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1.
Nanocrystalline titanium dioxide (TiO 2) thin films have been prepared using titanium(IV) isopropoxide as a precursor onto the glass and fluorine doped tin oxide coated glass substrates by chemical vapour deposition technique at 400 °C substrate temperature. X-ray diffraction study confirms the polycrystalline nature of TiO 2 with anatase phase having tetragonal crystal structure. The films are 975 nm thick and transparent having transmittance grater than 80%. Atomic force microscopy (AFM) images reveal the nanocrystalline morphology with grain size of 200 nm. The film shows a sharp absorption edge near 350 nm. Photoelectrochemical study shows that TiO 2 thin film sensitized with Brown Orange dye is found to exhibit relatively maximum Isc and Voc among the studied dyes. The values of fill factor (FF) and efficiency ( η) for the dye-sensitized solar cell (Brown Orange dye-sensitized TiO 2) are 0.54 and 0.17%, respectively. Such films would serve as better prospects for dye-sensitized solar cells. 相似文献
2.
The repetitive discoloration kinetics of the azo-dye Methyl Orange (taken as a model organic compound) was followed under solar simulated radiation (90 mW/cm 2) to assess the performance of the TiO 2/Tedlar ® composite photocatalyst. The influence of solution parameters on the photo-discoloration process: pH, dye concentration, applied light intensity and concentration of H 2O 2 were systematically investigated. During the photocatalysis a modification occurs in the TiO 2/Tedlar ® composite due to the TiO 2 interaction with the Tedlar ® film. Physical insight is given for the stabilization mechanism of the TiO 2 particles in the Tedlar matrix based on the data obtained by X-ray photoelectron spectroscopy (XPS). The F 1s peak of the Tedlar film indicates that the TiO 2 is loaded on the Tedlar fluoro-groups. The loading of TiO 2 on the 75 μm thick Tedlar ® film was 0.9% (w/w) as determined by atomic absorption spectrophotometry (AAS). Attenuated total reflection infrared spectroscopy (ATRIR) shows no formation of additional bands within the photodiscoloration reaction. This shows that an efficient catalysis taking place on the TiO 2/Tedlar ® surface. The rugosity (mean square roughness, rms) of the TiO 2/Tedlar ® film was determined by atomic force microscopy (AFM) to be 19.7 nm. This value remained constant during long-term operation. Transmission electron microscopy (TEM) reports the thickness and coverage of TiO 2 Degussa P-25 on the Tedlar ® surface before and after photocatalysis. 相似文献
3.
The photocatalytic degradation of organochlorine pesticides including -, β-, γ-, δ-hexachlorobenzene (BHC), dicofol and cypermethrin were carried out on a nano-TiO 2 coated films under UV irradiation in the air. The photocatalytic conditions, including the amount of TiO 2, irradiation time and the intensity of light were optimized. The pesticides were most effectively degraded under the condition of 2.24 mg/cm 2 on TiO 2 film and a 400 W UV irradiation of high-pressure mercury lamp with a wavelength of 365 nm. A typical organochlorine pesticide, 20 μg -BHC, was dipped onto the TiO 2 film surface and degraded completely within 20 min. In addition, the photocatalytic degradation pathways on the nano-TiO 2 coated film were discussed. 相似文献
4.
采用水热法合成了Zn 2+离子掺杂的TiO 2纳米粒子[Zn 2+掺杂量0.5%(物质的量的比)],并用光电化学方法研究了经Ru(bpy) 2(NCS) 2(bpy=2,2′bipyridine 4,4′dicarboxylicacid)分别敏化的掺杂Zn 2+的TiO 2电极(简写为Zn 2+-TiO 2)和CdS/Zn 2+-TiO 2复合半导体纳米多孔膜电极的光电化学行为.实验证明Ru(bpy) 2(NCS) 2敏化CdS/Zn 2+-TiO 2复合半导体纳米多孔膜电极比单独敏化Zn 2+-TiO 2电极的光电转换效率高,且敏化Zn 2+TiO 2电极和敏化CdS/Zn 2+TiO 2复合半导体纳米多孔膜电极比Zn 2+-TiO 2电极的光电流产生的起始波长都向长波方向移动.在360600nm范围内,Ru(bpy) 2(NCS) 2敏化CdS/Zn 2+-TiO 2复合半导体纳米多孔膜电极光电转换效率最好. 相似文献
5.
TiO 2 nanoparticles and H 2Ti 2O 5·H 2O, Na 2Ti 2O 4(OH) 2 nanotubes were synthesized by solvothermal method and their applications in the degradation of active Brilliant-blue (KN-R) solution were investigated. The experimental results revealed that the synthesized TiO 2 nanoparticles had a good crystallinity and a narrow size distribution (about 4–5 nm); the obtained H 2Ti 2O 5·H 2O, Na 2Ti 2O 4(OH) 2 were tubelike products with an average diameter of 20–30 and 200–300 nm length. The three catalysts we synthesized had some hydroxyl groups and the maximum absorption boundaries of the samples were all red-shifted, which indicated the samples had a promising prospect in photocatalysis. The results of the photocatalytic experiments indicated that the photocatalytic activity of the samples was: TiO2 > H2Ti2O5·H2O > Na2Ti2O4(OH)2, which was in good accordance with the fact of FTIR and UV–vis absorption spectra. The formation mechanism of these nanostructures was also discussed. 相似文献
6.
We review the design and fabrication of thin-film composite optical waveguides (OWG) with high refractive index for sensor applications. A highly sensitive optical sensor device has been developed on the basis of thin-film, composite OWG. The thin-film OWG was deposited onto the surface of a potassium-ion-exchanged (K +) glass OWG by sputtering or spin coating (5–9 mm wide, and with tapers at both ends). By allowing an adiabatic transition of the guided light from the secondary OWG to the thin-film OWG, the electric field of the evanescent wave at the thin film was enhanced. The attenuation of the guided light in the thin film layer was small, and the guided light intensity changed sensitively with the refractive index of the cladding layer. Our experimental results demonstrate that thin-film, composite OWG gas sensors or immunosensors are much more sensitive than sensors based on other technologies. 相似文献
7.
本工作通过修饰TiO 2制备半导体复合膜,提高其光吸收和光电化学性能,以期应用于光生阴极保护。先采用阳极氧化法在Ti表面制备TiO 2纳米管阵列膜,再应用水热处理法在膜表面沉积NiO纳米颗粒,形成具有异质结构纳米管复合膜。利用扫描电子显微镜、X-射线衍射、X-射线光电子能谱、紫外-可见吸收光谱、光致发光谱和光电化学技术对制备的纳米膜进行表征。结果表明,与纯TiO 2纳米管膜比较,NiO/TiO 2纳米管复合膜的光吸收扩展到可见光区。白光照射下,其在0.5 mol·L ?1 KOH和1 mol·L ?1 CH3OH混合液中的光电流密度达到176μA·cm ?2,是纯TiO 2纳米管膜的2倍。复合膜具有良好的光生阴极保护作用,与0.5 mol·L ?1 NaCl溶液中的403不锈钢耦连后,可使其电极电位下降440 mV,在光照2.5 h再转为暗态后,因具有电荷储存能力还可继续提供约15.5 h的阴极保护效应。 相似文献
8.
We reported on the preparation of a thin BaTiO 3-coated layer (2.27 nm) on the surface of TiO 2 and its further application in the dye-sensitized solar cells (DSCs). The as-prepared BaTiO 3–TiO 2 films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscope (TEM). The performances of the DSCs with and without BaTiO 3 coating were analyzed by cyclic voltammograms (CVs), electrochemical impedance spectroscopy (EIS), and current–voltage measurements. It was found that the BaTiO 3–TiO 2 films with about 12 μm thickness increased the dye adsorption, resulting in increased Jsc. In the meantime, the BaTiO 3 modification on the TiO 2 surface is beneficial to the formation of an energy barrier against the electron transfer from TiO 2 to I 3−, providing the increase of Voc due to the increased electron density in the TiO 2 that is caused by the increased electron lifetime. 相似文献
9.
通过水热法在氟掺杂氧化锡(FTO)导电玻璃基底上制备了垂直生长的二氧化钛(TiO 2)纳米棒阵列, 以TiO 2纳米棒阵列为模板采用电化学聚合法, 原位制备了TiO 2-聚三[2-(4-噻吩)苯]胺(PTPAT)纳米核/壳结构的复合薄膜, 相比于纯PTPAT薄膜, TiO 2-PTPAT复合薄膜显示出更好的电致变色(EC)性能. PTPAT薄膜在600 nm波长下的对比度为28%, 在1100 nm波长下的对比度为60%, 其褪色时间为3.86 s, 着色时间为5.52 s; TiO 2- PTPAT复合薄膜在600 nm波长下的对比度为43%, 在1100 nm波长下的对比度为79%, 其褪色时间为3.35 s, 着色时间为4.43 s, 表明核/壳复合结构薄膜的光学对比度和响应时间性能更加优异. 将PTPAT薄膜和TiO 2-PTPAT复合薄膜作为电致变色层组装成固态EC器件, 基于复合薄膜的器件具有更好的循环稳定性和更高的耐受电压. 复合薄膜在保持PTPAT薄膜原有的EC性能的基础上, 由于有序生长的纳米阵列结构的引入增加了薄膜的比表面积, 为电致变色过程中离子的掺杂和脱掺杂提供了更多有序通道, 从而加快了离子扩散速度. TiO 2阵列的引入也改善了聚合物薄膜与透明导电电极之间的界面结合情况, 从而提升了器件的稳定性. 相似文献
10.
Application of atmospheric pressure plasma as an alternative technology for the destruction of toluene is demonstrated in this study. Used TiO 2 colloidal solution was obtained by an improved sol–gel method, and coated on glass beads to prepare decomposition of toluene. The physical property of synthesized TiO 2 catalyst film was analyzed by XRD and SEM spectroscopy. From these results, it was identified that the catalyst film exhibited anatase structure with particle size of about 50–100 nm after calcination at 500 °C for 1 h. The decomposition of toluene in TiO 2/O 2 plasma system was investigated. Amounts of the catalyst and toluene concentration were fixed as 3 wt.% and 1000 ppm, respectively. The analyses for performance of toluene decomposition and intermediates in reaction were done by the in situ method using the mass spectroscopy and gas chromatography. The toluene of 40% was decomposed at pulse voltage of 13 kV in the only O 2 plasma condition without TiO 2 catalyst. Furthermore, the conversion enhanced remarkably in the TiO 2/O 2 plasma system, and it reached 70% at pulse voltage of 13 kV after 120 min. This result was very notable compared with that in photocatalytic system, with below 40% after 120 min reaction. 相似文献
11.
In this work, we describe the characterization of the complex [Fe(tpy-NH 2) 2](PF 6) 2 (tpy-NH 2 = bis[4′-(3-aminophenyl)-2, 2′:6′,2″-terpyridine]. The complex was oxidatively electropolymerized on glassy-carbon electrodes in CH 3CN/0.1 M tetraethylammonium perchlorate (TEAP) to generate polymer films that exhibit reversible oxidative electrochemical behavior in a wide potential range (0.0–1.6 V), as well as high conductivity and stability/durability. In situ spectrocyclic voltammetry of this modified electrode was carried out on a photodiode array spectrophotometer attached to a potentiostat, which provided UV–Vis absorption spectra of the redox species during the potential sweep. We determined charge transport parameters as a function of time and thickness of the modified electrode, and the results showed that poly-[[Fe(tpy-NH 2) 2] 2+] n can be made to exhibit three regimes of charge transport behavior by manipulation of the film thickness and the experimental time-scale. Morphological characterization of the film was provided by atomic force microscopy. 相似文献
12.
针对TiO_2半导体不能有效吸收可见光,光电转换效率较低等问题,可通过对TiO_2半导体进行修饰和改性,制备TiO_2复合材料,提高其光电化学性能。因此,本工作以Ti表面制备的TiO_2纳米管膜为基础,分别应用循环伏安电沉积法和脉冲电沉积法在膜表面先后沉积MoO3和ZnSe颗粒,获得具有级联能带结构的ZnSe/MoO3/TiO_2纳米管复合膜,并将其应用于对403不锈钢(403SS)实施光生阴极保护。相较于纯TiO_2纳米管膜,紫外-可见(UV-Vis)吸收光谱和光致发光(PL)谱测试表明,ZnSe/MoO3/TiO_2复合膜的吸收边红移,在可见光区具有良好的光吸收性能,光生载流子复合得到更有效抑制。光电化学测试表明,白光照射下,处于0.5 mol·L~(-1) KOH溶液中的ZnSe/MoO3/TiO_2复合膜的光电流密度达到了同条件下纯TiO_2膜的2倍,可使与之耦连的浸泡于0.5 mol·L-1 NaCl溶液中的403SS电极电位下降470 mV,显示出良好的光生阴极保护效应。复合膜还具有一定的储能特性,在光照后又转为暗态的22.5 h内仍对403SS具有一定阴极保护作用。 相似文献
13.
The perovskite CaCu 3Ti 4O 12 (CCT) has been obtained after calcination of oxalate precursors at 900–1000 °C in air. Those precursors are prepared using a soft chemistry method, the coprecipitation. The oxalate powders consist of disk-like particles of 2–3 μm diameter and 300–400 nm thickness. By varying the ratio of the initial amounts of metal chlorides, additional phases (CaTiO 3, TiO 2 and CuO) could be obtained besides CCT. The corresponding multiphased ceramics present improved dielectric properties. 相似文献
14.
Titania–zirconia mixed oxides with various ZrO 2 content in TiO 2 (10, 50 and 90 wt.%) were prepared by the sol–gel method. High specific surface areas (77–244 m 2/g) were obtained. Acidity determined by NH 3-TPD and FTIR-pyridine adsorption showed that in mixed oxides the number of acid sites is dramatically increased; it varies from 173 μmol NH 3/g for TiO 2 to 1226–1456 μmol NH 3/g for the mixed oxides. FTIR-pyridine adsorption showed the presence of Lewis sites in the catalysts. Basic sites were identified by FTIR-CO 2 adsorption, suggesting the formation of mixed oxides with acid–basic properties. XRD spectra identified anatase in the TiO 2 rich region, amorphous material in the mixed oxide 50–50 TiO 2–ZrO 2 and tetragonal and monoclinic crystalline phases in the ZrO 2 rich region. Activity in the isopropanol decomposition showed a good correlation between the acid–basic properties and the selectivity to propene, acetone and isopropyl ether. The latter was found as a product which mainly depends of the acid sites density. 相似文献
15.
Zn-doped and La/Zn co-doped TiO 2 nanoparticles were prepared by sol–gel method and utilized as the photocatalysts for the isomerization of norbornadiene to quadricyclane that has significant potential for solar energy storage and high-energy fuel synthesis. For Zn-doped samples, Zn ions do not enter the TiO 2 lattice, but distribute on the particle surface in the form of ZnO crystallites. These crystallites inhibit the agglomeration, growth and anatase-to-rutile phase transformation of TiO 2. The prepared particles contain considerable amount of surface-bound OHs, especially for 1%Zn/TiO 2. A red shift in the optical absorption is observed due to the electron transfer between TiO 2 and ZnO. In the photocatalytic isomerization reaction, Zn-doped TiO 2 exhibits higher activity than homogenous sensitizer like Ethyl Michler's Keton, and 1%Zn/TiO 2 produces the highest yield of quadricyclane. To further enhance the activity, 1%Zn/TiO 2 was co-doped with La. La 2O 3 crystallites also distribute on the surface of TiO 2, similar to the case of ZnO. The particle size is reduced to <7 nm but the surface-bound OHs are decreased to some degree. There is a significant blue shift in the optical absorption with a sharply increased absorbance in the UV region due to the quantum-size effect. 5%La–1%Zn/TiO 2 and 3%La–1%Zn/TiO 2 exhibit higher activity compared with 1%Zn/TiO 2, but higher or lower content of La is detrimental to the reaction. It is concluded that doping Zn can significantly increase the surface-bound OHs, whereas doping La reduces the particle to quantum-size at the expense of surface-bound OHs. A good compromise between the two factors eventually provides a high activity. The isomerization reaction over semiconductors is proposed to proceed through an exciplex (charge-transfer) intermediate. 相似文献
16.
Foam thin liquid films (TLF) and monolayers at the air–water interface formed by DMPC mixed with DMPE-bonded poly (ethylene glycol)s (DMPE-PEG 550, DMPE-PEG 2000 and DMPE-PEG 5000) were obtained. The influence of both (i) PEG chain size (evaluated in terms of Mw) and mushroom-to-brush conformational transition and (ii) of the liposome/micelle ratio in the film-forming dispersions, on the interfacial properties of mixed DMPC/DMPE-PEG films was compared. Foam film studies demonstrated that DMPE-PEG addition to foam TLFs caused (i) delayed kinetics of film thinning and black spot expansion and (ii) film stabilization. At the mushroom-to-brush transition, due to steric repulsion increased DMPE-PEG films thickness reached 25 nm while pure DMPC films were only 8 nm thick Newton black films. It was possible to differentiate DMPE-PEG2000/5000 from DMPE-PEG550 by the ability to change foam TLF formation mechanism, which could be of great importance for “stealth” liposome design. Monolayer studies showed improved formation kinetics and equilibrium surface tension decrease for DMPE-PEG monolayers compared with DMPC pure films. SEM observations revealed “smoothing” and “sealing” of the defects in the solid-supported layer surface by DMPE-PEGs adsorption, which could explain DMPE-PEGs ability to stabilize TLFs and to decrease monolayer surface tension. All effects in monolayers, foam TLFs and solid-supported layers increased with the increase of PEG Mw and DMPE-PEG concentration. However, at the critical DMPE-PEG concentration (where mushroom-to-brush conformational transition occurred) maximal magnitude of the effects was reached, which only slightly changed at further DMPE-PEG content and micelle/liposome ratio increase. 相似文献
17.
Ferrozine (3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine- p, p′-disulfonic acid, monosodium salt hydrate), an iron indicator, and HTPS (8-hydroxyl-1,3,6-pyrenetrisulfonic acid, trisodium salt), a pH indicator, were immobilized in sol–gel derived PDMDAAC-SiO 2 (where PDMDAAC stands for poly(dimethyldiallylammonium chloride), composite thin films via ion-exchange. The two indicators were immobilized in two adjacent sections of the same PDMDAAC-SiO 2 film which was supported on a glass optical substrate. The spectroscopic response of the film to both Fe 2+ and H + in solutions was investigated by attenuated total reflection (ATR) spectrometry at two well-separated wavelengths, 562 nm for Fe 2+ and 460 nm for H +. The Ferrozine/HPTS immobilized PDMDAAC-SiO 2 films had the following characteristics: linear range, 2.5×10 −6–5.0×10 −5 M for Fe 2+, pH 4.1–6.8 for H +; sensitivity, 2.2×10 4 Δ A/M for Fe 2+, 0.583 Δ A/pH for H +. 相似文献
18.
The composite electrode comprising n-type TiO 2 and p-type NiO oxides when sensitized with Ru-dye showed short-circuit photocurrent ( Isc) of 17 mA/cm 2 and open-circuit photovoltage ( Voc) of 730 mV compared to Isc of 12 mA/cm 2 and 700 mV for TiO 2 electrodes. Formation of a n–p junction between TiO 2 and NiO oxide layers contributes to the enhanced photocurrent, photovoltage, fill factor and efficiency. In addition to the junction effect, NiO acts as a barrier for charge recombination leading to higher cell performance. The efficiency of the NiO coated TiO 2 solar cell is 30% more than that of bare TiO 2. The negative shift of the flat-band potential of the NiO coated TiO 2 electrode compared to TiO 2 also could be one of the reasons for higher photovoltage observed for TiO 2/NiO electrode. The highest cell efficiencies were obtained immersing TiO 2 thin films in Ni 2+ solution and converting them to NiO by firing and the optimum NiO coating thickness was found to be only a few angstroms. The energy levels of the excited dye and the band positions of TiO 2 and NiO suggest that the electron transfer from the excited dye to the underlying n-type oxide layer occurs by tunneling through the p-type NiO layer. 相似文献
19.
In this work, the polymeric precursor method was used to prepare low-cost solid-state sensors for pH determination based on iridium oxide as the main pH sensitive material. The iridium content was reduced with addition of TiO 2, forming the binary system IrO x–TiO 2, whose electroanalytical properties were evaluated in comparison with a commercial glass pH electrode. The minimum iridium content which gave suitable results was 30 mol%, and the electrode presented Nernstian and fast response in the pH range from 1 to 13, with no hysteresis effect observed. Besides, the electrode showed high selectivity in the presence of alkali ions as Li +, Na + or K +. The amount of iridium in the prepared electrodes was very small (<0.1 mg), supporting the efficiency of this method on the simple preparation of functional low-cost pH electrodes. 相似文献
20.
Novel sul-containing fluorinated polyimides have been synthesized by the reaction of 2,2′-bis-(trifluoromethyl)-4,4′-diaminodiphenyl sulfide (TFDAS) with 1,4-bis-(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA), 2,2′-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 4,4′-oxydiphthalicanhydride (ODPA) or 3,4,3′,4′-biphenyl-tetracarboxylic acid dianhydride ( s-BPDA). The fluorinated polyimides, prepared by a one-step polycondensation procedure, have good solubility in many solvents, such as N-methyl-2-pyrrolidinone (NMP), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), cyclohexanone, tetrahydrofuran (THF) and m-cresol. The molecular weights ( Mn's) and polydispersities ( Mn/ Mw's) of polyimides were in the range of 1.24 × 10 5 to 3.21 × 10 5 and 1.59–2.20, respectively. The polymers exhibit excellent thermal stabilities, with glass-transition temperatures ( Tg) at 221–275 °C and the 5% weight-loss temperature are above 531 °C. After crosslinking, these polymers show higher thermal stability. The films of polymers have high optical transparency. The novel sul-containing fluorinated polyimides also have low absorption at both 1310 and 1550 nm wavelength windows. Rib-type optical waveguide device was fabricated using the fluorinated polyimides and the near-field mode pattern of the waveguide was demonstrated. 相似文献
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