Effect of Solvent Type and Viscosity on Modified Polyol Synthesis of Sn Nanoparticles

We report on the effect of solvent type on the synthesis of Sn nanoparticles via a modified polyol method at room temperature in an ambient atmosphere. In the synthesis, tin (II) 2-ethylhexanoate, sodium borohydride (NaBH4), and polyvinylpyrrolidone (PVP) were used as a precursor, reducing agent, and capping molecule, respectively. Transmission electron microscopy confirmed by that the Sn nanoparticles obtained in 1,5-pentanediol were smaller (9.2 mn) than 10 nm for an average diameter and had a narrow size distribution. We also observed that the average diameter of Sn nanoparticles obtained in 1,5-pentanediol increased slightly with a decreasing PVP molecular weight. The result can explain the synthesis mechanism in which Sn ions are not only preferential in forming a complex with the PVP but also preferentially reduced in a solvent, and the movement of reduced particles is influenced by the PVP. Consequently, an increase in PVP molecular weight may more effectively inhibit coalescence between nanoparticles, which are surrounded by a longer molecular chain and are highly viscous in the synthesis solution, all of which finally results in a decrease in the average particle size. On the basis of Fourier-transform infrared spectroscopy result, we demonstrated that the PVP on the Sn surface could be removed using an acetone/methanol mixed solvent.