14 research outputs found

    Visible-to-UV/Violet Upconversion Dynamics in Er3+-Doped Oxyfluoride Nanoscale Glass Ceramics

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    Visible-to-UV/violet upconversion luminescence is found and studied in oxyfluoride glass ceramics with Er3+ dopant concentrations of 3.5, 6.0, or 12.0 mol%, covering a broad pump-power range. The glass ceramics with doping levels of 3.5 and 6.0 mol% show the strongest upconversion luminescence intensity when compared to both higher doping levels and the respective precursor glasses. A comprehensive analysis of the involved upconversion mechanisms is presented. These materials could be useful to enhance the efficiency of the water-splitting systems by using UV/violet light upconverted from the green and red parts of the solar spectrum, which are an alternative to photovoltaic solar cells. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.status: publishe

    Imprinting the nanostructures on the high refractive index semiconductor glass

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    The centimeter range one-and two-dimensional nanostructures of 70nm pitch have been imprinted by hot pressing with a quartz, silicon or nickel mold, at 240 degrees C, onto the surface of Ge20As20Se14Te46 semiconductor glass. Excellent glass stability of this glass allows multiple re-pressing of the nano-structures. With increasing the Te/Se ratio in the glass formula, the refractive index reaches a value of 3.5 with an option of free electron absorption at elevated temperatures pointing out the use of such nanostructures in submicron and micron scale electronic devices/chips, moth eye structures and photonic crystals. (C) 2011 Elsevier B. V. All rights reserved.status: publishe

    Light-matter interactions mediated by nanoscale confinement in plasmonic resonators

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    Plasmonic resonators are nanosized metallic antennas that convert electromagnetic waves at optical frequencies into localized fields, providing an effective route to couple photons in and out of nanoscale volumes. This unique ability makes these nanostructures excellent tools to study and manipulate light-matter interaction at the nanoscale. The strong coupling of a plasmonic resonator to light, resulting in optical cross-sections of more than 10 times the particle-s physical size, is driven by collective oscillations of the conduction electrons in the metal - the so-called surface plasmon resonances.2 page(s

    Energy-transfer luminescence of a zinc oxide/ytterbium oxide nanocomposite

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    © The Royal Society of Chemistry 2012. A newly structured nanocomposite material based on nanocrystalline ZnO/Yb 2 O 3 has been prepared by thermal decomposition of Yb-doped zinc carbonate hydroxide. Transmission electron microscopy has revealed that the prepared nanopowder consists of ZnO nanocrystals of about 50 to 100 nm size decorated by attached smaller Yb 2 O 3 nanocrystals of about 10 to 15 nm size. X-Ray absorption spectroscopy, in particular XANES and EXAFS, indicate the charge of Yb ions equals to +3 and their coordination is oxygen octahedral with the Yb-O and Yb-Yb interatomic distances the same as in bulk Yb 2 O 3 . Photoluminescence spectroscopy unambiguously proves an efficient excitation energy transfer from the ZnO nanocrystals to the Yb 3+ ions. The energy transfer from the ZnO nanocrystals (absorption range from 250 to 400 nm) to the Yb 3+ ions (emission range from 950 to 1100 nm) has been explained by a model, which considers the quantum cutting effect. The prepared nanocomposite is promising for application as a down-conversion layer for enhanced solar cells.status: publishe

    Use of Polyguanidine-Derivatives-Based Biocides for Microbial Growth Inhibition and for the Development of A Novel Polyethylene-Based Composite Material Resistant to the Formation of Multispecies Microbial Biofilms

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    This study aimed to investigate the dependence of the biocidal activity of polyguanidine (co)polymers on their structure during the formation of biofilms by active PE-degrading cultures of model microorganisms. The Bc-2 copolymer of methacryloyl guanidine hydrochloride (MGHC) and diallyldimethylammonium chloride (DADMAC), which suppressed both the formation of biofilms and the growth of planktonic cultures, exhibited the highest activity. When PE was exposed in tropical soil, the composition of the microbial community on the PE surface differed significantly from that of the community in the surrounding soil. In particular, the proportion of Actinobacteria increased from 7% to 29%, while the proportion of Bacteroidetes decreased from 38% to 8%. Keywords: biofilms, polyhexamethylene guanidine salts, dynamics of biofilm formation, antibiofilm effect, composite material

    Nonlinear Optical Properties of Ag Nanoclusters and Nanoparticles Dispersed in a Glass Host

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    The nonlinear absorption of Ag atomic clusters and nanoparticles dispersed in a transparent oxyfluoride glass host has been studied. The as-prepared glass, containing 0.15 atom % Ag, shows an absorption band in the UV/violet attributed to the presence of amorphous Ag atomic nanoclusters with an average size of 1.2 nm. Upon heat treatment the Ag nanoclusters coalesce into larger nanoparticles that show a surface plasmon absorption band in the visible. Open aperture <i>z</i>-scan experiments using 480 nm nanosecond laser pulses demonstrated nonsaturated and saturated nonlinear absorption with large nonlinear absorption indices for the Ag nanoclusters and nanoparticles, respectively. These properties are promising, e.g., for applications in optical limiting and object’s contrast enhancement
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