A molecular probe layer modified organic thin film transistor on flexible platform for next generation cyanide sensor

Abstract

Organic thin film transistor (OTFT) based cyanide (CN−) sensor can be of an intense interest due to its simple operation, high sensitivity, system on chip (SoC) integration capacity and applicability towards environmental safety. So, mechanical flexibility of such sensors can extend them to conformable, bio-compatible and wearable applications. In our recent work, a novel OTFT based highly sensitive and mechanically flexible platform was developed to detect CN− in aqueous medium. The sensor was fabricated on a flexible polyethylene terephthalate (PET) substrate by simple spin coating and operated at a very low voltage of −3 V. For the sensing element, a chemically active dansyl-dervatized-triazole linked glucopyranosyl conjugate (DTGC) was used as a molecular probe on the semiconducting poly (3-hexylthiophene) P3HT layer in the device structure. The fabricated sensor was characterized electrically while using an aqueous solution of tetrabutylammonium cyanide (TBAC) as an analyte. Significant changes in device characteristics including 0.4 V shift in threshold voltage, 0.2 cm2v−1s−1 increment in mobility and 2 μA increase in drain current were observed for the OTFT based sensor with presence of CN− analyte. The concentration of the CN− was then varied and thus the minimum detection limit was found to be 1 μM. The sensor also exhibited excellent mechanical flexibility with its stable operation even up to a bending with 5 mm of bending radius. The sensing mechanism of the developed sensor has been explained through the possible charge transfer phenomena from the host semiconductor due to a chemical reaction between the probe layer and the analyte. The sensititvity and chemical reactivity of the molecular probe to the CN− were further confirmed from the microscopic studies and the change in the visual appearance (colour) of the probe with the presence of aqueous CN−.