The electrical conductive, paramagnetic, and luminescent properties of boron coordination compounds based on boron difluoride curcuminoid (1-[4′-(dimethylamino)-phenyl]-4-phenyl-but-1-ene-2,4-dionate) (1) were investigated. The single-crystal X-ray diffraction study of compound 1 was performed. The electrical conductivity of complex 1 in the crystalline state (∼10−4 S cm−1) is similar to the values characteristic of electrically conductive polymers from a number of aromatic amines. The UV irradiation of the crystals of 1 induces the formation of metastable paramagnetic centers, which have a lifetime lasting for hours at low temperatures. The luminescence spectrum of the crystals of 1 at λex = 370 nm shows two bands in the blue and near-IR regions (470 and 800 nm, respectively). The discovered semiconductor, luminescent, and paramagnetic properties of the crystals of 1 may be useful in the development of smart materials for optoelectronics.

This paper presents a method for preparing magnetic nanocomposite with hierarchical structure based on Na2Ti3O7 and Fe2O3 (alpha-phase). The nanocomposite was synthesized using hydrothermal technology through combined treatment of TiO2 and various amounts of FeCl3 in a highly alkaline NaOH medium. In this method, Na2Ti3O7 nanotubes and alpha-Fe2O3 nanospheres self-assemble the compositing microparticles. The combining of nanotubular Na2Ti3O7 with nanospherical alpha-Fe2O3 enhances its visible-light sensitization. The band gap decreases across increasing content of the alpha-Fe2O3 phase, up to 2.85 eV (from 3.29 eV). The nanocomposite exhibits superparamagnetic properties. Both blocking temperature and coercive force rise with increasing alpha-Fe2O3 particles content. The obtained results enhance an understanding of how to combine different nanomaterials to design functional nanocomposites.

Na2Ti3O7 has attracted attention as an alternative to hard carbon anode for Na-ion batteries due to suitable sodiation potential and, hence, no serious safety issues at high current densities. However, unfavorable electronic transport properties of Na2Ti3O7 need to be addressed to make it applicable for practice. Herein, a hydrothermal method was adopted to fabricate Na2Ti3O7 having a hierarchical micro/nano architecture and to dope it with copper through one stage. As compared to the non-doped Na2Ti3O7, the copper-containing product shows increased electronic conductivity (2.5 times higher) due to a smaller band gap (reduced by similar to 1 eV). Because of Cu-doping, the Na2Ti3O7 crystal structure has evolved, and its unit cell volume has increased by about 9.5 %. Doping with Cu enhances the electrochemical performance of Na2Ti3O7 in Na-ion batteries, which demonstrates higher rate capability (2.0-2.5 times more capacity at high current densities) and remarkable cycleability (85 % capacity retention over 300 cycles at 2C). The calculations show that Cu-doped Na2Ti3O7 is characterized by improved Na+ ion diffusion and increased contribution of the pseudocapacitive current during the sodiation-desodiation process. The research discloses the aspects of copper-doping strategy that enable to unfold the capability of Na2Ti3O7 for energy storage applications.

Because of the unique crystal framework, bronze TiO2 (or TiO2(B)) is considered the prospective choice for high-performance lithium-ion battery anodes. Nevertheless, TiO2(B) requires efficient modification, e.g., suitable doping with other elements, to improve the electronic properties and enhance the stability upon insertion/extraction of guest ions. However, due to the metastability of TiO2(B), doping is challenging. Herein, for the first time, TiO2(B) co-doped with Mn, F, and N were synthesized through a successive method based on a hydrothermal technique. The prepared doped TiO2(B) consists of ultrathin nanotubes (outer diameter of 10 nm, wall thickness of 2–3 nm) and exhibits a highly porous structure (pore volume of up to 1 cm3 g−1) with a large specific surface area near 200 m2 g−1. The incorporation of Mn, F, and N into TiO2(B) expands its crystal lattice and modifies its electronic structure. The band gap of TiO2(B) narrows from 3.14 to 2.18 eV upon Mn- and N-doping and electronic conductivity improves more than 40 times. Doping with fluorine improves the thermal stability of TiO2(B) and prevents its temperature-induced transformation into anatase. It was found that the diffusivity of Li is about two times faster in doped TiO2(B). These properties make Mn, F, and N co-doped TiO2(B) nanotubes promising for application as high-performance anodes in advanced lithium-ion batteries. In particular, it possesses a good reversible capacity (231.5 mAh g−1 after 100 cycles at 70 mA g−1) and prominent rate capability (134 mAh g−1 at 1500 mA g−1) in the half-cell configuration. The (Mn, F, N)-doped TiO2(B) possesses a remarkable low-temperature Li storage performance, keeping 70% of capacity at −20 °C and demonstrating potentialities to be employed in full-cell configuration with LiMn2O4 cathode delivering a reversible capacity of 123 and 79 mAh g−1 at 35 and 1500 mA g−1, respectively, at a voltage of ~2.5 V. This research underlies that regulation of electronic and crystal structure is desired to uncover capabilities of nanoparticulate TiO2(B) for electrochemical energy storage and conversion.

The gray-colored oxygen-deficient TiO2–δ(B) nanobelts have been synthesized through a combination of the hydrothermal method followed by an ion exchange process and vacuum annealing. Electron paramagnetic resonance reveals an existence of F-centers in the form of electron-trapped oxygen vacancies within the anionic sublattice of the gray bronze TiO2 that induces its colouration. The diffuse reflectance spectroscopy showed that the formation of oxygen vacancies into TiO2(B) significantly increases its absorption intensity in both visible and near infrared ranges. The band gap of TiO2(B) with anionic defects is equal to 3.03 eV (against 3.24 eV for white TiO2(B) treated in air). Room temperature ferromagnetism associated with the defects was detected in gray TiO2–δ(B), thus indicating it belongs it to the class of dilute magnetic oxide semiconductors. It was found that in the low-temperature range (4 K), the magnetic properties of vacuum annealed TiO2(B) do not differ from those for TiO2(B) treated in air. We hope that the findings are defined here make a contribution to further progress in fabrication and manufacturing of defective TiO2-based nanomaterials for catalysis, magnetic applications, batteries, etc.

Manganites doped with potassium ions La1 – xKxMnO3, where х = 0.0, 0.1, and 0.15, have been obtained by extraction-pyrolytic method at low temperature. The compounds have been studied by X-ray powder diffraction, electronic paramagnetic and ferromagnetic resonances. Unit cell parameters of La1 – xKxMnO3 samples have been calculated. According to magnetic resonance spectroscopy, La1 – xKxMnO3 exhibits phase delamination into paramagnetic and ferromagnetic phases. The fraction of the latter phase increases when temperature decreases. The temperature of transition from paramagnetic into ferromagnetic phase (Curie temperature, TC) for La1 – xKxMnO3 is –17.4, –13.7, and –4.8°С at х = 0.0, 0.1, and 0.15, respectively. The reason of symbate change in TC and potassium ion concentration in La1 – xKxMnO3 is supposed to be the change in the content of ferromagnetic pairs Mn3+–О2––Mn4+ in the manganites.

Sodium trititanate doped with nickel in different amounts for the first time have been prepared through one-step hydrothermal synthesis. Both cation substitution and interstitial doping are realized with a formation of oxygen -deficient Na2+xTi3-yNix+yO7-delta solid solutions. The Ni-doping results in the sodium trititanate unit cell expansion. The morphology was found to be evolved with increasing dopant concentration from nanotubes to nanosheets. The specific surface area ranges from 121 to 78 m2 g-1 depending on dopant content. With nickel-doping, the bandgap narrowed from 3.45 up to 2.94eV. The conductivity of sodium trititanate increases in 3-6 fold after the nickel incorporation. A deviation from the Arrhenius temperature dependence of the conductivity is observed above 350 K indicating that mixed ionic-electronic conductors based on Ni-doped sodium trititanate are formed. This paper contributes to the advance understanding doping principles and effects for Na2Ti3O7-based materials, which are currently under consideration.

Manganese-doped anatase with a nanosized morphology (as spherically shaped nanoparticles) has been synthesized under hydrothermal conditions. It has been shown that manganese is incorporated into the titanium dioxide structure to form substitutional solid solutions. At high dopant concentrations, part of the introduced manganese goes to the formation of α-MnO 2 . A significant increase in the optical activity in the visible range and a decrease in the bandgap width down to ~2.4 eV are observed for manganese-doped anatase because of the appearance of extrinsic (multivalent Mn ions) and intrinsic compensating (oxygen vacancies) defects. It has been found that manganese-doped samples are diluted magnetic semiconductors, and the magnetic characteristics increase with increasing manganese content. All manganese-containing samples demonstrate photocatalytic activity in the degradation reaction of indigo carmine when irradiated with visible light. The degree of dye degradation depends on the content of manganese in the samples and reaches >90%.

Materials based on nickel- and zinc-doped TiO2(B), consisting of mesoporous nanorods, are produced via hydrothermal synthesis. Complementary methods are used to study the mechanism of doping and the physicochemical properties of the synthesized samples. According to the results of testing of materials in the cells of lithium- and sodium-ion batteries, it is found that the doping of TiO2(B) with nickel and zinc has a favorable effect.

Nickel- and zinc-doped TiO2(B) nanobelts were synthesized using a hydrothermal technique. It was found that the incorporation of 5 at.% Ni into bronze TiO2 expanded the unit cell by 4%. Furthermore, Ni dopant induced the 3d energy levels within TiO2(B) band structure and oxygen defects, narrowing the band gap from 3.28 eV (undoped) to 2.70 eV. Oppositely, Zn entered restrictedly into TiO2(B), but nonetheless, improves its electronic properties (Eg is narrowed to 3.21 eV). The conductivity of nickel- (2.24 × 10−8 S·cm−1) and zinc-containing (3.29 × 10−9 S·cm−1) TiO2(B) exceeds that of unmodified TiO2(B) (1.05 × 10−10 S·cm−1). When tested for electrochemical storage, nickel-doped mesoporous TiO2(B) nanobelts exhibited improved electrochemical performance. For lithium batteries, a reversible capacity of 173 mAh·g−1 was reached after 100 cycles at the current load of 50 mA·g−1, whereas, for unmodified and Zn-doped samples, around 140 and 151 mAh·g−1 was obtained. Moreover, Ni doping enhanced the rate capability of TiO2(B) nanobelts (104 mAh·g−1 at a current density of 1.8 A·g−1). In terms of sodium storage, nickel-doped TiO2(B) nanobelts exhibited improved cycling with a stabilized reversible capacity of 97 mAh·g−1 over 50 cycles at the current load of 35 mA·g−1.

Here we discuss how the position of carboxyalkyl substitute and the type of the cross-linking agent affect properties of chitosan-based metal-affine sorbents. Using fluoroquinolone (ciprofloxacin) as a model compound we have shown that metal-chelates of N- and N,O-carboxyalkyl chitosan derivatives cross-linked with hexamethylene diisocyanate and epichlorohydrin differ in sorption properties. Despite high (> 90%) efficacy of ciprofloxacin recovery by Cu(II)- and Al(III)-chelates of N- and N,O-carboxyalkylchitosans from water, the latter were much sensitive to the increase of ionic strength and the presence of Ca2+ ions. The difference in the structure of Cu(II) complexes depending on the type of carboxyalkyl substitution was revealed by electron spin resonance (ESR) spectroscopy. Analysis of the metal ions release during ciprofloxacin sorption have shown that Cu(II)- and Al(III)-chelates of N,O-carboxyalkylchitosan were less stable and less efficient as metal-affine sorbents for ciprofloxacin than N-regioselectively substituted carboxyethylchitosan, which showed properties comparable to those of Cu(II)-chelates of commercial imido-diacetic acid (IDA)-agarose.

Hydrolytic lignin (HL) has been used in manufacturing of graphitized carbon via HL one-step physical activation. It was found that the layered carbon products of pyrolysis of hydrolytic lignin (AHL) at different temperatures may be used as cathode materials in primary current sources. The galvanostatic discharge of lithium battery at a current density of 100 μA/cm2 between 3.0 and 0.5 V shows that the specific capacity of thermally activated derivative is equal to 845 mA·h/g, while the untreated lignin yields only 190 mA·h/g. The fluorination of both the lignin and its thermally activated form results in higher operating voltage of lithium battery, as seems, due to the involvement of fluorine bound to carbon in electrochemical process. Some fluorinated AHL samples show the promise of their use as supercapacitor electrodes.

Spatially extended structures of nanosized π-conjugated regions and fragments of the carbon framework, including their two-dimensional electrically connected percolation networks, were found out and studied in films of graphene oxide (GO) and its thermally reduced derivatives (TRGO) by a set of complementary physical methods,. In films with a nanostructured carbon framework, an unusually high density of charge-carrier states near the Fermi level was discovered using magnetic investigation methods, signifying the existence of specific π-electronic states (topological zero modes), which can be stabilized in the zigzag parts of carbon network cracks (at zigzag edges of nanographenes). A conclusion is made about a potential suitability of these graphene oxide derivatives for the formation of percolation networks of nanographenes with predominantly zigzag edges in them.

В работе представлен метод моделирования рентгеновских дифрактограмм пленок термически восстановленных наноструктурированных производных оксида графена с помощью линейной комбинации теоретических профилей порошков квазидвумерно-разориентированных несколькослойных турбостратных нанографенов (нанографитов). Метод позволяет определять относительное содержание нанографитов с различными средними размерами и числом слоев, а также функцию плотности вероятности, характеризующую долю частиц в порошке повернутых на заданный полярный угол. Предложенная процедура моделирования пригодна также для аппроксимации экспериментальных рентгенограмм любых материалов, содержащих протяженные квазидвумерно-разориентированные структуры турбостратных нанографитов. The paper outlines the procedure of modeling X-ray diffractogram of films for thermally reduced nanostructured graphene oxide derivatives using a linear combination of the theoretical profiles for powders of quasi-two-dimensional misoriented few-layer turbostratic nanographenes (nanographites). The method allows us to determine the relative content of nanographites with various average sizes and number of layers, as well as a probability density function characterizing the fraction of particles in the powder, which is rotated by a certain polar angle. The proposed modeling procedure is also suitable for the approximation of experimental X-ray diffractograms of any materials containing extended quasi-two-dimensional misoriented structures of turbostratic nanographites.

The hydrolytic lignin (HL) derivatives have been prepared via its physical activation (high-temperature annealing in vacuum) followed by chemical modification (fluorination). It was found that the graphitized product of thermal activation up to 1000 °C at a low temperature gain rate of < 2 °C/min under high vacuum shows an enhanced specific surface area (215 m2/g), that makes it potentially useful as sorbent, catalytic substrate, or electrode material. It was revealed from the experimental data the manufactured graphitized material consists of nanometric structural blocks, possibly nanographites and/or few-layer nanographenes. The edges of graphenes in agglomerates in activated hydrolytic lignin (AHL) have armchair and zigzag shapes. The nontrivial electronic structure of the zigzag edges, along with the electronic conductivity and the ability of AHL to absorb oxygen, can cause an increase in the energy intensity of lithium battery (LB) manufactured using AHL.The carbon-fluorine bond of semi-ionic type was detected in HL and AHL fluorinated in the temperature range of synthesize 60 – 300 oC. The fluorinated forms of both HL and its thermally activated product show increased values of operating voltage due to the participation of fluorine bound to carbon in the electrochemical process.

Physics and chemistry of atomically smooth graphene edges. A.M. ZIATDINOV (Institute of Chemistry, FEBRAS, Vladivostok). E-mail: ziatdinov@ich.dvo.ru Real graphene has a finite lateral dimensions, therefore its properties depend on the shape and the chemical stateof the edges. Near zigzag edges of graphene the specific π-electronic band stabilizes with the sharp maximum of the density of states on the Fermi level coinciding in energy with the Dirac point (so-called topological zero mode). Theelectrons of mentioned band possess special quantum-mechanical properties being potentially capable of initiatingnon-trivial physical phenomena (magnetic ordering, superconductivity, high-temperature fractional quantizedconductivity, spin-dependent transport, etc.). Such a band does not exist on armchair edges of graphene; however,graphene nanoribbons with armchair edges are semiconductors whose energy gap varies inversely with their width. The chemical functionalization of graphene edges can radically change its properties. In particular, with a certain chemical modification of the armchair edges of graphene, an edge π-electron band with non-trivial quantum properties can also be stabilized near them. This article provides a brief overview of our own and literature data on the physics and chemistry of graphene edges, including methods of giving them atomically smooth forms and chemical functionalization, as well as methods for characterizing the edges. It is concluded that graphene derivatives with atomically smooth and chemically functionalized edges are promising materials for new technique and technologies.

This paper outlines the procedure for determining the sizes, structural parameters and percentage content of various particle types in nanographite powders by full-profile approximation of the X-ray diffractogram of sample with using a set of X-ray diffraction profiles for powders of model nanographites. It was shown that taking into account the model nanographites with the radial dependence of interatomic distances within the layer and the dependence of interlayer distances on average number of atoms in the layer allows to describe the X-ray diffraction profile of nanographite powder in the wide angular range including so-called γ-band in small angles without assumptions on presence of other structures in it.

Percolation networks of electrically connected nanographenes are the promising structures for solving the problem of the transfer of their peculiar quantum properties to the macroscopic level. In this work we report the results of investigations, conducted with using a set of complementary physical methods, on the origin, structural motifs and properties of such networks revealed in thermally reduced graphene oxide films. The presence of zero modes, which may be π-electronic states stabilized at the zigzag edges of network elements, has been established.