To examine the ability of the OCB to detect 4ABA as a capping agent to bind deposited nanoparticles, instead of as a ligand directly binding to the surface of AuAg NPs, MNPs functionalized with 4ABA were deposited on the OCB. Raman spectra were gathered by scattering from TE and TM polarized guided waves. The SER spectra showed peaks attributed to 4ABA directly bonded to AuAg NPs (Figure ), and these bands were also observed when SERS was excited from 4ABA-decorated MNPs bound to AuAg NPs on the OCB (Figure ). Nevertheless, a comparison of peak positions and relative intensities revealed differences between the two types of bound 4ABA (Figure and Figure ). The τNH2 and νsCOObands were blue-shifted and reduced in intensity for 4ABA-decorated MNPs, suggesting a change in the binding environment.