Investigating the interaction of aminopolycarboxylic acid (APCA) ligands with silver nanoparticles: A Raman, surface-enhanced Raman and density functional theoretical study

Abstract

Aminopolycarboxylic acid (APCA) ligands are polydentate chelating agents that have multiple binding sites viz. nitrogen atoms and short chain carboxylic groups and hence can form very stable complexes with metal ions. The interactions of these APCAs with silver nanoparticles have been investigated using surface-enhanced Raman scattering (SERS) which is supported with density functional theoretical (DFT) calculations using B3LYP functional and LANL2DZ basis set. From the observed enhancement of the CO2 symmetric stretching vibration, in addition to the red shift of ∼14–35 cm−1 for the various APCAs in the SERS spectra as well as theoretical calculations, it has been inferred that the APCAs are chemisorbed to the silver surface directly through the oxygen atoms of the carboxylate groups as well as the N atom of the substituted amino groups. The apparent enhancement factors for the CO2 symmetric stretching vibration of the APCAs are of the order of 106.