Complete wetting characteristics of micro/nano dual-scale surface by plasma etching to give nanohoneycomb structure

A variety of flat superhydrophilic surfaces have been fabricated for biological and industrial applications. We report here the preparation of a simple and inexpensive non-polar curved superhydrophilic surface. This surface has dual-scale surface roughness, on both micro- and nanoscales. Curved surfaces with a near-zero water contact angle and ‘complete wetting’ are demonstrated. By using a conventional plasma etching process, which creates microscale irregularity on an aluminum surface, followed by an anodization process which further modifies the plasma etched surface by creating nanoscale structures, we generate a surface having irregularities on two-scales. This surface displays a semi-permanent superhydrophilic property (if the surface has no damage by the exterior failure), having a near-zero contact angle with water drops. We further report a simple and inexpensive curved (i.e., non-planar) superhydrophilic structure with a near-zero contact angle. The dual-scale character of the surface increases the capillary force effect and reduces the energy barriers of the nanostructures.     

Optimization of effective parameters in the synthesis of nanopore anodic aluminum oxide membrane and arsenic removal by prepared magnetic iron oxide nanoparicles in anodic aluminum oxide membrane via ultrasonic-hydrothermal method

In this study, a new anodized aluminum oxide (AAO) nanostructure membrane was synthesized by anodization process under a constant voltage, in oxalic acid solution that was improved with trace amounts of sulfuric acid at room temperature. The effect of various parameters on the morphology of the synthesized nanostructures such as voltage, electrolyte composition, anodization time and type of stripping solution were investigated. According to the results, corrosion of the walls, size regularity, diameter and number of the pores increased in the presence of sulfuric acid (0.018 mol.L⁻¹). Nitrogen adsorption-desorption analysis confirmed significant porosity, array and uniformity of the pore size in the synthesized nanoporous membrane. A new modification method was used based on ultrasonic-hydrothermal method to modify the synthesized AAO with Fe₃O₄/SiO₂ nanoparticles for metals and metalloids removal from aqueous solution. In this method, Fe₃O₄/SiO₂ nanoparticles were placed very regularly and uniformly on the surface and inside the pores. This modification was confirmed by characterization techniques. The modified AAO@Fe₃O₄/SiO₂ membrane showed excellent results for removing arsenic from aqueous media.     

Formation Mechanistism Study of TiO2 Film Comprising Nanotubes and Nanoparticles

A novel titanium dioxide (TiO₂) film comprising both nanotubes and nanopaticles was fab-ricated by an anodization process of the modified titanium. The local electric field at the anodized surface was simulated and its influence on the morphology of the TiO₂ film was discussed. The results show that the electric field strength is enhanced by the covering. The growth rate of TiO₂ increases with the assist of the local electric field. However, TiO₂ dis-solution is hindered since the local electric field prevents [TiF₆]^6- from diffusing. It means that the balance condition for the formation of nanotubes is broken, and TiO₂ nanoparticles are formed. Moreover, the crystal structure of the TiO₂ film was confirmed using X-ray diffraction and Raman analysis. The anatase is a main phase for the proposed film.     

原位椭圆偏振光谱研究多孔阳极氧化铝初期生长过程

根据铝阳极氧化初期不同阶段Al-H2SO4体系的界面特征建立多个光学模型,并采用有效介质近似解析了高时间分辨率的原位椭圆偏振光谱数据,详细获得铝阳极氧化初期的Al2O3-Al界面层、Al2O3阻挡层以及多孔层组成、厚度变化的动态信息.根据光学模型及计算结果,可以清楚地分辨铝阳极氧化过程中的阻挡层形成、孔洞萌生、孔洞发展以及多孔层稳定生长等4个阶段.在多孔层稳定生长阶段,阻挡层厚度及多孔层孔隙率几乎不变,而多孔层厚度随时间线性增长,其速率为5.8nm·s-1.     

DL capacitance-emission spectroscopy of determining the electrochemical behavior of anodized aluminum in aqueous solutions

In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the double layer (DL) capacitance of aluminum samples during the initial stage of anodization processes in aqueous solution without any physical contact. In fact, because the DL capacitance values in this investigation were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the DL capacitance was called DL capacitance-emission spectroscopy. The anodization process (oxidation) of the aluminum samples was carried out chemically in different sulfuric acid concentrations (0.5-3.125% H₂SO₄) at room temperature. In the mean time, the real-time holographic interferometry was used to determine the difference of the DL capacitance of two subsequent values, dC, as a function of the elapsed time of the experiment for the aluminum samples in 0.5%, 1.0%, 1.5%, and 3.125% H₂SO₄ solutions. The DL capacitance-emission spectra of the present investigation represent a detailed picture of not only the rate change of the DL capacitance throughout the anodization processes, but also, the spectra represent the rate change of the growth of the oxide films on the aluminum samples in different solutions. Consequently, holographic interferometry is found very useful for surface-finish industries especially for monitoring the early stage of anodization processes of metals, in which the rate change of DL capacitance of the aluminum samples can be determined in situ.     

Nanoporous Gold Microelectrode: A Novel Sensing Platform for Highly Sensitive and Selective Determination of Arsenic (III) using Anodic Stripping Voltammetry

A home‐made gold microelectrode (Au‐μE) was fabricated and its surface was modified with nanoporous gold structures via a facile electrochemical approach (anodization followed by electrochemical reduction method). The fabricated nanoporous Au microelectrode (NPG‐μE) was used as a sensor probe for the determination of As(III) in 1.0 mol L⁻¹ HCl solution using square wave anodic stripping voltammetry (SWASV) technique. Field emission scanning electron microscopy (FE‐SEM) and cyclic voltammetry were used to characterize the surface morphology and assess the electrochemical surface area and the roughness factor of the NPG‐μE. SWASVs recorded with the NPG‐μE in As(III) solutions indicated linear behaviour in the concentration ranges of 10–200 μg L⁻¹ and 2–30 μg L⁻¹, with regression coefficients of 0.996 and 0.999 at a deposition time of 120 s, respectively. The limit of detection (LOD) was found to be 0.62 μg L⁻¹ with high sensitivity of 29.75 μA (μg L⁻¹)⁻¹ cm⁻². Repeatability and reproducibility were also examined and values were determined as 3.2 % and 9.0 %. Negligible interference from major interfering copper ion was noticed, revealing the excellent anti‐interference property of the proposed sensing platform. The developed NPG‐μE was successfully used for As(III) determination in tap water samples.     

高度有序的TiO2纳米管在有机电解液中的制备及碳掺杂TiO2纳米管的性能

"采用电化学阳极氧化法,在含有氟离子的有机电解液中,使纯钛表面形成一层高度有序的TiO2纳米管阵列．通过控制不同的阳极氧化电压和时间,可以得到形貌不同的TiO2纳米管．最长的TiO2纳米管接近60 1m,长径比约为600．TiO2纳米管在不同的温度(450、550和650 ℃)下焙烧2 h,采用SEM、XRD、EDS和UV-Vis分光光度仪对样品进行表征．X射线衍射仪测试结果表明制备的TiO2纳米管是无定型的,当在较高的温度下焙烧时,其结构由无定型转变为锐钛型和金红石型．EDS微量分析表明TiO2纳米管中     

Highly ordered combined structure of anodic TiO2 nanotubes and TiO2 nanoparticles prepared by a novel route for dye-sensitized solar cells

Combined structure of anodic TiO₂ nanotubes and TiO₂ nanoparticles (TiNTs-TiNPs) has been synthesized by a facile combination of hydrothermal and chemical vapor deposition methods. Ordered TiO₂ nanotubes with smooth walls were fabricated by two step anodization method in ethylene glycol containing NH₄F at 50 V. This nanotubular array after annealing at 450 °C was subjected to the hydrothermally produced gaseous environment in an autoclave with diluted TiCl₄ solution at its bottom. Vapors of TiCl₄ were allowed to react chemically with water vapors for predefined time durations at 180 °C that resulted in the deposition of TiO₂ nanoparticles on tubes’ surface and side walls. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed that for one hour reaction duration, nanoparticles were evenly coated on the walls of nanotubes, whereas, longer durations tend to deteriorate the tubular structure. Consequently, the ordered TiNTs-TiNPs array produced after one hour coating has shown better performance for dye-sensitized solar cell DSSC) in back illumination mode with 130% increase in efficiency as compared to the device based on bare TiO₂ nanotubes. The same photoanode has higher reflective properties with higher scattering ability. The solar cell based on this photoanode exhibits higher external quantum efficiency and effective charge transport properties. This study shows that porous ordered 1D structures based on TiO₂ are of crucial importance for the high performance of DSSCs.     

Preparation of binder-free thin film Li4Ti5O12 anode with an adjustable thickness through anodic TiO2 nanotubes

Binder-free thickness-controllable Li₄Ti₅O₁₂ for application in lithium ion batteries was fabricated by the reaction of Li₂CO₃ and anodic nanotubular TiO₂ at 800 °C. As the concentration of Li₂CO₃ increased, the thickness of Li₄Ti₅O₁₂ film increased, leading to increase in discharge capacity. The Li₄Ti₅O₁₂ film prepared at the optimized concentration of Li₂CO₃ of 3.8 × 10^?6 mol displayed the maximum capacity of 104 μA h cm^?2 at the first cycle, which corresponds to 103 mA h g^?1. We found that excess Li₂CO₃ led to creation of LiTiO₂ phases in the Li₄Ti₅O₁₂ film, which reduced the discharge capacity. For comparison, a Li₄Ti₅O₁₂ film was prepared by the reaction of Li₂CO₃ on a non-anodized Ti foil. In this case, discharge capacity was dramatically reduced due to the formation of Li₂TiO₃ phases in Li₄Ti₅O₁₂, which was confirmed by TEM and XRD analysis.     

由纳米管和纳米颗粒构成的TiO2膜的制备与机理研究

采用聚苯乙烯小球修饰Ti片表面,并进行阳极氧化,制备出一种由纳米颗粒和纳米管构成的TiO₂膜．通过数值模拟,分析了氧化表面附近的局部电场分布对TiO₂膜形貌的影响．结果表明,覆盖物增强了局部电场,从而加快了O^2-与Ti的反应速率,有利于TiO₂的生长;与此同时,[TiF₆]^6-的扩散受到阻碍,使得TiO₂的溶解速率减慢．可见,覆盖物打破了TiO₂纳米管形成的平衡条件,导致纳米颗粒的生成．此外,通过X射线衍射和Raman光谱的测试分析发现,所制备的TiO₂为锐钛矿结构.