Alloy Nanotubes Research Articles

A novel non-enzymatic amperometric glucose sensor based on a hollow Pt–Ni alloy nanotube array electrode with enhanced sensitivity

A non-enzymatic electrode is proposed as a glucose sensor based on Pt-replaced Ni nanowires which are prepared by constant current electro-deposition within the anodic alumina membrane and galvanic replacement reaction.

Highly stable PtP alloy nanotube arrays as a catalyst for the oxygen reduction reaction in acidic medium.

Nanostructured Pt-metal alloys have shown impressive catalytic properties for the oxygen reduction reaction (ORR) in acidic medium, but their long-term stability has not been satisfactory. Herein, we look beyond the traditional Pt-metal alloys and have developed a new kind of Pt-nonmetal alloy electrocatalyst for the ORR. Specifically, the novel catalyst is composed of interconnected platinum monophosphide (PtP) alloy nanocrystals (∼3-4 nm) and featured supportless nanotube array morphologies. Due to the unique combination of composition and structure, the obtained PtP alloy nanotube arrays not only exhibited remarkable ORR activity, but also showed almost no degradation of the half-wave potential after accelerated durability tests. The result suggests that alloying Pt with a nonmetallic element (such as P) is indeed an effective approach to address the poor stability of Pt-based catalysts in acidic medium.

One-step electrochemical growth of a three-dimensional Sn-Ni@PEO nanotube array as a high performance lithium-ion battery anode.

Various well-designed nanostructures have been proposed to optimize the electrode systems of lithium-ion batteries for problems like Li(+) diffusion, electron transport, and large volume changes so as to fulfill effective capacity utilization and increase electrode stability. Here, a novel three-dimensional (3D) hybrid Sn-Ni@PEO nanotube array is synthesized as a high performance anode for a lithium-ion battery through a simple one-step electrodeposition for the first time. Superior to the traditional stepwise synthesis processes of heterostructured nanomaterials, this one-step method is more suitable for practical applications. The electrode morphology is well preserved after repeated Li(+) insertion and extraction, indicating that the positive synergistic effect of the alloy nanotube array and 3D ultrathin PEO coating could authentically optimize the current volume-expansion electrode system. The electrochemistry results further confirm that the superiority of the Sn-Ni@PEO nanotube array electrode could largely boost durable high reversible capacities and superior rate performances compared to a Sn-Ni nanowire array. This proposed ternary hybrid structure is proven to be an ideal candidate for the development of high performance anodes for lithium-ion batteries.

Impact of Cu-Pt nanotubes with a high degree of alloying on electro-catalytic activity toward oxygen reduction reaction

Well-defined copper-platinum (Cu-Pt) nanotubes with a high degree of alloying were synthesized through a galvanic replacement reaction; this reaction utilized aqueous solutions containing H2PtCl6 and copper nanowires, which acted as the sacrificial templates, without other surfactants or organic solvents at room temperature. The size, morphology and alloy composition of the well-alloyed Cu-Pt nanotubes were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and inductively coupled plasma (ICP) mass spectrometry. The electrochemical replacement reaction generated a hollow one-dimensional (1D) structure and the high degree of alloying in the as-synthesized products. Compared to a commercial Pt/C catalyst (40wt.%, E-TEK), the as-synthesized Cu-Pt alloy nanotubes exhibited superior electro-catalytic activity and stability during oxygen reduction reaction in acidic solutions due to their unique hollow 1D structure and the high alloying degree. In addition, the kinetic parameters of the oxygen reduction over the Cu-Pt alloy nanotubes were calculated based on ring-disk electrode, Tafel plot, and electrochemical impedance spectra (EIS) measurements.

Quinary PdNiCoCuFe Alloy Nanotube Arrays as Efficient Electrocatalysts for Methanol Oxidation

Multi-metallic alloy nanotube arrays are highly favorable for superior electrocatalytic performance and efficient utilization of catalyst because of the special characteristics of alloys, hollow nanotubes, and array nanostructures. Here we firstly prepared the quinary PdNiCoCuFe alloy nanotube arrays (NTAs) by template-assisted electrodeposition method. The inner diameters, wall thicknesses, and lengths of PdNiCoCuFe alloy nanotubes are 300∼400nm, 150nm, and 1.8μm, respectively. Because of the high specific surface area, hollow nanotube arrays, and synergistic effects of various elements, the quinary PdNiCoCuFe alloy NTAs as efficient electrocatalysts showed superior catalytic activity and long-term cycle stability for methanol electrooxidation. The combination of compositionally and geometrically favorable factors provides a new method to design the novel catalysts with excellent electroactivity and durability.

Facile synthesis and characterization of Au–Cu, Pt–Cu nanotubes by sacrificial template method

Bimetallic nanotubes with noble metals have already shown more versatile performances than single-metallic nanotubes. However, most of the current methods to prepare bimetallic nanotubes are based on existed hard template, which could not be easily removed after the formation of bimetallic nanotubes. It is still a challenge for synthesizing bimetallic nanotubes without the template removing subsequently. In this research, we developed a novel method to prepare noble metal–copper (Cu) bimetallic nanotubes with Cu nanowires as the sacrificial template. The aqueous solutions with chloroauric acid or palladium chloride were used to bring displacement reaction with Cu nanowires. The simultaneous alloying effect and Kirkendall effect result in hollow nanostructures. The Cu nanowire was converted to a bimetallic hollow with Au–Cu or Pt–Cu alloy nanotubes. This facile method could achieve large-scale preparation of bimetallic nanotubes with noble metals. Furthermore, this alloy nanotube shows superior electrochemical catalytic performance than single-metallic nanoparticles.

Study on High Order TiO<sub>2</sub> Nanotube Arrays and the Mechanical Properties

In this paper surface modification was adopted on 3 kinds of titanium alloy and TiO2 nanotubes arrays were prepared on these surfaces by anodic oxidation method.nanoindentation and nanoscratch experiments were performed to test the mechanical properties of TiO2 film, such as micro hardness and elastic modulus.Through comparing and analyzing,it is seen that,The film generated on the TC4 has better mechanical properties than the others and TC4 is better substrate for surface modification by anodic oxidation as the implanted materials.

Dark-Field Imaging of Thin Specimens with a Forescatter Electron Detector at Low Accelerating Voltage

A forescatter electron detector (FSED) was used to acquire dark-field micrographs (DF-FSED) on thin specimens with a scanning electron microscope. The collection angles were adjusted with the detector distance from the beam axis, which is similar to the camera length of the scanning transmission electron microscope annular DF detectors. The DF-FSED imaging resolution was calculated with SMART-J on an aluminum alloy and carbon nanotubes (CNTs) decorated with platinum nanoparticles. The resolution was three to six times worse than with bright-field imaging. Measurements of nanometer-size objects showed a similar feature size in DF-FSED imaging despite a signal-to-noise ratio 12 times smaller. Monte Carlo simulations were used to predict the variation of the contrast of a CNT/Fe/Pt system as a function of the collection angles. It was constant for very high collection angles (>450 mrad) and confirmed experimentally. The reverse contrast between carbon black particles and the smallest titanium dioxide (TiO2) nanoparticles was predicted by Monte Carlo simulations and observed in the DF-FSED micrograph of a battery electrode coating. However, segmentation of the micrograph was not able to isolate the TiO2 nanoparticle phase because of the close contrast of small TiO2 nanoparticles compared to the C black particles.

Fabrication and magnetic properties of CoNi alloy nanotube arrays

CoNi nanotubes were prepared in pores of anodic aluminum oxide templates via a dc electrodeposition method. The dependence of product morphology on the applied potential was studied over the range −1.0 to −2.5V. The results showed that a critical potential related to the electrodeposition parameters exists, below which the deposited product was almost entirely in the form of nanotubes, whereas above which, nanowires are formed. Magnetic measurements showed hysteresis loops of the nanotubes are discontinuous. Theoretical analysis suggested the existence of some peculiar magnetization configuration such as vertical Bloch line which was responsible for the discontinuity of the hysteresis loops.

Highly stable FeCo/carbon composites: Magnetic properties and microwave response

Highly steady composites of FeCo alloy and carbon nanotubes have been synthesized by in situ catalytic decomposition of benzene over FeCo alloy nanoparticles generated through procedures of sol–gel fabrication and hydrogen reduction. Magnetic measurement indicates that the coercivity (HC) increases with the rise of Co concentration and the saturation magnetization (MS) rises in the order of FeCo13@C<FeCo31@C<FeCo22@C. The complex permittivity and permeability of the composites indicates that the maximum reflection loss (RL) is −6.7dB at 11.1GHz at thickness of 1.5mm for FeCo13@C, and as well as the electromagnetic wave absorption properties can be tuned by adjusting the composition of FeCo alloy and the absorption layer thickness.

The Application Research on Electrical Deposition Method for Preparing Pt-Ni Alloy Nanotubes and its Modified Sensor in the Detection of Dopamine

This paper states how to prepare Pt-Ni alloy nanotubes in PC spray gold template using electrical deposition method, modify it to the glassy carbon electrode and make into dopamine sensor. It compares that cyclic voltammetry behavior of the bare glassy carbon electrode and Pt-Ni alloy nanotubes modified glassy carbon electrode. The conditions that glassy carbon electrode is modified by Pt-Ni alloy nanotubes for determination of dopamine were optimized. Under the optimized conditions, the test linear is in the range of 1.0×10-6 ~ 1.0 × 10-3 mol/L, detection limit is 4.0×10-7 mol/L, the recovery rate is 95.2%. This method has the advantages of simple operation, little amount of sample, high sensitivity and good reproducibility.

Formation of single-walled bimetallic coinage alloy nanotubes in confined carbon nanotubes: molecular dynamics simulations

The growth of single-walled bimetallic Au-Ag, Au-Cu and Ag-Cu alloy nanotubes (NTs) and nanowires (NWs) in confined carbon nanotubes (CNTs) has been investigated by using the classical molecular dynamics (MD) method. It is found that three kinds of single-walled gold-silver, gold-copper and silver-copper alloy NTs could indeed be formed in confined CNTs at any alloy concentration, whose geometric structures are less sensitive to the alloy concentration. And an extra nearly pure Au (Cu) chain will exist at the center of Au-Ag (Au-Cu and Ag-Cu) NTs when the diameters of the outside CNTs are big enough, thus producing a new type of tube-like alloy NWs. The bonding energy differences between the mono- and hetero-elements of the coinage metal atoms and the quasi-one-dimensional confinement from the CNT play important roles in suppressing effectively the "self-purification" effects, leading to formation of these coinage alloy NTs. In addition, the fluid-solid phase transition temperatures of the bimetallic alloy NTs are found to locate between those of the corresponding pure metal tubes. Finally, the dependences of the radial breathing mode (RBM) frequencies and the tube diameters of the alloy NTs on the alloying concentration were obtained, which will be very helpful for identifying both the alloying concentration and the alloy tube diameters in future experiments.

Sonochemical fabrication of CdSexTe1−x/Au nanotubes and their potential application in biosensing

CdSexTe1-x semiconductor alloy nanotubes (with an external diameter of 140 nm and an internal diameter of 100 nm) were successfully prepared based on the sacrificial template of Cd(OH)Cl nanorods, and were further in situ assembled with gold nanoparticles (AuNPs) via a sonochemical approach to form the CdSexTe1−x/Au nanotubes. The prepared CdSexTe1−x/Au nanotubes were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive spectrometry, and X-ray photoelectron spectra. CdSexTe1−x/Au nanotubes could integrate the advantages of the electronic properties of CdSeTe and the biocompatible properties of AuNPs. A novel biosensor was fabricated after the immobilization of hemoglobin (Hb) on CdSexTe1−x/Au nanotubes. The immobilized Hb exhibited fast direct electron transfer and good electrocatalytic performance to H2O2.

Comparative study in fabrication and magnetic properties of FeNi alloy nanowires and nanotubes

FeNi alloy nanowires and nanotubes have been fabricated in the pores of the anodized aluminum oxide (AAO) templates by direct current electrodeposition with different potentials. The crystal structure and micrograph of FeNi alloy nanowires and nanotubes were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, and the content was confirmed by energy dispersive spectrometry. The results indicate that there is a critical potential in the formation of nanowires and nanotubes. FeNi alloy nanowires and nanotubes both present the (111) preferred orientation, and the content of Fe is reduced with the decrease of electrodeposition potentials. The magnetic behaviors of FeNi alloy nanowires and nanotubes with different ratios are investigated. The coercivity of FeNi alloy nanowires and nanotubes exhibits disparate behavior, which may attribute to their grain size and distinctive structure.

Shape- and Composition-Sensitive Activity of Pt and PtAu Catalysts for Formic Acid Electrooxidation

In this work, we have probed the shape- and composition-dependent activities of Pt and PtAu catalysts for formic acid electrooxidation. Pt-based hollow nanostructures such as Pt hollow nanospheres (Pt HNSs), Pt nanotubes (Pt NTs), and PtAu alloy nanotubes (PtAu NTs) with controlled Pt:Au compositions are successfully prepared via a galvanic replacement process using sacrificial Ag templates. The physicochemical properties of these Pt and PtAu catalysts are confirmed by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy techniques. The electrochemical activities of these hollow structured catalysts are compared for formic acid oxidation by cyclic voltammetry and chronoamperometry methods. Relative to the commercial Pt black and Pt/C nanoparticle catalysts, the hollow nanostructured Pt materials (Pt HNS, Pt NT) exhibit enhanced catalytic activities due to structural effects. Moreover, the bimetallic PtAu NT series shows improved catalytic activities over the monometallic Pt catalysts due to compositional effects. The present study demonstrates that the catalytic activity and the extent of surface poisoning are strongly dependent on both the structural and compositional variations of the nanostructured electrocatalysts, as shown by a systemically prepared series of nanostructured catalysts for formic acid oxidation.

Multimetallic Alloy Nanotubes with Nanoporous Framework

One-dimensional nanotubes (NTs) that consist of multiple metallic components are promising platforms for potential applications, whereas only a few synthetic methods of multimetallic NTs have been reported to date. In the present work, we developed a general synthesis route for the production of uniform multicomponent one-dimensional tubular nanostructures with various combinations of Pt, Pd, and Ag by using ZnO nanowires (NWs) as sacrificial templates. The ZnO NWs serve not only as physical templates but also as nucleation sites for the reduction of metal precursors, and thereby several metal precursors could be reduced simultaneously to produce multimetallic NTs. By using this approach, Pt-Pd, Pt-Ag, and Pd-Ag binary alloy NTs, and even Pt-Pd-Ag ternary alloy NTs could be successfully prepared. The prepared Pt-Pd binary alloy NTs exhibited improved electrocatalytic activity and stability toward ethanol oxidation due to their characteristic tubular morphology with well-interconnected nanoporous framework and synergism between two constituent metals. Furthermore, our approach can facilitate the fabrication of patterned multimetallic NT arrays on solid and flexible substrates with strong mechanical robustness. The present templating method does not require any extra steps to remove templates or additional surfactants which are often required to control the shape of nanostructures. This strategy offers a convenient, versatile, low-cost, and highly valuable approach to the fabrication of multimetallic nanostructures with various components and compositions.

Cu–Au alloy nanotubes with five-fold twinned structure and their application in surface-enhanced Raman scattering

Cu–Au alloy nanostructures have received considerable attention in recent years due to their widespread use in applications such as catalysis, photonics and surface-enhanced Raman scattering (SERS) detection. In this article, a template-based strategy has been developed to synthesize Cu–Au nanotubes with five-fold twinned structure by using Cu nanowires as templates and AuPPh3Cl as Au precursors in the organic phase of oleylamine. It was verified that high quality Cu–Au alloy nanotubes could result from the Cu–Au alloy effect, the Kirkendall effect, and the galvanic replacement reaction. It was also demonstrated that the Cu–Au alloy nanotubes may have potential applications in SERS detection because of their good stability and convenience for building “hot spots”.

Magnetic Interaction in FeCo Alloy Nanotube Array

An array of FeCo nanotubes has been successfully fabricated in the pores of porous anodic aluminum oxide (AAO) templates by wetting templates method. The morphology and structure of the nanotube array were characterized by scanning electron microscopy, transmission electron microscopy and x-ray diffraction. The average diameter of the nanotubes was about 200 nm, and the length was more than 10 μm. Vibrating sample magnetometer and superconducting quantum interference device were used to investigate the magnetic properties of the nanotube array. Interaction between the nanotubes has been found to be demagnetizing as expected and the switching field distribution is broad.

Hydrogen Storage Alloy and Carbon Nanotubes Mixed Catalyst in a Direct Borohydride Fuel Cell

In this study, carbon nanotubes (CNTs) were mixed with AB 5 -type hydrogen storage alloy (HSA), as catalyst for an anode in a direct borohydride fuel cell (DBFC). As comparision, a series of traditional carbon materials, such as acetylene black, Vulcan XC-72R, and super activated carbon (SAC) were also employed. Electrochemical measurements showed that the electrocatalytic activity of HSA was improved greatly by CNTs. The currentdensity of the DBFC employing the HSA/CNTs catalytic anode could reach 1550 mA-cm −2 (at −0.6 V vs the Hg/HgO electrode) and the maximum power density of 65 mW·cm −2 for this cell could be achieved at room temperature. Furthermore, the life time test lasting for 60 h showed that the cell displayed a good stability.

Fabrication of Carbon Nanotube-Emitters on Ag-Cu Alloy Film by Thermal Welding

A field emission electron source was fabricated on a Si substrate using Ag-Cu alloy (ACa) and carbon nanotubes (CNTs). The ACa was adopted as a binder material due to its excellent electrical conductivity, oxidation stability, and suitable melting point (783 degrees C). The surface morphology of the ACa-film was improved by introducing an Nb layer as an adhesion layer between the ACa-film and the Si substrate. The ACa-film thickness was varied from 100 to 500 nm. The spray method was employed to deposit a CNT film on the ACa/Nb/Si substrate for large area fabrication. After annealing the substrate at 700 degrees C for 10 min, the CNT film was tightly welded on the ACa-films, and the CNT-emitters fabricated on the 400-nm-thick ACa-film exhibited high current density and stability with a low turn-on voltage. It is worth noting that ACa could be applied to the glass substrate because the CNT-emitters fabricated at 500 degrees C exhibited good field emission characteristics.