Surfactant-aided surface-enhanced Raman scattering of Zn(II), Co(II), Ni(II), Cu(II) and free-base tetrakis(4-sulphonatophenyl)porphyrins

Although surface‐enhanced Raman scattering (SERS) has been recognized as a powerful tool for investigating the vibrational structure of molecules, the requirement that the molecules under study should have appropriate functional groups to interact with the metal surface has been a major problem in applying the SERS effect to many chemical or biological systems. It is shown that the introduction of a surfactant such as cetyltrimethylammonium bromide in a silver sol results in a strong Raman signal enhancement of negatively charged water‐soluble metallotetrakis(4‐sulphonatophenyl)porphyrins. Without introducing CTAB into a silver sol, these porphyrin molecules did not show any colour change and consequently no SERS effect was observed. Such a surfactant‐aided SERS effect will provide the possibility of applying SERS to new molecular systems.