Electrochemiluminescence cell fabrication using TiO2 nanotube produced by anodic oxidation

Electrochemiluminescence (ECL) cell using the electrode of TiO2 nanotube (NT) and Ru(ll) complex Ru(bpy)3(PF6)2 as a luminacence substance was fabricated. TiO2 NT were produced from the membrane of TiO2 NT arrays fabricated by anodic oxidation of approximately 100 microm thick Ti-plate. TiO2 NT arrays inject increasing number of electrons to the Ru(II) complex at the interface of TiO2 NTs. It allows the increasing exergonic oxidation/reduction reaction of Ru(II) complex. The ECL cell emits approximately 600 nm light in orange color. The cell structure is composed of a glass/F-doped SnO2(FTO)/TiO2 NT/Ru(II) complex in propylene carbonate/FTO/glass. The ECL efficiency of the cell consisting of the layer of TiO2 NT was approximately 255 cd/m2 at a bias of 4 V. The use of TiO2 NT increases ECL intensities by 5 times compared to the typical ECL cell without the use of TiO2 NT.     

The structure and electrical characteristics of Si/Ge heterojunctions II: The electrical characteristics of Si/Ge heterojunctions

The I–V characteristics of p-Ge/nn⁺ -Si and p-Ge_xSi_1?x/nn⁺ -Si heterojunctions produced by the vacuum epitaxy of germanium onto nn⁺ -Si were determined. The mechanisms of the d.c. and reverse current were investigated.     

Self-organized TiO2 nanotubes with controlled dimensions by anodic oxidation

The effect of ammonium fluoride (NH₄F) concentration on the dimensions (length, diameter, and wall thickness) of the self-organized nanotube arrays has been investigated. Results show that varying the concentration of NH₄F exerts a strong effect on changing the dimensions of the as-grown nanotube arrays. The length of the nanotube arrays increases gradually by increasing the concentration up to a maximum length at a concentration of 1.00 wt%, after which the length decreases slightly with the increase in NH₄F concentration. It was also observed that the diameter and wall thickness of the nanotube arrays vary with the change in concentration of NH₄F, where the diameter was found to alter between 80 and 140 nm, and the wall thickness decreases by increasing the NH₄F concentration. These results indicate that it is possible to entirely control the dimensions of the nanotube arrays, by tailoring the concentration of NH₄F besides the anodization time and voltage.     

Dye-sensitized solar cells based on thick highly ordered TiO(2) nanotubes produced by controlled anodic oxidation in non-aqueous electrolytic media

Dye-sensitized solar cells (DSSCs) were prepared using TiO(2) nanotubes, grown by controlled Ti anodic oxidation in non-aqueous media. Smooth, vertically oriented TiO(2) nanotube arrays, presenting a high degree of self-organization and a length of 20 μm, have been grown using ethylene glycol electrolyte containing HF. As-grown nanotubes exhibit an amorphous structure, which transforms to the anatase TiO(2) crystalline phase upon post-annealing in air at 450?°C. Atomic force microscopy (AFM) revealed the porous morphology together with high roughness and fractality of the surface. The annealed tubes were sensitized by the standard N719 ruthenium dye and the adsorption was characterized using resonance micro-Raman spectroscopy and adsorption-desorption measurements. The sensitized tubes were further used as active photoelectrodes after incorporation in sandwich-type DSSCs using both liquid and solidified electrolytes. The efficiencies obtained under air mass (AM) 1.5 conditions, using a back-side illumination geometry, were very promising: 0.85% using a composite polymer redox electrolyte, while the efficiency was further increased up to 1.65% using a liquid electrolyte.     

Fabrication of TiO2/Ti electrode by laser-assisted anodic oxidation and its application on photoelectrocatalytic degradation of methylene blue

A TiO2/Ti mesh electrode by laser calcination was prepared in this article. The resulting TiO2 film was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS), and it illuminated that the prepared electrode mainly consisted of anatase TiO2 nanoparticles on its surface and exhibited a superior photocatalytic activity. The photodegradation of methylene blue (MB) using the proposed electrode under different experimental conditions was investigated in terms of both UV absorbance at 664 nm and chemical oxygen demand (COD) removal. The electrical bias applied in photoelectrocatalytic (PEC) oxidation was also studied. The experimental results showed that under the optimal potential of +0.50 V (versus SCE), UV absorbance and COD removal during the photodegradation of MB by the proposed TiO2/Ti mesh electrode were 97.3% and 87.0%, respectively. Through the comparison between photocatalytic (PC) oxidation and photoelectrocatalytic (PEC) oxidation, it was found that PEC oxidation was a convenient and effective way to mineralize the organic matters and that laser-treated photoelectrode exceeded the oven-treated one.     

阳极氧化对炭纤维电镀镍的影响

采用阳极氧化法对炭纤维进行连续表面改性,并在其表面进行电镀镍处理,利用扫描电子显微镜(SEM)、X射线衍射(XRD)、热重分析和酸碱滴定等方法研究了炭纤维阳极氧化前后的物理化学结构及对炭纤维电镀镍镀层的影响。结果表明:经过阳极氧化处理后,炭纤维表面的总酸性官能团提高约10倍;炭纤维拉伸强度降低先慢后快;阳极氧化可以改善镀层的生长过程,使镍镀层的生长由(V-W)模式转变为(F-M)模式,并且促使镀层晶粒细晶化,N i晶粒尺寸由14.5nm降为11.2nm,提高了镀镍炭纤维的抗氧化性以及镀层与炭纤维的结合力,阳极氧化后镀镍的炭纤维初始氧化温度较镀镍炭纤维提高了50℃。     

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.     

TiO2-UV photocatalytic oxidation of Reactive Yellow 14: effect of operational parameters

The photocatalytic decolourisation and degradation of an azo dye Reactive Yellow (RY14) in aqueous solution with TiO(2) as photocatalyst in slurry form has been carried out using UV-A radiation (365 nm). The effect of various parameters such as catalyst loading, radiation intensity and initial dye concentration on the dye removal was investigated to find optimum conditions. The decolourisation and degradation kinetics have been analysed. Both follow modified Langmuir-Hinshelwood kinetic (L-H) model. A study on the effect of electron acceptors on photooxidation reveals that both decolourisation and degradation increase in the presence of H(2)O(2), (NH(4))(2)S(2)O(8), KBrO(3), to certain dosage beyond which the enhancement effect is negligible. But negative effects are observed in the presence of NaCl or Na(2)CO(3).     

Visible light driven photoelectrochemical water oxidation on nitrogen-modified TiO2 nanowires

We report hydrothermal synthesis of single crystalline TiO(2) nanowire arrays with unprecedented small feature sizes of ~5 nm and lengths up to 4.4 μm on fluorine-doped tin oxide substrates. A substantial amount of nitrogen (up to 1.08 atomic %) can be incorporated into the TiO(2) lattice via nitridation in NH(3) flow at a relatively low temperature (500 °C) because of the small cross-section of the nanowires. The low-energy threshold of the incident photon to current efficiency (IPCE) spectra of N-modified TiO(2) samples is at ~520 nm, corresponding to 2.4 eV. We also report a simple cobalt treatment for improving the photoelectrochemical (PEC) performance of our N-modified TiO(2) nanowire arrays. With the cobalt treatment, the IPCE of N-modified TiO(2) samples in the ultraviolet region is restored to equal or higher values than those of the unmodified TiO(2) samples, and it remains as high as ~18% at 450 nm. We propose that the cobalt treatment enhances PEC performance via two mechanisms: passivating surface states on the N-modified TiO(2) surface and acting as a water oxidation cocatalyst.     

阳极氧化制备TiO2纳米多孔膜

分别在氢氟酸和硫酸两种电解液体系下对纯钛(TA1)试样进行阳极氧化,在钛的表面获得TiO2纳米多孔膜.利用膜的颜色的不同来判断膜的厚度的变化,用FESEM观察了孔的形貌和结构并用XRD测试了TiO2膜的晶型,进而研究了阳极氧化电压对孔径和多孔膜晶型的影响并对多孔膜的形成机理进行了阐述.     

Growth of TiO2 anti-reflection layer on textured Si (100) wafer substrate by metal-organic chemical vapor deposition method

Recently anti-reflective films (AR) have been intensely studied. Particularly for textured silicon solar cells, the AR films can further reduce the reflection of the incident light through trapping the incident light into the cells. In this work, TiO2 anti-reflection films have been grown on the textured Si (100) substrate which is processed in two steps, and the films are deposited using metal-organic chemical vapor deposition (MOCVD) with a precursor of titanium tetra-isopropoxide (TTIP). The effect of the substrate texture and the growth conditions of TiO2 films on the reflectance has been investigated. Pyramid size of textured silicon had approximately 2-9 microm. A well-textured silicon surface can lower the reflectance to 10%. For more reduced reflection, TiO2 anti-reflection films on the textured silicon were deposited at 600 degrees C using titanium tetra-isopropoxide (TTIP) as a precursor by metal-organic chemical vapor deposition (MOCVD), and the deposited TiO2 layers were then treated by annealing for 2 h in air at 600 and 1000 degrees C, respectively. In this process, the treated samples by annealing showed anatase and rutile phases, respectively. The thickness of TiO2 films was about 75 +/- 5 nm. The reflectance at specific wavelength can be reduced to 3% in optimum layer.     

Titanium oxide films produced on commercially pure titanium by anodic oxidation with different voltages

Titanium oxide films produced on commercially pure Ti by anodic oxidation with different voltages were analyzed. Anodic oxidation was carried out at room temperature using 1.4 M H₃PO₄ electrolyte and a platinum counter-electrode, in potentiostatic mode under the following conditions: 50 V, 100 V, 150 V, 200 V and 250 V. It was observed that porous titanium layers were formed at all voltage values but morphological differences were observed. Initially, the film was thin but with increasing voltage it broke down locally and porous regions became evident due to the dielectric breakdown. The porosity and the pore size increased with the increasing voltage. The surface morphology in samples formed with 200 V had substantially different porous structures than those formed with other voltage values. The anodic film surface displayed pores and craters formed on the relatively flat ground oxide surface. AFM images showed that higher voltages produced thicker titanium oxide films.     

Improved tribo-mechanical behavior of CaP-containing TiO2 layers produced on titanium by shot blasting and micro-arc oxidation

The combination of shot blasting (SB) and micro-arc oxidation (or anodic oxidation—AO) in titanium surfaces was shown to provide enhanced conditions for cell differentiation and osseointegration than those provided by SB or AO alone. This study associated both methods aiming to attain titania layers on Ti with adequate tribo-mechanical features for bone implants. SB was performed using alumina particles, and titania layers were grown by AO using a CaP-based electrolyte. Mechanical properties and scratch resistance were characterized at nanoscale by instrumented indentation and nanoscratch, and correlated with morphological and microstructural changes (XRD, SEM, EDS, AFM, and profilometry). Analytical methods were employed to correct roughness and substrate effects on the indentation results. CaP-containing TiO₂ layers were produced on AO and SB + AO. The latter presented small pore size and inhomogeneous layer thickness and Ca/P ratios, caused by the non-uniform surface straining by SB that affects the oxide growth kinetics in the electrochemical process. Elastic modulus of SB + AO layer (37 GPa) were lower than the AO one (45 GPa); both of them were smaller than bulk Ti (130 GPa) and close to bone values. The hardness profiles of AO and SB + AO were similar to the substrate ones. Because of the improved load bearing capacity and unique layer features, the critical load to remove the SB + AO titania coating in scratch tests was three times as much or higher than in AO. Results indicate improved mechanical biocompatibility and tribological strength of anodic titania layers grown on sand blasted Ti surfaces.     

Creation and electrical properties of p-Cu2ZnSnS4/n-Si heterojunctions

Technical Physics Letters - Anisotype p-Cu2ZnSnS4/n-Si heterojunctions have been manufactured for the first type by sulfidation of base-metal layers predeposited onto polycrystalline silicon...     

Characterization of Si3N4/TiO2 nanocomposite coatings prepared via micro arc oxidation

Nanocomposite Si3N4/TiO2 coatings were prepared by micro arc oxidation with Si3N4 nanoparticles in solution and the effects of time and current density on the coatings formation and growth were studied. X-ray diffraction analysis was utilized to detect the nanocrystalline and amorphous characteristics of the composite coatings. Surface morphology and nanostructure of coatings were observed by scanning electron microscopy and atomic force microscopy. The results showed that current density had great effects on phase transformation of Si3N4 nanoparticles in composite coatings. The moderate current density conduced to homogeneous distribution of silicon nitride nanoparticles in the coatings. Moreover, fine nanoparticles that entered and homogeneously distributed in the composite coating led to an increase in the barriers for nucleation of oxide-based grains and inhibition of grain growth. Therefore, the introduction of nanoparticles resulted in the formation of smaller oxide-based grains.     

Synthesis of β-FeSi2/Si heterojunctions for photovoltaic applications by unbalanced magnetron sputtering

We report here the possibility of the growth of semiconducting FeSi₂ layers on Si(100) substrates by depositing iron with unbalanced magnetron sputtering. The originality of the study is the achievement of heterojunction without any further treatment of the deposited films. Pure iron is deposited on Si(100) substrates with unbalanced magnetron sputtering for the production of β-FeSi₂/Si heterojunctions. Prior to coating process the substrates are cleaned with neutral molecular source. Microstructure of β-FeSi₂ films were investigated by X-Ray Diffraction analysis and Raman Spectroscopy. Dark current-voltage characteristic of the deposited coatings showed a rectifying behavior for the β-FeSi₂/Si heterojuctions. Open-circuit voltage (V_oc) and short-circuit current density (J_sc) were measured under 100 mWcm^− 2 illumination and a V_oc of 360 mV and J_sc of 180 μAcm^− 2 were measured. The illumination of the silicon side gave higher photosensitivity than the illumination of the iron silicide side.     

A study of the effect of shadowing location and area on the Si solar cell electrical parameters

Shadowing location and percentage on the solar cell surface is experimentally investigated and discussed. Behavior of the solar cell electrical parameters is shown to be dissimilar according to the shadowing location on the solar cell surface. The diode model describes the solar cell characteristics using the cell physical parameters and the incident radiation intensity as inputs. In that model, cell characteristics with edge and central shadowing of its surface are indistinguishable, although they are experimentally found to behave differently. An increase in both voltage and fill factor was observed, which resulted from shadowing the edges of the cell in comparison with central shadowing of the cell with the same total covering area, and vice versa in case of current density. Both central and edge shading have negative effect on the cell efficiency, although edge shading has higher effect at very thin strips, which is easy to occur in the field.     

PLD法制备ZnO/Si异质结的I-V特性研究

用脉冲激光沉积法分别在不同电阻率的p型和n型Si( 100)衬底上制备了不掺杂ZnO薄膜,相应制成n-ZnO/p-Si和n-ZnO/n-Si异质结器件.利用X射线衍射和原子力显微镜对ZnO薄膜进行的结构和形貌测试表明,薄膜结晶情况良好,具有高度的c轴择优取向,表面颗粒大小、分布均匀.对器件的I-V特性测试表明,在无光条件下,制备的n-ZnO/p-Si异质结漏电流很低,而n-ZnO/n-Si同型异质结漏电流要稍大一些;随衬底电阻率的增大,上述器件的阈值电压变小;器件在光照下的漏电流明显比无光条件下的要大.     

TiO2掺杂的NiO-NiFe2O4电导率及合成动力学研究

采用固相合成法,在1173～1213K温度范围内合成了NiO-NiFe2O4和0.5%TiO2掺杂的NiO-NiFe2O4。用X射线衍射表征了合成产物。在合成过程中将试样置于两个铂片之间,通过连续测量加热过程中试样的电阻,获得了试样电导率随时间的变化规律,建立了稳态扩散控制的NiFe2O4合成动力学方程,并讨论了掺杂0.5%TiO2对NiFe2O4合成反应速率的影响,获得了0.5%TiO2掺杂的NiFe2O4合成反应的速率系数、活化能、Ni 2＋和Fe3＋离子的平均扩散系数。