chapter  30
12 Pages

Surveying the Silica Gel Surface with Excited States

Experimental Details . . . . . . . . . . . . . . . . . . . . . . . . 368

Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . 368

Sample Preparation . . . . . . . . . . . . . . . . . . . . . . . 368

Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . 369

Photophysics of Pyrene on Various Silica

Gel Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369

Photophysics of 1-Aminopyrene on Various

Silica Gel Surfaces . . . . . . . . . . . . . . . . . . . . . . . 369

Gaussian Distribution Model . . . . . . . . . . . . . . . . 372

Oxygen Quenching of Singlet Excited States

of Pyrene and DPA . . . . . . . . . . . . . . . . . . . . . . 374

Oxygen Adsorption Isotherms . . . . . . . . . . . . . . . 375

Langmuir-Hinshelwood Approach

to Oxygen Quenching . . . . . . . . . . . . . . . . . . . . 376

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . 377

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377

Time-resolved and steady-state fluorescence probing was used to study gas-solid and liquid-solid silica

gel interfaces. The molecular surveying probes pyrene, 1-aminopyrene, pyrenecarboxylic acid, and 9,10-

diphenylanthracene adsorbed at the silica gel surface give information about probe environment, mobility,

and accessibility. Reactions of surface-bound arene singlet excited states with molecular oxygen were

monitored over a range of temperatures; the reactions were assigned to a unique Langmuir-Hinshelwood

mechanism. The kinetics reflect the details of oxygen adsorption and movement on the silica gel surface.