Enhanced Raman Scattering from Molecules Adsorbed on Resonant Metal Particles
The wavelength-dependence of the intensity of Raman scattering by pyridine molecules adsorbed on colloidal gold particles and the Mie absorption and scattering intensities by the same particles have been measured, along with studies of the particle size and aggregation by electron microscopy. The Raman excitation profiles are shown to resemble to absorption spectra of the colloids more closely than they resemble the Mie scattering profiles. Electron microscopy confirms that the gold colloids which show large values of the adsorbate resonance Raman enhancement (> 104-fold) are aggregates consisting of strings of very small particles, and it is found that the large surface Raman enhancements result from excitation under the longitudinal plasma resonance of the particle strings but not from excitation under the transverse resonance.
KeywordsGold Colloid Pyridine Molecule SERS Enhancement Excitation Profile Raman Enhancement
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