Light-controlled self-assembly. Crystallization in the spotlight

Precise control over biotic and abiotic self- assembly processes is of fundamental interest, with practical implications for developing simple and scalable routes toward complex three-dimensional (3D) architectures with advanced functionalities. While techniques for achieving either local and static or dynamic and global control have been developed, local and dynamic control remains challenging. In this thesis, we harness light to achieve spatiotemporal control over the self- assembly of biorelevant crystals.
By utilizing photochemical reactions, we create local gradients of precursors that drive the nucleation and growth of bioinspired co-precipitation of barium carbonate nanocrystals and amorphous silica. Using a custom-built optical setup and optimizing the UV irradiation with the reaction conditions, we control self- assembly in terms of time, position, nucleation rate, and morphology.
By employing near- infrared (NIR) laser light , we demonstrate spatiotemporal control over the crystallization of retrograde soluble compounds induced by locally heating water. Modulating the NIR light intensity enables to start, steer, and stop crystallization of carbonate minerals with micrometer precision.
By integrating ion exchange into the light-driven self- assembly process, we introduce a two-step strategy based on self -organization and conversion reactions, shaping a diverse range of chemical compositions into user-defined designs. Considering thermodynamic stability and chemical reactivity, we design orthogonal conversion reactions for the sequential positioning of different metal chalcogenide semiconductors and the integration of various compositions into the same hybrid architecture.
This work opens previously unimaginable opportunities for light-directed self- assembly of functional composites, forging a genuine collaboration with self- assembly processes: simple hands-off autonomy when possible, and precise hands-on command when necessary.