Ion Pairing and Nucleation Pathways in Confined Electrolyte Solutions: A PDF Study in MCM-41 Mesopores

Understanding nucleation in confinement is key to revealing how ion associations control phase formation at the nanoscale. While multi-step nucleation with transient intermediates is well studied in bulk, its behavior under nanoconfinement is poorly known. In mesoporous silica MCM-41, confinement modifies electrostatic screening and hydration, altering ion-pair stability and mobility. This PhD project investigates sulfate- and chloride-based electrolyte solutions confined in 2–4 nm pores of MCM-41. High-energy X-ray total scattering with pair distribution function (PDF) analysis at ID15 will probe ion structures and correlations. The results will clarify whether ion pairs serve as prenucleation clusters that drive metastable phase formation and clogging in confinement, providing fundamental insight into nucleation pathways in natural and engineered systems.