Jiuxiang Dai

BiOBr photocatalysts with different surface vacancy associates were successfully synthesized. Vacancy associates of Br−Bi−Br triple atom vacancy (V_BrBiBr) and oxygen vacancies can generate benzonitrile with high selectivity in the photocatalytic ammoxidation of benzyl alcohol by providing adsorption activation sites for NH₃ and O₂ and reaction sites for the multi-step formation of imine intermediates and oxidation to benzonitrile.

Abstract

Photocatalytic organic functionalization reactions represent a green, cost-effective, and sustainable synthesis route for value-added chemicals. However, heterogeneous photocatalysis is inefficient in directly activating ammonia molecules for the production of high-value-added nitrogenous organic products when compared with oxygen activation in the formation of related oxygenated compounds. In this study, we report the heterogeneous photosynthesis of benzonitriles by the ammoxidation of benzyl alcohols (99 % conversion, 93 % selectivity) promoted using BiOBr nanosheets with surface vacancy associates. In contrast, the main reaction of catalysts with other types of vacancy sites is the oxidation of benzyl alcohol to benzaldehyde or benzoic acid. Experimental measurements and theoretical calculations have demonstrated a specificity of vacancy type with respect to product selectivity, which arises from the adsorption and activation of NH₃ and O₂ that is required to promote subsequent C−N coupling and oxidation to nitrile. This study provides a better understanding of the role of vacancies as catalytic sites in heterogeneous photocatalysis.

Nature, Published online: 11 October 2023; doi:10.1038/s41586-023-06504-8

In this study monomers with different functional groups are (co-)polymerized to 6 polymer thin films via initiated chemical vapor deposition (iCVD) and tested in three different biological environments. For biocompatibility tests, the films are tested with human fibroblasts. For antiviral and anticancer studies the samples are also modeled regarding their interaction with key proteins.

Abstract

Thin polymer coatings are used to improve the interface between biological species and functional materials. Their interaction is significantly influenced by the functional groups and roughness of the polymer film and prediction of the interaction is thus of great interest. However, for conventional polymer films, this cannot be examined independently because of the interplay of defects, residual solvent molecules, roughness, and functional groups. Solvent-free polymer films prepared by initiated chemical vapor deposition (iCVD) exhibit conformal, defect-free characteristics and enable precise tailoring of the functional groups. This facilitates to isolate the contribution of functional groups on the bio-interface performance. Consequently, in silico studies can enable a prediction of ligand interaction in anti-viral activity for SARS-CoV-2 based on defined polymer and key protein structures. Furthermore, the cell viability of human fibroblasts can be traced back to the functional groups of the repeating units. For human liver cancer cell culture, it turns out that more sophisticated models are needed. The insilico-iCVD approach can enable precise tailoring of complex polymer films optimized for the respective interfaces. In addition, this first big scan of the bio-interface performance of iCVD films enables a solid starting point in areas like anticancer, antiviral, and biocompatibility for future studies.

A strategy for fabricating molecular photoswitch devices with the combined self-assembled monolayers and eutectic gallium-indium techniques is reported. The current-voltage characteristics of EGaIn/GaO _x //molecule/TMDCs photoswitches exhibit reversibility as excellent as almost 100%. This work demonstrates the promise of transition metal dichalcogenides electrodes (TMDCs) to express the intrinsic molecular properties and opens a new path for the design and fabrication nanoelectronic devices.

Abstract

The molecule-electrode coupling plays an essential role in photoresponsive devices with photochromic molecules, and the strong coupling between the molecule and the conventional electrodes leads to/ the quenching effect and limits the reversibility of molecular photoswitches. In this work, we developed a strategy of using transition metal dichalcogenides (TMDCs) electrodes to fabricate the thiol azobenzene (TAB) self-assembled monolayers (SAMs) junctions with the eutectic gallium-indium (EGaIn) technique. The current-voltage characteristics of the EGaIn/GaO _x //TAB/TMDCs photoswitches showed an almost 100% reversible photoswitching behavior, which increased by ∼28% compared to EGaIn/GaO_x//TAB/Au^TS photoswitches. Density functional theory (DFT) calculations showed the coupling strength of the TAB-TMDCs electrode decreased by 42% compared to that of the TAB-Au^TS electrode, giving rise to improved reversibility. our work demonstrated the feasibility of 2D TMDCs for fabricating SAMs-based photoswitches with unprecedentedly high reversibility.

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.

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

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.

A new concept of nonvolatile memory organic light-emitting transistor (OLET) achieving by ferroelectric polymer is proposed for improving the integration density of pixel circuits of organic display. The performances of proposed device are greatly improved through interfacial modification approach. The integration of nonvolatile memory, switching and light-emitting functions within the ferroelectric OLET opens a different avenue toward on-chip advanced display technologies.

Abstract

In the field of active-matrix organic light emitting display (AMOLED), large-size and ultra-high-definition AMOLED applications have escalated the demand for the integration density of driver chips. However, as Moore's Law approaches the limit, the traditional technology of improving integration density that relies on scaling down device dimension is facing a huge challenge. Thus, developing a multifunctional and highly integrated device is a promising route for improving the integration density of pixel circuits. Here, a novel nonvolatile memory ferroelectric organic light-emitting transistor (Fe-OLET) device which integrates the switching capability, light-emitting capability and nonvolatile memory function into a single device is reported. The nonvolatile memory function of Fe-OLET is achieved through the remnant polarization property of ferroelectric polymer, enabling the device to maintain light emission at zero gate bias. The reliable nonvolatile memory operations are also demonstrated. The proof-of-concept device optimized through interfacial modification approach exhibits 20 times improved field-effect mobility and five times increased luminance. The integration of nonvolatile memory, switching and light-emitting capabilities within Fe-OLET provides a promising internal-storage-driving paradigm, thus creating a new pathway for deploying storage capacitor-free circuitry to improve the pixel aperture ratio and the integration density of circuits toward the on-chip advanced display applications.

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.

Atomically-thin holey 2D nanosheets of defect-engineered Mo₅N₆–MoN nanocomposites are synthesized by controlled nitridation of organic-assembled MoS₂ nanosheets. The basal expansion of MoS₂ nanosheets is crucial in stabilizing sub-nanometer–thick holey Mo₅N₆–MoN nanocomposite. The immobilization of Pt single atoms on holey Mo₅N₆–MoN nanosheet yields high-performance electrocatalysts with high mass activity due to enhanced interfacial interaction with Mo-deficient Mo₅N₆ domains.

Abstract

The defect engineering of inorganic solids has received significant attention because of its high efficacy in optimizing energy-related functionalities. Consequently, this approach is effectively leveraged in the present study to synthesize atomically-thin holey 2D nanosheets of a MoN–Mo₅N₆ composite. This is achieved by controlled nitridation of assembled MoS₂ monolayers, which induced sequential cation/anion migration and a gradual decrease in the Mo valency. Precise control of the interlayer distance of the MoS₂ monolayers via assembly with various tetraalkylammonium ions is found to be crucial for synthesizing sub-nanometer–thick holey MoN–Mo₅N₆ nanosheets with a tunable anion/cation vacancy content. The holey MoN–Mo₅N₆ nanosheets are employed as efficient immobilization matrices for Pt single atoms to achieve high electrocatalytic mass activity, decent durability, and low overpotential for the hydrogen evolution reaction (HER). In situ/ex situ spectroscopy and density functional theory (DFT) calculations reveal that the presence of cation-deficient Mo₅N₆ domain is crucial for enhancing the interfacial interactions between the conductive molybdenum nitride substrate and Pt single atoms, leading to enhanced electron injection efficiency and electrochemical stability. The beneficial effects of the Pt-immobilizing holey MoN–Mo₅N₆ nanosheets are associated with enhanced electronic coupling, resulting in improvements in HER kinetics and interfacial charge transfer.

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 work provides a comprehensive overview of the latest scientific advancements in the design and fabrication of graphene-based engineered living materials (ELMs). Four main methodologies for the fabrication of these ELMs are recognized and discussed in detail. Moreover, potential engineering applications and design principles for next-generation graphene-based ELMs are overviewed.

Abstract

With the rise of engineered living materials (ELMs) as innovative, sustainable and smart systems for diverse engineering and biological applications, global interest in advancing ELMs is on the rise. Graphene-based nanostructures can serve as effective tools to fabricate ELMs. By using graphene-based materials as building units and microorganisms as the designers of the end materials, next-generation ELMs can be engineered with the structural properties of graphene-based materials and the inherent properties of the microorganisms. However, some challenges need to be addressed to fully take advantage of graphene-based nanostructures for the design of next-generation ELMs. This work covers the latest advances in the fabrication and application of graphene-based ELMs. Fabrication strategies of graphene-based ELMs are first categorized, followed by a systematic investigation of the advantages and disadvantages within each category. Next, the potential applications of graphene-based ELMs are covered. Moreover, the challenges associated with fabrication of next-generation graphene-based ELMs are identified and discussed. Based on a comprehensive overview of the literature, the primary challenge limiting the integration of graphene-based nanostructures in ELMs is nanotoxicity arising from synthetic and structural parameters. Finally, we present possible design principles to potentially address these challenges.

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.

Publication date: October 2023

Source: Materials Today, Volume 69

Author(s): Laurie Winkless

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.

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.

Successive charge transfer channels were constructed by collaborating with the modest polarization electric field and facet junction induced built-in electric field, which strengthens the facet-selective charge separation in Bi₄NbO₈Cl single crystal nanosheets for boosting visible-light driven bifunctional water splitting for H₂ and O₂ evolution.

Abstract

Developing bifunctional water-splitting photocatalysts is meaningful, but challenged by the harsh requirements of specific-facet single crystals with spatially separated reactive sites and anisotropic charge transfer paths contributed by well-built charge driving force. Herein, tunable ferroelectric polarization is introduced in Bi₄NbO₈Cl single crystal nanosheets to strengthen the orthogonal charge transfer channels. By manipulating the in-plane polarization from octahedral off-centering of Nb⁵⁺ and out-of-plane polarization from lone pair electron effect of anisotropic Bi³⁺, both the fast charge recombination in bulk catalyst and the process of charge trapping into surface states can be effectively modulated. Collaborating with modest polarization electric field and facet junction induced built-in electric field, cooperative charge tractive force is constructed, which reinforces the spatial separation and migration of photogenerated electrons and holes to {110} reductive site facet and {001} oxidation site facet, respectively. While excessive polarization charges impair the facet-selective charge separation characteristics and conversely promote charge recombination on the surface. As a result, polarity-optimized Bi₄NbO₈Cl shows an excellent H₂ and O₂ evolution rate of 54.21 and 36.08 μmol ⋅ h⁻¹ in the presence of sacrificial reagents under visible light irradiation. This work unveils the function of ferroelectric polarization in tuning the intrinsic facet-selective charge transfer process of photocatalysts.

A versatile strategy for the synthesis of inorganic nanotubes through template reactions is presented. The outer and inner walls of boron nitride nanotubes promote the coaxial growth of few-nanometers-wide chalcogenide nanotubes with diverse structures, including alloys and Janus configurations. The strategy enables the comprehensive exploration of various nanotubes, paving the way for their potential applications in optoelectronics.

Abstract

Monolayers of transition metal dichalcogenides (TMDs) are an ideal 2D platform for studying a wide variety of electronic properties and potential applications due to their chemical diversity. Similarly, single-walled TMD nanotubes (SW-TMDNTs)—seamless cylinders of rolled-up TMD monolayers—are 1D materials that can exhibit tunable electronic properties depending on both their chirality and composition. However, much less has been explored about their geometrical structures and chemical variations due to their instability under ambient conditions. Here, the structural diversity of SW-TMDNTs templated by boron nitride nanotubes (BNNTs) is reported. The outer surfaces and inner cavities of the BNNTs promote and stabilize the coaxial growth of SW-TMDNTs with various diameters, including few-nanometers-wide species. The chiral indices (n,m) of individual SW-MoS₂NTs are assigned by high-resolution transmission electron microscopy, and statistical analyses reveals a broad chirality distribution ranging from zigzag to armchair configurations. Furthermore, this methodology can be applied to the synthesis of various TMDNTs, such as selenides and alloyed Mo_{1− x} W _x S₂. Comprehensive microscopic and spectroscopic analyses also suggest the partial formation of Janus MoS_{2(1− x )}Se_{2 x} nanotubes. The BNNT-templated reaction provides a universal platform to characterize the chirality-dependent properties of 1D nanotubes with various electronic structures.

In this study, a new design motif is introduced to synthesize edge-extended zigzag graphene nanoribbons (ZGNRs). Using scanning probe techniques and density functional theory, the chemical structure and electronic characteristics of a 3-zigzag-row ZGNR instance are confirmed. This approach expands the range of possible ZGNRs, contributing to further understanding of structure-dependent electronic properties in GNRs.

Abstract

Graphene nanoribbons (GNRs) have gained significant attention in nanoelectronics due to their potential for precise tuning of electronic properties through variations in edge structure and ribbon width. However, the synthesis of GNRs with highly sought-after zigzag edges (ZGNRs), critical for spintronics and quantum information technologies, remains challenging. In this study, a design motif for synthesizing a novel class of GNRs termed edge-extended ZGNRs is presented. This motif enables the controlled incorporation of edge extensions along the zigzag edges at regular intervals. The synthesis of a specific GNR instance—a 3-zigzag-rows-wide ZGNR—with bisanthene units fused to the zigzag edges on alternating sides of the ribbon axis is successfully demonstrated. The resulting edge-extended 3-ZGNR is comprehensively characterized for its chemical structure and electronic properties using scanning probe techniques, complemented by density functional theory calculations. The design motif showcased here opens up new possibilities for synthesizing a diverse range of edge-extended ZGNRs, expanding the structural landscape of GNRs and facilitating the exploration of their structure-dependent electronic properties.