PREPARATION AND OPTICAL-PROPERTIES OF SILICA-GELS IN WHICH SMALL GOLD PARTICLES WERE GROWN BY PHOTOREDUCTION

Small Au particles were grown in silica gels by a photoreduction technique. Photoreduction of AuCl4- ions in the silica gel was carried out by ultraviolet light irradiation at room temperature. X-ray photoelectron spectroscopy and X-ray diffraction measurement indicated the formation of Au particles in the silica gel. From transmission electron microscopy observation of the Au/silica gel with 1 wt% of Au, the diameter of Au particles was estimated to be similar to 30 nm. Subsequent to ultraviolet light irradiation for 10 min, a stable absorption band at 550 nm gradually developed at room temperature, indicating that the number of Au particles were increasing. The peak is due to the surface plasmon resonance absorption of Au particles.