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Originating from the hexagonal arrangement of magnetic ions in the presence of strong spin orbit coupling, α -RuCl3 is considered as model system for the Kitaev-Heisenberg model. While the magnetic properties of α -RuCl3 have been studied in bulk single crystals or micromechanically-exfoliated nanosheets, little is known about the nanosheets' properties after exfoliation by techniques suitable for mass production such as liquid phase exfoliation (LPE). Here, we demonstrate sonication-assisted LPE on α -RuCl3 single crystals in an inert atmosphere. Coupled with centrifugation-based size selection techniques, the accessible size- and thickness range is quantified by statistical atomic force microscopy. Individual nanosheets obtained after centrifugation-based size selection are subjected to transmission electron microscopy to confirm their structural integrity after the exfoliation. The results are combined with bulk characterisation methods, including Raman and x-ray photoelectron spectroscopy, and powder diffraction experiments to evaluate the structural integrity of the nanosheets. We report changes of the magnetic properties of the nanomaterial with nanosheet size, as well as photospectroscopic metrics for the material concentration and average layer number. Finally, a quantitative analysis on environmental effects on the nanomaterial integrity is performed based on time and temperature dependent absorbance spectroscopy revealing a relatively slow decay (half-life of ∼2000 h at 20 °C), albeit with low activation energies of 6–20 kJ mol−1. [ABSTRACT FROM AUTHOR]

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]

Increasing the energy density of lithium‐ion batteries requires the discovery of new electrode materials capable of achieving very high areal capacity. Here, liquid phase exfoliation is used to produce nanosheets of SnP3, a 2D material with extremely high theoretical capacity of 1670 mAh g−1. These nanosheets can be fabricated into solution‐processed thin films for use as lithium storing anodes. To maximize their performance, carbon nanotubes are incorporated into the electrodes to simultaneously enhance conductivity and toughness. As a result, electrodes of thickness >300 µm can be produced, which display active‐mass‐normalized capacities (≈1657 mAh g−1Active) very close to the theoretical value. These materials show maximum specific (≈1250 mAh g−1Electrode) and areal (>20 mAh cm−2) capacities, which are at the state‐of‐the‐art for 2D‐based electrodes, coupled with good rate performance and stability. In combination with commercial cathode materials, full‐cells are fabricated with areal capacities of ≈29 mAh cm−2 and near‐record energy densities approaching 1000 Wh L−1. [ABSTRACT FROM AUTHOR]

The compound {[Mn(teta)]4V16As4O42(H2O)}n ⋅ 10 H2O (teta=triethylenetetraamine) was synthesized under solvothermal conditions. The crystal structure consists of layers composed of {V16As4O42} moieties joined by O−Mn−O bridges. The crystal water molecules can be thermally removed and they are reintegrated in humid atmosphere. The water sorption occurs in two steps indicating differing strengths of hydrogen bonding interactions. Investigations of the magnetic properties present evidence that the antiferromagnetic exchange interactions between the spins of the Mn2+ and of the V4+ cations are relatively strong. The magnetocaloric effect could be observed but is relatively small due to the antiferromagnetic exchange. Using liquid phase exfoliation, small crystallites with thicknesses as low as 10 nm could be obtained, while larger crystallites exhibit thicknesses of 20–40 nm. [ABSTRACT FROM AUTHOR]

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]

In recent years, various functionalization strategies for transition‐metal dichalcogenides have been explored to tailor the properties of materials and to provide anchor points for the fabrication of hybrid structures. Herein, new insights into the role of the surfactant in functionalization reactions are described. Using the spontaneous reaction of WS2 with chloroauric acid as a model reaction, the regioselective formation of gold nanoparticles on WS2 is shown to be heavily dependent on the surfactant employed. A simple model is developed to explain the role of the chosen surfactant in this heterogeneous functionalization reaction. The surfactant coverage is identified as the crucial element that governs the dominant reaction pathway and therefore can severely alter the reaction outcome. This study shows the general importance of the surfactant choice and how detrimental or beneficial a certain surfactant can be to the desired functionalization. [ABSTRACT FROM AUTHOR]

In recent years, various functionalization strategies for transition‐metal dichalcogenides have been explored to tailor the properties of materials and to provide anchor points for the fabrication of hybrid structures. Herein, new insights into the role of the surfactant in functionalization reactions are described. Using the spontaneous reaction of WS2 with chloroauric acid as a model reaction, the regioselective formation of gold nanoparticles on WS2 is shown to be heavily dependent on the surfactant employed. A simple model is developed to explain the role of the chosen surfactant in this heterogeneous functionalization reaction. The surfactant coverage is identified as the crucial element that governs the dominant reaction pathway and therefore can severely alter the reaction outcome. This study shows the general importance of the surfactant choice and how detrimental or beneficial a certain surfactant can be to the desired functionalization. [ABSTRACT FROM AUTHOR]

High quality opal‐like photonic crystals containing graphene are fabricated using evaporation‐driven self‐assembly of soft polymer colloids. A miniscule amount of pristine graphene within a colloidal crystal lattice results in the formation of colloidal crystals with a strong angle‐dependent structural color and a stop band that can be reversibly shifted across the visible spectrum. The crystals can be mechanically deformed or can reversibly change color as a function of their temperature, hence their sensitive mechanochromic and thermochromic response make them attractive candidates for a wide range of visual sensing applications. In particular, it is shown that the crystals are excellent candidates for visual strain sensors or integrated time‐temperature indicators which act over large temperature windows. Given the versatility of these crystals, this method represents a simple, inexpensive, and scalable approach to produce multifunctional graphene infused synthetic opals and opens up exciting applications for novel solution‐processable nanomaterial based photonics. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) molybdenum disulfide (MoS2) holds great promise in electronic and optoelectronic applications owing to its unique structure and intriguing properties. The intrinsic defects such as sulfur vacancies (SVs) of MoS2 nanosheets are found to be detrimental to the device efficiency. To mitigate this problem, functionalization of 2D MoS2 using thiols has emerged as one of the key strategies for engineering defects. Herein, we demonstrate an approach to controllably engineer the SVs of chemically exfoliated MoS2 nanosheets using a series of substituted thiophenols in solution. The degree of functionalization can be tuned by varying the electron‐withdrawing strength of substituents in thiophenols. We find that the intensity of 2LA(M) peak normalized to A1g peak strongly correlates to the degree of functionalization. Our results provide a spectroscopic indicator to monitor and quantify the defect engineering process. This method of MoS2 defect functionalization in solution also benefits the further exploration of defect‐free MoS2 for a wide range of applications. [ABSTRACT FROM AUTHOR]

New luminogens for aggregation‐induced emission (AIE), which are characterized by a branched cross‐conjugated 2,6‐bis(1,2,2‐triarylvinyl)pyridine motif, have been synthesized exploiting the one‐pot Ti‐mediated tetraarylation of 2,6‐bis(arylethynyl)pyridines. Thin layer solid‐state emitters were prepared by spin‐coating of the luminogens, while AIE‐colloidal dispersions were investigated in terms of optical density and scattering behaviour. This has given insight into particle size distributions, time evolution of the aggregation and the influence of different functionalization patterns on the luminescence of molecular aggregates. In particular, a combination of extinction spectroscopy and dynamic light scattering is being proposed as a powerful method for investigating the dynamic aggregation process in AIE‐type colloids. [ABSTRACT FROM AUTHOR]

2D polymer sheets with six positively charged pyrylium groups at each pore edge in a stacked single crystal can be transformed into a 2D polymer with six pyridines per pore by exposure to gaseous ammonia. This reaction furnishes still a crystalline material with tunable protonation degree at regular nano‐sized pores promising as separation membrane. The exfoliation is compared for both 2D polymers with the latter being superior. Its liquid phase exfoliation yields nanosheet dispersions, which can be size‐selected using centrifugation cascades. Monolayer contents of ≈30 % are achieved with ≈130 nm sized sheets in mg quantities, corresponding to tens of trillions of monolayers. Quantification of nanosheet sizes, layer number and mass shows that this exfoliation is comparable to graphite. Thus, we expect that recent advances in exfoliation of graphite or inorganic crystals (e.g. scale‐up, printing etc.) can be directly applied to this 2D polymer as well as to covalent organic frameworks. [ABSTRACT FROM AUTHOR]

2D polymer sheets with six positively charged pyrylium groups at each pore edge in a stacked single crystal can be transformed into a 2D polymer with six pyridines per pore by exposure to gaseous ammonia. This reaction furnishes still a crystalline material with tunable protonation degree at regular nano‐sized pores promising as separation membrane. The exfoliation is compared for both 2D polymers with the latter being superior. Its liquid phase exfoliation yields nanosheet dispersions, which can be size‐selected using centrifugation cascades. Monolayer contents of ≈30 % are achieved with ≈130 nm sized sheets in mg quantities, corresponding to tens of trillions of monolayers. Quantification of nanosheet sizes, layer number and mass shows that this exfoliation is comparable to graphite. Thus, we expect that recent advances in exfoliation of graphite or inorganic crystals (e.g. scale‐up, printing etc.) can be directly applied to this 2D polymer as well as to covalent organic frameworks. [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]

Abstract: Identifying cheap, yet effective, oxygen evolution catalysts is critical to the advancement of water splitting. Using liquid exfoliated Co(OH)2 nanosheets as a model system, a simple procedure is developed to maximize the activity of any oxygen evolution reaction nanocatalyst. First the nanosheet edges are confirmed as the active areas by analyzing the catalytic activity as a function of nanosheet size. This allows the authors to select the smallest nanosheets (length ≈50 nm) as the best performing catalysts. While the number of active sites per unit electrode area can be increased via the electrode thickness, this is found to be impossible beyond ≈10 µm due to mechanical instabilities. However, adding carbon nanotubes increases both toughness and conductivity significantly. These enhancements mean that composite electrodes consisting of small Co(OH)2 nanosheets and 10 wt% nanotubes can be made into freestanding films with thickness of up to 120 µm with no apparent electrical limitations. The presence of diffusion limitations results in an optimum electrode thickness of 70 µm, yielding a current density of 50 mA cm−2 at an overpotential of 235 mV, close to the state of the art in the field. Applying this procedure to a high‐performance catalyst such as NiFeOx should significantly surpass the state of the art. [ABSTRACT FROM AUTHOR]

Liquid exfoliation and centrifugation based size selection has emerged as widely applied technique to produce nanosheets in a solution-processable form. Quantitative spectroscopic metrics to extract nanosheet size, thickness and monolayer content from optical spectra have previously been established. Such metrics are extremely useful and can be used to optimise the production technique (for example on scale-up) and size selection. However, it is not clear whether exfoliation, size selection, and spectroscopic metrics are robust or whether the result depends on the starting material or subtle details of the processing and analysis. By comparing two batches of WS2 exfoliated and size-selected in aqueous surfactant solution using different starting materials, protocols and equipment in each step, we show that the nanosheet size obtained after different steps in a cascade centrifugation is highly reproducible. A detailed statistical analysis on the nanosheet dimensions revealed well-defined relationships between nanosheet mean thickness and monolayer content. Spectroscopic metrics for nanosheet layer number, lateral size (from extinction) and monolayer content (from Raman/photoluminescence) do not depend on sample type and measurement conditions, albeit the data analysis may require adjustment as discussed. [ABSTRACT FROM AUTHOR]

Augmented plasmonic damping of dipole-resonant gold (Au) nanoparticles (NP) physicochemically bonded onto edges of tungsten disulfide (WS2) nanosheets, ostensibly due to hot electron injection, is quantified using electron energy loss spectroscopy (EELS). EELS allows single-particle spatial resolution. A measured 0.23 eV bandwidth expansion of the localized surface plasmon resonance upon covalent bonding of 20 nm AuNP to WS2 edges was deemed significant by Welch’s t-test. Approximately 0.19 eV of the measured 0.23 eV expansion went beyond conventional radiative and nonradiative damping mechanisms according to discrete dipole models, ostensibly indicating emergence of hot electron transport from AuNP into the WS2. A quantum efficiency of up to 11±5% spanning a 7 fs transfer process across the optimized AuNP-TMD ohmic junction is conservatively calculated. Putative hot electron transport for AuNP physicochemically bonded to TMD edges exceeded that for AuNP physically deposited onto the TMD basal plane. This arose from contributions due to (i) direct physicochemical bond between AuNP and WS2; (ii) AuNP deposition at TMD edge sites; and (iii) lower intrinsic Schottky barrier. This improves understanding of photoinduced doping of TMD by metal NP which could benefit emerging catalytic and optoelectronic applications. [ABSTRACT FROM AUTHOR]

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Two-dimensional materials have been restricted to systems in which strong chemical bonds hold atoms together in sheets. Now, 2D materials consisting of molecules linked by weak non-covalent bonds have been peeled from crystals.A top-down approach for making molecular 2D materials. [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]

Two-dimensional layered transition metal dichalcogenides (TMDs) have attracted great interest owing to their unique properties and a wide array of potential applications. However, due to their inert nature, pristine TMDs are very challenging to functionalize. We demonstrate a general route to functionalize exfoliated 2H-MoS2 with cysteine. Critically, MoS2 was found to be facilitating the oxidation of the thiol cysteine to the disulfide cystine during functionalization. The resulting cystine was physisorbed on MoS2 rather than coordinated as a thiol (cysteine) filling S-vacancies in the 2H-MoS2 surface, as originally conceived. These observations were found to be true for other organic thiols and indeed other TMDs. Our findings suggest that functionalization of two-dimensional MoS2 using organic thiols may not yield covalently or datively tethered functionalities, rather, in this instance, they yield physisorbed disulfides that are easily removed. [ABSTRACT FROM AUTHOR]

Two-dimensional layered transition metal dichalcogenides (TMDs) have attracted great interest owing to their unique properties and a wide array of potential applications. However, due to their inert nature, pristine TMDs are very challenging to functionalize. We demonstrate a general route to functionalize exfoliated 2H-MoS2 with cysteine. Critically, MoS2 was found to be facilitating the oxidation of the thiol cysteine to the disulfide cystine during functionalization. The resulting cystine was physisorbed on MoS2 rather than coordinated as a thiol (cysteine) filling S-vacancies in the 2H-MoS2 surface, as originally conceived. These observations were found to be true for other organic thiols and indeed other TMDs. Our findings suggest that functionalization of two-dimensional MoS2 using organic thiols may not yield covalently or datively tethered functionalities, rather, in this instance, they yield physisorbed disulfides that are easily removed. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (hBN) nanosheets are emerging as promising 2D materials for different types of applications. However, biodegradation of hBN materials is poorly explored owing to their high chemical inertness and strong oxidation resistance. The assessment of oxidation/biodegradation of hBN is important in developing biomedical tools. Herein, we report the first study on the biodegradability of hBN nanosheets comparing the enzymatic catalysis of two different peroxidases, horseradish peroxidase (HRP) and human myeloperoxidase (MPO), with the photo-Fenton (P.F.) reaction. The results show that degradation of hBN nanosheets is different to that of graphene and graphene oxide, since partial oxidation was found using MPO after 35 h, while HRP failed to degrade hBN up to 60 days. Nearly complete oxidation/degradation was occurred by P.F. reaction in 100 h. These results are helpful in designing advanced conjugates for biomedical uses of hBN. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (hBN) nanosheets are emerging as promising 2D materials for different types of applications. However, biodegradation of hBN materials is poorly explored owing to their high chemical inertness and strong oxidation resistance. The assessment of oxidation/biodegradation of hBN is important in developing biomedical tools. Herein, we report the first study on the biodegradability of hBN nanosheets comparing the enzymatic catalysis of two different peroxidases, horseradish peroxidase (HRP) and human myeloperoxidase (MPO), with the photo-Fenton (P.F.) reaction. The results show that degradation of hBN nanosheets is different to that of graphene and graphene oxide, since partial oxidation was found using MPO after 35 h, while HRP failed to degrade hBN up to 60 days. Nearly complete oxidation/degradation was occurred by P.F. reaction in 100 h. These results are helpful in designing advanced conjugates for biomedical uses of hBN. [ABSTRACT FROM AUTHOR]

While liquid phase exfoliation can be used to produce nanosheets stabilized in polymer solutions, very little is known about the resultant nanosheet size, thickness, or monolayer content. The present study uses semiquantitative spectroscopic metrics based on extinction, Raman, and photoluminescence (PL) spectroscopy to investigate these parameters for WS2 nanosheets exfoliated in aqueous poly(vinyl alcohol) (PVA) solutions. By measuring Raman and PL simultaneously, the monolayer content can be tracked via the PL/Raman intensity ratio while varying processing conditions. The PL is found to be maximized for a stabilizing polymer concentration of 2 g L−1. In addition, the monolayer content can be controlled via the centrifugation conditions, exceeding 5% by mass in some cases. These techniques have allowed tracking the ratio of PL/Raman in a droplet of polymer-stabilized WS2 nanosheets as the water evaporates during composite formation. No evidence of nanosheet aggregation is found under these conditions although the PL becomes dominated by trion emission as drying proceeds and the balance of doping from PVA/water changes. Finally, bulk PVA/WS2 composites are produced by freeze drying where >50% of the monolayers remain unaggregated, even at WS2 volume fractions as high as 10%. [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]

Layered two-dimensional (2D) inorganic transition-metal dichalchogenides (TMDs) have attracted great interest as a result of their potential application in optoelectronics, catalysis, and medicine. However, methods to functionalize and process such 2D TMDs remain scarce. We have established a facile route towards functionalized layered MoS2. We found that the reaction of liquid-exfoliated 2D MoS2, with M(OAc)2 salts (M=Ni, Cu, Zn; OAc=acetate) yielded functionalized MoS2–M(OAc)2 materials. Importantly, this method furnished the 2H-polytype of MoS2 which is a semiconductor. X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT–IR), and thermogravimetric analysis (TGA) provide strong evidence for the coordination of MoS2 surface sulfur atoms to the M(OAc)2 salt. Interestingly, functionalization of 2H-MoS2 allows for its dispersion/processing in more conventional laboratory solvents. [ABSTRACT FROM AUTHOR]

Layered two-dimensional (2D) inorganic transition-metal dichalchogenides (TMDs) have attracted great interest as a result of their potential application in optoelectronics, catalysis, and medicine. However, methods to functionalize and process such 2D TMDs remain scarce. We have established a facile route towards functionalized layered MoS2. We found that the reaction of liquid-exfoliated 2D MoS2, with M(OAc)2 salts (M=Ni, Cu, Zn; OAc=acetate) yielded functionalized MoS2-M(OAc)2 materials. Importantly, this method furnished the 2H-polytype of MoS2 which is a semiconductor. X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT-IR), and thermogravimetric analysis (TGA) provide strong evidence for the coordination of MoS2 surface sulfur atoms to the M(OAc)2 salt. Interestingly, functionalization of 2H-MoS2 allows for its dispersion/processing in more conventional laboratory solvents. [ABSTRACT FROM AUTHOR]