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Assemblies of single-walled carbon nanotubes with a specific chiral structure are promising future optofunctional materials because of their strong light–matter coupling arising from sharp optical resonances of quasi-one-dimensional excitons. Their strong optical resonances, which lie in the infrared-to-visible wavelength region, can be selected by their chiralities, and this selectivity promises a wide range of applications including photonic and thermo-optic devices. However, the broadband complex optical spectra of single-chirality carbon nanotube assemblies are scarce in the literature, which has prevented researchers and engineers from designing devices using them. Here, we experimentally determine broadband complex refractive index spectra of single-chirality carbon nanotube assemblies. Free-standing carbon nanotube membranes and those placed on sapphire substrates were fabricated via filtration of the nanotube solution prepared by the separation method using gel chromatography. Transmission and reflection spectra were measured in the mid-infrared to visible wavelength region, and the complex refractive indices of nanotube assemblies were determined as a function of photon energy. The real and imaginary parts of the refractive indices of the nanotube membrane with a bulk density of 1 g cm−3 at the first subband exciton resonance were determined to be approximately 2.7–3.6 and 1.3i–2.4i, respectively. We propose an empirical formula that phenomenologically describes the complex refractive index spectra of various single-chirality nanotube membranes, which can facilitate the design of photonic devices using carbon nanotubes as the material.

We present polarized Raman spectroscopy of the topological semimetal Co3Sn2S2, which was recently shown to host a Weyl semimetal phase. Stokes Raman spectra were obtained with the incident light parallel to the c‐axis of Co3Sn2S2. Two major phonon Raman peaks were observed at 289 and 386 cm−1 over continuous background emission signals. The intensity of the low‐wavenumber (289 cm−1) peak showed no polarization dependence. The high‐wavenumber (386 cm−1) peak and the continuous background signal were strongly polarized in the incident light polarization direction. These responses were almost independent of the in‐plane crystal orientation to the incident polarization, as is the manifestation of the D3d point group symmetry of the unit cell of Co3Sn2S2. According to the group theory and Raman tensor analyses, the low‐ and high‐wavenumber Raman signals are attributed to Γ point phonon modes with Eg and A1g symmetries, respectively. Furthermore, line shape analyses revealed that the high‐wavenumber A1g mode exhibited asymmetric peak feature well described by the Breit–Wigner–Fano function. These results suggest the Fano resonance between the A1g phonon scattering with the continuous electronic background associated with low energy excitations near the Fermi energy. The clarified phonon energies and symmetries, as well as the electronic contribution to the Raman scattering, will not only be useful as a fingerprint to readily verify the experimentally grown or theoretically calculated crystal structure but also suggest importance of Raman spectroscopy as an effective tool to study low energy excitations and their interactions in Co3Sn2S2. [ABSTRACT FROM AUTHOR]

Atomically thin transition metal dichalcogenides (TMDCs) are attractive materials for future optoelectronic applications because of their excellent electrical, optical, and quantum (spin‐valley) properties. In particular, in‐plane heterostructures based on TMDC monolayers provide opportunities to directly modulate band structures and lattice strains by the spatial distribution of constituent elements, leading to efficient control of their carrier transport and recombination. However, it is still challenging to create light‐emitting devices using such in‐plane heterostructures because of the technical difficulties associated with sample/device fabrication. This study demonstrated interfacial electroluminescence (EL) in diverse TMDC monolayer in‐plane heterostructures. Various combinations of large‐area, single‐crystalline in‐plane heterostructures with sharp interfaces are grown by chemical vapor deposition, followed by the adoption of electrolyte‐based light‐emitting devices to observe EL. The fine heterostructures enabled the capture of the linear‐shaped EL fixed along the junction interfaces. Significantly, the WS2/WSe2 in‐plane heterostructures exhibited circularly polarized EL with polarizability of 10% at room temperature. This can be explained by the interfacial strain‐mediated electronic structure evolution, in which the combination of electric fields and strain‐induced valley drifts realizes selective EL from the K/K' valley. These findings pave the way for expanding the potential of monolayer in‐plane heterostructures for use in functional optoelectronic devices. [ABSTRACT FROM AUTHOR]

Objective: To determine senescence‐associated changes in the gingival tissues of aged mice and gingival fibroblast cultures. Materials and Methods: The production of senescence‐associated β‐galactosidase (SA‐β‐gal) and mRNA expression of p16, p21, interleukin (IL)‐1β, and tumor necrosis factor α (TNF‐α) were evaluated in gingival tissues, gingival fibroblasts of 10‐ and 20‐month‐old C57BL/6NCrl mice, and multiple‐passaged and hydrogen peroxide‐stimulated human gingival fibroblasts (HGFs). Changes in molecular expression in HGF cultures due to senescent cell elimination by the senolytic drug ABT‐263 (Navitoclax) were analyzed. Results: Compared to 10‐week‐old mice, the 20‐month‐old mice had higher numbers of M1 macrophages. The proportion of cells expressing SA‐β‐gal were also higher in 20‐ month‐old mice than in 10‐week‐old‐mice. Gingival fibroblasts in 20‐month‐old mice expressed less collagen 1a1, collagen 4a1, and collagen 4a2 mRNA than those in 10‐week‐old mice. Compared to control cells, H2O2 treated HGF cells expressed higher levels of SA‐β‐gal and p16, p21, IL‐1β, and TNF‐α. Furthermore, ABT‐263 suppressed HGF cell expression of cytokines after senescence induction. Conclusions: Senescence‐associated changes were observed in the gingival tissues of aged mice and HGF cultures. In addition, the potential of senolytic drugs to modify aging‐related changes in the gingiva was shown. [ABSTRACT FROM AUTHOR]

Recognition‐driven modification has been emerging as a novel approach to modifying biomolecular targets of interest site‐specifically and efficiently. To this end, protein modular adaptors (MAs) are the ideal reaction model for recognition‐driven modification of DNA as they consist of both a sequence‐specific DNA‐binding domain (DBD) and a self‐ligating protein‐tag. Coupling DNA recognition by DBD and the chemoselective reaction of the protein tag could provide a highly efficient sequence‐specific reaction. However, combining an MA consisting of a reactive protein‐tag and its substrate, for example, SNAP‐tag and benzyl guanine (BG), revealed rather nonselective reaction with DNA. Therefore new substrates of SNAP‐tag have been designed to realize sequence‐selective rapid crosslinking reactions of MAs with SNAP‐tag. The reactions of substrates with SNAP‐tag were verified by kinetic analyses to enable the sequence‐selective crosslinking reaction of MA. The new substrate enables the distinctive orthogonality of SNAP‐tag against CLIP‐tag to achieve orthogonal DNA‐protein crosslinking by six unique MAs. [ABSTRACT FROM AUTHOR]

Van der Waals 2D heterostructures are the ideal platform for tunnel field‐effect transistors (TFETs) because of dangling‐bond‐free heterointerfaces. However, the limited selection of n+‐source materials restricts 2D‐TFET research. In this study, intrinsic electron transport properties and carrier density (n) of bulk PtS2 are experimentally examined by Hall measurements to explore its use as an n+‐source material suitable for TFETs in comparison with SnSe2. Despite the similar maximum depletion widths (WDm) and apparently metallic ID–VG curves at room temperature for both bulk samples, the Hall measurements elucidate that n ≈ 3.6 × 1017 cm−3 in PtS2 is much smaller than ≈4.7 × 1018 cm−3 in SnSe2. They also reveal that this difference comes from the depth of the donor level below the conduction band. Therefore, although band‐to‐band tunneling current is successfully observed in the n‐PtS2/p‐WSe2 TFET, VG modulates the n‐PtS2 source as well as p‐WSe2 channel due to the nondegenerate doping of PtS2, resulting in a degraded subthreshold swing. The analysis of the WDm–donor concentration (ND) relation elucidates that ND is not evaluated only by WDm but is largely affected by the energy gap. The general WDm–ND relation for different energy gaps provides a guide to select 2D materials suitable for TFETs. [ABSTRACT FROM AUTHOR]

Few-layered ReS2 with anisotropic electrical and optical properties has attracted much attention in the research field of two-dimensional (2D) materials. Recently, a stable charged exciton (trion) composed of bound states of two electrons and a hole with large binding energy has been experimentally observed in a few-layered ReS2. However, the dynamics of stable trions remain unclear. We studied the excited-state dynamics, including the radiative lifetime of the negative trion in three layer (3L)-ReS2 via temperature-dependent photoluminescence spectroscopy and phenomenological rate-equation analysis. The derived radiative lifetime of the trion increases linearly with increasing temperature, reaching a few nanoseconds at a high temperature of 150 K; this observation implies that the experimentally observed negative trion in 3L-ReS2 lies in the optically allowed state. Our results provide significant insights into the physics of excitonic states in 2D materials. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have been regarded as a promising next-generation photovoltaic technology that has shown unprecedented development in power conversion efficiency (PCE) during the last decade because of the intriguing optoelectronic qualities of perovskite materials. Although the certified PCE of PSCs has been enhanced up to 25.5% in the single-junction structure, long-term stability is still a critical restraining factor for their commercial application because the frail stability of organic–inorganic perovskite materials inevitably induces degradation of the photoactive layer, reduction in photovoltaic device performance, and increase in fabrication cost and impact potential applications. Moreover, the degradation of perovskite materials can cause leakage of lead compounds, which will lead to health and environmental issues. Therefore, it is necessary to recycle PSC components used for industrial fabrication. In this review, we discuss the necessity for recycling and different methods for recycling transparent conductive oxide substrates without/with carrier transport materials, toxic lead compounds in perovskites, metal electrodes and monolithic structures. Moreover, the recycling protocol has been discussed according to various stacked architectures. Finally, the outlook of next-stage recycling in perovskite photovoltaics has also been suggested for promoting eco-friendly large-scale fabrication and application. [ABSTRACT FROM AUTHOR]

The valley polarization dynamics of excitonic states (excitons and trions) in monolayer (1L)‐MoSe2 under strong magnetic field are investigated. The experimentally observed magnetic‐field‐induced valley polarizations of trions (excitons) are analyzed by the rate equation model. It is found that the magnetic‐field‐induced valley polarizations are attributed to the asymmetric valley scattering of trions from K+ to K− valley and vice versa due to the degeneracy lifting of K+ and K− valleys by valley Zeeman effect under magnetic field. Moreover, the feeding of the valley‐polarized excitons for trions formation and longer inter‐valley scattering time reaching to a few nanoseconds at 10 K contribute to the larger valley polarization of trions than that of excitons in 1L‐MoSe2. [ABSTRACT FROM AUTHOR]

Purpose: Although the onset mechanism of Alzheimer's disease, which co-occurs with aging, has been extensively studied, no effective methods that improve the decline in memory and learning abilities following aging have been developed. Tranexamic acid provided promising results for ameliorating photo-aging and extending the natural lifespan. However, it is unknown whether it affects the decline in memory and learning abilities due to aging. In this study, we examined the effect of tranexamic acid on memory and learning abilities of naturally aging mice. Methods: ICR mice were orally administered with tranexamic acid (12 mg/kg/day) three times weekly for 2 years, and their memory and learning abilities were compared between the tranexamic acid-treated and non-treated groups. Results: The decline in memory and learning abilities due to aging was ameliorated by tranexamic acid administration. The expression of plasmin and amyloid-β decreased following the treatment with tranexamic acid. Furthermore, the number of M1-type brain macrophages diminished and that of M2 macrophages increased. In addition, administration of tranexamic acid decreased the concentrations of interleukin (IL)-1β and tumor necrosis factor-α, while it increased the levels of IL-10 and transforming growth factor-α in the brain. Conclusion: These results indicated that tranexamic acid suppressed the secretion of the inflammatory cytokines aging M1-type macrophages, thereby improving age-related memory and learning abilities. [ABSTRACT FROM AUTHOR]

We studied the thermal conductivity of a van der Waals hetero-bilayer composed of 1L-MoS2 and 1L-MoSe2 monolayers. We determined the laser heating efficiency of the air-suspended and the h-BN-supported hetero-bilayer to be 1.2 and 0.77 K μW−1, respectively, through Raman spectroscopy. It was evaluated that the thermal conductivity of the hetero-bilayer was 115 (±25) W mK−1 using this result and numerical analysis using a heat equation. The interfacial thermal conductance between the hetero-bilayer and h-BN was also determined to be 0.9 (±0.3) MW m−2 K−1. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) using metal electrodes have been regarded as promising candidates for next‐generation photovoltaic devices because of their high efficiency, low fabrication temperature, and low cost potential. However, the complicated and rigorous thermal deposition process of metal contact electrodes remains a challenging issue for reducing the energy pay‐back period in commercial PSCs, as the ubiquitous one‐time use of a contact electrode wastes limited resources and pollutes the environment. Here, a nanoporous Au film electrode fabricated by a simple dry transfer process is introduced to replace the thermally evaporated Au electrode in PSCs. A high power conversion efficiency (PCE) of 19.0% is demonstrated in PSCs with the nanoporous Au film electrode. Moreover, the electrode is recycled more than 12 times to realize a further reduced fabrication cost of PSCs and noble metal materials consumption and to prevent environmental pollution. When the nanoporous Au electrode is applied to flexible PSCs, a PCE of 17.3% and superior bending durability of ≈98.5% after 1000 cycles of harsh bending tests are achieved. The nanoscale pores and the capability of the porous structure to impede crack generation and propagation enable the nanoporous Au electrode to be recycled and result in excellent bending durability. [ABSTRACT FROM AUTHOR]

We demonstrate the effect of p-type dopant F4TCNQ molecular adsorption on the photoluminescence (PL) and valley polarization properties of trions in monolayer (1L) MoS2 at 15 K using a spatial PL mapping method. Trion PL intensity considerably increased after the treatment, which was attributed to the extended trion nonradiative lifetime (∼70 ps). Trion valley polarization as high as 0.75 showed a negligible decrease after the chemical treatment, as is the manifestation of a long trion valley lifetime of more than nanoseconds order. The results suggest that this method will be useful for future optovalleytronics applications of these materials. [ABSTRACT FROM AUTHOR]

Novel nanotweezers consisting of two chiral porphyrins and phenanthrene in between are described. The studies have shown that only the single stereoisomer of (6,5)-single-walled carbon nanotubes (SWNTs) is highly enriched through the extraction of CoMoCAT-SWCNTs with phenanthrene-bridged chiral diporphyrin nanotweezers.