Understanding the mechanism of crystal growth through oriented attachment of nanoparticles, such as in the self-assembly of metal oxide minerals in aqueous solution, poses many challenges, but also opens vast opportunities for materials design. We present a theoretical approach for modeling solvent controlled interactions between nanoparticles that reaches into the mesoscale, while retaining molecular details of the interacting particle surfaces and intervening solvent. The total Hamiltonian of the system includes contributions from long-range particle-particle dispersion interactions across solvent, that accounts for the influence of solvent structuring on the high frequency dielectric response and ion screening of the static response, and contributions from ion-mediated interactions. The latter include direct Coulomb interactions between ions and mineral surfaces with discrete facet-dependent distribution of charges, image interactions, interactions arising from density (excluded volume) and charge density (ion correlation) fluctuations, ion-mineral and ion-water dispersion interactions. The, ion-mineral dispersion contribution depends on dynamic excess polarizabilities of ions in water and on the dynamic dielectric function of the mineral surfaces providing the link between macroscopic and microscopic dispersion terms.
The model was validated against its ability to reproduce ion activity in 1:1, 2:1 and 3:1 electrolyte solutions in the 0-2M concentration range, and its ability to capture the qualitative ion-specific effect in 1:1 electrolytes at the air-water interface. We apply the approach to understand the influence of pH on facet-dependent interactions between anatase TiO2 nanoparticles.