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Some layered phyllosilicates are characterized by spontaneous scrolling due to size mismatch between sublayers. The doping of layers by transition metal ions allows nanoscrolls to acquire magnetic properties. The magnetic behavior of synthetic (Mg1 –xCox)3Si2O5(OH)4 (x = 0.2, 0.4, 0.6, 0.8, 1) phyllosilicates with the chrysotile structure before and after partial hydrogen-induced reduction is studied. The dominant ferromagnetic behavior has been revealed in all studied phyllosilicates. Ensembles of cobalt metal nanoparticles in a silicate matrix have demonstrated a collective magnetic response at room temperature with a narrow hysteresis loop and fast saturation. [ABSTRACT FROM AUTHOR]

The subject of this study was Si-C composites for lithium-ion battery (LIB) anodes obtained by carbonization of nanodispersed silicon with carbon monofluoride. To determine the possibility of increasing the degree of graphitization of nanodispersed carbon forming shells around the silicon particles at lower temperatures, nickel in the form of an alcoholic solution of Ni(NO3)2 was introduced as a catalyst into the pellets of the resulting composite. The XRD, Raman scattering and EDS methods were used to investigate changes both in the phase and elemental composition of materials resulting from the annealing of the Ni-containing Si-C composite over the temperature range of 500–1100 °C. It was found for the first time that nickel silicides that emerged during the annealing became catalysts and, at the same time, intermediate products, of cubic silicon carbide (β-SiC) synthesis, which reduced its temperature formation from ~1100 °C to ~800 °C. The same compounds had a catalytic effect on the carbon atom association, leading to an increase in the degree of its graphitization. The influence of changing the composition of the investigated material on the electrochemical characteristics of the obtained negative LIB electrodes was traced.

Abstract Owing to the synergistic combination of a hybrid organic–inorganic nature and a chemically active porous structure, metal–organic frameworks have emerged as a new class of crystalline materials. The current trend in the chemical industry is to utilize such crystals as flexible hosting elements for applications as diverse as gas and energy storage, filtration, catalysis, and sensing. From the physical point of view, metal–organic frameworks are considered molecular crystals with hierarchical structures providing the structure‐related physical properties crucial for future applications of energy transfer, data processing and storage, high‐energy physics, and light manipulation. Here, the perspectives of metal–organic frameworks as a new family of functional materials in modern physics are discussed: from porous metals and superconductors, topological insulators, and classical and quantum memory elements, to optical superstructures, materials for particle physics, and even molecular scale mechanical metamaterials. Based on complementary properties of crystallinity, softness, organic–inorganic nature, and complex hierarchy, a description of how such artificial materials have extended their impact on applied physics to become the mainstream in material science is offered.

This article describes the possibilities of using anodic titania, zirconia, alumina and tin oxide as a basis for sensors. The mechanism of operation of anodic oxide based resistance and optical sensors is described. Possible mechanisms for the synthesis of anodic oxides are discussed, as well as the influence of synthesis parameters on the morphology of the synthesized oxide layer. A possible design of anodic oxide based sensors is shown along with their detection parameters. [ABSTRACT FROM AUTHOR]

The past two decades have been marked by an increased interest in the synthesis and the properties of geoinspired hydrosilicate nanoscrolls and nanotubes. The present review considers three main representatives of this group: halloysite, imogolite and chrysotile. These hydrosilicates have the ability of spontaneous curling (scrolling) due to a number of crystal structure features, including the size and chemical composition differences between the sheets, (or the void in the gibbsite sheet and SiO2 tetrahedron, in the case of imogolite). Mineral nanoscrolls and nanotubes consist of the most abundant elements, like magnesium, aluminium and silicon, accompanied by uncontrollable amounts of impurities (other elements and phases), which hinder their high technology applications. The development of a synthetic approach makes it possible to not only to overcome the purity issues, but also to enhance the chemical composition of the nanotubular particles by controllable cation doping. The first part of the review covers some principles of the cation doping approach and proposes joint criteria for the semiquantitative prediction of morphological changes that occur. The second part focuses on some doping-related properties and applications, such as morphological control, uptake and release, magnetic and mechanical properties, and catalysis.

Non‐centrosymmetric metal–organic frameworks (MOFs) have recently emerged as a promising class of coordination polymers for nonlinear optics and light conversion. Nevertheless, achieving high endurance and efficiency for the light conversion within the whole visible range by a single crystal of MOF remains a challenge. This article reports on the design of two non‐centrosymmetric MOFs based on a 1,3,5‐benzenetricarboxylic acid ligand and Er/Co ions, providing an efficient and simultaneous multiple second and third optical harmonic generations (SHG, THG) from 400 to 750 nm with a high endurance (over 100 cycles or 3 h of continuous operation). Optical experiments and quantum chemical modeling of the MOF single crystals confirm the polarization and chemistry‐dependent efficiency of SHG and THG, associated with the varied MOFs' symmetry and dipole moment. The observed coherent light conversion within the whole visible range by MOF single crystals at ambient conditions makes it possible to achieve the multicolor (up to three) coherent emission required for modern laser technologies, making MOFs highly competitive and sustainable materials for nonlinear optics. [ABSTRACT FROM AUTHOR]

Nickel-zinc ferrites, which have pronounced ferrimagnetic and semiconductor properties, can be used as promising magnetically controlled photocatalysts for the purification of aqueous media from organic pollutants. The value of the specific surface area largely affects the photocatalytic properties of the material; therefore, the possibility of its control and variation at the stage of synthesis is of great scientific and technical interest. In this study, nanocrystalline ferrite of the Zn0.5Ni0.5Fe2O4 composition is obtained under conditions of solution combustion using various types of organic fuel as the main factor affecting the formation of the specific surface area, and subsequent heat treatment in air at a temperature of 500°C for 2 h. The crystal structure, chemical composition, and morphology of Zn0.5Ni0.5Fe2O4 are studied by methods of X‑ray phase analysis, X-ray spectral microanalysis, and scanning electron microscopy. The values of the specific surface area of the synthesized nanopowders are calculated based on the method of liquid-phase adsorption from a Methylene Blue solution and the low-temperature adsorption-desorption of nitrogen. The results of the X‑ray phase analysis show that a single-phase nanocrystalline product with a spinel structure is formed, where the average crystallite size varies within 11–23 nm and is inversely related to the value of the specific surface area, respectively, after the reaction with succinic acid (39.1 m2/g) and with glycine (20.2 m2/g). It is established that the choice of the fuel largely affects the formation of nanocrystals and the specific surface area of the samples, and the approach used makes it possible to control its values. [ABSTRACT FROM AUTHOR]

A study of the electrochemical characteristics of titanium oxyfluoride obtained with the direct interaction of titanium with hydrofluoric acid is reported. Two materials T1 and T2 synthesized under different conditions in which some TiF3 is formed in T1 are compared. Both materials exhibit conversion-type anode properties. Based on the analysis of the charge–discharge curves of the half-cell, a model is proposed according to which the first electrochemical introduction of lithium occurs in two stages: the first stage is the irreversible reaction resulting in a reduction in Ti4+/3+, and the second stage is the reversible reaction with a change in the charge state Ti3+/1.5+. The difference in material behavior is quantitative: T1 has a higher reversible capacity but lower cycling stability and a slightly higher operating voltage. The Li diffusion coefficient determined from the CVA data for both materials averages 1.2–3.0 × 10−14 cm2/s. A distinctive feature of titanium oxyfluoride anodes is the asymmetry in kinetic characteristics that revealed themselves during lithium embedding and extraction. In the long cycling regime, the excess of Coulomb efficiency over 100% was found in the present study. [ABSTRACT FROM AUTHOR]

In hydrosilicates with the structure of chrysotile, pecoraite, and halloysite, elastic strains in the composite hydrosilicate layer are compensated by folding into nanoscrolls. A wide range of such particles with different compositions can be produced by hydrothermal synthesis, which, together with the structural and morphological characteristics, makes them promising adsorbents, capsules, catalysts, and reinforcing components of composite materials. For such potential applications as magnetically controlled adsorbents and catalysts, ferromagnetic chemical elements are included in the composition of the nanoscrolls. Studies of the individual nanoscrolls require special approaches. This article discusses the use of atomic force microscopy for such studies. [ABSTRACT FROM AUTHOR]

A group of phyllosilicate nanoscrolls conjoins several hydrosilicate layered compounds with a size mismatch between octahedral and tetrahedral sheets. Among them, synthetic Mg3Si2O5(OH)4 chrysotile nanoscrolls (obtained via the hydrothermal method) possess high thermal stability and mechanical properties, making them prospective composite materials fillers. However, accurate determination of these nano-objects with Young's modulus remains challenging. Here, we report on a study of the mechanical properties evolution of individual synthetic phyllosilicate nanoscrolls after a series of heat treatments, observed with an atomic force microscopy and calculated using the density functional theory. It appears that the Young's modulus, as well as shear deformation's contribution to the nanoscrolls mechanical behavior, can be controlled by heat treatment. The main reason for this is the heat-induced formation of covalent bonding between the adjacent layers, which complicate the shear deformation. [ABSTRACT FROM AUTHOR]

The subject of this study was Si-C composites for lithium-ion battery (LIB) anodes obtained by carbonization of nanodispersed silicon with carbon monofluoride. To determine the possibility of increasing the degree of graphitization of nanodispersed carbon forming shells around the silicon particles at lower temperatures, nickel in the form of an alcoholic solution of Ni(NO3)2 was introduced as a catalyst into the pellets of the resulting composite. The XRD, Raman scattering and EDS methods were used to investigate changes both in the phase and elemental composition of materials resulting from the annealing of the Ni-containing Si-C composite over the temperature range of 500–1100 °C. It was found for the first time that nickel silicides that emerged during the annealing became catalysts and, at the same time, intermediate products, of cubic silicon carbide (β-SiC) synthesis, which reduced its temperature formation from ~1100 °C to ~800 °C. The same compounds had a catalytic effect on the carbon atom association, leading to an increase in the degree of its graphitization. The influence of changing the composition of the investigated material on the electrochemical characteristics of the obtained negative LIB electrodes was traced. [ABSTRACT FROM AUTHOR]

Single-phase nanotubular hydrosilicates (Mg1 – xCox)3Si2O5(OH)4 (x = 0.2, 0.4, ..., 1) with a chrysotile structure were obtained by hydrothermal treatment at 200°C. Materials based on cobalt-containing hydrosilicates can be used as catalysts, sorbents, and sensors and in energy storage and accumulation devices. Nanotubular cobalt-containing hydrosilicates are difficult to produce because of the presence of oxygen in the system and, as a consequence, the oxidation of cobalt to Co3+. To stabilize Co2+, at the stage of hydrothermal treatment, a sodium sulfite solution was used to chemically remove oxygen from the system. The samples obtained were nanoscrolls of various morphologies. An increase in the cobalt content in the system led to the formation of multi-walled and double-walled cylinders, cones, tube-in-tube nanoscrolls, and also nanoscrolls with fully or partially closed ends, curved nanoscrolls, and spheroidal particles. [ABSTRACT FROM AUTHOR]