Interfacial redox mediation by amine/alkyne-functionalized silicon nanoparticles: surfactant-free gold nanoparticle...

We develop a surfactant-free synthesis method for gold nanoparticles (AuNPs) using 2-propynylamine-functionalized silicon nanoparticles as integrated redox-active supports. Surface-anchored amine groups act as built-in reducing sites for Au³⁺ precursors at the hexane-water interface under ambient conditions, enabling in situ AuNP nucleation and growth. Time-resolved UV-vis spectroscopy and dynamic light scattering track the emergence of plasmonic AuNPs, while quantitative morphology analysis reveals a final population dominated by spherical and near-spherical nanoparticles (∼74%), with faceted polyhedral structures (∼4%) and dendritic, hollow, irregular, and rod-like morphologies (∼22%) as minority species. The temporal evolution proceeds from early dendritic and irregular aggregates to a later-stage ensemble in which small spherical particles dominate numerically, whereas larger faceted structures persist as a minor but visually prominent component. Control experiments with unfunctionalized silicon, amine-functionalized silica, or free ligand alone do not yield AuNPs, underscoring the cooperative role of the semiconductor core and grafted primary amine ligands in mediating interfacial electron transfer. This ligand-enabled strategy provides a scalable route to surfactant-free AuNPs and Au-Si hybrids with potential applications in plasmonic sensing, catalysis, and biomedicine.