Oriented Crystallization of Barium Sulfate Confined in Hierarchical Cellular Structures

Biomineralization involves the controlled formation of inorganic matter within hierarchical biological scaffolds. Mimicking the crystallization of biominerals in such confinement is an important goal in the field of crystal engineering. Natural porous materials offer an interesting platform for studying mineral morphogenesis and texturing through template-directed mineralization. In this paper, we precipitate barium sulfate from aqueous salt solutions in the constrained micro- and nanoenvironment of pristine wood cells and cell walls. By employing spatially resolved characterization techniques, such as scanning electron microscopy (SEM), Raman spectroscopic imaging, and scanning wide-angle X-ray scattering (WAXS), we gain important insights into the deposition pattern, morphology, and crystallographic orientation of Barite crystals in the plant cell anatomy. The experimental findings suggest directed crystallization of BaSO4 at different hierarchical levels. SEM shows elongated, dendritic BaSO4 crystals growing inside the cell lumina closely associated with the interfacial cell wall region. WAXS measurements acquired from mineralized cell walls show a crystallographic co-orientation of Barite and cellulose, suggesting epitaxial crystal growth.