| Summary: | 碩士 === 逢甲大學 === 光電研究所 === 95 === By changing the concentration of silver nitrate solution and reducing agent(sodium borohydride),we can obtain the silver particles with size range from 35nm to 120nm and observe the particle’s size-effect on the Surface Enhanced Raman Scattering (SERS) of benzoic acid(BA) solutions excited by 488nm laser beam. The BA is dissolved in methanol and kept at the concentration 10-2 M。We analyzed the intensities of BA’s 1003 cm-1 and 1600 cm-1 vibrational modes relative to the 1033 cm-1 vibrational mode of methanol。
We found that BA’s SERS relative intensity of both modes first increases with the increase of silver particle’s size, and reach an optimum value at around 60nm. However, with further size’s increases, its SERS relative intensity starts to drop and becomes almost unnoticeable for the particle’s size of about 120nm.Whether BA two SERS of vibration relative intensity with silver particle size have a non-linear variation tendency.
Schatz have proposed an electromagnetic theory of SERS under different excited wavelength and different silver particle’s shape or size. Although this theoretical results are based on the single silver particle, we found that the theoretically estimated behavior of the size-effect on SERS qualitatively agrees quite well with our experimental results.
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