Surface Enhanced Raman Scattering Effect of Semiquinonediimine of ρ-Phenylenediamines Adsorbed on Silver Cluster

Surface enhanced Raman scattering （SERS） or ρ-Phenylenediamnine （PPD） derivatives （CD-2 and TMPPD） on silver cluster was studied. It was found that the reduced form of CD-2 and TMPPD adsorbed on ailver cluster do not give SERS effect, but their oxidized forms do.
The case of CD-2 and its oxided products was investigated in detail. It was suggostcd that scmiquinonediimine, the half oxidized form of CD-2 adsorbed on silver cluster via delocalized bond of the free radical. It was supposed that, there may be different reaction mechanisms of semiquinonediimine radical in the presence and absent of silver cluster. The behavior of silver cluster during oxidation of CD-2 by silver nitrate and oxygen was discussed.