Aptamer Functionalized CVD Grown Monolayer WS2 Based FETs for Real-Time Detection of E. coli

With advancing technology, the demand for the point of care device in real-time detection of pathological biomarkers is increasing. Field-effect transistors (FETs) based electrical biosensor is a type of label-free sensor for real-time detection of biomolecules and hence, has the potential to be used as a point of care device. We have fabricated WS2 monolayer based-FETs to detect Escherichia coli bacteria. Large area monolayer WS2 was grown on highly doped SiO2/Si substrate by chemical vapour deposition (CVD) at 940 °C. As a biorecognition element for the E. coli, ssDNA aptamers were used. Different concentrations of the aptamer solution ranging from 0.5 to 2 μM were used to functionalize the monolayer WS2. Photoluminescence (PL) spectroscopy was employed to understand the interaction between WS2 and aptamer. The PL emission of monolayer WS2 was quenched and the spectra showed systematic redshift upon increasing the aptamer concentrations. The spectral redshift and quenching of the PL indicate charge transfer from negatively charged aptamers to WS2. The optimal concentration of 1 μM aptamer was used to functionalize the final FET device for the detection of E. coli. We have successfully detected 103 cfu/ml E. coli bacteria in 5 μL of 1-X PBS solution at room temperature by monitoring a sharp drop of drain current with the addition of E. coli.