Surface Of Heterostructure Research Articles

High-performance hydrogen sensor based on γ-Fe2O3/α-Fe2O3 heterostructures produced by a one-step hydrothermal method

The construction of heterostructures is an effective strategy for enhancing the properties of functional materials. However, the problem of the weak built-in field at the heterointerface usually degrades the interfacial charge transfer efficiency, severely limiting the improvement of the sensing properties of gas sensors. To overcome this limitation, γ-Fe2O3/α-Fe2O3 (p-p) heterojunction structures were constructed via a one-step hydrothermal method. Interestingly, the morphology and structure of the Fe2O3 nanocrystals could be easily controlled by the amount of urea (CH4N2O). Thus, the response of Fe2O3-M to H2 (200 ppm) at 280 °C was 2.2 and 1.2 times greater than that of Fe2O3–R and Fe2O3–N, respectively. In addition, density functional theory (DFT) calculations were used to explore the sensing mechanism in detail, further confirming the experimental conclusions. The strong and ultrafast response to hydrogen was attributed to the synergistic effects of the unique heterostructure and large specific surface area. The development of efficient and stable new hydrogen-sensing materials will help further expand their application scope in the sensing field.

Quantum States Induced by Strong Interface Coupling in a 2D VSe2/Bi2Se3 Heterostructure.

We have successfully fabricated single-layer (SL) 1T-VSe2/Bi2Se3 heterostructures using molecular beam epitaxy (MBE), which exhibits uniform moiré patterns on the heterostructure surface. Scanning tunneling microscopy/spectroscopy (STM/STS) reveals a notable quantum state near the Fermi energy, robust across the entire moiré lattice. This quantum state peak shifts slightly across different domain ranges, suggesting an elastic strain dependence in SL VSe2, confirmed by geometric phase analysis (GPA) simulations. Density functional theory (DFT) calculations indicate that the enhanced quantum state results from charge redistribution between the substrate and the epifilm with the orbitals of Se atoms in the deformed VSe2 playing a dominant role.

Subnanoscale Ion Beam Modification-Assisted Smoothing of Heterostructure Surfaces.

Glass ceramic (GC) is the most promising material for objective lenses for extreme ultraviolet lithography that must meet the subnanometer precision, which is characterized by low values of high spatial frequency surface roughness (HSFR). However, the HSFR of GC is typically degraded during ion beam figuring (IBF). Herein, a developed method for constructing molecular dynamics (MD) models of GC was presented, and the formation mechanisms of surface morphologies were investigated. The results indicated that the generation of the dot-like microstructure was the result of the difference in the erosion rate caused by the difference in the intrinsic properties between ceramic phases (CPs) and glass phases (GPs). Further, the difference in the microstructure of the IBF surface under different beam angles was mainly caused by the difference in the two types of sputtering. Quantum mechanical calculations showed that the presence of interstitial atoms would result in electron rearrangement and that the electron localization can lead to a reduction in CP stability. To obtain a homogeneous surface, the effects of beam parameters on the heterogeneous surface were systematically investigated based on the proposed MD model. Then, a novel ion beam modification (IBM) method was proposed and demonstrated by TEM and GIXRD. The range of ion beam smoothing parameters that could effectively converge the HSFR of the modified surface was determined through numerous experiments. Using the optimized beam parameters, an ultrathin homogeneous modified surface within 3 nm was obtained. The HSFR of GC smoothed by ion beam modification-assisted smoothing (IBMS) dropped from 0.348 to 0.090 nm, a 74% reduction. These research results offer a deeper understanding of the morphology formation mechanisms of the GC surfaces involved in ion beam processing and may point to a new approach for achieving ultrasmooth heterostructure surfaces down to the subnanometer scale.

Nitrogen-metal-oxygen moieties enriched surface reconstruction in CoFe electrocatalysts for stabilizing high-valence Co sites enable water oxidation

Despite the potential of heterostructure construction and surface reconstruction strategies to significantly enhance the oxygen evolution reaction (OER) performance of transition metal compounds, integrating these approaches into a single material system remains a significant challenge. In this work, we report an efficient CoFe-LDH catalyst with multi-metal nitrides on the surface through simple and tunable N2-plasma treatment (PL CoFe-LDH). Structural characterization and theoretical calculations indicate a high concentration of defective sites in PL CoFe-LDH, which facilitates the exposure of a greater number of active NFeO and NCoO centers. During the initial stage of the OER process, there is a rapid phase transition of Fe and Co, leading to the formation of metal (oxy)hydroxides. Meanwhile, Co3+ species gradually accumulate on the surfaces, which is responsible for the excellent OER catalytic activity. Then, the neighboring N atoms function as electron reservoirs, donating electrons to the Co sites to prevent overoxidation and dissolution of Co in the electrolyte, thus significantly enhancing the stability of the OER. The catalysts enable the achievement of ultralow OER overpotential, measuring 161.1 and 205.5 mV at current densities of 10 mA cm−2 and 200 mA cm−2, respectively, while exhibiting exceptional stability.

Heterostructured three-dimension MXene/short carbon fiber to enhance thermal, mechanical and tribological properties of epoxy composites

Polymer composites play an essential role in the field of friction materials. However, severe environment is still big challenges for their application. Three-dimension MXene/short carbon fiber (SCF) was prepared to improve the thermal, mechanical, and tribological performance of epoxy resin. When the mass ratio of MXene to SCF is 1:150, the MXenes are uniformly anchored on the surface of SCF under the strong hydrogen bonding interaction, leading to stable heterostructure and abundant surface functional groups. Owing to the excellent synergy between the MXene and SCF, the modified epoxy composite exhibits superior mechanical and thermal properties, as well as high thermal conductivity. Moreover, it has excellent tribological performance with an average friction coefficient of 0.44 and a specific wear rate of 3.0 × 10-6 mm3·N-1 ⋅m-1 in 2 hours, which reduced by 35.3% and 97.1% than those of epoxy resin, respectively.

High-Efficiency Ag-Modified ZnO/g-C3N4 Photocatalyst with 1D-0D-2D Morphology for Methylene Blue Degradation.

Photocatalysts with different molar ratios of Ag-modified ZnO to g-C3N4 were prepared through an electrostatic self-assembly method and characterized through techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The resulting Ag-ZnO/g-C3N4 photocatalysts exhibited a unique 1D-0D-2D morphology and Z-type heterojunction. Moreover, g-C3N4 nanosheets with large layer spacing were prepared using acid treatment and thermal stripping methods. The Z-type heterostructure and localized surface plasmon resonance effect of Ag nanowires enabled high-speed electron transfer between the materials, while retaining large amounts of active substances, and broadened the light response range. Because of these features, the response current of the materials improved, and their impedance and photoluminescence reduced. Among the synthesized photocatalysts, 0.05Ag-ZnO/g-C3N4 (molar ratio of g-C3N4/ZnO: 0.05) exhibited the highest photocatalytic performance under UV-visible light. It degraded 98% of methylene blue in just 30 min, outperforming both g-C3N4 (21% degradation in 30 min) and Ag-ZnO (84% degradation in 30 min). In addition, 0.05Ag-ZnO/g-C3N4 demonstrated high cycling stability.

Quasicrystal Nanosheet/α-Fe2O3 Heterostructure-Based Low Power NO2 Sensors: Experimental and DFT Studies.

Industrial emissions, environmental monitoring, and medical fields have put forward huge demands for high-performance and low power consumption sensors. Two-dimensional quasicrystal (2D QC) nanosheets of metallic multicomponent Al70Co10Fe5Ni10Cu5 have emerged as a promising material for gas sensors due to their excellent catalytic and electronic properties. Herein, we demonstrate highly sensitive and selective NO2 sensors developed by low-cost and scalable fabrication techniques using 2D QC nanosheets and α-Fe2O3 nanoparticles. The sensitivity (ΔR/R%) of the optimal amount of 2D QC nanosheet-loaded α-Fe2O3 sensor was 32%, which is significantly larger about 3.5 times than bare α-Fe2O3 sensors for 1 ppm of NO2 at 150 °C operating temperature. The sensors exhibited p-type conduction, and resistance was reduced when exposed to NO2, an oxidizing gas. The enhanced sensing characteristics are a result of the formation of nanoheterojunctions between 2D QC and α-Fe2O3, which improved the charge transport and provided a large sensing signal. In addition, the heterojunction sensor demonstrated excellent NO2 selectivity over other oxidizing and reducing gases. Furthermore, density functional theory calculation examines the adsorption energy and charge transfer between NO2 molecules on the α-Fe2O3(110) and QC/α-Fe2O3(110) heterostructure surfaces, which coincides well with the experimental results.

Coordination engineering of the interfacial chemical bond and sulfur vacancies modulated S‐scheme charge transfer for efficient photocatalytic CO2 reduction

Surface charge localization and poor carrier separation efficiency limited the of photocatalytic CO2 reduction (PCR) activity. Creating heterojunctions between the interfacial layers was an important strategy used to enhance catalytic activity. Here, a core-shell structure S-scheme catalyst was constructed by growing of Bi2WO6 (BWO) nanospheres on the surface of Zn0.5Cd0.5S(VS-ZCS) nanospheres with abundant sulfur defect, and which was coordinated by the interface bonding and the sulfur vacancies (VS) for efficient PCR. Meanwhile, the surface potential was 91 mV, indicating the creation of strong interface electric field (IEF). As part of the strong synergy of the Bi-S bond, IEF and VS, the improved photocatalyst exhibited high CO evolution rate of 86.16 μmol⋅g−1, which was about 9.23 fold of the pristine VS-ZCS. This was attributed to production of *COOH intermediates on the VS-ZCS/BWO surface that had been proved to be crucial for PCR generation CO. Besides, electrons quickly migrated through the formed Bi-S bonds to the catalytic sites, accelerating charge separation. The use of VS as electron traps was beneficial for regulating the localization of photogenerated charges on the surface of S-scheme heterostructure. The Bi-S bonds and VS modulated S‐scheme charge transfer for efficient photocatalytic CO2 reduction provides new insights into photocatalytic CO2 reduction.

Novel CuBi2O4-BiOCl/rGO heterostructure nanocomposite as high-performance visible light photocatalyst for the disintegration of persistent antimicrobials in aquatic environment

The article highlights the fabrication of a novel CuBi2O4-BiOCl/rGO heterojunction nanocomposite as a renewable visible light photocatalyst for the quick disintegration of a persistent fluoroquinolone-based antimicrobial drug, i.e., enrofloxacin (ENF) in aquatics. CuBi2O4-BiOCl (CBO-BOC) nanocomposites (NCs) of varying BOC stoichiometric ratios were synthesized, of which CBO-(30%) BOC NC (CB-30) revealed top photocatalytic traits, which was analogously dispersed onto reduced graphene oxide (rGO) nanosheets, to serve as the visible light photon responsive materials. The electron microscopic and spectroscopic techniques were deployed to understand the CB-30/rGO heterostructure's surface topography and structural morphology. The FE-SEM, HR-TEM and XPS analysis confirmed the dispersion of CBO nanospheres onto the BOC nanoflakes and further confirmed the successful imbuement of CB-30 NCs onto the rGO nanosheets. The CB-30/rGO photocatalyst revealed excellent porosity and surface area for the fast dissipation of pharmaceutical pollutants. The impact of various operating parameters, such as solution pH, drug concentration, CBO-BOC stoichiometry, CB-30/rGO dosage, photosensitizers/electron acceptors, light intensity and matrix tolerance limits, were augmented to enhance the photocatalytic efficiency of the proposed new-age photocatalyst. Under optimized conditions, complete drug mineralization was achieved in ≤0.33 h for complete mineralization of 30 ppm of ENF, using 0.075 g of photocatalyst. The time-dependent profiling of photoproducts/intermediates derived from the photocatalytic degradation of ENF was monitored by HR-MS analysis. The acute and chronic toxicity effects of ENF and its organic intermediate were predicted using the ECOSAR model for selected aquatic life forms. The photocatalyst exhibited reusability up to seven cycles, with excellent thermal/chemical stability, for pollutant decontamination from industrial effluents and environmental samples.

Energizing Co Active Sites via d-Band Center Engineering in CeO2-Co3O4 Heterostructures: Interfacial Charge Transfer Enabling Efficient Nitrate Electrosynthesis.

The electrochemical nitrogen oxidation reaction (NOR) holds significant potential to revolutionize the traditional nitrate synthesis processes. However, the progression in NOR has been notably stymied due to the sluggish kinetics of initial N2 adsorption and activation processes. Herein, the research embarks on the development of a CeO2-Co3O4 heterostructure, strategically engineered to facilitate the electron transfer from CeO2 to Co3O4. This orchestrated transfer operates to amplify the d-band center of the Co active sites, thereby enhancing N2 adsorption and activation dynamics by strengthening the Co─N bond and diminishing the resilience of the N≡N bond. The synthesized CeO2-Co3O4 manifests promising prospects, showcasing a significant HNO3 yield of 37.96µg h-1 mgcat -1 and an elevated Faradaic efficiency (FE) of 29.30% in a 0.1m Na2SO4 solution at 1.81V versus RHE. Further substantiating these findings, an array of in situ methodologies coupled with DFT calculations vividly illustrate the augmented adsorption and activation of N2 on the surface of CeO2-Co3O4 heterostructure, resulting in a substantial reduction in the energy barrier pertinent to the rate-determining step within the NOR pathway. This research carves a promising pathway to amplify N2 adsorption throughout the electrochemical NOR operations and delineates a blueprint for crafting highly efficient NOR electrocatalysts.

Metal-organic framework-derived Se-blended ZrO2 with a nitrogen-doped carbon heterostructure for electrocatalytic overall water splitting.

Designing low cost, highly active and efficient non-noble metal bifunctional electrocatalysts with remarkable operational reliability for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is indispensable for large-scale water electrolysis and the development of clean energy conversion technologies. Herein, we decorated a two-dimensional (2D) selenium-blended zirconium dioxide (Se-ZrO2) on the surface of a nitrogen-doped carbon heterostructure (Se-ZrO2@NC), which was derived from Zr-metal-organic frameworks (Zr-MOFs), and loaded it on a stainless-steel mesh electrode. Accordingly, phenomenal electrocatalytic performance was observed for the Se-ZrO2@NC-loaded electrode with a minimum overpotential of 48 mV for the HER and 251 mV for the OER at 10 mA cm-2 current density in acidic and alkaline mediums, respectively. Moreover, a complete cell set up was constructed, where the OER and HER were studied at the anode and cathode, respectively, with a cell potential of 1.58 V to reach a current density of 10 mA cm-2 together with an exciting long-term stability of over 48 h. The developed Se-blended 2D transition metal dioxides on the 2D nitrogen-doped carbon heterostructure extended to a variety of catalytically active materials that would provide highly active and stable electrocatalysts for alkaline water splitting studies.

Enhanced photoelectrochemical nitrogen reduction to ammonia by a plasmon-active Au grating decorated with the gC3N4@MoS2 heterosystem and plasmon-active nanoparticles

Coupled plasmon triggering significantly enhanced the NRR efficiency on the surface of semiconductor heterostructure (2D/2D) gC3N4@MoS2.

ГЕНЕРАЦИЯ ПОВЕРХНОСТНЫХ АКУСТИЧЕСКИХ ВОЛН СЕГНЕТОЭЛЕКТРИЧЕСКОЙ ПЛЕНКОЙ BST ПРИ ДЕЙСТВИИ ОДНООСНОЙ НАГРУЗКИ

The electro-mechanical properties of a ferroelectric film of barium strontium titanate (BST) film located on a silicon substrate depend on applied external strain. A significant dependence is observed for concentrations close to values, where a phase transition for the ferroelectric film occurs. A model of single-crystal BST film near the phase transition under uniaxial strain is studied by the thermodynamic theory of phase transitions. The material properties of the film obtained by the model are used for numerical study of the excitation of Rayleigh’ acoustic waves on the surface of the film-substrate heterostructure. Shifting the extrema of S-parameters, characterizing the efficiency of excitation of surface acoustic waves, is shown under the applied strain. The change of S-parameters for the first three resonances determined principally by the geometry of the interdigital electrodes is presented. The largest shift of resonant frequency is observed in a case of the second resonance that corresponds to Sezava wave.

Solvent-Free Ultrafast Construction of Se-Deficient Heterojunctions of Bimetallic Selenides toward Flexible Sodium-Ion Full Batteries.

Flexible quasi-solid-state sodium ion batteries featuring their low-cost, high safety and excellent mechanical strength have attracted widespread interest in the field of wearable electronic devices. However, the development of such batteries faces great challenges including the construction of interfacial compatible flexible electrode materials and addressing the high safety demands of electrolyte. Here selenium-vacancies regulated bimetallic selenide heterojunctions anchored on waste cotton cloth-derived flexible carbon cloth (FCC) with robust interfacial C-Se-Co/Fe chemical bonds as a flexible anode material (CCFSF) is proposed by ultrafast microwave pyrolysis method. Rich selenium vacancies and CoSe2 /FeSe2-x heterostructures are synchronously formed that can significantly improve ionic and electronic diffusion kinetics. Additionally, a uniform carbon layer coating on the surface of Se-deficient heterostructures endows it with outstanding structural stability. The flexible cathode (PB@FCC) is also fabricated by directly growing Prussian blue nanoparticles on the FCC. Furthermore, an advanced flexible quasi-solid-state Na-ion pouch cell is assembled by coupling CCFSF anode, PB@FCC cathode with P(VDF-HFP)-based gel polymer electrolyte. The full cell not only demonstrates excellent energy storage performance but also robust mechanical flexibility and safety. The present work offers an effective avenue to achieve high safety flexible energy storage device, promoting the development of flexible wearable electronic devices.

Assembly of Arbitrary Designer Heterostructures with Atomically Clean Interfaces

AbstractVan der Waals heterostructures are an excellent platform for studying intriguing interface phenomena, such as moiré and proximity effects. Many of these phenomena occurring in such heterostructures' interfaces and surfaces have so far been hampered because of their high sensitivity to disorder and interface contamination. Here, it reports a dry polymer‐based assembly technique to fabricate arbitrary designer van der Waals heterostructures with atomically clean surfaces. The key features of the suspended dry pick‐up and flip‐over assembly technique are: 1) the heterostructure surface never comes into contact with polymers, 2) the assemble is entirely solvent‐free, 3) it is entirely performed in a glovebox, and 4) it only requires temperatures below 130 °C. By performing ambient atomic force microscopy and atomically‐resolved scanning tunneling microscopy on example heterostructures, it demonstrates the fabrication of air‐sensitive heterostructures with ultra‐clean interfaces and surfaces. It envisions that, due to the avoidance of polymer melting, this technique is potentially compatible with heterostructure assembly under ultra‐high vacuum conditions, which promises ultimate heterostructure quality.

Design of heterostructure one-port SAW resonator with improved bandwidth using Si and LiNbO3 layer

In this research work, we have designed a heterostructure one-port surface acoustic wave (SAW) resonator. The multi-layer one port SAW resonator is made of a silicon (Si) substrate as base material, 128 ͦ rotated Y-cut X- propagated lithium niobate (LiNbO3) as piezoelectric substrate, and Inter Digital Transducers (IDTs) made of aluminium. This model is designed to operate on a wide frequency of 4–5 GHz with a resonance frequency of 4.74 GHz. Various parameters are taken into consideration during the study and analysis such as high-quality factor, wider bandwidth, better electromechanical coupling coefficient, and a true Figure of merit (FoM). The obtained Quality factor and the electromechanical coupling coefficient (k2) of the designed model are 2700 and 0.18. By using the wide range of frequencies, the bandwidth for the designed model is 1.74 MHz. The obtained results show that the device’s performance of the one port multilayer SAW resonator using the Al/128°YXLiNbO3/Si multi-layered substrate exhibits a commercial application in the 5 G wireless communication system.

Visible light active and self-cleaning SiO2/N-TiO2 heterostructure surface with high transmittance for solar module glass cover: Experimental and DFT insights

Transparent, anti-reflective, visible-light-driven photocatalytically active and superhydrophilic heterostructure coating have been synthesized on glass substrates. Heterostructures consist of SiO2 as an anti-reflective layer at the bottom and nitrogen-doped TiO2 (N-TiO2) with varying concentrations (0, 2.5, 5, 7.5 and 10 wt%) at the top for visible-light-driven photocatalytic active surface. Porosity is induced in both materials by introducing a suitable pore-forming agent for better anti-reflective properties. Doped samples exhibited excellent photocatalytic activity in the sunlight owing to the significant absorption in the visible region, confirmed by experimental and theoretical studies. Disintegration and cleaning of pollutants are demonstrated by photodegradation of methylene blue (MB) dye solution. Optimized heterostructure exhibited 5% greater optical transmittance than pristine TiO2. The hydrophilicity of heterostructure also varies with nitrogen doping concentration and is found to be minimum (11.9º) for SiO2/2.5 N-TiO2. Simultaneous self-cleaning and high optical transmittance of SiO2/N-TiO2 support the removal of fine contaminants under sunlight irradiation. At the same time, it contributes to the enhancement of transmitting incident light to the absorber layer of the solar cell. These heterostructures are highly suitable for bifunctional, self-cleaning and anti-reflective coating applications on building glass and photovoltaic glass covers.

Pseudocapacitive charge storage behavior of cation-doped WS2 nanosheets electrode

Nanostructured two-dimensional layered semiconductors MX2 (M = Mo, W, and X = S, Se, Te) are potential candidates for electrochemical energy conversion and storage applications. Recently, different research strategies, including phase and heterostructure engineering, surface modification, and chemical doping have been employed with the aim to obtain high energy density MX2 supercapacitor electrodes. Here, we report the electrochemical supercapacitor performance of cation, Co, Ir, and Ru, doped WS2 nanosheets electrode in 1 M Na2SO4 and 2 M H2SO4 aqueous electrolyte. The structure of WS2 nanosheets is stabilized in the 2H hexagonal phase and the interlayer separation expanded after cation doping. The cation-doped WS2 nanosheet electrodes exhibit pseudocapacitive behavior with improved performance in both electrolytes. Among all, the best electrode, Ru doped WS2 nanosheets shows excellent energy storage capacity and attains a specific capacity of 438 Fg−1 in 2 M H2SO4 electrolyte. The analysis reveals that cation doping is one possible research strategy to improve the supercapacitor performance of WS2 nanosheets.

A performance comparison of heterostructure surface plasmon resonance biosensor for the diagnosis of novel coronavirus SARS-CoV-2.

This paper presents a performance comparison of heterostructure surface plasmon resonance (SPR) biosensors for the application of Novel Coronavirus SARS-CoV-2 diagnosis. The comparison is performed and compared with the existing literature based on the performance parameters in terms of several prisms such as BaF2, BK7, CaF2, CsF, SF6, and SiO2, several adhesion layers such as TiO2, Chromium, plasmonic metals such as Ag, Au, and two-dimensional (2D) transition metal dichalcogenides materials such as BP, Graphene, PtSe2 MoS2, MoSe2, WS2, WSe2. To study the performance of the heterostructure SPR sensor, the transfer matrix method is applied, and to analyses, the electric field intensity near the graphene-sensing layer contact, the finite-difference time-domain approach is utilized. Numerical results show that the heterostructure comprised of CaF2/TiO2/Ag/BP/Graphene/Sensing-layer has the best sensitivity and detection accuracy. The proposed sensor has an angle shift sensitivity of 390°/refractive index unit (RIU). Furthermore, the sensor achieved a detection accuracy of 0.464, a quality factor of 92.86/RIU, a figure of merit of 87.95, and a combined sensitive factor of 85.28. Furthermore, varied concentrations (0-1000nM) of biomolecule binding interactions between ligands and analytes have been observed for the prospects of diagnosis of the SARS-CoV-2 virus. Results demonstrate that the proposed sensor is well suited for real-time and label-free detection particularly SARS-CoV-2 virus detection.

Characterization of CdxTeyOz/CdS/ZnO Heterostructures Synthesized by the SILAR Method

CdxTeyOz/CdS/ZnO heterostructures were obtained by the SILAR method using ionic electrolytes. A CdS film was formed as a buffer layer for better adhesion of the cadmium-tellurium oxides to the substrate surface. In turn, the ZnO substrate was previously prepared by electrochemical etching to form a rough textured surface. In addition, an annealing mode was used in an oxygen stream to complete the oxidation process of the heterostructure surface. The resulting nanocomposite was investigated using RAMAN, XRD, SEM, and EDX methods. We assume that the oxides CdO and TeO4 initially form on the surface and later evolve into TeO2 and TeO3 when saturated with oxygen. These oxides, in turn, are the components of the ternary oxides CdTeO3 and CdTe3O8. It should be noted that this mechanism has not been fully studied and requires further research. However, the results presented in this article make it possible to systematize the data and experimental observations regarding the formation of cadmium-tellurium films.