Enhanced Bragg reflections from size-matched heterostructure photonic crystal thin films prepared by the Langmuir-Blodgett method

The Langmuir-Blodgett method was used to engineer photonic crystal thin films of an AB architecture. Structures were studied by transmittance and reflectance spectroscopies. For an AB structure in which the silica particle diameter B is twice that of A, reflectance features associated with the first order Bragg peak for the ``A'' domain are only observed when the structure is probed from the A side of the structure. Furthermore, this feature is enhanced in intensity compared to that for a structure consisting solely of A particles. These findings are attributed to a matching of first and second order Bragg processes

Synthetic opals made by the Langmuir-Blodgett method

Monodispersive synthetic opal particles were formed by the method of Stober et al. [J. Colloid Interface Sci. 26 (1968) 62] and were made hydrophobic by reacting them with 3-(trimethoxysilyl)propyl methacrylate. Groups of particles were dissolved in chloroform and were spread at the air/water interface using a Nima trough. Each group studied consisted of particles, which had almost identical diameters. Isotherms were obtained and these are illustrated. The use of an optimum value of surface pressure and a high level of hydrophobicity made it possible to deposit good quality multilayers by the Langmuir-Blodgett method but we found that the Langmuir-Schaefer method was easier to use for less hydrophobic particles. The layers obtained were studied by scanning electron microscopy and we present the images obtained from these results