In Situ Observation of Field-Induced Nanoprotrusion Growth on a Carbon-Coated Tungsten Nanotip.

Nanoprotrusion (NP) on metal surface and its inevitable contamination layer under high electric field is often considered as the primary precursor that leads to vacuum breakdown, which plays an extremely detrimental effect for high energy physics equipment and many other devices. Yet, the NP growth has never been experimentally observed. Here, we conduct field emission (FE) measurements along with in situ transmission electron microscopy (TEM) imaging of an amorphous-carbon (a-C) coated tungsten nanotip at various nanoscale vacuum gap distances. We find that under certain conditions, the FE current-voltage (I-V) curves switch abruptly into an enhanced-current state, implying the growth of an NP. We then run field emission simulations, demonstrating that the temporary enhanced-current I-V is perfectly consistent with the hypothesis that a NP has grown at the apex of the tip. This hypothesis is also confirmed by the repeatable in situ observation of such a nanoprotrusion and its continued growth during successive FE measurements in TEM. We tentatively attribute this phenomenon to field-induced biased diffusion of surface a-C atoms, after performing a finite element analysis that excludes the alternative possibility of field-induced plastic deformation.

Fast access of the lattice thermal conductivity and phonon quasiparticle spectra of Mo2TiC2T2 (T = -O and -F) and Janus Mo2TiC2OF MXenes from machine learning potentials.

The presence of strong anharmonic effects in surface functionalized MXenes greatly challenges the use of harmonic lattice dynamics calculations to predict their phonon spectra and lattice thermal conductivity at finite temperatures. Herein, we demonstrate the workflow for training and validating machine learning potentials in terms of moment tensor potential (MTP) for MXenes including Mo2TiC2, Mo2TiC2O2, Mo2TiC2F2 and Janus-Mo2TiC2OF monolayers. Then, the MTPs of MXenes are successfully combined with the harmonic lattice dynamics calculations to obtain the temperature renormalized phonon spectra, three-phonon scattering rates, phonon relaxation times and lattice thermal conductivity at finite temperatures. Furthermore, combining MTPs with classic molecular dynamics simulations at finite temperatures directly enables the calculation of phonon quasi-particle spectral energy density with a full inclusion of all anharmonic effects in MXenes. Our current results indicate that anharmonic effects are found to be relatively weak in Mo2TiC2 and Mo2TiC2O2 monolayers, whereas the phonon quasi-particle spectral energy densities largely resemble those of harmonic or renormalized lattice dynamics calculations. Significant broadening of spectral energy density at finite temperature is predicted for Mo2TiC2F2 and Janus-Mo2TiC2OF monolayers, implying strong anharmonic effects in those MXenes. Our work paves a new way for fast and reliable calculation of the phonon scattering process and lattice thermal conductivity of MXenes within MTPs trained from first-principles molecular dynamics simulations in the future.

[Comparison of effectiveness between unilateral biportal endoscopic and uniportal interlaminar endoscopic decompression in the treatment of lumbar spinal stenosis].

Objective: To compare the effectiveness between unilateral laminotomy and bilateral decompression (ULBD) with unilateral biportal endoscopy (UBE) and uniportal interlaminar endoscopy (UIE) in the treatment of lumbar spinal stenosis. Methods: A clinical data of 52 patients with lumbar spinal stenosis, who met the selection criteria and treated with ULBD between March 2021 and November 2022, was retrospectively analyzed. The patients were allocated into UBE group (23 cases) and UIE group (29 cases) according to the surgical methods. There was no significant difference ( P>0.05) in age, gender, body mass index, surgical segment, type of lumbar stenosis, and preoperative visual analogue scale (VAS) score of low back pain, VAS score of leg pain, Oswestry disability index (ODI), disc height, and dural sac area between the two groups. Perioperative indexes (incision length, operation time, hospital stay, and surgical complications), clinical indicators (VAS score of low back pain, VAS score of leg pain, and ODI before operation and at 3 days, 1 month, 6 months, and 12 months after operation), and imaging indicators (disc height and dural sac area before operation and at 1, 12 months after operation, and dural sac expansion area) were recorded and compared between the two group. Results: All operations in both groups were successfully completed. Compared with the UIE group, the UBE group had shorter operation time and longer incision length, with significant differences ( P<0.05). But there was no significant difference in hospital stay and incidence of complications between the two groups ( P>0.05). All patients were followed up 12-20 months (mean, 14 months). The VAS scores of low back pain and leg pain and ODI after operation significantly improved when compared with preoperative values ( P<0.05), and there was no significant difference in the above indicators between different time points after operation ( P>0.05). There was no significant difference between the two groups at different time points ( P>0.05). Imaging examination showed that there was no significant difference in disc height between the two groups at different time points after operation ( P>0.05). However, the dural sac area and dural sac expansion area were significantly larger in the UBE group than in the UIE group ( P<0.05). Conclusion: ULBD with UBE and UIE can achieve satisfactory effectiveness in the treatment of lumbar spinal stenosis. But the former has more thorough decompression and better dural sac expansion than the latter.

Unveiling the Potential of the Alkyl Chain of Isoleucine for Regulating the Electrical Double Layer and Enhancing the Zinc-Ion Battery Performance.

Amino acids are considered effective additives for regulating the electric double layer (EDL) in zinc-ion battery (ZIB) electrolytes. In comparison to their polar counterparts, nonpolar amino acids have received less attention in research. We demonstrated that isoleucine (ILE), benefiting from its nonpolar alkyl chain, emerges as a highly suitable electrolyte additive for aqueous ZIBs. ILE molecules preferentially adsorb onto the anode surface of zinc metal, subsequently creating a locally hydrophobic EDL facilitated by the alkyl chain. On one hand, this enhances the thermodynamic stability at the anode, while on the other hand, it accelerates the desolvation process of zinc ions, thereby improving the kinetics. Benefiting from the unique properties of ILE molecules, Cu//Zn cells with the ILE additive ultimately achieved an extended cycle life of 2600 cycles with an average coulombic efficiency of 99.695%, significantly outperforming other amino acid additives reported in the literature.

Fast Na+ Kinetics and Suppressed Voltage Hysteresis Enabled by a High-Entropy Strategy for Sodium Oxide Cathodes.

O3-type layered transition metal cathodes are promising energy storage materials due to their sufficient sodium reservoir. However, sluggish sodium ions kinetics and large voltage hysteresis, which are generally associated with Na+ diffusion properties and electrochemical phase transition reversibility, drastically minimize energy density, reduce energy efficiency, and hinder further commercialization of sodium-ion batteries (SIBs). Here, this work proposes a high-entropy tailoring strategy through manipulating the electronic local environment within transition metal slabs to circumvent these issues. Experimental analysis combined with theoretical calculations verify that high-entropy metal ion mixing contributes to the improved reversibility of redox reaction and O3-P3-O3 phase transition behaviors as well as the enhanced Na+ diffusivity. Consequently, the designed O3-Na0.9Ni0.2Fe0.2Co0.2Mn0.2Ti0.15Cu0.05O2 material with high-entropy characteristic could display a negligible voltage hysteresis (<0.09 V), impressive rate capability (98.6 mAh g-1 at 10 C) and long-term cycling stability (79.4% capacity retention over 2000 cycles at 5 C). This work provides insightful guidance in mitigating the voltage hysteresis and facilitating Na+ diffusion of layered oxide cathode materials to realize high-rate and high-energy SIBs.

Polarizable Nonvolatile Ferroelectric Gating in Monolayer MoS2 Phototransistors.

Given the requirements for power and dimension scaling, modulating channel transport properties using high gate bias is unfavorable due to the introduction of severe leakages and large power dissipation. Hence, this work presents an ultrathin phototransistor with chemical-vapor-deposition-grown monolayer MoS2 as the channel and a 10.2 nm thick Al:HfO2 ferroelectric film as the dielectric. The proposed device is meticulously modulated utilizing an Al:HfO2 nanofilm, which passivates traps and suppresses charge Coulomb scattering with Al doping, efficiently improving carrier transport and inhibiting leakage current. Furthermore, a bipolar pulses excitable polarization method is developed to induce a nonvolatile electrostatic field. The MoS2 channel is fully depleted by the switchable and stable floating gate originating from remanent polarization, leading to a high detectivity of 2.05 × 1011 Jones per nanometer of gating layer (Jones nm-1) and photocurrent on/off ratio >104 nm-1, which are superior to the state-of-the-art phototransistors based on two-dimensional (2D) materials and ferroelectrics. The proposed polarizable nonvolatile ferroelectric gating in a monolayer MoS2 phototransistor promises a potential route toward ultrasensitive photodetectors with low power consumption that boast of high levels of integration.

Encapsulation of Titanium Disulfide into MOF-Derived N,S-Doped Carbon Nanotablets Toward Suppressed Shuttle Effect and Enhanced Sodium Storage Performance.

Titanium disulfide (TiS2 ) is a promising anode material for sodium-ion batteries due to its high theoretical capacity, but it suffers from severe volume variation and shuttle effect of the intermediate polysulfides. To overcome the drawbacks, herein the successful fabrication of TiS2 @N,S-codoped C (denoted as TiS2 @NSC) through a chemical vapor reaction between Ti-based metal-organic framework (NH2 -MIL-125) and carbon disulfide (CS2 ) is demonstrated. The C─N bonds enhance the electronic/ionic conductivity of the TiS2 @NSC electrode, while the C─S bonds provide extra sodium storage capacity, and both polar bonds synergistically suppress the shuttle effect of polysulfides. Consequently, the TiS2 @NSC electrode demonstrates outstanding cycling stability and rate performance, delivering reversible capacities of 418/392 mAh g-1 after 1000 cycles at 2/5 A g-1 . Ex situ X-ray photoelectron spectroscopy and transmission electron microscope analyses reveal that TiS2 undergoes an intercalation-conversion ion storage mechanism with the generation of metallic Ti in a deeper sodiation state, and the pristine hexagonal TiS2 is electrochemically transformed into cubic rock-salt TiS2 as a reversible phase with enhanced reaction kinetics upon sodiation/desodiation cycling. The strategy to encapsulate TiS2 in N,S-codoped porous carbon matrices efficiently realizes superior conductivity and physical/chemical confinement of the soluble polysulfides, which can be generally applied for the rational design of advanced electrodes.

Overcoming Challenges: Extending Cycle Life of Aqueous Zinc-Ion Batteries at High Zinc Utilization through a Synergistic Strategy.

Aqueous zinc-ion batteries (AZIBs) face challenges in achieving high energy density compared to conventional lithium-ion batteries (LIBs). The lower operating voltage and excessive Zn metal as anode pose constraints on the overall energy storage capacity of these batteries. An effective approach is to reduce the thickness of the Zn metal anode and control its mass appropriately. However, under the condition of using a thin Zn anode, the performance of AZIBs is often unsatisfactory. Through experiments and computational simulations, the electrode structural change and the formation of dead Zn as the primary reasons for the failure of batteries under a high Zn utilization rate are identified. Based on this understanding, a universal synergistic strategy that combines Cu foil current collectors and electrolyte additives to maintain the structural and thermodynamic stability of the Zn anode under a high Zn utilization rate (ZUR) is proposed. Specifically, the Cu current collectors can ensure that the Zn anode structure remains intact based on the spontaneous filling effect, while the additives can suppress parasitic side reactions at the interface. Ultimately, the symmetric cell demonstrates a cycling duration of 900 h at a 70% ZU, confirming the effectiveness of this strategy.

Enabling Highly-Reversible Aqueous Zn-Ion Batteries via 4-Hydroxybenzoic Acid Sodium Salt Electrolyte Additive.

Due to the intrinsic safety and cost effectiveness, aqueous Zn-ion batteries (AZIBs) are considered a promising candidate for future energy storage systems. However, the widespread implementation of AZIBs faces significant obstacles due to various undesirable side reactions, including hydrogen evolution reaction (HER), corrosion, and uncontrolled dendrite growth at the anodes. Here, 4-hydroxybenzoic acid sodium salt (PHB) is employed in the ZnSO4 electrolyte to enable highly-reversible zinc anodes. PHB has a greater tendency to bind with the Zn surface, resulting in increased steric effects within the electrolyte. As a result, it hinders the direct interaction between anode and water while facilitating the uniform plating of Zn2+ . Zn/Zn batteries with PHB additives realized more than 1600 h stable cycling life under 1 mA cm-2 and 1 mAh cm-2 . Moreover, Zn/Cu batteries with PHB additives achieved a reversible plating/stripping process for over 500 cycles with high average CE of 98.6 %. In addition, the assembled Zn/NH4 V4 O10 batteries with PHB additive yielded 80.5 mAh g-1 after 1000 cycles at 10 A g-1 . The inexpensive and effective application of PHB as an electrolyte additive has the potential to significantly enhance the stability and dependability of ZIBs.

Improved ion adsorption capacities and diffusion dynamics in surface anchored MoS2⊥Mo4/3B2 and MoS2⊥Mo4/3B2O2 heterostructures as anodes for alkaline metal-ion batteries.

First-principles calculations were performed to analyze the atomic structures and electrochemical energy storage properties of novel MoS2⊥boridene heterostructures by anchoring MoS2 nanoflakes on Mo4/3B2 and Mo4/3B2O2 monolayers. Both thermodynamic and thermal stabilities of each heterostructure were thoroughly evaluated from the obtained binding energies and through first-principles molecular dynamics simulations at room temperature, confirming the high formability of the heterostructures. The electrochemical properties of MoS2⊥Mo4/3B2 and MoS2⊥Mo4/3B2O2 heterostructures were investigated for their potential use as anodes for alkaline metal ion batteries (Li+, Na+ and K+). It was revealed that Li+ and Na+ can form multiple stable full adsorption layers on both heterostructures, while K+ forms only a single full adsorption layer. The presence of a negative electron cloud (NEC) contributes to the stabilization of a multi-layer adsorption mechanism. For all investigated alkaline metal ions, the predicted ion diffusion dynamics are relatively sluggish for the adsorbates in the first full adsorption layer on MoS2⊥boridene heterostructures due the relatively large migration energies (>0.50 eV), compared to those of second or third full adsorption layers (<0.30 eV). MoS2⊥Mo4/3B2O2 exhibited higher onset and mean open circuit voltages as anodes for alkaline metal-ion batteries than MoS2⊥Mo4/3B2 hybrids because of enhanced interactions between the adsorbate and the Mo4/3B2O2 monolayer with the presence of O-terminations. Tailoring the size and horizontal spacing between two neighboring MoS2 nano-flakes in heterostructures led to high theoretical capacities for LIBs (531 mA h g-1), SIBs (300 mA h g-1) and PIBs (131 mA h g-1) in the current study.

Expression and Clinical Significance of microRNA-138-5p and TGF-ß3 in Peripheral Blood of Patients With Ankylosing Spondylitis.

STUDY DESIGN: Clinical study. OBJECTIVE: Our work was aimed at exploring the expression and clinical significance of microRNA-138-5p (miR-138-5p) and Transforming Growth Factor-beta 3 (TGF-ß3) in peripheral blood of patients with ankylosing spondylitis (AS). METHODS: Forty-seven patients with AS were selected as the AS group, and the staging of the enrolled AS patients was based on the BASDAI score: <4 points were classified as the stable stage (stable group) and ≥4 points were classified as the active stage (active group). Forty-seven cases were selected from the same period of healthy physical examination in our hospital as the control group. miR-138-5p and TGF-ß3 levels and disease activity factors in peripheral blood were measured in all patients. RESULTS: Compared to healthy subjects, reduced miR-138-5p levels and increased TGF-ß3 levels were found in AS patient. Even more, level of miR-138-5p was decreased and level of TGF-ß3 was found to be increased in active disease stage of AS in comparison to inactive disease. Correlation analysis disclosed that miR-138-5p expression in peripheral blood of AS patients was negatively correlated with TGF-ß3, HLA-B27, ESR, CRP, and BASDAI; serum TGF-ß3 was positively correlated with HLA-B27, ESR, CRP, and BASDAI. The ROC curve analysis disclosed that miR-138-5p and TGF-ß3 had certain diagnostic value for AS, and the combined detection could improve the clinical diagnostic capability of this disease. CONCLUSION: miR-138-5p and TGF-ß3 in peripheral blood of AS patients are potential biological markers for the diagnosis of AS and are expected to be new clinical diagnostic indicators.

Single injection technique with ultrasound-guided superficial cervical fascia block combined with brachial plexus block in clavicular surgery: a prospective randomized comparative trial.

BACKGROUND: To investigate the effects of a single injection technique with ultrasound-guided superficial cervical fascia block combined with brachial plexus block in clavicular surgery. METHODS: Forty patients, 25 males and 15 females, aged 18-85 years with ASA class I or II underwent unilateral clavicular fracture internal fixation. The patients were randomly divided into a superficial cervical plexus block group (group S, n = 20) and a superficial cervical fascia block group (group F, n = 20). First, the brachial plexus of the intermuscular sulcus of all patients was blocked with an ultrasound-guided injection of one injection with 15ml 0.33% ropivacaine 15ml in both groups. Second, the superficial cervical plexus was blocked by another injection of 5-8ml 0.33% ropivacaine in group S, and the superficial cervical fascia was blocked by an injection with 5-8ml 0.33% ropivacaine in Group F. We evaluated operation time, onset time of anaesthesia, effective time and the grades of nerve block effect in the two groups. Additionally, we evaluated the incidences of local anaesthetic poisoning, hoarseness, dyspnoea, and postoperative nausea and vomiting, and the number of patients requiring remedial analgesia within 24 h. Repeated measurements were analysed by repeated data analysis of variance, and count data were compared by the χ2 test. A P value < 0.05 was considered statistically significant. RESULTS: The operation time and onset time in Group F were significantly shorter than those in group S (P < 0.05); the effect of intraoperative block was better than that in group S (P < 0.05), and the effective time was significantly longer in group F than in group S (P < 0.05). However, no severe case of dyspnoea, local anaesthetic poisoning or hoarseness after anaesthesia occurred in either of two groups. There was no significant difference in the rate of postoperative salvage analgesia or that of postoperative nausea and vomiting between the two groups. CONCLUSIONS: The application of the single injection technique with ultrasound-guided superficial cervical fascia block combined with brachial plexus block in clavicular surgery is beneficial because it shortens the operation time, has a faster onset, produces a more effective block and prolongs the longer analgesia time. TRIAL REGISTRATION: Chinese Clinical Trial Registry- ChiCTR2200064642(13/10/2022).

Tuneable effects of pyrrolic N and pyridinic N on the enhanced field emission properties of nitrogen-doped graphene.

Graphene is one of the most potential field emission cathode materials and a lot of work has been carried out to demonstrate the effectiveness of nitrogen doping (N doping) for the enhancement of field emission properties of graphene. However, the effect of N doping on graphene field emission is lacking systematic and thorough understanding. In this study, undoped graphene and N-doped graphene were prepared and characterized for measurements, and the field emission property dependence of the doping content was investigated and the tuneable effect was discussed. For the undoped graphene, the turn-on field was 7.95 V µm-1 and the current density was 7.3 µA cm-2, and for the 10 mg, 20 mg, and 30 mg N-doped graphene samples, the turn-on fields declined to 7.50 V µm-1, 6.38 V µm-1, and 7.28 V µm-1, and current densities increased to 21.0 µA cm-2, 42.6 µA cm-2, and 13.2 µA cm-2, respectively. Density functional theory (DFT) calculations revealed that N doping could bring about additional charge and then cause charge aggregation around the N atom. At the same time, it also lowered the work function, which further enhanced the field emission. The doping effect was determined by the content of the pyrrolic-type N and pyridinic-type N. Pyridinic-type N is more favourable for field emission because of its smaller work function, which is in good agreement with the experimental results. This study would be of great benefit to the understanding of N doping modulation for superior field emission properties.

Improving the High-Temperature Energy Storage Performance of Epoxy Films: Moderately Reducing Unsaturation for Extremely High Efficiency.

The rapid development of renewable energy systems, electric vehicles, and pulsed equipment requires energy storage media to have a high energy storage density and efficiency in a wide temperature range. The state-of-the-art biaxially oriented polypropylene (BOPP) film is insufficient to meet the growing demand for energy storage devices due to its low energy storage density and working temperature, which make it a research hotspot for developing dielectric energy storage materials. In this manuscript, based on the epoxy materials that have been shown as a potential energy storage medium, we aim to reduce the influence of the benzene ring delocalization structure on the energy storage losses and enhance the efficiency by gradually replacing them with cyclohexane structures to adjust the segment unsaturation of epoxy materials. The results show that by partially reducing the unsaturation of the curing agent, the epoxy material achieves an excellent high-temperature energy storage density of 2.21 J/cm3 at 150 °C and 300 MV/m while maintaining an extremely high energy storage efficiency of 99.2%. Leakage current density and high-voltage dielectric spectroscopy tests confirm that a moderate reduction of the segment unsaturation of epoxy materials can greatly inhibit polarization loss at high temperatures, which may explain their high energy storage efficiency.

A Study on the Clinical Significance of Blood Exosomal PD-L1 in Non-Small Cell Lung Cancer Patients and its Correlation with PD-L1 in Tumor Tissues.

Exosomal programmed cell-death ligand 1 (ePD-L1) can influence immune inhibition and dysfunction. We were dedicated to unearthing the relation between ePD-L1 in blood and pathological characteristics as well as PD-L1 in tumor tissues. We recruited 65 non-small cell lung cancer (NSCLC) patients for exosome extraction and detected the blood ePD-L1 expression in these patients by enzyme-linked immunosorbent assay (ELISA) method. Besides, the correlation between blood ePD-L1 and patients' pathological characteristics was also analyzed. The expression of PD-L1 in tumor tissues was tested by immunohistochemistry (IHC) and its correlation with blood ePD-L1 expression level was analyzed by Spearman correlation coefficient. No significant correlation was observed in PD-L1 expression levels between blood-derived exosome and tumor tissue. Altogether, high blood ePD-L1 expression was relevant to NSCLC progression, while no such relevance to PD-L1 expression in tumor tissue.

Synthesis of violet phosphorus with large lateral sizes to facilitate nano-device fabrications.

Violet phosphorus has been proven to be the most stable phosphorus allotrope and has attracted much attention recently. The growth of violet phosphorus with large lateral sizes is crucial to obtain good quality violet phosphorene for nanodevice fabrication. Herein, a large number of violet phosphorus plates have been produced from molten lead using an optimized method to achieve red bronze luster. The crystal structure of the as-produced violet phosphorus was determined by single-crystal X-ray diffraction to be monoclinic with the space group P2/n (13) (CSD-2160375), identical to the one from the chemical vapor transport method (CSD-1935087). The as-produced violet phosphorus plates were found to have lateral sizes of 1.30 ± 0.41 mm2. The violet phosphorus plates were easily exfoliated and directly transferred to silicon substrates to facilitate building of a back-gate field-effect transistor. A hole mobility of 2.308 cm2 V-1 s-1 was obtained from a violet phosphorus nanosheet with a thickness of 52 nm under ambient conditions. The absolute responsivity of 130 mA W-1 with a fast response time of 27 ms was also obtained under the irradiation of a 530 nm laser.

Violet Antimony Phosphorus with Enhanced Photocatalytic Hydrogen Evolution.

Violet phosphorus (VP), a recently confirmed layered elemental structure, is demonstrated to have unique photoelectric, mechanical, and photocatalytic properties. Element substitution plays a significant role in modifying the physical/chemical properties of semiconducting materials. Herein, antimony is adopted to substitute some phosphorus atoms in VP crystals to tune their physical and chemical properties, resulting in a significantly enhanced photocatalytic hydrogen evolution performance. The antimony-substituted violet phosphorus single crystal (VP-Sb) is synthesized and characterized by single crystal X-ray diffraction (CSD-2214937). The bandgap of VP-Sb has been found to be lowered from that of VP by UV/vis diffuse reflectance spectroscopy and density-functional theory (DFT) calculation, enhancing the optical absorption during photocatalytic reaction. The conducting band minimum of VP-Sb is found to be upshifted from that of VP from measurements and calculation, enhancing its hydrogen reduction activity. The valance band maximum is found to be lowered to weaken its oxidation activity. The edge of VP-Sb is calculated to have an excellent H* adsorption-desorption performance and superior H2 generation kinetics. The H2 evolution rate of VP-Sb is demonstrated to be significantly enhanced to be 1473 µmol h-1 g-1 , about five times of that of pristine VP (299 µmol h-1 g-1 ) under the same experimental conditions.

Introducing Hybrid Defects of Silicon Doping and Oxygen Vacancies into MOF-Derived TiO2-X @Carbon Nanotablets Toward High-Performance Sodium-Ion Storage.

Titanium dioxide (TiO2 ) is a promising anode material for sodium-ion batteries (SIBs), which suffer from the intrinsic sluggish ion transferability and poor conductivity. To overcome these drawbacks, a facile strategy is developed to synergistically engineer the lattice defects (i.e., heteroatom doping and oxygen vacancy generation) and the fine microstructure (i.e., carbon hybridization and porous structure) of TiO2 -based anode, which efficiently enhances the sodium storage performance. Herein, it is successfully realized that the Si-doping into the MIL-125 metal-organic framework structure, which can be easily converted to SiO2 /TiO2-x @C nanotablets by annealing under inert atmosphere. After NaOH etching SiO2 /TiO2-x @C which contains unbonded SiO2 and chemically bonded SiOTi, thus the lattice Si-doped TiO2-x @C (Si-TiO2-x @C) nanotablets with rich Ti3+ /oxygen vacancies and abundant inner pores are developed. When examined as an anode for SIB, the Si-TiO2-x @C exhibits a high sodium storage capacity (285 mAh g-1 at 0.2 A g-1 ), excellent long-term cycling, and high-rate performances (190 mAh g-1 at 2 A g-1 after 2500 cycles with 95.1% capacity retention). Theoretical calculations indicate that the rich Ti3+ /oxygen vacancies and Si-doping synergistically contribute to a narrowed bandgap and lower sodiation barrier, which thus lead to fast electron/ion transfer coefficients and the predominant pseudocapacitive sodium storage behavior.

Thickness-Dependent Dielectric Screening in Few-Layer Phosphorus.

The dielectric screening plays a critical role in determining the fundamental electronic properties in semiconductor devices. In this work, we report a noncontact and spatially resolved method, based on Kelvin probe force microscopy (KPFM), to obtain the inherent dielectric screening of black phosphorus (BP) and violet phosphorus (VP) as a function of the thickness. Interestingly, the dielectric constant of VP and BP flakes increases monotonically and then saturates to the bulk value, which is consistent with our first-principles calculations. The dielectric screening in VP has a much weaker dependence on the number of layers. This could be ascribed to a strong electron orbital overlap between two adjacent layers of VP, resulting in a strong interlayer coupling. The findings of our work are significant both for fundamental studies of dielectric screening and for more technical applications in nanoelectronic devices based on layered 2D materials.

Self-healing of electrical damage in insulating robust epoxy containing dynamic fluorine-substituted carbamate bonds for green dielectrics.

Power systems and electrical grids are critical for the development of renewable energy. Electrical treeing is one of the major factors that lead to electrical damage in insulating dielectrics and decline in the reliability of power equipment and ultimately results in catastrophic failure. Here, we demonstrate that bulk epoxy damaged by electrical treeing is able to efficiently heal repeatedly to recover its original robust performance. The classical dilemma between the insulating properties and electrical-damage healability is overcome by dynamic fluorinated carbamate bonds. Moreover, the dynamic bond enables the epoxy to have admirable degradability, which is demonstrated to be used as an attractive green degradable insulation coating. When used as a matrix for fiber-reinforced composites, the reclaimed glass fibers after decomposing the epoxy maintained their original morphology and functionality. This design provides a novel approach for developing smart and green dielectrics to enhance the reliability, sustainability and lifespan of power equipment and electronics.