The effect of sulfuration reaction rates with sulphur concentration gradient dependence on the growth pattern and morphological evolution of MoS2 in laminar flow.

Sulfuration reactions dominate the synthesis of transition-metal dichalcogenides via chemical vapor deposition. A neglected critical issue is the evolution of crystal domain morphology and growth models caused by boundary layer development. In this study, we propose two growth models within a laminar flow field to investigate the kinetic mechanism of uniformly grown MoS2. We used supercritical fluid pre-deposition to obtain a well-distributed and low-crystallinity Mo precursor on the surface of a substrate to avoid non-stoichiometric supply in sulfuration. The development of the boundary layer was suppressed through mainstream force by adjusting the substrate slope angle. For growth within the underdeveloped laminar boundary layer, monolayer MoS2 with a size of 50 µm uniformly distributed on the full substrate with R = 85% (relative change in boundary layer thickness). Moreover, the growth constrained by surface chemical reactions tended to promote spatially uniform growth. However, within the fully developed laminar flow, the crystal domains preferentially grew vertically, which was attributed to the excessive crystal growth rate (g). Our results provide new insights into the controllable preparation of two-dimensional materials.

Vapor-Liquid-Solid Growth of Site-Controlled Monolayer MoS2 Films Via Pressure-Induc ed Supercritical Phase Nucleation.

In this study, a novel pressure-induced supercritical phase nucleation method is proposed to synthesize monolayer MoS2 films, which is promoter free and can avoid contamination of films derived from these heterogeneous promoters in most of the existing techniques. The low-crystallinity and size-controlled MoO2(acac)2 particles are recrystallized on the substrate via the pressure-sensitive solvent capacity of supercritical CO2 and these particles are used as growth sites. The size of single-crystal MoS2 on the substrate is found to be dependent on the wetting area of the pyrolyzed precursor droplets (MoO2) on the surface, and the formation of continuous films with high coverage is mainly controlled by the coalescence of MoO2 droplets. It is enhanced by the increase of the nucleation site density, which can be adjusted by the supersaturation of the supercritical fluid solution. Our findings pave a new way for the controllable growth of MoS2 and other two-dimensional materials and provide sufficient and valuable evidence for vapor-liquid-solid growth.

The production of graphene using impinging jet exfoliation in a binary system of CO2 and N-methyl pyrrolidone.

High quality and high quantity few-layer graphene was successfully prepared using a new impinging jet method. Natural graphite flakes were first agitated in N-methyl pyrrolidone (NMP) with the assistance of supercritical CO2, then the half-exfoliated graphite was further stripped using the shear stress derived from the impinging jets. After the energy conversion and stress analysis of the graphite particles during the whole exfoliation process, it was revealed that the size of the target mesh, the distance between the nozzle and the target, the decompression rate, and the size of the raw materials had a significant influence on the exfoliation process. Additionally, a microscopic view of the exfoliation and dispersion mechanism of graphene in the CO2-NMP system was investigated using molecular dynamics simulation, and CO2 was found to be beneficial for the penetration of NMP into the graphite sheets. Finally, the concentration and quality characteristics of the prepared graphene were characterized using ultraviolet-visible spectroscopy, transmission electron microscopy, Raman spectroscopy, and atomic force microscopy. The maximum concentration was as high as 0.689 mg ml-1, the thickness of 68% of the product was less than 2.5 nm, and the lateral dimension was from 0.5 to 3.0 µm. These results indicate that this impinging jet method is promising for large-scale industrial production.

[Characteristics of Dissolved CH4 and N2O Concentrations of Weihe River in Xinxiang Section in Spring].

Distributions of CH4 and N2O concentrations in Weihe River in Xinxiang City were monitored in spring of 2015, and their influencing factors were discussed. The result showed that CH4 and N2O were super-saturated in surface water of Weihe River. The variation ranges of two gases' saturations in the surface water of Weihe River were 147.59-2667.85 (CH4) and 4.06-188.25 (N2O). In the urban area, significant correlation existed between N2O and NH4⁺-N concentrations (P < 0.01), but in the new district, dissolved N2O concentration showed sharp increase because of the water input from the urban sewage plants, illustrating that the controlling mechanism on N2O production varied as pollutant characteristics changed. Stepwise regression analysis showed that CH4 concentrations could be explained by NH4⁺-N concentrations and water temperature, and CH4 concentrations in the surface water of Weihe River was significantly correlated with NH4⁺-N concentrations (R² = 0.70, P < 0.01), suggesting that NH4⁺-N was the key factor in regulating the production and assumption of CH4oxidation in Weihe River in spring. Besides, this study showed that when there was less NO3⁻-N but more NH4⁺-N in river water, CH4and N2O concentrations would be positively correlated, indicating that different nitrogen sources would impact the coupling mechanism of CH4and N2O productions.

Clinicopathological characteristics and outcome of primary sarcomatoid carcinoma and carcinosarcoma of the liver.

BACKGROUND: Primary sarcomatoid carcinoma (SC) and carcinosarcoma (CS) of the liver are rare tumors. PATIENTS AND METHODS: From November 1999 to June 2011, clinicopathological features and outcome of 10 SC and 14 CS patients were retrospectively studied. RESULTS: In the SC group, six patients had hepatocellular carcinoma and four had cholangiocellular carcinoma, while in the CS group, it was nine and five patients, respectively. All cases of the sarcomatous components were vimentin-positive. Pan-cytokeratin were stained in sarcomatous components of the SC group, but not in the CS group. The sarcomatous component in the SC group was negative for desmin, myoglobin, HHF35, SMA, CD68, Mac387, AAT, CD34, and S100. In the CS group, the sarcomatous components in six cases were malignant fibrous histiocytomas, six were fibrosarcomas, and two were rhabdomyosarcomas. Median survival times were 9.6 and 4.8 months for the SC and CS groups, respectively (P = 0.483). In univariate analysis, favorable predictors of overall survival were asymptomatic, Child-Pugh class A, no distant metastasis, and radical resection. CONCLUSIONS: SC and CS were highly aggressive malignancies with similar poor survival regardless of the histological and immunohistochemical findings. Early detection through regular physical examination and treatment with radical resection may improve the outcome of those patients.

Effect of tea polyphenol on oxidative injury in S180 cells induced hepatocarcinoma mice.

The purpose of this study was to evaluate the antioxidant nature of tea polyphenol on S180 cells induced liver cancer in mice. In the present study, hepatocellular carcinoma was induced by tumor transplantation of liver in situ. The antitumor activity of tea polyphenol has been determined in vivo in hepatocellular carcinoma mice after treatment of drug (50, 100, 150 mg/kg body weight) by gavage for 20 days. Results showed that a significant increase in serum aspartate transaminase (AST), alkaline phosphatase (ALP), alanine aminotransfere (ALT), malondialdehyde (MDA) level, decrease in serum white blood cells (WBC), serum total protein (TP), albumin (ALB), A/G, tumor necrosis factor-α (TNF-α) and interferon-gamma (IFN-γ), liver reduced glutathione (GSH) levels were observed. In addition, the levels of enzymic and non-enzymic antioxidants were decreased when subjected to S180 cells induction. These altered enzyme levels were ameliorated significantly by administration of tea polyphenol at the concentration of 50, 100, 150 mg/kg body weight in drug-treated animals. These results indicate that the protective effect of tea polyphenol was associated with inhibition of MDA induced by S180 cells and to maintain the antioxidant enzyme levels.