Thick Nanorods Research Articles

Surface and crack effects on longitudinal vibration of thick nanorods with various boundary conditions

Considering the effect of surface parameters and crack on the longitudinal vibration of nanorods is the aim of this study. The nanorod is assumed to be thick, and it is modeled based on Bishop theory of rods. In thick nanorods, the effects of the inertia of lateral motions and the shear stiffness are considered in the kinetic energy and the strain energy of the nanorod, respectively. In the present study, the crack is modeled as a linear spring in which its stiffness is related to the crack severity. The surface parameters considered are the surface Lamé constants, the surface density, and the surface stress. Considering all surface parameters causes inhomogeneity of governing equations and boundary conditions. After converting inhomogeneous equations to homogeneous ones, the resulted equations are solved numerically. All possible boundary conditions are introduced but only natural frequencies of nanorod with fixed-fixed and fixed-free are reported. In addition to considering the effect of type of boundary conditions on the natural frequencies, the effect of geometrical parameters like radius and length, and mode number is also considered. The results are presented for both thin and thick nanorods to compare the effect of various parameters especially surface parameters on longitudinal frequencies.

Improved photocatalytic performance of Li+/Eu3+-co-doped V2O5 ultralong nanowires

Layered-structure V2O5 has attracted extensive research attention as an ideal electrode material for lithium batteries and gas sensors, among others. In this study, we investigated the effects of Li+ and Eu3+ single- and co-doping on the electronic structure, optical properties, and pollutant-photodegradation efficiency of V2O5. All the samples were fabricated by a simple one-step hydrothermal method using NH4VO3 and phthalic acid as precursors. Pure and Eu3+-doped V2O5 developed into short, thick nanorods, while, Li+/Eu3+-co-doped V2O5 crystallized into ultralong nanowires. Furthermore, Li+ and Eu3+ doping significantly increased the ability of V2O5 to photodegrade Rhodamine B in solution. In order to elucidate the mechanism of this photochemical enhancement, the multivalence of V, charge dispersion characteristics, luminescence, and carrier lifetime were measured. The improved photocatalysis of Li+/Eu3+-co-doped V2O5 was found to be related to its increased specific surface area, multivalent V4+/5+ ions, prolonged charge lifetime, and accelerated charge dispersion. Experimental results showed that Eu3+ and Li + ions are present in the interlayers of V4O5 as pillars. Thus, co-doping represents a viable strategy to improve the photochemical properties of layered V2O5.

Effects of Reaction Parameters on the Geometry and Crystallinity of Hydrothermally Synthesized ZnO Nanorods for Bio-Fouling Applications

In this present work, we have successfully synthesized vertical aligned ZnO nanorod arrays (ZnO NRs) on conductive stainless-steel substrate. These ZnO NRs were obtained by using a low temperature, low cost, and eco-friendly hydrothermal approach. The effect of the sol-gel deposited ZnO seed layer on the vertical alignment ZnO NRs has been thoroughly studied. Characterizations of the seed layer and the as-obtained nanorods were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), high-resolution transmission electron microscopy (HR-TEM), and water contact angles (WCA) measurement. SEM analysis shows that these nanorods were grown with a high uniformity and density over the entire substrate. TEM and XRD studies confirmed the hexagonal wurtzite structure of ZnO nanorods. Finally, field immersion tests using the optimized samples were conducted in a coastal sea environment to study biofouling settlement. To the best of our knowledge, there are few articles that investigate the influence of the seed layer deposited on stainless steel on the formation of vertically aligned nanorods for antifouling applications. The novelty of this work is manifested by optimizing the ZnO seed layer to obtain either thick or fine ZnO nanorods (NRs). Moreover, another novelty of this study is the use of the hydrothermal deposition of ZnO NRs on stainless steel for biofouling to replace paints in marine applications.

Template-directed growth of Ag nanostructures: soft templates versus hard templates.

Hard template-directed growth methods present a compelling route for the synthesis of Ag nanostructures with precise size control. Meanwhile, soft template methods are effective and flexible for the synthesis of Ag nanostructures with various morphologies. However, the role of the soft template is ambiguous and obviously neglected in hard template-directed growth processes due to the strong confinement effect of the hard template, limiting the diversity of Ag nanostructures that can be obtained. Herein, we design Au nanoframes with deformable head structures as a hard template while using cetyltrimethylammonium chloride as a soft template, to direct the growth of Ag atoms on Au nanobipyramid seeds. When using the Au nanoframes with a closed head, the longitudinal growth of the Ag atoms is clearly limited by the hard template, leading to the formation of thick Ag nanorods with a five-fold twinned structure. The soft template starts to influence the growth process when the head structure of the Au nanoframes becomes hollow. In particular, the confinement effect of the hard template can be completely broken by selectively strengthening the role of the soft template, promoting the production of slender Ag nanorods similar to the results obtained in the absence of the hard template. Our results indicate that the morphology of the Ag nanostructures depends on the competition between the qualitatively confined energies of the hard and soft templates during the template-directed growth process. Moreover, this confined growth mechanism is also verified by the successful construction of various Ag nanostructures. The understanding of the collaborative competition mechanism between the soft and hard templates presents a great opportunity to construct novel Ag nanostructures through a template-directed method.

Different Reactivity of Birnessite and Cryptomelane toward Isoprene: Effect of Structure, Morphology, and Exposed Faces

This study investigates the adsorption and oxidation of isoprene, the most abundant biogenic volatile organic compound, on two common Mn(IV) (hydr)oxides in Earth’s surface environment, birnessite and cryptomelane. Both minerals show high adsorption capability toward isoprene under increasing environmental temperature and low relative humidity, whereas the adsorbed isoprene on birnessite is oxidized into carboxylate species, mainly formate. For both Mn(IV) (hydr)oxides, the adsorption of isoprene not only reduces Mn4+ to Mn3+ but also gives rise to the slight distortion of the crystal structure. Compared to cryptomelane, birnessite exhibits better adsorption and oxidation capability of isoprene, which is improved by the decrease in crystallinity. This is attributed to the high density of oxygen anions on the (001) surface, owing to the participation of lattice oxygen, electrophilic adsorbed oxygen, and hydroxyl groups in the oxidation of isoprene. For cryptomelane, the particles with short and thick nanorods show higher adsorption capacity but lower oxidizability than those with long and sharp nanorods, as the (001) surface of cryptomelane prefers to adsorb isoprene and Mn4+ in long sharp nanorods and accept more electrons from isoprene. Based on the experimental results, we propose that Mn(IV) (hydr)oxide in soil dust aerosols is an important regulator of atmospheric isoprene, which enhances the bioavailability of both isoprene and Mn(IV) (hydr)oxides.

Energy funneling and charge separation in CdS modified with dual cocatalysts for enhanced H2 generation

Anchoring molecular cocatalysts on semiconductors has been recognized as a general strategy to boost the charge separation efficiency required for efficient photocatalysis. However, the effect of molecular cocatalysts on energy funneling (i.e., directional energy transfer) inside semiconductor photocatalysts has not been demonstrated yet. Here we prepared CdS nanorods with both thin and thick rods and anchored the conjugated molecules 2-mercaptobenzimidazole (MBI) and cobalt molecular catalysts (MCoA) sequentially onto the surface of nanorods. Transient absorption measurements revealed that MBI molecules facilitated energy funneling from thin to thick rods by the electronic coupling between thin and thick nanorods, which is essentially a light-harvesting antenna approach to enhance the charge generation efficiency in the reaction center (here the thick rods). Moreover, MBI and MCoA molecules selectively extracted photogenerated holes and electrons of CdS nanorods rapidly, leading to efficient charge separation. Consequently, CdS/MBI/MCoA displayed 15 times enhanced photocatalytic H 2 evolution (1.65 mL) than pure CdS (0.11 mL) over 3 h of illumination. The amount of H 2 evolution reached 60 mL over 48 h of illumination with a high turnover number of 26294 and an apparent quantum efficiency of 71% at 420 nm. This study demonstrates a novel design principle for next-generation photocatalysts. For CdS/MBI/MCoA, the MBI and MCoA molecules selectively extracted photogenerated holes and electrons from CdS nanorods rapidly. Additionally, the MBI molecules facilitated energy funneling from thin to thick rods, endowing CdS/MBI/MCoA elevated photocatalytic H 2 evolution.

Size-Separation and Self-Assembly of Anisotropic Nanoparticles in a Coffee-Stain Ring

Nanoparticles deposition via droplet drying technique generally leads to a coffee-stain-like ring. In the case of different shapes and sizes of nanoparticles, such ring-like deposits also demonstrate various phases within the self-assembly superstructures. For broad spectrum sizes in suspension, size-separation effect has not been considered before. Herein, polydisperse gold anisotropic nanoparticles have been prepared via wet chemical synthesis technique. High-resolution scanning electron microscopy (HRSEM) at various positions of a coffee-stain ring displayed both size-separation and self-assembly of nanoparticles. Especially at the outer edges of a ring-like deposit, side-by-side organized arrays of anisotropic nanoparticles have been observed. Likewise, such ordered arrays generally begin with thin nanorods and the width of nanoparticles increases as one moves inward within such arrays. Also, assembly of deposited arrays is more orderly arranged at the periphery of the ring, whereas such order significantly decreases at the interior region of the ring. Furthermore, it has been observed for a mixture of thick–thin nanorods and spheres that only thick nanorods self-assemble into ordered arrays whereas thin rod-sphere was found disordered everywhere within the ring. Nanoscale interactions are quantified for these systems to understand self-assembly behavior of such anisotropic nanoparticles.

In-Plane Anisotropy of Transport Property in BaTbO3-Doped SmBa2Cu3O y Films

BaTbO 3 (BTbO) is one of artificial pinning center materials and forms thick rectangular nanorods with diameters of ~20 nm when it is doped high. We expected that the rectangular na-norods would produce in-plane anisotropy of flux pinning. In this study, we investigated in-plane anisotropy of transport properties in BTbO-doped SmBa 2 Cu 3 O y (SmBCO) films. SmBCO thin films with various contents of BTbO were fabricated by using a pulsed laser deposition method. To investigate the in-plane anisotropy, the critical current density J c was measured at 77 K, 0-9 T, and Φ = 0 o and 45 o , where Φ was defined as an in-plane angle from the a or b-axes of SmBCO. To fix the direction of current in the films, the micro-bridges were fabricated with different Φ = 0 o and 45 o by using the laser etching technique. As a result, J c at Φ = 0 o was higher than one at Φ = 45 o in the films with BTbO contents of 12.0 and 20.0 vol.% at 77 K and at fields of 5 T or more. The anisotropy of J c in high fields for current directions was possibly explained by the rectangular shape of the BTbO nanorods.

Shape-Controlled Hematite: An Efficient Photoanode for Photoelectrochemical Water Splitting

Photoelectrochemical water splitting has gained considerable interest in the past few decades because of its potential for harvesting solar light for H2 production. For harvesting solar light, the design of a semiconductor photoelectrode is the critical parameter to control performance. In this regard, vertically aligned, interconnected 2D nanosheets of α-Fe2O3 show the most efficient activity for PEC water splitting as compared to other morphologies like thick sheets and nanorods as the former absorb more light, provide less path length for photon penetration, and a short minority carrier (hole) diffusion length. Compared to thick sheets and nanorods, the separation efficiency of Fe2O3 nanosheet is 7.3, which is higher than the structures as mentioned above, at 1.23 V vs RHE. To further legitimize the efficacy of α-Fe2O3 nanosheet vis-a-vis the thick sheets and nanorods, Mott–Schottky analysis is performed to calculate carrier densities of 8.68 × 1020, 8.68 × 1019, and 2.89 × 1020 cm–3.

One-Dimensional Sb2Se3 Nanorods Synthesized through a Simple Polyol Process for High-Performance Lithium-Ion Batteries

The good crystalline Sb2Se3 nanorods have been successfully synthesized through a simple polyol process. The detailed morphological and structural characterizations reveal that nanorods are composed of Sb2Se3 single crystals oriented along the [120] orientation; the tiny Sb2Se3 nanorods are found to display a higher crystallinity with respect to thick Sb2Se3 nanorods. The nanorods have been applied as anode materials for lithium-ion batteries, with tiny Sb2Se3 nanorod anodes delivering the relatively high discharge capacity of 702 mAh g−1 at 0.1 C and could maintain the capacity of 230 mAh g−1 after 100 cycles. A more stable cycling performance is also demonstrated on tiny Sb2Se3 nanorods, which is ascribed to their more pronounced one-dimensional nanostructure.

An analytical study on the size dependent longitudinal vibration analysis of thick nanorods

In this paper, nonlocal free longitudinal vibration of thick nanorods is investigated by focusing on the inertia of lateral motions and shear stiffness effects. To this end, Bishop and nonlocal theories are used. Then, by implementing the Hamilton’s principle nonlocal governing equation of motion and boundary conditions are derived. The governing equation is solved analytically for fixed-fixed and fixed-free end conditions and the first five longitudinal natural frequencies of nanorod are obtained. In the next step, effects of various parameters like the length of nanorod, the diameter of nanorod and the nonlocal parameter value on natural frequencies are investigated. This study can be a useful reference for modeling of the multi-walled carbon nanotubes in which the interlayer shear plays a significant role in their various mechanical behaviors.

Optical properties of magnesium nanorods using time dependent density functional theory calculations.

Plasmonic nanostructures made of Earth-abundant and low-cost metals such as aluminum and magnesium have recently emerged as a potential alternative candidate to conventional plasmonic metals such as gold and silver. Here using computationally efficient time-dependent density-functional theory calculations, we explore optical response modulations of magnesium nanorods via aspect ratio and absolute size variations. We reveal that both the aspect ratio and absolute size of the nanorods are critical for elucidating their optical characteristics. We show that both tuning factors cause significant optical response modulations in the case of thin nanorods (emergence of localized surface plasmon resonances, significant spectral shifting and spectral intensity re-distributions), whereas, very marginal changes in the case of thick nanorods. We believe that our theoretical results would help in the design of magnesium based nano-plasmonic devices.

Free axial vibration analysis of axially functionally graded thick nanorods using nonlocal Bishop's theory

Free axial vibration of axially functionally graded (AFG) nanorods is studied by focusing on the inertia of lateral motions and shear stiffness effects. To this end, Bishop's theory considering the inertia of the lateral motions and shear stiffness effects and the nonlocal theory considering the small scale effect are used. The material properties are assumed to change continuously through the length of the AFG nanorod according to a power-law distribution. Then, nonlocal governing equation of motion and boundary conditions are derived by implementing the Hamilton's principle. The governing equation is solved using the harmonic differential quadrature method (HDQM), After that, the first five axial natural frequencies of the AFG nanorod with clamped-clamped end condition are obtained. In the next step, effects of various parameters like the length of the AFG nanorod, the diameter of the AFG nanorod, material properties, and the nonlocal parameter value on natural frequencies are investigated. Results of the present study can be useful in more accurate design of nano-electro-mechanical systems in which nanotubes are used.

Microreactor with copper oxide nanostructured films for catalytic gas phase oxidations

Three simple gas phase based methods were applied to copper foils with parallel microchannels to induce in-situ growth of nanostructured CuOx films. One method consisted in treating with vapors of NH4OH and H2O2 (VAP); another method consisted in heating in air at 500°C (CAL); and the third one was a sequence of both methods (CAL-VAP). The synthesized CuOx films/Cu foils were assembled as microreactors and tested for CO oxidation, showing high catalytic performance and stability in reaction. The physicochemical characteristics of the films were examined by Scanning Electron Microscopy (SEM), Temperature-Programmed Reduction (TPR), X-ray Diffraction (XRD), Laser Raman Spectroscopy (LRS), Reflectance Infrared Fourier Transformed Spectroscopy (DRIFTS) and ultrasound tests. The VAP films consisted of thick clustered nanorods containing Cu+ and Cu2+ species in the outer layer of the coating. The CAL films presented uniform growth of nanoneedles in which the outer layers were composed mainly of Cu2+. However, by submitting the CAL sample to the VAP procedure (CAL-VAP), part of CuO was reduced to Cu4O3 species. The developed microreactors with copper oxide nanostructures directly grown on microchannels with high thermal conductivity represent a low-cost, simple alternative for application in catalytic gas-phase reactions.

The alcohol-sensing behaviour of SnO2 nanorods prepared by a facile solid state reaction

SnO2 nanorods with the range of 12-85 nm in diameter were fabricated by a facile solid state reaction in the medium of NaCl-KCl mixture at room temperature and calcined at 600, 680, 760 and 840 oC, respectively. The XRD, TEM and XPS were employed to characterize the structure and morphology of the SnO2 nanorods. The influence of the calcination temperature on the gas sensing behaviour of the SnO2 nanorods with different diameter was investigated. The result showed that all the sensors had good response to alcohol. The response of the gracile nanorods prepared at a low calcined temperature demonstrated significantly better than the thick nanorods prepared at a high calcined temperature. The mechanism was attributed to the nonstoichiometric ratio of Sn/O and larger surface area of the gracile nanorods to enhance the oxygen surface adsorption.

Tuning aspect ratio of hierarchical ZnO nanotetrapod

Fine-tuning the aspect ratio is crucial for practical application and optimizing various properties of nanostructure. In this work, a mixed metal (Zn) and oxide (ZnO + C) powder was adopted as precursor to obtain initial high reagent vapour pressure and subsequent low reagent vapour pressure, and one kind of hierarchical ZnO nanotetrapod with legs composed of thick primary nanorod and thin secondary nanowire was successfully synthesized. Two growth stages controlled by the reagent supersaturation ratio were proposed to unveil the underlying growth mechanism of this hierarchical structure. Further, a series of comparative experiments were undertaken to validate the growth mode and explore the growth strategy tailoring the aspect ratio. Our results suggest one accessible approach to manipulate the aspect ratio, and the growth mode has some promises for preparing hierarchical nanoblocks with specific geometry demanding.

Epitaxy, phase separation and band-edge emission of spontaneously formed InGaN nanorods

An In-flux dependent study of the nature of epitaxy, compositional phase separation and band-edge emission of spontaneously formed c-oriented InGaN nanorods on c-sapphire is performed. At higher In flux-rates, m-faceted thick nanorods (≈700 nm) form with two in-plane epitaxial orientations, and display compositional phases with In composition varying from 14 to 63%. In these rods, photo-luminescent (PL) emission is seen to originate only from the localized high-In phase (63%) that is embedded in the low-In (14%) InGaN matrix. As the In flux-rate is reduced, nanorods of smaller diameter (≈60 nm) and a coalesced nanorod network are formed, with In incorporation of 15% and 9%, respectively. These faceted, c-aligned thinner nanorods are of a single compositional phase and epitaxy and display room-temperature PL emission. Optical absorption and emission properties of these nanostructures follow Vegard’s law of band-gaps, and the observed bowing parameter and Stokes shifts correlate to the observed compositional inhomogeneity and carrier localization.

"Secondary Growth" in Hydrothermal Synthesis of Aligned ZnO Nanostructures and Its Application in Dye-Sensitized Solar Cells.

One-dimensional (1D) aligned ZnO nanostructures were prepared on ZnO film seeded substrates using a low-temperature hydrothermal method, and zinc nitrate and hexamethylenetetramine (HMT) precursors. It was observed that increasing the concentration ratio of Zn2+/HMT from 1 to 100 led to a "secondary growth," and a change in the morphologies of the ZnO nanostructures from arrays of thick nanorods to arrays of thin nanorod-step-thick nanorods. The morphological evolution of ZnO nanostructures with increased growth time at high Zn2+/HMT concentration ratios showed the same transformation. Dye-sensitized solar cells (DSSCs) were fabricated using ZnO nanostructures as the photoanodes, and the electron transport properties were determined by electrochemical impedance spectroscopy (EIS). Although the DSSCs showed low power conversion efficiencies due to the short lengths, the arrays of the thin nanorods demonstrated excellent electron transport with an electron diffusion coefficient (Dn) of 1.57 x 10(-3) cm2/s, and an effective diffusion length (L) of 140 µm.

Magnetic Field of BG-VG Transition Depending on the Nanorods Shape in <inline-formula> <tex-math notation="TeX">$\hbox{BaHfO}_{3}$</tex-math></inline-formula>-Doped <inline-formula> <tex-math notation="TeX">$\hbox{SmBa}_{2}\hbox{Cu}_{3}\hbox{O}_{y}$</tex-math></inline-formula> Films

The vortex state under the magnetic held around vortex glass (VG)-Bose glass (BG) transition held was investigated in the SmBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> (SmBCO) films with BaHfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BHO) nanorods. We prepared two films with different forms of the nanorods (thick-straight and thin-tilted), and we used the magnetic held angular dependence of flux flow resistivity (p - θ) to identify a vortex state. From a comparison between the p - θ curves in completely BG and VG phases, it was revealed that the existence of deep and sharp dip structure along the c-axis direction of the SmBCO matrix (B//c) was an evidence of the BG state in both the films. In the magnetic held region around VG-BG transition, shallower and broader dips than the dips in the BG state were observed at B//c in both the films. In addition, the dips became deeper with increase of the magnetic held in this region in each film. Therefore, we considered the vortex state of both the films was an intermediate and/or a transient state of BG and VG. Under all magnetic fields, the film with thick and straight BHO nanorods showed stronger c-axis correlated flux pinning force than the film with thin and tilted nanorods. We suggested the intermediate state of the hlm with thicker and straighter nanorods was similar to the BG state compared with another hlm from the both of experimental results and reported theory.

TiO2 nanofibers supported on Ti sheets prepared by hydrothermal corrosion: effect of the microstructure on their photochemical and photoelectrochemical properties

TiO2 nanostructures were prepared by hydrothermal corrosion of Ti sheets for various heating temperatures and times. Their change from thick and short nanorods to thin and long nanowires by increasing these processing parameters led to improved photocatalytic properties.