Structure Of Nanowire Arrays Research Articles

Preparation, superior field emission properties and first principles calculation of electronic structure of SiC nanowire arrays on Si substrate

It is a crucial item to develop an available, efficient and stable cathode material for the application of flat-panel display, vacuum micro-electronic device, electron source and related area/equipment. In this work, oriented single-crystalline SiC nanowires (SiCNW) arrays were successfully fabricated onto the Si (100) substrate according to an easy Ni-catalyst-assisted chemical vapor deposition (CVD) process. The systematical characterization results suggested that product growth was modulated via the vapor-liquid-solid (VLS) mechanism. As the promising member in the candidate cathodes, SiCNW arrays with superior current emission stability (~ ± 6.1%) displayed decreased turn-on field (1.26 V/μm) along with threshold field (1.83 V/μm) at the optimal spacing between anode and cathode (about 500 μm), suggesting their great application potential as field emitters in the future. The positive effect of the stacking faults on the electronic structure and field emission (FE) properties were investigated through first principles calculation using Vienna ab initio Simulation package (VASP) of density functional theory (DFT). Furthermore, a reasonable synergetic electronic transmission mechanism based on peculiar morphology and electronic band structure was proposed to explain the superior field emission performances.

Ag nanoparticles capped TiO2 nanowires array based capacitive memory

Glancing angle deposition technique was used to fabricate Ag nanoparticles (NPs) capped TiO2 Nanowire (NW) array structure for capacitive memory application. Electron microscopes confirmed the sandwiched structure of Ag NPs between TiO2 thin-film (TF) and NW. The average length of the vertical TiO2 NW and diameter of Ag NPs (with density ~ 1012 cm2) were found to be ~ 350 ± 5 nm and ~ 3.2 ± 0.4 nm, respectively. An enhanced photoluminescence was observed in case of Ag NPs capped TiO2 NWs due to the presence of high carriers as compared to bare TiO2 NW. The capacitance (C)–voltage (V) hysteresis was measured for both Ag NPs capped TiO2 NW and bare TiO2 NW at different sweeping voltage (± 3– ± 10 V) at 1 MHz frequency. A high capacitive memory window of 7.12 V was obtained for Ag NP capped TiO2 NW at ± 10 V with an excellent endurance upto 1000 cycle. Significantly lesser charge loss of 23% was obtained after a span of 104 s with a hole and electron loss of 10.6% and 17.8% respectively. The program and erase process in the device was explained with the help of a band diagram.

Hierarchical carbon fiber cloth (CFC)/Co3O4 composite with efficient photo-electrocatalytic performance towards water purification

Photoelectrocatalysis (PEC) technology is one of the most effective means to remove color and organic pollutants from dyeing wastewater. In this work, hierarchical carbon fiber cloth (CFC)/Co3O4 composites are fabricated by a simple hydrothermal method and are employed as photoanode to treat simulated reactive dyeing effluent. The effect of hydrothermal temperature on the structure of as-obtained composites is investigated to achieve higher removal efficiency. The findings show that the morphology and surface coverage of Co3O4 on the CFC surface can be regulated by controlling the hydrothermal temperature. It is found that the CFC/Co3O4 composite prepared by the hydrothermal temperature of 120 °C (CFC/Co3O4-120 °C) has a more regular nanowire array structure and higher surface coverage, as compared with that of other hydrothermal temperatures. The as-obtained CFC/Co3O4-120 °C composite shows an excellent decolorization rate (as high as 94%) towards degrading simulated reactive dyeing effluent (reactive Brilliant Blue KN-R). The improvement in PEC activity of the CFC/Co3O4-120 °C composite can be ascribed to its higher active surface area, lower charge transfer resistance, and higher generation efficiency of hydroxyl radicals in comparison with other samples. Therefore, CFC/Co3O4-120 °C is expected to be a suitable anode material for PEC degradation of dyeing wastewater.

Nanowire-structured FeP-CoP arrays as highly active and stable bifunctional electrocatalyst synergistically promoting high-current overall water splitting

The design and construction of highly efficient and durable non-noble metal bifunctional catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media is essential for developing the hydrogen economy. To achieve this goal, we have developed a bifunctional nanowire-structured FeP-CoP array catalyst on carbon cloth with uniform distribution through in-situ hydrothermal growth and phosphating treatment. The unique nanowire array structure and the strong electronic interaction between FeP and CoP species have been confirmed. Electrochemical studies have found that the designed Fe0.14Co0.86-P/CC catalyst appears excellent HER (130 mV@10 mA cm−2)/OER (270 mV@10 mA cm−2) activity and stability. Moreover, the bifunctional Fe0.14Co0.86-P/CC(+/−) catalyst is also used in simulated industrial water splitting system, where the pair catalyst requires about 1.95 and 2.14 V to reach 500 and 1000 mA cm−2, even superior to the control RuO2(+)||Pt/C(−) catalyst, showing good industrial application prospects. These excellent electrocatalytic properties are attributed to the synergy between FeP and CoP species as well as the unique microstructure, which can accelerate charge transfer, expose more active sites and enhance electrolyte diffusion and gas emissions.

Construction of CuO/PPy heterojunction nanowire arrays on copper foam as integrated binder-free electrode material for high-performance supercapacitor

Herein, we report a synthesis of 3D CuO/PPy heterojunction nanowire arrays formed on Cu foam via anodizing and electropolymerization. The prepared electrode shows superior performance as a supercapacitor electrode. The CuO NAs are vertically grown on the 3D Cu foam with a diameter of about 200 nm and uniformly coated by conductive polypyrrole (PPy) nanosheets with a length of about 40 nm. The electrodeposition time of PPy also affects the morphology of the material and influences the material's electrochemical properties. The experimental electrochemical results indicate that the CuO/PPy NAs-600 electrode, the optimum electrodeposition time for PPy, could achieve an excellent real-capacitance of 1080 mF cm−2 (675 F g−1) at a current density of 2 mA cm−2. Surprisingly, even at the current density of 20 mA cm−2, the actual capacitance still has 880 mF cm−2, and it could reach 103.57% of the original capacitance after 8000 cycles. Besides, an asymmetric supercapacitor (ASC) using CuO/PPy NAs-600 as positive electrode and activated carbon (AC) as negative electrode can provide an energy density of 0.93 mWh cm−2 at a power density of 1.71 mW cm−2 at a current density of 2 mA cm−2. Furthermore, a 1.8 V LED is lighted for 2 min by three ASC in series. Benefiting from the 3D heterojunction nanowire array structures and the good electronic conductivity between CuO, PPy and Cu foam substrate, the CuO/PPy NAs electrode has potential applications in capacitive energy storage.

Cu nanowires modified with carbon-rich conjugated framework PTEB for stabilizing lithium metal anodes.

Lithium metal anodes provide a direction for the development of high-energy-density lithium-ion batteries. To overcome lithium dendritic growth and low Coulombic efficiency in lithium plating/stripping processes, the design of a three-dimensional (3D) host structure is a feasible solution. Herein, copper nanowires in situ-coated with a carbon-rich conjugated framework, poly(1,3,5-triethynylbenzene), and grown on copper foam were constructed as a 3D lithium host, and shown to effectively yield a low nucleation overpotential, smooth lithium deposition, and improved cycling stability. This well-designed 3D host structure achieved a high Coulombic efficiency of over 99% for 150 cycles and showed reversible lithium plating/stripping stability for over 800 h at 2 mA cm-2. This work has highlighted the benefits of using an interface modification strategy, and provided a feasible route for 3D host structure design in the development of lithium metal anodes.

In-situ synthesis of KCu7S4 nanowires array on nickel foam for high performance supercapacitor

An amazing KCu7S4 nanowire array structure in-situ grown on Ni foam skeleton was fabricated. The morphology and size of KCu7S4 nanowire array can be adjusted by temperature and additive (ethylene glycol). The unique structure and suitable size of KCu7S4 nanowire array greatly facilitate the charge transport of the electrode material and electrolyte, providing more active sites for redox reaction, which perfectly demonstrates the excellent electrochemical performance of the KCu7S4 electrode material. The KCu7S4 nanowire array with adding ethylene glycol in the synthesis process exhibits high specific capacitance of 2.57 F cm[Formula: see text] (807 F g[Formula: see text] at a current density of 3 mA cm[Formula: see text], good cycling stability with 80% retention at 10 mA cm[Formula: see text] for 1000 cycles and high energy density of 40.55 Wh kg[Formula: see text] at a power density of 185 W kg[Formula: see text]. Moreover, the investigation demonstrates the great potential application of KCu7S4 nanowire array in supercapacitors.

Design and fabrication of new wide-band and wide-angle solar cell absorbing layer

Cu–Zn– Sn– S (CZTS) is an ideal material for absorbing layer due to its high optical absorption coefficient and moderate bandgap. But, optical absorption and carrier recombination in thin films may lead to electron losses. Thus, introduction of radial PN junction nanostructures into thin film solar cells make light and current to travel along different paths. In this study, CZTS films were prepared by magnetron sputtering and crystalized at sputtering pressure of 3 mTorr, sputtering power of 120 W, and substrate temperature of 300 °C. The composition of CZTS thin films was closed to the optimal stoichiometry to be used as a solar cell absorption layer. These CZTS films were single-phase and vulcanized at 550 °C. A CZTS absorbing layer with a nanowire array structure had higher absorptivity in visible light region. The wideband optical absorptivity was also significantly higher than that of a planar thin film. The nanowire structure was simulated by the finite-difference time-domain method (FDTD), and its maximum absorption (with good size) reached up to 90% in 300 to ~ 2000 nm wide waveband. The mask was done after determining the ratio of the spreading agent (water to ethanol as 1:2), the surfactant concentration (4% wt.), the equilibrium time (2 min), and other parameters. The best results for normal incidence were evaluated as: D = 0.4 μm, h = 2 μm and f ≈ 0.8. According to calculations, the well-designed nanowires, in the visible light region, have an absorption rate of up to 90%.

Ion-exchange controlled surface engineering of cobalt phosphide nanowires for enhanced hydrogen evolution

Transition metal phosphides are promising alternatives to the precious metal catalysts for various electrocatalysis applications. Controllable and precise surface engineering of electrocatalysts is the key challenge to enhance their performance. Herein, we demonstrate an ion-exchange strategy to produce cobalt phosphide nanowires which have a conductive core and a thickness-controlled surface layer with sulfur dopants, phosphorus vacancies, and amorphous domains. They are applied for hydrogen evolution reaction with high stability, achieving a current density of 100 mA cm -2 at an overpotential of 114 mV. Based on both comprehensive state-of-the-art experimental characterizations and theoretical investigations, the excellent catalytic performance is attributed to increased active sites, facilitated charge transfer and transport, as well as weakened H adsorption and strengthened H 2 O adsorption due to the synergistic effects of S dopants and P vacancies. A controllable surface-layer-confined doping strategy to engineer the surface composition and structure of cobalt phosphide nanowire arrays based on an ion-exchange mechanism is developed toward superior electrocatalytic hydrogen evolution. • A controllable ion-exchange strategy to produce sulfur doped-cobalt phosphide nanowires (S-CoP) has been developed. • S-CoP has conductive core and thickness-controlled surface layer with sulfur dopants, phosphorus vacancies, and amorphous domains. • S-CoP can achieve the current density of 100 mA cm -2 at a low overpotential of 114 mV, much is lower than that of CoP ( η 100 = 134 mV). • We demonstrate a new strategy to precisely engineer a nanostructured catalyst based on state-of-the-art experimental characterization and theoretical analyses. • Mechanistic insights on interplays between dopants, vacancies and active centers have been provided.

Matching design of high-performance electrode materials with different energy-storage mechanism suitable for flexible hybrid supercapacitors

The realization of advanced hybrid supercapacitors needs the optimal match of different types of high-performance electrode materials. Porous biomass carbon with high specific surface area of 2217.8 m2 g−1 and large specific capacity of 112.5 mAh g−1 (337 F g−1) is prepared from cornstalk. Battery-type Ni3Se2 nanoarray materials with ultra-long nanowire array structure and the specific capacity of 132.4 mAh g−1 are synthesized via a facile solvothermal method. Due to the structure and performance advantages of porous biomass carbon and Ni3Se2 nanoarrays, flexible hybrid supercapacitors are assembled by matching-design of electrode materials with different energy-storage mechanism. This full-cell flexible hybrid device has a wide voltage window of 0–1.6 V, superior energy density of 38.8 Wh kg−1, excellent mechanical flexibility and low-temperature resistance. Therefore, the current work not only shows a feasible designing-method for flexible hybrid supercapacitors, but also provides a promising candidate for small, flexible, and smart electronic device.

Design and synthesis of 3D hierarchical NiMoS4@CuCo2S4 array electrode with excellent electrochemical performance

Large capacitance energy storage materials have a great application prospect due to the development of portable devices. An electrochemical deposition method was used to combine amorphous CuCo2S4 with NiMoS4, which was prepared by a two-step hydrothermal method. The resulting grass-like nanowire array structure greatly promotes the utilization rate of active materials. By the addition of two variable valence metal ions, there is an increase in electrolyte touchable active sites and a decrease in the impedance of the electrode materials. Compared with bare NiMoS4, the binder-free composite electrode has a significantly better capacitance characteristic. In particular, the NiMoS4@CuCo2S4−8 has excellent capacity performance with a specific capacitance of 13.14 F cm−2 at the current density of 5 mA cm−2. The electrode shows 73% capacitance retention after 2000 charge-discharge cycles. It is shown that the combined effect of the nanowires and the several variable valence metal ions is effective to increase the specific capacitance of bimetallic sulfides.

Density-dependent of gas-sensing properties of Co3O4 nanowire arrays

Abstract Well-oriented Co3O4 nanowire arrays were synthesized in-situ on Al2O3 substrates via a simple hydrothermal method without seed layers. The phase structure and array morphology of Co3O4 nanowire arrays were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was revealed that the array density of Co3O4 nanowire arrays could be controlled by the concentration of ammonium fluoride. The gas-sensing measurement revealed that the array structure on the surface of gas sensors exerted great impact on their performances. It was found the response value enhanced and then decayed with the increased array density of Co3O4 nanowires. We concluded that the Co3O4 nanowire arrays with moderate array density can possess highly exposed effective surface area to provide more pathways for gas diffusion than other samples. Our studies can provide a significant guidance on array design to fabricate high performance gas sensors. Moreover, the as-designed Co3O4 nanowire arrays have potential application in trimethylamine (TEA) detection.

Engineering Nanowire Array Structure of Copper Oxide/Cuprous Oxide for Enhanced Oxygen Evolution Reaction

Electrocatalytic activity towards oxygen evolution reaction (OER) could be significantly enhanced through generating nanowire array structure of transition-metal oxide on the substrate surface. However, the construction of nanowire array structure generally requires a complex process. Herein, we report a facile and effective approach in situ to generate the three-dimensional (3D) nanowire arrays of copper oxide/cuprous oxide (CuO/Cu2O) for enhanced OER. The resulting typical sample presents an excellent electrocatalytic OER performance with a low overpotential (246 mV) at 10 mA cm−2 and long-term stability, which may be attributed to the characteristics of nanowire array, mesoporous structures and high surface area for CuO/Cu2O composite as follows. The nanowire array and mesoporous structures are beneficial for the diffusion and transport of electrons and reactants, and the high surface area has the potential to provide more active sites in improving the OER activity. This research provides a worthy inspiration for preparation of CuO/Cu2O electrocatalyst with nanowire array structure by in situ conversion route.

Designing high electrochemical surface area between polyaniline and hydrogel polymer electrolyte for flexible supercapacitors

High electrochemical surface area (ECSA) is the precondition for high performance of flexible supercapacitors, but remains a considerable obstacle. Because of the lower fluidity of hydrogel polymer electrolyte (HPE, generally utilized to fabricate flexible supercapacitors) than aqueous electrolyte (AE, used in traditional supercapacitors), it is difficult to infill a porous electrode with HPE completely, leading to a low ECSA between electrode materials and HPE. In this work, the structures of the polyaniline nanowires are designed to increase the ECSA. In comparison with nanowire network structure, the patulous structure of the polyaniline nanowire arrays is beneficial to increase the ECSA. The polyaniline nanowire arrays show a specific capacitance of 373.6 F g−1 at 0.1 A g−1 with the HPE, which is comparable to that with the AE at 0.1 A g−1 (376.6 F g−1). Flexible supercapacitors based on the polyaniline nanowire arrays exhibit similar performances under flat, folded, and twisted conditions, demonstrating their high potential application in flexible electrochemical energy storage devices.

T61SUICIDE DEATHS SELECTED FOR GENETIC RISK: POLYGENIC RISK SCORE CHARACTERISTICS AND HIGH-IMPACT SEQUENCE VARIANTS

Plasmon lasers can support ultrasmall mode confinement and ultrafast dynamics with device feature sizes below the diffraction limit. At present in the single visible light frequency, the optical gain method of constraint SPP on metal nanowires structure reported less. We design the gold nanowire array structure, consisting of PMMA and R6G dye molecules as gain, by 488 nm pump in the middle of the nanowires position for wide range of light, use symmetry broken overcome that momentum does not match the photonic and SPP energy conversion. Theoretical analysis shows that dyes provide coherent optical feedback, resulting in nanowires face will observe laser properties of surface plasmons. Feature analysis: the incident light and pump joint strength is greater than the sum of strength which is the incident light, pump respectively. Under the effect of dye molecules gain effective, length of SPP transmission can increase 1 µm. The results achieved in a single optical frequency of stimulated radiation, application of dye optical gain can achieve continuous gain effect. This is for the future development of plasma amplifier and the wavelength laser.

Dendrite‐Free Flexible Fiber‐Shaped Zn Battery with Long Cycle Life in Water and Air

AbstractFiber‐shaped aqueous rechargeable Zn batteries (FARZBs) show flexibility, good reliability, cost‐effectiveness, high energy/power densities, and high safety that have attracted increasing attention as promising energy storage devices for future wearable applications. However, the development of FARZB is limited by its poor cycling life and inferior charge–discharge performance, mainly suffering from zinc dendrite growth and increasing electrode irreversibility. In this work, dendrite‐free fiber‐shaped Zn//Co3O4 rechargeable batteries with a long cycle life tested in water and air, are obtained via tuning the surface binding energy of Zn on the anode using the zincophilic N,O‐functional carbon fiber, as well as engineering the Co3O4 cathode with a nanowire array structure. The fiber‐shaped Zn//Co3O4 full battery demonstrates remarkable long cycle life in water and air with high energy density, impressive flexibility, and excellent waterproof ability (fully immersed and charged/discharged under water for more than 33 h for 3000 cycles with capacity retention of ≈80%). The reversible electrochemical mechanisms of the FARZBs, without obvious zinc dendrite deposits and structural change of Co3O4 nanowires, are confirmed by a series of characterizations. These results demonstrate that the FARZBs are promising power sources for emerging wearable electronics.

Enhancing the light extraction efficiency of AlGaN LED with nanowire photonic crystal and graphene transparent electrode

Abstract The performance of AlGaN deep ultraviolet(UV) light emitting diodes(LEDs) has been limited by the extremely low light extraction efficiency(LEE), which is due to the severe light absorption by metal electrode and unique transverse magnetic polarization. Here, we propose an ordered nanowire array structure UV-LEDs with transparent graphene electrode. By using the finite-difference time domain simulation, the relationship between LEE and different nanowire structures (including ordered and disordered nanowires array) was studied. We demonstrate that ordered nanowire arrays are better than disordered nanowires in improving the LEE. A high LEE about 80% can, in principle, be expected from top surface with optimized nanowire radius and spacing. In addition, by studying the distribution of electric field intensity on the side and top of UV-LEDs with graphene electrode and Ni/Au electrode, we show that the graphene electrode can reduce the absorption of ultraviolet light and improve LEE more effectively than the conventional Ni/Au electrode. This proposed structure could be a promising candidate for high light extraction efficiency UV-LEDs.

Electrochemical Cycling-Induced Spiky Cu x O/Cu Nanowire Array for Glucose Sensing.

The glucose level is an important biological indicator for diabetes diagnosis. In contrast with costly and unstable enzymatic glucose sensing, oxide-based glucose sensors own the advantages of low fabrication cost, outstanding catalytic ability, and high chemical stability. Here, we fabricate a self-supporting spiky CuxO/Cu nanowire array structure by electrochemical cycling treatment. The spiky CuxO/Cu nanowire is identified to be a Cu core passivated by a conformal Cu2O layer with extruded CuO petals, which provides abundant active sites for electrocatalytic reaction in glucose detection. An interruptive potential sweeping experiment is presented to elucidate the growth mechanism of the spiky CuxO/Cu nanostructure during the potential cycling treatment. The spiky CuxO/Cu nanowire array electrode exhibits a sensitivity of 1210 ± 124 μA·mM–1·cm–2, a wide linear detection range of 0.01–7 mM, and a short response time (<1 s) for amperometric glucose sensing. The study demonstrates a route to modulate oxide phase, crystal morphology, and electrocatalytic properties of metal/oxide core–shell nanostructures.

Li4Ti5O12 nanowire array as a sulfur host for high performance lithium sulfur battery

Lithium sulfur batteries (LSBs) have been recognized as one of the most promising next generation rechargeable batteries due to their high specific capacity and energy density. However, the practical application of LSBs is hindered by the low sulfur utilization due to the insulation nature of sulfur, and by the serious capacity fading of sulfur cathode arising from “shuttle effect” of polysulfides during the discharge-charge process. Herein we design and fabricate a 3D structured sulfur cathode based on Li4Ti5O12 nanowire array (LTOWA) to address these issues. In this cathode, the 3D nanowire array structure can facilitate electron transport and provide satisfactory electrochemically active surface where electron and Li ions can meet with the sulfur for fast conversion reaction, ensuring the high sulfur utilization of cathode even with a large areal sulfur content; in addition, we also show, by X-ray photoelectron spectroscopic and electrochemical analyses, that LTO can immobilize the migrating polysulfide intermediates via Ti–S bond more effectively than the conventionally used TiO2 (TO), which adsorbs polysulfide mainly through O–S bond. As a result, the LTOWA/sulfur composite cathode with a high sulfur loading (4 mg cm−2) shows a high utilization of sulfur (1100 mAh g−1 at 0.02C) and excellent cycle life (80% capacity retention after 300 cycles at 1C, namely 0.06% per cycle). Our work suggests that the performance of polar oxide/sulfur composite cathodes can be further improved by the synergistic effect of more effective chemical bonds and architectural design.

Improved responsivity performance of ZnO film ultraviolet photodetectors by vertical arrays ZnO nanowires with light trapping effect

The light trapping effect of zinc oxide (ZnO) ultraviolet photodetectors (UV PDs) has been established as a promising way to optimize the performance of optoelectronic devices. In this paper, we report a light trapping fabricated metal–semiconductor–metal structure, consisting of a ZnO nanowire array as a top layer light absorber supported by a ZnO film. The ZnO film is bridged between two interdigitated metal electrodes for collecting photo-generated carriers. In this connection, high-dense ZnO nanowires can be used as a light trapping unit and to transmit the photogenerated carriers towards the ZnO film. The photogenerated carriers diffuse along the longitudinal direction of the ZnO nanowire and then to the ZnO film and are collected by the applied bias electrode. Compared to present ZnO thin film UV PDs, our device has an effective light trapping effect and the enhancement of photo-generated carriers at the top interface by a ZnO nanowire array structure are highly beneficial to UV light detection as they can provide a long optical path and more surface area. In addition, when the device was connected with nanowires, a 10 times augment of responsivity appeared accompanied by a giant photo-to-dark current ratio (1.6 × 103). This novel work not only enhanced fundamental improvement of nanowires to ZnO film UV PDs, but also provided a distinct contrast between light trapping UV PDs and ZnO film UV PDs.