AVS 47th International Symposium
    Material Characterization Tuesday Sessions
       Session MC-TuP

Paper MC-TuP12
XPS Investigation of Counterion Exchange in SiO@sub 2@ Sol-gel Films Doped with Tris(2,2'-bipyridine)Ruthenium(II)

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: X. Wen, University of North Carolina at Chapel Hill
Authors: X. Wen, University of North Carolina at Chapel Hill
M. Sykora, University of North Carolina at Chapel Hill
T.J. Meyer, University of North Carolina at Chapel Hill
R.W. Linton, University of North Carolina at Chapel Hill
Correspondent: Click to Email
SiO@sub 2@-based sol-gels provide an attractive matrix for doping a variety of molecules. Ru complexes are among the most attractive dopant molecules for SiO@sub 2@ sol-gels due to their unique photophysical and redox properties. Applications of sol-gel films doped with Ru complexes are mostly based on the properties related to the metal-to-ligand charge transfer (MLCT) excited state of the complex. The MLCT excited states are very sensitive to not only the physical nature but also the compositions of the sol-gel matrix. This research work investigates the possible new method of tailoring the compositions of SiO@sub 2@ sol-gel thin films doped with [Ru(bpy)@sub 3@]Cl@sub 2@, which involves the exchange of the original counterions of Ru complexes with new counterions. SiO@sub 2@ sol-gel films doped with [Ru(bpy)@sub 3@]Cl@sub 2@ were prepared by spin-coating from sol/[Ru(bpy)@sub 3@]Cl@sub 2@ mixtures. XPS coupled with Ar@super +@ sputtering was used to study both the surface compositions and depth profiles of the sol-gel films before and after the counterion exchange experiments. The results indicated the original counterion, Cl@super -@, of Ru(II) complex completely leached out of the film after exposing the film to water. Cl@super -@ ion could be reintroduced into the film by putting the Cl@super -@ deprived film back in HCl solution. New counter ions, such as PF@sub 6@@super -@, were incorporated into the sol-gel film by immersing the Cl@super -@ deprived film in HPF@sub 6@ solution. The incorporation of PF@sub 6@@super -@ ions was both time and pH dependent. In addition, cations such as Na@super +@ could also be incorporated into the film by putting the sol-gel film in basic solutions such as Na@sub 2@HPO@sub 4@/NaH@sub 2@PO@sub 4@. This approach was used to calculate the ratio of total Si to the number of SiO@super -@H@super +@ sites that can be exchanged in the SiO@sub 2@ sol-gel films.