Surface Modification of Monolayer MoS2 by Baking for Biomedical Applications.

Yan Wang,Yuanjun Ma,Xiangyu Yan,Huilong Zhu,Jinping Shi,Kunpeng Jia,Jun Luo,Juan Li,Can Yang Zhang

doi:10.3389/fchem.2020.00741

Abstract

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.

Highlights

This study prepared a p-type doping MoS2 film with high exchange efficiency (EEE), and demonstrated that the baking process is a promising way to modify the surface of an MoS2 film, which encourages further investigations for biomedical applications
Some irregular parts of the silicon wafer were exposed that were not covered with MoS2 film because of the rupture of the monolayer MoS2 film during the CVD process
Photoluminescence Analysis Since we successfully synthesized the monolayer MoS2 film and prepared the p-type doping of the MoS2 film, we evaluated whether the luminescence of MoS2 was enhanced after the baking process using PL measurement (Figure 5)

Summary

INTRODUCTION

Two-dimensional materials (2DMs) have attracted extremely wide attention in the biomedical science field because of their various unique properties (Yin et al, 2016; Liu and Liu, 2018). 2DMs are a large family of materials that include semimetals (graphene), semiconductors (molybdenum disulfide (MoS2), black phosphorus, etc.), insulators (h-BN), superconductors (carbon nanotubes), thermoelectric materials (PbTe), and topological insulators (HgTe quantum wells) (Frindt, 1966; Wilson and Yoffe, 1969; Clement et al, 1978; Abruna and Bard, 1982; Mishra et al, 1997; Prasad and Zabinski, 1997; Poizot et al, 2000; Frey et al, 2003; Kane and Mele, 2005). Oxygen is frequently used for doping as pure physical adsorption of oxygen will have only a small effect, which can cause an increase in the threshold voltage and a decrease in the on-current; the interaction between oxygen and MoS2 films is too weak to overcome the intrinsic n-type doping In this case, some of the intrinsic properties of MoS2 can be altered by the oxygen plasma method (Nan et al, 2014), which is widely used to prepare p-type doping of. We report a simple and convenient method for the preparation of p-type doping of monolayer MoS2 through baking under ambient conditions. This study prepared a p-type doping MoS2 film with high EEE, and demonstrated that the baking process is a promising way to modify the surface of an MoS2 film, which encourages further investigations for biomedical applications

MATERIALS AND METHODS

RESULTS AND DISCUSSIONS

CONCLUSIONS

DATA AVAILABILITY STATEMENT