Energy Optimum Chiralities of Multiwalled Carbon Nanotubes

The energy optimum chiralities of neighboring layers of a multiwalled carbon nanotube (MWNT) are found to correlate with each other. Nearly identical chiralities are energy optimum in MWNTs with a large diameter. For a small tube, the chiral angle ratio of the outer to inner tubes decreases monotonically with decreasing tube diameter, and nearly identical zigzag chiralities become dominated for a very small tube. It is expected that low temperature control is necessary for achieving the optimum chiralities. The theory can explain most existing chirality characterizations of MWNTs synthesized at low temperature

Energy Optimum Chiralities of Multiwalled Carbon Nanotubes

The energy optimum chiralities of neighboring layers of a multiwalled carbon nanotube (MWNT) are found to correlate with each other. Nearly identical chiralities are energy optimum in MWNTs with a large diameter. For a small tube, the chiral angle ratio of the outer to inner tubes decreases monotonically with decreasing tube diameter, and nearly identical zigzag chiralities become dominated for a very small tube. It is expected that low temperature control is necessary for achieving the optimum chiralities. The theory can explain most existing chirality characterizations of MWNTs synthesized at low temperature

Non-Noble Metal Incorporated Transition Metal Dichalcogenide Monolayers for Electrochemical CO₂ Reduction: A First-Principles Study

Using non-noble metal atoms as catalysts is attractive for decreasing the cost of the CO2 reduction reaction (CO2RR). By screening first-row transition metals and noble metals through extensive first-principles calculations, non-noble Sc and Ti single atoms binding on vacancy-defected transition metal dichalcogenide (TMD) monolayers exhibit better catalytic performance and selectivity for electrochemical CO2RR than noble metal single atoms. The overpotentials of Sc and Ti atoms for the CO2RR can be reduced lower than 0.09 V after applying suitable biaxial tensile strains on vacancy-defected TMDs, which are approximately 1 order of magnitude lower than that of most reported metal atom catalysts. The vacancy defects of TMDs and charge transfer to metal atoms induced by tensile strain play a key role in improving the catalytic activity of non-noble metal single atoms. These results highlight a possible way to design new single atom catalysts for electrochemical CO2RR by utilizing the combination of non-noble metal atoms, defected TMDs, and strain engineering

Charge Exchange and Transfer between Water and van der Waals Monolayers Under Tensile Strains

Charge exchange and transfer between water and low-dimensional materials are critical for water-related nanogenerators to harvest electricity from water. By first-principles calculations and molecular dynamics simulations, the interface interaction and charge transfer between ion-containing or pure water and two-dimensional (2D) van der Waals monolayers including transition metal dichalcogenides, hexagonal boron nitride, and graphene have been systematically investigated. Applying uniaxial tensile strain or the introduction of defects on 2D monolayers could significantly enhance the interface interaction and charge transfer from 2D monolayers to water molecules, as the tensile strain or defect weakens the bonds of 2D monolayers and changes the hydrogen bond networks in the interfacial water layer. In contrast, the presence of ions in water suppresses the charge transfer from 2D monolayers to water molecules and reduces interfacial adhesion because of the formation of hydrated ions and stronger charge exchange between ions and water molecules. These results reveal the role of strain, defect, and ion in dominating the charge exchange and transfer between water and 2D monolayers

Diameter-Optimum Spreading for the Impinging of Water Nanodroplets on Solid Surfaces

The impinging of water nanodroplets on solid surfaces is crucial to many nanotechnologies. Through large-scale molecular dynamics simulations, the size effect on the spreading of water nanodroplets after impinging on hydrophilic, graphite, and hydrophobic surfaces under low impinging velocities has been systematically studied. The spreading rates of nanodroplets first increase and then decrease and gradually become constant with the increase of nanodroplet diameter. The nanodroplets with the diameters of 17–19 nm possess the highest spreading rates because of the combined effect of the strongest interfacial interaction and the strongest surface interaction within water molecules. The highest water molecule densities, hydrogen bond numbers, and dielectric constants of interface and surface layers mainly contribute to the lowest interface work of adhesion and surface tension values at optimal diameters. These results unveil the nonmonotonic characteristics of spreading velocity, interface work of adhesion and surface tension with nanodroplet diameter for nanodroplets on solid surfaces

Molecular Insights into Distinct Detection Properties of α‑Hemolysin, MspA, CsgG, and Aerolysin Nanopore Sensors

Protein nanopores have been widely used as single-molecule sensors for the detection and characterization of biological polymers such as DNA, RNA, and polypeptides. A variety of protein nanopores with various geometries have been exploited for this purpose, which usually exhibit distinct sensing capabilities, but the underlying molecular mechanism remains elusive. Here, we systematically characterize the molecular transport properties of four widely studied protein nanopores, α-hemolysin, MspA, CsgG, and aerolysin, by extensive molecular dynamics simulations. It is found that a sudden drop in electrostatic potentials occurs at the sole constriction in MspA and CsgG nanopores in contrast to the gradual potential change inside α-hemolysin and aerolysin pores, indicating the crucial role of pore geometry in ionic and molecular transport. We further demonstrate that these protein nanopores exhibit open-pore currents and ssDNA-induced current blockades both in the order MspA > α-hemolysin > CsgG > aerolysin, but an equivalent blockade percentage around 80%. In addition, the substitution of key amino acids at the pore constriction, especially by charged ones, provides an efficient way to modulate the pore electrostatic potential and ionic current. This work sheds new light on the search for high-performance nanopores, engineering of protein nanopores, and design of bioinspired solid-state nanopores

Strain Gradient Mediated Magnetism and Polarization in Monolayer VSe₂

To explore the coupling of spin magnetization and charge polarization is an intriguing aspect for low-dimensional materials. Here, we use first-principles calculations to unveil a particular magnetoelectric state consisting of flexomagnetism and flexoelectricity in VSe2 monolayers when they are wrinkled or corrugated. Due to the anomalous V–Se bond structures caused by the flexural deformation and the resulting discontinuous and inhomogeneous strain gradients, the magnetic moments of V atoms fluctuate sharply with the strain gradients and are dominated by the relative bond changes between their adjacent V atoms. Meanwhile, out-of-plane polarizations occur at the wrinkled VSe2 monolayers. The magnetism and polarization of the VSe2 monolayer can be simultaneously tuned by modifying the strain gradient and corrugation geometry. Our results highlight a possible route of utilizing the mechanical and structural design to achieve the desired magnetoelectric functionality in two-dimensional materials

Additional file 1 of Metabolic engineering of fast-growing Vibrio natriegens for efficient pyruvate production

Additional file 1: Figure S1. Analysis the functions of two inducible prophages in the genome of V. natriegens wild-type (WT) strain. Table S1. Fed-batch fermentation parameters for WT and engineered strains. Table S2. Primers used in this study

MOESM1 of QTL analysis reveals genomic variants linked to high-temperature fermentation performance in the industrial yeast

Additional file 1: Table S1. S. cerevisiae strains used in this study. Figure S1. Fermentation profiles of RHA and allele replacement strains of the causative genes