Atomistic Probing of Defect-Engineered 2H-MoTe2 Monolayers.

Point defects dictate various physical, chemical, and optoelectronic properties of two-dimensional (2D) materials, and therefore, a rudimentary understanding of the formation and spatial distribution of point defects is a key to advancement in 2D material-based nanotechnology. In this work, we performed the demonstration to directly probe the point defects in 2H-MoTe2 monolayers that are tactically exposed to (i) 200 °C-vacuum-annealing and (ii) 532 nm-laser-illumination; and accordingly, we utilize a deep learning algorithm to classify and quantify the generated point defects. We discovered that tellurium-related defects are mainly generated in both 2H-MoTe2 samples; but interestingly, 200 °C-vacuum-annealing and 532 nm-laser-illumination modulate a strong n-type and strong p-type 2H-MoTe2, respectively. While 200 °C-vacuum-annealing generates tellurium vacancies or tellurium adatoms, 532 nm-laser-illumination prompts oxygen atoms to be adsorbed/chemisorbed at tellurium vacancies, giving rise to the p-type characteristic. This work significantly advances the current understanding of point defect engineering in 2H-MoTe2 monolayers and other 2D materials, which is critical for developing nanoscale devices with desired functionality.

Full automation of point defect detection in transition metal dichalcogenides through a dual mode deep learning algorithm.

Point defects often appear in two-dimensional (2D) materials and are mostly correlated with physical phenomena. The direct visualisation of point defects, followed by statistical inspection, is the most promising way to harness structure-modulated 2D materials. Here, we introduce a deep learning-based platform to identify the point defects in 2H-MoTe2: synergy of unit cell detection and defect classification. These processes demonstrate that segmenting the detected hexagonal cell into two unit cells elaborately cropped the unit cells: further separating a unit cell input into the Te2/Mo column part remarkably increased the defect classification accuracies. The concentrations of identified point defects were 7.16 × 1020 cm2 of Te monovacancies, 4.38 × 1019 cm2 of Te divacancies and 1.46 × 1019 cm2 of Mo monovacancies generated during an exfoliation process for TEM sample-preparation. These revealed defects correspond to the n-type character mainly originating from Te monovacancies, statistically. Our deep learning-oriented platform combined with atomic structural imaging provides the most intuitive and precise way to analyse point defects and, consequently, insight into the defect-property correlation based on deep learning in 2D materials.

Efficacy and safety of CKD-495 in acute and chronic gastritis: A Phase III superiority clinical trial.

BACKGROUND: Despite the availability of numerous treatment options, many patients with gastritis experience only partial symptom relief. CKD-495, a newly developed product with the active ingredient extracted from Cinnamomum cassia Presl., has demonstrated anti-inflammatory and antioxidant activity in vitro and an in vivo protective effect against gastric damage by stimulating mucus secretion. This study compared the efficacy and safety of CKD-495 with Artemisiae argyi folium (AAF) for the treatment of acute and chronic gastritis. AAF, a gastric mucosa protective agent that promotes gastric mucosa regeneration, has been used clinically for about 20 years. METHODS: This phase III multicenter, randomized, double-blind, parallel-group trial (ClinicalTrials.gov; NCT04255589) assigned 242 patients with endoscopically-proven gastric mucosal erosions to receive CKD-495 75 mg (n = 122) or AAF 60 mg (n = 120), respectively, with placebo (for double-blind purposes) 3 times a day for 2 weeks. The primary efficacy endpoint was the erosion improvement rate. Secondary endpoints included erosion cure rates, and improvement rates for edema, redness, hemorrhage, and gastrointestinal (GI) symptoms. Drug-related adverse events were evaluated. RESULTS: The erosion improvement rate was significantly higher in the CKD-495 group than in the AAF group for both the full analysis set (55.9% vs 39.4%, P = .0063) and per-protocol set (54.6% vs 38.2%, P = .0084). In addition, the erosion improvement rate in patients with acute or chronic gastritis showed that the CKD-495 group had better improvement of erosion than the AAF group, especially in patients with chronic gastritis. Analysis of secondary endpoints, which included erosion cure rate and the improvement rates of edema, redness, hemorrhage, and GI symptoms, showed that the CKD-495 group was more effective than the AAF group. There were no significant between-group differences in safety profiles. No serious adverse events or adverse drug reactions occurred. CONCLUSIONS: These results demonstrate that CKD-495 75 mg is superior to AAF 60 mg in terms of the endoscopic improvement rate of erosions in patients with acute or chronic gastritis. This new mucoprotective agent, CKD-495, can be considered the therapy of choice for symptomatic relief and healing of gastritis.

HDAC inhibitor SB939 potentiates TRAIL-induced apoptosis in colorectal cancer cells.

Colorectal cancer (CRC) displays noticeable resistance to chemotherapeutic drugs or innovative tumor cell apoptosis-inducing agents such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Thus, sensitizers are needed to enhance the effects of TRAIL-based cancer therapies. Elevated tumor cell death has been reported when various HDAC inhibitors are administered with TRAIL in various human cancers; however, SB939-TRAIL combined treatment has not been reported. In this study, we determined the ability of SB939 and TRAIL, as single agents or in combination, to inhibit the growth and survival of colorectal cancer cells. Our results demonstrated the effects of SB939 and TRAIL on cell viability, apoptosis, and morphological changes in HT-29 cells. SB939 treatment induces hyper-acetylation of histones and death receptors (DR) by activating MAPK proteins in a dose- and time-dependent manner. The ability of SB939 to sensitize HT-29 cells suggests that SB939 can induce essential changes in cell signaling pathways. Thus, the pan-HDAC inhibitor SB939 sensitizes TRAIL-induced apoptosis via up-regulation of DR5, and SB939-TRAIL combined treatment may target the MAPK pathways and serve as an effective therapeutic strategy against CRC.

Initial treatment response and short-term mortality of spontaneous bacterial peritonitis in cirrhotic patients with hepatocellular carcinoma.

This study aimed to investigate the initial treatment response and short-term mortality of spontaneous bacterial peritonitis (SBP) in cirrhotic patients with hepatocellular carcinoma (HCC) compared with those without HCC. A total of 245 patients with liver cirrhosis diagnosed with SBP between January 2004 and December 2020 were included. Of these, 107 (43.7%) were diagnosed with HCC. Overall, the rates of initial treatment failure, 7-day and 30-day mortality were 91 (37.1%), 42 (17.1%), and 89 (36.3%), respectively. While the baseline CTP score, MELD score, culture-positive rate, and rates of antibiotic resistance did not differ between both groups, patients with HCC had a higher rate of initial treatment failure than those without HCC patients (52.3% vs. 25.4%, P < 0.001). Similarly, 30-day mortality was also significantly higher in patients with HCC (53.3% vs. 23.2%, P < 0.001). In the multivariate analysis, HCC, renal impairment, CTP grade C, and antibiotic resistance were independent factors for initial treatment failure. Furthermore, HCC, hepatic encephalopathy, MELD score, and initial treatment failure were independent risk factors for 30-day mortality, with statistically significant poor survival outcomes in patients with HCC (P < 0.001). In conclusion, HCC is an independent risk factor for initial treatment failure and high short-term mortality in patients with cirrhosis with SBP. It has been suggested that more attentive therapeutic strategies are required to improve the prognosis of patients with HCC and SBP.

Vaseline gauze packing for the treatment of acute hemorrhagic rectal ulcer: Two case reports.

RATIONALE: Acute hemorrhagic rectal ulcer (AHRU) is a relatively rare condition characterized by sudden onset, painlessness, and massive hematochezia in patients with severe underlying conditions. When AHRU is encountered, they can often be successfully controlled endoscopically, though recurrent bleeding is common and an alternative treatment must be sought if initial endoscopic treatment fails. We report 2 cases of AHRU which were successfully treated with Vaseline gauze packing after the failure of endoscopic hemostasis. PATIENT CONCERNS: The first patient was an 88-year-old female that visited our emergency department with hematochezia. She was immobilized because of a left pelvic bone fracture resulting from a slip-down. The initial endoscopy showed fresh blood in her rectum with diffuse ulceration near the dentate line but no active bleeding. However, Massive hematochezia has recurred during conservation. A second patient, an 86-year-old female, debilitated because of schizophrenia, dementia, and past subdural hemorrhage, visited our emergency department, also with massive hematochezia. Her initial endoscopy showed deep ulceration near the dentate line. After admission, she experienced massive hematochezia from an AHRU with an exposed vessel but endoscopic hemostasis failed to control bleeding. DIAGNOSES: Both patients were diagnosed as AHRU based on the endoscopic findings. INTERVENTIONS: In both cases, Vaseline gauze packing was performed for bleeding control. OUTCOMES: After Vaseline gauze packing, no further bleeding occurred and follow-up endoscopy showed definitive improvement of ulcers. LESSONS: Based on these cases, we suggest that Vaseline gauze packing may be the alternative treatment for the AHRU which is located near the dentate line when endoscopic hemostasis is difficult or failed. Although further research is needed, Vaseline gauze packing has several potential advantages for the treatment of AHRU, especially in cases involving critically ill elderly patients.

Atomically Thin Synapse Networks on Van Der Waals Photo-Memtransistors.

A new type of atomically thin synaptic network on van der Waals (vdW) heterostructures is reported, where each ultrasmall cell (≈2 nm thick) built with trilayer WS2 semiconductor acts as a gate-tunable photoactive synapse, i.e., a photo-memtransistor. A train of UV pulses onto the WS2 memristor generates dopants in atomic-level precision by direct light-lattice interactions, which, along with the gate tunability, leads to the accurate modulation of the channel conductance for potentiation and depression of the synaptic cells. Such synaptic dynamics can be explained by a parallel atomistic resistor network model. In addition, it is shown that such a device scheme can generally be realized in other 2D vdW semiconductors, such as MoS2 , MoSe2 , MoTe2 , and WSe2 . Demonstration of these atomically thin photo-memtransistor arrays, where the synaptic weights can be tuned for the atomistic defect density, provides implications for a new type of artificial neural networks for parallel matrix computations with an ultrahigh integration density.

Regression of gastric endoscopic submucosal dissection induced polypoid nodular scar after Helicobacter pylori eradication: A case report.

BACKGROUND: Endoscopic submucosal dissection (ESD) is the treatment of choice for early gastric cancer and premalignant gastric dysplasia. In some cases, ESD induced ulcer heals as a polypoid nodular scar (PNS). These scars may make the physicians raise several clinical implications such as post-ESD neoplastic recurrence. CASE SUMMARY: We described a case of gastric ESD induced PNS which is regressed after Helicobacter pylori (H. pylori) eradication. A 58-year-old male patient was referred to the outpatient clinic for evaluation and treatment of gastric low-grade dysplasia (LGD). ESD was performed. A PNS was developed at the ESD site. An endoscopic biopsy was done and there was no histological evidence of remnant tumor or recurrence but a hyperplastic mucosal change. The PNS showed increase in size in follow-up endoscopy, and the biopsy specimen demonstrated H. pylori infestation. H. pylori eradication was done and the PNS was regressed. CONCLUSION: H. pylori eradication is considerable for the regression of PNS if H. pylori infestation is confirmed.

Silent advanced large cell neuroendocrine carcinoma with synchronous adenocarcinoma of the colon: A case report.

BACKGROUND: Large cell neuroendocrine carcinoma (LCNEC) accounts for about 0.25% of colorectal cancer patients. Furthermore, synchronous LCNEC and adenocarcinoma coexistence in the colon is very rare. LCNEC are usually aggressive and have a poor prognosis. Usually, colorectal LCNEC patients complain of abdominal symptoms such as pain, diarrhea or hematochezia because it is often diagnosed as an advanced disease that accompanies metastatic lesions. CASE SUMMARY: We describe a case of relatively asymptomatic synchronous LCNEC and colon adenocarcinoma. A 62-year-old male patient visited our hospital due to anemia detected by a local health check-up. He did not complain of melena, hematochezia or abdominal pain. Physical examination was unremarkable and his abdomen was soft, nontender and nondistended with no palpable mass. Laboratory tests revealed anemia with hemoglobin 5.1 g/dL. Colonoscopy revealed an ulcerofungating lesion in the ascending colon and about a 1.5 cm-sized large sessile polyp in the sigmoid colon. Endoscopic biopsy of the ascending colon lesion revealed the ulcerofungating mass that was LCNEC and endoscopic mucosal resection at the sigmoid colon lesion showed a large polypoid lesion that was adenocarcinoma. Multiple liver, lung, bone and lymph nodes metastasis was found on chest/abdominal computed tomography and positron emission tomography. The patient was diagnosed with advanced colorectal LCNEC with liver, lung, bone and lymph node metastasis (stage IV) and synchronous colonic adenocarcinoma metastasis. In this case, no specific symptom except anemia was observed despite the multiple metastases. The patient refused systemic chemotherapy and was discharged after transfusion. CONCLUSION: We report a case of silent LCNEC of the colon despite the advanced state and synchronous adenocarcinoma.

Endoscopist-Driven Sedation Practices in South Korea: Re-evaluation Considering the Nationwide Survey in 2019.

Background/Aims: This study aimed to determine changes in endoscopist-driven sedation practices 5 years after the first nationwide survey in 2014 by the Korean Society of Gastrointestinal Endoscopy (KSGE). Methods: A 59-item survey covering current practices was electronically mailed to all members of the KSGE in 2019. Results: In total, 955 (12.8%) out of 7,486 questionnaires were returned. A total of 738 (77.7%) out of 955 respondents attended dedicated sedation education programs. The American Society of Anesthesiologists class was recorded by 464 (51.2%) out of 907 respondents. The recording rate was higher in respondents who completed sedation education (p=0.014) and worked in general or tertiary hospitals (p<0.001). Compared to that reported in the previous survey, the reported use of propofol was higher in 2019. The respondents had higher satisfaction scores for propofol-based sedation compared with midazolam monotherapy (p<0.001). The rates of oxygen supplementation (p<0.001) and oxygen saturation level monitoring (p<0.001) during sedative endoscopy were higher in 2019 than in the previous survey. A total of 876 (98.4%) out of 890 respondents reported a separate recovery bay, and 615 (70.5%) out of 872 respondents reported that personnel were assigned solely to the recovery bay. Conclusions: Endoscopist-driven sedation and monitoring practices in 2019 were significantly different than those in 2014. The respondents favored propofol-based sedation and utilized oxygen supplementation and monitoring of O2 saturation more frequently in 2019 than in 2014.

New sedatives and analgesic drugs for gastrointestinal endoscopic procedures.

Procedural sedation has become increasingly common in endoscopy. Sedatives and analgesics induce anxiolysis and amnesia. In addition, an appropriate level of sedation is necessary for safe procedures including therapeutic endoscopy. Midazolam and propofol are the most commonly used drugs in sedative endoscopy. In recent years, the need to ascertain the safety and effectiveness of sedation has increased in practice. Therefore, new sedatives and analgesic drugs for optimal sedative endoscopy, have recently emerged. This article reviews the characteristics of sedatives and analgesics, and describes their clinical use in gastrointestinal endoscopy.

2021 Korean Society of Gastrointestinal Endoscopy Clinical Practice Guidelines for Endoscopic Sedation.

Sedation can resolve anxiety and fear in patients undergoing endoscopy. The use of sedatives has increased in Korea. Appropriate sedation is a state in which the patient feels subjectively comfortable while maintaining the airway reflex for stable spontaneous breathing. The patient should maintain a state of consciousness to the extent that he or she can cooperate with the needs of the medical staff. Despite its benefits, endoscopic sedation has been associated with cardiopulmonary complications. Such cardiopulmonary complications are usually temporary, and most patients recover without sequelae. However, these events may progress to serious complications, such as cardiovascular collapse. Therefore, it is essential to screen high-risk patients before sedation and reduce complications by meticulous monitoring. Additionally, physicians should be familiar with the management of emergencies. The first Korean clinical practice guideline for endoscopic sedation was developed based on previous worldwide guidelines for endoscopic sedation using an adaptation process. The guideline consists of nine recommendations based on a critical review of currently available data and expert consensus when the guideline was drafted. These guidelines should provide clinicians, nurses, medical school students, and policy makers with information on how to perform endoscopic sedation with minimal risk.

Lipocalin 2 potentially contributes to tumorigenesis from colitis via IL-6/STAT3/NF-κB signaling pathway.

Lipocalin (LCN) 2 (LCN2), a member of the lipocalin superfamily, plays an important role in oncogenesis and progression in various types of cancer. However, the role of LCN2 in inflammation-associated cancer remains unknown. Here, we explored the functional role and mechanisms of LCN2 in tumorigenesis using murine colitis-associated cancer (CAC) models and human colorectal cancer (CRC) cells. Using murine CAC models, we found that LCN2 was preferentially expressed in colonic tissues from CAC models compared with tissues from normal mice. In vitro results demonstrated that the levels of LCN2 mRNA and protein were markedly up-regulated by interleukin (IL) 6 (IL-6) in human CRC cells. Interestingly, we found LCN2 up-regulation by IL-6 is diminished by nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) inhibition using specific inhibitors and small interfering RNA (siRNA). Reporter assay results determined that IL-6 induces LCN2 gene promoter activity under control of NF-κB/STAT3 activation. IL-6-induced LCN2 regulated cell survival and susceptibility of developmental factors to the NF-κB/STAT3 pathway. Taken together, our results highlight the unknown role of LCN2 in CAC progression and suggest that increased LCN2 may serve as an indicator of CRC development in the setting of chronic inflammation.

[2021 Korean Society of Gastrointestinal Endoscopy Clinical Practice Guidelines for Endoscopic Sedation].

Sedation can resolve anxiety and fear in patients undergoing endoscopy. The use of sedatives has increased in Korea. Appropriate sedation is a state in which the patient feels subjectively comfortable while maintaining the airway reflex for stable spontaneous breathing. The patient should maintain a state of consciousness to the extent that he or she can cooperate with the needs of the medical staff. Despite its benefits, endoscopic sedation has been associated with cardiopulmonary complications. Cardiopulmonary complications are usually temporary. Most patients recover without sequelae. However, they may progress to serious complications, such as cardiovascular collapse. Therefore, it is essential to screen high-risk patients before sedation and reduce complications by meticulous monitoring. Additionally, physicians should be familiar with the management of emergencies. The first Korean clinical practice guideline for endoscopic sedation was developed based on previous worldwide guidelines for endoscopic sedation using an adaptation process. The guideline consists of nine recommendations based on a critical review of currently available data and expert consensus when the guideline was drafted. These guidelines should provide clinicians, nurses, medical school students, and policy makers with information on how to perform endoscopic sedation with minimal risk.

2021 Korean Society of Gastrointestinal Endoscopy Clinical Practice Guidelines for Endoscopic Sedation.

Sedation can resolve anxiety and fear in patients undergoing endoscopy. The use of sedatives has increased in Korea. Appropriate sedation is a state in which the patient feels subjectively comfortable while maintaining the airway reflex for stable spontaneous breathing. The patient should maintain a state of consciousness to the extent that he or she can cooperate with the needs of the medical staff. Despite its benefits, endoscopic sedation has been associated with cardiopulmonary complications. Cardiopulmonary complications are usually temporary. Most patients recover without sequelae. However, they may progress to serious complications, such as cardiovascular collapse. Therefore, it is essential to screen high-risk patients before sedation and reduce complications by meticulous monitoring. Additionally, physicians should be familiar with the management of emergencies. The first Korean clinical practice guideline for endoscopic sedation was developed based on previous worldwide guidelines for endoscopic sedation using an adaptation process. The guideline consists of nine recommendations based on a critical review of currently available data and expert consensus when the guideline was drafted. These guidelines should provide clinicians, nurses, medical school students, and policy makers with information on how to perform endoscopic sedation with minimal risk.

IgA vasculitis mimicking drug-induced skin reaction and infectious colitis in an elderly patient: A case report.

RATIONALE: Immunoglobulin A vasculitis (IgAV) in adults is rare and shows worse symptoms and prognosis. In real-life clinics, IgAV in elderly patients may be difficult to diagnose because of its rarity and other common diseases to consider. This study reports a case of IgAV mimicking drug-induced skin reaction in an elderly patient. PATIENT CONCERNS: A 74-year-old female without any underlying disease presented to our emergency department as she was suffering from lower abdominal pain and diarrhea for 3 weeks. The patient was diagnosed with infectious colitis, and antibiotic treatment was administered at a local clinic. At presentation, the patient had rashes on both lower legs that developed after the antibiotic treatment, which was assumed as a drug eruption. Although antibiotic treatment was continued, the patient had persistent abdominal pain, diarrhea, hematochezia, and rashes. Proteinuria was developed on urinalysis. DIAGNOSES: Infectious colitis, IgAV. INTERVENTIONS: Sigmoidoscopy revealed easily bleeding erythematous mucosal lesions from the descending colon to the rectum. IgAV was suspected, and thus skin biopsy was performed. Histological findings of the skin biopsy showed leukocytoclastic vasculitis, which is compatible with IgAV. A nonsteroidal anti-inflammatory drug was administered for abdominal pain. The patient showed persistent proteinuria and a systemic steroid (prednisolone 50 mg [1 mg/kg]) was started. OUTCOMES: After administration of the nonsteroidal anti-inflammatory drug, the patient's abdominal pain was resolved rapidly. Under systemic steroid treatment, the patient showed significant symptomatic improvements, and after 2 weeks, the skin and colonic mucosal lesions were completely resolved. LESSONS: We present a case of adult-onset IgAV, which was initially diagnosed with infectious colitis and drug eruption. The history of skin reaction development after antibiotic treatment and the rarity of IgAV in elderly patients masked the diagnosis of IgAV. Despite its rarity, IgAV should be highly suspected in elderly patients with rashes, proteinuria, and signs of colitis.

Deep-ultraviolet electroluminescence and photocurrent generation in graphene/hBN/graphene heterostructures.

Hexagonal boron nitride (hBN) is a van der Waals semiconductor with a wide bandgap of ~ 5.96 eV. Despite the indirect bandgap characteristics of hBN, charge carriers excited by high energy electrons or photons efficiently emit luminescence at deep-ultraviolet (DUV) frequencies via strong electron-phonon interaction, suggesting potential DUV light emitting device applications. However, electroluminescence from hBN has not been demonstrated at DUV frequencies so far. In this study, we report DUV electroluminescence and photocurrent generation in graphene/hBN/graphene heterostructures at room temperature. Tunneling carrier injection from graphene electrodes into the band edges of hBN enables prominent electroluminescence at DUV frequencies. On the other hand, under DUV laser illumination and external bias voltage, graphene electrodes efficiently collect photo-excited carriers in hBN, which generates high photocurrent. Laser excitation micro-spectroscopy shows that the radiative recombination and photocarrier excitation processes in the heterostructures mainly originate from the pristine structure and the stacking faults in hBN. Our work provides a pathway toward efficient DUV light emitting and detection devices based on hBN.

The HDAC1 Inhibitor CBUD-1001 Enhances TRAIL-induced Apoptosis in Colorectal Cancer Cells.

BACKGROUND/AIM: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potential anti-tumor agent. However, resistance to TRAIL has been reported in a number of clinical trials. In this study, we investigated the molecular mechanisms by which a novel histone deacetylase (HDAC) inhibitor, CBUD-1001, sensitizes colorectal cancer (CRC) cells to TRAIL-induced apoptosis. MATERIALS AND METHODS: Apoptotic cell death induced by CBUD-1001 and/or TRAIL was assessed on human CRC cells using the MTT assay, FACS analysis and nuclei staining. The involved molecular mechanisms were explored through western blotting analysis. RESULTS: We demonstrated that combined with CBUD-1001, TRAIL significantly enhanced TRAIL-induced apoptosis in CRC cells via mitochondria-mediated pathways. We also found that hyper-acetylation of histone by CBUD-1001 treatment leads to up-regulation of death receptor (DR) 5 in a dose- and time-dependent manner. Furthermore, we identified that enhanced sensitivity to TRAIL by combination with CBUD-1001 depends on the MAPK/CHOP axis, being a key mediator of DR5. CONCLUSION: A novel HDAC inhibitor CBUD-1001 sensitizes TRAIL-induced apoptosis via up-regulation of DR5, and that CBUD-1001 and TRAIL combination treatment offers an effective strategy to overcome TRAIL resistance in CRC cells.

Heteroepitaxial van der Waals semiconductor superlattices.

A broad range of transition metal dichalcogenide (TMDC) semiconductors are available as monolayer (ML) crystals, so the precise integration of each kind into van der Waals (vdW) superlattices (SLs) could enable the realization of novel structures with previously unexplored functionalities. Here we report the atomic layer-by-layer epitaxial growth of vdW SLs with programmable stacking periodicities, composed of more than two kinds of dissimilar TMDC MLs, such as MoS2, WS2 and WSe2. Using kinetics-controlled vdW epitaxy in the near-equilibrium limit by metal-organic chemical vapour depositions, we achieved precise ML-by-ML stacking, free of interlayer atomic mixing, which resulted in tunable two-dimensional vdW electronic systems. As an example, by exploiting the series of type II band alignments at coherent two-dimensional vdW heterointerfaces, we demonstrated valley-polarized carrier excitations-one of the most distinctive electronic features in vdW ML semiconductors-which scale with the stack numbers n in our (MoS2/WS2)n SLs on optical excitations.