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Strain leads to a rich magnetic phase transition in PC3NR, that is, from bandgap-tunable bipolar magnetic semiconductors to spin-gapless semiconductors to ferromagnetic metals or half-metal magnets and ±100% SP over a wide energy interval around EF.

The unique edge states of the zigzag β-SiC7 nanoribbons aroused our attention, and therefore, based on first-principles calculations, we investigated their spin-dependent electronic transport properties by constructing controllable defects to modulate these special edge states. Interestingly, by introducing rectangular edge defects in the SiSi and SiC edge-terminated systems, not only the spin-unpolarized is successfully converted to completely spin-polarized, but also the direction of polarization can be switched, thus enabling a dual spin filter. The analyses further reveal that the two transmission channels with opposite spins are spatially separated and that the transmission eigenstates are highly concentrated at the relative edges. The specific edge defect introduced only suppresses the transmission channel at the same edge but reserves the transmission channel at the other edge. In addition, for the CSi and CC edge-terminated systems, an additional spin-down band exists due to spin splitting in the spin-up band at EF, so that besides the original spatially separated two spin-opposite channels, an extra spin channel is distributed at the upper edge, resulting in unidirectional fully spin-polarized transport. The peculiar spatially separated edge states and excellent spin filtering properties could open up further possibilities for β-SiC7-based electronic devices in spintronics applications.

The generation of spin currents is a significant issue in spintronics. A spin current can be induced by a temperature gradient in the spin-dependent Seebeck effect, which has attracted growing interest over recent years. Herein we propose spin caloritronic devices based on magnetic graphether nanoribbons and investigate the spin thermoelectric properties by first-principles calculations. Owing to the symmetrical spin-resolved transmission spectra, our devices exhibit a robust spin-dependent Seebeck effect and could generate a pure spin current. Moreover, they manifest a high spin Seebeck coefficient and a giant spin figure of merit. Our findings demonstrate that graphether-nanoribbon-based devices possess remarkable spin thermoelectric performance, and might be promising candidates for spin caloritronics.

The introduced gate voltage allows β-SiC7 nanoribbons to behave as an excellent electrically modulated reversible dual spin filter with surprisingly accurate control of spin polarization.

Different from conventional materials, structures with a negative Poisson's ratio (NPR) contract/expand laterally under a longitudinal compressive/tensile strain, usually exhibiting peculiar features. Through first-principles calculations, we investigate the electronic and transport properties of Pd

Searching for high-performance electrode materials is an important topic in rechargeable batteries. Using first-principles calculations, we systematically explore the potential application of a two-dimensional BP2 monolayer as a cathode material for Li-ion and Na-ion batteries. The pristine BP2 monolayer exhibits metallic characteristics, which facilitate the transportation of electrons. The Li and Na atoms bind strongly to the BP2 monolayer, indicating a good structural stability. Furthermore, the geometrical structure of BP2 is well maintained during the adsorption process. The Li and Na ions prefer to move along the zigzag direction with relatively low energy barriers. Especially, the ultralow Na diffusion barrier (0.03 eV) implies that monolayer BP2 has an excellent charge/discharge capability. The specific capacity and average electrode potential of Li (Na) are 619.45 (279.93) mA h g−1 and 2.89 (2.49) V, respectively. These results reveal that the BP2 monolayer is an appealing cathode material for alkali-metal batteries.

Sodium-ion batteries (SIBs) have been attracting great attention as the most promising alternative to lithium-ion batteries (LIBs) for large-scale energy storage. However, the absence of suitable anode materials is the main bottleneck for the commercial application of SIBs. Herein, the adsorption and diffusion behaviors of Na on graphether are predicted by first-principles density functional calculations. Our results show that Na atoms can be adsorbed on graphether forming a uniform and stable coverage on both sides. Even at low intercalated Na concentrations, the semiconducting graphether can be changed to a metallic state, ensuring good electrical conductivity. Due to the structural anisotropy of graphether, the Na+ ions show a remarkable one-dimensional diffusion with an ultralow energy barrier of 0.04 eV, suggesting ultrafast charge/discharge characteristics. The graphether monolayer has a high theoretical specific capacity of 670 mA h g-1, which is much higher than commercial graphite anode materials. Furthermore, the average voltage is 1.58 V, comparable with that of commercial TiO2 anode materials for LIBs (1.5 V). During the charge/discharge process, graphether could mostly preserve the structural integrity upon the adsorption of Na even at the maximum concentration, suggesting its good reversibility. All these results show that graphether is a promising anode material for high-performance SIBs.

Shrinking the size of a bulk metal into nanoscale leads to the discreteness of electronic energy levels, the so-called Kubo gap δ. Renormalization of the electronic properties with a tunable and size-dependent δ renders fascinating photon emission and electron tunneling. In contrast with usual three-dimensional (3D) metal clusters, here we demonstrate that Kubo gap δ can be achieved with a two-dimensional (2D) metallic transition metal dichalcogenide (i.e., 1T′-phase MoTe 2 ) nanocluster embedded in a semiconducting polymorph (i.e., 1H-phase MoTe 2 ). Such a 1T′/1H MoTe 2 nanodomain resembles a 3D metallic droplet squeezed in a 2D space which shows a strong polarization catastrophe while simultaneously maintaining its bond integrity, which is absent in traditional δ-gapped 3D clusters. The weak screening of the host 2D MoTe 2 leads to photon emission of such pseudometallic systems and a ballistic injection of carriers in the 1T′/1H/1T′ homojunctions which may find applications in sensors and 2D reconfigurable devices.

Compared with the conventional magnetic means (such as ferromagnetic contacts), controlling a spin current by electrical methods could largely reduce the energy consumption and dimensions of nano-devices, which has become a focus of research in spintronics. Inspired by recent progress in the synthesis of an iron-based metal-organic nanostructure, we investigate the spin-dependent electronic transport of the molecule of Fe3-terpyridine-phenyl-phenyl-terpyridine-Fe3 (Fe3-TPPT-Fe3) through first-principles calculations, and propose a three-terminal device without ferromagnetics. By applying a gate voltage, not only the spin polarization can be switched between 100% and -100% to achieve a dual-spin filter, but also its fine regulation can be realized, where the transmission with any ratio of spin-up to spin-down electron numbers is achievable. Analysis shows that the particular transmission spectra are the key mechanism, where two peaks reside discretely on both sides of the Fermi level with opposite spins. Such a feature is found to be robust to the number of Fe atoms and TPPT chain length, suggesting that it is an intrinsic feature of such systems and very conducive to practical applications. The electrical control (such as an electric field) of spin polarization is realized at the single-molecule level, showing great application potential.

Correction for ‘Rich magnetic phase transitions and completely dual-spin polarization of zigzag PC3 nanoribbons under uniaxial strain’ by Hui-Min Ni et al., Phys. Chem. Chem. Phys., 2023, https://doi.org/10.1039/d2cp05066h.

Due to the weak van der Waals (vdW) interlayer interaction, interfacial geometry of two-dimensional (2D) magnetic vdW materials can be freely assembled, and the stacking order between layers can be readily controlled, such as laterally shifting or rotating, which may trigger the variation of magnetic order. We investigate the H-type bilayer CrI3 where the two layers are aligned in anti-parallel directions. Based on first-principles calculations, we propose two states with different interlayer magnetic couplings, i.e., ferromagnetic and antiferromagnetic, and analyze the superexchange mechanism inside. It is found that the two magnetic coupling states are stacking-dependent, and could be switched by applying out-of-plane axial strain and electron doping. Our findings show great application potential in the design of heterostructural and spintronic devices based on 2D magnetic vdW materials.

Based on first-principles calculations, the spin-dependent electronic transport of nanoporous graphene nanoribbons is investigated. A three-terminal configuration is proposed, which can electronically control the spin polarization of transmission, instead of magnetic methods. By modulating the gate voltage, not only could the transmission be switched between completely spin up and spin down polarized states to realize a dual-spin filter, but also the spin polarization could be finely tuned between 100% and -100%. Any ratio of spin up to spin down transport electrons can be realized, providing more possibilities for the design of nanoelectronic devices. Further analysis shows that the transmission spectra, with two distinct transmission peaks with opposite spins around EF, are the key point, which are contributed by p orbitals. And such a phenomenon is robust to the width and length of the nanoporous graphene nanoribbons, suggesting that it is an intrinsic feature of these systems. The electrical control on spin polarization is realized in pure-carbon systems, showing great application potential.

Pavement icing is a worldwide problem causing serious traffic accidents every year. Recently, new strategic recommendation is made for applying conductive pavement materials to enhance the public safety in snow and ice conditions. Under the excitation of this research background, the aim of this work was to design a smart bituminous material combining anti-icing and self-healing functions using electrothermal graphene microcapsules containing oily rejuvenator. Microcapsule particles were fabricated with an average size of 20 um and 5.0 wt% graphene. Bitumen samples with various content microcapsules (1.0–10.0 wt%) had an increasing electric conductivity trend tested using a four-point probe electrical resistivity instrument. In addition, thermal conductivity of bitumen samples had been greatly enhanced because of the existence of graphene. Anti-icing capability of bitumen samples with graphene microcapsules was sharply increased under a direct voltage (50 V) based on their ice shear force values. Self-healing efficiency of bitumen samples was evaluated by an improved mechanical properties set-up named the beam on elastic foundation (BOEF). With the effect of electrothermal energy conversion, the bitumen samples kept a higher self-healing efficiency after five healing cycles under low temperature of 0 °C. These results imply that the graphene microcapsules containing oily rejuvenator is a promise approach to realize the smart pavement combining anti-icing and self-healing functions.

Smart microvascular self-healing bituminous composites are considered a promising approach to prolong pavement service life. The objective of this work was to investigate the microvascular self-healing capability of bituminous material by using hollow fibers with oily rejuvenator through a direct-tension mechanical experiment. The hollow fibers with oily rejuvenator were prepared using a wet-spinning approach by applying polyvinylidene fluoride material. The fixed-length hollow fibers with sealed ends were mixed in bitumen to form composite samples. Through a repetitive tensile method, the tension strength data were used to calculate the self-healing efficiency autonomously by considering crack closure and healing at various healing temperatures and times. The scanning-electron-microscope morphology showed that the polyvinylidene fluoride hollow fibers had a tight interfacial structure with bituminous material without debonding. X-ray computed tomography results indicated that the fibers were distributed homogeneously in bitumen. The fiber content and fiber orientation affected the self-healing capability of bituminous samples at 0 °C. To simplify the influence of the above two factors of the fibers, only one fiber was placed in bitumen samples parallel to the tension direction. With an increase in temperature from 0 to 30 °C, the self-healing capability of the bitumen samples increased dramatically. This phenomenon is attributed to the accelerated penetration speed of rejuvenator in the bitumen. An increase in time increased the self-healing capability of the bitumen samples. The rejuvenator may have sufficient time to leak from the hollow fibers and penetrate the bitumen. The results provide a guide to the microstructural design of the vascular fibers and the application of hollow fibers in self-healing asphalt pavement.

Due to the structure of three stacked layers, monolayer transition-metal dichalcogenides (TMDs) is different from graphene. Creating atomically flat graphene-like edges in them has long been expected, which is crucial to the modulation of electronic structures in two-dimensional systems. Recently, by thermal annealing, Chen et al. [21] successfully synthesized atomically flat Mo-terminated edge in monolayer MoS2. Inspired by this, through first-principles calculations, we studied the electronic and transport properties of typical TMD monolayers with transition atom-terminated flat zigzag edges, i.e., ScS2, VS2, CrS2, FeS2, NiS2, MoS2 and WS2. It is found that the nanoribbons with and without flat edges are both metallic. Interestingly, the vacancy in the flat edge could open a transmission gap at the Fermi level in the ScS2 ribbon, and trigger a metal-semiconductor transition. Further analysis shows that, the opening of bandgap around the Fermi level induced by the specific pattern of vacancies is the mechanism behind, which could be used as an modulating method for electronic structures. We believe our results are quite beneficial for the development of many other monolayer transition-metal dichalcogenides configurations, showing great application potential.

Hollow fiber containing rejuvenator is a promising smart material for vascular self-healing bituminous materials of pavement. The objective of this work was to experimentally observe the states of self-healing hollow fibers containing rejuvenator in pure bituminous material. Polyvinylidene fluoride (PVDF) hollow fibers containing oily rejuvenator were spun through single-wet-spinning method. The fixed-length hollow fibers with sealed ends were mixed in bitumen forming composite samples. The inter-surface and outer-surface microstructure of hollow fibers were observed by an environmental scan electron microscopy (ESEM). The micropores in fiber-shells were channels for rejuvenator to pass through. X-ray computed tomography (XCT) results indicated that these fibers distributed in bitumen with an integrality state. Three-dimensional reconstruction XCT (3D-XCT) images exhibited the details both of vertical and horizontal distribution of hollow fibers in bitumen. Thermogravimetic analysis (TGA) and a repeated thermal-cycle testament showed that the hollow fibers survived safely in bitumen. No debonding phenomenon was found between the fibers and bitumen. Oily rejuvenator released out of hollow fibers smoothly through the break point of hollow fiber/bitumen composite samples. The break images of hollow fibers in bitumen were also analyzed through 3D-XCT structures. At the same time, the movement tracks of oily rejuvenator out of hollow fibers were observed by a fluorescence microscopy. The rejuvenator permeated through the micropores on a hollow fiber into aged bitumen. These states mean that the self-healing can be triggered through the break points of hollow fibers as well as the self-rejuvenation when bitumen is aging. The above result is evidence that the hollow fibers containing rejuvenator will be a feasible approach to realize the self-healing and self-rejuvenating process of bitumen.

The recently synthesized two-dimensional C2N-h2D material has received extensive attention due to its similar honeycomb structure with graphene as well as uniform distribution of nitrogen atoms and holes. We perform first-principles calculations and find that armchair C2N-h2D nanoribbon (AC2NNR) is quite sensitive to edge modification. Edge unmodified and H-modified AC2NNRs are direct band gap semiconductors, while O-modified becomes an indirect band gap semiconductors. Interestingly, when both edge and sub-edge are modified with H or O atoms, it turns into a metal. Metal-semiconductor heterojunctions constructed from property-distinctive AC2NNRs all exhibit forward-blocking and reverse-conducting rectifying diode behaviors, and the maximum rectification ratio reaches an incredible value of 1010, showing good application prospects.

Unlike MoS2, single-layered Ag2S nanoribbons (Ag2SNRs) exhibit a nonmetal-shrouded and a zigzag-shaped buckling structure and possess two distinct edges, S- or Ag-terminated ones. By performing first principle calculations, the spin-dependent electron transport of Ag2SNRs in a ferromagnetic state has been investigated. It is found that the SS- and AgAg-terminated Ag2SNRs exhibit semi-metallic characteristics, but with opposite spin-polarized directions. And AgS-terminated ones show metallic characteristics, but with completely spin-unpolarized transmission. That is to say, all three states, i.e., spin up polarized, spin down polarized and spin unpolarized ones, could be achieved by modulating the edge geometry. Further analysis shows that, the spatial separation on edges of the energy states with different spins around EF is responsible for the switch in the three states. The system could operate as a dual spin-filter, and the direction of the spin polarization can be switched by the edge morphology. Furthermore, calculations show that such a phenomenon is robust to the width of the ribbon and strain, showing great application potential.

Searching for high-performance electrode materials is an important topic in rechargeable batteries. Using first-principles calculations, we systematically explore the potential application of a two-dimensional BP2 monolayer as a cathode material for Li-ion and Na-ion batteries. The pristine BP2 monolayer exhibits metallic characteristics, which facilitate the transportation of electrons. The Li and Na atoms bind strongly to the BP2 monolayer, indicating a good structural stability. Furthermore, the geometrical structure of BP2 is well maintained during the adsorption process. The Li and Na ions prefer to move along the zigzag direction with relatively low energy barriers. Especially, the ultralow Na diffusion barrier (0.03 eV) implies that monolayer BP2 has an excellent charge/discharge capability. The specific capacity and average electrode potential of Li (Na) are 619.45 (279.93) mA h g-1 and 2.89 (2.49) V, respectively. These results reveal that the BP2 monolayer is an appealing cathode material for alkali-metal batteries.

Magneto-optical materials represent a type of materials that intrinsically or extrinsically lack time-reversal symmetry and exhibit the nonreciprocal magneto-optical effects, which have been extended to two-dimensional layered materials recently. However, the corresponding magneto-optical investigations have thus far been limited to two-dimensional layered inorganic materials. Here we theoretically report the generation and manipulation of the magneto-optical effects in two-dimensional layered organic materials. It is found that monolayer hexagonal organometallic lattice intrinsically supports the nonzero Faraday rotation angle due to the joint contributions from spin-orbit coupling as well as its inherent ferromagnetism. In addition, its evolutions of the band structures and Berry curvatures induced by an external electric field grant us the controllable magneto-optical effects. The nontrivial magneto-optical effects of two-dimensional layered organic materials, in conjunction with their electric-field control, considerably endow the available organic magneto-optical candidates beyond what are currently used in the present magneto-optical fields.

Self-healing bituminous material has become a hot research topic in self-healing materials, and this smart self-healing approach is a promising a revolution in pavement material technology. The aim of this work was to investigate the electrothermal self-healing bituminous composite material using microcapsules containing rejuvenator with graphene/organic. The microcapsules owned electric conductivity capability because of the advent of graphene, and realized the self-healing through the two approaches of heat induction and rejuvenation. Microcapsule shells were fabricated using a strength hexamethoxymethylmelamine (HMMM) resin and graphene by a two-step hybrid polymerization. Experimental tests were carried out to character the morphology, integrity and shell structure. It was found that the electric charge balance determined the graphene/HMMM microstructure. The graphene content in shells could not be greatly increased under an electrostatic balance in emulsion. XPS, EDS, TEM and AFM results indicated that the graphene had deposited on shells. TGA/DTG tests implied that the thermal decomposition temperature of microcapsules with graphene had increased to about 350 °C. The thermal conductivity of microcapsules had been sharply increased to about 8.0 W/m2·K with 2.0 wt% graphene in shells. At the same time, electrical resistivity of microcapsules/bitumen samples had a decrease with more graphene in bitumen. The self-healing efficiency of composite samples was evaluated by a beam on elastic foundation (BOEF) mechanical process including loading-unloading-reloading cycles under temperature of 0 °C. It was found that the samples had an enhanced self-healing capability because of the electrothermal self-healing mechanism. The crack surfaces of bitumen were softened under electrothermal effect. Moreover, the released rejuvenator diffused into aged bitumen with a faster rate under the help of heat energy.

The aim of this work was to prepare and characterize a novel vascular self-nourishing and self-healing hollow fiber containing oily rejuvenator for aged bitumen. The hollow fibers containing oily rejuvenator were fabricated with micropores by a one-step wet-spinning method using polyvinylidene fluoride (PVDF) resin. Hollow fibers had been successfully prepared based on the test results of morphology, size and chemical structure. The hollow fibers had a good thermal stability with a decomposition temperature of 450 °C. The mechanical properties of fibers satisfied the requirements of use in bituminous materials. Because of the existence of micropores microstructure in fibers, the rejuvenator had the permeability out of fibers. The diffusion behaviors of rejuvenator were also measured by an attenuated total reflection flourier transformed infrared spectroscopy (FTIR-ATR) method. It was found that the diffusion coefficient greatly depended on the pore structure and temperature. A fitting model implied that the diffusion coefficient had a big deviation of Fick’s law and greatly influenced by the pore structure of hollow fibers. It is a guide to design and regulate the microstructure of hollow fibers with appropriate rejuvenator releasing behaviors. All above results implied that the existence of both self-nourishing and self-healing had been successfully proved in aged bitumen using hollow fibers containing oily rejuvenator.

In structure, a [n]cycloparaphenylene ([n]CPP) molecule is constructed by fully conjugated bent benzenes, i.e., hexangular rings. Based on first-principles calculations, the spin-dependent electronic transport of transition metal-doped CPP, X@[6]cycloparaphenylene (X@[6]CPP) (X = Fe, Co and Ni), contacted with Au electrodes is investigated. (Multiple) negative differential resistance (NDR) is observed for all the doping cases, suggesting it is the intrinsic feature of such systems. Due to the spin dependence of the NDR, electrical switch of the direction of spin polarization for a current is realized. Further analysis shows that it is the suppression of the transmission peaks around the Fermi level as the bias increases that results in the NDR. The suppression is caused by the decay of the local density of states on the scattering region. As electrically controlled spin polarization is a promising area in nanoelectronics, we believe our results would be quite beneficial to the development of spintronic devices.

A novel layered two-dimensional graphene-like material C2N-h2D with evenly distributed holes and nitrogen atoms has been synthesized via a bottom-up wet-chemical reaction [Nat. Commun. 6, 6486 (2015)]. The presence of holes provides a ground for further functionalization by doping. By performing a first-principles study, we have doped transition metals at the center of the holes of C2N-h2D nanoribbons and explored their doping effects on electronic, magnetic and transport properties. It is found that the doping can essentially regulate the electronic properties of C2N-h2D nanoribbons. The metallic zigzag ribbon is tuned into a semiconductor for Mn, Fe and Co-doped cases, but half-metal for Ni-doping. This transition is derived from the peculiar band morphology which has a big band gap between the edge state and the higher band, so when the energy of the edge state is reduced by the impurity state, the band gap falls too and crosses the Fermi level. In contrast, the pristine semiconducting armchair C2N-h2D nanoribbon is changed into metallic. Different from the zigzag case, its physical mechanism originates from the hybridization of 3 d orbitals of transition metal atoms and the p orbitals of carbon and nitrogen atoms which introduces several resonant peaks at the Fermi level in the density of states. Furthermore, the magnetic moments of all doped materials are enhanced compared to the pristine structures but decrease as the atomic number of the transition metal atom increases. And the spin polarization of armchair C2N-h2D nanoribbon is increased, while that of the zigzag structure is decreased except the Ni-doped one which is completely spin-polarized suggesting great prospects in the future of spintronics and nanoelectronics.

The two-dimensional material C3N has a honeycomb structure similar to graphene, but its heterogeneity of carbon and nitrogen elements makes it multifunctional. By performing a first-principles study, we find that edge morphology induces interesting electronic transport properties in step-like heterojunction devices composed of width-variable zigzag C3N nanoribbons. As long as the right part has an edge of all-carbon morphology, negative differential resistance and rectification effects will occur. If both edges are not of all-carbon morphology due to the presence of N atoms, a forward-conducting and reverse-blocking rectifier diode behavior will appear. These phenomena originate from the peculiar electronic structure of the zigzag C3N nanoribbons. The number of energy bands crossing the Fermi level gradually decreases from 2 to 0 as the number of all-carbon edges decreases, realizing a transition from metal to semiconductor. The band gap determines the cut-off region at low bias and the presence of an interface barrier causes the cut-off state to continue under high reverse bias. Diverse edge morphologies, simple cutting methods and rich electronic transport properties make C3N materials competitive in nanodevice applications.

Unlike graphene nanoribbons, zigzag monolayer hexagonal boron nitride nanoribbons (ZBNNRs) possess two distinct edges (B and N edges). Using first-principles calculations, we investigate the spin-dependent electronic transport of ZBNNRs with edge defects. It is found that the defects could make the system operate as a dual spin filter, where the direction of spin polarization is switched by the defect. Further analysis shows that the transmission eigenchannels for the opposite spins reside spatially separated on opposite edges. The defect on one edge could suppress the transmission for only one spin component, but preserve that for the other spin, resulting in a dual spin filter effect. This effect is found to be unaffected by the width of the ribbon and the length of the defect. Moreover, by constructing defects on both edges, the system exhibits two transmission peaks with opposite spins residing discretely on both sides of the Fermi level, suggesting that an electrically controlled dual spin filter based on ZBNNRs is also realizable. As controllable defects have been experimentally fabricated on monolayer boron nitride [T. Pham, A. L. Gibb, Z. Li, S. M. Gilbert, C. Song, S. G. Louie and A. Zettl, Nano Lett., 2016, 16, 7142-7147], our results may shed light on the development of B/N-based spintronic devices.

Based on first-principles calculations, the electronic transport of a recently synthesized all-benzene molecule of trefoil knot is investigated, by contacted with Au electrodes. Negative differential resistance behavior is observed. Further analysis shows that, it is resulted from the weaken of the states on the molecule modulated by the bias voltage, which suppresses the transmission eigenchannels and transmission peaks. Moreover, such a NDR behavior is also found in knot molecules with more benzene rings, indicating NDR is the intrinsic feature of such kind of molecules and robust to the number of benzene rings. These findings are expected to be extended to many other molecules with similar geometries, and may throw light on the development of future nanodevices.

Sodium manganese hexacyanoferrate (NaMnHCF) with low cost and high energy density is a promising cathode in Na-ion batteries (NIBs); however, the Jahn-teller effect of Mn3+ and large amounts of Fe(CN)64− defects significantly reduces the cycling life of the battery. Here, we introduce a chemically less soluble and structurally more stable layer to the NaMnHCF surface with a simple ion-exchange method to mitigate the irreversible structural change and side reactions associated with both the low-spin FeII/FeIII and the high-spin MnII/MnIII redox. The NaMnHCF cathode treated in Cu2+ solution shows much better cycling stability (80 vs. 30 mA h g−1 after 1000 cycles at 1 C) and rate performance than the unmodified NaMnHCF. The as-proposed chemical ion-exchange is a well-compatible and low-cost technology to realize surface modification of NaMnHCF and other hexacyanoferrates, which is of great significance for the development of high-performance NIB cathodes.

Lateral heterostructures provide new opportunities for tailoring the electronic properties of next-generation nanodevices. Hereon, the electronic properties and band alignment, as well as the width and strain effect of lateral heterostructures composed of germanium selenide (GeSe) and black phosphorus (BP) monolayer are systematically explored by first-principles calculations combined with nonequilibrium Green’s function (NEGF) theory. The results demonstrate that GeSe/BP lateral heterostructure is a direct band gap semiconductor with type-Ⅱ band alignment, in which electrons and holes are completely separated in BP and GeSe domain, respectively. The spontaneous separation of carriers is beneficial for their transport and has potential applications in unipolar electronic device. The band gaps gradually decrease with the increasing supercell width and in-layer tensile strain, and have an indirect-to-direct transition. In addition, band alignment calculations reveal that type-Ⅱ to quasi type-Ⅰ transition is observed through changing heterostructure width, while electron-hole pairs remain spontaneous separation with type-Ⅱ band alignment under small tensile strain. The present results provide vital guidance for the investigation and modulation of electronic properties based on GeSe/BP lateral heterostructure. Furthermore, this work may further attract investigation enthusiasms on the related research based on lateral heterostructures composed by other two-dimensional materials beyond GeSe and BP.

Oogenesis of Lygodium japonicum (Thunb.) Sw. is studied using TEM and cytochemical techniques. The early development of the archegonia of L. japonicum is similar to those of the core-leptosporangiate ferns. A mature archegonium always contains an egg, a ventral canal cell (VCC) and a binuclear neck canal cell (NCC). With the development of the egg, a separation cavity forms between the egg and the VCC. However, a pore region, with a diameter of about 3.5 μm, constantly connects the egg and the VCC. The canal cells degenerate gradually accompanied by the accumulation of mucilaginous secretions around the canal cells. PAS reaction reveals that these secretions are polysaccharide in nature. Later development of the archegonia of L. japonicum differs greatly from the core-leptosporangiate ferns. The egg nucleus becomes highly irregular and two types of nuclear evaginations are formed during oogenesis. When the egg matures, no egg envelope or fertilization pore are formed. Only a layer of amorphous material is deposited on the outer surface of the egg. This is the first observation of a fern species that has a pore region but does not result in the formation of a fertilization pore. The pore region appears to determine the formation of the fertilization pore. These observations are consistent with the hypothesized phylogenetic position of L. japonicum relative to the core leptosporangiate ferns.

The electronic transport of [n]cycloparaphenylenes ([n]CPPs) is investigated based on nonequilibrium Green's function formalism in combination with the density-functional theory. Negative differential resistance (NDR) phenomenon is observed. Further analysis shows that the reduction of the transmission peak induced by the bias changing near Fermi energy results in the NDR effect. Replacing the electrode (from carbon chain to Au electrode), doping with N atom and changing the size of the nanohoop (n = 5, 6, 8, 10) have also been studied and the NDR still exists, suggesting the NDR behavior is the intrinsic feature of such [n]CPPs systems, which would be quite useful in future nanoelectronic devices.

Microcapsules containing phase-change materials (microPCMs) have received increasing attention in the field of latent thermal storage. The addition of graphene in the shells could be a promising approach to enhance the physicochemical properties of microPCMs because of its superior characteristics particularly the thermal conductivity. The aim of this study was to prepare and investigate the chemical microstructure and physicochemical properties of novel microPCMs with graphene/organic hybrid structure shells. Paraffin was used as a phase-change material, which was microencapsulated by graphene and methanol-modified melamine-formaldehyde (MMF) through an in situ polymerization. The mean size and shell thickness were analyzed. The scanning electron microscopy (SEM) results showed that the microPCMs were spherical particles and graphene enhanced the smoothness of the shell surface. The contents of graphene in the shells were analyzed using X-ray photoelectron spectroscopy (XPS); the microstructure of the shells was investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). It was found that the shells had a graphene/organic hybrid structure, which was formed though the electric charge absorption and long-molecular entanglement. At the same time, the mechanical properties of the microcapsules were improved because of the graphene addition. Thermogravimetric analysis (TGA) tests showed that the microPCMs had a higher degradation temperature of 295 °C. In addition, graphene greatly enhanced the thermal stability of the microPCMs. The phase-change properties of the microPCMs were studied by differential scanning calorimetry (DSC) and thermal cycling tests. The results indicated that the phase-change temperature was regulated by the graphene addition and that graphene reduced the thermal barrier of the polymer shell material. The thermal conductivity of microPCMs with 1.0 wt% graphene was increased by about 100% compared to that of microPCMs without graphene. Moreover, the phase-change cycling tests implied that the microPCMs possessed a sensitivity response to heat because of the excellent thermal conductivity of graphene.

Spin caloritronics has drawn much attention as it combines thermoelectrics and spintronics together. Carbon-based structures, such as graphene, have been found to exhibit different kinds of spin caloritronic features. However, a study of spin caloritronics in carbon nanotubes (CNTs) is still lacking. Using first-principles calculations, we investigate the spin-Seebeck effect (SSE) in partially hydrogenated CNTs. It is found that linear hydrogenation could make CNTs acquire magnetism and exhibit the spin-Seebeck effect. Moreover, an odd-even effect of the SSE is observed, where the even cases could be used as spin-Seebeck diodes. Further analysis shows that, it is induced by the difference of band structures, where the band structure of a tube is a combination of that of graphene-nanoribbon parts "divided" by hydrogenation. This mechanism could be extended to nanotubes with different diameters, showing great application potential. We believe that our results are very useful for the development of nanotube-based spin caloritronic devices.

Unlike MoS2, single-layered Ag2S nanoribbons (Ag2SNRs) exhibit a nonmetal-shrouded and a zigzag-shaped buckling structure and possess two distinct edges, S- or Ag-terminated ones. By performing first principle calculations, the spin-dependent electron transport of Ag2SNRs in a ferromagnetic state has been investigated. It is found that the SS- and AgAg-terminated Ag2SNRs exhibit semi-metallic characteristics, but with opposite spin-polarized directions. And AgS-terminated ones show metallic characteristics, but with completely spin-unpolarized transmission. That is to say, all three states, i.e., spin up polarized, spin down polarized and spin unpolarized ones, could be achieved by modulating the edge geometry. Further analysis shows that, the spatial separation on edges of the energy states with different spins around EF is responsible for the switch in the three states. The system could operate as a dual spin-filter, and the direction of the spin polarization can be switched by the edge morphology. Furthermore, calculations show that such a phenomenon is robust to the width of the ribbon and strain, showing great application potential.

The electronic structures of phosphorene-like SnS/SnSe nanoribbons and the transport properties of a SnS-SnSe nanoribbon lateral heterostructure are investigated by using first-principles calculations combined with nonequilibrium Green's function (NEGF) theory. It is demonstrated that SnS and SnSe nanoribbons with armchair edges (A-SnSNRs and A-SnSeNRs) are semiconductors, independent of the width of the ribbon. Their bandgaps have an indirect-to-direct transition, which varies with the ribbon width. In contrast, Z-SnSNRs and Z-SnSeNRs are metals. The transmission gap of armchair SnSNR-SnSeNR is different from the potential barrier of SnSNR and SnSeNR. The I-V curves of zigzag SnSNR-SnSeNR exhibit a negative differential resistive (NDR) effect due to the bias-dependent transmission in the voltage window and are independent of the ribbon width. However, for armchair SnSNR-SnSeNR, which has a low current under low biases, it is only about 10-6 μA. All the results suggest that phosphorene-like MX (M = Sn/Ge, X = S/Se) materials are promising candidates for next-generation nanodevices.

The electron transport properties of zigzag graphene nanoribbons (ZGNRs) with upright standing carbon chains are investigated by using first-principles calculations. The calculated results show a significant odd-even dependence. The currents of even-numbered chain configurations are small because a suppression emerges around the Fermi energy in the transmission spectra under a finite bias. However the I − V curves of odd-numbered chain structures display metallic properties with a big transmission peak in the transmission spectra, indicating the high conductance. These properties offer an interesting method by modifying the odd-even parity of the carbon chains to tune the electron transport properties of ZGNRS.

The all-boron fullerene, B40, has been successfully experimentally synthesized [Zhai et al., Nat. Chem., 6, 727 (2014)]. Compared with C60, the smaller cage-like structure is more suitable to dope with metal atoms. Based on density functional theory and nonequilibrium Green’s function method, we investigate the spin-dependent transport of transition metal atom-encapsulated B40 fullerene, i.e., X@B40 (X = Fe, Mn, Ni, and Co), which are contacted with Au electrodes. The transmission spectra of Fe- and Mn-doped systems are spin-polarized, and those of Ni-doped ones are spin-unpolarized. Interestingly, in Co-doped systems, the transmission is highly spin-polarized for the hexagonal doping case, but spin-unpolarized for the heptagonal doping case. Further investigation shows that the screening effect of the electrodes on the magnetism of Co is the underlying physical mechanism, which is found to be robust to the electrode material. We believe that these findings are very useful for developing spintronic devices.

The solidification kinetics of polyolefins (PO) under three cooling conditions were investigated using an in situ measurement of the temperature decay within the PO resins. The phase-change temperature range of high-density polyethylene (HDPE) was located between 110 and 120°C, and those of low-density polyethylene (LDPE) and polypropylene (PP) were 90–110°C and 100–120°C, respectively. The cooling rate of the liquid-state stage is larger than that of the crystallization stage, primarily owing to the release of the latent heat of crystallization as well as the reduced temperature difference between the sample and cooling medium; they jointly slow down the cooling rate to an extent. The time with respect to phase transformation and its lasting period have close relations to the materials' molecular characteristics (e.g., Mw, MWD, LCB, etc.). Three empirical equations were proposed, and found to be applicable for the cooling analysis of the PO molten materials at relatively low cooling rates prior t...

Inspired by the recent experimental progress on the synthesization of a new type of molecule, a polyyne wire doped with the organometallic Ru ( dppe ) 2 fragment, which exhibits superior electronic properties to similar organic molecules reported before, we studied the electronic transport of it contacted with Au electrodes through first-principles calculations. Multiple striking negative differential resistance (NDR) behavior is observed, where the current could decrease to nearly zero. Moreover, such a phenomenon is found to be robust to the conformational change of the molecule, indicating it is the intrinsic feature of it. Further analysis shows that it is the suppression of the transmission peaks at the border of the bias window that results in the NDR. And, the suppression is resulted from the decay of the local density of states in the two-probe system, especially in the central axis of the molecule, where the states are found to originate from the p orbital of C atoms and the d orbital of Ru atoms. The multiple striking NDR behavior is achieved at the single-molecule level under low bias, showing great application potentials. These findings may throw light on the development of molecular devices.

Compared with conventional magnetic ways, modulating a spin-polarized current through electrical means could greatly reduce nano-devices’ energy consumption and dimensions, which emerges as a new research area in spintronics. Inspired by the experimental progress on the synthesis of helically twisted graphene, we study the electronic transport of kekulene-like helical graphene nanoribbons through first-principles calculations. By applying a gate voltage, the system can be switched between spin-unpolarized and completely spin-polarized states, realizing an electrically controlled spin filter. Moreover, a fine modulation of the spin polarization can also be achieved, where transmission with any ratio of spin-up to spin-down electrons can be obtained, beyond the traditional spin filter. The analysis shows that it is the particular transmission spectra that play a key role, where two wide peaks with opposite spins reside partially overlapped around the Fermi level. They originate from the p orbitals of the zigzag edge part in the helical structure. Since the configuration only consists of carbon atoms, the electrical control of spin polarization is realized in a pure-carbon nano-system, showing great application potentials.

Inspired by recent experiments on the successful synthesis of hydrofullerene C66H4 in Tian et al. (2019) [12] with two negatively curved heptagons. Based on the density functional theory and nonequilibrium Green's function method, we report the spin-dependent transport through transition-metal-atom-encapsulated C66H4 hydrofullerene, i.e., X@C66H4(X=Fe, Co, Mn, Ni), contacted by single gold atoms via semi-infinite non-magnetic Au electrodes. It is found that, Mn- and Fe-doped systems show highly spin-polarized transmission as well as considerable magnetic moments whereas Ni-doped systems show completely spin-unpolarized transmission and nonmagnetic. Interestingly, Co-doped systems show two spin states, i.e., spin-polarized and spin-unpolarized ones. Further analysis shows that, for Mn-, Fe- and Ni-doped systems, the spin-polarized/unpolarized state is caused by the finite/(nearly-)zero magnetism of the encapsulated metal atom. While the magnetism in Co-doped systems is quenched for the top hexagonal doping case, but not for the side heptagonal doping one, which induces the spin-unpolarized/spin-polarized state. And the screening effect of electrodes on the magnetism of Co is the underlying physical mechanism. Our findings would be beneficial to the design of spintronics devices.

Rejuvenator-containing microcapsules for spontaneously healing microcracks in bitumen have been developed and are already commercially available. Such smart self-healing approaches are promising for use in developing long-life pavements. The aim of this work was to investigate the rheological behavior of bitumen blended with self-healing microcapsules effected by physical and chemical interface structures. Based on a point of colloids, three self-healing microcapsule samples were used, with average diameters of 10, 20, and 30 μm. Bitumen composites with various microcapsule contents (1%, 2%, 3%, 4%, and 5%) were produced. Morphological analysis showed that the microcapsules were spherical and did not agglomerate. Fluorescence microscopy and X-ray transmission computed tomography showed that the microcapsules were homogeneously dispersed in the bitumen and did not rupture or agglomerate. The smaller microcapsules had larger specific surface areas. The size and content of the microcapsules affected the physical parameters of the bitumen, e.g., penetration, softening point, and ductility. Fourier-transform infrared spectroscopy showed that the bitumen was chemically linked with the microcapsules via functional group reactions. A dynamic shear rheometer was used to investigate the rheological behaviors of the bitumen/microcapsule samples. The complex shear modulus and phase angle data showed that the microcapsule content and size greatly affected the rheological behavior of the bitumen. The bitumen viscoelasticity depended strongly on the contact area and chemical bonds. A mechanistic analysis was performed to clarify the rheological behavior changes in terms of physics and chemistry. This result of this preliminary analysis will be helpful in the screening and application of self-healing microcapsule products.