Noncentrosymmetric
transition-metal dichalcogenides, particularly
their 3R polymorphs, provide a robust setting for
valleytronics. Here, we report on the selective growth of monolayers
and bilayers of MoS2, which were acquired from two closely
but differently oriented substrates in a chemical vapor deposition
reactor. It turns out that as-grown bilayers are predominantly 3R-type, not more common 2H-type, as verified
by microscopic and spectroscopic characterization. As expected, the
3R bilayer showed a significantly higher valley polarization
compared with the centrosymmetric 2H bilayer, which
undergoes efficient interlayer scattering across contrasting valleys
because of their vertical alignment of the K and K′ points in momentum space. Interestingly, the 3R bilayer showed even higher valley polarization compared
with the monolayer counterpart. Moreover, the 3R bilayer
reasonably maintained its valley efficiency over a very wide range
of excitation power density from ∼0.16 kW/cm2 to
∼0.16 MW/cm2 at both low and room temperatures.
These observations are rather surprising because valley dephasing
could be more efficient in the bilayer via both interlayer and intralayer
scatterings, whereas only intralayer scattering is allowed in the
monolayer. The improved valley polarization of the 3R bilayer can be attributed to its indirect-gap nature, where valley-polarized
excitons can relax into the valley-insensitive band edge, which otherwise
scatter into the contrasting valley to effectively cancel out the
initial valley polarization. Our results provide a facile route for
the growth of 3R-MoS2 bilayers that could
be utilized as a platform for advancing valleytronics.
Effectively utilizing eco-friendly solar energy for desalination and wastewater purification has immense potential to overcome the global water crisis. Herein, we demonstrate a highly efficient solar vapor generator (SVG) developed via a simple morphological alteration, from a twodimensional (2D) TiO 2 film (TF) to one-dimensional (1D) TiO 2 nanorods (TNRs) grown on a glassy carbon foam (CF). Given that evaporation is primarily a surface physical phenomenon, the 1D morphology of TNRs provides a higher evaporation surface area compared to their 2D counterpart. Additionally, the superhydrophilic nature of TNRs ensures an adequate supply of water to the evaporation surface via effective capillary action. Consequently, the 1D TNRs properly utilize photothermal heat, which results in a significant reduction in the convection heat loss. Owing to the synergistic effect of these characteristics, TNRs/CF acquires a high evaporation rate of ∼2.23 kg m −2 h −1 and an energy utilization efficiency of ∼67.1% under one sun irradiation. Moreover, the excellent stability, desalination, self-cleaning capabilities, and the facile fabrication method make TNRs/CF suitable for cost-effective, large-scale device application.
As a result of the obesity epidemic, Nonalcoholic fatty liver disease (NAFLD) and its complications have increased among millions of people. Consequently, a group of experts recommended changing the term NAFLD to an inclusive terminology more reflective of the underlying pathogenesis; metabolic-associated fatty liver disease (MAFLD). This new term of MAFLD has its own disease epidemiology and clinical outcomes prompting efforts in studying its differences from NAFLD. This article discusses the rationale behind the nomenclature change, the main differences, and its clinical implications.
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