Chelate Effect in Surface Enhanced Raman Scattering with Transition Metal Nanoparticles

Abstract

Over the years, several protocols have been designed to achieve surface enhanced Raman scattering (SERS) from noble/coinage metal nanoparticles preferably with silver and gold owing to the local electromagnetic field enhancement near their surface. However, the higher value of the imaginary component of the dielectric constant and the coupling between conduction and interband electron transitions result in poor SERS intensity for transition metals. Therefore, a good number of approaches such as the development of various surface roughening procedures have been made to increase the SERS sensitivity involving transition metal nanoparticles. This letter reports that chelating ligands such as 1,10-phenanthroline, ethylenediammine, and so forth have been found to be superior alternatives to bring forth the SERS activity from “3d” block transition metal nanoparticles (nickel and cobalt). Thus, a comparative account of SERS efficiency derived from these materials as well as from coinage metal nanoparticles engaging chelating and nonchelating (e.g., pyridine) ligands becomes intriguing.