Abstract
The charge-transfer fluorescence quenching of pyrene (Py) by '-diethylaniline (DEA) adsorbed on silica surfaces was investigated for silicas with average pore sizes (aps) ranging from 60 (Si-60) to 1000 A (Si-1000). For all silicas a complete lack of quenching activity was observed below the respective DEA monolayer value. Such inertness of DEA as a charge-tranfer quencher is interpreted in terms of its strong adsorption interactions with surface silanol groups. Above monolayer coverage the slopes of the quenching (Stern-Volmer) plots markedly increase with decreasing aps, reaching a solutionlike efficiency in the case of Si-60. The effect is attributed to a gradual nonhomogeneous pore volume fill up by DEA, which is sensitive to the aps distribution. The nature of the surface-quenching mechanism is discussed in light of the Py-DEA exciplex fluorescence wavelengths and relative yields. It appears that the irregularity of the surface affects the mutual1Py*-DEA geometry as well as the effective local polarity. Consequently, the relative weight of the exciplex, versus electron-transfer pathways, is markedly aps dependent.
Original language | English |
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Pages (from-to) | 48-54 |
Number of pages | 7 |
Journal | Langmuir |
Volume | 5 |
Issue number | 1 |
DOIs | |
State | Published - 1 Jan 1989 |