Nowe fotoaktywne materiały w oparciu o TiO2TiO_2 modyfikowany pochodnymi antrachinonu

Zaadsorbowane na powierzchni nanokrystalicznego dwutlenku tytanu pochodne antrachinonu tworza nowy rodzaj fotoaktywnych materiałów hybrydowych. Układy te sa zbudowane z organicznych barwników zakotwiczonych na powierzchni półprzewodnika poprzez atomy tlenu grup hydroksylowych lub karbonylowych. Wiazanie pomiedzy barwnikiem a atomem tytanu na powierzchni półprzewodnika wykazuje silny charakter kowalencyjny, co czyni materiał stabilnym w szerokim zakresie potencjałów, a takze w srodowisku kwasnym. W srodowisku zasadowym materiał ulega hydrolizie. Elektrody na bazie modyfikowanego TiO2 generuja fotoprady w zakresie 300-700 nm, podczas gdy elektrody z czystego TiO2 daja fotoprady w zakresie 300-400 nm. Tak wydajna fotosensybilizacja jest wynikiem wzajemnego połozenie poziomów energetycznych czasteczki oraz pasmami półprzewodnika.Anthraquinone derivatives chemisorbed at nanocrystalline TiO2 present a new type of photoactive hybrid materials. These systems consist of organic chromophores anchored to the semiconductor surface via oxygen atoms of hydroxyl or carbonyl group. The bond between the chromophore and the titanium atom at the semiconductor surface reveals strong covalent character which makes the material stable in wide spectrum of electric potential and in an acidic environment. In alkaline solutions hydrolysis can be observed. The electrodes made of a modified TiO2 generate photocurrents within 300-700 nm, compared, with 300-400 nm for unmodified TiO2. Such an efficient photosensitization is a result of mutual arrangement of energy levels of the molecule and energy bands of the semiconductor

Nowa metoda syntezy binarnych faz tlenkowych o charakterze półprzewodnikowym w polu mikrofalowym - PbMoO4PbMoO_4 i PbWO4PbWO_4

Krystaliczne proszki molibdenianu ołowiu i wolframianu ołowiu otrzymano metodą hydrotermalną w polu mikrofalowym za pomocą wysokociśnieniowego autoklawu mikrofalowego. Metodę ta można uznać za przyjazną dla środowiska, jak dotad nie odnotowano jej zastosowania do syntezy wymienionych związków ołowiu. Zbadano wpływ czasu trwania procesu na strukturę krystaliczną, morfologię i szerokość przerwy energetycznej proszków PbWO4 i PbMoO4. Szerokość pasma wzbronionego wyznaczono za pomocą spektroskopii refleksyjnej. Dla molibdenianu ołowiu otrzymane wartości oscylują wokół 3.2 eV, natomiast dla wolframianu ołowiu przerwa energetyczna jest szersza i wynosi ok. 4 eV. Szerokość pasma wzbronionego w obu przypadkach nie zależy od czasu syntezy.Highly crystalline powders of lead molybdate and tungstate were synthesized by a microwave assisted hydrothermal process in a microwave heated high pressure autoclave. Application of this novel and environmentally friendly technique in the synthesis of these compounds has never been reported before. The influence of a time of synthesis on a crystal structure, morphology and a value of a band gap for both PbMoO4 and PbWO4 was examined. The value of the band gap was determined using diffuse reflectance spectroscopy. For lead molybdate the medium value of the band gap equals to ca. 3.2 eV whereas for lead tungstate it oscillates around 4 eV and does not depend on the duration time of the synthesis

In Situ Regeneration of Copper-Coated Gas Diffusion Electrodes for Electroreduction of CO2 to Ethylene

This research was funded by the European Union’s Horizon 2020 research and innovation program under grant agreement No 768789 as well as by the Polish National Centre of Science under grant no 2017/26/D/ST8/00508. The Institute of Solid State Physics, University of Latvia, as a center of excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement no. 739508, project CAMART2.A key challenge for carbon dioxide reduction on Cu-based catalysts is its low faradic efficiency (FE) and selectivity towards higher-value products, e.g., ethylene. The main factor limiting the possibilities of long-term applications of Cu-based gas diffusion electrodes (GDE) is a relatively fast drop in the catalytic activity of copper layers. One of the solutions to the catalyst stability problem may be an in situ reconstruction of the catalyst during the process. It was observed that the addition of a small amount of copper lactate to the electrolyte results in increased Faradaic efficiency for ethylene formation. Moreover, the addition of copper lactate increases the lifetime of the catalytic layer ca. two times and stabilizes the Faradaic efficiency of the electroreduction of CO2 to ethylene at ca. 30%. It can be concluded that in situ deposition of copper through reduction of copper lactate complexes present in the electrolyte provides new, stable, and selective active sites, promoting the reduction of CO2 to ethylene. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Published under the CC BY 4.0 license.--//-- This is the published version of the article Bisztyga-Szklarz, M.; Mech, K.; Marzec, M.; Kalendarev, R.; Szaciłowski, K. In Situ Regeneration of Copper-Coated Gas Diffusion Electrodes for Electroreduction of CO2 to Ethylene. Materials 2021, 14, 3171. https://doi.org/10.3390/ma14123171.Polish National Centre of Science 2017/26/D/ST8/00508; H2020 768789; H2020 739508 CAMART2

Supramolecular assemblies of semiconductor quantum dots and a bis(bipyridinium) derivative : luminescence quenching and aggregation phenomena

We have synthesized CdSe and CdSe–ZnS core–shell luminescent nanocrystal quantum dots and studied their interaction with a ditopic bis(bipyridinium) compound in solution. The latter strongly quenches the luminescence of the quantum dots by a static mechanism, indicating that the nanocrystal and molecular components undergo association in the ground state. Photoexcitation of these inorganic–organic hybrids causes an electron-transfer process from the conduction band of the nanocrystal to the LUMO of the molecule. The ability of the bipyridinium-type species to trigger association of the quantum dots is evidenced by spectrofluorimetric titrations and DLS measurements in solution, and confirmed by TEM experiments on surfaces. The quantum dot–molecule complexes can be disassembled in solution by addition of a calixarene host capable of encapsulating the bipyridinium units of the molecular connector. Our results demonstrate that supramolecular chemistry offers convenient ways to control the aggregation of semiconductor nanocrystals, a crucial task for the generation of nanostructured arrays with well defined properties