Optical and transport properties of iron oxide nanoparticles

Electrical Engineering / Physical ElectronicsNanočestice oksida gvođža, posebno magnetita (Fe3O4), privlače pažnju zbog svojih superparamagnetnih osobina, biokompatibilnosti i niskog nivoa toksičnosti. Od mnoštva metoda za dobijanje nanočestica, elektrohemijska (EH) metoda se pokazala kao jednostavna, jeftina i ekološki prihvatljiva, a pored toga omogućava i dobru kontrolu osobina dobijenih čestica. Struktura, morfologija i veličina čestica, pa time i njihove magnetne, optičke i električne osobine, mogu se menjati promenom uslova u EH ćeliji tokom procesa sinteze i/ili njihovim naknadnim grejanjem u odgovarajućoj atmosferi. U ovoj disertaciji ispitivane su mogućnosti sinteze nanoprahova oksida gvožđa, EH metodom, u opsegu gustina struje J = 200-1000 mA/dm2 i temperatura T = 295-361 K. Takođe je proučeno preuređenje katjona i vakancija u magnetitu, prouzrokovano toplotom, kao i fazni prelazi magnetit-maghemit (γ-Fe2O3) i maghemit-hematit (α-Fe2O3). U disertaciji su prikazani rezultati ispitivanja strukture, morfologije i raspodele veličine čestica dobijenih nanoprahova, koji su dobijeni različitim tehnikama, kao što su difrakcija X-zračenja (XRD), skenirajuća i transmisiona elektronska mikroskopija (SEM, TEM) i dinamičko rasejanje laserske svetlosti. Magnetne osobine su određene merenjem zavisnosti magnetizacije od temperature Faradejevom metodom i merenjem histerezisa SQUID aparaturom.Izmereni su i infracrveni (IC) sprektri dobijenih prahova, kao i temperaturna zavisnost specifične električne otpornosti i specifične toplote. Da bi se ispitali načini vezivanja različitih organskih supstanci, koje se često koriste za oblaganje nanočestica oksida gvožđa, ravnotežne konformacije i vibracioni spektri molekula limunske kiseline, dekstrana (1-5 molekula), polietilen glikola (1-3 molekula), citozana (1-3 molecula) i oleinske kiseline proračunati su polu-empirijskom, kvantno-mehaničkom metodom AM1, a neki od molekula i metodom linearne kombinacija atomskih orbitala (LCAO), sa bazisom talasnih funkcija 631-G, korišćenjem programskog paketa HyperChem. Mogućnosti primene dobijenih nanoprahova oksida gvožđa u biosistemima, ispitane su tako što su neki neobloženi, kao i neki prahovi obloženi limunskom kiselinom (ferofluid), u različitim koncentracijama parenteralno administrirani Wistar pacovima in vivo, ili primenjeni na uzorke humane krvi, in vitro. 24 časa posle primene nanoprahova i ferofluida, analizirane su promene krvne slike, diferencijalne krvne slike, i ispitane metabolčke promene, pomoću VSC (Volume-Conductivity-Light Scatter) aparature. Utvrđeno je da primenjeni nanoprahovi i ferofluid na različite načine utiču na krv, ali da u primenjenim koncentracijama nisu štetni, ni na koji način.Iron oxide nanoparticles, especially Magnetite (Fe3O4), have attracted attention due to their biocompatibility, low toxicity and superparamagnetic properties. Among the numerous methods for nanoparticles preparation, the electrochemical (EH) method has been recognised as an easily feasible, low cost, and environmental friendly preparation process, which offers good possibillity for nanoparticles properties control. Structure, morphology, size, magnetic, optical, and electrical properties of the powders can be tuned by changing the conditions in the EH cell during the powder synthesis, and/or by their subsequent heating in the appropriate atmosphere.In this dissertation, the EH synthesis of iron oxide nanopowders of specific characteristics is investigated in the range of current density of J = 200–1000 mA/dm2, and temperature of T = 295–361 K. The temperature induced cation-vacancy reordering in magnetite, the magnetite to maghemite (γ-Fe2O3), and the maghemite to haematite (α- Fe2O3) phase transitions were examined, as well. For that reason structure, morphology and particle size distribution of the produced powders are investigated, using X-ray diffraction (XRD), Scanning and Transmition Electron Microscopy (SEM and TEM), and dynamic light scattering. The magnetic properties are established by temperature dependent magnetisation measurements using Faraday method, and hysteresis measurements by SQUID. Infrared spectra and temperature dependences of specific electrical resistivity and specific heat are also determined.In order to analyse the attachment of various surfactants, the properties of optimal ground-state conformation, and vibrational spectra of citric acid molecule, dextran (1-5 molecules), polyethylen glicol (1-3 molecules), chitosan (1-3 molecules), and oleic acid molecule are calculated at AM1 quantum-mechanical, and some of the molecules also at ab-initio LCAO (Linear Combination of Atomic Orbitals) 631-G level, using the HyperChem program package. The calculated results are compared with measured IR spectra, and some literature data. For the purpose of investigation of their applicability in biosystems, some of the obtained powders were covered with the citric acid layer (ferrofluid), and together with some noncovered powders parenterally administrated to Wistar rats in vivo, and human blood in vitro in various concentrations. 24 hours after the application of the powders and the ferrofluid, a Volume-Conductivity-Light Scatter apparatus is used to analyse the changes of blood test, differential blood test, and metabolic changes. It has been established that ferrofluid and plane powders influence blood in various ways, but that any of them is by no means harmful in the applied concentration