Effects of chain length of polyvinylpyrrolidone for the synthesis of silver nanostructures by a microwave-polyol method

When silver nanostructures were prepared by a microwave(MW)-polyol method in the presence of polyvinylpyrrolidone (PVP) as a capping reagent, besides spherical nanoparticles, nanosheets, polygonal nanoplates, nanorods, and nanowires were synthesized within 8 min. Effects of chain length of PVP were examined by using three different molecular weights of PVPs (10, 40, and 360 k). When a short chain PVP (10 k) was used, nanosheets and nanoplates were dominantly prepared, while nanorods and nanowires were preferentially synthesized by using longer chain PVPs (40, 360 k). The maximum aspect ratios of nanorods and nanowires were ∼ 7, ∼ 130, and ∼ 200 for PVP (10, 40, 360 k), respectively. These results indicated that shape and size of Ag nanostructures can be controlled by changing chain length of PVP. On the basis of UV and visible absorption spectra of product solutions, the number density of Ag nanostructures including spherical nanoparticles increased rapidly with increasing chain length of PVP.