Magnetic study of nanocrystalline 0.95MnO/0.05ZnO

Nanocrystalline 0.95MnO/0.05ZnO sample has been prepared by coprecipitation and calcination processes. X-ray diffraction showed the presence of Mn 3O 4 nanocrystallites with an average size of 43 nm. Magnetic properties of the 0.95MnO/0.05ZnO sample have been investigated by dc magnetization and magnetic resonances (electron paramagnetic resonance (EPR), ferromagnetic resonance (FMR)) methods. The magnetization study has shown the presence of dominating Mn 3O 4 paramagnetic and ferrimagnetic (below 46 K) phases. The blocking temperature determined from magnetization measurements was 41 K. An FMR study has shown the evidence of the spread of nanoparticles sizes. An EPR signal from paramagnetic phase of Mn 3O 4 was observed at temperatures above 45 K and from defects/spurious phases in the low temperature range (T<16 K). Magnetic anisotropies of the sample in the FMR spectra were taken into account by fitting the observed spectra by two lines corresponding to parallel and perpendicular orientations of nanoparticles in an applied magnetic field. © 2012 Elsevier B.V

Synthesis of antimicrobial silver nanoparticles through a photomediated reaction in an aqueous environment

Rafał Banasiuk,1,* Joanna E Frackowiak,2,* Marta Krychowiak,1 Marta Matuszewska,1 Anna Kawiak,1 Magdalena Ziabka,3 Zofia Lendzion-Bielun,4 Magdalena Narajczyk,5 Aleksandra Krolicka1 1Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, 2Department of Pathophysiology, Medical University of Gdansk, Gdansk, 3Faculty of Materials Science and Ceramics, Department of Ceramics and Refractories, AGH-University of Science and Technology, Kraków, 4Institute of Chemical and Environment Engineering, West Pomeranian University of Technology, Szczecin, 5Faculty of Biology, Laboratory of Electron Microscopy, University of Gdansk, Gdansk, Poland *These authors contributed equally to this work Abstract: A fast, economical, and reproducible method for nanoparticle synthesis has been developed in our laboratory. The reaction is performed in an aqueous environment and utilizes light emitted by commercially available 1 W light-emitting diodes (λ =420 nm) as the catalyst. This method does not require nanoparticle seeds or toxic chemicals. The irradiation process is carried out for a period of up to 10 minutes, significantly reducing the time required for synthesis as well as environmental impact. By modulating various reaction parameters silver nanoparticles were obtained, which were predominantly either spherical or cubic. The produced nanoparticles demonstrated strong antimicrobial activity toward the examined bacterial strains. Additionally, testing the effect of silver nanoparticles on the human keratinocyte cell line and human peripheral blood mononuclear cells revealed that their cytotoxicity may be limited by modulating the employed concentrations of nanoparticles. Keywords: antimicrobial activity, green synthesis, nanocubes, nanospheres&nbsp

Preferential oxidation of carbon monoxide in hydrogen-rich streams over CuO/CeO2 catalysts: How nano (and subnano) structure affects catalytic activity and selectivity

Preferential oxidation of carbon monoxide in hydrogen-rich streams needs a suitable catalyst that selectively oxidizes CO avoiding H2 oxidation. Among the proposed catalysts, copper oxide supported on ceria (CuO/CeO2) received wide interest due to its intrinsic activity and selectivity and low cost with respect to noble metals. In particular, it has been shown that the performances are significantly affected by optimizing the copper-ceria interaction, and then the copper dispersion. In this light, reducing to nanoscale levels has been proven to be the solution. In this chapter, results of the effect of nano and subnano structures of CuO/CeO2 catalysts on the CO-PROX performance are reviewed and critically discussed. At nanosize, Cu dispersion and oxygen mobility are both enhanced. Furthermore, the copper reduction to the metallic Cu (H2 oxidation sites) is limited and CO2 desorption is activated at lower temperatures. The role of dopants and/or supports as graphene and carbon nanotubes in improving the intrinsic activity and the resistance to the inhibiting effect of carbon dioxide and water vapor are also discussed, highlighting the effect of dopants on the modification of the redox properties by increasing bulk and/or surface oxygen vacancies