SURFACE-ENHANCED RAMAN-SCATTERING OF PYRIDINE IN SILVER COLLOIDS EXCITED IN THE NEAR-INFRARED REGION

A scanning Raman spectrometer and an Nd: YAG laser operating at 1.06 m um were used to observe the surface-enhanced Raman scattering (SERS) o f pyridine in yellow silver colloids. Enhancement factors for the tria ngle ring breathing vibration mode at 1006 cm-1 and for the totally sy mmetric breathing mode at 1036 cm-1 are about 16.5 and 21 times larger , respectively, than those found for excitation at 514.5 nm. The large enhancement factors for excitation in the near-infrared region sugges t that further refinement of the theories currently proposed to explai n the SERS effect is necessary.