1. Synthesis and Photocatalytic Properties of 2D Transition Metal Dichalcogenides

Nanotechnology is the emerging technology of the twenty-first century. It deals with the synthesis and investigation of ultrafine materials and their use in technology for numerous applications. It is an interdisciplinary field that combines the principles of physics, chemistry, and engineering, such as structural analysis, electrical engineering, mechanical design, computer science and systems engineering. Two-dimensional (2D) materials are crystalline materials consisting of layered arranged atoms or molecules. In the last few years, 2D materials have been extensively explored for their unique 2D geometry, high surface-to-volume ratio, and nanoscale thickness. Two-dimensional transition metal dichalcogenide (2D-TMDCs) materials have the common formula MX₂, where X = sulfur (S), selenium (Se) or tellurium (Te), and M belongs to the elements of group of 4, 5, and 6 of the periodic table. MX₂ layers are covalently bound by the van der Waals force between the layers. The weak van der Waals bonds between the layers facilitate separation of the layers to form 2D materials. Many synthesis methods, like as CVD, hydrothermal, and CVT method, have been used to synthesize the 2D-TMDCs materials. Titanium disulfide (TiS₂) is an important layered material among the TMDCs family. It crystallizes in the hexagonal structure similar to CdI₂. It is a multi-layered compound with repeating subunits formed from a layer of Ti atoms and a layer of S. TiS₂ has a band gap varying between 0.05 and 2.5 eV; the Bohr’s radius of approximately 6.43 nm and the lattice parameter constants a (a = b) and c of TiS₂ are 3.40 A°, 5.96 A° respectively. The present chapter deals with the review of research work reported on 2D metal dichalcogenides with a special emphasis of TiS₂.