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1. Unprecedented Multifunctionality in 1D Nb 1‐ x Ta x S 3 Transition Metal Trichalcogenide Alloy

   https://doi.org/10.1002/adfm.202205214  

   Hemmat, Zahra ; Ahmadiparidari, Alireza ; Wang, Shuxi ; Kumar, Khagesh ; Zepeda, Michael ; Zhang, Chengji ; Dandu, Naveen ; Rastegar, Sina ; Majidi, Leily ; Jaradat, Ahmad ; et al ( June 2022 , Advanced Functional Materials)

   1D materials, such as nanofibers or nanoribbons are considered as the future ultimate limit of downscaling for modern electrical and electrochemical devices. Here, for the first time, nanofibers of a solid solution transition metal trichalcogenide (TMTC), Nb_1‐xTa_xS₃, are successfully synthesized with outstanding electrical, thermal, and electrochemical characteristics rivaling the performance of the‐state‐of‐the art materials for each application. This material shows nearly unchanged sheet resistance (≈740 Ω sq⁻¹) versus bending cycles tested up to 90 cycles, stable sheet resistance in ambient conditions tested up to 60 days, remarkably high electrical breakdown current density of ≈30 MA cm⁻², strong evidence of successive charge density wave transitions, and outstanding thermal stability up to ≈800 K. Additionally, this material demonstrates excellent activity and selectivity for CO₂conversion to CO reaching ≈350 mA cm⁻²at −0.8 V versus RHE with a turnover frequency number of 25. It also exhibits an excellent performance in a high‐rate Li–air battery with the specific capacity of 3000 mAh g⁻¹at a current density of 0.3 mA cm⁻². This study uncovers the multifunctionality in 1D TMTC alloys for a wide range of applications and opens a new direction for the design of the next generation low‐dimensional materials.

    

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2. Scalable Core–Shell MoS 2 /Sb 2 Se 3 Nanorod Array Photocathodes for Enhanced Photoelectrochemical Water Splitting

   https://doi.org/10.1002/solr.201900442  

   Guo, Liping ; Shinde, Pravin S. ; Ma, Yanxiao ; Li, Lin ; Pan, Shanlin ; Yan, Feng ( November 2019 , Solar RRL)

   Photoelectrochemical (PEC) hydrogen generation is a promising solar energy harvesting technique to address the concerns about the ongoing energy crisis. Antimony selenide (Sb₂Se₃) with van der Waals‐bonded quasi‐1D (Q1D) nanoribbons, for instance, (Sb₄Se₆)_n, has attracted considerable interest as a light absorber with Earth‐abundant elements, suitable bandgap, and a desired sunlight absorption coefficient. By tuning its anisotropic growth behavior, it is possible to achieve Sb₂Se₃films with nanostructured morphologies that can improve the light absorption and photogenerated charge carrier separation, eventually boosting the PEC water‐splitting performance. Herein, high‐quality Sb₂Se₃films with nanorod (NR) array surface morphologies are synthesized by a low‐cost, high‐yield, and scalable close‐spaced sublimation technique. By sputtering a nonprecious and scalable crystalline molybdenum sulfide (MoS₂) film as a cocatalyst and a protective layer on Sb₂Se₃NR arrays, the fabricated core–shell structured MoS₂/Sb₂Se₃NR PEC devices can achieve a photocurrent density as high as −10 mA cm⁻²at 0 V_RHEin a buffered near‐neutral solution (pH 6.5) under a standard simulated air mass 1.5 solar illumination. The scalable manufacturing of nanostructured MoS₂/Sb₂Se₃NR array thin‐film photocathode electrodes for efficient PEC water splitting to generate solar fuel is demonstrated.

    

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3. Electrically Insulating Flexible Films with Quasi‐1D van der Waals Fillers as Efficient Electromagnetic Shields in the GHz and Sub‐THz Frequency Bands

   https://doi.org/10.1002/adma.202007286  

   Barani, Zahra ; Kargar, Fariborz ; Ghafouri, Yassamin ; Ghosh, Subhajit ; Godziszewski, Konrad ; Baraghani, Saba ; Yashchyshyn, Yevhen ; Cywiński, Grzegorz ; Rumyantsev, Sergey ; Salguero, Tina T. ; et al ( February 2021 , Advanced Materials)

   Polymer composite films containing fillers comprising quasi‐1D van der Waals materials, specifically transition metal trichalcogenides with 1D structural motifs that enable their exfoliation into bundles of atomic threads, are reported. These nanostructures are characterized by extremely large aspect ratios of up to≈10⁶. The polymer composites with low loadings of quasi‐1D TaSe₃fillers (<3 vol%) reveal excellent electromagnetic interference shielding in the X‐band GHz and extremely high frequency sub‐THz frequency ranges, while remaining DC electrically insulating. The unique electromagnetic shielding characteristics of these films are attributed to effective coupling of the electromagnetic waves to the high‐aspect‐ratio electrically conductive TaSe₃atomic‐thread bundles even when the filler concentration is below the electrical percolation threshold. These novel films are promising for high‐frequency communication technologies, which require electromagnetic shielding films that are flexible, lightweight, corrosion resistant, inexpensive, and electrically insulating.

    

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4. Turbulence in the Sub-Alfvénic Solar Wind

   https://doi.org/10.3847/2041-8213/ac51da  

   Zank, G. P. ; Zhao, L. -L. ; Adhikari, L. ; Telloni, D. ; Kasper, J. C. ; Stevens, M. ; Rahmati, A. ; Bale, S. D. ( February 2022 , The Astrophysical Journal Letters)

   The Parker Solar Probe (PSP) entered a region of sub-Alfvénic solar wind during encounter 8, and we present the first detailed analysis of low-frequency turbulence properties in this novel region. The magnetic field and flow velocity vectors were highly aligned during this interval. By constructing spectrograms of the normalized magnetic helicity, cross-helicity, and residual energy, we find that PSP observed primarily Alfvénic fluctuations, a consequence of the highly field-aligned flow that renders quasi-2D fluctuations unobservable to PSP. We extend Taylor’s hypothesis to sub- and super-Alfvénic flows. Spectra for the fluctuating forward and backward Elsässer variables (z^±, respectively) are presented, showing thatz⁺modes dominatez⁻by an order of magnitude or more, and thez⁺spectrum is a power law in frequency (parallel wavenumber)f^−3/2($k_{\parallel }^{-3/2}$) compared to the convexz⁻spectrum withf^−3/2($k_{\parallel }^{-3/2}$) at low frequencies, flattening around a transition frequency (at which the nonlinear and Alfvén timescales are balanced) tof^−1.25at higher frequencies. The observed spectra are well fitted using a spectral theory for nearly incompressible magnetohydrodynamics assuming a wavenumber anisotropy$k_{\perp }\sim k_{\parallel }^{3/4}$, that thez⁺fluctuations experience primarily nonlinear interactions, and that the minorityz⁻fluctuations experience both nonlinear and Alfvénic interactions withz⁺fluctuations. The density spectrum is a power law that resembles neither thez^±spectra nor the compressible magnetic field spectrum, suggesting that these are advected entropic rather than magnetosonic modes and not due to the parametric decay instability. Spectra in the neighboring modestly super-Alfvénic intervals are similar.

    

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5. Metallic vs. semiconducting properties of quasi-one-dimensional tantalum selenide van der Waals nanoribbons

   https://doi.org/10.1039/d1nr07772d  

   Kargar, Fariborz ; Krayev, Andrey ; Wurch, Michelle ; Ghafouri, Yassamin ; Debnath, Topojit ; Wickramaratne, Darshana ; Salguero, Tina T. ; Lake, Roger K. ; Bartels, Ludwig ; Balandin, Alexander A. ( April 2022 , Nanoscale)

   We conducted a tip-enhanced Raman scattering spectroscopy (TERS) and photoluminescence (PL) study of quasi-1D TaSe 3− δ nanoribbons exfoliated onto gold substrates. At a selenium deficiency of δ ∼ 0.25 (Se/Ta = 2.75), the nanoribbons exhibit a strong, broad PL peak centered around ∼920 nm (1.35 eV), suggesting their semiconducting behavior. Such nanoribbons revealed a strong TERS response under 785 nm (1.58 eV) laser excitation, allowing for their nanoscale spectroscopic imaging. Nanoribbons with a smaller selenium deficiency (Se/Ta = 2.85, δ ∼ 0.15) did not show any PL or TERS response. The confocal Raman spectra of these samples agree with the previously-reported spectra of metallic TaSe 3 . The differences in the optical response of the nanoribbons examined in this study suggest that even small variations in Se content can induce changes in electronic band structure, causing samples to exhibit either metallic or semiconducting character. The temperature-dependent electrical measurements of devices fabricated with both types of materials corroborate these observations. The density-functional-theory calculations revealed that substitution of an oxygen atom in a Se vacancy can result in band gap opening and thus enable the transition from a metal to a semiconductor. However, the predicted band gap is substantially smaller than that derived from the PL data. These results indicate that the properties of van der Waals materials can vary significantly depending on stoichiometry, defect types and concentration, and possibly environmental and substrate effects. In view of this finding, local probing of nanoribbon properties with TERS becomes essential to understanding such low-dimensional systems. 

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