Silica aerogels are extensively used as catalyst supports due to their mesoporous
structure and chemical inertness. In this study, SiO2–AuNP aerogels containing gold
nanoparticles (AuNPs) were synthesized using the sol-gel method followed by supercritical
CO2 drying. The inclusion of polyvinyl pyrrolidone (PVP) as a stabilizing agent preserved
the gold particle sizes during the gelation process. In contrast, aerogels synthesized
without PVP contained enlarged AuNP aggregates, resulting in a shift in the plasmon
resonance color from red to bluish or blue–grey. Thermal treatment of these bluish-colored
aerogels at high temperatures restored their red coloration, visually indicating the
breakdown of large gold clusters into individual nanoparticles. Both types of aerogels
were characterized using SEM, TEM, 3D optical microscopy, UV–vis and ATR-IR spectroscopy,
and N2 porosimetry, with their properties analyzed as a function of annealing temperature.
Their catalytic activity was evaluated through the reduction of 4-nitrophenol with
sodium borohydride, and both aerogel types demonstrated catalytic activity. This thermal
conversion of large clusters into individual nanoparticles within an aerogel matrix
introduces a new and promising approach for creating catalytically active nanogold-containing
aerogel catalysts.
