Compose and Convert: Controlling Shape and Chemical Composition of Self-Organizing Nanocomposites

Organizing the right material at the right place has the potential to revolutionize bottom-up assembly of functional architectures. Despite tremendous progress, this is still difficult in particular because control over chemical composition and morphology are typically inherently entangled. Here a two-step strategy is introduced based on self-organization and conversion reactions to shape a wide selection of chemical compositions into user-defined designs. First, photogeneration of CO2 induces precipitation of nanocomposites of barium carbonate nanocrystals and amorphous silica (BaCO3/SiO2) with control over shape and location following arbitrary illumination patterns. Second, the resulting nanocrystals are converted by sequential ion exchange into a palette of chemical compositions, while the original shape is preserved. By considering thermodynamic stability and chemical reactivity, orthogonal conversion reactions are designed for sequentially positioning nanocomposites of different metal chalcogenide semiconductors next to each other. Based on these strategies, different compositions are integrated into the same hybrid architecture, and the functionality potential is demonstrated by forming a light-emitting perovskite semiconductor that is embedded into an optical waveguide. Combining light-controlled self-organization and shape-preserving ion-exchange reactions offers exciting opportunities for shaping up materials.