One-Dimensional High-Entropy Compounds.

One-dimensional (1D) high-entropy compounds (HECs) with subnano diameters are highly attractive because long-range electron delocalization may occur along the high-entropy atomic chain, which results in extraordinary properties. Nevertheless, synthesizing such 1D HECs presents a substantial challenge, and the physicochemical attributes of these novel structures remain ambiguous. Herein, we developed a comelting-filling-freezing-modification (co-MFFM) method for synthesizing 1D high-entropy metal phosphide (HEP) by simultaneously encapsulating various metal cations within single-walled carbon nanotubes (SWCNTs) followed with a phosphorization process. The resulting 1D HEP nanowires confined within SWCNTs exhibit crucial features, including an ultrafine, high-entropy, and amorphous structure, along with a core-shell arrangement. The SWCNT as a shell could donate π electrons to 1D HEP for enhanced electron delocalization and protect 1D HEP as an atomically single-layered protective covering, thus boosting high electrocatalytic activity and stability. Moreover, the co-MFFM method demonstrates scalability for mass production and displays universal applicability to the synthesis of various 1D HECs.

Interfacial Electron Transfer in PbI2@Single-Walled Carbon Nanotube van der Waals Heterostructures for High-Stability Self-Powered Photodetectors.

Acquiring a deep insight into the electron transfer mechanism and applications of one-dimensional (1D) van der Waals heterostructures (vdWHs) has always been a significant challenge. Herein, through direct observation using aberration-corrected transmission electron microscopy (AC-TEM), we verify the stable formation of a high-quality 1D heterostructure composed of PbI2@single-walled carbon nanotubes (SWCNTs). The phenomenon of electron transfer between PbI2 and SWCNT is elucidated through spectroscopic investigations, including Raman and X-ray photoelectron spectroscopy (XPS). Electrochemical testing indicates the electron transfer and enduring stability of 1D PbI2 within SWCNTs. Moreover, leveraging the aforementioned electron transfer mechanism, we engineer self-powered photodetectors that exhibit exceptional photocurrent and a 3-order-of-magnitude switching ratio. Subsequently, we reveal its unique electron transfer behavior using Kelvin probe force microscopic (KPFM) tests. According to KPFM, the average surface potential of SWCNTs decreases by 80.6 mV after filling. Theoretical calculations illustrate a charge transfer of 0.02 e per unit cell. This work provides an effective strategy for the in-depth investigation and application of electron transfer in 1D vdWHs.

Interlayer Charge Transfer Induced Electrical Behavior Transition in 1D AgI@sSWCNT van der Waals Heterostructures.

The emergence of one-dimensional van der Waals heterostructures (1D vdWHs) opens up potential fields with unique properties, but precise synthesis remains a challenge. The utilization of mixed conductive types of carbon nanotubes as templates has imposed restrictions on the investigation of the electrical behavior and interlayer interaction of 1D vdWHs. In this study, we efficiently encapsulated silver iodide in high-purity semiconducting single-walled carbon nanotubes (sSWCNTs), forming 1D AgI@sSWCNT vdWHs. We characterized the semiconductor-metal transition and increased the carrier concentration of individual AgI@sSWCNTs via sensitive dielectric force microscopy and confirmed the results through electrical device tests. The electrical behavior transition was attributed to an interlayer charge transfer, as demonstrated by Kelvin probe force microscopy. Furthermore, we showed that this method of synthesizing 1D heterostructures can be extended to other metal halides. This work opens the door for the further exploration of the electrical properties of 1D vdWHs.

Iterative Strategy for Sorting Single-Chirality Single-Walled Carbon Nanotubes from Aqueous to Organic Systems.

Significant advancements in electronic devices and integrated circuits have been facilitated by semiconducting single-walled carbon nanotubes (SWCNTs) sorted by conjugated polymers (CPs). However, the variety of CPs with single-chirality selectivity is limited, and the sorting results are strongly dependent on the chiral distribution of the starting materials. To address this, we develop an iterative strategy to achieve single-chirality SWCNT separation from aqueous to organic systems, based on a multistep tandem extraction technique that allows a gentle and nondestructive separation of surfactants from SWCNTs, ensuring an efficient system transfer. In parallel, we refined the iterative sorting process between CPs. Employing two starting materials with narrow diameter distributions, using three CPs, we successfully sorted out five single-chirality SWCNTs of the (9,5), (8,6), (10,5), (8,7), and (11,3) species in organic systems. This strategy bridges the gap between aqueous and organic separation systems, achieving efficient complementarity between them.

Molecular Doping Modulation and Applications of Structure-Sorted Single-Walled Carbon Nanotubes: A Review.

Single-walled carbon nanotubes (SWCNTs) that have a reproducible distribution of chiralities or single chirality are among the most competitive materials for realizing post-silicon electronics. Molecular doping, with its non-destructive and fine-tunable characteristics, is emerging as the primary doping approach for the structure-controlled SWCNTs, enabling their eventual use in various functional devices. This review provides an overview of important advances in the area of molecular doping of structure-controlled SWCNTs and their applications. The first part introduces the underlying physical process of molecular doping, followed by a comprehensive survey of the commonly used dopants for SWCNTs to date. Then, it highlights how the convergence of molecular doping and structure-sorting strategies leads to significantly improved functionality of SWCNT-based field-effect transistor arrays, transparent electrodes in optoelectronics, thermoelectrics, and many emerging devices. At last, several challenges and opportunities in this field are discussed, with the hope of shedding light on promoting the practical application of SWCNTs in future electronics.

Boosting the Output Performance of the MoS2 Monolayer-Based Piezoelectric Nanogenerator by Artificial Dual Strain Concentration.

Piezoelectric nanogenerators (PENGs) with molybdenum disulfide (MoS2) monolayers have been intensively studied owing to their superior mechanical durability and stability. However, the limited output performance resulting from a small active area and low strain levels continues to pose a significant challenge that should be overcome. Herein, we report a novel strategy for the epoch-making output performance of a PENG with a MoS2 monolayer by adopting the additive strain concentration concept. The simulation study indicates that strain in the MoS2 monolayer can be initially augmented by the wavy structure resulting from the prestretched poly(dimethylsiloxane) (PDMS) and is further increased through flexural deformation (i.e., bending). Based on these studies, we have developed concentrated strain-applied PENGs with MoS2 monolayers. The wavy structures effectively applied strain to the MoS2 monolayer and generated a piezoelectric output voltage and current of around 580 mV and 47.5 nA, respectively. Our innovative approach to enhancing the performance of PENGs with MoS2 monolayers through the artificial dual strain concept has led to groundbreaking results, achieving the highest recorded output voltage and current for PENGs based on two-dimensional (2D) materials, which provides unique opportunities for the 2D-based energy harvesting field and structural insight into how to improve the net strain on 2D materials.

Unconventional polarization fatigue in van der Waals layered ferroelectric ionic conductor CuInP2S6.

Recent progress in two-dimensional ferroelectrics greatly expands the versatility and tunability in van der Waals heterostructure based electronics. However, the switching endurance issue that widely plagues conventional ferroelectrics in practical applications is hitherto unexplored for van der Waals layered ferroelectrics. Herein, we report the observation of unusual polarization fatigue behaviors in van der Waals layered CuInP2S6, which also possesses finite ionic conductivity at room temperature. The strong intertwinement of the short-range polarization switching and long-range ionic movement in conjunction with the van der Waals layered structure gives rise to unique morphological and polarization evolutions under repetitive electric cycles. With the help of concerted chemical, structural, lattice vibrational and dielectric analyses, we unravel the critical role of the synergy of ionic migration and surface oxidation on the anomalous polarization enhancement and the eventual polarization degradation. This work provides a general insight into the polarization fatigue characteristics in ionically-active van der Waals ferroelectrics and delivers potential solutions for the realization of fatigue-free capacitors.

Efficient Synthesis of Highly Crystalline One-Dimensional CrCl3 Atomic Chains with a Spin Glass State.

One-dimensional (1D) magnetic material systems have attracted widespread interest from researchers because of their peculiar physical properties and potential applications in spintronics devices. However, the synthesis of 1D magnetic atomic chains has seldom been investigated. Here, we developed an iodine-assisted vacuum chemical vapor-phase transport (I-VCVT) method, utilizing single-walled carbon nanotubes (SWCNTs) with 1D cavities as templates, and high-quality and high-efficiency fabrication of 1D atomic chains of CrCl3 was achieved. Furthermore, the structure of CrCl3 atomic chains in the confined space of SWCNTs was analyzed in detail, and the charge transfer between the 1D atomic chains and SWCNTs was investigated through spectroscopic characterization. A comprehensive study of the dynamic magnetic properties revealed the existence of spin glass states and freezing of the 1D CrCl3 atomic chains at around 3 K, which has never been seen in bulk CrCl3. Our work established an effective strategy for the control synthesis of 1D magnetic atomic chains with promising potential applications in further magnetic-based spintronics devices.

Berry Curvature Dipole Induced Giant Mid-Infrared Second-Harmonic Generation in 2D Weyl Semiconductor.

Due to its inversion-broken triple helix structure and the nature of Weyl semiconductor, 2D Tellurene (2D Te) is promising to possess a strong nonlinear optical response in the infrared region, which is rarely reported in 2D materials. Here, a giant nonlinear infrared response induced by large Berry curvature dipole (BCD) is demonstrated in the Weyl semiconductor 2D Te. Ultrahigh second-harmonic generation response is acquired from 2D Te with a large second-order nonlinear optical susceptibility (χ(2) ), which is up to 23.3 times higher than that of monolayer MoS2 in the range of 700-1500 nm. Notably, distinct from other 2D nonlinear semiconductors, χ(2) of 2D Te increases extraordinarily with increasing wavelength and reaches up to 5.58 nm V-1 at ≈2300 nm, which is the best infrared performance among the reported 2D nonlinear materials. Large χ(2) of 2D Te also enables the high-intensity sum-frequency generation with an ultralow continuous-wave (CW) pump power. Theoretical calculations reveal that the exceptional performance is attributed to the presence of large BCD located at the Weyl points of 2D Te. These results unravel a new linkage between Weyl semiconductor and strong optical nonlinear responses, rendering 2D Te a competitive candidate for highly efficient nonlinear 2D semiconductors in the infrared region.

Broadband sensory networks with locally stored responsivities for neuromorphic machine vision.

As the most promising candidates for the implementation of in-sensor computing, retinomorphic vision sensors can constitute built-in neural networks and directly implement multiply-and-accumulation operations using responsivities as the weights. However, existing retinomorphic vision sensors mainly use a sustained gate bias to maintain the responsivity due to its volatile nature. Here, we propose an ion-induced localized-field strategy to develop retinomorphic vision sensors with nonvolatile tunable responsivity in both positive and negative regimes and construct a broadband and reconfigurable sensory network with locally stored weights to implement in-sensor convolutional processing in spectral range of 400 to 1800 nanometers. In addition to in-sensor computing, this retinomorphic device can implement in-memory computing benefiting from the nonvolatile tunable conductance, and a complete neuromorphic visual system involving front-end in-sensor computing and back-end in-memory computing architectures has been constructed, executing supervised and unsupervised learning tasks as demonstrations. This work paves the way for the development of high-speed and low-power neuromorphic machine vision for time-critical and data-intensive applications.

Giant photon momentum locked THz emission in a centrosymmetric Dirac semimetal.

Strong second-order optical nonlinearities often require broken material centrosymmetry, thereby limiting the type and quality of materials used for nonlinear optical devices. Here, we report a giant and highly tunable terahertz (THz) emission from thin polycrystalline films of the centrosymmetric Dirac semimetal PtSe2. Our PtSe2 THz emission is turned on at oblique incidence and locked to the photon momentum of the incident pump beam. Notably, we find an emitted THz efficiency that is giant: It is two orders of magnitude larger than the standard THz-generating nonlinear crystal ZnTe and has values approaching that of the noncentrosymmetric topological material TaAs. Further, PtSe2 THz emission displays THz sign and amplitude that is controlled by the incident pump polarization and helicity state even as optical absorption is only weakly polarization dependent and helicity independent. Our work demonstrates how photon drag can activate pronounced optical nonlinearities that are available even in centrosymmetric Dirac materials.

Label-free plasmonic-based biosensing using a gold nanohole array chip coated with a wafer-scale deposited WS2 monolayer.

This paper reports the fabrication, testing and obtained performance of a plasmonic sensor employing a gold (Au) nanohole array chip coated with tungsten disulphide (WS2), which is then functionalized for the detection of protein-protein interactions. A key novelty is that the WS2 was deposited as a monoatomic layer using a wafer-scale synthesis method that successfully provided a film of both high quality and uniform thickness. The deposited WS2 film was transferred onto a Au nanohole array chip using a novel method and was subsequently functionalized with biotin. The final sensor was tested and it demonstrated efficient real-time and label-free plasmonic detection of biotin-streptavidin coupling. Specifically, compared to a standard (i.e. uncoated) Au nanohole-based sensor, our WS2-coated Au nanohole array boosted the spectral shift of the resonance wavelength by ∼190%, resulting in a 7.64-fold improvement of the limit of detection (LOD).

Continuously tunable ferroelectric domain width down to the single-atomic limit in bismuth tellurite.

Emerging functionalities in two-dimensional materials, such as ferromagnetism, superconductivity and ferroelectricity, open new avenues for promising nanoelectronic applications. Here, we report the discovery of intrinsic in-plane room-temperature ferroelectricity in two-dimensional Bi2TeO5 grown by chemical vapor deposition, where spontaneous polarization originates from Bi column displacements. We found an intercalated buffer layer consist of mixed Bi/Te column as 180° domain wall which enables facile polarized domain engineering, including continuously tunable domain width by pinning different concentration of buffer layers, and even ferroelectric-antiferroelectric phase transition when the polarization unit is pinned down to single atomic column. More interestingly, the intercalated Bi/Te buffer layer can interconvert to polarized Bi columns which end up with series terraced domain walls and unusual fan-shaped ferroelectric domain. The buffer layer induced size and shape tunable ferroelectric domain in two-dimensional Bi2TeO5 offer insights into the manipulation of functionalities in van der Waals materials for future nanoelectronics.

Room-temperature logic-in-memory operations in single-metallofullerene devices.

In-memory computing provides an opportunity to meet the growing demands of large data-driven applications such as machine learning, by colocating logic operations and data storage. Despite being regarded as the ultimate solution for high-density integration and low-power manipulation, the use of spin or electric dipole at the single-molecule level to realize in-memory logic functions has yet to be realized at room temperature, due to their random orientation. Here, we demonstrate logic-in-memory operations, based on single electric dipole flipping in a two-terminal single-metallofullerene (Sc2C2@Cs(hept)-C88) device at room temperature. By applying a low voltage of ±0.8 V to the single-metallofullerene junction, we found that the digital information recorded among the different dipole states could be reversibly encoded in situ and stored. As a consequence, 14 types of Boolean logic operation were shown from a single-metallofullerene device. Density functional theory calculations reveal that the non-volatile memory behaviour comes from dipole reorientation of the [Sc2C2] group in the fullerene cage. This proof-of-concept represents a major step towards room-temperature electrically manipulated, low-power, two-terminal in-memory logic devices and a direction for in-memory computing using nanoelectronic devices.

Impact of sarcopenia on intertrochanteric femoral fracture in the elderly.

Objective: The aim of this study was to investigate the effect of skeletal sarcopenia on the prognosis of intertrochanteric fracture in the elderly. Methods: We collected information on 144 patients with femoral intertrochanteric fracture (FIF). The influence of sarcopenia on the chance of death was determined using binary Probit regression analysis. For additional analysis, the Chow test was utilized to select the best distinguishing node in the instrumental activities of daily living (IADL) score. We looked for characteristics that were linked to a higher probability of death and a poor IADL outcome within 1 year. The data collected above were analyzed using logistic regression analysis. The internal calibration degree and model validity were assessed by GiViTI calibration. Results: Sarcopenia, EuroQol-5D 1 month score, age, gender, and hypertension were identified as risk factors for death in older patients with FIF within a year by logistic regression analysis. Sarcopenia, psychotropics, BMI, and length of hospital stay were all found to be risk factors for poor IADL outcomes (P < 0.1). The calibration curves indicated that the anticipated and actual probabilities of these two models were very close. The study's reliability coefficient was 0.671, showing a satisfactory level of reliability. Conclusion: In elderly patients with FIF, sarcopenia, EuroQol-5D score, age, gender, and hypertension were risk factors for death; sarcopenia, hospital stay length, BMI were risk factors for poor quality of life.

Fabrication of high-performance carbon nanotube/copper composite fibers by interface thiol-modification.

Carbon nanotube (CNT)/copper (Cu) composite fibers are placed great expectations as the next generation of light-weight, conductive wires. However, the electrical and mechanical performances still need to be enhanced. Herein, we demonstrate a strategy that is electrodeposition Cu on thiolated CNT fibers to solve the grand challenge which is enhancing the performance of CNT/Cu composite fibers. Thiol groups are introduced to the surface of the CNT fibers through a controllable O2plasma carboxylation process and amide reaction. Compared with CNT/Cu composite fibers, there are 82.7% and 29.6% improvements in electrical conductivity and tensile strength of interface thiol-modification composite fibers. The enhancement mechanism is also explored that thiolated CNT fibers could make strong interactions between Cu and CNT, enhancing the electrical and mechanical performance of CNT/Cu composites. This work proposes a convenient, heat-treatment-free strategy for high-performance CNT/Cu composite fibers, which can be manufactured for large-scale production and applied to next-generation conductive wires.

Controllable synthesis of high-quality two-dimensional tellurium by a facile chemical vapor transport strategy.

Recently, as an elementary material, tellurium (Te) has received widespread attention for its high carrier mobility, intriguing topological properties, and excellent environmental stability. However, it is difficult to obtain two-dimensional (2D) Te with high crystalline quality owing to its intrinsic helical chain structure. Herein, a facile strategy for controllable synthesis of high-quality 2D Te nanoflakes through chemical vapor transport in one step is reported. With carefully tuning the growth kinetics determined mainly by temperature, tellurium nanoflakes in lateral size of up to ∼40 µm with high crystallinity can be achieved. We also investigated the second harmonic generation of Te nanoflakes, which demonstrates that it can be used as frequency doubling crystals and has potential applications in nonlinear optical devices. In addition, field effect transistor devices based on the 2D Te nanoflakes were fabricated and exhibited excellent electrical properties with high mobility of 379 cm2 V-1 s-1.

2D PtS nanorectangles/g-C3N4 nanosheets with a metal sulfide-support interaction effect for high-efficiency photocatalytic H2 evolution.

Cocatalyst design is a key approach to acquire high solar-energy conversion efficiency for photocatalytic hydrogen evolution. Here a new in situ vapor-phase (ISVP) growth method is developed to construct the cocatalyst of 2D PtS nanorectangles (a length of ∼7 nm, a width of ∼5 nm) on the surface of g-C3N4 nanosheets. The 2D PtS nanorectangles/g-C3N4 nanosheets (PtS/CN) show an unusual metal sulfide-support interaction (MSSI), which is evidenced by atomic resolution HAADF-STEM, synchrotron-based GIXRD, XPS and DFT calculations. The effect of MSSI contributes to the optimization of geometrical structure and energy-band structure, acceleration of charge transfer, and reduction of hydrogen adsorption free energy of PtS/CN, thus yielding excellent stability and an ultrahigh photocatalytic H2 evolution rate of 1072.6 µmol h-1 (an apparent quantum efficiency of 45.7% at 420 nm), up to 13.3 and 1532.3 times by contrast with that of Pt nanoparticles/g-C3N4 nanosheets and g-C3N4 nanosheets, respectively. This work will provide a new platform for designing high-efficiency photocatalysts for sunlight-driven hydrogen generation.

Machine Learning Driven Synthesis of Few-Layered WTe2 with Geometrical Control.

Reducing the lateral scale of two-dimensional (2D) materials to one-dimensional (1D) has attracted substantial research interest not only to achieve competitive electronic applications but also for the exploration of fundamental physical properties. Controllable synthesis of high-quality 1D nanoribbons (NRs) is thus highly desirable and essential for further study. Here, we report the implementation of supervised machine learning (ML) for the chemical vapor deposition (CVD) synthesis of high-quality quasi-1D few-layered WTe2 NRs. Feature importance analysis indicates that H2 gas flow rate has a profound influence on the formation of WTe2, and the source ratio governs the sample morphology. Notably, the growth mechanism of 1T' few-layered WTe2 NRs is further proposed, which provides new insights for the growth of intriguing 2D and 1D tellurides and may inspire the growth strategies for other 1D nanostructures. Our findings suggest the effectiveness and capability of ML in guiding the synthesis of 1D nanostructures, opening up new opportunities for intelligent materials development.