Investigation of the role of polyol molecular weight in the polyol synthesis of silver nanoparticles

The polyol synthesis method is a popular approach for fabricating long silver nanowires. Additionally, the polyol method has been claimed to produce various shapes and sizes of nanoparticles by altering certain parameters of the reaction, such as the molecular weight of the solvent. Yet the effect of varying the molecular weight of the polyol solvent on the synthesis product is not well understood, since studies that report an effect that the solvent use substantially different procedures. Here, we analyze the effect of changing the polyol solvent, from ethylene glycol to poly(ethylene glycol) with different molecular weights, on the shape and size of silver nanoparticles using the same procedure. Using ethylene glycol, silver nanowires (up to 2 μm in length) are synthesized, similar to what has been widely reported. Under the same conditions, poly(ethylene glycol) of any molecular weight yields shorter nanoparticles (<500 nm) with different shapes. Additionally, the impacts that synthesis variables have differ with polyol molecular weight. Using ethylene glycol, chloride ions are required to obtain nanowires; the length of which can be shortened by adjusting the reaction time or the concentration of capping agent. Using poly(ethylene glycol), these synthesis variables have different outcomes: chloride ions do not affect the yield of anisotropic nanoparticles; neither does the concentration of the capping agent.