Graphene transistors for real-time monitoring molecular self-assembly dynamics

Mastering the dynamics of molecular assembly on surfaces enables the engineering of predictable structural motifs to bestow programmable properties upon target substrates. Yet, monitoring self-assembly in real time on technologically relevant interfaces between a substrate and a solution is challenging, due to experimental complexity of disentangling interfacial from bulk phenomena. Here, we show that graphene devices can be used as highly sensitive detectors to read out the dynamics of molecular self-assembly at the solid/liquid interface in-situ. Irradiation of a photochromic molecule is used to trigger the formation of a metastable self-assembled adlayer on graphene and the dynamics of this process are monitored by tracking the current in the device over time. In perspective, the electrical readout in graphene devices is a diagnostic and highly sensitive means to resolve molecular ensemble dynamics occurring down to the nanosecond time scale, thereby providing a practical and powerful tool to investigate molecular self-organization in 2D. Molecular self-assembly provides the desired functions to substrates, but investigation and control of its dynamics is challenging for the large area over which it must be detected. Here the authors report the use of graphene field effect devices to monitor with sub-second time resolution the photoinduced supramolecular assembly of a spiropyran derivative on graphene, covering an area of 100x100 mu m(2).