The extraordinary versatility and tunability of the optical and electrical properties of two-dimensional transition metal dichalcogenides (2D-TMD) paves the way for employing this material family for next-generation devices in nanoelectronics and optics. In this thesis transport studies, photoluminescence and Raman spectroscopy on intrinsic 2D 2H-WSe2 and 2H-MoS2 are addressed, allowing the analysis of the dominant transport mechanisms and the material thickness. Moreover, the successful transfer of 2D layers onto structured surfaces, such as nm-sized tips and electrical contacts, by means of the self-made dry transfer setup, has been demonstrated by atomic force microscopy. This has encouraged the fabrication of field-effect-transistors (FETs) based on 2D WSe2 and MoS2, which allowed carrying out an in-depth study of temperatureand magnetic field-dependent transport mechanisms under the influence of an external gate voltage. By switching between different gatings, the conversion of 2D-TMDs from n- to p-type and vice versa has been achieved, entailing the enhancement of carrier concentration and mobility. When comparing the transport results for gate voltages driven through the SiO2/Si substrate (backgating) and through ionic gel PEO:KClO4 drop cast onto WSe2 and MoS2 layers (topgating), the impact of the 2D layer-to-substrate-adhesion, the ionic gel characteristics and the SiO2 stoichiometry have been addressed. The transport results suggest that topgating FETs based on 2D-TMDs via ionic gel is an attractive way for enhancing the material conductivity, which is a factor 10^6-10^7 larger than for an equivalent backgating.