Gold nanoplates of truncated triangular or hexagonal shape within 100 nm were prepared by UV irradiation of solution containing HAuCl4, poly(vinylpyrrolidone) (PVP) and gold nanoseeds at room temperature within 30 min. Energy-dispersive X-ray spectra, electron diffraction and X-ray diffraction analyses revealed that the nanoplates were highly pure face-centered cubic gold single crystals with {111} planes as their basal planes. Infrared transmittance spectra analysis suggested there existed interaction between PVP and gold. The nanoplates showed two surface plasmon resonance (SPR) absorption bands in UV-Vis absorption spectra due to their anisotropic structure. The absorption spectra of products under various experimental conditions indicated that PVP reacted as both reductant and capping agent, high-intensity UV irradiation accelerated the reaction, and the gold seeds imposed catalysis effect on the reaction. The adding amount of seeds held an optimum value at which the average size of the nanoplates reached top as large as 80 nm together with their in-plane dipolar SPR absorption band locating at 950 nm. The size of the nanoplates decreased and the in-plane dipolar band blue-shifted when the adding amount of seeds exceeded that value.

Key words: gold nanoplate, UV irradiation, seed, poly(vinylpyrrolidone), surface plasmon resonance