The study investigates the phosphorescent emission characteristics of aerogels containing two strontium aluminate europium dysprosium phosphor powders (50 μm particle size): Yellow-Green (YG) and Pineapple (PYL), with potential application in passive emergency signage systems. Three sample configurations were examined: loose aerogel powder, aerogel monoliths, and xerogel. Phosphorescence spectra were obtained using a spectrophotometer with excitation and emission wavelengths of 421 nm and 520 nm for YG and 475 nm and 501 nm for PYL. To prepare the aerogels and xerogels, wet-gel samples were prepared from a mixture of tetramethyl orthosilicate, methanol, water, and an ammonia solution as a catalyst. Polypropylene glycol (PPG) is added as a viscous additive to help retain phosphor particles within the aerogel during gelation. The phosphor (0.7 g) was introduced after the gelation solution began to thicken, allowing them to become incorporated into the aerogel. Gelation takes 5-15 minutes, depending on how fresh the ammonia was. To ensure measurement reliability, four repeated PTI MD‑4000 spectrometric runs were performed for each sample under identical conditions.
The results show consistent emission profiles across repeated runs. Monolithic aerogel samples exhibited the highest emission intensities, with peak values ranging from approximately 100,000 to 130,000 a.u. Both YG-HP and PYL-HP samples displayed sharp emission peaks followed by exponential decay tails. In contrast, xerogel samples produced little to no emission signal, indicating no detectable phosphorescence under the same experimental conditions. All decay curves were best described by double exponential fits, indicating multiple emission pathways where different phosphor populations contribute to the afterglow at different rates. Sample orientation within the spectrophotometer also influenced the measured intensity, suggesting anisotropic emission behavior. These findings show the potential of phosphorescent aerogel as energy-independent materials for passive signage, where prolonged visibility following power loss is critical in low-visibility environments.