Fabrication of Phosphorescent Aerogels

Aerogel is a low density nanoporous solid that is generally formed using a supercritical extraction process which results in a material with a  high surface area and low density. The aim of this project was to entrap phosphors in a silica aerogel and analyze how long the aerogel would phosphoresce (i.e. glow) after being exposed to ultraviolet light. To make the aerogel I first started with the silica aerogel precursors including tetramethoxysilane, water, methanol, and used ammonia as a catalyst. An aqua colored phosphor material, comprised of strontium illuminate, europium, and dysprosium particles, each around 50 microns in size, was introduced into the precursor solution. The solution was periodically mixed until the precursor solution fully gelled, forming a wet gel. To process the wet gel and make an aerogel, a hydraulic hot press was used to perform supercritical extraction. An Ultra Violet spectrometer was used to perform Emission Spectra and Lifetime tests on the resulting aerogels. The excitation and emission wavelength were found to be 495 nm and 416-600 nm respectively for the aerogel with aqua phosphor indicating that we had successfully entrapped the phosphor. The emission spectrum tests showed that phosphor aerogels with colors closer to the high end of the electromagnetic spectrum emitted the most intense and vibrant glow. However these results could be affected by the inconsistent mixing process which could result in impurities within the aerogel, diminishing its intensity compared to a fully mixed counterpart. Furthermore, I discovered that increasing the phosphor concentration during the mixing process correlated with heightened phosphorescence intensity. Lifetime tests confirmed that aerogels with the highest phosphor concentration, exhibited on average a greater intensity over a longer period of time.