Formulation and characterization of nanofibers made of titanium oxynitride and carbon

Nanovlakna predstavljajo enega izmed naprednih nanomaterialov, katere odlikuje izredno veliko razmerje med površino in volumnom. Nanovlakna na osnovi titanovega oksinitrida (TiON) predstavljajo razmeroma nov material, ki pa zaradi visoke elektroprevodnosti in manjše tendence adhezije trombocitov ter vezave fibrinogena izkazuje potencial na področju elektrokemije, fotokatalize in medicine. Ključna pomanjkljivost TiON je njegova mehanska krhkost, ki omejuje njegovo uporabnost na daljši rok. Za rešitev tega izziva dodajamo v nanovlakna snovi, npr. ogljik, ki povečuje mehansko trdnost materiala. Posledično je bil namen magistrske naloge z metodo elektrostatskega sukanja izdelati različna enoslojna in dvoslojna nanovlakna na osnovi TiON in ogljika ter jih morfološko in fizikalno-kemijsko ovrednotiti z različnimi analiznimi metodami. V prvem delu smo razvili različna polimerna nanovlakna iz raztopin polivinilpirolidona (PVP) in poliakrilonitrila (PAN) v N,N – dimetilformamidu (DMF) ali etanolu. Za pripravo organsko-anorganskih kompozitnih nanovlaken smo v polimerno raztopino dodali titanov(IV) izopropoksid, kot prekurzor TiO2 in v določenih primerih sol platine. Nanovlakna iz PVP smo izdelali iz obeh topil, medtem ko je PAN nanovlakna možno pripraviti le iz DMF. Ugotovili smo tudi, da pri raztopinah PVP v DMF potrebujemo bistveno višje koncentracije polimera kot v etanolu, da uspešno izdelamo nanovlakna brez vozlov. Pripravljena nanovlakna smo termično obdelali v atmosferi amonijaka in pripravili TiON in ogljikova nanovlakna, ki so bila tanjša v primerjavi z nanovlakni pred termično obdelavo. V drugem delu smo poskusili izdelati tri različne vrste dvoslojnih nanovlaken: (i) jedro iz TiON in ovojnica iz platine, (ii) ogljikovo jedro in ovojnica iz TiON in platine ter (iii) ogljikovo jedro in ovojnica iz platine. Ugotovili smo, da je izdelava dvoslojnih nanovlaken bolj kompleksna v primerjavi z enoslojnim. S pomočjo transmisijske elektronske mikroskopije smo potrdili delno dvoslojno strukturo, saj med elektrostatskim sukanjem prihaja do mešanja raztopin notranje in zunanje raztopine. S pomočjo rentgenske praškovne difrakcije smo pri enoslojnih in dvoslojnih nanovlaknih potrdili prisotnost TiON, ogljika in platine. Rezultati eksperimentov predstavljajo pomembno izhodišče za nadaljnji razvoj nanovlaken na osnovi ogljika in TiON in njihovo uporabnost na različnih področjih.Nanofibers are among the most promising nanomaterials, with an extraordinary area-to-volume ratio. Titanium oxynitride (TiON) nanofibers represent a relatively new material that shows potential in the field of electrochemistry and photocatalysis due to its high conductivity properties, while in medical field the major advantage is lower tendency to platelet adhesion and fibrinogen binding. However, the major drawback of TiON is its mechanical fragility, which limits its long-term use. To solve this problem, carbon can be added to the material to increase its mechanical strength. Therefore, the aim of this master thesis is to develop monolithic and core-shell TiON carbon nanofibers by the electrospinning method and evaluate their morphology and physicochemical properties by different analytical methods. In the first part, we developed various polymer nanofibers from polyvinylpyrrolidone (PVP) and polyacrylonitrile (PAN) solutions in N,N-dimethylformamide (DMF) and ethanol. To develop organic-inorganic composite nanofibers, titanium(IV) isopropoxide (TIP) as TiO2 precursor and in some cases Pt salt were added to the polymer solution. PVP nanofibers were prepared from both solvents, while the preparation of PAN nanofibers was possible only from DMF. We found that PVP solutions dissolved in DMF required a much higher concentration of polymer than those dissolved in ethanol to successfully produce nanofibers without beads. The developed nanofibers were thermally treated in NH3 atmosphere and prepared TiON and carbon nanofibers were thinner than the nanofibers before thermal treatment. In the second part, we tried to develop three different types of core-shell nanofibers: (i) nanofibers composed of a TiON core and a Pt shell, (ii) a carbon core and a TiON shell with Pt, and (iii) a carbon core and a Pt shell. We have found that production of core-shell nanofibers is even more challenging than production of monolithic nanofibers. Using transmission electron microscopy, we confirmed a partial core-shell structure as inner and outer polymer solutions mixed during electrospinning. Using X-ray diffraction, we confirmed the presence of TiON, carbon, and platinum in monolithic and core-shell nanofibers. The results of the experiments represent an important basis for further development of nanofibers based on carbon and TiON and their applicability in various fields