Influences of Organic-Inorganic Surface Interactions on Crystallization in Liquid-Solid Systems

Organic-inorganic materials including diverse oxides, biominerals and semiconductors are of considerable academic and technological interest due to the ability to tailor their properties for a wide-range of applications. The macroscopic properties of these materials depend on their chemical compositions, crystalline structures, morphologies, and the interactions between organic and inorganic components. Importantly, organic-inorganic surface interactions play a crucial role in the nucleation, growth, and hierarchical structuring of these hybrid materials. However, in many material systems the mechanisms by which organic species interact on a molecular level with inorganic components are not well understood. This is largely due to the challenges associated with the molecular characterization of interactions in heterogeneous liquid-solid mixtures of diverse components that also evolve with time.;Herein, the influences of organic-inorganic surface interactions on the growth of crystalline or disordered structures are established in hydrating aluminate/silicate cements and solution-grown zinc chalcogenide nanoparticles. The molecular-level compositions, structures, and surface interactions have been measured in these diverse material systems composed of liquid and solid phases. Molecular interactions are correlated with specific structural features to identify the processes that govern the hydration or growth of these technologically important materials. Advanced one- and two-dimensional NMR techniques are primarily used to characterize surface structures where interactions with adsorbed organic species influence cement hydration or nanoparticle growth. Specifically, these measurements identify the structural transformations of closely related saccharides that account for their dramatically different influences on the hydration of aluminate and silicate species in cements. Similar characterization techniques establish the structural transformations of alkylamine surfactants exposed to carbon dioxide that lead to different shapes and supramolecular assemblies of zinc chalcogenide nanoparticles. These results help identify the processes that control cement hydration and nanoparticle growth and establish that crystallization is governed by the binding of organic molecules at specific inorganic surface sites. The new insights are expected to contribute directly and broadly towards understanding molecular-level interactions in similar systems and help establish molecular criteria for the design or selection of organic species that mediate cement hydration and nanoparticle growth.