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Role of Metal Cations in Plasmon-Catalyzed Oxidation: A Case Study of p‑Aminothiophenol Dimerization
journal contribution
posted on 2017-10-09, 00:00 authored by Zhiyang Zhang, Virginia Merk, Anja Hermanns, Wolfgang E. S. Unger, Janina KneippThe
mechanism of the plasmon-catalyzed reaction of p-aminothiophenol
(PATP) to 4,4′-dimercaptoazobenzene (DMAB)
on the surface of metal nanoparticles has been discussed using data
from surface-enhanced Raman scattering of DMAB. Oxides and hydroxides
formed in a plasmon-catalyzed process were proposed to play a central
role in the reaction. Here, we report DMAB formation on gold nanoparticles
occurring in the presence of the metal cations Ag+, Au3+, Pt4+, and Hg2+. The experiments were
carried out under conditions where formation of gold oxide or hydroxide
from the nanoparticles can be excluded and at high pH where the formation
of the corresponding oxidic species from the metal ions is favored.
On the basis of our results, we conclude that, under these conditions,
the selective oxidation of PATP to DMAB takes place via formation
of a metal oxide from the ionic species in a plasmon-catalyzed process.
By evidencing the necessity of the presence of the metal cations,
the reported results underpin the importance of metal oxides in the
reaction.