Indication of a very large proton diffusion in ice i_h. III. Fluorescence quenching of 1-naphthol derivatives

The effects of excess protons on the fluorescence quenching process of 1-naphthol-4-sulfonate (1N4S) and 1-naphthol-3-sulfonate (1N3S) in methanol-doped ice samples were studied by employing a time-resolved emission technique. We found that the fluorescence quenching of the deprotonated form RO-* of both photoacids by protonation is very efficient in ice, whereas in liquid water the proton fluorescence quenching is rather small. Using the Smoluchowski diffusion-assisted binary collision model under certain assumptions and approximations, we found that the calculated proton diffusion constant in ice in the temperature range of 240-260 K was 10 times greater than that of water at 295 K.