Two-dimensional (2D) lateral heterostructures have emerged as a hot topic in the fast evolving field of advanced functional materials , but their fabrication is challenging. The layer-structured WS2 was theoretically demonstrated to be inert to oxidation except for the monolayer, which can be selectively oxidized owing to the simultaneous interaction of oxygen with both sides. Combined with the theoretical calculations, a new method was developed for the successful construction of 2D lateral heterostructures of WS2 /WO3 ⋅H2 O in an ambient environment, based on a simple liquid-phase solution exfoliation. These lateral heterostructures of WS2 /WO3 ⋅H2 O have interesting properties, as indicated by enhanced photocatalytic activity toward the degradation of methyl orange (MO).
Syntheses of transition-metal dichalcogenides
(TMDs) using colloidal-chemistry
approaches are gaining significant interest in recent years, as these
methods enable the morphology and properties of the nanocrystals to
be tuned for targeted applications. In this work, by only varying
the ligand used during synthesis, we synthesized nanoflowers with
oleic acid (OA) and 1T′ phase dominated WSe2 nanosheets
with oleylamine (OLA). WSe2 nanocrystals show slower rate
of formation for the metastable 1T′ phase. Surface chemistry
analyses of the synthesized nanocrystals by solution NMR establish
that neither of the ligands bind strongly to the surface of nanocrystals
but are in a dynamic coordination with the WSe2 surface.
A further examination of the coordination of tungsten hexacarbonyl
(W(CO)6) with the respective ligands confirms that W(CO)6 decomposes in OA, losing its octahedral symmetry, which leads
to fast reactivity in the flask. In contrast to this, W(CO)6 reacts with OLA to form a new complex, which leads to slower reactivity
and crystallization of the synthesized nanocrystals in the octahedral
1T′ phase. These insights into the influence of precursor-ligand
chemistry on reaction outcome and the peculiar surface chemistry of
colloidal TMD nanocrystals will be instrumental in developing future
colloidal TMD nanocrystals.
We show that bulk MoS2 can be efficiently exfoliated into ultrathin nanosheets in supercritical CO2 with ethanol as cosolvent. Moreover, such tailored MoS2 nanostructures, when they are directly used as labels for bioimaging, show excellent imaging effects with strong fluorescence and nontoxicity.
In recent years, hot injection synthesis has emerged as a promising route for the production of nanostructured transition metal dichalcogenides, in large due to its better control over the crystallinity and monodispersity compared to other solution based methods. Understanding the photophysics of excitons in the thus obtained colloidal nanosheets is of great importance to explore their potential for applications in optoelectronics. Here, we study the carrier dynamics in these few-layer colloidal WS2 nanosheets by use of broadband transient absorption spectroscopy. The dynamics of both the bleach, linewidth broadening and energy shift across the entire visible and near-infrared spectrum, allows us to identify subpicosecond electron trapping as the main carrier loss channel. A more quantitative analysis shows that the intrinsic properties of colloidally synthesized nanosheets are on par with other synthesis methods, paving the way for this method to produce high quality nanosheets.
AimTo evaluate the type of venous involvement in Chinese Budd-Chiari syndrome (BCS) patients and the relative diagnostic accuracy of the different imaging modalities.MethodsUsing digital subtraction angiography (DSA) as a reference standard, color Doppler ultrasound (CDUS), computed tomography angiography (CTA), and magnetic resonance angiography (MRA) were performed on 338 patients with BCS. We analyzed the course of the main and any accessory hepatic veins (HVs) and the inferior vena cava (IVC) to assess the etiology of obstructed segments and diagnostic accuracy of CDUS, CTA and MRA.ResultsAmong the 338 cases, there were 8 cases (2.4%) of isolated IVC membranous obstruction, 45 cases (13.3%) of isolated HV occlusion, and 285 cases (84.3%) with both IVC membranous obstruction and HV occlusion. Comparing with DSA, CDUS, CTA had a diagnostic accuracy of 89.3% and 80.2% in detecting BCS, and 83.4% of cases correctly correlated by MRA.ConclusionIn Henan Province, most patients with BCS have complex lesions combining IVC and HV involvement. The combination of CDUS and CTA or MRI is useful for diagnosis of BCS and guiding therapy.
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