Photosensitized electron transfer processes in SiO/sub 2/ colloids and sodium lauryl sulfate micellar sytems: correlation of quantum yields with interfacial surface potentials

Journal Article · Wed Sep 30 20:00:00 EDT 1981 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.78.10.5928· OSTI ID:6037022

Laane, C ^[1]; Willner, I; Otvos, J W; Calvin, M

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1. Agricultural Univ., Wageningen, Netherlands

The effectiveness of negatively charged colloidal SiO/sub 2/ particles in controlling photosensitized electron transfer reactions has been studied and compared with that of the negatively charged sodium lauryl sulfate (NaLauSO/sub 4/) micellar system. In particular, the photosensitized reduction of the zwitterionic electron acceptor propylviologen sulfonate (PVS/sup 0/) with tris(2,2'-bi-pyridinium)ruthenium(II) (Ru(bipy)/sub 3//sup 2 +/) as the sensitizer and triethanolamine as the electron donor is found to have a quantum yield of 0.033 for formation of the radical anion (PVS) in the SiO/sub 2/ colloid compared with 0.005 in the homogeneous system and 0.0086 in a NaLauSO/sub 4/ micellar solution. The higher quantum yields obtained with the SiO/sub 2/ colloidal system are attributed to substantial stabilization against back reaction of the intermediate photoproducts - i.e., Ru(bipy)/sub 3//sup 3 +/ and PVS/sup -/ - by electrostatic repulsion of the reduced electron acceptor from the negatively charged particle surface. The binding properties of the SiO/sub 2/ particles and NaLauSO/sub 4/ micelles were investigated by flow dialysis. The results show that the sensitizer binds to both interfaces and that the SiO/sub 2/ interface is characterized by much higher surface potential than the micellar interface. The effect of ionic strength on the surface potential was estimated from the Gouy-Chapman theory, and the measured quantum yields of photosensitized electron transfer were correlated shows that the quantum yield is not affected by surface potentials smaller than approx. = -40 mV. At larger potentials, the quantum yield increases rapidly. These results indicate that the surface potential is the dominant factor in the quantum yield improvement for PVS/sup 0/ reduction.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6037022
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 78:10; ISSN PNASA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ALKALI METAL COMPOUNDS
AMINES
AZINES
BIPYRIDINES
CHALCOGENIDES
CHEMICAL REACTIONS
COLLOIDS
COMPLEXES
DISPERSIONS
ELECTRON TRANSFER
ESTERS
HETEROCYCLIC COMPOUNDS
INTERFACES
MICELLAR SYSTEMS
MINERALS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PYRIDINES
RADICALS
REACTION INTERMEDIATES
REDUCTION
RUTHENIUM COMPLEXES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SODIUM COMPOUNDS
SULFONIC ACID ESTERS
SULFURIC ACID ESTERS
TRANSITION ELEMENT COMPLEXES
YIELDS