Few-layer graphene, with Bernal stacking order, is of particular interest to the graphene community because of its unique tunable electronic structure. A synthetic method to produce such large area graphene films with precise thickness from 2 to 4 layers would be ideal for chemists and physicists to explore the promising electronic applications of these materials. Here, large-area uniform Bernal-stacked bi-, tri-, and tetralayer graphene films were successfully synthesized on a Cu surface in selective growth windows, with a finely tuned total pressure and CH(4)/H(2) gas ratio. On the basis of the analyses obtained, the growth mechanism is not an independent homoexpitaxial layer-by-layer growth, but most likely a simultaneous-seeding and self-limiting process.

Semiconductive transition metal dichalcogenides (TMDs) have been considered as next generation semiconductors, but to date most device investigations are still based on microscale exfoliation with a low yield. Wafer scale growth of TMDs has been reported but effective doping approaches remain challenging due to their atomic thick nature. In this work, we report the synthesis of wafer-scale continuous few-layer PtSe 2 films with effective doping in a controllable manner. Chemical component analyses confirm that both n-and pdoping can be effectively modulated through the controlled selenization process. We systematically study the electrical properties of PtSe 2 films by fabricating top-gated field effect transistors (FETs). The device current on/off ratio is optimized in two-layer PtSe 2 FETs, and four-terminal configuration displays a reasonably high effective field effect mobility (14 and 15 cm 2 V -1 s -1 for p-and n-type FETs, respectively) with a nearly symmetric p-and n-type performance. Temperature dependent measurement reveals that the variable range hopping is dominant at low temperature. To further establish the feasible application based on controllable doping of PtSe 2 , a logic inverter and vertically stacked p-n junction arrays are demonstrated. These results validate that PtSe 2 is a promising candidate among the family of TMDs for future functional electronic applications.

Because of the strong quantum confinement effect, few-layer γ-InSe exhibits a layer-dependent band gap, spanning the visible and near infrared regions, and thus recently has been drawing tremendous attention. As a two-dimensional material, the mechanical flexibility provides an additional tuning knob for the electronic structures. Here, for the first time, we engineer the band structures of few-layer and bulk-like InSe by uniaxial tensile strain and observe a salient shift of photoluminescence peaks. The shift rate of the optical gap is approximately 90-100 meV per 1% strain for four- to eight-layer samples, which is much larger than that for the widely studied MoS monolayer. Density functional theory calculations well reproduce the observed layer-dependent band gaps and the strain effect and reveal that the shift rate decreases with the increasing layer number for few-layer InSe. Our study demonstrates that InSe is a very versatile two-dimensional electronic and optoelectronic material, which is suitable for tunable light emitters, photodetectors, and other optoelectronic devices.

Chronic inhalation of cigarette smoke is the major cause of sterile inflammation and pulmonary emphysema. The effect of carbon black (CB), a universal constituent of smoke derived from the incomplete combustion of organic material, in smokers and non-smokers is less known. In this study, we show that insoluble nanoparticulate carbon black (nCB) accumulates in human myeloid dendritic cells (mDCs) from emphysematous lung and in CD11c+ lung antigen presenting cells (APC) of mice exposed to smoke. Likewise, nCB intranasal administration induced emphysema in mouse lungs. Delivered by smoking or intranasally, nCB persisted indefinitely in mouse lung, activated lung APCs, and promoted T helper 17 cell differentiation through double-stranded DNA break (DSB) and ASC-mediated inflammasome assembly in phagocytes. Increasing the polarity or size of CB mitigated many adverse effects. Thus, nCB causes sterile inflammation, DSB, and emphysema and explains adverse health outcomes seen in smokers while implicating the dangers of nCB exposure in non-smokers.DOI: http://dx.doi.org/10.7554/eLife.09623.001

2D layered materials (2DLMs) have gained tremendous interest for their potential applications in next-generation electronic, optoelectronic, [1][2][3] and energy devices. Although graphene possesses the highest reported mobility, its gapless nature motivates the pursuit of semiconductive transition metal dichalcogenides (TMDs) such as MoS 2 , [4][5][6] which has been intensively investigated based on mechanically exfoliated sheets. Yet for practical Atomic thin transition-metal dichalcogenides (TMDs) are considered as an emerging platform to build next-generation semiconductor devices. However, to date most devices are still based on exfoliated TMD sheets on a micrometer scale. Here, a novel chemical vapor deposition synthesis strategy by introducing multilayer (ML) MoS 2 islands to improve device performance is proposed. A four-probe method is applied to confirm that the contact resistance decreases by one order of magnitude, which can be attributed to a conformal contact by the extra amount of exposed edges from the ML-MoS 2 islands. Based on such continuous MoS 2 films synthesized on a 2 in. insulating substrate, a top-gated field effect transistor (FET) array is fabricated to explore key metrics such as threshold voltage (V T ) and field effect mobility (μ FE ) for hundreds of MoS 2 FETs. The statistical results exhibit a surprisingly low variability of these parameters. An average effective μ FE of 70 cm 2 V −1 s −1 and subthreshold swing of about 150 mV dec −1 are extracted from these MoS 2 FETs, which are comparable to the best top-gated MoS 2 FETs achieved by mechanical exfoliation. The result is a key step toward scaling 2D-TMDs into functional systems and paves the way for the future development of 2D-TMDs integrated circuits. Field Effect TransistorsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.201803465. application, wafer-scale synthesis of highquality, continuous MoS 2 film is highly desired. Recently, the chemical vapor deposition (CVD) technique has been applied to produce single-layer (1L) MoS 2 films with moderate electrical performance [7][8][9][10] and so far the largest number of logic gates is 115. [11][12][13] Mechanically exfoliated multilayer (ML) MoS 2 have shown improved mobility and drive currents because of thicker channel with higher density of states. [14,15] A smaller bandgap associated with ML-MoS 2 [16,17] is also more appropriate for device performance engineering. [18][19][20] However, it is rather difficult to grow a uniform and continuous multilayer MoS 2 film since precise control of layer number of stacked MoS 2 remains unsolved, [21,22] and vertical growth is limited by the interlayer diffusion rate of S atoms (much slower than in-plane diffusion) and high surface energy. [23] Besides, it is rather difficult to maintain a planar growth in a controllable manner, instead most results simultaneously produce a mixture of monolayer, multilayer, and empty islands. [24,25] Despite the demand of high-quality wa...