SURFACE-ENHANCED RAMAN-SPECTROSCOPY USING PHOTODEPOSITED GOLD PARTICLES IN POROUS SOL-GEL SILICATES

A new optically transparent, porous material is prepared that acts as a substrate for surface-enhanced Raman spectroscopy (SERS). The material is a silica matrix synthesized by the sol-gel method containing gold particles. Small molecules, such as pyrazine, diffuse into the matrix and are detected by using SERS. The gold particles are produced by a photochemical method that allows systematic and simple optimization which is appropriate for the SERS applications. The silica matrix stabilizes the gold particles compared to colloids in liquid media. SERS is verified by the enhancement of the Raman bands of pyrazine. The effect is further characterized by studying the change in the Raman depolarization ratio. Organometallic gold precursor compounds are dissolved in the sol and encapsulated in growing silicate network. Irradiation of doped monoliths with ultraviolet light causes the photodeposition of gold particles within the silica gel or xerogel. The particle size is controlled by the irradiation time and by the form of the matrix. The particles are characterized by electronic absorption spectra, X-ray diffraction, and transmission electron microscopy.