Ionic Conductivity Measurements-A Powerful Tool for Monitoring Polyol Reduction Reactions.

The reduction of metal precursors during the polyol synthesis of metal nanoparticles was monitored by ex situ ionic conductivity measurements. Using commonly used platinum precursors (KPtCl, HPtCl, and KPtCl) as well as iridium and ruthenium precursors (IrCl and RuCl), we demonstrate that their reduction in ethylene glycol at elevated temperatures is accompanied by a predictable change in ionic conductivity, enabling a precise quantification of the onset temperature for their reduction. This method also allows detecting the onset temperature for the further reaction of ethylene glycol with HCl produced by the reduction of chloride-containing metal precursors (at ≈120 °C).