title: Polymer-assisted self-assembly of superparamagnetic iron oxide nanoparticles into well-defined clusters: controlling the collective magnetic properties.
abstract: The combination of superstructure-forming amphiphilic block copolymers and superparamagnetic iron oxide nanoparticles produces new nano/microcomposites with unique size-dependent properties. Herein, we demonstrate the controlled clustering of superparamagnetic iron oxide nanoparticles (SPIOs) ranging from discretely encapsulated SPIOs to giant clusters, containing hundreds or even more particles, using an amphiphilic polyisoprene-block-poly(ethylene glycol) diblock copolymer. Within these clusters, the SPIOs interact with each other and show new collective properties, neither obtainable with singly encapsulated nor with the bulk material. We observed cluster-size-dependent magnetic properties, influencing the blocking temperature, the magnetoviscosity of the liquid suspension, and the r2 relaxivity for magnetic iron oxide nanoparticles. The clustering methodology can be expanded also to other nanoparticle materials [CdSe/CdS/ZnS core/shell/shell quantum dots (QDs), CdSe/CdS quantum dots/quantum rods (QDQRs), gold nanoparticles, and mixtures thereof].
authors.affiliation: Institute of Physical Chemistry, University of Hamburg , Grindelallee 117, 20146 Hamburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schmidtke
authors.forename: Robin
authors.initials: R
authors.lastname: Eggers
authors.forename: Robert
authors.initials: R
authors.lastname: Zierold
authors.forename: Artur
authors.initials: A
authors.lastname: Feld
authors.forename: Hauke
authors.initials: H
authors.lastname: Kloust
authors.forename: Christopher
authors.initials: C
authors.lastname: Wolter
authors.forename: Johannes
authors.initials: J
authors.lastname: Ostermann
authors.forename: Jan-Philip
authors.initials: JP
authors.lastname: Merkl
authors.forename: Theo
authors.initials: T
authors.lastname: Schotten
authors.forename: Kornelius
authors.initials: K
authors.lastname: Nielsch
authors.forename: Horst
authors.initials: H
authors.lastname: Weller
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry*; D060328:Magnetic Phenomena; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D005290:Ferric Compounds; D011108:Polymers; D018036:Selenium Compounds; D013440:Sulfides; D013501:Surface-Active Agents; C034939:cadmium sulfide; C000499:ferric oxide; C058667:cadmium selenide