Wozu Labor? Zur vernachlässigten Erkenntnistheorie hinter der Labordidaktik

Der Beitrag beleuchtet die Struktur und Funktion forschender Laborpraxis vor dem Hintergrund verschiedener erkenntnis- und wissenschaftstheoretischer Positionen. Das Labor kann in seiner Relevanz unterschätzt werden – mit Blick auf die darin verrichteten praktischen Tätigkeiten, auf dabei erforderliche Urteilsbildungen und nicht zuletzt auf unverzichtbare Impulse für die Wissenschaft. Die abstrakte Gegenüberstellung von Theorie und Praxis ist aufzugeben. Zugleich sollte Wissenschaft weder allein über das Labor noch über die Theoriebildung bestimmt werden. Abschließend plädiert der Beitrag dafür, die skizzierten Fragestellungen in die Labordidaktik sowie in die Planung und Durchführung von Lernlaboren einzubeziehen

Porous Ultra-Thin Films from Photocleavable Block Copolymers: In-Situ Degradation Kinetics Study of Pore Material

On the basis of the major application for block copolymers to use them as separation membranes, lithographic mask, and as templates, the preparation of highly oriented nanoporous thin films requires the selective removal of the minor phase from the pores. In the scope of this study, thin film of polystyrene-block-poly(ethylene oxide) block copolymer with a photocleavable junction groups based on ortho-nitrobenzylester (ONB) (PS-hν-PEO) was papered via the spin coating technique followed by solvent annealing to obtain highly-ordered cylindrical domains. The polymer blocks are cleaved by means of a mild UV exposure and then the pore material is washed out of the polymer film by ultra-pure water resulting in arrays of nanoporous thin films to remove one block. The removal of the PEO materials from the pores was proven using the grazing-incidence small-angle X-ray scattering (GISAXS) technique. The treatment of the polymer film during the washing process was observed in real time after two different UV exposure time (1 and 4 h) in order to draw conclusions regarding the dynamics of the removal process. In-situ X-ray reflectivity measurements provide statistically significant information about the change in the layer thickness as well as the roughness and electron density of the polymer film during pore formation. 4 H UV exposure was found to be more efficient for PEO cleavage. By in-situ SFM measurements, the structure of the ultra-thin block copolymer films was also analysed and, thus, the kinetics of the washing process was elaborated. The results from both measurements confirmed that the washing procedure induces irreversible change in morphology to the surface of the thin film

Recovery of noble metals by the use of functional adsorber textiles

Recikliranje i oporaba skupih plemenitih metala, poput platine, zlata, paladija i srebra, odnosno rijetkih i strateških metala, poput indija, galija i rijetki zemljanih metala iz otpadnih metala i otpadnih voda dobit će na važnosti u sljedećih nekoliko godina. Stoga je potrebno usmjeriti pozornost na iznalaženje potenijalno korisnih sekundarnih izvora i razvoj jeftinih i energetski štedljivih postupaka kojima bi se selektivno razdvojili i oporabili metali (urbano rudarstvo). Zajedno s elektroničkim otpadom, industrijski procesi i otpadna voda predstavljaju značajan izvor plemenitih metala. Nedavno smo uspješno razvili inovativni tekstilni filtarski materijal za adsorpciju metala temeljen na poliesterkim vlaknima oslojenim polivinilaminom. Površinske modifikacije vlaknatog materijala lako je postići konvencionalnim metodama tekstilne dorade i tako dobiti trajno adsorpcijsko sredstvo visoke učinkovitosti, a istovremeno niske cijene. Naši se rezultati temelje na uobičajenim postupcima teksilne dorade i na adsorpciji iona plemenitih metala ovisnoj o pH vrijednosti. Provedivost čitavog postupka prikazana je na postupku obrade vode bogate paladijem, dobivene od jednog njemačkog proizvođača tiskanih ploča. Pored toga, isti inovativni adsorpcijski materijal može se koristiti za pročišćavanje površinskih voda i tla zagađenih kromatima. Najnovija istraživanja usmjerena su na korištenje ovog materijala za selektivnu oporabu rijekih zemljanih metala iz industrijske proizvodnje FCC katalizatora za naftnu industriju.The recycling and recovery of high-prized noble metals such as platinum, gold, palladium and silver or rare and strategic metals like indium, gallium, and rare earth metals from scrap metals and wastewaters will be from steadily increasing importance within the next years. Therefore, the focus has to be set on the detection of potentially usable secondary resources and the development of inexpensive and energy-saving processes to separate and recover the metals selectively (urban mining). Beside electronic scrap industrial process and wastewaters represent a considerable source for noble metals. Recently, we have successfully developed an innovative metal-adsorbing textile filter material based on polyvinylamine-coated polyester fibers. The surface modification of the fibrous material is easy to realize with common methods in textile finishing yielding a durable, high-performing and even cheap adsorbent for water-dissolved metal ions. We present results on the general textile finishing procedure and the pH-depending adsorption of noble metal ions. The feasibility of the overall process is demonstrated on palladium containing process waters obtained from a German producer of curcuit boards. Moreover, the same innovative adsorber material is useful for the decontamination of chromate-polluted ground waters and soils. Our latest investigations focus their use in the selective recovery of rare earth metals from large-scale FCC catalyst production for the petroleum refining industry

Singlet-Oxygen Generation by Peroxidases and Peroxygenases for Chemoenzymatic Synthesis

Singlet oxygen is a reactive oxygen species undesired in living cells but a rare and valuable reagent in chemical synthesis. We present a fluorescence spectroscopic analysis of the singlet-oxygen formation activity of commercial peroxidases and novel peroxygenases. Singlet-oxygen sensor green (SOSG) is used as fluorogenic singlet oxygen trap. Establishing a kinetic model for the reaction cascade to the fluorescent SOSG endoperoxide permits a kinetic analysis of enzymatic singlet-oxygen formation. All peroxidases and peroxygenases show singlet-oxygen formation. No singlet oxygen activity could be found for any catalase under investigation. Substrate inhibition is observed for all reactive enzymes. The commercial dye-decolorizing peroxidase industrially used for dairy bleaching shows the highest singlet-oxygen activity and the lowest inhibition. This enzyme was immobilized on a textile carrier and successfully applied for a chemical synthesis. Here, ascaridole was synthesized via enzymatically produced singlet oxygen. © 2020 Wiley-VCH Gmb

SiCO Ceramics as Storage Materials for Alkali Metals/Ions: Insights on Structure Moieties from Solid‐State NMR and DFT Calculations

Polymer‐derived silicon oxycarbide ceramics (SiCO) have been considered as potential anode materials for lithium‐ and sodium‐ion batteries. To understand their electrochemical storage behavior, detailed insights into structural sites present in SiCO are required. In this work, the study of local structures in SiCO ceramics containing different amounts of carbon is presented. ¹³C and ²⁹Si solid‐state MAS NMR spectroscopy combined with DFT calculations, atomistic modeling, and EPR investigations, suggest significant changes in the local structures of SiCO ceramics even by small changes in the material composition. The provided findings on SiCO structures will contribute to the research field of polymer‐derived ceramics, especially to understand electrochemical storage processes of alkali metal/ions such as Na/Na⁺ inside such networks in the future

Preparation of a Textile-Based Dye-Sensitized Solar Cell

Solar energy conversion is an object of continuous research, focusing on improving the energy efficiency as well as the structure of photovoltaic cells. With efficiencies continuously increasing, state-of-the-art PV cells offer a good solution to harvest solar energy. However, they are still lacking the flexibility and conformability to be integrated into common objects or clothing. Moreover, many sun-exposed surface areas are textile-based such as garments, tents, truck coverings, boat sails, and home or outdoor textiles. Here, we present a new textile-based dye-sensitized solar cell (DSC) which takes advantage from the properties inherent to fabrics: flexibility, low weight, and mechanical robustness. Due to the necessary thermostability during manufacturing, our DSC design is based on heat-resistant glass-fiber fabrics. After applying all needed layers, the overall structure was covered by a transparent and simultaneously conductive protective film. The light and still flexible large-area devices (up to 6 cm2 per individual unit) are working with efficiencies up to 1.8% at 1/5 of the sun. Stability tests assure no loss of photovoltaic activity over a period of at least seven weeks. Therefore, our technology has paved the way for a new generation of flexible photovoltaic devices, which can be used for the generation of power in the mentioned applications as well as in modern textile architecture

Morphology and photoluminescence study of titania nanoparticles

Titania nanoparticles are prepared by sol–gel chemistry with a poly(ethylene oxide) methyl ether methacrylate-block-poly(dimethylsiloxane)-block-poly(ethylene oxide) methyl ether methacrylate triblock copolymer acting as the templating agent. The sol–gel components—hydrochloric acid, titanium tetraisopropoxide, and triblock copolymer—are varied to investigate their effect on the resulting titania morphology. An increased titania precursor or polymer content yields smaller primary titania structures. Microbeam grazing incidence small-angle X-ray scattering measurements, which are analyzed with a unified fit model, reveal information about the titania structure sizes. These small structures could not be observed via the used microscopy techniques. The interplay among the sol–gel components via our triblock copolymer results in different sized titania nanoparticles with higher packing densities. Smaller sized titania particles, (∼13–20 nm in diameter) in the range of exciton diffusion length, are formed by 2% by weight polymer and show good crystallinity with less surface defects and high oxygen vacancies

Entwicklung von Ausrüstungen zur Verbesserung der Scheuer- bzw. Abrasionsbeständigkeit von textilen Flächengebilden. - (DTNW-Mitteilung Nr. 108) - Forschungsvorhaben IGF-Nr. 18059 N der Forschungsvereinigung Forschungskuratorium Textil e.V., Reinhardtstr. 12-14, 10117 Berlin

Im Rahmen des Forschungsprojektes sollten die Möglichkeiten und Grenzen des Einsatzes von Sol-Gel-Ausrüstung für die Verbesserung der Scheuer-/Abrasionsbeständigkeit für Gewebe aus unterschiedlichen Fasermaterialien untersucht werden. Dabei lag der Schwerpunkt auf Textilien für die Bereiche Bekleidung- /Berufsbekleidung sowie Bezugsstoffe (Möbel, Automotive, Personentransport)