Molecule-induced n-type behavior of phosphorene-based field-effect transistor for highly sensitive detection of sialic acid

Low-concentration detection of sialic acid (SA) seems to be a promising method in early cancer prognosis. In this work, a phosphorene-based field-effect-transistor (Ph-FET) device has been introduced for detecting various concentrations of SA. The device was fabricated using successive hydrogen plasma treatment to start from the red phosphorus layer and to realize highly crystalline black phosphorus sheets. The morphology and crystalline quality of phosphorene sheets have been extensively examined by transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. By utilizing this device, we can detect different concentrations of SA from 3 to 2400 mu M owing to its negative charge. The detection limit of SA is as low as 2.8 mu M. This technique offers a straightforward method for the fabrication of high-performance Ph-FET with no need for exfoliation or sheet transfer. We have fabricated a Ph-FET with a mobility of 10 cm2 V -1 s- 1, a carrier concentration of 3.9 x 1011 cm-2, and an on/off current ratio of 103. Moreover, we have observed that exposure to SA solution would change the carrier type of the transistor from a p-type channel into an n-type channel device due to the interaction of SA molecules with the phosphorene atoms at the top of the puckered structure that weakens the P-P lattice anti-bonding orbitals and screens the trapped sites.