Optimization of synthesis of superparamagnetic nanoparticales CoFe2O4 with ultra thin gold layer

Abstract

U ovom diplomskom radu nanočestice kobalt ferita sintetizirane su koprecipitacijskom metodom u vodenoj otopini soli željezova klorida heksahidrata ($FeCl_{3}$ × $6H_{2}O$) i kobaltova klorida heksahidrata ($CoCl_{2}$ × $6H_{2}O$) u prisutnosti natrijeva hidroksida (NaOH). Istražen je utjecaj temperature i vremena reakcije na veličinu i oblik nanočestica. Sintezom pri temperaturi od 60 ℃ su nastale nanočestice promjera oko 30 nm, dok su produženim stajanjem u reakcijskoj smjesi nastali nanokristali kubične strukture. Prilikom sinteze uz nanočestice $CoFe_{2}O_{4}$ nastaje znatna količina hidroksidnih međuprodukata. Magnetskom dekantacijom su produkti pročišćeni prilikom čega je promjer nanočestica očuvan kao i njihova svojstva. Površina sintetiziranih nanočestica $CoFe_{2}O_{4}$ je modificirana redukcijom tetrakloroaurične kiseline s askorbinskom kiselinom pri čemu dolazi do formacije sloja zlata na površini nanočestica. Nanočestice su okarakterizirane dinamičkim raspršenjem svjetlosti (DLS), transmisijskim elektronskim mikroskopom (TEM), infracrvenom spektroskopijom s Fourierovom transformacijom (FT-IR), rentgenskom difrakcijom (PXRD), termogravimetrijskom analizom (TGA), diferencijalno pretražnom kalorimetrijom (DSC) i UV/VIS spektroskopijom.This master thesis deals with the synthesis of cobalt ferrite nanoparticles by co-precipitation method from aqueous solution containing iron chloride hexahydrate ($FeCl_{3}$ × $6H_{2}O$) and cobalt chloride hexahydrate ($CoCl_{2}$ × $6H_{2}O$) with sodium hydroxide (NaOH). The effect of temperature and reaction time on nanoparticles size and shape were studied. Synthesis at a temperature of 60 ℃ resulted in nanoparticles with a diameter of 30 nm, while prolonged reaction time resulted in cubic nanoparticles of cobalt ferrite. During synthesis a considerable amount of hydroxide intermediates were formed. The products were purified by magnetic decantation, while the size of the nanoparticles and their characteristic were preserved. The surface of synthesised $CoFe_{2}O_{4}$ nanoparticles was modified by the reduction of tetrachloroauric acid with ascorbic acid whereby a layer of gold was formed on the surface of the nanoparticles. Nanoparticles are characterised by dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (PXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and UV/VIS spectroscopy