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A. O. Naumova, A. S. Mugabutaeva, P. V. Melnikov, N. K. Zaitsev

The photoprotolytic reactions in the systems immobilized on silica with a cationic polyelectrolyte


The protolytic and photoprotolytic reactions were studied for the model systems of 2-naphthol and for sulfonated 2-naphthols in the immobilized state. It was found that the fixation of indicators with a cationic polyelectrolyte leads to the shift of pKa of the ground state to a more acidic value. The value of this shift depends on the number of sulfo-groups in the molecule and reaches 1.2 units for the disodium salt of 2-naphthol-3,6,8-trisulfonic acid. However, the photoprotolytic reaction in the lower singlet-excited state proceeds in the same way as for an unimmobilized substance, and no significant shift in pKa* is observed. The possibility of a flow-through acidity sensor using the ratio of the intensities of the fluorescence bands of the protonated and deprotonated forms of the indicator is shown.
Key words: acid-base indicators, optical pH sensors, photoinduced proton transfer, sulphonated derivatives of 2-naphthol, organic dyes, cationic polyelectrolyte.
Moscow University Chemistry Bulletin.
2021, Vol. 62, No. 2, P. 86

Copyright (C) Chemistry Dept., Moscow State University, 2002
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