Materials Chemistry and Physics 132 (2012) 196–202 Contents lists available at SciVerse ScienceDirect Materials Chemistry and Physics jo u rn al hom epage : www.elsevier.com/locate/matchemphys Fe 3 O 4 inverse spinal super paramagnetic nanoparticles Obaid ur Rahman, Subash Chandra Mohapatra, Sharif Ahmad ∗ Materials Research Lab, Department Of Chemistry, Jamia Millia Islamia, New Delhi 110025, India a r t i c l e i n f o Article history: Received 15 June 2011 Received in revised form 3 November 2011 Accepted 14 November 2011 Keywords: Ferrite nanoparticles Superparamagnetism VSM and EPR a b s t r a c t The present article reports an energy efficient method for the synthesis of superparamagnetic ferrite (Fe 3 O 4 ) nanoparticles (10–40 nm) and their annealing effect on the morphology, size, curie temperature and magnetic behavior at 50, 300, 400 and 500 ◦ C. The synthesized nanoparticles were characterized by various spectroscopic techniques like FT-IR and UV–visible. The crystalline structure and particle size were estimated through solid phase as well as the liquid phase using XRD, TEM and DLS techniques. Superparamagnetic behavior of nanoparticles was confirmed by VSM. The EPR study reveals that the main feature of X-Band solid state EPR spectrum has strong transition at g eff ∼ 3.23 (2100G) and a relatively weak transition at g eff ∼ 2.05 (3300G). The later transition further confirms the super paramagnetic nature of these nano ferrites. The activation energy and order of weight losses of nano ferrites were found to be: 39.6 KJ mol -1 and 0.21 orders (600–800 ◦ C), respectively, analyze with the help of TGA while the specific surface area (23.1 m 2 g -1 ) and pore size (9 ˚ A) were determined by Quanta chrome BET instrument. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Among the various nanostructure materials, metal oxide nanoparticles are the important class of materials as their optical, magnetic and electrical properties find a wide range of high tech applications [1]. Fe 3 O 4 nanoparticles are common ferrite with an inverse cubic spinal structure. These class of compounds exhibit unique electrical and magnetic properties due to the transfer of electrons between Fe 2+ and Fe 3+ on octahedral sites [2]. Fe 3 O 4 nanoparticles have been the subject of intense interest because of their potential applications in several advance technological areas due to their promising physical and chemical properties. Generally, these properties depend on the size and structure of particles [3,4]. Fe 3 O 4 nanoparticles find wide applications in the field of biomedical, as anticancer agent [5,6], corrosion protective pigments in paints and coatings [7]. The magnetic atoms or ions in such solid materials are arranged in a periodic lattice and their mag- netic moments collectively interact through molecular exchange fields, which give rise to a long-range magnetic ordering. Among all iron oxide nanoparticles, Fe 3 O 4 represent the most interest- ing properties due to of its unique structure i.e. the presence of iron cations in two valence states, Fe 2+ , Fe 3+ on tetrahedral and octahedral sites with an inverse cubic spinel structure. The coerciv- ity and remenance values for the super paramagnetic nano Fe 3 O 4 nanoparticles have been found to be zero by the earlier reported methods [8]. Presently, cell labelling strategies find application of ∗ Corresponding author. Tel.: +91 11 26827508x3268; fax: +91 11 2684 0229. E-mail address: sharifahmad jmi@yahoo.co.in (S. Ahmad). superparamagnetic ferrite either through conjugating the magnetic nanoparticles to the cellular surface of the stem cell or by inter- nalization of the particles into the cell. Superparamagnetic ferrite can work in both of these ways, since the potential to manipu- late their surface chemistry is plentiful and their sizes along with other attributes promote their successful uptake into cells. The superparamagnetic nano ferrites also interface well with MRI tech- nology. The use of superparamagnetic particles play a crucial role in the diagnostic imaging modality technique finds application in the study of stem cell [9]. Karaoglu et al. report the poly ethylene glycol (PEG) assisted hydrothermal route to study the influence of the hydrolyzing agent on the properties of PEG-iron oxide (Fe 3 O 4 ) nano composites and Köseoglu et al. reports the investigation on the structural and mag- netic properties of Mn 0.2 Ni 0.8 –Fe 2 O 4 nanoparticles synthesized by a PEG assisted hydrothermal rout [10,11]. Guobin Ding et al. reports the development and characterization of a magnetic micel- lar nanocarrier based on the amphiphilic copolymer [methoxy poly (ethylene glycol)-poly(d,l-lactideco-glycolide)] MPEG-PLGA and magnetite (Fe 3 O 4 ) nanoparticles, and discuss its potential for double-targeted hydrophobic drug delivery [12]. Cheng-Hao Liu et al. reports the development of a reusable, single-step system for the detection of specific substrates using oxidase-functionalized Fe 3 O 4 nanoparticles (NPs) as a bienzyme system and using amplex ultrared (AU) as a fluorogenic substrate [13]. Phadatare et al., reports The PEG assisted NiFe 2 O 4 nanoparticles for the possible biomedical applications such as magnetic resonance imaging, drug delivery, tissue repair, magnetic fluid hyperthermia, etc. [14]. Literatures available on the synthesis of nanoferrite using (PEG) based polyol methods as reported by Karaoglu et al., [10] the 0254-0584/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2011.11.032