Vertical nanocrystal whiskers or nanowiskers are one-dimensional crystals that look like rods or threads several nanometers in diameter. The rods are often cultivated using the elements of the third and fifth groups of the periodic table. The most common nanocrystals of the third and firth groups are gallium arsenide and indium phosphide. These semiconducting materials present competition to silicon in the electronics field as diodes and transistors built using them are faster in operation. In addition, due to their ability to emit and absorb radiation with 1.55 micrometer wavelength such nanocrystals can be used to transmit information via fiber-optic lines.

Up until recently, it was common knowledge that a cubic structure is formed with all nanowhiskers of the 3-5 groups (except for nitrogen-containing) during crystallisation. Several experiments showed, however, that the structure can be hexagonal as well, with a hexagon as a base. This finding draw increased attention to nanowhiskers. On the one hand, such structure is unstable and can have a negative effect on the quality of the materials being produced, but on the other hand the hexagonal crystals of the 3-5 group are not very well studied yet and therefore it is possible to anticipate the discovery of new promising features. In any case, the primary target of the research must be the synthesis condition responsible for the formation of cubic or hexagonal nanowhisker crystal lattice.

Researchers at the St. Petersburg Academic University, and the Ioffe Technical Physical Institute have been exploring the subject for a long time. An article by Vladimir Dubrovsky et al. has been published recently in the Journal of Technical Physics, describing a model of nanowhisker growth and structure that they had developed. The study was supported by the Russian Foundation for Basic Research, the Presidium of Russian Academy of Sciences, and the Ministry of Education and Science of the Russian Federation.

The researchers studied the most common mechanism of nanowhisker growth — vapour-liquid-crystal. This method cultivation requires the vapours of the substance in question are precipitated on a substrate in the form of a drop that later solidifies forming a homogeneous structure. The growth surfaces are often activated using metallic catalyst drops which is presented by gold. In that case, a nanocrystal grows under the drop and after solidification it looks like a rod with a golden cap on its upper end. The size of the crystal depends on the amount of the substance precipitating on the substrate it grows on.

The model developed by St. Petersburg-based physicists takes into account not only the consecutive transition of the atoms from gaseous form into liquid and then into solid forms, but also other processes such as immediate precipitation of the gas on the surface of the crystal, and the diffusion of adsorbed atoms (adatoms) from the substrate surface into the growing crystal. The model allows to determine the probability of formation of cubic and hexagonal crystals depending on the precipitation conditions, substrate properties, and gaseous medium saturation. According to the discovery of the same research group made in 2009, the most important factor influencing the crystal structure if its transversal dimension. Nanowhiskers up to 50–70 nanometers in diameter grow in the cubic phase, whereas crystals of larger sizes grow in the hexagonal phase. The researchers note that the model can be used to forecast the crystal growth with various precipitation methods applied.

Ekaterina Shershunova

Nickel nanoparticles are used as a catalyst to produce various substances — for example, synthetic hydrocarbons. Broad use of this inexpensive catalytic metal is limited by the fact that researchers have no effective method of generating nanoparticles of similar structure and of closely varied sizes.

Experts at the Nanotechnologies and Nanomaterials Research Centre at Tambov Derzhavin State University have suggested making nickel nanoparticles of a certain size using metal precipitation on carbon nanotubes — as some “scaffolding” for nickel nanoparticles. The research report was published in the Letters of Technical Physics Journal. The study was supported by the Federal Task Program “Scientific and Pedagogical Resources of Innovative Russia, and the Analytic Departmental Task Program “The Development of Scientific Potential of Higher School of Education.”

The nanoparticles were generated by galvanic chemical precipitation (the effect of electric field on nickel-containing electrolyte). Nanotube water suspension was put on the polished surface of the copper cathode in advance. After the water dried out, carbon nanotubes were left on the cathode surface, with nickel precipitating of them later. The structure of the resultant particles was studied using an electronic microscope.

Nickel nanoparticles precipitated mainly on various defect parts of the nanotubes, as well as on their ends. In the course of the growth process, the nickel nanoparticles formed “beads” on the carbonic nanotubes. The acquired structure consisted of nickel nanoparticles situated on the carbonic nanotubes frame, with a slight variation to the particle sizes. The researchers noted that the mass of carbon nanotubes with the nickel particles applied on them was highly transparent for a flow of fluid or gas, unlike common nickel particle powder. This allows an assumption that the catalytic activity of the nickel particles applied on the nanotubes can be more significant.

The cost price of carbonic nanotubes is still rather high and therefore the researchers have conducted a preliminary cost-effectiveness assessment of the nanotube usage as a frame for nickel catalyst. It was proved that the total area of the nickel nanoparticles is twice as large as the nanotube surface or more. That justifies the use of carbonic nanotubes as “scaffolding” for nickel nanoparticles.

The proposed structure will be able to broaden the use of the nanotubes as well — as bioactive materials, for example. Nanotubes can be easily absorbed by cells and therefore can serve as transport for various molecules necessary for treatment and diagnostics. Nickel magnetic properties can help in developing the methods for target medicine delivery into the cells, and the increase of the total surface will allow to “load” the nanotube with more molecules.

Dmitry Tsendin

Scientists at the Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, have generalized the known facts about the influence of technogeneous nanoparticles on water-dwelling organisms. The report published in the Newsletter of Russian Academy of Sciences, the Biological Series, showed that the presence of nanoparticles in water negatively affected hydrocoles; the researchers noted, however, that there still was insufficient information to draw final conclusions.

Nanoparticles are objects the size of which in at least one dimension does not exceed 100 nanometer. They can be of carbon or metal origin; they can be made of metal oxide; or they can present semiconductors, organic polymers, etc. Nanoparticles were put into a single category as their small size itself leads to uncommon physical and chemical properties. Nanoparticles usually feature high penetrating power, large surface area and chemical activity.

The researches show that nanoparticles can penetrate organisms of animals and humans through skin coverings, via accidental inhaling, or with water and food. Water-dwelling organisms are most affected by nanoparticles, believe the scientists. Nanoparticles get into the bronchia and digestive tract of water dwellers and can possibly move along the food chains — for example, from maxillopoda to fish — and accumulate in the organisms positioned on the upper steps of the food pyramid.

Nanoparticles can be toxic for organisms due to their size and physical and chemical properties. The presence of nanoparticles in the water decreases the fertility of hydrocoles; causes various physiological changes, behaviour disorders and increased death rate. The toxicity is influenced by the size of the particles, their chemical nature, water solubility. It is a known fact that nanoparticles of zinc oxide, copper oxide and silver oxide are more toxic as compared to the nanoparticles of other metals and metal oxides. The researchers note, however, that the data on nanomaterial toxicity is quite controversial and ambiguous — for example, the effects of chronic nanoparticle influence are virtually unexplored.

The scientists note that the development of nanotechnologies is mush ahead of the assessments of their influence on the environment. Therefore, all issues associated with the behaviour of nanomaterials in the environment and their influence on living organisms and ecosystems require great attention and serious systematic research.

Further information: Evgeny Krysanov, Ph. D. (Biology), senior staff scientist, the Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow; (499)135-7218, krysanov@sevin.ru    

Source of information: Е. Yu. Krysanov, D. S. Pavlov, T. B. Demidova, Yu. Yu. Dgebuadze: “Nanoparticles in the Environment and their Influence on Hydrocoles.” Newsletter of Russian Academy of Sciences. The Biology Series, 2010, #4

Researchers at the University of Orenburg have tested the effect of various carbon nanoparticles on bacteria. It was discovered that the bacteria-growth-inhibiting properties of nanotubes declined as the quality of purification lowered; the bacteria were neutral towards fullerenes unless the latter were modified by amine groups.

Over 1.800 different nanomaterials are currently available in the market. Broader use could lead to polluting of natural ecosystems and human habitat. Physicochemical properties of nanoparticles differ from those of large crystals; and their interaction with living systems is virtually unexplored. The group of researchers led by Dmitry Deryabin at Orenburg State University studied the influence of various carbon nanoparticles on Escherichia coli bacteria (colon bacillus). The research is to be published in issue 11-12 of the Russian Nanotechnologies magazine.

Four samples of single-shell carbon nanotubes of various purification efficiency levels as well as multi-shell carbon tubes, fullerenes and chemically modified fullerenes (containing carboxyl and amine groups) were used for the experiment. The nanoparticle suspension was mixed with the bacterial suspension in proportion of 1:4 and kept at 37°С for an hour; later the mixture was dried and examined using the atomic-force microscopy method. In addition, the bactericidal effect was assessed by plating the microorganisms that had contacted with nanoparticles into the nutrient medium and comparing the number of viable individuals in the experimental and the reference groups.

The researchers provided detailed description of peculiarities of each carbon nanomaterial sample. In general, poorly purified nanotubes demonstrated the most effective bactericidal action. Microscopic research showed that the cells of bacteria incubated in contact with the tubes decreased in size (178 nanometer vs. 201 nanometer) and had flat fragments free of cell content. The scientists believe that the damage of the surface bacterial structures is more probably associated with the effect of admixtures (amorphous carbon, metallic catalysts) rather than with the action of the carbon tubes themselves. The study of purified nanoparticles showed that they also contacted with the surface of the bacterial cells but the researchers did not identify reliable effect on the culture viability. The fullerenes and their carboxyl modification had no influence on the viability and morphology of the bacteria whereas the fullerene modified with amine groups (-NH2) was actively interacting with the bacteria and had an evident bactericidal effect. The substance showed a high level of bacterial cell wall affinity as about 97 per cent of nanoparticles got bound with it, and only 3 per cent of particles were preserved in the solution. As a result, a characteristic nanoparticle graininess emerged on the surface of the bacteria accompanied with the changes in the cell length, width and height. After contacting with fullerene modified with amine groups, 60 per cent of bacteria were dead, as compared to the reference group.

The research was supported by the Scientific and Pedagogical Personnel in Innovative Russia Federal Task Program.

Source of information: D. G. Deryabin, А. S. Vasilchenko, Е. S. Aleshina, А. S. Tlyagulova, А. N. Nikiyan. “Studying the Interaction Between Carbon Nanomaterials and Escherichia coli Cells Using Atomic-Force Microscopy.” The Russian Nanotechnologies, 2010, #11-12.

Further information: Dmitry Deryabin, head of the Microbiology department at the Chemico-Biological faculty, Orenburg State University. +7(3532)37-24-81, dgderyabin@yandex.ru

Experiments on rats carried out by Russian researchers have demonstrated that silica nanoparticles can be used to deliver drugs to the heart in case of myocardial ischemia.

One of the most promising directions in contemporary medicine is development of substances that are able to deliver drugs to a disordered organ. Nanoparticles can be used as carriers, as a lot of abnormal changed tissues selectively accumulate some substances. Research on directed drug delivery by nanoparticles is mainly carried out in oncology, but this method can be also applicable in other areas. Mikhail Galagudza and other specialists at the V.A. Almazov Federal Center of Heart, Blood and Endocrinology, St. Petersburg State Medical University and Faculty of Chemistry of St. Petersburg State University have studied possibility of directed silica nanoparticles delivery into the myocardium in case of ischemia (blood supply disturbance). Though, this was so far done on rats and without involving drugs. The article about the research will be published in the next issue of the “Russian Nanotechnologies” journal.

Silica, or silicon dioxide (SiO2), is a substance that is very widespread in nature, therefore, nanoparticles made of it will be commonly used in future. In the above research, the scientists worked with 7 nm silica particles. Specific surface of one gram of such particles makes from 170 through 380 m2. Fluorescent dye was attached to nanoparticles, so that the researchers could later watch their distribution in the organism.

Any investigation of a new substance starts with identification of its acute toxicity: it is impossible to make a drug delivery system based on particles, which could have a negative impact on the organism. To check toxicity, the nanoparticle suspension was injected to laboratory rats to assess reaction of their cardiovascular system. Having confirmed that the preparation does not have any explicit poisonous influence on the rat’s organism, the researchers embarked on the main experiment. The rats were divided into three groups. The coronary artery was pinched with the animals in the first group to simulate myocardial ischemia, and 25 minutes after that silica nanoparticles suspension was injected to them. The second group consisted of the animals, which were injected the particles suspension but their coronary artery was not pinched. The third group consisted of the intact animals, which were exposed neither to operation nor to particles injection. They were necessary in order to calculate normal silicon content in tissues.

To evaluate the result, the rats’ heart and liver was taken for analysis after the experiment was over. Nanoparticle distribution in the organism was studied via the fluorescence microscopy method, and the silicon content was estimated by the atomic absorption spectroscopy method. It has turned out that the silicon content in the heart of rats that underwent experimental ischemia is ten times higher than in the heart of intact rats, that is, silica particles selectively enter into the damaged tissue. A possible mechanism of passive directed silica nanoparticles delivery into the abnormality zone is increasing myocardium micro-vascular permeability during ischemia.

Further investigations of nanoparticles toxicity are necessary. The researchers have demonstrated that the suspension injection provides high concentration of siliceous particles in the liver, lungs and spleen. A short-term experiment is unable to show if this is dangerous for health, lengthy observation of animals is required to this end. If outcomes of further experiments are favorable, nanoparticles will be used as drug carriers. The specialists believe that they will be able to load nanoparticles with cardioprotectors (for example, bradykinin, erythropoietin, etc.), and they will selectively deliver drugs to the damaged cardiac muscle. The need in new methods for ischemic heart disease treatment is very high as heart diseases make one of the most widespread causes of people’s death.

Source of information: M.M. Galagudza, D.V. Korolev, D.L. Sonin, I.V. Alexandrov, V.N. Postnov, G.V. Papayan, E.V. Shliakhto. “Passive directed delivery of drugs into ischemic myocardium with utilization of silica nanoparticles”. “Russian Nanotechnologies”, 2010, #11-12.

Further information: Mikhail Mikhailovich Galagudza, head of scientific research laboratory of myocardium metabolism, V.A. Almazov Federal Center of Heart, Blood and Endocrinology. E-mail: galagoudza@mail.ru

Russian researchers have suggested a new method to form crystalline nanostructure of the Fe-Cu-Nb-Si-B alloys. The nanostructures obtained under the action of gas discharge optical radiation possess better magnetic and mechanical characteristics as compared to their analogues produced via temperature methods.

Creation of materials resistant to strong mechanical and magnetic action is one of important nanotechnology tasks. New nanostructural materials based on  the Fe-Cu-Nb-Si-B (iron, copper, niobium, silicon, boron) alloys that possess a high value of permeability are potentially able to replace permalloy – the iron/nickel alloy, which is now used extensively for magnetic field shielding.

So far, the Fe-Cu-Nb-Si-B crystals have possessed a significant drawback: low mechanical strength. Researchers at Kazan State Unversity and Kazan Technology University  have managed to develop a method to solve the problem. To get nanocrystals in the Fe-Cu-Nb-Si-B alloys, high-temperature annealing has been used so far, under which a disordered alloy structure turns into a crystalline structure under high-temperature action. The specimens obtained in this way acquire the necessary magnetic properties but they become very fragile and their surface oxidizes. Rouslan Nazipov, Anatoly Mitin and Nikolai Ziuzin have suggested a new alloy annealing method – processing by gas discharge. The article published this week describes that they obtained the Fe-Cu-Nb-Si-B nanocrystals by effecting the material by optical radiation of a gas-discharge flash lamp (powerful electromagnetic source with the band varying from infrared through ultraviolet). The obtained material is a polycrystalline one, i.e., it consists of multiple differently-oriented crystals called crystallites or grains.

The researchers have determined the alloy structure dependence on the power supporting it, and described crystal creation conditions. Full crystallization of experimental specimen of an alloy (30×10×0.025 mm) into the 150-nm grains required 1,529 joules (approximately the same amount of energy is spent by a human being to walk 10 meters). To create similar structures via thermal annealing, the specimen should be heated up to 900 degrees Celsius under vacuum conditions (to avoid metal oxidation). Consequently, gas discharge utilization does not only improve mechanical properties of crystals but also enables to save power significantly.

Source of information: R.A. Nazipov, A.V. Mitin, N.A. Ziuzin. “Crystallization of amorphous alloy of the Fe-Cu-Nb-Si-B system under the action of powerful pulse optical radiation”. Preprint of the article is available at http://arxiv.org/PS_cache/arxiv/pdf/1010/1010.5010v1.pdf

Further information: Nazipov Rouslan Airatovich – assistant at department of solid state physics, Kazan State University, е-mail: Ruslan.Nazipov@ksu.ru

Russian researchers have developed a method for assessing biological accumulation of nanoparticles in planktonic organisms, and have demonstrated that algae and seed shrimps intensively accumulate titanium dioxide particles.

It is known that nanoparticles can be transferred along food chains: a predator assimilates particles that were contained in the prey body. Majority of food chains in seas and lakes begin with plankton (microscopic organisms drifting in water mass), and therefore it is important to know how actively planktonic organisms accumulate nanoparticles when they get into water.

Yuri Morgalev and his colleagues at the Center “Biotest-Nano” of Tomsk University and Siberian State Medical University have investigated nanoparticles accumulation in chlorella and daphnids. Chlorella is the genus of unicellular algae, typical representatives of phytoplankton, and Daphnia is the genus of microscopic crustacea, widespread in zooplankton. Both organisms are often applied for water quality investigations.

The researchers dealt with titanium dioxide nanoparticles as these particles are already used now for production of paint, drugs, beauty aids and other products. It has become clear that titanium dioxide nanoparticles accumulate quickly and in large quantities in phyto- and zooplantkton. The work will be published in the next issue of the “Russian Nanotechnologies” journal.

The researchers obtained titanium dioxide particles (their size making 5 nm) via the electric explosion method. These particles were placed into water at concentrations from 10 mg/l through 1 g/l, and the researchers watched their behavior in aqueous environment. At high concentrations, nanoparticles coalesce and precipitate, stable nanoparticle suspension exists at the concentration lower than 2 mg/l. The experiment used dispersed solutions of titanium dioxide nanoparticles at the concentration of 1 mg/l.

Starting from the 5^th day of chlorella cultivation in the presence of nanoparticles, the researchers estimated titanium presence in water and algae cells. The mass spectrometry method was used to this end. The biologists have proved that on the 5^th day the titanium concentration in the cultivation environment decreased, and it made 246±12 mcg/g in chlorella cells. In a month, titanium concentration in chlorella increased, although insignificantly. To determine what part of titanium is firmly bound with chlorella, concentrate of its cells was exposed to sixfold washing. After the procedure, the titanium content reduced to 92.50±3.20 mcg/g – this particular quantity of titanium penetrated inside cells or was firmly bound with their surface. Titanium content in algae cells exceeded titanium content in the external environment by more than 200 times.

Daphnids biology peculiarities make it difficult to get an absolutely precise result because it is necessary to feed the animals and to clean up their aquarium, these processes bring some distortions in titanium concentration in water. Nevertheless, the researchers managed to prove that on the 5^th day the seed shrimps concentrate contains 100±8 mcg/g of titanium, and after washing, its concentration reduces to 58±5 mcg/g – this particular quantity of the element gets bound with seed shrimps tissues. This is twice less than that of chlorella, but it is a hundred times more than titanium concentration in the environment.

So, experiments have proved that titanium nanoparticles are accumulated in aquatic tissues rather quickly (within 4-5 days) and in rather large quantities. They are accumulated both by algae – initial link of food chain - and by seed shrimps, which are at the nest stage. As zooplankton serves food for a lot of fish species, it can be expected that titanium nanoparticles will be transferred further along the food chain and appear in products of industrial fishery and aquaculture. Subsequent research will be required to assess if it is harmful and to what extent.

Source of information: Yu. N. Morgalev, N.S. Khoch, T.G. Morgaleva, E.S. Goulik, G.A. Borilo, U.A. Bulatova, S. Yu. Morgalev, E.V. Poniavina. “Biotesting of nanomaterials: about a possibility of nanoparticles translocation into food chains”. Russian Nanotechnologies, 2010, #11-12.

Further information: Morgalev Yuri Nikolayevich, Center “Biotest-Nano” of Tomsk State University.  Tel.: +7 (3822) 53-44-35, e-mail: morgalev@tsu.ru

In the course of plasma magnetic traps’ operation, erosion their walls’ occurs, and nano-dimensional films and dust particles are formed. Researchers at the Russian Scientific Center “Kurchatov Institute” assert: the dust can favorably influence the reactor’s operation.

A tokamak (a toroidal chamber with magnetic coils) is a closed magnetic trap intended for high-temperature plasma creation and confinement. Controlled thermonuclear fusion can be accomplished in such reactors – fusion of lighter nuclei that provides heavier nuclei and energy release. Plasma is the state in which all substances are transferred under strong heating (the temperature is measured by hundreds of millions of degrees). In plasma, not only bonds between molecules are destroyed (like under evaporation) but also bonds between atoms and even between atoms’ neuclei and electrons. Plasma consists of charged particles and, therefore, it can be retained by magnetic field. Under normal conditions, plasma should not touch the internal surface of tokamak but sometimes certain particles do reach the walls, thus causing erosion.

“The nanostructures being formed as a result of erosion of plasma-facing tokamak chamber elements mainly have a negative effect”, wrote specialists at the Kurchatov Institute  in the article about nanodust published at the “Physical Sciences Progress” journal. Nanostructures accumulate tritium – this causes damage to the reactor safety as this hydrogen isotope is radioactive, besides, its losses cause significant financial damage: the price of tritium is about 10 000 000 $/kg. Should water get into the chamber (in emergency situation), nanostructures can serve as a catalyst for its decomposition into oxygen and hydrogen, thus creating explosion hazard. Radioactive dust presence in the air represents danger for specialists during reactor opening.

Studying nanodust in tokamaks has demonstrated that the films being formed mainly consist of carbohydrates and tungsten. They can be smooth or possess a complicated relief. Nanoparticles can unite into the approximately 15-nm clusters or form a disordered structure. The hydrogen isotopes (deuterium and tritium) adsorption mechanism was studied on smooth films, and researchers suggested the thermodesorption method - deuterium and tritium removal from films under heating.

The researchers have found out that the dust being formed on the reactor chamber surface can also play a favorable role: it enables to support plasma discharge stability due to plasma density increase and plasma temperature decrease. Besides, the authors draw attention to complicated latticed nanostructures with large surface area, which are being formed from particles settling on the reactor surface. Probably, this by-product of reactor work will be used in the future to solve some other processing tasks.

Source of information: “Nanostructures in controlled thermonuclear fusion plants”,  V.I. Krouz, Yu.V. Martynenko, N. Yu. Svechnikov, V.P. Smirnov, V.G. Stankevich, L.N. Khimchenko, Uspekhi fizicheskikh nauk (Physical Sciences Progress), Vol. 180, #10, 2010, http://ufn.ru/ufn10/ufn10_10/Russian/r1010c.pdf

Further information: Yuri Vladimirovich Martynenko – specialist, Kurchatov Institute, e-mail: martyn@nfi.kiae.ru

Researchers at the Kazan State Technical University named after A.N. Tupolev  have developed mathematical models that describe structure of various nanotube types. They allow to adjust existing theoretical ideas and design methods for various nanotube characteristics. As model application experience is accumulated, these models can help to forecast nanotube properties as well as to develop their automatic sorting methods. The work was published in the last issue of the Scientific Israel - Technological Advantages journal.

“There is nothing but somehow located atoms in any crystal, including cylindrical ones, – explained one of research authors, Zufar Khalitov, to a reporter of “Informnauka”. – This determines all its properties, including electric ones.”

To use unusual electric properties of nanotubes, it is necessary to get sufficient quantity of tubes with a similar structure. The problem is that there is no synthesis method now that allows to get only one nanotube variety. During any reaction, a mixture of products with different characteristics is formed. It means that effective nanotube application in electronics requires development of methods for sorting reaction products according to certain criteria. Research groups all over the world are solving the task.

Zufar Khalitov and his colleagues believe that the key to this problem solution can be found in diffraction methods of nanotube structure analysis. Utilization of various beams (X-ray beams, electron and neutron streams) and analysis of their interaction with the investigated substance will enable to determine nanotube selection criteria and to develop a method for their isolation. To make diffraction analysis really useful, it is necessary not to determine the crystal structure from scratch but to be guided by a previously developed model.

“The structural model of the crystal is the very “initial point” where everybody begins at: both those who want to calculate some of its properties (for example, conductivity), and those who want to develop methods for its identification and parameter measurement, for example, based on electron diffraction or X-ray beams, – pointed out the researcher. – It is impossible to begin any important developments until structural models are available. One can act as alchemists did, by the hit-and-miss method, which has been done to a large degree during the last 20 years.”

The researchers have got expressions that explicitly determine coordinates of any atom in nanotubes of various geometrical types. The models developed by the researchers applied the notion of unit cell, “building block”, parallel translation of which can provide the whole nanotube. Such method is applied in crystallography to describe crystals that possess natural symmetry.

Three types of multilayer nanotube structure are singled out. In the circular nanotube, the layers are nested like in a nested-doll. The chiral type resembles the circular one, but in this case the layers are curled on-the-mitre to the nanotube axis. Spiral nanotubes are curled like a bolt of wallpaper. This classification is normally used to describe carbonic nanotubes, however, other substances can also form a nanotube: there exist chrisotile, sulfide, and boron-nitride tubes.

The mathematical model based on utilization of unit cells notion enabled to develop equations not only for circular and chiral nanotubes but also for spiral ones. Besides, the suggested model, in contrast to previously developed analogues, allows to describe not only carbonic nanotubes but also tubes of any chemical composition.

The researchers have already compared the developed models to experimental data. “Our models of nanotubes do not contradict to experimental data, and we have managed for the first time to describe some diffraction effects taking place in the experiment, – said Khalitov. – We have also used our models in the course of theoretical analysis of wave processes in the nanotube cavity and obtained very interesting results.”

In the future, the researchers are planning to carry out a larger-scale checkup of obtained models. After improvements are made in accordance with experimental data, the models can be applied for development of new diffraction methods for nanotube identification and measurement of their structural paramenters. Later on, utilization of the model will help in development of methods for automatic sampling of nanotubes of pre-assigned structural type. Moreover, “as experience in such analysis is accumulated, we shall be able to forecast nanotube properties, i.e., to forecast nanotube structure and methods for synthesis of nanotubes with required properties”, – says the researcher.

Khadiev Azat

Researchers at the Institute of Electrophysics, Ural Branch, Russian Academy of Sciences in Yekaterinburg have suggested that the industrial ytterbium fiber laser should be used to get functional nanopowers. The work published in the Journal of Applied Physics compared productivity and power inputs when getting nanopowders via fiber and carbon dioxide laser. The work substantiated advantages of the first option. The effort has been accomplished with financial sponsorship of the Presidium of the Russian Academy of Sciences  and the Federal Targeted Program “Scientific and Educational Research Staff of Innovative Russia”.

Nanopowders are applied in making structural ceramics, they are used in hydrogen power engineering, many of them are capable of luminescence. Target evaporation with the help of laser radiation is a promising method for obtaining nanopowders.

Utilization of carbon dioxide laser, which was also investigated in their previous efforts by the Yekaterinburg researchers, enables to get particles about 20 nm in dimension. Differences in size, which inevitably occur when getting nanoparticles, are insignificant in case of carbon dioxide laser. However, engineering deficiencies of such laser – capacity instability, low efficiency of conversion of electrical energy into emission, impressive dimensions – are connected with considerable inconveniences, and encourage researchers to seek for new solutions.

A group of researchers guided by Yuri Kotov  has suggested that ytterbium fiber lasers should be used in a similar process flow. The experiment involved lasers, produced by the Scientific and Technical Association “IRE-Polus”. They are more efficient than carbon dioxide lasers, however, their wavelength makes 1.07 micrometers (10 times less than that of carbon dioxide laser), and possibility of their utilization to get nanopowders required experimental check.

The target – a material blank for getting substances of required composition - consisted of compressed micron-sized powders of yttrium (Y) and zinc (Zn) oxides. Laser radiation was transmitted via fiber cable to the optical system and was focused on the target. The material blank was equipped by a drive that ensured the target horizontal displacement and rotation for uniform surface processing. The molecules vaporized from the surface were taken away by the inert gas stream and they condensed upon a specially prepared substrate layer.

Under uninterrupted seventeen-hour laser work, the powder output was 390 g – it is approximately three times higher than when using carbon dioxide laser. Additional analysis has confirmed obtaining of practically homogeneous nanopowder, which is close in composition to the target. A set of experiments on getting optical ceramics nanopowders has also proved that ytterbium laser utilization ensures that the final composition of the mixture as compared to the initial composition of the target is distorted to a much less extent than in case of carbon dioxide laser utilization. The researchers primarily connect the above effect with high monochromaticity of the ytterbium laser.

Special attention was paid by the specialists to the search of optimum condition for laser operation. The obtained experimental dependence of productivity on pulse duration upon fixed pulse energy has a typical peak in the range of 100 microseconds. Thus, in the researchers’ opinion, already now “ytterbium fiber lasers should be considered more promising for getting nanopowders, taking into account their higher consumer properties.”

Petrov Mikhail

Laser waves focused on the tumor area can damage cancer cells and blood vessels feeding them. The process becomes more efficient if nanoparticles are preliminary introduced into the tumor. At the conference “Nanotechnologies in Oncology in 2010”, Russian oncologists explained how laser irradiation is absorbed by nanoparticles, what particular nanoparticles should be used and to what extent their application increases therapeutic effect with animals suffering with cancer.

Pulsed laser hyperthermia is the tumor elimination method based on injecting sensitizers (nanoparticles) into the pathological tissue and further irradiation by high-energy laser pulses, the wave length of which is the area of applied nanoparticles absorption. Efficiency and mechanism of action of this approach were studied by specialists of the  Moscow Scientific Research Institute of Oncology named after P.A. Hertzen, State Research Center “NIOPIK” and the A.N. Frumkin Institute of Physical Chemistry and Electrochemistry. Andrei Pankratov and his colleagues investigated more than 15 nanostructure varieties of different chemical nature, structure and size. Nanoparticles of zinc phthalocyanine (ZnPc) were researched in most detail. The researchers have demonstrated that pulsed laser hyperthermia involving ZnPc particles use results in lengthy inhibition in growth of tumors of various nature: sarcomata, colon carcinoma, carcinoma of lung, melanoma. Part of the animals (from 10 to 70%, depending on cancer разновидности рака and investigated treatment method) has demonstrated complete recovery.

The mechanism of antitumoral action of pulsed laser hyperthermia with nanoparticles used as sensitizers has not been fully studied yet. The new research enables to state that the main reason of therapeutic effect is destruction of the tumor vascular system. When the tumor is laser-irradiated, nanoparticle microexplosions occur in blood vessels feeding it. The researchers have demonstrated that significant decrease of oxygen partial pressure is observed in the tumor tissues after irradiation: from 40-60 down to 0.5-5 mm of mercury. After irradiation is over, oxygen partial pressure level was not restored with the majority of animals that had underwent treatment with ZnPc particles. Blood vessel destruction in the tumor was also observed when investigation tissues under a microscope. A day after irradiation, blood vessel density in the tumor was almost 10 times lower than that in the reference group (unfortunately, several days after irradiation, vessel growth restarts in the tumor).

The researchers have also investigated safety of nanoparticles they used. They have demonstrated that ZnPc nanoparticles are removed from the blood flow within 3 hours, that the maximum endurable dose in case of intravenous induction exceeds the minimal dose necessary for treatment by 35 times, and that nanoparticles at the 0.2% concentration do not lead to blood corpuscle destruction. Nanoparticles are able to accumulate in the lungs, liver, kidneys and spleen, however, a year after nanoparticle injections, including those in high doses, the researchers did not reveal abnormal changes in these organs.

Source of information: Pankratov A.A., Andreeva T.N.., Yakubovskaya R.I., Kogan B.Ya., Butenin A.V., Feizulova R.A., Rudoi V.M. “Nanostructure composites for laser hyperthermia: various aspects of safety”. Report theses for the “Nanotechnologies in Oncology in 2010” conference.

Further information: Andrei Alexandrovich Pankratov, senior staff scientis, department of modifiers and protectors for antitumoral therapy, Moscow Scientific Research Institute of Oncology named after P.A. Hertzen. Tel. + 7(494)945-87-16, e-mail andreimnioi@yandex.ru.

The majority of drugs do not penetrate from blood into the brain because of the hematoencephalic barrier existing between them. This creates a lot of difficulties for brain tumor treatment. Russian researchers have developed a system for drug delivery into the brain with the help of nanoparticles and demonstrated its efficiency on laboratory animals.

Glioblastoma is the most widespread and the most dangerous variety of the brain malignant tumor. At the moment, chemotherapy of such tumors has little effect due to existence of the hematoencephalic barrier – the filter that prevents alien agents (including drugs) from passing into the brain. Researchers worldwide are working to create medicinal systems, which could be used for glioblastoma therapy.

A substancial progress in development of new treatment has been achieved by a group of researchers from the Moscow State Academy of Fine Chemical Technology , Scientific Research Institute of Human Morphology (Russian Academy of Medical Sciences)  and Limited Liability Company - Research and Production Company “Nanosystem” . The research findings were shared by the researchers at the “Nanotechnologies in Oncology”  conference that took place in Moscow on October 30. Svetlana Gelperina and her colleagues applied the Doxorubicine antitumoral antibiotic. This substance is frequently used in malignant tumors chemotherapy, but it is not used for brain tumor treatment as it poorly penetrates the hematoencephalic barrier. The researchers joined Doxorubicine with polybutylcyanoacrylate nanoparticles covered by polysorbate 80. Such nanoparticles are being intensely studied now at multiple laboratories due to their potential ability to penetrate into the brain. The researchers have experimentally demonstrated that the antibiotic-nanoparticles complex created by them enables to achieve efficient drug concentration in the brain of rats suffering from Glioblastoma. The sick animals that received experimental treatment, lived on average 85% longer than the ones in the reference group that did not receive the treatment. Prolonged remission was observed with more than 20% of rats – six months after the treatment, no further tumor growth was detected with these animals.

The researchers have managed to demonstrate one more important benefit of the drug formulation developed by them. It has turned out that the Doxorubicine-nanoparticle complex penetrates worse into animals’ heart and testicles than Doxorubicine does alone, and consequently, toxic action on these organs reduced in the course of treatment.

Source of information: Gelperina S.E., Khalansky A.S., Shvets V.I. “Chemotherapy of experimental glioblastoma with the help of nanocormial form of Doxorubicine”. Report theses for the “Nanotechnologies in Oncology 2010” conference.

Further information: Gelperina Svetlana Emmanuilovna, Director for Science, Research and Production Complex “Nanosystem”, svetlana.gelperina@gmail.com

Researchers at the Ioffe Technical Physical Institutehave developed a new method of synthesising composite materials from synthetic opal and vanadium oxides. Such materials have unusual optical properties. Previously, they were generated by depositing vanadium oxides (V₂O₅ and VO₂) from a solution, but in their latest work the researchers demonstrated the greater effectiveness of using melted vanadium oxide V₂O₅.

Synthetic opal presents a porous matrix consisting of silicon dioxide (SiO₂). Two types of such matrixes exist — these are three-dimensional and film. Nanocomposites where opal pores are filled with vanadium oxides invoke significant interest. Such structures can be used as gas sensors, switches and limiters of visible and infrared light emission. In addition, nanocomposites have the properties of three-dimensional photon crystal. It means that their structure is characterised with periodic changes in the refractive index. Such substances are capable of capturing photons and are of great demand in optoelectronics.

Today, nanocomposite opal-V₂O₅ and opal-VO₂ are produced using solution methods, that is, wash the matrix in the oxide solution until its pores are filled. The process must be repeated several times which increases the production time; it also leads to unwanted impurities in the resultant material.

Dmitry Kurdyukov and his colleagues suggested and tested a new method to synthesise such nanocomposites. The study report was published in the Solid-State Physicsmagazine. The researchers used melted vanadium oxide (V₂O₅) and an opal sample previously synthesised on the fused quartz substrate. The substances were put into the crucible at the temperature of 690°С, and were further heated uniformly. The vanadium oxide melt moistens the surface of silicon dioxide which allows it to fill the pores in the opal crystal completely. Cooling of the mixture results in the desired nanocomposite. The metal oxide shrinks with cooling and therefore the opal pores get only 70 per cent filled but this level of filling allows the material to preserve its properties. Based on the resulting opal-V₂O₅ it is possible to produce opal-VO₂ – it requires a reaction of vanadium oxide reduction with hydrogen in the pores of the sample.

In order to confirm that the new methodology resulted in the synthesis of the desired nanocomposite, the researchers used the data provided by electron microscopy and Raman spectroscopy. The created substance was subjected to chemical etching to remove vanadium oxides from the near-surface opal layers. The scientists note that the nanocomposites generated after the synthesis have areas of lower pore filling levels, that concentrate near the surface. At the same time, the level of filling the pores located close to the substrate reaches 100 per cent. It means that the development of the three-dimensional photon-crystal structure begins during the first stage of the nanocomposite processing.

Source of information: D. А. Kurdyukov, S. А. Grudinkin, А. V. Nashchekin, N. Smirnov, Е. Yu. Trofimov, М. А. Yagovkina, А. B. Pevtsov, V. G. Golubev: “Melting Synthesis and Structural Properties of opal-V₂O₅ and opal-VO₂ nanocomposites.” The Solid-State Physics, 2011, vol. 53, issue 2

Further information: Dmitry Kurdyukov, the Ioffe Technical Physical Institute, Russian Academy of Sceinces, (812)292-73-93 E-mail: Kurd@gvg.ioffe.ru. Sergey Grudinkin, the Ioffe Technical Physical Institute, Russian Academy of Sceinces, (812)292-73-93 E-mail: Grudink@gvg.ioffe.ru

Specialists at the A.F. Ioffe Institute of Applied-Physics (Russian Academy of Sciences) have developed a new methodology for nano-dimensional heterostructure composition analysis. Along with the composition, the depth of layer occurrence is also identified. Experimental check of the methodology has proved that the data obtained through it on semiconductor structure constitution well agrees with measurement results achieved by other method, the data having low error.

Layer structures consisting of semiconductors with different width of forbidden band (i.e., with different conductivity) are known as heterostructures. Development of such materials is one of the most promising directions in nanotechnology advance. The 2000 Nobel prize was awarded to Academician Zh. I. Alferov for “advancement of semiconductor heterostructures for high-speed optoelectronics”.

At the moment, heterostructures have found wide application in optoelectronics, various light-emitting diodes (LEDs). Their utilization in solar batteries also seems very promising. Researchers’ special attention is drawn by heterostructures with nano-dimensional semiconductor layers. However, at the moment there exists no universally recognized method for analysis of such materials, which creates great problems for their practical application.

Tatiana Popova and her colleagues at the A.F. Ioffe Institute of Applied Physics, Russian Academy of Sciences, have developed a new method for analysis of heterostructure composition with nano-dimensional layers and have written the software that enables to identify composition and the depth of analyzable structure and the depth of its layer occurrence. The work was published in the “Semiconductor Physocs and Technology”  journal.

X-ray spectroscopic analysis is one of widely applicable methods for analyzing substance. The substance is exposed to X-ray impact, atoms get actuated, thus enabling to judge about the specimen qualitative and quantitative composition by the amount of secondary X-rays quanta radiated by them. However, this method has an inadmissibly low accuracy when investigating nano-dimesional heterostructures because the layer depth is too small.

The researchers have developed a new algorithm of X-ray spectroscopic microanalysis that allows to reduce error of method. The signal is processed by a special program, which introduces a correction for small layer dimension. The layer dimension data required to this end is preliminary obtained via transmission electron microscopy. Besides, the obtained signal is compared to calibration signals obtained from substances of known composition, which also improves material identification accuracy.

To check the method, some samples of InGaAs and ZnCdSe (indium-gallium-arsenic and zinc-cadmium-selenium) heterostructures were measured. The researchers have confirmed that the material composition/structure data obtained via the new method well agrees with the data obtained via analyzing by X-ray diffraction and transmission electron microscopy, and it has low error. The researchers point out that the obtained results can be used to control the new heterostructure creation technology.

Source of information: “X-ray spectroscopic microanalysis of heterostructures with nano-dimensional layers”. Semiconductor Physics and Technology, 2011, Vol. 45, issue 2

Further information: Tatiana Borisovna Popova, A.F. Ioffe Institute of Applied-Physics, Russian Academy of Sciences, Tel.: + 7(812)292-73-93 E-mail: T.Popova@mail.ioffe.ru

Zamorianskaya Maria Vladimirovna, A.F. Ioffe Institute of Applied-Physics, Russian Academy of Sciences, Tel.: + 7 (812)292-73-93 E-mail: Zam@mail.ioffe.ru

Physicists from Yekaterinburg have generated yttrium-aluminum-garnet nanopowder using the laser-induced evaporation method. The powder with particles sized about 10 nanometers was used to create optic ceramics with a high infrared light transmission factor.

The laser-induced evaporation method also known as laser ablation or laser spark is based on removing a substance from the surface during laser irradiation. The method works in several stages: the material evaporation from the target; plasma torch development from the particles of the substance being irradiated; deposition and growth of the crystal material on the substrate. The process can be used for chemical analysis of substances as well as for technologies associated with surface processing and nanostructure generation.

The task of creating nanopowders with predetermined stoichiometry — that is, pre-determined ratio of the masses of chemical elements included in the powder — is a promising one. The main challenge of the technology is associated with excessive substance evaporation; therefore laser irradiation with optimum parameters is required. The laser used to produce the powder must be high-power and with a short radiation pulse at the same time. Experts at the Institute of Electrophysics, Ural Branch of Russian Academy of Sciences, suggested using carbon-dioxide laser for the purpose (the active environment of such laser is a gaseous mixture with a high level of CO₂ content). The physicists describe the advantages of such laser for generating nanopowders with predetermined stoichiometry in a report that is to be published in the January issue of the Letters to the Technical Physics Journal that is already made available at the journal Web site.

Physicists Vladimir Osipov, Vasily Lisenkov and Vyacheslav Platonov developed a theoretical model of the laser beam interaction with the substance, and subsequently confirmed the model experimentally. In order to obtain nanopowder, a laser complex consisting of a pulse-periodic CO₂ laser, evaporative chamber, and a separation and nanopowder capturing system was used. The laser received impulses with peak capacity of up to 10 kilowatt and repetition frequency of 500H. Yttrium and aluminium oxides served as impulse targets, with the particles sized from one to ten micron. As a result of ablation, the researchers generated an amorphous yttrium-aluminium oxide powder (also called yttrium aluminum garnet as synthetic precious stone is made from the substance on the microlevel). The size of the particle was 10 nanometer. The speed of the powder production depends on the radiant energy. The use of the CO₂ laser allowed to generate 24 grams of the powder per hour.

In order to show the practical importance of the resultant nanopowder, the researchers used it to make several samples of transparent optical ceramics. Such ceramics lets through 77 per cent of infrared radiation which makes it a promising material for electronics to manufacture infrared windows (areas transparent for infrared irradiation).

Source of information: “The Laser Synthesis of Nanopowders in the Yttrium Aluminum Garnet Stoichiometry,” V. V. Osipov, V. V. Lisenkov, V. V. Platonov, the Letters to the Technical Physics Journal, 2011, vol. 37, issue 1, pp. 103-110

Further information: Vasily Lisenkov, Ph. D. (Physics and Mathematics), the Quantum Electronics laboratory. Telephone: +7 (343) 267-87-79, e-mail: lisenkov@iep.uran.ru

Andrey Oksogoev at the Institute of High Technologies (Ulan-Ude) has carried out an experiment that proves assumptions made earlier. Research of S.P. Kurdumov’s school dealt with energy division into thermal and nonthermal components upon changes in the environment structure. This possibility is the most important objective for establishing self-organizing nanotechnologies.

A.A. Oksogoev carried out a numerical experiment on deformative analysis of metallic material collision with grit at threshold temperatures. The study of obtained outcomes enabled to single out a special mode called an intensification mode connected with heat inertia effect. Thus, the work done confirms the heat inertia effect predicted earlier and apparent in heat-conducting environments.

The intensification mode concept may become the basis for creating self-controlled (extreme) nanotechnologies. It will make possible to control metallic material properties during their synthesis, face-hardening processing and functioning of materials in a finished engineering construction.

The conducted investigation proves that when additional heat arrives in the environment, the heat does not spread but concentrates in a certain volume for some time. The computing experiment allowed to detect and to demonstrate manifestation of heat inertia effect with the intensification mode in the near-surface layer of the cup central zone in collision crater, as well as to study dynamics of temperature field front profile distribution at the point of grit recoil. To study the thermodeformative state of the near-surface barrier layer, the researchers used aluminium alloy type AVT-1, 8 mm thick, in the course of its high-speed interaction with the ShKh15 steel grit, Ø 4.0 mm.

Heat inertia effect becomes apparent upon increased energy «pumping» into the environment, heat dissipation (conversion of other types of energy into heat) does not spread for some time. The obtained heat concentrates in a certain existing volume. This system status accounts for transition from linear heat conductivity to non-linear one. This results in self-organization of structures that adapt the system to its new existence conditions.

Nanotechnologies development is directly connected with synergetics principle observance, which is the self-organizing systems theory. As follows from the above principles, to obtain considerable results, it is necessary to ensure conditions that meet the fullest adaptation of self-organizing structures to external action.

The distinction of traditional nanotechnologies from self-organizing ones is based on differences in the nature of energy sources that ensure environment structure changes. In the first case, environment structuring occurs at the expense of nonthermal (cold) part of released energy that ensures self-organization processes. In the second case, this happens owing to dissipation (conversion of other types of energy into heat) with the help of energy obtained by the system from environment.

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