AAO Template Research Articles

Wetting characteristic of nanoporous aluminum oxide films

Nanoporous aluminium oxide film template has been widely used over the last decade for development of numerous functional nanostructures such as nano sensors and nanophotonic devices. In this study, the nanoporous aluminum oxide film on silicon substrates were prepared from a 500 nm-thick aluminum film by low-temperature anodization process in a mixed solution of phosphoric and oxalic acids at different anodization voltage (10-50 Voltage). The morphology and wettability of nonporous aluminum oxide films were investigated by field emission scanning electron microscope and contact angle measurement, respectively. The result shown that the interpore of AAO template increase with anodization voltage increases. In addition, the wettability of the template depends on the pore size on the film surface.

Metal Nanowires Subjected to Relavant Hydrated Metal Ions

The hcp-Co and fcc-Ni nanowires with the diameter of ~ 50nm were successfully prepared at different overpotentials by using potentiostatic electrochemical deposition in the pores of AAO templates. The prepared nanowires were characterized by X-ray diffraction, and the morphology of the nanowires was investigated by scanning electron microscope. In this study a new way is established to understand the growth rate of nanowires. The effect of work function on the growth rate of Co and Ni nanowires having same electrolyte’s concentration, same pH value, and same overpotentials, has been discussed. The growth rate of metal nanowires in ECD is determined by the tunneling current between a metal and hydrated metal ions. The higher the tunneling current, the higher will be the growth rate. The tunneling current probably relates to the work function of metal. The larger is the value of work function the lower is the probability of electron tunneling. Lowering the work function causes increase in the current density. The hydrated Co and Ni ions are of octahedral structure with M-O distance of 2.08 A and 2.05 A, respectively. The work function of Co is smaller, this lead to higher tunneling current density. Therefore, the measured current density is higher for Co than for Ni and the Co nanowires grow faster than that of the Ni nanowires.

Electrocatalytic reduction of chloroform at nanostructured silver electrodes

In this work we report the comparison of the electrocatalytic properties of silver nanowire (NW) array, nanohemisphere (NHS) array, and silver rod (Ag-bulk) electrodes in an alkaline solution. The silver nanohemisphere (Ag-NHS) and nanowire (Ag-NW) array electrodes were fabricated by electrodeposition into nanoporous aluminum oxide (AAO) templates. The silver nanohemisphere array electrodes were synthesized by metal sputtering on the Al2O3/Al substrate having hemispherical nanopores followed by electrodeposition of Ag. To fabricate the AAO with hemispherical pores on Al substrate, repeated cycles of alternating anodization and pore widening treatment were performed. On the other hand, the silver nanowires electrodes were prepared by electrodeposition of Ag into the nanoporous AAO template. The electrocatalytic properties of synthesized nanostructured Ag electrodes toward electroreduction of chloroform were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). All experiments were carried out in an Ar-saturated 0.1M NaOH solution. A long-term response of Ag-NW and Ag-NHS electrodes to CHCl3 was investigated after 14 and 28days of storage in air. It was found that the storage time does not significantly affect the electrocatalytic performance of electrodes. To investigate the possible changes in the chemical composition and surface morphology of Ag NW array electrode caused by electrocatalytic reduction of chloroform during CV cycling, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used.

Fabrication of Sesame Sticks-like Silver Nanoparticles/Polystyrene Hybridnanotubes and Their Catalytic Effects.

A novel and efficient catalyst is one of the goals in the material field, and the involvement of nanoscience and technology has brought new vigor to the development of catalyst. This research aimed to develop a simple two-step route to fabricate Fe3O4@PS/PDA-Ag hybridnanotubes with size-controllable and highly dispersed silver nanoparticles (NPs). First, Fe3O4@PS nanotubes of a sound mechanical property were prepared using polystyrene (PS)/toluene solution containing highly dispersed oleic acid modified Fe3O4 particles in a commercial AAO template. Next, the facile technique was used to form in situ silver NPs on the surface of magnetic PS (Fe3O4@PS) nanotubes through dopamine coating. The catalytic effects of the prepared Fe3O4@PS/PDA-Ag hybridnanotubes with highly dispersed AgNPs were characterized using a range of analytical methods, including transmission electron microscopy, thermogravimetric analysis, UV-Visible spectroscopy, and X-ray diffraction. It was found that such prepared Fe3O4@PS/PDA-Ag hybridnanotubes had a large specific surface area. They possessed excellent activities in catalyzing the reduction of 4-nitrophenol (4-NP) by NaBH4 in the aqueous phase. Furthermore, they were readily separated from fluid and retrieved by an external magnet. Their catalyst activity and recyclability demonstrated that this approach we proposed had the potential to become a new idea and route for catalytic platform.

Optical transmission versus ac magnetization measurements for monitoring colloidal Ni nanorod rotational dynamics

Ni nanorods with an average length nm and diameter nm were synthesized using the AAO template method. The magnetization and optical transmission of nanorod colloidal dispersions in alternating magnetic fields were measured and analyzed with the objective of comparing the intrinsic Brownian relaxation times obtained with the two methods. The different physical origin of the measured signal, related to different moments of the orientation distribution function, and the non-linear effects expected for the large magnetic moments of the Ni nanorods at common field amplitudes required a comprehensive modelling. The time-dependent magnetization and optical transmission in ac magnetic fields was derived by numerical solution of the Fokker–Planck equation. The simulated time-dependent magnetization and optical transmission at a given frequency and field amplitude were analyzed analogous to experimental data to determine characteristic relaxation frequencies. Empirical relationships were derived which enabled extraction of the intrinsic Brownian relaxation time from the characteristic frequencies measured in the non-linear regime. Despite large differences in the characteristic frequencies obtained from magnetization and optical transmission measurements, the retrieved intrinsic Brownian relaxation times were found to agree well. The potential of ac magnetic field-dependent optical transmission for biosensing applications was demonstrated by monitoring the adsorption of the protein gelatine on the nanorod labels.

Electrochemical Properties of LiNi0.85Co0.10Al0.05O2 synthesized By Using AAO(Anodic Aluminum Oxide) Template

Recently, among various cathode materials for lithium batteries, LiCoO2 has been still use on the market due to electrochemical stability. However, LiCoO2 cathode materials have low thermal stability, high cost, low capacity. [1-2] Co and Al co-synthesized materials, Li(Ni,Co,Al)O2, are one of the most applicable materials due to the low cost, thermal stability than LiCoO2. Thus, the battery properties of lithium ion cell with LiNi0.85Co0.10Al0.05O2 cathode are better than LiCoO2. But, LiNi0.85Co0.10Al0.05O2 still show that capacity fading. [3] Anodizing method is an effective means of improving electrochemical performance. To improve the electrochemical properties of cathode material LiNi0.85Co0.10Al0.05O2 for a lithium-ion battery, LiNi0.85Co0.10Al0.05O2 cathode powders were prepared by sol-gel method in AAO template followed by heat treatment. The prepared compounds were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) studies and were subjected to charge-discharge cycling performance studies at different C-rates. Though the SEM, AFM, it was confirm that nano-rod for cathode material was obtained. [4] References [1] T. J. Park, J. B. Lim, and J. T. Son, Bull. Korean Chem. Soc. 2014 , Vol. 35, No. 2 357 [2] Z. R. Chang, X.Z. Yuan and H. Wang, Powder Technology 207 (2011) 396 – 400 [3] H. Kondo, T. Kamiyama and Y. Ukyo, J. Power Sources 174 (2007) 1131–1136 [4] S. B. Yang, C. Kim, B. C. Jang, and J. T. Son, J. Korean Physical Soc. Vol. 67, No.4 728~732 Acknowledgement This study was supported by the granted financial resource from Korea National University of Transportation in 2016, the Ministry of Trade program of the Industry & Energy, Republic of Korea (G02N03620000901) and the Global Excellent Technology Innovation of the Korea Institute of Energy Technology Evaluation and Planning (KETEP).

AAO (Anodized Aluminium Oxide) template 제조 및 이를 이용해 제조한 탄소 및 산화 금속 나노 섬유 물질에 관한 연구

AAO (Anodized Aluminium Oxide) template 제조 및 이를 이용해 제조한 탄소 및 산화 금속 나노 섬유 물질에 관한 연구

Analysis of the static magnetic field-dependent optical transmission of Ni nanorod colloidal suspensions

The magnetic field-dependent optical transmission of dilute Ni nanorod aqueous suspensions was investigated. A series of four samples of nanorods were synthesized using the AAO template method and processed to stable colloids. The distributions of their length and diameter were characterized by analysis of TEM images and revealed average diameters of ∼25 nm and different lengths in the range of 60 nm–1100 nm. The collinear magnetic and optical anisotropy was studied by static field-dependent transmission measurements of linearly polarized light parallel and perpendicular to the magnetic field direction. The experimental results were modelled assuming the field-dependent orientation distribution function of a superparamagnetic ensemble for the uniaxial ferromagnetic nanorods in liquid dispersion and extinction cross sections for longitudinal and transversal optical polarization derived from different approaches, including the electrostatic approximation and the separation of variables method, both applied to spheroidal particles, as well as finite element method simulations of spheroids and capped cylindrical particles. The extinction cross sections were compared to reveal the differences associated with the approximations of homogeneous polarization and/or particle shape. The consequences of these approximations for the quantitative analysis of magnetic field-dependent optical transmission measurements were investigated and a reliable protocol derived. Furthermore, the changes in optical cross sections induced by electromagnetic interaction between two nanorods in parallel end-to-end and side-by-side configuration as a function of their separation were studied.

The breakage of nanopore in AAO template

In the present work, AAO template is fabricated in oxalic acid solution under a constant voltage by several steps. By the Bernoulli principle, the pressure on the wall of hole increases which lead to the breakage of nanopore as a result of the reducing effective migration rate of Al3+. The quantity of the breakage of nanopore rises with the increase of the concentration of Al3+. Further, nanopore is closed by oxide due to the decrease of effective migration rate of Al3+. Finally, a “nanoflower-like” shape can be observed in experiments.

Interfacial Interaction in Anodic Aluminum Oxide Templates Modifies Morphology, Surface Area, and Crystallization of Polyamide-6 Nanofibers.

Here, we demonstrated that, when the precipitation process of polyamide-6 (PA6) solution happens in cylindrical channels of an anodized aluminum oxide membrane (AAO), interface interactions between a solid surface, solvent, non-solvent, and PA6 will influence the obtained polymer nanostructures, resulting in complex morphologies, increased surface area, and crystallization changes. With the enhancing interaction of PA6 and the AAO surface, the morphology of PA6 nanostructures changes from solid nanofibers, mesoporous, to bamboo-like, while at the same time, metastable γ-phase domains increase in these PA6 nanostructures. Brunauer-Emmett-Teller (BET) surface areas of solid, bamboo-like, and mesoporous PA6 nanofibers rise from 16, 20.9, to 25 m(2)/g. This study shows that interfacial interaction in AAO template fabrication can be used in manipulating the morphology and crystallization of one-dimensional polymer nanostructures. It also provides us a simple and novel method to create porous PA6 nanofibers with a large surface area.

Tunable magnetocrystalline easy axis in cobalt nanowire arrays by zinc additive

Abstract A new approach to tuning the crystalline characteristics and magnetic properties of cobalt nanowire (NW) arrays embedded in AAO templates is reported using zinc additive. This is realized by adding low concentrations of Zn when pulse-electrodepositing cobalt NWs while also increasing the solution pH from 3 to 5. Using hysteresis loop measurements with a magnetic field applied parallel to the NW axis, coercivity and squareness of pure cobalt NWs increased from 890 Oe and 0.45 to 2150 Oe and 0.93 in Co 97 Zn 3 NWs, respectively, using a Zn concentration of 0.01 M at pH = 4. XRD patterns obtained from the cobalt-rich CoZn NWs revealed that the crystalline texture of cobalt changes from [1 0 0] direction to [1 0 1] and [0 0 2] at pH = 3 and 4, respectively. For the latter, the magnetocrystalline easy axis of cobalt rotates from nearly perpendicular to parallel to the NW axis, induced by the incorporation of zinc into the hcp structure of cobalt.

Fabrication of high aspect ratio copper nanowires using supercritical CO2 fluids electroplating technique in AAO template

This study utilizes the supercritical and post-supercritical electroplating technique, to fabricate copper nano-wires inside ultra-high aspect ratio Anodic Aluminum Oxide templates (AAO templates). Comparisons of the electroplating capabilities and results were made between these methods and the more common traditional electroplating techniques. Under identical experimental conditions and on ultra-high aspect ratio AAO template with thickness of 60µm (aspect ratio of 1:490), it is evident from the results that the supercritical electroplating process has the fastest electroplating velocity of the three processes (~1.33µm/min), followed by post-supercritical electroplating (~1µm/min) and traditional electroplating is the slowest (~0.67µm/min). This study also discusses the electroplating quality of the copper nano-wires. Samples were sliced along the cross-section, and Field Emission Scanning Electron Microscopy (FESEM) was utilized to observe the copper nano-wires. X-Ray Diffraction (XRD) was used to observe that the crystal structures is polycrystalline, and with the use of equations it is determined that grain size will not be severely affected by changes in current density and supercritical pressure in themselves, but instead the different processes do produce an evident change. The grain size achieved with supercritical electroplating is the smallest, followed by the post-supercritical electroplating, and the largest was given by the traditional electroplating process. Through these results it can be proved that supercritical electroplating process indeed provides grain refinement capabilities. The supercritical fluid-enabled electroplating process utilized for these experiments does not need addition of any surfactants to aid filling of the structures, but only relies on the intrinsic properties of supercritical fluids to achieve complete filling of nano-holes, and because there are no surfactants, we can achieve higher degree of purity in the copper nano-wires.

Self-assembly of aligned CuO nanorod arrays using nanoporous anodic alumina template by electrodeposition on Si substrate for IR photodetectors

Hexagonally highly-ordered thin nanoporous anodic alumina (AAO) template of pre-deposited Al thin film onto Si substrate was fabricated under controllable conditions through a two-step anodization for the growth of nanostructured materials. The obtained AAO template has approximately 60nm of pore diameter and 1200nm length with 110nm interpore distances within an area of 0.75cm2. A bottom barrier layer of the AAO template was removed by wet etching using phosphoric acid (5wt%) for several minutes at room temperature. As an application, Cu nanorod-arrays embedded in AAO template was prepared by dc electrodeposition. The electrodeposited Cu nanorod-arrays onto Si based AAO template were oxidized at optimized conditions inside a conventional furnace to produce high-quality CuO nanorod arrays. The free-standing CuO nanorod arrays were formed after subsequent removal of AAO template. Fast with high-performance CuO nanorod-arrays IR photodetector based on MSM were fabricated with Al contact electrodes and its optoelectronic properties were examined. The electrical performance and photoelectric response performance were studied and the results showed that IR photodetector exhibited a high sensitivity to 808nm IR laser light. Both the response and recovery time were found to be fast; 0.19 and 0.17s, respectively, which are much shortest time compared to other IR photodetectors reported in the literature.

Fabrication of Nickel Nanotube Using Anodic Oxidation and Electrochemical Deposition Technologies and Its Hydrogen Storage Property

Electrochemical deposition technique was utilized to fabricate nickel nanotubes with the assistance of AAO templates. The topography and element component of the nickel nanotubes were characterized by TEM and EDS. Furthermore, the nickel nanotube was made into microelectrode and its electrochemical hydrogen storage property was studied using cyclic voltammetry. The results showed that the diameter of nickel nanotubes fabricated was around 20–100 mm, and the length of the nanotube could reach micron grade. The nickel nanotubes had hydrogen storage property, and the hydrogen storage performance was higher than that of nickel powder.

Synthesis and Application of ZnO Nanorods Using the Ultra-Thin Porous AAO Template Fabricated by New Method.

Electron transport in DSSCs with the TiO2 nanoparticles photoanode become more difficult by the tremendous grain boundaries and disordered pore structures. So, one-dimensional nanostructures have great attractions due to the increased carrier diffusion length by a structural property such as direct pathways for electron transport. In this study, we investigated DSSCs using ZnO nanorod arrays and ZnO nanoparticle/nanorod composite layer as a photoanode. To prevent aggregation of ZnO nanorods, ZnO nanorods were synthesized on the nano-patterned seed dots using ultra-thin porous AAO template fabricated by new method. We confirmed that ZnO naonrods were sparsely grown as the nano-patterned seed dots were used.

Fabrication of silver nanoparticles decorated anodic aluminum oxide as the SERS substrate for the detection of pesticide thiram

An efficient surface-enhanced Raman scattering (SERS) substrate is developed based on silver nanoparticles decorated anodic aluminum oxide (Ag/AAO). The AAO templates were fabricated using a two-step anodization approach, and silver nanoparticles (AgNPs) were obtained by thermal decomposition of Ag nitrate in AAO. The structure of Ag/AAO hybrid substrate is characterized by scanning electron microscopy (SEM). The results show that the as-prepared SERS substrates consist of high-density AgNPs with sizes of tens of nanometers. The AgNPs are adsorbed on the surface of AAO template in the form of network structure which is called “hot spot”. The SERS enhancement ability of the nanostructure is verified using thiram as probing molecules. The limit of detection is as low as 1×10−9 mol/L. The results indicate that the as-prepared substrate possesses excellent SERS sensitivity, high stability and uniformity enhancement.

Self-assembly of semicrystalline PE-b-PS diblock copolymers within AAO nanoporous templates

Strongly segregated polyethylene-b-polystyrene (PE-b-PS) diblock copolymers were infiltrated within anodic aluminum oxide nanoporous templates (AAO) (with 60 nm diameter). After carefully removing the nanofibers from the nanopores, TEM revealed their morphology. This is the first time that the morphology of semi-crystalline diblock copolymers infiltrated within AAO templates is observed. Regardless of their composition, the infiltrated nanofibers are constituted by core–shell or pseudo core–shell self-assembled nanocylinders. The affinity of PE to the AAO walls tailors the morphology towards PE shells with PS cores. The PS cores for some compositions have PE inclusions whose morphology is expected on the basis of previous computer simulation studies. Morphological observations successfully explain the confined crystallization of the PE block within the nanopores and the origin of novel double confinement effects (induced by glassy PS block and rigid AAO walls) on the PE block.

Fabrication of Thermally Stable Ultra-High Density Particle-in-Cavity Nanostructure with Tunable Size and Density

This work reports a simple and effective method to fabricate large scale particle-in-cavity (PIC) nanostructure with tunable size from 10-100 nm. By using pre-patterned anodized alumina template (AAO) as a mask for reactive ion etching, the hexagonally ordered nanoporous structure can be transferred onto various substrates including glass, ITO-coated glass, and silicon. With the protection of an organic polystyrene layer, the AAO template can be easily transferred with great consistency and minimal contamination. This method also provides versatility in fabricating multiple unique nanostructures depending on the choice of gas used for RIE. Additionally, the nanoparticles can be deposited into nano-cavities using a variety of techniques such as e-beam evaporation, sputtering with annealing or spincoating of pre-made nanoparticle suspension. Furthermore, Au PIC nanostructure has demonstrated excellent thermal stability compared to Au nanoparticles deposited on flat surface. This method provides great potential not only for the investigation of nanopatterning and nanoparticle assembly but also for enhanced surface Raman scattering and many nanowire based devices including sensors, electronics and photovoltaics.

Preparation and characterization of single crystalline In–Sn oxide nanowires

Indium tin oxide (ITO; Indium oxide with tin doping) nanowires were first prepared via the electrochemical deposition and an oxidization method based on an AAO template. FE-SEM results show the synthesized ITO nanowires to have an approximate length of 8–10 μm with an aspect ratio close to 167. ITO nanowires with an In/Sn weight ratio of 8.8 (∼9:1) were observed from EDS. The crystal structure of ITO nanowires showed that all the peaks within the spectra can be indexed to In2O3 with a cubic structure. The ITO nanowire is single-crystalline determined from selected area electron diffraction (SAED) patterns. An optical energy gap (Eg) of the ITO nanowire is 3.8 eV.

AAO-assisted synthesis of CuI nanowires by vacuum melting and gas pressure injection

CuI nanowires with uniform diameter were successfully fabricated by vacuum melting and gas pressure injection via AAO template. The nanowires exhibit the characteristics of continuous and compact at the gas pressure of 5MPa, and the gas pressure can be reduced to 1MPa with a CuI pre-processed AAO template, The results of XRD and EDS indicate that the nanowires belong to the zinc-blende structure and the amount of copper is more than that of iodide in the sample. The CuI nanowires present a weak near-band emission with a fast decay time and a strong defect emission with a slow decay time, and the intensity of fast emission component can be improved by iodine doping.