Characterization of parotid gland tumors using diffusion-relaxation correlation spectrum imaging: a preliminary study

AIM

To assess the performance of diffusion-relaxation correlation spectrum imaging (DR-CSI) in the characterization of parotid gland tumors.

MATERIALS AND METHODS

Twenty-five pleomorphic adenomas (PA) patients, 9 Warthin's tumors (WT) patients and 7 malignant tumors (MT) patients were prospectively recruited. DR-CSI (7 b-values combined with 5 TEs, totally 35 diffusion-weighted images) was scanned for pre-treatment assessment. Diffusion (D)-T2 signal spectrum summating all voxels were built for each patient, characterized by D-axis with range 0∼5 × 10-3 mm2/s, and T2-axis with range 0∼300ms. With boundaries of 0.5 and 2.5 × 10-3 mm2/s for D, all spectra were divided into three compartments labeled A (low D), B (mediate D) and C (high D). Volume fractions acquired from each compartment (VA, VB, VC) were compared among PA, WT and MT. Diagnostic performance was assessed using receiver operating characteristic analysis and area under the curve (AUC).

RESULTS

Each subtype of parotid tumors had their specific D-T2 spectrum. PA showed significantly lower VA (8.85 ± 4.77% vs 20.68 ± 10.85%), higher VB (63.40 ± 8.18% vs 43.05 ± 7.16%), and lower VC (27.75 ± 8.51% vs 36.27 ± 11.09) than WT (all p<0.05). VB showed optimal diagnostic performance (AUC 0.969, sensitivity 92.00%, specificity 100.00%). MT showed significantly higher VA (21.23 ± 12.36%), lower VB (37.09 ± 6.43%), and higher VC (41.68 ± 13.72%) than PA (all p<0.05). Similarly, VB showed optimal diagnostic performance (AUC 0.994, sensitivity 96.00%, specificity 100.00%). No significant difference of VA, VB and VC was found between WT and MT.

CONCLUSIONS

DR-CSI might be a promising and non-invasive way for characterizing parotid gland tumors.

Recent progress in emerging two-dimensional organic-inorganic van der Waals heterojunctions

Two-dimensional (2D) materials have attracted significant attention in recent decades due to their exceptional optoelectronic properties. Among them, to meet the growing demand for multifunctional applications, 2D organic-inorganic van der Waals (vdW) heterojunctions have become increasingly popular in the development of optoelectronic devices. These heterojunctions demonstrate impressive capability to synergistically combine the favourable characteristics of organic and inorganic materials, thereby offering a wide range of advantages. Also, they enable the creation of innovative device structures and introduce novel functionalities in existing 2D materials, avoiding the need for lattice matching in different material systems. Presently, researchers are actively working on improving the performance of devices based on 2D organic-inorganic vdW heterojunctions by focusing on enhancing the quality of 2D materials, precise stacking methods, energy band regulation, and material selection. Therefore, this review presents a thorough examination of the emerging 2D organic-inorganic vdW heterojunctions, including their classification, fabrication, and corresponding devices. Additionally, this review offers profound and comprehensive insight into the challenges in this field to inspire future research directions. It is expected to propel researchers to harness the extraordinary capabilities of 2D organic-inorganic vdW heterojunctions for a wider range of applications by further advancing the understanding of their fundamental properties, expanding the range of available materials, and exploring novel device architectures. The ongoing research and development in this field hold potential to unlock captivating advancements and foster practical applications across diverse industries.

Phase and Composition Engineering of Self-Intercalated 2D Metallic Tantalum Sulfide for Second-Harmonic Generation

Self-intercalation in two-dimensional (2D) materials is significant, as it offers a versatile approach to modify material properties, enabling the creation of interesting functional materials, which is essential in advancing applications across various fields. Here, we define ic-2D materials as covalently bonded compounds that result from the self-intercalation of a metal into layered 2D compounds. However, precisely growing ic-2D materials with controllable phases and self-intercalation concentrations to fully exploit the applications in the ic-2D family remains a great challenge. Herein, we demonstrated the controlled synthesis of self-intercalated H-phase and T-phase Ta1+xS2 via a temperature-driven chemical vapor deposition (CVD) approach with a viable intercalation concentration spanning from 10% to 58%. Atomic-resolution scanning transmission electron microscopy-annular dark field imaging demonstrated that the self-intercalated Ta atoms occupy the octahedral vacancies located at the van der Waals gap. The nonperiodic Ta atoms break the centrosymmetry structure and Fermi surface properties of intrinsic TaS2. Therefore, ic-2D T-phase Ta1+xS2 consistently exhibit a spontaneous nonlinear optical (NLO) effect regardless of the sample thickness and self-intercalation concentrations. Our results propose an approach to activate the NLO response of centrosymmetric 2D materials, achieving the modulation of a wide range of optoelectronic properties via nonperiodic self-intercalation in the ic-2D family.

Liquid metal catalyzed chemical vapor deposition towards morphology engineering of 2D epitaxial heterostructures

The past decades have witnessed significant advancements in the growth of two-dimensional (2D) materials, offering a wide range of potential applications in the fields of electronics, optoelectronics, energy storage, sensors, catalysis, and biomedical treatments. Epitaxial heterostructures based on 2D materials, including vertical heterostructures, lateral structures, and superlattices, have emerged as novel material systems to manipulate the intrinsic properties and unlock new functionalities. Therefore, the development of controllable preparation methods for tailored epitaxial heterostructures serves as a fundamental basis for extensive property investigation and further application exploration. However, this pursuit presents formidable challenges due to the incomplete understanding of growth mechanisms and limited designable strategies. Chemical vapor deposition (CVD) is deemed as a promising and versatile platform for the controlled synthesis of 2D materials, especially with regard to achieving lattice matching, a critical factor in epitaxial growth. Consequently, CVD holds potential to overcome these hurdles. In this Feature Article, we present our recent breakthroughs in the controllable preparation of 2D epitaxial heterostructures using CVD. Our focus revolves around the processes of morphology engineering, interface engineering, size and density engineering, and striking the delicate balance between growth and etching. Using molten metals or alloys as primary catalysts, we have achieved remarkable control over the fabrication of graphene/hexagonal boron nitride (hBN) super-ordered arrays, enabled multistage etching of graphene/hBN heterostructures, and successfully realized the construction of graphene/MXene heterostructures. Furthermore, our research endeavors encompass both bottom-up and top-down fabrication methods, offering a novel perspective on the synthesis of 2D epitaxial heterostructures. The resulting products hold immense potential for enhancing the efficiency of critical reactions such as oxygen reduction, CO2 reduction, and hydrogen evolution reactions. By presenting our methodologies for obtaining 2D epitaxial heterostructures through CVD, we aspire to inspire fellow researchers in this field to devise more feasible and controllable fabrication techniques while also fostering the exploration of diverse heterostructure configurations. Together, these advancements will undoubtedly pave the way for further breakthroughs in atomic manufacturing and novel applications.

Ultralow-Power Vertical Transistors for Multilevel Decoding Modes

Organic field-effect transistors with parallel transmission and learning functions are of interest in the development of brain-inspired neuromorphic computing. However, the poor performance and high power consumption are the two main issues limiting their practical applications. Herein, an ultralow-power vertical transistor is demonstrated based on transition-metal carbides/nitrides (MXene) and organic single crystal. The transistor exhibits a high J_ON of 16.6 mA cm^-2 and a high J_ON /J_OFF ratio of 9.12 × 10⁵ under an ultralow working voltage of -1 mV. Furthermore, it can successfully simulate the functions of biological synapse under electrical modulation along with consuming only 8.7 aJ of power per spike. It also permits multilevel information decoding modes with a significant gap between the readable time of professionals and nonprofessionals, producing a high signal-to-noise ratio up to 114.15 dB. This work encourages the use of vertical transistors and organic single crystal in decoding information and advances the development of low-power neuromorphic systems.

Additive-Assisted Growth of Scaled and Quality 2D Materials

2D materials are increasingly becoming key components in modern electronics because of their prominent electronic and optoelectronic properties. The central and premise to the entire discipline of 2D materials lie in the high-quality and scaled preparations. The chemical vapor deposition (CVD) method offers compelling benefits in terms of scalability and controllability in shaping large-area and high-quality 2D materials. The past few years have witnessed development of numerous CVD growth strategies, with the use of additives attracting substantial attention in the production of scaled 2D crystals. This review provides an overview of different additives used in CVD growth of 2D materials, as well as a methodical demonstration of their vital roles. In addition, the intrinsic mechanisms of the production of scaled 2D crystals with additives are also discussed. Lastly, reliable guidance on the future design of optimal CVD synthesis routes is provided by analyzing the accessibility, pricing, by-products, controllability, universality, and commercialization of various additives.

Continuous orientated growth of scaled single-crystal 2D monolayer films

Single-crystal 2D materials have attracted a boom of scientific and technological activities. Recently, chemical vapor deposition (CVD) shows great promise for the synthesis of high-quality 2D materials owing to high controllability, high scalability and ultra-low cost. Two types of strategies have been developed: one is single-seed method, which focuses on the ultimate control of the density of nucleation into only one nucleus and the other is a multi-seed approach, which concentrates on the precise engineering of orientation of nuclei into a uniform alignment. Currently, the latter is recognized as a more effective method to meet the demand of industrial production, whereas the oriented domains can seamlessly merge into a continuous single-crystal film in a short time. In this review, we present the detailed cases of growing the representative monocrystalline 2D materials via the single-seed CVD method as well as show its advantages and disadvantages in shaping 2D materials. Then, other typical 2D materials (including graphene, h-BN, and TMDs) are given in terms of the unique feature under the guideline of the multi-seed growth approach. Furthermore, the growth mechanism for the 2D single crystals is presented and the following application in electronics, optics and antioxidation coatings are also discussed. Finally, we outline the current challenges, and a bright development in the future of the continuous orientated growth of scaled 2D crystals should be envisioned.

A minireview on chemical vapor deposition growth of wafer-scale monolayer h-BN single crystals

Hexagonal boron nitride (h-BN), with its excellent stability, flat surface, and large bandgap, plays a role in a variety of fundamental science and technology fields. The past few years have witnessed significant development in the scaled growth of h-BN single crystals. Currently, the size of h-BN crystal can be reached up to wafer-scale, paving the way towards industrial production and commercial applications. In this minireview, recent academic breakthroughs regarding the controlled growth of large-sized h-BN single crystals via chemical vapor deposition (CVD) are presented. The as-developed technique in terms of growth parameters, choice of catalysts, and the mechanism is fully emphasized, offering a guideline in enhancing the size and quality of h-BN. Several typical metal catalysts have been used in shaping scaled h-BN single crystals, of which the metal Cu substrate has drawn the most intensive attention. The significant advances in expanding the size of h-BN single crystals will largely push forward the way to h-BN industrialization and commercialization. The past few years have witnessed significant development in the scaled growth of h-BN single crystals. Currently, the size of h-BN crystal can be reached up to wafer-scale, paving the way towards industrial production and commercial applications. In this minireview, recent academic breakthroughs regarding controlled growth of large-sized h-BN single crystals via chemical vapor deposition (CVD) are present. The as-developed technique in terms of growth parameters, choice of catalysts and mechanism is fully emphasized, offering a guideline in enhancing size and quality of h-BN. Several typical metal catalysts are exhibited in shaping scaled h-BN single crystals, of which the metal Cu substrate has drawn the most intensive attentions.

When graphene meets white graphene - recent advances in the construction of graphene and h-BN heterostructures

2D heterostructures have very recently witnessed a boom in scientific and technological activities owing to the customized spatial orientation and tailored physical properties. A large amount of 2D heterostructures have been constructed on the basis of the combination of mechanical exfoliation and located transfer method, opening wide possibilities for designing novel hybrid systems with tuned structures, properties, and applications. Among the as-developed 2D heterostructures, in-plane graphene and h-BN heterostructures have drawn the most attention in the past few decades. The controllable synthesis, the investigation of properties, and the expansion of applications have been widely explored. Herein, the fabrication of graphene and h-BN heterostructures is mainly focused on. Then, the spatial configurations for the heterostructures are systematically probed to identify the highly related unique features. Moreover, as a most promising approach for the scaled production of 2D materials, the in situ CVD fabrication of the heterostructures is summarized, demonstrating a significant potential in the controllability of size, morphology, and quality. Further, the recent applications of the 2D heterostructures are discussed. Finally, the concerns and challenges are fully elucidated and a bright future has been envisioned.

Controlled growth of 2D ultrathin Ga2O3 crystals on liquid metal

2D metal oxides (2DMOs) have drawn intensive interest in the past few years owing to their rich surface chemistry and unique electronic structures. Striving for large-scale and high-quality novel 2DMOs is of great significance for developing future nano-enabled technologies. In this work, we demonstrate for the first time controllable growth of highly crystalline 2D ultrathin Ga₂O₃ single crystals on liquid Ga by the chemical vapor deposition approach. With the introduction of oxygen into the growth process, large-area hexagonal α-Ga₂O₃ crystals with a uniform size distribution have been produced. At high temperature, fast diffusion of oxygen atoms onto the liquid surface facilitates reaction with Ga and thus leads to in situ formation of 2D ultrathin crystals. By precisely controlling the amount of oxygen, the vertical growth of the Ga₂O₃ single crystal has been realized. Furthermore, phase engineering can be achieved and thus 2D β-Ga₂O₃ crystals were also prepared by precisely tuning the growth temperature. The controlled growth of 2D Ga₂O₃ crystals offers an applicable avenue for fabrication of other 2D metal oxides and can further open up possibilities for future electronics.

Recent Advances in Growth of Large-Sized 2D Single Crystals on Cu Substrates

Large-scale and high-quality 2D materials have been an emerging and promising choice for use in modern chemistry and physics owing to their fascinating property profile. The past few years have witnessed inspiringly progressing development in controlled fabrication of large-sized and single-crystal 2D materials. Among those production methods, chemical vapor deposition (CVD) has drawn the most attention because of its fine control over size and quality of 2D materials by modulating the growth conditions. Meanwhile, Cu has been widely accepted as the most popular catalyst due to its significant merit in growing monolayer 2D materials in the CVD process. Herein, very recent advances in preparing large-sized 2D single crystals on Cu substrates by CVD are presented. First, the unique features of Cu will be given in terms of ultralow precursor solubility and feasible surface engineering. Then, scaled growth of graphene and hexagonal boron nitride (h-BN) crystals on Cu substrates is demonstrated, wherein different kinds of Cu surfaces have been employed. Furthermore, the growth mechanism for the growth of 2D single crystals is exhibited, offering a guideline to elucidate the in-depth growth dynamics and kinetics. Finally, relevant issues for industrial-scale mass production of 2D single crystals are discussed and a promising future is expected.

Correlations between microbiota and metabolites after faecal microbiota transfer in irritable bowel syndrome

Faecal microbiota transfer (FMT) consists of the infusion of donor faecal material into the intestine of a patient with the aim to restore a disturbed gut microbiota. In this study, it was investigated whether FMT has an effect on faecal microbial composition, its functional capacity, faecal metabolite profiles and their interactions in 16 irritable bowel syndrome (IBS) patients. Faecal samples from eight different time points before and until six months after allogenic FMT (faecal material from a healthy donor) as well as autologous FMT (own faecal material) were analysed by 16S RNA gene amplicon sequencing and gas chromatography coupled to mass spectrometry (GS-MS). The results showed that the allogenic FMT resulted in alterations in the microbial composition that were detectable up to six months, whereas after autologous FMT this was not the case. Similar results were found for the functional profiles, which were predicted from the phylogenetic sequencing data. While both allogenic FMT as well as autologous FMT did not have an effect on the faecal metabolites measured in this study, correlations between the microbial composition and the metabolites showed that the microbe-metabolite interactions seemed to be disrupted after allogenic FMT compared to autologous FMT. This shows that FMT can lead to altered interactions between the gut microbiota and its metabolites in IBS patients. Further research should investigate if and how this affects efficacy of FMT treatments.

The study on pathological mechanism and solution method for spinal cord ischemia reperfusion injury

OBJECTIVE

We aimed at investigating the pathological mechanism changing of injury during reperfusion injury, reperfusion time correlation and compliance, finding the blood supply and improving the secondary damage.

MATERIALS AND METHODS

A total of 180 patients who underwent a surgical procedure and that received normal saline intraperitoneally immediately after the patients' aortic occlusions were investigated. Patients were divided in three groups. Experimental conditions and programs were designed for various approaches.

RESULTS

Thirty min after the onset of ischemia, we found a decrease in the local blood flow in the lumbar spinal cord, almost -77.48% of the baseline, which was reversed partially by initial reperfusion, even exceeding the baseline level. However, 1 hour after reperfusion, the blood flow was again decreased to the level below the baseline, followed by a decline to 207.13% ± 38.25 PU for 3 h without any recovery. Attenuating this secondary damage with neuroprotective strategies requires an understanding of these pathophysiologic processes.

CONCLUSIONS

This study showed the pathological mechanism changes during reperfusion injury and reperfusion time correlation and compliance, and analyzed some of the important pathophysiologic processes involved in secondary damage after spinal cord injury. Moreover, our research discusses a number of pharmacologic therapies that have either been studied or have future potential for this devastating injury.

Graphene-Induced in Situ Growth of Monolayer and Bilayer 2D SiC Crystals Toward High-Temperature Electronics

A reproducible graphene-induced in situ process is demonstrated for the first time for growing large-scale monolayer and bilayer cubic silicon carbide (SiC) crystals on a liquid Cu surface by chemical vapor deposition (CVD) method. Precise control over the morphology of SiC crystals is further realized by modulating growth conditions, thus leading to the formation of several shaped SiC crystals ranging from triangular, rectangular, pentagonal, and even to hexagonal kind. Simulations based on density functional theory are carried out to elucidate the growth mechanism of SiC flakes with various morphologies, which are in striking consistency with experimental observations. In the liquid Cu-assisted CVD system, growth temperature (∼1100 °C) enables sublimation and deposition of silicon oxide (SiO₂) derived from quartz tube, while liquid Cu facilitates preformation of graphene originated from methane. The SiO₂ and graphene, grown and reacted in situ in the CVD process, are served as the silicon and carbon source for the cubic SiC crystals, respectively. Moreover, the gradual transformation process from SiO₂ particles to SiC flakes is directly observed, with several middle stages clearly displayed. The direct in situ growth of SiC crystals offers a novel method for scaled production of SiC crystals and is beneficial to understand its growth mechanism, and thus push forward the way to develop high-temperature and high-frequency electronic devices.

High-Concentration Niobium-Substituted WS2 Basal Domains with Reconfigured Electronic Band Structure for Hydrogen Evolution Reaction

Extrinsically controlling the intrinsic activity and stability of two-dimensional (2D) semiconducting materials by substitutional doping is crucial for energy-related applications. However, an in situ transition-metal doping strategy for uniform and large-area chemical vapor deposited 2D semiconductors remains a formidable challenge. Here, we successfully synthesize highly uniform niobium-substituted tungsten disulfide (Nb-WS₂) monolayers, with a doping concentration of nearly 7% and sizes reaching 100 μm, through a metal dopant precursor route, using salt-catalyzed chemical vapor deposition (CVD). Our results reveal unusual effects in the structural, optical, electronic, and electrocatalysis characteristics of the Nb-WS₂ monolayer. The Nb dopants readily induce a band restructuring effect, providing the most active site with a hydrogen adsorption energy of 0.175 eV and hence greatly improving its hydrogen evolution activity_. The combined advantages of the unusual physics and chemistry by in situ CVD doping technique open the possibility in designing 2D-material-based electronics and catalysts of novel functionalities.

Effects of zoledronic acid on bone mineral density around prostheses and bone metabolism markers after primary total hip arthroplasty in females with postmenopausal osteoporosis

INTRODUCTION

To investigate the effect of zoledronic acid on periprosthetic bone mineral density (BMD) and bone metabolism markers after primary total hip arthroplasty in females with postmenopausal osteoporosis.

METHODS

From November 2015 to April 2016, 40 female patients who met the inclusion criteria were randomized into two groups: a control group (calcium + calcitriol) and a zoledronic acid group (calcium + calcitriol + zoledronic acid). At 1 week and 3, 6, and 12 months after operation, BMD was obtained through dual-energy X-ray absorptiometry (DEXA). At pre-operation and at 3, 6, and 12 months after the operation, levels of bone metabolism markers were obtained by serum examination.

RESULTS

Loss of BMD was significantly more pronounced in the control group than in the ZOL group in zones 1, 4, 6, and 7 at 6 months and in zones 1, 2, 4, 6, and 7 at 12 months after the operation. The levels of bone-resorption marker (β-CTX) were significantly lower in the ZOL group than in the control group at 3, 6, and 12 months after operation. The levels of bone-formation marker (TP1NP) performed statistically differences only at 12 months after the operation in these two groups.

CONCLUSIONS

Receiving an intravenous infusion of 5 mg zoledronic acid after THA can effectively reduce periprosthetic BMD loss and improve bone remodeling in females with postmenopausal osteoporosis. Zoledronic acid significantly inhibited bone mass loss in zones 1, 2, 4, 6, and 7 after THA and inhibited bone-resorption marker (β-CTX) to improve bone remodeling. Zoledronic acid treatment is potentially important for patients with osteoporosis after THA.

Primary Nucleation-Dominated Chemical Vapor Deposition Growth for Uniform Graphene Monolayers on Dielectric Substrate

Direct chemical vapor deposition growth of high quality graphene on dielectric substrates holds great promise for practical applications in electronics and optoelectronics. However, graphene growth on dielectrics always suffers from the issues of inhomogeneity and/or poor quality. Here, we first reveal that a novel precursor-modification strategy can successfully suppress the secondary nucleation of graphene to evolve ultrauniform graphene monolayer film on dielectric substrates. A mechanistic study indicates that the hydroxylation of silica substrate weakens the binding between graphene edges and substrate, thus realizing the primary nucleation-dominated growth. Field-effect transistors based on the graphene films show exceptional electrical performance with the charge carrier mobility up to 3800 cm² V^-1 s^-1 in air, which is much higher than those reported results of graphene films grown on dielectrics.

Edge Segregated Polymorphism in 2D Molybdenum Carbide

Molybdenum carbide (Mo₂ C), a class of unterminated MXene, is endowed with rich polymorph chemistry, but the growth conditions of the various polymorphs are not understood. Other than the most commonly observed T-phase Mo₂ C, little is known about other phases. Here, Mo₂ C crystals are successfully grown consisting of mixed polymorphs and polytypes via a diffusion-mediated mechanism, using liquid copper as the diffusion barrier between the elemental precursors of Mo and C. By controlling the thickness of the copper diffusion barrier layer, the crystal growth can be controlled between a highly uniform AA-stacked T-phase Mo₂ C and a "wedding cake" like Mo₂ C crystal with spatially delineated zone in which the Bernal-stacked Mo₂ C predominate. The atomic structures, as well as the transformations between distinct stackings, are simulated and analyzed using density functional theory (DFT)-based calculations. Bernal-stacked Mo₂ C has a d band closer to the Fermi energy, leading to a promising performance in catalysis as verified in hydrogen evolution reaction (HER).

Thermal-Assisted Vertical Electron Injections in Few-Layer Pyramidal-Structured MoS2 Crystals

The interlayer screening effects and charge conduction mechanisms in atomically thin two-dimensional (2D) materials are crucial for electronics and optoelectronics applications. However, such effects remain largely unexplored in chemical vapor deposition (CVD)-grown molybdenum disulfide (MoS₂) crystals. Here, we report a controllable CVD-grown monolayer MoS₂ and layer-by-layer pyramidal-structured MoS₂ crystals with an oxidized Mo foil precursor. The interlayer screening effects and charge conduction mechanisms in the pyramidal-structured MoS₂ crystals are studied. Although the Fowler-Nordheim (FN) tunneling model is widely adopted to describe the vertical charge transport mechanism at the 2D semiconductor/bulk metal interface, we found that such a mechanism cannot satisfactorily explain the electrical measurement obtained from our CVD-grown MoS₂ samples. Instead, our analysis reveals that Richardson-Schottky (RS) emission is the dominant transport mechanism when V_bias < 1 V. Our findings provide a fundamental understanding of the charge conduction mechanism in CVD-grown MoS₂ crystals, which is crucial for development of MoS₂ electronics and optoelectronics devices.

Effects of precursor pre-treatment on the vapor deposition of WS2 monolayers

Transition metal oxide powders have been widely used as the growth precursors for monolayer transition metal dichalcogenides (TMDCs) in chemical vapor deposition (CVD). It has been proposed that metal oxide precursors in the gas phase undergo a two-step reaction during CVD growth, where transition metal sub-oxides are likely formed first and then the sulfurization of these sub-oxides leads to the formation of TMDCs. However, the effects of stoichiometry of transition metal oxide precursors on the growth of TMDC monolayers have not been studied yet. In this contribution, we report the critical role of the WO3 precursor pre-annealing process on the growth of WS2 monolayers. Besides, several WO3 precursors with different types of oxygen vacancies have also been prepared and investigated by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and density functional theory calculation. Among all the non-stoichiometric WO3 precursors, thermally annealed WO3 powder exhibits the highest oxygen vacancy concentration and produces WS2 monolayers with significantly improved quality in terms of lateral size, density, and crystallinity. Our comprehensive study suggests that the chemical composition of transition metal oxide precursors would be fundamentally critical for the growth of large-area and high-quality WS2 monolayers, which further pave the way for revealing their intrinsic properties and unique applications.

Location-selective growth of two-dimensional metallic/semiconducting transition metal dichalcogenide heterostructures

An electrical contact between metallic electrodes and semiconductors is critical for the performance of electronic and optoelectronic devices. Two-dimensional (2D) transition metal dichalcogenides (TMDs) contain semiconducting, metallic and insulating material members, which enables the fabrication of highly integrated electronic devices fully based on 2D TMDs. However, location-selective synthesis of metallic/semiconducting heterostructures by a chemical vapor deposition (CVD) method has rarely been reported. In this study, a two-step CVD method was applied to fabricate 2D metallic/semiconducting heterostructures. Semiconducting WS2 was first synthesized and served as the template for the following CVD growth of metallic NbS2. In the growth process, NbS2 flakes selectively nucleate at the edges of WS2 monolayers, thus resulting in the formation of NbS2 islands circling around the WS2 monolayers. The as-grown NbS2/WS2 heterostructure was further systematically characterized by Raman spectroscopy, atomic force microscopy (AFM) and scanning transition electron microscopy (STEM). The NbS2 layers epitaxially grown on the WS2 monolayers exhibit a 3R phase and there was no discernible lattice strain in the NbS2/WS2 van der Waals (vdW) heterostructure. The growth of the metallic/semiconducting 2D heterostructures could benefit the nanoelectronic device fabrication and provide a platform for the 2D contact resistance study.

Association of serum galectin-3 with risks of death and vascular events in acute ischaemic stroke patients: the role of hyperglycemia

BACKGROUND AND PURPOSE

Whether the association between galectin-3 and stroke outcome is modified by fasting plasma glucose (FPG) is unknown. The aim was to evaluate the prognostic effect of galectin-3 amongst ischaemic stroke patients stratified by FPG.

METHODS

In all, 3082 ischaemic stroke patients were included in this study and serum galectin-3 was tested at baseline. The primary outcome was a composite outcome of death and vascular events, and secondary outcomes were death, stroke recurrence and vascular events within 1 year after stroke.

RESULTS

Increased galectin-3 was significantly associated with the primary outcome, stroke recurrence and vascular events in the patients with hyperglycemia but not in those with normoglycemia (P for interaction < 0.05 for all). The multivariate-adjusted hazard ratios (95% confidence intervals) were 1.72 (1.05-2.84), 2.64 (1.14-6.12) and 2.68 (1.33-5.38) for the primary outcome, stroke recurrence and vascular events, respectively. A linear association between galectin-3 and the primary outcome was observed in hyperglycemic patients (P for linearity = 0.007).

CONCLUSION

Increased galectin-3 was associated with the primary outcome, stroke recurrence and vascular events within 1 year after stroke in the patients with hyperglycemia, suggesting that galectin-3 may be an important prognostic factor for ischaemic stroke patients with hyperglycemia.

Recent Advances in Growth of Novel 2D Materials: Beyond Graphene and Transition Metal Dichalcogenides

Since the discovery of graphene just over a decade ago, 2D materials have been a central focus of materials research and engineering because of their unique properties and potential of revealing intriguing new phenomena. In the past few years, transition metal dichalcogenides (TMDs) have also attracted considerable attention because of the intrinsically opened bandgap. The exceptional properties and potential applications of graphene and TMDs have inspired explosive efforts to discover novel 2D materials. Here, emerging novel 2D materials are summarized and recent progress in the preparation, characterization, and application of 2D materials is highlighted. The experimental realization methods for these materials are emphasized, while the large-area growth and controlled patterning for industrial productions are discussed. Finally, the remaining challenges and potential applications of 2D materials are outlined.

Two-Dimensional Polymer Synthesized via Solid-State Polymerization for High-Performance Supercapacitors

Two-dimensional (2-D) polymer has properties that are attractive for energy storage applications because of its combination of heteroatoms, porosities and layered structure, which provides redox chemistry and ion diffusion routes through the 2-D planes and 1-D channels. Here, conjugated aromatic polymers (CAPs) were synthesized in quantitative yield via solid-state polymerization of phenazine-based precursor crystals. By choosing flat molecules (2-TBTBP and 3-TBQP) with different positions of bromine substituents on a phenazine-derived scaffold, C-C cross coupling was induced following thermal debromination. CAP-2 is polymerized from monomers that have been prepacked into layered structure (3-TBQP). It can be mechanically exfoliated into micrometer-sized ultrathin sheets that show sharp Raman peaks which reflect conformational ordering. CAP-2 has a dominant pore size of ∼0.8 nm; when applied as an asymmetric supercapacitor, it delivers a specific capacitance of 233 F g^-1 at a current density of 1.0 A g^-1, and shows outstanding cycle performance.

Mo-Terminated Edge Reconstructions in Nanoporous Molybdenum Disulfide Film

The catalytic and magnetic properties of molybdenum disulfide (MoS₂) are significantly enhanced by the presence of edge sites. One way to obtain a high density of edge sites in a two-dimensional (2D) film is by introducing porosity. However, the large-scale bottom-up synthesis of a porous 2D MoS₂ film remains challenging and the correlation of growth conditions to the atomic structures of the edges is not well understood. Here, using molecular beam epitaxy, we prepare wafer-scale nanoporous MoS₂ films under conditions of high Mo flux and study their catalytic and magnetic properties. Atomic-resolution electron microscopy imaging of the pores reveals two new types of reconstructed Mo-terminated edges, namely, a distorted 1T (DT) edge and the Mo-Klein edge. Nanoporous MoS₂ films are magnetic up to 400 K, which is attributed to the presence of Mo-terminated edges with unpaired electrons, as confirmed by density functional theory calculation. The small hydrogen adsorption free energy at these Mo-terminated edges leads to excellent activity for the hydrogen evolution reaction.

Homoepitaxial Growth of Large-Scale Highly Organized Transition Metal Dichalcogenide Patterns

Controllable growth of highly crystalline transition metal dichalcogenide (TMD) patterns with regular morphology and unique edge structure is highly desired and important for fundamental research and potential applications. Here, single-crystalline MoS₂ flakes are reported with regular trigonal symmetric patterns that can be homoepitaxially grown on MoS₂ monolayer via chemical vapor deposition. The highly organized MoS₂ patterns are rhombohedral (3R)-stacked with the underlying MoS₂ monolayer, and their boundaries are predominantly terminated by zigzag Mo edge structure. The epitaxial MoS₂ crystals can be tailored from compact triangles to fractal flakes, and the pattern formation can be explained by the anisotropic growth rates of the S and Mo edges under low sulfur chemical potential. The 3R-stacked MoS₂ pattern demonstrates strong second and third-harmonic-generation signals, which exceed those reported for monolayer MoS₂ by a factor of 6 and 4, correspondingly. This homoepitaxial growth approach for making highly organized TMD patterns is also demonstrated for WS₂ .

Direct Synthesis of Large-Area 2D Mo2 C on In Situ Grown Graphene

As a new member of the MXene group, 2D Mo₂ C has attracted considerable interest due to its potential application as electrodes for energy storage and catalysis. The large-area synthesis of Mo₂ C film is needed for such applications. Here, the one-step direct synthesis of 2D Mo₂ C-on-graphene film by molten copper-catalyzed chemical vapor deposition (CVD) is reported. High-quality and uniform Mo₂ C film in the centimeter range can be grown on graphene using a Mo-Cu alloy catalyst. Within the vertical heterostructure, graphene acts as a diffusion barrier to the phase-segregated Mo and allows nanometer-thin Mo₂ C to be grown. Graphene-templated growth of Mo₂ C produces well-faceted, large-sized single crystals with low defect density, as confirmed by scanning transmission electron microscopy (STEM) measurements. Due to its more efficient graphene-mediated charge-transfer kinetics, the as-grown Mo₂ C-on-graphene heterostructure shows a much lower onset voltage for hydrogen evolution reactions as compared to Mo₂ C-only electrodes.

Serum 25-hydroxyvitamin D deficiency predicts poor outcome amongst acute ischaemic stroke patients with low high density lipoprotein cholesterol

BACKGROUND AND PURPOSE

Current observational studies indicate that a lower vitamin D level is associated with a higher risk of poor ischaemic stroke prognosis. Whether this association is affected by lipid levels is unclear. Our aim was to examine the effect of serum vitamin D especially its deficiency on the global outcome of ischaemic stroke stratified by individual lipid component level.

METHODS

A total of 3181 ischaemic patients from China Antihypertensive Trial in Acute Ischaemic Stroke were included in this study and their baseline serum 25-hydroxyvitamin D levels were tested. They were prospectively followed up for death, major disability and vascular events for 3 months after acute ischaemic stroke. A multivariable logistic model was used to evaluate the association between serum 25-hydroxyvitamin D levels and clinical outcomes of ischaemic stroke in the 3-month period of follow-up in all patients and in different lipid-level subgroups.

RESULTS

Vitamin D deficiency was associated with poor clinical outcomes only in ischaemic stroke patients with high density lipoprotein cholesterol (HDLC) <1.04 mmol/l rather than all patients. The multivariable adjusted odds ratios (95% confidence intervals) of major disability and composite adverse events were 1.98 (1.08-3.63) and 2.24 (1.22-4.12), respectively. There was a significant interaction effect between vitamin D and HDLC levels on major disability and the composite outcome (P for interaction < 0.05 for both). A significant linear trend existed between 25-hydroxyvitamin D and risk of poor prognosis (P = 0.03).

CONCLUSIONS

Vitamin D deficiency may be merely an independent risk factor of poor prognosis in ischaemic stroke patients with low HDLC level.

Chemical Vapor Deposition of High-Quality Large-Sized MoS2 Crystals on Silicon Dioxide Substrates

Large-sized MoS2 crystals can be grown on SiO2/Si substrates via a two-stage chemical vapor deposition method. The maximum size of MoS2 crystals can be up to about 305 μm. The growth method can be used to grow other transition metal dichalcogenide crystals and lateral heterojunctions. The electron mobility of the MoS2 crystals can reach ≈30 cm2 V-1 s-1, which is comparable to those of exfoliated flakes.

Effect of single nucleotide polymorphisms in the ATP-binding cassette B1 gene on the clinical outcome of traumatic brain injury

The critical role of ATP-binding cassette B1 (ABCB1) in the function of the blood-brain barrier led us to conducted this prospective study in order to investigate the clinical outcome of patients suffering from severe traumatic brain injury. A total of 182 patients with traumatic brain injury were included in our study. Genotyping of ABCB1 C3435T and G2677T/A was conducted using polymerase chain reaction-restriction fragment length polymorphism. Using multivariate-logistic regression analysis, we found that patients carrying the CT+CC genotype of ABCB1 C3435T were more likely to have a better neurological outcome when compared with the TT genotype (odds ratio = 2.71, 95% confidence interval = 1.12-6.86). However, no significant association was found between the G2677T/A polymorphism and outcome of traumatic brain injury patients. Our study provides important information regarding the prognostic value of ABCB1 C3435T, and the ABCB1 C3435T polymorphism may be used as a predictive marker for the outcome of traumatic brain injury patients.

Graphene single crystals: size and morphology engineering

Recently developed chemical vapor deposition (CVD) is considered as an effective way to large-area and high-quality graphene preparation due to its ultra-low cost, high controllability, and high scalability. However, CVD-grown graphene film is polycrystalline, and composed of numerous grains separated by grain boundaries, which are detrimental to graphene-based electronics. Intensive investigations have been inspired on the controlled growth of graphene single crystals with the absence of intrinsic defects. As the two most concerned parameters, the size and morphology serve critical roles in affecting properties and understanding the growth mechanism of graphene crystals. Therefore, a precise tuning of the size and morphology will be of great significance in scale-up graphene production and wide applications. Here, recent advances in the synthesis of graphene single crystals on both metals and dielectric substrates by the CVD method are discussed. The review mainly covers the size and morphology engineering of graphene single crystals. Furthermore, recent progress in the growth mechanism and device applications of graphene single crystals are presented. Finally, the opportunities and challenges are discussed.

Controlled growth of single-crystal twelve-pointed graphene grains on a liquid Cu surface

The controlled fabrication of single-crystal twelve-pointed graphene grains is demonstrated for the first time by ambient pressure chemical vapor deposition on a liquid Cu surface. An edge-diffusion limited mechanism is proposed. The highly controllable growth of twelve-pointed graphene grains presents an intriguing case for the fundamental study of graphene growth and should exhibit wide applications in graphene-based electronics.

Layer-stacking growth and electrical transport of hierarchical graphene architectures

Hierarchical graphene architectures (HGAs) that grow by stacking of layers are produced on a liquid copper surface using chemical vapor deposition. The stacking mode--for example hexagonal-hexagonal-hexagonal or hexagonal-snowflake-dendritic--can be simply controlled. Measurements of the electrical properties of HGAs indicate that hierarchical stacking of graphene may be a simple and effective way of tailoring their properties without degrading them.

Controllable fabrication of ultrathin free-standing graphene films

Graphene free-standing film-like or paper-like materials have attracted great attention due to their intriguing electronic, optical and mechanical properties and potential application in chemical filters, molecular storage and supercapacitors. Although significant progress has been made in fabricating graphene films or paper, there is still no effective method targeting ultrathin free-standing graphene films (UFGFs). Here, we present a modified filtration assembly method to prepare these ultrathin films. With this approach, we have fabricated a series of ultrathin free-standing graphene oxide films and UFGFs, up to 40 mm in diameter, with controllable thickness from micrometre to nanoscale (approx. 40 nm) dimensions. This method can be easily scaled up and the films display excellent optical, electrical and electrochemical properties. The ability to produce UFGFs from graphene oxide with a scalable, low-cost approach should take us a step closer to real-world applications of graphene.

Near-equilibrium chemical vapor deposition of high-quality single-crystal graphene directly on various dielectric substrates

By using near-equilibrium chemical vapor deposition, it is demonstrated that high-quality single-crystal graphene can be grown on dielectric substrates. The maximum size is about 11 μm. The carrier mobility can reach about 5650 cm(2) V(-1) s(-1) , which is comparable to those of some metal-catalyzed graphene crystals, reflecting the good quality of the graphene lattice.

Clinical significance of fibroblast growth factor receptor-3 mutations in bladder cancer: a systematic review and meta-analysis

Mutations in the fibroblast growth factor receptor-3 (FGFR3) gene are frequently found in bladder cancer, but their prognostic value remains controversial. To globally summarize the association between FGFR3 mutations and the grade and stage of bladder cancer, and to analyze the predictive role of FGFR3 mutations with respect to survival, eligible studies were identified and assessed for quality through multiple search strategies. Risk ratio (RR) data were collected from studies comparing the number of FGFR3 mutants among low-grade and early-stage bladder cancer patients to the number among high-grade and late-stage patients. Hazard ratio (HR) data were collected from studies comparing survival in patients with mutant FGFR3 genes to those with wild-type genes. Studies were pooled, and the RRs of grade and stage and the HRs of survival were calculated. Thirty studies were included in the present meta-analysis. FGFR3 mutations were found to be closely associated with low-grade and early-stage bladder cancer, showing pooled RRs = 2.948 [95% confidence interval (CI) = 2.357-3.688] and 2.845 (95%CI = 2.145- 3.773), respectively. Notably, patients with FGFR3 mutations tended to show better disease-, progress-, and recurrence-free survival (HR = 0.561, 95%CI = 0.405-0.779), and better disease-specific survival (HR = 0.363, 95%CI = 0.266-0.496). This study demonstrated that FGFR3 mutations are closely related to low grade, early stage, and better survival among bladder cancer patients.

A general approach for fast detection of charge carrier type and conductivity difference in nanoscale materials

A general method using a biased atomic force microscopy tip that allows a qualitative, fast, and reliable determination of key electronic properties such as metallic, n-, or p-doped characteristics has been reported for the first time. This method eliminates the detrimental effect of contact in the traditional transport measurement and is much simpler than the common-electrostatic force microscopy detection method, thus providing a powerful tool for fast characterizations of nanomaterials.

Gram-scale synthesis of graphene sheets by a catalytic arc-discharge method

Flake graphite is used as carbon source and ZnO or ZnS as catalyst in the synthesis of high-quality graphene sheets. A catalytic growth mechanism for cathode-part graphene synthesis in the arc-discharge apparatus and an exfoliation mechanism for wall-part graphene synthesis are introduced. N-doped cathode-part graphene and undoped wall-part graphene are formed simultaneously.