title: Assembly and manipulation of Fe(3)O(4)/coumarin bifunctionalized submicrometer Janus particles.
abstract: Magnetic and fluorescent bifunctionalized Janus particles were fabricated via sequential particle embedding and surface modifications. The two hemispherical surfaces of a 500 nm silica particle were separately functionalized with Fe3O4 nanoparticles and coumarin dye molecules. The Fe3O4 hemisphere exhibited magnetically driven particle orientation and alignment, whereas the coumarin hemisphere served as an anisotropic emission indicator. The photoluminescence of these orientated and solidified Janus particles revealed anisotropic emission contrast as high as 40% between the magnet-aspect and the dye-aspect excitations. The dynamic anisotropic emission of the bifunctionalized Janus suspension under magnetic manipulation also revealed a nonsynchronized bulk correlation time that was much slower than that of an individual 500 nm particle. Under a static magnetic field, the suspended Janus particles assembled into a grape-like bunch, with random particle orientation. Unlike their microscale counterparts, the submicrometer magnetic Janus particles were less sensitive to gravity and more vulnerable to particle-particle interactions.
authors.affiliation: Department of Materials Science and Engineering, National Cheng Kung University , Tainan, 701-01, Taiwan.
authors.forename: Yi-Cheng
authors.initials: YC
authors.lastname: Chao
authors.forename: Wei-Hao
authors.initials: WH
authors.lastname: Huang
authors.forename: Keng-Ming
authors.initials: KM
authors.lastname: Cheng
authors.forename: Changshu
authors.initials: C
authors.lastname: Kuo
mesh_terms: D003374:Coumarins / Q000737:chemistry*; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D003374:Coumarins; D058185:Magnetite Nanoparticles; D011108:Polymers; C030123:coumarin