Origins of Bound-Probe Fluorescence Decay Heterogeneity in the Distribution of Binding Sites on Silica Surfaces
- University of Utah, Salt Lake City, UT (United States)
Inhomogeneous fluorescence decay kinetics have been observed from 3-(1-pyrenyl)-propyldimethylsilane (3PPS) covalently bound to silica surface. The excited-state decay kinetics were found to follow a discrete biexponential model rather than a continuous lifetime distribution model and were attributed to the specific site heterogeneity on the silica surface. The existence of two distinguisable silanol sites on silica surface was further supported by the difference in fluorescence decays when a chlorosilane versus a hydroxysilane reagent is used to bind pyrene to the surface. It was also found, for chlorosilane-bound pyrene, that the decay kinetics became more heterogeneous with increasing reaction time or upon exposure of the derivatized sample to water. These results can be explained by a selective reaction between the hydroxysilane and a small population of active silanols, while chlorosilane reacts indiscriminately with the surface under kinetic control. Furthermore, fluorescence quenching studies of surface-immobilized pyrene by iodine were also conducted; enhanced quenching rates for the shorter-lived excited-state population were observed and attributed to the adsorption of quencher molecules to active silanol sites which also caused a faster decay rate of the surface-bound pyrene probe.
- Research Organization:
- University of Utah, Salt Lake City, UT (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB)
- Grant/Contract Number:
- FG03-93ER14333
- OSTI ID:
- 2481365
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 46 Vol. 99; ISSN 0022-3654
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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