Kinetic Ionic Permeation and Interfacial Doping of Supported Graphene

Abstract

Due to its outstanding electrical properties and chemical stability, graphene finds widespread use in various electrochemical applications. Although the presence of electrolytes strongly affects its electrical conductivity, the underlying mechanism has remained elusive. Here, we employ terahertz spectroscopy as a contact-free means to investigate the impact of ubiquitous cations (Li+, Na+, K+, and Ca2+) in aqueous solution on the electronic properties of SiO2-supported graphene. We find that, without applying any external potential, cations can shift the Fermi energy of initially hole-doped graphene by ∼200 meV up to the Dirac point, thus counteracting the initial substrate-induced hole doping. Remarkably, the cation concentration and cation hydration complex size determine the kinetics and magnitude of this shift in the Fermi level. Combined with theoretical calculations, we show that the ion-induced Fermi level shift of graphene involves cationic permeation through graphene. The interfacial cations located between graphene and SiO2 electrostatically counteract the substrate-induced hole doping effect in graphene. These insights are crucial for graphene device processing and further developing graphene as an ion-sensing material.

Drift Suppression of Solution-Gated Graphene Field-Effect Transistors by Cation Doping for Sensing Platforms

“…The results indicate that the ions were the main n-dopants. Jia et al demonstrated that ions slowly penetrated between graphene and substrates, and graphene was gradually n-doped over time [33]. This phenomenon should also occur in the proposed system.…”

“…In addition, cation-π interactions should also facilitate the adsorption of Na + onto the graphene's surface [33,34]. Furthermore, based on the results, Na + as well as other cations, such as K + , should be adsorbed.…”

“…Although we demonstrated that pre-immersion in the electrolyte solution suppressed the CNP drift, it still remains unclear which ions in D-PBS(-) account for drift suppression. It is known that cations, including K + , Na + , and Ca 2+ , are adsorbed onto graphene via cation-π interactions, leading to the same n-doping effect on graphene [33,34]. Therefore, we presumed that the cations in the electrolyte solution may have a significant impact on the CNP drift.…”

Phononics of Graphene Interfaced with Flowing Ionic Fluid: An Avenue for High Spatial Resolution Flow Sensor Applications

“…23 Therefore, adsorption of H 2 PO 4 − ions may have contributed significantly to the large n-doping observed for no flow case in Figure 2b. It is also noteworthy that Na + ions may contribute to this overall n-doping via specific mechanisms, such as intercalation between graphene and glass through holes and defects, 24 as well as bonding to oxygen functionalities on the graphene surface. 25 Now we turn our attention to the impact of the electrolyte flow on the graphene doping level.…”

Dual-mode surface-enhanced Raman scattering sensors assembled from graphene plasmonic nanoresonator on photoactive SOI

“…[16][17][18][19][20][21][22] Compared with noble metals, graphene-based materials have the advantages of chemical stability and low cost. [23][24][25][26] Unfortunately, the weak ability to absorb light (only 2.3%) of a 2D-graphene monolayer means light interacts poorly with the matter, limiting its performance in practical Raman enhancement applications. 27 3D-graphene is a natural graphene plasmonic nanoresonator arranged vertically growing on a target substrate.…”