Nanocrystalline spinel ferrite (MFe 2 O 4 , M = Ni, Co, Mn, Mg, Zn) powders prepared by a simple aloe vera plant-extracted solution hydrothermal route Santi Phumying a,b , Sarawuth Labuayai a,b , Ekaphan Swatsitang a,b , Vittaya Amornkitbamrung a,b , Santi Maensiri c, * a Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand b Integrated Nanotechnology Research Center (INRC), Khon Kaen University, Khon Kaen 40002, Thailand c School of Physics, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand 1. Introduction The synthesis of nanocrystalline spinel ferrite (with the general formula MFe 2 O 4 (e.g. M = Mn, Co, Ni, Cu, Zn, Mg)) has become an important part of modern ceramic research. The study of nanocrystalline spinel ferrite particles has great relevance to modern technological applications in several industrial and biological fields, including magnetic recording media and magnet- ic fluids for the storage and/or retrieval of information, magnetic resonance imaging (MRI) enhancement, catalysis, magnetically guided drug delivery, sensors, and pigments [1,2]. It is well known that the chemical, structural, and magnetic properties of spinel ferrite particles are strongly influenced by their composition and microstructures, which are sensitive to the preparation method- ologies [3,4]. Many synthesis routes have been used to prepared particles of spinel ferrite [5–15]. Among the other methods, hydrothermal route has been recently received much attention. Recently, many conditions have been applied to the preparation via hydrothermal process of spinel ferrite. Baykal et al. [13] reported hydrothermal synthesized NiFe 2 O 4 nanocrystals from ferric chloride hexahidride (FeCl 3 6H 2 O) and nikel chloride (NiCl 2 ), using cetyltrimethylammonium bromide (CTAB) as the surfactant and NH3 and NaOH as hydrolyzing agents. Yu et al. [14] hydrothermally synthesized ZnFe 2 O 4 using metal Zn sheet and FeCl 2 as reactants in ammonia solutions. Recently, Liu et al. [15] successfully prepared CoFe 2 O 4 nanoplateletes and nanoparticles by hydrothermal reaction from ferric chloride (FeCl 3 ), cobalt dodecyl sulfate (Co(DS) 2 ) and NaOH aqueous solution. However, most of these conditions involve a strictly controlled synthesis environment, expensive reagent and complicated procedures. Therefore, simple and cost effective conditions via hydrothermal process to synthesize spinel ferrite particles by utilization of cheap, nontoxic and environmentally benign precursors are still the key issues. Aloe vera (Aloe barbadensis Mill.) is a perennial succulent belonging to the Liliaceal family, and it is a cactus-like plant that grows in hot, dry climates [16]. For many years, aloe vera has been reported to possess immunomodulatory, anti-inflammatory, UV protective, antiprotozoal, and wound- and burn-healing promot- ing properties [17–20]. Recently, the extract of aloe vera plant has been successfully used to synthesize single crystalline triangular gold nanoparticles (50–350 nm in size) and spherical silver nanoparticles (15 nm in size) in high yield by the reaction of aqueous metal source ions (chloroaurate ions for Au and silver ions for Ag) with the extract of the aloe vera plant [21]. Recently our group has reported the use of aloe vera plant for the synthesis of Materials Research Bulletin 48 (2013) 2060–2065 A R T I C L E I N F O Article history: Received 18 July 2012 Received in revised form 8 February 2013 Accepted 12 February 2013 Available online 28 February 2013 Keywords: A. Magnetic materials B. Chemical synthesis C. Electron microscopy C. X-ray diffraction D. Magnetic properties A B S T R A C T Nanocrystalline spinel ferrite MFe 2 O 4 (M = Ni, Co, Mn, Mg, Zn) powders were synthesized by a novel hydrothermal method using Fe(acac) 3 , M(acac) 3 (M = Ni, Co, Mn, Mg, Zn) and aloe vera plant extracted solution. The X-ray diffraction and selected-area electron diffraction results indicate that the synthesized nanocrystalline have only spinel structure without the presence of other phase impurities. The crystal structure and morphology of the spinel ferrite powders, as revealed by TEM, show that the NiFe 2 O 4 and CoFe 2 O 4 samples contain nanoparticles, whereas the MnFe 2 O 4 and MgFe 2 O 4 samples consist of many nanoplatelets and nanoparticles. Interestingly, the ZnFe 2 O 4 sample contains plate-like structure of networked nanocrystalline particles. Room temperature magnetization results show a ferromagnetic behavior of the CoFe 2 O 4 , MnFe 2 O 4 and MgFe 2 O 4 samples, whereas the samples of NiFe 2 O 4 and ZnFe 2 O 4 exhibit a superparamagnetic behavior. ß 2013 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +66 44 224957; fax: +66 44 224651. E-mail address: santimaensiri@gmail.com (S. Maensiri). Contents lists available at SciVerse ScienceDirect Materials Research Bulletin jo u rn al h om ep age: ww w.els evier.c o m/lo c ate/mat res b u 0025-5408/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.materresbull.2013.02.042