Growth Inhibition of Hexagonal Silver Nanoplates by Localized Surface Plasmon Resonance

Characteristic light absorption occurred in silver citrate solution irradiated by monochromatic visible light above a threshold fluence (Φ thes ) due to the localized surface plasmon resonance (LSPR) of hexagonal silver nanoplates. The peak energy of the predominant absorption ( E hex ) at Φ thes was nearly the same as the incident energy ( E irrad ) and showed a slow decrease with the fluence (Φ). Transmission electron microscopy indicated that the edge length of the hexagons ( D hex ) increased from 25 to 58 nm with a decrease in E hex, but the thickness was constant at about 8 nm despite the difference in D hex . The slow decrease in E hex with Φ suggests gentle planar growth of the hexagonal nanoplates. When E irrad switched successively from 2.34 to 2.46 eV during light irradiation, the slow decrease in E hex with Φ showed a temporal stagnation. Thus, the LSPR acted as an inhibitory agent for the planar growth of hexagonal nanoplates. Some precursors formed below Φ thes begin to transform into critical seeds, and the growth of critical seeds is inhibited when the size is sufficient for LSPR excitation by E irrad . Hence, hexagonal nanoplates are size-selectively formed by monochromatic light irradiation.