Biomimetic synthesis of silica hollow spheres using poly (L-lysine) and mechanism research

The biomimetic synthesis of silica hollow spheres induced by poly (L-lysine) (PLL) under mild conditions is reported in this paper. A number of analytical techniques, such as scanning electron microscopy, energy dispersive spectroscopy, circular dichroism analysis, thermogravimetric analysis, fourier transform infrared spectroscopy, laser scanning confocal microscopy, and liquid atomic force microscopy, were used to investigate the synthesis and characterization of the materials. While the PLL peptide backbone interacted with the silicate species in the solution via electrostatic interactions and hydrogen bonding, the surfaces of PLL served as catalytic sites for the hydrolysis and condensation of tetraethoxysilane. The continuous process of biomineralization from nucleation to the formation of hollow spheres was observed, providing direct proof of biosilica in situ mineralization. A three-step mechanism was proposed. PLL directed the nucleation of the silica precursor and crystalline growth. Silica nanoparticles aggregated and self-assembled to form hollow spheres. The results obtained suggest that it is possible to control the synthesis of silica biomimetic materials under mild chemical and physical conditions.