The effect of CF4 plasma treatment on the structure and THz absorption of vertically aligned carbon nanotube (vCNT) arrays is studied in the present contribution as a function of their height (40 divided by 100 mu m) and processing time (2 divided by 70 min) using X-ray photoelectron and Raman spectroscopy (XPS), scanning electron microscopy and sheet resistance (Rs) measurements. XPS shows that a semi-ionic fluorine (C-Fsi) grafting decreases from 4 % to 2 % when the fluorination time increases from 2 to 10 min and is completely replaced by a covalent C-C4F bonding (15 %) after 70 min. Unlike fluorine, the oxygen amount increases from 2 % (pristine CNTs) to 10 % after a 2 min processing and further rises to 16 %. The effect of CF4 plasma treatment on the THz absorption is observed most clearly for a 40 mu m high vCNT array. In this case, 4 % of C-Fsi causes a 17 % decrease in Rs, which leads to the THz absorption rise by 6 % and 40 % in short- and long-wavelength spectrum ranges, respectively. On the contrary, 15 % of C-C4F provides a 2.5-times increase in Rs, which decreases the THz absorption by over 50 % and 6 % in short- and long-wavelength regions, respectively. The role of oxygen in the suppression of C-Fsi grafting is discussed.

A mononuclear complex [Zn(phbz) 2 (phen)] ( 1 , Hphbz = 4-biphenylcarboxylic acid, phen is 1,10-phenanthroline) is obtained, and its structure is determined by single crystal X-ray diffraction (XRD). It is additionally characterized by powder XRD, IR and NMR spectroscopy. The theoretic simulation (DFT B3LYP/Def2-TZVP) of the dimerization process of the complex shows that one of the reasons for the lack of experimental detection of dimeric structures of this type may be a low stabilization energy of the hypothetical binuclear compound [Zn 2 (phbz) 4 (phen) 2 ].

The spin state of the cobalt(II) phenylborate hexa-n-butylsulfide clathrochelate in solutions is studied by paramagnetic NMR spectroscopy. This cage complex is shown to undergo the temperature-induced spin transition in solvents of different nature (acetonitrile, chloroform, dichloromethane, and benzene). The previously developed method for an analysis of paramagnetic shifts in NMR spectra allows the determination of the thermodynamic parameters (enthalpy and entropy) of the spin equilibrium in the solutions. In spite of the conformational rigidity of the macrobicyclic tris(dioximate) molecules, substantial changes in the electronic structures and spin equilibrium parameters are observed depending on the polarity of the solvent used. This provides opportunities for fine tuning of spin switch characteristics by changing this parameter of the medium.

A spin state of the phenylbon-capped hexa-n-butylsulfide cobalt(II) clathrochelate in solutions was studied by paramagnetic NMR spectroscopy. This cage complex is found to undergo the temperature – induced spin crossover in solvents of different nature (acetonitrile, chloroform, dichloromethane, and benzene). The previously developed method for an analysis of paramagnetic shifts in NMR spectra allows to calculate of the thermodynamic parameters (enthalpy and entropy) of a given spin equilibrium in the solutions. In spite of the conformational rigidity of the macrobicyclic tris-α-dioximate molecules, the substantial changes in their electronic structures and spin crossover parameters were observed, being affected by a polarity of the solvent used. This provides an opportunity for the fine tuning of spin switch characteristics by changing this medium parameter.

The influence of the application of silicon oxide produced from a gas precursor, i.e., monosilane SiH 4 and an organosilicon precursor, i.e., tetraethoxysilane (TEOS) on the optical characteristics of dielectric Bragg mirrors is compared. The use of tetraethoxysilane as a precursor in plasma-enhanced chemical vapor deposition (PECVD) demonstrates a decrease in the average roughness of the deposited film. The same method of film deposition also makes it possible to fabricate a SiN x /SiO x pair in one process chamber without breaking vacuum. It is experimentally shown that a mirror fabricated from a TEOS precursor possesses better characteristics than a mirror fabricated using monosilane, thus, the reflectivity increases by 20% and optical losses decrease twofold. The roughness average R a of the surface of a SiN x /SiO x (TEOS) mirror decreases fivefold when compared to a SiN x /SiO x (SiH 4 ) mirror. The application of a TEOS precursor substantially increases the quality of the interfaces of the deposited layers which leads to a gain in the reflectivity of the Bragg mirror and a decrease in the roughness average R a from 11.04 down to 2.31 nm. As a consequence, improvement of the SiN x /SiO x interfaces leads to a twofold reduction in the losses. These results can be considered as a significant advantage that leads to a drop in the costs of materials during the fabrication of multilayer mirrors.

In this study, we investigate the structural changes, electronic properties, and charge redistribution within azo-bithiophene (Azo-BT)-chemisorbed monolayers under different light stimuli using the density functional theory and molecular dynamics simulations. We consider two types of switches, Azo-BT and BT-Azo, with different arrangements of the Azo and BT blocks counting from the anchor thiol group. The chemisorbed monolayers of pure cis- and trans-isomers with a surface concentration of approximately 2.7 molecules per nm2 are modeled on a gold surface using the classical all-atom molecular dynamics. Our results reveal a significant shrinkage of the BT-Azo layer under UV illumination, whereas the thicknesses of the Azo-BT layer remain comparable for both isomers. This difference in behavior is attributed to the ordering of the trans-molecules in the layers, which is more pronounced for Azo-BT, leading to a narrow distribution of the inclination angle to the gold surface. Conversely, both layers consisting of cis-switches exhibit disorder, resulting in similar brush heights. To study charge transfer within the immobilized layers, we analyze each snapshot of the layer and calculate the mean charge transfer integrals using Nelsen’s algorithm for a number of interacting neighboring molecules. Combining these integrals with reorganization energies defined for the isolated molecules, we evaluate the charge transfer rates and mobilities for electron and hole hopping within the layers at room temperature based on Marcus’ theory. This research offers new perspectives for the innovative design of electrode surface modifications and provides insights into controlling charge transfer within immobilized layers using light triggers. Additionally, we identify molecular properties that are enhanced via specific molecular design, which contributes to the development of more efficient molecular switches for various electronic applications.

The possibility of the complex formation of three bispidines with copper( ii ) chloride and acetate in a deuterated DMF solution was studied by NMR titration. For all ligands, the formation of complexes with copper( ii ) chloride was clearly detected based on the changes in the signals in the proton NMR spectra. The formation of complexes with copper( ii ) acetate was not observed for any of the ligands. The results of the study can be used in the design of metal complex catalysts for the Henry reaction.

This article compares TiN layers produced by electron beam evaporation (EBE) and atomic layer deposition (ALD) for the effect of barrier layer deposition technology on the formation of carbon nanotube (CNT) growth catalyst nanoparticles. The layers obtained by EBE have a roughness 1.5 times higher than the layers deposited by the ALD method (Ra=1 nm and Ra=0.6 nm). Nanoparticles formed on the surface of the EBE layer are characterized by a large average size (about 30 nm) and a 1.3 times greater dispersion of the distribution compared to nanoparticles formed on the ALD layer. TiN layers obtained by EBE are characterized by better surface wettability in comparison with ALD layers. The contact angle for catalyst nanoparticles on the surface of the EBE layer of TiN is about 30 degrees and approaches 90 degrees for ALD layers. Catalyst spreading is due to the Wenzel model. It is shown that the higher surface roughness of the EBE samples is associated with the crystallization of TiN, since the layer formation process proceeds at a higher temperature compared to the ALD process. For this reason, the use of barrier layers obtained by the ALD method is preferable for the formation of CNT growth catalyst nanoparticles on their surface. Keywords: electron beam evaporation, atomic layer deposition, roughness, wetting, catalyst nanoparticles.

This article compares TiN layers produced by electron beam evaporation (EBE) and atomic layer deposition (ALD) for the effect of barrier layer deposition technology on the formation of carbon nanotube (CNT) growth catalyst nanoparticles. The layers obtained by EBE have a roughness 1.5 times higher than the layers deposited by the ALD method (Ra = 1 nm and Ra = 0.6 nm). Nanoparticles formed on the surface of the EBE layer are characterized by a large average size (about 30 nm) and a 1.3 times greater dispersion of the distribution compared to nanoparticles formed on the ALD layer. TiN layers obtained by EBE are characterized by better surface wettability in comparison with ALD layers. The contact angle for catalyst nanoparticles on the surface of the EBE layer of TiN is about 30 degrees and approaches 90 degrees for ALD layers. Catalyst spreading is due to the Wenzel model. It is shown that the higher surface roughness of the EBE samples is associated with the crystallization of TiN, since the layer formation process proceeds at a higher temperature compared to the ALD process. For this reason, the use of barrier layers obtained by the ALD method is preferable for the formation of CNT growth catalyst nanoparticles on their surface.

Структура и морфология массивов вертикально ориентированных УНТ (ВОУНТ), выращенных методом CVD на подложках Fe—Al2O3/Si(001), исследованы с помощью сканирующей и высокоразрешающей просвечивающей электронной микроскопии (ВРЭМ) и комбинационного рассеяния света (КРС). Найдено, что для воспроизводимого роста сплошных массивов ВОУНТ толщина напыленного слоя Fe должна составлять не менее 2 нм, при этом размер частиц катализатора, сформированного отжигом при 700 °C, варьируется в диапазоне 2—10 нм, а массив состоит преимущественно из одно- и двустенных УНТ диаметром 1—6 нм. Спектр КРС характеризуется наличием радиальной дышащей моды в интервале 95—232 см–1 и интенсивной G моды с расщеплением на пики 1594 см–1 и 1568 см–1 при возбуждении лазером с длиной волны λ = 785 нм. Обе моды и наличие дышащих мод в спектре КРС, согласно опубликованным данным, указывают на доминирующий полупроводниковый характер трубок в массиве. Измерение поверхностного сопротивления массива ВОУНТ дает значение 320±20 Ом/□.

The formation of nanosized catalyst particles for the growth of carbon nanotubes can be carried out during the crystallization of amorphous films consisting of two metals, one of which has higher free energy of the oxide. During annealing in the presence of oxygen, this metal is oxidized with the reduction of the second metal, which leads to the formation of nanoparticles embedded in the oxide of the first metal. This the process has been experimentally and theoretically studied by the example of the formation of cobalt nanoparticles on the surface of amorphous Co-Zr-O films as a result of the decomposition of a supersaturated solid solution and mechanical stresses arising during the oxidation of zirconium. We have proposed a mechanism for the formation of catalyst nanoparticles and phenomenological model of this process developed on the basis of the phase-field theory.

Azomethine HL was synthesized by the reaction of o-aminophenol with 2-acetylbenzimidazole and used to prepare the cobalt(III) complex [CoL2]2(ClO4)2⋅3H2O (I). The structure of complex I was established by NMR spectroscopy in solution and by single crystal X-ray diffraction (CIF file CCDC no. 2051279). The cobalt ion in the +3 oxidation state has an octahedral environment. The crystals are monoclinic, space group C2/c, a = 12.405(7), b = 13.946(11), c = 18.907(13) Å, α = 109.87(3)°, β = 94.534(12)°, γ = 104.564(19)°, V = 2928(3) Å3, ρ(calcd.) = 1.521 g/cm 3, Z = 2. The complex is diamagnetic. Study of the electrochemical behavior of I in acetonitrile showed that it can be reduced to neutral and radical anion forms.

The structure and morphology of vertically aligned CNT (VACNT) arrays grown by CVD on Fe–Al2O3/Si(001) substrates are studied using scanning and high-resolution transmission electron microscopy (HRTEM) methods and Raman scattering. It is established that reproducible growth of continuous VACNT arrays is achieved only if the deposited Fe layer is at least 2 nm thick, while the particle size of the catalyst formed by annealing at 700 °C varies in a range of 2-10 nm and the array consists mainly of single- and double-walled CNTs with a diameter of 1-6 nm. The Raman spectrum is characterized by the presence of a radial breathing mode in the region 95-232 cm–1 and an intense G mode that is split into peaks at 1594 cm–1 and 1568 cm–1 upon laser excitation at the wavelength λ = 785 nm. According to the literature data, both modes indicate predominantly semiconductor nature of tubes in the array. The measured surface resistance of the VACNT array is 320±20 Ω/□.

The formation of nanosized catalyst particles for the growth of carbon nanotubes can be carried out during the crystallization of amorphous films consisting of two metals, one of which has higher free energy of the oxide. During annealing in the presence of oxygen, this metal is oxidized with the reduction of the second metal, which leads to the formation of nanoparticles embedded in the oxide of the first metal. This the process has been experimentally and theoretically studied by the example of the formation of cobalt nanoparticles on the surface of amorphous Co-Zr-O films as a result of the decomposition of a supersaturated solid solution and mechanical stresses arising during the oxidation of zirconium. We have proposed a mechanism for the formation of catalyst nanoparticles and phenomenological model of this process developed on the basis of the phase-field theory. Keywords: carbon nanotubes, nanoparticles of catalyst, phase transitions, decomposition of supersaturated solid solutions.

Complexes [Сu2L4(MeOH)2] (I) and [СoL2] (II) are synthesized by the reactions of copper(II) and cobalt(II) acetates with 3-[5-p-tolyl)-1,3,4-oxadiazol-2-yl]acrylic acid (HL). The crystal structure of complex I is determined by X-ray diffraction (XRD) (CIF file CCDC no. 2052347). The crystals are monoclinic, space group C2/c, a = 26.056(4), b = 19.677(3), c = 13.998(2) Å, β = 91.571(3)°, V = 7175(2) Å3, ρcalc = 1.026 g/cm3, Z = 4. In a molecule of complex I, the pair of centrosymmetric copper atoms is bound by four bridging carboxyl groups. The intramolecular Cu…Cu distance is 2.654(2) Å. The coordination polyhedron CuO5 is a distorted square pyramid. The magnetic interactions between the copper(II) ions in complex I are shown to be antiferromagnetic (2J = –185 cm–1). In the case of complex II, the application of an external magnetic field decreases the magnetic relaxation rate. The Raman mechanism and direct mechanism are the most probable route for magnetization relaxation. Unlike the copper(II) complex, complex II is probably mononuclear in both the solution and solid phase.

Thermal oxidation of polyethylene was carried out in oxygen-enriched sc CO2 and in pure oxygen under a pressure of 215 and 14 bar, respectively. Oxygen to polymer weight ratio was varied. At lower oxygen content, the products were brown to dark brown pastes; at higher oxygen content, the products were dark yellow to dark-brown liquids. For the oligomeric fraction of the products, the data on molecular weights obtained by means of diffusion-ordered NMR and gel permeating chromatography was compared. Thermogravimetric analysis demonstrated that oxygen content strongly affects the yield of volatile products. The volatile products were further analyzed by means of H-1, C-13 NMR, gas chromatography-mass spectrometry and potentiometric titration. All the results obtained suggest that sc CO2 influence is more pronounced at lower oxygen to polymer mass ratio, which may be useful for carrying out chemical recycling of polyethylene through thermal oxidation while minimizing the amount of oxygen required.

Tris-pyridineoximate iron, cobalt, and nickel(II) pseudoclathrochelates with apical ferrocenyl substituent were obtained in the reasonable yields (50–70%) in a boiling ethanol by the template condensation of 2-acetylpyridineoxime with ferrocenylboronic acid on the corresponding M 2+ ion as a matrix. The composition and structure of new ditopic compounds, isolated in the forms of their ionic associates with perchlorate anion, were determined using elemental analysis, UV-vis spectroscopy, MALDI-TOF mass spectrometry, and NMR spectroscopy. According to the magnetometry data, the iron(II) pseudoclathrochelate is a diamagnetic compound, while the temperature dependences of magnetic susceptibility of the nickel and cobalt(II) complexes are characteristic of the high-spin systems with S = 1 and 3/2, respectively. As follows from the X-ray diffraction data for the iron and nickel(II) pseudoclathrochelates, the Ni–N distances (2.15–2.17 Å) are characteristic of the high-spin Ni 2+ complexes, while they in its iron(II)-containing analog, slightly exceed of 2 Å, thus suggesting the low-spin state of this ion.

In this study, we investigated the influence of silicon oxide roughness produced from the gas precursor monosilane (SiH$_4$) and the silicon-organic precursor tetraethoxysilane (TEOS) on the optical qualities of a distributed Bragg reflector (DBR). A significant influence of the precursors from which SiOx is deposited on the optical qualities of DBR mirrors is demonstrated in this study. It has been shown experimentally that a mirror produced from the TEOS precursor is endowed with better qualities than a mirror produced using SiH4, that is, the reflectivity increased by 20% and optical losses decreased by half. The roughness average (Ra) of the SiN$_x$/SiO$_x$ / (TEOS) mirror surface decreased by a factor of five compared to that of the SiN$_x$/SiO$_x$ / (SiH4) mirror

Focused laser beams allow controlling mechanical motion of objects and can serve as a tool for assembling complex micro and nano structures in space. While in a vast majority of cases small particles experience attractive gradient forces and repulsive radiation pressure, introduction of additional degrees of freedom into optomechanical manipulation suggests approaching new capabilities. Here we analyze optical forces acting on a high refractive index silicon sphere in a focused Gaussian beam and reveal new regimes of particles anti-trapping. Multipolar analysis allows separating an optical force into interception and recoil components, which have a completely different physical nature resulting in different mechanical actions. In particular, interplaying interception radial forces and multipolar resonances within a particle can lead to either trapping or anti-trapping scenarios, depending of the overall system parameters. At the same time, the recoil force generates a significant azimuthal component along with an angular-dependent radial force. Those contribution enable enhancing either trapping or anti-trapping regimes and also introduce bending reactions. These effects are linked to the far-field multipole interference resulting and, specifically, to its asymmetric scattering diagrams. The later approach is extremely useful, as it allows assessing the nature of optomechanical motion by observing far-field patterns. Multipolar engineering of optical forces, being quite general approach, is not necessarily linked to simple spherical shapes and paves a way to new possibilities in microfluidic applications, including sorting and micro assembly of nontrivial volumetric geometries.

We uncover a novel mechanism for superscattering of subwavelength resonators closely associated with the physics of bound states in the continuum. We demonstrate that superscattering occurs as a consequence of constructive interference driven by the Friedrich-Wintgen mechanism, and it may exceed the currently established limits for the cross-section of a single open scattering channel, within the channel itself. We develop a non-Hermitian model to describe interfering resonances of quasi-normal modes to show that this effect can only occur for scatterers violating the spherical symmetry, and therefore it cannot be predicted with the classical Mie solutions. Our results reveal unusual physics of non-Hermitian systems having important implications for functional metadevices.