Graphene monolayer-based pH sensor shows promise for new designs
Graphene monolayer-based pH sensor shows promise for new designs lead image
Due to its ability to transduce absorption events of ions into detectable electrical signals, graphene has garnered attention in recent years for sensors. However, graphene’s relatively low number of chemically active sites limits its ability to selectively bind the analytes and, therefore, has hampered its widespread use.
Kaiser et al. report on a graphene monolayer-based pH sensor. Drawing on a van der Waals heterostructure based on a monolayer graphene and an amino-terminated carbon nanomembrane (CNM) in a solution-gated graphene field-effect transistor (GFET), the device possesses chemically active groups in graphene’s vicinity while maintaining its charge carrier transport properties.
The unique properties of the device’s layer-by-layer assembly points to a path forward for new classes of sensing materials.
“Although GFETs are very sensitive to any adsorption event, in order to develop a reliable sensor a non-destructive and robust functionalization has to be achieved,” said author Andrey Turchanin. “This functionalization needs to result in highly selective, reproducible and reversable adsorption of the analytes, as in our case, protons.”
The device detected minimal pH changes with resolutions of roughly 0.01 pH at pH 2 and 0.04 pH at pH 12, all within seconds.
“One of the biggest surprises was that CNMs have demonstrated superior performance also as a dielectric layer leading to a low gate leakage current of the FETs devices in solution,” said author David Kaiser. “Therewith, no additional insolation was necessary enabling the minimum possible distance between functional groups in CNMs and the channel material graphene.”
The authors hope their work presents a universal methodology for non-destructive functionalization of FETs based not only on graphene but also on other 2D materials.
Source: “pH sensors based on amino-terminated carbon nanomembrane and single layer graphene van der Waals heterostructures,” by D. Kaiser, Z. Tang, M. Küllmer, C. Neumann, A. Winter, R. Kahle, L. Georgi, T. Weimann, M. Siegmann, S. Gräfe, A. Centeno, A. Zurutuza, and A. Turchanin, Applied Physics Reviews (2021). The article can be accessed at https://doi.org/10.1063/5.0040442 .
