Novel nanoparticle synthesis in self-organizing water-based systems

Nanoparticle synthesis has evolved into a highly diverse discipline, characterized by increasingly sophisticated precursor designs, reactor engineering, and templating strategies to achieve precise control over particle properties. Although this diversity has significantly advanced the field, it has also diverted attention from the fundamental physicochemical principles governing nanoparticle formation. This thesis adopts an alternative approach: instead of increasing synthetic complexity, it seeks to mechanistically elucidate nanoparticle formation in simple, water-based systems under mild conditions, and to exploit this understanding to control and, where feasible, optimize particle properties for targeted applications. Three (and a half) structurally distinct systems were investigated: surfactant-free ternary mixtures for Stöber-type silica synthesis; spontaneous, one-pot coprecipitation of transition metal carbonates and sulfides within silica matrices, including the effects of ligand-controlled precipitation phenomena on this coprecipitation process; and polyacrylic acid/transition-metal coacervates as templates for nanoparticle formation. In all systems, particle formation was determined to depend more on the kinetics governing the availability, interaction, and assembly of the relevant building blocks than on the complexity of the synthesis route. Interfacial diffusion across microemulsion boundaries, pH-coupled silica condensation, precursor complex stability, ligand-mediated surface passivation, and confinement-induced changes in chemical potential were each identified as tunable, rate-limiting steps. Based on these insights, highly monodisperse nanoscale silica particles, silica-encapsulated transition-metal carbonate and sulfide nanodots, precursor- and ligand-tuned CdS/ZnS quantum dots, and coacervate-templated ultra-small carbonate, sulfide, and oxide nanoparticles were synthesized using only water as the solvent under near-ambient conditions. Building on this mechanistic understanding, application-oriented optimization was conducted for selected synthesized materials. Notably, iron oxide/silica core–shell particles produced via the coprecipitation route were developed into heterogeneous Fenton-like catalysts that operate at circumneutral pH, achieving activity comparable to or surpassing that of more complex multistep systems. Additional application-specific optimization was performed for the remaining materials and is discussed in conjunction with the relevant mechanistic findings. Collectively, these results demonstrate that a kinetically informed understanding of nanoparticle formation offers a robust and transferable framework for the rational, application-driven design of functional nanomaterials using simple, sustainable, and scalable water-based synthesis methods.