Quantum and electrochemical interplays in hydrogenated graphene

Abstract

The design of electrochemically gated graphene field-effect transistors for detecting charged species in real time, greatly depends on our ability to understand and maintain a low level of electrochemical current. Here, we exploit the interplay between the electrical in-plane transport and the electrochemical activity of graphene. We found that the addition of one H-sp3 defect per hundred thousand carbon atoms reduces the electron transfer rate of the graphene basal plane by more than five times while preserving its excellent carrier mobility. Remarkably, the quantum capacitance provides insight into the changes of the electronic structure of graphene upon hydrogenation, which predicts well the suppression of the electrochemical activity based on the non-adiabatic theory of electron transfer. Thus, our work unravels the interplay between the quantum transport and electrochemical kinetics of graphene and suggests hydrogenated graphene as a potent material for sensing applications with performances going beyond previously reported graphene transistor-based sensors.

Ultrasensitive Field‐Effect Biosensors Enabled by the Unique Electronic Properties of Graphene

“…In the meanwhile, k 0 first sharply drops from 6.77 × 10 −4 cm s −1 down to ≈1.70 × 10 −4 cm s −1 (within 5 s) and then stabilizes at 1.50 × 10 −4 cm s −1 after 30 s of hydrogenation (Figure d). Thus, these studies on the interplay between the electrochemical activity and the electrical in‐plane transport of graphene, indicate that the addition of one H sp 3 defect per 100 000 carbon atoms reduces the electron transfer rate of the graphene basal plane by more than five times while preserving its excellent μ to a large extend . Indeed, quantum capacitance measurements demonstrated that the mild hydrogenation within 1–5 s effectively depresses the average density of state (ADOS) in graphene (Figure d).…”

“…In practice, the maximum transconductance point of p‐type doped graphene devices occurs in the hole conduction regime, and vice versa for n‐type doped devices. The doping effect could result from the water molecules trapped at the interface or from an unknown chemical doping, induced by the external environment or process …”

“…Such experimental artifacts at moderate or relatively high electrolyte‐gate voltages are considered of electrochemical nature, rooting on the exchange ionic current between the graphene channel and possible redox active molecules in the solution phase. As we will discuss in detail in Section , where we will probe into the interplay between the electrical in‐plane transport and the electrochemical activity of graphene, it is possible to maintain a lower level of the gate leakage by tuning the density of H‐sp 3 defects introduced by using plasma treatment …”

“…d) The electron transfer rate k 0 and average DOS (ADOS) of graphene under hydrogen radical plasma treatment with different time. Reproduced with permission . Copyright 2018, Springer Nature.…”

Bioelectronics and Interfaces Using Monolayer Graphene

“…It is reported that electronic and chemical properties of graphene are strongly dependent on the atomic arrangement of grain boundaries, intrinsic ripples and wrinkles . In the last years, many efforts have been made to understand the effect of the local defects in monolayer graphene on the observed reactivity ,,. Raman spectroscopy has proven to be a powerful tool for quantifying the density of defects in graphene samples.…”