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Green and Low Temperature Synthesis of Nanocrystallinetransition Metal Ferrites by Simple Wet Chemistry Routes

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Green and Low Temperature Synthesis of Nanocrystallinetransition Metal Ferrites by Simple Wet Chemistry Routes Nano Research 1 DOINano 10.1007/s12274Res -014-0466-3 Green and Low Temperature Synthesis of NanocrystallineTransition Metal Ferrites by Simple Wet Chemistry Routes Stefano Diodati1, Luciano Pandolfo2, Andrea Caneschi3, Stefano Gialanella4 and Silvia Gross1,2 () Nano Res., Just Accepted Manuscript • DOI: 10.1007/s12274-014-0466-3 http://www.thenanoresearch.com on April 1, 2014 © Tsinghua University Press 2014 Just Accepted This is a “Just Accepted” manuscript, which has been examined by the peer-review process and has been accepted for publication. A “Just Accepted” manuscript is published online shortly after its acceptance, which is prior to technical editing and formatting and author proofing. 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Green and low temperature synthesis of nanocrystalline transition metal ferrites by simple wet chemistry routes Stefano Diodati, Luciano Pandolfo, Andrea Caneschi, Stefano Gialanella and Silvia Gross* Dr. Stefano Diodati, Dr. Silvia Gross Istituto per l’Energetica e le Interfasi, IENI-CNR and INSTM, UdR, via Marzolo, 1, I-35131, Padova, Italy E-mail: [email protected] Prof. Luciano Pandolfo Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo, 1, I-35131, Padova, Italy Prof. Andrea Caneschi Coprecipitation of oxalates and hydrothermal synthesis are combined Laboratory of Molecular Magnetism - LAMM to prepare highly crystalline cobalt, nickel, zinc and manganese spinel Dipartimento di Chimica e UdR INSTM di Firenze ferrites CoFe2O4, NiFe2O4, ZnFe2O4 and MnFe2O4 at 75°C Polo Scientifico - Via della Lastruccia 3 50019 Sesto Fiorentino (Fi) - Italy Prof. Stefano Gialanella Dipartimento di Ingegneria Industriale, Università degli Studi di Trento, via Mesiano 77, I-38123 Trento, Italy Page Numbers. The font is ArialMT 16 (automatically inserted by the publisher) Stefano Diodati, Luciano Pandolfo and Silvia Gross, http://www.chimica.unipd.it/m3/group.html Andrea Caneschi, http://www.lamm.unifi.it/STAFF/andrea_caneschi.html Stefano Gialanella, http://www.ing.unitn.it/dimti/people/gialanella.php 1 Nano Res DOI (automatically inserted by the publisher) Review Article/Research Article Please choose one Green and Low Temperature Synthesis of Nanocrystalline Transition Metal Ferrites by Simple Wet Chemistry Routes Stefano Diodati1, Luciano Pandolfo2, Andrea Caneschi3, Stefano Gialanella4 and Silvia Gross1,2 () 1 Istituto per l’Energetica e le Interfasi, IENI-CNR and INSTM, UdR di Padova, via Marzolo, 1, I-35131, Padova, Italy 2 Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo, 1, I-35131, Padova, Italy 3 Laboratory of Molecular Magnetism, LAMM Dipartimento di Chimica e UdR INSTM di Firenze, Polo Scientifico, Via della Lastruccia, 3, 50019, Sesto Fiorentino (FI), Italy 4 Dipartimento di Ingegneria Industriale, Università degli Studi di Trento, via Mesiano 77, I-38123, Trento, Italy Received: day month year / Revised: day month year / Accepted: day month year (automatically inserted by the publisher) © Tsinghua University Press and Springer-Verlag Berlin Heidelberg 2011 ABSTRACT Crystalline and nanostructured cobalt (CoFe2O4), nickel (NiFe2O4), zinc (ZnFe2O4) and manganese (MnFe2O4) spinel ferrites are synthesized with high yields, crystallinity and purity through an easy, quick, reproducible and low‐temperature hydrothermal assisted route starting from an aqueous suspension of coprecipitated metal oxalates. The use of water as a reaction medium is a further advantage of the chosen protocol. Additionally, the zinc spinel is also prepared through an alternative route combining coprecipitation of oxalates from an aqueous solution with thermal decomposition under reflux conditions. The nanocrystalline powders are obtained as a pure crystalline phase already at the extremely low temperature of 75°C and no further thermal treatment is needed. The structure and microstructure of the prepared materials is investigated by means of X‐Ray Powder Diffraction (XRPD), while X‐Ray Photoelectron Spectroscopy (XPS) and Inductive Coupled Plasma ‐ Atomic Emission Spectroscopy (ICP‐AES) analyses are used to gain information on the surface and bulk composition of the samples, respectively, confirming the expected stoichiometry. To investigate the effect of the synthesis protocol on the morphology of the obtained ferrites, transmission electron microscopy (TEM) observations are performed on selected samples. The magnetic properties of the cobalt and manganese spinels are also investigated through Superconducting Quantum Device Magnetometer (SQUID) revealing hard and soft ferrimagnetic behavior respectively. KEYWORDS ferrites, hydrothermal, low temperature, wet chemistry, green highly attractive due to the ever growing concern 1 Introduction for long‐term sustainability [1‐4]. In particular, low Green chemistry synthesis routes are currently temperature and water‐based preparation methods ———————————— Address correspondence to Silvia Gross, [email protected] 2 are a subject of great interest within the context of ferrites [33‐36] the synthesis of inorganic compounds. Recently we addressed by this route, coupled with Among inorganic materials, ferrites (described by annealing at high temperatures (T=900°C), the the general chemical formulae M2+Fe23+O4, M2+Fe4+O3 synthesis of strontium perovskite (SrFeO3‐δ) [37] and or M3+Fe3+O3, where M = metal ion) are gaining manganese perovskite (MnFeO3) [38] as well as of increasing attention: thanks to their high thermal, cobalt, nickel, zinc and magnesium spinels mechanical and chemical stability [5‐9], coupled (CoFe2O4, ZnFe2O4, MgFe2O4, NiFe2O4) [38]. with numerous functional properties (catalytic, However, to the best of our knowledge, this electric, magnetic, etc.), they find applications in a procedure has never been combined with large number of different fields such as magnetism hydrothermal treatment in order to synthesize and electronics [10, 11], sensor design [12], catalysis nanosized ferrites. (e.g. water splitting) [13‐15], and medicine [16]. The main advantage of hydrothermal synthesis over In particular, spinel ferrites, the topic of the present conventional wet‐chemistry methods is that it work, find numerous applications in disparate areas occurs in non‐standard conditions and that of interest, ranging from electronics, to ferrofluid non‐classical crystallization pathways can be technologies and diagnostic medicine [17, 18], explored [39, 40]. By operating at autogenous where their magnetic properties, depending on relatively high pressures (generated by heating the both the crystal structure of the compound and on reaction mixture within a closed vessel) several the nature of the M metal [5, 19‐21] make them properties which are relevant for the solubilization invaluable functional materials. (such as ionic product, density, viscosity and In the synthesis of ferrites, and in view of their dielectric constant) dramatically change, thus potential functional applications, it is mandatory to allowing for the solubilization of compounds which gain a fine control over the final features of the are not normally soluble in standard conditions [23, material of choice. In this regard, it is particularly 39]. relevant to employ preparative methods allowing to In this paper we report on the synthesis of achieve a specific composition and microstructure nanosized crystalline cobalt, nickel, zinc and of the products. The commonly used solid state manganese spinel ferrites CoFe2O4, NiFe2O4, synthetic routes besides being highly ZnFe2O4 and MnFe2O4 through a hydrothermal energy‐consuming [22, 23], do not allow a fine low‐temperature route, starting from an aqueous control over the reaction pathways during the suspension of the different metal oxalates. This process. Wet chemistry routes instead appear a method, in addition to being carried out at low suitable alternative, also due to the fact that at low temperatures, has the advantage of not requiring temperatures they yield smaller sized products. toxic or hard to manage reagents, and not requiring Among wet‐synthesis routes, the most commonly complex purification steps. Moreover, and more explored procedures for ferrite synthesis are importantly, the process takes place in an aqueous thermal decomposition of suitable precursors [24], environment, thus making the method greener than solvo‐ and hydrothermal synthesis [25, 26], reverse other routes. In the literature, a study by Zhou et al. micelle synthesis [27, 28], polyol assisted synthesis [41] is reported concerning the synthesis of NiFe2O4 [29], nonaqueous sol‐gel [30] and coprecipitation at 60°C using a similar protocol. The reported [31]. Particularly, coprecipitation of oxalates procedure is however based on sulphate precursors, (followed
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