title: Synthesis of highly monodisperse particles composed of a magnetic core and fluorescent shell.
abstract: Highly monodisperse particles composed of a magnetic silica core and fluorescent polymer shell were synthesized with a combined technique of heterocoagulation and soap-free emulsion polymerization. Prior to heterocoagulation, monodisperse, submicrometer-sized silica particles were prepared with the Stober method, and magnetic nanoparticles were prepared with a modified Massart method in which a cationic silane coupling agent of N-trimethoxysilylpropyl- N, N, N-trimethylammonium chloride was added just after coprecipitation of Fe (2+) and Fe (3+). The silica particles with negative surface potential were heterocoagulated with the magnetic nanoparticles with positive surface potential. The magnetic silica particles obtained with the heterocoagulation were treated with sodium silicate to modify their surfaces with silica. In the formation of a fluorescent polymer shell onto the silica-coated magnetic silica cores, an amphoteric initiator of 2,2'-azobis[ N-(2-carboxyethyl)-2-2-methylpropionamidine] (VA-057) was used to control the colloidal stability of the magnetic cores during the polymer coating. The polymerization of St in the presence of a hydrophobic fluorophore of pyrene could coat the cores with fluorescent polymer shells, resulting in monodisperse particles with a magnetic silica core and fluorescent polymer shell. Measurements of zeta potential for the composite particles in different pH values indicated that the composite particles had an amphoteric property originating from VA-057 initiator.
authors.affiliation: Department of Chemical Engineering, Graduate School of Engineering, Tohoku University, 6-6-07, Aoba, Aramaki-aza, Aoba-ku, Sendai 980-8579, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nagao
authors.forename: Mikio
authors.initials: M
authors.lastname: Yokoyama
authors.forename: Noriko
authors.initials: N
authors.lastname: Yamauchi
authors.forename: Hideki
authors.initials: H
authors.lastname: Matsumoto
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Mikio
authors.initials: M
authors.lastname: Konno
mesh_terms: D002412:Cations; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D008280:Magnetics; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry; D010316:Particle Size; D011108:Polymers / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D017640:Silicates / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013499:Surface Properties
chemical_list: D002412:Cations; D011108:Polymers; D012821:Silanes; D017640:Silicates; D012822:Silicon Dioxide; D007501:Iron; C005691:sodium silicate