Preparation and photoelectrocatalytic activity of ZnO nanorods embedded in highly ordered TiO(2) nanotube arrays electrode for azo dye degradation

In this article, the ZnO nanorods embedded in highly ordered TiO(2) nanotube arrays (ZnO/TiO(2) NR/Ts) electrodes were fabricated through two steps: (1) electrosynthesis of TiO(2) nanotube arrays (TiO(2) NTs) in HF solution by anodization method; (2) followed by cathodic electrodeposition of ZnO embedded in the TiO(2) nanotube arrays. The morphological characteristics and structures of ZnO/TiO(2) NR/Ts electrodes were examined by field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD) analysis, and UV-vis spectra. The linear-sweep photovoltammetry response on the ZnO/TiO(2) NR/Ts electrode was presented and the photocurrent was dramatically enhanced on the ZnO/TiO(2) NR/Ts electrode, comparing with that on bare TiO(2) NTs electrode. The photocatalytic and photoelectrocatalytic activity of ZnO/TiO(2) NR/Ts electrode was evaluated in degradation of methyl orange (MO) in aqueous solution.     

Enhanced photoelectrochemical cell property from alpha-Fe2O3 nanoparticle decoration on vertically grown TiO2 nanotubes arrays

TiO2 nanotube arrays decorated with alpha-Fe2O3 were prepared by forming a nanotube-like TiO2 film on a Ti sheet using an anodization process, followed by electrochemical deposition to decorate hematite (alpha-Fe2O3) nanoparticles on the TiO2 nanotube arrays. The SEM and XRD results revealed that the alpha-Fe2O3 nanoparticles were homogeneously embedded on the surface of the TiO2 nanotube arrays. The photoelectrochemical properties of the alpha-Fe2O3/TiO2 nanotube arrays as photoanode were studied by photocurrent-potential behavior in 1 M NaOH electrolyte under 100 mW/cm2 UV-Visible light irradiation. Also, the length dependence of TiO2 nanotubes and the amount dependence of alpha-Fe2O3 nanoparticles on the photocatalytic ability were studied and thus the optimum conditions were determined.     

Effects of TiO2 nanorod length and post-annealing on the electrical properties of TiO2 nanobarbed fiber structures

TiO2 nanobarbed fiber (NBF) structures consisting of TiO2 nanorods (NRs) on TiO2 nanofibers (NFs) were fabricated. The mean length and diameter of the TiO2 NRs grown for 6 h was 1.38 microm and 71 nm, respectively. One NR was connected to other NRs and the junction points between the TiO2 NRs increased with increasing TiO2 NR length. The crystal structure of the TiO2 NFs and NRs was rutile and anatase, respectively. After post-annealing, only the intensity of the TiO2 NBF peaks increased without any significant structural changes. Raman spectroscopy showed that the TiO2 NBF structure consisted of anatase (TiO2 NFs) and rutile (TiO2 NRs). The bandgap of the TiO2 NBF structure prepared during a TiO2 NR growth time from 0 to 6 h decreased from 3.23 eV to 3.10 eV. The conductivity of the TiO2 NBFs with longer NRs was enhanced by post-annealing.     

Fabrication of vertically aligned CuInSe2 nanorod arrays by template-assisted mechanical approach

A facile, low cost, and vacuum free method for fabricating vertically aligned copper indium diselenide (CuInSe₂) nanorod (NR) arrays from pre-synthesized CuInSe₂ nanoparticles (NPs) by mechanical approach using porous anodic aluminum oxide (AAO) as a template was demonstrated. This approach utilizes a rubbing technique to fill CuInSe₂ NPs suspension into AAO template. X-ray diffraction and Raman spectroscopy study is employed to confirm the phase of CuInSe₂ NPs before and after the formation of NRs. The polycrystallinity and composition of NRs are confirmed by using transmission electron microscopy. Optical studies of CuInSe₂ NPs film reveal a reflectance of ∼9.8% while a significant reduction of the reflectance to ∼1.2% is observed after the formation of CuInSe₂ NR arrays. The observed low reflectance behavior is attributed to a concept of gradual refractive index with vertical array structures. From differential reflectance spectra of CuInSe₂ NRs, a band gap of ∼1.01 eV was observed, which is identical to its bulk value.     

Hydrothermal Growth of TiO2 Nanorod Arrays and In Situ Conversion to Nanotube Arrays for Highly Efficient Quantum Dot‐Sensitized Solar Cells

TiO₂ nanorod (NR) and nanotube (NT) arrays grown on transparent conductive substrates are attractive electrode for solar cells. In this paper, TiO₂ NR arrays are hydrothermally grown on FTO substrate, and are in situ converted into NT arrays by hydrothermally etching. The TiO₂ NR arrays are reported as single crystalline, but the TiO₂ NR arrays are demonstrated to be polycrystalline with a bundle of 2–5 nm single crystalline nanocolumns grown along [001] throughout the whole NR from bottom to top. TiO₂ NRs can be converted to NTs by hydrothermal selective etching of the (001) core and remaining the inert sidewall of (110) face. A growth mechanism of the NR and NT arrays is proposed. Quantum dot‐sensitized solar cells (QDSCs) are fabricated by coating CdSe QDs on to the TiO₂ arrays. After conversion from NRs to NTs, more QDs can be filled in the NTs and the energy conversion efficiency of the QDSCs almost double.     

Ru nanostructure fabrication using an anodic aluminum oxide nanotemplate and highly conformal Ru atomic layer deposition

We fabricated metallic nanostructures directly on Si substrates through a hybrid nanoprocess combining atomic layer deposition (ALD) and a self-assembled anodic aluminum oxide (AAO) nanotemplate. ALD Ru films with Ru(DMPD)(EtCp) as a precursor and O(2) as a reactant exhibited high purity and low resistivity with negligible nucleation delay and low roughness. These good growth characteristics resulted in the excellent conformality for nanometer-scale vias and trenches. Additionally, AAO nanotemplates were fabricated directly on Si and Ti/Si substrates through a multiple anodization process. AAO nanotemplates with various hole sizes (30-100?nm) and aspect ratios (2:1-20:1) were fabricated by controlling the anodizing process parameters. The barrier layers between AAO nanotemplates and Si substrates were completely removed by reactive ion etching (RIE) using BCl(3) plasma. By combining the ALD Ru and the AAO nanotemplate, Ru nanostructures with controllable sizes and shapes were prepared on Si and Ti/Si substrates. The Ru nanowire array devices as a platform for sensor devices exhibited befitting properties of good ohmic contact and high surface/volume ratio.     

One-step anodization fabrication and morphology characterization of porous AAO with ideal nanopore arrays

A fabrication method for one-step anodization of an anodic aluminum oxide (AAO) template with nanopore arrays using pretreated high purity aluminum foil is reported in this article. Morphology of the AAO was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Results showed that porous AAO with ideal nanopore arrays can be fabricated by one-step anodization fabrication technology on high purity aluminum foil which had been anodized at 45?V direct current (DC), in 0°C, 0.5?M H₂C₂O₄ solution for 48 hours. The average pore diameter and the interpore distance were 80?nm and 120?nm, respectively. Nanopores in porous AAO had very narrow size distribution and were arranged into hexagonal array. The formation mechanism of nanopore arrays in porous AAO is discussed. Porous AAO with ideal nanopore arrays provide an ideal template for preparation of many one-dimensional nanomaterials. One-step anodization of AAO is a simpler procedure and more applicable in industrial application than the previous two-step anodization technology.     

Visible light photoelectrochemical performance of W-loaded TiO2 nanotube arrays: structural properties

Well aligned TiO2 nanotubes were successfully synthesized by anodization of Ti foil at 60 V in a fluorinated bath comprised of ethylene glycol with 5 wt% of NH4F and 5 wt% of H2O2. In order to enhance the visible light absorption and photoelectrochemical response of pure TiO2 nanotube arrays, a mixed oxide system (W-TiO2) was investigated. W-TiO2 nanotube arrays were prepared using radio-frequency (RF) sputtering to incorporate the W into the lattice of TiO2 nanotube arrays. The W atoms occupy the substitutional position within the vacancies of TiO2 nanotube arrays. The as-anodized TiO2 is amorphous in nature while the annealed TiO2 is anatase phase. The mixed oxide (W-TiO2) system in suitable TiO2 phase plays important roles in efficient electron transfers due to the reduction in electron-hole recombination. In this article, the effect of the sputtered W into the as-anodized/annealed TiO2 nanotube arrays on the photoelectrochemical response was presented.     

Fabrication of free standing anodic titanium oxide membranes with clean surface using recycling process

Large area of self-organized, free standing anodic titanium oxide (ATO) nanotube membranes with clean surfaces were facilely prepared to desired lengths via electrochemical anodization of highly pure Ti sheets in an ethylene glycol electrolyte, with a small amount of NH4F and H2O at 50 V, followed by self-detachment of the ATO membrane from the Ti substrate using recycling processes. In the first anodization step, the nanowire oxide layer existed over the well-arranged ATO nanotube. After sufficiently rinsing with water, the whole ATO layer was removed from the Ti sheet by high pressure N2 gas, and a well-patterned dimple layer with a thickness of about 30 nm existed on the Ti substrate. By using these naturally formed nano-scale pits as templates, in the second and third anodization process, highly ordered, vertically aligned, and free standing ATO membranes with the anodic aluminum oxide (AAO)-like clean surface were obtained. The inter-pore distance and diameter was 154 +/- 2 nm and 91+/- 2 nm, the tube arrays lengths for 25 and 46 hours were 44 and 70 microm, respectively. The present study demonstrates a simple approach to producing high quality, length controllable, large area TiO2 membrane.     

Photocatalytic degradation of methyl orange using a TiO2/Ti mesh electrode with 3D nanotube arrays

To further improve the photocatalytic techniques for water purification and wastewater treatment, we successfully prepared a new type of TiO(2)/Ti mesh photoelectrode, by anodization in ethylene glycol solution. The three-dimensional arrays of nanotubes formed on Ti mesh show a significant improvement in photocatalytic activity, compared to the nanotube arrays formed on foil. This can be demonstrated by about 22 and 38% enhancement in the degradation efficiency per mass and per area, respectively, when TiO(2)/Ti mesh electrode was used to photocatalyze methyl orange (MO). Furthermore, the effects of different parameters on MO photodegradation were investigated, such as different photoelectrode calcination temperature, the initial pH value of MO solution, and the present of hydrogen peroxide. The superior photocatalytic activity could be achieved by the TiO(2)/Ti mesh photoelectrode calcinated at 550 °C, due to the appearance of mixed crystal phases of anatase and rutile. In strong acidic or caustic conditions, such as pH 1 or 13, a high degradation efficiency can be both obtained. The presence of H(2)O(2) in photocatalytic reactions can promote photocatalytic degradation efficiencies. Moreover, the experimental results demonstrated the excellent stability and reliability of the TiO(2)/Ti mesh electrode.     

An integrated power pack of dye-sensitized solar cell and Li battery based on double-sided TiO2 nanotube arrays

We present a new approach to fabricate an integrated power pack by hybridizing energy harvest and storage processes. This power pack incorporates a series-wound dye-sensitized solar cell (DSSC) and a lithium ion battery (LIB) on the same Ti foil that has double-sided TiO(2) nanotube (NTs) arrays. The solar cell part is made of two different cosensitized tandem solar cells based on TiO(2) nanorod arrays (NRs) and NTs, respectively, which provide an open-circuit voltage of 3.39 V and a short-circuit current density of 1.01 mA/cm(2). The power pack can be charged to about 3 V in about 8 min, and the discharge capacity is about 38.89 μAh under the discharge density of 100 μA. The total energy conversion and storage efficiency for this system is 0.82%. Such an integrated power pack could serve as a power source for mobile electronics.     

硅掺杂TiO2纳米管阵列的制备及光电催化活性的研究

通过电化学沉积,在阳极氧化法制备的高度有序TiO2纳米管阵列表面均匀地沉积Si元素.扫描电子显微照片显示Si掺杂的TiO2纳米管垂直于基底定向生长.X射线衍射分析表明,所引入的Si可能掺入到TiO2的晶格中,因而提高了TiO2的热稳定性,抑制了金红石相的生成及晶粒的长大.紫外-可见漫反射分析表明Si掺杂的TiO2纳米管吸收边带发生了明显的蓝移,并且在紫外区的吸收强度明显增强.与未掺杂的TiO2纳米管相比,Si掺杂TiO2纳米管电极的紫外光电化学响应显著提高,其光电流密度是未掺杂的1.48倍.硅掺杂TiO2纳米管阵列光电催化降解五氯酚的动力学常数(1.651h-1)是未掺杂TiO2纳米管电极(0.823h-1)的2.0倍.     

Solvothermally grown ZnO nanorod arrays on (101) and (002) single- and poly-crystalline Zn metal substrates

One-dimensional (1D) ZnO nanorod (NR) arrays were grown on (101) and (002) single- and poly-crystalline Zn substrates via direct surface-oxidation in solution, i.e. solvothermal method. The surface-oxidation was done in a solvent mixture of water and 1-propanol with the optimum pH adjusted by adding ammonia. X-ray diffraction patterns revealed that the ZnO NRs grown on the Zn substrates were of single-crystalline with wurtzite structure. The ZnO NRs grown on the (002) single- and poly-crystalline substrates grew in the <001> direction, in contrast to the NRs grown on the (101) single-crystal substrate which were oriented predominantly in the <101> direction. The texture coefficient of the grown ZnO NRs was calculated from the XRD data. Well-aligned NRs that had tips of various shapes were examined by scanning electron microscopy and transmission electron microscopy techniques. The optical properties of the ZnO NRs grown on the Zn substrates were characterized by photoluminescence (PL) spectroscopy.     

Plasma treatment effect on dye-sensitized solar cell efficiency of hydrothermal-processed TiO2 nanorods

Atmospheric plasma (AP) treatment was carried out on TiO2 nanorods (NRs) that were hydrothermally grown on F-doped SnO2 (FTO)/glass. The effects of AP treatment on the surface of the TiO2 NRs were investigated, where the treatment involved the use of the reactive gases H2, N2, and O2. The surface energy of AP-treated TiO2 NRs was about 1.5 times higher than that of untreated TiO2 NRs (364.3 mJ/m2). After AP treatment, the increase of the peak area ratios of the Ti2O3 and TiO2 peaks in the XPS spectra resulted in a decrease in the number of oxygen vacancies in the TiO2 NRs. The efficiency of a dye-sensitized solar cell (DSSC) based on the N2-plasma-treated TiO2 NRs, which was approximately 1.11%, was about 79% higher than that of a DSSC based on the untreated TiO2 NRs.     

不同制备条件对二氧化钛纳米管阵列及其结构的影响

采用阳极氧化法以NH4F/乙二醇为电解液制备高度有序的TiO2纳米管,研究了不同电解液浓度、电解电压、电解时间等参数对TiO2纳米管的影响.在不同温度下对TiO2纳米管进行退火处理.分别利用转靶X射线衍射仪(XRD)和场发射扫描电子显微镜(SEM)对TiO2纳米管阵列的物相结构和形貌变化进行表征.结合氧化过程电流密度变...     

硫掺杂TiO2/Ti光电极制备及其可见光光电催化性能

为了提高TiO2/Ti光电极在可见光下的光电催化活性,采用阳极氧化法制备了一种新型的硫掺杂TiO2/Ti光电极.采用扫描电子显微镜、X射线衍射、X射线荧光光谱等技术对光电极进行了表面形貌、结晶形态、晶粒尺寸、硫的掺杂量和价态以及吸光性能表征.研究表明:硫掺杂TiO2/Ti光电极的最佳制备条件为:成膜电压160V、电流密度100mA/cm2、Na2SO3质量浓度750mg/L;所制备的光电极具有良好的光电催化氧化降解邻苯二甲酸二甲酯活性,并能有效地矿化其中间产物;与TiO2/Ti电极相比,硫的掺杂可以显著提高其在可见光下的光电催化性能.     

F掺杂TiO2纳米管阵列的可见光催化活性和电子结构

采用电化学阳极氧化法,在纯Ti表面一步制得原位生长的F掺杂TiO2纳米管阵列.对煅烧后样品进行扫描电镜(SEM)、X射线多晶衍射(XRD)表征.结果表明,所得TiO2纳米管排列整齐、平均管径约40 nm,平均管长约700 nm.XPS蚀刻分析发现,少量F原子以F-Ti-O键的形式掺杂进了TiO2晶格,同时产生活性物质T...     

Free-standing TiO(2) nanotube arrays made by anodic oxidation and ultrasonic splitting

A facile and green method was employed to prepare large-scale free-standing TiO(2) nanotube (TNT) arrays, in which as-anodized TiO(2) nanotube films prepared in organic electrolytes with thickness ranging from seven to tens of micrometers were then ultrasonicated in a mix solution of ethanol and water. By controlling the ratio of ethanol to water, the time and the power of ultrasonication, large-scale free-standing TiO(2) nanotube arrays without any crack could be detached from the Ti substrates. Hydrogen sensing results demonstrated that the free-standing TNT film is more sensitive than a film with Ti substrates when exposed to 1000?ppm hydrogen ambient.     

自持TiO2纳米管阵列薄膜与TiO2/FTO透明光电极制备工艺的研究

利用电化学阳极氧化法,采用三步氧化工艺,成功制备出大面积高度有序、孔洞分布均匀、孔道垂直取向且与金属钛基相分离的自持TiO2纳米管阵列膜。然后将其转移粘接至FTO导电玻璃上,形成高度有序的TiO2/FTO纳米管阵列透明光电极。利用场发射扫描电镜、X射线衍射仪、紫外-可见-近红外分光光度计分别对样品的形貌、晶相结构以及光学特性做了表征。研究表明,由三步阳极氧化工艺制备的自持TiO2纳米管阵列膜,其结构参数（如管径、管长及管壁厚度）在很大范围内可控,将其转移粘结至FTO导电玻璃上能制成多种用途的高质量透明光电极;另外,阳极氧化电压对TiO2纳米管阵列薄膜的光学能隙（Eg）也有较为明显的调制作用。显然,这项新工艺对基于TiO2纳米有序阵列复合结构的有机-无机光电器件的应用研究将是非常有益的。     

A novel route to large-scale and robust free-standing TiO2 nanotube membranes based on N2 gas blowing combined with methanol wetting

We present a novel and straightforward approach to fabricate large-scale and robust free-standing TiO(2) nanotube (TNT) membranes. Simply by blowing N(2) gas onto as-anodized TNTs that are wetted with methanol, free-standing TNT membranes are produced. The approach also provides homogeneous and honeycomb-like Ti substrates after the detachment of TNT membranes. Through the second anodization of the honeycomb-like Ti substrates following the N(2) blowing, TNT membranes comprising hexagonally close-packed and regularly ordered TNTs with clear open ends can be achieved. Characterization of the free-standing TNT membranes using Raman spectroscopy and a high-resolution transmission electron microscope reveals that anatase TiO(2) and crystalline graphitic carbon are embedded in the bottom surface of the free-standing TNT membranes.