Core-shell Nanowires Research Articles

Room temperature lasing from InGaAs quantum well nanowires on silicon-on-insulator substrates

In this work we demonstrate room temperature lasing from core-shell nanowires consisting of a radial InGaAs quantum well as the active material. The nanowires with the GaAs/InGaAs/InGaP quantum well structures are arranged in a deformed honeycomb lattice, forming a photonic crystal surface emitting laser (PCSEL). We demonstrate lasing from devices with three different nanowire diameters from undeformed, stretched, and compressed honeycomb lattices. Under optical pumping we show that the PCSEL lases at the wavelength of 966 nm (stretched pattern), with the lasing threshold of 103 μJ/cm2. The lasing wavelength increases as the nanowire diameter increases. Combining photoluminescence results and numerical simulations on the field profile and the quality factors of the devices, we establish that the lasing of the device is from the radial quantum well structure.

Plateau-Rayleigh Instability in Soft-Lattice Inorganic Solids.

Plateau-Rayleigh instability─a macroscopic phenomenon describing the volume-constant breakup of one-dimensional continuous fluids─has now been widely observed in adatoms, liquids, polymers, and liquid metals. This instability enables controlled wetting-dewetting behavior at fluid-solid interfaces and, thereby, the self-limited patterning into ordered structures. However, it has yet to be observed in conventional inorganic solids, as the rigid lattices restrict their "fluidity". Here, we report the general fluid-like Plateau-Rayleigh instability of silver-based chalcogenide semiconductors featuring soft-lattice ionic crystals. It enables postsynthetic morphing from conformal core-shell nanowires to periodically coaxial ones. We reveal that such self-limited reconstruction is thermodynamically driven by the surface energy and interface energy and kinetically favored by the high ionic diffusion coefficients of subnanoscale soft-lattice shells. The resulting periodic heterostructures can be topotactically transformed for epitaxial combinations of functional semiconductors free from the lattice-matching rule. This fluid-like behavior in soft inorganic solids thus offers routes toward sophisticated nanostructures and controllable patterning at all-inorganic solid-solid interfaces.

Investigation of resistive switching behavior driven by active and passive electrodes in MoO2–MoS2 core shell nanowire memristors

Memristive devices based on layered materials have the potential to enable low power electronics with ultra-fast operations toward the development of next generation memory and computing technologies. Memristor performance and switching behavior crucially depend on the switching matrix and on the type of electrodes used. In this work, we investigate the effect of different electrodes in 1D MoO2–MoS2 core shell nanowire memristors by highlighting their role in achieving distinct switching behavior. Analog and digital resistive switching are realized with carbon based passive (multi-layer graphene and multiwall carbon nanotube) and 3D active metal (silver and nickel) electrodes, respectively. Temperature dependent electrical transport studies of the conducting filament down to cryogenic temperatures reveal its semiconducting and metallic nature for passive and active top electrodes, respectively. These investigations shed light on the physics of the filament formation and provide a knob to design and develop the memristors with specific switching characteristics for desired end uses.

Self-standing TiO₂@CC@PANI core–shell nanowires as flexibles lithium-ion battery anodes

Self-standing TiO₂@CC@PANI core–shell nanowires as flexibles lithium-ion battery anodes

Kerr birefringent switching mechanism in core-shell nanowires transformed by stark anti-crossing

Stark anti-crossing (SAC) serves as a new approach to switch the Kerr birefringence effect of the off-centered core-shell square nanowires (OSN). The intensity of SAC induced by an electric field is inversely correlated with the degree of the core displacement from the center. To the best of our knowledge, it is the first demonstration that SAC is equipped with efficacy in suppressing Kerr birefringence of OSN by intensifying energy degeneracy and mitigating the parity symmetry distortion of wavefunction due to core displacement. Such a novel mechanism lies in the formation of two quasi-degenerate energy levels with nearly identical energies but opposite parity wavefunctions. It demonstrates a transform from polarization-dependent to -independent response of refractive index changes at mid-infrared wavelengths longer than 10 µm.

Design and synthesis of Au nanoparticles decorated NiCo2O4@MnO2 core-shell nanowires for high-performance supercapacitors

Design and synthesis of Au nanoparticles decorated NiCo2O4@MnO2 core-shell nanowires for high-performance supercapacitors

Constructing Long and Stable Ag‐Al2O3 Core–Shell Nanowires for Humidity Sensing and Triboelectric Energy Generation

Silver nanowires (AgNWs) are a promising alternative material to indium tin oxide as flexible transparent electrodes owing to their excellent optoelectrical properties and mechanical performance. However, the main challenge is the poor stability under diverse environments, ranging from high humidity, chemical exposure, and dynamic mechanical deformation. Herein, ultralong AgNWs (≈100 μm) have been synthesized via controlling growth kinetics by a facile acetic acid‐assisted solvothermal method, further decorated with a thin Al2O3 layer by electrodeposition to form a core–shell architecture. The resultant films based on Ag‐Al2O3 core–shell nanowires (NWs) possess a higher conductivity while preserving the optical transparency due to the enhanced NWs contact. More importantly, the constructed films exhibit strong resistance to various conditions, such as exposure to high temperature/humidity and immersion in NaCl, HCl, and Na2S solutions. The laser‐etched interdigital electrodes based on the chemically stable AgNWs are further integrated with graphene oxide layer for humidity sensing and respiration monitoring. Furthermore, the developed NWs with superior mechanical stability are constructed as triboelectric nanogenerators for electricity generation, and reliable output performance has been demonstrated. This work provides a convenient, scalable, and cost‐effective solution that offers great potential for designing robust, transparent electrodes for next‐generation flexible electronics.

Flexible Ag@Au core–shell nanowires electrode fabrication with controllable nanogold size and thickness on silver nanowires/PDMS substrate toward enhanced ethanol electrooxidation

The synthesis of gold nanowires (AuNWs) is challenging due to difficulties in obtaining AuNWs of variable diameters and lengths. In this study, an effective approach to fabricating AuNWs with controllable lengths and diameters was developed on a flexible silver nanowires (AgNWs)/polydimethylsiloxane (PDMS) substrate. Gold nanoparticles were uniformly electrodeposited onto the flexible AgNWs/PDMS to form bimetallic Ag@Au core–shell NWs/PDMS. The results showed that the diameters and the lengths of the Ag@Au NWs were easily fine-tuned. The flexible Ag@Au NWs/PDMS electrode exhibited excellent mechanical, electrical, and electrochemical properties. In ethanol oxidation reaction (EOR), the Ag@Au NWs/PDMS achieved a peak current density of 28541.55 μA cm−2 (10 times higher than that of a commercial Au electrode) and 63.39% retaining activity in a stability test by chronoamperometry (over 2 times stable than values in literature). Finally, EOR and chromium (VI) determination by the Ag@Au NWs/PDMS in flexible integrated electrodes were performed to showcase the versatile feasibilities of this new material.

ZnO@NiO core-shell heterojunction photoanode modified with NiOOH co-catalyst for high-performance self-powered photoelectrochemical-type UV photodetector

ZnO, a promising photoanode material, faces significant challenges in achieving high-efficient photoelectrochemical (PEC) type UV photodetectors due to inadequate charge separation and sluggish surface reaction kinetics. Constructing heterojunction nanostructures by coupling of p-NiO to n-ZnO nanowire arrays with well-aligned energy band positions presents a feasible strategy for enhancing PEC-type photodetector performance. Herein, we demonstrate that the designed ZnO@NiO core–shell nanowire arrays form a spatial charge transfer channel, facilitating efficient generation and extraction of charge carriers. The exceptional catalytic properties of NiOOH, derived from the transformation of NiO in an aqueous alkaline environment, serve as a potent co-catalyst, effectively accelerating the kinetics of the surface oxygen evolution reaction. Benefiting from the synergistic effect of the heterojunction and cocatalyst, the optimized photoanode achieves a high responsivity of 438.36 mA/W, a large detectivity of 4.85 × 1012 Jones, and rapid response time of 150.05/150.26 ms, while simultaneously exhibiting long-time PEC stability. This work highlights the critical role of nanostructure design in developing high-performance self-powered UV photodetectors.

Influence of different morphologies on the catalytic activity of Pt-Pd nanostructures for methanol oxidation

Developing efficient and durable catalysts for methanol oxidation in acidic media remains a significant challenge in electrochemical energy conversion. This study addresses this issue by synthesizing Pt-Pd bimetallic electrocatalysts with different morphologies, including nanowires, core-shell nanoparticles, and core-shell nanowires, and evaluating their catalytic activities. The electrocatalysts were prepared via chemical reduction of metal precursors using formic acid as a reducing agent. X-ray diffraction analysis revealed distortions in the lattice parameters of the nanostructured bimetallic catalysts, and STEM/EDX analysis confirmed the formation of the different morphologies on the carbon support. Electrochemical assessments showed that the bimetallic catalysts exhibited superior catalytic activities to nanostructured Pt/C catalysts. The Pd@Pt/C core-shell nanowires displayed the highest catalytic efficiency, with the lowest methanol oxidation onset potential (468 mV) and the highest mass and specific activities. Electrochemical impedance measurements revealed the lowest charge transfer resistance value for the Pd@Pt/C core-shell nanowires. Chronoamperometric tests further indicated that the Pd@Pt/C core-shell nanowires catalyst exhibited superior tolerance to inactivation by reaction intermediates, achieving mass and specific activities approximately twice as high as those of the Pt/C catalyst. The enhanced catalytic performance of the Pd@Pt/C core-shell nanowires was attributed to the synergistic effects of the two morphologies that alter the electronic and geometric structures of the Pt within the catalyst.

Simulation of the functionality of ZnO, TiO2 and Ta2O5, and MoO2 carrier selective contacts of GaAs0.99Bi0.01 nanowire-based solar cells

Abstract Photovoltaic performance of perpendicularly aligned GaAs0.99Bi0.01/CSC/ITO core-shell nanowire solar cell is thoroughly investigated in this simulation based theoretical study for both electron selective contact (ESC) and hole selective contact (HSC) as carrier selective contact (CSC) shell around GaAs0.99Bi0.01 core nanowire. The overall performance has been compared with radial PiN doped GaAs0.99Bi0.01 NWSC to mark the improvement caused by carrier selectivity. ZnO, TiO2, and Ta2O5 materials have been chosen as ESC material and MoO2 is chosen as HSC material in order to carry out this comparative study. We have thoroughly performed geometry optimization test over a wide range of periods in order to select the optimized ITO (Indium Tin Oxide) thickness for obtaining maximum photo current generation. The maximum short circuit photo current density (Jsc) of 38.76 mA/cm2 is obtained with ZnO coated nanowire solar cell (NWSC) for a pitch (P) of 400 nm and ITO shell thickness of 90 nm. For this optimized geometry, TiO2, Ta2O5 and MoO2 coated structures offered Jsc of 35.82 mA/cm2, 35.69 mA/cm2, and 35.27 mA/cm2 respectively and the uncoated NW generated Jsc of 31.15 mA/cm2. The planar structure without coating exhibits a Jsc of 24.86 mA/cm2, which is significantly lower than the nanostructured solar cells. Finally Lumerical 3D charge transport simulator is used to perform the electrical stimulation of ZnO coated structure, which offers maximum ideal Jsc. A detailed electrical performance analysis of GaAs0.99Bi0.01/CSC/ITO unit nanowire solar cell for ZnO, TiO2, Ta2O5 as ESC and MoO2 as HSC have also been covered in this article which reveals that ZnO as ESC possesses promising potential for designing highly efficient solar cells as it offers a photo conversion efficiency(PCE) of the order of 25% and open circuit voltage (Voc) even for very less minority carrier lifetime (Ʈn) 0.1 ns of GaAs0.99Bi0.01 and 1ps Ʈn of ZnO.

Unraveling Interdiffusion Phenomena and the Role of Nanoscale Diffusion Barriers in the Copper-Gold System.

Diffusion is one of the most fundamental concepts in materials science, playing a pivotal role in materials synthesis, forming, and degradation. Of particular importance is solid state interdiffusion of metals which defines the usable parameter space for material combinations in the form of alloys. This parameter space can be explored on the macroscopic scale by using diffusion couples. However, this method reaches its limit when going to low temperatures, small scales, and when testing ultrathin diffusion barriers. Therefore, this work transfers the principle of the diffusion couples to small scales by using core-shell nanowires and in situ heating. This allows us to delve into the interdiffusion dynamics of copper and gold, revealing the interplay between diffusion and the disorder-order phase transition. Our in situ TEM experiments in combination with chemical mapping reveal the interdiffusion coefficients of Cu and Au at low temperatures and highlight the impact of ordering processes on the diffusion behavior. The formation of ordered domains within the solid-solution is examined using high-resolution imaging and nanodiffraction including strain mapping. In addition, we examine the effectiveness of ultrathin Al2O3 barrier layers to control interdiffusion of the diffusion couple. Our findings indicate that a 5 nm thick layer serves as an efficient diffusion barrier. This research provides valuable insights into the interdiffusion behavior of Cu and Au on the nanoscale, offering potential applications in the development of miniaturized integrated circuits and nanodevices.

Tailoring thermal transport and confinement effect of GaN/Si3N4 nanowires utilizing core–shell architecture

The thermal transport properties of nanowires (NWs) can be significantly influenced by the implementation of a core-shell structure, which introduces interface scattering and phonon localization effects, opening avenues for novel applications. In this paper, we use the method of non-equilibrium molecular dynamics to simulate the effects of system temperature, cross-sectional width, and nanopillar interface on the thermal transport of GaN/Si3N4core-shell NWs. The thermal transport process of phonons in core-shell NWs is studied by calculating the vibrational density of states, phonon participation rate, and dispersion curve. The results show that the core-shell NWs characterized by smooth interfaces exhibit a 17.4% decrease in thermal conductivity (TC) at room temperature when contrasted with pristine GaN NWs. Furthermore, the TC of GaN/Si3N4core-shell NWs can be further reduced by adding nanopillars at the interface. Due to resonance effect, thus effectively regulating the thermal transport. The presence of nanopillars increases phonon-surface scattering intensity at low-frequency and modifies phonon dispersion to decrease the group velocity. In addition, the hybridization of phonon modes between those of the nanopillars and the Si3N4shell gives rise to numerous dispersionless resonance phonon modes that span the entire phonon spectrum. This research delves into the effects of nanopillars and interfaces on thermal transport, providing important guidance for understanding confinement effects and establishing a robust theoretical basis for the regulation of thermal transport.

Formation mechanism and luminescence properties of silicon carbide nanowires with core-shell structure

For the preparation of SiC nanowires (SiC NWs) by carbothermal reduction, it is of great significance to study the formation mechanism of sic nanowires for process optimization and the controllable preparation. Although first-principles molecular dynamics (FPMD) can simulate systems of hundreds of atoms on a picosecond time scale, the results of FPMD are still insufficient to elucidate the formation mechanism of core-shell SiC nanowires. To make up this deficiency, this article has conducted Deep Potential Molecular Dynamics (DPMD) simulation on nanoseconds timescales with near FPMD accuracy for systems containing thousands of atoms, the results more concretively show the formation process of core-shell SiC nanowires. DPMD simulation results show when CO molecules react with SiO molecules, CO molecules are wrapped by SiO molecules to form agglomerates, SiO molecules in the agglomerates that can come into contact with the wrapped CO molecules will react with wrapped CO molecules to form the SiC core, and SiO molecules that in the outer layer of the agglomerates will disproportionate into the amorphous SiO2 shell. Furthermore, the formation mechanism of SiC nanowires was validated in combination with thermodynamics and experimental methods. Thermodynamic results show that vacuum conditions are favorable for the formation of SiO and CO and lower the temperature of SiC preparation. Finally, the core-shell structure of SiC NWs with good luminescence properties were successfully prepared by carbothermal reduction method using carbon black and silicon dioxide as raw materials under the pressure of less than 5 kPa.

A Modified Galvanic Cell Synthesis of Pd@Pt Core–Shell Nanowire Catalysts: Structural Insights and Enhanced ORR Performance

A Modified Galvanic Cell Synthesis of Pd@Pt Core–Shell Nanowire Catalysts: Structural Insights and Enhanced ORR Performance

Effect of Stone-Wales defects on the mechanical properties of TiAl/CNT core-shell nanowires

In this study, the effect of Stone-Wales (SW) defects on the mechanical properties of TiAl/CNT core-shell nanowire was studied using molecular dynamics simulations. Our study revealed that SW defects can reduce the ultimate tensile strength and the fracture strain of TiAl/CNT core-shell nanowires. Notably, the ultimate tensile strength of TiAl/CNT core-shell nanowires initially decreased and then increased with the increasing number of SW defects. Conversely, the effect of SW defects on the Young’s modulus of TiAl/CNT core-shell nanowires was less pronounced, with the Young’s modulus showing little dependence on the presence of SW defects. The effect on the mechanical properties is a result of the combined effect of lattice changes, Stair-rod and Hirth dislocations, laminar faults and voids brought by the SW defects. These results provide new insights for further design and fabrication of advanced materials.

Preparation and Assembly of Carbon Nanotube/Silica Core-Shell Nanowires to Realize High-Density and Well-Aligned Nanotube Arrays with Uniform and Tunable Pitch

This study introduces a novel method to fabricate high-density, well-aligned arrays of carbon nanotubes (CNTs) with tunable pitch, utilizing a core-shell nanowire structure of CNTs and silica. The approach involves a modified Stober process to achieve controlled deposition of silicon dioxide around individual CNTs, forming robust core-shell nanowires. By optimizing the Stober process, the shell size can be precisely controlled down to sub 10nm scale while maintaining the individualized nature of the CNTs. Densely packed and precisely aligned CNT arrays are created using Langmuir-Schaefer process. After assembly, the silica shell, acting as a physical spacer, can be easily removed by HF etching, exposing the CNTs while maintaining their alignment. The developed high-density, well-aligned CNT arrays with tunable pitch show significant promise for applications in nanoelectronics, sensors, and other emerging technologies. This methodology offers a robust and scalable approach for CNT array fabrication, opening avenues for tailoring array properties to meet specific application requirements.

N-doped MoS2@indium tin oxide (ITO) core–shell nanowires for high-performance ammonium ion micro-supercapacitor

Ammonium (NH4+) ion aqueous supercapacitors have gained significant attention due to their notable cost-effectiveness, safety profile, and environmental benefits. Despite this, the optimization of the capacitive performance of electrode materials for NH4+ ion storage remains inadequate. To tackle these challenges, we present a composite electrode depend upon molybdenum disulfide (MoS2) and indium tin oxide nanowires (MoS2@ITO NWs) as the primary host for (NH4+) ions. Additionally, we introduce a straightforward radio frequency nitrogen (N) plasma technique to incorporate nitrogen doping into the MoS2 film, thereby enhancing its performance. The introduction of N plasma doping into two-dimensional MoS2 results in an expansion of the interlayer distance and an improvement in electronic conductivity. This, in turn, facilitates the facile and highly reversible insertion and extraction of NH4+ ions during cycling. Consequently, the N plasma doping significantly enhances the device areal capacitance of MoS2@ITO NWs, increasing it from 78.6 to 161.8 mF cm−2 at 1 mA cm−2, with an exceptional capacity retention (>89.2% after 10 000 cycles) and superior rate capability up to 10 mA cm−2. The integration N of atoms within the straightforward hierarchical core–shell design strategy exhibits promising prospects for bolstering the performance of metal sulfide electrodes and other high-capacity electrode materials aimed at energy storage applications.

Cu2O/TiO2 core–shell nanowire heterojunction for high-performance self-powered photodetector

High-performance self-powered photodetectors (PDs) have great commercial value in optical communication, intelligent sensing and medical diagnosis. However, the limited active area of traditional thin film heterojunction seriously restricts the photoelectric performance of the detector. In this paper, the Cu2O/TiO2 core-shell nanowire (NW) heterojunction PD was synthesized for the first time by simple hydrothermal and electrochemical deposition methods, which effectively improved the response performance and response speed of the device based on its broad photoactive area and ordered carrier transport path. The PD exhibits significant diode behavior, with rectification ratios of 543 at ±2 V. The responsivity is as high as 6.8 mA W−1 at zero bias under 490 nm illumination. The short rise and decay times measured are 0.09 and 0.18 s at zero bias, respectively. Obviously, this low-cost, high-performance self-powered Cu2O/TiO2 core-shell NW heterojunction PD shows great promise in future optoelectronic device applications.

Customized Vascular Repair Microenvironment: Poly(lactic acid)-Gelatin Nanofibrous Scaffold Decorated with bFGF and Ag@Fe3O4 Core-Shell Nanowires.

Vascular defects caused by trauma or vascular diseases can significantly impact normal blood circulation, resulting in serious health complications. Vascular grafts have evolved as a popular approach for vascular reconstruction with promising outcomes. However, four of the greatest challenges for successful application of small-diameter vascular grafts are (1) postoperative anti-infection, (2) preventing thrombosis formation, (3) utilizing the inflammatory response to the graft to induce tissue regeneration and repair, and (4) noninvasive monitoring of the scaffold and integration. The present study demonstrated a basic fibroblast growth factor (bFGF) and oleic acid dispersed Ag@Fe3O4 core-shell nanowires (OA-Ag@Fe3O4 CSNWs) codecorated poly(lactic acid) (PLA)/gelatin (Gel) multifunctional electrospun vascular grafts (bAPG). The Ag@Fe3O4 CSNWs have sustained Ag+ release and exceptional photothermal capabilities to effectively suppress bacterial infections both in vitro and in vivo, noninvasive magnetic resonance imaging (MRI) modality to monitor the position of the graft, and antiplatelet adhesion properties to promise long-term patency. The gradually released bFGF from the bAPG scaffold promotes the M2 macrophage polarization and enhances the recruitment of macrophages, endothelial cells (ECs) and fibroblast cells. This significant regulation of diverse cell behavior has been proven to be beneficial to vascular repair and regeneration both in vitro and in vivo. Therefore, this study supplies a method to prepare multifunctional vascular-repair materials and is expected to represent a significant guidance and reference to the development of biomaterials for vascular tissue engineering.