Two-dimensional Molybdenum disulfide electrochemical-based sensors for biomedical applications

The era of 2D materials started in 2004, exactly with the discovery of graphene by the group of Andre Geim and Konstantin Novoselov. They were awarded the Nobel Prize in 2010 for isolating the atomic layer of graphene from graphite, demonstrating the unique properties of this material. In addition to graphene, 2D nanomaterials, comprising individual nanosheets or layered multi-sheet planar materials, have been among the most intriguing nanomaterials of the last ten years. These thin 2D nanomaterials have special characteristics and properties that differentiate them from bulk ones. Among these 2D materials, we find transition metals dichalcogenides (TMDs), which this thesis deals with, thanks to their crucial properties such as the indirect-to-direct bandgap conversion going from bulk to monolayer, large surface-tovolume area, high carrier mobility, etc... This Ph.D. project deals with the most famous 2D-TMDs, molybdenum disulfide (MoS2). Recently, this material has been used in different research applications, particularly chemical sensors, which haven’t stopped growing due to the real necessity to replace the costly techniques used at the moment. This thesis work was done in collaboration between CNR-IPCF Messina and the University of Messina, in which materials synthesis and characterization were done at CNR-IPCF Messina while sensors’ development was done at the University of Messina. Herein, MoS2 has been exfoliated using the Liquid Phase Exfoliation (LPE) technique first and then with Liquid Cascade Centrifugation (LCC). The obtained materials were characterized using microscopic techniques such as scanning electron microscopy and atomic force microscopy and spectroscopic techniques such as UV-Visible spectroscopy, Raman spectroscopy, and Dynamic Light scattering. The 2D property of the as-prepared materials was confirmed from all these characterizations, and all the basic parameters like concentration, size, and thickness were computed. The materials prepared via LPE were then used to modify different commercial screenprinted electrodes, gold, and carbon, used for the simultaneous and selective determination of Tyrosine, Dopamine, and Riboflavin. Using the same material together with gold nanoparticles, an electrochemical sensor was developed for Folic Acid determination. On the other hand, the materials obtained via LCC were then used to study the electrochemical and sensing properties of 2D-MoS2 nanosheets using different biomolecules for comparison.