Zinc oxide (ZnO) powders with diverse morphologies were synthesized with various solvothermal techniques.Water, 1-butanole and ethylene glycol were used as the solvents, while the temperature of the solvothermal synthesis was varied from 90 °C to 120 °C. Resazurin and caffeine were used for the evaluation of the photocatalytic activity of all the prepared samples, and in particular to compare ZnO with commercial titanium dioxide photocatalytic material (P25 Evonik Degussa) using UV–vis spectroscopy. The composition, crystallinity, and morphology of the prepared materials were investigated with FTIR, XRD, TEM and FEG-SEM techniques. The band gaps of the obtained semiconductors were measured because the band gap of hydrozincite, determined in this study to be 4.1 eV, has not been reported previously.The specific surface area (BET) and the porosity of the prepared particles were estimated. The crystal size in one dimension was estimated and was found to play an important role in the photocatalytic activity, which increased with a smaller size. A higher degree of aggregation caused the opposite effect. Thus, a more aggregated material with a larger surface area than a less aggregated one exhibited a lower photocatalytic activity. The particle morphology strongly influenced the photocatalytic process.
COBISS.SI-ID: 5188890
We report on the synthesis of highly transparent and UV-absorbing PMMA/ZnO nanocomposites prepared by hydrolysis of a ZnO precursor, the A-b-(AB) diblock copolymer, poly(methyl methacrylate)-block-poly(methyl methacrylate-co-(zinc methacrylate acetate)), PMMA-b-P(MMA-co-ZnMAAc), synthesized by RAFT polymerization. The zinc content of the block copolymers was in the range from 3 to 13 wt%. The PMMA block provides inherent compatibility with the PMMA matrix, whereas the second block, P(MMA-co-ZnMAAc) with zinc ions, acts as a polymeric precursor for the formation of ZnO nanoparticles. The amphiphilic block copolymer self-organizes in THF and THF/H2O in ordered nanostructures, thereby influencing the nanoparticle formation during the hydrolysis of the precursor block copolymer with KOH in a solvent mixture THF/H2O. The ZnO nanoparticles were rod-shaped with lengths up to 80 nm and a diameter of 14 nm and were redispersible in THF. Dispersions in THF and thin films of PMMA/ZnO nanocomposite exhibit excellent transparency in the visible range and good absorption in the UV range below 400 nm. The block copolymer was characterized by SEC, NMR, DLS, and TGA, while PMMA/ZnO nanocomposites were characterized by IR, XRD, UV-vis, and STEM.
COBISS.SI-ID: 5295642
In the present work, we studied the rheological properties of TISS paints and their effect on the spectral selectivity of dry coatings, which were applied on the substrate with the spraying application method. The final aim of our study was to determine the influence of spraying parameters (nozzle, spray gun pressure, and speed of substrate) on the selectivity and to establish the phenomenon of pigment distribution and flake orientation during spraying application.
COBISS.SI-ID: 5163802
This publication is important result of slovenian research project Z1-4219. Syntheses of various N-Heterocyclic carbenes (NHC) and their precursors is presented. NHC could be used as powerful catalysts for the preparation of various polyhedral silsesquioxanes. NHCs also catalyze a rearrangement of existing cages and a scrambling between two different cages. For this purpose either free isolable carbenes or their cryptoforms could be used. Polyhedral silsesquioxanes could be prepared from hydrolyzates of trifunctional silanes, silsesquioxane resins or existing silsesquioxane cages in process where these precursors are exposed to organocatalytic action of carbenes in organic solvent at appropriate temperature. Carbenes are excellently soluble in reaction media so they are active at a concentrations as low as 1 mol%.
COBISS.SI-ID: 5241626
Transformation of commercially available products in the environment may result in the formation of a wide array of their metabolites. Personal care products in swimming pools and in drinking water reservoirs may undergo oxidation or chlorination. Therefore, reliable identification of all possible transformation products as well as a thorough study of their physicochemical and biological properties is of high priority. The present study deals with the identification of the products of the aquatic chlorination of the DHHB UV filter. HPLC/MS and HPLC/MS/MS with accurate mass measurements were used for this purpose. As a result three chlorinated transformation products were identified.
COBISS.SI-ID: 2932731