Morphology-Controlled Green Synthesis of Magnetic Nanoparticles Using Extracts of 'Hairy' Roots: Environmental Application and Toxicity Evaluation.

Magnetic nanoparticles (MNPs) were "green" synthesized from a FeCl3/FeSO4/CoCl2 mixture using ethanolic extracts of Artemisia tilesii Ledeb 'hairy' roots. The effect of chemical composition and reducing power of ethanolic extracts on the morphology, size destribution and other features of obtained MNPs was evaluated. Depending on the extract properties, nanosized magnetic materials of spherical (8-11 nm), nanorod-like (15-24 nm) and cubic (14-24 nm) shapes were obtained via self-assembly. Microspherical MNPs composed of nanoclusters were observed when using extract of the control root line in the synthesis. Polyhedral magnetic nanoparticles with an average size of ~30 nm were formed using 'hairy' root ethanolic extract without any additive. Studied samples manifested excellent magnetic characteristics. Field-dependent magnetic measurements of most MNPs demonstrated a saturation magnetization of 42.0-72.9 emu/g with negligible coercivity (∼0.02-0.29 emu/g), indicating superparamagnetic behaviour only for solids with a magnetite phase. The synthesized MNPs were minimally aggregated and well-dispersed in aqueous medium, probably due to their stabilization by bioactive compounds in the initial extract. The nanoparticles were tested for magnetic solid-phase extraction of copper (Cu), cadmium (Cd) and arsenic (As) pollutants in aqueous solution, followed by ICP-OES analysis. The magnetic oxides, mainly magnetite, showed high adsorption capacity and effectively removed arsenic ions at pH 6.7. The maximum adsorption capacity was ~150 mg/g for As(III, V) on the selected MNPs with cubic morphology, which is higher than that of previously reported adsorbents. The best adsorption was achieved using Fe3O4-based nanomaterials with low crystallinity, non-spherical form and a large number of surface-localized organic molecules. The phytotoxicity of the obtained MNPs was estimated in vitro using lettuce and chicory as model plants. The obtained MNPs did not exhibit inhibitory activity. This work provides novel insights on the morphology of "green" synthesized magnetic nanoparticles that can be used for applications in adsorption technologies.

High-Yielding Green Hydrothermal Synthesis of Ruthenium Nanoparticles and Their Characterization.

Using hydrothermal techniques, a novel synthetic approach to prepare ruthenium nanoparticles has been developed. At 180 degrees C and under autogenous pressure, starting from an aqueous solution of ruthenium trichloride, the method yielded nanoparticles whose form and size both depended on the reducing agent: sodium citrate (hexagonal shaped nanocrystals, 1-20 nm), ascorbic acid (spherical nanoparticles, 3-5 nm) and succinic acid (spherical nanoparticles, 1-120 nm). Depending on the reaction variables, the nature and concentration of partially reduced species determines the characteristics of the final products. HRTEM image analysis along with the simulation techniques were stabilized preferential growth of nanoparticles on specific directions. Ruthenium samples have been investigated by Temperature-Programmed Reduction (TPR) showing that the reduction temperature of nanoparticles is correlated to their nanocrystalline size.