Synthesis, characterization and magnetic properties of Fe 3 O 4 doped chitosan polymer E. Karaca a , M. Şatır a , S. Kazan a , M. Açıkgöz b,n , E. Öztürk c , G. Gürdağ d , D. Ulutaş c a Gebze Institute of Technology, Department of Physics, 41400 Çayırova, Kocaeli, Turkey b Faculty of Arts and Sciences, Bahçeşehir University, Beşiktaş 34353, Istanbul, Turkey c Istanbul University, Faculty of Science, Physics Department, Vezneciler, Istanbul, Turkey d Istanbul University, Chemical Engineering Department, 34320 Avcılar, Istanbul, Turkey article info Available online 14 February 2014 Keywords: Composite polymer Fe 3 O 4 nanoparticle Reflection loss Magnetization abstract Fe 3 O 4 nanoparticles doped into chitosan films were prepared by the solution casting technique. Various samples were synthesized in atmospheric medium and in vacuum. The morphological properties of the samples were characterized by high resolution transmission electron microscopy (HR-TEM) and Scanning Electron Microscopy (SEM). The structural, magnetic, and microwave absorption properties of magnetic chitosan films have been carried out using the Vibrating Sample Magnetometer (VSM) and Ferromag- netic Resonance (FMR). It is shown that the composite polymer behaves like a superparamagnetic material with high blocking temperature. The effective magnetization shows gradual increments with the concentration of dopant Fe 3 O 4 nanoparticles. The microwave absorption characteristic of super- paramagnetic composite polymer shows low reflection loss. & 2014 Elsevier B.V. All rights reserved. 1. Introduction Magnetic nanoparticles have a great interest due to their wide application areas in science, technology and healthcare field such as magnetic resonance imaging (MRI) technique, bioactive mole- cule separation, information storage systems, medical diagnosis techniques, and targeted drug therapies [1]. Magnetite (Fe 3 O 4 ) being used widely in biomedical application is a common magnetic iron oxide that has a cubic inverse spinel structure with face-centered cubic closed packing and iron cations occupying interstitial tetrahedral sites and octahedral sites [2,3]. Fe 3 O 4 has attracted increasing interest during the recent years because of its magnetic properties and application areas such as cancer therapy, MRI, drug delivery systems, etc. [3,4]. Dispersion of magnetite onto organic polymers provides increasing biocompatibility, protection of particle surfaces from oxidation and reduction susceptibility to leaching, besides enhancing chemical stability and reducing toxicity. Magnetic interactions between the Fe 3 O 4 particles and Vander Waals force lead to flocculation. To effectively stabilize iron oxide particles, polymers are used so that agglomeration is avoided [5]. Dispersing Fe 3 O 4 in a suitable polymer matrix prevents aggregation. Chitosan is synthesized by deacetylation of chitin. Chitin, found in the exoskeleton of crustaceans, is the most abundant naturally occurring biopolymer after cellulose [6,7]. Chitosan is a cationic heteropolysaccharide composed mainly of β-(1,4)-2- deoxy-2-amino- glucopyranose units, and partially of β-(1,4)-2- deoxy-2-acetamido- glucopyranose [7]. Furthermore, chitosan has unique functional, nutritional and biomedical properties. Thus, it has been widely used in biomedical applications, drug delivery, food industry, biotechnology, pharmaceuticals, biome- dicine, packaging, wastewater treatment, cosmetics, etc. [8]. The insolubility of chitosan in water provides thermally and chemi- cally inert film forming, which allows it to be used as a biosensor [9,10]. Conductive and nonconductive polymers were also widely used in modern X-band radar technology by dispersion of magnetic nanoparticles into polymer matrix to enhance the absorbing effect of materials [11–17]. In the present study we aim to prepare Fe 3 O 4 magnetic chitosan thin films, to examine the structural characterization using High- Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (SEM), and Energy Dispersive X-Ray Spectro- scope (EDX) and to investigate the magnetic and microwave absorption properties of these magnetic chitosan polymer films utilizing the Vibrating Sample Magnetometer (VSM) and Ferromag- netic Resonance (FMR). Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials http://dx.doi.org/10.1016/j.jmmm.2014.02.016 0304-8853 & 2014 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: macikgoz@bahcesehir.edu.tr (M. Açıkgöz). Journal of Magnetism and Magnetic Materials 373 (2015) 53–59