Self-assembled monolayer field-effect transistors (SAMFETs): A new synthetic approach for sensing applications

Johannes Bintinger1,  Roland Bittner1,  Shyuan Yang2,  Ole Bethge3,  Helmuth Hoffman1,  Thomas Krober4,  Hannes Mikula1,  Annette Foelske-Schmitz5,  Klaudia Hradil6,  Wolfgang Knoll4,  Ioannis Kymissis2,  Johannes Frohlich1
1Institute of Applied Synthetic Chemistry, Vienna University of Technology, Austria, 2Department of Electrical Engineering, Columbia University, USA, 3Institute of Solid State Electronics, Vienna University of Technology, Austria, 4Austrian Institute of Technology, BioSensor Technologies, Austria, 5Analytical Instrumentation Center, Vienna University of Technology, Austria, 6X-Ray Center, Vienna University of Technology, Austria

Abstract

Self-assembled monolayer field-effect transistors have recently attracted much attention due to their manifold of potential applications especially in sensing. Self-assembly is the autonomous organization of components into patterns and structures and one of the biggest challenges for Organic Electronics. Applied to OFETs this means that a semiconducting core is connected via a spacer to a reactive group which anchors covalently to the dielectric. The result is a spontaneously formed highly ordered, densely packed, defect free monolayer of the OSC on the gate dielectric. This design improves OFET performance as on/off ratios are enhanced because of the absence of any bulk current, prevents delamination during bending in flexible devices due to the covalent fixation of the OSC, guarantees minimal material usage and opens up new possibilities for sensor applications.2 It is important to acknowledge that in such a device, the OSC serves a dual function, as an active charge carrier transport layer and as a functional sensing surface. Partially covered SAMFETs could be the ultimate sensor5, since the electrostatic interactions are stronger when the distance between the analyte and the channel is decreased; this distance is pushed to the extreme when applied in a monolayer thick device.3 While a few reports on the use of SAMFETs in sensing application have been published, so far no covalently functionalized SAMFET-sensor for the selective detection of an analyte class has been reported. Hence the experimental proof of concept of the above mentioned statement is still missing. In this work we report on preliminary results on a novel building-block like-, bottom-up- approach for developing alkyne functionalized perylene bisimides based n-type SAMFETs using click-chemistry. Our procedure is based on a reliable synthetic route yielding a densely packed, azide functionalized SAM film (block 1). In a second step this SAM-film is converted into a SAMFET-material using a readily available alkynated perylene diimide precursor in a click reaction (block 2). This alkyne functionalized SAMFET, is a key intermediate for a versatile sensing platform as it offers access towards a broad range of biological recognition units by applying click-chemistry. We intend to employ and test this material as a gas sensor on a newly developed ultra-low cost (<1$), lightweight (<2g), portable sensor platform. When plugged into a PC via USB it automatically performs measurements of the environment. Therefore we think that it is an ideal platform for a drone based, large area, environmental monitoring system.