increase was noted in oxides. The tests proved that the value of the surface free energy of the Ti6Al4V titanium alloy increased as a result of ozone treatment. The highest increase in the surface free energy was observed for Variant 4 samples, and amounted to 17% compared to the untreated samples, while the lowest increase was equal to 14%. For the analyzed data, the maximum value of standard deviation was 0.99 [mJ/m2].

CRYSTAL STRUCTURE AND CHEMICAL BOND IN INTERMEDIATE COMPOUNDS OF Tl2Se–In2Se3–”P2Se4” SYSTEM

Perspective compounds that are widely used in production of working elements for semiconductor IR and laser technology, thermal generation, solar power, are materials based on complex chalcogenide compounds. Special attention is paid to compounds of the M2P2Se6 type, derived from Sn2P2S6(Se6). Modification of the composition of M2P2Se6 type compounds by isovalent substitutions of the chalcogen S®Se, which form the sublattice of the anionic group [P2X6]4–, as well as Sn2+®Pb2+, heterovalent substitutions 2Sn2+®4M1+ (M1 – K+, Na+, Rb+, Tl+, Ag+, Cu+), 2Sn2+®M1++M23+ (M2 – In3+, Sb3+, Bi3+, Fe3+) leads to the formation of new structures with different structure of cation sublattice, which is accompanied by a change in crystal-chemical parameters.Study of physical-chemical interaction in the Tl2Se–In2Se3–“P2Se4” system showed that intermediate complex selenides which melts congruently In2Se3 (1192 К), TlInSe2 (1023 К), Tl4P2Se6 (758 К), In4(P2Se6)3 (880 К), TlInP2Se6 (875 К) form five quasi-binary eutectic type sections with formation of limited solid solution.Crystalstructure studies of complex chalcogenides of the Tl2Se–In2Se3–“P2Se4” system were carried out by a powder method. Refinement of the structural parameters of intermediate compounds was carried out by the Rietveld method. Crystal-chemical parameters of compounds in the Tl2Se–In2Se3–“P2Se4” system are: In2Se3 hexagonal, Р61, a=7.129, c=19.381 A; Tl2Se tetragonal, Р/n, а=8,540; с=12,380 A; TlInSe2 tetragonal, I4/mcm, a=8.064, c=6.833 A; Tl4P2Se6 monoclinic, P121/c1, a=12.239, b=9.055, c=12.328 A, b=98.83о; In4(P2Se6)3 trigonal, R3h, a=6.381, c=20.014; TlInP2Se6 triclinic, P-1(2), a=6.449, b=7.542, c=12.166 A,a=100.72, b=93.63 о, g=113.32 о.The crystal-chemical analysis of the М2P2Se6 type compounds showed that in their structure anionic group of atoms [P2Se6]4– can be isolated in the form of two fused tetrahedron, a pair of P–P from Phosphorus atoms occupy octahedron voids between the planes of Selenium atoms, cations of atoms (Tl, In) occupy position between layers of atoms of anionic groups. In the transition of In4(P2Se6)3®TlInP2Se6®Tl4P2Se6 with a decrease in the total electronegativity of the atoms of the cationic group (an increase in the total number of cations atoms per anionic group [P2Se6]4–), there is a corresponding decrease in the interatomic distances between a pair of Phosphorus P–Р atoms from 3,082 A®2,278 A®2,217 A, as well as the connections of P–Se 2,193¸2,233 A® 2,184¸2,235 A®2,100¸2,246 A, indicating an increase in the stability of the anionic group [P2Se6]4–. For compound Tl4P2Se6 there is a discernible deformation of fused tetrahedron [P2Se6]4–.An analysis of crystal-chemical studies has shown that binary compounds characterized by a mixed type of chemical bond – ionic-covalent. Transition from binary compounds to complex compounds TlInSe2, TlInP2Se6, In4(P2Se6)3 and TlInP2Se6, due to trans-effects in the Tl–P–Se bonds system, increases the polarization of Tl–Se bonds, indicating an increase in contribution ionic component of chemical bonding. The opposite processes is observed for In–Se bonds, the polarization of which decreases, which leads to an increase in the power of the covalent component. An increase in the ion bond between cations of Tl+, In3+ and Se2– anionic groups also leads to decrease in the contribution of the metallic component in the ternary and quartery compounds to binary selenides.

Hybrid XNBR composites with carbon and aluminosilicate nanofillers

The objective of the work was to investigate the possibility of simultaneous application of different types of nanofillers: graphene oxide with carboxylic groups and modified bentonite nanoparticles to carboxylated acrylonitrile–butadiene rubber (XNBR), and to determine the effect on the structural, mechanical and barrier properties of the composites. The composites were designed for use in protective clothing and gloves. Rubber compounds were crosslinked by a hybrid set with simultaneous use of sulphur (1.5 phr) and magnesium oxide (2.5 phr). Graphene oxide and bentonite particles were characterised by BET test method. The XNBR composites with nanofillers were studied in terms of structure (WAXS) and types of chemical bonds (FTIR), barrier properties against chemical substances (mineral oil) and swelling properties, as well as mechanical properties (puncture resistance, tear resistance, cut resistance, abrasion resistance, tensile strength). Simultaneous incorporation into XNBR of two types of nanofillers, bentonite in the amount of 1.0–4.0 phr and graphene oxide with carboxylic groups in the amount of 1.0–2.0 phr, affected positively the mechanical parameters. The most significant improvement was noted for the parameter specifying the puncture resistance, almost threefold improvement from 34 ± 2 N for unfilled XNBR composite to 91 ± 5 N for XNBR composite filled with 2 phr of bentonite (XNBR Bent. 2), or one and a half to 56 ± 5 N for XNBR composite filled with 2 phr of bentonite and 2 phr of graphene oxide (XNBR Bent 2 GO 2). The composites showed equally high resistance to penetration of the selected test chemical—mineral oil. The breakthrough time for XNBR composites without the nanofiller and containing differential amounts of nanofillers was very long and similar to that obtained for the reference sample (480 min).

The effect of benzotriazole gradual change on the corrosion performance of nanocomposite multilayer self-healing coating based on Titania-Alumina-Benzotriazole on AA7075

Abstract Today, lots of coatings are being used for protection against the corrosion; however, if a crack or scratch damage the coated surface, it could not protect itself. Nano-structured titanium oxide coatings have oxidation and corrosion resistance. Also, aluminum oxide coatings are widely used because of wear and corrosion resistance. In the present study, a combination of Titania and alumina and benzotriazole (C6H5N3) as an inhibitor was synthesized to create a corrosion resistant coating with self-healing properties via Sol-gel method. The gradual change in the amount of benzotriazole in layers produced different corrosion behaviors in the coatings. Microstructural and morphological behaviors of the coatings were characterized by Grazing Incidence X-ray Diffraction (GIXRD) analysis, Raman Spectroscopy, Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscope (AFM), respectively. According to GIXRD results, the structure of the formed coatings was utterly amorphous. FESEM images showed that the coatings were homogeneously formed in all specimens and achieving the nanostructured coatings with uniform distribution of grains depends on the optimal amount of Benzotriazole. According to AFM results, the thickness of all coatings was less than 200 nm. Raman spectroscopy results identified the chemical bond types such as Ti–O–Ti, Ti–O, and O–C–C groups. The corrosion behavior and self-healing properties of hybrid ceramic coating were investigated by electrochemical measurements, including Electrochemical Impedance Spectroscopy (EIS) and polarization test in the solution of 3.5 wt % NaCl in different periods. The results showed that benzotriazole could prevent corrosion progression due to self-healing capabilities and improve the corrosion resistance of the uncoated sample about 130 times after immersion for 96 h.

Anticancer mechanism of Pisangulin angulata through in silico and development as teaching material

This study aims to reveal the anticancer mechanism of the bioactive compound of Pisangulin angulata and to assess the feasibility of that results as teaching material. This research includes descriptive explorations. In the first stage, an in silico analysis was performed by molecular docking method between physalin compounds and GLI1 protein. The second steps of this study aim to develop teaching materials based research using the Analysis, Reorganizing, Piloting Class, and Evaluating (ARPE models). Feasibility test was carried out by experts and practitioners. Think Pair Share was used in the pilot project. Student motivation and misconception were recorded using SMI and CRI instrument. This study reveals that physalin B has higher activities than controls. The type of chemical bond that is formed between GLI1 amino acids residues with physalin is hydrogen bonds and hydrophobic bonds. The visualization of the types of bonds in that molecular docking between GLI1 amino acid residues and physalin has a high degree of feasibility (89) and can be used to enrich Chemistry for Biology lectures. The visualization of these chemical bonds can increase learning motivation and can improve the understanding of the concept of chemical bonds.

Tl2Se–TlInSe2–Tl4P2Se6 QUASITERNARY SYSTEM

Complex chalcogenide compound are widely used as working elements for semiconductor optical technology, thermal generation, solar power. Special attention is paid to compounds of the M2P2Se6 type (M – Ag, Cu) which due to its layer crystal structure possess promising ferroelectric, thermoelectric and electro-optical properties. Heterovalent substitutions of cations 2М2+ ® 4M1+ in the composition of M2P2Se6 type compounds must leads to deformation of the crystal structure, changing in the value of the dipole moment and, accordingly, to change the electro-physical properties.
 The Tl2Se–In2Se3–“P2Se4” system characterized by the formation of intermediate complex compounds which melts congruently TlInSe2 (1023 К), Tl4P2Se6 (758 К), TlInP2Se6 (875 К) and TlIn5Se8 (melts incongruently L+In2Se3«TlIn5Se8 at 1029 К), In4(P2Se6)3 (formed by syntactic reaction at 880 К). Triangulation of the Tl2Se–In2Se3–“P2Se4” system was shown that then divided on secondary quasiternary systems, one of them is Tl2Se–TlInSe2–Tl4P2Se6.
 Phase equilibria in the Tl2Se – TlInSe2 – Tl4P2Se6 quasiternary system were studied using classical methods of physicochemical analysis DTA (chromel-alumel thermocouple, with an accuracy of ±5 K), XRD (DRON-3-13 diffractometer, Cu Ka radiation, Ni filter, Guinier Huber G670 diffractometer, CuKα1 radiation), MSA (metallographic microscope Lomo Metam R1) in combination with the simplex method of mathematical modeling of phase equilibria in multi-component systems. Crystal structure calculation was carried out with program WinCSD.
 Investigation of physical-chemical interaction allowed to constructed perspective view of phase state diagram and liquidus surface projection of the Tl2Se–TlInSe2–Tl4P2Se6 ternary system. In the ternary system formed the boundary solid solution: a- on the basis of Tl2Se, b- on the basis of TlInSe2, g-, d-, e- on the basis of ltm-, mtm- and htm-Tl4P2Se6 (ltm, mtm, htm – low, middle and high temperature modification, respectively). The liquidus of the ternary system consists of primary crystallization areas: Tl2Se-е1-Е1-е2-Tl2Se (a phase), TlInSe2-е3-U2-U1-E1-TlInSe2 (b phase), m1-U1-E1-e2-m1 (g phase), m2-U2-U1-m1-m2 (d phase) and Tl4P2Se6-e5-U2-m2-Tl4P2Se6 (ε phase). The Tl2Se–TlInSe2–Tl4P2Se6 quasiternary system is characterized by the processes: monovariant eutectic L«htmTl4P2Se6+TlInSe2 (e5-U2, 776-693 К), monovariant eutectic L«Tl2Se+TlInSe2 (e1-Е1, 614-539 К), monovariant eutectic L«Tl2Sе+ltmTl4P2Se6 (e2-Е1, 610-539 К); monovariant peritectic L+mtmTl4P2Se6«ltmTl4P2Se6 (m1-U1, 640-620 К); monovariant peritectic L+htmTl4P2Se6« mtmTl4P2Se6 (m2-U2, 747-693 К); monovariant peritectic L+mtmTl4P2Se6«TlInSe2 (U2-U1, 693-620 К); monovariant peritectic L+ltmTl4P2Se6«TlInSe2 (U1-E1, 620-539 К). Lines of the monovariant equilibria are crossed in three point: U2 – invariant peritectic process L+htmTl4P2Se6«TlInSe2+mtmTl4P2Se6 (12 mol.% Tl2Se, 20 mol.% TlInSe2, 68 mol.% Tl4P2Se6, 693 К), U1 – invariant peritectic process L+mtmTl4P2Se6«TlInSe2+ltmTl4P2Se6 (38 mol.% Tl2Se, 9 mol.% TlInSe2, 53 mol.% Tl4P2Se6, 620 К), E1 – invariant eutectic process L « Tl2Se+TlInSe2+ltmTl4P2Se6 (47 mol.% Tl2Se, 7 mol.% TlInSe2, 46 mol.% Tl4P2Se6, 539 К). New complex compounds were not observed in the ternary system. Limited solid solutions on the basis of TlInSe2, Tl4P2Se6 initial compounds are not up to 5–8 mol%.
 Crystal-structure studies of Tl2Se, TlInSe2 and Tl4P2Se6 complex chalcogenides were carried out by a powder method, refinement of the structural parameters – by the Rietveld method. The lattice parameters are: Tl2Se – Р4/n, а=8,540; с=12,380 Å, TlInSe2 – I4/mcm, a=8.064, c=6.833 Å, Tl4P2Se6 – P121/c1, a=12.239, b=9.055, c=12.328 Å, b=98.83. Crystal-chemical analysis of the compounds showed that they are characterized by a mixed ion-covalent type of chemical bond. During the transition from the binary Tl2Se to TlInSe2 ternary compound the covalent component of the In–Se bond is enhanced, the opposite change is observed for Tl4P2Se6, an increase in the ion component of the Tl–Se bond. The study of the mechanisms of formation of solid solutions showed that with the reciprocal solubility of the TlInSe2, Tl4P2Se6 ternary compounds characterized by the formation of substitution structure, the dissolution of Tl2Se in ternary selenides follows the substitution and subtraction mechanism.

Determination of light elements C, N, O in various minerals and synthetic compounds using X-ray microanalysis

The goal of the study is developing of the methodology of X-ray microanalysis of light elements C, N and O which are jointly present in various minerals and synthetic compounds, including ultrafine diamonds, carbon filamentous fibers, etc. An accelerating voltage of 10 kV high enough to reduce the contribution of the sample surface to the intensity of the lines, and at the same time prevent from the overestimation of the corrections for the line absorption was used. The beam current ranged within 90 - 120 nA. The lines of nitrogen and oxygen are particularly strongly absorbed by carbon. The background intensity is measured near the line. In the region of Kα lines of C and O, the background changes linearly, while for oxygen exhibits a large slope. The shape of continuous X-ray spectrum from the sample at 10 kV in the region of the nitrogen line can be approximated by a polynomial dependence. We used a differential mode of the amplitude discrimination of the signal. It is shown that the position and shape of the carbon line depends on the type of the chemical bond: from covalent (diamond, graphite) to a more ionic bond with oxygen (carbonates). Wide in diamond and graphite Kα lines are shifted in carbonates to the shortwave region and substantially narrowed. An additional maximum appears due to admixing of the wave functions of 2p electrons of carbon to the wave functions of 2s electrons of oxygen. The errors related to the influence of the type of chemical bond on the shape of the spectra can be avoided by the analysis of the integrated intensities. In some cases, the resistance of the samples to the impact of the electron beam is increased by the raster mode of size 5-8 micron or by moving the sample within the area ~100 x 100 pm 2 . Calculation of the concentrations was carried out in the PAP program using B. L. Henke absorption coefficients. Some errors in the correction factors for the line absorption are usually corrected by selecting the absorption coefficients. The detection limit of carbon is 0.10 % wt. and for oxygen in carbonates it ranges within 0.39 - 0.90 % wt., whereas in the samples grown from nano-diamond colloids attains 0.75 wt. %.

Structure and Optical Properties of ZnO and ZnO<sub>2</sub> Nanoparticles

Zinc oxide (ZnO) and Zinc peroxide (ZnO2) nanoparticles were synthesized by colloidal method at low temperature. The thermal stability of ZnO2 was studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-Ray diffraction (XRD). The crystalline structure and phase change from ZnO2 to ZnO by heat treatment was studied in detail. Morphology and particle size was examined using Transmission Electron Microscopy (TEM), for as synthesized ZnO and ZnO2 the shape of particles were cuasi-spherical for both materials with average size of 10±2.2 nm and 2.5±0.4 nm, respectively; The crystal size for ZnO obtained by heat treatment was 8±2.2 nm. Electron density contours show the chemical bond type ionic and covalent for ZnO and ZnO2. The vibrational properties were analyzed by Raman and IR spectroscopy. Band gap values were obtained from ultraviolet-visible (UV-Vis) absorbance spectrum. Photoluminescence (PL) spectrum for ZnO shows two emission edges located at 445 and 492 nm and in the case of ZnO2 presents one edge at 364 nm originated from the band edge emission. The optical spectra present a hypsochromic shift, compared with some reported in the literature.

Enhancing the photovoltaic characteristics of organic solar cells by introducing highly conductive graphene as a conductive platform for a PEDOT:PSS anode interfacial layer

We propose a remarkably conductive polymer composite that results from highly conductive pristine graphene (PG) being doped with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). With the addition of PG to a PEDOT:PSS (B-PE) dispersion acting as a conductive platform, the sheet resistance can be lowered from 368.54 Ω/sq to 114.67 Ω/sq for the graphene-PEDOT:PSS (G-PE) over a bare glass substrate. Importantly, this only causes a minor decrease in optical transmittance of approximately 4.16% at 550 nm, and generates a noticeable decrease in the surface roughness profile of ~ 11.42 nm. XRD, Raman spectroscopy, and XPS analyses were used to verify that various types of chemical bonds are formed between the PG sheets and B-PE molecules. Due to these chemical interactions, a huge number of electrons are transferred from the PG sheets to the PEDOT, creating a net positive charge among the carbon atoms in the PG sheets. This results in an increase in the conductivity of the G-PE composite and, consequently, improves the power-conversion efficiency (PCE; 4.52%) of organic solar cells utilizing G-PE composite hole transport layers (HTLs). This enhancement in the PCE of G-PE HTL-based devices is compared with devices fabricated from either B-PE or PG HTLs alone, these devices achieved a PCE of only 4.18% and 3.87%, respectively.

Effect of pyrolysis conditions on the improvement of the physicochemical structure of activated carbon obtained from Jixi bituminous coal

AbstractDifferent pyrolysis conditions have been confirmed as a useful way to improve the physicochemical structure of Jixi bituminous char to obtain fully developed porosity after a low burn‐off during activation. In this paper, a series of coal‐char samples were prepared at different pyrolysis temperatures, rates, and residence times. The effect of the pyrolysis temperature on the physicochemical structure in coal char is important because it can control the breakage and recombination of different types of chemical bonds. The impact of the pyrolysis rate gradually increases with increasing temperature, indicating that its influence is closely related to the pyrolysis temperature. However, an extension of the residence time at different pyrolysis temperatures and rates can only help the evolution of the chemical structure. It was determined that the typical char (KJX800‐40) produced by rapid pyrolysis at 800°C over a long residence time (40 min) is the most suitable for subsequent activation due to its disordered carbon structure, abundant initial pores, and active sites. The initial pores that developed in the KJX800‐40 char facilitate the diffusion of activated gas to avoid serious carbon losses on the surface of the particles; alternatively, more active sites help the etching of the carbon structure to promote the rapid and continuous development of the micropores, following nonhierarchical development. On the basis of these results, a pyrolysis condition with a high SBET (859.14 m2/g)/burn‐off ratio (25.2%) of 34.09 m2/(g•%) was identified.

Correlations between Density-Based Bond Orders and Orbital-Based Bond Energies for Chemical Bonding Analysis.

Quantum chemistry-based codes and methods provide valuable computational tools to estimate reaction energetics and elucidate reaction mechanisms. Electronic structure methods allow directly studying the chemical transformations in molecular systems involving breaking and making of chemical bonds and the associated changes in the electronic structure. The link between the electronic structure and chemical bonding can be provided through the crystal orbital Hamilton population (COHP) analysis that allows quantifying the bond strength by computing Hamilton-weighted populations of localized atomic orbitals. Another important parameter reflecting the nature and strength of a chemical bond is the bond order that can be assessed by the density derived electrostatic and chemical (DDEC6) method which relies on an electron and spin density-partitioning scheme. Herein, we describe a linear correlation that can be established between the DDEC6-derived bond orders and the bond strengths computed with the COHP formalism. We demonstrate that within defined boundaries, the COHP-derived bond strengths can be consistently compared among each other and linked to the DDEC6-derived bond orders independent of the used model. The validity of these correlations and the effective model independence of the electronic descriptors are demonstrated for a variety of gas-phase chemical systems, featuring different types of chemical bonds. Furthermore, the applicability of the derived correlations to the description of complex reaction paths in periodic systems is demonstrated by considering the zeolite-catalyzed Diels–Alder cycloaddition reaction between 2,5-dimethylfuran and ethylene.