title: Structurally coloured secondary particles composed of black and white colloidal particles.
abstract: This study investigated the colourful secondary particles formed by controlling the aggregation states of colloidal silica particles and the enhancement of the structural colouration of the secondary particles caused by adding black particles. We obtained glossy, partially structurally coloured secondary particles in the absence of NaCl, but matte, whitish secondary particles were obtained in the presence of NaCl. When a small amount of carbon black was incorporated into both types of secondary particles, the incoherent multiple scattering of light from the amorphous region was considerably reduced. However, the peak intensities in the reflection spectra, caused by Bragg reflection and by coherent single wavelength scattering, were only slightly decreased. Consequently, a brighter structural colour of these secondary particles was observed with the naked eye. Furthermore, when magnetite was added as a black particle, the coloured secondary particles could be moved and collected by applying an external magnetic field.
authors.affiliation: Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan. ytakeoka@apchem.nagoya-u.ac.jp
authors.forename: Yukikazu
authors.initials: Y
authors.lastname: Takeoka
authors.forename: Shinya
authors.initials: S
authors.lastname: Yoshioka
authors.forename: Midori
authors.initials: M
authors.lastname: Teshima
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takano
authors.forename: Mohammad
authors.initials: M
authors.lastname: Harun-Ur-Rashid
authors.forename: Takahiro
authors.initials: T
authors.lastname: Seki
mesh_terms: D003102:Colloids / Q000737:chemistry* / Q000528:radiation effects; D003116:Color; D060526:Magnetic Fields; D058185:Magnetite Nanoparticles / Q000737:chemistry* / Q000528:radiation effects*; D008422:Materials Testing; D010316:Particle Size
chemical_list: D003102:Colloids; D058185:Magnetite Nanoparticles
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