Synthesis, Characterisation and Applications of Iron Oxide Nanoparticles
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Synthesis, Characterisation and Applications of Iron Oxide Nanoparticles GERMAN SALAZAR-ALVAREZ Doctoral Thesis Stockholm, Sweden 2004 KTH Materialvetenskap ISRN KTH/MSE--04/59--SE+CHEM/AVH SE-100 44 Stockholm ISBN 91-7283-884-1 SWEDEN Akademisk avhandling som med tillst˚andav Kungl Tekniska h¨ogskolan framl¨agges till offentlig granskning f¨or avl¨aggande av filosofie doktorsexamen fredagen den 17 december 2004 kl 10.00 i D3, Huvudbyggnaden, Kungliga Tekniska h¨ogskolan, Lindstedtsv¨agen 5, Stockholm. c German Salazar-Alvarez, december 2004 Tryck: Universitetsservice US AB iii Abstract This thesis deals with the synthesis, characterisation, and some applications of ferrimagnetic iron oxide nanoparticles. The iron oxide systems presented in this work are Fe3O4, γ-Fe2O3, NixFe3−xO4, CoxFe3−xO4. Iron oxide nanoparticles were prepared using chemical synthesis methods. Nanoparticles with a narrow size distribution were synthesised using zone confi- nement methods such as nanoemulsions and the novel flow injection synthesis. The flow injection method consisted of the precipitation of iron oxide nanopar- ticles in a continuous or segmented flow in a capillary reactor under laminar flow. Also, the preparation of particles in a ∼ 40 g/batch scale was carried out in a computer controlled stirred reactor which allowed reproducible synthesis conditions such a ∆pH ∼ 0.1 and ∆T ∼ 1 ◦C. Several chemical and hydrodyna- mic parameters were optimised to achieve high phase purity and magnetisation. These methods allowed the preparation of particles with tailored mean particle size from 3 up to 12 nm. Spinel iron oxide nanoparticles were also doped with Ni and Co. The influence of the synthesis parameters on the morphological and magnetic pro- perties of nickel- and cobalt-doped magnetite (NixFe3−xO4 and CoxFe3−xO4) was studied. Particle size, morphology, and composition of the materials are strongly dependent on reaction conditions, e.g., metal to hydroxide ratio and temperature. Cubic, spherical, and particles of CoxFe3−xO4 with varying mor- phology could be obtained by varying the metal to hydroxide ratio. M¨ossbauer studies indicated a disordered structure with a relatively low degree of inver- sion in the spinel structure. The coercivity of the particles increased with the cobalt content. High resolution microscopy and electron diffraction studies showed that cubic particles are monocrystalline. Iron oxide nanoparticles (Fe3O4 and γ-Fe2O3) with a particle size of about 10 nm were coated with layers of inorganic materials such as silica and gold to render the particles higher functionality and vary the surface properties. Iron oxide nanoparticles were coated with silica in a controlled manner producing either single coated particles, with a mean particle size varying from 12 to 60 nm, or multiparticle-beads with mean particle size in the range of 50-250 nm. The use of iron oxide nanoparticles in two applications was studied, i.e., for DNA purification and as optical power limiting agents. Silica-coated iron oxide particles were investigated for use in magnetic purification of plasmid DNA of the size range 0.1–1.7 kbp. The prepared nanoparticles have shown higher DNA recovery yields when compared to commercial particles. Single silica-coated nanoparticles have DNA recovery yield of about 70%, while the beads of multiple particles showed a recovery of approximately 50%. The optical power limiting application of coated and non-coated iron oxide nanoparticles was investigated. Both aqueous suspensions of pristine iron oxide nanoparticles consisting mainly of γ-Fe2O3 and silica-coated iron oxide nano- particles had a clamping level of about 3 µJ. The photoinduced nonlinear light scattering is the dominating nonlinear mechanism. Silica-coated nanoparticles have shown a better performance as a result of their higher colloidal stability. iv Sammanfattning I denna avhandlingen diskuteras syntes, karakterisering och till¨ampningar f¨or nanopartiklar av j¨arnoxid. De olika j¨arnoxidsystem som presenteras i arbetet best˚arav Fe3O4, γ-Fe2O3, NixFe3−xO4, CoxFe3−xO4. Nanopartiklarna av j¨arnoxid har framst¨allts via kemiska syntesmetoder. Nanopartiklar med liten varians i storleken (σ < 20%) och en storleksdistri- bution 3-8 mm framst¨alldes i den zon isolering fr˚aninverterade miceller och i ett nyutvecklat metod som bygger p˚afl¨odesinjektion (flow injection synthesis). A˚ andra sida, f¨or att f˚areproducerbar betingelser vid syntes av nanopartik- lar i 40 grams skala har en automatiserad reaktor anv¨ants (∆pH ∼ 0.1 och ∆T ∼ 1 ◦C). Flera kemiska och hydrodynamiska parametrar optimiserades f¨or att h¨ogre fasrenhet och b¨attre magnetiska egenskaper skulle erh˚allas.Des- sa reaktionsbetingelser till˚ater framst¨allning av nanopartikar i relativt stora m¨angder i storleksomr˚adet 3-12 nm. J¨arnoxid nanopartiklar med spinell struktur framst¨alldes via doping med nickel och kobolt. Effekterna fr˚ansyntesbetingelserna p˚amorfologin och magne- tiska egenskaper hos partiklarna har studerats hos nickel och koboltdopad mag- netit (NixFe3−xO4 respektive CoxFe3−xO4) . Partiklarnas storlek, morfologi och kemiska sammans¨attning var beroende av koncentrationsf¨orh˚allandet mel- lan metall-/ hydroxidjon. Via ¨andringar i detta f¨orh˚allande kunde CoxFe3−xO4 partiklarnas utseende styras s˚aatt kubiska, sf¨ariska eller till och med odefinie- rade partiklar bildades. M¨ossbauersspektroskopi har pekat p˚aen oregelbunden katjondistribution i strukturen. Partiklarnas koercivitet ¨okade med kobolthal- ten. H¨oguppl¨osande transmissionselektronmikroskopi och elektrondiffraktion visade att de kubiska partiklarna var monokristaller. F¨or att kunna p˚averka partiklarnas funktionalitet och ytkemiska egenska- per har nanopartiklar av j¨arnoxid med en partikelstorlek p˚a10 nm framst¨allts med ett ytskikt av oorganiskt material, s˚asom kiseloxid och guld. Kiseloxid och guld anv¨andes f¨or att de har v¨alk¨anda kemiska egenskaper och har anv¨ants un- der en l¨angre tid inom biologiska applikationer och i supraledareindustrin. Ett ytlager av kiseloxid har belagts b˚ade p˚aytan av enskilda nanopartiklarna i stor- leksordningen 12-60 nm och p˚apartikelaggregat, s k beads i storleksordningen 50-250 nm. Kiselbelagda nanopartiklar av j¨arnoxid har studerats f¨or anv¨andning inom till¨ampningar f¨or reng¨orning av plasmid DNA i storleksspannet 0,1-1,7 kbp, och som optiska limiter. Atervinning˚ av DNA med enskilda partiklar ¨ar upp till 70%, medan beads visat ˚atervinning av ca 50%. Optiska begr¨ansning studerades med suspensioner av coatade och uncoa- tade j¨arnoxid nanopartiklar. B˚ada suspensionerna har en kl¨amniv˚aav ca 3 µJ. Ickelinj¨ara spridning av laserljuset ¨ar den dominerande mekanism. v Ïðîãóëêà â ìèëþ ñ ëþáèìîé æåíùèíîé ñîñòàâëÿåò ëèøü ñòî øàãîâ. Äàøåíüêå Preface My graduate studies were originally related to studies on the recovery of heavy metals from aqueous media by polymeric membranes. This was an extension of the studies I carried out in Mexico and for which I received my Bachelor in Science in 1999. The work was completed by presenting the Licentiate in Engineering in 2001. During the period 1999-2001, most of my colleagues were working with the synthesis of nanoparticles for various applications ranging from electronic to bio- medical. It was this interdisciplinary environment what caught my interest. After a discussion with my supervisor I started to perform some experiments and read more about the nanoworld immediately after presenting my Licentiate. Within half a year I joined the European project magnanomed, which was oriented towards some biomedical applications of iron oxide-based nanoparticles. During the time of the project we produced nanomaterials to be used for DNA separation and purifi- cation, work which we carried out in collaboration with the Max Planck Institute for Molecular Genetics in Berlin-Dahlem. The initial magnetic characterisation of the materials was undertaken by Liquids Research Ltd. at Bangor, Wales. Shortly after the end of the magnanomed project, in 2003, discussion were held with people from the Department of Polymer Technology at KTH to produce nanopar- ticles of substituted ferrites to be incorporated into polymeric composite structures. The discussions were extended a bit and they turned into two manuscripts -so far. Concomitantly with the main research efforts, during the period 2001-2004 small projects were carried out in collaboration with FOI to investigate the applicability of nanomaterials as optical limiting agents against laser radiation. During this last stage, collaborations were also established with the Department of Physics at Uni- versitat Aut`onoma de Barcelona and the Department of Physicochemical, Inorganic and Structural Chemistry at Stockholm University. Regarding the present work, I would like to point out certain things. As far as it was possible, SI units and terminology∗ were used throughout the thesis and the manuscripts. The values for various physical and chemical constants were obtai- ned from the Compendium of Chemical Terminology edited by the IUPAC.† Also, ∗The definition of several terms can be found in http://wikipedia.org/ †For more information about the chemical symbols, values of universal constants, etc., please refer to http://www.iupac.org/ vii viii PREFACE in addition to the regular bibliographic information provided by the references to scientific articles, the document object identifier, DOI, was added whenever it was available.∗ G.S.A. ∗For more information about the DOI please refer to http://www.doi.org/.