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Oberflächen- und Grenzflächenanalytik

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Application of near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) in an in-situ analysis of the stability of the surface-supported metal-organic framework HKUST-1 in water, methanol and pyridine atmospheres (2021)
Kjaervik, Marit ; Dietrich, P. M. ; Thissen, A. ; Radnik, Jörg ; Nefedov, A. ; Natzeck, C. ; Wöll, C. ; Unger, Wolfgang
Surface-supported metal-organic frameworks HKUST-1 (Hong Kong University of Science and Technology) were used as a model system for a development of a near ambient pressure (NAP) XPS based approach to investigate interaction with atmospheres of water, methanol or pyridine at pressures ranging from 1 to 4 mbar. The films were grown on a gold substrate functionalized with a COOH-terminated self-assembled monolayer using liquidphase epitaxy in a step-by-step fashion. Measurement protocols were developed and optimised for different gases in order to obtain spectra of similar quality in terms of signal intensity, noise and shape. Peak shapes were found to depend on the efficiency of charge compensation. Reference measurements in argon proved to be a useful strategy not only for the evaluation of the Cu(II)-fraction in pristine samples, but also to identify the contributions by the respective gas atmosphere to the C 1s and O 1s photoelectron spectra. Reduced copper was found during the exposition of HKUST-1 to water vapour and pyridine, but this effect was not observed in case of methanol. Additionally, it was established that there are no changes in relative Cu(II) percentage with increasing exposure time. This indicates that saturation was reached already at the lowest time of gas exposure. A detailed elucidation of the mechanism of Cu(II) reduction to Cu(I) in HKUST-1 mediated by water and pyridine is part of ongoing work and not in the scope of the present paper.
Graphene Sheets with Defined Dual Functionalities for the Strong SARS-CoV-2 Interactions (2021)
Donskyi, Ievgen S. ; Nie, C. ; Ludwig, K. ; Trimpert, J. ; Ahmed, R. ; Quaas, E. ; Achazi, K. ; Radnik, Jörg ; Adeli, M. ; Haag, R. ; Osterrieder, K.
Search of new strategies for the inhibition of respiratory viruses is one of the urgent health challenges worldwide, as most of the current therapeutic agents and treatments are inefficient. Severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) has caused a pandemic and has taken lives of approximately two Million people to date. Even though various vaccines are currently under development, virus, and especially its spike glycoprotein can mutate, which highlights a Need for a broad-spectrum inhibitor. In this work, inhibition of SARS-CoV-2 by graphene platforms with precise dual sulfate/alkyl functionalities is investigated. A series of graphene derivatives with different lengths of aliphatic chains is synthesized and is investigated for their ability to inhibit SARS-CoV-2 and feline coronavirus. Graphene derivatives with long alkyl chains (>C9) inhibit coronavirus replication by virtue of disrupting viral envelope. The ability of these graphene platforms to rupture viruses is visualized by atomic force microscopy and cryogenic electron microscopy. A large concentration window (10 to 100-fold) where graphene platforms display strongly antiviral activity against native SARS-CoV-2 without significant toxicity against human cells is found. In this concentration range, the synthesized graphene platforms inhibit the infection of enveloped viruses efficiently, opening new therapeutic and metaphylactic avenues against SARS-CoV-2.
Do Interfacial Layers in Thin Films Act as an Independent Layer Within Thin Films? (2021)
Madkour, Sherif ; Garwek, Marcel ; Hertwig, Andreas ; Schönhals, Andreas
The thermodynamic behavior of thin PVME films including the irreversible adsorbed layer on the substrate is investigated. In a first step, the growth kinetics of the adsorbed layer was studied combining a leaching technique and atomic force microscopy. Further, it was shown that there is a critical initial film thickness for the formation of a surface-filling adsorbed layer. Additionally, spectroscopic ellipsometry measurements were carried out to investigate the influence of the adsorbed layer on the glass transition temperature of the thin films. For 30 nm films and below, the influence of the adsorbed layer percolates strongly to the bulk-like layer of the film. Finally, the molecular dynamics of the adsorbed layer was studied by broadband dielectric spectroscopy, employing nanostructured-electrode systems. One process was revealed, which was assigned either to molecular fluctuations taking place in a loosely-bounded the part of the adsorbed layer, or to the desorption/adsorption of segments at the substrate.
Preparation of Nanoparticles for ToF-SIMS and XPS Analysis (2020)
Bennet, Francesca ; Müller, Anja ; Radnik, Jörg ; Hachenberger, Y. ; Jungnickel, H. ; Laue, P. ; Luch, A. ; Tentschert, J.
Nanoparticles have gained increasing attention in recent years due to their potential and application in different fields including medicine, cosmetics, chemistry, and their potential to enable advanced materials. To effectively understand and regulate the physico-chemical properties and potential adverse effects of nanoparticles, validated measurement procedures for the various properties of nanoparticles need to be developed. While procedures for measuring nanoparticle size and size Distribution are already established, standardized methods for analysis of their surface chemistry are not yet in place, although the influence of the surface chemistry on nanoparticle properties is undisputed. In particular, storage and preparation of nanoparticles for surface analysis strongly influences the analytical results from various methods, and in order to obtain consistent results, sample preparation must be both optimized and standardized. In this contribution, we present, in detail, some standard procedures for preparing nanoparticles for surface analytics. In principle, nanoparticles can be deposited on a suitable substrate from suspension or as a powder. Silicon (Si) Wafers are commonly used as substrate, however, their cleaning is critical to the process. For sample preparation from suspension, we will discuss drop-casting and spin-coating, where not only the cleanliness of the substrate and purity of the suspension but also its concentration play important roles for the success of the preparation methodology. For nanoparticles with sensitive ligand shells or coatings, deposition as powders is more suitable, although this method requires particular care in fixing the sample.
Nanoanalytical Identification of Siderite Dissolution-Coupled Pb Removal Mechanisms from Oxic and Anoxic Aqueous Solutions (2020)
Füllenbach, L.C. ; Perez, J. P. H. ; Freeman, H.M. ; Thomas, A.N. ; Mayanna, S. ; Parker, J. E. ; Göttlicher, J. ; Steininger, R. ; Radnik, Jörg ; Benning, L.G. ; Oelkers, E.H.
Lead(II) is a toxic pollutant often found in metalcontaminated soils and wastewaters. In acidic aqueous environments, Pb(II) is highly mobile. Chemical treatment strategies of such systems therefore often include neutralization agents and metal sorbents. Since metal solubility and the retention potential of sorbents depend on the redox state of the aqueous system, we tested the efficiency of the naturally occurring redox-sensitive ferrous iron carbonate mineral siderite to remove Pb(II) from acidic aqueous solutions in batch experiments under oxic and anoxic conditions over a total of 1008 h. Siderite dissolution led to an increase in reactive solution pH from 3 to 5.3 and 6.9, while 90 and 100% of the initial aqueous Pb(II) (0.48 × 10−3 mol kg−1) were removed from the oxic and anoxic systems, respectively. Scanning and transmission electron microscopy, combined with X-ray absorption and photoelectron spectroscopy, indicated that under oxic conditions, Pb(II) was consumed by cerussite precipitation and inner-sphere surface complexation to secondary goethite. Under anoxic conditions, Pb(II) was removed by the rapid precipitation of cerussite. This efficient siderite dissolution-coupled sequestration of Pb(II) into more stable solid phases demonstrates this potential method for contaminated water Treatment regardless of the redox environment.
Enrichment of aluminium in the near‐surface region of natural quartzite rock after aluminium exposure (2020)
Hünger, K.-J. ; Kositz, M. ; Danneberg, M. ; Radnik, Jörg
Alkali–silica reaction (ASR) is an ongoing problem that causes damage to concrete constructions and reduces their durability. Therefore, minimizing this undesired reaction is of great interest for both safety and economic reasons. Additives containing high aluminium content are very effective in reducing the release of silica and enhancing the durability of concrete; however, the mechanism for this effect is still under discussion. In this study, an enrichment of aluminium in the near‐surface region was observed for natural quartzite rock after storage in Al (OH)3 and metakaolin as aluminium sources, from which we conclude that the formation of aluminosilicate sheets of a few nanometres inhibits the silica release; this hypothesis is supported by high‐resolution spectra of Al 2p, Si 2p and O 1s.
Experimental raw data for "Specific adsorption sites and conditions derived by thermal decomposition of activated carbons and adsorbed carbamazepine" (2020)
Dittmann, Daniel
This is the repository of all experimental raw data used in the Scientific Reports publication "Specific adsorption sites and conditions derived by thermal decomposition of activated carbons and adsorbed carbamazepine" by Daniel Dittmann, Paul Eisentraut, Caroline Goedecke, Yosri Wiesner, Martin Jekel, Aki Sebastian Ruhl, and Ulrike Braun. It includes - overview_measurements.xlsx and overview_measurements.ods containing a list of all TGA experiments (TGA, TGA-FTIR, TED-GC-MS, and ramp-kinetics) - TED-GC-MS.zip containing gas chromatography-mass spectrometry experimtent files for the Chemstation and OpenChrom - TGA.zip containing thermogravimetric analyses raw data on evolved gas analyses experiments (TGA-FTIR and TED-GC-MS) - TGA_kinetics.zip containing thermogravimetric analyses raw data on decomposition kinetic experiments (ramp-kinetics) - TGA-FTIR.zip containing Fourier-transform infrared spectroscopy series files for OMNIC - XRF.zip containing x-ray flourescence data on elemental composition
kowarik-labs/AI-reflectivity: v0.1 (2019)
Kowarik, Stefan ; Pithan, L.
AI-reflectivity is a code based on artificial neural networks trained with simulated reflectivity data that quickly predicts film parameters from experimental X-ray reflectivity curves. This project has a common root with (ML-reflectivity)[https://github.com/schreiber-lab/ML-reflectivity] and evolved in parallel. Both are linked to the following publication: Fast Fitting of Reflectivity Data of Growing Thin Films Using Neural Networks A. Greco, V. Starostin, C. Karapanagiotis, A. Hinderhofer, A. Gerlach, L. Pithan, S. Liehr, F. Schreiber, S. Kowarik (2019). J. Appl. Cryst. For an online live demonstration using a pre-trained network have a look at github.
Combining HR‑TEM and XPS to elucidate the core–shell structure of ultrabright CdSe/CdS semiconductor quantum dots (2020)
Weigert, Florian ; Müller, A. ; Häusler, I. ; Geißler, Daniel ; Skroblin, D. ; Unger, Wolfgang ; Radnik, Jörg ; Resch-Genger, Ute
Controlling thickness and tightness of surface passivation shells is crucial for many applications of core–shell nanoparticles (NP). Usually, to determine shell thickness, core and core/shell particle are measured individually requiring the availability of both nanoobjects. This is often not fulfilled for functional nanomaterials such as many photoluminescent semiconductor quantum dots (QD) used for bioimaging, solid state lighting, and display technologies as the core does not show the applicationrelevant functionality like a high photoluminescence (PL) quantum yield, calling for a whole nanoobject approach. By combining high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS), a novel whole nanoobject approach is developed representatively for an ultrabright oleic acid-stabilized, thick shell CdSe/CdS QD with a PL quantum yield close to unity. The size of this spectroscopically assessed QD, is in the range of the information depth of usual laboratory XPS. Information on particle size and monodispersity were validated with dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) and compared to data derived from optical measurements. In addition to demonstrating the potential of this novel whole nanoobject approach for determining architectures of small nanoparticles, the presented results also highlight challenges faced by different sizing and structural analysis methods and method-inherent uncertainties.
Rezension: Einführung in die Physikalische Chemie (2020)
Bäßler, Ralph
Unabhängig vom im Chemieunterricht erworbenen Wissensstand der Studienanfänger liefert dieses, in der Reihe „De Gruyter Studium“ erschienene Lehrbuch einen Einstieg in die Physikalische Chemie. Basierend auf den Erfahrungen seiner Lehrtätigkeit für Erstsemester der Fachrichtung Chemie an der Universität des Saarlandes geht der Autor auf beinahe alle Themengebiete der Physikalischen Chemie ein, wobei die Schwerpunkte auf klassischer Thermodynamik und Grundlagen der chemischen Bindung liegen. Dieses Lehrbuch ist nicht nur für Studierende im Bachelorstudium der Chemie sowohl im Haupt‐ als auch im Nebenfach geeignet. Es liefert zudem Interessierten anderer Fachrichtungen einen übersichtlichen und verständlichen Einstieg in die komplexe Welt der Physikalischen Chemie und sorgt für ein Grundverständnis.
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