Silica–Chitosan Gel Composites: Effect of Chitosan Addition on Optical and Thermal Properties

Silica–chitosan hybrid composites containing up to 3.5 % chitosan were prepared via a reproducible and simple sol–gel route through the hydrolysis and condensation of tet-raethoxysilane (TEOS). The obtained gels were systematically characterized in terms of their textural, optical and thermal properties using UV–Vis spectroscopy, TG/DTA analysis, scanning electron microscopy (SEM), X-Ray diffraction and thermal conduc-tivity measurements. The bulk gel density was found to increase with chitosan content, indicating gradual compaction of the silica network and high sample homogeneity. These structural changes were accompanied by alterations in thermal stability, optical transparency, and heat transfer properties. DTA analysis revealed a broad exothermic feature, which may indicate a thermally induced process, such as partial carbonization. The resulting composites are suitable for various applications, including thermal insu-lation with controlled thermal conductivity, optical devices, biocompatible coatings, adsorbents for pollutant removal, controlled drug delivery, catalytic supports, and sensors. UV/Vis measurements display an intense absorption feature of the composites at 280 – 305 nm, which is promising for optical filter applications in combination with the increased mechanical stability due to chitosan addition.