2013 Volume 17 Issue 2 Pages 23-29
Photoinduced electron transfer (PET) was investigated in multicomponent aqueous suspensions composed of tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)_3^<2+>, photocatalyst), methylviologen (1,1'-dimethyl-4,4'-bipyridinium dication, MV^<2+>, electron acceptor), and ethylenediaminetetraacetate (EDTA, sacrificial electron donor) together with particles of smectite-type clays, where Ru(bpy)_3^<2+> and MV^<2+> are present in excess compared with CEC of the clay minerals. Clays with different particle sizes - fluorohectorite (FH) and montmorillonite (Mont) with large particle sizes (>0.1μm), and hectorite (Hect) and saponite (Sapo) with small particle sizes (〜30nm) - were examined, and the PET reaction proceeded in all of the suspensions to yield methylviologen radical cation (MV^<+・>) as the product. However, the difference in the clay particle size gave different product distribution; the large-size clays dominantly gave MV^<+・> dimers whereas the small-size clays mainly produced MV^<+・> monomers similarly to a homogeneous aqueous solution. Also, the large-size clays more stabilized the MV^<+・> species than the small-size ones. These results evidenced contribution of the clay-water interfaces to the reaction.
