A few-layered molybdenum disulfide (MoS ₂ ) thin film grown by plasma enhanced chemical vapor deposition was etched using a CF ₄ inductively coupled plasma, and the possibility of controlling the MoS ₂ layer thickness to a monolayer of MoS ₂ over a large area substrate was investigated. In addition, damage and contamination of the remaining MoS ₂ layer surface after etching and a possible method for film recovery was also investigated. The results from Raman spectroscopy and atomic force microscopy showed that one monolayer of MoS ₂ was etched by exposure to a CF ₄ plasma for 20 s after an initial incubation time of 20 s, i.e., the number of MoS ₂ layers could be controlled by exposure to the CF ₄ plasma for a certain processing time. However, XPS data showed that exposure to CF ₄ plasma induced a certain amount of damage and contamination by fluorine of the remaining MoS ₂ surface. After exposure to a H ₂ S plasma for more than 10 min, the damage and fluorine contamination of the etched MoS ₂ surface could be effectively removed.

This paper reports a biosensor based on a MoS₂-graphene (MG) composite that can measure the parathyroid hormone (PTH) concentration in serum samples from patients. The interaction between PTH and MG was analysed via an electrochemical sensing technique. The MG was functionalized using l-cysteine. Following this, PTH could be covalently immobilized on the MG sensing electrode. The properties of MG were evaluated using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectrometry. Following optimization of immobilized materials—such as MG, PTH, and alkaline phosphatase (ALP)—the performance of the MG sensor was investigated via cyclic voltammetry, to assess its linearity, repeatability, and reproducibility. Electrochemical impedance spectroscopy was performed on graphene oxide (GO) and MG-modified electrodes to confirm the capture of a monoclonal antibody (MAb) targeting PTH. Furthermore, the ALP-PTH-MG sensor exhibits a linear response towards PTH from artificial serum over a range of 1–50 pg mL⁻¹. Moreover, patient sera (n = 30) were evaluated using the ALP-PTH-MG sensor and compared using standard equipment (Roche E 170). The P-value is less than 0.01 when evaluated with a t-test using Welch’s correction. This implies that the fabricated sensor can be deployed for medical diagnosis.