Authors: S. Portal, M.A. Vallvé, O. Arteaga, J. Ignes-Mullol, E. Bertran
Affilation: FEMAN group, Spain
Pages: 700 - 703
Keywords: nanoparticles, 2D crystals, spectroscopic ellipsometry, optical anisotropy
The self-assembly of nanometric size particles in large area compact monolayers has recently attracted considerable interest in terms of the fabrication of new optical nanostructured devices of macroscopic dimensions. These nanometric arranged surfaces present a photonic band, which is directly associated to the self-assembled nanometric structure and to the nature of the used material. In this work, silica nanoparticles were arranged in compact periodical arrays and the optical properties of the resulting nanoparticle film were studied. Nanoparticles were synthesized by sol-gel process and were constituted of monodisperse silica spheres of less than 300 nm diameter. Commercial latex nanoparticles were also used in this work for comparison. Synthesized and commercial nanoparticles were arranged in monolayers showing hexagonal structure on squared-inch glass substrates by means of Langmuir-Blodgett technique. The prime novelty of this work is the creation of a surface with an optical spectral anisotropy related to the periodical structure and to the presence of defects in the nanoparticles arrangement. Optical properties of the resulting film were studied by UV-visible spectroscopic ellipsometry and transmittance measurements whereas morphology and structural arrangements were determined by electronic microscopy. Possible applications of these anisotropic nanoparticle monolayer films are opal effect for application in jewellery, narrow-band polarizing filters and 2D-gratings in the UV-visible range for photonic applications.