Self-templated growth of carbon-nanotube walls at high temperatures

Interlayer Sodium Plating/Stripping in Van der Waals-Layered Quantum Dot Superstructure

Assembling quantum dots (QDs) into van der Waals (vdW)-layered superstructure holds great promise for the development of high-energy-density metal anode. However, designing such a superstructure remains to be challenging. Here, a chemical-vapor Oriented Attachment (OA) growth strategy is proposed to achieve the synthesis of vdW-layered carbon/QDs hybrid superlattice nanosheets (Fe₇ S₈ @CNS) with a large vdW gap of 3 nm. The Fe₇ S₈ @CNS superstructure is assembled by carbon-coated Fe₇ S₈ (Fe₇ S₈ @C) QDs as building blocks. Interestingly, the Fe₇ S₈ @CNS exhibits two kinds of edge dislocations similar to traditional atom-layered materials, suggesting that Fe₇ S₈ @C QDs exhibit quasi-atomic growth behavior during the OA process. More interestingly, when used as host materials for sodium metal anodes, the Fe₇ S₈ @CNS shows the interlayer sodium plating/stripping behavior, which well suppresses Na dendrite growth. As a result, the cell with Fe₇ S₈ @CNS anode can keep stable cycling for 1000 h with a high Coulombic efficiency (CE) of ≈99.5% at 3.0 mA cm^-2 and 3.0 mAh cm^-2 . Noticeably, the Na@Fe₇ S₈ @CNS||Na₃ V₂ (PO₄ )₃ full cells can attain a capacity of 88.8 mAh g^-1 with a retention of 97% after 1000 cycles at 1.0 A g^-1 (≈8 C), showing excellent cycle stability for practical applications. This work enriches the vdW-layered QDs superstructure family and their application toward energy storage.

A Microwave-Assisted, Solvent-Free Approach for the Versatile Functionalization of Carbon Nanotubes

While the functionalization of carbon nanotubes (CNTs) has attracted extensive interest for a wide range of applications, a facial and versatile strategy remains in demand. Here, we report a microwave-assisted, solvent-free approach to directly functionalize CNTs both in raw form and in arbitrary macroscopic assemblies. Rapid microwave irradiation was applied to generate active sites on the CNTs while not inducing excessive damage to the graphitic network, and a gas-phase deposition afforded controllable grafting for thorough or regioselective functionalization. Using methyl methacrylate (MMA) as a model functional group and a CNT sponge as a model assembly, homogeneous grafting was exhibited by the increased robust hydrophobicity (contact angle increase from 30 to 140°) and improved structural stability (compressive modulus increased by 135%). Therefore, when our MMA-functionalized CNTs served as a solar absorber for saline distillation, high operating stability with a superior water evaporation rate of ∼2.6 kg m^-2 h^-1 was observed. Finally, to highlight the efficacy and versatility of this functionalization approach, we fabricated asymmetrically hydrophobic CNT sponges by regioselective functionalization to serve as a moisture-driven generator, which demonstrated a stable open-circuit voltage of 0.6 mV. This versatile, solvent-free approach can complement conventional solution-based techniques in the design and fabrication of multifunctional nanocarbon-based materials.

Towards nanoprinting with metals on graphene

Graphene and carbon nanotubes are envisaged as suitable materials for the fabrication of the new generation of nanoelectronics. The controlled patterning of such nanostructures with metal nanoparticles is conditioned by the transfer between a recipient and the surface to pattern. Electromigration under the impact of an applied voltage stands at the base of printing discrete digits at the nanoscale. Here we report the use of carbon nanotubes as nanoreservoirs for iron nanoparticles transfer on few-layer graphene. An initial Joule-induced annealing is required to ensure the control of the mass transfer with the nanotube acting as a ‘pen' for the writing process. By applying a voltage, the tube filled with metal nanoparticles can deposit metal on the surface of the graphene sheet at precise locations. The reverse transfer of nanoparticles from the graphene surface to the nanotube when changing the voltage polarity opens the way for error corrections.

The precise delivery of materials onto graphene is important for nano-processing but little is known about the mechanisms of such processes. Here, the authors use a range of microscopic techniques for the real-time observation of nanoparticle transfer from the inner channel of a carbon nanotube onto graphene.

Edge-mediated dislocation processes in multishell carbon nano-onions?

We report in situ electron microscopy observations of dislocation dissociation and annihilation processes in individual nanometer-sized carbon onions. Essential for these processes is the counterintuitive motion of the 1/2(0001) edge from the outer surface to the inner region, which cross-links or unlinks a large number of shells. The correlation with atomistic simulations and analysis of the energy which separates the strain and edge components indicates that this inward glide originates in the reduction of edge with each inwards glide step, an effect specific to the spherical topology.