Research

In 2018 and 2019, two new Collaborative Research Centres/Transregios were launched or approved, CRC/TRR 247 “Heterogeneous Oxidation Catalysis in the Liquid Phase” and CRC/TRR 270 “HoMMage – Hysteresis Design of Magnetic Materials for Efficient Energy Conversion”, which are largely carried by CENIDE members. Together with CRC 1242 “Non-Equilibrium Dynamics of Condensed Matter in the Time Domain”, which has been in existence since 2016, CENIDE members are now significantly involved in three CRC/TRRs and active in another one with six subprojects.

The other highlights from CENIDE’s six main research areas are briefly described below:

Dynamic processes in solids:

Biological, chemical and physical processes usually take place at breakneck speed and in the tiniest of spaces. In CRC 1242 “Non-Equilibrium Dynamics of Condensed Matter in the Time Domain”, these dynamics are investigated in solids, on surfaces or in nanostructures with the highest-possible time resolution. The researchers use the “pump-probe technique”: At time zero, the system under investigation is stimulated by an ultrashort and intense laser pulse. It then returns to its basic state. Before this happens, its current state is examined using a second ultrashort pulse, e.g. by measuring the optical absorption. This is repeated with increasing time intervals between stimulation and interrogation to obtain snapshots of the system, which together represent an ultrafast process. Two-dimensional materials offer an interesting area for the investigation of such non-equilibrium dynamics. Other examples of research within the CRC are data storage with new phase change materials and the super slow-motion recording of plasmon waves on the femtosecond scale. In the next funding period, the researchers want to go one step further and shift their focus from observation to controlling the dynamics of the processes.

Gas phase synthesis of nanomaterials:

The gas phase synthesis of functional nano­materials is a long-standing focus of CENIDE. The work ranges from understanding the basics to developing processes that are scalable for industrial production. Experiments, modelling and simulation are closely linked in order to understand the underlying processes.

The DFG Research Unit (FOR) 2284 “Model-Based Scalable Gas Phase Synthesis of Complex Nanoparticles” focuses on the synthesis of complex nanostructured materials from gaseous and vaporized precursors. “Complex” here means that the materials should not only be uniform in composition, size and crystal structure, they should also have defined secondary and tertiary structures such as core and shell, different porosity and different surface structures.

As an alternative to the use of gaseous precursors, the members of the DFG Priority Programme (SPP) 1980 “Nanoparticle Synthesis in Spray Flames SpraySyn: Measurement, Simulation, Processes” are investigating spray flame-based synthesis methods, in particular for the production of polyvalent oxides. As a basis for the coordinated research in the SPP, the CENIDE researchers have developed a standard experiment, the SpraySyn burner, which has now been distributed to around 20 laboratories worldwide (see photo p. 22). The investigation of the spray flame synthesis of nanoparticles on a well-defined standard burner allows a comprehensive data set to be generated with different established and new measurement methods.

Catalysis:

More than 80% of all chemical products are created using catalytic processes. But powerful catalysts are also essential for new applications in energy conversion and storage, e.g. in fuel cells. Within CENIDE the focus is on the synthesis and characterisation of highly active, selective and stable nanomaterials for heterogeneous catalysis. The aim is to understand the mechanisms and, based on this, to identify and specifically produce high-performance catalysts.

Catalysis research in CENIDE is led by two major third-party funded projects: the DFG-funded Collaborative Research Centre/Transregio (CRC/TRR) 247 “Heterogeneous Oxidation Catalysis in the Liquid Phase”, which was launched in July 2018, and the BMBF-funded project KontiKat, which aims to establish a contamination-free process chain for catalysts based on pulsed laser ablation.

The University of Duisburg-Essen, the Ruhr-Universität Bochum, the Max Planck Institute (MPI) für Kohlenforschung, the MPI for Chemical Energy Conversion and the Fritz Haber Institute are all collaborating in CRC/TRR 247. Together they want to better understand the active centres and mechanisms of oxidation reactions at the solid-liquid interface. This knowledge can be used to develop new high-quality catalysts for catalytic processes under favourable conditions.

Magnetic materials:

In November 2019, the UDE, together with the TU Darmstadt, succeeded in obtaining funding for the new Collaborative Research Centre/­Transregio (CRC/TRR) 270 “HoMMage – Hysteresis Design of Magnetic Materials for Efficient Energy Conversion”. The scientists are working together on new processes for the production of innovative magnetic materials by changing only individual atoms, as well as deforming and reshaping entire workpieces. Artificial intelligence helps to accelerate the search for the most promising material combinations and the discovery of new suitable materials.

One of the research topics is magnetocaloric materials, in which – to put it simply – the temperature of a material can be precisely changed using a magnetic field. In this way, it is possible to run refrigerators and air conditioners quietly, with very low energy consumption and without climate-damaging gases. Researchers are also working on this technology within the Priority Programme (SPP) 1599 “Caloric Effects in Ferroic Materials: New Concepts for Cooling”. In this thematic area, the fusion of basic research and materials research with high application potential forms the basis for close cooperation with industry.

Nanomaterials for health:

Biomaterials are natural or artificial substances that come into contact with biological systems. CENIDE focuses on the study of the interaction between materials, surfaces, particles and macromolecules: from the destruction of pathogens and cancer cells to the formation of self-developing structures. Six CENIDE members play a key role in CRC 1093 “Supramolecular Chemistry of Proteins”. This Collaborative Research Centre applies the latest findings and methods of supra­molecular chemistry to achieve specific interactions with proteins using artificial ligands.

For example, a healing-promoting coating of neuronal implants with biocompatible metallic nanoparticles is being developed that also increases the acceptance of the exogenous material.

The focus of another project is combating multi-resistant pathogens (MRE) with “guided nanorockets”. The “nanorockets” are equipped with antibacterial nanosilver, which they release locally to destroy bacteria while leaving body tissue undamaged.

In contrast, new nanomaterials such as fluorescent calcium phosphate nanoparticles are suitable for cellular microscopic imaging. They can be bound with other molecules via click chemistry and afterwards used for targeting or as therapeutic agents, thus paving the way for multi­modal theranostic nanoparticles. At CENIDE, newly developed magnetite-gold-nanohybrids can also be used for theranostics (= therapy + diag­nostics). In magnetic resonance imaging, they proved to be superior to commercial contrast agents and also offer a 2-in-1 service: In addition to the fluorescent dye for imaging, they can be loaded with drugs that can be released locally and precisely. In addition, CENIDE researchers have succeeded in identifying the first nanoantibiotic-specific resistance mechanism, thus providing an explanation as to why nanoantibiotics exhibit reduced activity in clinically relevant environments.

Nanotechnology in energy applications:

The sustainable provision of usable energy and in particular its storage and conversion are among the major challenges of the 21st century, and CENIDE is working on them. Within this research area, different approaches for nanoscale materials are investigated in relation to batteries, fuel cells, photovoltaics, thermoelectrics and light emitters from a theoretical, synthesis and processing perspective. Here are some highlights.

In cooperation with The hydrogen and fuel cell center ZBT GmbH (ZBT), high-purity nanoparticles were produced by laser ablation, which allow direct contact with the carbon carrier and thus enable very good conductivity. A demonstrator of a proton exchange membrane fuel cell was accordingly built and tested under realistic conditions. Compared to a commercially available reference catalyst, it showed improved catalyst stability and activity.

Graphene generated from the gas phase has also been successfully used to further improve the already excellent performance of gas phase-synthesized silicon nanoparticles for lithium-ion battery anodes. Tests showed that the gas phase graphene significantly improves the long-term stability and efficiency of the composite material compared to pure silicon.

Thermoelectricity plays an important role in energy conversion and the recovery of waste heat. CENIDE’s scientists are investigating new mechanisms for improving the thermoelectrics of transition metal oxides and their heterostructures through powerful computer simulations. The researchers have shown that the transition from metal to insulator in certain perovskite superlattices leads to a greatly improved thermoelectric response.

Light-emitting electrochemical cells (LECs) are promising for large-scale flexible lighting solutions. However, the lack of deep blue emitters that are at the same time efficient, bright and stable in the long term is preventing the formation of white LECs suitable for everyday use. CENIDE’s researchers have succeeded for the first time in producing QLEC (quantum dot LECs) components with homogeneous white light emission.