It is also noted that propagating TE or TM guided waves yields slightly different SERS profiles. Compared to their TE counterparts, the τNH2, νsCOO -and ν19b bands have slightly stronger intensities, while the peak at 1598 cm -1 is noticeably weaker. The presence of bands attributable to τNH2 and νsCOO -indicate that at least some NH2 and COO -groups have partially dissociated from the MNP surface and may have bonded with the AuAg surface. However, the fact that these two bands were no longer dominant suggested that 4ABA did not assume the same orientation observed when binding to AuAg NPs in the absence of MNPs.