Synthesis of fibroin/silica adsorbent for thin layer chromatography

The main aim of this work is to synthesize microspherical fibroin/silica adsorbent through a one-step in situ synthesis that integrates silk fibroin into the hydrolytic polycondensation of tetraethoxysilane (TEOS). The kinetics of the sol-gel process is studied at varying ratios of the initial reagents - fibroin, TEOS and ammonium hydroxide in a 4% formic acid solution under different temperatures and stirring rates. It was demonstrated that the sol-gel transition in all cases occurs within a few minutes. The highest yield of the target product was observed at a fibroin:TEOS ratio of 0.03:1 and the addition of 2.3 ml of 25 % ammonium hydroxide solution. The obtained samples were analyzed using scanning electron microscopy with EDS, nitrogen porosimetry, IR spectroscopy, diffractometry and thermogravimetry. The morphologically obtained fibroin/silica adsorbent consists of microspherical particles measuring 10 ?m in size, with a pore size distribution of 10–30 nm and a specific surface area of 318 m2·g-1. The IR study of the obtained nanohybrid fibroin/silica adsorbent reveals absorption bands at 3410 cm–1 characteristics of ?Si-OH groups and at 1063 cm–1 related to vibrations of the siloxane group ?Si-O-Si? in the silica structure. The characteristic absorption bands of Amide I at 1638 cm–1 and Amide II at 1512 cm–1 confirm the presence of fibroin. The interactions between fibroin macromolecules and the formed silica structure are evidenced by a reduction in crystallinity of the fibroin within the obtained samples. The nitrogen adsorption and desorption isotherm reveals the presence of a hysteresis loop, indicating that the obtained nanohybrid fibroin/silica adsorbent possesses the mesoporous structure. According to the IR spectral, X-ray structural and thermal characteristics, the obtained product comprises silica and fibroin phases and differs from its constituent components, which confirm its nature as a hybrid nanocomposite material. Additionally, its potential application for separating nitroaniline isomers using high-performance thin-layer chromatography has been demonstrated.