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Adsorption equilibriums in aqueous aluminum and iron oxides nanosuspensions stabilized by SDBS and TX-100 were investigated using UV spectrophotometry. It was established that the non-ionic surfactant TritonX-100 is not adsorbed from aqueous solution on a hydrophilic surface of both aluminum and iron oxide nanoparticles. At the same time adsorption of the anionic surfactant SDBS was observed in both oxides nanoparticles. In the investigated range of concentrations adsorption isotherms SDBS from aqueous solution on the surfaces of nanoparticles Al 2 O 3 and γ-Fe 2 O 3 not reach saturation. The share of the particles surface occupied by surfactant molecules were estimated based on the value of an area of molecules SDBS in the adsorption layer, which was derived from the isotherm of surface tension (0.10 nm2). The calculations showed that at the investigated concentrations SDBS Al 2 O 3 employed approximately 30 % of surface of nanoparticles, and for γ-Fe 2 O 3 – up to 10%.

Deaggregated nonaqueous suspensions of ZrO2 nanopowders stabilized by Y2O3 (YSZ) with an average diameter of particles of 11 nm obtained by laser evaporation and condensation are studied using dynamic light scattering (DLS). Two types of suspensions with an average size of aggregates of 108 and 66 nm are obtained by ultrasonic machining (USM) and centrifugation. It is shown that the combination of USM and centrifugation allows us to obtain narrow size distributions for the particles in YSZ suspensions. Coatings are obtained using electrophoretic deposition (EPD) from two types of YSZ suspensions with different degrees of deaggregation, and it is shown that no difference in the structure and morphology of suspensions is observed. It is established that, by EPT of the particles, a mechanism of electrochemical coagulation is realized at the electrode from the suspensions with different degrees of deaggregation.

This paper studies the echo-contrast properties of an alumina nanopowder suspension using ultrasonography (US) fully corresponding in its characteristics to the techniques of medical ultrasound diagnostics of organs and tissues. The purpose of this study was to search for the possible effect of the ionic and protein composition of the biological medium on the intensity of the reflected echo signal of the contrast material based on nanoparticles. It was found that the pH of the blood promotes the maximum use of echo contrast options of alumina nanopowder suspensions. Particle size measurements in the suspension using the dynamic light scattering technique showed the stabilizing effect of blood serum and plasma on the nanopowder suspension, resulting in the attenuation of the echo signal. The data offer a basis for the development of new contrast materials based on nanoparticles for the ultrasound imaging of the heart and blood vessels. The considered mechanisms of the established phenomena make it possible to elucidate the processes of interaction of metal oxide nanoparticles with biological molecules. © 2013 Pleiades Publishing, Ltd.

The aggregation of air-dry Al2O3 nanopowders prepared by electrical wire explosion (EWE) and plasma deposition in a gas atmosphere was studied by dynamic laser light scattering during redispersion in water. The specific surface of nanopowders was from 9 to 38 m2/g. It was shown that aqueous suspensions of nanopowders stabilized by a double electric layer with an electrokinetic ξ-potential magnitude of 30–40 mV contain coexisting individual particles and their primary aggregates (35–50 wt %). The average size of the primary aggregate is approximately three times larger than the average size of an individual particle. The former probably consists of a central particle surrounded by the first coordination sphere. As the medium pH varies from 2.5 to 11.5, the electrokinetic potential of the Al2O3 nanoparticle suspension monotonically decreases from +40 to −40 mV. Near the isoelectric point (IEP), aggregation is significantly enhanced, which results in the formation of larger secondary aggregates of 103–104 individual particles. The use of Na citrate as an electrostatic stabilizer prevents the formation such large aggregates, and only an increase in the fraction of primary aggregates and a decrease in the number of individual particles occur near the IEP.

The feasibility of using aqueous suspensions of several metal oxide nanoparticles as contrast agents for ultrasonic cardiovascular visualization has been investigated. Nanopowders of Al, Fe, and Zr oxides were prepared by the electrical explosion of metallic wires, and characteristics such as particle size, specific area, and particle size distribution, were obtained, as were TEM photographs. Dynamic light-scattering data demonstrated that the aggregation of nanoparticles took place in their aqueous suspensions in the function of mean particle size. Acoustic properties of stable suspensions of nanopowders were studied in an experimental model of circulation with simultaneous measurements performed by a commercially available standard ultrasonic apparatus used in medical institutions. The results indicate that the intensity of the reflected echo signal depends on the chemical nature of the metal oxide and the structure of nanoparticles and aggregates that are formed in an aqueous medium. The presented data show the high ultrasonic echo activity of several metal oxides and, at the same time, form a scientific background for a better understanding of the interactions between nanoparticles and the ultrasonic wave.

The particle-size distribution, electrooptical potential, and acid properties of the surface of Al2O3 nanoparticles in aqueous media were studied by dynamic light scattering, electroacoustic spectral analysis, and potentiometric titration. The nanopowder with the mean particle size 22 nm was obtained by the oxidation of aluminum wire in the vapor phase using electrical explosion in oxygen-argon mixture. In spite of the presence of aggregates, aqueous suspensions of nanoparticles, as distinct from suspensions of micropowders, are stable without the addition of special stabilizers because of the spontaneous formation of a double electrical layer on their surface, the electrokinetic potential of which is positive and exceeds 30 mV. The most probable reason for electrostatic self-stabilization of suspensions of nanopowders is the adsorption of Al ions formed in the hydrolysis of aluminum nitrates, small amounts of which are produced in electrical discharges during preparation.

Magnetic nanoparticles of iron oxide (MNPs) were prepared by the laser target evaporation technique (LTE). The main focus was on the fabrication of de-aggregated spherical maghemite MNPs with a narrow size distribution and enhanced effective magnetization. X-ray diffraction, transmission electron microscopy, magnetization and microwave absorption measurements were comparatively analyzed. The shape of the MNPs (mean diameter of 9 nm) was very close to being spherical. The lattice constant of the crystalline phase was substantially smaller than that of stoichiometric magnetite but larger than the lattice constant of maghemite. High value of M s up to 300 K was established. The 300 K ferromagnetic resonance signal is a single line located at a field expected from spherical magnetic particles with negligible magnetic anisotropy. The maximum obtained concentration of water based ferrofluid was as high as 10g/l of magnetic material. In order to understand the temperature and field dependence of MNPs magnetization, we invoke the core-shell model. The nanoparticles is said to have a ferrimagnetic core (roughly 70 percent of the caliper size) while the shell consists of surface layers in which the spins are frozen having no long range magnetic order. The core-shell interactions were estimated in frame of random anisotropy model. The obtained assembly of de-aggregated nanoparticles is an example of magnetic nanofluid stable under ambient conditions even without an electrostatic stabilizer.

A total of 25130 newborns were examined, which was 91% of all babies born alive in the Krasnoyarsk region. For detecting hypothyrosis, TTH levels were measured in dry blood stains on special paper filters using Delfia diagnostic kit in accordance with the manufacturer’s instructions. Hyperthyrotropinemia was detected in 3.76% of all samples examined (primary positive results of screening), but subsequent examinations of newborns with suspected thyroid insufficiency confirmed congenital hypothyrosis in only 6 patients, or 0.99% of all infants examined repeatedly. In 99.01% of cases the detected hyperthyrotropinemia was transitory. According to the findings of neonatal screening, the incidence of congenital hypothyrosis was 1 per 4134 newborns. Congenital hypothyrosis is most often confirmed in cases with the primary positive value of TTH higher than 100 pU/ml. At lower TTH levels the probability of the diagnosis validation was lower, although not ruled out