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Element doping allows manipulation of the electronic properties of 2D materials. Enhanced transport performances and ambient stability of black-phosphorus devices by Te doping are presented. This provides a facile route for achieving airstable black-phosphorus devices.

Owing to their excellent physical properties, atomically thin layers of molybdenum disulfide (MoS₂) have recently attracted much attention due to their nonzero-gap property, exceptionally high electrical conductivity, good thermal stability, and excellent mechanical strength, etc. MoS₂-based devices exhibit great potential for applications in optoelectronics and energy harvesting. Here, a comprehensive review of various doping strategies is presented, including wet doping and dry doping of atomically crystalline MoS₂ thin layers, and the progress made so far for their doping-based prospective applications is also discussed. Finally, several significant research issues for the prospects of doped-MoS₂ in industry, as a guide for 2D material community, are also provided.

Various strategies for doping of molybdenum disulfide are comprehensively reviewed, including wet doping and dry doping of MoS₂ thin layers and the progress made so far for their doping-based industrial applications. Finally, a few important opening study directions for future prospects of doped atomically crystalline MoS₂ layers in optoelectronics and energy harvesting, as a guide for the 2D material community, are also provided.

A novel layered SnSSe material is designed as a high-performance anode for sodium-ion batteries with characteristics of high capacity, superior cyclability, facile synthetic method, and large-scale production ability. The transformation from bulk SnSSe particles into closely packed nanoplate aggregates with greater resistance to structure pulverization and the partial pseudocapacitive capacity contribution may engender excellent cycling performance and rate capability.

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.

Very stable suspensions of high-quality single- or few-layer antimonene were obtained by liquid-phase exfoliation under sonication without the need for a surfactant. The Raman spectrum of antimonene was found to strongly depend on its thickness, which was also rationalized by quantum-mechanical calculations.

The environmental instability of single- or few-layer black phosphorus (BP) has become a major hurdle for BP-based devices. The degradation mechanism remains unclear and finding ways to protect BP from degradation is still highly challenging. Based on ab initio electronic structure calculations and molecular dynamics simulations, a three-step picture on the ambient degradation of BP is provided: generation of superoxide under light, dissociation of the superoxide, and eventual breakdown under the action of water. The well-matched band gap and band-edge positions for the redox potential accelerates the degradation of thinner BP. Furthermore, it was found that the formation of P-O-P bonds can greatly stabilize the BP framework. A possible protection strategy using a fully oxidized BP layer as the native capping is thus proposed. Such a fully oxidization layer can resist corrosion from water and leave the BP underneath intact with simultaneous high hole mobility.

Protected by native oxide: A three-step picture of the ambient degradation of black phosphorus (BP) is given. A possible protection strategy using a fully oxidized BP layer as the capping is proposed. Such a fully oxidized layer can resist corrosion from water and leave the BP underneath intact with simultaneous high hole mobility.

On page 6985, J.-H. Park and co-workers report a high-performance ReS₂-based thin-film transistor and photodetector with high on/off-current ratio (10⁴), high mobility (7.6 cm² V⁻¹ s⁻¹), high photoresponsivity (2.5 × 10⁷ A W⁻¹), and fast temporal response (rising and decaying time of 670 ms and 5.6 s, respectively) through O₂-plasma treatment.

Ultrasmall black phosphorus quantum dots (BPQDs) serve as the near-infrared light absorber and charge transfer layer in the photocathode of a bifacial n-type dye sensitized solar cell. Wideband light absorption and ≈20% enhancement in the light-to-electron efficiency are accomplished due to the fast carrier transfer and complementary light absorption by the BPQDs demonstrating that BP has large potential in photovoltaics.

Large-scale colloidal synthesis and integration of uniform-sized molybdenum disulfide (MoS₂) nanosheets for a flexible resistive random access memory (RRAM) array are presented. RRAM using MoS₂ nanosheets shows a ≈10 000 times higher on/off ratio than that based on exfoliated MoS₂. The good uniformity of the MoS₂ nanosheets allows wafer-scale system integration of the RRAM array with pressure sensors and quantum-dot light-emitting diodes.

On page 6332, J. Gómez-Herrero, F. Zamora, and co-workers describe the isolation of antimonene, a new allotrope of antimony that consists of a single layer of atoms. They obtain antimonene flakes by the scotch tape method; these flakes are highly stable in ambient conditions and even when immersed in water. The 1.2 eV gap calculated in this study suggests potential applications in optoelectronics.

Two-dimensional (2D) boron sheets have been successfully synthesized in recent experiments, however, some important issues remain, including the dynamical instability, high energy, and the active surface of the sheets. In an attempt to stabilize 2D boron layers, we have used density functional theory and global minimum search with the particle-swarm optimization method to predict four stable 2D boron hydride layers, namely the C2/m, Pbcm, Cmmm, and Pmmn sheets. The vibrational normal mode calculations reveal all these structures are dynamically stable, indicating potential for successful experimental synthesis. The calculated Young's modulus indicates a high mechanical strength for the C2/m and Pbcm phases. Most importantly, the C2/m, Pbcm, and Pmmn structures exhibit Dirac cones with massless Dirac fermions and the Fermi velocities for the Pbcm and Cmmm structures are even higher than that of graphene. The Cmmm phase is reported as the first discovery of Dirac ring material among boron-based 2D structures. The unique electronic structure of the 2D boron hydride sheets makes them ideal for nanoelectronics applications.

In an attempt to stabilize 2D boron layers, DFT and a global minimum search with the particle-swarm optimization method were used to predict four stable 2D boron hydride layers, namely C2/m, Pbcm, Cmmm, and Pmmn sheets. All of these structures are dynamically stable and possess a Dirac cone feature with massless Dirac fermions. The Fermi velocities for the Pbcm and Cmmm structures are even higher than that of graphene.

We report an unsurpassed solution characterization technique based on analytical ultracentrifugation, which demonstrates exceptional potential for resolving particle sizes in solution with sub-nm resolution. We achieve this improvement in resolution by simultaneously measuring UV/Vis spectra while hydrodynamically separating individual components in the mixture. By equipping an analytical ultracentrifuge with a novel multi-wavelength detector, we are adding a new spectral discovery dimension to traditional hydrodynamic characterization, and amplify the information obtained by orders of magnitude. We demonstrate the power of this technique by characterizing unpurified CdTe nanoparticle samples, avoiding tedious and often impossible purification and fractionation of nanoparticles into apparently monodisperse fractions. With this approach, we have for the first time identified the pure spectral properties and band-gap positions of discrete species present in the CdTe mixture.

Size guide: nanoparticle sizes can be determined with sub-nm resolution, in solution without purification and fractionation. Using an analytical ultracentrifuge equipped with a newly developed multiwavelength detector, simultaneous UV/Vis spectra are measured during the hydrodynamic separation of a mixture. The power of the method is demonstrated for the characterization of CdTe Nanoparticles.

In recent years, 2D layered materials have been considered as promising photon absorption channel media for next-generation phototransistors due to their atomic thickness, easily tailored single-crystal van der Waals heterostructures, ultrafast optoelectronic characteristics, and broadband photon absorption. However, the photosensitivity obtained from such devices, even under a large bias voltage, is still unsatisfactory until now. In this paper, high-sensitivity phototransistors based on WS₂ and MoS₂ are proposed, designed, and fabricated with gold nanoparticles (AuNPs) embedded in the gate dielectric. These AuNPs, located between the tunneling and blocking dielectric, are found to enable efficient electron trapping in order to strongly suppress dark current. Ultralow dark current (10⁻¹¹ A), high photoresponsivity (1090 A W⁻¹), and high detectivity (3.5 × 10¹¹ Jones) are obtained for the WS₂ devices under a low source/drain and a zero gate voltage at a wavelength of 520 nm. These results demonstrate that the floating-gate memory structure is an effective configuration to achieve high-performance 2D electronic/optoelectronic devices.

This study reports a novel float-gated memory structure phototransistor based on multilayer WS₂ with gold nanoparticles embedded in the gate dielectric. The device represents excellent photodetection capabilities demonstrating that the float-gated memory is an effective configuration to achieve high-performance 2D optoelectronic devices.

A 2D system of Er-doped MoS₂ layered nanosheets is developed. Structural studies indicate that the Er atoms can be substitutionally introduced into MoS₂ to form stable doping. Density functional theory calculation implies that the system remains stable. Both NIR-to-NIR up-conversion and down-conversion light-emissions are observed in 2D transition metal dichalcogenides, ascribed to the energy transition from Er³⁺ dopants.

MoS₂ spirals grown by the chemical vapor deposition method, driven by a threading dislocation, has a peculiar rhombohedral-like structure. This threading dislocation can carry helical current in the vertical direction and greatly enhances the vertical conductance in the MoS₂ multilayer samples.

The development of high performance lubricants has been driven by increasingly growing industrial demands and environmental concerns. Herein, we demonstrate oil-soluble polymer brush-grafted inorganic nanoparticles (hairy NPs) as highly effective lubricant additives for friction and wear reduction. A series of oil-miscible poly(lauryl methacrylate) brush-grafted silica and titania NPs were synthesized by surface-initiated atom transfer radical polymerization. These hairy NPs showed exceptional stability in poly(alphaolefin) (PAO) base oil; no change in transparency was observed after being kept at −20, 22, and 100 °C for ≥55 days. High-contact stress ball-on-flat reciprocating sliding tribological tests at 100 °C showed that addition of 1 wt % of hairy NPs into PAO led to significant reductions in coefficient of friction (up to ≈40 %) and wear volume (up to ≈90 %). The excellent lubricating properties of hairy NPs were further elucidated by the characterization of the tribofilm formed on the flat. These hairy NPs represent a new type of lubricating oil additives with high efficiency in friction and wear reduction.

Oil-soluble polymer brush grafted nanoparticles (hairy NPs) were synthesized and evaluated as lubricant additives. These hairy NPs exhibited exceptional stability in a lubricating base oil at both low and high temperatures. High contact stress tribological tests at 100 °C revealed that the addition of 1 wt % of hairy NPs into the oil led to significant reductions in friction and wear volume.

A flexible transparent molybdenum trioxide nanopaper, assembled via ultralong molybdenum trioxide nanobelts, displays an excellent average transmittance of ≈90% in the visible region. The free-standing nanopaper electrode delivers an outstanding specific capacitance of 1198 F g⁻¹ and shows an excellent long-term stability performance over 20 000 cycles with a retention rate of 99.1%.