Field-effect transistor with a chemically synthesized MoS₂ sensing channel for label-free and highly sensitive electrical detection of DNA hybridization

A field-effect transistor (FET) with two-dimensional (2D) few-layer MoS₂ as a sensing-channel material was investigated for label-free electrical detection of the hybridization of deoxyribonucleic acid (DNA) molecules. The high-quality MoS₂-channel pattern was selectively formedthrough the chemical reaction of the Mo layer with H₂S gas. The MoS2 FET was very stable in an electrolyte and inert to pH changes due to the lack of oxygen-containing functionalities on the MoS2 surface. Hybridization of single-stranded target DNA molecules with single-stranded probe DNA molecules physically adsorbed on the MoS₂ channel resulted in a shift of the threshold voltage (V_th) in the negative direction and an increase in the drain current. The negative shift in V_th is attributed to electrostatic gating effects induced by the detachment of negatively charged probe DNA molecules from the channel surface after hybridization. A detection limit of 10 fM, high sensitivity of 17 mV/dec, and high dynamic range of 10⁶ were achieved. The results showed that a bio-FET with an ultrathin 2D MoS₂ channel can be used to detect very small concentrations of target DNA molecules specifically hybridized with the probe DNA molecules.