Photo-promoting Fabrication of Silver Nanoparticles in the Presence of Anthracenyl-Focal PAMAM Dendrons

Silver nanoparticles protected by first to third generation poly(amido amine) dendrons with an anthracenyl-focal point were fabricated by photo-promotion of silver ions in aqueous dendron solutions. The reaction solutions colored from light to deep brown and displayed a broad plasmon band at 450 nm, indicating the formation of silver nanoparticles. The formation of particles progressed with time, although it slowed down at the light-shielding (dark) condition. The light-promoted electron transfer from amine groups of dendron to silver ions through anthracenyl moiety might concern to the formation of silver nanoparticles. According to the images of transmission electron microscopy, the shape of nanoparticles was not only spherical (15–20 nm in size) but also polygonal (20–35 nm in size). It was confirmed from the crystallographic analysis of electron diffraction patterns that the polygon was a hexagonal-close-packing (hcp) single crystal, whereas the crystal structure of spherical nanoparticles was face-centered-cubic (fcc). The reaction was fastest when the second generation dendron was used, indicating the competition of increasing number of amine groups and reducing efficiency of photo-promoted electron transfer with generation.