Two-dimensional (2D) materials show promising electronical, optical, magnetic and mechanical properties. In this thesis, we investigate the preparation of two dimensional materials through chemical vapor deposition, and perform electronic, optical and magnetic measurements on these materials and their heterstructures, including Molybdenum Disulfide (MoS2), Vanadium Sulfides (VS2, V5S8) and Iron oxide (Fe2O3). We argue that these materials can be potential candidates for harvesting solar energy to generate electricity and hydrogen, as well as making energy efficient spintronic devices. Moisture content is one of the key parameters in controlling the synthesis of 2D MoS2. We found that moisture present in the MoO3 powder will have significant effect on the synthesis of monolayer MoS2. Having understood the role of moisture in the process, we achieved highly-reproducible, high-yield, and high-quality monolayer MoS2 growth by adopting an unglazed surface crucible to absorb the water during the process. The photoluminescence (PL) performance of individual 2D material can be very different when they are combined together. We study the inter-layer coupling behaviors of hetero-bilayers of MoS2 and WS2 and MoS2-black phosphorous (BP), WS2-BP hetero-stacks. The interactions between the MoS2 and WS2 layers retain a direct band gap for MoS2 while form an indirect gap for the WS2. The MoS2-BP hetero-stack shows a type-II band alignment and WS2-BP hetero-stack has a type-I band alignment. The build-in electric fields in these hetero-stacks are strong enough to split the excitons, leading to a significant reduction in their recombination and subsequently a strongly-quenched PL peak of the WS2 and MoS2. Singe crystalline VS2 nanosheets can be prepared by CVD. We determine the hexagonal 1T crystalline structures of VS2 using XRD and TEM. We investigate the electrocatalytic hydrogen evolution reaction (HER) activities of the 1T-VS2, which shows extremely low overpotential of -68 mV at 10 mA cm-2, and small Tafel slopes of ∼34 mV/decade as well as high stability, demonstrating its potential as a candidate non-noble metal catalyst for HER. Finally, two magnetic 2D materials: V5S8 and Fe2O3 were synthesized and studied. V5S8 maintains its antiferromagnetic properties down to ~ 11 nm thickness, and possible quantum phase transition at accessible fields (~18 T). Due to its minimum surface energy, the unique epsilon phase Fe2O3 was found to be a more stable phase among all other phases in 2D forms. Magnetic Kerr rotation measurements indicated the room-temperature ferromagnetism of epsilon phase Fe2O3. Combing its air-stable nature, ultra-thin 2D epsilon Fe2O3 can be an excellent platform for compact and energy efficient spintronic devices.