A 3D hierarchical structure of MoSe₂/NiSe₂ exhibits superior HER activity because of more active sites and faster transfer of electrons.

First-principle calculation based on density functional theory is performed to study the lattice vibration, heat capacity, and thermal conductivity of graphene under strain. Two degenerate optical branches in the phonon dispersion curves split near the G points due to the reduced crystal symmetry, and the frequencies of the optical phonon modes shift down thus inducing more phonon modes at a given temperature. The heat capacity is increased, but the thermal conductivity is reduced because of enhanced Umklapp scattering among more phonons. This phenomenon should be considered when determining the heat management of graphene-based devices.

Active packaging that can extend the shelf-life of fresh fruits and vegetables after picking can assure food quality and avoid food waste. Such packaging can prevent the growth of microbial and bacterial pathogens or delay the production of ethylene, which accelerates the ripening of fruits and vegetables after harvesting. Proposed technologies include packaging that enables the degradation of ethylene, modified atmosphere packaging, and bioactive packaging. Packaging that can efficiently adsorb/desorb ethylene, and thus control its concentration, is particularly promising. However, there are still large challenges around toxicity, low selectivity, and consumer acceptability. Metal–organic framework (MOF) materials are porous, have a specific surface area, and have excellent gas adsorption/desorption performance. They can encapsulate and release ethylene and are thus good candidates for use in ethylene-adjusting packaging. This review focuses on MOF-based active-packaging materials and their applications in post-harvest fruit and vegetable packaging. The fabrication and characterization of MOF-based materials and the ethylene adsorption/desorption mechanism of MOF-based packaging and its role in fruit and vegetable preservation are described. The design of MOF-based packaging and its applications are reviewed. Finally, the potential future uses of MOF-based active materials in fresh food packaging are considered.

Stress arising from structural or thermal misfit impacts the reliability of graphene-related devices. The deformation behaviour of graphene nanoribbons (GNRs) with Stone–Wales defects under stress studied by molecular dynamics shows that nearly all the SW defects annihilate via inverse rotation of C–C bonds. The fracture stress of defective GNRs is comparable to that of perfect ones and similar to mechanical annealing observed from bulk metals. It is a competition between bond rotation and fracture and depends on the strain rate and temperature. At a lower strain rate, such as 10⁻⁵ ps⁻¹, the rotation velocity of C–C bonds of 4.2 Å ps⁻¹ is three orders of magnitude larger than the velocity of the collective movement of atoms (1.2 × 10⁻³ Å ps⁻¹). There is enough time for the C–C bond rotation to respond to the external load, but it becomes more difficult at higher strain rates. This stress-induced SW defect annihilation can be enhanced at higher temperatures because of enhanced exchange of atomic momentum and energy. The results reveal the dominant influence of SW defects on the mechanical properties of two-dimensional materials.

Molecular dynamics (MD) simulations are conducted to study the deformation behavior and strain distribution in two-dimensional (2D) nano-rings of graphene, single-layer black phosphorus (SLBP) and single-layer MoS₂ (SLMoS₂) under circular torsion. Interestingly, fan-blade shaped wrinkling is generated, in which the maximum torsion angle (Δθ) and the potential energy change per atom (ΔPe) increase with increasing inner radius but decrease with increasing temperature. As the inner radius is increased, the wave number of wrinkling increases but the wave amplitude decreases. The geometrical characteristics of wrinkling are closely related to the intrinsic elastic modulus (E) and Poisson's ratio (ν). Specifically, the graphene nano-rings possess the largest Δθ and ΔPe but the smallest wave amplitude, while the SLBP nano-rings exhibit the smallest Δθ and ΔPe but the largest wave amplitude. Furthermore, the strongly anisotropic E and ν values of SLBP result in orientation-dependent geometrical characteristics of wrinkles, and fan-blade shaped wrinkling with a strain vortex is induced, which might substantially enhance the pseudomagnetic fields and optical funnel effect for the separation of photon-induced electron–hole pairs, and thus be exploited to improve the photoelectric properties of 2D materials.