Jiuxiang Dai

In 1865 Johann Wilhelm Hittorf discovered violet phosphorus and it took until 1969 when Thurn and Krebs determined the structure of orthogonally arranged tubes with pentagonal cross-sections. Different to their claim, the structure determined by Zhang et al. in 2020 depicted in orange is identical to the 1969 structure shown in green and should not be referenced as a new polymorph.

Abstract

The structure described in the publication “Structure of Violet Phosphorus and Its Phosphorene Exfoliation” (Angew. Chem. Int. Ed. 2020, 59, 1074–1080) is identical to the structure by Thurn and Krebs determined already in 1969 and therefore by no means a new modification.

Nature Nanotechnology, Published online: 19 April 2024; doi:10.1038/s41565-024-01650-0

Plasmonic tunnel junctions integrated with a monolayer semiconductor are found to emit photons with energies exceeding the input electrical potential. This peculiar phenomenon is ascribed to being triggered by inelastic electron tunnelling dipoles inducing optically forbidden transitions in the carrier injection electrode.

Biofabrication of biomimetic architectures leveraging on cell-rich living inks matching human tissue cellular densities can lead to unprecedented advances in generating architectures with life-like features and biofunctionalities, thus moving far beyond conventional biofabricated constructs where biomaterial-to-cell ratios remain nonphysiologic. This review showcases recent advances in the design of cell-rich inks and discusses key challenges toward translation to mainstream clinical applications.

Abstract

Advancing biofabrication toward manufacturing living constructs with well-defined architectures and increasingly biologically relevant cell densities is highly desired to mimic the biofunctionality of native human tissues. The formulation of tissue-like, cell-dense inks for biofabrication remains, however, challenging at various levels of the bioprinting process. Promising advances have been made toward this goal, achieving relatively high cell densities that surpass those found in conventional platforms, pushing the current boundaries closer to achieving tissue-like cell densities. On this focus, herein the overarching challenges in the bioprocessing of cell-rich living inks into clinically grade engineered tissues are discussed, as well as the most recent advances in cell-rich living ink formulations and their processing technologies are highlighted. Additionally, an overview of the foreseen developments in the field is provided and critically discussed.

The InBiTe₃ nanosheets-based photodetector complements the strengths and weaknesses of In₂Te₃ and Bi₂Te₃, providing a strategy for broadband detection by achieving bandgap transition and electromagnetic-induced potential well mechanism. And it realizes the performance of NEP = 75 pW Hz^-1/2 and response time τ ≈100 µs in visible to infrared band, and NEP = 6.7 × 10^-3 pW Hz^-1/2, τ ≈8 µs in terahertz region.

Abstract

Broadband room-temperature photodetection has become a pressing need as application requirements for communication, imaging, spectroscopy, and sensing have evolved. Topological insulators (TIs) have narrow bandgap structures with a wide absorption spectral response range, which should meet the requirements of broadband detection. However, owing to their high carrier concentration and low carrier mobility resulting in poor noise equivalent power (NEP), they are generally considered unsuitable for photodetection. Here, InBiTe₃ alloy nanosheet formed by doping In₂Te₃ into Bi₂Te₃(≈ 1:1) is utilized, effectively improving carrier mobility by over ten times while maintaining a narrow bandgap structure, to fabricate a broadband photodetector covering a wide response range from visible to millimeter wave (MMW). Under the synergistic multi-mechanism of the photoelectric effect in the visible−infrared region and the electromagnetic-induced potential well (EIW) effect in Terahertz band, the performance of NEP = 75 pW Hz^−1/2 and response time τ ≈100 µs in visible to infrared band and the performance of NEP = 6.7 × 10⁻³ pW Hz^−1/2, τ ≈8 µs in Terahertz region are achieved. The results demonstrate the promising prospects of topological insulator alloy (like InBiTe₃) nanosheet in optoelectronic detection applications and provide a direction for the research into high-performance broadband photoelectric detectors via TIs.

The influence of carbon toward epitaxial h-BN growth is examined using high-resolution microscopy. For most of the film, carbon induced a polytype transition from h-BN to local r-BN to turbostatic-BN ending epitaxial growth. In some localized BN structures, carbon is absent, here the epitaxial film growth is sustained to higher thickness with a uniform polytype transition from h-BN to r-BN.

Abstract

Boron nitride (BN) is a promising 2D material as well as a potential wide-bandgap semiconductor. Chemical vapor deposition (CVD) is commonly used to deposit single layers or thin films of BN, but the deposition process is insufficiently understood at an atomic scale. the CVD of BN is studied using two boron precursors, the organoboranes, triethylborane, and trimethylborane. Using high resolution (scanning) transmission electron microscopy and electron energy loss spectroscopy, this study shows that hexagonal-BN (h-BN) nucleates and grows epitaxially for ≈4 nm before it either polytype transforms to rhombohedral-BN (r-BN), turns to less ordered turbostratic-BN or is terminated by a layer of amorphous carbon. this study proposes that the carbon in the organoboranes deposits on the epitaxially growing h-BN surface and this either leads to the polytype transition to r-BN, the transition to less ordered BN growth, or complete surface poisoning with carbon terminating BN growth. These results question the use of organoboranes in CVD of epitaxial BN films, and the polytype stability of h-BN growing on graphene.

Vertically-aligned graphene helices are created through a dual-component self-assembly process, designed to generate optical chirality specifically in the terahertz (THz) range. The configuration of these vertical helices is predetermined and programmed prior to the assembly process. Once formed, the continuous monolayer graphene helices in this vertical alignment exhibit pronounced optical chirality, rendering them exceptionally suitable for applications within the THz spectrum.

Abstract

Graphene's emergence enables creating chiral metamaterials in helical shapes for terahertz (THz) applications, overcoming material limitations. However, practical implementation remains theoretical due to fabrication challenges. This paper introduces a dual-component self-assembly technique that enables creating vertically-aligned continuous monolayer graphene helices at microscale with great flexibility and high controllability. This assembly process not only facilitates the creation of 3D microstructures, but also positions the 3D structures from a horizontal to a vertical orientation, achieving an aspect ratio (height/width) of ≈2700. As a result, an array of vertically-aligned graphene helices is formed, reaching up to 4 mm in height, which is equivalent to 4 million times the height of monolayer graphene. The benefit of these 3D chiral structures made from graphene is their capability to infinitely extend in height, interacting with light in ways that are not possible with traditional 2D layering methods. Such an impressive height elevates a level of interaction with light that far surpasses what is achievable with traditional 2D layering methods, resulting in a notable enhancement of optical chirality properties. This approach is applicable to various 2D materials, promising advancements in innovative research and diverse applications across fields.

Strong and anisotropic second- and third-harmonic generation (SHG and THG) processes are observed in a novel 2D material, niobium oxide dibromide (NbOBr₂). Both SHG and THG processes in NbOBr₂ are significantly enhanced up to hundreds of times by coupling with a Fabry-Pérot (F-P) microcavity. The enhancement factor is anisotropic and reaches maximum along the crystal b–axis.

Abstract

2D materials are burgeoning as promising candidates for investigating nonlinear optical effects due to high nonlinear susceptibilities, broadband optical response, and tunable nonlinearity. However, most 2D materials suffer from poor nonlinear conversion efficiencies, resulting from reduced light-matter interactions and lack of phase matching at atomic thicknesses. Herein, a new 2D nonlinear material, niobium oxide dibromide (NbOBr₂) is reported, featuring strong and anisotropic optical nonlinearities with scalable nonlinear intensity. Furthermore, Fabry-Pérot (F-P) microcavities are constructed by coupling NbOBr₂ with air holes in silicon. Remarkable enhancement factors of ≈630 times in second harmonic generation (SHG) and 210 times in third harmonic generation (THG) are achieved on cavity at the resonance wavelength of 1500 nm. Notably, the cavity enhancement effect exhibits strong anisotropic feature tunable with pump wavelength, owing to the robust optical birefringence of NbOBr₂. The ratio of the enhancement factor along the b– and c–axis of NbOBr₂ reaches 2.43 and 5.27 for SHG and THG at 1500 nm pump, respectively, which leads to an extraordinarily high SHG anisotropic ratio of 17.82 and a 10° rotation of THG polarization. The research presents a feasible and practical strategy for developing high-efficiency and low-power-pumped on-chip nonlinear optical devices with tunable anisotropy.

A high-quality room-temperature ferromagnetic material Fe₃GaTe₂ is synthesized by the chemical vapor transport method. An unconventional room-temperature antisymmetric magnetoresistance is observed in 2D Fe₃GaTe₂ devices with the planar symmetry breaking. This work provides new routes to achieve magnetic random storage and logic devices by utilizing the room-temperature thickness-controlled antisymmetric magnetoresistance.

Abstract

Van der Waals (vdW) ferromagnetic materials have emerged as a promising platform for the development of 2D spintronic devices. However, studies to date are restricted to vdW ferromagnetic materials with low Curie temperature (T _c) and small magnetic anisotropy. Here, a chemical vapor transport method is developed to synthesize a high-quality room-temperature ferromagnet, Fe₃GaTe₂ (c-Fe₃GaTe₂), which boasts a high T _c = 356 K and large perpendicular magnetic anisotropy. Due to the planar symmetry breaking, an unconventional room-temperature antisymmetric magnetoresistance (MR) is first observed in c-Fe₃GaTe₂ devices with step features, manifesting as three distinctive states of high, intermediate, and low resistance with the sweeping magnetic field. Moreover, the modulation of the antisymmetric MR is demonstrated by controlling the height of the surface steps. This work provides new routes to achieve magnetic random storage and logic devices by utilizing the room-temperature thickness-controlled antisymmetric MR and further design room-temperature 2D spintronic devices based on the vdW ferromagnet c-Fe₃GaTe₂.

Nature Reviews Materials, Published online: 18 April 2024; doi:10.1038/s41578-024-00680-3

The increasing popularity of electric vehicles as an alternative to internal combustion engine vehicles brings new realities, challenges and opportunities for scientists and engineers. A key element of this transition will be to develop solutions for lubrication, thermal management, electrical compatibility and corrosion inhibition. Two-dimensional materials are well poised to address these challenges and enhance the performance, efficiency, durability and, hence, sustainability of electric vehicles during this century and beyond.

Nature Synthesis, Published online: 18 April 2024; doi:10.1038/s44160-024-00519-3

Monolayer gold could exhibit properties of benefit to various applications, but has been challenging to synthesize. Now, the exfoliation of two-dimensional single-atom-thick gold layers — termed goldene — is achieved through wet-chemically etching away Ti3C2 from Ti3AuC2, a nanolaminated MAX-phase. Goldene shows lattice contraction and an increase in the gold 4f binding energy compared with the bulk.

Light: Science & Applications, Published online: 19 April 2024; doi:10.1038/s41377-024-01408-2

This work studies luminescence from monocrystalline gold flakes down to 13 nm thick. It reveals this signal is photoluminescence, with signals reproduced by density functional theory, resolving a decade-old puzzle.

Proceedings of the National Academy of Sciences, Volume 121, Issue 17, April 2024.

Nature Synthesis, Published online: 16 April 2024; doi:10.1038/s44160-024-00518-4

Atomically thin gold nanosheets are predicted to have interesting properties but their synthesis is challenging. Here the exfoliation of two-dimensional single-atom-thick gold, termed goldene, is achieved through wet-chemically etching Ti3C2 from Ti3AuC2. The synthesized goldene has promising properties as a heterocatalyst.

Nature Materials, Published online: 16 April 2024; doi:10.1038/s41563-024-01862-8

Ion exchange is a powerful method to access metastable materials for energy storage, but identifying lithium and sodium interchange in layered oxides remains challenging. Using such model materials, vacancy level and corresponding lithium preference are shown to be crucial for ion exchange pathway accessibility.

This work discusses the electrical properties of domains with varying conductance in strained SrMnO₃ thin films, as probed by conducting atomic force microscopy (cAFM) and complemented by scanning electron microscopy. The temporal evolution of the domains is revealed through AFM and X-ray diffraction analysis. The microstructural analysis by transmission electron microscopy provides an understanding of their formation and stabilization.

Abstract

Domains and domain wall engineering have been extensively explored in ferroic materials for a wide range of applications in nanoelectronics and spintronics. Complex oxides exhibiting strongly correlated properties are model platforms for such studies where response to strain or external stimuli such as electric field, temperature and light can be probed. Here, domains in strained SrMnO₃ films, grown on a degenerate semiconductor, allowing for conduction in an out-of-plane geometry, are studied using a combination of microscopy probes. Using conductive atomic force microscopy, electrically isolated domains with varying conductance are found and their temporal evolution is investigated. Further, their formation and microstructure are studied using scanning transmission electron microscopy and secondary electron contrast in scanning electron microscopy. An important contribution is establishing that the observed domains are formed by cracks, driven by inhomogeneous strain relaxation throughout the film, resulting in significantly high strain planes. The potential of secondary electrons to detect domain dependent contrast over a large area, ensuing due to the use of a degenerate semiconductor correlates with the conductive properties of the domains and serves as a new direction to probe domains and domain walls in ferroic materials.

A MoS₂/Ta₂NiS₅/WSe₂ vertical double heterostructure is fabricated. Noticeably, the anti-ambipolar behavior and polarization-sensitive detection can be simultaneously achieved. An ultrahigh peak-to-valley ratio of 4.3 × 10⁴, high responsivity of 120.58 A W⁻¹, and superior photocurrent anisotropic ratio of 15.31 are obtained. This designed architecture prevails potential application in “all-in-one” integrated circuits.

Abstract

Double van der Waals heterojunctions (vdWHs) based on 2D materials showcase multifunctional properties, including anti-ambipolar behavior and polarization-sensitive photodetection capabilities, providing a new degree of freedom for the development of next-generation integrated electronics and optoelectronics. Herein, this work reports an anti-ambipolar transistor with high polarized photosensitivity based on MoS₂/Ta₂NiS₅/WSe₂ double vdWH with back-to-back type-I band alignment. It demonstrates a noticeable negative differential transconductance with an ultrahigh peak-to-valley ratio of 4.3 × 10⁴ and a bidirectional transconductance variation from 41.6 to −17.5 nS when V_D = 2 V. It is ascribed to the effective gate-modulation of the reversed band edge bending at the double vdWH interfaces. Additionally, the structure benefits from a photogating effect and the anisotropic Ta₂NiS₅ interlayer, achieving a peak responsivity of 120.58 A W⁻¹ and a decent specific detectivity of 2.65 × 10¹² Jones at V_D = 2 V and V_g = 5 V and exhibiting an exceptional photocurrent anisotropic ratio of 15.31 via the photovoltaic effect under 635 nm light. These findings not only expand the potential applications of the advanced 2D Ta₂NiS₅ material but also offer valuable insights for the development of multifunctional optoelectronic devices leveraging 2D double vdWHs.

Nature, Published online: 17 April 2024; doi:10.1038/d41586-024-01074-9

Static electricity generated by the foot striking the ground can be captured to kill pathogens.