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Gallery of the 2021 pictures

Picture of the Month - January 2021

In-Depth Characterization of Lithium Metal Surfaces

Bild des Monats Januar

The use of lithium metal as anode is an intensively explored option to significantly increase the energy density of batteries. As lithium is highly reactive, its surface is natively covered with a passivation layer that affects the cell performance. However, the passivation layer is mostly not considered and characterized. Therefore, we systematically characterized various lithium samples with X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and complementary energy-dispersive X-ray spectroscopy (EDX), to give a complete three-dimensional chemical picture of the surface passivation layer. Besides, we explored the factors influencing the passivation layer and the experimental design which is needed to reliably characterize a highly reactive analyte like lithium.

Svenja-K. Otto et al. accepted for publication at ACS Chemistry of Materials

This picture was submitted by Dr. Anja Henß.


Further insights into the research activities of the ZfM groups can be found in the Gallery.

 

 

Picture of the Month - February 2021

Characterisation of LIPON model structures and interphases by means of DFT

Bild des Monats Januar

The performance of solid-state batteries is affected by Li-ion transport through the solid-state electrolyte and the interphase to the electrodes. Deep atomic-level insights into lithium ion transport and interface properties can be provided by density functional theory studies. In our study, the formation and transport of Li vacancies and Li interstitial ions were characterized in several lithium phosphorus oxynitride (LIPON) model structures with different anionic building blocks as a function of POuN4-u units. In addition, common density functionals for battery materials were investigated with the uncertainty concept to provide activation energies, diffusion coefficients and ionic conductivities with a range of fluctuation of the DFT approach. Interphases of LIPON to metallic Li and lithium titanate (LTO) were also investigated using the DFT method. Various methods such as kernel density estimation or coordination numbers were used to accurately characterize the interface and identify possible decomposition products.

This picture was submitted by Pascal Henkel, group of Prof. Doreen Mollenhauer.


Further insights into the research activities of the ZfM groups can be found in the Gallery.

 

 

Picture of the Month - March 2021

Rings on Fire – Cycloparaphenylenes under UV-light

Bild des Monats Januar

Cycloparaphenylenes are unusual macrocylic compounds with a bend circular π-electron system which is perpendicular to the molecule's plane. This structural feature provides special challenges for their synthesis, but offers also unique opportunities in material sciences. Recently, a one-pot method for their preparation was presented by J. Griwatz and H.A. Wegner (DOI: 10.1055/s-0040-1721082). The group of H. A. Wegner is also looking into supramolecular assemblies of this class of molecules as well as their electrochemical features (DOI: 10.1002/anie.201909126).

This picture was submitted by Jan Griwatz, group of Prof. Hermann A. Wegner.


Further insights into the research activities of the ZfM groups can be found in the Gallery.

 

 

Picture of the Month - April 2021

Innovative Materials for Future Solar Cells

Bild des Monats April

Organic-inorganic perovskites are important materials for future solar cells with record performances of 20 % and higher. Material scientists use doping and alloying to modify and enhance the materials properties and device performance.

Recently, the teams of Johanna Heine (Inorganic Chemistry, Philipps-Universität Marburg), Ralf Tonner (Theoretical Chemistry, Universität Leipzig), and Sangam Chatterjee (Optical Spectroscopy, Justus-Liebig-Universität Gießen), each an expert in the respective field, have collaborated to provide deep insights into doping materials for future solar cell applications.

They have presented model compounds featuring antimony and bismuth doped lead anions that represent precise cut‐outs of doped perovskites. Optical spectroscopy reveals surprisingly low band gaps due to the significant electronic interactions between the constituent metal atoms.

These compounds are the first examples of a promising new class of materials that may expand the useful properties of lead halide perovskites for optoelectronic applications. The article is available at Angewandte Chemie with open access under DOI: 10.1002/anie.202014696.

This picture was submitted by Philip Klement, group of Prof. Sangam Chatterjee.


Further insights into the research activities of the ZfM groups can be found in the Gallery.

Picture of the Month - May 2021

Polymer Coatings for increased Performance of Solid-State Batteries

Bild des Monats Mai

Solid-state batteries with inorganic solid electrolytes contain interfaces in the anode and cathode at which electrochemical degradation can cause the cell performance to decrease. Interlayers and protective coatings are applied to improve the stability of the interfaces. Using polymers as interlayers is expected to be beneficial as the mechanical properties of the polymers can be adapted continuously over a wide range by varying the polymer composition. For example, a conformal polymer coating was applied to vapor grown carbon fibers (VGCF) by Nina Herrmann and Dr. Sudeshna Sen (see SEM images). The group of Felix Richter develops polymers as coatings, interlayers and binders for solid-state batteries with inorganic solid electrolytes.

This picture was submitted by Dr. Felix Richter.


Further insights into the research activities of the ZfM groups can be found in the Gallery.

Picture of the Month - June 2021

Let it click on silicon

Bild des Monats Juni

Organic architectures on silicon surfaces may lead to new applications beyond the possibilities of standard silicon technology (“more than Moore”). Two different routes were recently developed for the first steps of synthesizing such architectures on the highly reactive Si(001) surface which is seen through the window of a UHV apparatus. In both cases, the surface was first functionalized in UHV via chemoselective adsorption of cyclooctyne derivatives. A second organic layer was then either coupled via a UHV-compatible click chemistry reaction based on enolether/tetrazine coupling as sketched in the image. Alternatively, alkyne-azide coupling was efficiently performed after transferring the sample directly from UHV into the reactive solution. The work was performed in a close collaboration between the groups of Ulrich Koert (Organic Chemistry, Philipps University Marburg), Ralf Tonner (Theoretical Chemistry, University Leipzig), and Michael Dürr (Applied Physics, JLU Giessen); it opens the route to synthesizing complex organic architectures on silicon.

Publications: T. Glaser, et al., J. Phys. Chem. C 125, 4021 (2021), DOI: 10.1021/acs.jpcc.0c11353; T. Glaser, et al., Chem. Eur. J. 27, 8082 (2021), DOI: 10.1002/chem.202005371.

This picture was submitted by Prof. Dr. Michael Dürr.


Further insights into the research activities of the ZfM groups can be found in the Gallery.

Picture of the Month - July/August 2021

Ruthenium-Iridium Mixed Oxides as Promising Catalyst Materials

Bild des Monats Juli

The Pechini sol-gel method allows ruthenium dioxide and iridium dioxide to be mixed at the atomic scale to form promising materials for heterogeneously catalyzed oxidation reactions such as the total oxidation of CO and methane. X-ray diffraction reveals the successful intermixture of ruthenium and iridium at atomic level and X-ray photoelectron spectroscopy experiments allow for examining of the catalytic active surface area. The product yield (space time yield) is normalized to the number of active noble metal sites for proper comparison of the intrinsic activities. The mixed oxides RuxIr1-xO2 show improved catalytic performance for both the prototypic CO oxidation (Ru0.875Ir0.125O2) and the more complex methane combustion (Ru0.25Ir0.75O2), thus revealing a synergistic effect of ruthenium and iridium. For the methane combustion iridium oxide is able to activate the C-H bond at low temperatures, while ruthenium dioxide is a superior oxidation catalyst for the further oxidation of methane fragments.

Publications:

  • O. Khalid, T. Weber, G. Drazic, I. Djerdj, and H. Over, Journal of Physical Chemistry C, 2020, 124, 18670-18683, DOI: 10.1021/acs.jpcc.0c06392.
  • O. Khalid, A. Spriewald Luciano, G. Drazic, and H. Over, 2021, submitted to ChemCatChem, 2020.

This picture was submitted by Prof. Dr. Herbert Over.


Further insights into the research activities of the ZfM groups can be found in the Gallery.

Picture of the Month - September 2021

Smart Preparation of Tailored Nanostructures

Bild des Monats September

Atomic Layer Deposition (ALD) is a key technology for the miniaturization of modern microelectronics in computer chips to sub-5 nm device scales to boost their performance while decreasing power consumption. Material is deposited atom layer by atom layer and enables atomic-level thickness control with high conformity. Further, material deposition may be enabled only in specific areas which eliminates alignment errors inherent to conventional approaches.

Recently, the teams of Sangam Chatterjee (Optical Spectroscopy & Materials Deposition), Matthias T. Elm (Physical Chemistry) and Christian Heiliger (Theoretical Physics) have collaborated to provide a new strategy for the smart preparation of tailored nanostructures by area-selective ALD.

They manipulate the surface diffusion of species to form nanostructures with tailored aspect ratios. Titanium oxide (TiO2) species diffuse on the surface of poly (methyl methacrylate) (PMMA) and accumulate at the interface of the growth (SiO2) and no-growth areas (PMMA). Kinetic Monte-Carlo calculations reveal diffusion as the origin and confirm experimental results.

Controlling the surface diffusion may enable the smart preparation of tailored nanostructures with a wide range of applications in modern microelectronics. The article was published in ACS Applied Materials & Interfaces under DOI: 10.1021/acsami.0c22121

This picture was submitted by Philip Klement, AG Prof. Chatterjee.


Further insights into the research activities of the ZfM groups can be found in the Gallery.

Picture of the Month - October 2021

Reactivity of alkylating Agents

Bild des Monats Oktober

Aziridinium ions are highly reactive electrophiles. They can be applied in organic synthesis as well as for the functionalization of molecules and surfaces. Furthermore, they are the intermediates of the alkylation of DNA by nitrogen mustards within a chemotherapy.

We are interested in tuning the reactivity of these electrophiles and for this purpose are studying bicyclic aziridinium ions, which we used to cross-link RNA and analyze its higher order structure. (doi.org/10.1093/nar/gkab468) Recently we were able to isolate the intermediate bicyclic aziridinium ions, obtain crystal structures and perform kinetic studies with these reactive species. (doi.org/10.1002/ejoc.202101072)

In the center of the picture, the crystal structure of a bicyclic aziridinium ion is shown together with its generation from a 3-chlorpiperidine and its reaction with a nucleobase. The background shows multiple stacked NMR spectra of a kinetic analysis and a DNA-fragment.

This picture was submitted by Prof. Dr. Richard Göttlich.


Further insights into the research activities of the ZfM groups can be found in the Gallery.

Picture of the Month - November 2021

Electrochromic tungsten oxide films for Smart Windows

Bild des Monats November

Chromogenic thin films are critical building blocks for Smart Windows, allowing the flow of visible light and thermal radiation to be modulated in buildings for an improved climate control. Electrochromic materials such as tungsten oxide are well established in those devices. By intercalation of suitable ions and the resulting electrochemical reduction, the material can be switched from a colorless transparent to a deep blue optical state. Tungsten oxide thin films were grown by ion-beam sputter-deposition, a variant of sputter deposition, which allows a more precise control of the sample temperature. Suitable coating properties for the electrochromic application can be achieved by specific selection of the gas composition used in the process. Here, morphological as well as compositional properties, among others, play a crucial role and can be studied by scanning electron microscope (SEM) or X-ray photoelectron spectroscopy (XPS).

Publication: Mario Gies, Fabian Michel, Christian Lupó, Derck Schlettwein, Martin Becker, Angelika Polity „Electrochromic switching of tungsten oxide films grown by reactive ion-beam sputter deposition“
J Mater Sci 56, 615–628 (2021), https://doi.org/10.1007/s10853-020-05321-y.

This picture was submitted by Mario Gies, group of Dr. Angelika Polity.


Further insights into the research activities of the ZfM groups can be found in the Gallery.

Picture of the Month - Dezember 2021

Selective Aerobic Hydroxylations: The Clip-and-Cleave Concept

Bild des Monats Dezember

Aliphatic or aromatic aldehydes and ketones can be easily transformed to chelate ligands by imine condensation with a diamine (Clip reaction). These ligands can form copper(I) complexes which react with dioxygen to form a bis(m-oxido) copper dioxygen intermediate (top left: Stopped-Flow UV-Vis spectrum of the intermediate at −80 °C) which then hydroxylates the aldehyde/ketone substrate selectively. The hydroxylation product can then easily be isolated by hydrolysis (Cleave reaction). A quite special reaction is the hydroxylation of adamantane-1-carbaldehyde in secondary position (top right: molecular structure of the hydrazone protected derivative), which is usually the unfavourable position in adamantane chemistry involving electrophilic or radical C-H bond activation, in comparison to the tertiary position. Aerobic oxygenation reactions are quite desirable, since dioxygen is the “greenest” oxidant, due to its high abundancy and formation of water and hydrogen peroxide as side products.

More details can be found here:

Chem. Eur. J. 2015, 21, 11735-11744 (DOI: 10.1002/chem.201501003)

Chem. Eur. J. 2018, 24, 15543-15549 (DOI: 10.1002/chem.201802607)

Eur. J. Inorg. Chem. 2021, 1961-1970 (DOI: 10.1002/ejic.202100185)

This picture was submitted by Alexander Petrillo, group of Prof. Dr. Siegfried Schindler.


Further insights into the research activities of the ZfM groups can be found in the Gallery.