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A kind of CdS/Cd-BiOCl immobilized films photocatalyst was prepared. The optical and physicochemical properties of the CdS/Cd-BiOCl photocatalysts were analysed, and the detailed characterization revealed CdS/Cd-BiOCl films photocatalyst with good charge carrier separation effect. The reusabilities and photocatalytic properties of the samples were studied. The 15%CdS/Cd-BiOCl photocatalyst exhibited superior performance in photocatalytic degradation of tetracycline (TC) and favorable stability under visible light irradiation. As for the photodegradation rate of TC, 15%CdS/Cd-BiOCl exhibited an excellent photodegradation activity, which is 4.06 and 9.53 times higher than that of CdS/Cd and BiOCl, respectively. The results showed that dominant active species are •O2− and •OH radicals during photodegradation. The charge transfer in Z-scheme CdS/Cd-BiOCl films photocatalyst could synchronously generate conduct band (CB) electrons in BiOCl and valence band (VB) holes in CdS, and metal Cd served as electron mediator. This work can be a reference for the design of film photocatalysts and new insight for photodegradating towards contaminants.

Metal contacts to two-dimensional (2D) semiconductors are often plagued by the strong Fermi level pinning (FLP) effect which reduces the tunability of the Schottky barrier height (SBH) and degrades the performance of 2D semiconductor devices. Here, we show that MoSi2N4 and WSi2N4 monolayers—an emerging 2D semiconductor family with exceptional physical properties—exhibit strongly suppressed FLP and wide-range tunable SBH. An exceptionally large SBH slope parameter of S ≈ 0.7 is obtained which outperforms the vast majority of other 2D semiconductors. Such intriguing behavior arises from the septuple-layered morphology of MoSi2N4 and WSi2N4 monolayers in which the semiconducting electronic states are protected by the outlying Si–N sublayer. We identify Ti, Sc, and Ni as highly efficient Ohmic contacts to MoSi2N4 and WSi2N4 with zero interface tunneling barrier. Our findings reveal the potential of MoSi2N4 and WSi2N4 as a practical platform for designing high-performance and energy-efficient 2D semiconductor electronic devices.

The performance of adding 0–3 wt% B2O3-CuO as a sintering aid to lower the sintering temperature of La0.5Sr0.5Co0.96Ni0.04O3-δ (LSCN) was investigated through solid-state reaction method. Results of linear shrinkage curve, bulk density, and microstructure indicated that BCu addition could promote the sintering process and enhance the densification of LSCN ceramics. With the increase of BCu content, low absolute value of TCR could be achieved, while the conductivity was deteriorated obviously. For LSCN ceramics sintered at 950 °C, the bulk density, conductivity, and TCR were worse than those sintered at higher temperatures. Consequently, the BCu-doped LSCN ceramics might not suitable for the application in the field of LTCC.

The aim of this work was to encapsulate sea buckthorn (Hippophae rhamnoides L.) pulp oil (SBPO) by spray drying. Gum Arabic (GA) and maltodextrins (MD) were used as wall materials. The effects of several factors, including GA to MD ratio, total solids content of emulsion, wall to core ratio, and inlet air temperature, on the microencapsulation efficiency (ME) were investigated. The optimization of operation conditions was realized by response surface methodology (RSM). The optimal conditions were as follows: GA to MD ratio 2.38, total solids content 39%, wall to core ratio 5.33, and inlet air temperature 154°C. Under the optimal conditions, the ME of SBPO microcapsules was 94.96 ± 1.42%. The physicochemical properties of microcapsules were also invested. SBPO microcapsules obtained had low water activity, low moisture content, high water solubility, and high bulk density. For the morphological characteristics, cracks and pores were not observed in most microcapsules, which was beneficial for the protection of ingredients in microcapsules. The particle size of SBPO microcapsules ranged from 0.01 to 5 μm, and the mean diameter d4,3 was 2.55 μm. The analysis results of fourier transform infrared spectroscopy (FTIR) informed the presence of SBPO in microcapsules. There were no significant differences in the content of the main fatty acids in SBPO before and after spray drying. The results of oxidative stability showed that the microencapsulation by spray drying could effectively protect SBPO from oxidation and extend the shelf life of SBPO.

The application of BiOCl in photocatalysis has been restricted by its low utilization of solar energy and fast recombination of charge carriers. In this study, zero-dimensional (0D) Bi2WO6 nanoparticles/two-dimensional (2D) layered BiOCl heterojunction composite was successfully constructed by facile hydrothermal and solvothermal methods. The most favorable sunlight photocatalytic activity was achieved for the as-prepared Bi2WO6–BiOCl composites with a ratio of 1%. The photocatalytic rate and mineralization efficiency of one typical antibiotic (i.e., oxytetracycline) over 1% Bi2WO6–BiOCl was about 2.7 and 5.3 times as high as that of BiOCl. Both experimental characterizations and density functional theory (DFT) calculations confirmed that the excellent photocatalytic performance mainly arised from the effective charge separation along the Bi2WO6 and BiOCl heterojunction interface. The effective electron transfer was driven by the internal electric field at the interfacial junction. In addition, 1% Bi2WO6–BiOCl exhibited excellent stability, and no apparent deactivation was observed after 4 test cycles. Therefore, the 0D/2D Bi2WO6–BiOCl heterojunction showed a great potential for the photocatalytic degradation of emerging organic pollutants.

Interlayer interaction could substantially affect the electrical transport in transition metal dichalcogenides, serving as an effective way to control the device performance. However, it is still challenging to utilize interlayer interaction in weakly interlayer-coupled materials such as pristine MoS2 to realize layer-dependent tunable transport behavior. Here, we demonstrate that, by substitutional doping of vanadium atoms in the Mo sites of the MoS2 lattice, the vanadium-doped monolayer MoS2 device exhibits an ambipolar field effect characteristic, while its bilayer device demonstrates a heavy p-type field effect feature, in sharp contrast to the pristine monolayer and bilayer MoS2 devices, both of which show similar n-type electrical transport behaviors. Moreover, the electrical conductance of the doped bilayer MoS2 device is drastically enhanced with respect to that of the doped monolayer MoS2 device. Employing first-principle calculations, we reveal that such striking behaviors arise from the presence of electrical transport networks associated with the enhanced interlayer hybridization of S-3pz orbitals between adjacent layers activated by vanadium dopants in the bilayer MoS2, which is nevertheless absent in its monolayer counterpart. Our work highlights that the effect of dopant not only is confined in the in-plane electrical transport behavior but also could be used to activate out-of-plane interaction between adjacent layers in tailoring the electrical transport of the bilayer transitional metal dichalcogenides, which may bring different applications in electronic and optoelectronic devices.

The increasing demand for wearable electronics and the intensification of electromagnetic pollution have boosted the exploration of high-performance flexible microwave absorption (MA) materials. Herein, the hierarchical Ti3C2Tx MXene/Ni chain/ZnO array hybrid nanostructures are rationally constructed on cotton fabric for acquiring enhanced MA performance and durable self-cleaning ability. Based on the high dielectric loss capacity of MXenes and ZnO arrays, by controlling dip-coating numbers of Ni chains, the magnetic loss can be manipulated to modulate the impedance matching, reflection loss (RL), and effective absorption bandwidth (EAB, the bandwidth of RL < -10 dB). The minimum RL value of the designed fabric can reach -35.1 dB at 8.3 GHz with a thickness of 2.8 mm, and its EAB can cover the whole X-band with only a 2.2 mm thickness. In addition, the designed fabric also exhibits superior liquid repellency and durable self-cleaning ability due to the combination of the hybrid nanostructures and a superhydrophobic coating. This work provides an insight for rational design of textile-based MA materials, showing potential applications in flexible and wearable functional electronics.

The silicone rubber mold (SRM) has large applications for the pilot runs in the mold industry because it is capable of reducing the cost and time in a new product development phase. However, the cooling performance in the cooling stage is not acceptable after the injection molding due to low thermal conductivity of this material. To improve the cooling performance, five different fillers were added into the silicone rubber (SR) to develop SRM with better cooling performance in the cooling stage after injection molding. It was found that the alcohol used to remove the polyvinyl butyral resin cooling channels is less volatile, environmentally friendly, and less harmful to the operator compared with conventional method using acetone to remove the acrylonitrile butadiene styrene cooling channels. The cooling time of the molded wax pattern can be saved by 42.7%, 53.8%, 45.7%, 50.9%, and 16.7% for SRM with 60 wt.% Al, 80 wt.% Fe, 70 wt.% Cu, 25 wt.% graphite (G), and 20 wt.% carbon black powders compared with that for SRM without any fillers. The SR filled with 20 wt.% G powder seems to be the optimal method for producing an SRM with better cooling performance based on the heat transfer coefficient, production cost, and production yield of SRM.

In view of the serious emulsification existing in Changqing condensate gas emulsion, the unclear oil-water interface and the poor application effect of demulsifier used in the field, it is urgent to study an efficient demulsifier. In this paper, PM and XP-1221 two kinds of demulsifiers are used to solve the emulsification problem. The PM demulsifier was compounded with XP-1221 chemical demulsifier to solve the emulsification problem of Changqing condensate. The effect of temperature and demulsifier concentration on demulsification performance was studied by bottle test method. The results showed that XP-1221 and PM could be effectively combined. The demulsification efficiency was high and the dehydrated water was clear. Studies have shown that XP-1221 has a good synergistic effect with PM. The suitable ratio of the composite demulsifier is 1:1, and the demulsifier effect of the demulsifier can meet the requirements of the oil field demulsifier. The composite demulsifier can meet the requirements of current oilfield demulsifiers.

Metal–TEMPO hybrids are a family of novel and promising catalysts for aerobic oxidation of alcohols, yet the underlying mechanisms have not been understood theoretically. Using density functional theory, we probe the hydrogen abstraction mechanisms of FeCl3/TEMPO on two characteristic substrates, 9,10-dihydroanthracene and benzyl alcohol. We found that the low spin state of FeCl3/TEMPO is more favourable, and that the N atom is the preferred hydrogen acceptor. Moreover, dispersion interactions assist the reaction, as well as nuclear tunnelling, which even at room temperature can speed up the process by almost two orders of magnitude. We also predict that pronounced kinetic isotope effects (KIE) could be observed due to tunnelling. Our findings provide insights into improving the substrate scope and the development of new transformations for the FeCl3/TEMPO system., Chemical Communications, 58 (4), ISSN:1359-7345, ISSN:1364-548X

Multilayered photovoltaic absorbers have triggered widespread attention for their unique structure and properties. However, multilayered materials in the randomly oriented polycrystalline thin‐film lead to ineffective carrier transport and collection, which hinders the process of achieving high‐performance solar cells. Herein, this issue is tackled by producing the three‐dimensional (3D) heterojunction BiI3 nanosheets (NSs) solar cells, which embed vertically aligned monocrystalline BiI3 NSs into spiro‐OMeTAD. The preferred orientation of BiI3 NSs and large p‐n junction areas of 3D heterojunction structure enable a strong light absorption and effective carrier transport and collection, and thus a power conversion efficiency (PCE) of 1.45% was achieved. Moreover, this PCE is the highest ever reported for BiI3 based solar cells to our best knowledge. Moreover, the nonencapsulated device remained 96% of the initial PCE after 24 h continuous one sun illumination at ~70% humidity condition, and 82% of the initial PCE after 1‐month storage at ~30% humidity condition.

Yolk-shell structure magnetic metal–organic framework nanoparticles were prepared via post solvothermal method and employed as a magnetic solid-phase extraction adsorbent for selective pre-concentration of 5′-ribonucleotides by π stacking interaction, hydrogen bonding, and the strong interaction between titanium ions (Ti4+) and phosphate group. The properties of the materials were confirmed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectrometry, vibrating sample magnetometer, infrared spectroscopy, thermogravimetric analysis, and Brunauer–Emmett–Teller analysis. The main parameters affecting the adsorption–desorption process, including adsorbent amount, incubation time, incubation temperature, sample pH, shaking speed, elution solution, and elution time, were systematically optimized. Finally, 1.0 mg of adsorbent mixed with 1.0 mL sample solution (10.0 mmol⋅L−1 NaCl, pH 3.0) and shaken at 135 rpm for 5 min at 40 °C, washed with 1.0 mL Na3PO4-NH3∙H2O under vortex for 5 min were selected as optimized adsorption–desorption conditions. The binding performance of adsorbent towards five nucleotides was evaluated by static adsorption experiments. The data are well-fitted to the Langmuir isotherm model and the maximum adsorption capacity is 27.8 mg g−1 for adenosine 5′-monophosphate. The limit of detection of the method is 19.44–38.41 ng mL−1. Under the optimal conditions, the adsorbent was successfully applied to magnetic solid-phase extraction and high performance liquid chromatography determination of five nucleotides in octopus, chicken, fish, and pork samples.

The ultrafast photoexcited carrier and coherent phonon dynamics of 20 nm PtTe2 film on fused silica substrate were investigated systematically at room temperature using degenerate and non-degenerate femtosecond (fs) pump-probe spectroscopy. After 780 nm optical pump, photo-induced bleaching (PB) signal was observed, which originated from the band filling effect. The incoherent relaxation processes can be reproduced well with a double-exponential decay function, which have been assigned as the cooling of the thermal carriers and the recombination of electron-hole pairs mediated by phonon, respectively. Two distinct oscillation modes were identified, the low-frequency mode corresponds to the excitation of coherent acoustic phonon by photolaunched stress wave, and the high frequency mode is due to the coherent optical phonon stemming from out-of-plane (A1g) lattice motion. Our study provides an in-depth understanding to the relaxation mechanisms and phonons behavior of PtTe2 film in nonequilibrium states, and might pave the way for the design of electronic and optoelectronic devices.

Actuators mimic the unique motion of bacteria, which are realized by self-organizing photoresponsive cholesteric liquid crystals., Rotation-translation conversion is a popular way to achieve power transmission in machinery, but it is rarely selected by nature. One unique case is that of bacteria swimming, which is based on the collective reorganization and rotation of flagella. Here, we mimic such motion using the light-driven evolution of a self-organized periodic arch pattern. The range and direction of translation are altered by separately varying the alignment period and the stimulating photon energy. Programmable self-propelling actuators are realized via a specific molecular assembly within a photoresponsive cholesteric medium. Through rationally presetting alignments, parallel transports of microspheres in customized trajectories are demonstrated, including convergence, divergence, gathering, and orbital revolution. This work extends the understanding of the rotation-translation conversion performed in an exquisitely self-organized system and may inspire future designs for functional materials and intelligent robotics.

In this study, a magnetic yolk-shell structured metal-organic framework material (Fe3O4@YS-UiO-66-NH2) is prepared by the directional etching of Co2+/peroxymonosulfate and in situ magnetization. The characteristic properties of the material were investigated by using field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometer, Brunauer-Emmett-Teller, and contact angle test. The Fe3O4@YS-UiO-66-NH2 shows the advantages of large surface area, good magnetic property, and satisfactory stability, as well as giving high affinity to alkaloids (ALs) via hydrophilic interaction, hydrogen bonding, and π-π interaction. The results of static adsorption experiment indicate that the Fe3O4@YS-UiO-66-NH2 possesses high adsorption capacity towards ALs and the adsorption behaviors are fitted with Langmuir adsorption isotherm model. Furthermore, a magnetic solid-phase extraction using Fe3O4@YS-UiO-66-NH2 and HPLC method was developed for the analysis of ALs in spiked samples with the recovery of 89.6-100.8%. In addition, the proposed method was successfully applied in the pharmacokinetics study of berberine, coptisine, and palmatine in the rat. In short, the developed method might be used for high-efficient recognition and determination of ALs in plasma sample, which would also provide a new way to fabricate magnetic functionalized metal-organic framework in separation science.

As a newly emergent type-II Dirac semimetal, Platinum Telluride (PtTe2) stands out from other 2D noble-transition-metal dichalcogenides for the unique structure and novel physical properties, such as high carrier mobility, strong electron-phonon coupling and tunable bandgap, which make the PtTe2 a good candidate for applications in optoelectronics, valleytronics and far infrared detectors. Although the transport properties of PtTe2 have been studied extensively, the dynamics of the nonequilibrium carriers remain nearly uninvestigated. Herein we employ optical pump-terahertz (THz) probe spectroscopy (OPTP) to systematically study the photocarrier dynamics of PtTe2 thin films with varying pump fluence, temperature, and film thickness. Upon photoexcitation the THz photoconductivity (PC) of 5 nm PtTe2 film shows abrupt increase initially, while the THz PC changes into negative value in a subpicosecond time scale, followed by a prolonged recovery process that lasted hundreds of picoseconds (ps). This unusual THz PC response observed in the 5 nm PtTe2 film was found to be absent in a 2 nm PtTe2 film. We assign the unexpected negative THz PC as the small polaron formation due to the strong electron-Eg-mode phonon coupling, which is further substantiated by pump fluence- and temperature-dependent measurements as well as the Raman spectroscopy. Moreover, our investigations give a subpicosecond time scale of sequential carrier cooling and polaron formation. The present study provides deep insights into the underlying dynamics evolution mechanisms of photocarrier in type-II Dirac semimetal upon photoexcitation, which is fundamental importance for designing PtTe2-based optoelectronic devices., 18 pages, 4 figures

A novel spin gapless semiconductor material Ba2MnTeO6 is found and reported by first-principles calculations. In this paper, we study the influence of spin orbit coupling, strain and Coulomb interaction on the properties of ferromagnetic Ba2MnTeO6 in order to test the stability of physical properties. It turns out that the spin orbit coupling has no significant effect on the electronic structures of the Ba2MnTeO6 at equilibrium state. Under the action of uniform compressive strain and tensile strain, Ba2MnTeO6 transforms from spin gapless semiconductor to semiconductor and half-metal respectively. At the same time, as the strain increases, the semiconductor band gap gradually widens, and the half-metallic gap gradually narrows. After considering Coulomb interaction, Ba2MnTeO6 will also be transformed into a semiconductor, and the semiconductor band gap will increase with the increasing of U values. Furthermore, the mechanical performance studies show that Ba2MnTeO6 is an anisotropic material with stable structure. As the first pure double perovskite type spin gapless semiconductor, the high spin polarization and accurately adjustable physical properties of ferromagnetic Ba2MnTeO6 indicate that it has broad application prospects in the fields of spintronics and optoelectronic materials and devices.

Recently, extensive research has been done to explore the potential thermoelectric performance of p-Type Zintl compounds AB2Sb2 (A = Ca, Yb, Eu, Sr, Mg; B = Zn, Mn, Cd, Mg), mainly focus on A-site substitution and/or B-site substitution effect. Herein, we report that both power factors and thermal conductivities are simultaneously optimized to increase ZT values via substitution of Sb atoms with the isoelectronic Bi atoms in YbZn2Sb2−xBix compounds. We found that the power factor could be enhanced by 27%, as a result of improved electrical conductivities and the maintained Seebeck coefficients. The former is obtained from an increase of carrier density through a shift of Fermi level via Bi doping, which is supported by XPS analysis. The Seebeck coefficients are maintained due to the increased effective mass. Moreover, the lowest lattice thermal conductivity (0.47 Wm−1 K−1 at 723K) is below the lattice thermal conductivity limit due to enhanced phonon scattering via Bi-doping, which is analyzed by the Callaway model. Benefiting from the synergistic effect, the ZT of Bi-doping samples are significantly enhanced compared with that of the pristine one. These results probably offer a synergistic strategy to enhance ZT for p-Type Zintl compounds AB2Sb2 and other high-efficiency thermoelectric materials.

Atomically precise enantiomeric metal clusters are scarce, and copper(I) alkynyl clusters with intense circularly polarized luminescence (CPL) responses have not been reported. A pair of chiral alkynyl ligands, (R/S)-2-diphenyl-2-hydroxylmethylpyrrolidine-1-propyne (abbreviated as R/S-DPM) we successfully prepared and single crystals were characterized of optically pure enantiomeric pair of atomically-precise copper(I) clusters, [Cu14 (R/S-DPM)8 ](PF6 )6 (denoted as R/S-Cu14 ), which feature bright red luminescence and CPL with a high luminescence anisotropy factor (glum ). A dilute solution containing R/S-Cu14 was nonluminescent and CPL inactive at room temperature. Crystallization- and aggregation-induced emission (CIE and AIE, respectively) contribute to the triggering of the CPL of R/S-Cu14 in the crystalline and aggregated states. Their AIE behavior and good biocompatibility indicated applications of these copper(I) clusters in cell imaging in HeLa and NG108-15 cells.

Benefiting from the nanoscale effect, some metastable compounds can be synthesized in nanoparticles under normal conditions. The new intermetallic NiSn5 phase is synthesized by us for the first time by using a seed crystal induction method. This tetragonal phase in the P4/ mcc space group has stoichiometric Ni atom defects, yielding Ni0.62Sn5. A study of the growth mechanism reveals that the FeSn5/CoSn5 seed crystal plays a vital role in the formation of the NiSn5 phase. An investigation of the phase evolution during lithiation/delithiation processes indicates the irreversibility of NiSn5 as an anode for lithium ion batteries.

The ampholytic surfactant Lauramidopropyl betaine (LAB) is a multifunctional amphoteric surfactant, which is widely used in washing formulations and is the main component of many softeners and detergent formulations. It has the advantages of less irritation to skin, mild performance and easy biodegradability. It is superior to other amphoteric surfactants. In this paper, new surfactants were synthesized by using LAB as the main component and the molar ratios of LAB to formaldehyde were 1:1, 1:2, 1:3 and 1:4, respectively. The new functional group hydroxymethyl was introduced into the LAB, and the effect of hydroxymethyl on the properties of raw materials was discussed. And the surface properties were studied, including high temperature resistance, methanol resistance and salt resistance. The results showed that the high temperature resistance of R2 is better below 50 °C, R0 has better high temperature resistance above 50 °C; In the aspect of methanol resistance, the methanol resistance of R4 is better at 10% and 20% methanol content; The effect of R0 is better in salt resistance. Finally, it can be concluded that the introduction of methylol groups improves the performance of the prepared new surfactants in certain properties.

Multiwavelength erbium-doped fiber lasers can be applied to many fields, such as wavelength division multiplexing optical communication and others attracting considerable attention. To meet the requirements of different applications, we propose a compact dual-wavelength continuous-wave erbium-doped fiber laser based on nonlinear amplifying loop mirror. An all-polarization-maintaining fiber cavity is adopted in which there are only three intracavity devices besides fiber itself:a wavelength division multiplexer, a 2×2 fiber coupler and a fiber reflector. The intensity-dependent loss effect induced by the nonlinear amplifying loop mirror is used to equalize the intensity in the cavity. The input laser with higher power suffers a higher loss than the one with lower power. This feature can be used to suppress mode competition and achieve stable multiwavelength oscillation. With a pump power of 260 mW, dual-wavelength erbium-doped fiber laser can be achieved, with wavelengths of 1 560.5 nm and 1 563.2 nm, respectively. The side-mode suppression ratio is 46.8 dB. As pump power increases, the laser can operate in single-, dual-and triple-wavelength regions in proper order. As the multi-wavelength lasing oscillation is a balance between intensity-dependent loss and mode competition, the intensity change breaks the original balance state, resulting in the change in number and wavelength of lasing lines. This laser is simply structured and easy to operate. It can have applications in many fields.

A series of wear and flame resistant polyamide 6 (PA6) composites were prepared using glass fiber (GF) and talc (T) as reinforcer, polytetrafluoroethylene (PTFE) and graphite (Gr) as solid lubricants, red phosphorus (RP) and zinc borate (ZB) as flame retardant. The tribological property, mechanical property, flame retardant property and the flame retardant mechanism were investigated. The tests show that the formula of the wear resistant PA6 composite (WRPA 6) is PA6/GF/T/PTFE/Gr in the ratio of 100/15/5/10/5 by mass. Because this composite exhibits the lowest friction coefficient (0.1429) and no wear mass loss, the introduction of RP and ZB can increase the flame resistance of WRPA6, and the synergistic effect of RP and ZB is obtained. Detailedly, the composite with 4 parts of ZB and 12 parts of RP shows the best flame retardant property, achieving the highest limiting oxygen index (LOI) (30.2 vol%) and a UL94 V-0 rating, and the flame retardant mechanisms may be gas phase along with condense phase mechanism.

Defect engineering plays an important role in tailoring the electronic transport properties of van der Waals materials. Methods reported so far mainly rely on the $e\phantom{\rule{0}{0ex}}x\phantom{\rule{0.333em}{0ex}}s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ engineering of defect type and concentration, hindering the realization of new types of device functionalities associated with defect engineering. Here, the authors report temperature-sensitive spatial redistribution of defects in PdSe${}_{2}$ thin flakes through scanning tunneling microscopy. The spatial characteristics of defect distribution is strongly related to the electronic transport properties such as anisotropic carrier mobility and phase coherent length, indicating a different avenue for creating novel device functionalities based on $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0.333em}{0ex}}s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ modulation of defect distribution.

The growth of connected intelligent devices in the Internet of Things has created a pressing need for real-time processing and understanding of large volumes of analogue data. The difficulty in boosting the computing speed renders digital computing unable to meet the demand for processing analogue information that is intrinsically continuous in magnitude and time. By utilizing a continuous data representation in a nanoscale crossbar array, parallel computing can be implemented for the direct processing of analogue information in real time. Here, we propose a scalable massively parallel computing scheme by exploiting a continuous-time data representation and frequency multiplexing in a nanoscale crossbar array. This computing scheme enables the parallel reading of stored data and the one-shot operation of matrix-matrix multiplications in the crossbar array. Furthermore, we achieve the one-shot recognition of 16 letter images based on two physically interconnected crossbar arrays and demonstrate that the processing and modulation of analogue information can be simultaneously performed in a memristive crossbar array., Comment: 18 pages, 4 figures

Structure evolution has become an effective way to assemble novel monolayer-protected metal nanomolecules. However, evolution with alkynyl-stabilized metal clusters still remains rarely explored. Herein, we present a carboranealkynyl-protected gold nanocluster [Au28 (C4 B10 H11 )12 (tht)8 ]3+ (Au28 , tht=tetrahydrothiophene) possessing an open-shell electronic structure with 13 free electrons, which was isolated by a facile self-reduction method with 9-HC≡C-closo-1,2-C2 B10 H11 as the two-in-one reducing and protecting agent. Notably, Au28 undergoes a complete transformation in methanol into a stable and smaller-sized nanocluster [Au23 (C4 B10 H11 )9 (tht)6 ]2+ (Au23 ) bearing 12 valence electrons and crystal-field-like split superatomic 1D orbitals. The transformation process was systematically monitored with ESI-MS and UV/Vis absorption spectra. Au28 and Au23 both display optical absorption covering the UV/Vis-NIR range and NIR emission, which facilitates their potential application in the biomedical and photocatalytic fields.

Reconfigurable field-effect transistors have attracted enormous attention over the past decades because of their potential in implementing logic and analog circuit functions with fewer resources of transistors compared with complementary metal-oxide-semiconductor transistors. However, the miniaturization of traditional reconfigurable transistors is still a challenge owing to their inherent planar multi-gate structure. Herein, we fabricated a dual-gate vertical transistor based on graphene/MoTe2/graphite van der Waals heterostructure and demonstrated a switchable n-type, V-shape ambipolar and p-type field-effect characteristics by varying the voltages of the top gate and drain electrodes. According to the band diagram analysis, we reveal that the reconfiguring ability of the field-effect characteristics stems from the asymmetric injection efficiency of the carriers through the gate-tunable barriers at the interfaces. Our results offer a potential approach to achieve device miniaturization of reconfigurable transistors.

Metalenses are developing fast towards versatile and integrated terahertz (THz) apparatuses, while tunable ones are highly pursued. Here, we propose a strategy that integrates dielectric metasurfaces with liquid crystals (LCs) to realize the dynamic focal spot manipulation. The silicon pillar meta-units of the metasurface are properly selected to generate different phase profiles for two orthogonal linear polarizations, permitting a laterally or axially altered focal spot. After LCs integrated, polarization-multiplexed focusing can be achieved via electrically varying the LC orientations. We demonstrate two metalenses with distinct functions. For the first one, the uniformly aligned LC works as a polarization converter, and further switches the focal length by altering the bias. For the second one, an LC polarization grating is utilized for rear spin-selective beam deflection. Consequently, a THz port selector is presented. This work supplies a promising method towards active THz elements, which may be widely applied in THz sensing, imaging, and communication.

By virtue of the layered structure, van der Waals (vdW) magnets are sensitive to the lattice deformation controlled by the external strain, providing an ideal platform to explore the one-step magnetization reversal that is still conceptual in conventional magnets due to the limited strain-tuning range of the coercive field. In this study, a uniaxial tensile strain is applied to thin flakes of the vdW magnet Fe3 GeTe2 (FGT), and a dramatic increase of the coercive field (Hc ) by more than 150% with an applied strain of 0.32% is observed. Moreover, the change of the transition temperatures between the different magnetic phases under strain is investigated, and the phase diagram of FGT in the strain-temperature plane is obtained. Comparing the phase diagram with theoretical results, the strain-tunable magnetism is attributed to the sensitive change of magnetic anisotropy energy. Remarkably, strain allows an ultrasensitive magnetization reversal to be achieved, which may promote the development of novel straintronic device applications.

Modeling dynamical effects in chemical reactions, such as post-transition state bifurcation, requires ab initio molecular dynamics simulations due to the breakdown of simpler static models like transition state theory. However, these simulations tend to be restricted to lower-accuracy electronic structure methods and scarce sampling because of their high computational cost. Here, we report the use of statistical learning to accelerate reactive molecular dynamics simulations by combining high-throughput ab initio calculations, graph-convolution interatomic potentials and active learning. This pipeline was demonstrated on an ambimodal trispericyclic reaction involving 8,8-dicyanoheptafulvene and 6,6-dimethylfulvene. With a dataset size of approximately31,000 M062X/def2-SVP quantum mechanical calculations, the computational cost of exploring the reactive potential energy surface was reduced by an order of magnitude. Thousands of virtually costless picosecond-long reactive trajectories suggest that post-transition state bifurcation plays a minor role for the reaction in vacuum. Furthermore, a transfer-learning strategy effectively upgraded the potential energy surface to higherlevels of theory ((SMD-)M06-2X/def2-TZVPD in vacuum and three other solvents, as well as the more accurate DLPNO-DSD-PBEP86 D3BJ/def2-TZVPD) using about 10% additional calculations for each surface. Since the larger basis set and the dynamic correlation capture intramolecular non-covalent interactions more accurately, they uncover longer lifetimes for the charge-separated intermediate on the more accurate potential energy surfaces. The character of the intermediate switches from entropic to thermodynamic upon including implicit solvation effects, with lifetimes increasing with solvent polarity. Analysis of 2,000 reactive trajectories on the chloroform PES shows a qualitative agreement with the experimentally-reported periselectivity for this reaction. This overall approach is broadly applicable and opens a door to the study of dynamical effects in larger, previously-intractable reactive systems.

Early processing of visual information takes place in the human retina. Mimicking neurobiological structures and functionalities of the retina provide a promising pathway to achieving vision sensor with highly efficient image processing. Here, we demonstrate a prototype vision sensor that operates via the gate-tunable positive and negative photoresponses of the van der Waals (vdW) vertical heterostructures. The sensor emulates not only the neurobiological functionalities of bipolar cells and photoreceptors but also the unique synaptic connectivity between bipolar cells and photoreceptors. By tuning gate voltage for each pixel, we achieve reconfigurable vision sensor for simultaneously image sensing and processing. Furthermore, our prototype vision sensor itself can be trained to classify the input images, via updating the gate voltages applied individually to each pixel in the sensor. Our work indicates that vdW vertical heterostructures offer a promising platform for the development of neural network vision sensor., Comment: 20 pages, 4 figures

Nano-structuring is an extremely promising path to high performance thermoelectrics. Favorable improvements in thermal conductivity are attainable in many material systems, and theoretical work points to large improvements in electronic properties. However, realization of the electronic benefits in practical materials has been elusive experimentally. A key challenge is that experimental identification of the quantum confinement length, below which the thermoelectric power factor is significantly enhanced, remains elusive due to lack of simultaneous control of size and carrier density. Here we investigate gate tunable and temperature-dependent thermoelectric transport in $\gamma$ phase indium selenide ($\gamma$ InSe, n type semiconductor) samples with thickness varying from 7 to 29 nm. This allows us to properly map out dimension and doping space. Combining theoretical and experimental studies, we reveal that the sharper pre-edge of the conduction-band density of states arising from quantum confinement gives rise to an enhancement of the Seebeck coefficient and the power factor in the thinner InSe samples. Most importantly, we experimentally identify the role of the competition between quantum confinement length and thermal de Broglie wavelength in the enhancement of power factor. Our results provide an important and general experimental guideline for optimizing the power factor and improving the thermoelectric performance of two-dimensional layered semiconductors., Comment: 26 page, 5 figures

In order to experimentally measure the heat build-up within a polymer matrix composite under cyclic loading, the real-time temperature monitoring of a solid composite propellant (HTPB propellant) subjected to cyclic uniaxial, strain-controlled fatigue tests at various loading conditions was carried out. The results obtained show that surface temperature of HTPB propellant during the fatigue test increased by up to dozens of degrees, which due to its viscoelastic nature. The effect of applied strain levels and frequencies of tested material on the deterioration of HTPB propellants during fatigue process were quantitatively assessed by the variation of dynamic moduli. It has confirmed that the influences of self-heating on tested materials mainly lies in softening polymeric matrix and extended debonding along particle/matrix interface. Additionally, the pattern of increased fatigue lifetime with a reduction in loading frequency and strain level under was also observed. Moreover, based on an uncoupled thermomechanical coupling algorithm, the finite element analysis incorporating a hyper-viscoelastic constitutive model of tested material was proposed to simulate the mechanical and thermal responses of tested material. The results of simulation agree well with experimental ones, which helps to validate the accuracy of proposed model.

Semiconducting nanowires offer many opportunities for electronic and optoelectronic device applications due to their special geometries and unique physical properties. However, it has been challenging to synthesize semiconducting nanowires directly on SiO2/Si substrate due to lattice mismatch. Here, we developed a catalysis-free approach to achieve direct synthesis of long and straight InSe nanowires on SiO2/Si substrate through edge-homoepitaxial growth. We further achieved parallel InSe nanowires on SiO2/Si substrate through controlling growth conditions. We attributed the underlying growth mechanism to selenium self-driven vapor-liquid-solid process, which is distinct from conventional metal-catalytic vapor-liquid-solid method widely used for growing Si and III-V nanowires. Furthermore, we demonstrated that the as-grown InSe nanowire-based visible light photodetector simultaneously possesses an extraordinary photoresponsivity of 271 A/W, ultrahigh detectivity of 1.57*10^14 Jones and a fast response speed of microsecond scale. The excellent performance of the photodetector indicates that as-grown InSe nanowires are promising in future optoelectronic applications. More importantly, the proposed edge-homoepitaxial approach may open up a novel avenue for direct synthesis of semiconducting nanowire arrays on SiO2/Si substrate., 19 pages, 4 figures, published in Small

Maintaining the rapid development of information technology by scaling down a metal-oxide semiconductor field-effect transistor faces two serious challenges. First, the gate field loses control of the channel as it continuously decreases. Second, the fundamental thermionic limit restricts the reduction in supply voltage. Thus, further scaling down necessitates alternative device structures and different switching mechanisms. Here, we report impact-ionization transistors (IITs) based on nanoscale (∼30 nm) vertical graphene/black phosphorus (BP)/indium selenide (InSe) heterostructures. By facilitating the carrier multiplication of the ballistic impact-ionization process as the internal gain mechanism in sub-mean-free-path (sub-MFP) channels, the IITs exhibit a low average subthreshold swing (SS1 mV/dec) over five current levels. High stability (10 000 cycles) and small hysteresis (1%) switching properties are also obtained. The experimental demonstration of such transistor combining steep SS, high ON-state current density, reliable robustness, miniature footprint, and low bias voltage approaches fulfillments of targets for next-generation devices in the International Technology Roadmap for Semiconductors.

van der Waals (vdW) heterostructures made of two-dimensional materials have been demonstrated to be versatile architectures for optoelectronic applications due to strong light--matter interactions. However, most light-controlled phenomena and applications in the vdW heterostructures rely on positive photoconductance (PPC). Negative photoconductance (NPC) has not yet been reported in vdW heterostructures. Here we report the observation of the NPC in the ReS2/h-BN/MoS2 vdW heterostructure-based floating gate phototransistor. The fabricated devices exhibit excellent performance of nonvolatile memory without light illumination. More interestingly, we observe a gate-tunable transition between the PPC and the NPC under the light illumination. The observed NPC phenomenon can be attributed to charge transfer between the floating gate and the conduction channel. Furthermore, we show that control of NPC through light intensity is promising in realization of light-tunable multibit memory devices. Our results may enable potential applications in multifunctional memories and optoelectronic devices.

Layered metal chalcogenide materials provide a versatile platform to investigate emergent phenomena and two-dimensional (2D) superconductivity at/near the atomically thin limit. In particular, gate-induced interfacial superconductivity realized by the use of an electric-double-layer transistor (EDLT) has greatly extended the capability to electrically induce superconductivity in oxides, nitrides and transition metal chalcogenides and enable one to explore new physics, such as the Ising pairing mechanism. Exploiting gate-induced superconductivity in various materials can provide us with additional platforms to understand emergent interfacial superconductivity. Here, we report the discovery of gate-induced 2D superconductivity in layered 1T-SnSe2, a typical member of the main-group metal dichalcogenide (MDC) family, using an EDLT gating geometry. A superconducting transition temperature Tc around 3.9 K was demonstrated at the EDL interface. The 2D nature of the superconductivity therein was further confirmed based on 1) a 2D Tinkham description of the angle-dependent upper critical field, 2) the existence of a quantum creep state as well as a large ratio of the coherence length to the thickness of superconductivity. Interestingly, the in-plane approaching zero temperature was found to be 2-3 times higher than the Pauli limit, which might be related to an electric field-modulated spin-orbit interaction. Such results provide a new perspective to expand the material matrix available for gate-induced 2D superconductivity and the fundamental understanding of interfacial superconductivity., Comment: 18 pages, 4 figures, accepted by Nano Letters

Conventional strategies for advancing thermoelectrics via nanocompositing focus on the enhanced phonon scattering induced by nanostructured phase. Here, an effective approach of combining carrier mobility promotion and strengthened phonons scattering to simultaneously improve electrical and thermal transport properties is demonstrated. For the p-type YbZn2Sb2 with InSb nanoinclusions, the Hall mobility is effectively enhanced by InSb in the whole measured temperature, from 56 cm2 V−1 s−1 to 162 cm2 V−1 s−1 at 300 K. Meanwhile, the carrier density optimization by tuning Yb vacancies leads to 46% improvement in the Seebeck coefficient, overcoming the negative contribution from InSb. Moreover, with the help of interface scattering caused by nanoinclusions, the lattice thermal conductivity is reduced by 45% at 720 K. As a result, the thermoelectric figure of merit ZT is enhanced nearly a factor of three. We believe our method provides a “combined strategy” to enhance thermoelectric performance of YbZn2Sb2 based compounds and should be applicable to other thermoelectric materials.

Steel wire reinforced thermoplastic pipe (PSP) is a polymer–matrix composite pipe of excellent quality, and it shows great potential in different industries. In this study, bearing capacity of PSP under combined internal pressure and bending moment at various temperatures was investigated. Tests were conducted through a specifically designed mechanical testing system, and the temperatures varied from 20 °C to 60 °C. With a pre-set internal pressure of 2.8 MPa, bending moment was applied until failure. It was found that the fracture of steel wires leads to the failure of pipe, and higher temperature has a negative effect on the pipes’ bending capacity. A finite element (FE) model was subsequently established to analyze the failure process and influence factors of PSP under combined loads.

The thermoelectric voltage generated at an atomically abrupt interface has not been studied exclusively because of the lack of established measurement tools and techniques. Atomically thin 2D materials provide an excellent platform for studying the thermoelectric transport at these interfaces. Here, we report a novel technique and device structure to probe the thermoelectric transport across Au/h-BN/graphene heterostructures. An indium tin oxide (ITO) transparent electrical heater is patterned on top of this heterostructure, enabling Raman spectroscopy and thermometry to be obtained from the graphene top electrode in situ under device operating conditions. Here, an AC voltage V(ω) is applied to the ITO heater and the thermoelectric voltage across the Au/h-BN/graphene heterostructure is measured at 2ω using a lock-in amplifier. We report the Seebeck coefficient for our thermoelectric structure to be −215 μV/K. The Au/graphene/h-BN heterostructures enable us to explore thermoelectric and thermal transport on nanometer length scales in a regime of extremely short length scales. The thermoelectric voltage generated at the graphene/h-BN interface is due to thermionic emission rather than bulk diffusive transport. As such, this should be thought of as an interfacial Seebeck coefficient rather than a Seebeck coefficient of the constituent materials.

Graphene's unique electronic and optical properties have made it an attractive material for developing ultrafast short-wave infrared (SWIR) photodetectors. However, the performance of graphene SWIR photodetectors has been limited by the low optical absorption of graphene as well as the ultrashort lifetime of photoinduced carriers. Here, we present two mechanisms to overcome these two shortages and demonstrate a graphene-based SWIR photodetector with high responsivity and fast photoresponse. In particular, a vertical built-in field is employed in the graphene channel for trapping the photoinduced electrons and leaving holes in graphene, which results in prolonged photoinduced carrier lifetime. On the other hand, plasmonic effects were employed to realize photon trapping and enhance the light absorption of graphene. Thanks to the above two mechanisms, the responsivity of this proposed SWIR photodetector is up to a record of 83 A/W at a wavelength of 1.55 μm with a fast rising time of less than 600 ns. This device design concept addresses key challenges for high-performance graphene SWIR photodetectors and is promising for the development of mid/far-infrared optoelectronic applications.

Room temperature mesophases were achieved by blending donors 2,3,6,7,10,11-hexakis-(hexyloxy)-triphenylene (H6TP) with acceptors N , N ′-bis(1-heptyloctyl)-perylene-3,4,9,10-tetracarboxylic diimide (PDI) via charge transfer interactions and size match. Compared with H6TP (mesophase temperature range: 97 °C–51 °C) and PDI (119 °C–108 °C), H6TP/PDI = 1/2 (138 °C - room temperature), 1/1 (139 °C–40 °C) and 1/0.5 (130 °C–31 °C) blends showed increase of clearing points and decrease of crystallization temperatures with wide mesophase temperature ranges. Different from edge-on orientation of PDI and no preferred alignment of H6TP, face-on alignments of all mixtures films could be achieved and stable at room temperature by cooling from isotropic state. It was inferred that stabilised columnar mesophases of H6TP/PDI blends were caused by charge transfer (CT) interactions and size match of them in hexagonal columnar phases. The existence of CT interactions was demonstrated by upfield shifts of aromatic protons in the 1 H NMR spectra of H6TP/PDI blends solutions and obvious fluorescent quenching in the blends films.

Capillary electrochromatography, which combined the high selectivity of high-performance liquid chromatography and the high separation efficiency of capillary electrophoresis, is an attractive separation tool. In this review, the developments on monolithic and open tubular capillary electrochromatography during 2017 to August 2019 are summarized. Considering the development of novel stationary phases is the most active research field in capillary electrochromatography, monolithic capillary electrochromatography is classified according to the polymer-based and hybrid monolithic columns, while open-tubular capillary electrochromatography is categorized by cyclodextrin, silica, polymer, nanomaterials, microporous materials, and biomaterials-based open tubular columns.

Two-dimensional transition metal oxychlorides (MOCl, $M$ = Fe, Cr, V, Ti, Sc) with the metal-oxygen plane sandwiched by two layers of chloride ions possess many exotic physical properties. Nevertheless, it is of great challenge to grow two-dimensional single-crystal MOCl because polyvalent nature of transition metal elements usually gives rise to mixed oxyhalides compounds with distinct physical properties. Here, we take VOCl as an example to present a solution for synthesizing 2D freestanding MOCl with various thicknesses through chemical vapor deposition (CVD) method. The single crystal and elementary composition as well as elements ratio of as-grown samples have been characterized through measurements of X-ray diffraction, X-ray photoelectron spectroscopy and energy-dispersive spectroscopy, respectively. Furthermore, we demonstrate that 2D VOCl-based memristive devices show low power consumption and excellent device reliability due to the layered-structure and electrically insulating properties of 2D VOCl flakes. Besides, we utilize the feature of multilevel resistive switching that memristive devices exhibit to emulate depression and potentiation of synaptic plasticity. This method developed in this study may open up a new avenue for the growth of 2D MOCl with single crystal and pave the way for high-performance electronic applications.

The electronic structure and magnetic properties of ten formamidinium transition metal iodides in the ground state and under strain have been studied. These formamidinium transition metal iodides have a stable cubic perovskite structure. In the ground state, FAVI3 is a spin gapless semiconductor, and FAScI3, FATiI3, FACrI3, FAFeI3, FACoI3 and FANiI3 are ferromagnetic half-metals. They all have 100% spin polarization and integer total magnetic moment. Under the action of strain, the high spin polarization of some formamidinium transition metal iodides can still be well maintained, and several novel spin gapless semiconductors such as FATiI3, FAFeI3 and FACoI3 have been discovered. Magnetic studies show that these formamidinium transition metal iodides with half-metal, semiconductor and spin-gapless semiconductor properties have integral total magnetic moments under strain ranging from −10.0% to 10.0%. These newly discovered half-metallic ferromagnetic materials and spin gapless semiconductors have broad application prospects in the field of spintronics due to their high spin polarization.

Since the discovery of extremely large non-saturating magnetoresistance (MR) in WTe2, much effort has been devoted to understanding the underlying mechanism, which is still under debate. Here, we explicitly identify the dominant physical origin of the large non-saturating MR through in-situ tuning of the magneto-transport properties in thin WTe2 film. With an electrostatic doping approach, we observed a non-monotonic gate dependence of the MR. The MR reaches a maximum (10600%) in thin WTe2 film at certain gate voltage where electron and hole concentrations are balanced, indicating that the charge compensation is the dominant mechanism of the observed large MR. Besides, we show that the temperature dependent magnetoresistance exhibits similar tendency with the carrier mobility when the charge compensation is retained, revealing that distinct scattering mechanisms may be at play for the temperature dependence of magneto-transport properties. Our work would be helpful for understanding mechanism of the large MR in other nonmagnetic materials and offers an avenue for achieving large MR in the non-magnetic materials with electron-hole pockets., 16 pages, 3 figures, accepted by Nano Letters

We propose and demonstrate an active spin-selected lens with liquid crystal (LC) in the terahertz (THz) range. The lens is a superposition of two geometric phase lenses with separate centers and conjugated phase profiles. Its digitalized multidirectional LC orientations are realized via a dynamic micro-lithography-based photo-patterning technique and sandwiched by two graphene-electrode-covered silica substrates. The specific lens can separate the focusing spots of incident light with opposite circular polarizations. Its focusing performance from 0.8 to 1.2 THz is characterized using a scanning near-field THz microscope system. The polarization conversion efficiency varies from 32.1% to 70.2% in this band. The spin-selected focusing functions match well with numerical simulations. Such lens exhibits the merit of dynamic functions, low insertion loss and broadband applicability. It may inspire various practical THz apparatuses.