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The electrolysis of water using renewable energy inputs is a promising sustainable approach to produce clean hydrogen fuel. The conventional water electrolysis, where the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are tightly coupled to satisfy the thermodynamic potential of at least 1.23 V, occasionally encounters gas crossover through the membrane, resulting in the formation of explosive gas mixtures and reactive oxygen species. In this study, an asymmetric cell design of 3 M H2SO4|V(II)/V(III)|1 M KOH equipped with nickel foam electrodes is used for achieving decoupled HER and OER under kinetically favorable conditions by dividing the process into two steps using vanadium ions as redox mediators. The actual overall water splitting at an average cell voltage of 1.3 V and a current density of 10 mA cm−2 is accomplished even in the presence of membranes with outstanding cycling stability. The well-designed system for decoupled water electrolysis can allow the production of clean energy fuel using a low-power input in renewables–to–hydrogen conversion.

International audience; Stainless steel, a cost-effective material comprising Fe, Ni, and Cr with other impurities, is considered a promising electrode for green electrochemical energy storage and conversion systems. However, the Cr in stainless steel and its passivating property in electrochemical systems hinder the commercial use of stainless steel in the energy conversion and storage industry. Therefore, many studies have revealed the usability of stainless steel by developing various surface treatment techniques to modify the electrode surface to take advantage of the intrinsically active elements in stainless steel. In this review, we present the recent advances and breakthroughs in surface treatment approaches to adjust surface composites and the electrochemical performance and rational design of electrodes in green energy storage and conversion systems, including (photo)electrochemical water splitting, Li-ion batteries, and supercapacitors. © 2022 Elsevier B.V.

Anodic TiO2 nanotubes were simultaneously grown and doped with RuO2 by single-step anodization in a negatively-charged RuO4− precursor. Subsequently, a high positive voltage was imposed on the nanotubes in an F−-based electrolyte (a process referred to as potential shock), which led to the formation of a through-hole RuO2-doped TiO2 nanotube membrane without significant loss of the RuO2 catalyst. XPS results confirmed that the doped Ru metal was converted into RuO2 as the potential shock voltage increased. Further increases in the potential shock voltage led to the formation of RuOx/Ru in the TiO2 nanotubes. All of our results clearly showed that a through-hole catalyst-doped TiO2 nanotube membrane can be produced by a sequence consisting of single-step anodization and the potential shock process.

Ant-nest nanostructured α-Fe2O3 films with a thickness of 10 μm are anodically grown on stainless steel without any binder, and the resulting material functioned as a current collector in the negative electrode of Li-ion batteries. Phase of Fe2O3 in the structure is the key factor determining the battery performance for a high capacity and cyclability. For example, single anodization allows Fe to be dissolved faster than other components such as Cr, resulting in a high Cr ratio in the stainless steel, which deteriorates the retention of the battery capacity during cycling. On the other hand, the Fe–Cr–Ni ratio is not significantly changed if a proper pretreatment for activation, which is able to dissolve all components with a similar dissolution rate in the subsequent anodization step, is performed. The anodic ant-nest nanostructures play a vital role in not only the pathway of Li ions but also releasing the stress of volume expansion during Li insertion/extraction. The optimized electrode delivers a high reversible capacity of 737 μAh cm−2 (737 mAh cm−3 or 1157 mAh g−1) at a current density of 650 μA cm−2 (1 C-rate) and sustains up to 500 cycles with only 0.13% capacity fading per cycle.

A SnO2–TiO2 electrode was prepared via anodization and subsequent anodic potential shock for a binder-free anode for lithium-ion battery applications. Perpendicularly oriented TiO2 microcones are formed by anodization; SnO2, originating in a Na2SnO3 precursor, is then deposited in the valleys between the microcones and in their hollow cores by anodic potential shock. This sequence is confirmed by SEM and TEM analyses and EDS element mapping. The SnO2–TiO2 binder-free anode is evaluated for its C-rate performance and long-term cyclability in a half-cell measurement apparatus. The SnO2–TiO2 anode exhibits a higher specific capacity than the one with pristine TiO2 microcones and shows excellent capacity recovery during the rate capability test. The SnO2–TiO2 microcone structure shows no deterioration caused by the breakdown of electrode materials over 300 cycles. The charge/discharge capacity is at least double that of the TiO2 microcone material in a long-term cycling evaluation.

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The anodization of ADC12 aluminum alloy was investigated in the metal anionic acid media. Anodic oxide films containing foreign elements were formed on ADC12 Al alloy by anodization in the anion complex solution. Furthermore, the rough surface and cracks were considerably smoothened by the deposit of metal anions. When the size of metal anion was small, relatively large amount of metal anions was loaded in anodic films. Existence of MoO₃, TiO₂ and MgO was confirmed by XPS. According to the results of Tafel analysis, Mo oxide represented the most noble anti-corrosion potential due to MoS2 formation. Corrosion current densities were generally higher than that of pristine anodic oxide without anion complexes.

To study the dispersion factors of silica sol prepared from fumed silica powder, we prepared silica sol under an aqueous system using a batch type bead mill. The dispersion properties of silica sol have a close relationship to dispersion factors such as pH, milling time and speed, the size and amount of zirconia beads, the solid content of fumed silica, and the shape and diameter of the milling impellers. Especially, the silica particles in silica sol were found to show dispersion stability on a pH value above 7, due to the electrostatic repulsion between the particles having a high zeta potential value. The shape and diameter of the impellers installed in the bead mill for the dispersion of fumed silica was very important in reducing the particle size of the aggregated silica. The median particle size (D50) of silica sol obtained after milling was also optimized according to the variation of the size and amount of the zirconia beads that were used as the grinding medium, and according to the solid content of fumed silica. The dispersion properties of silica sol were investigated using zeta potential, turbiscan, particle size analyzer, and transmission electron microscopy.

MnO 2 was homogenously doped into anodic nanotubular TiO 2 by a potential shock method, in which a high potential was imposed on the anodic nanotubes immediately after anodization process. We found that the potential shock process is inapplicable in a high-conductivity aqueous electrolyte, e.g. a MnO 2 precursor solution (herein, 0.006 M KMnO 4 : 852–933 μS/m). To avoid exceeding the output compliance of the current source, the potential shock voltage was optimized in ethylene glycol for the application of water oxidation. We found an optimal potential shock voltage of 140 V, which led to the doping of 0.7 at. % MnO 2 into the high-aspect-ratio nanotubular TiO 2 within 10 s. The TiO 2 nanotubes doped with MnO 2 were successfully employed as electrodes for the non-noble catalysis of water oxidation. Although the doping concentration of Mn was found to be linearly proportional to the applied potential shock voltages, potential shocks greater than 140 V significantly increased the thickness of the barrier oxide layer, which increased the overpotential in the water oxidation process.

The surface composition of a stainless steel 304 electrode, composed of Fe, Ni, and Cr, was adjusted through electrochemical oxidation under harsh anodizing conditions. As the electrochemical oxidation progressed, the Ni and Cr atoms in the Fe medium moved via the synergetic effect of electromigration and drag force, creating a Ni-rich surface on the electrodes with fast kinetics for the hydrogen evolution reaction. This study investigated the optimal duration of electrochemical oxidation affecting the cation contribution of Cr, which forms a passivation layer with high charge transfer resistance on the electrode. Electrochemical oxidation for 60 min induced a significant enhancement in the electrochemical catalytic activity as the cation contribution of Cr decreased.

Chlorodifluoromethane, a refrigerant that will be phased out in the future, is decomposed by nitrogen thermal plasmas with a 99.99% destruction and removal efficiency discharging wastewater containing halide ions. Titanium dioxide nanotubes having a pore size less than 9 nm are produced via electrochemical anodization of titanium using wastewater containing fluoride and chloride ions generated by the decomposition of chlorodifluoromethane. Titanium dioxide spontaneously detached from the substrate into the electrolyte as the period of anodization increased due to weak adhesion between the oxide and substrate. The amount of nanopowder produced was accelerated by nitrate ions, which originated from the nitrogen plasma during the thermal decomposition process. The nitrate ions, which is naturally generated in wastewater due to nitrogen plasma act as a catalyst to accelerate the mass production of TiO2 powder by up to two-fold, compared to that in an electrolyte without nitrate ions. The basic property originated by NaOH neutralizer of the electrolyte leads to the smooth surface morphology.

Nonmetal-doped TiO2 powders consisting of one-dimensional nanotube bundles are prepared using electrolytes containing different kinds of anion additives via a one-step rapid breakdown anodization (RBA) process in a short time. The results show that although no nitrogen species are observed when nitrate is used as an additive, it acts as a catalyst to increase current density during the RBA process. However, substitutional P- or S-doped TiO2 nanotube powders with reduced band gap energy are obtained when electrolytes containing phosphate or sulfate are used. Compared with that of undoped-TiO2 nanotube powders, S-doped TiO2 nanotube powders exhibit significantly reduced band gap energy, from 3.36 eV to 2.93 eV as the concentration of sulfate ions increases. Keywords: TiO2 nanotube powders, Anion additive, Rapid breakdown anodization, Band gap energy, Doping

Reduced graphene oxide (RGO)-coated TiO2 microcones have been synthesized via simple anodization and cyclic voltammetry for use in lithium-ion batteries (LIBs). Microcones had a perpendicularly oriented hollow core, an anatase structure, and a high surface area, allowing higher capacity than other nanosized TiO2 structures. TiO2 has low electrical conductivity, leading to the limitation of fast charging and high capacity; however, this was improved by the application of an RGO coating in this work. As anode materials of LIB, the obtained RGO microcone showed a capacity of 157 mAh g–1 at 10C (fully charged within ∼360 s) and sustained 1000 cycles with only 0.02% capacity fading per cycle. The capacity was 1.5 times higher than that of conventional microcone. We speculated that the decrease in the charge-transfer resistance (Rct) played a crucial role in increasing the capacity with fast charging.

Sol-gel binder was prepared by hydrolysis and condensation reaction using boehmite sol and methyltrimethoxysilane as a function of aging-time. The coating slurry was composed of a plate-shape alumina in the sol-gel binder for the EPD process, in which particles dispersed in the slurry were deposited on the electrode under an electric field due to the surface charge. We studied the effects of three parameters: the content of boehmite, the aging time, and the applied voltage, on the physical, thermal, and electrical properties of the hybrid composite films by EPD. The amount of boehmite was 10 ~ 20 wt% and the aging time was 0.5 ~ 72 , with a fixed amount of plate-shape alumina of 10 wt%. The condition of applied voltage was 5 ~ 30 V with a distance of 2 ㎝ between the electrode during the EPD process. We confirmed that a structure of hybrid composite films of well-ordered plate alumina was deposited on the substrate when the film was prepared using a sol-gel binder composed of 15 wt% boehmite with 1 hr aging time and EPD at 10 V. The process shows a weight loss of 7% at 500℃ in TGA and a breakdown voltage of 8 kV at 87 ㎛.

In this research, hematite nanoparticles were synthesized by DC thermal plasma process to increase the overall surface area. The effect of binders on hematite electrodes was investigated by changing the type and composition of binders when preparing electrodes. Nitrogen gas was also added to the DC thermal plasma process in order to dope the hematite with N for enhancing photoelectrochemical properties of hematite nanoparticles. The efficiency of water splitting reaction was measured by linear sweep voltammetry (LSV) under solar simulator. In LSV measurements, the onset potential and maximum current density at a fixed voltage were measured. The durability of electrodes was checked by repeating LSV measurements. CMC (carboxymethyl cellulose) binder with 50 : 1 composition exhibits the highest current density of 12 mA/cm 2 and CMC binder

전기화학적 양극산화 기법으로 제조한 타이타늄 나노튜브는 타이타늄 특유의 강한 화학내구성 및 나노튜브의 높은 종횡비로 인하여 넓은 범위에 응용된 소재이다. 전해질의 구성 성분과 종류, pH, 전압, 온도 그리고 양극산화 시간이 타이타늄 나노튜브의 성상을 결정짓는 요소들이며 도핑을 통해 촉매능을 부여할 수 있다. 비금속 및 금속 원소 모두도핑 가능하며 도핑 방법 역시 다양하다. 도핑 방법에는 합금 양극산화, 열처리법, 함침법, 전기도금법 등 다양한 방법들이 이용되며 점차 간단하고 빠른 도핑 방법을 찾는 방향으로 연구가 진행되고 있다. 본 총설에서는 타이타늄 나노튜브의 생성 원리와 상용된 제법들에 관하여 기술하고 도핑과 그 응용 및 최근의 도핑 연구 동향을 다루도록 하겠다.

A novel method for homogenous incorporation of Ru (RuO2, or RuO3) into high aspect ratio anodic TiO2 NTs was studied. TiO2 NTs were prepared by anodization in HF based electrolyte, after which very short high applied potential, referred to as potential shock, was imposed on the TiO2 NTs in KRuO4 electrolyte. The high potential shock induced massive flow of RuO4− to positively-biased TiO2 NTs, resulting in the incorporation of Ru as a form of Ru, RuO2, and RuO3 in the TiO2 NTs. Optimal potential shock, which allowed the most suitable amount and incorporation state of Ru catalysts in TiO2 NTs, was determined by SEM, TEM, EDS, XPS, and LSV. It was demonstrated that electrochemical potential shock (simply imposed on the anodic TiO2 for a few seconds in the electrolyte of KRuO4) resulted in homogenous incorporation of Ru into the whole nanotubes without the need for any complicated steps or facilities. Keywords: Nanotubes, TiO2, Potential shock, Water oxidation

9¦ ." b# ,¯#*`, #&*' &# z, 9o#*j3# pits #:¯%E'v5F#&²#," .#- +Þ#:i, 9o*š ~ . i5^*AE#:O:#,ž: .b+Þ#%F+C9o*†# 10 min s)â#*j3+Þ#.^:#9o# J –# b*¾"š#:O, #8o #+ž*j#.Z –# ž C, # › ›# 10 µm*U# 5 µm o#,2#,¯ AE ¶#*j3# pits # š0E9o*š ~ . We describe the preparation of highly-ordered etching pits on the Nb foil through a micromachining. The effects of electro-chemical polishing on the formation of uniformly-patterned protective epoxy layer was investigated. Unlike the previous proc-ess using O

Anodic TiO2 films with a doping of Ru ions on the surface were coincidently prepared by facile one-step anodization for application of the electrode in electrolysis. We found that the amount of Ru ions on the surface of the oxide could be determined based on the applied potential in KRuO4 electrolyte, which provided negative RuO4– ions through dissociation. Overpotentials for the evolution of both O2 and Cl2 were greatly reduced when the coincidently-Ru-doped TiO2 was employed. The Ru-doped electrode prepared at 60 V showed the highest electrocatalytic activity due to the largest amount of Ru incorporation in the oxide. Keywords: Anodization, Titanium oxide, Ruthenium oxide, Electrolysis

Nanotubes of the transition metal oxide, TiO2, prepared by electrochemical anodization have been investigated and utilized in many fields because of their specific physical and chemical properties. However, the usage of bare anodic TiO2 nanotubes in (photo)electrochemical reactions is limited by their higher charge transfer resistance and higher bandgaps than those of semiconductor or metal catalysts. In this review, we describe several techniques for doping TiO2 nanotubes with suitable catalysts or active materials to overcome the insulating properties of TiO2 and enhance its charge transfer reaction, and we suggest anodization parameters for the formation of TiO2 nanotubes. We then focus on the (photo)electrochemistry and photocatalysis-related applications of catalyst-doped anodic TiO2 nanotubes grown on Ti foil, including water electrolysis, photocatalysis, and solar cells. We also discuss key examples of the effects of doping and the resulting improvements in the efficiency of doped TiO2 electrodes for the desired (photo)electrochemical reactions.

Most of biomaterials come in direct contact with the body, making standardized methods of evaluation and validation of biocompatibility an important aspect to biomaterial development. However, biomaterial validation guidelines have not been fully established, until now. This study was to compare the in vitro behavior of osteoblasts cultured on nanomaterial surfaces to osteoblast behavior on culture plates. Comparisons were also made to cells grown in conditioned media (CM) that creates an environment similar to the in vivo environment. Comparisons were made between the different growth conditions for osteoblast adhesion, proliferation, differentiation, and functionality. We found that the in vivo-like system of growing cells in concentrated CM provided a good validation method for biomaterial development and in vivo implant therapy. The materials were biocompatible, showing similar behavior to that observed in vivo. This study provided valuable information that would aid in the creation of guidelines into standardization and evaluation of biocompatibility in biomaterials.

Studies on niobium anodization in the mixture of 1 M and 1 wt % HF at galvanostatic anodization are described here in detail. Interestingly, duplex niobium oxide consisting of thick barrier oxide and correspondingly thick porous oxide was prepared at a constant current density of higher than 0.3 , whereas simple porous type oxide was formed at a current density of lower than 0.3 . In addition, simple barrier or porous type oxide was obtained by galvanostatic anodization at a single electrolyte of either 1 M or 1 wt % HF, respectively. The formation mechanism of duplex type structures was ascribed to different forming voltages required for moving anions.

Nanoporous WO3 with a thickness of about 2.6 μm was achieved by photoelectrochemical anodization; this thickness was around twice the thickness possible with normal (photo-absent) anodic film. The thickness increase is ascribed to the much formation of a protective crystalline oxide on the surface and acceleration of dissolution at the tip by holes generated during illumination. The nanoporous WO3 film prepared by photoelectrochemical anodization shows photocurrents of 1.85 mA/cm2 in 0.33 M H3PO4 under AM 1.5 illumination, a value nearly four times higher than that for film prepared with normal anodization. Keywords: Anodization, Tungsten oxide, Photoelectrochemistry

The degree of self-assembly and the size variation of nanotubular structures in anodic titanium oxide prepared by the anodization of titanium in ethylene glycol containing 0.25 wt % at 40 V were investigated as a function of anodization time. We found that the degree of self-assembly and the size of the nanotubes were strongly dependent on thickness deviation and thus indirectly on anodization time, as the thickness deviation was caused by the dissolution of the topmost tubular structures at local areas during long anodization. A large deviation in thickness led to a large deviation in the size and number of nanotubes per unit area. The dissolution primarily occurred at the bottoms of the nanotubes () in the initial stage of anodization (up to 6 h), which led to the growth of nanotubes. Dissolution at the tops () was accompanied by after the formed structures contacted the electrolyte after 12 h, generating the thickness deviation. After extremely long anodization (here, 70 h), was the dominant mode due to increase in pH, meaning that there was insufficient driving force to overcome the size distribution of nanotubes at the bottom. Thus, the nanotube array became disorder in this regime.

We describe that the surface and thickness of nanoporous WO 3 fabricated by bothlight-induced and light-absent anodization are affected by pre-annealing process from 200 o C to600 o C. As a result, the nanoporous WO 3 with a thickness of 1.83 µ m can be achieved by anod-ization for 6 hours after pre-annealing at 400 o C without illumination of light. Moreover, thethickness of nanoporous WO 3 fabricated by pre-annealing is thicker than that of WO 3 preparedby non-annealing process. However, the light illumination during anodization leads to convert thecrystalline structure obtained by pre-annealing, which interfere the growth of nanoporous WO 3 .In this paper, we discuss about the growth mechanism of these different nanoporous WO 3 films. Keywords : Pre-anealing, Light-induced anodizaton, Tungsten oxide 1. 서론 텅스텐 산화물은 고유한 물리적, 화학적 성질로 인하여물 분해, 전기변색 소자 1-3) , 화학전지 4) 등의 여러 분야에연구되고 있다. 특히, 2.6~2.8eV 비교적 낮은 Band gapenergy를 갖기 때문에 자외선 (UV light) 영역뿐 아니라가시광선 (visible light) 영역에서도 높은 광반응을 나타내는 것으로 알려져 있다.

Electrochemical etching for surface enlargement of niobium was investigated for electrolytic capacitor applications. We obtained a niobium capacitor with a capacitance of 271.4 μF/cm2, which is approximately four times larger than a conventional aluminum capacitor. The enhanced capacitance was attributed to surface enlargement by a factor of more than 40, which was prepared by the etching of niobium at 20 V in propanolic HF (2 wt.%) for 6 h. Electrochemical conditions and their corresponding capacitance are discussed. Keywords: Metal oxides, Electrolytic capacitor, Niobium oxides, Etching

In this work, we investigate anodization of Pb in ethylene glycol containing small amount of NH4F, demonstrating that β-PbF2 particles with octahedral morphology can be prepared by adjusting the applied potential and anodizing time. FE-SEM images and XRD measurements of anodic nanostructures as a function of anodizing time clearly show that PbO is first formed on Pb. Subsequently, a local dissolution of PbO leads to formation of skeleton structure of PbO, releasing Pb 2+ ions in the electrolyte. The lead ions can be precipitated on the walls or intersection of the skeleton walls when the concentration of lead ions is saturated. The method described in this article shows the feasibility of formation of metal fluoride crystal by anodization of metal in a fluoride containing solution.

Effects of Cetyl Trimethyl Ammonium Bromide (CTAB), which is a kind of cationic surfactants, and Sodium Dodecyl Sulfate (SDS), which is a kind of anionic surfactants on the anodic formation of nanoporous niobium oxide were compared. The addition of SDS could protect the surface from dissolution for long time, leading to the formation of niobium oxide with a double thickness (~400 nm) compared to that prepared without surfactant, whereas dissolution seriously occurred in the solution containing CTAB. The different behaviors were attributed to the interaction between the surfactants with positive (or negative) charge and positively charged niobium oxide.

Simple and cost-effective process for the fabrication of a nanodot strip which can electrochemically determine blood coagulation time was described in detail. We observed that the beginning of blood coagulation on the nanodot surface gives rise to increase in resistance against current flow, leading to suddenly increase in potential when constant current is applied between the nanodot electrodes. Interestingly, such dramatic increase in potential was not observed in the plain surface and non-controlled rough surface. Keywords: Blood coagulation, TiO2, Nanodots, Anodization, Epoxy

In this work we investigate the fabrication of self-assembled stripe arrays of zinc oxides by anodization of Zn in ethanolic H2SO4. H2O-selective dissolution of ZnO and flow of H2O by convection are attributed to the formation of the self-controlled stripes. The stripes consist of ZnO with morphology of polygonal flakes perpendicular to the surface. Effects of H2SO4 concentration, applied potential, and anodizing time on the formation of stripes will be discussed in detail. Keywords: Anodization, ZnO, Dissolution, Valve metal, Etching

In this report, the self-templating synthesis of polyaniline nanowires on prestructured aluminum is described, emphasizing that anodization and electropolymerization can occur at the same time by a single electrochemical process. The method is based on the principle that the anodization of predefined aluminum in H2SO4 leads to the formation of highly ordered porous alumina and aniline monomer can be electrochemically polymerized in the formed porous alumina by the anodic reaction. XPS analysis reveals that polyaniline nanowires prepared in this work is protonated emeraldine. Keywords: Anodization, Electropolymerization, Self-templating synthesis, Polyaniline, Anodic alumina oxide (AAO)

The work describes a simple and convenient process for highly efficient and direct DNA separation with functionalized silica-coated magnetic nanoparticles. Iron oxide magnetic nanoparticles and silica-coated magnetic nanoparticles were prepared uniformly, and the silica coating thickness could be easily controlled in a range from 10 to 50 nm by changing the concentration of silica precursor (TEOS) including controlled magnetic strength and particle size. A change in the surface modification on the nanoparticles was introduced by aminosilanization to enhance the selective DNA separation resulting from electrostatic interaction. The efficiency of the DNA separation was explored via the function of the amino-group numbers, particle size, the amount of the nanoparticles used, and the concentration of NaCl salt. The DNA adsorption yields were high in terms of the amount of triamino-functionalized nanoparticles used, and the average particle size was 25 nm. The adsorption efficiency of aminofunctionalized nanoparticles was the 4-5 times (80-100%) higher compared to silica-coated nanoparticles only (10-20%). DNA desorption efficiency showed an optimum level of over 0.7 M of the NaCl concentration. To elucidate the agglomeration of nanoparticles after electrostatic DNA binding, the Guinier plots were calculated from small-angle X-ray diffractions in a comparison of the results of energy diffraction TEM and confocal laser scanning microscopy. Additionally, the direct separation of human genomic DNA was achieved from human saliva and whole blood with high efficiency.

Electrochemical DNA biosensors based on a thin gold film sputtered on anodic porous niobium oxide (Au@Nb(2)O(5)) are studied in detail here. We found that the novel DNA biosensor based on Au@Nb(2)O(5) is superior to those based on the bulk gold electrode or niobium oxide electrode. For example, the novel method does not require any time-consuming cleaning step in order to obtain reproducible results. The adhesion of gold films on the substrate is very stable during electrochemical biosensing, when the thin gold films are deposited on anodically prepared nanoporous niobium oxide. In particular, the novel biosensor shows enhanced biosensing performance with a 2.4 times higher resolution and a three times higher sensitivity. The signal enhancement is in part attributed to capacitive interface between gold films and nanoporous niobium oxide, where charges are accumulated during the anodic and cathodic scanning, and is in part ascribed to the structural stability of DNA immobilized at the sputtered gold films. The method allows for the detection of single-base mismatch DNA as well as for the discrimination of mismatch positions.

Titanium oxide (TiO_2) nanowires were prepared for an electrolytic capacitor application by the automatic dipping technique using a porous alumina template. The automatic dipping technique allows us to exactly control the dipping rate so that we can obtain homogenous infiltration of nanowires in the porous alumina membrane, even though the solution is very acidic. From the TEM, SEM and XRD measurements, we confirmed that anatase phase TiO2 nanowires are highly infiltrated into the porous alumina template. In addition, the electrostatic capacitance of nanowires was measured and compared with a theoretical calculation using an effective thickness (delta e). We found that the effective thickness corresponds to the mean radius of nanowires and the experimental measurements were in good agreement with the calculations.

We describe the preparation of a tungsten pillar nanoimprint stamp without the use of lithography and etching techniques. Structures with heights of 15 nm were prepared on the basis of self-ordered porous alumina templates and this was followed by DC sputtering of tungsten. The stamp was successfully used to prepare an aluminium surface to obtain highly ordered porous anodic alumina films after a single anodization step. The preparation efficiency for highly ordered porous alumina was dramatically improved as compared to the more conventional two-step anodization–strip-anodization method, as a sacrificial layer with a thickness of a few hundred micrometres was not required. In addition, by fractal calculations, we have evaluated the degree of ordering of the asperities on the nanoimprint master stamp.