FTIR Spectroscopy of Heat Treated Sol-Gels.
Acid catalyzed sol-gels, which have not been thoroughly washed to remove residual solvent, change from a colorless gel to a black xerogel upon being heated to high temperatures ~900 degrees Celsius. The darkening of the acid catalyzed sol-gels is a result of its small pores, enabling it to capture the hydrocarbons that are left behind during the evaporation of the solvent phase. Base catalyzed sol-gels (which have larger pores) do not turn black upon heating because its larger pores permit the solvent to evaporate. At this point, two separate batches of acid catalyzed sol-gels were prepared in order to analyze how the structure may change upon heat treatment. The first batch was separated into 9 heating boats and heated up to 900 degrees Celsius, removing a heating boat after each 100 degree Celsius increase. This procedure was repeated with the second batch after washing it for 4 days. As anticipated, the washed batch remained colorless while the unwashed batches turned progressively black.. Each sample from the heating boats will be further examined through FTIR spectroscopy. Furthermore, in a earlier study by Au, Green, Grey, and Sailor, gels that were produced through the reaction of TEOS or TMOS with organic carboxylic acids--formic, lactic, acetic, etc--and heat treatment emitted intense white photoluminescence during UV excitation. The photoluminescence of some of these gels was verified through a duplication of their experimental procedure. Future studies will be made to analyze the structure of the PL gels through FTIR spectroscopy.
Quach, Hung, "FTIR Spectroscopy of Heat Treated Sol-Gels." (1999). URC Student Scholarship.
Support provided by:National Science Foundation