Jiuxiang Dai

Large-area and uniform 2D covellite CuS synthesized using a deposited ultrathin Cu film via subsequent room-temperature sulfurization exhibit an anomalous Raman effect owing to charge transfer and dipole–dipole interactions between the analyte molecules and ultrathin 2D CuS.

Abstract

In surface-enhanced Raman spectroscopy (SERS), 2D materials are explored as substrates owing to their chemical stability and reproducibility. However, they exhibit lower enhancement factors (EFs) compared to noble metal-based SERS substrates. This study demonstrates the application of ultrathin covellite copper sulfide (CuS) as a cost-effective SERS substrate with a high EF value of 7.2 × 10⁴. The CuS substrate is readily synthesized by sulfurizing a Cu thin film at room temperature, exhibiting a Raman signal enhancement comparable to that of an Au noble metal substrate of similar thickness. Furthermore, computational simulations using the density functional theory are employed and time-resolved photoluminescence measurements are performed to investigate the enhancement mechanisms. The results indicate that polar covalent bonds (Cu─S) and strong interlayer interactions in the ultrathin CuS substrate increase the probability of charge transfer between the analyte molecules and the CuS surface, thereby producing enhanced SERS signals. The CuS SERS substrate demonstrates the selective detection of various dye molecules, including rhodamine 6G, methylene blue, and safranine O. Furthermore, the simplicity of CuS synthesis facilitates large-scale production of SERS substrates with high spatial uniformity, exhibiting a signal variation of less than 5% on a 4-inch wafer.

A method to prepare large-scale vertically interconnected CFETs based on a thermal evaporation process is reported. The thermally-evaporated Te and Bi₂S₃ are chosen to serve as p-type and n-type semiconductor channels. The CFET inverter exhibits a clear switching behavior, indicating that thermal evaporation provides a powerful and reliable route to facilitate vertically stacked CMOS circuits.

Abstract

With the rapid development of integrated circuits, there is an increasing need to boost transistor density. In addition to shrinking the device size to the atomic scale, vertically stacked interlayer interconnection technology is also an effective solution. However, realizing large-scale vertically interconnected complementary field-effect transistors (CFETs) has never been easy. Currently-used semiconductor channel synthesis and doping technologies often suffer from complex fabrication processes, poor vertical integration, low device yield, and inability to large-scale production. Here, a method to prepare large-scale vertically interconnected CFETs based on a thermal evaporation process is reported. Thermally-evaporated etching-free Te and Bi₂S₃ serve as p-type and n-type semiconductor channels and exhibit FET on-off ratios of 10³ and 10⁵, respectively. The vertically interconnected CFET inverter exhibits a clear switching behavior with a voltage gain of 17 at a 4 V supply voltage and a device yield of 100%. Based on the ability of thermal evaporation to prepare large-scale uniform semiconductor channels on arbitrary surfaces, repeated upward manufacturing can realize multi-level interlayer interconnection integrated circuits.

The assembly of functional materials into microstructures with enhanced features has gained prominence in various fields. Achieving high-performance electronics requires highly regular and large-scale patterns through controllable assembly methods. Liquid-assisted manipulation of materials enables controllable dewetting, regular molecule packing, and customized performances. This review summarizes recent advances in preparation technologies and diverse applications of microstructure-based electronics.

Abstract

The assembly of functional materials into microstructures, which extends unique features such as enlarged specific surface areas, effective conduction paths, higher material utilization ratios, and ordered alignment compared to continuous films, has gained prominence in various fields. Achieving high performance in electronics requires cooperation among building blocks, fabrication methods, and device design. However, the remaining challenge is obtaining highly regular and large-scale patterns with controllable assembly methods while maximizing device performances. Manipulating functional materials with liquid assistance is a feasible approach to realizing controllable dewetting, regular molecule packing, and customized performances. This review focuses on the recent advances in preparing and applying liquid-induced microstructures. The predominant preparation technologies are summarized, including flow-enabled assembly, nanoimprint lithography, and capillary-bridge-mediated assembly. Furthermore, diverse applications of various microstructure-based electronics, such as flexible and transparent electrodes, organic field-effect transistors, gas sensors, photodetectors, and solar cells, are demonstrated.

Inspired by the re-foldability of origami, a universal and programmable re-foldability strategy that can integrate multiple origami patterns into a single soft origami actuator is reported. This strategy leverages variable stiffness fibers to selectively activate and deactivate origami creases, thereby enabling a series of re-foldable soft origami actuators and multifunctional soft robots.

Abstract

Origami is a rich source of inspiration for creating soft actuators with complex deformations. However, implementing the re-foldability of origami on soft actuators remains a significant challenge. Herein, a universal and programmable re-foldability strategy is reported to integrate multiple origami patterns into a single soft origami actuator, thereby enabling multimode morphing capability. This strategy can selectively activate and deactivate origami creases through variable stiffness fibers. The utilization of these fibers enables the programmability of crease pattern quantity and types within a single actuator, which expands the morphing modes and deformation ranges without increasing their physical size and chamber number. The universality of this approach is demonstrated by developing a series of re-foldable soft origami actuators. Moreover, these soft origami actuators are utilized to construct a bidirectional crawling robot and a multimode soft gripper capable of adapting to object size, grasping orientation, and placing orientation. This work represents a significant step forward in the design of multifunctional soft actuators and holds great potential for the advancement of agile and versatile soft robots.

The intercalation and electrochemical exfoliation of layered vdW-crystal CrSBr into ferromagnetic fibers and atomically thin and few-layered nanoribbons are reported. The antiferromagnetism exhibited by multilayered CrSBr gives precedence to ferromagnetic ordering in the intercalated CrSBr. CrSBr nanoribbons to fabricate the photodetector are employed and demonstrated its responsivity up to 30 µA cm⁻² in the visible spectrum. Moreover, the CrSBr-based anode for lithium-ion batteries exhibits high performance and self-improving abilities.

Abstract

Recent studies dedicated to layered van der Waals crystals have attracted significant attention to magnetic atomically thin crystals offering unprecedented opportunities for applications in innovative magnetoelectric, magneto-optic, and spintronic devices. The active search for original platforms for the low-dimensional magnetism study has emphasized the entirely new magnetic properties of two dimensional (2D) semiconductor CrSBr. Herein, for the first time, the electrochemical exfoliation of bulk CrSBr in a non-aqueous environment is demonstrated. Notably, crystal cleavage governed by the structural anisotropy occurred along two directions forming atomically thin and few-layered nanoribbons. The exfoliated material possesses an orthorhombic crystalline structure and strong optical anisotropy, showing the polarization dependencies of Raman signals. The antiferromagnetism exhibited by multilayered CrSBr gives precedence to ferromagnetic ordering in the revealed CrSBr nanostructures. Furthermore, the potential application of CrSBr nanoribbons is pioneered for electrochemical photodetector fabrication and demonstrates its responsivity up to 30 µA cm⁻² in the visible spectrum. Moreover, the CrSBr-based anode for lithium-ion batteries exhibited high performance and self-improving abilities. This anticipates that the results will pave the way toward the future study of CrSBr and practical applications in magneto- and optoelectronics.

This work demonstrated a method for coplanar epitaxial growth of single crystals of arbitrarily shaped 2H-MoTe₂ on the etched edges of MoS₂ to obtain coplanar MoS₂−MoTe₂ heterostructures with the same crystal orientation. Furthermore, scanning transmission electron microscopy and fast Fourier transform indicate that MoTe₂ inherits the crystal orientation of MoS₂ and is seamlessly stitched with it.

Abstract

Two-dimensional (2D) coplanar heterostructure enables high-performance optoelectronic devices, such as p–n heterojunctions. However, realizing site-controllable and shape-specific 2D coplanar heterojunctions composed of two semiconductors with the same crystal orientation still requires the development of new growth methods. Here, a route to fabricate MoS₂–MoTe₂ coplanar heterojunctions with the same crystal orientation is reported by exploiting the properties of phase transition and atomic rearrangement during the growth of 2H-MoTe₂. Raman spectroscopy and electron microscopy techniques reveal the chemical composition and lattice structure of the heterostructure. Both MoS₂ and MoTe₂ in the heterojunction are single crystals and have the same lattice orientation, and their shapes can be arbitrarily defined by electron beam lithography. Electrical measurements show that the MoS₂ and MoTe₂ channels exhibit n-type and p-type transfer characteristics, respectively. The coplanar epitaxy technology can be used to prepare more coplanar heterostructures with novel device functions.

Crystalline Sb₃N₅ has been synthesized from the high-pressure and high-temperature chemical reaction of antimony and nitrogen in a laser heated diamond anvil cell. The Cmc2₁ structure of Sb₃N₅, determined by single crystal synchrotron X-ray diffraction, contains two types Sb atoms in octahedral and trigonal prismatic (square antiprismatic) coordination, respectively forming alternated double- and mono-layers stacked in the bc plane.

Abstract

A chemical reaction between Sb and N₂ was induced under high-pressure (32–35 GPa) and high-temperature (1600–2200 K) conditions, generated by a laser heated diamond anvil cell. The reaction product was identified by single crystal synchrotron X-ray diffraction at 35 GPa and room temperature as crystalline antimony nitride with Sb₃N₅ stoichiometry and structure belonging to orthorhombic space group Cmc2₁. Only Sb−N bonds are present in the covalent bonding framework, with two types of Sb atoms respectively forming SbN₆ distorted octahedra and trigonal prisms and three types of N atoms forming NSb₄ distorted tetrahedra and NSb₃ trigonal pyramids. Taking into account two longer Sb−N distances, the SbN₆ trigonal prisms can be depicted as SbN₈ square antiprisms and the NSb₃ trigonal pyramids as NSb₄ distorted tetrahedra. The Sb₃N₅ structure can be described as an ordered stacking in the bc plane of bi- layers of SbN₆ octahedra alternated to monolayers of SbN₆ trigonal prisms (SbN₈ square antiprisms). The discovery of Sb₃N₅ finally represents the long sought-after experimental evidence for Sb to form a crystalline nitride, providing new insights about fundamental aspects of pnictogens chemistry and opening new perspectives for the high-pressure chemistry of pnictogen nitrides and the synthesis of an entire class of new materials.

This paper develops an innovative and universal strategy by using a dual dielectric layer to simultaneously suppress the air breakdown and dielectric charge leakage of the triboelectric nanogenerator with high surface charge density (HCD-TENG), and the output charge density is enhanced to 2.2 mC m⁻².

Abstract

Charge generation and charge decay are two essential factors that determine the surface charge density of a triboelectric nanogenerator (TENG). However, research mainly focuses on boosting charge generation, and little attention is paid to suppressing charge decay. Here, a strategy of suppressing charge decay, including the air breakdown and dielectric charge leakage, of TENG with high surface charge density (HCD-TENG) is proposed by utilizing a dual dielectric layer. A series of parameters of different dielectric materials are tested with the assistance of a charge excitation TENG (CE-TENG) to reveal the relationships between charge generation, air breakdown, and dielectric charge leakage in the atmospheric environment. Further, the phenomenon of dielectric charge leakage limiting the maximum output of TENG prior to air breakdown is observed for the first time. With the simultaneous suppression of the air breakdown and dielectric charge leakage, the output of TENG is enhanced to 2.2 mC m⁻². This work not only provides new insight into the performance optimization and material selection of TENG, but also provides significant guidance for obtaining high-output TENG in the future.

Microfluidic channels incorporating barriers with various geometries are used. The oscillation of the inlet tube leads to the formation of vortices across the upstream and downstream of the barriers. The vortices are generated harmonically, and their size can be modulated by varying the magnitude and frequency of tube oscillation. These dynamic vortices are utilized for the mixing of liquids.

Abstract

Here, the generation of dynamic vortices across microscale barriers using the tube oscillation mechanism is demonstrated. Using a combination of high-speed imaging and computational flow dynamics, the cyclic formation, expansion, and collapse of vortices are studied. The dynamics of vortices across circular , triangular, and blade-shape barriers are investigated at different tube oscillation frequencies. The formation of an array of synchronous vortices across parallel blade-shaped barriers is demonstrated. The transient flows caused by these dynamic vortex arrays are harnessed for the rapid and efficient mixing of blood samples . A circular barrier scribed with a narrow orifice on its shoulder is used to facilitate the injection of liquid into the microfluidic channel, and its rapid mixing with the main flow through the dynamic vortices generated across the barrier. This approach facilitates the generation of vortices with desirable configurations, sizes, and dynamics in a highly controllable, programmable, and predictable manner while operating at low static flow rates.

This perspective focuses the latest advances on the growth of large-scale single-crystal two-dimensional (2D) transistion metal dichalcogenide (TMD) monolayers in the light of enhancing their industrial applicability. Recent progress and challenges of 2D TMD materials for various potential applications are highlighted.

Abstract

Due to extraordinary electronic and optoelectronic properties, large-scale single-crystal two-dimensional (2D) semiconducting transition metal dichalcogenide (TMD) monolayers have gained significant interest in the development of profit-making cutting-edge nano and atomic-scale devices. To explore the remarkable properties of single-crystal 2D monolayers, many strategies are proposed to achieve ultra-thin functional devices. Despite substantial attempts, the controllable growth of high-quality single-crystal 2D monolayer still needs to be improved. The quality of the 2D monolayer strongly depends on the underlying substrates primarily responsible for the formation of grain boundaries during the growth process. To restrain the grain boundaries, the epitaxial growth process plays a crucial role and becomes ideal if an appropriate single crystal substrate is selected. Therefore, this perspective focuses on the latest advances in the growth of large-scale single-crystal 2D TMD monolayers in the light of enhancing their industrial applicability. In the end, recent progress and challenges of 2D TMD materials for various potential applications are highlighted.

Nature Synthesis, Published online: 02 January 2024; doi:10.1038/s44160-023-00443-y

Publication date: April 2024

Source: Progress in Materials Science, Volume 142

Author(s): Yangyang Si, Tianfu Zhang, Chenhan Liu, Sujit Das, Bin Xu, Roman G. Burkovsky, Xian-Kui Wei, Zuhuang Chen

Nature Nanotechnology, Published online: 02 January 2024; doi:10.1038/s41565-023-01574-1

Through electrospinning technology coupled with SiO₂ spheres as templates, a universal approach is reported for flexible functional carbon-based membrane composed of rGO bubbles-modified N-doped porous carbon fiber embedded with few-layer MoSSe nanosheets (MoSSe/rGO-NPCF) with controllable rGO bubble arrangement. The assembled flexible K-ion capacitors and K-based dual-ion batteries with MoSSe/rGO-NPCF anode exhibit high energy/power densities and exceptional cycling stabilities.

Abstract

Widespread integration of carbon-based membranes into prevailing fields like energy storage and material engineering is thwarted by a lack of functionality, customization, and compatibility, making the development of such carbon-based membranes urgency yet challenging. Herein, a “graphene bubble bridging” strategy is adopted to fabricate the multifunctional carbon fiber membrane, in which graphene bubbles with optimized assembling not only endow the carbon fiber with superior flexibility and integrity by embedded bridging function, but also enhance the fast electron transport capability and electrolyte wettability. Few-layer MoSSe nanosheets with expanded interlayer spacing as a typical energy storage material contribute to plentiful ion intercalation/deintercalation that can be well buffered within the robust fibers. The interlaced carbon fibers enable a self-supporting framework that ensures good conductivity and mechanical stability as well. Such functional, customized, and compatible membranes with synergies can boost the attributes of advanced K⁺ storage devices, such as flexible K-ion capacitors and K-based dual-ion batteries. This work can afford new insights for designing flexible electrode in the energy storage field, as well as various types of conformations that can bring more opportunities on developing flexible functional membranes for other fields (e.g., catalysts, electromagnetic shielding).

A post-synthetic cascade resurfacing approach is developed for uniform indium antimonide (InSb) colloidal quantum dots (CQDs), which enables removal of native oxides, complete surface passivation, and electronic coupling among CQDs. Short-wave infrared photodetectors fabricated using these resurfaced CQDs as the active layer achieve the highest EQE among III–V CQD photodetectors sensitive to 1400 nm light.

Abstract

Heavy-metal-free III–V colloidal quantum dots (CQDs) are promising materials for solution-processed short-wave infrared (SWIR) photodetectors. Recent progress in the synthesis of indium antimonide (InSb) CQDs with sizes smaller than the Bohr exciton radius enables quantum-size effect tuning of the band gap. However, it has been challenging to achieve uniform InSb CQDs with band gaps below 0.9 eV, as well as to control the surface chemistry of these large-diameter CQDs. This has, to date, limited the development of InSb CQD photodetectors that are sensitive to 1400 nm light. Here we adopt solvent engineering to facilitate a diffusion-limited growth regime, leading to uniform CQDs with a band gap of 0.89 eV. We then develop a CQD surface reconstruction strategy that employs a dicarboxylic acid to selectively remove the native In/Sb oxides, and enables a carboxylate-halide co-passivation with the subsequent halide ligand exchange. We find that this strategy reduces trap density by half compared to controls, and enables electronic coupling among CQDs. Photodetectors made using the tailored CQDs achieve an external quantum efficiency of 25 % at 1400 nm, the highest among III–V CQD photodetectors in this spectral region.

This work demonstrates electrically confined electroluminescence of neutral excitons in WSe₂ light-emitting transistors (LETs). By balancing injected electrons and holes, and electrically confining neutral excitons, WSe₂ LETs exhibit strong electroluminescence with a high external quantum efficiency of ≈8.2 % at room temperature. This work shows a promising approach to enhancing efficiency and modulating the recombination of exciton complexes for 2D excitonic devices.

Abstract

Monolayer transition metal dichalcogenides (TMDs) have drawn significant attention for their potential in optoelectronic applications due to their direct band gap and exceptional quantum yield. However, TMD-based light-emitting devices have shown low external quantum efficiencies as imbalanced free carrier injection often leads to the formation of non-radiative charged excitons, limiting practical applications. Here, electrically confined electroluminescence (EL) of neutral excitons in tungsten diselenide (WSe₂) light-emitting transistors (LETs) based on the van der Waals heterostructure is demonstrated. The WSe₂ channel is locally doped to simultaneously inject electrons and holes to the 1D region by a local graphene gate. At balanced concentrations of injected electrons and holes, the WSe₂ LETs exhibit strong EL with a high external quantum efficiency (EQE) of ≈8.2 % at room temperature. These experimental and theoretical results consistently show that the enhanced EQE could be attributed to dominant exciton emission confined at the 1D region while expelling charged excitons from the active area by precise control of external electric fields. This work shows a promising approach to enhancing the EQE of 2D light-emitting transistors and modulating the recombination of exciton complexes for excitonic devices.

Nature Nanotechnology, Published online: 04 January 2024; doi:10.1038/s41565-023-01579-w

Long-term accumulation in the reticuloendothelial system restrains clinical applications of Lanthanide neodymium-based nanocrystals. Here, a biodegradable hollow virus-like neodymium oxide nanoprobe is presented and modified with cyclic arginineglycine-aspartic acid pentapeptide, showing rapid urine excretion, negligible systematic toxicity, remarkable cancer-targeting ability, and the second near-infrared fluorescence imaging features. Generally, these nanocrystals enable great potential for future clinical translation during breast-conservative surgery.

Abstract

Lanthanide neodymium (Nd)-based nanocrystals exhibit exceptional near-infrared II (NIR-II) fluorescence imaging properties, like narrow and multi-peak emissions, long luminescence lifetime, and good photostability. However, long-term accumulation in the reticuloendothelial system restrains their clinical applications due to toxicity in vivo. Here, a biodegradable hollow virus-like neodymium oxide (Nd₂O₃) Nd-nanoprobe is presented that is modified with cyclic arginine-glycine-aspartic acid (cRGD) pentapeptide, showing remarkable cancer-targeting ability and NIR-II fluorescence imaging features. The nanoprobe is biodegraded to 4–6 nm Nd₂O₃ nanogranules in vivo, and the pharmacokinetics of the nanoprobe demonstrated its rapid urine excretion and negligible systematic toxicity. Moreover, this nanoprobe can accurately identify malignant lesions from normal tissues in xenograft and transgenic mice models and precisely navigate breast cancer surgery under NIR-II imaging guidance. Taken together, this Nd₂O₃-based nanoprobe enables real-time, dynamic delineation and accurate resection of cancers guided by NIR-II fluorescence imaging with great potential for future clinical translation during breast-conservative surgery.

Nature Materials, Published online: 03 January 2024; doi:10.1038/s41563-023-01715-w

Nature Materials, Published online: 04 January 2024; doi:10.1038/s41563-023-01754-3

Nature Materials, Published online: 04 January 2024; doi:10.1038/s41563-023-01709-8