Herbal medicines (HMs) are much appreciated for their significant contribution to human survival and reproduction by remedial and prophylactic management of diseases. Defining the scientific basis of ...HMs will substantiate their value and promote their modernization. Ever‐increasing evidence suggests that gut microbiota plays a crucial role in HM therapy by complicated interplay with HM components. This interplay includes such activities as: gut microbiota biotransforming HM chemicals into metabolites that harbor different bioavailability and bioactivity/toxicity from their precursors; HM chemicals improving the composition of gut microbiota, consequently ameliorating its dysfunction as well as associated pathological conditions; and gut microbiota mediating the interactions (synergistic and antagonistic) between the multiple chemicals in HMs. More advanced experimental designs are recommended for future study, such as overall chemical characterization of gut microbiota‐metabolized HMs, direct microbial analysis of HM‐targeted gut microbiota, and precise gut microbiota research model development. The outcomes of such research can further elucidate the interactions between HMs and gut microbiota, thereby opening a new window for defining the scientific basis of HMs and for guiding HM‐based drug discovery.
Electrospun ZnO‐SnO2 heterojunction nanofibers are demonstrated to be promising candidates for easily assembled fully transparent high‐performance photodetectors.
The application of nanofilm networks made of branched ZnS‐ZnO nanostructures as a flexible UV photodetector is demonstrated. The fabricated devices show excellent operational characteristics: tunable ...spectral selectivity, widerange photoresponse, fast response speed, and excellent environmental stability.
We report ambipolar charge transport in α‐molybdenum ditelluride (MoTe2) flakes, whereby the temperature dependence of the electrical characteristics was systematically analyzed. The ambipolarity of ...the charge transport originated from the formation of Schottky barriers at the metal/MoTe2 contacts. The Schottky barrier heights as well as the current on/off ratio could be modified by modulating the electrostatic fields of the back‐gate voltage (V
bg) and drain‐source voltage (V
ds). Using these ambipolar MoTe2 transistors we fabricated complementary inverters and amplifiers, demonstrating their feasibility for future digital and analog circuit applications.
We demonstrate the possibility in quantifying the Raman intensities for both specimen and substrate layers in a common stacked experimental configuration and, consequently, propose a general and ...rapid thickness identification technique for atomic-scale layers on dielectric substrates. Unprecedentedly wide-range Raman data for atomically flat MoS2 flakes are collected to compare with theoretical models. We reveal that all intensity features can be accurately captured when including optical interference effect. Surprisingly, we find that even freely suspended chalcogenide few-layer flakes have a stronger Raman response than that from the bulk phase. Importantly, despite the oscillating intensity of specimen spectrum versus thickness, the substrate weighted spectral intensity becomes monotonic. Combined with its sensitivity to specimen thickness, we suggest this quantity can be used to rapidly determine the accurate thickness for atomic layers.
Two-dimensional semiconductors are structurally ideal channel materials for the ultimate atomic electronics after silicon era. A long-standing puzzle is the low carrier mobility (μ) in them as ...compared with corresponding bulk structures, which constitutes the main hurdle for realizing high-performance devices. To address this issue, we perform a combined experimental and theoretical study on atomically thin MoS2 field effect transistors with varying the number of MoS2 layers (NLs). Experimentally, an intimate μ–NL relation is observed with a 10-fold degradation in μ for extremely thinned monolayer channels. To accurately describe the carrier scattering process and shed light on the origin of the thinning-induced mobility degradation, a generalized Coulomb scattering model is developed with strictly considering device configurative conditions, that is, asymmetric dielectric environments and lopsided carrier distribution. We reveal that the carrier scattering from interfacial Coulomb impurities (e.g., chemical residues, gaseous adsorbates, and surface dangling bonds) is greatly intensified in extremely thinned channels, resulting from shortened interaction distance between impurities and carriers. Such a pronounced factor may surpass lattice phonons and serve as dominant scatterers. This understanding offers new insight into the thickness induced scattering intensity, highlights the critical role of surface quality in electrical transport, and would lead to rational performance improvement strategies for future atomic electronics.
Understanding the interfacial electrical properties between metallic electrodes and low-dimensional semiconductors is essential for both fundamental science and practical applications. Here we report ...the observation of thickness reduction induced crossover of electrical contact at Au/MoS2 interfaces. For MoS2 thicker than 5 layers, the contact resistivity slightly decreases with reducing MoS2 thickness. By contrast, the contact resistivity sharply increases with reducing MoS2 thickness below 5 layers, mainly governed by the quantum confinement effect. We find that the interfacial potential barrier can be finely tailored from 0.3 to 0.6 eV by merely varying MoS2 thickness. A full evolution diagram of energy level alignment is also drawn to elucidate the thickness scaling effect. The finding of tailoring interfacial properties with channel thickness represents a useful approach controlling the metal/semiconductor interfaces which may result in conceptually innovative functionalities.
Two-dimensional layered crystals could show phonon properties that are markedly distinct from those of their bulk counterparts, because of the loss of periodicities along the c-axis directions. Here ...we investigate the phonon properties of bulk and atomically thin α-MoTe2 using Raman spectroscopy. The Raman spectrum of α-MoTe2 shows a prominent peak of the in-plane E1 2g mode, with its frequency upshifting with decreasing thickness down to the atomic scale, similar to other dichalcogenides. Furthermore, we find large enhancement of the Raman scattering from the out-of-plane B1 2g mode in the atomically thin layers. The B1 2g mode is Raman inactive in the bulk, but is observed to become active in the few-layer films. The intensity ratio of the B1 2g to E1 2g peaks evolves significantly with decreasing thickness, in contrast with other dichalcogenides. Our observations point to strong effects of dimensionality on the phonon properties of MoTe2.
Indium phosphide (InP) core/shell quantum dots (QDs) without intrinsic toxicity have shown great potential to replace the widely applied cadmium‐containing QDs in next‐generation commercial display ...and lighting applications. However, it remains challenging to synthesize InP core/shell QDs with high quantum yields (QYs), uniform particle size, and simultaneously thicker shell thickness to reduce nonradiative Förster resonant energy transfer (FRET). Here, thick InP‐Based QLEDs shell InP/GaP/ZnS//ZnS core/shell QDs with high stability, high QY (≈70%), and large particle size (7.2 ± 1.3 nm) are successfully synthesized through extending the growth time of shell materials along with the timely replenishment of shelling precursor. The existence of GaP interface layer minimizes the lattice mismatch and reduces interfacial defects. While thick ZnS shell, which suppresses the FRET between closely packed QDs, ensures high PL QY and stability. The robustness of such properties is demonstrated by the fabrication of green electroluminescent LEDs based on InP core/shell QDs with the peak external quantum efficiency and current efficiency of 6.3% and 13.7 cd A−1, respectively, which are the most‐efficient InP‐based green quantum dot light‐emitting diodes (QLEDs) till now. This work provides an effective strategy to further improve heavy‐metal‐free QLED performance and moves a significant step toward the commercial application of InP‐based electroluminescent device.
Thick‐shell InP/GaP/ZnS core/shell quantum dots (QDs) with high stability, high quantum yield, and large particle size (7.2 ± 1.3 nm) are successfully synthesized. The electroluminescent device based on the QDs displays a current efficiency of 13.7 cd A−1 and an external quantum efficiency of 6.3%.
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