title: Highly birefringent vaterite microspheres: production, characterization and applications for optical micromanipulation.
abstract: This paper reports on a simple synthesis and characterization of highly birefringent vaterite microspheres, which are composed of 20-30 nm sized nanocrystalls. Scanning electron microscopy shows a quite disordered assembly of nanocrystals within the microspheres. However, using optical tweezers, the effective birefringence of the microspheres was measured to be Deltan = 0.06, which compares to Deltan = 0.1 of vaterite single crystals. This suggests a very high orientation of the nanocrystals within the microspheres. A hyperbolic model of the direction of the optical axis throughout the vaterite spherulite best fits the experimental data. Results from polarized light microscopy further confirm the hyperbolic model.
authors.affiliation: University of Queensland, School of Mathematics and Physics, Queensland, Australia.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Parkin
authors.forename: Robert
authors.initials: R
authors.lastname: Vogel
authors.forename: Martin
authors.initials: M
authors.lastname: Persson
authors.forename: Maren
authors.initials: M
authors.lastname: Funk
authors.forename: Vincent L Y
authors.initials: VL
authors.lastname: Loke
authors.forename: Timo A
authors.initials: TA
authors.lastname: Nieminen
authors.forename: Norman R
authors.initials: NR
authors.lastname: Heckenberg
authors.forename: Halina
authors.initials: H
authors.lastname: Rubinsztein-Dunlop
mesh_terms: D016880:Anisotropy; D001718:Birefringence; D004867:Equipment Design; D007834:Lasers; D008855:Microscopy, Electron, Scanning / Q000379:methods*; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008863:Microspheres; D053758:Nanoparticles; D036103:Nanotechnology / Q000379:methods; D055095:Optics and Photonics; D010316:Particle Size; D014961:X-Ray Diffraction