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

[Display omitted] •Direct surface charge transfer behavior of glutamic acid (GLU) on 2D MoS2 were studied.•Surface charge transfer of GLU to MoS2 was experimentally demonstrated for the first time.•GLU molecules exposed onto MoS2 exhibited n-type charge transfer and increased channel currents, which can be exploited as sensing properties.•With electrode encapsulation methods, our MoS2 sensor shows highly stable sensing properties toward GLU exposure with clear concentration dependencies.•This work can contribute as fundamental approach to exploit direct surface charge transfer of biomolecules onto MoS2 as sensing platform without extra enzymes or acceptors. 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.