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7 pages; International audience; An engineering approach towards combined photonic band gap properties and magnetic functionalities, based on independent nanoscale engineering of two different materials at different length scales, is conceptually presented, backed by simulations, and experimentally confirmed. Large (>200 nm)monodisperse nanospheres of transparent silica self-assemble into a photonic crystal with a visible band gap, which is retained upon infiltration of small (

Coating gold colloids with a well controllable silica shell is finding many applications in the fields of bioconjugation and photonic crystals. In this work, we report on ravine-structured surface morphology changes on silica-coated gold (Au@SiO 2 ) colloids as observed using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) characterizations. These Au@SiO 2 colloids were prepared in the direct Stober synthetic route and the silica-shell thickness was varied between 20 to 100 nm. An aggregation mechanism is proposed to successfully model the silica-shell growth on the gold nanoparticles (NPs) and explain the formation of the ravine-structured surface of the Au@SiO 2 colloids. Furthermore, it is found that the ravine-structured surface strongly influences the formation of the Au@SiO 2 colloidal crystal films. The improved understanding of the surface morphology changes provides a suitable methodology for tailoring the growth of the core–shell structured colloids and assembling them into highly ordered colloidal crystal films.

Faraday rotation for magnetic field sensing can find applications in satellite altitude monitoring. Enhancing and tuning Faraday rotation is demonstrated in hybrid magnetic photonic crystals, based on an independent nanoscale engineering of two different materials (silica and iron oxide) at different length scales ( 200 nm). An engineering approach towards combined photonic band gap properties and magnetic functionalities, based on independent nanoscale engineering of two different materials at different length scales, is conceptually presented, backed by simulations, and experimentally confirmed. Large (> 200 nm) monodisperse nanospheres of transparent silica self-assemble into a photonic crystal with a visible band gap, which is retained upon infiltration of small (< 20 nm) nanoparticles of magnetic iron oxide. Enhancing and tuning Faraday rotation in photonic crystals is demonstrated.