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The in-plane piezoelectricity increases with increasing the number of layers for O@MoS2. The vertical piezoelectricity of trilayer reaches 101.632 pm V−1, reaching the level of piezoelectric coefficients in state-of-the-art perovskites.

For the first time, we determined the phytochemical profile of alkaloids from N. officinalis by ultraperformance liquid chromatography-quadrupole-time-of-flight-tandem mass spectrometry (UPLC-Q-TOF-MS/MS). A rapid, specific, and sensitive high-performance liquid chromatography-tandem mass spectrometry method was subsequently developed and fully validated for simultaneous determination of 12 major alkaloid constituents in N. officinalis: pumiloside, naucleoxoside A, naucleoxoside B, nauclefine, angustidine, angustoline, (3S,19S)-3,14-dihydroangustoline,〖[α]〗_D^20: (-)191°, (3S,19R)-3,14-dihydroangustoline, 〖[α]〗_D^20: (-) 294.7°, strictosamide, angustine, vincosamide, and 3,14-dihydroangustine. The analytes were detected by electrospray ionization (ESI) source and multiple reaction monitoring (MRM) using positive scanning mode. Three pairs of epimers (naucleoxoside A and naucleoxoside B, (3S,19S)-3,14-dihydroangustoline,〖[α]〗_D^20: (-) 191° and (3S,19R)-3,14-dihydroangustoline, 〖[α]〗_D^20: (-) 294.7°, and strictosamide and vincosamide) were successfully separated using an ACQUITY UPLC® BEH C18 column (2.1 mm×100 mm, 1.7 μm) at 30°C, with a gradient mobile phase consisting of 0.1% formic acid aqueous solution (A) and acetonitrile (B), a flow rate of 0.2 mL min-1, and a total run time of 30 min. All calibration curves exhibited excellent linear regressions (r>0.999) within the test range. The precision, repeatability, and stability of the 12 alkaloid compounds were less than 2.0% in terms of the relative standard deviation (RSD). All mean recoveries of each compound were between 98.7% and 101.1%, with RSD ranging from 0.55% to 1.7% for N. officinalis samples.

Electrets are dielectric materials that have a quasi-permanent dipole polarization. A single-molecule electret is a long-sought-after nanoscale component because it can lead to miniaturized non-volatile memory storage devices. The signature of a single-molecule electret is the switching between two electric dipole states by an external electric field. The existence of these electrets has remained controversial because of the poor electric dipole stability in single molecules. Here we report the observation of a gate-controlled switching between two electronic states in Gd@C82. The encapsulated Gd atom forms a charged centre that sets up two single-electron transport channels. A gate voltage of ±11 V (corresponding to a coercive field of ~50 mV A–1) switches the system between the two transport channels with a ferroelectricity-like hysteresis loop. Using density functional theory, we assign the two states to two different permanent electrical dipole orientations generated from the Gd atom being trapped at two different sites inside the C82 cage. The two dipole states are separated by a transition energy barrier of 11 meV. The conductance switching is then attributed to the electric-field-driven reorientation of the individual dipole, as the coercive field provides the necessary energy to overcome the transition barrier. A Gd@C82 molecule shows electric polarization switching behaviour under a gate bias voltage, thus demonstrating a single-molecule electret device.

A size-selected beam of Au923±20 clusters is generated in a gas-phase condensation cluster source equipped with a lateral time-of-flight mass selector. The beam current reaches up to 9.13 nA for small clusters and 80 pA for Au923±20 clusters, which are then analyzed using a scanning transmission electron microscope. Four types of metastable structures are observed for the Au923±20 clusters, including ino-decahedron (Dh), cuboctahedron and icosahedron (Ih). The proportion of bulk-favorable cuboctahedron (i.e. face center cubic (Fcc)) structure takes up only 10–20%, while the penta-rotating symmetrical structures (Dh/Ih) are the dominant ones which take up over three quarters. Changing the beam condition may optimize the clusters from Dh-dominant to the Ih-dominant phase, which paves the way towards nanoparticle control beyond the diameters.

A pair of new diastereoisomers neolignans (1-2) and a new alkaloid (7) were isolated from the stems of Nauclea officinalis: naucleaoxyneolignoside A (1), naucleaoxyneolignoside B (2), (2S,3S)-javaniside (7), together with nine known compounds, 2S-3,3-di-(4-hydroxy-3-methoxyphenyl)-propane-1,2-diol (3), threo-1,2-bis-(4-hydroxy-3-methoxyphenyl)-propane-1,3-diol (4), nauclefine (5), angustidine (6), naucleoxoside A (8), naucleoxoside B (9), angustoline (10), (3S,19S)-3,14-dihydroangustoline (11), and (3S,19R)-3,14-dihydroangustoline (12).The structures of 1, 2 and 7 were elucidated by extensive spectroscopic methods and the known compounds were identified by comparison of their data with those reported in the literature. The absolution configurations of 1, 2, 7,11 and 12 were confirmed by the quantum chemical CD calculation method. Compounds 1-9 showed weak to moderate inhibitory activity on nitric oxide (NO) production induced by lipopolysaccharide in mouse macrophage RAW 264.7 cells in vitro with IC

The development of hydrogen sensors is of paramount importance for timely leak detection and remains a crucial unmet need. Palladium-based materials, well known as hydrogen sensors, still suffer from poisoning and deactivation. Here, a hybrid hydrogen sensor consisting of a Pd nanocluster (NC) film, a metal-organic framework (MOF), and a polymer, are proposed. The polymer coating, as a protection layer, endows the sensor with excellent H

Ethnopharmacological relevance Nauclea officinalis, a widely used Li medicine, has been used for the treatment of cold, fever, bronchitis, pneumonia, acute tonsillitis, and other ailments. Modern pharmacological studies have demonstrated that the most abundant and active components in N. officinalis are alkaloids, which possess various biological properties such as antibacterial and antitumor activities. Aim of the study To investigate the phytochemical profile of a selected group of alkaloids from the N. officinalis total alkaloids, and to determine the chemical profile of the alkaloids extracted from rat plasma. Further investigation was conducted to determine the pharmacokinetic behaviors of 11 selected major alkaloids, including pumiloside, naucleoxoside A, naucleoxoside B, nauclefine, angustidine, angustoline, (3S,19S)-3,14-dihydroangustoline, [ α ] D 20 : (−)191°, (3S,19R)-3,14-dihydroangustoline, [ α ] D 20 : (−) 294.7°, strictosamide, angustine, and 3,14-dihydroangustine. Materials and methods N. officinalis total alkaloids were extracted with 79% ethanol and enriched with AB-8 macroporous resin. The phytochemical profile of alkaloids from the N. officinalis total alkaloids and the chemical profile of the alkaloids extracted from rat plasma were first analyzed by UPLC-Q-TOF-MS/MS. A simple, convenient, and sensitive LC-ESI-MS/MS method was subsequently developed and validated for the simultaneous determination of major active alkaloids in rat plasma after oral administration of N. officinalis total alkaloids. After addition of an internal standard (verapamil), plasma samples were pretreated first by protein precipitation with methanol and then underwent liquid-liquid extraction with ethyl acetate. Chromatographic separation was achieved using a Waters BEH C18 column (2.1 mm × 100 mm, 1.7 μm) at 30 °C, with gradient elution using a mobile phase consisting of 0.1% formic acid aqueous solution (A) and acetonitrile (B), a flow rate of 0.2 mL/min, and a total run time of 30 min. The detection was performed using an electrospray ionization triple quadrupole tandem mass spectrometer with multiple reaction monitoring and positive ionization mode. Results Based on the fragmentation patterns of 11 authentic alkaloids and previous reports, 55 alkaloids were identified or tentatively identified in the N. officinalis total alkaloids. Among them, 25 alkaloids were absorbed through the gastrointestinal tract in rats after administration of the N. officinalis total alkaloids. The 11 alkaloids were selected for quantitative analysis. The established quantitative method was fully validated and proved to be sensitive and specific. Satisfactory linearity of the 11 alkaloids obtained in the respective concentration ranges (r > 0.9931). The lower limits of quantification for strictosamide was 20.86 ng/ml, and the other ten alkaloids were all less than 4.47 ng/ml in rat plasma. The intra-and inter-day precision was less than 15% for all 11 alkaloids in terms of relative standard deviation, and the accuracies ranged from −11.4% to 11.1% in terms of relative error. Extraction recovery, matrix effect, and stability were within the required limits in rat plasma. Conclusion The validated method was successfully applied to investigate the pharmacokinetics of the 11 alkaloids in rat plasma after oral administration of N. officinalis total alkaloids. Eleven alkaloids were rapidly absorbed to achieve a maximum plasma concentration with Tmax from 0.25 h to 1.5 h after oral administration. The pharmacokinetic parameters and plasma concentration-time profiles will prove valuable in pre-clinical and clinical investigations on the disposition of N. officinalis total alkaloids.

Indium selenide (InSe) is a promising two-dimensional photodetector material. However, the photogenerated electron-hole pairs are easy to recombine in simplex InSe semiconductor. Here, we design InSe-based van der Waals heterostructure, InSe/antimonene (β-Sb), based on first-principles. InSe/β-Sb heterostructure possesses intrinsic type-II electronic structure. Simultaneously, the work function of InSe (β-Sb) layer is −5.7 eV (−4.5 eV) which also promotes electrons transfer. In addition, the good optical absorption performance of InSe and β-Sb sublayer is preserved in the heterostructure. Moreover, different stacking mode between InSe/β-Sb does not affect the efficient carrier separation which is convenient to the application of optoelectronics.

Using first-principles calculations, we study the growth process of bismuth (Bi) films on Cu (111) substrate. By analyzing the formation mechanism of single layer α‑bismuthene and stability of multilayered Bi layers, we reveal that Bi atoms show quasi-one-dimensional growth model by developing periodic zigzag chains, and eventually form a Bi atomic layer on Cu (111) surface. Flat surface α‑bismuthene (Fα-Bi) can be formed by depositing two Bi atomic layers on Cu (111) and maintains its stability below 60 K. In the multilayered Bi atomic layers, the stability of Bi films shows an oscillatory behavior. It is more stable for Bi films with even layers. The charge density between even and odd films shows that the stability is associated with the saturation of pz orbital of Bi atoms. Besides, the distorted surface α‑bismuthene (Dα-Bi) can maintain its stability up to 450 K on Cu (111) surface. Further study shows that the Cu substrate strongly affects the properties of Fα-Bi than that of Dα-Bi. Our studies provide guidance for fabricating stable Bi (110) thin films based devices.

Grain boundaries (GBs) in polycrystalline graphene could significantly modulate the physicochemical properties of graphene films, and have attracted intense interest. However, fundamental magnetotransport mechanisms of GBs in bilayer graphene grown by chemical vapour deposition (CVD) are scarcely reported. In this work, we synthesize bilayer graphene bicrystals on polycrystalline Cu foils and measure the electronic properties of such grains as well as of individual graphene grain boundaries. Interestingly, the pronounced metallic character of GB is observed, which is dramatically different from individual grains. Large linear magnetoresistance in graphene bicrystals is observed, which attributes to inhomogeneous charge transport, decorated by quantum interference effects at low temperatures. The measurement data show that individual boundaries between coalesced grains impede electrical transport, suppress the magnetoresistance and enhance intervalley scattering, leading to degradation of electrical performance of CVD graphene. Nevertheless, GBs embedded in a perfect graphene sheet can tune its electronic structure at the nanoscale, act as quasi-one-dimensional metallic wires and can be used as good candidates for strong magnetic field sensors. This work is beneficial to the fundamental understanding of the role of GBs in CVD-grown graphene and opens a potential avenue of application for polycrystalline bilayer graphene in functional devices.

We present a sequential microdisplacement press–expand method. On this basis, we develop an efficient core–shell cluster algorithm with a given core-cluster structure from the arbitrary initial shell-cluster structure and further develop a global minima algorithm from the arbitrary initial structure. Many tests of stable clusters reveal that the structure of the stable core–shell clusters is an optimal atomic distribution of the outer atoms according to the potential fields of the core cluster. On this basis, we identify a new core–shell A@B8@C10 cluster. Applying a spin-polarized density functional theory (DFT) approach, we investigate the structural stability and magnetic properties of a B@Mn8@Mg10 cluster, which has high stability because of the strong p–d hybridization between B and Mn atoms and the strong s–d hybridization between Mn and Mg atoms. The most stable state is one in which the interface layer (Mn) atoms have an axial paramagnetic moment, whereas the Mn atoms have large local magnetic mome...

Metal halide perovskites (MHPs) with highly sensitive photoelectric response and ultrahigh absorption coefficient in the visible range exhibit huge potential as building blocks for optoelectronic devices. However, these perovskites suffer from poor absorption efficiency in the infrared range due to the weak coupling of infrared light. In this work, we report a new class of MHP-based heterostructures by the integration of two-dimensional Cs3+nPbnSb2I9+3n perovskites with GaN nanosheets for the realization of highly efficient carrier separation and broadband absorption. We find that the formation of the Cs/GaN(0001) interface in Cs3+nPbnSb2I9+3n/GaN heterostructures can induce the shift of the vacuum level below the conduction band minimum, resulting in negative electron affinity (NEA). Moreover, the NEA of the heterostructures is not sensitive to the thickness of perovskite and GaN layers. Owing to the type-II band alignment and NEA of these heterostructures, they exhibit highly efficient carrier separation and enhanced optical absorption from the infrared to ultraviolet light region, which result in maximum power conversion efficiency as high as 28.5%. The findings suggest the large potential of Cs3+nPbnSb2I9+3n/GaN heterostructures for optoelectronic applications, such as solar cells, photodetectors, and field emission devices.

Alongside the rise in fully automated equipment and wearable devices, there is currently a high demand for optically transparent and flexible gas sensors operating at room temperature. Nanoparticle films are ideal H2-sensing materials that can be coupled with flexible substrates because of their discrete nanogranular structure and unique interparticle electrical responsiveness. In this work, we present an optically transparent and flexible H2 sensor based on a Pd nanoparticle film, prepared on a polyethylene terephthalate sheet using a straightforward nanocluster deposition technique. Hundreds of bending cycles demonstrated that the sensor has good electrical stability and mechanical robustness without significant degradation in H2-sensing performance. The H2-sensing behaviors under bent state were systematically evaluated. The loading of tensile and compressive strains under bent state produced a positive and negative influence, respectively, on the sensing performances. The possible influence mechanism ...

The plasmonic response of gold clusters with atom number (N) = 100–70 000 was investigated using scanning transmission electron microscopy-electron energy loss spectroscopy. For decreasing N, the bulk plasmon remains unchanged above N = 887 but then disappears, while the surface plasmon firstly redshifts from 2.4 to 2.3 eV above N = 887 before blueshifting towards 2.6 eV down to N = 300, and finally splitting into three fine features. The surface plasmon's excitation ratio is found to follow N0.669, which is essentially R2. An atomically precise evolution picture of plasmon physics is thus demonstrated according to three regimes: classical plasmon (N = 887–70 000), quantum confinement corrected plasmon (N = 300–887) and molecule related plasmon (N

A size-selected beam of Au

Through the density functional theory, we studied molecular devices composed of single tetrathiafulvalene (TTF) molecules connected with zigzag graphene nanoribbon electrodes by four different junctions. Interestingly, some devices have exhibited half-metallic behavior and can bring out a perfect spin filtering effect and remarkable negative differential resistance behavior. The current–voltage characteristics show that these four devices possess different spin current values. We found that all the TTF molecules were stretched due to interactions with the electrodes in the four devices. This leads to the Fermi levels of the three devices being down-shifted to the valence band; therefore, these devices exhibit half-metallic properties. The underlying mechanisms of the different spin current values are attributed to the different electron transmission pathways (via chemical bonds or through hopping between atoms). These results suggest that the device properties and conductance are controlled by different junctions. Our work predicts an effective way for designing high-performance spin-injected molecular devices.

The icosahedral CuxAg13−x (x = 0–13) clusters are calculated using an effective sampling method and first-principle calculations based on density functional theory. And the segregation effect and its influence on the stability and electronic properties of the clusters are investigated. The calculation results show that the stability of CuxAg13−x greatly depends on the occupation position of Cu atoms and their segregation degree. The HOMO–LUMO gap of CuxAg13−x is closely related to the segregation degree of Cu atoms as well as the composition ratio between Cu and Ag. And an optimized Cu7Ag6 cluster, in which Cu atoms have the largest segregation degree, is found to be the largest HOMO–LUMO gap. By analyzing the local density of states, bond strength, bond length and bond ratio, we reveal the origin of the segregation effect and its influence on the HOMO–LUMO gap of CuxAg13−x. The results presented in this work are helpful to design the bimetallic clusters with stable structures and desired electronic properties.

Electrets are dielectric materials that have a quasi-permanent dipole polarization. A single-molecule electret is a long-sought-after nanoscale component because it can lead to miniaturized non-volatile memory storage devices. The signature of a single-molecule electret is the switching between two electric dipole states by an external electric field. The existence of these electrets has remained controversial because of the poor electric dipole stability in single molecules. Here we report the observation of a gate-controlled switching between two electronic states in Gd@C

The effect of in-plane uniaxial strain on band structures and electronic properties of graphene/blue phosphorene (Gr/BPh) bilayer has been investigated by using first-principles calculations. The results show that the intrinsic electronic properties of graphene and blue phosphorene are preserved well in the unstrained bilayer. Upon the application of in-plane uniaxial strain, the band gap of the Gr/BPh bilayer can be easily opened by ∼120 meV near ±2%, and the value of band gap increases with increasing the strain value. A maximum gap value ∼240 meV is obtained around ±4% strain. By analyzing the projected density of states and charge density differences, we reveal that the opened band gap under strain is closely related to the change in electronic structure of Gr/BPh bilayer, which is greatly influenced by the electron redistribution between graphene and BPh layers as well as the orbital hybridizations between carbon and phosphorus atoms. Further study finds that the band gap can not be opened when the in-plane biaxial strain is applied to the Gr/BPh bilayer. The present work provides us an effective avenue to tune the electronic structures and band gap for Gr/BPh bilayer.

Pd nanoparticles with a mean diameter of 6.7 nm are prepared by gas phase cluster beam deposition. The Pd nanoparticle films exhibit excellent catalytic activity and stability for methanol oxidation. 3D hybrid nanostructures combined with multi-walled carbon nanotubes and few-layer graphene sheets are used as supports to further enhance the methanol electro-oxidation activity of the Pd nanoparticle catalysts by a factor of more than 2.7. The catalytic activity towards methanol electro-oxidation is characterized with cyclic voltammetry measurements. An ultrahigh electrochemical active surface area (ECSA) as large as 311 m 2 g −1 pd and a mass specific current corresponding to methanol oxidation levels as high as 4038 mA mg −1 pd are realized. These results can be attributed to the high electrochemical activity of the Pd nanoparticles and the unique conductive structure of the multi-walled carbon nanotubes/few-layer graphene sheets.

In this article, we present a modified Velocity-Verlet algorithm that makes cluster system converge rapidly and accurately. By combining it with molecular dynamics simulations, we develop an effective global sampling method for extracting isomers of bimetallic clusters. Using this method, we obtain the isomers of icosahedral PdxAg13−x (x = 0–13). Additionally, using the first-principle spin-polarized density functional theory approach, we find that each isomer still retains its icosahedral structure because of strong s-d orbital hybridization, and the cluster is more stable when a Pd atom is at the center of the cluster. With increasing x value, the magnetic moment decreases linearly from 5.0 μB at x = 0, until reaching zero at x = 5, and then increases linearly up to 8.0 μB at x = 13. By calculating the atom-projected density of states (PDOS), we reveal that the magnetic moment of PdxAg13−x mainly originates from s electrons of Ag when 0 ≤ x d electrons of Pd when 5 xAg13−x tends to transform from a semiconductor state to semi-metallic state when x gradually increases from 0 to 13.

In this work, we proposed a novel three-dimensional (3D) plasmonic nanostructure based on porous graphene/nickel foam (GNF) and gas-phase deposited Ag nanoparticles (NPs). Ag NPs with high density were directly deposited on the surface of 3D GNF by performing a novel cluster beam deposition approach. In comparison with traditional Ag substrate (SiO2/Ag), such hot-spots enriched 3D nanostructure showed extremely high electromagnetic field enhancement under incident light irradiation which could be used as a sensitive chemical sensor based on surface enhanced Raman scattering (SERS). The experimental results demonstrated that the proposed nanostructure showed superior SERS performance in terms of Raman signal reproducibility and sensitivity for the probe molecules. 3D full-wave simulation showed that the enhanced SERS performance in this 3D hierarchical plasmonic nanostructure was mainly obtained from the hot-spots between Ag NPs and the near-field coupling between Ag NPs and GNF scaffolds. This work can provide a novel assembled SERS substrate as a SERS-based chemical sensor in practical applications.

We report a nonenzymatic H2O2 sensor based on a glassy carbon electrode modified with bilayer graphene films (BGFs) that were decorated with well-defined Pd nanoparticles. The BGFs were synthesized with a chemical vapor deposition process, and the Pd nanoparticle films were produced by gas phase cluster beam deposition. The BGFs provide great accessible active surface area and excellent conductive interfaces for electron transfer, which largely enhance the electrocatalytic performance of the modified electrodes. A rapid response time of less than 3 s and a wide linear range from 4 μM to 13.5 mM was exhibited in the amperometric detection of H2O2.

Based on the first principles calculations, we have investigated the magnetic properties of Irn+1 clusters modulated by Co atoms. The research conclusions show that the amplitude of magnetic anisotropy energy (MAE) and magnetization direction of the small Irn+1 can be manipulated by Co atom if we can control the size very precisely. Such regulatory mechanism of MAE is ascribed to the distributing variation of Ir-5d orbits around the Fermi level induced by Co atom. More importantly, the colossal MAE values, 67.4 meV/atom, 40.26 meV/atom and 91.37 meV/atom, can be obtained for Ir2, Ir4, and CoIr clusters, respectively. Such high values provide a promising avenue for developing high-density magnetic storage units at sub-nanometer size.

Single-crystal bilayer graphene is attractive for functional electronic and photonic devices because of its high carrier mobility as well as a tunable band gap induced by a perpendicular electric field. Chemical vapor deposition (CVD) has been increasingly reported for the production of single-crystal bilayer graphene, but it is limited with respect to grain size because of nonsynchronic growth between the second layer and the first layer of bilayer graphene. In this research, we established a nonisothermal atmosphere CVD (NI-APCVD) system to realize synchronization of nucleation and growth of single-crystal bilayer graphene that contains the surface adsorption for the decomposed carbons and the shallow bulk phase segregation for the dissolved carbons. Based on the above process engineering, we successfully produced large hexagonal single-crystal bilayer graphene (∼1.0 mm) on the polycrystalline Cu foils. This work paves a pathway to the synchronous growth of wafer-scale single-crystal bilayer graphene, w...

To solve the fundamental dilemma in data storage applications, it is crucial to manipulate the magnetic anisotropy energy (MAE). Herein, using first-principles calculations, we predict that the system of double-vacancy graphene decorated by iridium atoms possesses high stability, giant MAE, perpendicular-anisotropy and long-range ferromagnetic coupling. More importantly, the amplitude of MAE can be manipulated by electric fields. This is due to the change in the occupation number of Ir-5d orbitals. The present hybrid system could be a high-performance nanoscale information storage device with ultralow energy consumption.

Pd clusters were generated with a DC magnetron plasma gas aggregation cluster source. The dependence of the size distribution and ionization degree of the Pd clusters on the discharge power was studied. By tuning the discharge power from 15W to 50W, the mean size of the Pd clusters decreased from 13.8 nm to 4.2 nm, and the ratio of neutral and charged Pd clusters to the total rose from about 16.7% to about 76.7%. The effect was explained with a model by considering the enhanced production of Pd ions at higher magnetron discharge power. A simulation based on Direct Simulation Monte Carlo (DSMC) method verified the proposed mechanism of cluster growth.

Indium selenide (InSe) is a promising two-dimensional photodetector material. However, band-gap and work-function of low-dimension InSe are too large to act as photodetector devices. Here, we design InSe-based vdWs heterostructure, InSe/hBN (hexagonal boron nitride), using first-principles. InSe/hBN possesses rather low work-function (~3.0 eV) compared with that of isolated InSe monolayer due to strong interlayer coupling. Besides, strong interlayer coupling induces extra emerging states, markedly reducing band-gap of InSe/hBN. Meanwhile, these emerging states ensure red-shift of optical absorption, from infrared to ultraviolet light-harvesting. Moreover, different heterostructure stacking mode doesn’t affect optical absorption and electron emission, convenient to the application of optoelectronics.

A lateral heterojunction of topological insulator Sb2Te3/Bi2Te3 was successfully synthesized using a two-step solvothermal method. The two crystalline components were separated well by a sharp lattice-matched interface when the optimized procedure was used. Inspecting the heterojunction using high-resolution transmission electron microscopy showed that epitaxial growth occurred along the horizontal plane. The semiconducting temperature-resistance curve and crossjunction rectification were observed, which reveal a staggered-gap lateral heterojunction with a small junction voltage. Quantum correction from the weak antilocalization reveals the well-maintained transport of the topological surface state. This is appealing for a platform for spin filters and one-dimensional topological interface states.

Polystyrene(PS)/ZnO micronano hierarchical structures were fabricated on a flat surface by depositing ZnO nanoparticles from a cluster beam at oblique incidence on the surface predeposited with PS microspheres. The hierarchical structure was composed of submicron-sized PS particle layers covered with dense films of columnar ZnO nanoparticle piles separated with nanoscale pores. It was demonstrated that the cooperative effect that combines the microlens function of the PS microspheres and the enhanced Rayleigh scattering of the ZnO nanoparticle porous layers can be used to greatly reduce the total internal reflection at the medium-air interface. The PS/ZnO hierarchical structures were fabricated on the surface of GaN-based light-emitting diode (LED) chips to enhance the light-extraction efficiency. A 77.7% improvement on the light-output power was realized, which was much greater than that obtained with the PS microstructures alone.

High-mobility (Smx Bi1-x )2 Se3 topological insulators (with x = 0.05) show a Curie temperature of about 52 K, and the carrier concentration and Fermi wave vector can be manipulated by intentional Te introduction with no significant influence on the Curie temperature. The origin of the ferromagnetism is attributed to the trivalent Sm dopant, as confirmed by X-ray magnetic circular dichroism and first-principles calculations. The carrier concentration is on the order of 10(19) cm(-3) and the mobility can reach about 7200 cm(2) V(-1) s(-1) with pronounced Shubnikov-de Haas oscillations.

Dirac Fermions with different helicities exist on the top and bottom surfaces of topological insulators, offering a rare opportunity to break the degeneracy protected by the no-go theorem. Through the application of Co clusters, quantum Hall plateaus were modulated for the topological insulator BiSbTeSe2, allowing an optimized surface transport. Here, using renormalization group flow diagrams, we show the extraction of two sets of converging points in the conductivity tensor space, revealing that the top surface exhibits an anomalous quantization trajectory, while the bottom surface retains the 1/2 quantization. Co clusters are believed to induce a sizeable Zeeman gap ( > 4.8 meV) through antiferromagnetic exchange coupling, which delays the Landau level hybridization on the top surface for a moderate magnetic field. A quasi-half-integer plateau also appears at −7.2 Tesla. This allows us to study the interesting physics of parity anomaly, and paves the way for further studies simulating exotic particles in condensed matter physics., The topological surface states usually appear in pairs in a topological insulator, with one on the top surface and the other on the bottom surface. Here, Zhang et al. utilize Co cluster to induce a Zeeman gap on one surface through antiferromagnetic exchange coupling, and observe a quasi-half-integer plateau, suggesting the parity anomaly of Dirac fermions.

Coating a polymeric membrane for gas separation is a feasible approach to fabricate gas sensors with selectivity. In this study, poly(methyl methacrylate)-(PMMA-)membrane-coated palladium (Pd) nanoparticle (NP) films were fabricated for high-performance hydrogen (H2) gas sensing by carrying out gas-phase cluster deposition and PMMA spin coating. No changes were induced by the PMMA spin coating in the electrical transport and H2-sensing mechanisms of the Pd NP films. Measurements of H2 sensing demonstrated that the devices were capable of detecting H2 gas within the concentration range 0–10% at room temperature and showed high selectivity to H2 due to the filtration effect of the PMMA membrane layer. Despite the presence of the PMMA matrix, the lower detection limit of the sensor is less than 50 ppm. A series of PMMA membrane layers with different thicknesses were spin coated onto the surface of Pd NP films for the selective filtration of H2. It was found that the device sensing kinetics were strongly affe...

Unsaturated magnetoresistance (MR) has been reported in WTe2, and remains irrepressible up to very high field. Intense optimization of the crystalline quality causes a squarely-increasing MR, as interpreted by perfect compensation of opposite carriers. Herein we report our observation of linear MR (LMR) in WTe2 crystals, the onset of which is first identified by constructing the mobility spectra of the MR at low fields. The LMR further intensifies and predominates at fields higher than 20 Tesla while the parabolic MR gradually decays. The LMR remains unsaturated up to a high field of 60 Tesla and persists, even at a high pressure of 6.2 GPa. Assisted by density functional theory calculations and detailed mobility spectra, we find the LMR to be robust against the applications of high field, broken carrier balance, and mobility suppression. Angle-resolved photoemission spectroscopy reveals a unique quasilinear energy dispersion near the Fermi level. Our results suggest that the robust LMR is the low bound of the unsaturated MR in WTe2.

Enterocutaneous fistula (ECF) is a serious complication of Crohn's disease (CD). Enteral nutrition (EN) is believed as one of therapeutic strategies of CD. This study is dedicated to identify predictors of response to EN in CD, which may lead to a better selection of fistula patients for this therapy.Forty-eight CD patients with ECF treated with short-peptide-based EN for 3 months were included in this study. All patients were followed up for at least 6 months. Logistic regression was performed to investigate the potential predictors of response to EN in these patients.In total, 30 out of 48 patients were confirmed with a successful closure of fistula after 3 months' EN therapy. The average closure time was 32.4±8.85 days. Inflammatory parameters (erythrocyte sedimentation rate, C-reactive protein (CRP) and platelet count) improved significantly after EN therapy in all enrolled patients. Specifically, the improvement of CRP after therapy in closed group was more important compared with that in unclosed group (P=0.035). Nutrition status (body weight, body mass index (BMI), hemoglobin, serum albumin (ALB), serum prealbumin and total protein (TP)) improved as well (P0.05). Similarly, after treatment, the improvement of serum albumin (P=0.046) and prealbumin (P=0.006) in closed group was much more important than those in unclosed group. Logistic regression analysis discovered that a decreased CRP level and an elevated BMI level would be beneficial to the response to EN in CD patients with ECF.In CD patients with ECF, lower CRP and higher BMI are associated with higher possibility of closure after EN treatment. EN therapy can lead to a closure of ECF in a certain proportion of patients. EN therapy could also ameliorate inflammatory condition and improve nutrition status.

TiO₂ nanoparticle layers composed of columnar TiO₂ nanoparticle piles separated with nanoscale pores were fabricated on the bottom surface of the hemispherical glass prism by performing gas phase cluster beam deposition at glancing incidence. The porosity as well as the refractive index of the nanoparticle layer was precisely tuned by the incident angle. Effective extraction of the light trapped in the substrate due to total internal reflection with the TiO₂ nanoparticle layers was demonstrated and the extraction efficiency was found to increase with the porosity. An enhanced Rayleigh scattering mechanism, which results from the columnar aggregation of the nanoparticles as well as the strong contrast in the refractive index between pores and TiO₂ nanoparticles in the nanoporous structures, was proposed. The porous TiO₂ nanoparticle coatings were fabricated on the surface of GaN LEDs to enhance their light output. A nearly 92% PL enhancement as well as a 30% EL enhancement was observed. For LED applications, the enhanced light extraction with the TiO₂ nanoparticle porous layers can be a supplement to the microscale texturing process for light extraction enhancement.

The recent discovery of a Weyl semimetal in TaAs offers the first Weyl fermion observed in nature and dramatically broadens the classification of topological phases. However, in TaAs it has proven challenging to study the rich transport phenomena arising from emergent Weyl fermions. The series MoxW1−xTe2 are inversion-breaking, layered, tunable semimetals already under study as a promising platform for new electronics and recently proposed to host Type II, or strongly Lorentz-violating, Weyl fermions. Here we report the discovery of a Weyl semimetal in MoxW1−xTe2 at x=25%. We use pump-probe angle-resolved photoemission spectroscopy (pump-probe ARPES) to directly observe a topological Fermi arc above the Fermi level, demonstrating a Weyl semimetal. The excellent agreement with calculation suggests that MoxW1−xTe2 is a Type II Weyl semimetal. We also find that certain Weyl points are at the Fermi level, making MoxW1−xTe2 a promising platform for transport and optics experiments on Weyl semimetals., A Type II Weyl fermion semimetal has been predicted in Mo x W1−x Te2, but it awaits experimental evidence. Here, Belopolski et al. observe a topological Fermi arc in Mo x W1−x Te2, showing it originates from a Type II Weyl fermion and offering a new platform to study novel transport phenomena in Weyl semimetals.