Papers by Keyword: Ureasil

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Authors: Julia T. Gonçalves, Victor I. Boev, Alexey Solovyev, Carlos J.R. Silva, M.J.M. Gomes
Abstract: Transparent hybrid organic-inorganic ureasil xerogels with embedded PbS nanoparticles were prepared by exposing the xerogels doped with lead (II) nitrate to hydrogen sulphide atmosphere. Absorbance spectrum of the nonocomposites showed well defined peaks at 560 nm and 370 nm attributed to 1s(v) - 1s(c) and 1s(v) - 2p(c) exciton transitions, respectively. After four days of thermal treatment at 50 °C under argon atmosphere the obtained materials showed enhanced photoluminescence response in the near infra-red region.
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Authors: Taras Kavetskyy, Ondrej Šauša, Jozef Krištiak, Tamara Petkova, Plamen Petkov, Viktor Boev, N. Lyadov, Andrey L. Stepanov
Abstract: The new organic-inorganic materials, based on polyether chains covalently linked to a silica framework through urea bridges, referred as ureasilicates or ureasils, and semiconducting As2S3-ureasil composites are investigated using positron annihilation lifetime spectroscopy (PALS) and scanning electron microscopy (SEM) techniques. The results obtained show that incorporation of the As2S3 clusters into ureasil affects on the ortho-positronium (o-Ps) intensity or positronium formation probability and micro-/nanoscopic structure compared to the pure polymer, the effect is more essential as the loading fraction of As2S3 increases.
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