Single-walled carbon nanotubes (SWNTs) offer extraordinary physical and chemical properties such as high carrier mobility and current-carrying capacity, unique optoelectronic properties, large surface area, and high electrochemical stability, thus showing great potential for applications in thin-film transistors, novel electronic and optoelectronic devices, logic circuits, solar cells, and lithium-sulfur batteries.

In Chapter 1, the fundamental properties of SWNTs are introduced, including their structure, electronic and spectroscopy properties, growth method, thin film preparation, and potential applications. In chapter 2, sulfur encapsulation of SWNTs were prepared and studied by Raman and UV-Vis-NIR spectroscopy techniques. We discovered a giant Raman response to the encapsulation of sulfur in narrow diameter SWNTs with the appearance of new peaks at 319, 395 and 710 cm-1 which originate from the sulfur species within the SWNTs. The encapsulated species also shift the near-IR interband electronic transitions to lower energy by more than 10%. These effects seem to originate from the van der Waals interaction of the confined sulfur species with the walls of the SWNTs.

In chapter 3, we utilized a semitransparent film of p-type semiconducting single-walled carbon nanotubes (SC-SWNTs) with an energy gap of 0.68 ±0.07 eV in combination with a molecular beam epitaxy grown n-ZnO layer to build a vertical p-SC-SWNT/n-ZnO heterojunction-based UV photodetector. The resulting device shows a current rectification ratio of 103, a current photoresponsivity up to 400 A/W in the UV spectral range from 370 to 230 nm, low dark current, and UV-to-Visible photoresponsivity ratio of 105

In chapter 4, the CVD grown single-layer MoS2 with Au metal electrodes based gas sensor was utilized. Red light illumination was used to induce a photocurrent which was employed instead of dark current for NO2 gas sensing. Resulted Au/MoS2/Au optoelectronic gas sensor showed a significant enhancement of the device sensitivity S toward ppb level of NO2 gas exposure reaching S=4.9%/ppb (4900%/ppm) and extremely low limit of detection of NO2 gas at the level of 0.2 ppb was obtained.