Transition metal dichalcogenides (TMDC) monolayers are being investigated intensively due to their unique optoelectronic properties as two-dimensional materials beyond graphene. Here, we interface and modify TMDC monolayers with various chirality carbon nanotubes and dopants to modulate their optical and electronic properties. We synthesize and employ large area TMDC (MoS2, MoSe2, WS2, or WSe2) monolayers via chemical vapor deposition, where the TMDCs are laterally grown to tens of microns. For this study, we are observing changes in the photoluminescence (PL) of the TMDCs when interfaced with carbon nanotubes or doped with n- and p-type dopants (e.g. F4-TCNQ). When the TMDC monolayers are interfaced with carbon nanotubes, we observe changes in the PL that is potentially due to charge transfer between the TMDC and carbon nanotubes. We confirm the adsorption of carbon nanotubes on TMDC monolayers via the confocal Raman spectroscopy and X-ray photoelectron spectroscopy. Similarly, we see changes to the PL when the TMDC monolayers are modified with dopants, which is likely due to quenching of carriers. We observe that the photoluminescence blue shifts when modified by p-type dopants, which can be contributed to trions converting to excitons. Interestingly, such doping effects vary from the edge to the center of the monolayer. We also examine the electronic properties such as time resolved microwave conductivity to investigate the carrier mobility. Our findings and hypotheses would help the further understanding of two-dimensional materials and facility their potential applications in solar fuel and photovoltaic.