New Insights into the Electronic Transport of Reduced Graphene Oxide Using Scanning Electrochemical Microscopy

Electronic Transport of MoS2 Monolayered Flakes Investigated by Scanning Electrochemical Microscopy

The amazing properties of 2D materials are envisioned to revolutionize several domains such as flexible electronics, electrocatalysis, or biosensing. Herein we introduce scanning electrochemical microscopy (SECM) as a tool to investigate molybdenum disulfide in a straightforward fashion, providing localized information regarding the electronic transport within chemical vapor deposition (CVD)-grown crystalline MoS₂ single layers having micrometric sizes. Our investigations show that within flakes assemblies some flakes are well electrically interconnected, with no detectable contact resistance, whereas others are not electrically connected at all, independent of the size of the physical contact between them. Overall, the work shows how the complex electronic behavior of MoS₂ flake assemblies (semiconducting nature, contact quality between flakes) can be investigated with SECM.

Silver-decorated reduced graphene oxides as novel building blocks for transparent conductive films

Silver-decorated reduced graphene oxides as the building blocks for transparent conducting electrodes.

Current and future directions in electron transfer chemistry of graphene

The participation of graphene in electron transfer chemistry, where an electron is transferred between graphene and other species, encompasses many important processes that have shown versatility and potential for use in important applications.

Synergistic Amination of Graphene: Molecular Dynamics and Thermodynamics

Functionalization of graphene using organic moieties constitutes an affordable way to modulate its physical and chemical properties. Finding an exact structural formula of functionalized graphene using experimental approaches is challenging. We studied in detail the thermal stability and thermodynamics of amino- and ethylamino-graphene and found a surprising synergistic effect: more amino groups stabilize functionalized graphene favoring further amination, whereas a small concentration of amino groups is unstable in many cases. The functional groups can be attached either on the same side or simultaneously on different sides of the graphene sheet. Deformation of functionalized graphene is proportional to the number of amino groups. Complete amination leading to formation of the ultimate product, Cx(NH2)x, is hindered sterically. Our study assists in the determination of the structure of chemically modified graphene and makes specific predictions that can be tested and validated experimentally.

Versatile Wafer-Scale Technique for the Formation of Ultrasmooth and Thickness-Controlled Graphene Oxide Films Based on Very Large Flakes

We present a new strategy to form thickness-adjusted and ultrasmooth films of very large and unwrinkled graphene oxide (GO) flakes through the transfer of both hemispherical and vertical water films stabilized by surfactants. With its versatility in terms of substrate type (including flexible organic substrates) and in terms of flake density (from isolated flakes to continuous and multilayer films), this wafer-scale assembly technique is adapted to a broad range of experiments involving GO and rGO (reduced graphene oxide). We illustrate its use through the evaluation of transparent rGO electrodes.

Patterned Carboxylation of Graphene Using Scanning Electrochemical Microscopy

A simple, direct, and versatile scanning electrochemical microscopy (SECM) approach for local carboxylation of multilayered graphene on nickel is demonstrated, in which carbon dioxide serves as the carboxylation agent under reductive conditions in N,N-dimethylformamide. The use of SECM gives control over both the spatial dimensions and the degree of carboxylation. While the pattern size, in general, is governed by the dimension of the SECM tip, the degree of modification, expressed as the surface coverage of carboxylate groups introduced at the graphene substrate, is found to be controlled by the electrolysis time. This is supported by electrochemical measurements, two-dimensional X-ray photoelectron spectroscopy, Raman spectroscopy mapping, and He ion microscopy. Surprisingly, intercalation of the supporting electrolyte in the multilayered graphene on nickel occurs to a relatively small extent when compared to corresponding results obtained in previously described carboxylations of this kind of multilayered graphene.