title: SiO2 coating effects in the magnetic anisotropy of Fe3-xO4 nanoparticles suitable for bio-applications.
abstract: We present radio frequency transverse susceptibility (TS) measurements on oleic acid-coated and SiO2-coated Fe3-xO4 magnetite nanoparticles. The effects of the type of coating on the interparticle interactions and magnetic anisotropy are evaluated for two different particle sizes in powder samples. On the one hand, SiO2 coating reduces the interparticle interactions as compared to oleic acid coating, the reduction being more effective for 5 nm than for 14 nm diameter particles. On the other hand, the magnetic anisotropy field at low temperature is lower than 1 kOe in all cases and independent of the coating used. Our results are relevant concerning applications in biomedicine, since the SiO2 coating renders 5 and 14 nm hydrophilic particles with very limited agglomeration, low anisotropy, and superparamagnetic behavior at room temperature. The TS technique also allows us to discriminate the influence on the anisotropy field of interparticle interactions from that of the thermal fluctuations.
authors.affiliation: Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Zaragoza, Spain. figueroa@unizar.es
authors.forename: A I
authors.initials: AI
authors.lastname: Figueroa
authors.forename: C
authors.initials: C
authors.lastname: Moya
authors.forename: J
authors.initials: J
authors.lastname: Bartolomé
authors.forename: F
authors.initials: F
authors.lastname: Bartolomé
authors.forename: L M
authors.initials: LM
authors.lastname: García
authors.forename: N
authors.initials: N
authors.lastname: Pérez
authors.forename: A
authors.initials: A
authors.lastname: Labarta
authors.forename: X
authors.initials: X
authors.lastname: Batlle
mesh_terms: D016880:Anisotropy; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D008280:Magnetics; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology; D019301:Oleic Acid / Q000737:chemistry; D010316:Particle Size; D011846:Radio Waves; D012822:Silicon Dioxide / Q000737:chemistry*; D013696:Temperature
chemical_list: D020099:Coated Materials, Biocompatible; D058185:Magnetite Nanoparticles; D019301:Oleic Acid; D012822:Silicon Dioxide