Jiuxiang Dai

The topochemical azide-alkyne cycloaddition (TAAC) reaction of a designed monomer yields a structurally perfect rope-ladder polymer in a single-crystal-to-single-crystal (SCSC) manner. The polymerization happens step-wise, first forming a topochemical cocrystal intermediate which consists of the monomer and dimer in a 1:1 ratio. A dimerization event triggers the polymerization, connecting the stiles via robust 1,5-triazolyl-linkages.

Abstract

Here, we report a single-crystal-to-single-crystal (SCSC) synthesis of a fully organic ladder polymer via a topochemical azide-alkyne cycloaddition (TAAC) reaction. A designed monomer featuring a rigid benzene core with flexible peptide-linked azide and alkyne groups crystallized with three conformers in the asymmetric unit, as evidenced by the single-crystal X-ray diffraction (SCXRD) analysis. Hydrogen bonding between the amino acid residues facilitates the organization of the monomer in a reactive geometry with inter-conformer azide-alkyne end-to-end distances within Schmidt's criteria. Upon thermal activation, two of the three monomer-conformers reacted to form a dimer, leading to an intermediate 1:1 cocrystal of monomer and dimer. The intermediate cocrystal reacted further, forming a structurally perfect ladder polymer in an SCSC manner. SCXRD analysis confirmed the regiospecificity of the reaction yielding 1,5-triazolyl linkages in both the intermediate dimer and the polymer. The polymerization process was also studied by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FT-IR). This study demonstrates the scope of topochemical polymerization strategies to synthesize architecturally attractive crystalline polymers that enable precise structural elucidation.

2D nano-quartz aerogels (QAs) with various configurations (e.g., ultrafine or hollow fiber, thin film, lightweight monolith, etc.) are all successfully cloned by chemical vapor deposition of silica source onto graphene aerogel skeletons to form ultrathin ceramic layers with carbon-leaving induced crystallization during subsequent etching of carbon atoms.

Abstract

Artificial synthesis of silica aerogel, either with crystalline quartz building blocks rather than present amorphous ones, or with greater than 0D building blocks rather than present nano-spherical ones, has become a century-old problem in light of its invention in 1931. Herein, 2D nano-quartz aerogels (QAs) with various configurations (e.g., ultrafine or hollow fiber, thin film, lightweight monolith, etc.) are all successfully cloned by chemical vapor deposition of silica source onto graphene aerogel skeletons to form ultrathin ceramic layers with carbon-leaving-induced crystallization during subsequent carbon etching. These QAs not only possess large amounts of graphene-like nanosheets with typical α-quartz phase, but exhibit ultralow density (as low as 1.5 mg cm⁻³), large specific surface area (up to 836 m² g⁻¹), superior thermal-insulation (∼20 mW m⁻¹·K⁻¹ in air), configuration-dependent flexibility, more than 600 °C higher thermal stability than traditional amorphous silica aerogel, and promising high-power (>10² W) light-scattering ability, indicating these QAs might be used as the distinct diffusers for high-power laser-driven lighting and high power laser shielding. This research might open numerous possibilities in developing quartz-like crystalline aerogels with 2D nano-building blocks.

Nature Materials, Published online: 06 May 2025; doi:10.1038/s41563-025-02222-w

A class of moiré quasiperiodic crystals with unexpected electronic properties is presented, exhibiting flat bands and correlation-induced gaps that signal the emergence of correlated quantum states.

Nature Photonics, Published online: 07 May 2025; doi:10.1038/s41566-025-01678-1

Tiniest LEDs light up

Nature Photonics, Published online: 07 May 2025; doi:10.1038/s41566-025-01661-w

Local measurements of biological voltage production are key drivers of understanding in neurobiology and neurological and cardiac pathophysiology. Researchers have now shown that exciton–trion conversion in a two-dimensional semiconductor, MoS2, can be used to optically image cardiomyocyte action-potentials in real-time.

This work provides an in-depth analysis of the interface dynamics during diamond epilayer growth on ion-implanted commercial diamond substrates. Cross-sectional microscopy and spectroscopy reveal that graphitic transformation bypasses high-temperature annealing. The epilayer demonstrates significantly higher purity and superior quality compared to the substrate. Electrochemical lift-off yields reusable substrates, advancing scalable diamond technologies for electronics and photonics.

Abstract

The development of high-quality diamond films is pivotal for driving advances in quantum technology, power electronics, and thermal management. The ion implantation and lift-off technique has emerged as a crucial method for fabricating diamond films with controlled thickness and scalable production of large-area diamond wafers. This study advances the understanding of critical interface dynamics during diamond epilayer growth on ion-implanted commercial diamond substrates. Leveraging high-resolution cross-sectional electron microscopy and spectroscopic analyses, the direct transformation of the damaged diamond layer is revealed into a graphitic layer during epilayer overgrowth, eliminating the need for high-temperature annealing. Raman and photoluminescence spectroscopy mappings along the side section highlight the exceptional quality and purity of the epilayer, showcasing nitrogen-vacancy center densities comparable to electronic-grade diamond, making it highly suitable for quantum and electronic applications. Finally, the epilayer detaches efficiently via electrochemical etching, leaving a substrate with low surface roughness that is reusable for multiple growth cycles. These results provide valuable insights into refining the ion implantation and lift-off process, bridging critical gaps in interface evolution, and establishing a foundation for sustainable, high-performance diamond films across diverse technological applications.

Catalyst-assisted chemical vapor deposition method has been developed to regulate the graphite domain size, closed-pore size, and defect level of hard carbon. The optimized hard carbon achieves a superior reversible specific capacity of 457 mAh g⁻¹ and a high initial coulomb efficiency of 90.6% at 30 mA g⁻¹.

Abstract

Hard carbon is recognized as a promising anode material for sodium-ion batteries due to its low voltage plateau and abundant availability. However, designing advanced hard carbon anodes that exhibit both high specific capacity and high initial Coulombic efficiency (ICE) remains a substantial challenge. This study introduces a catalyst-assisted chemical vapor deposition (CA-CVD) method utilizing CH₄ as the gas precursor and porous carbon as the substrate to prepare hard carbon with controllable graphite domains and rich closed pores. The optimized Fe catalyst can reduce the decomposition energy barrier of CH₄, thereby enhancing the decomposition efficiency. Besides, it can promote microstructure rearrangement of pyrolytic carbon, which extends the graphite domains and minimizes surface defects. This level of precise control allows the synthesized hard carbon to achieve a high reversible specific capacity of 457 mAh g⁻¹ and an impressive ICE of 90.6%. Furthermore, pairing such hard carbon anode with an O3-NaFe_1/3Ni_1/3Mn_1/3O₂ cathode, the assembled pouch cell maintains a specific capacity of over 400 mAh g⁻¹. This work paves the way for future advancements in the synthesis and application of hard carbon anodes, contributing significantly to the development of high-energy-density sodium-ion batteries.

A Cu_xS multilevel rod-like heterostructure with overall axial symmetry by a nanostructured epitaxial step-growth technique is prepared. It introduces localized asymmetry through variations in component hierarchy and multilevel rod dimensions, effectively addressing the aforementioned balance between wideband and strong absorption. The obtained multilevel rod-like microstructure achieves efficient broadband absorption across a 6.3 GHz bandwidth with just 2.0 mm thickness.

Abstract

When interacting with an external Electromagnetic (EM) field, symmetric nanostructures, characterized by their periodic crystalline arrangement, typically resonate at specific frequencies. This resonance enhances local electromagnetic fields, leading to strong EM absorption, yet within a narrow absorption range. Conversely, asymmetric nanostructures, distinguished by their complex electric field polarization and distributions, provide broader frequency responses, albeit with generally weaker electromagnetic loss across the broadband. Therefore, striking a balance between wideband and strong absorption using either symmetric or asymmetric nanostructures remains a challenge. Here, a nanostructured epitaxial step-growth technique is demonstrated that fabricates a Cu_xS multilevel rod-like heterostructure with overall axial symmetry. This structure introduces localized asymmetry through variations in a component hierarchy and multilevel rod dimensions during the epitaxial growth process, effectively addressing the aforementioned balance between wideband and strong absorption. Experimental evidence and theoretical simulations confirm that nanostructures possessing these characteristics achieve efficient broadband absorption across a 6.3 GHz bandwidth with just 2.0 mm thickness, owing to the generation of multiple continuous local electric fields and enhanced electric field polarization. It is convincing that this methodology and design concept hold enlightening significance for advancing material and technological innovations in the realm of broadband absorption.

In-situ atomic-scale electron microscopy reveals that vacuum-annealed ferroelectric BaTiO₃ (001) surfaces exhibit BaO termination with periodic Ba deficiency and TiO_x adunits. Planar oxygen vacancy accumulation in the subsurface TiO₂ layer mitigates the depolarization field, facilitating cooperative rumpling of surface and subsurface layers in a tail-to-tail dipole configuration, where downward polarization is relatively more stable than upward polarization.

Abstract

The interplay between surface reconstruction and depolarization of ferroelectric oxide surfaces is strongly influenced by oxygen vacancies (V_O). Using in-situ atomic-resolution electron microscopy imaging and spectroscopy techniques, it is directly observed that a clean BaTiO₃ (001) surface stabilizes into (2 × 1) BaO-terminated reconstruction during vacuum annealing. This surface reconstruction is achieved with accommodating BaO deficiency and incorporates TiO_x adunits. The cooperative atomic rumpling in both the surface and subsurface layers, arranged in a tail-to-tail configuration, is stabilized by planar accumulation of V_O in the subsurface TiO₂ layer. This reduces the net polarization of surface unit cells, contributing to overall depolarization. Under this atomic rumpling, the polarization-down (P↓) state is energetically favored over the polarization-up (P↑) state, as the P↓ state requires less atomic relaxation in the bulk layers to achieve dipole inversion at the subsurface. The energetic preference for V_O in the subsurface TiO₂ layer of the P↓ state is confirmed through calculations of V_O formation energy and the energy barrier for surface-to-subsurface migration. These findings reveal that the presence of V_O in the subsurface layer lifts the degeneracy in the double-well potential between the P↓ and P↑ states in BaTiO₃ (001).

Nature Reviews Methods Primers, Published online: 02 May 2025; doi:10.1038/s43586-025-00397-9

X-ray magnetic circular dichroism is an element-specific technique that uses circularly polarized X-rays to probe the spin and orbital magnetic moments of materials and explore their magnetic structures, including spin textures and dynamic behaviours. This Primer looks at the fundamental principles of X-ray magnetic circular dichroism, its application in advanced imaging methods and in investigating a wide array of magnetic phenomena.

Nature Communications, Published online: 02 May 2025; doi:10.1038/s41467-025-59325-w

Here, the authors demonstrate moiré collective vibrations, the mechanical counterparts of moiré excitons, at heterointerfaces of twisted tungsten diselenide/tungsten disulfide heterobilayers.

npj 2D Materials and Applications, Published online: 02 May 2025; doi:10.1038/s41699-025-00556-2

Two-dimensional materials for artificial sensory devices: advancing neuromorphic sensing technology

Monolayers of transition-metal dichalcogenides exhibit strong exciton resonances for light-matter interactions at RT, though substrate effects limit performance. This work presents a planar microcavity with a suspended WS₂ monolayer, eliminating substrate-induced losses. The system shows enhancement of strong coupling and preserves the spin-dependent polaritonic interactions, achieving a record exciton interaction constant close to theoretical predictions. This approach reveals the intrinsic optical and spintronic properties of 2D materials, paving the way for advanced polaritonic.

Abstract

Transition-metal dichalcogenides monolayers exhibit strong exciton resonances that enable intense light-matter interactions. The sensitivity of these materials to the surrounding environment and their interactions with the substrate result in the enhancement of excitonic losses through scattering, dissociation and defects formation, hindering their full potential for the excitation of optical nonlinearities in exciton-polariton platforms. The use of suspended monolayers holds the potential to completely eliminate substrate-induced losses, offering unique advantages for the exploitation of intrinsic electronic, mechanical, and optical properties of 2D materials-based polaritonic systems, without any influence of proximity effects. In this work, we report a novel fabrication approach enabling the realization of a planar microcavity filled with a suspended tungsten disulfide (WS₂) monolayer in its center. We experimentally demonstrate a 2-fold enhancement of the strong coupling at room temperature, due to the larger exciton binding energy and reduced overall losses as compared to similar systems based on dielectric-filled microcavities. As a result, spin-dependent polaritonic interactions are significantly amplified, leading to achievement of a record exciton interaction constant approaching the theoretically predicted value. This approach holds promises for pushing 2D materials-based polaritonic systems to their intrinsic limits, paving the way for the realization of novel polaritonic devices with superior performance.

The precise synthesis of 1D materials has enabled the discovery of physical properties only accessible in length scales close to the atomic scale. Herein, it is demonstrated that encapsulation within single-walled carbon nanotubes with matching diameters leads to a stoichiometric quasi-1D van der Waals polymorph of a 2D pnictogen chalcogenide, Sb₂Te₃, with a blue-shifted band gap in the short-wave infrared regime.

Abstract

The discovery and synthesis of atomically precise low-dimensional inorganic materials have led to numerous unusual structural motifs and nascent physical properties. However, access to low-dimensional van der Waals (vdW)-bound analogs of bulk crystals is often limited by chemical considerations arising from structural factors like atomic radii, bonding or coordination, and electronegativity. Using single-walled carbon nanotubes (SWCNTs) as confinement templates, we demonstrate the synthesis of a short-wave infrared-absorbing quasi-1D (q-1D) chain polymorph of Sb₂Te₃ ([Sb₄Te₆]_n) that is structurally and electronically distinct from its 2D counterpart. It is found that the q-1D chain polymorph has both three- and five-coordinate Sb atoms covalently bonded to Te and is thermodynamically stabilized by the electrostatic interaction between the encapsulated chain and the model SWCNT. The complementary experimental and computational results demonstrate the synthetic advantage of vdW nanotube confinement in the discovery of low-dimensional polytypes with drastically altered physical properties and potential applications in energy conversion processes.

A dual-stimuli-responsive photonic crystal composite film integrating chemical (photochromic) and physical (thermochromic) units. By combining UV and thermal activation, the system achieves four distinct optical states through structural and chromatic modulation. Roll-shear technology enables scalable fabrication of long-range ordered films with robust mechanical properties, offering multi-level encryption for anti-counterfeiting and dynamic displays.

Abstract

Responsive photonic crystals have garnered significant attention in recent years due to their remarkable capability of exhibiting dynamic color changes in response to external stimuli. Herein, a novel multistage anti-counterfeiting photonic crystal device that integrates chemical (luminescent material) and physical (photonic crystal structure) elements is reported. Based on photochromic materials and thermochromic capsules, a four-state thermochromic/photochromic photonic crystal (TPPC) composite film with dual responsiveness is developed through in situ emulsion polymerization and a straightforward roll shear technology. This innovative approach successfully resolved the issue of short-range order and long-range disorder in conventional photonic crystal films. Through the integration of a multilayer structure and a mask plate process, the dual effects of photochromic and thermochromic are seamlessly combined, enabling the film to exhibit four different optical states under the combined stimuli of temperature and UV light. Unlike tristate systems, the film integrates dual stimuli (UV + heat) for enhanced complexity. Notably, the film demonstrates multilevel responsiveness and dynamic decorative capabilities, allowing flexible switching between four optical states. Furthermore, the TPPC film boasts excellent mechanical properties (with a tensile strength exceeding 2 MPa), emphasizing its strong potential for applications in anti-counterfeiting, information encryption, and dynamic display technologies.

By the pulsed laser deposition (PLD), the oxygen vacancies are formed along the LaAlO₃/SrTiO₃ (LAO/STO) interface and featured with the 2D conductance. Fabricated into a pressure sensor, the LAO/STO heterojunction sensitively and repeatably responses to the environmental pressure variations, confirming feasibility of the 2D conductance toward high-performance pressure detection.

Abstract

Dominated by the pressure-origin of strain gradient, the sensitivity of pressure sensor is usually enhanced by reducing the bulk thickness. Considering the degraded robustness of the thin sensing block, it is anticipated to achieve the pressure sensing with high sensitivity and robustness. To address the trade-off between the sensitivity and stability, this investigation explores the two-dimensional (2D) conductance along the LaAlO₃/SrTiO₃ (LAO/STO) heterojunction as the pressure-sensing block. In details, by the pulsed laser deposition (PLD), LAO is synthesized on the (001) STO substrate and the oxygen vacancies are formed along the LAO/STO interface. These heterojunction vacancies exhibit 2D conductance in characterization about the magnetic-field orientation-dependent magnetoresistance. The deionization energy of the oxygen vacancy is estimated to be 0.03 eV, by which the Fermi level is lifted to enable the LAO/STO heterojunction with the metallic characteristic. Fabricated into a pressure sensor, the LAO/STO heterojunction exhibits the sensitivity of 2.9 × 10⁻⁶ Pa⁻¹ which is robust during the repeatability tests more than 100 times. It is confirmed that the 2D conductance can be explored toward pressure detection with comparable sensitivity and durativity.

Van der Waals (vdW) epitaxy of continuous, strain-free, high-crystalline quality vdW heterostructure consisting of 2D hexagonal gallium telluride (h-GaTe) on epitaxial graphene on SiC. The interlayer diffusion of adatoms plays a crucial role in achieving smooth GaTe films.

Abstract

A scalable epitaxy of 2D layered materials and heterostructures constitutes a crucial step in developing novel optoelectronic applications based on high-crystalline quality 2D materials. Here, the formation of continuous, strain-free, high-crystalline quality 2D hexagonal gallium telluride (h-GaTe) directly on epitaxial graphene using molecular beam epitaxy is demonstrated. Morphological and structural characterizations evidence a coherent layer at the heterostructure interface having an in-plane lattice constant of 4.05 ± 0.01 Ȧ$\dot{\textrm {A}}$. The few-layer thick graphene determines the epitaxial registry of the h-GaTe with grains of sixfold symmetry and a multilayer-type homoepitaxial growth. Deposition temperature- and time-dependent surface topography indicate that the interlayer diffusion of adatoms plays a crucial role in achieving smooth GaTe films. Contrastive principal component analysis allows for screening large in situ diffraction data as a function of growth parameters. In this way, the trajectory of the 2D h-GaTe growth is mapped through phase space. These results are relevant for integrating epitaxial material in the fabrication of high-performance multifunctional devices.

npj 2D Materials and Applications, Published online: 03 May 2025; doi:10.1038/s41699-025-00553-5

Andreev pair injection into a transition metal dichalcogenide monolayer

This study investigates the electrical breakdown properties of 2H-MoTe₂-based devices, demonstrating that Te dissociation, triggered by Joule heating, leads to structural instability and device failure. The role of van der Waals pinning by hBN in impeding defect initiation, thereby significantly enhancing electric-field tolerance is highlighted. This research provides novel perspective for the development of robust 2D electronic materials.

Abstract

The performance and reliability of electronic devices based on 2D materials under high electric fields are still the main issues limiting their rapid development. Many works have reported the electrical breakdown of channel materials and the breakdown electric field (E_BD) has a wide distribution spanning at least one order of magnitude. hBN encapsulation has been demonstrated to be an effective strategy to improve the electric-field tolerance of 2D materials (e.g., 2H-MoTe₂), which can effectively shield channel materials from contamination of O₂ and H₂O and further increase its E_BD. However, a new mechanism of the protective effect of hBN that is different from the widely accepted passivation effect of hBN is revealed. Combining experimental characterizations, molecular dynamics, and density functional theory simulations, it is find that the formation of the hBN/MoTe₂ interface can reduce the atomic activity of Te and introduce a physical barrier that prevents Te dissociation, ultimately improving the electric field tolerance. By employing dual hBN encapsulation and interface cleaning, the breakdown electric field and current are significantly increased by 150% and 210%, respectively. This approach offers a promising way to enhance the electric-field tolerance of 2D semiconductors and thus achieve robust 2D electronic devices.