Natural biocomposites such as wood and plant cell walls exhibit prominent mechanical properties largely attributed to the nanoscale organization of fibrous components, such as cellulose, which often adopt chiral arrangements. However, resolving the three-dimensional (3D) arrangement of these structures at the nanoscale remains a significant challenge, particularly in beam-sensitive materials. This study introduces a method for 3D reconstruction of orientation based on scanning electron diffraction (SED), enabling the quantitative mapping of chiral supramolecular organization with sub-100 nm spatial resolution. By acquiring low-dose SED data at multiple tilt angles and applying a symmetry-based reconstruction algorithm, we resolved the 3D orientation of cellulose fibrils in native oat husk and birch wood. Our results reveal a multilayered cell wall architecture with alternating helical handedness, providing precise measurements of 3D fibril orientation. This method reveals complex hierarchical structures at the nanoscale, enabling rapid data acquisition and analysis using widely available instrumentation. The ability to resolve such chiral organization provides insights into material properties as well as opportunities for designing bioinspired materials with tunable mechanical and functional properties that extend far beyond natural biocomposite materials.

Transparent wood composites provide new functionalities through active additives distributed at the nanoscale. Scalable nanotechnology includes processing where nanoparticles and molecules are brought into the dense wood cell wall. A novel cell wall swelling step through green chemistry is therefore investigated. Sub-zero centigrade NaOH treatment provides extensive cell wall swelling. Cell wall accessibility is vastly increased so that chemicals can readily impregnate the nanostructured cell wall. Transparent wood with a thickness of up to 15 mm can therefore be fabricated. The optical transmittance and the attenuation coefficient are improved since the polymer is distributed inside the cell wall as a matrix for the nanoscale cellulose fibrils. The proposed technology paves the way for scalable wood nanoengineering.

The properties of fiber-based composite materials are highly anisotropic and depend on the orientation and organization of their fibers. In natural systems, such as wood or arthropod exoskeletons, nanofibrils like cellulose and chitin are arranged in complex hierarchical structures that enhance strength, toughness, and sometimes iridescence. These native nanofibrils are crystalline, consisting of tightly packed chains of sugar-based molecules (polysaccharides) organized in nanostructures with anisotropic mechanical behavior. This thesis introduces a methodology using scanning electron diffraction (SED) to analyze the nanoscale orientation of structural polysaccharides in both natural and synthetic composite materials. By scanning a nearly parallel electron beam of just a few nanometers across the sample and capturing a diffraction pattern at each probe position, the local crystallographic orientation of nanofibrils can be determined with significantly improved spatial resolution compared to existing methods. Tilt-series acquisition further enables the reconstruction of the complete three-dimensional fibril orientation, revealing the chirality of the fibrillar organization. Applying this method to electron-beam-sensitive materials, such as cellulose and chitin, presents significant challenges. Their crystalline structures are easily damaged by beam radiation, and they generate weak diffraction signals due to their composition of light elements. To address these issues, low-dose conditions and a specialized data analysis pipeline were developed and integrated into a dedicated workflow. While this work focuses on cellulose and chitin, which are increasingly important in creating advanced hybrid materials, the developed method shows potential for broader applications with other fibrous assemblies, such as those found in bone and spider silk.

Hierarchical assembly is used to construct complex materials using elementary building units, mainly depending on the non-covalent interactions involving dynamic bonds. Here we present a hierarchical assembly strategy to build highly crystalline tubular frameworks. A multi-level assembly process driven by dynamic covalent bonds and coordination bonds is shown to produce a supramolecular nanotubular framework and three tubular covalent organic frameworks (COFs). These materials consist of well-ordered triangular nanotubes assembled in an oriented manner. In tubular COFs, the spacing between adjacent nanotubes can be systematically adjusted by altering the connector lengths to create mesoporous structures with adjustable pore size. Moreover, reversible transformations between tubular COFs and layered COFs were achieved by the reversible addition and removal of Zn(NO3)2. The facile demetallation–remetallation process confers tuneable structural properties to the materials and enables the layered COFs to serve as efficient ‘sponges’ for metal ions. This study represents a notable advance in hierarchical assembly; incorporating covalent bonding into this process is expected to greatly accelerate the development of new materials. (Figure presented.)

Cellulose, being a renewable and abundant biopolymer, has garnered significant attention for its unique properties and potential applications in hybrid materials. Understanding the hierarchical arrangement of cellulose nanofibers is crucial for developing cellulose-based materials with enhanced mechanical properties. In this study, the use of Scanning Electron Diffraction (SED) is presented to map the nanoscale orientation of cellulose fibers in a bio-composite material with a preserved wood cell structure. The SED data provides detailed insights into the ordering of cellulose with an extraordinary resolution of approximate to 15 nm. It enables a quantitative analysis of the fiber orientation over regions as large as entire cells. A highly organized arrangement of cellulose fibers within the secondary cell wall is observed, with a gradient of orientations toward the outer part of the wall. The in-plane fiber rotation is quantified, revealing a uniform orientation close to the middle lamella. Transversely sectioned material exhibits similar trends, suggesting a layered cell wall structure. Based on the SED data, a 3D model depicting the complex helical alignment of fibers throughout the cell wall is constructed. This study demonstrates the unique opportunities SED provides for characterizing the nanoscale hierarchical arrangement of cellulose nanofibers, empowering further research on a range of hybrid materials. Fundamental knowledge about the hierarchical arrangement of cellulose nanofiber is of great importance in developing new cellulose-based hybrid materials. Scanning electron diffraction is employed to map the cellulose nanofiber orientations throughout a wood-derived bio-based material. SED data reveals insights into cellulose alignment and enables precise quantitative fiber orientation analysis with a nanoscale spatial resolution.image

Transparent wood composites (TWs) offer the possibility of unique coloration effects. A colored transparent wood composite (C-TW) with enhanced fire retardancy was impregnated by metal ion solutions, followed by methyl methacrylate (MMA) impregnation and polymerization. Bleached birch wood with a preserved hierarchical structure acted as a host for metal ions. Cobalt, nickel, copper, and iron metal salts were used. The location and distribution of metal ions in C-TW as well as the mechanical performance, optical properties, and fire retardancy were investigated. The C-TW coloration is tunable by controlling the metal ion species and concentration. The metal ions reduced heat release rates and limited the production of smoke during forced combustion tests. The potential for scaled-up production was verified by fabricating samples with a dimension of 180 × 100 × 1 (l × b × h) mm³.

Photonic crystals are optical materials that are often fabricated by assembly of particles into periodically arranged structures. However, assembly of lignin nanoparticles has been limited due to lacking methods and incomplete understanding of the interparticle forces and packing mechanisms. Here we show a centrifugation-assisted fabrication of photonic crystals with rainbow structural colors emitted from the structure covering the entire visible spectrum. Our results show that centrifugation is crucial for the formation of lignin photonic crystals, because assembly of lignin nanoparticles without centrifugation assistance leads to the formation of stripe patterns rather than photonic crystals. We further prove that the functions of centrifugation are to classify lignin nanoparticles according to their particle size and produce monodispersed particle layers that display gradient colors from red to violet. The different layers of lignin nanoparticles were assembled in a way that created semi-closed packing structures, which gave rise to coherent scattering. The diameter of the lignin nanoparticles in each color layer is smaller than that predicted by a modified Bragg’s equation. In situ optical microscope images provided additional evidence on the importance of dynamic rearrangement of lignin nanoparticles during their assembly into semi-closed packing structures. The preparation of lignin nanoparticles combined with the methodology for their classification and assembly pave the way for sustainable photonic crystals.

Computer-assistance allows selecting the most adequate low-cost organic structure directing agents (OSDAs) for the crystallization of Al-rich CHA-type zeolites. The host-guest stabilization energies of tetraethylammonium (TEA), methyltriethylammonium (MTEA) and dimethyldiethylammonium (DMDEA), in combination with Na, were first theoretically evaluated. This ab-initio analysis reveals that two TEA show a serious steric hindrance in a cha cavity, whereas two MTEA would present excellent host-guest confinements. The synthesis of Al-rich CHA-type zeolites has been accomplished using TEA and MTEA. Electron diffraction and high-resolution transmission electron microscopy reveal large CHA-domains with narrow faulted GME-domains in the CHAtype material synthesized with TEA, confirming the better OSDA-directing roles of MTEA cations towards the cha cavity, in good agreement with DFT calculations. Cu-exchanged Al-rich CHA-type samples achieved with MTEA and TEA show excellent catalytic activity and hydrothermal stability for the selective catalytic reduction (SCR) of NOx with ammonia under conditions relevant for future heavy duty diesel conditions.

Structure determination of pharmaceutical compounds is invaluable for drug development but remains challenging for those that form as small crystals with defects. Bismuth subsalicylate, among the most commercially significant bismuth compounds, is an active ingredient in over-the-counter medications such as Pepto-Bismol, used to treat dyspepsia and H. pylori infections. Despite its century-long history, the structure of bismuth subsalicylate is still under debate. Here we show that advanced electron microscopy techniques, namely three-dimensional electron diffraction and scanning transmission electron microscopy, can give insight into the structure of active pharmaceutical ingredients that are difficult to characterize using conventional methods due to their small size or intricate structural features. Hierarchical clustering analysis of three-dimensional electron diffraction data from ordered crystals of bismuth subsalicylate revealed a layered structure. A detailed investigation using high-resolution scanning transmission electron microscopy showed variations in the stacking of layers, the presence of which has likely hindered structure solution by other means. Together, these modern electron crystallography techniques provide a toolbox for structure determination of active pharmaceutical ingredients and drug discovery, demonstrated by this study of bismuth subsalicylate. Pepto-Bismol has been used to treat gastrointestinal disorders for over a century, yet the structure of its active ingredient is still under debate. Here, the authors apply electron crystallography to unveil the structure of bismuth subsalicylate.

A novel ab initio methodology based on high-throughput simulations has permitted designing unique biselective organic structure-directing agents (OSDAs) that allow the efficient synthesis of CHA/AEI zeolite intergrowth materials with controlled phase compositions. Distinctive local crystallographic ordering of the CHA/AEI intergrowths was revealed at the nanoscale level using integrated differential phase contrast scanning transmission electron microscopy (iDPC STEM). These novel CHA/AEI materials have been tested for the selective catalytic reduction (SCR) of NOx, presenting an outstanding catalytic performance and hydrothermal stability, even surpassing the performance of the well-established commercial CHA-type catalyst. This methodology opens the possibility for synthetizing new zeolite intergrowths with more complex structures and unique catalytic properties.