Few-layer black phosphorus (BP) is a new two-dimensional material which is of great interest for applications, mainly in electronics. However, its lack of environmental stability severely limits its synthesis and processing. Here we demonstrate that high-quality, few-layer BP nanosheets, with controllable size and observable photoluminescence, can be produced in large quantities by liquid phase exfoliation under ambient conditions in solvents such as N-cyclohexyl-2-pyrrolidone (CHP). Nanosheets are surprisingly stable in CHP, probably due to the solvation shell protecting the nanosheets from reacting with water or oxygen. Experiments, supported by simulations, show reactions to occur only at the nanosheet edge, with the rate and extent of the reaction dependent on the water/oxygen content. We demonstrate that liquid-exfoliated BP nanosheets are potentially useful in a range of applications from ultrafast saturable absorbers to gas sensors to fillers for composite reinforcement.

Graphene, a truly two-dimensional and fully π-conjugated honeycomb carbon network, is currently evolving into the most promising successor to silicon in micro- and nanoelectronic applications. However, its wider application is impeded by the difficulties in opening a bandgap in its gapless band-structure, as well as the lack of processability in the resultant intrinscially insoluble material. Covalent chemical modification of the π-electron system is capable of addressing both of these issues through the introduction of variable chemical decoration. Although there has been significant research activity in the field of functionalized graphene, most work to date has focused on the use of graphene oxide. In this Article, we report on the first wet chemical bulk functionalization route beginning with pristine graphite that does not require initial oxidative damage of the graphene basal planes. Through effective reductive activation, covalent functionalization of the charged graphene is achieved by organic diazonium salts. Functionalization was observed spectroscopically, and successfully prevents reaggregation while providing solubility in common organic media.

Although transition metal dichalcogenides such as MoS2 have been recognized as highly potent two-dimensional nanomaterials, general methods to chemically functionalize them are scarce. Herein, we demonstrate a functionalization route that results in organic groups bonded to the MoS2 surface via covalent C-S bonds. This is based on lithium intercalation, chemical exfoliation and subsequent quenching of the negative charges residing on the MoS2 by electrophiles such as diazonium salts. Typical degrees of functionalization are 10-20 atom % and are potentially tunable by the choice of intercalation conditions. Significantly, no further defects are introduced, and annealing at 350 °C restores the pristine 2H-MoS2. We show that, unlike both chemically exfoliated and pristine MoS2, the functionalized MoS2 is very well dispersible in anisole, confirming a significant modification of the surface properties by functionalization. DFT calculations show that the grafting of the functional group to the sulfur atoms of (charged) MoS2 is energetically favorable and that S-C bonds are formed.

We report on a fast and simple method to produce highly stable isopropanol/water (4:1) suspensions of few‐layer antimonene by liquid‐phase exfoliation of antimony crystals in a process that is assisted by sonication but does not require the addition of any surfactant. This straightforward method generates dispersions of few‐layer antimonene suitable for on‐surface isolation. Analysis by atomic force microscopy, scanning transmission electron microscopy, and electron energy loss spectroscopy confirmed the formation of high‐quality few‐layer antimonene nanosheets with large lateral dimensions. These nanolayers are extremely stable under ambient conditions. Their Raman signals are strongly thickness‐dependent, which was rationalized by means of density functional theory calculations.

Herein, we have developed a systematic study on the oxidation and passivation of mechanically exfoliated black phosphorus (BP). We analyzed the strong anisotropic behavior of BP by scanning Raman microscopy providing an accurate method for monitoring the oxidation of BP via statistical Raman spectroscopy. Furthermore, different factors influencing the environmental instability of the BP, i.e., thickness, lateral dimensions or visible light illumination, have been investigated in detail. Finally, we discovered that the degradation of few-layer BP flakes of <10 nm can be suppressed for months by using ionic liquids, paving the way for the development of BP-based technologies.

Black phosphorus (BP) was functionalized with organic moieties on the basis of liquid exfoliation. The treatment of BP with electron-withdrawing 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) led to electron transfer from BP to the organic dopant. On the other hand, the noncovalent interaction of BP with a perylene diimide was mainly due to van der Waals interactions but also led to considerable stabilization of the BP flakes against oxygen degradation.

Single-wall carbon nanotubes (SWNTs) are emerging as materials with much potential in several disciplines, in particular in electronics and photovoltaics. The combination of SWNTs with electron donors or acceptors generates active materials, which can produce electrical energy when irradiated. However, SWNTs are very elusive species when characterization of their metastable states is required. This problem mainly arises because of the polydispersive nature of SWNT samples and the inevitable presence of SWNTs in bundles of different sizes. Here, we report the complete and thorough characterization of an SWNT radical ion-pair state induced by complexation with a perylene dye, which combines excellent electron-accepting and -conducting features with a five-fused ring π-system. At the same time, the perylene dye enables the dispersion of SWNTs by means of π-π interactions, which gives individual SWNTs in solution. This work clears a path towards electronic and optoelectronic devices in which regulated electrical transport properties are important.

We present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures. We adopt a ‘hands-on’ approach, providing practical details and procedures as derived from literature as well as from the authors’ experience, in order to enable the reader to reproduce the results. Section is devoted to ‘bottom up’ approaches, whereby individual constituents are pieced together into more complex structures. We consider graphene nanoribbons (GNRs) produced either by solution processing or by on-surface synthesis in ultra high vacuum (UHV), as well carbon nanomembranes (CNM). Production of a variety of GNRs with tailored band gaps and edge shapes is now possible. CNMs can be tuned in terms of porosity, crystallinity and electronic behaviour. Section covers ‘top down’ techniques. These rely on breaking down of a layered precursor, in the graphene case usually natural crystals like graphite or artificially synthesized materials, such as highly oriented pyrolythic graphite, monolayers or few layers (FL) flakes. The main focus of this section is on various exfoliation techniques in a liquid media, either intercalation or liquid phase exfoliation (LPE). The choice of precursor, exfoliation method, medium as well as the control of parameters such as time or temperature are crucial. A definite choice of parameters and conditions yields a particular material with specific properties that makes it more suitable for a targeted application. We cover protocols for the graphitic precursors to graphene oxide (GO). This is an important material for a range of applications in biomedicine, energy storage, nanocomposites, etc. Hummers’ and modified Hummers’ methods are used to make GO that subsequently can be reduced to obtain reduced graphene oxide (RGO) with a variety of strategies. GO flakes are also employed to prepare three-dimensional (3d) low density structures, such as sponges, foams, hydro- or aerogels. The assembly of flakes into 3d structures can provide improved mechanical properties. Aerogels with a highly open structure, with interconnected hierarchical pores, can enhance the accessibility to the whole surface area, as relevant for a number of applications, such as energy storage. The main recipes to yield graphite intercalation compounds (GICs) are also discussed. GICs are suitable precursors for covalent functionalization of graphene, but can also be used for the synthesis of uncharged graphene in solution. Degradation of the molecules intercalated in GICs can be triggered by high temperature treatment or microwave irradiation, creating a gas pressure surge in graphite and exfoliation. Electrochemical exfoliation by applying a voltage in an electrolyte to a graphite electrode can be tuned by varying precursors, electrolytes and potential. Graphite electrodes can be either negatively or positively intercalated to obtain GICs that are subsequently exfoliated. We also discuss the materials that can be amenable to exfoliation, by ...