Electrochemically exfoliated graphene (EEG) possesses optical and electronic properties that are markedly different from those of the more explored graphene oxide in both its pristine and reduced forms. EEG also holds a unique advantage compared to other graphenes produced by exfoliation in liquid media: it can be obtained in large quantities in a short time. However, an in-depth understanding of the structure-properties relationship of this material is still lacking. In this work, we report physicochemical characterization of EEG combined with an investigation of the electronic properties of this material carried out both at the single flake level and on the films. Additionally, we use for the first time microwave irradiation to reduce the EEG and demonstrate that the oxygen functionalities are not the bottleneck for charge transport in EEG, which is rather hindered by the presence of structural defects within the basal plane.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are continuously attracting attention for both fundamental studies and technological applications. The physical and chemical properties of ultrathin TMD sheets are extraordinarily different from those of the corresponding bulk materials and for this reason their production is a stimulating topic, especially when the preparation method enables to obtain a remarkable yield of nanosheets with large area and high quality. Herein, we present a fast (<1 hour) electrochemical exfoliation of molybdenum disulfide (MoS 2) via lithium-ion intercalation, by using a solution of lithium chloride in dimethyl sulfoxide (DMSO). Unlike the conventional intercalation methods based on dangerous organolithium compounds, our approach leads to the possibility to obtain mono-, bi-and tri-layer thick MoS 2 nanosheets with a large fraction of the semiconducting 2H phase (~60%), as estimated by X-ray photoelectron spectroscopy (XPS). The electrical properties of the exfoliated material were investigated through the fabrication and characterization of back-gated field-effect transistors (FETs) based on individual MoS 2 nanosheets. As-fabricated devices displayed unipolar semiconducting behavior (n-type) with field-effect mobility µ FE ≤ 10-3 cm 2 V-1 s-1 and switching ratio I on /I off ≤ 10, likely limited by 1T/2H polymorphism and defects (e.g. sulfur vacancies) induced during the intercalation/exfoliation process. A significant enhancement of the electrical performances could be achieved through a combination of vacuum annealing (150 °C) and sulfur-vacancy healing with vapors of short-chain alkanethiols, resulting in µ FE up to 2×10-2 cm 2 V-1 s-1 and I on /I off ≈ 100. Our results pave the way towards the fast preparation ─ under ambient conditions ─ of semiconducting MoS 2 nanosheets, suitable for application in low cost (opto-)electronic devices.

Within the last two decades, dynamic covalent chemistry (DCC) has emerged as an efficient and versatile strategy for the design and synthesis of complex molecular systems in solution. While early examples of supramolecularly assisted covalent synthesis at surfaces relied strongly on kinetically controlled reactions for post-assembly covalent modification, the DCC method takes advantage of the reversible nature of bond formation and allows the generation of the new covalently bonded structures under thermodynamic control. These structurally complex architectures obtained by means of DCC protocols offer a wealth of solutions and opportunities in the generation of new complex materials that possess sophisticated properties. In this focus review we examine the formation of covalently bonded imine-based discrete nanostructures as well as one-dimensional (1D) polymers and two-dimensional (2D) covalent organic frameworks (COFs) physisorbed on solid substrates under various experimental conditions, for example, under ultra-high vacuum (UHV) or at the solid-liquid interface. Scanning tunneling microscopy (STM) was used to gain insight, with a sub-nanometer resolution, into the structure and properties of those complex nanopatterns.

properties, thereby allowing NOT and NAND gates with wellcentered trip point and good noise margin. Our findings provide unambiguous evidence that Ti 3 C 2 T x surface electronic property can be tuned by intercalant chemistry and surface termination, which further alters the device characteristics by enhancing their functional complexity. Finally, the presented results and methodology provide an intercalant-engineering perspective for hybrid devices based on 2D materials and functional molecules.

Dispersions of high-quality 2D nanosheets are produced by liquid-phase exfoliation of vermiculite clay, resulting in thermally insulating printable inks.

No abstract

Here we show how temperature and reaction time are key towards efficient chemical exfoliation of MoS2 into monolayer thick flakes with controlled content of metallic vs. semiconductive sheets.

Transition metal carbides and nitrides (MXenes) are an emerging class of 2D materials, which are attracting ever-growing attention due to their remarkable physicochemical properties. The presence of various surface functional groups on MXenes' surface, e.g., -F, -O, -OH, -Cl, opens the possibility to tune their properties through chemical functionalization approaches. However, only a few methods have been explored for the covalent functionalization of MXenes and include diazonium salt grafting and silylation reactions. Here, an unprecedented two-step functionalization of Ti 3 C 2 T x MXenes is reported, where (3-aminopropyl)triethoxysilane is covalently tethered to Ti 3 C 2 T x and serves as an anchoring unit for subsequent attachment of various organic bromides via the formation of C-N bonds. Thin films of Ti 3 C 2 T x functionalized with linear chains possessing increased hydrophilicity are employed for the fabrication of chemiresistive humidity sensors. The devices exhibit a broad operation range (0-100% relative humidity), high sensitivity (0.777 or 3.035), a fast response/recovery time (0.24/0.40 s 𝚫H −1 , respectively), and high selectivity to water in the presence of saturated vapors of organic compounds. Importantly, our Ti 3 C 2 T x -based sensors display the largest operating range and a sensitivity beyond the state of the art of MXenes-based humidity sensors. Such outstanding performance makes the sensors suitable for real-time monitoring applications.