title: Layer-by-layer assembly of conjugated polyelectrolytes on magnetic nanoparticle surfaces.
abstract: Composite nanoparticles with magnetic core and fluorescent shell were facilely prepared by the layer-by-layer deposition of conjugated polyelectrolytes over the negatively charged nanoparticles (NPs) of superparamagnetic iron oxide. The alternate assembly of cationic and anionic fluorescent polyelectrolytes leads to reversal in the sign of zeta-potentials. The even numbers of adsorption layer corresponding to the anionic polyelectrolyte (PFS) have negative values (-13 to -24 mV), whereas odd numbers of coating relative to the cationic polyelectrolyte (PFN) have positive values (26 to 28 mV). The composite nanoparticles can respond to both external magnetic field and ultraviolet light excitation. Forster resonance energy transfer (FRET) between oppositely charged polyelectrolytes (PFN and ThPFS) layers was also found, indicating dense packing of the polymer coatings. The fluorescence of the positively charged nanoparticles (NPs/PFN) can be quenched with very high efficiency by a small molecule anionic quencher [Fe(CN)6(4-)], while the same quencher has far less effect on the fluorescence of the negatively charged nanoparticles (NPs/PFN/PFS).
authors.affiliation: Department of Polymer Science & Engineering and Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210093, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Sun
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Ke-Jun
authors.initials: KJ
authors.lastname: Gu
authors.forename: Qun-Dong
authors.initials: QD
authors.lastname: Shen
authors.forename: Yan
authors.initials: Y
authors.lastname: Yang
authors.forename: Heng
authors.initials: H
authors.lastname: Song