The Innovative Electron Microscopy Department is developing and applying electron microscopy methodologies for nanoscale and atomic-resolution characterization of soft functional materials and their interfaces using a synergy of materials science’ and biological electron microscopy approaches.
The department’s specific focus is soft-hard interfaces. Due to the strong mismatch between physical and chemical properties of components (chemical reactivity, adaptability to environment, etc.), these interfaces become the place where many exceptional physicochemical phenomena occur. Our goal is to advance the understanding of these processes at the atomic and molecular levels and to guide the design of hybrid materials for energy and biomedical applications.
Mitarbeiter
Publikationen
Jianu, Teodor | Szalad, Horatju | Roddatis, Vladimir | Antonietti, Markus | Tarakina, Nadezda V.
DOI:
Engineering interfaces between organic semiconductors is an effective way to tailor organic electronic device performance, as charge transport and light interaction efficiency are strongly influenced by electronic coupling at molecular interfaces. Scanning transmission electron microscopy is routinely used to analyze interfaces at the atomic scale; however, its use for organic materials is limited due to the electron beam sensitivity of organic molecules, buried interfaces, and the semicrystalline nature of organics. In this work, we developed a workflow to correlate charge behavior at organic interfaces with their chemistry and structure, even when interface components are chemically and structurally similar and mixed at the nanoscale. We used this workflow to reveal the nanoscale mechanism behind enhanced charge transfer at the heterojunction between two-dimensional carbon nitride catalysts (poly-heptazine imide (PHI) and poly-triazine imide (PTI)) during the oxygen reduction reaction. We found that PHI crystallites grow on PTI layers formed at the gas–liquid interface in the salt melt, following the [001]PTI/[001]K-PHI orientation. This crystallographic alignment promotes the charge transfer from PTI to PHI and creates an electron-rich interface. Electron energy loss spectroscopy showed quaternary N atoms in the heterojunction, which aid O2 adsorption and 2e– reduction to H2O2, as well as a higher proportion of terminal and bridging N atoms, promoting charge separation during the reaction.
Khaykelson, Daniel | Diab, Gabriel A.A. | Cohen, Sidney R. | Kashti, Tamar | Bendikov, Tatyana | Pinkas, Iddo | Teixeira, Ivo F. | Tarakina, Nadezda V. | Houben, Lothar | Rybtchinski, Boris
DOI:
Structurally heterogeneous materials present major challenges for characterization due to their complex nanoscale order. Sodium poly(heptazine imide) (NaPHI), a layered carbon nitride photocatalyst, exemplifies this complexity, with its precise structure remaining unresolved. Here, we uncover new structural insights into NaPHI using energy-filtered four-dimensional scanning transmission electron microscopy combined with machine-learning-based diffraction image segmentation, supported by transmission electron microscopy, atomic force microscopy, X-ray diffraction, and Raman spectroscopy. At the mesoscale, NaPHI flakes display bent morphologies, while nanodiffraction patterns reveal features characteristic of stacking disorder. Based on these insights, we modeled a NaPHI-layered structure incorporating out-of-plane undulations (waves) with amplitudes of ∼0.5 Å and wavelengths of 2–3 nm. This model reproduces the observed line features in nanodiffraction patterns and agrees with powder X-ray diffraction data, thereby bridging local and bulk structural information. The introduced approach uses data-driven machine learning to identify statistically significant features, offering a robust framework for structural analysis of semi-crystalline materials.