title: No aging phenomena in ferrofluids: the influence of coating on interparticle interactions of maghemite nanoparticles.
abstract: The influence of coating on interparticle interactions in ferrofluids has been investigated using various techniques such as Mossbauer spectroscopy, magnetometry, transmission electron microscopy, photon correlation spectroscopy, X-ray diffraction, X-ray photoelectron, and resonance micro-Raman spectroscopy. Aging and spin-glass-like behavior was investigated in frozen ferrofluids of various concentrations from dense, initial value of 40 mg of coated nanoparticles per 1 mL of water, to dilute 1:10 (4 mg/mL). The as-prepared nanoparticles, core size 7-8 nm, were subsequently coated with a gummic acid corona of 20 nm thickness, which was observed to prevent agglomeration and to delay aggregation even in dense ferrofluids. The resulting separation of magnetic cores due to the coating eliminated all magnetic interparticle interaction mechanisms, such as exchange and dipoledipole, thus ensuring no aging effects of the magnetic particle system, as manifested in particle agglomeration and precipitation.
authors.affiliation: Institute of Materials Science, NCSR Demokritos, 15310 Aghia Paraskeui, Athens, Greece. irabias@ims.demokritos.gr
authors.forename: Ioannis
authors.initials: I
authors.lastname: Rabias
authors.forename: Michael
authors.initials: M
authors.lastname: Fardis
authors.forename: Eamonn
authors.initials: E
authors.lastname: Devlin
authors.forename: Nikos
authors.initials: N
authors.lastname: Boukos
authors.forename: Danai
authors.initials: D
authors.lastname: Tsitrouli
authors.forename: George
authors.initials: G
authors.lastname: Papavassiliou
mesh_terms: D000327:Adsorption; D003460:Crystallization / Q000379:methods*; D005290:Ferric Compounds / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D012996:Solutions; D013499:Surface Properties
chemical_list: D005290:Ferric Compounds; D046911:Macromolecular Substances; D012996:Solutions; C000499:ferric oxide