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Liquid-phase exfoliation (LPE) has been introduced as a versatile and scalable production method for two-dimensional (2D) materials. This method yields dispersions that allow for the fabrication of printable and flexible electronic devices. However, the fabrication of uniform and homogeneous films from LPE dispersions with a performance similar to that of bottom-up grown materials remains a challenge, as the film quality strongly influences the optical and electrical performance of devices. Furthermore, long-term stability remains a major challenge for all 2D material based applications. In this study, we report on highly conductive tiled network films made of platinum diselenide (PtSe2) flakes derived using a scalable LPE method. We characterized the homogeneous films in terms of morphology and electrical behavior. As an example of applicability, we produce a chemiresistive sensor structure with the PtSe2 films and show significant resistance changes upon periodic ammonia gas exposures, revealing a sub-0.1 part per million (ppm) detection limit (DL). More remarkably the devices are fully functional after 15 months, underlining the high stability of PtSe2 based devices. [ABSTRACT FROM AUTHOR]

Sonication-assisted liquid phase exfoliation was applied to six different layered coordination polymers (CPs) in aqueous surfactant solution. The resulting nanosheets were investigated for structural and compositional integrity and microscopic analysis gives insights into the relationship between the crystal structure of the materials and their exfoliability. Larger open pores seem to favour the production of nanosheets with higher aspect ratio of lateral size to thickness. [ABSTRACT FROM AUTHOR]

To address "why we need entropy for new carbon discovery", entropy (not limited to thermodynamic entropy) is the only way to connect every carbon material. We name the Z-axis "meso-entropy world" because I want the readers to understand that "the entropy world is a dynamic world", because the Z-axis goes from the "start" to the "end" and right now in this paper (DOI: 10.1039/ c9fd00115h) it is located in the "meso" region, and because specic kinds of material (e.g. carbons) can be distinguished by their entropy values. In the case of carbon materials, for example, the entropy of amorphous carbon is larger than that of graphite and diamond since diamond's crystal structure is more ordered than that of graphite and amorphous carbon. And, we are developing higher or lower entropy sp 2 -carbons (e.g.,C 82,C 222, azulene containing PAHs,grain boundariesof graphene, etc.)every day, unfortunately randomly and independently. The lucky thing is more and more different kinds of entropies are arising, e.g., vibrational entropy, rotational entropy, conguration entropy, information Discussions FaradayDiscussions Thisjournalis©TheRoyalSocietyofChemistry2021 Faraday Discuss.,2021, 227,141-162 | 151 entropy, etc., and can be applied to understand the relationships within the rich carbon family. [Extracted from the article]

3 Thermogravimetric analysis (TGA) of Na-PHI, Ru-PHI, Pt-PHI and Ni-PHI. Could the authors comment on the stability study, such as the zeta-potential of EG/metal oxides, the particle size of metal oxides? Ivo Teixeira answered: The Na-PHI displays a very high thermal stability, i.e. 600 C(seeFig.3here).Aerthemetalexchange,itsthermalstabilityisaffected, once the metals catalyze the PHI structure decomposition. About our samples, we still do not have EXAFS for the samples Ru-PHI and Pt-PHI reported in this manuscript (DOI: 10.1039/c9fd00112c), however, we just performed EXAFS for Ni-PHI, Fe-PHI and Co-PHI all prepared by the same cationexchangemethod. [Extracted from the article]

Alessandro Molle responded: Al 2 O 3 encapsulation of Xenes was engineered to minimizeornullifytheeffectonthesiliceneandmoregenerallyontheXenes. Alessandro Molle answered: The DFT simulation is reported as a conceptual experiment to sustain the experimental picture resulting from the XPS and Raman spectroscopy evidence of silicene stabilization aer encapsulation. Claudia Backes, Szymon Bartus, Cinzia Casiraghi, Andrea Ferrari, Ali Reza Kamali, Miroslav Kol ' ibal, Vimal Kumar, Alessandro Molle, Andrea Oyarzun, Vincenzo Palermo, Amretashis Sengupta, Alessandro Silvestri and Hua Zhang DOI: 10.1039/D1FD90006D Alessandro Silvestri opened the discussion of the paper by Alessandro Molle: Can the encapsulation technique described in the paper affect the chemicalphysical properties of the 2D material encapsulated? Thisfact stems from the details of the Al 2 O 3 growth, namely Al 2 O 3 is sequentially grown aer silicene,developingrstthroughAlsinglelayergrowthfollowedbyAl-O 2 co-deposition at room temperature, eventually ending up with a nal Al 2 O 3 layer with controlled thickness. [Extracted from the article]

In the case of Raman spectroscopy, bulk hBN gives a prominent E 2g phonon mode around 1340-1345 cm 1, whereas, the hBN akes give a Raman signal slightly lower than the bulk material, and hBN QDs give a much weaker phonon mode as compared to both the bulk andakes. Claudia Backes, Ranjan Kumar Behera, Alberto Bianco, Cinzia Casiraghi, Huan Doan, Alejandro Criado, Fernando Galembeck, Stuart Goldie, Alfredo Maria Gravagnuolo, Hui-Lei Hou, Ali Reza Kamali, Kostas Kostarelos, Vimal Kumar, WaiHinLee,NataliaMartsinovich, VincenzoPalermo,MatteoPalma, Jinbo Pang, Maurizio Prato, Paolo Samori, Alessandro Silvestri, Suman Singh, Michael Strano and Cecilia Wetzl DOI: 10.1039/D1FD90003J Ali Reza Kamali opened a general discussion of the paper by Alberto Bianco: Nicework! If we talk about hBN, the relationship between the hBN quantum dot size and PL emission is not, however, explored by the researchers as far as our information is concerned, as this material is relatively new. (2) Mechanical exfoliation (sonication) is the most common method used for the synthesis of hBN quantum dots and hBNakes from the bulk hBN material. [Extracted from the article]

The layered compound Ni2P2S6 was electrochemically characterized for application as an anode material in sodium-ion batteries (SIBs). A high reversible capacity of 621 mA h g−1 at 1 A g−1 was achieved after 190 cycles. The investigation of the complex reaction mechanism of the conversion reaction was performed applying complementary techniques including X-ray powder diffraction, pair distribution function analysis, X-ray absorption spectroscopy, 19F/23Na/31P MAS NMR, TEM and nano-EDX. The results highlight that Na uptake for up to 5 Na per formula unit (f.u.) led to reduction of Ni2+ to metallic Ni nanoparticles and concomitant formation of an intermediate compound Na4P2S6. Increasing the Na content to 12 Na per f.u. generates nanocrystalline Na2S, which is accompanied by the loss of the long-range order of the pristine sample. In the completely discharged state elemental Ni and Na2S are present, but in contrast to literature reports, no evidence for the formation of NaxP phases was found. During the charge process, Ni3S2 is formed upon the release of ∼11.7 Na per f.u. [ABSTRACT FROM AUTHOR]

Thus far, research activities of 2D materials in optics, photonics and optoelectronics predominantly focus on micromechanically cleaved or grown nanosheets. Here, we show that high quality liquid-exfoliated nanosheets offer an alternative approach. Starting from well-defined, monolayer rich WS2 dispersions obtained after liquid exfoliation and size selection in aqueous surfactant, we present an optimised protocol facilitating transfer of the nanosheets to a polymer solution in organic media. From such dispersions, we fabricate WS2–polymer thin films by spin coating. The characteristic photoluminescence of WS2 monolayers is retained in the film at 2.04 eV without broadening (line width 40 meV) or significant changes in the line-shape. This confirms that nanosheet aggregation is efficiently prevented on transfer and deposition. The films are extremely smooth and uniform over large areas with a root mean square roughness <0.5 nm. To demonstrate the potential in optical applications, the nonlinear optical response was studied, revealing promise as optical limiter. In addition, we show that the photoluminescence can be manipulated by coupling the exciton response to cavity photons in a Ag microcavity. [ABSTRACT FROM AUTHOR]

Hierarchical nanostructures have attracted considerable attention for rechargeable battery systems since they combine the benefits of size effects induced by nanoscaling with the integrity of bulk materials. Despite significant progress, the hierarchical structures reported so far are designed only down to the nanoscale. To improve the battery performance, downsizing the designed building blocks of the hierarchical structure to smaller scales (molecular or even atomic level) is essential. This novel concept has been realized in a MoS2/C composite system, where MoS2 and N-doped carbon molecular layers are alternately stacked to form nanosheet building blocks, which are further assembled into a porous nanorod structure. This hierarchical heterostructure converts the guiding principle of sub-nanoscale engineering into practice, aiming at increasing the interfaces between MoS2 and carbon towards the largest possible molecular contact level. The resultant MoS2/N-doped carbon porous nanorods (MoS2/NC-PNR) electrode exhibits outstanding performances in lithium-ion batteries including high initial discharge capacity of ∼1300 mA h g−1, cycling stability for 700 cycles and excellent rate performance (443 mA h g−1 at 10C). The outstanding performance of the MoS2/NC-PNR superstructure illustrates the enormous potential of the hierarchically designed 2D compounds from molecular layer level, which could be extended to other layered materials. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) semiconductors, such as ultrathin layers of transition metal dichalcogenides (TMDs), offer a unique combination of electronic, optical and mechanical properties, and hold potential to enable a host of new device applications spanning from flexible/wearable (opto)electronics to energy-harvesting and sensing technologies. A critical requirement for developing practical and reliable electronic devices based on semiconducting TMDs consists in achieving a full control over their charge-carrier polarity and doping. Inconveniently, such a challenging task cannot be accomplished by means of well-established doping techniques (e.g. ion implantation and diffusion), which unavoidably damage the 2D crystals resulting in degraded device performances. Nowadays, a number of alternatives are being investigated, including various (supra)molecular chemistry approaches relying on the combination of 2D semiconductors with electroactive donor/acceptor molecules. As yet, a large variety of molecular systems have been utilized for functionalizing 2D TMDs via both covalent and non-covalent interactions. Such research endeavours enabled not only the tuning of the charge-carrier doping but also the engineering of the optical, electronic, magnetic, thermal and sensing properties of semiconducting TMDs for specific device applications. Here, we will review the most enlightening recent advancements in experimental (supra)molecular chemistry methods for tailoring the properties of atomically-thin TMDs – in the form of substrate-supported or solution-dispersed nanosheets – and we will discuss the opportunities and the challenges towards the realization of novel hybrid materials and devices based on 2D semiconductors and molecular systems. [ABSTRACT FROM AUTHOR]

Here we demonstrate that liquid phase exfoliation can be used to convert layered crystals of nickel hydroxide into Ni(OH)2 nanosheets in relatively large quantities and without the need for ion intercalation. While other procedures require harsh synthesis conditions and multiple reaction steps, this method involves ultrasonication of commercially available powders in aqueous surfactant solutions and so is relatively mild and potentially scalable. Such mild exfoliation is possible because the surface energy of Ni(OH)2, as measured by inverse gas chromatography, is relatively low at ∼70 mJ m−2, similar to other layered materials. TEM, AFM, XPS and Raman spectroscopy show the exfoliated nanosheets to be relatively thin (mean ∼10 monolayers thick) and of good quality. Size selection by liquid cascade centrifugation allowed the production of samples with mean nanosheet lengths ranging from 55 to 195 nm. Optical measurements on dispersions showed the optical absorption coefficient spectra to be relatively invariant with nanosheet size while the scattering coefficient spectra varied strongly with size. The resultant size-dependence allows the extinction spectra to be used to estimate nanosheet size as well as concentration. We used the exfoliated nanosheets to prepare thin film electrodes for use in supercapacitors and as oxygen evolution catalysts. While the resultant capacitance was reasonably high at ∼1200 F cm−3 (20 mV s−1), the catalytic performance was exceptional with currents of 10 mA cm−2 observed at overpotentials as low as 297 mV, close to the state of the art. [ABSTRACT FROM AUTHOR]

An efficient, high-throughput method for the formation of densely packed molecular films on graphene is reported. The films exhibit high stability and remain intact during a subsequent derivatisation reaction, offering a versatile route for the non-covalent functionalisation of graphene. [ABSTRACT FROM AUTHOR]

Solution-exfoliated MoS2 nano-platelets were formed into thin films by deposition onto a water surface followed by transfer to indium tin oxide coated glass. After drying, a gold electrode was evaporated on top to give a sandwich structure with quasi-Ohmic contacts. Illumination of this device with broadband light of ∼1 kW m−2 intensity gave a fourfold increase in conductivity. The photocurrent increased sub-linearly with intensity and exponentially with time indicating the presence of traps. The photo-responsively at low intensity was ∼10−4 A per W at 15 V. This work demonstrates the potential for liquid-exfoliated, inorganic nanosheets to be fabricated into low-cost optoelectronic devices. [ABSTRACT FROM AUTHOR]

HiPco and CoMoCAT single-walled carbon nanotubes (SWCNT) were fractionated with the aid of a novel perylene bisimide surfactant by combined co-surfactant and replacement density gradient ultracentrifugation (DGU). [ABSTRACT FROM AUTHOR]

HiPco and CoMoCAT single-walled carbon nanotubes (SWCNT) were fractionated with the aid of a novel perylene bisimide surfactant by combined co-surfactant and replacement density gradient ultracentrifugation (DGU). [ABSTRACT FROM AUTHOR]

Sonication-assisted liquid phase exfoliation was applied to six different layered coordination polymers (CPs) in aqueous surfactant solution. The resulting nanosheets were investigated for structural and compositional integrity and microscopic analysis gives insights into the relationship between the crystal structure of the materials and their exfoliability. Larger open pores seem to favour the production of nanosheets with higher aspect ratio of lateral size to thickness.