Photoelectrochemical Properties of Sol-Gel Processed Ag-TiO2 Nanocomposite Thin Films

Ag-TiO₂ thin films were prepared with a sol-gel route, using titanium isopropoxide and silver nitrate as precursors, at 0, 0.03 and 0.06 Ag/Ti nominal atomic ratios. After drying at 80°C, the films were fired at 300°C, 500°C, and 600°C for 30 min and 5 h. Glancing angle X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS), with depth profiling of the concentration, were used to study the films. XPS analysis showed the presence of C and N as impurities in the nanocomposite films. Their concentration decreased with increasing the firing temperature. Chemical state analysis showed that Ag was present in metallic state, except for the outer layer where it was present as Ag⁺. For the films prepared with a Agt/Ti concentration of 0.06, depth profiling measurements of the film fired at 300°C showed a strong Ag enrichment at the outer surface, while composition remained almost constant within the rest of the film, at Ag/Ti atomic ratio of 0.02. Two layers were found for the films heated to 500°C, where the Ag/Ti ratios were 0.015 near the surface and 0.03 near the substrate. The photoelectrochemical properties of Ag-TiO₂ were studied for thin films deposited on ITO substrates. Photocurrents of Ag-TiO₂ nanocomposite electrodes fired at 300°C were observed even at visible light, for wavelengths longer than 400 nm.     

Sol-Gel Preparation and Characterization of Ag-TiO2 Nanocomposite Thin Films

Ag-TiO₂ thin films were prepared with a sol-gel route, using titanium isopropoxide and silver nitrate as precursors, at 0.03 and 0.06 Ag/Ti nominal atomic ratios. After drying at 80°C, the films were fired at 300°C and 500°C for 30 min. The films were analysed by X-ray diffraction (XRD) with glancing angle, and X-ray photoelectron spectroscopy (XPS), with depth profiling of the concentration. XPS analysis showed the presence of C and N as impurities in the nanocomposite films. Their concentration decreased with increasing the firing temperature. Chemical state analysis showed that Ag was present in metallic state, except for the very outer layer where it was present as Ag⁺. For the films prepared with a Ag/Ti concentration of 0.06, depth profiling measurements of the film fired at 300°C showed a strong Ag enrichment at the outer surface, while composition remained almost constant within the rest of the film, at 0.019. For the films heated to 500°C, two layers were found, where the Ag/Ti ratios were 0.015 near the surface and 0.026 near the substrate.     

Increasing the Hydrophobicity of a PP Film Using a Helium/CF<Subscript>4</Subscript> DBD Treatment at Atmospheric Pressure

Plasma surface modification is widely used to tailor the surface properties of polymeric materials. Most treatments are performed using low pressure plasma systems, but recently, atmospheric dielectric barrier discharges (DBDs) have appeared as interesting alternatives. Therefore, in this paper, an atmospheric He + CF₄ DBD is used to increase the hydrophobicity of a polypropylene (PP) film. The surface characterization of the PP film is performed using contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results show that the hydrophobic properties of the polymer films are greatly enhanced after plasma treatment as evidenced by an increased contact angle. The incorporation of fluorine on the surface is significant (45 at%), demonstrating the ability of the used DBD set-up to generate fluorine-containing functional groups on the PP surface.     

Thermo-responsive and antifouling PVDF nanocomposited membranes based on PNIPAAm modified TiO2 nanoparticles

A novel hydrophilic nanocomposite additive(TiO2-g-PNIPAAm) was synthesized by the surface modification of titanium dioxide(TiO2) with N-isopropylacrylamide(NIPAAm) via "graft-from" technique. And the nanocomposite membrane of poly(vinylidene fluoride)(PVDF)/TiO2-g-PNIPAAm was fabricated by wet phase inversion. The graft degree was obtained by thermo-gravimetric analysis(TGA). Fourier transform infrared attenuated reflection spectroscopy(FTIR-ATR) and X-ray photoelectronic spectroscopy(XPS) characterization results suggested that TiO2-g-PNIPAAm nanoparticles segregated on membrane surface during the phase separation process. Scanning electron microscopy(SEM) was conducted to investigate the surface and cross-section of the modified membranes. The water contact angle measurements confirmed that TiO2-g-PNIPAAm nanoparticles endowed PVDF membranes better hydrophlilicity and thermo-responsive properties compared with those of the pristine PVDF membrane. The water contact angle decreased from 92.8° of the PVDF membrane to 61.2° of the nanocompostie membrane. Bovine serum albumin(BSA) static and dynamic adsorption experiments suggested that excellent antifouling properties of membranes was acquired after adding TiO2-gPNIPAAm. The maximum BSA adsorption at 40 °C was about 3 times than that at 23 °C. The permeation experiments indicated the water flux recover ratio and BSA rejection ratio were improved at different temperatures.     

The Effect of SiO2 Addition on the Grain Size and Photocatalytic Activity of TiO2 Thin Films

The uniform transparent TiO₂/SiO₂ nanometer composite thin films were prepared via sol-gel method on the soda lime glass substrates, and were characterized by X-ray photoelectron spectroscopy (XPS), FTIR spectroscopy, UV-VIS spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET surface areas. It was found that the addition of SiO₂ to TiO₂ thin films could suppress the grain growth of TiO₂ crystal and increase the hydroxyl content of the surface of TiO₂ films. The photocatalytic activity of the as-prepared TiO₂/SiO₂ composite thin films increases for SiO₂ content of less than 5 mol%.     

Electrodeposition of Zn–TiO<Subscript>2</Subscript> nanocomposite films—effect of bath composition

Zn–TiO₂ nanocomposite films were prepared by pulsed electrodeposition from acidic zinc sulphate solutions on a Ti support. The influence on the composite structural and morphological characteristics of Zn²⁺ and TiO₂ concentrations in the deposition bath has been investigated. The characterisation of the samples was made by X-ray diffraction and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS). For all the obtained coatings, the anatase and rutile phases’ most intense diffraction lines were observed between 24° and 28° 2θ, confirming the formation of the Zn–TiO₂ nanocomposite. X-ray diffraction data show that the presence of the TiO₂ nanoparticles plays a remarkable influence on the preferred orientation of the metal matrix. For the more diluted solution, a dependence between the metallic matrix grain size and the concentration of TiO₂ in bath is observed. The grain size decreases with the increasing on the nanoparticle amounts. The SEM results for Zn and Zn–TiO₂ deposits indicate that the nanoparticles have a strong influence on the deposit surface morphology, which is caused by the changes on the deposition mechanism.     

Application of response surface methodology for optimization of the stability of asphaltene particles in crude oil by TiO2/SiO2 nanofluids under static and dynamic conditions

In this work, the onset of asphaltene flocculation for an Iranian crude oil by titration of samples with heptane in the presence and absence of the TiO₂/SiO₂ nanofluids was obtained by Near-IR spectroscopy. Nanoparticles and nanocomposites were characterized by BET, FESEM, EDX, XRD, and XRF analysis. Modeling and optimization of inhibition of asphaltene flocculation process by TiO₂/SiO₂ nanofluids were conducted by response surface methodology (RSM). Under optimum conditions (nanocomposite composition = 0.04 wt% (80%TiO₂:20%SiO₂), salinity = 4.01 wt%, and pH = 3.42), the onset point increased. For nanofluids stability analysis, the optimum nanofluid was compared with the two other nanofluids (SiO₂ and TiO₂) by visual observation method. The results indicated that high stability and surface area of the 80%TiO₂ nanocomposites increase asphaltene adsorption on the particles surface that subsequently increases the onset point. In addition, the optimum nanofluid performance on the carbonate rocks was evaluated by contact angle and core flooding experiments. The 80% TiO₂ nanofluid changed the wettability of carbonate rocks from strongly oil-wet to strongly water-wet condition and also decreased the residual oil saturation and enhanced the oil recovery with an increase in the recovery factor of about 15%.     

Alkoxide Derived SrBi2Ta2O9 Phase Pure Powder and Thin Films

Phase pure powder and thin films of the novel ferroelectric materials SrBi₂Ta₂O₉ (SBT) have been prepared using the organic precursors. The xero-gel formed was dried and characterized using TGA and DTA to determine the organic burn out and crystallization temperature of SBT. Powder X-ray diffraction was used systematically to check the crystallinity of SBT. Phase pure SBT powder was formed as low as 650°C and thin films at 600°C in comparison to other earlier reported work. SEM micrographs show a grain size of ≈0.1 μm and show crack free films with a film thickness of 2 μm.     

Structure and Optical Properties of 0.1BiFeO3-0.9SrBi2Nb2O9 Thin Films Using a Modified Sol-Gel Technique

Fe-doped SrBi₂Nb₂O₉ precursor solution was synthesized using bismuth nitrate Bi(NO₃)₃·5H₂O, strontium nitrate Sr(NO₃)₂, iron nitrate Fe(NO₃)₃·9H₂O, and niobium ethoxide Nb(OC₂H₅)₅ as starting materials, ethylene glycol monomethyl ether (C₃H₈O₂) as the solvent. 0.1BiFeO₃-0.9SrBi₂Nb₂O₉ thin films were prepared on fused quartz substrates using sol-gel processing. The surface morphology and crystal structure and optical properties of the thin films were investigated. The thin film annealing at 400°C were found to be amorphous, and the thin films crystallize to a perovskite structure after a post-deposition annealing at 600°C for 1 h in air. The grain of thin film was evenly distributed. The thin films exhibit the designed optical transmission, while the optical transition is indirect in nature. Their optical band gap is about 2.5 eV.     

Switchable Adhesion of Superhydrophobic ZnO Nanorod Film

We have fabricated superhydrophobic zinc surface with reversible transformation between sliding state and adhesion by a simple hydrothermal method. Uniformly ZnO₂ nanorod was obtained at 120°C. After self-assembling of a film of n-octadecanethiol, the surface with a water contact angle (CA) of 153 ± 2°, exhibited a nonwetting property. The surface showed switchable adhesion just upon introducing UV illumination and heating treatment in turn.     

Surface modification of polyester by oxygen‐ and nitrogen‐plasma treatment

In this paper, we present a study on the surface modification of polyethyleneterephthalate (PET) polymer by plasma treatment. The samples were treated by nitrogen and oxygen plasma for different time periods between 3 and 90 s. The plasma was created by a radio frequency (RF) generator. The gas pressure was fixed at 75 Pa and the discharge power was set to 200 W. The samples were treated in the glow region, where the electrons temperature was about 4 eV, the positive ions density was about 2 × 10¹⁵ m^?3, and the neutral atom density was about 4 × 10²¹ m^?3 for oxygen and 1 × 10²¹ m^?3 for nitrogen. The changes in surface morphology were observed by using atomic force microscopy (AFM). Surface wettability was determined by water contact angle measurements while the chemical composition of the surface was analyzed using XPS. The stability of functional groups on the polymer surface treated with plasma was monitored by XPS and wettability measurements in different time intervals. The oxygen‐plasma‐treated samples showed much more pronounced changes in the surface topography compared to those treated by nitrogen plasma. The contact angle of a water drop decreased from 75° for the untreated sample to 20° for oxygen and 25° for nitrogen‐plasma‐treated samples for 3 s. It kept decreasing with treatment time for both plasmas and reached about 10° for nitrogen plasma after 1 min of plasma treatment. For oxygen plasma, however, the contact angle kept decreasing even after a minute of plasma treatment and eventually fell below a few degrees. We found that the water contact angle increased linearly with the O/C ratio or N/C ratio in the case of oxygen or nitrogen plasma, respectively. Ageing effects of the plasma‐treated surface were more pronounced in the first 3 days; however, the surface hydrophilicity was rather stable later. Copyright © 2008 John Wiley & Sons, Ltd.     

Surface modification of plasma‐pretreated expanded poly (tetrafluroethylene) films by graft copolymerization

A two‐step process based on a low‐pressure helium plasma treatment followed by acrylic acid‐grafting copolymerization was used for the surface modification of expanded polytetrafluoroethylene (ePTFE) films. The effects of plasma treatment power and treatment time on the hydrophilicity of the film surface were investigated. The wettability of the ePTFE film surface was characterized by water contact angle, and the surface compositions of the untreated and treated ePTFE samples were evaluated by atomic force microscopy and XPS. Contact angle measurements revealed that the hydrophilicity of the ePTFE film surface was greatly enhanced by the combined actions of the plasma treatment and acrylic acid grafting, and the contact angle decreased from 145° to 66°. Atomic force microscopy analyses showed that the surface roughness increased after the plasma treatment. XPS analyses showed substantial increase in the concentration of carbon and oxygen atoms and a decrease in the concentration of fluorine atoms at the film surface. T‐peel strength showed an improved bonding strength between the film and an adhesive tape after the treatment. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and Characterization of an α-Fe2O3-Decorated g-C3N4 Heterostructure for the Photocatalytic Removal of MO

This study describes the preparation of graphitic carbon nitride (g-C₃N₄), hematite (α-Fe₂O₃), and their g-C₃N₄/α-Fe₂O₃ heterostructure for the photocatalytic removal of methyl orange (MO) under visible light illumination. The facile hydrothermal approach was utilized for the preparation of the nanomaterials. Powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), and Brunauer–Emmett–Teller (BET) were carried out to study the physiochemical and optoelectronic properties of all the synthesized photocatalysts. Based on the X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance (DRS) results, an energy level diagram vs. SHE was established. The acquired results indicated that the nanocomposite exhibited a type-II heterojunction and degraded the MO dye by 97%. The degradation ability of the nanocomposite was higher than that of pristine g-C₃N₄ (41%) and α-Fe₂O₃ (30%) photocatalysts under 300 min of light irradiation. The formation of a type-II heterostructure with desirable band alignment and band edge positions for efficient interfacial charge carrier separation along with a larger specific surface area was collectively responsible for the higher photocatalytic efficiency of the g-C₃N₄/α-Fe₂O₃ nanocomposite. The mechanism of the nanocomposite was also studied through results obtained from UV-vis and XPS analyses. A reactive species trapping experiment confirmed the involvement of the superoxide radical anion (O₂^•−) as the key reactive oxygen species for MO removal. The degradation kinetics were also monitored, and the reaction was observed to be pseudo-first order. Moreover, the sustainability of the photocatalyst was also investigated.     

Investigation of RuO2-IrO2-SnO2 thin film evolution

The thermal evolution process of RuO₂–IrO₂–SnO₂ mixed oxide thin films of varying noble metal contents has been investigated under in situ conditions by thermogravimetry-mass spectrometry (TG-MS), infrared emission spectroscopy (IR) and cyclic voltammetry (CV). The gel-like films prepared from aqueous solutions of the precursor compounds RuOHCl₃, H₂IrCl₆ and Sn(OH)₂(CH₃COO)_2–xCl_x on titanium metal support were heated in an atmosphere containing 20% O₂ and 80% Ar up to 600°C. Chlorine evolution takes place in a single step between 320 and 500°C accompanied with the decomposition of the acetate ligand. The decomposition of surface species formed like carbonyls, carboxylates and carbonates occurs in two stages between 200 and 500°C. The temperature of chlorine evolution and that of the final film formation increases with the increase of the iridium content in the films. The anodic peak charge shows a maximum value at 18% iridium content.     

Preparation of PANI-TiO2 nanocomposites and their solid-phase photocatalytic degradation

A series of polyaniline-anatase TiO₂ (PANI-TiO₂) nanocomposite powders with different PANI:TiO₂ ratios were prepared by ‘in-situ’ deposition oxidative polymerization of aniline hydrochloride using ammonium persulfate (APS) as oxidant in the presence of ultrafine grade powder of anatase TiO₂ cooled in an ice bath. And the solid-phase photocatalytic degradation of PANI-TiO₂ nanocomposites was investigated under the ambient air in order to assess the feasibility of developing photodegradable polymers. The photodegradation of the composite powders was compared with that of pure PANI powders by performing weight loss monitoring, elemental analysis, FT-IR and UV-vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The PANI-TiO₂ nanocomposite powders showed highly enhanced photodegradation and the photodegradation increased with decreasing ratios of PANI:TiO₂. A weight loss of about 6.8% was found for the PANI-TiO₂ (1:3) nanocomposite; however, the weight loss of the PANI-HCl powder was only 0.3% after being irradiated for 60 h under air. The photocatalytic degradation of the nanocomposite powders accompanied the peak intensity decrease in the FT-IR spectra at 1235 cm⁻¹, attributed to C-N stretching mode for benzenoid unit, and the depigmentation of the powders due to the visible light scattering from growing cavities. The elemental analysis and XPS analysis of the composite showed that the bulk and surface concentrations of N decreased with irradiation. A possible mechanism for the photocatalytical oxidative degradation was also mentioned.     

低温吸附制备Au-TiO2复合薄膜及其光电化学性质

在低温条件下将预先合成的Au溶胶吸附到TiO₂薄膜上以制备纳米Au-TiO₂复合薄膜,以超高分辨率场发射扫描电镜(FESEM)、X射线衍射(XRD)及X射线光电子能谱(XPS)表征Au-TiO₂膜,并在UV辐照下测定了Au-TiO₂薄膜电极的光电化学性质。纳米Au呈金属态,平均粒径为(4.3±1.2) nm,负载量高,均匀地沉积于TiO₂薄膜表面。光电化学测试表明,沉积纳米Au后,TiO₂电极的光生电流提高近5倍,光生电压明显向负值增大,说明纳米Au可增强光生载流子的分离效率,促进电荷在电极与溶液界面间的转移。Au-TiO₂电极的电荷传递法拉第阻抗(R_ct)是TiO₂电极的一半,说明负载的纳米Au粒抑制了光生电子-空穴的复合,提高了电极中载流子浓度。     

Dispersion state of CuO on CeO2

XRD and XPS are used to study the dispersion state of CuO on ceria surface. The dispersion capacity values of CuO measured by the two methods are consistent, which are of 1.20 mmol CuO/100 m² CeO₂. In addition, the results reveal that highly dispersed Cu²⁺ ions are formed at low CuO loadings and that increasing the CuO content to a value higher than its dispersion capacity produces crystalline CuO after the surface vacant sites on CeO₂ are filled. The atomic composition of the outermost layer of the CuO/CeO₂ samples has been probed by using static secondary ion mass spectroscopy (SSIMS), and the ratim of Cu/Ce are found to be 0.93 and 0.46 for the 1.22 and 0.61 mmol CuO/CeO₂ samples respectively. Temperature-programmed reduction (TPR) profile with two reduction peaks at 156 and 165°C suggests that the reduction of highly dispersed Cu²⁺ ions consists of two steps and is easier than that of CuO crystallites, in which the TPR profile has only one reduction peak at about 249°C. The above experimental results are in good agreement with the prediction of the incorporation model. Project supported by the National Natural Science Foundation of China.     

火焰辅助热解方法制备Ag_2O/TiO_2及其光催化制氢性能

以钛酸丁酯和硝酸银为前驱体,采用一步火焰辅助热解法制备了Ag_2O/TiO_2光催化剂并研究了样品在紫外-可见光照射下的光催化制氢性能。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis DRS)对样品进行了表征。XRD结果表明TiO_2均为锐钛矿晶型,Ag的引入对XRD结果无明显影响。SEM图显示未修饰的TiO_2是微球形貌,随着引入Ag含量的增加,微球减少直至消失。通过XPS分析和化学沉淀法表明样品中Ag的存在形式为Ag_2O。UV-Vis DRS测试发现引入Ag后提高了样品的光吸收。前驱体中Ag的量影响样品的光催化活性,最高的光催化制氢的活性可以达到相同条件下的P25的15倍。对光催化反应后的样品进行分析,认为在光催化过程中部分Ag_2O通过光生电子转化为Ag形成Ag/TiO_2,进一步提高光催化制氢活性。     

Preparation and characterization of poly(l-lactic acid)/TiO2 nanoparticle nanocomposite films with high transparency and efficient photodegradability

Poly(l-lactic acid)-TiO₂ nanoparticle nanocomposite films were prepared by incorporating surface modified TiO₂ nanoparticles into polymer matrices. In the process of preparing the nanocomposite films, severe aggregation of TiO₂ nanoparticles could be reduced by surface modification by using carboxylic acid and long-chain alkyl amine. As a result, the nanocomposite films with high transparency, similar to pure PLA films, were obtained without depending on the amount of added TiO₂ nanoparticles. A TEM micrograph of the nanocomposite films suggests that the TiO₂ nanoparticles of 3-6 nm in diameter were uniformly dispersed in polymer matrices. Photodegradation of PLA-TiO₂ nanoparticle nanocomposite films was also investigated. The results showed that nanocomposite films could be efficiently photodegraded by UV irradiation in comparison with pure PLA.     

Parameters controlling the photocatalytic performance of ZnO/Hombikat TiO2 composites

Commercial TiO₂ (Hombikat, UV-100) was impregnated with different loadings of zinc nitrate solution and subsequently calcined at different temperatures in order to obtain a stable homogeneous solid composite of ZnO/TiO₂. The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), UV-vis and Raman spectroscopy, inductively coupled plasma mass spectroscopy (ICP), X-ray photoelectron spectroscopy (XPS) as well as N₂ adsorption and desorption measurements. Results show that ZnO was incorporated within the TiO₂ crystals and did not form a separate bulky phase or metallic zinc. Moreover, the calcination temperature dramatically modifies the texture properties of the prepared samples compared with original Hombikat TiO₂. The photocatalytic performance of the prepared samples was evaluated by monitoring the degradation of methyl orange dye under black light illumination. Three main parameters were studied; ZnO loading, surface area and initial pH of the methyl orange solution. The variation in ZnO loading appears to have less influence on the catalytic activity than either the surface area or the pH.