One-step Anodization Method Research Articles

One Step before Synthesis: Structure-Property-Condition Relationship Models to Sustainable Design of Efficient TiO2-Based Multicomponent Nanomaterials.

To control the photocatalytic activity, it is essential to consider several parameters affecting the structure of ordered multicomponent TiO2-based photocatalytic nanotubes. The lack of systematic knowledge about the relationship between structure, property, and preparation parameters may be provided by applying a machine learning (ML) methodology and predictive models based on the quantitative structure-property-condition relationship (QSPCR). In the present study, for the first time, the quantitative mapping of preparation parameters, morphology, and photocatalytic activity of 136 TiO2 NTs doped with metal and non-metal nanoparticles synthesized with the one-step anodization method has been investigated via linear and nonlinear ML methods. Moreover, the developed QSPCR model, for the first time, provides systematic knowledge supporting the design of effective TiO2-based nanotubes by proper structure manipulation. The proposed computer-aided methodology reduces cost and speeds up the process (optimize) of efficient photocatalysts' design at the earliest possible stage (before synthesis) in line with the sustainability-by-design strategy.

One-step synthesis of N-doped porous wall TiO2 nanotube arrays for efficient removal of dibutyl phthalate under visible light

The N-doped porous wall TiO2 nanotube arrays (N@p-TNTAs) was synthesized by one-step anodization method for the first time. The excellent adsorption performance and visible light response of N@p-TNTAs result in significantly superior photocatalytic activity, due to the porous wall nanotube array structure and the successful doping of N element. The photocatalytic activity of catalyst was evaluated by using the refractory organic pollutants dibutyl phthalate (DBP) as target pollutant. >97 % of DBP was degraded after 3 h of irradiation with visible light, and the degradation kinetic constant was nearly 88 and 9 times higher than that of TiO2 nanotube arrays (TNTAs) and TiN, respectively. During the calcination process, due to the N doping, the orbital of N 2p and O 2p were mixed to produce new valence bands, which effectively shortened the bandgap width of N@p-TNTAs to have visible light response. Meanwhile, a part of N escaped in the form of gas, forming the structure of porous wall. In addition, N@p-TNTAs still showed outstanding photocatalytic activity after 6 cycles, which indicated that the structure of material was stable and can be widely used in environmental photocatalysis.

Development of Capacitive-Type Sensors by Electrochemical Anodization: Humidity and Touch Sensing Applications.

This work describes the development of a capacitive-type sensor created from nanoporous anodic aluminium oxide (NP-AAO) prepared by the one-step anodization method conducted in potentiostatic mode and performed in a low-cost homemade system. A series of samples were prepared via an anodization campaign carried out on different acid electrolytes, in which the anodization parameters were adjusted to investigate the effect of pore size and porosity on the capacitive sensing performance. Two sensor test cases are investigated. The first case explores the use of highly uniform NP-AAO structures for humidity sensing applications while the second analyses the use of NP-AAO as a capacitive touch sensor for biological applications, namely, to detect the presence of small “objects” such as bacterial colonies of Escherichia Coli. A mathematical model based on equivalent electrical circuits was developed to evaluate the effect of humidity condensation (inside the pores) on the sensor capacitance and also to estimate the capacitance change of the sensor due to pore blocking by the presence of a certain number of bacterial microorganisms. Regarding the humidity sensing test cases, it was found that the sensitivity of the sensor fabricated in a phosphoric acid solution reaches up to 39 (pF/RH%), which is almost three times higher than the sensor fabricated in oxalic acid and about eight times higher than the sensor fabricated in sulfuric acid. Its improved sensitivity is explained in terms of the pore size effect on the mean free path and the loss of Brownian energy of the water vapour molecules. Concerning the touch sensing test case, it is demonstrated that the NP-AAO structures can be used as capacitive touch sensors because the magnitude of the capacitance change directly depends on the number of bacteria that cover the nanopores; the fraction of the electrode area activated by bacterial pore blocking is about 4.4% and 30.2% for B1 (E. Coli OD600nm = 0.1) and B2 (E. Coli OD600nm = 1) sensors, respectively.

One-step synthesis of mesoporous Cobalt sulfides (CoSx) on the metal substrate as an efficient bifunctional electrode for overall water splitting

Electrocatalysts based on transition metal sulfides (TMSs) are drawing accelerating concerns in renewable energy research because of their intrinsically excellent activities towards both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). To date, considerable efforts are made to improve the performance of these catalysts, but ignoring the improper synthesis strategy would incur additional cost to the catalyst. Herein, a convenient, one-step anodization method is developed for fast construction of cobalt sulfides (CoSx). Without any high-temperature or long-time treatment, mesoporous CoSx is self-grown on the metal substrate in minutes. As a result, as-anodic CoSx requires overpotentials of 102 mV for HER and 284 mV for OER to achieve a current density of 10 mA m−2 in alkaline solution. Moreover, the tandem bifunctional as-anodic CoSx exhibits a required cell voltage of 1.64 V for overall water splitting in alkaline solution, exceeding most of the documented Co-based electrocatalysts.

Super-spreading on superamphiphilic micro-organized nanochannel anodic aluminum oxide surfaces for heat dissipation

SummaryNature-inspired superamphiphilic surfaces have drawn tremendous attention owing to its extreme liquid-loving behaviors. Herein, a micro-organized nano-channel (Mo-Na) superamphiphilic anodic aluminum oxide (AAO) surface with long-lasting superamphiphilic property is prepared by a facile one-step anodization method with controllable temperature change. Analysis of dynamic wetting behaviors on superamphiphilic Mo-Na AAO surfaces for various liquids reveals that the spreading factor is in negative correlation with the surface tension and liquid polarity. Detailed observation of the three-phase contact line shows a micro-scale capillary film on superamphiphilic Mo-Na AAO surfaces, which results from the horizontal component of the capillary force. Taking advantage of the superamphiphilic property, water droplets can spread completely on these Mo-Na AAO surfaces within a short time, which can be applied for efficient heat dissipation. Moreover, the unique AAO surface with Mo-Na structures also offers an effective template for future efforts in AAO-based composite devices.

Influence of anodizing voltage and electrolyte concentration on Al-1 wt% Si thin films anodized in H2SO4

Porous anodic alumina (PAA) templates have been extensively studied due to their unique morphology and extensive applications. The fabrication of PAA can be modulated to achieve a self-ordered pore structure with desired pore size and interpore separation. PAA thin film templates were fabricated from silicon doped aluminum film, Al-1 wt% Si, based on one-step anodization method at 22 °C. Effects of anodizing potential (10–20 V) as well as sulfuric acid concentrations (0.6–1.8 M) on current density, interpore distance, anodization rate, and volume expansion were evaluated. The results indicated that current density increased largely exponentially with a concentration of the electrolyte at a given anodizing voltage. In addition, distinct and well-ordered pores were obtained for anodization conducted at 15 V and 20 V. The volume expansion factor is proportional to the applied voltage. At 1.8 M sulfuric acid, the expansion factor increases with pore regularity with 1.4 considered as the transition point. The minimum current density (2.1 ± 0.15 mA cm−2) was observed at the minimum anodizing condition (0.6 M, 10 V). Also, maximum anodizing condition (1.8 M, 20 V) resulted in the highest current density of 34 ± 4 mA cm−2. As expected, anodization time decreases with an increase in both anodization voltage and electrolyte concentration.

Fabrication of CdS quantum dots sensitized TiO2 nanowires/nanotubes arrays and their photoelectrochemical properties

Herein, CdS quantum dots (QDs) sensitized TiO2 nanowires/nanotubes arrays (CdS–TiO2 NWs/NTs) have been successfully fabricated through an optimized one-step anodization method, followed by successively ion layer adsorption and reaction strategy. The structures of the as-prepared samples were characterized by scanning electrons microscopy, X-ray diffraction and X-ray photoelectron microscopy. Results indicated that TiO2 NWs/NTs were comprised of well-ordered NTs arrays in the bottom and NWs at the mouth of the NTs. CdS QDs were uniformly adhered to the surface of the NWs, as well as inner walls of the NTs. In addition, optical and photoelectronchemical properties of the as-prepared samples were investigated. All results showed that CdS–TiO2 NWs/NTs exhibited excellent photoelectric and photocatalytic activities, a photocurrent density of 1.04 mA cm−2, a photocatalytic efficiency of degradation methyl blue of 97.8% after 120 min, and the rate of repeated degradation maintained at 95.8% after 5 cycles. A possible mechanism was described to lay the foundation for future applications.

Enhanced field emission properties of the copper sulfide nanowalls with optimized 3-D morphology

The three-dimensional (3-D) copper sulfide nanowalls with sharp edges were successfully prepared by one-step anodization method. An interesting finding was that the morphology and microstructure of 3-D copper sulfide nanowalls can be regulated and optimized by abjusting the anodization time, and the corresponding field emission (FE) characteristics were significantly improved. The value of turn-on field can be dramatically reduced from 11.84 to 2.84 V/μm and the field enhancement factor up to 19899. Besides, the optimal 3-D copper sulfide nanowalls showed a long-term thermal stability and better conductivity. Preliminary researches indicate that as a promising field emitter, the 3-D copper sulfide nanowalls have potential applications in the field of vacuum micro- or nano-electronic devices.

The Photocatalytic Properties and Mechanistic Study of ZnO,Ag Multiphase Co-Composited TiO2 Nanotube Arrays Film Prepared by One-Step Anodization Method

ZnO/Ag multi-phase composited TiO2 nanotube arrays (TiO2 TNAs) films were prepared on pure Ti substrate through one-step anodizing method using double pulse plating power supply. The deposition amount of Ag and ZnO were adjusted by changing the concentration of Zn(NO3)2·6H2O and AgNO3 and reverse voltage. The results showed that ZnO deposited in the wall of TiO2 NTAs dispersedly; sedimentary phase and dispersed phase are the two forms of deposited Ag in TiO2 NTAs. The bandgap narrowed 0.33 eV, and the recombination rate of photo-generated electron-hole pairs also decreased obviously due to the doping energy level synergistic effect of ZnO and the Surface Plasmon Resonance (SPR) effect of Ag. Furthermore, the sample with 1 mM ZnO+0.4 mM Ag and 5 V reverse voltage has the best photocatalytic properties, the degradation rate of Methylene blue (MB) reached 86% which improved 15% compared with undoped TiO2 NTAs.

A high-performance supercapacitor electrode based on three-dimensional poly-rowed copper hydroxide nanorods on copper foam

Three-dimensional (3D) poly-rowed copper hydroxide [Cu(OH)2] nanorods nanostructures have been synthesized on copper foam slices, using copper foam as copper source, current collector and 3D substrate, through a facile and scalable one-step anodization method. The synthesized products can be directly used as binder free electrodes of supercapacitors. The synthesized material exhibited a 3D connect and quasi connect network structure which can facilitate ion mobility and increase the amount of active sites for redox reactions. These merits together lead to a high areal specific capacitance of 1.889 F cm−2 at a scan rate of 2 mV s−1, excellent rate capability (75.39% retention upon increasing the current density by 15 times), low intrinsic resistance (0.792 Ω cm−2) and good cycling stability (87.23% capacitance retention after 5000 cycles), demonstrating a good potential for high performance energy storage devices applications.

A fast response and recovery H2S gas sensor based on free-standing TiO2 nanotube array films prepared by one-step anodization method

Abstract The free-standing TiO2 nanotube (TiNT) array film was firstly synthesized by a one-step anodization method. The characterization results with SEM, TEM, XRD and EDX indicated that the main compound on the TiNT array film was titania with anatase phase, and the average inner diameter of the nanotube was around 110 nm with a wall thickness of 16 nm and a layer thickness of 3.8 µm. Subsequently, the TiNT-based gas sensor was fabricated and its sensing properties toward H2S were investigated. The results showed that, operating under the optimum temperature of 300 °C, the TiNT-based gas sensor not only had excellent reversibility, selectivity and stability, but also attained the response values 4.5–26.2 to the detected H2S gas at 1–50 ppm, and good linearity between the sensor response and H2S concentration could be observed. Meanwhile, the response and recovery time of the sensor to 50 ppm H2S gas were as low as 22 s and 6 s, respectively. In addition, the growth mechanism of the free-standing TiNT array film and the gas sensing mechanism of the TiNT-based gas sensor towards H2S were also given in the article. Lastly, the outstanding gas sensing properties and easy fabrication of the TiNT-based gas sensor presented the potential industrial applications in the future.

Effects of NH4F quantity on N-doping level, photodegradation and photocatalytic H2 production activities of N-doped TiO2 nanotube array films

Series of N-doped TiO2 nanotube array (NTA) films with various N-doping levels and tube lengths were prepared by a facile one-step anodization method, simply changing NH4F quantity in electrolyte. The crystal structures, morphologies and compositions of the samples were analyzed by XRD, SEM, TEM and X-ray photoelectron spectra (XPS). The optical properties were investigated by means of UV–vis absorption spectra and photoluminescence (PL) spectra. Their photocatalytic activities were assessed by photodegradation of rhodamine B (RhB) solution and photocatalytic water splitting to generate hydrogen, respectively. The photocatalytic reaction mechanism was investigated and discussed. The results show that NH4F quantity greatly influences the N-doping level and tube length of the TiO2 NTA, which subsequently affects the optical properties and photocatalytic activities. The photodegradation and photocatalytic H2 production activities of the N-doped TiO2 NTAs can be simply regulated by tuning NH4F quantity in electrolyte during preparation.

Characterization of arrangement and geometry of porous anodic alumina formed by one-step anodization of Al-1 wt% Si thin films

In the current work, porous anodic alumina (PAA) thin films have been fabricated from doped aluminum films, Al-1 wt% Si, using a one-step anodization method at room temperature. Two different electrolytes, namely, oxalic and phosphoric acids, have been utilized to obtain the PAA. A Fast Fourier transform based arrangement analysis for the obtained nanopores is reported. It is found that the nanoporous oxide layer is formed in Al-1 wt% Si with poor arrangement due to the poor spatial distribution of the nanopores, although they are in perfect circular shape. Moreover, the transient curves during the anodization, pore density, pore diameter, and interpore distance have been investigated.

Tailoring the porous nanostructure of porous anodic alumina membrane with the impurity control

Porous Anodic Alumina (PAA) membranes have been fabricated from pure and doped aluminum films (Pure Al, Al–0.5wt.%Cu and Al–1wt.%Si) by the one-step anodization method at room temperature. Formation of the PAA has been performed by three different electrolytes, namely: sulfuric (1 M), oxalic (0.3 M) and phosphoric (0.75 M) acids. For this purpose, potentiostatic anodization in a two-electrode cell configuration has been carried out. High quality alumina with straight pores have been obtained starting from pure aluminum metal films. It is found that, different types of branched structures are formed by aluminum films doped with impurities such as Si and Cu. The relationship between the electrochemical current response and the obtained pore architectures are discussed. Oxide formation rates, barrier layer thickness, vertical and horizontal inter-pore distances are investigated. The present synthesized templates have a large surface area make it one of the mostpopular nanomaterial with applications across a gamut of areas including, energy storage, sensors and biosensors.

In situ growth and phenyl functionalization of titania nanoparticles coating for solid-phase microextraction of ultraviolet filters in environmental water samples followed by high performance liquid chromatography–UV detection

Based on TiO2-nanoparticles coating fabricated by a one-step anodization method on titanium wire substrate, a novel phenyl functionalized solid-phase microextraction (SPME) fiber coating was prepared by simple and rapid in situ chemical assembling technique between the fiber surface titanol groups and trichlorophenylsilane reaction. The as-fabricated fiber exhibited good extraction capability for some UV filters and was employed to determine the ultraviolet (UV) filters in combination with high performance liquid chromatography–UV detection (HPLC–UV). The main parameters affecting extraction performance were investigated and optimized. Under the optimized conditions, the developed method was applied to detect several UV filters at trace concentration levels with only 8mL of sample volume. They were determined in the range from 0.005 to 25μgL−1 with detection limits (S/N=3) from 0.1 to 50ngL−1. The relative standard deviations (RSDs) for single fiber repeatability varied from 4.6 to 6.5% (n=5) and fiber-to-fiber reproducibility (n=5) ranged from 5.5 to 9.1%. The linear ranges spanned two-four magnitudes with correlation coefficients above 0.9990. Five real water samples including four Yellow River water samples and one rain water sample were determined sensitively with good recoveries ranging from 86.2 to 105.5%. The functionalized fiber coating performed good reproducible manner, high mechanical strength, good stability and long service life. Moreover, this study proposed an efficient sample pretreatment method for the determination of UV filters from environmental water samples.

Facile and scalable fabrication of three-dimensional Cu(OH)2nanoporous nanorods for solid-state supercapacitors

3-D Cu(OH)2nanoporous nanorods are fabricated by a facile and scalable one-step anodization method for high-performance binder-free solid-state supercapacitors.

A facile approach for preparing biomimetic polymer macroporous structures with petal or lotus effects

In this paper, three kinds of superhydrophobic polymethylmethacrylate (PMMA) macroporous membranes with controlled adhesion were fabricated by a simple hierarchical alumina template wetting method. This alumina template was obtained through a convenient one-step anodization method, achieving a hierarchical structure combining the upper macroporous structure and lower nanopore topography. These final PMMA products perfectly replicate the original macroporous structure of the template. By simply controlling the reaction temperature, we can obtain the different PMMA surfaces with diverse topographies. The testing results confirm that the PMMA samples not only could achieve superhydrophobicity after the post-modification treatment but also present huge differences in adhesive abilities. The shallow bowl-shape structure presents a slippery property, which has a low sliding angle (SA) of 3°; the deep bowl-shape morphology possesses a SA of 30°, presenting a little sticky performance; the deep honey-comb texture possesses a large SA, which can hold a 10 μL water droplet even upside down, totally showing strong sticky water adhesion. Noticeably, the as-prepared superhydrophobic PMMA samples have remarkable resistivity to acid/alkali, various organic solvents and a long-time period. Moreover, the approach in this work can also be applied to any other soluble polymers. It is believed that our work provide a convenient and promising method to prepare polymer superhydrophobic surfaces with controlled adhesion, which has been rarely reported up to now.

Triple-layered nanostructured WO3 photoanodes with enhanced photocurrent generation and superior stability for photoelectrochemical solar energy conversion

Unique nanorods/nanoparticles/nanoflakes (NRs/NPs/NFs) WO3 triple-layers are grown on a metallic W foil by a simple one-step anodization method. The triple-layered structure is formed through a self-organization process, the film thickness (up to 3 μm) being controlled by the anodization time. A first layer made of an array of WO3 densely-packed vertically-aligned NRs (1.2-1.4 μm in height) grow atop the tungsten foil, followed by a second layer of small NPs (50-80 nm) and finally a third layer made of rectangular NFs (200-300 nm). When irradiated by white light in a photoelectrochemical cell these WO3 triple-layers generate a photocurrent as high as 0.9 mA cm(-2) at 1.2 V/RHE. Moreover, we show that the stability of the triple-layered WO3 photoanodes can be considerably enhanced by adding an ultrathin (10 nm) TiO2 protective overlayer.

Designing robust alumina nanowires-on-nanopores structures: Superhydrophobic surfaces with slippery or sticky water adhesion

Hierarchical alumina surfaces with different morphologies were fabricated by a simple one-step anodization method. These alumina films were fabricated by a new raw material: silica gel plate (aluminum foil with a low purity of 97.17%). The modulation of anodizing time enabled the formation of nanowires-on-nanopores hybrid nanostructures having controllable nanowires topographies through a self-assembly process. The resultant structures were demonstrated to be able to achieve superhydrophobicity without any hydrophobic coating layer. More interestingly, it is found that the as-prepared superhydrophobic alumina surfaces exhibited high contrast water adhesion. Hierarchical alumina film with nanowire bunches-on-nanopores (WBOP) morphology presents extremely slippery property which can obtain a sliding angle (SA) as low as 1°, nanowire pyramids-on-nanopores (WPOP) structure shows strongly sticky water adhesion with the adhesive ability to support 15μL inverted water droplet at most. The obtained superhydrophobic alumina surfaces show remarkable mechanical durability even treated by crimping or pressing without impact on the water-repellent performance. Moreover, the created surfaces also show excellent resistivity to ice water, boiling water, high temperature, organic solvent and oil contamination, which could expand their usefulness and efficacy in harsh conditions.

Tube‐in‐Tube TiO2 Nanotubes with Porous Walls: Fabrication, Formation Mechanism, and Photocatalytic Properties

Self-organized, freestanding TiO2 nanotube arrays that exhibit tube-in-tube morphology are fabricated using a one-step anodic method. These arrays are uniform and compact. The tubes within the arrays are several micrometers long with a 200 nm outer diameter. They have a coarse lateral profile that leads to a large aspect ratio and guarantees good photocatalytic properties.