Capping Modes in PVP-Directed Silver Nanocrystal Growth: Multi-Twinned Nanorods versus Single-Crystalline Nano-Hexapods

Silver nanostructures with different morphology and crystal structure are successfully synthesized using poly(vinyl pyrrolidone) (PVP) molecules with different molecular weight (MW) in the polyol process. Multitwinned nanorods and single-crystalline nanohexapods are obtained using PVP-H (MW ≈ 1 300 000) and PVP-L (MW ≈ 30 000), respectively. The nanorods and the nanohexapods both have face-centered cubic (FCC) crystal structures but with different lattice constants, i.e., a = 4.0862 Å for the nanorods and a = 9.6193 Å for the nanohexapods. The growth mechanism for the Ag nanostructures is studied in details. The control on the shape and the crystal structure is attributed to the different capping modes for the PVP-directed Ag nanocrystal growth.