Unlocking the Secrets of Optical Materials: A Conversation with Anna Krawczuk

A 7-minute read

Introduction

In the world of materials science, understanding structure-property relationships is key to designing innovative materials with enhanced optical and electronic properties. Dr. Anna Krawczuk, a junior Professor at Göttingen University, is at the forefront of this pursuit, combining experimental and theoretical approaches in quantum crystallography. Recently, she has been leveraging a one-of-a-kind setup that integrates an Excillum MetalJet X-ray source, a Bruker goniometer, and a DECTRIS detector. In this interview, she shares insights into her research and how this unique instrumentation has transformed her investigations.

Exploring Functional Materials

What is your research focus and the scientific challenges you are addressing?

The main goal of my research group is to design materials with significant physical properties, particularly optical properties such as refractive index and fluorescence. Since solid-state materials provide the most reliable structural insights, we rely on X-ray diffraction techniques to establish structure-property correlations. Our approach combines experimental data with theoretical methods in quantum crystallography to better understand electronic structures and chemical bonding. The ultimate aim is to identify transferable molecular features that can be fine-tuned to enhance material performance.

What are the broader applications of your work for the scientific community?

Our research has several potential applications. For instance, developing materials with tailored refractive indices is crucial for optoelectronics. While inorganic or halogen-based materials are commonly used, we are exploring sustainable alternatives free from metal ions and halogens. Organic compounds often exhibit superior optical responses but lack mechanical stability. Our goal is to find a balance between efficiency and durability. Additionally, our fluorescence studies have applications in sensing, where we recently developed molecules sensitive to the presence of metal ions like copper and zinc.

The Power of Advanced Instrumentation

What equipment do you use in your research, and how does it support your objectives?

I have the unique opportunity to work with an exceptional experimental setup: a MetalJet X-ray source from Excillum, combined with a Bruker goniometer and a DECTRIS direct detector. This combination is rare and, to my knowledge, one of a kind. The MetalJet source uses a liquid indium-gallium alloy, providing high-intensity radiation. For charge density studies, I specifically use indium radiation to avoid artifacts from gallium.

The DECTRIS detector has been a game-changer for us. It allows energy cutoff filtering, eliminating gallium contamination completely. Before switching to this detector, we struggled with unwanted gallium radiation using our previous Photon III detector. The need for additional attenuators significantly reduced intensity, making high-resolution charge density studies impractical. With the DECTRIS detector, we can now fully exploit the capabilities of the MetalJet source.

The experimental set up for single crystal diffraction with a Bruker goniometer, an Excillum MetalJet and the EIGER2 1M CdTe from DECTRIS

Advancing High-Pressure Crystallography

You also conduct high-pressure experiments. How does your setup enhance these studies?

 High-pressure crystallography requires compressing crystals between diamond anvils, which significantly reduces diffraction intensity due to X-ray absorption by the diamonds. Sensitivity and high photon flux are crucial for successful measurements. The combination of the MetalJet source and the DECTRIS detector has been instrumental in improving our data quality. Typically, high-pressure studies suffer from incomplete datasets because of the limited rotation range imposed by the diamond anvil cell. Our setup enables us to achieve 50% completeness from a single crystal, a significant improvement over conventional sources and detectors. With multiple crystals in different orientations, we can push completeness close to 100%, which is particularly beneficial for organic compounds that often crystallize in low-symmetry structures.

Breakthroughs and Future Directions

Have you observed any notable breakthroughs using this setup?

Despite a seven-month hiatus due to equipment issues, we have already obtained exciting results. We recently conducted high-pressure studies on anthracene derivatives, correlating structural changes with shifts in optical properties. Additionally, our work on nickel complexes demonstrated pressure-induced phase transitions, which were presented as a poster at ECM in Padova and won a prize from Bruker. These findings underscore the capabilities of our setup in exploring structure-property relationships under extreme conditions.

What excites you most about your future research, and what role do advances in instrumentation play?

One of the most exciting discoveries in my research is the ability to induce chemical bond formation under pressure, effectively creating new compounds with novel properties. This opens avenues for pressure-responsive optical switches, where applying and releasing pressure dynamically alters material properties.

Instrumentation advancements are crucial in realizing these ideas. While hardware has reached an impressive level of precision, software remains a bottleneck. Improved data analysis tools are needed to fully harness the potential of modern detectors and X-ray sources. Additionally, integrating complementary techniques, such as simultaneous fluorescence and X-ray diffraction measurements, could provide deeper insights into property anisotropies and phase transitions.

Conclusion

Dr. Anna Krawczuk’s research highlights the importance of cutting-edge instrumentation in pushing the boundaries of materials science. The combination of a MetalJet source, a Bruker goniometer, and a DECTRIS detector has enabled her to tackle complex questions in optical materials and high-pressure crystallography with unprecedented precision. As she continues to explore novel materials and experimental methodologies, we eagerly anticipate the breakthroughs her work will bring to the field.

If you want to learn more about how DECTRIS' range of high-performance laboratory detectors can support you in your research, please contact Marcus Müller.