Engineering Curved Strontium Sulfate Crystals through Biomimetic Crystallization

Nanoscale molecular interactions between growing crystals and charged polyelectrolytes are crucial to understand the self-assembly of hierarchical organic–inorganic superstructures. Little is known about earth alkaline sulfate biominerals. Yet, a detailed understanding of bioinspired crystallization is crucial for developing general descriptors for bottom-up syntheses of complex ceramics. This study investigates biomimetic strontium sulfate (SrSO 4 ) crystallization in the presence of poly(α-glutamic acid) using multiscale microscopy and vibrational spectroscopy. Using scanning electron microscopy, we observed doughnut-shaped spherulites with granular surface texture. Biomolecule inclusion led to pronounced peak broadening in synchrotron X-ray powder diffraction, wide-angle X-ray scattering, and Raman spectroscopy, commensurate with nanoscale domain sizes and pronounced lattice strain. Texture-like wide-angle X-ray scattering patterns and nanosized domains in transmission electron microscopy support the notion of mesocrystalline organization. Based on Z -contrast STEM imaging, intercalated organics are organized as elongated nanoclusters. Diffracting planes radiate outward from the crystal center, indicating a centrosymmetric strain field. The three-dimensional (3D) chemistry was investigated using atom probe tomography, which revealed a helical distribution of organic inclusions. This approach exemplifies how organic–inorganic templating can guide the evolution of intricate biomorphic crystal shapes. Round strontium sulfate crystals bear technological potential in the field of optoelectronics, such as IR–vis conversion materials or curved waveguides.