In Vivo Quantitative Study of Sized-Dependent Transport and Toxicity of Single Silver Nanoparticles Using Zebrafish Embryos

Nanomaterials possess distinctive physicochemical properties (e.g., small sizes and high surface area-to-volume ratios) and promise a wide variety of applications, ranging from the design of high quality consumer products to effective disease diagnosis and therapy. These properties can lead to toxic effects, potentially hindering advances in nanotechnology. In this study, we have synthesized and characterized purified and stable (nonaggregation) silver nanoparticles (Ag NPs, 41.6 ± 9.1 nm in average diameter) and utilized early developing (cleavage-stage) zebrafish embryos (critical aquatic and eco- species) as in vivo model organisms to probe the diffusion and toxicity of Ag NPs. We found that single Ag NPs (30-72 nm diameters) passively diffused into the embryos through chorionic pores via random Brownian motion and stayed inside the embryos throughout their entire development (120 hours-post-fertilization, hpf). Dose-and size-dependent toxic effects of the NPs on embryonic development were observed, showing the possibility of tuning biocompatibility and toxicity of the NPs. At lower concentrations of the NPs (≤0.02 nM), 75-91% of embryos developed into normal zebrafish. At the higher concentrations of NPs (≥0.20 nM), 100% of embryos became dead. At the concentrations in between (0.02-0.2 nM), embryos developed into various deformed zebrafish. Number and sizes of individual Ag NPs embedded in tissues of normal and deformed zebrafish at 120 hpf were quantitatively analyzed, showing deformed zebrafish with higher number of larger NPs than normal zebrafish and size-dependent nanotoxicity. By comparing with our previous studies of smaller Ag NPs (11.6 ± 3.5 nm), we found striking size-dependent nanotoxicity that, at the same molar concentration, the larger Ag NPs (41.6 ± 9.1 nm) are more toxic than the smaller Ag NPs (11.6 ± 3.5 nm)

Correlations of Mechanical Stresses and Magnetical Behaviour of Ion Implanted Magneto-Optical Layers

Magneto-optical materials such as TbFeCo are used for data storage in a wide range. Especially the perpendicular magnetic anisotropy is necessary for high density recording. But the origin of the perpendicular magnetic anisotropy in these magneto-optical layers is not exactly known. In our experiments magneto-optical layers were implanted with heavy ions, with the aim to change the magnetic behaviour of these layers. After the implantation there is a dramatical change in the magnetical and mechanical behaviour, too

Photophysics of nanostructured metal and metal-contained composite films

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Tuning the surface plasmon resonance by preparation of gold-core/silver-shell and alloy nanoparticles

For many applications like surface enhanced Raman scattering or fluorescence microscopy in which the optical field enhancement associated with surface plasmon excitation is exploited, tunability of this collective resonance over a wide energy range is required. For this purpose we have investigated Au/Ag alloyed and Au-core/Ag-shell nanoparticles with different shell thicknesses. The core-shell nanoparticles were prepared by subsequent deposition of Au and Ag atoms on quartz substrates followed by diffusion and nucleation. The surface plasmon frequency could be stabilized at 2.2 eV independent of the Ag-shell thickness. Annealing of the core-shell nanoparticles makes possible tuning of the resonance frequency from 2.2 eV ($\lambda = 564$ nm) to 2.6 eV ($\lambda = 477$ nm). Theoretical modelling allows us to attribute this observation to the formation of alloy nanoparticles