Aleksandr S. Lozhkomoev

Synthesis of core-shell AlOOH hollow nanospheres by reacting Al nanoparticles with water

A novel route for the synthesis of boehmite nanospheres with a hollow core and the shell composed of highly crumpled AlOOH nanosheets by oxidizing Al nanopowder in pure water under mild processing conditions is described. The stepwise events of Al transformation into boehmite are followed by monitoring the pH in the reaction medium. A mechanism of formation of hollow AlOOH nanospheres with a well-defined shape and crystallinity is proposed which includes the hydration of the Al oxide passivation layer, local corrosion of metallic Al accompanied by hydrogen evolution, the rupture of the protective layer, the dissolution of Al from the particle interior and the deposition of AlOOH nanosheets on the outer surface. In contrast to previously reported methods of boehmite nanoparticle synthesis, the proposed method is simple, and environmentally friendly and allows the generation of hydrogen gas as a by-product. Due to their high surface area and high, slit-shaped nanoporosity, the synthesized AlOOH nanostructures hold promise for the development of more effective catalysts, adsorbents, vaccines and drug carriers.

Effect of low-dimensional alumina structures on viability of L 929 cells

In the study, we estimated the cytotoxicity of alumina nanoparticles differing in shape (nanofibers, nanoplates, nanosheets, agglomerates of nanosheets) and close in physicochemical properties (particle size, specific surface area, phase composition, and zeta potential). The alumina structures were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) data, low-temperature nitrogen adsorption, and dynamic light scattering (DLS). The cytotoxicity was estimated on fibroblast cells of the L929 line. It was found that a more adverse effect on the cells was exerted by alumina nanofibers and nanosheets. The action of nanosheets on the cells was inhibitory and was of about the same level, irrespective of the observation period. The effect of alumina nanosheet agglomerates and nanoplates on the cell proliferation was weak even at an exposure time of 72 h.

Synthesis of low-size flower-like AlOOH structures

Al/Cu, Al/Zn, and Al/Fe bimetallic nanoparticles have been obtained using the method of simultaneous electrical explosion of metal pairs in an argon atmosphere. The nanoparticles are chemically active and interact with water at 60°C forming flower-like hierarchical porous structures with a high specific surface area. As the Al/Cu nanopowder is oxidized with water, flower-like pseudoboehmite composite structures are formed with the size of under 1.0 μm; structurally heterogeneous electron-dense spherical inclusions of unreacted metal copper and intermetallides are identified inside them. Al/Fe product transformations are presented by the flower-like pseudoboehmite surrounded by lamellar structures enriched with ferric oxides. Al/Zn nanoparticles react with water, forming the flower-like pseudoboehmite and mainly hexagonal zinc oxide laminae. The composite particles obtained can be used as antibacterial agents in manufacturing medical supplies.

Formation of micro/nanostructured AlOOH hollow spheres from aluminum nanoparticles

Micro/nanostructured AlOOH hollow spheres have been obtained via one-step synthesis. Spherical aluminum nanoparticles coated with amorphous oxide film are used as a precursor. Hollow spheres of AlOOH are formed during the oxidation of aluminum nanoparticles with water. In order to study the evolution of hollow spheres, electron microscopy studies of the reaction intermediates at various stages of the process are carried out. Micro/nanostructured AlOOH hollow spheres have a diameter of 500–800 nm, and their shells consist of boehmite nanosheets with a planar size of 200–300 nm and a thickness of 2–10 nm. It is shown that the formation of AlOOH hollow spheres occurs through dissolution of aluminum core, the diffusion of Al3+ ions through the surface oxide film, and the formation of islands of amorphous Al(OH)3 at the particle–water interface. Further, the formation and growth of AlOOH nanosheets and the formation of a porous shell from nanosheets take place. As a result, the oxide film serves as a substrate for growth of boehmite nanosheets and the formation of micro/nanostructured AlOOH hollow sphere. Morphology and physicochemical properties of the hollow spheres are characterized by transmission and scanning electron microscopy, X-ray diffraction, energy-dispersive analysis, and low-temperature nitrogen adsorption.

Specific features of aluminum nanoparticle water and wet air oxidation

The oxidation processes of the electrically exploded aluminum nanopowders in water and in wet air are examined in the paper. The morphology of the intermediate reaction products of aluminum oxidation has been studied using the transmission electron microscopy. It was shown that the aluminum nanopowder water oxidation causes the formation of the hollow spheres with mesoporous boehmite nanosheets coating. The wedge-like bayerite particles are formed during aluminum nanopowder wet air oxidation.

Formation regularities of AlOOH hollow spheres during aluminum nanopowder water oxidation

There described a novel environmentally friendly synthesis route of micro/nanostructured hollow spheres of AlOOH by oxidation of Al nanopowder in pure water under mild processing conditions. The reaction kinetics of the aluminum nanopowder interaction with water was studied using the method of continuous recording of suspension pH and temperature. There observed the change in Al3+ concentration in the reaction medium and the rate of hydrogen release as well as TEM investigations of the intermediate reaction products at different stages of the process were performed. It is shown that AlOOH hollow spheres are formed through the aluminum core dissolution, Al3+ ion diffusion through the surface oxide film and AlOOH nanosheets formation on the surface of the precursor oxide film.

Acid-base and adsorption properties of the AlOOH 2D nanostructures as factors for regulating parameters of model biological solutions

We have studied the acid-base, adsorption, and electrokinetic properties of 2D nanostructures—agglomerates of pseudoboehmite (AlOOH) nanosheets 2–5 nm in thickness—that were synthesized from electro-explosive Al/AlN nanopowder. By the example of adsorption of anionic dye eosin and cationic dye methylene blue, it is found that the synthesized nanostructures have pronounced anion-exchange properties. It is shown that agglomerates of AlOOH nanosheets exhibit properties of a weak base when they are added to the biological model solutions (cell-culture medium and sodium phosphate buffer) and deionized water; in this case, an increase in pH in the media takes place both due to the release of the OH groups and the ionexchange adsorption. The possible impact of the synthesized AlOOH 2D nanostructures on the suppression of tumor-cell proliferation is considered via changes in the parameters (acidity and ionic composition) of their microenvironment.

Low-dimensional pseudoboehmite structures for microorganism adsorption

Low-dimensional structures consisting of pseudoboehmite nanopetals are synthesized by hydrolysis of electroexplosive aluminum nanopowder. The physical and chemical properties of the synthesized nanostructures are studied, such as morphology, particle size, specific surface area, phase composition, and zeta-potential. The production of a hybrid material on the basis of cellulose acetate microfibers and low-dimensional pseudoboehmite structures is described. Using the example of gram-negative and gram-positive bacteria, we show the microorganism adsorption capacity of pseudoboehmite nanopetals and the hybrid material.

Antimicrobial activity of nanostructured composites produced in Al/Zn nanoparticle oxidation in aqueous-alcoholic solutions

The paper studies the morphology, phase and elemental composition of bimetallic Al/Zn nanoparticles. It is found that metallic Al and Zn phases have interfaces within a single particle. The conversion mechanisms of Al/Zn nanoparticles in aqueous-alcoholic solutions with different water concentration are studied. It is shown that at 7 mass% water content aluminum oxidation and pseudoboehmite formation begin. Aluminum conversion increases with water content growth. At 20 mass% water content aluminum is oxidized completely, giving way to zinc oxidation. Microbiological studies show that samples containing AlOOH-Zn-ZnO phases exhibit the highest antimicrobial activity. Two-component metallic Al/Zn nanoparticles and composite particles in which initial components are completely oxidized to AlOOH-ZnO have the smallest inhibition zone.

Iron oxide and gold nanoparticles in cancer therapy

Continuous research activities in the field of nanomedicine in the past decade have, to a great extent, been focused on nanoparticle technologies for cancer therapy. Gold and iron oxide nanoparticles (NP) are two of the most studied inorganic nanomaterials due to their unique optical and magnetic properties. Both types of NPs are emerging as promising systems for anti-tumor drug delivery and for nanoparticle-mediated thermal therapy of cancer. In thermal therapy, localized heating inside tumors or in proximity of tumor cells can be induced, for example, with Au NPs by radiofrequency ablation heating or conversion of photon energy (photothermal therapy) and in iron oxide magnetic NPs by heat generation through relaxation in an alternating magnetic field (magnetic hyperthermia). Furthermore, the superparamagnetic properties of iron oxide nanoparticles have led to their use as potent MRI (magnetic resonance imaging) contrast agents. Surface modification/coating can produce NPs with tailored and desired prope...