Presence Of Nanowires Research Articles

Straw-sheaf-like AgVO3 nanowires for remarkable Zn2+ storage properties

Zinc-ion batteries (ZIBs) have received considerable attention as promising energy storage devices because of their impressive energy densities and inexpensive cost. However, there are still challenges to be addressed regarding the performance and cycling stability of ZIBs. In this work, a straw-sheaf-like AgVO3 structure assembled from multiple strongly bonded nanowires was successfully synthesized using a one-step hydrothermal route. We investigate the structural advantages offered by the AgVO3 compound for ZIBs. The AgVO3, which is distinguished by one-dimensional nanowires and a straw-sheaf-like architecture, possesses remarkable properties that facilitate efficient zinc ion deintercalation and electron transfer processes. These include the shortened diffusion length caused by the presence of nanowires, which allows for faster ion migration. The tightly bundled nanowires also provide robust structural support, accommodating the significant volume changes caused by repeated electrochemical reactions. Notably, a single crystal structure enables excellent conductivity and electrochemical kinetics. Remarkably, the straw-sheaf-like AgVO3 electrode exhibited excellent reversible capacity (292.3 mAh g−1 at 0.1 A g−1) and long cycling stability. The remarkable electrochemical properties illuminate the potential of AgVO3 as a viable material for ZIBs, paving the way for improved performance and durability in this promising energy storage technology.

Lithiophilic Nanowire Architectures as Hosts for Lithium Metal Anodes

Lithium (Li) metal is considered the ‘holy grail’ of battery anodes and has attracted enormous interest due to its low density (0.59 g cm-3), high theoretical capacity (3860 mAh g-1) and lowest electrochemical potential (-3.07 V vs. standard hydrogen electrode - SHE) [1-2]. However, several issues during its cycling in a Li-metal battery (LMB) have hindered its commercialization. Some notable problems include the formation of an unstable solid electrolyte interphase (SEI), excessive dendrite growth and subsequent short-circuiting during the Li stripping/plating process [3-4].In our poster presentation, we will detail the design of a hierarchical nanowire (NW) – Carbon paper (CP) host for dendrite-free and stable cycling in LMBs. These NWs were grown on high surface area carbon paper substrate via a modified Vapour-Liquid-Solid (VLS) approach. The lithiophilic NWs enabled quick Li infusion (< 10 sec) in the NW-CP substrate whereas no Li infusion was possible in lithiophobic bare CP substrate (without the presence of NWs). Additionally, the NW morphology helped in reducing the localized current density on the surface of the NW-CP host, thereby promoting uniform Li deposition during plating/stripping process. With careful design of the NW-CP host, symmetric cell performance with high current density (3 mA cm-2) and areal capacity (3 mAh cm-2) was achieved for up to 500 h while a typical Li metal anode failed within 200 h. High loading NMC811 and high specific capacity Sulfur (S) cathodes demonstrated superior performance using NW-CP host as compared to pristine Li anodes.In addition, we will also present some new concepts of NW decorated lithiophilic interlayers, which can be integrated with pristine Li metal anodes for uniform Li deposition. These lithiophilic interlayers can promote ‘bottom-up’ Li infilling between the Li-interlayer interface such that dendrite formation near the separator and eventual short-circuit is avoided. Detailed electrochemical as well as density functional theory (DFT) analysis shedding light on the improved lithiophilic properties of NW use in stabilizing Li metal anodes will also be presented. Overall, our work is aimed to develop high energy density (ED) Li metal anodes to meet the rising ED demands of electric vehicle (EV) industry.

Growth kinetic study of electrochemically active bacterium Shewanella putrefaciens MTCC 8104 on acidic effluent of jute stick pyrolysis

ABSTRACT Production of bioelectricity from waste streams using electrochemically active bacteria (EAB) has a great prospect. This article focuses on the assessment of the assimilation of acid-rich pyroliquid (APL), appearing from the waste stream of pyrolysis unit of jute stick, by one of EAB, Shewanella putrefaciens MTCC 8104. At the optimum temperature ( = 37°C) and pH ( = 4), the strain can assimilate up to 230 ppm of acetic acid per hour. Microscopic analysis indicates the presence of nanowires in the bacteria. Diauxic growth pattern is exhibited when both APL and whey are used as carbon sources. The minimum inhibitory concentration of acetic acid against S. putrefaciens has been determined to be 8000 ppm. Growth kinetics of the strain has been determined by using APL having acetic acid concentration between 100 and 7500 ppm, as carbon source. While the Monod model can explain the growth in the uninhibited zone, Wayman model has been proved to be the fittest by statistical analysis using the Akaike Information Criterion. The kinetic parameters μmax, Ks and Ki are 0.11 h−1, 13.17 and 75930.1 mg/L, respectively, with R 2 value of 0.977.

Effect of Etching Duration on the Morphological and Opto-Electrical Properties of Silicon Nanowires Obtained by Ag-Assisted Chemical Etching

Silicon nanowires (SiNWs) were obtained on p-Si (100) substrate by Ag-assisted chemical etching method in two-step process. The influence of the etching duration on the morphological, optical and electrical properties of SiNWs samples was investigated. SEM images show clearly the presence of nanowires and the existence of porous silicon structure especially for low etching duration. Fourier Transformed Infrared spectroscopy (FTIR) measurements allow identifying several particles on the SiNWs surfaces such as oxygen and hydrogen elements. The optical properties of the SiNWs layer were investigated by Photoluminescence spectroscopy (PL). A strong broad PL band was observed at room temperature for an etching time of 30 s. The PL spectra exhibit multi-band profile in the red-green region. The luminescence of SiNWs is mainly attributed to Si-oxide interface states and oxygen deficient centers. Ag/SiNWs/Si Schottky diodes were analyzed by X-ray diffraction (XRD) and studied by current - voltage (I-V) measurements. Diode parameters such as ideality factor (n), series resistance (Rs), saturation current (Is) and energy barrier (φb) were determined by analyzing the I-V characteristics. Ag/SiNWs/Si diode for an etching duration of 30 s exhibits a rectifying behavior with a factor ideality of 2.8 and a low threshold voltage of about 0.44 V in forward bias. Space charge limited current (SCLC) model is the dominant transport mechanism through Ag/SiNWs/Si diode. The trap states, on the Ag/SiNWs interface, play in important role in the conduction phenomenon through these structures.

Unravelling Resistive Switching Mechanism in ZnO NW Arrays: The Role of the Polycrystalline Base Layer

The physical mechanism involved in resistive switching phenomena occurring in devices based on ZnO nanowire (NW) arrays may vary considerably, also depending on the structure of the switching layer. In particular, it is shown here that the formation of a ZnO base layer between the metallic catalyst substrate and the NW, which is typical of CVD-grown ZnO NW arrays, should not be neglected when explaining the switching physical mechanism. The structural and electrical properties of this layer are investigated after the mechanical removal of NWs. Electrical measurements were performed in the presence of NWs and, after their removal, showed that the base alone exhibits resistive switching properties. The proposed switching mechanism is based on the creation/rupture of an oxygen vacancies conductive path along grain boundaries of the polycrystalline base. The creation of the filament is facilitated by the high concentration of vacancies at the grain boundaries that are oriented perpendicularly to the electrode...

Synthesis of RuO2 Nanowires by Alkali-Assisted Oxidation of Ruthenium in Plasma Afterglow at Atmospheric Pressure

RuO2 nanowires are synthesized by oxidation of ruthenium thanks to a micro-post-discharge at atmospheric pressure. However, RuO2 nanowires form islands. The growth mechanism depending on surface defects, the surface density of the nanowires is limited. We report on the influence of two alkali salts, NaCl and KCl, deposited as grains on ruthenium to act as defects and increase the nanowire density. These grains induce the growth of RuO 2 nanowires all around them, creating a circular area where nanowires are found. Nanowires start growing at the triple point at the grain base where the alkali-salt grain, ruthenium from the substrate, and oxidizing gaseous species coexist. When nanowires grow, the stress induced in the surrounding layer creates new cracks, making possible the radial propagation of the nanowires. The presence of nanowires on grains is due to the etching mechanism that converts the alkali salt into an oxide, enabling onward oxidation of ruthenium.

Functional Hierarchical Nanocomposites Based on ZnO Nanowire and Magnetic Nanoparticle as Highly Active Recyclable Photocatalysts

A novel magnetic hierarchical nanocomposite based on ZnO nanowire/Fe3O4@SiO2 nanoparticle has been successfully synthesized by multistep chemical methods without calcinations. The magnetic cores of Fe3O4 act as the center for the growth of ZnO nanowires. As a result, the zinc oxide nanowires grown around Fe3O4 magnetic cores form a chestnut-like hybrid structure. The length of these ZnO nanowires was controlled by growth time. When used in the photodegradation of rhodamine B (RhB), these ZnO–Fe3O4@SiO2 nanocomposites show high photocatalytic activity. The large surface areas and the presence of nanowires, in which the electron transport rate is fasten to reduce the recombination of the photogenerated electrons and holes, are considered to make the major contribution to the enhanced photocatalysis. In addition, the as-obtained nanocomposites inherit the magnetic property from the Fe3O4 nanoparticles with the saturation magnetization (Ms) about 3 emu/g. It has been demonstrated that this photocatalyst can b...

Anisotropy effect on the nonlinear optical properties of a three-dimensional quantum dot confined at the center of a cylindrical nano-wire

The effect of geometrical anisotropy is numerically investigated on the linear and nonlinear optical properties of a GaAs quantum dot which is located at the center of a Ga1-xAlxAs cylindrical nano-wire. The finite difference approximation has been used for obtaining energy eigenvalues and corresponding wave functions. Also, the compact density matrix formalism is applied to investigate linear, third order nonlinear and total optical absorption coefficients (ACs) and refractive index (RI) changes. The optical properties and oscillator strength are calculated as a function of the incident photon energy for different ellipsoid aspect ratio, dot radius and incident optical intensity for 1–2, 2–3 and 1–3 transitions. The results clearly reveal that the dot anisotropy plays an important role in determining the magnitude of nonlinear AC and RI changes which enable us to adjust saturation condition. We found that the dot anisotropy shifts absorption spectrum towards both lower and higher energies which depend on the shape of dot (spherical, prolate or oblate quantum dot), dot radius and states between which transitions will occur. Additionally, it is shown that the presence of nano-wire (second confinement) causes (I) a large increment in RI changes (II) a decrement in total AC for prolate QDs with respect to the dot radius (III) an increment in third order AC with respect to the ellipsoid aspect ratio and (IV) a blue shift in optical spectrum.

Collective behaviors of mammalian cells on amine-coated silicon nanowires

Intensive studies with vertical nanowire (NW) arrays have illustrated broad implications for manipulating mammalian cells in vitro, but how cellular responses are influenced by the presence of NWs has not been thoroughly investigated. Here, we address collective cellular behaviors, including surface area of cells, membrane trafficking, focal adhesion distribution and dynamics, and cytoskeletal protein distribution on amine-coated silicon (Si) NWs with different physical properties. The degree of HeLa cell spreading was inversely proportional to the surface area occupied by the NWs, which was not affected by manipulation of membrane trafficking dynamics. In the presence of a diffusive focal complex around the NWs, strong, well organized focal adhesion was hardly visible on the NWs, implying that the cells were interacting weakly with the NW-embedded surface. Furthermore, we found that actin filament formation of the cells on long NWs was not favorable, and this could explain our observation of reduced cell spreading, as well as the decreased number of focal adhesion complexes. Taken together, our results suggest that cells can survive on silicon NWs by adjusting their morphology and adhesion behavior through actively organizing these molecules.

Bacterial Recognition of Silicon Nanowire Arrays

Understanding how living cells interact with nanostructures is integral to a better understanding of the fundamental principles of biology and the development of next-generation biomedical/bioenergy devices. Recent studies have demonstrated that mammalian cells can recognize nanoscale topographies and respond to these structures. From this perspective, there is a growing recognition that nanostructures, along with their specific physicochemical properties, can also be used to regulate the responses and motions of bacterial cells. Here, by utilizing a well-defined silicon nanowire array platform and single-cell imaging, we present direct evidence that Shewanella oneidensis MR-1 can recognize nanoscale structures and that their swimming patterns and initial attachment locations are strongly influenced by the presence of nanowires on a surface. Analyses of bacterial trajectories revealed that MR-1 cells exhibited a confined diffusion mode in the presence of nanowires and showed preferential attachment to the nanowires, whereas a superdiffusion mode was observed in the absence of nanowires. These results demonstrate that nanoscale topography can affect bacterial movement and attachment and play an important role during the early stages of biofilm formation.

Synthesis of niobium oxide nanowires using an atmospheric pressure plasma jet

A rapid synthesis of niobium oxide nanowires using an oxygen atmospheric pressure plasma jet sustained by repetitive DC pulse power is presented. Using this plasma jet to treat niobium foils, niobium oxide nanowires (NWs) with the length up to 3–6 μm and the diameter of 100–200 nm can be fabricated within 20 s. Parametric studies show that a high growth rate can be obtained with the synergetic effect of the temperature and the reactivity of the plasma jet. The structural analysis of the jet treated niobium foil shows that in the case that no NW is formed, the major phases are Nb 6O and orthorhombic Nb 2O 5 while with the presence of NWs, high crystalline monoclinic Nb 2O 5 is the dominant phase.

Synthesis, characterization and optical properties of silver and gold nanowires embedded in mesoporous MCM-41

Abstract Uniform nanowires of silver and gold inside the channels of MCM-41 were prepared by controlled reduction of their respective metal salts with sodium borohydride (NaBH4). Presence of nanowires of silver and gold in MCM-41 were confirmed by high angle X-ray diffraction (XRD) data (peaks between 2ϑ = 30 − 60°) and transmission electron microscopy (TEM) confirmed the diameter of the nanowires. Diameter of nanowires is found to be ∼ 2.8 nm which is coincident with channel diameter of MCM-41. Optical properties of these heterostructured materials Ag-MCM-41 and Au-MCM-41 reveals the presence of surface plasmon absorption peaks of silver and gold respectively, and the shift in the absorption bands are associated to agglomeration of clusters inside the channels. Room temperature photoluminescence spectra exhibits interesting optical properties as observed for direct band gap semiconductors. Non-linear optical properties (NLO) corresponding to second harmonic generation (SHG) values were also recorded for self supported films of these heterostructured materials. Enhanced optical non-linearity was found to be arising from a corresponding increase of local field near the surface plasmon resonance. Further enhancement in SHG was found with poling due to an induction of orientation order.

Development of 3-D Magnetic Nano-Arrays by Electrodeposition into Mesoporous Silica Films

ABSTRACTThe development of periodic nanostructures fabricated by self-assembly of surfactants and block co-polymers has opened up the possibility of generating periodic magnetic nanostructures of types not accessible by self-assembly of nano-particles. The fabrication of mesoporous silica thin films around self-assembled block co-polymers is well established. Common structures for such films are SBA-15 which consists of hexagonal arrays of cylindrical pores and SBA-16 which has face centered arrays of spherical voids. These pores are connected by 1-2 nm thick flaws in the continuous silica phase producing an effectively continuous porous phase. After removal of the block co-polymer template, electrodeposition into the mesoporous silica thin films produces arrays of 5-10 nm diameter nano-wires and nano-particles. We have demonstrated that such materials can be fabricated on a wide range of metal substrates. Characterization by Scanning Electron Microscopies shows that the mesoporous silica is well ordered over micron scale areas. Grazing Incidence Small Angle X-ray Scattering (GISAXS) studies shows diffraction spots, consistent with the entire film being well ordered. GISAXS also shows that the mesoporous silica films survive removal of the template and electrodeposition of nickel and cobalt into the mesoporous silica films. Such films are of interest for their magnetic properties, as the nanophase and scale can be independently varied. Further, the presence of nanowires inside an insulator suggests that these films might also be of interest as the current confining element for Confined Current Path-Current Perpendicular to Plane GMR sensors.

Investigation of the profile effect on the sensitivity enhancement of nanowire-mediated localized surface plasmon resonance biosensors

Localized surface plasmon resonance (SPR) biosensors with metallic nanowires regularly patterned on a gold film are considered for sensitivity enhancement. The theoretical investigation was conducted using rigorous coupled wave analysis in terms of various design metrics, such as the resonance angle shift, the SPR curve angular width, and the minimum reflectance at resonance. The results show that nanowires of a T-profile present more effective sensitivity enhancement than an inverse T-profile. The sensitivity enhancement mediated by the presence of nanowires has also been clarified qualitatively based on the dispersion relation between metal film involving nanowires and surrounding dielectric medium. The study is expected to provide extremely high sensitivity in SPR-based biosensing.