Surface Modification of Monolayer MoS₂ by Baking for Biomedical Applications

Molybdenum disulfide (MoS₂), a transition metal dichalcogenide material, possesses great potential in biomedical applications such as chemical/biological sensing, drug/gene delivery, bioimaging, phototherapy, and so on. In particular, monolayer MoS₂ has more extensive applications because of its superior physical and chemical properties; for example, it has an ultra-high surface area, is easily modified, and has high biodegradability. It is important to prepare advanced monolayer MoS₂ with enhanced energy exchange efficiency (EEE) for the development of MoS₂-based nanodevices and therapeutic strategies. In this work, a monolayer MoS₂ film was first synthesized through a chemical vapor deposition method, and the surface of MoS₂ was further modified via a baking process to develop p-type doping of monolayer MoS₂ with high EEE, followed by confirmation by X-ray photoelectron spectroscopy and Raman spectroscopy analysis. The morphology, surface roughness, and layer thickness of monolayer MoS₂ before and after baking were thoroughly investigated using atomic force microscopy. The results showed that the surface roughness and layer thickness of monolayer MoS₂ modified by baking were obviously increased in comparison with MoS₂ without baking, indicating that the surface topography of the monolayer MoS₂ film was obviously influenced. Moreover, a photoluminescence spectrum study revealed that p-type doping of monolayer MoS₂ displayed much greater photoluminescence ability, which was taken as evidence of higher photothermal conversion efficiency. This study not only developed a novel MoS₂ with high EEE for future biomedical applications but also demonstrated that a baking process is a promising way to modify the surface of monolayer MoS₂.