Metal nanoparticles have been attracting considerable attention over the past decades, because of their unique electronic, catalytic and optical properties that are found highly dependent on the size and shape. To minimize trial and error and realize controlled synthesis with desired nanoparticle morphologies and specific properties, we need a better understanding of the interactions between the metal, ligands and solvent system and their effects on the synthesis mechanism and kinetics. We will present our study on investigating the effect of solvents on ligand-metal interactions and how the solvent can be used to control the synthesis of Pd nanoparticles of specific sizes. By combining in-situ small-angle X-ray scattering (SAXS), X-ray absorption fine structure spectroscopy (XAFS) and nuclear magnetic resonance (NMR) techniques, we show that the coordinating ability of solvents affects the ligand-Pd interactions, resulting in different nucleation and growth kinetics and final sizes (4.2 nm in pyridine, a coordinating solvent, and 1.3 nm in toluene, a non-coordinating solvent). Furthermore, using these insights, we systematically varied the solvent properties to synthesize Pd nanoparticles of sizes ranging from around 1 nm to 5 nm with low polydisopersity (~10-15%). We will show the correlation between the solvent properties and ligand-metal interactions, and how they can affect the kinetics and final size. The results provide a better understanding of the critical solvent and ligand effects on the synthesis kinetics and show the potential for tailoring the solvent-ligand-metal interactions to realize controlled synthesis of metal colloidal nanoparticles without trial and error.

Solvent effect on ligand-metal interactions in Pd nanoparticle synthesis

253rd National Meeting (2017)

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