Nanowire Arrays Research Articles

Electrodeposition Decoration of Pd0 on F‐Co(OH)2 Nanoarrays with Intentionally Introduced Pd2+ Species for Efficient Electrocatalytic Hydrodechlorination of 2,4‐Dichlorophenol

AbstractDeveloping a Pd‐based catalyst possessing high efficiency and low mass loading remains a big obstacle for the large‐scale application of electrocatalytic hydrodechlorination (EHDC) of chlorophenols (CPs). Herein, high dispersion Pd nanoparticles imbedded in Pd2+ hydroxide species are decorated on the surface of F−Co(OH)2 nanowire arrays with a newly developed electrodeposition and hydrolysis coupled process. EHDC of 2,4‐dichlorophenol (2,4‐DCP) with the as‐obtained Pd/F−Co(OH)2/NF‐a exhibits superior performance than other control samples in this work and literature reports. A 100 % removal of 2,4‐DCP is accomplished within 120 min, featuring fast reaction kinetics (kobs=5.0×10−2 min−1) and mass activity (MA=22.2 min−1 g−1Pd). Mechanism investigation shows that the intentionally introduced Pd2+ sites play a pivotal role in the adsorption of 2,4‐DCP, while high dispersion of Pd facilitates the generation of active H*, thus promoting the catalytic performance. This work presents a valuable example for designing high‐performance Pd‐based EHDC catalysts by composition tuning.

Nano‐Patterned CuO Nanowire Nanogap Hydrogen Gas Sensor with Voids

AbstractHydrogen (H2) is increasingly employed in industrial applications, such as developing hydrogen fuel cells for vehicles and power plants. However, H2 explodes at a concentration limit of 4%, necessitating the development of ultrasensitive hydrogen sensors capable of early‐stage detection of hydrogen leaks. In this study, nano‐patterned polycrystalline cupric oxide (CuO) nanowire array nanogap gas sensors with voids are fabricated using electron‐beam lithography and ex situ oxidization by annealing, which could detect 5 ppb H2 and show response and recovery times of less than 10 s without a baseline shift. Combining a pre‐H2 annealing process in Ar/H2 for Cu nanowires and a low‐rate oxidation process enhances the crystallinity of CuO nanowires, facilitating the preparation of polycrystalline CuO nanowires with voids, which is a significantly practical approach for the improvements of gas sensing properties. Response and recovery times of <10 s can be obtained for a gap separation of ≈30 nm. These improvements are discussed based on a high electric field of ≈1.3 MV cm−1. The relationship between the normalized response and H2 concentration is discussed based on the power law. This paper presents highly reliable and fast H2 sensors without a baseline shift to meet the demands of the hydrogen industry.

High-Throughput Spectroscopy of Geometry-Tunable Arrays of Axial InGaAs Nanowire Heterostructures with Twin-Induced Carrier Confinement.

Predicting the optical properties of large-scale ensembles of luminescent nanowire arrays that host active quantum heterostructures is of paramount interest for on-chip integrated photonic and quantum photonic devices. However, this has remained challenging due to the vast geometrical parameter space and variations at the single object level. Here, we demonstrate high-throughput spectroscopy on 16800 individual InGaAs quantum heterostructures grown by site-selective epitaxy on silicon, with varying geometrical parameters to assess uniformity/yield in luminescence efficiency, and emission energy trends. The luminescence uniformity/yield enhances significantly at prepatterned array mask opening diameters (d0) greater than 50 nm. Additionally, the emission energy exhibits anomalous behavior with respect to d0, which is notably attributed to rotational twinning within the InGaAs region, inducing significant energy shifts due to quantum confinement effects. These findings provide useful insights for mapping and optimizing the interdependencies between geometrical parameters and electronic/optical properties of widely tunable sets of quantum nanowire heterostructures.

Gamma-ray back emission from nanowire array irradiated by ultra-intense relativistic laser pulse

A highly energetic photon is emitted via nonlinear inverse Compton scattering after an electron undergoes scattering with an ultra-intense relativistic laser pulse. In the laser-nanostructured interaction, gamma photons are emitted in different directions due to different electron heating mechanisms. However, the physics that leads to such gamma-photon emission directionality still requires further understanding. This paper shows that ∼53% of the photons emitted from the nanowires fall into the forward-directed cone, with ∼21% of the backward-emitted photons. Using the two-dimensional particle-in-cell simulations, we found that the backward-emitted photons are mainly ascribed to the j × B heating and reflux electrons. The direction of photon emission from the nanowire tip is in the direction of the ponderomotive force. Furthermore, we also demonstrate that the nanowire target attached to the supporting substrate helps to enhance forward photon emission and reduce emission from reflux electrons. Understanding the correlation between the laser heating mechanisms and the directionality of photon emission could provide insights into the generation of collimated gamma rays using nanowire targets for various applications.

Diffusion-Induced Ordered Nanowire Growth: Mask Patterning Insights.

Innovative methods for substrate patterning provide intriguing possibilities for the development of devices based on ordered arrays of semiconductor nanowires. Control over the nanostructures' morphology in situ can be obtained via extensive theoretical studies of their formation. In this paper, we carry out an investigation of the ordered nanowires' formation kinetics depending on the growth mask geometry. Diffusion equations for the growth species on both substrate and nanowire sidewalls depending on the spacing arrangement of the nanostructures and deposition rate are considered. The value of the pitch corresponding to the maximum diffusion flux from the substrate is obtained. The latter is assumed to be the optimum in terms of the nanowire elongation rate. Further study of the adatom kinetics demonstrates that the temporal dependence of a nanowire's length is strongly affected by the ratio of the adatom's diffusion length on the substrate and sidewalls, providing insights into the proper choice of a growth wafer. The developed model allows for customization of the growth protocols and estimation of the important diffusion parameters of the growth species.

High‐Performance Flexible Silicon Nanowire Field Effect Transistors on Plastic Substrates

AbstractInorganic semiconductor nanowires, known for their exceptional electronic properties and mechanical flexibility, are widely regarded as the ideal 1D channel materials for creating high‐performance flexible electronics. In this work, the integration of ordered arrays of silicon nanowire (SiNW) field effect transistors (FETs) directly onto flexible plastic substrates is showcased. The self‐aligned crystalline SiNW multi‐channels are first grown through an in‐plane solid–liquid–solid mechanism on rigid substrates, and then efficiently transferred in‐batch onto flexible polyethylene terephthalate (PET) plastics. The FETs constructed on these transferred SiNW channels exhibit outstanding performance, with a high on/off current ratio of >105, a low subthreshold swing of 175 mV dec−1, and remarkable mechanical stability that can endure an extremely small bending radius of 0.5 mm for 1000 cycles. Furthermore, inverter logics are also successfully demonstrated on plastic substrates, highlighting a prominent routine for scalable integration of high‐quality SiNW channels in the development of low‐cost, high‐performance flexible displays and wearable electronics.

Morphology and Magnetic Properties of Ni Nanowires in Thin Film Anodic Alumina Templates

The features of the morphology and magnetic properties of Ni nanowire arrays have been studied. Aluminum oxide matrices are used as a template for electrolytic deposition of nanowires. The matrices are obtained by anodizing the aluminum films with a thickness of 2 μm that are formed on glass substrates by high frequency ion sputtering. Electrochemical deposition of the metal is carried out using direct and alternating currents. Morphology and microstructure studies show that the nanowire arrays are polycrystalline and have a branched dendritic structure due to the morphological features of aluminum oxide matrices. A relationship between the magnetization reversal patterns and the modes of electrodeposition of Ni nanowire arrays is established. The process of magnetization reversal of an array of this kind of structures is simulated.

High-performance PANI sensor on silicon nanowire arrays for sub-ppb NH3 detection

For industrial production and disease diagnosis, real-time detection of low concentrations of NH3 is crucial, necessitating a gas-sensitive sensor compatible with integrated processes and exhibiting excellent performance. Herein, we employed wet etching and rapid in-situ polymerization on silicon nanowire substrates to grow polyaniline fibers, thereby fabricating NH3 gas sensors with p-p heterojunction and three-dimensional network structures. Characterization and gas sensing performance testing were conducted. The results demonstrate the outstanding NH3 detection capabilities of the sensor, providing stable responses down to concentrations as low as 1 ppb, which indicates its LOD is one to two orders of magnitude lower than current similar products. It also exhibits verified selectivity and long-term reliability. The excellent sensing performance is attributed to the high surface area from the silicon nanowire structure and efficient synergy of p-p heterojunction. Additionally, the influence of doping types of the substrates and annealing process were explored. This work serves as a reference for the design of silicon-based gas sensors with high sensitivity, low detection limits, and extended operational lifetimes, suitable for deployment in commercial integrated monitoring systems.

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.

Optical and Structural Properties of Anisotropic ZnS Nanoparticle Suspensions.

We studied the optical and structural properties of highly ordered arrays of surfactant-capped ZnS nanowires (NWs) and nanorods (NRs) in organic suspensions. The photoluminescence (PL) emission measured under different concentrations and postsynthesis washing cycles interestingly showed increasing emission upon decreasing nanoparticle (NP) concentration. Synchrotron small angle X-ray scattering measurements elucidated the liquid-crystal-like structure of the NPs in suspension under different concentrations and temperatures. The NWs are stacked in a simple structure with a hexagonal cross-section, whereas the structure of the NRs is more complex, resembling a smectic-c liquid crystal, and shows unusual thermal expansion versus temperature. The results point out that a certain amount of bound surfactant must be present on the NP surface to maximize the PL intensity.

Engineering Fano resonances in plasmonic metasurfaces for colorimetric sensing and structural colors

In this paper, we present the design and fabrication of a plasmonic metasurface based on titanium dioxide (TiO2) nanowire arrays integrated with plasmonic layers. The structure is engineered to produce Fano resonances within the visible spectrum, resulting from the coupling of localized surface plasmon resonances, lattice modes, and nanowire's optical modes. Experimentally, we show that by tuning the geometrical features of the metasurface, such as the length, diameter, and period of the nanowires, a high-quality factor single peak can be achieved in the reflection spectra, resulting in vivid structural colors in bright field. To our knowledge, this is the first demonstration of such vivid colors with nanowire arrays in bright field reflections. When characterized by refractive index fluids around the refractive index of water, the plasmonic metasurface also showed great potential for biochemical colorimetric sensing. The best design demonstrated a bulk sensitivity of 183 nm/RIU with high Q resonance features and linear changes in color values using image processing.

In-Situ Fabricated Transparent Flexible Nanowire Device with Wavelength-Regulated Dual-Function of Photodetector and Photonic Synapse.

Integrating the dual functionalities of a photodetector and photonic synapse into a single device is challenging due to their conflicting requirements for photocurrent decay rates. This study addresses this issue by seamlessly depositing transparent indium tin oxide (ITO) electrodes onto self-oriented copper hexadecafluoro-phthalocyanine (F16CuPc) nanowires growing horizontally along hot-stamped periodic nanogrooves on a transparent flexible polyimide plastic film. This in-situ-fabricated device achieves bending-stable dual functionalities through wavelength regulation while maintaining high transparency and flexibility. Upon exposure to 450-850 nm light, the device exhibits a rapid and sensitive photoresponse with excellent bending stability, making it ideal for optical sensing in both visible and near-infrared spectra. More importantly, the device exhibits a bending-stable excitation postsynaptic current when exposed to light spikes below 405 nm. This enables the successful emulation of various biological synaptic functionalities, including paired-pulse facilitation, spike-number-dependent plasticity, spike-duration-dependent plasticity, spike-rating-dependent plasticity, configurable plasticity between short-term plasticity and long-term plasticity, and memory learning capabilities. Utilizing this device in an artificial neural network achieves a recognition rate of 95% after 57 training epochs. Its ability to switch between photodetection and synaptic modes by adjusting the light wavelength marks a significant advancement in the field of multifunctional flexible electronics based on nanowire arrays.

Hyperspectral Analysis of Silicon Nanowires Manufactured Through Metal-Assisted Chemical Etching

Abstract This study used hyperspectral imaging to analyze localized near-field interactions between incident electromagnetic waves and silicon nanowire (SiNW) arrays manufactured through catalytic etching of Si wafers for different durations. The results revealed that the unetched upper surface area on Si wafers and reflection of incident light decreased with increasing etching time. A light reflection band peaking at approximately 880 nm was generated from arrays etched for more than 1 h. We used six separate hyperspectral images to analyze the wavelength-dependent spatial optical responses of the fabricated SiNW arrays. The images revealed hot spots of light reflection from unetched Si surfaces in the wavelength range of 470–750 nm and a resonant peak at 880 nm for a photonic crystal derived from a random SiNW array. Accordingly, hyperspectral imaging enables the assessment of localized optical responses of SiNW arrays, which can then be optimized to cater to various applications.

The key role of anti-solvent temperature in quantum dot/perovskite core-shell nanowire array solar cells

Combining perovskite with infrared quantum dots to construct a core-shell nanostructure nanowire array solar cell can increase the light absorption range and enhance the light absorption and carrier transport efficiency of the solar cell. However, the preparation of a perovskite absorber layer on a nanowire array with quantum dots often presents issues such as high roughness and a large number of lattice defects, which have a negative impact on the photovoltaic performance. The anti-solvent method is a commonly used technique to improve the quality of perovskite. The temperature variation of the anti-solvent can change solubility, and influence the reaction rate and crystal formation process of perovskite, thus affecting its photovoltaic performance. In this study, the quality of perovskite in the core-shell nanostructure nanowire array was improved by controlling the temperature of the anti-solvent (toluene). Experimental results show that as the temperature of toluene increases, the photovoltaic performance is gradually improved. When the toluene temperature was maintained at 75 °C, the device exhibited significantly improved photovoltaic performance with an efficiency of 12.64 %, surpassing the efficiency obtained without any anti-solvent modification. As the temperature of the anti-solvent increases, the absorption of visible and near-infrared light spectrum by the nanowire arrays is enhanced, which promotes the efficient generation of photo-generated carriers. Furthermore, defects in the nanowire arrays gradually decrease, leading to a reduction in carrier recombination. These findings provide valuable insights for advancing core-shell nanostructure nanowire array solar cells.

Sulfur dioxide gas sensor based on vanadium oxide doped TiO2 nanopaper

Abstract The gas sensor based on TiO2 nanomaterials is promising for both industry and daily life because of its simple fabrication, low cost, high sensitivity, and easy application to micro-devices. However, its selectivity is relatively low and strongly influenced by the environment, thus limiting its practical application. In this work, we prepared TiO2 nanopaper by methods of hydrothermal synthesis and conventional paper preparation. To improve the selectivity, we added V2O5 by immersing the as-prepared nanopaper in an ammonium metavanadate (NH4VO3) solution evenly dispersed in ethanol. Nanopaper is a random array of long nanowires and nanofibers, which retains its shape and structure at high temperature, unlike pure nanowires, due to its high porosity and mechanical stability. V2O5 leads to a selective sensing performance with high catalytic activity for SO2 gas. The surface structure of the sensing material and its porosity were characterized by SEM, XRD, XPS. The improved sensing material exhibited a high response of about 22.6 for 100 ppm SO2 and a fast response and recovery of 9 s and 14 s, respectively. It also exhibited good reproducibility and selectivity in other interfering gases. Furthermore, the long-term sensing performance in the atmospheric environment was maintained for about 50 days.

Rolled‐Up Membranes from GaAs/AlOx Core‐Shell Nanowire Ensembles Through Natural Oxidation

AbstractThe formation of rolled‐up cylindrical membranes stemming from the strain deformation‐induced delamination of a film‐like nanowires array composed of coalesced GaAs nanowires embedded in AlOx with a buried GaAs/AlAs core‐shell structure is reported. The delamination of the nanowires array film is driven by natural oxidation resulting from prolongated exposure to ambient atmosphere. Investigation of the structural characteristics of the nanowires in the array reveals an analytical description of the oxidation mechanism leading to the formation of the rolled‐up structures. The membrane can easily transfer by simply shaking off the surface membranes of the sample. The cylindrical membranes maintain the optical properties of the core GaAs nanowires surrounded by native oxide. The findings show the prospects for area‐saving and transferable semiconductor devices with advanced nanoscale optical functions.

Growth mechanism and SERS effect of Ag nanowire arrays prepared by solid-state ionics method

Solid-state ionic method has attracted more and more attention due to its simple operation and controllable preparation, but its growth mechanism is still uncertain. In this work, Ag nanowire (Ag NW) arrays prepared by solid-state ionics method at 5 μA impressed currents using fast ionic conductor RbAg4I5 films and different metal electrodes were reported. The conduction mode of Ag+ in RbAg4I5 films, the growth mechanism of Ag NW arrays prepared by solid-state ionics method and the effect of microscopic morphology on surface-enhance Raman scattering (SERS) performance were investigated. The results show that Ag nanoparticles (Ag NPs) with diameters from 40 nm to 70 nm were attached to the surface of Ag NW arrays with diameters of 80–150 nm prepared with different metal electrodes, which lead to Ag NW arrays have high surface roughness. The conduction velocity and stability of Ag+ in RbAg4I5 films are closely related to the morphology of Ag NW arrays. The irregular electrode interface and apical growth advantage resulted in the fractal dimension of Ag NW arrays prepared with Ag electrodes is 1.69 due to macroscopic dendritic structure. Ag NW arrays have excellent SERS performance due to the many Ag NPs attached to the surface of the closely aligned Ag NWs, the limit of detection (LOD) for Basic Fuchsin (BF) and Crystal Violet (CV) detected by Ag NW arrays SERS substrates prepared with Ag electrodes are as low as 10−11and 10−14mol/L, respectively. This paper provides a reference for the preparation method of metal nanostructures, Ag NW arrays have good potential for application in the field of trace analysis.

Solar evaporation of liquid marbles with composite nanowire arrays

Solar interfacial evaporation is a sustainable technology to produce fresh water. The synergistic realization of broadband light absorption and good thermal insulation is crucial to improving the thermal efficiency. Here, we propose a new structure over the surface of liquid marbles, which via nanowire arrays assembled with composite nanomaterials (Fe3O4/CNT nanoparticles) to enhance the evaporation efficiency. The composite materials can effectively absorb light across the entire solar spectrum. Multiple reflections of light over nanowire array further improve light absorption. The narrow spaces and local particle aggregation of the nanowire array enhance thermal insulation to improve the evaporation efficiency. A series of experiments were conducted to verify the concept. The results showed that liquid marbles with upward Fe3O4/CNT nanowire arrays (Fe3O4/CNT-ULM) enhance the light harvesting ability and thermal insulation. Fe3O4/CNT-ULM at a volume ratio 1:2 provides the highest evaporation rate of 12.25 μg/s, which is about 1.16 and 1.53 times higher than that of Fe3O4 and CNT, respectively. Numerical analysis further illustrates that the combination of composite materials and nanowire arrays enhances concentration of electromagnetic field and heat at the air/water interfaces. This promotes rapid evaporation at the thermal boundary region, which has important implications for the structure design of solar interfacial evaporator.

Enhancement of photoresponse for InGaAs infrared photodetectors using plasmonic WO3-x/CsyWO3-xnanocrystals.

Fast and accurate detection of light in the near-infrared (NIR) spectral range plays a crucial role in modern society, from alleviating speed and capacity bottlenecks in optical communications to enhancing the control and safety of autonomous vehicles through NIR imaging systems. Several technological platforms are currently under investigation to improve NIR photodetection, aiming to surpass the performance of established III-V semiconductor p-i-n (PIN) junction technology. These platforms include in situ-grown inorganic nanocrystals and nanowire arrays, as well as hybrid organic-inorganic materials such as graphene-perovskite heterostructures. However, challenges remain in nanocrystal and nanowire growth, large-area fabrication of high-quality 2D materials, and the fabrication of devices for practical applications. Here, we explore the potential for tailored semiconductor nanocrystals to enhance the responsivity of planar metal-semiconductor-metal (MSM) photodetectors. MSM technology offers ease of fabrication and fast response times compared to PIN detectors. We observe enhancement of the optical-to-electric conversion efficiency by up to a factor of ~2.5 through the application of plasmonically-active semiconductor nanorods and nanocrystals. We present a protocol for synthesizing and rapidly testing the performance of non-stoichiometric tungsten oxide (WO3-x) nanorods and cesium-doped tungsten oxide (CsyWO3-x) hexagonal nanoprisms prepared in colloidal suspensions and drop-cast onto photodetector surfaces. The results demonstrate the potential for a cost-effective and scalable method exploiting tailored nanocrystals to improve the performance of NIR optoelectronic devices.

Epitaxial growth of bottom-crosslinked ZnGa2O4 nanowire arrays on c-plane GaN/Al2O3 substrate

The epitaxial growth of highly ordered ZnGa2O4 nanowire arrays and the construction of connectivity states between the individually segregated nanowires would significantly improve the performance of ZnGa2O4-based devices and expand their application fields. Herein, a strategy to construct high crystalline quality and well-aligned bottom-crosslinked ZnGa2O4 nanowire arrays along seven equivalent crystallographic directions of [111], [111̅], [11̅1], [1̅11], [11̅1̅], [1̅11̅] and [1̅1̅1] on Au-coated (0001) GaN/Al2O3 substrates using chemical vapor deposition (CVD) is proposed. The vapor-liquid-solid (VLS) mechanism dominates the entire growth process. The horizontal nanowires induced to nucleate and grow by catalyst droplets encountered and then turned towards inclined nanowires. Meanwhile, catalyst droplets that failed to move horizontally were enclosed by horizontal nanowires, resulting in the induction of perpendicular nanowire growth. The film-like horizontal nanowires connected all the inclined and perpendicular nanowires to form the bottom-crosslinked nanowire arrays. Additionally, the morphology, structure and optical properties of the ZnGa2O4 nanowire arrays, as well as the influence of Au layer thickness and growth time on the growth of ZnGa2O4 nanowires, were further characterized and thoroughly investigated. The proposed strategy achieved the growth of epitaxial well-aligned ZnGa2O4 nanowire arrays with bottom cross-linking, which is conducive to the application of ZnGa2O4 nanowires in optoelectronics.