Surface-Enhanced Raman Spectra of Aza-aromatics on Nanocrystals of Metallic ReO₃

Surface-enhanced Raman spectra (SERS) of pyridine have been investigated on the surfaces of the metallic ReO3 nanocrystals with diameters in the range of 12−32.5 nm. On ReO3 nanocrystal surfaces, the Raman bands of pyridine generally shift toward lower frequencies, accompanied by enhancement of intensity. The frequency shift does not vary with particle size, but band intensification is highest with the 17 nm nanocrystals. The study establishes how an oxide metal can be employed equally effectively to observe SERS of molecules. On the basis of the success with the study of pyridine, we have extended the study to SERS of pyrimidine and pyrazine on 17 nm ReO3 nanocrystals. The SERS effect observed in the three aza-aromatics demonstrates the presence of bonding interaction between the ReO3 surface and the adsorbed molecules.