In the present study, ZnO nanostructures have been successfully synthesized by hydrothermal, sonochemical and precipitation methods using polyvinyl pyrrolidone (PVP) as the capping agent. The ZnO nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-Visible spectroscopy and photoluminescence (PL) techniques. The XRD results revealed the hexagonal wurtzite structure of the ZnO nanostructures for all the samples. Furthermore, the morphology of the ZnO particles was obtained from FESEM micrographs. Particles prepared by hydrothermal method were found to be rice grain shaped and that prepared by precipitation and sonochemical methods were spherical shaped. Sunlight driven photocatalytic degradation of methylene blue (MB) was studied for ZnO nanostructures synthesized by various methods. The ZnO nanostructures were further decorated with Ag nanoparticles to enhance its dye degradation efficiency. The Ag decorated ZnO nanoparticles exhibited a higher degradation rate as compared to pure ZnO nanoparticles which was independent of pH. Since this process of dye degradation relies on the degradation of dye due to oxidation by highly reactive hydroxyl radicals, there are many factors which affect the efficiency of this process. Hence a study was conducted on the effect of various parameters on ZnO viz amount of catalyst, reaction pH and concentration of MB dye.
The boundary between the boreal and arctic biomes in northwest Europe has been a
matter of debate for many years. Some authors consider that the boundary is
marked by the northern limit of tree growth in the northernmost Norwegian
mainland. In this study we have collected air and soil temperature data from 37
heath stands from northern Finnmark (71°N), the northernmost part of the
Norwegian mainland, through Bear Island (74°N) in the Barents sea, to
Adventsdalen (78)°N (in Spitsbergen) in Svalbard archipelago. In Finnmark, plots
both south and north of the treeline were investigated. Vegetation and soil
chemistry analyses were performed on the plots in Finnmark and Svalbard.
Significant decreasing south-north trends in air and soil temperatures were
observed from Finnmark to Spitsbergen. Soils in Finnmark were acidic and rich in
organic matter, while those on Adventsdalen were basic and poor in organic
matter. Vegetational analysis identified five communities: three in Finnmark and
two on Adventsdalen. The communities in Finnmark had marked mutual similarities
but were very different from those on Adventsdalen. No significant ecological
differences between heaths south and north of the treeline in Finnmark were
observed. Air and soil temperature variables in Finnmark were outside the
recognized range for the arctic biome and inconsistent with the presence of
permafrost both south and north of the treeline. A major difference between
Finnmark and Spitsbergen was amount of soil frost and length of the growing
season. Our results suggest that the boreal biome extends all the way to the
north coast of mainland Norway; and previously used division of heaths in
Finnmark into boreal, alpine and arctic biomes is not justified.
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