P29 表面増強ラマン法による金属表面吸着分子の超音波洗浄過程の観察

抄録

We observed ultrasonic cleaning process of molecules absorbed on metal surface by surface enhanced Raman scattering. The metal is silver, and adsorbed molecules are rhodamine 6G (R6G). Metal surface is treated by oxidation-reduction cycle, and saturated with R6G in 10^<-9>M solution. The ultrasonic bath is shown in Fig. 1, which is consisted of 477 Hz transducer, glass inner cylinder, and acrylic outer cylinder. The sample is excited by argon ion laser. The scattering light is focused onto a spectrograph and detected by CCD. Raman spectrum is shown in Fig.2. Broad background emission is fluorescence, and sharp peaks are SERS. Fluorescence decreased quickly, whereas SERS decreased slowly. SERS intensity of Raman spectrum around 1700 cm^<-1> is shown in Fig.3. Although the decrease in SERS intensity occurs gradually without sonication, the decay rate greatly enhanced by ultrasound, which indicates that the R6G molecules adsorbed on the silver plate are desorbed on decomposed by the ultrasound. Comparing the results with different ultrasonic powers, SERS is lost within 5 minutes under 26 W ultrasound, while small amount of SERS remains after the 30minutes irradiation of 5 W ultrasound. It means that the absorbed R6G is lost more efficiently with stronger ultrasound.