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ELECTRON AND ENERGY TRANSFER IN ILLUMINATED POROUS VYCOR GLASS
Author(s) -
Wong P. K.
Publication year - 1974
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1974.tb06531.x
Subject(s) - electron paramagnetic resonance , triphenylamine , radical , photochemistry , quantum yield , adsorption , electron acceptor , electron transfer , acceptor , chemistry , bromide , x ray photoelectron spectroscopy , materials science , analytical chemistry (journal) , inorganic chemistry , chemical engineering , organic chemistry , nuclear magnetic resonance , fluorescence , optics , physics , condensed matter physics , engineering
— Porous Vycor glass samples containing adsorbed molecules were illuminated at 77 K by a mercury lamp jacketed by a filter cutting off wavelengths below 250 nm. Oxygen or carbon dioxide on Vycor produces an asymmetric electron paramagnetic resonance (EPR) signal best described as holes trapped in the glass. Methyl bromide produces an identical EPR signal plus four other lines due to methyl radicals. Evidence is presented that the products result from excitonic energy transfer from the Vycor to the adsorbed materials. Triphenylamine (TPA) adsorbed on Vycor can also be photoionized by similar illumination, and the cation radical TPA + can be stabilized at 77 K if an electron acceptor is also adsorbed. Attachment of the photoejected electron by carbon dioxide forms CO 2 ‐ , and that by methyl bromide leads to methyl radicals. The CH 3 radical yield is dependent on the surface separation between the electron donor (TPA) and the acceptor (CH 3 Br). By monitoring the relative quantum yield of the methyl radicals as a function of distance separating the TPA and CH 3 Br, it is shown that the photoelectron is capable of migrating on the Vycor glass surface.