Jing Zhang

An innovative gate-free Fe₇S₈@MoS₂ heterostructure wherein a defect-rich Fe₇S₈ core is enveloped snugly by a curved MoS₂ dome shell is developed to realize the effective photocarrier trapping through the exploitation of intrinsic defects in the Fe₇S₈ core. The resultant neuromorphic devices exhibit remarkable light-tunable synaptic behaviors, thus demonstrating great advances in simulating visual recognition system.

Abstract

The optoelectronic synaptic devices based on two-dimensional (2D) materials offer great advances for future neuromorphic visual systems with dramatically improved integration density and power efficiency. The effective charge capture and retention are considered as one vital prerequisite to realizing the synaptic memory function. However, the current 2D synaptic devices are predominantly relied on materials with artificially-engineered defects or intricate gate-controlled architectures to realize the charge trapping process. These approaches, unfortunately, suffer from the degradation of pristine materials, rapid device failure, and unnecessary complication of device structures. To address these challenges, an innovative gate-free heterostructure paradigm is introduced herein. The heterostructure presents a distinctive dome-like morphology wherein a defect-rich Fe₇S₈ core is enveloped snugly by a curved MoS₂ dome shell (Fe₇S₈@MoS₂), allowing the realization of effective photocarrier trapping through the intrinsic defects in the adjacent Fe₇S₈ core. The resultant neuromorphic devices exhibit remarkable light-tunable synaptic behaviors with memory time up to ≈800 s under single optical pulse, thus demonstrating great advances in simulating visual recognition system with significantly improved image recognition efficiency. The emergence of such heterostructures foreshadows a promising trajectory for underpinning future synaptic devices, catalyzing the realization of high-efficiency and intricate visual processing applications.

Hyperbolic shear polaritons are observed in β-Ga₂O₃ nanostructures using electron energy loss spectroscopy. The propagation and reflection of polariton modes are studied. The tunable broad spectral polaritons in β-Ga₂O₃ expand the scope of β-Ga₂O₃ from its application in traditional electronic devices to applications in nanophotonics and metamaterials.

Abstract

Phonon polaritons, quasiparticles arising from strong coupling between electromagnetic waves and optical phonons, have potential for applications in subdiffraction imaging, sensing, thermal conduction enhancement, and spectroscopy signal enhancement. A new class of phonon polaritons in low-symmetry monoclinic crystals, hyperbolic shear polaritons (HShPs), have been verified recently in β-Ga₂O₃ by free electron laser (FEL) measurements. However, detailed behaviors of HShPs in β-Ga₂O₃ nanostructures still remain unknown. Here, by using monochromatic electron energy loss spectroscopy in conjunction with scanning transmission electron microscopy, the experimental observation of multiple HShPs in β-Ga₂O₃ in the mid-infrared (MIR) and far-infrared (FIR) ranges is reported. HShPs in various β-Ga₂O₃ nanorods and a β-Ga₂O₃ nanodisk are excited. The frequency-dependent rotation and shear effect of HShPs reflect on the distribution of EELS signals. The propagation and reflection of HShPs in nanostructures are clarified by simulations of electric field distribution. These findings suggest that, with its tunable broad spectral HShPs, β-Ga₂O₃ is an excellent candidate for nanophotonic applications.

A complete hardware-based and secure user authentication scheme using public key cryptography with integrated circuits constructed using monolayer molybdenum disulfide (MoS₂) memtransistors is demonstrated. A key highlight of this study involves exploiting the unique properties of homomorphic encryption where computations are performed on the encrypted data while preserving the integrity of the underlying information.

Abstract

User authentication is a critical aspect of any information exchange system which verifies the identities of individuals seeking access to sensitive information. Conventionally, this approachrelies on establishing robust digital signature protocols which employ asymmetric encryption techniques involving a key pair consisting of a public key and its matching private key. In this article, a user verification platform constructed using integrated circuits (ICs) with atomically thin two-dimensional (2D) monolayer molybdenum disulfide (MoS₂) memtransistors is presented. First, generation of secure cryptographic keys is demonstrated by exploiting the inherent stochasticity of carrier trapping and detrapping at the 2D/oxide interface trap sites. Subsequently, the ability to manipulate the functionality of logical NOR is leveraged to create a secure one-way hash function which when homomorphically operated upon with NAND, XOR, OR, NOT, and AND logic circuits generate distinct digital signatures. These signatures when subsequently decrypted, verify the authenticity of the receiver while ensuring complete preservation of data integrity and confidentiality as the underlying information is never revealed. Finally, the advantages of implementing a NOR-based hashing techniques in comparison to the conventional XOR-based encryption method are established. This demonstration highlights the potential of 2D-based ICs in developing critical hardware information security primitives.

Herein, a chemical vapor deposition method is reported to synthesize 2D CuCrSe₂ single crystal. The ultrathin CuCrSe₂ nanosheet exhibits a high Curie temperature T _C of 800 K. The in-plane and out-of-plane ferroelectricity in 2D CuCrSe₂ are characterized by piezo-response force microscopy measurements and confirmed by the lateral and vertical devices.

Abstract

Ultrathin 2D ferroelectrics with high Curie temperature are critical for multifunctional ferroelectric devices. However, the ferroelectric spontaneous polarization is consistently broken by the strong thermal fluctuations at high temperature, resulting in the rare discovery of high-temperature ferroelectricity in 2D materials. Here, a chemical vapor deposition method is reported to synthesize 2D CuCrSe₂ nanosheets. The crystal structure is confirmed by scanning transmission electron microscopy characterization. The measured ferroelectric phase transition temperature of ultrathin CuCrSe₂ is about ≈800 K. Significantly, the switchable ferroelectric polarization is observed in ≈5.2 nm nanosheet. Moreover, the in-plane and out-of-plane ferroelectric response are modulated by different maximum bias voltage. This work provides a new insight into the construction of 2D ferroelectrics with high Curie temperature.

Ferroelectric polarization screening reconstruction occurs in single-domain PbTiO₃ nanoplate by selective epitaxial growth of SrTiO₃ film on the positively poled surface, which promotes the formation of oxygen vacancies on the negatively poled surface and regulation of the bound charge on the positively poled surface. This strategy causes good dispersion of cocatalysts and a favorable reaction path for photocatalytic overall water splitting.

Abstract

A large depolarization field in single-domain PbTiO₃ is anticipated to drive the spatial separation of photogenerated charge carriers and enable potential active sites for photocatalytic overall water splitting reaction. However, the negatively polarized surface usually cannot provide sufficient active sites for water oxidation to oxygen because of lacking oxygen vacancies, inevitably hindering photocatalytic water splitting reaction. Here, the ferroelectric polarization screening is reconstructed by a heteroepitaxial SrTiO₃ film on the positively polarized surface of PbTiO₃ nanoplates to generate abundant oxygen vacancies on the negatively polarized surface as active sites for water oxidation. Moreover, it is experimentally and theoretically revealed that the epitaxial SrTiO₃ layer on the positively polarized surface is also beneficial for good dispersion of cocatalyst and the formation of low Schottky barrier height at the interface between the heterostructure and the cocatalyst for efficient electron transfer. Compared with pristine PbTiO₃, the obtained PbTiO₃/SrTiO₃ heteroepitaxial structure with the simultaneous regulation of positively and negatively polarized surfaces delivered a greatly enhanced photocatalytic overall water splitting with stoichiometric ratio (2:1) of hydrogen and oxygen evolution by a factor of 15 times. These findings might open up a new avenue for the design of ferroelectric photocatalysts with excellent activity.

Nature Communications, Published online: 19 February 2024; doi:10.1038/s41467-024-45994-6

Author Correction: Super-resolution multicolor fluorescence microscopy enabled by an apochromatic super-oscillatory lens with extended depth-of-focus

Nature Chemistry, Published online: 19 February 2024; doi:10.1038/s41557-023-01422-8

Valence tautomerism in lanthanide-based materials is rare. Now a one-dimensional samarium–pyrazine polymer has been shown to exhibit a temperature-induced hysteretic Sm(III)-to-Sm(II) reversible switch. The transition temperature is modulated in a 150 K window by alloying with Yb(II), presenting a strategy for developing new materials with chemically tunable magnetic switchability.

In response to the low ionic conductivity of polymer electrolytes at room temperature, a LaF₃-doped PVDF solid-state electrolyte is developed and the lithium environment is optimized to create a high throughput lithium-ion channel; the stability of the electrode/electrolyte interface is effectively improved to ensure efficient and stable interfacial lithium conduction.

Abstract

The inherent low ionic conductivity of PVDF-based electrolytes at room temperature and lithium dendrite penetration hinder its further application. Herein, a LaF₃ doped Poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-ctfe)) quasi-solid electrolyte is developed. High-flux channels are created due to the optimization of the lithium environment that lanthanum preferentially competes coordination with anionic species for relaxing lithium hopping. Lithium carriers are therefore highly free and unbound at the molecular level, resulting in a high ionic conductivity (σ) of 0.7 mS cm⁻¹ and a transfer number (t _Li+) of 0.79 at 25 °C. Moreover, the in situ organic–inorganic LiF-rich dielectric layer effectively improves the stability and compatibility of the electrode/electrolyte interface, ensuring interfacial lithium conduction while facilitating stable Li⁺ plating/stripping. As a result, the optimized Li/ATCSE-3%/Li can deliver favorable compatibility at 0.1 and 0.3 mA cm⁻² for stable Li⁺ plating/stripping for 2000 and 1200 h, respectively. The high-mass loading (6.4 mg cm⁻²) pouch cell delivers a stable cycling performance over 100 cycles with a capacity retention of 85.8% at 0.3 °C. This work is anticipated to provide considerable insight into the creative design of lithium transport of polymer-based for practical quasi-solid-state lithium metal batteries.

A Tb³⁺ ion doped glass-ceramic (GC) obtained by the traditional melt-quenching method, is employed as the converter to combine with a silicon photo-resistor for the development of a solar-blind UV detector. Due to the efficient conversion of broadband solar-blind UV light (188–400 nm) into visible light by the GC, the device exhibits meaningful photovoltage response at a low bias voltage. The research results of this work are of great significance for the development of efficient broadband solar-blind UV detectors at a low cost.

Abstract

Oxyfluoride transparent glass-ceramics (GC) are widely used as the matrix for rare-earth (RE) ions due to their unique properties such as low phonon energy, high transmittance, and high solubility for RE ions. Tb³⁺ doped oxyfluoride glasses exhibit a large absorption cross section for ultraviolet (UV) excitation, high stability, high photoluminescence quantum efficiency, and sensitive spectral conversion characteristics, making them promising candidate materials for use as the spectral converter in UV photodetectors. Herein, a Tb³⁺ doped oxyfluoride GC is developed by using the melt-quenching method, and the microstructure and optical properties of the GC sample are carefully investigated. By combining with a Si-based photo-resistor,a solar-blind UV detector is fabricated, which exhibits a significant photoelectric response with a broad detection range from 188 to 400 nm. The results indicate that the designed UV photodetector is of great significance for the development of solar-blind UV detectors.

Orthogonal UCL is realized in crystals with a simple structure simply by introducing modulator Tm³⁺ ions to control the photon transition processes between different energy levels of activator Er³⁺ ions. The obtained crystals emit red and green luminescence under excitation of 980 nm and 808 nm lasers, respectively, and are shown to be well suited for advanced optical encryption.

Abstract

Optical encryption shows great potential in meeting the growing demand for advanced anti-counterfeiting in the information age. The development of upconversion luminescence (UCL) materials capable of emitting different colors of light in response to different external stimuli holds great promise in this field. However, the effective realization of multicolor UCL materials usually requires complex structural designs. In this work, orthogonal UCL is achieved in crystals with a simple structure simply by introducing modulator Tm³⁺ ions to control the photon transition processes between different energy levels of activator Er³⁺ ions. The obtained crystals emit red and green UCL when excited by 980 nm and 808 nm lasers, respectively. The orthogonal excitation-emission properties of crystals are shown to be very suitable for high-level optical encryption, which is important for information security and anti-counterfeiting. This work provides an effective strategy for obtaining orthogonal UCL in simple structural materials, which will encourage researchers to further explore novel orthogonal UCL materials and their applications, and has important implications for the development of the frontier photonic upconversion fields.

This study demonstrates a novel strategy to stabilize LiCoO₂ at 4.6 V by doping with Er and Mg at the Li-site and Co-site, respectively, which is different from the traditional method of doping foreign elements solely at the Co-site.

Abstract

Charging LiCoO₂ to high voltages yields alluring specific capacities, yet the deleterious phase-transitions lead to significant capacity degradation. Herein, this study demonstrates a novel strategy to stabilize LiCoO₂ at 4.6 V by doping with Er and Mg at the Li-site and Co-site, respectively, which is different from the traditional method of doping foreign elements solely at the Co-site. Theoretical calculations and experiments jointly reveal that the inclusion of Mg²⁺-dopants at the Co-site curbs the hexagonal-monoclinic phase transitions ≈4.2 V. However, this unintentionally compromises the stability of lattice oxygen in LiCoO₂, exacerbating the undesired phase transition (O3 to H1-3) above 4.45 V. Fascinatingly, the introduction of Er³⁺-dopants into Li-sites enhances the stability of lattice oxygen in LiCoO₂, effectively mitigating phase transitions above 4.45 V. Therefore, the Er, Mg co-doped LiCoO₂ exhibits high stability over 500 cycles when tested in a half-cell with a cut-off voltage of 4.6 V. Furthermore, the Er, Mg-doped LiCoO₂//graphite pouch-type full cell demonstrates a high energy density of 310.8 Wh kg⁻¹, preserving 91.3% of its energy over 100 cycles.

Full-color “off–on” thermochromic fluorescent fibers with good mechanical properties, high fluorescent emission contrast, great reversibility, and controlled response temperatures are designed and constructed based on self-crystallinity phase change and Förster resonance energy transfer for long-term and passive body-temperature monitoring. This simple and versatile strategy is especially significant for various personalized customization of flexible sensors with higher comprehensive performance.

Abstract

Responsive thermochromic fiber materials capable of miniaturization and integrating comfortably and compliantly onto the soft and dynamically deforming human body are promising materials for visualized personal health monitoring. However, their development is hindered by monotonous colors, low-contrast color changes, and poor reversibility. Herein, full-color “off–on” thermochromic fluorescent fibers are prepared based on self-crystallinity phase change and Förster resonance energy transfer for long-term and passive body-temperature monitoring, especially for various personalized customization purposes. The off–on switching luminescence characteristic is derived from the reversible conversion of the dispersion state and fluorescent emission by fluorophores and quencher molecules, which are embedded in the matrix of a phase-change material, during the crystallizing/melting processes. The achievement of full-color fluorescence is attributed to the large modulation range of fluorescence colors according to primary color additive theory. These thermochromic fluorescent fibers exhibit good mechanical properties, fluorescent emission contrast, and reversibility, showing their great potential in flexible smart display devices. Moreover, the response temperature of the thermochromic fibers is controllable by adjusting the phase-change material, enabling body-temperature-triggered luminescence; this property highlights their potential for human body-temperature monitoring and personalized customization. This work presents a new strategy for designing and exploring flexible sensors with higher comprehensive performances.

A disposable thermally triggered photonic crystal (PC) anti-counterfeiting tag with irreversible response and multi-step color changes is developed based on the thermochromic Silica/(Polyethylene glycol-Ethoxylated trimethylolpropane triacrylate) double-layer film. The invisible PC pattern on the tag can be revealed part by part upon heating and become invisible again after overheating, which offered diversified visual effects and enhanced anti-counterfeiting performances.

Abstract

Thermochromic photonic crystal (PC) is a promising material for anti-counterfeiting applications, but there are still challenges to further improve the anti-counterfeiting performance and the practicability in usage. Here, a disposable thermally triggered PC anti-counterfeiting tag with irreversible response and multi-step color changes is developed based on the thermochromic Silica/(Polyethylene glycol-Ethoxylated trimethylolpropane triacrylate) (SiO₂/(PEG-ETPTA)) double-layer film. The fast and irreversible thermal response come from the quick melting and infiltration of PEG-ETPTA into the PCs upon heating. The multi-step color change at different temperatures originated from the regioselective control of the UV curing degree of the PEG-ETPTA layer and the resulting thermochromic temperature of the double-layer film. Therefore, the invisible PC pattern on the tag can be revealed part by part upon heating and became invisible again after overheating, which offered diversified visual effects and enhanced anti-counterfeiting performances.

The significance of 2D molecularly woven material has inspired us to prepare polarity driven self-assembly of left/right handed helical threads with the strong intermolecular H-bonding, forming molecularly woven 2° MW and non-woven 2° NMW. 2° MW forms flexible 2D thin film exhibiting remarkable mechanical strength, self-healing molecular sieving.

Abstract

Molecularly woven materials with striking mechanical resilience, and 2D controlled topologies like textiles, fishing nets, and baskets are highly anticipated. Molecular weaving exclusively apprehended by the secondary interactions expanding to laterally grown 2D self-assemblies with retained crystalline arrangement is stimulating. The interlacing entails planar molecules screwed together to form 2D woven thin films. Here, secondary interactions led 2D interlaced molecularly woven material (2^°MW) built by 1D helical threads of organic chromophores twisted together via end-to-end CH···O connections, held strongly at inter-crossing by multiple OH···N interactions to prevent slippage is presented. Whereas, 1D helical threads with face-to-face O–H···O connections sans interlacing led the non-woven material (2^°NW). The polarity-driven directionality in 2^°MW led the water-actuated epitaxial growth of 2D-sheets to lateral thin films restricted to nano-scale thickness. The molecularly woven thin film is self-healing, flexible, and mechanically resilient in nature, while maintaining the crystalline regularity is attributed to the supple secondary interactions (2^°).

Nature Communications, Published online: 17 February 2024; doi:10.1038/s41467-024-45986-6

The enantiomer fraction strategy can achieve continuous control of the phase transition temperature, chiroptical properties, SHG intensity and other properties of chiral two-dimensional lead bromide ferroelectrics.

Anti-ambipolar behavior and polarization-sensitive properties are achieved by sandwiching p-GeSe in a MoTe₂/MoS₂ heterojunction, with a peak-to-valley current ratio of more than10⁴, polarization ratio as high as 11.2, and noise spectral density as low as 1 fA Hz^-1/2. Photocurrent polarity reversal through external voltage modulation provides the basis for multifunctional integration applications.

Abstract

The ability to modulate the polarity of carrier transport and photo-response in assembled heterostructure devices remains a huge challenge for the development of multifunctional optoelectronics. Herein, a polarity-switchable and polarization-sensitive photodetector is developed based on a van der Waals (vdW) MoTe₂/GeSe/MoS₂ sandwich heterostructure. By varying the gate voltage, an anti-bipolar transfer characteristic is obtained with significant peak-valley current ratio (PVCR) exceeding 10⁴, showing the extraordinary potential to realize electronic functions in logic circuits. Under 635 nm laser irradiation, the device exhibits a gate-controlled polarity transition of photocurrent, namely, the sign reversal of photocurrent occurs by changing the gate voltage. Furthermore, the device achieves broadband photovoltaic effect and high photodetection performance with responsivity (R) of 723 mA·W⁻¹, noise spectral density (S_n ) of 1 fA Hz^−1/2, and specific detectivity (D^* ) of 2.3×10¹² Jones in the absence of external bias, which greatly outperforms the MoTe₂/MoS₂ device. Leveraging the in-plane anisotropic structure of GeSe, the device is also endowed with an additional capability of polarization-sensing for linearly polarized laser, possessing a high polarization ratio (PR) value of 11.2. Thus, this work proposes an effective and facile strategy to realize the gate-modulated polarity transition and polarization-sensitive photodetection, offering a broad perspective for multifunctional integrated applications.

This study paves the way for NIR-excitable semiconductors with inherent self-sufficient electron donor capabilities, highlighting the promising application of LIG-Yb-Bi₂S₃/PMA photoelectrode materials in ultrasensitive PEC sensing. Moreover, a wearable PEC aptasensor, integrated with an intelligent signal interaction system, is devised to enable nonirritating and in situ analysis of trace NPY dynamics in sweat during daily activities.

Abstract

Transition metal sulfides have garnered significant interest in the realm of photoelectrochemical (PEC) sensors due to their remarkable optical and electrical properties. However, their intrinsic UV–vis adsorption and electron-donor consumption severely hinder their nonirritating and in situ epidermal PEC applications. Herein, a NIR-808 nm light-excited heterojunction, phosphomolybdic acid-encapsulated ytterbium-doped bismuth sulfide (Yb-Bi₂S₃/PMA), is synthesized by hydrothermal method for self-sufficient electron donor-based PEC sensing. Further, the Yb-Bi₂S₃/PMA heterojunction is decorated on flexible and integrated laser-induced graphene electrode arrays, providing ultrafast charge carrier transfer capacity and robust mechanical durability (300 bending cycles) for subsequent wearable PEC sensing. As a showcase, the aptamer molecular recognition-based wearable PEC sensor for sweat trace Neuropeptide Y (NPY, a stress or depression biomarker) presents an ultra-low detection limit (0.39 fM) and good anti-interference ability. Moreover, the integration of wearable PEC aptasensor with signal processing and wireless communication facilitates nonirritating and in situ analysis of sweat trace NPY dynamics in various real scenarios (feeding behaviors, physiological stress, and circadian rhythm). More broadly, this research establishes the foundation for NIR-excitable semiconductors equipped with self-sufficient electron donor capabilities, unlocking the potential for ultrasensitive wearable PEC sensing applications.

This work demonstrates a simple strategy for the additive manufacturing of tough and self-healable soft robotic gripper. The resin based on deep eutectic solvents can be rapidly cured to form tough ionogels without chemical crosslinkers by harnessing its intense hydrogen bonding interactions. Furthermore, the ionogels show not only efficient energy-dissipating behavior, but also rapid self-recovery.

Abstract

Inspired by nature's flexible and adaptable organisms, soft robotics are motorless robots made from highly compliant materials to work in confined environments and manipulate delicate objects. However, soft robots often suffer from early failure because of unexpected damage. At the same time, it is challenging to manufacture the geometrically complex structures of soft robots. This study introduces resins based on deep eutectic solvents (DES) to fabricate a pneumatically driven soft gripper using digital light processing (DLP). The resins consist of choline chloride (ChCl) as a hydrogen bond acceptor, glycerol (Gly), and acrylamide (AAm) as hydrogen bond donors. By utilizing the intense hydrogen bonding within DES, the resin can be rapidly cured by photopolymerization to form tough ionogels without chemical crosslinkers. The DES ionogels exhibit remarkable toughness and self-healing performance compared to common hydrogels. Furthermore, the ionogels show not only efficient energy-dissipating behavior but also achieve rapid self-recovery. Finally, the DLP-printed soft gripper from the DES-based resin performs successful actuation and healing of macroscopic damages. This work presents a simple strategy to 3D print a soft robotic gripper with high toughness and self-healing capability.

Nature Nanotechnology, Published online: 16 February 2024; doi:10.1038/s41565-023-01572-3

Assessment of the health risks of exposure to anthropogenic nanomaterials is crucial to maximize their potential applications. This double-blind, randomized controlled study in healthy humans evaluates the impact of inhalation of graphene oxide nanosheets on acute pulmonary and cardiovascular functions.

Macrophages-based microrobots are constructed with the fusion of macrophages and metal–organic frameworks to exert functions such as tumor-targeted, fluorescent navigation, and photothermal conversion. Active tumor accumulation of microrobots is achieved for inherent tumor tropism. Photothermal-enhanced tumor-specific pyroptosis induces robust and adaptive immune response, achieving photothermal immunotherapy for breast tumor proliferation and lung metastasis.

Abstract

Pyroptosis-based immunotherapy can escape drug resistance as well as inhibit metastasis. It is urgently required to develop a delivery platform to induce targeted tumor-specific pyroptosis for cancer immunotherapy. Herein, macrophages-based biohybrid microrobots (IDN@MC) are constructed with IR-macrophage and decitabine-loaded Metal-organic frameworks (DZNPs). The integration of fluorescence photosensitizers and pH-sensitive DZNPs endow the microrobots properties such as photothermal conversion, fluorescent navigation, targeted drug delivery, and controlled drug release. In light of the inherent tumor targeting, tumor accumulation of IDN@MC is facilitated. Due to the sustained release of decitabine from packaged DZNPs, the host macrophages are differentiated into M1 phenotypes to exert the tumor phagocytosis at the tumor site, directly transporting the therapeutic agents into cancer cells. With laser control, the rapid and durable caspase 3-cleaved gasdermin E (GSDME)-related tumor pyroptosis is achieved with combined photothermal-chemotherapy, releasing inflammatory factors such as lactate dehydrogenase and interleukin-18. Subsequently, the robust and adaptive immune response is primed with dendritic cell maturation to initiate T-cell clone expansion and modulation of the immune suppressive microenvironment, thus enhancing the tumor immunotherapy to inhibit tumor proliferation and metastasis. This macrophages-based biohybrid microrobot is an efficient strategy for breast cancer treatment to trigger photo-induced pyroptosis and augment the immune response.

Boron nanostructures on the Cu(111) substrate undergo an evolution from amorphous boron to the striped-phase borophene and then to β-type borophene on the substrate surface or embedded in the topmost Cu layer with the gradual elevation of annealing temperature. The ⟨11¯0⟩$\langle {1\bar{1}0} \rangle $ edges of Cu(111) trigger the formation of the striped-phase borophene, acting as the transition phase for β-type borophene.

Abstract

Borophene, a promising material with potential applications in electronics, energy storage, and sensors, is successfully grown as a monolayer on Ag(111), Cu(111), and Au(111) surfaces using molecular beam epitaxy. The growth of two-dimensional borophene on Ag(111) and Au(111) is proposed to occur via surface adsorption and boron segregation, respectively. However, the growth mode of borophene on Cu(111) remains unclear. To elucidate this, scanning tunneling microscopy in conjunction with theoretical calculations is used to study the phase transformation of boron nanostructures under post-annealing treatments. Results show that by elevating the substrate temperature, boron nanostructures undergo an evolution from amorphous boron to striped-phase borophene (η = 1/6) adhering to the Cu ⟨11¯0⟩$\langle {1\bar{1}0} \rangle $ step edge, and finally to irregularly shaped β-type borophene (η = 5/36) either on the substrate surface or embedded in the topmost Cu layer. dI/dV spectra recorded near the borophene/Cu lateral interfaces indicate that the striped-phase borophene is a metastable phase, requiring more buckling and electron transfer to stabilize the crystal structure. These findings offer not only an in-depth comprehension of the β-type borophene formation on Cu(111), but also hold potential for enabling borophene synthesis on weakly-binding semiconducting or insulating substrates with 1D active defects.

In this study, the OER and ORR bifunctional catalytic activities of 16 SACs based on 1T′-MoS₂ monolayers are systematically investigated based on first-principle computational methods. It is found that Ir@ReS₂ and Pd@ReS₂ exhibited excellent catalytic activities for both OER and ORR with overpotentials {η_OER η_ORR} of {0.44 0.26 V} and {0.44 0.27 V}, respectively.

Abstract

Developing efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) bifunctional electrocatalysts is attractive for rechargeable metal–air batteries. Meanwhile, single metal atoms embedded in 2D layered transition metal chalcogenides (TMDs) have become a very promising catalyst. Recently, many attentions have been paid to the 2D ReS₂ electrocatalyst due to its unique distorted octahedral 1T’ crystal structure and thickness-independent electronic properties. Here, the catalytic activity of different transition metal (TM) atoms embedded in ReS₂ using the density functional theory is investigated. The results indicate that TM@ReS₂ exhibits outstanding thermal stability, good electrical conductivity, and electron transfer for electrochemical reactions. And the Ir@ReS₂ and Pd@ReS₂ can be used as OER/ORR bifunctional electrocatalysts with a lower overpotential for OER (η_OER) of 0.44 V and overpotentials for ORR (η_ORR) of 0.26 V and 0.27 V, respectively. The excellent catalytic activity is attributed to the optimal adsorption strength for oxygen intermediates coming from the effective modulation of the electronic structure of ReS₂ after Ir/Pd doping. The results can help to deeply understand the catalytic activity of TM@ReS₂ and develop novel and highly efficient OER/ORR electrocatalysts.

Nature Communications, Published online: 15 February 2024; doi:10.1038/s41467-024-45709-x

Sliding ferroelectricity occurs in stacks of van der Waals materials. Depending on the particular stacking, the system can host a spontaneous polarization, and under an applied electric field, polarization domain walls will propagate transverse to the electric field. Here, Yang et al use an optical approach to directly observe this sliding of domain walls in bilayer MoS2.

2D Materials

In article number 2309777 by Samuel W. LaGasse and co-workers, optical coupling of monolayer transition metal dichalcogenides (TMDs) to hexagonal boron nitride (hBN) slab waveguides is studied. The results provide a direct route for waveguide-based interrogation of layered materials, as well as a way to integrate layered materials into future photonic devices at arbitrary positions whilst maintaining their intrinsic properties.

The GAA-MOCVD is introduced to realize the epitaxial growth of one additional layer on monolayer MoS₂, resulting in bi-layer MoS₂ film with spatial homogeneity and high-quality, which is challenging to achieve in conventional MOCVD techniques using powder alkali metals. The FETs fabricated by bi-layer MoS₂ films exhibit superior electrical properties including sheet conductance, electron mobility, and on/off ratio.

Abstract

2D MoS₂ has gained attention for the post-silicon material owing to its atomically thin nature and dangling bond-free surface. The bi-layer MoS₂ is considered a promising material for electronic devices due to its better electrical properties than monolayer MoS₂. However, the uniform growth of bi-layer MoS₂ is still challenging. Herein, the uniform growth of bi-layer MoS₂ is demonstrated using gas-phase alkali metal-assisted metal–organic chemical vapor deposition (GAA-MOCVD). Thanks to enhanced metal reactant diffusion length in GAA-MOCVD, the uniform growth of bi-layer MoS₂ film is achieved even at fast nucleation kinetics for a shorter growth time compared to previously reported MOCVD. The bi-layer MoS₂ field-effect transistors (FETs) show superior electrical properties such as sheet conductance and electron mobility than monolayer MoS₂ FETs. The electron mobility of bi-layer MoS₂ FETs with bismuth contacts reaches a maximum of 92.35 cm² V⁻¹ s⁻¹. Using the partially grown epitaxial bi-layer (PGEB) MoS₂, it is demonstrated that a photodetector showed a near-infrared photoresponse with a low dark current that is advantageous for both monolayer and bi-layer applications. The potential expansion of the growth technique to layer-by-layer growth can result in boosted performance across a wide spectrum of electronic and optoelectronic devices employing MoS₂.