Obtención de nanohojas de disulfuro de molibdeno y su caracterización morfológica y eléctrica.

Abstract

Two-dimensional (2D) nanomaterials have received much attention in recent years due to their attractive properties associated with their morphology, especially their ultra-thin thickness. In addition to graphene, transition metal dichalcogenides (TMD’s) are another family of 2D materials that have become very important today. Of these materials, molybdenum disulfide (MoS2) stands out due to its important semiconductor properties. MoS2 is a material that in bulk presents an indirect bandgap of 1.2 eV; however, this bandgap depends on its thickness. Thus, different studies show that MoS2, at the monolayer level, presents a direct bandgap of 1.9 eV. This situation makes it a semiconductor analogue of graphene. This study explores a simple route to obtain MoS2 nanosheets; the liquid-phase exfoliation (LPE). Employing this technique, MoS2 nanosheets have been obtained using different solvents: 45 % ethanol/water, N-methyl-pyrrolidone (NMP) and N, Ndimethylformamide (DMF). The material obtained was characterized by different microscopic and spectroscopic techniques. The results show that the nanosheets obtained, although nanometric size, do not correspond to monolayers of material; otherwise, they are multilayer. Furthermore, it is shown that the use of 45 % ethanol/water as solvent leads to a higher percentage of exfoliation of the bulk material; however, it is the DMF that leads to obtaining thinner nanosheets. Finally, the material’s bandgap was evaluated experimentally from Tauc analysis of UV-Vis spectra and, more directly, through tunnel effect microscopy. This study shows that the nanosheets obtained present an indirect bandgap of greater magnitude than the bulk MoS2. Thus, this study confirms that the semiconductor properties of MoS2 depend on the thickness of the material.