Thinking Green with Molecular Silver Nanoparticle Production

Solution-phase (NP) syntheses involve large amounts of solvent and produce small quantities of product. Although dry methods of making NPs exist (e.g. ball milling), for ligand-passivated colloidal NPs the costs (financial, environmental, health, etc.) associated with solvent use seem to be inevitable. A partially solid-state synthesis was recently proposed wherein the amount of solvent was significantly reduced, however it was not well developed and lacked generality. We have studied this process to understand the limits of the solid-state approach and to leverage the best features of both solid-state and liquid-state approaches. Most importantly, we used a silver-thiolate paste as a precursor, instead of a metal salt solution, to achieve intimate mixing of solid-state reagents, eliminate solvent waste, and retain the high mobility needed for a high yield reaction. The synthesis yielded solid NPs, in paste form, which may be processed using a nominal quantity of solvent. This produced only Na$_{\mathrm{4}}$Ag$_{\mathrm{44}}(p$-MBA)$_{\mathrm{30}}$ NPs with an 89{\%} yield and reduced solvent use by \textasciitilde 90{\%}.