Investigation of direct surface charge transfer of glutamic acids on 2D monolayer molybdenum disulfide and its sensing properties

2D transition metal dichalcogenides (TMDs) have attracted significant attention because of their potential in biomolecular sensing applications owing to their sensitive surface interactions with analytes. In particular, glutamic acid (GLU) as representative of amino acids (AAs) are considered not only basic metabolites in proteins and food, but also vital biomarkers of body status and diseases. In addition, monitoring GLU profiles appears to be a highly effective real-time and early diagnostic technique. In this study, a biomolecular GLU sensor that uses a 2D polycrystalline MoS₂ as channel material, based on the effect of the direct surface charge transfer, was fabricated. As fundamental approach, the direct charge transfer of adsorbed GLU onto MoS₂ was experimentally demonstrated for the first time. The sensor exhibited sensitive responses to GLU exposure, without any enzymes or receptors. In addition, the electrode-encapsulated MoS₂ sensor showed comparably stable responses to the non-encapsulated MoS₂ sensor. The results confirmed that the 2D TMDs such as polycrystalline MoS₂ could be a viable platform for highly sensitive and stable biomolecular sensor applications based on direct surface interactions. In addition, this study can contribute to the extended researches such as the effect of surface functionalization by metal nanoparticles, and other types of AAs.