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Nanotehnologija v zadnjih letih predstavlja eno izmed najbolj obetavnih področij v farmaciji. V farmacevtski nanotehnologiji je zelo aktualen razvoj nanodelcev, ki imajo pred konvencionalnimi dostavnimi sistemi številne prednosti. Običajno je produkt priprave nanodelcev disperzija, ki je dovzetna za različne vrste nestabilnosti. Posledično se za izboljšanje fizikalne in kemijske stabilnosti disperzij nanodelcev v zadnjih letih pospešeno proučujejo različni pristopi, med drugim tudi različne metode sušenja za pretvorbo disperzij nanodelcev v bolj stabilno suho obliko. Sušenje disperzij nanodelcev predstavlja velik tehnološki izziv. Z do danes razvitimi metodami sušenja je težko izdelati suh, nepraškast produkt ter sočasno preprečiti agregacijo nanodelcev med procesom sušenja in tako ohraniti njihovo prvotno velikost. Namen magistrske naloge je zato bil raziskati metodo elektrostatskega sukanja kot alternativno metodo za pretvorbo disperzij nanodelcev v suho obliko, ki bi premostila pomanjkljivosti do danes razvitih metod sušenja disperzij nanodelcev. Pred procesom elektrostatskega sukanja smo v etanolno (magnetni nanodelci) oz. vodno (polimerni nanodelci) disperzijo nanodelcev dodali polimera polietilenoksid in poloksamer 188 (v masnem razmerju 1:1), ki sta se v preteklosti že izkazala kot ustrezna za izdelavo suhega elektrostatsko sukanega produkta, ki se hitro dispergira v vodnem mediju. S sistematičnim spreminjanjem vsebnosti nanodelcev v disperziji smo določili največjo vsebnost nanodelcev, ki je še zagotavljala ustrezno redispergiranje le-teh iz suhega produkta. Tako smo v suh produkt uspešno vključili do 50 % (m/m) magnetnih nanodelcev oz. do 11 % (m/m) polimernih nanodelcev. Metoda elektrostatskega sukanja je za razliko od ostalih metod za sušenje disperzij nanodelcev omogočila izdelavo suhega produkta z nanodelci v nepraškasti obliki, kar je izrednega pomena z vidika varnosti pri rokovanju s posušenimi nanodelci. Suh produkt z magnetnimi nanodelci, ki smo ga izdelali iz etanolne disperzije, je bil v obliki nanovlaken, medtem ko suh produkt s polimernimi nanodelci, ki smo ga izdelali iz vodne disperzije nanodelcev, ni imel morfologije nanovlaken. Domnevamo, da je razlika v morfologiji produkta posledica vpliva disperznega medija na obnašanje polimerov med elektrostatskim sukanjem. Kljub razlikam v morfologiji je bilo iz obeh vrst suhih produktov mogoče z enostavnim stresanjem nanodelce pretvoriti nazaj v obliko disperzije. In recent years, nanotechnology has become one of the most promising fields in pharmacy. The development of nanoparticles is a hot topic in pharmaceutical nanotechnology because it offers a number of advantages over conventional drug delivery systems. Most nanoparticles are usually prepared in the form of dispersions, which are susceptible to vary instabilities. To improve the physical and chemical stability of nanoparticle dispersions, various approaches have been investigated in recent years, including the conversion of nanoparticle dispersions into a more stable dry form by different drying methods. Drying of nanoparticle dispersions is an important technological challenge. With the drying methods developed so far, it is difficult to produce a dry, non-powdered product, while preventing the aggregation of nanoparticles during the drying process and thus preserving their original size. Therefore, the aim of this Master's thesis was to investigate electrospinning as an alternative method for converting dispersions of nanoparticles into a dry form that would overcome the drawbacks of current drying methods. To successfully convert the aforementioned nanoparticle dispersions into a dry form, polyethylene oxide and poloxamer 188 (in a 1:1 weight ratio), which have been shown to be suitable for the preparation of a dry, easily dispersible product, were added to ethanol (magnetic nanoparticles) or aqueous (polymeric nanoparticles) dispersions before the electrospinning process. By systematic increase in the content of nanoparticles in the dry product, we determined the maximum content of nanoparticles in the dry product, which still ensured their adequate redispersion from the dry product. We successfully incorporated up to 50% (w/w) of magnetic nanoparticles or up to 11% (w/w) of polymer nanoparticles into dry product. Unlike other methods for drying nanoparticle dispersions, the electrospinning method allowed us to produce a dry product with nanoparticles in a non-powder form, which is important from a safety perspective. The dry product with magnetic nanoparticles, prepared from the ethanol dispersion, was in the form of nanofibers, whereas the dry product with polymeric nanoparticles prepared from the aqueous nanoparticle dispersions, was not. We assume that the difference in product morphology is due to the influence of the dispersion medium on the behaviour of the polymers during electrospinning. Despite the differences in morphology, the nanoparticles were successfully reconstituted from both types of dry product by simple shaking.

Pomen magnetnih nanodelcev kot potencialnih nosilcev biomolekul v biotehnologiji in biomedicini hitro raste. V zadnjih letih so pokazali tudi odlične rezultate na področju mikropretočnih sistemov, saj predstavljajo zmogljivo orodje za imobilizacijo biokatalizatorja, ki ga je mogoče enostavno manipulirati z uporabo zunanjega magnetnega polja. Zaradi možne funkcionalizacije se uporabljajo v številnih biokatalitskih aplikacijah in separacijah celic. Funkcionalizirani magnetni nanodelci kot trdni nosilci ponujajo možnost tvorbe kovalentne vezi preko epoksidnih, metilnih ali aminopropilnih skupin ter koordinacijske vezave s kovinskimi ioni. Uporabljajo se lahko za tarčno zdravljenje, imobilizacijo encimov ali inkapsulacijo biomolekul. Magnetni nanodelci se pogosto nahajajo v mikroreaktorskih komorah, pri čemer se njihovo zadrževanje nadzira z zunanjim magnetnim poljem. Takšni mikroreaktorji so zelo učinkoviti pri biodetekcijah ter biokatalitskih in bioanalitskih aplikacijah. Na temeljih obravnave literature v tem delu lahko zaključim, da je uporaba magnetnih nanodelcev v magnetnem polju ena izmed najbolj obetavnih tehnik imobilizacije biokatalizatorjev v mikropretočnih sistemih. The importance of magnetic nanoparticles as potential carriers of biomolecules in biotechnology and biomedicine is growing rapidly. In recent years, they have also shown excellent results in the field of microfluidic systems because they represent a powerful tool for biocatalyst immobilization that can be easily manipulated using an external magnetic field. Due to their possible functionalization, they are used in many biocatalytic applications and cell separations. Functionalized magnetic nanoparticles as solid supports offer the possibility of covalent bond formation through epoxy, methyl, or aminopropyl groups and coordination bonding with metal ions. They can be used for targeted therapy, immobilization of enzymes, or encapsulation of biomolecules. Magnetic nanoparticles are often located in microreactor chambers. In the process, their retention is controlled by an external magnetic field. Such microreactors are very effective in biodetection, as well as in biocatalytic and bioanalytical applications. Based on the examination of literature in this work, I can conclude that the use of magnetic nanoparticles in a magnetic field is one of the most promising techniques for the immobilization of biocatalysts in microflow systems.

One of the key technological challenges in the development of iron-oxide-based magnetic nanoparticles (MNPs) is their long-term physical stability in colloidal dispersions. This can be improved by their transformation into a dry form. Here, we introduce electrospinning as a drying method for ethanol-based and water-based MNP dispersions, which enables the preparation of high-loaded dry MNP products. The obtained easily dispersible electrospun product contained up to 50 % (w/w) of MNPs, homogeneously distributed in the fibrillar structure, which is much more compared to the products of currently available methods for drying MNP dispersions. The polymers used as building blocks of nanofibers, namely poloxamer 188 and polyethylene oxide, improved the tolerance of MNPs to high ionic strength dispersion medium and thus enhanced the short-term physical stability of MNP dispersions after reconstitution. The dry product was stable for up to 1 month at room temperature and relative humidity up to 70 %. It was in the form of a nanofiber mat, which prevented the aerosolization of MNPs and their unintentional ambient exposure. Therefore, the electrospun product with MNPs is expected to be a safer dry formulation of MNPs than the nanoparticulate powders, which are usually the final products of the conventional drying methods.

V okviru diplomskega dela sem raziskovala vpliv oplaščenja magnetnih nanodelcev na zeta potencial in njihove magnetne lastnosti. Delce smo sintetizirali v laboratoriju iz dveh raztopin soli, nato pa jih oplaščili s citronsko kislino in cetiltrimetilamonijevim bromidom. Fokus moje raziskave je bil posvečen funkcializaciji in karakterizaciji oplaščenih magnetnih delcev za namene polifenolne ekstrakcije iz lesne biomase. Nanodelci so morali imeti točno določeno koncentracijo in izražati superparamagnetne lastnosti za njihovo nadaljnjo uporabo. Tako bi lahko na ekološko prijazen način iz lesne biomase ekstrahirali polifenole in izboljšali uporabo lesnega odpadka. Ugotovili smo, da vsi nanodelci izražajo superparmagnetne lastnosti, kot boljši surfaktant pa se je izkazala citronska kislina, saj so bile izmerjene vrednosti zeta potenciala višje, prav tako pa je oplaščenje znižalo izoelektrično točko, s tem pa je postala suspenzija bolj stabilna pri fizioloških pogojih As part of my bachelor thesis, I investigated the influence of the coating of magnetic nanoparticles on the zeta potential. The particles were synthesized from two salt solutions and then coated with citric acid or cetyltrimethylammonium bromide. Our research was focused on the functionalization and characterization of coated magnetic particles for polyphenolic extraction from wood biomass. The nanoparticles had to have a specific concentration and express superparamagnetic properties for their further use. In this way, polyphenols could be extracted from wood biomass in an environmentally friendly way, thus improving the use of wood waste. We found that all nanoparticles exhibit superparamagnetic properties, and citric acid proved to be a more suitable surfactant, as the measured zeta potential values were higher than in the sample coated with CTAB. The citric acid coating also lowered the isoelectric point, making the suspension more stable at the desired conditions.

Doktorska disertacija zajema dva dela, v prvem delu smo se osredotočili na sintezo magnetnega nosilca, modificiranega z organskim polimerom karboksimetil dekstranom (CMD). V sintezni postopek smo vpeljali tri različne koncentracije CMD (0,25 g/mL, 0,40 g/mL in 0,50 g/mL CMD) ter sintetizirali tri različne modificirane magnetne nanodelce (CMD1-MNPs, CMD2-MNPs in CMD3-MNPs). Sintetizirane CMD-MNPs smo okarakterizirali z različnimi analiznimi metodami: Fourier-transformirano infrardečo spektroskopijo (FT-IR), termogravimetrično analizo (TGA), vrstično elektronsko mikroskopijo (SEM), energijsko disperzijsko spektroskopijo (EDS), transmisijsko elektronsko mikroskopijo (TEM), z meritvami dinamičnega sipanja svetlobe (DLS). Magnetne lastnosti smo določili z elektronsko paramagnetno resonanco (EPR) in vibracijskim magnetometrom (VSM). Uspešno smo sintetizirali magnetne nosilce CMD-MNPs z ozkimi porazdelitvami nanovelikosti od 27-30 nm. S FT-IR analizo smo določili prisotnost karboksilnih in hidroksilnih skupin na površini CMD-MNPs, kar potrjuje prisotnost polimerne prevleke CMD na sintetiziranih MNPs. Z meritvami EPR in VSM smo dokazali, da imajo sintetizirani CMD-MNPs magnetne lastnosti ter feromagnetni sistem. Določili smo inhibitorne lastnosti CMD-MNPs na rast dveh bakterijskih kultur. Inhibitorne učinke na rast testnih mikroorganizmov smo zaznali pri CMD3-MNPs, medtem ko ostali CMD-MNPs in neprevlečeni MNPs ne izkazujejo antimikrobne učinkovitosti. Proučevali smo tudi inhibitorne lastnosti MNPs modificiranih s hitozanom (HIT-MNPs) in aminosilanom (AMS-MNPs) na petih različnih bakterijskih kulturah, pri katerih nismo zaznali inhibiornega učinka na rast izbranih mikororganizmov. Za nadaljnje raziskave smo izbrali CMD3-MNPs, na katerega smo vezali encim alkohol dehidrogenazo (ADH). V drugem delu doktorske disertacije smo nosilec CMD3-MNPs površinsko funkcionalizirali z epiklorohidrinom (EClH). Optimalna koncentracija EClH je znašala 4 % (v/v). Proučevali smo vpliv različnih procesnih parametrov na preostalo aktivnost in učinkovitost imobilizacije ADH na CMD3-MNPs. Pri optimalnih pogojih imobilizacije ADH na CMD3-MNPs smo dosegli 89,6 % preostalo aktivnost imobilizirane ADH in 99,5 % učinkovitost imobilizacije. Nadaljevali smo s postopkom koimobilizacije, pri čemer smo na funkcionaliziran nosilec CMD3-MNPs koimobilizirali encim ADH in kofaktor β-nikotinamid adenin dinukleotid (β-NAD). S spreminjanjem procesnih parametrov smo proučevali njihov vpliv na preostalo aktivnost imobilizirane ADH s kofaktorjem β-NAD na CMD3-MNPs in učinkovitost koimobilizacije. Pri optimalnih pogojih koimobilizacije ADH in β-NAD na CMD3-MNPs smo dosegli 73,3 % preostalo aktivnost ADH ter 93,8 % učinkovitost imobilizacije. Izvedli smo še študijo termične stabilnosti proste ADH, ADH imobilizirane na CMD3-MNPs in ADH koimobilizirane z β-NAD na CMD3-MNPs pri različnih temperaturah. ADH imobilizirana na CMD3-MNPs je ohranila skoraj 60 % svoje začetne aktivnosti po 24. urah inkubacije pri temperaturah 20 °C in 40 °C. ADH koimobilizirana z β-NAD na CMD3-MNPs je pri temperaturi 30 °C ohranila 75,4 % začetne aktivnosti, pri 50 °C pa 66,5 % začetne aktivnosti po 5. urah inkubacije. Proučili smo še stabilnost ADH imobilizirane na CMD3-MNPs in ADH koimobilizirane z β-NAD na CMD3-MNPs, ki smo ju skladiščili pri 4 °C. Po treh tednih sta obe obliki imobilizrane ADH ohranili 60 % svoje začetne aktivnosti. Magnetne nosilce HIT-MNPs in AMS-MNPs smo funkcionalizirali z mrežnim povezovalcem glutaraldehidom (GA) in amino-donorjem pentaetilenheksaminom (PEHA), na katere smo imobilizirali encim β-galaktozidazo (β-GAL) ter optimirali koncentraciji GA in PEHA. Pri kombinaciji obeh GA in PEHA smo dosegli hiperaktivacijo encima (128,9 %), do katere pride zaradi konformacijskih sprememb encima. Hiperaktivacijo smo dosegli tudi pri imobilizaciji β-GAL na AMS-MNPs. Najvišjo preostalo aktivnost β-GAL smo dosegli, kadar smo kot mrežni povezovalec uporabili 20 % (v/v) PEHA (154,4 %). Doctoral thesis consists of two parts, in the first part synthesis of magnetic carrier and modification with organic polymer carboxymethyl dextran (CMD) was performed. Three different CMD concentrations were applied into the synthesis process (0,25 g/mL, 0,40 g/mL in 0,50 g/mL CMD), which resulted in three different modified magnetic carriers (CMD1-MNPs, CMD2-MNPs and CMD3-MNPs). All CMD-MNPs were characterized with various analytical methods: Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), transmission electron microscopy (TEM), dynamic light scattering (DLS). Magnetic properties were analyzed with electron paramagnetic resonance (EPR) and magnetization measurements with vibrating sample magnetization (VSM). CMD-MNPs were successfully synthesized with average diameters from 27-30 nm and size distribution revealed most consistent sizes of CMD3-MNPs. Hydroxyl and carboxyl groups were confirmed on the CMD-MNPs surface, which confirms the presence of CMD layer on the surface of CMD-MNPs. EPR and VSM measurements confirmed magnetic properties of all CMD-MNPs and a ferromagnetic system. Inhibition properties were determined of all CMD-MNPs on two different bacterial cultures, where CMD3-MNPs displayed inhibition zone, confirming antimicrobial properties, whereas with other CMD-MNPs no inhibition was detected. Toxicity was also determined on MNPs coated with chitosan (HIT-MNPs) and aminosilane (AMS-MNPs) on five different bacterial cultures, where no inhibition was detected. CMD3-MNPs was chosen for further investigation of enzyme immobilization in the second part of doctoral thesis, because of its most favourable properties. In second part of doctoral thesis nano-carrier CMD3-MNPs was surface functionalized with epoxy cross-linking, using epoxy cross-linker epichlorohydrin (EClH) to covalently bind enzyme alcohol dehydrogenase (ADH). With optimization of process parameters EClH with 4 % (v/v) was used, which resulted in the highest residual activity of immobilized ADH. Epoxy-functionalized CMD3-MNPs were used in immobilization protocol, where effect of process parameters was investigated on the residual activity and immobilization efficiency of ADH. After successful optimization ADH immobilized onto CMD3-MNPs managed to obtain 89,6 % of residual activity and 99,5 % of immobilization efficiency. Further on, co-immobilization of enzyme ADH and cofactor β-nicotinamide adenine dinucleotide (β-NAD) was performed. Again, effect of process parameters on residual activity and immobilization efficiency of co-immobilization were investigated. After successful optimization, ADH co-immobilized with β-NAD onto CMD3-MNPs managed to obtain 73,3 % of residual activity and 93,8 % of immobilization efficiency. Thermal stability of immobilized ADH at different temperatures was investigated. ADH immobilized onto CMD3-MNPs obtained almost 60 % of its initial activity after 24 hours at 20 °C and 40 °C, ADH co-immobilized with β-NAD onto CMD3-MNPs managed to obtain 75,4 % of its initial activity at 30 °C and 66,5 % of its initial activity at 50 °C after 5 hours. Storage stability of ADH immobilized onto CMD3-MNPs and ADH co-immobilized with β-NAD onto CMD3-MNPs were investigated at 4 °C, where both obtained almost 60 % of its initial activity after three weeks. Magnetic carriers HIT-MNPs and AMS-MNPs were functionalized with cross-linker glutaraldehyde (GA) and amino-donor pentaethylenehexamine (PEHA). Functionalized HIT-MNPs and AMS-MNPs were immobilized with enzyme β-galactosidase (β-GAL). When using combination of 0,5 % (v/v) GA and 30 % (v/v) PEHA 128,9 % of residual activity was achieved, which resulted in hyper-activation of enzyme due to its conformational changes. Hyper-activation was achieved also with immobilizing β-GAL onto AMS-MNPs and the highest residual activity was obtained with with 20 % (v/v) of PEHA (154,4 %).

Možnosti ravnanja z odpadnimi goščami iz komunalnih čistilnih naprav, zaradi povišane vsebnosti težkih kovin, omejuje zakonodaja. Kljub visokemu deležu organskih snovi in hranil, je njihova uporaba v kmetijstvu prepovedana. Ena izmed obetajočih naprednih metod odstranjevanja težkih kovin je adsorpcija na magnetne nanodelce, ki se jih po čiščenju odstrani z magnetno separacijo. Pri magistrskem delu smo sintetizirali in okarakterizirali tri sisteme magnetnih nanokompozitov: maghemit – L-lizin, ki so se razlikovali po načinu vezave L-lizina. Za uspešno se je izkazala le kovalentna vezava. Ta sistem je pri čiščenju vzorca mulja dosegel 37 % učinkovitost odstranitve Zn, 27 % Cr(VI) in 26 % Cu. Due to increased content of heavy metals, possibilities of waste sludge management from municipal wastewater treatment plants are limited by legislation. Despite of high content in organic substances and nutrients, sludge use in agriculture is restricted. One of the advanced methods for metal removal is adsorption on magnetic nanoparticles, which can later be removed by magnetic separation. Three systems of magnetic nanocomposites: maghemite – L-lysine, which differed in the L-lysine binding method, were synthesized and characterized. Only chemical bonding was successful. This system achieved 37, 27 and 26 % removal efficiency of Zn, Cr(VI), and Cu from a sludge sample respectively.

Zagotavljanje čiste in kvalitetne vode postaja problem sodobne družbe. Težke kovine so eno izmed najnevarnejših onesnaževal, saj niso biološko razgradljive, se kopičijo v naravi in toksično učinkujejo na žive organizme že pri zelo nizkih koncentracijah. V primerjavi z ostalimi metodami za odstranjevanje težkih kovin iz odpadnih vod, se je adsorpcija na različne adsorbente izkazala kot bolj ekonomična in učinkovita. Z razvojem nanotehnologije so bili magnetni nanodelci deležni pozornosti mnogih raziskav za iskanje najprimernejši adsorbentov težkih kovin. Namen diplomske naloge je bila sinteza stabilnih maghemitnih nanodelcev ter njihova funkcionalizacija s hitozanom po treh različnih metodah. Ugotoviti je bilo treba, kateri delci so najprimernejši za odstranjevanje Cr(VI) ionov iz raztopine in pri kateri pH vrednosti je adsorpcija najučinkovitejša. Maghemitne delce smo sintetizirali z metodo koprecipitacije in jih nato funkcionalizirali s hitozanom po treh različnih metodah (metoda kovalentne vezave, mikroemulzijska metoda in suspenzijska zamreževalna metoda). Delce smo dodali v raztopino z znano koncentracijo Cr(VI) ionov, da je potekla adsorpcija. Adsorpcijo smo izvedli pri treh različnih pH vrednostih (pH 3, 4 in 5) ter določili optimalno vrednost za adsorpcijo težkih kovin na posamezne magnetne nanodelce. Kvantitativno analizo Cr(VI) v raztopini po adsorpciji smo izvedli spektrofotometrijsko z 1,5- difenilkarbazidom. Po opravljeni analizi smo primerjali uspešnost adsorpcije in določili delce, ki so dosegli najvišje odstotke adsorpcije. Ugotovili smo, da so najprimernejši delci za odstranjevanje Cr(VI) iz vode maghemitni delci funkcionalizirani z mikroemulzijsko metodo. Izkazalo se je tudi, da so najboljšo adsorpcijo vsi delci dosegli pri vrednosti pH 3. Providing clean and quality water is one of the major challenges of the modern world. Heavy metals are one of the most dangerous contaminants due to their non- degradability and persistence in the environment. Heavy metals accumulate through the food chain, moreover, they can be toxic and harmful to living organisms, even in small amounts of exposure. Among numerous technologies that have been developed for the removal of heavy metals from wastewater, adsorption has been proved as one of the most economical and efficient methods. As nanotechnology is progressing rapidly, magnetic nanoparticles have been gaining increasing interest as adsorbents for heavy metals. The aim of the diploma thesis was preparation of stable maghemite nanoparticles and their functionalization with chitosan, using three different methods. The main objectives were determining which magnetic nanoparticles are the most suitable for removal of Cr(VI) and evaluating removal efficiency at different pH. Maghemite nanoparticles were synthesized by co-precipitation method and then functionalized with chitosan by three different methods (covalent binding method, microemulsion method and suspension cross-linking technique). Different nanoparticles were used as magnetic adsorbents for removal of Cr(VI) from aqueous solution. In order to determine the effect of pH on the process od adsorption, we conducted experiments at different pH value (pH 3, 4, and 5). For quantitative determination of Cr(VI) concentrations in aqueous solutions after adsorption process, we used spectrophotometric method with 1,5-diphenylcarbazide. After analysis we ascertained which magnetic nanoparticles have achieved efficient removal rates of Cr(VI). The study reveals that the maghemite nanoparticles functionalized with chitosan by microemulsion method, are most effective adsorbents for removal of Cr(VI) from aqueous solutions. All off the tested maghemite nanoparticles achieved higher removal rates with a pH value decrease.

V tem diplomskem delu smo se ukvarjali s problematiko sinteze nanodelcev, specifično s sintezo nanodelcev z ustrezno Curiejevo temperaturo (TC), ki je v idealnem primeru v območju terapevtske temperature, 41 °C – 46 °C. Za sintezo smo uporabili mikroemulzijsko tehniko, s sestavo 60:30:10 (izooktan : (CTAB+1-butanol) : vodna faza raztopljenih magnezijevih, železovih in titanovih soli) v ternarnem diagramu. Za obarjanje hidroksidov smo uporabili raztopino amoniaka. Naš cilj je bil sintetizirati nanodelce s sestavo Mg1+xFe2-2xTixO4, pri čemer smo izbrali x = 0.37. Po sintezi smo nanodelce čistili z etanolom in nato z vodo v ultrazvočni kopeli. Po posedanju delcev v centrifugi je sledila kalcinacija na zraku pri izbrani temperaturi. Sintetizirane delce smo analizirali s termoanalitskim sistemom TGA/SDTA v območju od 25 °C do 1000 °C ter jim na modificirani aparaturi določili tudi TC. Sledila je nadaljnja analiza z rentgensko praškovno difraktometrijo (RTG). In this diploma work, we addressed the problematics of nanoparticle synthesis, specifically synthesis of nanoparticles with a lower Curie temperature (TC), that would be, in an idealized case, somewhere in the narrow therapeutic temperature range, 41 °C – 46 °C. Reverse microemulsion method was used, with a composition ratio of 60:30:10 (isooctane : (CTAB+1-butanol) : aqueous phase of dissolved magnesium, iron and titanium salts) in the ternary phase diagram. Ammonia solution was used for the precipitation of hidroxides. The goal was to synthesize nanoparticles, with a composition of Mg1+xFe2-2xTixO4, where x= 0.37. After the synthesis, the nanoparticles were cleaned using ethanol and water in the ultrasonic bath. Finally, after centrifugation the samples were calcined in air at various temperatures. For the characterisation of synthesized nanoparticles, we used thermoanalytical system TGA/SDTA, with temperatures up to 1000 °C. With small modifications, the same equipment was used for determining TC. For further analysis, we used X-Ray powder diffraction (XRD).

V magistrskem delu smo raziskali vpliv superkritičnega ogljikovega dioksida (SC CO2) na aktivnost proste in imobilizirane transglutaminaze (TGM), ob spreminjanju različnih parametrov, ki lahko vplivajo na aktivnost encima kot so tlak, temperatura in čas izpostavitve v SC CO2. Pripravili smo dve obliki imobiliziranega encima in sicer z metodo obarjanja in zamreženja smo pripravili imobilizirano TGM brez nosilca (CLEAs) ter z metodo koprecipitacije imobilizirano TGM na magnetni nanonosilec, modificiran z aminosilanom (mCLEAs). Rezultati kažejo, da je TGM zamrežena v encimske skupke (CLEAs) stabilen katalizator ter primerna za izvedbo encimskih reakcij v SC CO2, saj smo pri optimalnih pogojih izpostavitve v SC CO2 (24 urna inkubacija, tlak 100 bar in temperatura 50 °C) dosegli 123 % preostale aktivnosti imobiliziranega encima. Kljub temu, da se je aktivnost CLEAs po izpostavitvi v SC CO2 za 24 h pri 100 bar povečala pa so bile aktivnosti CLEAs in mCLEAs po izpostavitvi pri atmosferskem tlaku pri enakih pogojih višje. Preostala aktivnost CLEAs pri atmosferskem tlaku je znašala 187 % in mCLEAs 139 %. Do podobnih ugotovitev smo prišli pri spreminjanju časa poteka encimske reakcije. Predpostavljamo, da SC CO2 povzroči konformacijske spremembe v proteinu, kadar je le ta imobiliziran in tako se zmanjša njegova aktivnost. Kljub manjši stabilnosti imobiliziranega encima v obliki CLEAs in mCLEas pa je bila možna njuna ponovna uporaba. In the contex of this master thesis we explored the influence of supercritical carbon dioxide (SC CO2) on free and immobilized transglutaminase activity (TGM), while changing various parameters that influence the activity of the enzyme such as pressure, temperature and reaction time. Two forms of immobilized enzyme were prepared. Using the precipitation and crosslinking method a immobilized TGM without carrier (CLEA) was prepared, additionally with the co-precipitation method a immobilized TGM was applied to a magnetic nanocarrier modified by aminosilane (mCLEAs). The results show that TGM crosslinked in enzymatic aggregates (CLEAs) is a stable catalyst and suitable for the implementation of enzymatic reactions in SC CO2, under optimum conditions of exposure to SC CO2 (24 hour incubation, 100 bar pressure and 50 °C temperature), we achieved 123% of the remaining activity. Despite the fact that CLEAs activity after exposure in SC CO2 for 24 h at 100 bar increased, CLEAs and mCLEAs activities at atmospheric pressure were higher. The remaining CLEAs activity at atmospheric pressure was 187% and 139% for mCLEAs. Similar findings were obtained in changing the duration of the enzyme reaction. We assumed that SC CO2 causes conformational changes in protein when it is immobilized and thus reduces its activity. Despite the lower stability of the immobilized enzyme, their reuse was possible.

Namen magistrske naloge je bil sintetizirati magnetne nanodelce s koprecipitacijo železovih oksidov, jih prevleči z CM-dekstranom ter na njih preučiti koimobilizacijo encima ADH ter kofaktorja NAD+. Po aktivaciji nanonosilcev z mrežnim povezovalcem EClH smo na njih koimobilizirali ADH in NAD+. Prostemu in imobiliziranemu encimu smo določali aktivnost z encimskim aktivnostnim testom ter izračunali preostalo aktivnost encima. Bradfordova metoda nam je služila za določanje koncentracije proteinov, s pomočjo katere smo imobilizirani ADH izračunali učinkovitost imobilizacije. Postopek koimobilizacije smo optimizirali s spreminjanjem imobilizacijskih pogojev, in sicer mase magnetnih nanodelcev, izbire mrežnega povezovalca (EClH ali GA), časa aktivacije magnetnih nanodelcev, zaporedja, časa in temperature koimobilizacije, koncentracije kofaktorja in koncentracije encima. Po določitvi optimalnih pogojev smo raziskali termično stabilnost prostega in imobiliziranega encima ter možnost skladiščenja imobiliziranega encima. Eksperimentalno smo Michaelisovi konstanti določili (KM) prosti in imobilizirani ADH. Pri optimalnih imobilizacijskih pogojih (50 mg magnetnih nanodelcev, 2 h aktivacije nanonosilcev z EClH, 2 h imobilizacije NAD+ s koncentracijo 20 mM, 4 h imobilizacije ADH s koncentracijo 0,01 mg/mL, sobna temperatura, hitrost stresanja 350 obr/min) smo dosegli najvišjo 73 % preostalo aktivnost ADH in 94 % učinkovitost imobilizacije. Imobiliziran encim je bil v primerjavi s prostim encimom termično stabilnejši, prav tako ga je bilo mogoče skladiščiti pri 4 °C. Eksperimentalno določena KM je bila pri imobilizirani ADH višja. The purpose of the master's thesis was to synthesize magnetic nanoparticles (MNPs) by coprecipitation method of ferric and ferrous ions and later on, coated with CM-dextran. Co-immobilization of the ADH enzyme and the NAD+ cofactor on CM-dextran coated MNPs was studied. After activation of nanoparticles with cross-linking agent EClH, ADH and NAD+ were co-immobilized. Activity of free and immobilized ADH was determined, using ADH activity assay, and residual activity of enzyme was calculated. The Bradford method was used to determine protein concentration and immobilization efficiency of immobilized ADH was calculated. The co-immobilization procedure was optimized by changing the immobilization conditions, which included: mass of MNPs, choice of cross-linking agents (EClH or GA), activation time of MNPs, sequence, time and temperature of co-immobilization process, concentration of cofactor and concentration of enzyme. After determining optimal conditions, thermal stability of free and immobilized ADH was investigated, Storage of immobilized ADH was studied, as well.. We experimentally determined Michaelis's constant (KM) of free and immobilized ADH. At optimal immobilization conditions (50 mg of MNPs, 2 hours activation of MNPs with EClH, 2 hours immobilization of NAD+ with a concentration of 20 mM, 4 hours immobilization of ADH with a concentration of 0.01 mg/mL, at room temperature and 350 rpm) the highest residual activity of ADH (73 %) and immobilization effciency (94 %) was achieved.. The immobilized enzyme was thermally more stable compared to the free enzyme, and could also be stored at 4 °C. The experimentally determined KM of immobilized ADH was higher than of free ADH.

V diplomskem delu smo raziskovali vpliv sinteznih pogojev na obliko, velikost in magnetne lastnosti stroncij heksaferitnih nanodelcev. Stroncij heksaferit (SrFe12O19) smo sintetizirali s hidrotermalno metodo, katere cilj je izboljšanje magnetnih lastnosti (nasičeno in remanentno magnetizacijo ter koercitivnost) preiskovanega materiala v primerjavi z do sedaj doseženimi vrednostmi tako sintetiziranega SrFe12O19. S spreminjanjem temperature in časa sinteze se spreminja morfologija delcev in posledično tudi njihove magnetne lastnosti. Od temperature in časa sinteze je odvisna velikost nanodelcev kakor tudi čistost produkta, ki vpliva na magnetne lastnosti vzorcev. Magnetne lastnosti sintetiziranega materiala smo še dodatno izboljšali z žarjenjem. In this diploma work, we have been investigating the influence of synthesis parameters on the morphology, size and magnetic properties of strontium hexaferrite nanoparticles. Strontium hexaferrite (SrFe12O19) has been synthesised by hydrothermal method, the purpose of which was to enhance magnetic properties (saturation magnetization, remanence and coercivity) of the investigated material in comparison to recently obtained values. By changing the temperature and time of the synthesis we were able to tailor nanoparticles' morphology and by doing so their magnetic properties have changed. Temperature and time of the synthesis dictate particle size and purity of product material, which influences its magnetic properties. Further enhancement of the magnetic properties of strontium ferrite was achieved by annealing.

Stabilne suspenzije magnetnih nanodelcev prevlečenih z bioaktivnimi molekulami predstavljajo velik potencial v terapevtskih aplikacijah. Goli magnetni nanodelci v vodnih suspenzijah imajo težnjo po aglomeraciji, z adsorpcijo aminokislin nanje pa lahko vplivamo na njihov površinski naboj in tako pripravimo stabilne suspenzije. V magistrskem delu smo želeli pripraviti stabilne suspenzije magnetnih nanodelcev maghemita prevlečenih s polipeptidom na enostaven in cenovno ugoden način, primeren za masovno industrijsko proizvodnjo. Preučevali smo tudi obstojnost peptidne prevleke v biološko pomembnem mediju, fosfatnem pufru, ki ima veliko afiniteto do površine nanodelca. Magnetne nanodelce smo sintetizirali s soobarjanjem Fe2+/Fe3+ ionov iz vodne raztopine. Na tako pripravljene nanodelce smo adsorbirali aminokislini lizin in asparaginsko kislino v različnih razmerjih. Za zamreženje adsorbiranih aminokislin smo uporabili zamreževalni reagent 1-etil-3-(-3-dimetilaminopropil) karbodiimid hidroklorid (EDC), ki je znan po nizki toksičnosti in sposobnosti modifikacije stranskih skupin proteinov. Z adsorpcijo aminokislin na površino magnetnih nanodelcev in naknadnim dodatkom zamreževalnega reagenta nismo uspeli pripraviti koloidno stabilnih suspenzij. S FT-IR meritvami smo potrdili nastanek peptida na površini magnetnih nanodelcev. Na podlagi HPLC meritev aminokislin v supernatantih suspenzij nanodelcev sklepamo, da se na nanodelce v prisotnosti EDC adsorbira precejšen del aminokislin, pri čemer se asparaginska kislina adsorbira v večji meri kot lizin. Meritve zeta potenciala so pokazale obstojnost peptidne prevleke na nanodelcih v prisotnosti fosfatnega pufra s koncentracijo, ki se uporablja v bioloških aplikacijah. Stable suspensions of magnetic nanoparticles coated with bioactive molecules show great potential for therapeutic applications. Magnetic nanoparticles in aqueous suspensions have the tendency to agglomerate, and with their adsorption of amino acids we can influence their surface charge, thus preparing stable suspensions. In this Master’s thesis, we aimed to prepare stable suspensions of maghemite magnetic nanoparticles coated with a polypeptide in a simple and cost-effective manner suitable for mass industrial production. We also researched the stability of a peptide coating in a biologically important medium, a phosphate buffer, which has a great affinity for the surface of the nanoparticle. The magnetic nanoparticles were synthesized through the co-precipitation of the Fe2+/Fe3+ ions in the aqueous solution. Once the nanoparticles were prepared, we adsorbed the amino acids lysine and aspartic acid in varying proportions. In order to cross-link the adsorbed amino acids we used the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) cross-linking reagent, which is known for its low toxicity and its ability to modify side groups of proteins. With the adsorption of the amino acids onto the surface of the magnetic nanoparticles and the subsequent addition of the cross-linking reagent, we were unable to prepare colloidally stable suspensions. FT-IR measurements confirmed the formation of a peptide on the surface of magnetic nanoparticles. Based on our HPLC measurements of amino acids in supernatant nanoparticle suspensions, we can conclude that in the presence of EDC nanoparticles adsorb a substantial portion of the amino acids, of which aspartic acid is adsorbed to a greater extent than lysine. Our measurements of the zeta potential demonstrated the persistence of the peptide coating on the nanoparticles in the presence of a phosphate buffer at a concentration used in biological applications.

Pripravili smo zamrežene magnetne encimske skupke (mCLEAs) iz lakaze. Metoda sestoji iz dveh delov: obarjanje encima z ustreznim obarjalnim reagentom in imobilizacija dobljenega agregata v zamrežene encimske skupke z zamreževalcem glutaraldehidom. S centrifugiranjem smo produkt ločili na pelet in supernatant. Supernatant smo uporabili za test koncentracije proteinov, na peletu pa smo izmerili preostalo aktivnost lakaze. Namen diplomske naloge je bil pripraviti mCLEAs z najvišjo preostalo aktivnostjo lakaze in učinkovitostjo imobilizacije. Preizkušali smo vpliv naslednjih parametrov: koncentracija magnetnih nanodelcev, koncentracijo glutaraldehida, količina NaBH3CN, temperatura, čas ter koncentracija encima. Raztopini encima smo dodajali ogrodne proteine: albumin iz govejega seruma (BSA) ter albumin iz kokošjih jajc (EA). mCLEAs z visoko preostalo aktivnostjo smo pripravili z uporabo 10 mg magnetnih nanodelcev v 100 µL raztopine lakaze koncentracije 20 mg/ml. Obarjali smo z 900 µL obarjalnega reagenta 2-propanol. Zamreževali smo z 15% (v/v) GA (150 µL) in dodali 50 µL NaBH3CN. Zamreževanje se je vršilo tri ure s hlajenjem. Magnetic cross-linked enzyme aggregates (mCLEAs) of lacasse were prepared. The method consists of two parts: precipitation of enzyme with an appropriate precipitant agent and immobilization of the resulting aggregate into a cross-linked enzyme aggregates with the glutaraldehyde as cross-linker. After centrifugation, product was separated on pellet and supernatant. Supernatant was used to test protein concentration and pellet was used to measuse the residual activity of cross-linked lacasse. The purpose of diploma work was to prepare mCLEAs with the highest residual activity and immobilization efficiency. We tested the influence of the following parameters: concentration of magnetic nanoparticles, amount ob NaBH3CN, concentration of glutaraldehyde, time, temperature and concentration of lacasse. Proteins bovine serum albumin (BSA) and chicken egg albumin (EA) were added to enzyme solution. mCLEAs with highest residual activity were prepared using 10 mg of magnetic nanoparticles in 100 µL enzyme solution concentration of 20 mg/ml. 900 µL of 2-propanol was used as the most suitable precipitation reagent. Cross-linking was performed with 15% (v/v) GA. We also added 50 µL NaBH3CN. Cross-linking lasted for three hours with cooling.

Namen magistrskega dela je bil s koprecipitacijo Fe2+ in Fe3+ ionov sintetizirati magnetne nanodelce, jih modificirati z dekstranom in proučiti njihovo uporabo kot nosilcev za imobilizacijo encima transglutaminaza. Sintetizirane nanodelce smo najprej aktivirali z mrežnim povezovalcem GA in/ali PEHA in jih nato uporabili za kovalentno imobilizacijo encima. Določali smo učinkovitost imobilizacije in aktivnost proste ter imobilizirane transglutaminaze. Proces imobilizacije smo optimirali s spreminjanjem koncentracije mrežnih povezovalcev (GA, PEHA), časa imobilizacije, koncentracije encima, koncentracije stabilizacijskih proteinov (EA, BSA), temperature imobilizacije, hitrosti stresanja in s spreminjanjem zaporedja dodajanja stabilizacijskih proteinov ter vrste nosilca. Določali smo tudi termično stabilnost encima in možnost ponovne uporabe. Rezultati kažejo, da so dekstranski nanodelci primeren nanonosilec za imobilizacijo transglutaminaze, saj smo pri optimalnih pogojih imobilizacije (aktivacija nosilca z 10 vol. % PEHA, stabilizacija encima s 50 mg/mL BSA, 100 mg/mL TGM, 4-urna imobilizacija pri 10 °C in 400 obr/min) dosegli hiperaktivacijo encima in s tem 99 % učinkovitost imobilizacije ter 110 % preostalo aktivnost encima. Hiperaktivacijo encima smo zaznali tudi z imobilizacijo encima na dekstransko-oleinske nanodelce. Imobiliziran encim je bil stabilen pri višjih temperaturah, prav tako je bila možna tudi njegova ponovna uporaba. The purpose of the master’s thesis was a synthesis of magnetic nanoparticles by the coprecipitation of Fe2+ in Fe3+ ions, their modification with dextran, and an examination of their use as carriers for immobilization of the enzyme transglutaminase. Synthesized nanoparticles were first activated with a cross-linking agent (GA and/or PEHA) and then used for covalent immobilization of the enzyme. The effectiveness of immobilization and the activity of free and immobilized transglutaminase was determined. The process of immobilization was optimized by changing the concentration of cross-linking agents (GA, PEHA), the time of immobilization, enzyme concentration, the concentration of stabilizing proteins (EA, BSA), immobilization temperature, agitation rate, type of carrier, and by changing the sequence of adding stabilizing proteins. The thermal stability and reusability of the enzyme were also investigated. The results indicate that the dextran nanoparticles are a suitable nanocarrier for the immobilization of transglutaminase, since under optimal immobilization conditions (activation of the carrier with 10 vol. % PEHA, stabilization of the enzyme with 50 mg/mL BSA, 100 mg/mL TGM, 4-hour immobilization at 10 °C and 400 rpm) the enzyme was hyperactivated and shows 99% immobilization efficiency and 110% residual activity. Hyperactivation of the enzyme was also achieved by the immobilization of TGM onto dextran-oleic nanoparticles. The immobilization enzyme was stable at higher temperatures and its reuse was also possible.

Namen našega dela je bil pripraviti zamrežene encimske skupke (CLEA) in magnetne zamrežene encimske skupke (mCLEA) iz encima β-galaktozidaze. Doseči smo želeli čim višjo preostalo aktivnost encima in čim višjo učinkovitost imobilizacije. Zamreženje smo preizkušali v štirih obarjalnih reagentih (acetonu, etanolu, 1-propanolu in 2-propanolu), dodajali smo ogrodne proteine in mrežne povezovalce v različnih kombinacijah in koncentracijah. Eksperimentalno delo je obsegalo pripravo vzorcev (obarjanje in zamreženje), aktivnostni test in Bradfordovo metodo za določanje koncentracije proteinov. Proces smo optimirali pri konstantni koncentraciji encima (50 mg/ml) in konstantnem dodatku glutaraldehida (GA). Ugotovili smo, da je optimalna količina dodanega mrežnega povezovalca GA 1.5% (v/v) in da mrežni povezovalec pentaetilenheksamin (PEHA) negativno vpliva na zamreženje, razen če ga dodajamo v kombinaciji z ogrodnimi proteini. V tem primeru se preostala aktivnost zviša, medtem ko učinkovitost imobilizacije močno upade. The purpose of our work was to create cross-linked enzyme aggregates (CLEA) and magnetic cross-linked enzyme aggregates (mCLEA) off enzyme β-galactosidase. The aim of our work was to achive the highest possible residual activity and maximize the efficiency of immobilization. The cross-linking was tested in four most optimal precipitation reagents (acetone, ethanol, 1-propanol, 2-propanol) while stability proteins and cross-linkers in various combinations and concentrations were added to the synthesis reaction. The experimental work included preparation of samples (precipitation and cross-linking), activity test and the Bradford protein assay for determination of proteins. The process was optimized at a constant concentration enzyme (50 mg/ml), and a constant addition of glutaraldehyde (GA). It was concluded that the optimal quantity of added cross-linker is 1.5% (v/v) and that the cross-linker pentaetilenheksamin (PEHA) negatively affects the cross-linking, unless it is added in combination with stability proteins. In this case, the residual activity is increased, while the efficacy of immobilization drops significantly.

In this study, magnetic maghemite nanoparticles were prepared with the coprecipitation method, due to its simplicity and productivity. Thereafter, chitosan-coated magnetic nanoparticles were synthesized with three different methods, the micro-emulsion process, the suspension cross-linking technique and the covalent binding. Subsequently, a comparison of the used methods was done using various analyses such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetry (TGA), differential scanning calorimetry (DSC), vibrating-sample magnetometry (VSM) and dynamic light scattering (DLS). The characterization results from Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) indicated a successful binding of chitosan on the magnetic nanoparticles. SEM pictures showed that spherical structured particles with an increased particle size were obtained as the chitosan layer around the particles was increased. Considering that the magnetic-separation technique has the advantages of rapidity, high efficiency, cost-effectiveness and lack of negative effect on the biological activity, these carriers may be applied in enzyme immobilization. V prispevku je opisana enostavna priprava magnetnih nanodelcev, prevlečenih s hitozanom. Postopek je potekal v dveh stopnjah. V prvi smo sintetizirali magnetne nanodelce s koprecipitacijo železovih ionov. V drugi smo nanodelce prevlekli s hitozanom, da bi preprečili aglomeracijo, z uporabo treh različnih postopkov: z metodo mikroemulzije, metodo zamreženja in s kovalentno vezavo. Karakterizacija tako pripravljenih nanodelcev je bila izvedena s Fourierjevo transformacijsko infrardečo spektroskopijo (FTIR), z vrstično elektronsko mikroskopijo (SEM), s termogravimetrično analizo (TGA), z diferencialno dinamično kalorimetrijo (DSC), z analizo vibracijskega magnetometra (VSM) in dinamičnim sipanjem laserske svetlobe (DLS). Rezultati analiz FTIR in TGA so potrdili vezavo hitozana na magnetne nanodelce, medtem ko je bila oblika in debelina sloja hitozana določena s SEM-analizo. Ker ima tehnika magnetnih nanodelcev veliko prednosti pri ločevanju, cenejši proizvodnji in nima negativnih učinkov na biološko aktivnost, se lahko potencialno uporablja pri encimski imobilizaciji.

V prispevku opisujemo sintezo nanodelcev kobaltovega ferita z ozko porazdelitvijo velikosti z metodo termičnega razpada organskega kompleksa. Sinteza nanodelcev je potekala v dveh stopnjah. V prvi smo sintetizirali železov in kobaltov oleat z reakcijo kobaltovega (II) in železovega (III) klorida z natrijevim oleatom v mešanici topil. V drugi stopnji smo raztopino oleatov, ki smo ji dodali različne količine oleinske kisline, segreli do vrelišča topila (heksadeken 282 °C ali oktadeken 316 °C). Na povišani temperaturi oleati razpadejo in tvorijo oksidne nanodelce. Na nanodelce je vezan monomolekulski sloj oleinske kisline, ki omogoča dispergiranje nanodelcev v nepolarnih topilih. Povprečna velikost nanodelcev kobaltovega ferita je odvisna od temperature, časa siteze in količine dodane oleinske kisline. Sintetizirani nanodelci v območju velikosti med 9 nm in 20 nm izkazujejo ferimagnetno vedenje ter magnetne lastnosti, ki se spreminjajo s povprečno velikostjo nanodelcev. Predpostavili smo mehanizem nastanka nanodelcev kobaltovega ferita, ki vključuje koalescenco manjših nanodelcev in njihovo rekristalizacijo. A synthesis method for the preparation of narrow-size-distribution Co-ferrite nanoparticles by thermal decomposition of oleates is presented. A two-step method was used to produce the nanoparticles. In the first step cobalt and iron oleates were synthesized by reacting iron (III) and cobalt (II) chlorides with sodium oleate in a mixture of solvents. In the second step the oleates solution, to which different amounts of oleic acid were added, was heated to the solvents’ boiling point (hexadecene 282 °C or oktadecene 316 °C). At elevated temperatures oleates decompose and oxide nanoparticles are formed. The nanoparticles are than coated with a mono-molecular layer of oleic acid, are hydrophobic and can be dispersed in non-polar organic solvents. The average size of the cobalt ferrite nanoparticles depends on the temperature, time of the synthesis and the concentration of oleic acid. In the size range between 9 nm and 20 nm the synthesized nanoparticles exhibited ferromagnetic behavior and size-dependent magnetic properties. A mechanism for the formation of cobalt ferrite nanoparticles with re-crystallization of nanoparticles composed of smaller nanoparticles is proposed.

V magistrskem delu so bili sintetizirani nanodelci po Stöberjevi sol-gel metodi v alkoholnem mediju in amonijakom kot katalizatorjem, pri pH 10-11 in množinskem razmerju prekurzorjev TEOS:APTMS za 1:2 in 1:4. Za karakterizacijo materialov smo uporabili BET metodo za določanje specifične površine, infrardečo spektroskopijo s Fourierjevo transformacijo (FTIR) za določevanje funkcionalnih skupin, rentgensko praškovno difrakcijo (XRD) in presevno elektronsko mikroskopijo (TEM) ter za analizo učinkovitosti odstranjevanja svinčevih ionov (Pb2+) in skupnega kroma (skupni Cr) z AAS metodo. Adsorpcija svinca (Pb2+) in skupnega Cr na funkcionalizirane nanodelce (SiO2@NH2) in funkcionalizirane magnetne nanodelce (MND@SiO2@NH2) se je pokazala kot uspešna metoda za odstranjevanje ionov težkih kovin iz odpadnih voda. Pri velikosti MND@SiO2@NH2 delcev od 9 – 16 nm z debelino prevleke od 2- 5 nm smo odstranili od 95 % do 99 % Pb2+, Cr6+ in skupnega Cr iz modelnih voda. Z R (%) > 95 se sintetizirani material izkazal kot zelo učinkovit tudi pri odstranjevanju Pb2+ in skupnega Cr iz modelne mešanice ionov težkih kovin. Visoko učinkovitost omogoča velika specifična površina delcev in površinska funkcionalizacija z amino skupinami (-NH2). The nanoparticles used, were synthesised via Stober's sol-gel method in an alcoholic medium and using ammonia as a catalyst at a pH of 10-11 and the relative abundances of the precursors TEOS:APTMS of 1:2 and 1:4. For characterisation of the prepared material the BET method was used in order to estimated the specific surface area. Additional methods such as Fourier Transform Infrared Spectroscopy (FTIR), X-Ray powder diffraction (XRD) and Transmission Electron Microscopy (TEM). For efficiency analysis of heavy metal ion removal (Pb2+ and Cr total), analysis with AAS spectroscopy were performed. Results show that lead and chrome absorption on functionalised silica nanoparticles (SiO2@NH2) and functionalised magnetic nanoparticles (MNP@SiO2@NH2) is a succesful method of heavy metal ion removal from wastewater. . In the case of MNP@SiO2@NH2 with particle size from 9 to 16 nm with a coating thickness of 2 to 5 nm, between 95 to 99 % of Pb, Cr6+ and total Cr species were removed from model samples. With R values of 99 % for Pb2+ and 96 % for total Cr the synthesised material is very effective at removing Pb2+ and total Cr from a model mixture of heavy metal ions. This is due to the large specific area of the particles and the functionalisation of the surface with amino (-NH2) groups

Nanomateriali in med njimi nanodelci, so med najbolj obetajočimi adsorpcijskimi materiali za čiščenje oljnih razlitij, saj imajo visoko specifično površino in jih lahko obdamo z molekulami, ki kažejo visoko afiniteto do adsorpcije olj. Kadar pa ti nanodelci izkazujejo še ustrezne magnetne lastnosti, jih lahko ob prisotnosti zunanjega magnetnega polja enostavno in hitro ločimo iz raztopine, kar je dodatna prednost teh materialov. Z metodo soobarjanja smo sintetizirali magnetne nanodelce kobalt ferita (CoFe2O4), jih elektrostatsko stabilizirali in funkcionalizirali z različnimi silani (difenildimetoksisilan (DPDMS), trimetoksi(3,3,3-trifluoropropil)silan (F-TriMOS), 1H,1H,2H,2H-perfluorodeciltrietoksisilan (FDTES), propiltrimetoksisilan (P-TriMOS), metiltrimetoksisilan (M3MS), etiltrimetoksisilan (ETMS), etiltrietoksisilan (ETES), dimetildiklorosilan (DMDCLS), metiltriklorosilan (MTCLS), trimetoksi(1H,1H,2H,2H-nonafluoroheksil)silan (NFHTMS)) v različnih množinskih razmerjih (P=[TEOS]/[silan]=2, 1, 0,5 in 0,25). Pripravljene nanomateriale smo okarakterizirali z metodami rentgenske praškovne difrakcije (XRD), presevne elektronske mikroskopije (TEM), infrardeče spektroskopije s Fourierjevo transformacijo (FT-IR), prav tako smo določali specifično površino nanodelcev z metodo BET, specifično magnetizacijo (VSM), stični kot z vodo in kapaciteto adsorpcije olja na nanodelce. Z rentgensko praškovno difrakcijo smo dokazali spinelno kristalno strukturo nanodelcev CoFe2O4, katerih velikost smo določili na tri načine, in sicer s presevnim elektronskim mikroskopom (TEM) (11,5 ± 1,9 nm), z metodo BET (14 nm), in iz XRD difraktograma (11,4 nm). Rezultati meritev FT-IR nakazujejo, da smo vse vzorce uspešno funkcionalizirali z izbranimi silani, saj se na IR spektrih pojavljajo značilni absorpcijski vrhovi za karakteristične vezi, ki nastanejo pri funkcionalizaciji CoFe2O4 nanodelcev z izbranimi silani. Specifična magnetizacija nasičenja (Ms) vzorca CoFe2O4 pa je bila 52,0 emu/g. Z meritvami VSM smo ugotovili, da pri večini vzorcev specifična magnetizacija upade zaradi nemagnetne prevleke okoli magnetnega jedra nanodelca. Pripravljeni materiali so kljub temu dobro magnetno odzivni in primerni za magnetno ločevanje, kar smo potrdili tudi pri poskusih določevanja kapacitete adsorpcije olja na pripravljene nanodelce. Pri meritvah specifične površine vzorcev se je izkazalo, da ima večina vzorcev pri večji množini dodanega silana manjšo specifično površino, pri adsorpciji olj pa so se bolje izkazali vzorci z večjo specifično površino. Površine funkcionaliziranih nanodelcev kažejo večjo stopnjo hidrofobnosti kot nefunkcionalizirani nanodelci. Kapaciteta adsorpcije olja je znašala največ 3,5 g motornega olja/ g nanodelcev, in sicer pri vzorcu P-TriMOS@SiO2@CoFe2O4 pri množinskem razmerju P= 1. Tudi ostali vzorci, z izjemo vzorcev z močno fluorirano silikatno prevleko (NFHTMS@SiO2@CoFe2O4 in FDTES@SiO2@CoFe2O4), so izkazovali relativno dobro adsorpcijo olja (med 2,6 in 3,5 g olja/g nanodelcev). Na dveh vzorcih, ki sta se izkazala kot najboljša (P-TriMOS@SiO2@CoFe2O4 pri P=1 in M3MS@SiO2@CoFe2O4 pri P=1), smo preizkusili možnost regeneracije in ponovne uporabe ter ugotovili, da je regeneracija precej uspešna, saj kapaciteta adsorpcije po ponovni uporabi bistveno ne upade (

Nanoparticles of inorganic magnetic core surrounded by layers of functional coatings are potential representatives of nanostructures for immobilization of bio-substances. Magnetic nanoparticles (MNPs) are often bound in aggregates due to a strong magnetic dipole, which has a lot of advantages, such as large surface area for binding biologically active substances. Chitosan is a polysaccharide polymer that is non-toxic, hydrophilic, biocompatible and has hydroxy and amino groups in its structure. Because of these chemical and biological properties it is a desirable bio-product for immobilization of enzymes and for binding of other biologically active substances. Magnetic micro and nanoparticles were synthesized with chitosan by three different methods microemulsion process, suspension cross-linking technique and covalent binding of chitosan. Toxic effect of the prepared magnetic particles was determined as well and was examined on five different bacterial cultures Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis and Klebsiella pneumoniae. At concentrations of 10-30 mg of magnetic particles per 0.5 McFarland Standard solution of E. coli and per 400 CFU of S. aureus, P. aeruginosa, E. faecalis in K. pneumonia, no inhibition on the chosen bacterial cultures was detected. Nanodelci iz magnetnega anorganskega jedra, oblečeni z večslojno funkcionalno prevleko, predstavljajo pomemben razred nanostrukturiranih delcev za vezavo biosubstanc. Zaradi možnega magnetnega dipola se magnetni nanodelci pogosto združujejo v skupke, kar pa ima številne prednosti, kot na primer velika površina, na katero lahko pritrdimo različne biološke komponente. Hitozan je polisaharidni polimer, ki je nestrupen, hidrofilen, biokompatibilen in vključuje prisotnost hidroksilne in amino skupine v svoji strukturi. Zaradi naštetih kemijskih in bioloških lastnosti spada hitozan med zaželjene biomateriale za imobilizacijo encimov in vezavo drugih biološko aktivnih substanc. Magnetne nanodelce, prevlečene s hitozanom, smo pripravili po treh različnih postopkih s postopkom mikroemulzije, s postopkom suspenzijske zamreževalne tehnike ter s postopkom kovalentne vezaven hitozana. Toksikološke vplive pripravljenih magnetnih delcev smo preverili na petih različnih bakterijskih kulturah Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis in Klebsiella pneumoniae. Pri koncentracijah 10-30 mg magnetnih delcev na 0.5 McFarland standardne raztopine bakterijske kulture E.coli in na 400 CFU bakterijskih kultur S. aureus, P. aeruginosa, E. faecalis in K. pneumonia do inhibicije rasti mikroorganizmov ni prišlo.

A chemical and a physical method have been applied for the preparation of chromium-nickel alloy nanoparticles. These particles were designed to be used for controlled magnetic hyperthermia applications. Microemulsions with $Ni^{2+}$ and $Cr^{3+}$ and/or $NaBH_4$ as precursors were prepared using the isooctane/CTAB, n-butanol/$H_2O$ system. The samples of $Cr_xNi_{1-x}$ nanoparticles with the desired composition were obtained after the reduction of their salts with $NaBH_4$ and afterwards heat treated in a TGA in a $N_2$ atmosphere at various temperatures. The $Cr_xNi_{1-x}$ materials were also prepared by mechanical milling. Utilizing a ball-to-powder mass ratio of 20 : 1 and selecting the proper alloy compositions we were able to obtain nanocrystalline $Cr_xNi_{1-x}$ particles. Thermal demagnetization in the vicinity of the Curie temperature of the nanoparticles was studied using a modified TGA-SDTA method. The alloyʼs phase composition, size and morphology were determined with XRD measurements and TEManalyses. Za pripravo nanodelcev zlitine $Cr_xNi_{1-x}$ smo uporabili kemijsko in fizikalno metodo. Delci so namenjeni uporabi v biomedicini, zlasti na področju kontrolirane magnetne hipertermije. Najprej smo pripravili mikroemulzije z $Ni^{2+}$, $Cr^{3+}$ in/ali $NaBH_4$ prekurzorji v sistemu izooktan/CTAB, n-butanol/$H_2O$. Vzorce $Cr_xNi_{1-x}$ nanodelcev z željeno sestavo smo dobili po redukciji njihovih soli z $NaBH_4$ in naknadnem segrevanju v TGA v atmosferi $N_2$ pri različnih temperaturah. Nanodelce $Cr_xNi_{1-x}$ smo sintetizirali tudi s pomočjo mehanskega mletja zmesi kromovih in nikljevih prahov. Mleli smo v visokoenergijskem krogličnem mlinu SPEX 8000M. Z uporabo primernega masnega razmerja med mlevnimi kroglicami in prahom 20:1 in izbiro primerne sestave smo dobili nanodelce zlitine $Cr_xNi_{1-x}$. Curiejevo temperaturo nanodelcev smo določili z uporabo modificirane TGA-SDTA metode. Sestavo nanozlitine, velikost in morfologijo delcev smo določili s pomočjo meritev XRD in TEM analize.

V magistrskem delu smo preučevali vpliv deleža dopanta gadolinija oziroma disprozija na strukturne in magnetne lastnosti Mg-Ti ferita ter hkrati primerjali dopirane delce z nedopiranimi. Za sintezo spinelnega ferita smo uporabili metodo koprecipitacije, vzorce pa smo nato še dodatno temperaturno obdelali s postopkom kalciniranja. Nastale produkte smo analizirali z rentgensko praškovno difrakcijo (XRD), termogravimetrijo (TGA), z magnetometrom z vibrirajočim vzorcem (VSM) in jim določili Curiejeve temperature z modificirano termogravimetrično aparaturo. Rezultati kažejo, da nam je v vseh primerih uspelo sintetizirati nanodelce spinelnega magnezijevega ferita, katerega kristaliničnost, ocenjena velikost kristalitov in Curiejeva temperatura se je razlikovala glede na delež železa oziroma dopanta, vrsto dopanta in temperaturo kalciniranja. Najprimernejše Curiejeve temperature za uporabo v magnetni hipertermiji je izkazoval nedopirani magnezijev ferit (x=0,34 in 0,37), ki smo ga kalcinirali pri temperaturi od 800 °C do 900 °C ter pri 1000 °C. Med dopiranimi nanodelci bi lahko za magnetno hipertermijo uporabili le delce Mg1,34Fe1,22Gd0,10Ti0,34O4. Pri primerjavi magnetizacije smo ugotovili, da pri procesu dopiranja ferita x=0,37 z 10% deležem gadolinija, magnetna nasičenost naraste iz 6,34 emu/g na 13,25 emu/g. In this master's degree we studied the influence of doping fraction of gadolinium or dysprosium on the structural and magnetic properties of Mg-Ti ferrite and also compared doped particles with undoped ones. The coprecipitation method was used for the synthesis of spinel ferrite and then the particles were heat treated by calcination process. The resulting products were characterized by X-ray powder diffraction (XRD), thermogravimetry (TGA), a vibrating sample magnetometer (VSM) and we determined the Curie temperatures by modified thermogravimetric apparatus. The results show that we have been able to synthesize nanoparticles of magnesium spinel ferrite, whose crystallinity, estimated crystallite size and Curie temperature is different, depending on iron or dopant fraction, dopant type and calcining temperature. The most suitable Curie temperature for magnetic hyperthermia application showed undoped magnesium ferrite (x=0,34 in 0,37), which was calcined at a temperature of 800 °C to 900 °C and 1000 °C. Among the doped nanoparticles, only particles Mg1,34Fe1,22Gd0,10Ti0,34O4 could be used for magnetic hyperthermia. When we compared the magnetization, we found that magnetic saturation increases from 6,34 emu/g to 13,25 emu/g in the process of doping ferrite (x=0,37) with 10% fraction of gadolinium.

Doktorska disertacija je razdeljena na dva sklopa, v katerih smo razširili dosedanje raziskave na področju priprave magnetnih nanodelcev, njihove funkcionalizacije in imobilizacije encimov na tako pripravljene mikro- in nanonosilce. Osrednji cilj disertacije je priprava magnetnih nanodelcev z metodo obarjanja ali koprecipitacije železovih (II) in železovih (III) ionov v alkalnem mediju, funkcionaliziranih s hitozanom po treh različnih metodah metodi mikroemulzije, suspenzijske zamreževalne tehnike in kovalentne vezave. Podrobna karakterizacija tako pripravljenih nosilcev je bila izvedena s pomočjo presevne elektronske mikroskopije, vrstične elektronske mikroskopije, rentgenske praškovne difrakcije, z dinamičnim sipanjem laserske svetlobe, laserskim granulometrom in merjenjem specifične magnetizacije. Tako smo opazovali morfologijo in lastnosti magnetnih nosilcev. Površinsko funkcionalizacijo s hitozanom za doseganje višje funkcionalnosti smo potrdili s pomočjo energijskodisperzijske spektroskopije, termične analize, potenciometrične titracije in s Fourierevo transformacijo. Z mikrobiološkim testiranjem je bil določen vpliv magnetnih mikro- in nanonosilcev na rast mikrobnih kultur. Nadalje smo magnetne mikro- in nanodelce, prevlečene s plastjo hitozana, uporabili kot nosilce za imobilizacijo holesterol oksidaze (EC 1.1.3.6). S spreminjanjem različnih pogojev, kot so koncentracija encima, koncentracija in vrsta mrežnega povezovalca glutaraldehida ali pentaetilen heksamina ter hitrost stresanja, smo ugotovili, kako se spreminja učinkovitost imobilizacije encima ter kolikšen delež aktivnosti se pri tem ohrani v primerjavi s prostim encimom. Aktivnost imobilizirane holesterol oksidaze smo določili z reakcijo oksidacije holesterola. Optimalni reakcijski pogoji imobilizacije holesterol oksidaze na magnetne mikro- in nanonosilce so bili doseženi pri koncentraciji encima 1 mg/mL ob uporabi 0,02 M pentaetilenheksamina kot mrežnega povezovalca. Aktivnost imobilizirane holesterol oksidaze pri optimalnih reakcijskih pogojih je bila 79,03 %. Prav tako je bila stabilnost imobilizirane holesterol oksidaze pri ponovni uporabi dobra. V drugem sklopu je opisana priprava zamreženih encimskih skupkov iz encima celulaze (EC 3.2.1.4). Postopek priprave zamreženih encimskih skupkov vključuje dva pomembna koraka, in sicer obarjanje encima z dodatkom obarjalnega reagenta in zamreženje encimskih molekul z glutaraldehidom. Optimalni reakcijski pogoji sinteze zamreženih encimskih skupkov so bili doseženi pri koncentraciji glutaraldehida 0,0625 % (v/v) in uporabi etanola kot obarjalnega reagenta. Aktivnost imobilizirane celulaze v obliki zamreženih encimskih skupkov smo določili z reakcijo hidrolize celuloze. Aktivnost imobilizirane celulaze v obliki zamreženih encimskih skupkov pri optimalnih reakcijskih pogojih je bila 93,95 %. Prav tako je bila stabilnost imobilizirane celulaze pri ponovni uporabi dobra. The PhD thesis is divided in two parts, in which we enhanced existing research in the filed of preparation of magnetic nanoparticles and their functionalization and enzyme immobilization on micro- and nanocarriers. The main objective of the thesis is the preparation of magnetic nanoparticles by precipitation method of iron (II) and iron (III) ions in an alkaline medium and the functionalization with chitosan by three different methods microemulsion, suspension cross-linking technique and covalent binding. Detailed characterization of these carriers was performed using transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction, with dynamic laser light scattering, laser granulometry and the measurement of specific magnetization. Thus, we observe the morphology and the characteristics of magnetic carriers. Surface functionalization of the chitosan in order to achieve higher functionality was confirmed by energy dispersive spectroscopy, thermal analysis, potentiometric titration and Fourier transformation. The microbiological testing determined the influence of magnetic micro- and nanocarriers on the growth of microbial cultures. Furthermore, the magnetic nanoparticles coated with chitosan were used as a carriers for the immobilization of cholesterol oxidase (EC 1.1.3.6). By changing various conditions such as the enzyme concentration, concentration and type of cross-linker glutaraldehyde or pentaetylenehexamine and shaking rate, we determined an immobilization efficiency and retained activity of immobilized enzyme compared to free enzyme. The activity of the immobilized cholesterol oxidase was determined by reaction of the cholesterol oxidation. The optimal reaction conditions of cholesterol oxidase immobilization to the magnetic micro- and nanocarriers were obtained using 1mg/mL of the enzyme concentration and 0,02 M pentaetilenhexamine, as a cross-linker. Activity of the immobilized cholesterol oxidase under optimal conditions was 79,03 %. Also, the stability of immobilized cholesterol oxidase revealed good reusability. The second part describes the preparation of cross-linked enzyme aggregates of cellulase (EC 3.2.1.4). The preparation process of cross-linked enzyme aggregates includes two important steps, such as the precipitation of the enzyme by the addition of the precipitation reagent and the cross-linking of enzyme molecules with glutaraldehyde. The optimum reaction conditions of cross-linked enzyme aggregates of cellulase have been achieved at a 0,0625 % concentration of glutaraldehyde (v/v) and using ethanol as a precipitation reagent. The activity of immoblized cellulase as cross-linked enzyme aggregates was determined by reaction of hydrolysis of cellulose. Activity of the immobilized cellulase as cross-linked enzyme aggregates under optimal conditions was 93,95 %. Also, the stability of immobilized cellulase revealed good reusability.

CM-dextran-covered maghemite particles for applications in magnetic hyperthermia treatments were synthesized and their physical, magnetic and morphological properties were examined. Magnetic fluids were prepared and their heating proper ies in an alternating magnetic field were studied. The results reveal that the particle size and the thickness of the carboxy-methyl-dextran (CM-dextran) coatings have a decisive influence on the heating properties: specific absorption rate (SAR). The majority of the magnetic dissipation comes from the Neel relaxation, while the Brown contribution is small. A thermal steady state at the selected temperature (42 °C) can be achieved using synthesized maghemite particles with proper particle morphology and by controlling the magnetic field intensity or the frequency. V prispevku je predstavljena sinteza in karakterizacija magnetnih maghemitnih nanodelcev prevlečenih s karboksimetil dekstranom (CM-dekstran), primernih za uporabo v magnetni hipertermiji. Stopnjo specifične absorpcije (SAR) stabilne magnetne tekočine pripravljene iz maghemitnih nanodelcev prevlečenih s CM-dekstranom, smo preverili s pomočjo kalorimetričnih meritev magnetne tekočine izpostavljene zunanjemu izmeničnemu magnetnem polju. Rezultati kažejo, da velikost magnetnih nanodelcev in debelina prevleke CM-dekstrana vplivata na stopnjo specifične absorpcije (SAR), pri čemer večji del toplotnih izgub izhaja iz Neel-ove relaksacije, medtem ko je prispevek Brown-ove relaksacije majhen. Termično ravnotežje pri ciljni temperaturi (42 °C) lahko dosežemo s primernimi morfološkimi lastnostmi sintetiziranih magnetnih nanodelcev maghemita in s kontroliranjem jakosti ali frekvence zunanjega izmeničnega magnetnega polja.

Cobalt ferrite (CoFe2O4) nanoparticles prepared via co-precipitation method were modified with tetraethoxysilane (TEOS) and additional funkcionalized with 3-mercaptopropyl trimethoxysilane (MPTMS) with purpose of cleaning waste water contaminated with heavy metal ions (Pb2+ and Hg2+). The influence of different experimental parameters (reaction time, reaction temperature and different TEOS:MPTMS ratios) on silica coating of CoFe2O4 nanoparticles and additional on thiol group was systematically studied. Silanes adsorb to the particle surface with alkoxy (Si(OR)4) groups at one end, while functional substituents (-SH) at the opposite end stay extended into surrounding aqueous medium and chemically interact with heavy metal contaminates. Thiol functionalized CoFe2O4 nanoparticles were characterized using IR spectroscopy, X-ray diffraction (XRD), transmission electron microscopy/high-resolution transmission electron microscopy (TEM/HRTEM), energy-dispersive X-ray spectroscopy (EDXS) and vibrating-sample magnetometer (VSM). The thiol functionalized CoFe2O4 nanoparticles were used for Pb2+ and Hg2+ions adsorption from aqueous media. Effect of treatment has been demonstrated using atomic absorption spectroscopy (AAS). Razvoj novih nanomaterialov za odstranjevanje težkih kovin je v zadnjem času pritegnil veliko pozornost, saj postaja onesnaževanja s strupenimi kovinskimi ioni, kot so Pb2+, Hg2+, Ni2+, Cd2+, Ag+, Co2+ in tem podobni, resen okoljski in zdravstveni problem. Velik problem s težkimi kovinami predstavlja njihova sposobnost, da se kopičijo v okolju in povzročajo zastrupitve. Za razliko od nekaterih organskih onesnaževal, težke kovine niso biorazgradljive. Znano je, da ioni težkih kovin kot so Pb2+, Hg2+, Cd2+, Ni2+ in Cu2+ lahko povzročajo resne zdravstvene težave za ljudi in živali, saj se specifično vežejo na proteine, nukleinske kisline in majhne metabolite v živih organizmih, s čimer zavirajo njihove funkcije. Za odstranjevanje ionov težkih kovin iz odpadnih vod, obstaja več metod, kot so kemijsko obarjanje, ionska izmenjava, tekoče-tekoča ekstrakcija, elektroliza, koagulacija, flotacija, flokulacija, filtracija, oksidacija, reverzna osmoza, biosorpcija in adsorpcija. (Singh in sodelavci, 2011) Vsaka od naštetih metod ima svoje pomanjkljivosti v smislu učinkovitosti, stroškov in kompleksnosti. Proces elektrolize je povezan z visokimi operativnimi stroški, kemijsko obarjanje proizvede sekundarni odpadek, pri filtraciji je problematično mašenje membran in cena le-teh. Uporaba večine naštetih metod je ekonomsko neprimernih, kadar gre za nizke koncentracije težkih kovin. Zaradi tega se danes vedno bolj uporabljajo nizkocenovni biosorbenti, kot so glineni materiali, biomasa, zeoliti, aktivni ogljik in smole za ionsko izmenjavo, vendar pa se morajo izboljšati njihove adsorpcijske kapacitete, separacijska stopnja in oblika. Tudi ti adsorbenti imajo nekatere slabosti pri odstranjevanju ionov težkih kovin iz vodnih medijev, in sicer niso odzivni na spremembe parametrov kot so pH, koncentracija elektrolitov, soli in prisotnost drugih topljencev, temperature in ionske moči medija. (Ozay in sodelavci, 2010) Idealen adsorbent mora imeti močno afiniteto do ionov težkih kovin, kar je povezano z visoko specifično površino, poroznostjo, številom veznih mest, ipd. Znano je, da večja kot je specifična površina, večja je adsorpcijska kapaciteta adsorbenta. V primeru magnetnih nanodelcev bi moral idealen adsorbent zagotoviti primerno adsorpcijo pri različnih reakcijskih pogojih in bi ga kot takega lahko uporabljali za vse odpadne vode, onesnažene s težkimi kovinami, saj ga bi po končani uporabi enostavno odstranili z zunanjim magnetnim poljem, predvsem na odlagališčih nevarnih odpadkov, kjer se vsakodnevno pred izpustom vode v kanalizacijo in okolje soočajo s prekomerno vsebnostjo težkih kovin. Magnetni adsorbenti bi lahko povečali učinkovitost pridobivanja oz. recikliranja težkih kovin iz odpadnih vod pri procesih kovinsko-predelovalne in oplemenitile industrije. Da bi zadostili vsem okoljevarstvenim predpisom so se v industriji primorani posluževati najnaprednejših tehnik. Monodisperzni, enodomenski nanodelci na osnovi spinelnih feritov so znanstveno in tehnološko izkazali kot zanimivi materiali za adsorpcijo ionov težkih kovin, zaradi svojih posebnih lastnosti, ki so določene s superparamagnetizmom (El-Okr in sodelavci, 2011). Superparamagnetni nanodelci s prilagojenimi površinskimi lastnostmi in visoko specifično površino izkazujejo ustrezne adsorpcijske karakteristike in predstavljajo novost na področju razvoja novih adsorpcijskih materialov. Njihova prednost v primerjavi z obstoječimi adsorbenti je tudi v tem, da jih tudi po adsorpciji lahko enostavno in hitro odstranimo iz raztopine z uporabo zunanjega magnetnega polja. V zadnjih letih se je veliko raziskovalcev ukvarjalo s sintezo magnetnih materialov, kot so magnetit (Fe3O4) za odstranjevanje ionov težkih kovin iz vodnih suspenzij, kot so Pb2+ (Yantasee in sodelavci, 2007 Li in sodelavci, 2011 Liu in sodelavci, 2009) in Hg2+ (Hakami in sodelavci, 2012 Dong in sodelavci, 2008 Parham in sodelavci, 2012 Girginova in sodelavci, 2010). Nekaj raziskovalcev se je v zadnjih letih tudi ukvarjalo s sintezo kobalt feritnih

V doktorskem delu smo obravnavali sintezo in karakterizacijo nanodelcev zlitin NiCu in NiCr za uporabo v samoregulativni magnetni hipertermiji. V prvem delu smo pripravili zlitine NiCu in NiCr s tremi različnimi sinteznimi postopki: mehansko mletje, sinteza s pomočjo mikroemulzij in sol-gel metoda, pri čemer smo preučevali reakcijske pogoje posamezne sinteze. Sledila je karakterizacija pridobljenih zlitin s pomočjo rentgenske praškovne difrakcije, transmisijske elektronske mikroskopije, magnetnih meritev, meritev Curiejeve temperature in kalorimetričnih meritev. S pomočjo mehanskega mletja smo uspeli sintetizirati zlitine NiCu in NiCr, z različnimi sestavami, v inertni atmosferi dušika. Kot rezultat smo dobili superparamagnetne nanodelce, njihova ocenjena velikost je okrog 14 nm za NiCu in 11 nm za NiCr. Pomerjene vrednosti Curiejevih temperatur rastejo z naraščanjem vsebnosti niklja. Vzorca sestave Ni72Cr28 in Ni72.5Cu27.5 imata Curiejevo temperaturo, ki je v območju od 42 °C do 46 °C, kar ustreza uporabi v magnetni hipertermiji. Pod vplivom zunanjega izmeničnega magnetnega polja se delci zelo dobro odzivajo. Dosežene stacionarne temperature so prav tako v območju uporabe v magnetni hipertermiji. S pomočjo transmisijske elektronske mikroskopije smo ugotovili, da je porazdelitev velikosti delcev široka, da so sintetizirani nanodelci sestavljeni iz večjih agregatov, da so nehomogeni, kar pripisujemo posledicam mehanskega mletja. S pomočjo mikroemulzijske metode smo sintetizirali nanodelce zlitin NiCr in NiCu, ti imajo ožjo porazdelitev velikosti, vendar pa so nehomogeni, saj so oksidacijski potenciali kovin različni in dobimo tako imenovano "core-shell" strukturo. Homogenizacija pri zlitinah NiCr ni bila uspešna, medtem ko smo zlitine NiCu uspeli ustrezno prevleči z 10 nm plastjo silike oziroma smo jih vgradili v matrici NaCl, da smo preprečili aglomeracijo med samo homogenizacijo. Homogenizacija pri zlitinah NiCu je bila uspešna, kar kaže Curiejeva temperatura. Specifična magnetizacija za oblečene delce je veliko manjša kot za neoblečene, kar je posledica diamagnetne prevleke SiO2, vendar pa lahko to prevleko poljubno tanjšamo oziroma odstranimo s pomočjo raztopine NaOH, prav tako lahko odstranimo tudi matrico NaCl. Vzorcem smo določili še specifično absorpcijsko hitrost (SAR), ki narašča z naraščajočim magnetnim poljem. Sol-gel metoda se je izkazala kot najuspešnejša za sintezo zlitin NiCu z različnimi sestavami, saj smo kot rezultat dobili okrogle monodisperzne nanodelce. Pripravili smo homogene zmesi kovinskih oksidov v SiO2 matrici s kalcinacijo prekurzorjev v gelu in naknadno homogenizacijo in redukcijo produkta v cevni peči v inertni atmosferi Ar/H2. Velikost delcev, ocenili smo jo s pomočjo Sherrerjeve formule, magnetnih meritev in s pomočjo transmisijske elektronske mikroskopije, je znašala okrog 16 nm. S pomočjo raztopine NaOH in hidrazina smo SiO2 uspešno izlužili. Curiejeve temperature vzorcev naraščajo z naraščajočo vsebnostjo niklja in so v okviru predvidenih temperatur za uporabo v magnetni hipertermiji. Tudi vrednosti magnetizacije in temperaturni odziv v kalorimetru rasteta z naraščajočo vsebnostjo niklja. The doctoral thesis considers the synthesis and characterization of NiCu and NiCr nanoparticles for the magnetic hyperthermia applications. The synthesis of nanoparticles of NiCu and NiCr alloys using three different methods: mechanical milling, microemulsion method and sol-gel method, were studied with respect to the reaction conditions. We characterized the alloys nanoparticles by XRD measurements, transmission electron microscopy, magnetic measurements, Curie temperature determination and calorimetric measurements. The NiCu and NiCr particles with the desired composition were synthesized by mechanical milling under an inert atmosphere of N2. We prepared superparamagnetic NiCu nanoparticles with an average size of around 14 nm and around 11 nm for NiCr. The measurements of the Curie temperature of various compositions showed that the Curie temperature increased with the increasing of the Ni content. The nanoparticles of Ni72.5Cu27.5 and Ni72Cr28 exhibit a Curie temperature in the range between 42 °C to 46 °C, what corresponds to the application demand in the magnetic hyperthermia. The magnetic particles also showed a significant heating effect and might be the good candidates for hyperthermia applications. Transmission electron microscopy of mechano-chemically synthesized particles showed a broad size distribution with the presence of some larger grains in the shape of platelets at some locations. NiCu and NiCr nanoalloys with a narrow size distribution were synthesized by microemulsion method. The Curie temperatures of samples were high, indicating a compositional heterogeneity and probably a “core-shell” structure. To prevent the agglomeration during the homogenization of the NiCu alloys, we coated particles with a 10 nm thick layer of silica or we performed thermally homogenization in a NaCl matrix. The relatively low magnetization of the silica coated NiCu particles was a result of the diamagnetic envelope of SiO2, which can be thinned and/or remowed with sodium hydroxide. In parallel the NaCl matrix can be removed with dissolution in water. The calculated specific absorption rate (SAR) increases with the increasing of the magnetic field. Nickel-copper (NiCu) alloy magnetic nanoparticles with a narrow size distribution were prepared by a sol-gel method. We used the temperature resistant silica matrix as a nanoparticles holder during high-temperature treatment of metal oxides and a specially developed etching procedure that subsequently removes silica matrix, leaving the alloy nanoparticles intact. We estimated the size of the particles around 16 nm, using the Sherrer equation, magnetic measurements and transmission electron microscopy. The Curie temperature, the magnetization and the temperature response in the calorimeter increase as well with the increase of the Ni content.

Namen diplomskega dela je bil sintetizirati CuNi nanodelce z različnimi sestavami (Cu30Ni70, Cu32,5Ni67,5, Cu35Ni65, Cu37,5Ni62,5 in Cu40Ni60) s sol-gel metodo. Sintetizirane vzorce smo po sušenju in staranju izpostavili termični homogenizaciji v cevni peči pri 850 °C, 24 ur v redukcijski atmosferi Ar/H2. Vzorcu, ki je pokazal najboljše lastnosti in primerno Curiejevo temperaturo smo izluževali (spirali) matrico iz silike s pomočjo raztopine NaOH ob prisotnosti različnih reducentov (askorbinska kislina, hidrazin). Z uporabo termogravimetrične analize (TGA) smo določali Curiejevo temperaturo (Tc) CuNi nanodelcev v vzorcih z različnimi sestavami. Želeli smo dobiti delce s primerno Curiejevo temperaturo, kateri bodo uporabni v magnetni hipertermiji. Rentgensko praškovno difrakcijo (XRD) smo uporabili za kvalitativno fazno analizo vzorcev. Z infrardečo spektroskopijo smo določali vsebnost silike v vzorcih pred in po spiranju. Rezultati so pokazali, da se temperatura (Tc) znižuje z manjšanjem vsebnosti Ni v vzorcu. Pri spiranju silike, pa je IR analiza pokazala, da ima vzorec, ki je bil najdlje izpostavljen alkalnemu mediju in hidrazinu, najmanj silike, ki obdaja delce. The aim of this diploma work was to synthesize CuNi nanoparticles of different compositions (Cu30Ni70, Cu32,5Ni67,5, Cu35Ni65, Cu37,5Ni62,5 and Cu40Ni60) using the sol-gel method. After drying and aging processes, the synthesized samples were exposed to thermal homogenization in a tube furnace at 850 °C for 24 hours in an Ar/H2 reduction atmosphere. We etched the silica matrix from the sample with the appropriate Curie temperature, with the help of a NaOH solution in the presence of various types of reducing agents (ascorbic acid, hydrazine). Using the thermogravimetric analysis (TGA), we determined the Curie temperature (Tc) of CuNi nanoparticles for samples of different compositions. We were looking for particles with appropriate Curie temperature, suitable for magnetic hyperthermia. The X-ray diffraction (XRD) has been used for qualitative phase analysis of samples. With the help of infrared spectroscopy (IR), we determined the presence of silica in samples before and after etching. Results showed that the temperature (Tc) decreases with lowering Ni content in the samples. Whereas, the infrared spectroscopy analysis for silica etching indicates that the sample, which has been exposed to an alkaline medium or hydrazine for the longest period of time, contains the lowest amount of silica, surrounding the particles.

Magnetni nanodelci baker-nikelj (CuNi) zlitine z različnimi sestavami so bili pripravljeni v procesu, ki vključuje štiri korake: priprava začetnega prekurzorja v SiO2 matrici s sol gel metodo in naknadno dekompozicijo, toplotno obdelavo in redukcijo. Redukcija ima dva namena, prvi je redukcija mešanih CuNi oksidov do CuNi zlitine, drugi pa je homogenizacija nanodelcev CuNi zlitine v redukcijski atmosferi. Rentgensko praškovno difrakcijo smo uporabili za kvalitativno analizo in oceno velikosti CuNi nanodelcev. S transmisijsko elektronsko mikroskopijo (TEM) smo pregledali morfologijo sintetiziranih vzorcev. Z modificirano termogravimetrično analizo (TGA) smo določili Curiejevo temperaturo (Tc) pripravljenih CuNi nanodelcev. Rezultati z modificirano TGA analizo kažejo, da Curiejeva temperatura raste z vsebnostjo Ni v vzorcu po termični obdelavi v cevni peči pri 850°C v redukcijski Ar/H2 atmosferi, kar potrjuje naša pričakovanja. Cilj diplomskega dela je bil sintetizirati magnetne nanodelce CuNi v SiO2 matrici, ki imajo primerne magnetne lastnosti in Curiejevo temperaturo okoli 42°C, ki je optimalna temperatura za propad rakavih celic. Taki magnetni nanodelci so samoregulativni in se lahko uporabljajo v magnetni hipertermiji. Magnetic nanoparticles of copper-nickel (CuNi) alloys with different stoichiometry were prepared in a process which involves four steps: preparation of starting precursor in SiO2 matrix by sol-gel method and subsequent decomposition, annealing and reduction. The reduction step has two purposes: first is reduction of the CuNi mixed oxides to a CuNi alloy and second is the homogenization of a CuNi alloy nanoparticles in a reductive atmosphere. We used X-ray powder diffraction (XRD) for qualitative analysis and estimation of the crystallite size of CuNi nanoparticles. Transmission electronic microscope (TEM) was used to inspect the morphology of synthesized samples. By modified thermogravimetric analysis (TGA) we determined Curie temperature (Tc) of prepared CuNi nanoparticles. Results from modified TGA - measurements show that Curie temperature increases with Ni content in the sample after thermal treating in a tube furnace at 850°C in reducing Ar/H2 atmosphere, which confirms our expectations. The aim of this diploma work was to synthesize the magnetic nanoparticles of CuNi in SiO2 matrix, which have appropriate magnetic properties and Curie temperature near 42°C, which is an optimal temperature to cause necrosis of cancer cells. Such magnetic nanoparticles are self-regulative and can be used in application of magnetic hyperthermia.

Namen diplomskega dela je bil sinteza magnetnih CuNi nanodelcev določenih sestav z metodo soobarjanja v reverznih micelah znotraj stabilnih mikroemulzij. Nanodelce, ki so pokazali najboljšo dispergiranost in homogenost, smo uporabili v nadaljevanju za površinsko obdelavo magnetnih delcev. Namen silikatne prevleke, s katero smo prevlekli delce, je preprečevanje aglomeracije in rasti zrn ter služi hkrati kot biokompatibilna zaščitna plast, ki omogoča uporabo magnetnih nanodelcev v medicinske namene. Z uporabo dinamičnega sipanja laserske svetlobe (DLS) smo določili velikost delcev, sintetiziranih iz vodnih faz z različno koncentracijo kovinskih prekurzorjev. Koncentracijo, pri kateri smo dobili najugodnejše rezultate, smo uporabili za nadaljnje sinteze, kjer smo spreminjali sestavo posameznih faz ali pa smo spremljali vpliv ostalih komponent. Magnetni nanodelci, ki so pokazali najboljši polidisperzni indeks ter primerno velikost delcev, so bili pozneje oblečeni s prevleko iz silike ter tudi termično modificirani. Nanodelce CuNi smo poskusili obleči tudi s srebrom, vendar smo dobili heterogeno zmes srebrovih in CuNi nanodelcev. Vzorce smo kvalitativno analizirali z rentgensko praškovno difrakcijo (XRD). S pomočjo termogravimetrične analize smo jim določili Curie-jevo temperaturo (Tc). Dispergiranost in velikost ter porazdelitev velikosti delcev smo merili z dinamičnim laserskim sipanjem svetlobe (DLS). Morfologijo vzorcev smo preučili s transmisijskim elektronskim mikroskopom (TEM). Curie-jeva temperatura sintetiziranih vzorcev je odvisna od parametrov sinteze. S spreminjanjem teh parametrov lahko vplivamo na končne velikosti delcev. Z oblačenjem teh delcev s siliko smo preprečili aglomeracijo med termično homogenizacijo in dosegli primerno Curiejevo temperaturo (Tc) za uporabo v magnetni hipertermiji. The aim of the diploma work was to study the synthesis of magnetic CuNi nanoparticles with desired compositions using the co-precipitation method in reverse micelles within stable microemulsions. Nanoparticles, which exhibit the best dispersion and homogeneity, were then applied for the surface modification. The purpose of the silica coating was to prevent the agglomeration and grain coarsening and also serves as a biocompatible protecting layer for applications in medicine. By using the dynamic laser light scattering (DLS), the size of the particles synthesized particles was determined. The concentration of the aqueous phase which yields the best result was used for the further syntheses, where we followed the composition of various phases formed and/or the influence of the particular components was examined. The magnetic nanoparticles which exhibit the best polydispersion index and the appropriate size were then coated with silica, and thermally homogenised. An attempt to cover the CuNi nanoparticles with silver was made, however this action results in a heterogeneous mixture of silver and CuNi nanoparticles. A qualitative analysis of the samples was carried out using the X-ray diffraction (XRD). Thermogravimetric analysis was employed to determine Curie temperature (Tc). Dispersion, size and distribution of the particles were measured with the dynamic laser light scattering (DLS). By using the dynamic laser light scaterring (DLS), the size of the particles, synthesized from metal precursors in various aqueous phases was determined. The morphology of the samples was studied with the help of transmission electron microscope (TEM). The Curie temperature of these synthesized samples depends on the synthesis parameters. By changing these parameters, as for instance the optimizing of the homogenisation temperature, the lowering of Tc and an improving of the dispersion and particle size can be achieved. By coating these particles with silica, the agglomeration did not take place and the synthesized particles were then thermally treated to obtain more homogeneous particles with a therapeutic Curie temperature (Tc) appropriate for the use in the magnetic hyperthermia.

Namen diplomskega dela je bil sinteza nanodelcev CrNi z mikroemulzijsko metodo. V območju stabilnosti mikroemulzij v ternarnem diagramu (voda/CTAB, n-butanol/izooktan) smo izbrali dve točki z različnimi masnimi deleži (20/40/40 in 20/50/30) in v teh dveh točkah sintetizirali CrNi magnetne nanodelce z različnimi sestavami: Cr1-xNix (x=0.7, 0.8, 0.9), pri čemer smo kot reducent uporabili NaBH4. Delce smo najprej termično obdelali s pomočjo termoanaliznega sistema TGA-SDTA v N2 atmosferi pri 500 ° C z namenom njihove homogenizacije. Zaradi možne aplikacije v medicinske namene (magnetna hipertermija) smo želeli pridobiti delce z ustrezno Curiejevo temperaturo. Delce smo v ta namen še dodatno homogenizirali v cevni peči pri temperaturi 900°C, 12 ur, v redukcijski atmosferi (Ar/H2). S tem smo hkrati želeli preprečiti oksidacijo delcev. Vzorce smo kvalitativno analizirali z rentgensko praškovno difrakcijo (XRD). S pomočjo termogravimetrične analize (TGA) smo vzorce segreli na 500 °C in jim s prirejeno TGA aparaturo določili Curiejevo temperaturo (Tc). Diploma work focuses on synthesis of nanoparticles CrNi with microemulsion method. We prepared two different compositions of microemulsions in the region of microemulsion stability with mass % (20/40/40 and 20/50/30) in ternary water/CTAB, n-butanol/isooctane diagram. In those two compositions we synthesized CrNi magnetic nanoparticles of different alloy compositions: Cr1-xNix whereas (x = 07, 08 and 09). The reducing agent was NaBH4. The particles were first thermal treated with the TGA-SDTA thermoanalytical system in N2 at 500°C because of homogenization. Because of the application for medical purposes (magnetic hyperthermia) we tried to get the particles with appropriate Curie temperature. So, we additionally homogenised particles in a tube furnace at 900°C for 12 hours under reducing atmosphere (Ar/H2). With that, we tried to prevent the particles from oxidation. A qualitative analysis of the samples was carried out using the X-ray diffraction (XRD) and the Curie temperature measured with thermogravimetric analysis (TGA) which was also used to heat the samples to 500°C.

Nano-kristalinični prah stroncijevega heksaferita (SrFe12O19) smo sintetizirali s klasičnim soobarjanjem in mikroemulzijsko metodo. Prekurzor, ki je bil pripravljen z obarjanjem Sr2+ in Fe2+ ionov z uporabo tetrametilamonijevega hidroksida, smo termično obdelali pri različnih temperaturah v območju od 400 °C do 1000 °C v zračni atmosferi. Proučevali smo vpliv molskega razmerja Sr2+ / Fe3+ in temperature termične obdelave na formiranje produkta in njegovih magnetnih lastnosti. Nanodelce SrFe12O19 z relativno visoko nasičeno magnetizacijo σs = 64 Am2/kg, remanentno magnetizacijo σr = 39 Am2/kg in koercitivnostjo Hc = 430 kA/m smo dosegli pri molskem razmerju Sr2+ / Fe3+ = 1 : 8 ter termični obdelavi pri 900 °C. Pripravljen prah SrFe12O19 smo okarakterizirali s pomočjo rentgenske praškovne analize (XRD), termogravimetrične analize (TGA), diferenčne termične analize (DTA), presevnega elektronskega mikroskopa (TEM), dinamičnega laserskega sipanja svetlobe (DLS) in z merjenjem specifične površine delcev z metodo BET. Magnetne lastnosti materiala smo določili z uporabo magneto-susceptometra DSM-10. V nadaljevanju smo se posvetili pripravi nanokompozitov za absorpcijo elektromagnetnega valovanja, ki temeljijo na magnetnem polnilu sestavljenem iz faz znotraj sistema SrO - Fe2O3, ki je homogeno vmešan v polimerno matrico iz polifenilensulfida (PPS) v utežnem razmerju 80 : 20. Nanodelce SrFe12O19 in Fe3O4, ki sta bili glavni magnetni fazi smo pripravili s klasičnim soobarjanjem pri različnem molskem razmerju Sr2+ / Fe3+ ter termično obdelavo v temperaturnem intervalu od 600 °C do 1000 °C v zračni atmosferi. Elektromagnetne parametre nanokompozitov smo merili z vektorskim mrežnim analizatorjem v frekvenčnem območju od 400 MHz do 32 GHz. Rezultati kažejo, da lahko pripravimo široko paleto mikrovalovnih absorberjev. Nanokompoziti, ki vsebujejo za magnetno polnilo delce spinelne faze so primerni za absorpcijo elektromagnetnega valovanja v nižjem GHz območju, medtem ko so nanokompoziti vsebujoč heksagonalno fazo primerni za delovanje v območju frekvenc nad 32 GHz. Nano-crystalline strontium hexaferrite (SrFe12O19) powder was synthesized using the classical co-precipitation and microemulsion methods. The precursors were obtained by precipitating Sr2+ and Fe2+ ions using tetramethylammonium hydroxide and calcinating at different temperatures ranging from 400 °C to 1000 °C in air. The influence of the Sr2+ / Fe3+ mol ratio and the calcination temperature on the product formation and their magnetic properties were studied. The formation of nanosized particles of SrFe12O19 with a relatively high saturation magnetization σs = 64 Am2/kg, remanent magnetization of σr = 39 Am2/kg and a coercitivity of Hc = 430 kA/m was achieved at a Sr2+ / Fe3+ mol ratio of 1 : 8 calcined at 900 °C. The formation of the SrFe12O19 was inspected using X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA), transmission electron microscopy (TEM), dynamic light scattering analysis (DLS) and specific surface area measurements (BET). The magnetic properties were inspected using magneto-susceptometer DSM-10. Furthermore, we have investigated nanocomposites designed for absorption of electromagnetic waves based on magnetic filler, composed of phases within the SrO - Fe2O3 system, embedded in a polymer matrix based on polyphenylene sulfide (PPS) with a concentration ratio of 80 : 20 by weight. The formation of the nanosized particles of SrFe12O19 and Fe3O4, as the principal magnetic phases, was achieved via the classical co-precipitation of Sr2+ / Fe3+ ions using different molar ratios. The various precursors obtained were calcined between 600 °C and 900 °C in air atmosfere. The electromagnetic parameters of the nanocomposites were measured with a vector network analyzer in frequency range from 400 MHz to 32 GHz. The results show that with a nancomposite composed of a complex magnetic filler comprising the nanoparticles of two magnetically diverse phases, i.e., a spinel phase as the electromagnetic wave absorber in the lower GHz range and a hexagonal phase operating at a higher GHz range, above 32 GHz, a microwave absorber with an broad absorption range can be prepared.

Magnetne tekočine sodijo v kategorijo nano-materialov in so po definiciji stabilne koloidne disperzije magnetnih nanodelcev, trajno suspendiranih v nosilni tekočini. Kot takšne imajo določene specifične lastnosti, ki jih s pridom izkoriščajo na različnih področjih, kot na primer v mehaniki za rotacijsko tesnjenje, mehansko blaženje, odvajanje toplote in tudi v biomedicini za ciljno doziranje zdravilnih učinkovin, kontrastni agenti pri slikanju z magnetno resonanco, hipertermiji, itd. Ne glede na aplikacijo pa je za varno in učinkovito rabo potrebno dobro poznavanje fizikalnih lastnosti materiala. V doktorski disertaciji smo obravnavali nekatere lastnosti magnetnih tekočin s poudarkom na obnašanju v izmeničnem magnetnem polju. V tem primeru se magnetni delci oziroma vektor magnetizacije delcev poravnajo s smerjo magnetnega polja, kar opisujeta pojava Brownove in Néelove relaksacije. Obračanje magnetnih domen znotraj materiala opisujemo kot magnetne izgube, katerih posledica je povišanje temperature tekočine. Z višanjem amplitude in frekvence magnetnega polja so izgube intenzivnejše. Ravno ta pojav, ki ga imenujemo hipertermija, se izkorišča v medicini in predstavlja alternativno metodo zdravljenja rakavih tkiv, kjer z vbrizganjem magnetne tekočine v tkivo in njeni izpostavitvi visokofrekvenčnemu magnetnemu polju dosežemo njihovo termično uničenje. Za uspešno izvajanje takšnega zdravljenja pa je bistvenega pomena karakterizacija magnetnih izgub magnetne tekočine. Glavni namen doktorske disertacije je izgradnja merilnega sistema, ki omogoča merjenje parametrov za določitev magnetnih izgub magnetih tekočin. Merilni sistem je zasnovan tako, da z uporabo kalorimetrične metode na osnovi povišane temperature tekočine določi parameter izgub SAR (specific absorption rate). V tem primeru gre za izboljšanje uveljavljene metode, kjer je poudarek na homogenosti magnetnega polja ter na boljši toplotni izolaciji vzorca in okolice. Druga metoda za določitev magnetnih izgub pa je metoda magnetnega merjenja, kjer lahko na osnovi površine histerezne zanke določimo specifične moči izgub SPL (specific power loss). Bistvo metode sta dve merilni tuljavici okoli merjenega vzorca, ki sta bili predhodno umerjeni v magnetni normali in merita inducirani napetosti, na osnovi katerih lahko izračunamo magnetno poljsko jakost v sistemu ter gostoto magnetnega pretoka vzorca. Ta dva signala definirata histerezno zanko, katere površina je proporcionalna magnetnim izgubam. Za komercialno dostopen vzorec magnetne tekočine je izvedena karakterizacija izgub po obeh metodah, kjer so izgube podane v odvisnosti od amplitude in frekvence magnetne poljske jakosti, določena pa je tudi njihova temperaturna odvisnost. V disertaciji je predstavljena tudi analiza magnetnega polja merilnega sistema s pomočjo metode končnih elementov (MKE), v istem sistemu pa je izvedena še termična analiza, kjer temperaturno odvisne izgube povzročijo časovno spremembo temperature vzorca, rezultati obeh analiz pa so skladni z meritvami. fluids fall into the category of nano-materials and are, by definition, a stable colloidal dispersion of magnetic nanoparticles permanently suspended in a carrier liquid. As such, they are distinguished by certain specific characteristics which are effectively utilized in various fields such as mechanics as rotary seals, mechanical dampers, heat conductors and in biomedicine to target the dosage of medicinal substances, contrast agents for magnetic resonance imaging, magnetic fluid hyperthermia, etc. For safe and effective use of the material a good knowledge of its physical properties is required, regardless of the applications. In this thesis, some properties of magnetic fluids with an emphasis on its behavior in the alternating magnetic field are discussed. In this case, the magnetic particles or its magnetization vector align with the direction of magnetic field, which describes the Brownian and Neel’s relaxation. Rotating magnetic domains, within the material, are recognized as magnetic losses that among others result in an increase of fluids’ temperature that intensify with increasing amplitude and frequency of magnetic field. This exact property is used in the application of medical hyperthermia, which represents an alternative method for cancer treatment, where the magnetic fluid is injected into the tumor tissue and heated by means of magnetic field to achieve thermal destruction of tumor. For successful implementation of such treatment the characterization of magnetic losses of magnetic fluids represents the essential role. The main purpose of this dissertation is to build a measurement system that enables the measurement of crucial parameters for determining the losses of magnetic fluid. The measurement system is designed in a way that allows the determination of loss parameter SAR (Specific Absorption Rate) using a calorimetric method. In this case, we deal with the improvement of established method, where the emphasis is on the homogeneity of the magnetic field and a better thermal insulation of the sample and its surroundings. Second method for determining the magnetic losses that is tackled in this dissertation is method of magnetic measurement. It is based on determination of the hysteresis loops area for determination of the parameter of SPL (specific power loss). The essential parts of this method are two pickup coils wound around the measured sample. They are calibrated in the magnetic normal and therefore enable the calculation of magnetic field strength in the system and the magnetic flux density of the measured sample out of measured induced voltages. These two variables define the hysteresis loop whose area is proportional to magnetic losses. Characterization of magnetic losses is carried out by both methods for commercially available sample of magnetic fluid, where the results are given as a function of amplitude and frequency magnetic field. This thesis also presents a magnetic field analysis of the measurement system using the finite element method (FEM) and thermal field analysis results of both analyses are consistent with measurements.

Namen diplomskega dela, je bil sintetizirati magnetne nanodelce Cu0,3Ni0,7 s poliolno metodo in pri tem ugotoviti vpliv različnih parametrov na potek reakcije ter velikost in obliko delcev. Kot poliol smo uporabili etilenglikol (EG) in dietilenglikol (DEG). Naredili smo različne sinteze, pri katerih smo spreminjali čas refluksa, množino soli, količino NaOH in količino PVP. S pomočjo difraktogramov, katere smo dobili kot rezultat rentgenske praškovne difrakcije, (RPD) smo ocenili velikost nanodelcev CuNi in določili faze v vzorcih. S termogravimetrično analizo (TGA) smo določili Curiejevo temperaturo vzorca. Na koncu smo preučili še morfologijo nanodelcev s pomočjo transmisijskega elektronskega mikroskopa (TEM). Iz rezultatov je mogoče razbrati vplive posameznih parametrov na velikost in obliko delcev. Izmerili smo optimalno Curiejevo temperaturo 43ºC, pri sintetiziranem vzorcu s poliolno metodo, z uporabo poliola EG. Vzorec je bil predhodno segret v cevni peči na 700 ºC, v Ar/H2 atmosferi. The aim of this work was to synthesize magnetic nanoparticles with composition Cu0,3Ni0,7 by the polyol method and to determine the effect of various parameters on the course of the reaction and the size and shape of the particles. We used ethylene glycol (EG) and diethylene glycol (DEG) as polyol. We preformed various syntheses in which the time of reflux, the both amounts of salts, the amounts of NaOH and the amounts of PVP was varied. The size of magnetic nanoparticles was estimated by Scherrer equation. Samples were characterized with XRD analysis. Curie temperature of the sample was studied using a modified TGA – SDTA method. The morphology of nanoparticles was studied with transmission electron microscopy (TEM). The results showed the effects of individual parameters on the size and shape of the particles. We measured the Curie temperature of 43ºC at sample with composition: Cu0,3Ni0,7, which was synthesized by standard polyol procedure (with ethylene glycol). The sample was tempered at 700 ºC in tube furnace in Ar/H2 atmosphere.

Namen diplomskega dela je bil poiskati parametre sinteze z metodo obarjanja v reverznih micelah oz. mikroemulzijah in nadaljnje obdelave, ki bi dajali CuNi magnetne nanodelce, za uporabo v magnetni hipertermiji. Z uporabo titracijske metode in ternarnih faznih diagramov smo preverili obmocja stabilnosti mikroemulzij, ki vsebujejo prekurzorje, potrebne za sintezo. Sintetizirali smo CuNi magnetne nanodelce razlicnih sestav, katere smo nadalje termicno modificirali. Vzorcem smo dolocili velikost delcev in jih kvalitativno analizirali z rentgensko praškovno difrakcijo (XRD). S termogravimetricno analizo (TGA) smo vzorcem dolocili Curiejevo temperaturo (Tc). Morfologijo nanodelcev smo preucili s transmisijskim elektronskim mikroskopom (TEM). Na koncu smo izvedli še magnetne meritve na magnetometru z vibrirajocim vzorcem (VSM). Oblika histerezne krivulje kaže, da imajo sintetizirani, "as prepared", delci vzorca množinske sestave Cu30Ni70 histerezno zanko z majhno koercitivnostjo. Morfologija sintetiziranega vzorca je kazala na mocno aglomeracijo delcev. Ta vzorec, ki smo ga nadalje termicno izotermno obdelovali tri ure na 500 °C v Ar/H2 atmosferi, je imel željeno Curiejevo temperaturo 45 °C. Tako pripravljen vzorec bi bil najbolj primeren za uporabo v magnetni hipertermiji. Iz rezultatov sklepamo, da so potrebne dodatne raziskave v smeri zmanjšanja aglomeracije med sintezo delcev. The purpose of this work was to find parameters of the synthesis by microemulsion method (in reverse micelles) with chemical coprecipitation and further modification, that would give CuNi magnetic nanoparticles that are appropriate for the application in the magnetic hyperthermia. With use of the titration method and ternary phase diagrams we checked area of stability of microemulsions that contain precursors needed in the synthesis. Nanoparticles (CuNi) of various compositions were synthesized. Later, they were thermal modified. Samples size measurements and characterization were done by x-ray diffraction (XRD) analysis. With modified thermogravimetric analysis (TGA), Curie temperatures of samples were determined. Morphology of nanoparticles was studied with transmission electron microscope (TEM). At the end magnetic measurements were made with vibrating sample magnetometer (VSM). The slope of hysteresis curve shows low coercitivity. Morphology of that sample indicated agglomeration of particles. This sample was further isothermally modified for three hours at 500 °C in Ar/H2 atmosphere. It showed Curie temperature of 45 °C, so this sample would be the most suitable for the use in magnetic hyperthermia. Results revealed that further researches are needed to lower degree of agglomeration in process of the synthesis.

V doktorski nalogi je nazorno predstavljen postopek sinteze magnetnih nanodelcev iz železovega oksida maghemita, γ-Fe2O3, za vezavo biokatalizatorja. Magnetni nanodelci, ki v zadnjih letih vse bolj pridobivajo na vrednosti kot potencialni encimski nosilci, so bili najprej sintetizirani z metodo obarjanja ali koprecipitacije železovih (II, Fe2+) in železovih (III, Fe3+) ionov v alkalnem mediju pri hitrem mešanju in visoki temperaturi. Površinska funkcionalizacija magnetnih nanodelcev je bila izvedena v dveh stopnjah. Primarna funkcionalna prevleka iz silicijevega dioksida (SiO2), ki delcem daje predvsem višjo stabilnost, je bila sintetizirana pri striktno kontroliranih reakcijskih pogojih iz natrijevega silikata ali Na2SiO3. Sekundarni funkcionalni sloj za doseganje višje funkcionalnosti in reaktivnosti površine nanodelcev je bil sintetiziran iz organskih molekul aminosilana ali 3-(2-aminoetilamino)-propil-dimetoksimetilsilana v kislem mediju. V nadaljnjem so bili tako površinsko spremenjeni magnetni nanodelci uporabljeni za imobilizacijo specifičnega biokatalizatorja holesterol oksidaze (ChOx, EC 1.1.3.6) iz Corynebacterium sp. Analiza magnetnih nanodelcev z imobilizirano ChOx je pokazala, da so imeli nanodelci značilno obliko kroglice ali sfere s povprečnim premerom 50,2 nm. Vezava holesterol oksidaze je bila uspešno potrjena tudi s FT-IR tehniko. Učinkovitost imobilizacije na magnetni nosilec je znašala 92 % pri uporabljeni koncentraciji encima 100 µg mL-1. Aktivnost imobilizirane ChOx na magnetne nanodelce, prevlečene s tanko plastjo silikatne prevleke premera 3 nm, je bila 57 % v primerjavi z aktivnostjo ChOx. Študija vpliva pH-vrednosti in temperature na aktivnost in stabilnost encimskega preparata je pokazala, da ima imobilizirana ChOx višjo toleranco na spremembo pH-vrednosti okolja in višjo termično stabilnost. Prav tako je bila stabilnost imobilizirane ChOx pri ponovni uporabi dobra. V drugem delu doktorske disertacije je opisana priprava aktivnih encimskih skupkov iz encima peroksidaze (HRP, EC 1.11.1.7), pridobljenega iz navadnega hrena (lat.: Armoracia rusticana or Cochlearia armoracia), in postopek zamreženja le-teh z glutaraldehidom za pripravo končne oblike stabilnih zamreženih encimskih skupkov ali na kratko CLEAs. Postopek priprave CLEAs je bil razdeljen na dva ključna dela, in sicer, na obarjanje topnega ali nativnega encima s pomočjo ustreznega obarjalnega reagenta, in na nadaljnjo zamreženje tako izoborjenega encima s pomočjo mrežnega povezovalca. Končni videz CLEAs je podoben motni suspenziji, v kateri so jasno vidni skupki encimov, značilne sferične oblike in premera okrog 250 nm. Uspešno smo sintetizirali zamrežene encimske skupke iz hrenove peroksidaze pod različnimi testnimi pogoji. Končna aktivnost encimskih skupkov iz HRP je bila 83 %. Zamrežene encimske skupke smo sintetizirali v prisotnosti encima albumina iz kokošjih jajc in funkcionalnega aditiva, penta-etilen-heksanamina (PEHA). Encim albumin poveča stabilnost encimskih skupkov, medtem ko PEHA poveča število prostih amino skupin (-NH2) na zunanji površini encima HRP, kar poenostavi postopek zamreženja encimskih delcev z mrežnim povezovalcem. The research work offers a concise guide of the synthesis of maghemite magnetic nanoparticles, γ-Fe2O3, for immobilization of a biocatalyst. Magnetic nanoparticles, that are gaining an exceptionally increased attention as potential enzyme support in the recent years, were synthesized by the coprecipitation technique of ferrous (II, Fe2+) and ferric (III, Fe3+) ions in alkaline medium at harsh stirring and high temperature, respectively. Surface functionalization of magnetic nanoparticles was carried out stepwise and divided into two major steps. Primary functional layer of silica (SiO2) that enhanced the stability of magnetic nanoparticles was synthesized under strictly regulated reaction conditions from sodium silicate. Next, the secondary functional layer formed of organic molecules of amino silane or 3-(2-Aminoethylamino)-propyl-dimethoxymethylsilane in order to achieve higher functionality and reactivity of the surface of magnetic nanoparticles was synthesized in acidic reaction medium. Furthermore, the prepared magnetic nanocomposites were used for the immobilization of a specific biocatalyst cholesterol oxidase (ChOx, EC 1.1.3.6) from Corynebacterium sp. The analysis of the magnetic nanoparticles with immobilized ChOx showed that the nanoparticles adopted a typical spherical shape with a mean diameter of 50,2 nm. The binding of ChOx was successfully confirmed by FT-IR technique. The binding efficiency was 92 % and was maximally achieved at enzyme concentration of 100 µg mL-1. The activity of immobilized ChOx onto magnetic nanoparticles, coated with a thin functional layer of silica with a thickness of 3 nm, was estimated to be 57 % in comparison to its native ChOx. The effects of pH and temperature also indicated the bound ChOx had better pH-tolerance and exhibited higher thermal stability. Furthermore, the immobilized system revealed also good reusable stability. The second part of the PhD work was focused on the synthesis of active enzyme aggregates of peroxidase (HRP, EC 1.11.1.7) from horse radish roots (lat.: Armoracia rusticana or Cochlearia armoracia), further cross-linked with glutaraldehyde in order to obtain the final form of stable cross-linked enzyme aggregates or CLEAs. The procedure to prepare CLEAs was divided into two major steps, that involves first the precipitation of the soluble enzyme with a suitable precipitant such and second the crosslinking step with an appropriate cross-linker. The final suspension of CLEAs obtained was moderately turbid and enzyme particles could be normally observed with an average diameter of 250 nm. The CLEAs of HRP were successfully produced under different testing conditions afterwards. The final recovery activity of the CLEAs attained was 83 % compared to the activity of native enzyme. The synthesised CLEAs were prepared in the presence of egg albumin and functional additive as pentaethylenehexamine (PEHA). The role of albumin in CLEAs preparation plays a significant role as a stabilizing agent of CLEAs particles, whereas the addition of PEHA was fundamental to obtain fully cross-linked HRP aggregates. For, the HRP possesses only 6 Lys (lysine) amino residues, that substantially impedes the cross-linking of the enzyme to completion, the addition of PEHA increased the free amino groups (-NH2) on the outer surface of the enzyme, making the cross-linking more feasible.

Namen diplomskega dela je bil ugotoviti, s katerim načinom sinteze lahko sintetiziramo magnetne nanodelce CuNi z ustrezno sestavo za nadaljnjo uporabo pri pripravi magnetnih tekočin, ki bi bile primerne za uporabo pri magnetni hipertermiji. S pomočjo rentgenske praškovne difrakcije (RPD) smo karakterizirali velikost nastalih nanodelcev zlitine in določili faze v vzorcih. Fizikalne lastnosti vzorcev (izgubo mase) smo, pri kontroliranem segrevanju, določili s termogravimetrično analizo (TGA). Magnetne lastnosti nastalih nanodelcev smo izmerili z suscepto-magnetometrom DSM — 10. Na koncu smo preučili še morfologijo delcev s transmisijskim elektronskim mikroskopom (TEM). Rezultati so pokazali, da je najprimernejša metoda za sintezo magnetnih nanodelcev CuNi z različnimi sestavami mehanokemijska metoda. Sintetizirani delci so kazali močne magnetne lastnosti. Čas mletja vpliva na velikost nastalih nanodelcev in stopnjo zreagiranosti reaktantov. The aim of this work was to determine, which way of synthesis is the most succesful for preparation of magnetic nanoparticles CuNi with suitable composition for further preparation of magnetic fluids, which can be used in magnetic hyperthermia. The size of magnetic nanoparticles was estimated with Scherrer equation. Samples were characterized with XRD analysis. Physical properties (loss of weight) of the samples were, during controlled heating, measured with termogravimetric analysis (TGA). Magnetic properties of the samples were measured with DSM – 10 magnetometer. At the end we studied morphology of the synthesized nanoparticles with transmission electronic microscope (TEM). The results showed that the most suitable method of synthesis of magnetic nanoparticles CuNi with varying composition is mechanochemical method. Synthesized nanoparticles were strongly magnetic. Time of milling has effect on size of synthesized nanoparticles.

Namen diplomskega dela je bil ugotoviti, kateri način sinteze, bi bil bolj primeren za pripravo magnetnih nanodelcev Cu-Ni z ustrezno sestavo za nadaljno uporabo pri pripravi magnetnih tekočin, uporabljenih v magnetni hipertermiji. Nanodelce smo sintetizirali s pomočjo mletja in mikroemulzij. S pomočjo rezultatov rentgenske praškovne difrakcije (XRD) smo ocenili velikost nanodelcev CuNi in kvalitativno karakterizirali vzorce. S termogravimetrično analizo (TGA) smo pri kontroliranem segrevanju določali Curiejevo temperaturo vzorcev. Morfologijo nanodelcev smo preučevali s transmisijskim elektronskim mikroskopom (TEM). Na koncu so bile izvedene še magnetne meritve z VSM magnetometrom. Optimalna Curijeva temperatura (Tc) 45°C je bila izmerjena pri vzorcu sestave: Cu27,5Ni72,5, ki smo ga pripravili z mletjem. Magnetne meritve so pokazale, da vzorci nimajo koercitivnosti, kar kaže na superparamagnetne lastnosti magnetnih delcev. Morfologija nanodelcev posneta s pomočjo TEM, nam kaže manjše zaglomerirane delce, ki ležijo na večjih ploščicah. Nanodelci vzorca Cu27,5Ni72,5 , ki smo ga sintetizirali z mletjem, bi bili torej najbolj primerni za uporabo v magnetni hipertermiji. The aim of this work was to determine, which way of synthesis is more appropriate for preparation of magnetic nanoparticles CuNi with suitable composition for further preparation of magnetic fluids, which can be used in magnetic hyperthermia. The size of magnetic nanoparticles was estimated by Scherrer equation. Samples were characterized with XRD analysis. Curie temperatures of the samples were mesured with termogravimetric analysis (TGA), during controlled heating. The morphology of nanoparticles was studied with transmission electron microscopy (TEM). Further, the magnetic properties of the samples were measured with VSM magnetometer. The results showed that the optimal Curie temperature (Tc) of 45°C was measured at sample composition: Cu27,5Ni72,5, prepared by milling method. Magnetic measurements indicate that magnetic nanoparticles exhibit superparamagnetic properties. The morphology of nanoparticles showed small agglomerated particles, which are located on large plates. Nanoparticles of sample Cu27,5Ni72,5 synthesized by milling method, would be most suitable for use in magnetic hyperthermia.

V pričujočem delu sem se ukvarjal s sintezo superparamagnetnih nanokompozitov na osnovi nanodelcev γ-Fe2O3 in PMMA. Nanodelce sem sintetiziral s koprecipitacijo Fe2+/Fe3+ ionov v vodni raztopini. Nanodelce prevlečene z oleinsko ali ricinolejsko kislino sem sintetiziral s koprecipitacijo Fe2+/Fe3+ ionov v vodni raztopini v prisotnosti oleinske oz. ricinolejske kisline. Preliminarne raziskave so jasno pokazale, da je nemogoče pripraviti superparamagnetne nanokompozite γ-Fe2O3 v PMMA matrici brez ustrezne funkcionalizacije površine magnetnih nanodelcev. Iz slik s presevnega elektronskega mikroskopa (TEM) sem zaključil, da je vzorec pripravljen z mešanje nanodelcev γ-Fe2O3 s PMMA v acetonu in kasnejšim obarjanjem polimera v vodi, fazno separiran. Vzorec je sestavljen iz aglomeratov nanodelcev γ-Fe2O3, ki niso vgrajeni v polimerno matrico. Nanokompozite sem pripravil z obarjalno polimerizacijo PMMA v prisotnosti nanodelcev prevlečenih z oleinsko kislino. Koloidno stabilni suspenziji nanodelcev prevlečenih z oleinsko kislino v n-dekanu sem dodal monomer metil metakrilat. Polimerizacijo monomera sem izvedel pri povišani temperaturi. Delež nanodelcev v nanokompozitu sem kontroliral preko razmerja nanodelci/monomer. S pomočjo TEM analize sem ugotovil, da so nanodelci homogeno porazdeljeni v polimerni matrici. Z višanjem razmerja prehaja mehanizem nastanka polimernih zrn preko homogene v heterogeno nukleacijo. Nanokompozit ohrani superparamagnetno naravo tudi ob vgradnji relativno velikega deleža vgrajenih nanodelcev, do 48 ut. %. Vgradnja velikega deleža magnetnih nanodelcev je razlog za visoko nasičeno magnetizacijo nanokompozitov, do 31 emu/g. Nanokompozitne delce sem pripravil s polimerizacijo monomera metil metakrilata v prisotnosti nanodelcev v miniemulziji. Koloidno stabilno suspenzijo sestavljeno iz nanodelcev prevlečenih z ricinolejsko kislino, ultrahidrofoba in iniciatorja v monomeru, sem dodal k vodni raztopini surfaktanta. Miniemulzijo sem pripravil s pomočjo ultrazvoka. Polimerizacijo sem izvajala pri povišani temperaturi. S spreminjanjem deleža surfaktanta sem prilagajal povprečni premer nanokompozitnih delcev v razponu med ~25 nm in ~50 nm. Zaradi visokega ζ-potenciala je suspenzija nanokompozitnih delcev v vodi koloidno stabilna. S TEM slik nanokompozitnih delcev sem ugotovil, da so nanokompozitni delci sestavljeni iz nanodelcev, ki tvorijo jedro delca in tankega sloja polimera okrog jedra. V nanokompozitne delce sem uspel vgraditi do 39 ut. % magnetnih nanodelcev, ne glede na velikost nanokompozitnih delcev. Nasičena magnetizacija nanokompozitnih delcev znaša 27 emu/g. Presented work describes synthesis of superparamagnetic nanocomposites, based on superparamagnetic γ-Fe2O3 nanoparticles and PMMA. Nanoparticles were synthesized by the coprecipitation of Fe2+/Fe3+ ions from an aqueous solution. Oleic or ricinoleic acid coated nanoparticles were synthesized by the coprecipitation of Fe2+/Fe3+ ions from an aqueous solution in the presence of oleic or ricinoleic acid. Preliminary study clearly demonstrated that it is impossible to prepare superparamagnetic nanocomposite of the γ-Fe2O3 in the PMMA matrix without nanoparticles functionalization. Sample prepared by the mixing of the γ-Fe2O3 and the PMMA in the acetone and subsequent precipitation of the polymer by water addition, was composed of two separated phases, as observed by transmission electron microscopy (TEM). The phases were identified as agglomerates of the γ-Fe2O3 which were not encapsulated by the PMMA matrix. Nanocomposites were prepared by the precipitation polymerization of the methyl methacrylate in the presence of oleic acid coated nanoparticles. Methyl methacrylate was added to the colloidal suspension of the oleic acid coated nanoparticles in n-decane and in-situ polymerization was carried out at elevated temperatures. The content of nanoparticles was controlled by varying the nanoparticles/monomer ratio. The TEM analysis showed that the nanoparticles were well dispersed in the polymer matrix. The mechanism of formation of the polymer grain changes from homogeneous to heterogeneous nucleation as the ratio is increased. Nanocomposites retained their superparamagnetic nature even when encapsulated by polymer with concentrations up to 48 wt. %. The high loading of magnetic nanoparticles resulted in relatively high saturation magnetizations of the nanocomposites, up to 31 emu/g. Nanocomposite particles were prepared using the mini-emulsion polymerization of a monomer in the presence of the nanoparticles. A colloidal suspension composed of ricinoleic acid coated iron-oxide nanoparticles, the initiator and the ultrahydrophobe in the monomer, methyl methacrylate, was added to an aqueous solution of surfactant and then ultrasonified to promote the formation of the mini-emulsion. The polymerization was initiated by raising the temperature. By changing the content of surfactant, nanocomposite particles with an average diameter ranging from 25 to 50 nm were obtained. Because of the high ζ-potential, the nanocomposite particles formed a stable suspension in water. TEM showed that the core of the prepared nanocomposite particles was composed of iron-oxide nanoparticles homogeneously distributed within a polymer matrix and a thin polymer shell. The content of magnetic nanoparticles dispersed in the polymer was as high as 39 wt. %, resulting in a high saturation magnetization of 27 emu/g.