CHARACTERIZATION, FUNCTIONALIZATION AND BIOLOGICAL EVALUATION OF CARBON NANOSTRUCTURES

Carbon nanostructures are gaining attention due to their promising properties for a wide range of applications from electrochromic devices to drug nanocarriers. Among the members of carbon nanostructure family, nanodiamonds (NDs), graphene quantum dots (GQDs), carbon dots (CDs) and multi-walled carbon nanotubes (MWCNTs) were used in this research project. Different functionalization reactions were performed on carbon nanostructures and the obtained products were characterized and evaluated. Rhamnose, imidazolium containing ionic liquids, 2-(2-(2-(2-aminoethoxy)ethoxy)ethyl)isoindoline-1,3-dione and tert-butyl (2-(2-(2-aminoethoxy)ethoxy)ethyl)carbamate were some organic molecules used for functionalizations in order to improve the solubility of carbon nanostructures and add different physical, electronic and biological properties. Despite promising properties, nanodiamonds tend to create big aggregates in aqueous media and this is the main obstacle for biological applications. It was shown that NDs with proper functionalizations can be dispersed in water and create stable dispersions. Thanks to fluorescent labeling with fluorescein isothiocyanate, NDs have been demonstrated to be promising nanocarrier for the delivery of functionalized molecules on their surface. The functionalization reactions of NDs were performed with different methodologies. NDs were demonstrated to be a performance tuning additive in electrochromic devices. Graphene Quantum Dots were produced with a methodology developed by the research group. Different modifications were performed in order to improve the production. GQDs were functionalized with different organic molecules with different methodologies such as amide bond generation and cycloaddition. It was demonstrated that GQDs have big potential to improve the performance of electrochromic devices. Carbon dots were produced from natural chitin resources: insect exoskeleton and shell of shrimp. It is shown that CDs produced from these natural and renewable resources are strongly fluorescent. CDs obtained from the new production methodology were characterized. Two different types of MWCNTs were functionalized and characterized for the comparison with other carbon nanostructures. The functionalization reactions were optimized in order to obtain high degree of functionalization. New physical, biological and electronic properties were introduced to carbon nanostructures through various functionalization reactions. Graphene quantum dots and carbon dots were produced by using new methodologies. Characterization studies were performed with different techniques, such as TGA, AFM and Raman spectroscopy. Nanodiamonds were evaluated in human peripheral blood mononuclear cells for biomedical applications. Graphene quantum dots and nanodiamonds were evaluated in electrochromic devices for possible performance improvements.