Spectrofluorimetric Determination of the Water Content of the SiO2 Gels During the Solvent Exchange in Propylene Carbonate Solutions

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Changes of water content were determined by spectrofluorimetric methods in three different types of SiO2 gels after solvent exchanges in PC, 0.2 M LiPF6-PC or 0.2 M LiBF4-PC. Pyranine was used as a photophysical probe. The exchanges were carried out in bottles inside a glove-box flushed by dry nitrogen. It was found that the liquid inside the pores of the gels before the exchanges contained about 20–25 vol% of water. After the exchanges the water content decreased to about 4 vol%. The residual water could not be removed by subsequent exchanges. Possible causes for the presence of residual water are discussed.

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