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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.