Switchable, Tunable, and Directable Exciton Funneling in Periodically Wrinkled WS2.

The extreme elastic strain of monolayer transition metal dichalcogenides provides an ideal platform to achieve efficient exciton funneling via local strain modulation; however, studies conducted thus far have focused on the use of substrates with fixed strain profiles. We prepared 1L-WS2 on a flexible substrate such that the formation of topographic wrinkles could be switched on or off, and the depth or the direction of the wrinkle could be modified by external strain, thereby providing full control of the periodic undulation of the band gap profile of 1L-WS2 in the range 0-57 meV. Nanoscale photoluminescence (PL) imaging unambiguously evinced that the photoexcited excitons of 1L-WS2 were accumulated at the top regions of the wrinkles with less band gap than the valley region. Our results of broad tunability of the two-dimensional (2D) exciton funneling suggest a promising route to control exciton drift for enhanced optoelectronic performances and future 2D exciton devices.

Growth and Interlayer Engineering of 2D Layered Semiconductors for Future Electronics.

Layered materials that do not form a covalent bond in a vertical direction can be prepared in a few atoms to one atom thickness without dangling bonds. This distinctive characteristic of limiting thickness around the sub-nanometer level allowed scientists to explore various physical phenomena in the quantum realm. In addition to the contribution to fundamental science, various applications were proposed. Representatively, they were suggested as a promising material for future electronics. This is because (i) the dangling-bond-free nature inhibits surface scattering, thus carrier mobility can be maintained at sub-nanometer range; (ii) the ultrathin nature allows the short-channel effect to be overcome. In order to establish fundamental discoveries and utilize them in practical applications, appropriate preparation methods are required. On the other hand, adjusting properties to fit the desired application properly is another critical issue. Hence, in this review, we first describe the preparation method of layered materials. Proper growth techniques for target applications and the growth of emerging materials at the beginning stage will be extensively discussed. In addition, we suggest interlayer engineering via intercalation as a method for the development of artificial crystal. Since infinite combinations of the host-intercalant combination are possible, it is expected to expand the material system from the current compound system. Finally, inevitable factors that layered materials must face to be used as electronic applications will be introduced with possible solutions. Emerging electronic devices realized by layered materials are also discussed.

Measurement of Quantum Yields of Monolayer TMDs Using Dye-Dispersed PMMA Thin Films.

In general, the quantum yields (QYs) of monolayer transition metal dichalcogenides (1L-TMDs) are low, typically less than 1% in their pristine state, significantly limiting their photonic applications. Many methods have been reported to increase the QYs of 1L-TMDs; however, the technical difficulties involved in the reliable estimation of these QYs have prevented the general assessment of these methods. Herein, we demonstrate the estimation of the QYs of 1L-TMDs using a poly methyl methacrylate (PMMA) thin film embedded with rhodamine 6G (R6G) as a reference specimen for measuring the QYs of 1L-TMDs. The PMMA/R6G composite films with thicknesses of 80 and 300 nm demonstrated spatially homogeneous emissions with the incorporation of well-dispersed R6G molecules, and may, therefore, be used as ideal reference specimens for the QY measurement of 1L-TMDs. Using our reference specimens, for which the QY ranged from 5.4% to 22.2% depending on the film thickness and R6G concentrations, we measured the QYs of the exfoliated or chemical vapor deposition (CVD)-grown 1L-WS2, -MoSe2, -MoS2, and -WSe2 TMDs. The convenient procedure proposed in this study for preparing the thin reference films and the simple protocol for the QY estimation of 1L-TMDs may enable accurate comparisons of the absolute QYs between the 1L-TMD samples, thereby enabling the development of a method to improve the QY of 1L-TMDs.

Factors Associated with Indeterminate and False Negative Results of QuantiFERON-TB Gold In-Tube Test in Active Tuberculosis.

BACKGROUND: The sensitivities and specificities of interferon-gamma release assays (IGRAs) vary among different population studies, and the data on the routine use of IGRAs are limited. The aim of this study was to evaluate the role of QuantiFERON-TB Gold In-Tube (QFT-GIT) test in the diagnosis of active tuberculosis. METHODS: We conducted a prospective study, enrolling 77 patients with suspected pulmonary tuberculosis (TB), at a secondary care teaching hospital in Seoul. RESULTS: In total, 12 (15.6%) patients showed indeterminate results due to positive control failure on the QFT-GIT test. Indeterminate results were significantly associated with the elderly, history of the intensive care unit stay, lymphocytopenia, especially low CD4 count, increased C-reactive protein and decreased protein levels. Of the 77 patients, 44 (57.1%) were diagnosed with active pulmonary tuberculosis, and the percentage of false negative results of the QFT-GIT was 36.4% (vs. 31.8% with TST). In the TB group with >65 years old (n=12), the proportions of the indeterminate (33.3% vs. 3.1%) and the false negative results (58.3% vs. 25.0%) of the QFT-GIT were significantly higher than in the younger TB group (n=32). CONCLUSION: Indeterminate and false negative results of QFT-GIT test were not infrequent in tuberculosis, especially in the elderly. Care should be considered for the interpretation with the elderly, immunocompromised, chronic and severely diseased patients.

Identification of CD23 as a functional receptor for the proinflammatory cytokine AIMP1/p43.

Aminoacyl-tRNA-synthetase-interacting multifunctional protein 1 (AIMP1/p43) can be secreted to trigger proinflammatory molecules while it is predominantly bound to a cytoplasmic macromolecular protein complex that contains several different aminoacyl-tRNA synthetases. Although its activities as a secreted signaling factor have been well characterized, the functional receptor for its proinflammatory activity has not yet identified. In this study, we have identified the receptor molecule for AIMP1 that mediates the secretion of TNF-α from THP-1 monocytic cells and primary human peripheral blood mononuclear cells (PBMCs). In a screen of 499 soluble receptors we identified CD23, a known low-affinity receptor for IgE, as a high affinity binding partner of AIMP1. We found that downregulation of CD23 attenuated AIMP1-induced TNF-α secretion and AIMP1 binding to THP-1 and PBMCs. We also observed that in THP-1 and PBMCs, AIMP1-induced TNF-α secretion, mediated by CD23, involved activation of ERK1/2. Interestingly, endothelial monocyte activating polypeptide II (EMAP II), the C-terminal fragment of AIMP1 that is also known to work as a proinflammatory cytokine, was incapable of binding to CD23 and of activating ERK1/2. Therefore, identification of CD23 not only explains the inflammatory function of AIMP1 but also provides the first evidence by which the mode of action of AIMP1 can be distinguished from that of its C-terminal domain, EMAP II.

Secreted human glycyl-tRNA synthetase implicated in defense against ERK-activated tumorigenesis.

Although adaptive systems of immunity against tumor initiation and destruction are well investigated, less understood is the role, if any, of endogenous factors that have conventional functions. Here we show that glycyl-tRNA synthetase (GRS), an essential component of the translation apparatus, circulates in serum and can be secreted from macrophages in response to Fas ligand that is released from tumor cells. Through cadherin (CDH)6 (K-cadherin), GRS bound to different ERK-activated tumor cells, and released phosphatase 2A (PP2A) from CDH6. The activated PP2A then suppressed ERK signaling through dephosphorylation of ERK and induced apoptosis. These activities were inhibited by blocking GRS with a soluble fragment of CDH6. With in vivo administration of GRS, growth of tumors with a high level of CDH6 and ERK activation were strongly suppressed. Our results implicate a conventional cytoplasmic enzyme in translation as an intrinsic component of the defense against ERK-activated tumor formation.