The emergence of the field of nanofluidics in the last decade has led to the development of important applications including water desalination, ultrafiltration and osmotic energy conversion. Most applications make use of carbon nanotubes, boron nitride nanotubes, graphene and graphene oxide. In particular, understanding water transport in carbon nanotubes is key for designing ultrafiltration devices and energy-efficient water filters. However, although theoretical studies based on molecular dynamics simulations have revealed many mechanistic features of water transport at the molecular level, further advances in this direction are limited by the fact that the lowest flow velocities accessible by simulations are orders of magnitude higher than those measured experimentally. Here, we extend molecular dynamics studies of water transport through carbon nanotubes to flow velocities comparable with experimental ones using massive crowd-sourced computing power. We observe previously undetected oscillations in the friction force between water and carbon nanotubes and show that these oscillations result from the coupling between confined water molecules and the longitudinal phonon modes of the nanotube. This coupling can enhance the diffusion of confined water by more than 300%. Our results may serve as a theoretical framework for the design of new devices for more efficient water filtration and osmotic energy conversion devices.

Due to its innate instability, the degradation of black phosphorus (BP) with oxygen and moisture was considered the obstacle for its application in ambient conditions. Here, a friction force reduced by about 50% at the degraded area of the BP nanosheets was expressly observed using atomic force microscopy due to the produced phosphorus oxides during degradation. Energy-dispersive spectrometer mapping analyses corroborated the localized concentration of oxygen on the degraded BP flake surface where friction reduction was observed. Water absorption was discovered to be essential for the degraded characteristic as well as the friction reduction behavior of BP sheets. The combination of water molecules as well as the resulting chemical groups (P-OH bonds) that are formed on the oxidized surface may account for the friction reduction of degraded BP flakes. It is indicated that, besides its layered structure, the ambient degradation of BP significantly favors its lubrication behavior.

Developing an easily recyclable and reusable biosorbent for highly efficient removal of very toxic Hg­(II) ions from bodies of water is of special significance. Herein, a thiol-functionalized nanocellulose aerogel-type adsorbent for the highly efficient capture of Hg­(II) ions was fabricated through a facile freeze-drying of bamboo-derived 2,2,6,6-tetra­methyl­piperidine-1-oxyl (TEMPO) oxidized nanofibrillated cellulose (TO-NFC) suspension in the presence of hydrolyzed 3-mercapto­propyl-trimethoxy­silane (MPTs) sols. Notably, the modified aerogel was able to effectively and selectively remove more than 92% Hg­(II) ions even in a wide range of Hg­(II) concentrations (0.01–85 mg/L) or coexistence with other heavy metals. Besides, the adsorption capacity of the aerogel was not compromised much by the variation in pH values of Hg­(II) solutions over a wide pH range. The fitting results of adsorption models suggested the monolayer adsorption and chemisorptive characteristics with the maximal uptake capacity as high as 718.5 mg/g. The adsorption mechanism of the MPTs-modified TO-NFC aerogel toward Hg­(II) was studied in detail. For the simulated chloralkali wastewater containing Hg­(II) ions, the novel aerogel-type adsorbent exhibited a removal efficiency of 97.8%. Furthermore, its adsorption capacity for Hg­(II) was not apparently deteriorated after four adsorption/desorption cycles while almost maintaining the original structural integrity.

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The interfaces between two-dimensional (2D) materials and the silicon dioxide (SiO2)/silicon (Si) substrate, generally considered as a solid–solid mechanical contact, have been especially emphasized for the structure design and the property optimization in microsystems and nanoengineering. The basic understanding of the interfacial structure and dynamics for 2D material-based systems still remains one of the inevitable challenges ahead. Here, an interfacial mobile water layer is indicated to insert into the interface of the degraded black phosphorus (BP) flake and the SiO2/Si substrate owing to the induced hydroxyl groups during the ambient degradation. A super-slippery degraded BP/SiO2 interface was observed with the interfacial shear stress (ISS) experimentally evaluated as low as 0.029 ± 0.004 MPa, being comparable to the ISS values of incommensurate rigid crystalline contacts. In-depth investigation of the interfacial structure through nuclear magnetic resonance spectroscopy and in situ X-ray photoelectron spectroscopy depth profiling revealed that the interfacial liquid water was responsible for the super-slippery BP/SiO2 interface with extremely low shear stress. This finding clarifies the strong interactions between degraded BP and water molecules, which supports the potential wider applications of the few-layer BP nanomaterial in biological lubrication.

Ultralow friction polymer composites were prepared by adding oil-loaded microcapsules into epoxy (EP) resin. Mono-dispersed polystyrene (PS)/poly alpha olefin (PAO) microcapsules with a diameter of ~2 μm and a shell thickness of ~30 nm were prepared by solvent evaporation method in an oil-in-water emulsion. The lubrication behaviors of the EP resin composites with oil-loaded microcapsules have been investigated under different loads and sliding speeds. As compared with the pure EP resin, the friction coefficient of the composite could be reduced to 4% (from 0.71 to 0.028) and the wear rate could be decreased up to two orders of magnitude. It was demonstrated that the released PAO oil from the microcapsules during the friction process produced a boundary lubricating film, which could prevent the direct contact of two rubbing surfaces, and thus leading to an extremely low friction coefficient and wear rate. Moreover, the composites with microcapsules could achieve comparable lubrication properties to the case under the external lubrication condition, while the former case could effectively minimize the lubricant leakage and improve the lubrication efficiency.

Sr-doped LaMnO 3 (LSM) which is the firstgeneration cathode for solid oxide fuel cells (SOFCs) has been tailored with Zn ions, aiming to achieve improved protonation ability for proton-conducting SOFCs (H-SOFCs). The new Sr and Zn co-doped LaMnO 3 (LSMZ) can be successfully synthesized. The first-principle studies indicate that the LSMZ improves the protonation of LSM and decreases the barriers for oxygen vacancy formation, leading to high performance of the LSMZ cathode-based cells. The proposed LSMZ cell shows the highest fuel cell performance among ever reported LSMbased H-SOFCs. In addition, the superior fuel cell performance does not impair its stability. LSMZ is stable against CO 2 , as demonstrated by both in-situ CO 2 corrosion tests and the first-principles calculations, leading to good long-term stability of the cell. The Zn-doping strategy for the traditional LSM cathode with high performance and good stability brings back the LSM cathode to intermediate temperatures and paves a new way for the research on the LSM-based materials as cathodes for SOFCs.

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