One of the main subjects of this thesis is to design a novel synthetic route to covalently functionalize carbon nanotubes with various molecules in a non-toxic way on both surface and suspension. Functionalized carbon nanotubes are of great interest in the field of molecular electronics, materials science and nano-bio applications because of their remarkable structural, chemical and physical properties. First, the single-walled carbon nanotubes are functionalized with gold nanoparticles by the route, which involves silanization and copper-free click chemistry (SPAAC). We characterize the functionalized nanotubes through XPS, IR and Raman spectroscopic techniques to identify the surface attachment of molecules after each step. We observe a drastic change in homogeneity and functionalization density of single-walled carbon nanotubes with gold nanoparticles concerning solvent through TEM. Employing the same route, biomolecules such as fluorescent dyes and single-stranded DNA molecules are integrated with SWNTs. Fluorescence lifetime analysis of AF647 functionalized SWNTs is reduced compared to free dye due to the fluorescence quenching phenomenon of carbon nanotubes. Functionalized SWNTs are characterized with FLIM, SEM, and Raman for better correlation at the same area of interest. Furthermore, the nanotubes are resolved at the nanoscale level through STORM imaging technique with a limited photon budget. Single-stranded DNA molecules of different lengths are used to investigate the fluorescence quenching as they are distance-dependent. DNA-PAINT is engaged in imaging the functionalized SWNTs with an unlimited photon budget, overcoming STORM's challenge. Lastly, the route is transferred to surface-grown CNTs through the CVD technique, in which both the gold nanoparticles and fluorescent dyes are grafted with nanotubes selectively. CVD is carried out on different substrates Si/SiO2, quartz substrate and quartz coverslip for substrate functionalization. Catalyst deposition plays a significant role in not only the CVD growth but also in the lifetime analysis of the substrate functionalized nanotubes. We observe similar fluorescence quenching of nanotubes in the substrate compared with nanotubes functionalized in suspension. Surface-grown nanotubes in the optically transparent substrate can be resolved through STORM at the nanoscale level. In conclusion, we demonstrate a synthetic design to functionalize SWNTs which provides the possibility to be versatile and non-toxic. Moreover, we show that the nanotubes can be functionalized through this route homogeneously and selectively on both surface and suspension. This work lays the foundation for tailoring SWNTs with not only a wide range of molecules and to study their functional characteristics but also to carry out functionalization on different substrates for various applications.

The subject of this thesis is to study the interaction between carbon nanotubes (CNTs) and antiferromagnetic tetrametallic molecules attached to them. By employing quantum transport measurements, the sensitivity to sense the interactions is greatly increased, because the quantum dot is very susceptible to changes in its environment. The properties of carbon nanotubes can be altered by chemical functionalization with the aforementioned molecules, where the attachment is performed covalently via a ligand exchange with the CNT. The thesis is partitioned into two main parts: the first part presents experiments performed on tetramanganese functionalized CNTs, whereas for the second similar studies are conducted, except manganese is replaced by cobalt. Both complexes exhibit an antiferromagnetic ground state, yet the metal spin of manganese (S=5/2) is reduced to S=3/2 for cobalt. Additionally, an altered device preparation has been employed during the second part, leading to a strong suppression of the background signal. Quantum transport measurements at T=4K on manganese-functionalized CNTs show a very regular pattern of Coulomb diamonds, indicating only a mild disturbance of the quantum dot's electron system by the covalent bond. Moreover, the charging energy reveals a wave function extending over the entire device dimensions. However, at T=30mK in the tunneling current a strong noise emerges, when repeatedly measuring over an hour while keeping external biases constant. Additionally, these time traces are superimposed by a long-term background, which is removed by a correction algorithm plus a subsequent digitization. The remaining signal reveals a random telegraph signal (RTS) which is extensively studied and from its statistics the equivalent temperature of T=654mK for the excitation of the system is extracted. The quantum transport experiments conducted on cobalt-functionalized CNTs show a much better data quality of the coulomb diamonds, which is ascribed to the alteration in the device's preparation. From the line shape of the Coulomb oscillations as well as from the Coulomb staircases an electron temperature of about T=500mK is extracted. Moreover, a magnetic field dependence of the stability diagrams is apparent, attributable to Zeeman splitting. The respective Landé factor of g=1.73 is, compared to similar CNT quantum dot systems, unusually low. It is as attributed to an increased spin-orbit interaction between the conduction electrons and the cobalt's nuclei. The respective time traces exhibit or lack an RTS signal, depending on their external biases. Regarding the Coulomb diamonds, an essential prerequisite for the occurrence of an RTS is the proximity to a resonance, which is equatable to a high sensitivity of the quantum dot detector. Considering the available energy, the underlying process that is the cause for the emergence of the RTS is ascertained to be an internal excitation of the antiferromagnetic states of the metallic core.