On the Conversion of Nanocomposite Architectures

Imagine if a house would not need effort to be build, but rather assembled on its own. Or if a car would repair itself if it broke down. This might sound like a futuristic perspective, but in nature it is quite a common phenomenon: a chick `assembles' itself inside an egg without any outside interference, and a broken bone can repair itself over time. What if we could unravel the processes behind this self-assembly and use it to build our own materials? In this thesis, a bioinspired strategy is used to bring self-assembly processes to man-made materials. In this strategy, barium carbonate (BaCO3) co-precipitates with silica (SiO2) to form nanocomposites: a material where nanocrystals of BaCO3 are embedded in a supporting matrix of SiO2. These nanocomposites have two particular properties that we exploit in this thesis: First, their shape can be sculpted during the co-precipitation, allowing the overall nanocomposite's architecture to be tailor-made for its intended application. Second, the small size of the BaCO3 crystals makes them very reactive, whereas the SiO2 gives the nanocomposites mechanical stability. This combination of chemical reactivity and mechanical stability is used here to change the composition of the nanocomposites, where the new composition inherits the shape of the original nanocomposite. This allows for materials suited for specific applications to be sculpted, which is demonstrated in this thesis for materials suitable for catalysis and photovoltaics. Moreover, this thesis shows that the material’s inherited shape can boost their performance in their intended application.