Two-dimensional ordering of Stِber silica particles at the air/water interface

Monolayers of Stöber silica particles were prepared on the surface of water and deposited onto glass substrates by the Langmuir–Blodgett method. Prior to film formation the surface of the silica particles was methoxylated by washing with methanol at room temperature. The surface methoxylation was characterized by FTIR, 13C CP MAS NMR and 29Si MAS NMR investigations. Good quality hexagonally close-packed (hcp) films of silica particles were prepared from methanol dispersions of the methoxylated spherical (d=689 nm) monodisperse particles. Large (10×10 μm of size), perfectly hcp ordered domains were found in scanning electron microscopic pictures of such monolayers deposited on glass substrates. Addition of the cationic surfactant decyltrimethyl ammonium bromide (DTABr) to the spreading suspensions decreased the ordering quality. All the particle monolayers showed first and second order Bragg diffraction at the wavelengths λ=1450 and 780–790 nm, respectively. The SiO2 background light transmission decreased with loss of ordering caused by the addition of DTABr.