Metallic Nanotube Arrays Research Articles

Electrochemical nonenzymatic glucose sensors catalyzed by Au nanoclusters on metallic nanotube arrays and polypyrrole nanowires

Monitoring blood glucose level is critical, since its abnormality leads to diabetes and causes death, even though glucose is essential for human living. Herein, the sensing study was performed on electrochemical nonenzymatic glucose sensors, which are composed of an Au nanocluster (AuNC) catalyst deposited on a metallic nanotube array (MeNTA) and polypyrrole nanowire (PPyNW). The AuNC was produced by irradiating a femtosecond pulse laser to the Au precursor solution, and it is a simple and facile method. The successful deposition of AuNC on both MeNTA and PPyNW was confirmed by means of the surface morphology and the Au content increase. On the exploration by cyclic voltammetry in alkaline condition, AuNC/MeNTA electrodes showed better performance than AuNC/PPyNW electrodes: The former was a remarkable electrocatalytic detector towards glucose oxidation with better sensitivity, lower detection limit, wider linear range, and longer-term stability without interference from potential interfering agents such as ascorbic acid, urea, NaCl, KCl, etc. Moreover, nonenzymatic AuNC/MeNTA electrodes exhibited high precision and accuracy in real human blood samples and, thus, can be a promising candidate in glucose sensing applications.

Fabrication and characterization of a hybrid magnetic structure based on highly ordered metallic nanotube arrays

Metallic nanotube arrays (MeNTAs) are used in a wide range of applications, including optoelectronic devices, drug delivery, and catalysis. This paper presents a hybrid MeNTA structure in which the nanotubes are filled with Fe3O4 nanoparticles (NPs) to enhance their utility. The proposed fabrication scheme allows the adjustment of the magnetic properties and size of Fe3O4 NPs simply by altering the ratio of reducing agents during the hydrothermal synthesis process. Our research demonstrated that MeNTAs can be functionalized through the application of Fe3O4 magnetic NPs to create a hybrid magnetic structure of high resolution with specific magnetic properties. The vibrating sample magnetometry results revealed that the ferromagnetism of the proposed hybrid MeNTA/Fe3O4 structure was not as strong as that of the Fe3O4 NPs themselves; however, we provide conclusive evidence that the hybrid highly ordered MeNTA structure possesses magnetic properties.

Core-shell metallic nanotube arrays for highly sensitive surface-enhanced Raman scattering (SERS) detection

Here, we demonstrate the application of highly ordered, periodic Ag/Au core-shell triangle nanotube arrays as an ultrasensitive and low-cost surface-enhanced Raman scattering (SERS) substrate for the first time. The arrays of core-shell nanotube, with an outer diameter of 1.5 μm, were fabricated using top-down wafer-scale lithography followed by sequential sputter deposition of Ag and Au. The SERS activity of various combinations of core-shell structures was evaluated. It was found that Ag-core nanotubes overlaid with the Au-shell resulted in the highest Raman intensity, where the enhancement factor for R6G as a probe molecule is determined to be 1.38 × 107. Meanwhile, the limit of detections for R6G and ketoprofen analytes was evaluated to be 10−10 and 10−6 M, respectively. Linear correlations between the SERS signal intensities and logarithmical scale of both analytes in different concentrations were also established, ranging 10−4–10−10 and 10−2–10−6 M for R6G and ketoprofen, respectively. The Raman R6G peak intensity mapping suggests our metal nanotube arrays act as effective plasmonic hotspots and, thus, are useful for SERS sensing applications.

Fabrication of high aspect-ratio metallic nanotube array with highly-ordered periodicity using HiPIMS

Metal alloys are increasingly being used in the synthesis of nanostructures, such as nanotubes. This study was an attempt to expand the applicability of metallic nanotube arrays (MeNTAs) by fabricating structures with a high aspect ratio with the aim of increasing the active surface area. MeNTAs comprising thin-film metallic glass (TFMG) and bronze were fabricated via high-power impulse magnetron sputtering (HiPIMS) over a contact-hole array created using photoresist. MeNTAs were designed with 2 aspect ratios (2 and 4). MeNTAs with an AR of 2 were fabricated via single-layer deposition using both alloys. When fabricating MeNTA with an AR of 4, the resulting single-layer structures were unable to withstand the photoresist removal process, thereby necessitating the inclusion of a WNiB TFMG as the buffer layer for reinforcement. The percentage of intact AR 4 bronze MeNTA was far higher under multilayer deposition (98.4%) than under single-layer deposition (74%). Plasma diagnostic methods involving a Langmuir probe were used to monitor plasma properties (e.g., plasma potential, plasma density, electron temperature, and ion flux) during the deposition process. These results provide valuable reference for trench filling and the manufacture of nanostructures with a high aspect ratio using HiPIMS.

Development of p-type zinc oxide nanorods on zirconium-based metallic glass nanotube arrays by facile hydrothermal method for gas sensing applications

In this study, p-type zinc oxide (ZnO) nanorods grown on zirconium-based metallic glass nanotube arrays were developed for hydrogen gas sensing applications. Heterogeneous zirconium-based metallic glass nanotube arrays were synthesized by sputter deposition of metallic glass (Zr60Cu25Al10Ni5) over contact-hole arrays created using a photoresist template (diameter, 2 µm). To provide nucleation sites for the growth of nanorods inside the zirconium-based metallic glass nanotube arrays, a ZnO seed layer was deposited. ZnO nanorods were grown using the hydrothermal method. The developed p-type ZnO nanorods were systematically characterized, and the reason behind the change from n-type ZnO to p-type ZnO was explained based on experimental findings. The sample was then sputtered with Pt electrodes to obtain a hydrogen sensing device. The fabricated zirconium-based metallic glass nanotube arrays with ZnO nanorods (Zr-ZnO nanorods) exhibited outstanding hydrogen gas sensing property of 28% sensor response at room temperature. Besides, the H2 gas sensing performance of the developed sensor is better than that of the ZnO-based H2 gas sensors in the open literatures. It also presented excellent cyclic and long-term stability, which is crucial for practical applications. The preparation method is also easy, fast, and at low temperatures. Therefore, this study paves the way for the development of p-type ZnO with potential applications in various areas; the developed sensor can be used for environmental remediation and monitoring.

Nanostructured Nickel-based Non-enzymatic Electrochemical Glucose Sensors.

Glucose detection is considered a significant area and has remained the topic of considerable attention. Remarkable technological advancements have been observed in diabetes monitoring in the past decades. This continual progress helps to track recent trends in development as well as identify challenging issues in glucose sensor construction. Thus, a comprehensive synopsis of the most recent advancements and developments in the study of nickel (Ni) nanostructure-based sensors for efficient trace-level glucose detection, following non-enzymatic and electrochemical methods, is provided in this review. Moreover, this review is intensively focused on the methodologies for the structure, morphology, preparation, and enforcement of a variety of Ni nanostructures, including Ni nanosheets with metals, Ni nanospheres with metals/mixed metals, Ni-metal nanocomposites, metal nanoparticles-decorated Ni nanowires, Ni nanoparticles, Ni-decorated metal nanotube arrays, Ni nanoneedles and nanorods with metals, nanoporous, nanoplates, nanocoated Ni with metal composites, and Ni-composed hybrid nanostructures. Various demonstrations and categorizations are provided on Ni-based nanostructures for a clear understanding for diverse readers.

Functionalized metallic carbon nanotube arrays for gas phase explosives detection

Gas phase detection of explosive molecules is a sensing application of wide interest. Light weight, low power sensors are needed for mobility and wide dissemination, however low vapor pressures and the presence of similar functional groups in a variety of explosive molecules make the development of sensitive and selective detection systems difficult. Experimental research has reported some success in the development of carbon nanotube (CNT) based explosives sensors, however safety considerations and strict controls on the distribution of explosive materials hamper experimental progress. Ab initio modeling of functionalized carbon nanotubes suggests that chemiresistive sensor arrays employing hydroxyl, carboxylic acid, oxygen, and amine groups can distinguish common background gases from both nitroaromatic and nitramine explosives, distinguish between nitroaromatic and nitramine explosives, and distinuguish similar nitramine explosives from each other. The modeling results on functionalized CNT sensing arrays suggest that they offer important opportunities for future experimental research.

Cost-effective large-area Ag nanotube arrays for SERS detections: effects of nanotube geometry

This study demonstrated highly-ordered metallic nanotube arrays (MeNTAs) with a precisely controlled geometric shape to promote surface-enhanced Raman scattering (SERS). Using both simulation and experimental methods, we designed and fabricated MeNTAs with nanotube geometries that possess a large surface area to absorb probe molecules as well as geometric features capable of inducing hot spots for SERS enhancement. The proposed top-down wafer-scale lithographic and sputter-deposition process is a simple and cost-effective approach to the fabrication of 1 mm × 1 mm MeNTA at room temperature. Simulation results of nanotubes with various materials (Au, Ag, and Cu), diameters (100–1500 nm), geometric shapes (circle, equilateral triangle and square) and triangle corner curvatures (ranging from 0 to 300 nm) identified Ag triangles with sharp tips as the geometry best suited to SERS enhancement. The SERS spectra of crystal violet molecules generated from the Ag MeNTAs verified the patterns observed in computational simulations, wherein the effects of MeNTA on SERS decreased with an increase in the size of the nanotubes. Enhancement factor of 1.06 × 109 was obtained from our triangular Ag MeNTA, confirming its efficacy as an ultrahigh sensitivity SERS-active substrate.

Large-area alloy nanotube arrays with highly-ordered periodicity: Fabrication and characterization

For the most part, the fabrication of nanostructures has been limited to some certain materials. In fact, many researchers view alloys as the last piece of the materials puzzle in the field of nanotechnology. This is the first paper to report on the creation of metallic nanotube arrays (MeNTAs) with highly-ordered periodicity using ferrous (stainless steel) and nonferrous (Cu-, Ni-, Al-, and Ti-based) alloys, as well as elemental metals (Cu, Ag, and Au). The proposed 7 mm × 7 mm MeNTAs were fabricated via sputtering over a contact-hole array template created in photoresist. Extensive analysis revealed many properties typical of nanostructures, including enhanced surface-enhanced Raman scattering (SERS) and high hydrophobicity. The proposed nanotubes can be fabricated over a wide range of heights and diameters (from a few hundred nm to 10 µm) in a variety of shapes, including tall cylinders and dishes. MeNTAs could potentially be used as a platform for the development of nanohybrids in conjunction with nanomaterials such as ZnO nanowires.

ZnO-NWs/metallic glass nanotube hybrid arrays: Fabrication and material characterization

In this work, we fabricated first-ever nanohybrids ZnO nanowires (ZnO-NWs)/Metallic Nanotube Arrays (MeNTA) structure for the large-scale fabrication of highly dense laterally and vertical aligned ZnO-NWs. To prepare heterogeneous surface MeNTA by using sputter-deposition of different metallic glasses (Zr55Cu30Al10Ni5, Cu47Zr42Al7Ti4, Pd72Cu12Si16, W50Ni25B25 and Ni54B0.3Si36Cr2.7Fe7) over on contact-hole arrays created by a photoresist template with 650 nm height and various diameter (2, 10 and 20 μm). A ZnO seed layer is deposited by sputtering method on MeNTA to provide the nucleation sites to grow the nanowires inside the MeNTA. To perform the material analysis like surface morphology, crystal structural, and optical properties were characterized by using scanning electron microscopy, X-ray diffraction, Raman, XPS and photoluminescence, respectively. Our results confirm that, the nanowires having the hexagonal wurtzite structure and presenting strong UV emissions can be used in optoelectronics, sensors, piezoelectric-nanogenerator, solar cells and battery applications.

Non-precious metal nanotube arrays hybrid catalyst prepared by a mutual template method for efficient water oxidation in alkaline medium

A mutual template route was designed to prepare Ni-P/Fe(OH)3-Cu nanotube arrays with a high electrocatalytic activity for OER. In 1.0 M KOH solution, the as-obtained hybrid electrocatalyst required only a low overpotential of 271 mV to achieve a current density of 20 mA cm−2 with a small Tafel slope of 57.7 mV dec−1. After 1000 CV cycles at the scan rate of 100 mV s−1, the overpotential of the catalyst hardly increased; and after continuously catalyzing for 130 h at 20 mA cm−2, the potential only slightly increased, implying that the as-obtained hybrid electrocatalyst possessed excellent cycle stability and long-term stability. The above outstanding electrocatalytic activity should be ascribed to its special tubular structure and the synergicaction between Ni-P alloy and Fe(OH)3 nanotubes. Moreover, the presence of elemental copper, which was formed by the in-situ electrochemical reduction of Cu(OH)2, also enhanced the catalytic performance due to its excellent electrical conductivity.

Wafer-scale SERS metallic nanotube arrays with highly ordered periodicity

The development of surface-enhanced Raman scattering (SERS) substrates has been hampered by difficulties in scaling up fabrication and an inability to obtain meaningful, statistical measurements of nanostructures, due to the effects of molecular adsorption. This paper reports on the wafer-scale fabrication of ultrahigh sensitivity SERS substrates using metallic glass nanotube arrays with highly ordered periodicity. Systematic micro-Raman spectroscopic analysis revealed that the fabricated array could function as a SERS-active substrate with crystal violet (CV) and folic acid as analytes (detection limit of 10−11 M and enhancement factor of 4.21 × 106 for CV). This work was the first to fabricate wafer-scale metallic nanotube arrays with SERS properties, which represents an important step toward realizing the large-scale fabrication of ultrasensitive SERS-active materials.

Revisiting Metal Electrodeposition in Porous Anodic Alumina: Toward Tailored Preparation of Metal Nanotube Arrays

Metal electrodeposition in porous anodic aluminum oxide (AAO) is a complicated and multi-step process, consisting of diffusion of metal ions in the pores, reduction of metal ions and crystallization of metal atoms. The growth mechanism is also complex and changing with electrodeposition conditions. In this paper, we present new insights into the growth of metal nanostructures in AAO via electrodeposition. Two different growth modes for metal electrodeposition in porous AAO, namely center growth mode and lateral growth mode, are revealed, opening a new approach to preparing metal nanotube arrays with tailored structures. This strategy is broadly applicable to varieties of metals, such as Ni, Cu, and Ag. The resultant metal nanotube arrays give rise to improved electro-catalytic activity to small molecule oxidation (such as ethanol and urea) due to the larger surface areas. These findings help to deeply understand the metal electrodeposition in AAO, extend the application of template-assisted electrodeposition and provide innovative ideas to prepare novel metal nanomaterials.

Metallic glass nanotube arrays: Preparation and surface characterizations

Metallic glass nanotube arrays: Preparation and surface characterizations

Metallic glass nanotube arrays: Preparation and surface characterizations

Abstract In this study, we fabricated first-ever metallic glass nanotubes (MGNTs) in a distinct pattern on a Si substrate, by sputter-depositing a coating of metallic glass (Zr55Cu30Al10Ni5) over a contact-hole array template created in photoresist. The resulting nanotubes were 500 or 750 nm in height with a diameter of 500 or 750 nm and wall thickness ranging from 44 nm to 103 nm. The structure of the nanotubes was preserved by the high strength and ductility of the metallic glass during the removal of the photoresist template under ultrasonic vibration. We observed an increase in the hydrophobicity of the MGNT with an increase in the thickness of the walls, with the thickest walls presenting an apparent contact angle of 139°. The hydrophobicity is due to air trapped within the tubes, which prevents the intrusion of water into the nanostructures. We also observed thermal-response behavior on the surface of the MGNT array. Surface cooling produced negative pressure within the nanochambers, which created a sucking force against the water droplets. Surface heating produced positive pressure within the nanochambers, which actually lifted the droplets. This thermal-response behavior was shown to be reversible for at least five cycles between 25 and 55 °C. The MGNT created adhesion forces reaching 14.2 N cm−2, which was sufficient to secure the water droplets even when the surface was tilted or completely inverted. The MGNT array in this study represents a biomimetic analog with switchable contact interface, the behavior of which can be controlled simply by altering the surface temperature.

Fabrication of ordered metallic glass nanotube arrays for label-free biosensing with diffractive reflectance

In this study, a photoresist template with well-defined contact hole array was fabricated, to which radio frequency magnetron sputtering process was then applied to deposit an alloyed Zr55Cu30Al10Ni5 target, and finally resulted in ordered metallic glass nanotube (MGNT) arrays after removal of the photoresist template. The thickness of the MGNT walls increased from 98 to 126nm upon increasing the deposition time from 225 to 675s. The wall thickness of the MGNT arrays also increased while the dimensions of MGNT reduced under the same deposition condition. The MGNT could be filled with biomacromolecules to change the effective refractive index. The air fraction of the medium layer were evaluated through static water contact angle measurements and, thereby, the effective refractive indices the transverse magnetic (TM) and transverse electric (TE) polarized modes were calculated. A standard biotin–streptavidin affinity model was tested using the MGNT arrays and the fundamental response of the system was investigated. Results show that filling the MGNT with streptavidin altered the effective refractive index of the layer, the angle of reflectance and color changes identified by an L*a*b* color space and color circle on an a*b* chromaticity diagram. The limit of detection (LOD) of the MGNT arrays for detection of streptavidin was estimated as 25nM, with a detection time of 10min. Thus, the MGNT arrays may be used as a versatile platform for high-sensitive label-free optical biosensing.

In Situ Derived NixFe1-xOOH/NiFe/NixFe1-xOOH Nanotube Arrays from NiFe Alloys as Efficient Electrocatalysts for Oxygen Evolution.

Herein, NixFe1-xOOH/NiFe/NixFe1-xOOH sandwich-structured nanotube arrays (SNTAs) supported on carbon fiber cloth (CFC) (NixFe1-xOOH/NiFe/NixFe1-xOOH SNTAs-CFC) have been developed as flexible high-performance oxygen evolution reaction (OER) catalysts by a facile in situ electrochemical oxidation of NiFe metallic alloy nanotube arrays during oxygen evolution process. Benefiting from the advantages of high conductivity, hollow nanotube array, and porous structure, NixFe1-xOOH/NiFe/NixFe1-xOOH SNTAs-CFC exhibited a low overpotential of ∼220 mV at the current density of 10 mA cm-2 and a small Tafel slope of 57 mV dec-1 in alkaline solution, both of which are smaller than those of most OER electrocatalysts. Furthermore, NixFe1-xOOH/NiFe/NixFe1-xOOH SNTAs-CFC exhibits excellent stability at 100 mA cm-2 for more than 30 h. It is believed that the present work can provide a valuable route for the design and synthesis of inexpensive and efficient OER electrocatalysts.

Turning Lead into Gold: Systematic Electrocatalytic Water Oxidation Current Enhancement at Nanostructured Fe2O3 Electrode Surface

We coat the pore walls of an anodic nanoporous template with atomic layer deposition (ALD) to obtain structured electrode surfaces that provide the experimentalist with a well-defined, tunable geometry. Indeed, the platform consists of a hexagonally ordered array of metallic or oxidic nanotubes of cylindrical shape, embedded in an inert matrix. The diameter of the tubes can be defined between 20 and 300 nm and their length between 0.5 and 100 μm, approximately. We utilize them as a model system in which the electrode's specific surface area can be increased and its effect on the electrocatalytic current characterized systematically. Diffusion-limited electrochemical transformations remain unaffected by changes in the length of the electrode's pores, whereas the steady-state galvanic current density observed for slow multielectron transformations increases linearly with the pore length. In particular, this approach enables us to increase the electrochemical water oxidation turnover at iron oxide surfaces by two to three orders of magnitude at the optimal point. An additional roughening effect occurring upon annealing and steady-state electrolysis is further evidenced by a combination of spectroscopic, microscopic, and electrochemical methods. These results highlight a strategy for optimizing electrochemical energy transformation devices which could be generalized: the geometric tuning of catalytically mediocre but abundant and cost-effective material systems. We acknowledge the Center for Optical and Laser Materials Research and the Interdisciplinary Resource Center for Nanotechnology at Saint Petersburg State University for their participation. Figure 1

Adjustable transmission properties through ring-shaped nanotube arrays using finite-difference time-domain method

Metallic ring-shaped nanotube arrays are proposed and its optical transmission properties are studied by using finite-difference time-domain (FDTD) method. Compared with the transmission spectra of conventional circular nanotube arrays, two photonic band gaps are emerged in the transmission spectra of ring-shaped nanotube arrays, the two band gaps and transmission spectra are adjusted by the length, inner radius, intertube spacing and the dielectric constants of the core and embedding medium, and magnitude modification, redshift and blueshift of the resonance modes are observed. A metallic ring-shaped nanotube arrays for subwavelength band-stop filter in the range of visible light can be achieved. To understand its physical origin, field-interference mechanism was suggested by the field distributions. The proposed nanostructures and results may have great potential applications in subwavelength near-field optics.

Theoretical calculation of magneto-optical properties in cobalt nanotube array with hexagonal symmetry

The extended Fourier components and effective electric dipole model allowing for the proper treatment of magneto-optical (MO) activity are presented. The scattering-matrix approach is employed to analyze the MO properties of hexagonal array of magnetic metallic nanotubes embedded in a dielectric medium in the presence of magnetic field. It is found the MO properties of the nanotube array are more prominent than those of the nanodisk array for the same value of the cobalt filling ratio in specific wavelength range. The spectral position of the Kerr maxima can be tuned by the nanotube's length, wall thickness, separation of the neighboring nanotubes and the filling medium.