Graphene nanoribbons (GNRs) are materials with properties distinct from those of other carbon allotropes. The all-semiconducting nature of sub-10-nm GNRs could bypass the problem of the extreme ...chirality dependence of the metal or semiconductor nature of carbon nanotubes (CNTs) in future electronics. Currently, making GNRs using lithographic, chemical or sonochemical methods is challenging. It is difficult to obtain GNRs with smooth edges and controllable widths at high yields. Here we show an approach to making GNRs by unzipping multiwalled carbon nanotubes by plasma etching of nanotubes partly embedded in a polymer film. The GNRs have smooth edges and a narrow width distribution (10-20 nm). Raman spectroscopy and electrical transport measurements reveal the high quality of the GNRs. Unzipping CNTs with well-defined structures in an array will allow the production of GNRs with controlled widths, edge structures, placement and alignment in a scalable fashion for device integration.
Graphene nanoribbons have attracted attention because of their novel electronic and spin transport properties, and also because nanoribbons less than 10 nm wide have a bandgap that can be used to ...make field-effect transistors. However, producing nanoribbons of very high quality, or in high volumes, remains a challenge. Here, we show that pristine few-layer nanoribbons can be produced by unzipping mildly gas-phase oxidized multiwalled carbon nanotubes using mechanical sonication in an organic solvent. The nanoribbons are of very high quality, with smooth edges (as seen by high-resolution transmission electron microscopy), low ratios of disorder to graphitic Raman bands, and the highest electrical conductance and mobility reported so far (up to 5e(2)/h and 1,500 cm(2) V(-1) s(-1) for ribbons 10-20 nm in width). Furthermore, at low temperatures, the nanoribbons show phase-coherent transport and Fabry-Perot interference, suggesting minimal defects and edge roughness. The yield of nanoribbons is approximately 2% of the starting raw nanotube soot material, significantly higher than previous methods capable of producing high-quality narrow nanoribbons. The relatively high-yield synthesis of pristine graphene nanoribbons will make these materials easily accessible for a wide range of fundamental and practical applications.
Two-dimensional atomic crystals, such as two-dimensional oxides, have attracted much attention in energy storage because nearly all of the atoms can be exposed to the electrolyte and involved in ...redox reactions. However, current strategies are largely limited to intrinsically layered compounds. Here we report a general strategy that uses the surfaces of water-soluble salt crystals as growth templates and is applicable to not only layered compounds but also various transition metal oxides, such as hexagonal-MoO3, MoO2, MnO and hexagonal-WO3. The planar growth is hypothesized to occur via a match between the crystal lattices of the salt and the growing oxide. Restacked two-dimensional hexagonal-MoO3 exhibits high pseudocapacitive performances (for example, 300 F cm(-3) in an Al2(SO4)3 electrolyte). The synthesis of various two-dimensional transition metal oxides and the demonstration of high capacitance are expected to enable fundamental studies of dimensionality effects on their properties and facilitate their use in energy storage and other applications.
Developing controlled approaches for synthesizing high‐quality two‐dimensional (2D) semiconductors is essential for their practical applications in novel electronics. The application of chemical ...vapor transport (CVT), an old single‐crystal growth technique, has been extended from growing 3D crystals to synthesizing 2D atomic layers by tuning the growth kinetics. Both single crystalline individual flakes and continuous films of 1 L MoS2 were successfully obtained with CVT approach at low growth temperatures of 300–600 °C. The obtained 1 L MoS2 exhibits high crystallinity and comparable mobility to mechanically exfoliated samples, as confirmed by both atomic resolution microscopic imaging and electrical transport measurements. Besides MoS2, this method was also used in the growth of 2D WS2, MoSe2, MoxW1−xS2 alloys, and ReS2, thus opening up a new way for the controlled synthesis of various 2D semiconductors.
Layer by layer: The controllable synthesis of highly crystalline two‐dimensional (2D) semiconducting atomic layers has been achieved by using an old crystal growth technique, chemical vapor transport. This approach opens a new avenue for the chemical synthesis of high‐quality 2D semiconductors.
Two‐dimensional (2D) PtSe2 shows the most prominent layer‐dependent electrical properties among various 2D materials and high catalytic activity for hydrogen evolution reaction (HER), and therefore, ...it is an ideal material for exploring the structure–activity correlations in 2D systems. Here, starting with the synthesis of single‐crystalline 2D PtSe2 with a controlled number of layers and probing the HER catalytic activity of individual flakes in micro electrochemical cells, we investigated the layer‐dependent HER catalytic activity of 2D PtSe2 from both theoretical and experimental perspectives. We clearly demonstrated how the number of layers affects the number of active sites, the electronic structures, and electrical properties of 2D PtSe2 flakes and thus alters their catalytic performance for HER. Our results also highlight the importance of efficient electron transfer in achieving optimum activity for ultrathin electrocatalysts. Our studies greatly enrich our understanding of the structure–activity correlations for 2D catalysts and provide new insight for the design and synthesis of ultrathin catalysts with high activity.
Through thick and thin: Since the thickness of two‐dimensional (2D) PtSe2 flakes can be controlled by adjusting synthesis conditions, their layer‐dependent catalytic activity for the hydrogen evolution reaction could be investigated from both theoretical and experimental perspectives. Structure–activity correlations were drawn, providing new insights for the design and synthesis of ultrathin catalysts.
We report on the experimental and numerical investigations of dissipative rogue waves (DRWs) among noise-like pulses, in a thulium-doped fiber laser mode locked by a monolayer MoS 2 saturable ...absorber. By increasing the pumping power or weakening the effective cavity spectral filtering, the statistics distributions of the pulse events deviate from the Gaussian statistics to the L-shaped distributions with long tail, accompanied by the increase of the DRWs proportion. Our observations reveal the dissipat-ive nature of rogue waves in dissipative systems.
Aligned, ultralong single‐walled carbon nanotubes (SWNTs) represent attractive building blocks for nanoelectronics. The structural uniformity along their tube axis and well‐ordered two‐dimensional ...architectures on wafer surfaces may provide a straightforward platform for fabricating high‐performance SWNT‐based integrated circuits. On the way towards future nanoelectronic devices, many challenges for such a specific system also exist. This Review summarizes the recent advances in the synthesis, identification and sorting, transfer printing and manipulation, device fabrication and integration of aligned, ultralong SWNTs in detail together with discussion on their major challenges and opportunities for their practical application.
Aligned, ultralong single‐walled carbon nanotubes represent attractive building blocks for nanoelectronics. The structural uniformity along the tube axis and well‐ordered two‐dimensional architectures on a wafer surface may provide a straightforward platform for fabricating high‐performance SWNT‐based integrated circuits. We summarize the recent advances in synthesis, identification, device fabrication and integration of aligned, ultralong SWNTs together with a discussion on the major challenges and opportunities for practical applications.
Schottky effect of two-dimensional materials is important for nanoscale electrics. A ReSe
2
flake is transferred to be suspended between an Au sink and an Au nanofilm. This device is initially ...designed to measure the transport properties of the ReSe
2
flake. However, a rectification behavior is observed in the experiment from 273 to 340 K. The rectification coefficient is about 10. The microstructure and elements composition are systematically analyzed. The ReSe
2
flake and the Au film are found to be in contact with the Si substrate from the scanning electron microscope image in slant view of 45°. The ReSe
2
/Si and Si/Au contacts are p-n heterojunction and Schottky contacts. Asymmetry of both contacts results in the rectification behavior. The prediction based on the thermionic emission theory agrees well with experimental data.
The impact of parental phubbing has attracted the attention of researchers, especially concerning adolescents’ online behavior. However, limited research has studied the influence of parental ...phubbing on interpersonal aggression, including the underlying mechanism. Grounded in parental acceptance–rejection theory, the present study investigated the association between parental phubbing and interpersonal aggression as well as the mediating role of rejection sensitivity among adolescents. Additionally, school climate was explored as a moderator based on social ecological theory. The multiple questionnaires were completed by 914 Chinese adolescents (M = 12.61; SD = 1.73; 49.78% girls). The results revealed a positive correlation between parental phubbing and aggression, which was mediated by rejection sensitivity. That is, adolescents who experienced parental phubbing were more likely to exhibit rejection sensitivity, which further triggered aggression. Moreover, school climate acted as a moderator in the model. Specifically, we found no significant moderating effect of school climate on parental phubbing and aggression. However, school climate moderated the relationship between rejection sensitivity and aggression. A positive school climate buffered the associations of rejection sensitivity and aggression. Additionally, school climate moderated the relationship between parental phubbing and rejection sensitivity. The relationship between parental phubbing and rejection sensitivity became nonsignificant when adolescents were in a negative school climate, and those adolescents reported higher rejection sensitivity whether they experienced parental phubbing or not. Parental phubbing was more strongly associated with adolescents’ rejection sensitivity in a positive school climate. With a lower level of parental phubbing, rejection sensitivity is sharply reduced. The results deepen our understanding of the relationship between parental phubbing and aggression and its underlying mechanisms. It also implicates preventative interventions to reduce the risk of parental phubbing in interpersonal aggression among adolescents.
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