Jing Zhang

Nature Nanotechnology, Published online: 24 July 2023; doi:10.1038/s41565-023-01454-8

Topological parameters of channels network created in twisted bilayer graphene can be controlled by lithium atoms intercalation.

Preparation of a series of long lifetime delayed fluorescence copolymers with water and temperature tolerability based on charge separated states is proposed. The P3 copolymer can emit an afterglow for 1.00 s. After immersing P3 in water for 49 days, the afterglow duration remains unchanged. Significantly, the afterglow can persist for 0.43 s at 323 K.

Abstract

Long lifetime delayed fluorescent materials have great potential applications in bioimaging, anti-counterfeiting encryption, lighting, and other fields. However, the preparation of functionalized long lifetime fluorescent materials with simple chemical structure and tunable luminescent behavior still poses significant challenges. In this article, a simple and effective method to prepare a series of long lifetime delayed fluorescent copolymers with temperature and humidity tolerance is presented. This method involves the copolymerization of 2-bromo-5-hydroxybenzaldehyde derivative monomer (M1), which contains electron-withdrawing groups, with naphthalimide derivative fluorescent monomer (M2), which contains electron-donating groups. The results demonstrate that long-range charge transfer occurs between the two components in copolymers, forming charge-separated states that emit long lifetime delayed fluorescence after exciton recombination. The delayed luminescent behavior of the copolymer is directly influenced by the content of the M2 component. The maximum delayed fluorescence lifetime can reach 13.7 ms, and the fluorescence quantum yield is 39%. Interestingly, the polymer film of P3 can emit a maximum afterglow of 1.00 s after photoactivation. Even after being immersed in water for 49 days, the afterglow remains unchanged. Besides, the afterglow of P3 can exist for ≈0.43 s at 323 K. Even at 373 K, the afterglow for 0.2 s can still be observed.

2D Cr₂O₃–CrN mosaic heterostructures consisting of a Cr₂O₃ flake with embedded CrN subdomains are synthesized by a designed chemical vapor deposition method. These mosaic heterostructures exhibit room-temperature ferromagnetism that correlates with the interface. By changing the component ratio of CrN and Cr₂O₃ in mosaic heterostructures, the magnetic properties can be modulated.

Abstract

2D magnets have generated much attention due to their potential for spintronic devices. Heterostructures of 2D magnets are interesting platforms for exploring physical phenomena and applications. However, the controlled growth of 2D room-temperature ferromagnetic heterostructures is challenging. Here, one-pot chemical vapor deposition growth of stable 2D Cr₂O₃–CrN mosaic heterostructures (MHs) is reported with a controlled ratio of components that possess robust room-temperature ferromagnetism. The 2D MHs consist of Cr₂O₃ flakes with embedded CrN subdomains and the CrN:Cr₂O₃ ratio can be tuned from 0% to 100% during growth. By changing the CrN:Cr₂O₃ ratio, the ferromagnetism of the MHs (e.g., saturation magnetization, coercive field), which originates from the interfacial coupling between Cr₂O₃ and CrN, can be controlled. Importantly, the obtained Cr₂O₃–CrN MHs are stable in air at elevated temperatures and have robust ferromagnetism with Curie temperature >400 K. This work presents a facile method for fabricating 2D MHs with tunable magnetism which will benefit high-temperature spintronics.

Nature Communications, Published online: 21 July 2023; doi:10.1038/s41467-023-40123-1

Crystalline high-κ dielectric materials are desired for the development of future 2D electronic devices. Here, the authors report the in-plane and out-of-plane chemical vapor deposition growth of ultrathin Bi2SiO5 crystals with dielectric constant >30 and a band gap of ~3.8 eV, showing their effective application as gate dielectric layers of MoS2 transistors.

“MAPLA” employs magnetic-field-assisted pulse laser annealing to control perovskite crystal orientation on substrates, enhancing crystal size, orientation, and stability. Magnetic nanoparticles guide orientational gathering into nanoclusters. Device performance improves with responsivity and detectivity increasing two times, and photocurrent three orders higher than pulsed laser annealing. MAPLA enhances stability by preventing Pb²⁺ reduction, making MAPLA promising for stable electro-optical thin films.

Abstract

The orientation of crystals on the substrate and the presence of defects are critical factors in electro-optic performance. However, technical approaches to guide the orientational crystallization of electro-optical thin films remain challenging. Here, a novel physical method called magnetic-field-assisted pulse laser annealing (MAPLA) for controlling the orientation of perovskite crystals on substrates is reported. By inducing laser recrystallization of perovskite crystals under a magnetic field and with magnetic nanoparticles, the optical and magnetic fields are found to guide the orientational gathering of perovskite units into nanoclusters, resulting in perovskite crystals with preferred lattice orientation in (110) and (220) perpendicular to the substrate. The perovskite crystals obtained by MAPLA exhibit significantly larger grain size and fewer defects compared to those from pulsed laser annealing (PLA) and traditional thermal annealing, resulting in improved carrier lifetime and mobility. Furthermore, MAPLA demonstrates enhanced device performance, increasing responsivity and detectivity by two times, and photocurrent by nearly three orders compared with PLA. The introduction of Fe₂O₃ nanoparticles during MAPLA not only improves crystal size and orientation but also significantly enhances long-term stability by preventing Pb²⁺ reduction. The MAPLA method has great potential for fabricating many electro-optical thin films with desired device properties and stability.

Two ultrastrong magnon–magnon couplings and one chirality switching process are demonstrated in antiferromagnet CrPS₄, and the magnetocrystalline anisotropy is shown to play a key role in these observed physical mechanisms. As magnetic anisotropy can be easily controlled by electric ways, these findings offer a straightforward route for quantum information and spintronic applications based on antiferromagnetic dynamics.

Abstract

As new information carriers, antiferromagnetic magnons have great potential in the fields of spintronics and quantum information. However, the strong exchange interaction between sublattice spins in conventional antiferromagnets results in their frequencies up to the terahertz (THz) range, hindering further exploration of related applications and physics. Recently, emerging van der Waals A-type antiferromagnets with the weak exchange interaction may bring about a change. In this study, it demonstrates two distinct tunable ultrastrong magnon–magnon couplings in the gigahertz (GHz) band using this type of antiferromagnet, CrPS₄, with a maximum normalized coupling strength (η) of 0.31. It establishes orthorhombic and monoclinic models for theoretical analyses, unambiguously showing that the ultrastrong coupling strength is caused by unique magnetocrystalline anisotropy rather than exchange enhancement. Furthermore, for the first time, it observes a continuous switching process of sublattice magnon chirality arising from the orthorhombic nature of anisotropy. These findings not only deepen the understanding of antiferromagnetic spin dynamics but also offer a powerful platform for building magnonic quantum systems and chirality-based spintronics.

Ferroelastic domain exhibits great importance in thin film design and optimization. While current studies focus on their 2D domain wall characteristics, this study improves the understanding of ferroelastic domain from 2D to 3D. Specifically, it identifies the presence of ferroelectric and dislocation characteristics on the lateral side of the domain wall, which dominate their 3D domain propagation.

Abstract

Perovskite ferroelectric thin films exhibit unique dielectric and piezoelectric properties owing to their internal polarized domains that accommodate the out-of-plane (ferroelectric) and in-plane (ferroelastic) polarization-induced electrostatic and elastic energy. These domains are generally treated as 2D defects with distinctive differences in domain morphology and domain-wall characteristics, although they are indeed 3D volumetric defects. Here, by using atomistic simulation and microscopy characterization, a “pseudo-ferroelectric domain” that has the morphology similar to a ferroelectric domain but holds the same defect character of ferroelastic domain-wall, i.e., semi-coherent (100) _matrix ||(100) _domain interface is identified. Such pseudo-ferroelectric domain walls will play a critical role in the migration kinetics of ferroelastic domains and in the piezoelectric responses of ferroelectric thin films during cyclic mechanical/electrical loading. The study throws light on a novel aspect of domains, namely, the 3D configuration and mobility of domain walls, and their role in the overall domain engineering.

Nature Nanotechnology, Published online: 20 July 2023; doi:10.1038/s41565-023-01445-9

Interaction of two-dimensional transition metal dichalcogenide grains with exposed oxygen–aluminium atomic plane in sapphire is a more dominant factor than step-edge docking in controlling the single-crystal epitaxy of these materials.

Nature, Published online: 19 July 2023; doi:10.1038/s41586-023-06290-3

Transport measurements of dual-gated devices constructed by slightly rotating a monolayer graphene sheet atop a thin bulk graphite crystal are performed, showing that moiré potential transforms the electronic properties of an entire graphitic thin film.

Nature, Published online: 19 July 2023; doi:10.1038/s41586-023-06264-5

The electronic states in three-dimensional crystals such as graphite can be tuned by a superlattice potential occurring at the interface with crystallographically aligned hexagonal boron nitride.

Nature, Published online: 19 July 2023; doi:10.1038/s41586-023-06294-z

A moiré quasicrystal constructed by twisting three layers of graphene with two different twist angles shows high tunability between a periodic-like regime at low energies and a strongly quasiperiodic regime at higher energies alongside strong interactions and superconductivity.

Intercalation anodes that accommodate large-sized potassium usually experience significant layer expansion and structural distortion, leading to severe capacity decay. This study demonstrates that 1T’’’ MoS₂ with corner-sharing Mo₃ triangular trimers and puckered S interlayer can speed up electron transfer and achieve uniform K⁺ insertion, which ultimately shows excellent cycle stability.

Abstract

Intercalation anodes usually exhibit better cyclability than conversion and alloying anodes for lithium or sodium storage due to the robust layered structure. However, for larger-sized potassium accommodation, these intercalation anodes usually undergo huge layer expansion and structural distortion, triggering severe capacity fading. Herein, the novel 1T’’’ MoS₂ is revealed the intercalation anode for stable K⁺ storage, in which metallic Mo─Mo bonds and puckered S layers accelerate the charge transfer and homogeneous K⁺ insertion. Moreover, the ultralow strain (3.5%) induced by the non-detachable potassium ions pillar sustains the layered structure. Consequently, 1T’’’ MoS₂ achieves a reversible capacity of 125 mA h g⁻¹ at 0.2 C and keeps nearly 100% capacity retention at 1 C over 500 cycles. In situ characterizations and density functional theory simulations reveal the in-depth intercalation reaction accompanied by the MoS₂ phase transformation between 1T’’’ and 1T’ during cycling. Furthermore, a 1T’’’ MoS₂//MCMB K-dual ion battery displays a superior cycling lifespan with 98% capacity retention over 250 cycles. This study provides a new intercalation anode and contribute to the electrode design for stable potassium ion storage.

Nature Nanotechnology, Published online: 19 July 2023; doi:10.1038/s41565-023-01472-6

‘Rotating’ contact for bias-free photodetection with 2D materials

A monolithic three-dimensional (M3D) design is proposed to construct ultra-flexible complementary metal-oxide-semiconductor electronics with high electrical-performance and integration by stacking n- and p-type transistors vertically and saving inter tier vias used in conventional M3D structure. The ultra-flexible and high-integration circuits enable a wearable light recorder to collect the harmful blue light illuminated into human eyes by attaching the circuits on a contact lens.

Abstract

Flexible electronics based on complementary metal-oxide-semiconductor (CMOS) technology have enabled a smart soft world. However, the trade-off among flexibility, density, and electrical performance has been a long-lasting unresolved issue. Here, a monolithic three-dimensional (M3D) CMOS design is proposed to address this problem and realize ultra-flexible electronics with high electronic-performance and integration. This design utilizes vertically stacked p-type carbon nanotube transistors and n-type indium gallium zinc oxide ones, which share common gates and drains, saving the inter tier vias required in the traditional M3D structure to reduce routing and improve flexibility. With this design, CMOS logic gates, multi-stage circuits, ring oscillators (ROs) and memory modules, are demonstrated. This design enables circuits to save up to 45% of area compared with their planar counterparts. Particularly, inverters exhibit a record-high gain of 191, and 55-stage ROs can operate well even after bending at a 500-µm radius for 50 cycles, exhibiting the highest flexibility among the reported ones. The ultra-flexible and high-integration RO enables a wearable light recorder to collect harmful blue light shining into human eyes by simply attaching the circuits on a contact lens. This integration method provides possibilities for developing complex-function wearable electronics.

Nature Photonics, Published online: 17 July 2023; doi:10.1038/s41566-023-01250-9

By engineering the plasmonic response of a nanopatterned silver gate electrode, the radiative decay rate of excitons in a tungsten disulfide monolayer can be enhanced via the Purcell effect, creating high modulation efficiencies at room temperature.

Nature Electronics, Published online: 17 July 2023; doi:10.1038/s41928-023-00983-3

Aligned carbon nanotubes can be used to create six-transistor static random-access memory cells with an area of less than 1 μm2 and performance superior to cells made using 90-nm-node silicon transistors, as well as field-effect transistors with scaled contacted gate pitch comparable with the 10 nm silicon technology node.

This study explores the potential of lanthanum oxide (La₂O₃) for resistive switching (RS) applications. The devices display bipolar RS characteristics with excellent endurance and stable retention properties and mimicking bio-synaptic behavior. The results demonstrate that La₂O₃ is a promising solid electrolyte for non-volatile memory and brain-inspired applications.

Abstract

In recent years, many metal oxides have been rigorously studied to be employed as solid electrolytes for resistive switching (RS) devices. Among these solid electrolytes, lanthanum oxide (La₂O₃) is comparatively less explored for RS applications. Given this, the present work focuses on the electrodeposition of La₂O₃ switching layers and the investigation of their RS properties for memory and neuromorphic computing applications. Initially, the electrodeposited La₂O₃ switching layers are thoroughly characterized by various analytical techniques. The electrochemical impedance spectroscopy (EIS) and Mott–Schottky techniques are probed to understand the in situ electrodeposition, RS mechanism, and n-type semiconducting nature of the fabricated La₂O₃ switching layers. All the fabricated devices exhibit bipolar RS characteristics with excellent endurance and stable retention. Moreover, the device mimics the various bio-synaptic properties such as potentiation-depression, excitatory post-synaptic currents, and paired-pulse facilitation. It is demonstrated that the fabricated devices are non-ideal memristors based on double-valued charge-flux characteristics. The switching variation of the device is studied using the Weibull distribution technique and modeled and predicted by the time series analysis technique. Based on electrical and EIS results, a possible filamentary-based RS mechanism is suggested. The present results assert that La₂O₃ is a promising solid electrolyte for memory and brain-inspired applications.

Atomically thin 2D oxide crystals have attracted considerable attention owing to their remarkable physical properties and great potential for versatile applications. This review discusses the recent progress in the synthesis of 2D oxide crystals for applications in electronics, optoelectronics, magnetics, and ferroelectric devices. Finally, the challenges and prospects in this exciting field are discussed.

Abstract

Atomically thin two-dimensional (2D) oxide crystals have garnered considerable attention because of their remarkable physical properties and potential for versatile applications. In recent years, significant advancements have been made in the design, preparation, and application of ultrathin 2D oxides, providing many opportunities for new-generation advanced technologies. This review focuses on the controllable preparation of 2D oxide crystals and their applications in electronic and optoelectronic devices. Based on their bonding nature, the various types of 2D oxide crystals are first summarized, including both layered and nonlayered crystals, as well as their current top-down and bottom-up synthetic approaches. Subsequently, in terms of the unique physical and electrical properties of 2D oxides, recent advances in device applications are emphasized, including photodetectors, field-effect transistors, dielectric layers, magnetic and ferroelectric devices, memories, and gas sensors. Finally, conclusions and future prospects of 2D oxide crystals are presented. It is hoped that this review will provide comprehensive and insightful guidance for the development of 2D oxide crystals and their device applications.

Modifications to improve the optical properties of devices based on indirect bandgap transition metal dichalcogenides and their emerging applications in optoelectronic sensors are the focus of this review. Various engineering techniques are discussed to overcome their limitations derived from the indirect bandgap of multilayer transition metal dichalcogenides as well as future directions of these materials for optoelectronic applications.

Abstract

The unique electrical and optical properties of transition metal dichalcogenides (TMDs) make them attractive nanomaterials for optoelectronic applications, especially optical sensors. However, the optical characteristics of these materials are dependent on the number of layers. Monolayer TMDs have a direct bandgap that provides higher photoresponsivity compared to multilayer TMDs with an indirect bandgap. Nevertheless, multilayer TMDs are more appropriate for various photodetection applications due to their high carrier density, broad spectral response from UV to near-infrared, and ease of large-scale synthesis. Therefore, this review focuses on the modification of the optical properties of devices based on indirect bandgap TMDs and their emerging applications. Several successful developments in optical devices are examined, including band structure engineering, device structure optimization, and heterostructures. Furthermore, it introduces cutting-edge techniques and future directions for optoelectronic devices based on multilayer TMDs.

A cucurbit[7]uril-confined tunable full-color luminescent lanthanide supramolecular assembly is constructed by CB[7], naphthylimidazolium dicarboxylic acid, lanthanide, and carbon quantum dots, which is applied to the multi-level logic gate and intelligent multicolor anti-counterfeiting inks.

Abstract

Macrocyclic confinement-induced supramolecular luminescence materials have important application value in the fields of bio-sensing, cell imaging, and information anti-counterfeiting. Herein, a tunable multicolor lanthanide supramolecular assembly with white light emission is reported, which is constructed by co-assembly of cucurbit[7]uril (CB[7]) encapsulating naphthylimidazolium dicarboxylic acid (G₁)/Ln (Eu³⁺/Tb³⁺) complex and carbon quantum dots (CD). Benefiting from the macrocyclic confinement effect of CB[7], the supramolecular assembly not only extends the fluorescence intensity of the lanthanide complex G₁/Tb³⁺ by 36 times, but also increases the quantum yield by 28 times and the fluorescence lifetime by 12 times. Furthermore, the CB[7]/G₁/Ln assembly can further co-assemble with CD and diarylethene derivatives (DAE) to realize the intelligently-regulated full-color spectrum including white light, which results from the competitive encapsulation of adamantylamine and CB[7], the change of pH, and photochromic DAE. The multi-level logic gate based on lanthanide supramolecular assembly is successfully applied in anti-counterfeiting system and information storage, providing an effective method for the research of new luminescent intelligent materials.

Here we perform angle and time-resolved photoelectron spectroscopy on the commensurate charge density wave (CDW) phase of 1T-TaS2. Data with different probe pulse polarization are employed to map the dispersion of electronic states below and above the chemical potential. Upon photoexcitation, the fluctuations of CDW order erase the band dispersion and squeeze the electronic states near to the chemical potential. This transient phase sets within half a period of the coherent lattice motion and is favored by strong electronic correlations. The experimental results are compared to density-functional theory calculations with a self-consistent evaluation of the Coulomb repulsion. Our simulations indicate that the screening of Coulomb repulsion depends on the stacking order of the TaS2 layers. The entanglement of such degrees of freedom suggest that both the structural order and electronic repulsion are locally modified by the photoinduced CDW fluctuations.

A universal internal plasticization strategy is proposed to construct intrinsically stretchable and efficient fully π-conjugated polymers for the flexible deep-blue polymer light-emitting diodes (PLEDs). The introduction of pendant phenyl-ester plasticizers in polyfluorenes can simultaneously obtain excellent intrinsic stretchability, robust deep-blue electroluminescence, and comparable charge-transport behavior. Stable deep-blue PLEDs based on stretchable layers are also fabricated with a CIE of (0.15, 0.08).

Abstract

Intrinsically stretchable polymeric semiconductors are essential to flexible polymer light-emitting diodes (PLEDs) owing to their excellent strain tolerance capacity under long-time deformation operation. Obtaining intrinsic stretchability, robust emission properties, and excellent charge-transport behavior simultaneously from fully π-conjugated polymers (FCPs) is difficult, particularly for applications in deep-blue PLEDs. Herein, an internal plasticization strategy is proposed to introduce a phenyl-ester plasticizer into polyfluorenes (PF-MC4, PF-MC6, and PF-MC8) for narrowband deep-blue flexible PLEDs. Compared with controlled poly[4-(octyloxy)-9,9-diphenylfluoren-2,7-diyl]-co-[5-(octyloxy)-9,9-diphenylfluoren-2,7-diyl] (PODPFs) (2.5%), the freestanding PF-MC8 thin film shows a fracture strain of >25%. The three stretchable films exhibit stable and efficient deep-blue emission (PLQY > 50%) because of the encapsulation of π-conjugated backbone via pendant phenyl-ester plasticizers. The PF-MC8-based PLEDs show deep-blue emission, which corresponds to CIE and EQE values of (0.16, 0.10) and 1.06%, respectively. Finally, the narrowband deep-blue electroluminescence (FWHM of ≈25 nm; CIE coordinates: (0.15, 0.08)) and performance of the transferred PLEDs based on the PF-MC8 stretchable film are independent of the tensile ratio (up to 45%); however, they show a maximum brightness of 1976 cd m⁻² at a ratio of 35%. Therefore, internal plasticization is a promising approach for designing intrinsically stretchable FCPs for flexible electronics.

Mimicking ion channeling and neuron signaling, synthesis of artificial K⁺-selective membrane, and its integration with the hydrogel-based ionic device are demonstrated, achieving K⁺-selective ion-to-ion amplification in complex biomixtures. The membrane exclusively allows K⁺ transport without water leakage; it is 250× and 17× more permeable toward K⁺ than Cl⁻ and NMDG⁺, respectively, and permits a 500% larger K⁺ signal than Li⁺.

Abstract

Living cells efflux intracellular ions for maintaining cellular life, so intravital measurements of specific ion signals are of significant importance for studying cellular functions and pharmacokinetics. In this work, de novo synthesis of artificial K⁺-selective membrane and its integration with polyelectrolyte hydrogel-based open-junction ionic diode (OJID) is demonstrated, achieving a real-time K⁺-selective ion-to-ion current amplification in complex bioenvironments. By mimicking biological K⁺ channels and nerve impulse transmitters, in-line K⁺-binding G-quartets are introduced across freestanding lipid bilayers by G-specific hexylation of monolithic G-quadruplex, and the pre-filtered K⁺ flow is directly converted to amplified ionic currents by the OJID with a fast response time at 100 ms intervals. By the synergistic combination of charge repulsion, sieving, and ion recognition, the synthetic membrane allows K⁺ transport exclusively without water leakage; it is 250× and 17× more permeable toward K⁺ than monovalent anion, Cl⁻, and polyatomic cation, N-methyl-d-glucamine⁺, respectively. The molecular recognition-mediated ion channeling provides a 500% larger signal for K⁺ as compared to Li⁺ (0.6× smaller than K⁺) despite the same valence. Using the miniaturized device, non-invasive, direct, and real-time K⁺ efflux monitoring from living cell spheroids is achieved with minimal crosstalk, specifically in identifying osmotic shock-induced necrosis and drug-antidote dynamics.

Hybrid Low-Dimensional Phase Structure

The presence of evenly distributed 3D-like phases with vertical orientation can significantly facilitate charge transport and suppress charge recombination in the quasi-2D perovskites-based photodetector, outperforming the prevalent phase structure with a vertical dimension gradient. In article 2300216, Wanzhu Cai, Jian Qing, Guanhaojie Zheng, and co-workers explore the correlation between quasi-2D perovskites' phase structure and their charge transport properties. A combination of exceptional figures of merit is realized.

Multi-metallic multivariate (MTV) rare earth (RE) metal−organic frameworks (MOFs) are highly desirable for the construction of complex multifunctional materials. Now, the use of an icosahedral carborane-based linker is found to facilitate the synthesis of a multi-metal MTV RE MOF incorporating up to eight different RE cations in the structure.

Abstract

Multi-metallic multivariate (MTV) rare earth (RE) metal−organic frameworks (MOFs) are of interest for the development of multifunctional materials, however examples with more than three RE cations are rare and obstructed by compositional segregation during synthesis. Herein, this work demonstrates the synthesis of a multi-metallic MTV RE MOF incorporating two, four, six, or eight different RE ions with different sizes and in nearly equimolar amounts and no compositional segregation. The MOFs are formed by a combination of RE cations (La, Ce, Eu, Gd, Tb, Dy, Y, and Yb) and a 1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane (mCB-L) linker. The steric bulkiness and acidity of mCB-L is crucial for the incorporation of different size RE ions into the MOF structure. Demonstration of the incorporation of all RE cations is performed via compositional and structural characterization. The more complex MTV MOF, including all eight RE ions (mCB-8RE), are also characterized using optical, thermal, and magnetic techniques. Element-selective X-ray absorption spectroscopy and X-ray Magnetic Circular Dichroism measurements allow us to characterize spectroscopically each of the eight RE ions and determine their magnetic moments. This work paves the way for the investigation of MTV MOFs with the possibility to combine RE ions à la carte for diverse applications.

Ordered hierarchical microhump arrays are introduced into triboelectric nanogenerator (TENG) by a simple, low-cost, and scalable one-step fabrication process, that is, template-assisted electrospinning process. Benefiting from the unique microstructure, remarkable TENG performances are achieved. The assembled single-electrode TENG based on the patterned nanofiber films with microhump arrays (NFM-TENG) is proven to hold enormous potential as self-powered sensors and human–machine interfaces, including high-precision handwriting recognition, sport/healthcare monitoring, and a novel animal voice-emotion identification.

Abstract

The development of flexible and adaptable multifunctional sensing systems for human–machine interaction, especially for animal voice-emotion identification, is highly desirable yet quite challenging. Herein, a multifunctional triboelectric nanogenerator (TENG) based on ordered hierarchical microhump arrays is proposed and fabricated by template-assisted electrospinning with a facile, low-cost, and expandable manufacturing process. Performances of a single-electrode TENG based on the patterned nanofiber films with microhump arrays (NFM-TENG) are studied in detail by varying mesh number of the template. Electric field structure of the collector is altered by pore sizes, wire diameters, and protrusions of the receiving templates subjected to different mesh numbers, generating different degrees of microhump arrays on the surface of the nanofiber film. NFM-TENG demonstrates high sensitivity (15.94 mV Pa⁻¹), fast response and recovery time (76 and 58 ms), a large power density of 122 mW m⁻², and excellent ability of structural retention. Integrated with four functions of energy harvesting, pressure sensing, human physiological sensing, and animal voice-emotion identification, NFM-TENG achieves real-time monitoring of human physiological, motion, handwriting, and animal voice-emotion signals without an external power supply. This study shows significant application strategies for self-powered human–machine interaction devices, novel animal voice-emotion identification, biodiversity conservation, and so on.

Nature Nanotechnology, Published online: 10 July 2023; doi:10.1038/s41565-023-01436-w

Intercellular calcium waves drive numerous biological processes. Here light-activated molecular machines that—via nanomechanical action—stimulate ICW are reported, opening up avenues for the modulation of downstream biological processes using molecular-scale devices.

In this study, the structure of Yb³⁺-doped perovskite nanocrystals is stabilized by modifying Na⁺ ions in the crystal lattice, and solving the issue of poor structural stability at high Yb³⁺ doping concentration. It reports near-infrared light-emitting diodes that provide an external quantum efficiency of 6.4% at 990 nm, fully 1.3-fold as high as a pristine sample.

Abstract

Lanthanide ions (Yb³⁺ or Er³⁺) alloying of CsPb(Cl_1-xBr_x)₃ quantum dots (QDs) to emit approaching 1000 nm show promise in near-infrared light-emitting diodes (NIR-LEDs). High Yb³⁺ alloying ratio increases the electroluminance efficiency of emission at 990 nm and enables high external quantum efficiency (EQE) of NIR-LEDs, however, the high alloying ratio also results in inferior material stability and PLQY drop because of Yb³⁺-induced nanocrystal precipitation. This study finds that the heavy alloying of Yb³⁺ ions causes lattice distortion and coherent energy reduction of Yb³⁺: CsPb(Cl_1-xBr_x)₃ QDs, induced by two Yb³⁺ ions replacing three Pb²⁺, which leads to the collapse of the octahedral structure in ambient conditions. It posits that spontaneous monovalent ion (Na⁺) alloying can address the trade-off between material stability and emission intensity. The Na⁺ occupies the vacancy of Pb²⁺ ions, relaxing the distortion in the lattice and improving the phase stability of octahedral structure, and this optimized structure in turn allows a higher Yb³⁺ alloying ratio. Stability measurements show that the Na⁺/Yb³⁺ co-alloyed films show ten-fold higher material stability and 2.0-fold emission efficiency related to controls. It reports that as a result Na⁺/Yb³⁺ co-alloyed NIR-LEDs have an EQE of 6.4% at 990 nm, which is among the highest perovskite NIR-LEDs beyond 950 nm.

Ultrasonic stripping force is used to selectively remove the lying seeds interacting with the substrate through weak van der Waals forces while retaining the standing seeds connected with the substrate via tightly covalent bonds. The standing seeds then induce the growth of low-dimensional crystal-structural films with standing orientation.

Abstract

Ultrasonication-assisted liquid exfoliation of layered materials is widely used to produce a large number of 2D nanosheets due to its simplicity, universality, and mass production. Here, the utility of ultrasonication is extended from liquid exfoliation to seed screening in the case of layered GeSe and GeS. It is found that the ultrasonic stripping force can also be used to selectively remove the lying seeds interacting with substrate through weak van der Waals (vdW) forces while retaining the standing seeds connected with substrate via tightly covalent bonds. The standing seeds then induce the growth of 2D crystal-structural films with standing orientation. This thereby enables efficient carrier transport within covalently bonded layers, instead of poor transport between layers held together by vdW forces. The resulting standing-oriented GeSe films exhibit a 21-times increase in carrier mobility compared to lying-oriented films. As a result, this study demonstrates the highest power conversion efficiencies of 6.1% and 10.5% under AM1.5G 1- and 0.01-sun illumination reported for GeSe solar cells, respectively.

The short-channel tunneling transistor comprising all 2D components is developed, exhibiting high switching performance due to the energy band modulation of vertical heterojunction through the dual-gates. Leveraging the unique short-channel and tunneling mechanism, it can circumvent the general issues of voltage spikes and long reverse recovery time, realizing an access to high-frequency integrated circuits (IC) interface.

Abstract

With continuous size scaling, the surface dangling bonds and short-channel effects will degrade silicon based transistor performance. Thus, it is of great importance to seek new channel materials and transistor architectures to further continue Moore's law. Herein, a new ultra-thin short-channel tunneling transistor is developed comprising all 2D- components. Distinct from usual 2D planar transistor, this device is configured with vertical MoS₂/WSe₂ junction and in-plane WSe₂ channel, the switch states are realized by the gate-regulated barrier height of heterojunction, enabling the transition of transport mechanism between thermionic-emission and tunneling. Under dual-gate configuration, the transistor exhibits high performance with drive current of 4.58 µA, on/off ratio of 4 × 10⁷, subthreshold swing (SS) of 97 mV decade⁻¹ and drain-induced barrier lowering (DIBL) of 12 mV V⁻¹, that can meet the requirement of logical applications in integrated circuits (IC). Taking advantage of the high-speed tunneling current and unique short-channel architecture, the device overcomes the issues of voltage spikes and long reverse recovery time that exist in usual electric components, and thus gains an access to the IC interface. This work provides a proof-of-concept transistor architecture relying on dual-gate modulation, opening up a promising perspective for next generation low-power, high-density, and large-scale IC technologies.