Effectiveness and safety of SR-ENS-600endoscopic surgical system in benign and malignant gynecological diseases: a prospective, multicenter, clinical trial with 63 cases.

Single-port laparoscopy has gained more attention, but inherent technical challenges hinder its wider use. To overcome the disadvantage of traditional single-port surgery, robotic laparoendoscopic single-site surgery system was designed and clinically utilized. This multi-center single-arm trial was aimed to present the clinical outcomes of the SHURUI robotic endoscopic single-site surgery system. 63 women with ovary cysts, myoma, cervical epithelial neoplasm, or endometrial carcinoma were recruited at 6 academic medical centers in different districts of China. The trial was registered on September 5, 2023, with the register number: ChiCTR2300075431, retrospectively registered. Patients underwent robotic LESS surgery with the SHURUI endoscopic surgical system from January 17 to May 26, 2023. Demographic information, perioperative parameters, complications, scar healing, and operator satisfaction scores were recorded. Patients were followed up for 30 ± 4 days. Average operative time and estimated blood loss were 157.03 ± 75.24 min and 63.86 ± 98.33 ml, respectively, for all surgeries. Average anal exhaust time and hospitalization stay were 30.99 ± 14.25 h and 3.63 ± 1.59 days, respectively. Patients' postoperative rehabilitation assessment showed satisfactory results on the day of discharge and 30 ± 4 days after surgery. The surgery achieved good cosmetic benefits and was surgeon friendly. There were no conversions to alternative surgical modalities, complications, or readmissions. The SHURUI endoscopic surgical system showed both the technical feasibility and safety of this surgical modality for gynecologic patients. Further randomized studies comparing this modality with traditional LESS surgery are suggested.

Effects of long-term no-tillage and different stover mulching amounts on soil carbon and nitrogen contents and enzyme activities of carbon and nitrogen cycle in Mollisols.

To understand the effects of different stover mulching amounts in no-tillage on soil carbon and nitrogen contents and enzyme activities, finding a stover mulching amount which can meet the requirement of soil carbon and nitrogen accumulation while maximizing economic benefits, we conducted a long-term conservation tillage field experiment since 2007 in Mollisols area of Northeast China. We analyzed soil carbon and nitrogen contents, enzyme activities and economic benefits under conventional tillage (Control, CT), no-tillage without stover mulching (NT0), no-tillage with 33% stover mulching (NT33), no-tillage with 67% stover mulching (NT67), and no-tillage with 100% stover mulching (NT100) before planting in May 2020. The results showed that compared with CT, NT0 did not affect soil organic carbon (SOC) and total nitrogen (TN) contents, but increased soil organic carbon recalcitrance and decreased the availability of dissolved organic nitrogen (DON) and ammonium nitrogen. Compared with NT0, no-tillage with stover mulching significantly increased SOC contents in 0-10 cm layer and increased with the amounts of stover. In addition, NT67 and NT100 significantly increased SOC stocks, facilitating the accumulation of soil organic matter. The effects of different stover mulching amounts on soil nitrogen content in 0-10 cm layer were different. Specifically, NT33 increased DON content and DON/TN, NT67 increased DON content, while NT100 increased TN content. Compared with CT, NT0 decreased peroxidase (POD) activity in 0-10 cm layer. Compared with NT0, NT33 increased ß-glucosidase (ßG), cellobiase (CB), 1,4-ß-N-acetylglucosaminidase (NAG), polyphenol oxidase (PPO) and POD activities, while NT67 only increased CB, NAG and POD activities in 0-10 cm soil layer, both alleviated microbial nutrient limitation. NT100 increased PPO activity in 10-20 cm layer. NT33 increased carbon conversion efficiency of stover compared with NT100, and had the highest economic benefit. In all, no-tillage with 33% stover mulching was the optimal strategy, which could promote nutrient circulation, boost stover utilization efficiency, improve the quality of Mollisols, and maximize guaranteed income.

Human Papillomavirus Infections and Increased Risk of Incident Osteoporosis: A Nationwide Population-Based Cohort Study.

Patients with viral infections are susceptible to osteoporosis. This cohort study investigated the correlation between human papillomavirus (HPV) infections and the risk of osteoporosis via 12,936 patients with new-onset HPV infections and propensity score-matched non-HPV controls enrolled in Taiwan. The primary endpoint was incident osteoporosis following HPV infections. Cox proportional hazards regression analysis and the Kaplan-Meier method was used to determine the effect of HPV infections on the risk of osteoporosis. Patients with HPV infections presented with a significantly high risk of osteoporosis (adjusted hazard ratio, aHR = 1.32, 95% CI = 1.06-1.65) after adjusting for sex, age, comorbidities and co-medications. Subgroup analysis provided that populations at risk of HPV-associated osteoporosis were females (aHR = 1.33; 95% CI = 1.04-1.71), those aged between 60 and 80 years (aHR = 1.45, 95% CI = 1.01-2.08 for patients aged 60-70; aHR = 1.51; 95% CI = 1.07-2.12 for patients aged 70-80), and patients with long-term use of glucocorticoids (aHR = 2.17; 95% CI = 1.11-4.22). HPV-infected patients who did not receive treatments for HPV infections were at a greater risk (aHR = 1.40; 95% CI = 1.09-1.80) of osteoporosis, while the risk of osteoporosis in those who received treatments for HPV infections did not reach statistical significance (aHR = 1.14; 95% CI = 0.78-1.66). Patients with HPV infections presented with a high risk of subsequent osteoporosis. Treatments for HPV infections attenuated the risk of HPV-associated osteoporosis.

Effects of no-tillage and different stover mulching amounts on soil microbial community and microbial residue in the Mollisols of China.

To investigate the effects of no-tillage and different amounts of stover mulch on soil microbial community composition and their residues, we set up a field experiment of different amounts of stover mulch under no-tillage on the long-term maize conservation tillage station located in the Mollisols area of Northeast China (built in 2007), including without stover mulch (NT0), 1/3 stover mulch (NT1/3), 2/3 stover mulch (NT2/3) and full stover mulch (NT3/3), and the conservation tillage (plowing without stover mulch, CT) as control. We analyzed phospholipid fatty acid, amino sugar biomarker and soil physicochemical properties at different soil layers (0-5 cm, 5-10 cm, 10-20 cm). The results showed that compared to CT, no-tillage without stover mulch (NT0) did not affect soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon and nitrogen (DOC, DON), water content, microbial community and their residue. The main effects of no-tillage and stover mulch were found in the topsoil. Specifically, the NT1/3, NT2/3 and NT3/3 significantly increased SOC content by 27.2%, 34.1% and 35.6%, respectively, phospholipid fatty acid content was significantly increased under NT2/3 and NT3/3 by 39.2% and 65.0%, respectively, and NT3/3 significantly increased the content of microbial residue-amino sugar by 47.2% in the depth of 0-5 cm compared with CT. The variations in soil properties and microbial community induced by no-tillage and different amounts stover mulch decreased with soil depth, with almost no difference in the 5-20 cm soil layer. SOC, TN, DOC, DON, and water content were the main factors influencing the composition of the microbial community and the accumulation of microbial residue. Microbial biomass was positively correlated with microbial residue, particularly fungal residue. In conclusion, all stover mulch treatments promoted SOC accumulation to different degrees. When there is sufficient stover, it is advisable to opt for no-tillage with full stover mulch, as it is most conducive to the increases of soil microbial biomass, microbial residue and SOC. In case when the amount of stover is inadequate, however, no-tillage with 2/3 stover mulch can still improve soil microbial biomass and SOC content. This study would provide practical guidance for stover management in conservation tillage and sustainable agricultural development in the Mollisols area of Northeast China.

Xiaoaiping injection combined with chemotherapy for advanced gastric cancer: An updated systematic review and meta-analysis.

Aim: To evaluate the clinical efficacy and safety of Xiaoaiping injection combined with chemotherapy in the treatment of advanced gastric cancer by meta-analysis. Methods: Seven databases, including China National Knowledge Infrastructure (CNKI), Wanfang Database, VIP Database, Cochrane Library, PubMed, Embase, and Web of Science, were searched by computer for randomized controlled clinical trials of Xiaoaiping injection combined with chemotherapy in the treatment of gastric cancer. Risk of bias assessment and meta-analysis were performed by Review Manager 5.3 software. Results: There were 16 articles that met the inclusion criteria, with a total of 1,236 patients, 617 in the observation group and 619 in the control group. The results of meta-analysis showed that the observation group was better than chemotherapy alone control group in RR [OR = 1.86, p < 0.00001]; disease control rate (DCR) [OR = 2.45, p < 0.00001]; Karnofsky performance status (KPS) score [OR = 3.21, p < 0.00001] or [MD = 7.73, p = 0.001]. In terms of biochemical indicators, Xiaoaiping significantly reduced inflammation factors level, including tumor necrosis factor alpha (TNF-α) [MD = -15.00, p < 0.00001]; interleukin-6 (IL-6) [MD = -13.00, p < 0.00001]; C-reaction protein (CRP) [MD = -5.80, p < 0.00001]. Xiaoaiping could enhance immune function, significantly reducing myeloid-derived suppressor cells (MDSCs) [MD = -6.20, p < 0.00001] and Treg [MD = -1.70, p < 0.00001]. Xiaoaiping injection combined with chemotherapy could significantly decrease tumor markers, including carcinoembryonic antigen (CEA) [MD = -11.64, p < 0.00001]; CA199 [MD = -33.57, p = 0.02]; CA242 [MD = -20.66, p < 0.00001]; CA125 [MD = -12.50, p = 0.0005]. In the comparison of adverse reactions, the incidence rate of Xiaoaiping injection group was significantly lower than that of control group. The funnel plot showed that the left and right sides are basically symmetrical, and it can be considered that there is no obvious publication bias. Conclusion: Xiaoaiping injection combined with chemotherapy has better curative effect and less adverse reactions in the treatment of gastric cancer. However, limited by the quality of the included studies, more high-quality studies are still needed to be verified. Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022353842], identifier [CRD42022353842].

Titania spheres with nanochannel-restricted NaNO2/MgO for improving cyclic CO2 adsorption stability.

NaNO2/MgO/titania spheres prepared via aerosol-assisted self-assembly (AASA) were used as sorbents for CO2 adsorption at moderate temperature. The titania framework as support would allow MgO to disperse well, thereby increasing the contact between MgO and NaNO2 to enhance carbonation. In this study, the effect of Mg/Ti molar ratio and NaNO2 addition amount on CO2 adsorption was investigated. Results showed that the sorbent prepared by AASA with Mg/Ti molar ratio of 2 following the introduction of 30 wt% NaNO2 presented ∼1 µm particle size with rough sphere surface morphology and mesoporous properties, where the surface area and pore volume were 72 m2/g and 0.18 cm3/g, respectively. With NaNO2 addition, the kinetics and capacity of CO2 adsorption significant increased. In the cyclic adsorption/desorption experiment, the superior stability over the NaNO2/MgO/titania spheres was mainly ascribed to the confined space suppressed the degree of the sintering effect. These results indicated the potential application of the nanochannel-restricted sorbent for rapid, high-capacity, and stable CO2 capture at moderate temperatures.

Multicycle Performance of CaTiO3 Decorated CaO-Based CO2 Adsorbent Prepared by a Versatile Aerosol Assisted Self-Assembly Method.

Calcium oxide (CaO) is a promising adsorbent to separate CO2 from flue gas. However, with cycling of carbonation/decarbonation at high temperature, the serious sintering problem causes its capture capacity to decrease dramatically. A CaTiO3-decorated CaO-based CO2 adsorbent was prepared by a continuous and simple aerosol-assisted self-assembly process in this work. Results indicated that CaTiO3 and CaO formed in the adsorbent, whereas CaO gradually showed a good crystalline structure with increased calcium loading. Owing to the high thermal stability of CaTiO3, it played a role in suppressing the sintering effect and maintaining repeated high-temperature carbonation and decarbonation processes. When the calcium and titanium ratio was 3, the CO2 capture capacity was as large as 7 mmol/g with fast kinetics. After 20 cycles under mild regeneration conditions (700 °C, N2), the performance of CO2 capture of CaTiO3-decorated CaO-based adsorbent nearly unchanged. Even after 10 cycles under severe regeneration conditions (920 °C, CO2), the performance of CO2 capture still remained nearly 70% compared to the first cycle. The addition of CaTiO3 induced good and firm CaO dispersion on its surface. Excellent kinetics and stability were evident.

GaS:WS2 Heterojunctions for Ultrathin Two-Dimensional Photodetectors with Large Linear Dynamic Range across Broad Wavelengths.

Two-dimensional (2D) photodetectors based on photovoltaic effect or photogating effect can hardly achieve both high photoresponsivity and large linear dynamic range at the same time, which greatly limits many practical applications such as imaging sensors. Here, the conductive-sensitizer strategy, a general design for improving photoresponsivity and linear dynamic range in 2D photodetectors is provided and experimentally demonstrated on vertically stacked bilayer WS2/GaS0.87 under a parallel circuit mode. Owing to successful band alignment engineering, the isotype type-II heterojunction enables efficient charge carrier transfer from WS2, the high-mobility sensitizer, to GaS0.87, the low-mobility channel, under illumination from a broad visible spectrum. The transferred electron charges introduce a reverse electric field which efficiently lowers the band offset between the two materials, facilitating a transition from low-mobility photocarrier transport to high-mobility photocarrier transport with increasing illumination power. We achieved a large linear dynamic range of 73 dB as well as a high and constant photoresponsivity of 13 A/W under green light. X-ray photoelectron spectroscopy, cathodoluminescence, and Kelvin probe force microscopy further identify the key role of defects in monolayer GaS0.87 in engineering the band alignment with monolayer WS2. This work proposes a design route based on band and interface modulation for improving performance of 2D photodetectors and provides deep insights into the important role of strong interlayer coupling in offering heterostructures with desired properties and functions.

Atomistic Mechanics of Torn Back Folded Edges of Triangular Voids in Monolayer WS2.

Triangular nanovoids in 2D materials transition metal dichalcogenides have vertex points that cause stress concentration and lead to sharp crack propagation and failure. Here, the atomistic mechanics of back folding around triangular nanovoids in monolayer WS2 sheets is examined. Combining atomic-resolution images from annular dark-field scanning transmission electron microscopy with reactive molecular modelling, it is revealed that the folding edge formation has statistical preferences under geometric conditions based on the orientation mismatch. It is further investigated how loading directions and strong interlayer friction, interplay with WS2 lattice's crack preference, govern the deformation and fracture pattern around folding edges. These results provide fundamental insights into the combination of fracture and folding in flexible monolayer crystals and the resultant Moiré lattices.

miR-34c inhibits PDGF-BB-induced HAVSMCs phenotypic transformation and proliferation via PDGFR-ß/SIRT1 pathway.

The purpose of this study was to explore the effect of miR-34c on PDGF-BB-induced HAVSMCs phenotypic transformation and proliferation via PDGFR-ß/SIRT1 pathway, so as to find a new method for early diagnosis and treatment of cardiovascular disease. HA-VSMCs were treated with platelet-derived growth factor-BB (PDGF-BB) at 0 h, 12 h, 24 h, 48 h or 36 h to explore the optimal time for phenotypic transformation of VSMCs. And then, PDGF-BB-induced HA-VSMCs were transfected with miR-34c mimics/mimics NC and pcDNA3.1-PDGFR-ß/pcDNA3.1-NC to observe cell biological behaviour. CCK8 was used to detect cell proliferation activity. Transwell chamber assay was used to detect cell invasion. Early apoptosis was analyzed by flow cytometry. The expression of α-SMA and Smemb was detected by immunofluorescence staining. The expressions of PDGFR-ß, IRF9, Acetyl-NF-κB/p65, Acetyl-p53 and CyclinD1 were analyzed by Western blot analysis. The expression of miR-34a, miR-34b and miR-34c was detected by RT-PCR, and the targeting relationship between miR-34c and PDGFR-ß was detected by luciferase reporting assay. The results indicated the proliferation and migration of PDGF-BB-induced HA-VSMCs significantly increased, and apoptosis significantly decreased. Besides, α-SMA decreased significantly, while Smemb increased significantly. Furthermore, expressions of PDGFR-ß, IRF9, Acetyl-NF-κB/p65, Acetyl-p53 and CyclinD1 increased significantly, and SIRT1 decreased significantly. Experimental results showed that, miR-34c mimics significantly inhibited cell proliferation and migration, and promoted cell apoptosis, and miR-34c inhibitor had the opposite effects. MiR-34c mimics significantly increased α-SMA expression and decreased Smemb expression, while the opposite effects were reflected after transfection with miR-34c inhibitor. Moreover, miR-34c mimics significantly decreased the expressions of PDGFR-ß, IRF9, Acetyl-NF-κB/p65, Acetyl-p53 and CyclinD1, and significantly increased the expression of SIRT1, while miR-34c inhibitor had the opposite effects. Luciferase assay confirmed that PDGFR-ß was a potential target of miR-34c. Subsequently, PDGF-BB-induced HA-VSMCs were co-transfected with miR-34c mimics and pcDNA3.1-PDGFR-ß. The results indicated that PDGFR-ß reversed the biological function of miR-34c mimic. The results revealed the potential application value of miR-34c as a marker molecule of phenotypic transformation, providing a potential target for improving phenotypic transformation.

TMPyP-bound guanosine-borate supramolecular hydrogel as smart hemoperfusion device with real-time visualized/electrochemical bi-modal monitoring for selective blood lead elimination.

Blood lead poisoning is a universal and severe health problem that greatly threatens human health in various industries. Elimination of blood lead relying on chelating agents and combination with hemoperfusion adsorbents has achieved considerable progress, but it is still suffering from the compromised selectivity of adsorbents as well as in absence of real time monitoring during treatment. Herein, we proposed a selective blood lead adsorbent integrated with real-time visualized/electrochemical bi-modal monitoring based on TMPyP-bound guanosine-borate (GB) supramolecular hydrogel as potential smart hemoperfusion device. The GB hydrogel possessed stability in physiological environment, self-healing ability resistant to fluid shear, blood compatibility, selective adsorption of lead ions superior to conventional adsorbents, anti-fouling performance to blood components and renewability. Benefiting from binding with TMPyP and the intrinsic conductivity, GB hydrogel was endowed with the ability to qualitatively diagnose the presence of blood lead via simple color change and quantitatively reflect the amount of adsorbed lead from blood accurately through electrochemical technique. This work puts forward an integrated treatment/monitoring hemoperfusion device with high selectivity, simple fabrication and low-cost, providing a paradigm for next generation design of intelligent, monitorable theranostic hemopurification system, which is also an extensible platform for the other research fields such as environmental monitoring and remediation.

Ghrelin inhibits IKKß/NF-κB activation and reduces pro-inflammatory cytokine production in pancreatic acinar AR42J cells treated with cerulein.

BACKGROUND: Previous studies have provided conflicting results regarding whether the serum ghrelin concentration can reflect the severity of acute pancreatitis (AP). The present study examined the correlation between the serum ghrelin concentration and AP severity in animal models and investigated whether altered ghrelin expression in pancreatic acinar cells influences IKKß/NF-κB signaling and pro-inflammatory cytokine production. METHODS: Mild or severe AP was induced in rats by intraperitoneal injection of cerulein or retrograde cholangiopancreatic duct injection of sodium taurocholate, respectively. After successful model induction, serum ghrelin, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) concentrations were determined by enzyme-linked immunosorbent assay, and IKKß/NF-κB activation was assessed by immunohistochemistry. Subsequently, stable overexpression or knockdown of ghrelin in AR42J cells was achieved by lentiviral transfection. After transfected cells and control cells were treated with cerulein for 24 h, the TNF-α and IL-1ß levels in the supernatants were determined by enzyme-linked immunosorbent assay, and the expression levels of p-p65, IKKß, and p-IKKß were detected by Western blotting. RESULTS: In rat AP models, AP severity was correlated with increased IKKß/NF-κB activation, pro-inflammatory cytokine production, and ghrelin secretion. The levels of pro-inflammatory cytokines TNF-α and IL-1ß as well as IKKß/NF-κB signaling activity were increased upon knockdown of ghrelin in the AP acinar cell model and decreased with ghrelin overexpression. CONCLUSIONS: Serum ghrelin is related to the severity of AP. Ghrelin may play a protective role in the pathogenesis of AP by inhibiting the pro-inflammatory cytokines and the activation of the IKKß/NF-κB signaling pathway.

Studies on the substrate-dependent photocatalytic properties of Cu2O heterojunctions.

Cu2O is a promising material for photocatalysis because of its absorption ability in the ultraviolet (UV)-visible light range. Cu2O deposited on conductive Ti and fluorine-doped tin oxide (FTO) substrates behaves as a photocathode. Cu2O deposited on an n-type semiconductor such as TiO2 nanotube arrays (TNA)/Ti behaves as a photoanode and has demonstrated better photocatalytic activity than that of TNA/Ti. The substrate-dependent photocatalytic properties of Cu2O heterojunctions are not well studied. In this work, the photocatalytic properties of a Cu2O/TNA/Ti junction as a photoanode and of Cu2O/Ti and Cu2O/FTO junctions as photocathodes without bias were systematically studied to understand their performance. The Cu2O/TNA/Ti photoanode exhibited higher photocurrent spectral responses than those of Cu2O/Ti and Cu2O/FTO photocathodes. The photoanodic/photocathodic properties of those junctions were depicted in their energy band diagrams. Time-resolved photoluminescence indicated that Cu2O/TNA/Ti, Cu2O/Ti, and Cu2O/FTO junctions did not enhance the separation of photogenerated charges. The improved photocatalytic properties of Cu2O/TNA/Ti compared with TNA/Ti were mainly attributed to the UV-visible light absorption of Cu2O.

Phase Variations and Layer Epitaxy of 2D PdSe2 Grown on 2D Monolayers by Direct Selenization of Molecular Pd Precursors.

Two-dimensional (2D) materials and van der Waals heterostructures with atomic-scale thickness provide enormous potential for advanced science and technology. However, insufficient knowledge of compatible synthesis impedes wafer-scale production. PdSe2 and Pd2Se3 are two of the noble transition-metal chalcogenides with excellent physical properties that have recently emerged as promising materials for electronics, optoelectronics, catalyst, and sensors. This research presents a feasible approach to synthesize PdSe2 and Pd2Se3 with inherently asymmetric structure on honeycomb lattice 2D monolayer substrates of graphene and MoS2. We directly deposit a molecular transition-metal precursor complex on the surface of the 2D substrates, followed by low-temperature selenization by chemical vapor flow. Parameter control leads to tuning of the material from monolayer nanocrystals with Pd2Se3 phase, to continuous few-layer PdSe2 films. Annular dark-field scanning transmission electron microscopy (ADF-STEM) reveals the structure, phase variations, and heteroepitaxy at the atomic level. PdSe2 with unconventional interlayer stacking shifts appeared as the kinetic product, whereas the bilayer PdSe2 and monolayer Pd2Se3 are the thermodynamic product. The epitaxial alignment of interlayer rotation and translation between the PdSe2 and underlying 2D substrate was also revealed by ADF-STEM. These results offer both nanoscale and atomic-level insights into direct growth of van der Waals heterostructures, as well as an innovative method for 2D synthesis by predetermined nucleation.

Controlling Defects in Continuous 2D GaS Films for High-Performance Wavelength-Tunable UV-Discriminating Photodetectors.

A chemical vapor deposition method is developed for thickness-controlled (one to four layers), uniform, and continuous films of both defective gallium(II) sulfide (GaS): GaS0.87 and stoichiometric GaS. The unique degradation mechanism of GaS0.87 with X-ray photoelectron spectroscopy and annular dark-field scanning transmission electron microscopy is studied, and it is found that the poor stability and weak optical signal from GaS are strongly related to photo-induced oxidation at defects. An enhanced stability of the stoichiometric GaS is demonstrated under laser and strong UV light, and by controlling defects in GaS, the photoresponse range can be changed from vis-to-UV to UV-discriminating. The stoichiometric GaS is suitable for large-scale, UV-sensitive, high-performance photodetector arrays for information encoding under large vis-light noise, with short response time (<66 ms), excellent UV photoresponsivity (4.7 A W-1 for trilayer GaS), and 26-times increase of signal-to-noise ratio compared with small-bandgap 2D semiconductors. By comprehensive characterizations from atomic-scale structures to large-scale device performances in 2D semiconductors, the study provides insights into the role of defects, the importance of neglected material-quality control, and how to enhance device performance, and both layer-controlled defective GaS0.87 and stoichiometric GaS prove to be promising platforms for study of novel phenomena and new applications.

Ultrathin All-2D Lateral Graphene/GaS/Graphene UV Photodetectors by Direct CVD Growth.

UV-sensitive lateral all-two-dimensional (2D) photodetecting devices are produced by growing the large band gap layered GaS between graphene electrode pairs directly using chemical vapor deposition methods. The use of prepatterned graphene electrode pairs on the Si wafer enables more than 200 devices to be fabricated simultaneously. We show that the surface chemistry of the substrate during GaS leads to selective growth in graphene gaps, forming the lateral heterostructures, rather than on the surface of graphene. The graphene/GaS/graphene lateral photodetecting devices are demonstrated to be sensitive to UV light only, with no measurable response to visible light. Furthermore, we demonstrate UV-band discrimination in photosensing, with measured photocurrents only produced for middle-UV and not for near-UV wavelength regions. The detection limit could reach down to 2.61 µW/cm2 with a photoresponsivity as high as 11.7 A/W and a photo gain of 53.7 under 270 nm excitation. Gate-dependent modulation of the photocurrent is also demonstrated. The photodetectors exhibit long-term stability and reproducible ON-OFF switching behavior, with a response time lower than 60 ms. These results provide insights into how ultrathin UV sensing devices can be created using only 2D materials by exploiting large band gap 2D semiconductors such as GaS.

Atomically Sharp Dual Grain Boundaries in 2D WS2 Bilayers.

It is shown that tilt grain boundaries (GBs) in bilayer 2D crystals of the transition metal dichalcogenide WS2 can be atomically sharp, where top and bottom layer GBs are located within sub-nanometer distances of each other. This expands the current knowledge of GBs in 2D bilayer crystals, beyond the established large overlapping GB types typically formed in chemical vapor deposition growth, to now include atomically sharp dual bilayer GBs. By using atomic-resolution annular dark-field scanning transmission electron microscopy (ADF-STEM) imaging, different atomic structures in the dual GBs are distinguished considering bilayers with a 3R (AB stacking)/2H (AA' stacking) interface as well as bilayers with 2H/2H boundaries. An in situ heating holder is used in ADF-STEM and the GBs are stable to at least 800 °C, with negligible thermally induced reconstructions observed. Normal dislocation cores are seen in one WS2 layer, but the second WS2 layer has different dislocation structures not seen in freestanding monolayers, which have metal-rich clusters to accommodate the stacking mismatch of the 2H:3R interface. These results reveal the competition between maintaining van der Waals bilayer stacking uniformity and dislocation cores required to stitch tilted bilayer GBs together.

Postgrowth Substitutional Tin Doping of 2D WS2 Crystals Using Chemical Vapor Deposition.

Doping of two-dimensional materials provides them tunable physical properties and widens their applications. Here, we demonstrate the postgrowth doping strategy in monolayer and bilayer tungsten disulfide (WS2) crystals, which utilizes a metal exchange mechanism, whereby Sn atoms become substitutional dopants in the W sites by energetically favorable replacement. We achieve this using chemical vapor deposition techniques, where high-quality grown WS2 single crystals are first grown and then subsequently reacted with a SnS precursor. Thermal control of the exchange doping mechanism is revealed, indicating that a sufficiently high enough temperature is required to create the S vacancies that are the initial binding sites for the SnS precursor and metal exchange occurrence. This results in a better control of dopant distribution compared to the tradition all-in-one approach, where dopants are added during the growth phase. The Sn dopants exhibit an n-type doping behavior in the WS2 layers based on the decreased threshold voltage obtained from transistor device measurements. Annular dark-field scanning transmission electron microscopy shows that in bilayer WS2 the Sn doping occurs only in the top layer, creating vertical heterostructures with atomic layer doping precision. This postgrowth modification opens up ways to selectively dope one layer at a time and construct mixed stoichiometry vertical heterojunctions in bilayer crystals.

Atomic structural catalogue of defects and vertical stacking in 2H/3R mixed polytype multilayer WS2 pyramids.

We examine the atomic structure of chemical vapour deposition grown multilayer WS2 pyramids using aberration corrected annular dark field scanning transmission electron microscopy coupled with an in situ heating holder. The stacking orders and specific types of defects after partial degradation by S and W atomic loss at high temperature are resolved layer-by-layer. Our study of an individual WS2 pyramid with at least six layers, reveals a mixed 2H and 3R polytype stacking. Etching occurred both top and bottom of the WS2 pyramid, which aids in determining the exact vertical layer stacking configurations in the thicker regions. We provide an extensive catalogue of the contrast profiles associated with defects in WS2 as a function of layer number and stacking type, as imaged using ADF-STEM. These results provide extensive details about the identification of a wide range of defects in S2 layers, and the unique ADF-STEM contrast patterns that arise from complex multilayer stacking.