Jing Zhang

A 2D van der Waals heterostructure-based multifunctional floating gate memory device is fabricated, which exhibits superior nonvolatile electronic/optoelectronic memory behaviors when subjected to intense stimuli and volatile memory behaviors after weakening the input stimuli. Leveraging its rich dynamics, a multimodal reservoir computing system, which can pave the way for future smart computing systems at the edge, is demonstrated.

Abstract

The demand for economical and efficient data processing has led to a surge of interest in neuromorphic computing based on emerging two-dimensional (2D) materials in recent years. As a rising van der Waals (vdW) p-type Weyl semiconductor with many intriguing properties, tellurium (Te) has been widely used in advanced electronics/optoelectronics. However, its application in floating gate (FG) memory devices for information processing has never been explored. Herein, an electronic/optoelectronic FG memory device enabled by Te-based 2D vdW heterostructure for multimodal reservoir computing (RC) is reported. When subjected to intense electrical/optical stimuli, the device exhibits impressive nonvolatile electronic memory behaviors including ≈10⁸ extinction ratio, ≈100 ns switching speed, >4000 cycles, >4000-s retention stability, and nonvolatile multibit optoelectronic programmable characteristics. When the input stimuli weaken, the nonvolatile memory degrades into volatile memory. Leveraging these rich nonlinear dynamics, a multimodal RC system with high recognition accuracy of 90.77% for event-type multimodal handwritten digit-recognition is demonstrated.

Semiconducting polymer nanoparticles (SPNs) have been widely used in tumor treatment. Through modification, SPNs can encapsulate or conjugate with various types of immune modulators. This review summarizes the recent progress of SPNs-based combination cancer immunotherapy and highlights the synergetic effect that amplifies the anti-tumor immune response.

Abstract

Cancer immunotherapy has become a promising method for cancer treatment, bringing hope to advanced cancer patients. However, immune-related adverse events caused by immunotherapy also bring heavy burden to patients. Semiconducting polymer nanoparticles (SPNs) as an emerging nanomaterial with high biocompatibility, can eliminate tumors and induce tumor immunogenic cell death through different therapeutic modalities, including photothermal therapy, photodynamic therapy, and sonodynamic therapy. In addition, SPNs can work as a functional nanocarrier to synergize with a variety of immunomodulators to amplify anti-tumor immune responses. In this review, SPNs-based combination cancer immunotherapy is comprehensively summarized according to the SPNs’ therapeutic modalities and the type of loaded immunomodulators. The in-depth understanding of existing SPNs-based therapeutic modalities will hopefully inspire the design of more novel nanomaterials with potent anti-tumor immune effects, and ultimately promote their clinical translation.

Monolayer graphdiyne is synthesized by in situ acetylenic homocoupling of hexaethynylbenzene within the sub-nanometer interlayer space of Mxene. Free-standing monolayer graphdiyne flakes with micrometer-scale lateral are exfoliated from MXene interlayer assisted with ion intercalation. The free-standing monolayer graphdiyne presents excellent electronic properties which are superior to various previously reported multilayer graphdiyne materials.

Abstract

Graphdiyne (GDY) is an artificial carbon allotrope that is conceptually similar to graphene but composed of sp- and sp ²-hybridized carbon atoms. Monolayer GDY (ML-GDY) is predicted to be an ideal 2D semiconductor material with a wide range of applications. However, its synthesis has posed a significant challenge, leading to difficulties in experimentally validating theoretical properties. Here, it is reported that in situ acetylenic homocoupling of hexaethynylbenzene within the sub-nanometer interlayer space of MXene can effectively prevent out-of-plane growth or vertical stacking of the material, resulting in ML-GDY with in-plane periodicity. The subsequent exfoliation process successfully yields free-standing GDY monolayers with micrometer-scale lateral dimensions. The fabrication of field-effect transistor on free-standing ML-GDY makes the first measurement of its electronic properties possible. The measured electrical conductivity (5.1 × 10³ S m⁻¹) and carrier mobility (231.4 cm² V⁻¹ s⁻¹) at room temperature are remarkably higher than those of the previously reported multilayer GDY materials. The space-confined synthesis using layered crystals as templates provides a new strategy for preparing 2D materials with precisely controlled layer numbers and long-range structural order.

Bifacial semitransparent CuInSe₂ thin film can be diversely applicable not only to provide transparency in semitransparent solar cells, but also to achieve high power generation in tandem devices. When the semitransparent CuInSe₂ bottom cell is combined with perovskite top cell in bifacial semitransparent tandem device, it increases bifacial power generation density by aggressively utilizing the rear-side illumination.

Abstract

Although various types of bifacial solar cells exist, few studies have been conducted on bifacial semitransparent CuInSe₂ solar cells (BS-CISe SCs) despite the attractive potential in power generation from both sides in an albedo environment. The optimized BS-CISe SCs with 300 and 800 nm-thick absorber via a streamlined single-stage co-evaporation process exhibit a power conversion efficiency (PCE) of 6.32% and 10.6%, respectively. When double-sided total 2.0 sun illumination is assumed in an albedo environment, the bifacial power generation densities (BPGD) of them increases to 9.41% and 13.9%. Four-terminal bifacial semitransparent tandem solar cells (4T-BST SCs) are fabricated to increase the BPGD by mechanically stacking a BS-perovskite (PVK) top cell on top of a BS-CISe bottom cell with the 300 and 800 nm-thick absorber layers. When summed up, the best top and bottom cell PCEs of the 4T-BST SC with 300 and 800 nm-thick BS-CISe SC are 18.8% and 21.1%, respectively. However, the practical BPGD values of the 4T-BST SC under total 2 sun illumination are interestingly 23.4% and 24.4%, respectively. This is because the BS-CISe bottom cell's thickness affects how much rear-side illumination is transmitted to the BS-PVK top cell, increasing its current density and BPGD.

Nature Materials, Published online: 19 October 2023; doi:10.1038/s41563-023-01667-1

The authors report the emergence of quadrupolar excitons in WS2/WSe2/WS2 trilayer heterostructures where the electron is layer-hybridized in WS2 layers and the hole localizes in WSe2. Quadrupolar excitons exhibit distinct behaviour under electric fields, enriching exciton–exciton interactions.

Reconfigurable in situ memory of the Boolean logic gates is realized in a single Gaussian transistor, giving rise to an ultra-low transistor consumption of 13% of the silicon based logic circuits, which enables multiple image processing tasks. These findings demonstrate Gaussian transistor as a reliable device architecture to promote the advancement of parallel computing from the hardware level.

Abstract

Reconfigurable logic-in-memory device, albeit a promising hardware platform for constructing parallel computing architectures, still suffers from high power-consumption and low area-efficiency arising from the circuit redundancy in silicon (Si) based technical path. 2D materials are identified as potential building blocks to significantly reduce the circuit footprints with outstanding power-efficiency, owing to their atomically thin nature and unique electronic properties. However, the present 2D logic devices are primarily based on single channel materials with homogeneous transport polarities, limiting the device reconfigurability for multi-functional applications. Here, 2D p–n junction based dual-gate Gaussian-type transistors for simplified reconfigurable logic circuits are reported. All fundamental Boolean logic operators are implemented in a single device with electrically driven reconfigurability, giving rise to an ultra-low transistor consumption down to 13% of the traditional circuits. The device is also demonstrated as a reliable image processing unit for various computing tasks (pixel processing, comparing, and ciphering) by executing the corresponding logic operations. Moreover, in situ memory of the Boolean logics is achieved by engineering the dielectric properties of the transistor without compromising its reconfigurability. These findings provide a potential approach to achieving reconfigurable logic-in-memory operations at the hardware level, with significant implications for the advancement of parallel computing.

A universal “all-in-one” blowing strategy, that integrates the carbonization and chalcogenization processes, is developed to fabricate as many as 32 kinds of transition metal chalcogenides/carbon nanosheets composites (termed TMCs@CNS). Both physical and chemical evolution processes have been studied to reveal the blowing mechanism. The highly tunable composition and structure of the products confer on them great promise in diverse fields.

Abstract

Transition metal chalcogenides (TMCs) belongs to the most promising class of materials with unique properties and widespread applications. Coupling with carbon materials allows further enhancement of the specific performance of TMCs by mitigating their intrinsic deficiencies. However, the synthesis of a wide variety of TMCs/carbon composites with a universal strategy especially in a scalable manner remains challenging. In this work, by utilizing the gas-liquid interfaces in viscous gel precursors, an “all-in-one” blowing strategy is proposed to achieve the synchronous growth of TMCs and carbon nanosheets, obviating the additional chalcogenization process. The generality of the proposed blowing strategy is validated by the fabrication of 32 different TMCs/carbon composites, including 24 binary TMCs, 4 ternary TMCs and 4 high-entropy sulfides. In-depth mechanistic study is accomplished by investigating the physical evolution of blowing process and accompanying chemical reactions systematically. Also, the structure of the resulting foam is adjustable by controlling the heating rate and viscosity of the precursors is demonstrated. As an illustrative example for the application of energy storage, MoS_2xSe_2(1-x)@CNS exhibits great Li⁺ storage capacity and cycling stability. Overall, this methodology serves as an effective general strategy for the rational discovery of TMCs/carbon composites and inorganic solid foams.

All-electrical measurements of interconversion devices based on SrTiO₃ 2D electron gases are reported. The electrical injection of pure spin current is detected via inverse Edelstein effect as a transverse voltage in the devices. The output signal is then studied as a function of a back-gate voltage, showing a modulation of ≈50%.

Abstract

The Magnetoelectric Spin-Orbit (MESO) technology aims to bring logic into memory by combining a ferromagnet with a magnetoelectric (ME) element for information writing, and a spin-orbit (SO) element for information read-out through spin-charge conversion. Among candidate SO materials to achieve a large MESO output signal, oxide Rashba two-dimensional electron gases (2DEGs) have shown very large spin-charge conversion efficiencies, albeit mostly in spin-pumping experiments. Here, all-electrical spin-injection and spin-charge conversion experiments in nanoscale devices harnessing the inverse Edelstein effect of SrTiO₃ 2DEGs are reported. Nanodevices aredesigned, patterned, and fabricated in which a spin current injected from a cobalt layer into the 2DEG is converted into a charge current. The spin-charge conversion signal is optimized by applying back-gate voltages and studied its temperature evolution. It further disentangles the inverse Edelstein contribution from spurious effects such as the planar Hall effect, the anomalous Hall effect, or the anisotropic magnetoresistance. The combination of non-volatility and high energy efficiency of these devices can potentially lead to new technology paradigms for beyond-CMOS computing architectures.

Field-Effect Transistor-Based Biosensors

In article number 2301919, Heekyeong Park, Sunkook Kim, and co-workers develop sensitive bio-FETs for point-of-care diagnostics. It utilizes nanoporous MoS₂ channels with a non-planar Al₂O₃ dielectric layer, enabling ultra-low detection of 1 fg mL⁻¹ for a prostate cancer biomarker. The device demonstrates excellent selectivity, sensitivity, and reliability, offering promising advancements in FET-based sensor technology for future point-of-care devices.

Conducting Polymer Hydrogels

In article number 2305705, Ji Liu, Baoyang Lu, and co-workers report a strategy to fabricate conducting polymer hydrogels with anisotropic structures and mechanics through a combined freeze-casting and salting-out process. The as-fabricated conducting polymer hydrogels exhibit a high fatigue threshold, low Young's modulus, as well as long-term strain sensing robustness.

Nanoscrolls

In article number 2303526, Sefaattin Tongay and co-workers report the first packed vdW nanoscrolls made from Janus transition metal dichalcogenides through a simple one-drop solution technique. The Bohr radius difference between the top sulfurand the bottom selenium atoms within Janus M^S _Se results in a permanent compressive surface strain that acts as a nanoscroll formation catalyst after small liquid interaction.

A non-volatile III-V-on-silicon photonic phase shifter based on a HfO₂ memristor with sub-pJ switching energy (≈400 fJ) is reported, representing over an order of magnitude improvement in energy efficiency compared to the state-of-the-art. The non-volatile phase shifter can be switched reversibly using a single 100 ns pulse and exhibits excellent endurance over 800 cycles.

Abstract

Silicon photonics has evolved from lab research to commercial products in the past decade as it plays an increasingly crucial role in data communication for next-generation data centers and high-performance computing. Recently, programmable silicon photonics has also found new applications in quantum and classical information processing. A key component of programmable silicon photonic integrated circuits (PICs) is the phase shifter, traditionally realized via thermo-optic or free-carrier effects that are weak, volatile, and power hungry. A non-volatile phase shifter can circumvent these limitations by requiring zero power to maintain the switched phases. Previously non-volatile phase modulation is achieved via phase-change or ferroelectric materials, but the switching energy remains high (pico to nano joules) and the speed is slow (micro to milliseconds). Here, a non-volatile III-V-on-silicon photonic phase shifter based on a HfO₂ memristor with sub-pJ switching energy (≈400 fJ), representing over an order of magnitude improvement in energy efficiency compared to the state of the art, is reported. The non-volatile phase shifter can be switched reversibly using a single 100 ns pulse and exhibits excellent endurance over 800 cycles. This technology can enable future energy-efficient programmable PICs for data centers, optical neural networks, and quantum information processing.

The proposed platform can conveniently generate a monolithic high-speed optical helicity-dependent switching at room temperature, and more importantly, it carries full reconfigurability to control magnetic domains, which is highly desirable but far from being realized based upon the prior research results in the field.

Abstract

To address the ever-increasing need for higher speed and density of information storage, recent developments in ultrafast optical switching have focused on deterministic control of magnetic properties of materials using femtosecond circularly polarized optical pulses. However, a monolithic high-speed optical helicity-dependent switching at room temperature has remained elusive. In recent years, ultra-thin flat optical structures, known as metasurfaces, have been developed that offer a versatile way to manipulate electromagnetic fields using subwavelength spatial resolution. Here, a monolithic multilayer nanostructure capable of achieving optical helicity-dependent switching in arbitrary geometries using femtosecond meta-circularly polarized optical pulses is theoretically described and experimentally demonstrated at room temperature. The proposed monolithic meta-magnetic platform provides a practical route to reform the current data memory, storage, and information processing technologies in integrated opto-magnetic systems, holding great promise for cutting-edge applications in information, spintronics, sensing, and memory storage devices.

Nature Communications, Published online: 12 October 2023; doi:10.1038/s41467-023-41779-5

2D semiconductors have been proposed as a potential option to replace or complement silicon electronics at the nanoscale. Here, the authors discuss the recent progress and remaining challenges that need to be addressed by the academic and industrial research communities towards the commercialization of 2D transistors.

Resistive Switching

In article number 2302979, Wen-Wei Wu and co-workers systematically investigate the resistive-switching performance and mechanisms of high-entropy oxide (HEO)-based memristors. The SET/RESET behavior is induced by the migration of oxygen ions, leading to a structural transformation between spinel and rock salt. This novel high-performance resistive random-access memory (RRAM) device paves a new avenue toward memristors and holds great potential for various applications.

This review explores thin-film transistor integrated circuits (TFT ICs), highlighting their potential for enhancing healthcare, edge computing, and Internet of Things (IoT) applications. It discusses the development of various channel materials, from conventional silicon-based types to amorphous oxide semiconductors and emerging low-dimensional alternatives, and addresses manufacturing challenges and future directions in this field.

Abstract

High-performance thin-film transistors (TFTs) integrated circuits (ICs) have become increasingly necessary to meet the emerging demands such as healthcare, edge computing, and the Internet of Things, etc. This article aims to point out the potential development trends and bottlenecks of TFT ICs, enhancing their performance in terms of electronic performance, stability, consistency, CMOS design, and manufacturing capability. Basic device structures and overall metrics of TFT ICs are explored, as well as their superiority compared to silicon-based ultrathin chips. Hydrogenated amorphous silicon, low-temperature polycrystalline silicon, and amorphous oxide semiconductors are widely used in displays due to their ability to be deposited on large areas at low processing temperatures and low cost, and are validated in many prototypes for TFT ICs. Their conduction mechanisms, process flows, performance evaluation, and recent advances are comprehensively viewed. In addition, the potential of emerging low-dimensional materials as next-generation channel materials is discussed, along with their limitations and progress in this field. Finally, the major challenges in manufacturing high-performance TFT ICs and future perspectives are summarized.

Conductive hydrogel microfibers with high mechanical strength are designed via microfluidics in a one-step manner. By integrating the microfluidics with 3D printing technology, ultrastretchable electronic skin (e-skin) based on conductive hydrogel microfibers can be constructed. Benefiting from the impressive stretching and sensitivity, the e-skin realizes attractive application values in motion monitoring and gesture recognition.

Abstract

Conductive microfibers play a significant role in the flexibility, stretchability, and conductivity of electronic skin (e-skin). Currently, the fabrication of conductive microfibers suffers from either time-consuming and complex operations or is limited in complex fabrication environments. Thus, it presents a one-step method to prepare conductive hydrogel microfibers based on microfluidics for the construction of ultrastretchable e-skin. The microfibers are achieved with conductive MXene cores and hydrogel shells, which are solidified with the covalent cross-linking between sodium alginate and calcium chloride, and mechanically enhanced by the complexation reaction of poly(vinyl alcohol) and sodium hydroxide. The microfiber conductivities are tailorable by adjusting the flow rate and concentration of core and shell fluids, which is essential to more practical applications in complex scenarios. More importantly, patterned e-skin based on conductive hydrogel microfibers can be constructed by combining microfluidics with 3D printing technology. Because of the great advantages in mechanical and electrical performance of the microfibers, the achieved e-skin shows impressive stretching and sensitivity, which also demonstrate attractive application values in motion monitoring and gesture recognition. These characteristics indicate that the ultrastretchable e-skin based on conductive hydrogel microfibers has great potential for applications in health monitoring, wearable devices, and smart medicine.

By adopting the metal-assisted transfer approach, tunable metal–semiconductor contacts of Ohmic contact, Schottky contact, and asymmetric contact are achieved in Bi₂O₂Se nanosheet MSM photodetectors. With the asymmetric contact, the MSM photodetector displays the typical self-powered NIR photodetection behaviors with a low dark current of 0.04 pA, and high I _light/I _dark ratio of 380.

Abstract

Owing to the Fermi pinning effect arose in the metal electrodes deposition process, metal–semiconductor contact is always independent on the work function, which challenges the next-generation optoelectronic devices. In this work, a metal-assisted transfer approach is developed to transfer Bi₂O₂Se nanosheets onto the pre-deposited metal electrodes, benefiting to the tunable metal–semiconductor contact. The success in Bi₂O₂Se nanosheets transfer is contributed to the stronger van der Waals adhesion of metal electrodes than that of growth substrates. With the pre-deposited asymmetric electrodes, the self-powered near-infrared photodetectors are realized, demonstrating low dark current of 0.04 pA, high I _light/I _dark ratio of 380, fast rise and decay times of 4 and 6 ms, respectively, under the illumination of 1310 nm laser. By pre-depositing the metal electrodes on polyimide and glass, high-performance flexible and omnidirectional self-powered near-infrared photodetectors are achieved successfully. This study opens up new opportunities for low-dimensional semiconductors in next-generation high-performance optoelectronic devices.

Two different nanostructures of two dissimilar highly-potent active electrocatalysts, P-dopped metallic-(1T)-Fe-VSe₂ (P,Fe-(1T)-VSe₂) nanosheet and P-dopped Fe-CoSe₂ (P,Fe-CoSe₂) nanorods are hybridized and integrated into a single heterostructure (P,Fe-(VCo)Se₂) on Ni-foam for high-performance water splitting.

Abstract

Two different nanostructures of two dissimilar highly-potent active electrocatalysts, P-dopped metallic-(1T)-Fe-VSe₂ (P,Fe-1T-VSe₂) nanosheet and P-dopped Fe-CoSe₂ (P,Fe-CoSe₂) nanorods are hybridized and integrated into a single heterostructure (P,Fe-(VCo)Se₂) on Ni-foam for high-performance water splitting (WS). The catalytic efficiency of VSe₂ nanosheets is first enhanced by enriching metallic (1T)-phase, then forming bimetallic Fe-V selenide, and finally by P-doping. Similarly, the catalytic efficiency of CoSe₂ nanorods is boosted by first fabricating Fe-Co bimetallic selenide and then P-doping. To develop super-efficient electrocatalysts for WS, two individual electrocatalysts P,Fe-1T-VSe₂ nanosheet and P,Fe-CoSe₂ are hybridized and integrated to form a heterostructure (P,Fe-(VCo)Se₂). Metallic (1T)-phase of transition metal dichalcogenides has much higher conductivity than the 2H-phase, while bimetallization and P-doping activate basal planes, develop various active components, and form heterostructures that develop a synergistic interfacial effect, all of which, significantly boost the catalytic efficacy of the P,Fe-(VCo)Se₂. P,Fe-(VCo)Se₂ shows excellent performance requiring very low overpotential (η _HER = 50 mV@10 mAcm⁻² and η _OER = 230 mV@20 mAcm⁻²). P,Fe-(VCo)Se₂ (+, −) device requires a cell potential of 1.48 V to reach 10 mA cm⁻² for overall WS.

Bioinspired Artificial Visual System

In article number 2303539, Ye Zhou, Su-Ting Han, and co-workers report a 2D WSe₂-based retinal perception array that demonstrates an artificial vision system integrating sense and memory visual information. Highly linearly symmetric synaptic plasticity can be achieved based on the modulation of carrier types in WSe₂ with different thicknesses, facilitating a high level of training accuracy for optical neural networks.

Nature Nanotechnology, Published online: 10 October 2023; doi:10.1038/s41565-023-01518-9

Two-photon lithography has advantages for precise additive manufacturing at the nanoscale, but its printing speed is currently too slow for large-scale practical applications. A sensitive photoresist based on zirconium oxide hybrid nanoparticles is shown to increase the linear printing speed of two-photon lithography up to the order of metres per second.

Printed thin film nanosheet networks show remarkable promise for a range of electrical applications. Their conductivity relies heavily on their morphology, which may be altered via compression. This work provides the first exploration of the compressive properties of printed networks of graphene and MoS₂ to explore properties of elastic modulus, plastic yield, viscoelasticity, tensile failure, and sheet bending versus slippage.

Abstract

Thin film networks of solution processed nanosheets show remarkable promise for use in a broad range of applications including strain sensors, energy storage, printed devices, textile electronics, and more. While it is known that their electronic properties rely heavily on their morphology, little is known of their mechanical nature, a glaring omission given the effect mechanical deformation has on the morphology of porous systems and the promise of mechanical post processing for tailored properties. Here, this work employs a recent advance in thin film mechanical testing called the Layer Compression Test to perform the first in situ analysis of printed nanosheet network compression. Due to the well-defined deformation geometry of this unique test, this work is able to explore the out-of-plane elastic, plastic, and creep deformation in these systems, extracting properties of elastic modulus, plastic yield, viscoelasticity, tensile failure and sheet bending vs. slippage under both out of plane uniaxial compression and tension. This work characterizes these for a range of networks of differing porosities and sheet sizes, for low and high compression, as well as the effect of chemical cross linking. This work explores graphene and MoS₂ networks, from which the results can be extended to printed nanosheet networks as a whole.

The work demonstrates the exfoliation of wafer-scale GaN films and its application in flexible light-emitting diodes (LEDs). First-principles calculations reveal that the adsorption energy of Al atoms on O₂-plasma-treated h-BN is stronger than that of Ga atoms, and a strain-relaxation model for nitrides on h-BN is proposed. The flexible free-standing LED exhibits ≈66% luminescence enhancement compared to that before transfer.

Abstract

Epitaxy growth and mechanical transfer of high-quality III-nitrides using 2D materials, weakly bonded by van der Waals force, becomes an important technology for semiconductor industry. In this work, wafer-scale transferrable GaN epilayer with low dislocation density is successfully achieved through AlN/h-BN composite buffer layer and its application in flexible InGaN-based light-emitting diodes (LEDs) is demonstrated. Guided by first-principles calculations, the nucleation and bonding mechanism of GaN and AlN on h-BN is presented, and it is confirmed that the adsorption energy of Al atoms on O₂-plasma-treated h-BN is over 1 eV larger than that of Ga atoms. It is found that the introduced high-temperature AlN buffer layer induces sufficient tensile strain during rapid coalescence to compensate the compressive strain generated by the heteromismatch, and a strain-relaxation model for III-nitrides on h-BN is proposed. Eventually, the mechanical exfoliation of single-crystalline GaN film and LED through weak interaction between multilayer h-BN is realized. The flexible free-standing thin-film LED exhibits ≈66% luminescence enhancement with good reliability compared to that before transfer. This work proposes a new approach for the development of flexible semiconductor devices.

Nature Electronics, Published online: 09 October 2023; doi:10.1038/s41928-023-01039-2

Out-of-plane polarized spin current generated by the Weyl semimetal tantalum iridium telluride can be used to achieve the field-free switching of the perpendicular magnetic anisotropy ferromagnet cobalt iron boron at room temperature.

The photoluminescent property of monometallic cyanide clusterfullerenes is investigated. By encapsulating a triangular erbium (Er)-cyanide cluster into a C ₂(5)-C₈₂ cage, photoluminescence of mono-Er-metallofullerene is switched on. Combined with three medium-bandgap di-erbium-metallofullerenes, the bandgap threshold for judging whether an Er-metallofullerenes is photoluminescent is determined to be between 0.83 and 0.74 eV.

Abstract

Encapsulating photoluminescent lanthanide ions like erbium (Er) into fullerene cages affords photoluminescent endohedral metallofullerenes (EMFs). Few reported photoluminescent Er-EMFs are all based on encapsulation of multiple (two to three) metal atoms, whereas mono-Er-EMFs exemplified by Er@C₈₂ are not photoluminescent due to its narrow optical bandgap. Herein, by entrapping an Er-cyanide cluster into various C₈₂ cages to form novel Er-monometallic cyanide clusterfullerenes (CYCFs), ErCN@C₈₂ (C ₂(5), C_s (6), and C _{2 v} (9)), the photoluminescent properties of CYCFs are investigated, and obvious near-infrared (NIR) photoluminescence only is observed for ErCN@C ₂(5)-C₈₂. Combined with a comparative photoluminescence study of three medium-bandgap di-Er-EMFs, including Er₂@C_s (6)-C₈₂, Er₂O@C_s (6)-C₈₂, and Er₂C₂@C_s (6)-C₈₂, this study proposes that the optical bandgap can be used as a simple criterion for switching the photoluminescence of Er-EMFs, and the bandgap threshold is determined to be between 0.83 and 0.74 eV. Furthermore, the photoluminescent patterns of these three di-Er-EMFs differ dramatically. It is found that the location of the Er atom within the same C_s (6)-C₈₂ cage is almost fixed and independent on the endo-unit; thus the previous statement on the key role of metal position in photoluminescence of di-Er-EMFs seems erroneous, and the geometric configuration of the endo-unit, especially the bridging mode of two Er ions, is decisive instead.

This work demonstrates the emergence of robust spin-polarization in graphene on a ferrimagnetic insulating oxide Tm₃Fe₅O₁₂ (TmIG) with large spin-splitting energy of up to hundreds of meV. Moreover, the induced spin-splitting energy can be tuned over a broad range by field cooling technique. The observed spin polarization in graphene with large and tunable spin-splitting energy promises the field of 2D spintronics.

Abstract

Spin-polarized two-dimensional (2D) materials with large and tunable spin-splitting energy promise the field of 2D spintronics. While graphene has been a canonical 2D material, its spin properties and tunability are limited. Here, this work demonstrates the emergence of robust spin-polarization in graphene with large and tunable spin-splitting energy of up to 132 meV at zero applied magnetic fields. The spin polarization is induced through a magnetic exchange interaction between graphene and the underlying ferrimagnetic oxide insulating layer, Tm₃Fe₅O₁₂, as confirmed by its X-ray magnetic circular dichroism (XMCD). The spin-splitting energies are directly measured and visualized by the shift in their Landau-fan diagram mapped by analyzing the measured Shubnikov-de-Haas (SdH) oscillations as a function of applied electric fields, showing consistent fit with the first-principles and machine learning calculations. Further, the observed spin-splitting energies can be tuned over a broad range between 98 and 166 meV by field cooling. The methods and results are applicable to other 2D (magnetic) materials and heterostructures, and offer great potential for developing next-generation spin logic and memory devices.

Based on functional unit and organization (FUO) paradigm, a physical model is established to describe the effects of nanotwin units and orientation organization on mechanical properties. The predicted anisotropic elastic constants and yield strengths have comparable accuracy to molecular dynamics results with much less time cost. The model is beneficial to fast screen high mechanical-performance structure through FUO paradigm.

Abstract

Functional unit and organization (FUO) paradigm starts with functional units and assembles these functional units into specific organizations to optimize material performance. An advantage of FUO paradigm is interpretation of physical essence of traditional structure–performance relationships. Experimental achievements based on FUO paradigm abound in recent years, demanding theoretical explanations for further quantitative material design. Following FUO paradigm, here a three-step model (bond-region-structure) of nanotwin (NT) unit and orientation organization to optimize mechanical performance is established. First, anisotropic elasticities of representative bonds and assembled regional elastic constants are evaluated. Second, yield conditions of different regions, which are summarized as critical resolved shear stress (CRSS) criteria of NT structure, are quantified. Third, anisotropic yield strengths of NT structure from the regional elastic constants and CRSS criteria are derived. This FUO-based model is implemented into InSb, GaAs, and ZnS, predicted elastic constants and yield strengths are validated with molecular dynamics (MD) simulations. The method is more efficient than MD with comparable accuracy, and is also flexible to combine with density function theory and experiment. This demonstration sets foundation of NT unit and orientation organization design for achieving optimum mechanical performance.

A multi-functional platform is fabricated entirely from 2D ferroelectric semiconductor α-In₂Se₃ integrated with three functions: i) Highly distinguishable optoelectronic demodulation; ii) Reconfigurable non-volatile optoelectronic logic gates; iii) Visual information preprocessing with gate voltage modulation. The platform can respond to the lights in visible to infrared (up to 1800 nm) range. The optical-engineered ferroelectric polarization switch behavior is observed.

Abstract

2D layered semiconductors with excellent light−matter interaction and atomic-scale thickness have been envisioned as promising candidates for more than Moore and beyond Moore technologies. Here, for the first time, a multi-functional platform is reported that is fabricated entirely from wrinkle-free 2D ferroelectric semiconductor α-In₂Se₃ integrated with a photodetector, reconfigurable logic switching, and visual perception processing functions. The intensity- and wavelength-dependent resistance is used to demodulate broadband optical information into electrical signals and perform reconfigurable logic switching. Moreover, the platform offers dynamically modulated photosensitive visual sensing in different working modes at the pixel level. Using photo-assisted piezoresponse force microscopy, the optical-engineered ferroelectric polarization switch behavior is explored. The platform has excellent sensitivity to both optical and electrical stimuli and can respond to lights in the visible to short-wavelength infrared region in volatile/non-volatile manner under gate voltage modulation, with a response of 98 mA W⁻¹ (to 1800 nm light), a current on/off ratio of over 10⁶, and a high field-effect mobility of 137.55 cm² V⁻¹ s⁻¹. With its simple structure, unique photoelectric interaction, and controllable operating mechanism, the platform has the potential to simplify the complexity of neuromorphic computing circuitry systems, paving the way for high-performance hybrid technologies suitable for artificial intelligence applications.

Low-melting-point metals, including liquid metals, possess exceptional physical and chemical properties like conductivity, surface tension, and biocompatibility. The melting point significantly influences their properties and applications. This review summarizes recent studies on gallium- and bismuth-based alloys, discussing properties, applications in flexible electronics and biomedicine, and addressing opportunities and challenges. It aims to advance low-melting-point materials, particularly in biomedicine.

Abstract

In recent years, low-melting-point metals including liquid metals, exhibiting outstanding physical and chemical properties such as excellent thermal and electrical conductivity, high surface tension, and biocompatibility, have garnered increasing attention from researchers. The melting point of such metals profoundly influences their properties and determines their range of applications, and comprehending the characteristics and properties of low-melting-point metals is crucial for their future applications. Although studies related to liquid metals are growing exponentially in particular, reports exploring the properties and applications of low-melting-point metals from the perspective of the melting point are still in their early stages. This review aims to comprehensively summarize the key properties and relevant applications of current low-melting-point metals described in recent studies, focusing on gallium- and bismuth-based metal alloys. In addition, this review discusses the opportunities and challenges associated with low-melting-point metals, and it is anticipated that this review will contribute to the advancement of low-melting-point materials in the fields of flexible electronics and biomedicine, particularly for biomedical applications.

This report presents a substrate–sensor isolated, transparent, and stretchable piezoelectric strain sensor with a Lego-like reconfigurable design. This approach eliminates the need for pre-design modifications, expanding its potential applications. By adjusting stress propagation through a structural approach, the sensor demonstrates diverse responses with different geometric models. The study suggests practical uses as wearable and biomedical devices.

Abstract

Stretchable sensors that utilize machine-assisted printing techniques afford significant benefits in terms of both bulk and output uniformities. These sensors have found extensive utility across diverse fields, such as wearables, robotics, and biomedical applications. However, existing printed sensor systems, once printed, are limited in their model variations and are heavily dependent on passive materials owing to their substrate-bound nature. In this study, a printed sensor that utilizes a substrate–sensor isolation strategy is reported, thereby allowing size and design reconfigurability and a Lego-like assembly. This approach enables device customization through post-design modifications of specific sensing targets. The electrohydrodynamic printing process is utilized for sensor production, offering a high electrical bias between the substrate and nozzle during printing; this enables in situ dipole alignment, eliminating the need for a separate poling process. The mechanical and electrical stabilities of the sensors are assessed by cyclic testing at 50% strain for 1200 cycles. To illustrate the practical applications of these sensor models, sensors are implemented in wearable and in vivo biomedical applications.