title: Seeded growth of titania colloids with refractive index tunability and fluorophore-free luminescence.
abstract: Titania is an important material in modern materials science, chemistry, and physics because of its special catalytic, electric, and optical properties. Here, we describe a novel method to synthesize colloidal particles with a crystalline titania, anatase core and an amorphous titania-shell structure. We demonstrate seeded growth of titania onto titania particles with accurate particle size tunability. The monodispersity is improved to such an extent so that colloidal crystallization of the grown microspheres becomes feasible. Furthermore, seeded growth provides separate manipulation of the core and shell. We tuned the refractive index of the amorphous shell between 1.55 and 2.3. In addition, the particles show luminescence when trace amounts of aminopropyl-triethoxysilane are incorporated into the titania matrix and are calcined at 450 °C. Our novel colloids may be useful for optical materials and technologies such as photonic crystals and optical trapping.
authors.affiliation: Soft Condensed Matter, Debye Institute for Nanomaterials Science, Department of Physics and Astronomy, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands. A.F.Demirors@uu.nl
authors.forename: Ahmet Faik
authors.initials: AF
authors.lastname: Demirörs
authors.forename: Anita
authors.initials: A
authors.lastname: Jannasch
authors.forename: Peter D J
authors.initials: PD
authors.lastname: van Oostrum
authors.forename: Erik
authors.initials: E
authors.lastname: Schäffer
authors.forename: Arnout
authors.initials: A
authors.lastname: Imhof
authors.forename: Alfons
authors.initials: A
authors.lastname: van Blaaderen
mesh_terms: D003102:Colloids; D008163:Luminescent Measurements; D018613:Microscopy, Confocal; D010316:Particle Size; D044367:Phase Transition; D011437:Propylamines; D012821:Silanes / Q000737:chemistry; D013696:Temperature; D014025:Titanium / Q000737:chemistry*
chemical_list: D003102:Colloids; D011437:Propylamines; D012821:Silanes; C009495:titanium dioxide; D014025:Titanium; C477625:amino-propyl-triethoxysilane