Figure 1. A MoS₂ nanosheet biosensor and contact angles of different surfaces.

(a) Schematic of a MoS₂ biosensor configured as a PSA, detecting label-free immunoassay, illustrating PSA antibody functionalized MoS₂ surface (top) and subsequent binding of PSA antigen with antibody receptors. The MoS₂ nanosheet biosensor consists of a gate insulator of SiO₂ (300 nm) and a drain-source metal contact of Ti/Au (15 nm/300 nm) (b) The water contact angle measurement to confirm hydrophobic characteristics of different substrates: the water contact angle of MoS₂, Au, and SiO₂ substrate are 75.75°, 75.72°, and 23.1°, respectively. The contact angle of MoS₂ surface, which is more hydrophobic than Si-based substrates, is comparable to that of Au surface. This suggests that MoS₂ nanosheet is an excellent candidate for functionalizing antibody and protein due to its hydrophobic surface.