Temperature dependence of photoinduced Au particle formation in polyvinyl alcohol films

Au particles were embedded in polyvinyl alcohol films (Au/PVA films) by a photoreduction technique. Formation of Au particles in the films was investigated at temperatures between 0 and 50 degreesC in the dark. The Au/PVA film was colorless at 0 degreesC for 20 h after the photoreduction. On the other hand, the film became purple with increasing ambient temperatures. In the optical absorption spectra of the film, the absorption band of surface plasmon resonance of Au particles became clear with time. The average diameter of the Au particles in the film was estimated to be 29.1 nm from transmission electron microscopy observation. A thermal-sensing reagent was fabricated using the Au particles in PVA. The color of the reagent irreversibly changed from white to purple when the ambient temperature increased from 0 to 25 degreesC. (C) 2000 American Institute of Physics. [S0003-6951(00)02847-3].