Microstructural and chemical variation of TiO2 electrodes in DSSCs after ethanol vapour treatment

TiO₂ based dye-sensitized solar cells (DSSCs) have great potential to solve many energy challenges, however, their low energy conversion rate is still a barrier for further applications. Ethanol vapour post-treatment can improve the DSSC's conversion efficiency without changing its architecture, and a stable 2–3% improvement was found in our experiments. Microstructural and chemical factors were investigated using scanning electron microscopy and analytical electron microscopy on treated and untreated electrodes. The vapour treatment improved the porosity and surface-to-volume ratio of the TiO₂ particles, decreased electron transport loss between TiO₂ and fluorine doped tin oxide, and increased hydroxyl sites on the TiO₂ particle's surface. The modification therefore enhanced the dye uptake and dye–TiO₂ coupling, and it reduced the energy loss during the carrier transfer.     

Microstructural and optical characterization of TiO2 doped with ytterbium synthesized by sol-gel and Solar physical vapor deposition process

Pure and ytterbium doped TiO2 nanopowders in anatase phase have been prepared by sol-gel method (SGM) and Solar Physical Vapour Deposition process (SPVD). The physico-chemical parameters of the nanopowders have been described based on the results of micro-structural characterization performed by X-ray diffractometry, scanning electron microscopy, atomic force microscopy, and nitrogen sorption measurements. Thus, final micro-structural properties of SGM and SPVD titania nanopowders have been compared in detail revealing significant changes in the structure and morphology of these two types of materials. Addition of ytterbium had no significant effect on above-mentioned properties, although it modifies significantly the optical properties of the investigated materials. The luminescent properties of developed material were found to be comparable to bulk oxide materials and better than these reported earlier for ytterbium doped titania. In particular it has been shown that the luminescence of SPVD nanopowders is significantly stronger than this of SGM samples.     

Structural, optical and photocatalytic properties of sol-gel synthesized mesoporous TiO2 film

TiO2 surfactant-templated nanostructured film was fabricated by supramolecular templating technique using TiCl4 and P-123 as raw material and surfactant, respectively. The film was produced by sol-gel dip coating procedure. Characterization of the product was carried out by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface areas, thermogravimetry (TG), and UV-vis absorption spectroscopy. Detailed characterization reveals that film is transparent and has a wormlike mesostructured with high surface area. It is about 2 microm thick and is composed of closely packed anatase particles. The estimated band gap value of TiO2 thin film in the present work is 3.69 eV which is about 0.3 eV larger than value reported in literature for anatase thin film. It could be due to quantum size effect arising from the small size of TiO2 nanocrystallite in this thin film. The photocatalytic activity of the prepared TiO2 film was evaluated by Crystalviolet dye degradation. The film has excellent photocatalytic efficiencies and more than 70% of dye was decolorized in 60 minutes.     

Microstructural,electrical and optical properties of indium tin oxide (ITO) nanoparticles synthesized by co-precipitation method

In the present study, the synthesis of Tin doped indium oxide (ITO) nanopowder at different compositions (In/Sn = 0, 5, 10, 15 at %) was carried out by co-precipitation method. The decomposition of precipitated indium tin acetylacetonate precursor to form In₂O₃–SnO₂ (Sn_1?xIn_xO₂) at 400 °C was confirmed by the thermal and FTIR studies. The changes in strain and grain size of the synthesized particle with respect to dopant concentration were determined from the X-ray diffraction (XRD) analysis. Transmission electron microscopy (TEM) images support to confirm the grain size. The optical properties on ITO nanoparticles were analyzed with UV–visible spectroscopy, and band gap was found to vary from 3.62 to 3.89 eV with Sn dopant concentration. This variation was ascribed to the quantum confinement effect.     

Aspartame optical biosensor with bienzyme-immobilized eggshell membrane and oxygen-sensitive optode membrane

An aspartame optical biosensor has been fabricated by employing a bienzyme system composed of alpha-chymotrypsin and alcohol oxidase immobilized onto an eggshell membrane and an oxygen-sensitive optode membrane as the transducer. The detection schemes involve the enzymatic reactions of aspartame leading to the depletion of the oxygen level of the medium with a concomitant enhancement of the fluorescence intensity of the oxygen-sensitive membrane. The scanning electron and transmission electron micrographs show the microstructure of the eggshell membrane which is successfully immobilized with bienzyme. Using this novel immobilization technique, the aspartame biosensor shows extremely good stability with a shelf life of at least 8 months. The rate change of the fluorescence intensity in 4 min is found to be linearly related to the concentration of aspartame. The useful analytical working range of the biosensor is from 0.056 to 3.07 mM aspartame. The effects of temperature, pH, and ionic strength on the response of the aspartame biosensor are investigated in detail. Citric acid, cyclamic acid, D-fructose, D-galactose, D-glucose, hydrogen peroxide, DL-malic acid, L-phenylalanine, saccharin, sodium benzoate, and sucrose show no interferences but ethanol interferes strongly. The aspartame biosensor has been applied to determine aspartame contents in some commercial products.     

Microstructural, optical, and mechanical properties of reactive electron-beam-coevaporated TiO(2)-MgF(2) composite films

The composition-dependent structural, microstructural, optical, and mechanical properties of TiO(2)-MgF(2) composite films prepared by reactive electron-beam coevaporation at a substrate temperature of 280 °C are systematically investigated with an x-ray diffractometer, transmission electron microscope, spectrophotometer and varied angle of incidence spectroscopic ellipsometry, and microhardness tester, respectively. A comparison of the films prepared by reactive ion-assisted coevaporation shows that the films prepared by reactive electron-beam coevaporation have lower refractive indices and hardnesses. However, TiO(2)-MgF(2) composite films prepared by both techniques exhibit similar softening and hardening phenomena and similar microstructures.     

微乳液模板法制备多孔二氧化钛光催化薄膜

通过在钛溶胶中掺入阳离子型微乳液,并控制掺入量和pH值,使混合溶胶稳定,涂膜后经过适当热处理得到了TiO2纳米多孔薄膜.借助XRD、FT-IR、DTA、AFM、BET等测试手段,分析讨论了微乳液模板的加入对多孔二氧化钛薄膜的结晶行为、表面形貌和孔结构的影响.光催化结果表明,适当的表面形貌和孔结构可以显著提高TiO2薄膜的光催化能力.     

Microstructural properties of electrochemically synthesized ZnSe thin films

In this study, we report the electrosynthesis of zinc selenide (ZnSe) thin films on indium-doped tin oxide-coated glass substrates. The deposited ZnSe thin films have been characterized for structural (X-ray diffraction), surface morphological (scanning electron microscopy), compositional (energy dispersive analysis by X-rays), photo luminescence property, and optical absorption analysis. Formation of cubic structure with preferential orientation along the (111) plane was confirmed from structural analysis. In addition, the influence of the deposition potential on the microstructural properties of ZnSe is plausibly explained. The optical properties of ZnSe thin films are estimated using the transmission spectrum in the range of 400–1200 nm. The optical band gap energy of ZnSe thin films was found to be in the range between 2.52 and 2.61 eV. Photoluminescence spectra were observed at blue shifted band edge peak. The morphological studies depict that the spherical and cuboid shaped grains are distributed evenly over the entire surface of the film. The sizes of the grains are found to be in the range between 150 and 200 nm. The ZnSe thin film stoichiometric composition was observed at optimized deposition condition.     

银、铜硫化物纳米球的活性模板合成及其光学性能研究

首次利用胶棉人工活性膜模板．在隔膜组装体系中．一步高效地合成了具有良好光学性能且形貌较规则的Ag2S、CuS纳米球,所得产物分别为单斜多晶结构和六方多晶结构,平均粒径分别为28、20nm。两种纳米球均保留了半导体材料的红外透过性能和荧光发光性能．紫外一可见光谱中有新的吸收峰出现．不同于体相材料,表现出明显的量子尺寸效应。     

胶晶模板法合成三维有序大孔TiO2

以自然沉积的聚苯乙烯(PS)胶体晶体为模板,一定比例钛酸丁酯、乙醇、醋酸、盐酸和水配制的溶胶溶液为前驱体进行填充,溶胶在PS模板间隙内发生原位凝胶,最后通过煅烧除去模板得到了三维有序大孔(3DOM)TiO2材料.从SEM照片可观察到,3DOMTiO2可以看成是PS模板的逆复制,孔径大小均匀,排列整齐,整体上呈面心立方结构.孔径在280nm左右,收缩率为22%,孔壁填充完全,孔与孔之间由小窗口相连.XRD分析表明,制备的3DOM TiO2孔壁为锐钛矿晶型.     

Analysis of optical properties of TiO2 nanoparticles and PAN/TiO2 composite nanofibers

The aim of the study was the production of thin composite nanofibrous mats PAN/TiO₂ nanoparticles using the electrospinning method from solution of PAN/TiO2/DMF. TiO₂ nanoparticles were obtained using sol-gel method. To prepare sol mixture, organic alkoxides precursor of titanium isopropoxide and water solution were used. Calcination of TiO-gel and following milling were carried out to obtain nanoparticles of TiO₂ rutile phase. In order to analyze the structure of the obtained particles, we used X-ray diffraction analysis (XRD) and energy dispersive spectrometer (EDS). Analysis of the morphology and chemical composition of the resulting composite nanofibers were carried out using a scanning electron microscope (SEM) with EDS. The analysis of the optical properties and the energy band structure prepared nanoparticles and thin composite nanofibrous mats were determined by spectral analysis of the absorbance as a function of the energy of radiation obtained using a UV–Vis spectrophotometer.     

Study of optical properties of GeO2 nanocrystals as synthesized by hydrothermal technique

The GeO₂ nanocrystals (α-quartz type structure) with β-phase are synthesized at relatively lower temperature by hydrothermal route using autoclave. All samples are characterized by XRD, FESEM, EDS, TEM, photoluminescence (PL) and UV–vis absorption spectroscopy techniques. Synthesized nanocrystals have uniform shape and uniform size distribution for a particular synthesis condition, which is about 30–300 nm depending on synthesis conditions. The XRD results indicate that grown GeO₂ crystals only shows peak related to α-quartz structure with lattice parameters a = 4.985 Å and c = 5.648 Å. UV–vis absorption spectroscopy measurements reveal the bandgap energies corresponding to the GeO₂ α-quartz structure. Synthesized nanocrystals are capable to emit strong blue light around 425–435 nm under excitation of 300 nm and 325 nm and consequently the as synthesized material can be used in integrated optical devices.     

Structural and optical properties of Eu2O3 coated TiO2 nanoparticles and their application for dye sensitized solar cell

Specialized applications of dye sensitized solar cells (DSSCs) have attracted much attention as an economical substitute to first and second generation solar cells. Surface modification of TiO₂ nanoparticles with high band gap Eu₂O₃ coating has been carried out by chemical precipitation arrested solvothermal method. The characterizations have been done through X-ray diffraction, transmission electron microscopy, diffuse UV–visible, and photoluminescence spectroscopy. Scanning electron microscopy results reveal an increase in surface roughness in case of Eu₂O₃/TiO₂ electrode, which leads to enhancement in the dye loading capability. The synthesized nanoparticles have been employed for the fabrication of DSSCs. Effect of Eu₂O₃ coating on their performance has been studied. Eu₂O₃/TiO₂ electrode provides better surface area for the dye adsorption, which slows down the electron–hole recombination, and thus, improves the DSSC performance. The photocurrent density–voltage (J–V) characteristics reveal that the efficiency of DSSCs fabricated from Eu₂O₃/TiO₂ nanoparticles is 52 % higher than that from bare TiO₂ nanoparticles.     

Different TiO2 nanotubes for back illuminated dye sensitized solar cell: fabrication,characterization and electrochemical impedance properties of DSSCs

In the present work we reported the fabrication of different TiO₂ nanotube arrays (TiO₂ NTs) by anodization method. When used in dye-sensitized solar cells, the TiO₂ NTs prepared in the two-step anodization process (2-step TiO₂ NTs) showed better efficiency than those of TiO₂ NTs prepared in one step anodization process (1-step TiO₂ NTs). The 2-step TiO₂ NTs show a remarkable efficiency of 1.56 %. This is higher than those of TiO₂ NTs prepared in one step anodization process. Electrochemical impedance spectroscopy has been performed for qualitative analysis of charge transport process in dye-sensitized solar cells.     

TiO2膜光催化水处理设备的研制和应用

以大流量处理微污染水为目的,采用溶胶-凝胶法在炻器管内壁负载纳米TiO2膜,以150 W低压汞灯为主要光源置于管内组成光催化反应膜管,由多根膜管组成的光催化水处理设备的总膜面积为6.13 m2,总反应容积为105.38 L,低压汞灯总功率为2 100 W.当处理量为0.5 t/h时,某印染废水、制药废水和南京秦淮河水的CODCr值分别由初始的104 mg/L,63mg/L,24 mg/L降低为37 mg/L,19 mg/L,12 mg/L,去除率分别为64.4%,70%,50%.降低处理量可提高CODCr去除率,但能耗增加.南京秦淮河水样含细菌总数4.1×106个/L,大肠菌群数1.7×104个/L,经光催化设备处理后,灭菌率为100%,日光照射10 h无细菌复活.采用1 mol/L的H2SO4溶液浸泡24 h,污染的TiO2膜光催化降解能力可以恢复到初始的95%.     

不同衬底上溅射TiO2薄膜的光学性能研究

在硅片和石英上利用射频溅射法沉积了TiO2薄膜,并分别在空气中进行了退火处理。利用椭偏光谱仪对硅片上薄膜进行了椭偏测试,利用紫外-可见分光光度计对石英上薄膜进行了透射光谱测试。利用解谱软件对椭偏谱和透射谱进行了建模解谱,获得了不同基片上薄膜在不同退火温度下的折射指数和消光系数,发现和TiO2块材的光学常数也有明显的区别。通过计算得到了系列薄膜的光学带隙,带隙值范围从3.35～3.88eV,可以为薄膜态TiO2体系的光学应用、设计和相关理论研究提供一定的依据。