High yield polyol synthesis of round- and sharp-end silver nanowires with high aspect ratio

Long silver nanowires (average length of 28 μm, average aspect ratio of 130) with uniform diameter along their length were produced by polyol synthesis of AgNO3 in ethylene glycol in the presence of PVP as preferential growth agent. Nanowires were produced with no addition of chloride salts such as NaCl or CuCl2 (or other additives such as Na2S) which are usually used for lowering reduction rate of Ag ions by additional etchant of O2/Cl−. Lower reduction rate was obtained by increasing the injection time of PVP and AgNO3 solutions, which was the significant factor in the formation of nanowires. Therefore, there was enough time for reduced Ag atoms to be deposited preferentially in the direction of PVP chains, resulting in high yield (the fraction of nanowires in the products) of nanowires (more than 95%) with high aspect ratio. The produced nanowires had both round- and sharp-ends with pentagonal cross section. Higher energy level of Ag atoms in borders of MTPs, which increases the dissolution rate of precipitated atoms, in addition to partial melting of MTPs at high synthesis temperatures, leads to the curving of the surfaces of exposed (111) crystalline planes in some MTPs and the formation of round-end silver nanowires.