Structural and physical-chemical characterization of redox active CeO2nanoparticles synthesized by precipitation in water-alcohol solutions.

A set of cerium dioxide nanoparticles (CeO2NPs) was synthesized by precipitation in water-alcohol solutions under conditions when the physical-chemical parameters of synthesized NPs were controlled by changing the ratio of the reaction components. The size of CeO2NPs is controlled largely by the dielectric constant of the reaction solution. An increase of the percentage of Ce3+ions at the surface was observed with a concomitant reduction of the NP sizes. All synthesized CeO2NPs possess relatively high positive values of zeta-potential (ζ > 40 mV) suggesting good stability in aqueous suspensions. Analysis of the valence- and size-dependent rate of hydrogen peroxide decomposition revealed that catalase/peroxidase-like activity of CeO2NPs is higher at a low percentage of Ce3+at the NP surface. In contrast, smaller CeO2NPs with a higher percentage of Ce3+at the NP surface display a higher oxidase-like activity.

Biological activity of cerium dioxide nanoparticles.

Cerium dioxide nanoparticles (CeO2 NPs) with a high value of ζ-potential (≥30 mV) have been synthesized in reverse microemulsions and they are able to form the high-stable aqueous suspension without any additional stabilizers. It has been shown that the interaction of such CeO2 NPs with transport proteins, such as BSA, affects their molecular conformation and biochemical activity. The observed changes in the UV-absorbance spectrum and intrinsic fluorescence quenching of BSA molecule are indicative of the occurrence of structural changes caused by binding with the surface of CeO2 NPs. Low affinity between BSA and CeO2 NPs has been confirmed by differential scanning calorimetry (DSC). Moreover, CeO2 NPs can act as regenerative free-radical scavengers, and their antioxidant activity depends on the concentration. The positive charge of CeO2 NPs can be attributed to their low toxicity toward human malignant lymphocytes MT-4 and breast cancer cells MCF-7 however, the morphofunctional features of MCF-7 cells interacting with CeO2 NPs are indicative of the decrease in oncogenicity.

Profound Interfacial Effects in CoFe2O4/Fe3O4 and Fe3O4/CoFe2O4 Core/Shell Nanoparticles.

Two sets of core/shell magnetic nanoparticles, CoFe2O4/Fe3O4 and Fe3O4/CoFe2O4, with a fixed diameter of the core (~ 4.1 and ~ 6.3 nm for the former and latter sets, respectively) and thickness of shells up to 2.5 nm were synthesized from metal chlorides in a diethylene glycol solution. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, and magnetic measurements. The analysis of the results of magnetic measurements shows that coating of magnetic nanoparticles with the shells results in two simultaneous effects: first, it modifies the parameters of the core-shell interface, and second, it makes the particles acquire combined features of the core and the shell. The first effect becomes especially prominent when the parameters of core and shell strongly differ from each other. The results obtained are useful for optimizing and tailoring the parameters of core/shell spinel ferrite magnetic nanoparticles for their use in various technological and biomedical applications.

Effect of Synthesis Method of La1 - xSr x MnO3 Manganite Nanoparticles on Their Properties.

Nanoparticles of lanthanum-strontium manganite were synthesized via different methods, namely, sol-gel method, precipitation from non-aqueous solution, and precipitation from reversal microemulsions. It was shown that the use of organic compounds and non-aqueous media allowed significantly decreasing of the crystallization temperature of nanoparticles, and the single-phased crystalline product was formed in one stage. Morphology and properties of nanoparticles depended on the method and conditions of the synthesis. The heating efficiency directly depended on the change in the magnetic parameters of nanoparticles, especially on the magnetization. Performed studies showed that each of these methods of synthesis can be used to obtain weakly agglomerated manganite nanoparticles; however, particles synthesized via sol-gel method are more promising for use as hyperthermia inducers.PACS: 61.46.Df 75.75.Cd 81.20. Fw.

Effect of Synthesis Temperature on Structure and Magnetic Properties of (La,Nd)0.7Sr0.3MnO3 Nanoparticles.

Two sets of Nd-doped La0.7Sr0.3MnO3 nanoparticles were synthesized via sol-gel method with further heat treatment at 1073 and 1573 K, respectively. Crystallographic and magnetic properties of obtained nanoparticles were studied, and the effect of synthesis conditions on these properties was investigated. According to X-ray data, all particles crystallized in the distorted perovskite structure. Magnetic parameters, such as saturation magnetization, coercivity, Curie temperature, and specific loss power, which is released on the exposure of an ensemble of nanoparticles to AC magnetic field, were determined for both sets of samples. The correlation between the values of Curie temperature and maximal heating temperature under AC magnetic field was found. It was revealed that for the samples synthesized at 1573 K, the dependences of crystallographic and magnetic parameters on Nd content were monotonous, while for the samples synthesized at 1073 K, they were non-monotonous. It was concluded that Nd-doped La0.7Sr0.3MnO3 nanoparticles are promising materials for self-controlled magnetic hyperthermia applications, but the researchers should be aware of the unusual behavior of the particles synthesized at relatively low temperatures.

Iron-Doped (La,Sr)MnO3 Manganites as Promising Mediators of Self-Controlled Magnetic Nanohyperthermia.

Fe-doped La0.77Sr0.23Mn1 - y Fe y O3 nanoparticles have been synthesized by sol-gel method, and ceramic samples based on them were sintered at 1613 K. Crystallographic and magnetic properties of obtained nanoparticles and ceramic samples have been studied. It has been established that cell volume for nanoparticles increases with growing of iron content, while this dependence displays an opposite trend in the case of ceramic samples. Mössbauer investigations have shown that in all samples, the oxidation state of iron is +3. According to magnetic studies, at room temperature, both nanoparticles and ceramic samples with y ≤ 0.06 display superparamagnetic properties and samples with y ≥ 0.08 are paramagnetic. Magnetic fluids based on La0.77Sr0.23Mn1 - y Fe y O3 nanoparticles and aqua solution of agarose have been prepared. It has been established that heating efficiency of nanoparticles under an alternating magnetic field decreases with growing of iron content.