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1.
Titanium dioxide (TiO2) is one of the best semiconductor photocatalysts with optical band gap of 3.2 eV. The optical band gap and photocatalytic properties could be further tuned by tailoring shape, size, composition, and morphology of the nanostructures. Hydrothermal synthesis methods have been applied to produce well-controlled nanostructured TiO2 materials with different morphologies and improved optoelectronic properties. Among various morphologies, one-dimensional (1D) TiO2 nanostructures are of great importance in the field of energy, environmental, and biomedical because of the directional transmission properties resulting from their 1D geometry. Particularly, TiO2 nanorods (NRs) have gained special attention because of their densely packed structure, quantum confinement effect, high aspect ratio, and large specific surface area that could specially improve the directional charge transmission efficiency. This results in the effective photogenerated charge separation and light absorption, which are really important for potential applications of TiO2-based materials for photocatalytic and other important applications. In this review, hydrothermal syntheses of TiO2 NRs including the formation chemistry and the growth mechanism of NRs under different chemical environments and effects of various synthesis parameters (pH, reaction temperature, reaction time, precursors, solvents etc.) on morphology and optoelectronic properties have been discussed. Recent developments in the hydrothermal synthesis of TiO2 NRs and tailoring of their surface properties through various modification strategies such as defect creation, doping, sensitization, surface coating, and heterojunction formation with various functional nanomaterials (plasmonic, oxide, quantum dots, graphene-based nanomaterials, etc.) have been reported to improve the photocatalytic activities. Furthermore, applications of TiO2 NRs/tailored TiO2 NRs as superior photocatalysts in degradation of organic pollutants and bacterial disinfection have been discussed with emphasis on mechanisms of action and recent advances in the fields. 相似文献
2.
Matiullah Khan Junna Xu Ning Chen Wenbin Cao Asadullah Zahid Usman D. F. Khan 《Research on Chemical Intermediates》2013,39(4):1633-1644
The electronic and optical properties of pure and Ag-doped anatase TiO2 have been calculated by spin-polarized density functional theory. Ag-doped TiO2 with different Ag doping concentrations ranging from 2.08 to 8.33 % was investigated, and the electronic and optical properties evaluated. Substitutional Ag doped at Ti sites introduced Ag 4d states just above the valence-band maximum, which may help in shifting visible-light excited electrons to the conduction band. Our results show that increasing the doping concentration will enhance visible-light absorption up to Ag doping concentration of 6.25 %; however, further increase of the doping concentration leads to a decrease in visible-light absorption. These results indicate the possibility of tailoring the band gap and optical absorption of TiO2 doped with Ag by varying the doping concentration. The enhanced visible-light absorption for Ag-doped TiO2 with doping concentration of 6.25 % may be due to the existence of widely distributed Ag 4d states above the valence-band maximum and the optimal doping concentration. Ag doping shifted the absorption edge of TiO2 towards visible light, consistent with recent experimental results. Our calculation results provide a reasonable explanation for the experimental findings. 相似文献
3.
TiO2- and Ag/TiO2-nanotubes (NTs) were synthesized by hydrothermal methods and microwave-assisted preparation, respectively. Scanning electron microscopy, high resolution transmission electron microscopy, Brunauer-Emmett-Teller particle surface area measurement and X-ray diffraction were used to characterize the nanotubes. Rutile TiO2-NTs with Na2Ti5O11 crystallinity had a length range of 200-400 nm and diameters of 10-20 nm. TiO2- and Ag/TiO2-NTs with a 0.4% deposition of Ag had high surface areas of 270 and 169 m2 g−1, respectively. The evaluation of photocatalytic activity showed that Ag/TiO2-NTs displayed higher photocatalytic activity than pure TiO2-NTs and a 60.91% degradation of Rhodamine-B with 0.8% deposition of Ag species. Also 60% of Rhodamine-6G was physisorbed and 40% chemisorbed on the surface of TiO2-NTs. In addition, the photocatalytic degradations of organochlorine pesticides taking α-hexachlorobenzene (BHC) and dicofol as typical examples, were compared using Ag/TiO2-NTs, and found that their degradations rates were all higher than those obtained from commercial TiO2. 相似文献
4.
Shan Wang Haiou Liang Tong Xu Chunping Li Weiyan Sun 《Journal of Dispersion Science and Technology》2014,35(6):777-782
Ag nanoparticles (Ag NPs) embedded titanium dioxide (TiO2) nanofibers were fabricated by colloidal sol process, electrospinning, and calcination technique. Calcination of the electrospun nanofibers were heat treated at 600°C for 180 minutes in air atmosphere. X-ray diffraction patterns exhibited that the anatase phase and silver coexisted in the resulted Ag NPs/TiO2 nanofibers; transmission electron microscopy demonstrated Ag NPs well spread in the porous microstructure of composite fibers. The prepared nanofibers were utilized as photocatalyst for degradation of methyl orange. The degradation rate of methyl orange dye solution containing Ag/TiO2 composite nanofibers is 99% only after irradiation for 3 hours. It is proposed that these new Ag NPs/TiO2 composite nanofibers will have potential application in water pollution treatment. 相似文献
5.
According to binding energy calculations in a unit cell model of anatase TiO2, the doping limits for Cr, V, W, Mo, Zr, and Nb are predicted to increase in this order. In our experimental test of doping limits, Cr and W are considered in this series of transition metals, since their low doping limits suggest greater difficulty of doping into anatase structure than the others, thereby providing a challenging test for the prediction. Besides, noble metals such as Ag and Pt are selected for doping into TiO2 for comparison. Thus, our investigation includes twofold research activities. One is to prepare metal-doped TiO2 nanopowders of four different kinds, and the other is to determine the doping limit of each resulting powder. For the former, a sonochemical process has been used to produce metal-doped TiO2 nanoparticles. For the latter, we resorted to electron probe microanalysis. In addition, we performed analysis by X-ray diffraction, transmission electron microscopy, and diffuse reflectance spectroscopy, as well as photocatalytic reaction with methylene blue. Thus, the resulting physicochemical properties of our metal-doped nanoparticles are expected to provide a basis for comparison of doping limits among them. 相似文献
6.
Wanda Ziemkowska Dariusz Basiak Patrycja Kurtycz Agnieszka Jastrzębska Andrzej Olszyna Antoni Kunicki 《Chemical Papers》2014,68(7):959-968
Nano-titania doped with noble metals (Au/TiO2, Ag/TiO2, Pd/TiO2) has been synthesized by mild hydrolysis of the mixture of metal salts or complexes and titanium isopropoxide ((iPr-O)4Ti). After thermal decomposition of the obtained precursors, nanomaterials were formed. Morphological characterization of the nanomaterials was provided by scanning electron microscopy (SEM) and stereological analysis, determining the BET specific surface area, and BJH nanoporosity (pore volume, pore size). It has been found that the structure of nanomaterials (size of nanoparticles and agglomerates) depended strongly on the method of the (iPr-O)4Ti hydrolysis. A minor dependence on the kind of solvents and precursors of noble metals was observed. The presence of doping metal nanoparticles was confirmed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). Nanomaterial phases were identified by X-ray diffraction (XRD). According to the XRD patterns, Ag/TiO2 and Pd/TiO2 products with doping metals in their oxidized form contain Ag-Ti and Pd-Ti phases. Peaks of the metal oxides Ag2O and PdO are absent in the XRD patterns. The average size of TiO2 nanoparticles is situated in the region of 20–60 nm, whereas metals are present as about 10–15 nm sized particles and fine nanoparticles. 相似文献
7.
《Journal of Saudi Chemical Society》2014,18(4):291-298
This research work presents the efficiency of the TiO2 and Ag–TiO2 thin films prepared by the sol–gel method and coated onto the surface of 304 stainless steel sheets used in the photocatalytic nitrate reduction processes. The Ag–TiO2 thin films had the weight by weight (w/w) ratio of Ag+/TiO2 of 0.1% as Ag atom. The XRD results showed that the crystalline phase structure of TiO2 on the Ag–TiO2 thin films was anatase. The optical band gaps of the TiO2 and 0.1% Ag–TiO2 thin films were respectively 3.27 and 2.70 eV, while the surface of the prepared catalysts was hydrophobic with the respective average water contact angles of 94.8° and 118.5° for the TiO2 and 0.1% Ag–TiO2 thin films. The net efficiencies of photocatalytic nitrate reduction of TiO2 and 0.1% Ag–TiO2 were 41.4% and 70.0%, respectively. The loading of Ag only influenced the nitrate removal efficiency without affecting the stoichiometric ratio of formate to nitrate. The net stoichiometric ratio of formate to nitrate of all experiments was 2.8:1.0, which is close to the stoichiometric ratio of 2.5:1.0 of the nitrate reduction to nitrite and then to nitrogen gas. 相似文献
8.
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Ag2O/TiO2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TiO2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TiO2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Ag2O。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Ag2O通过光生电子转化为Ag形成Ag/TiO2,进一步提高光催化制氢活性。 相似文献
9.
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。 相似文献
10.
Composite nano‐TiO2 with doping Fe3+ and Ag was prepared, and further modified by 3‐methacryloxypropyltrimethoxysilane. They were characterized by Zetasizer Nano ZS Particle and Zeta Potential Analyzer, X‐ray diffraction, UV–Vis spectrophotometer, FT–IR spectra, and transmission electron microscopy. The modified composite nano‐TiO2 was applied to prepare multifunctional fluorocarbon coatings (FCC). Antibacterial activity of multifunctional FCC containing modified composite nano‐TiO2 was investigated. Its photocatalytic antibacterial activity reached 92%. The influence of doping ingredients, amount of composite nano‐TiO2, different light houses, or surface modification was discussed. The surface of FCC cannot be easily smirched by oiliness, dust or water because of hydrophobic fluorosilicone emulsion. It would be an available modern interior building coating for its remarkable photocatalytic antibacterial property as well as self‐cleaning function. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
11.
M. M. Rahman Jia-Zhao Wang David Wexler Yu-Yuan Zhang Xin-Jun Li Shu-Lei Chou Hua-Kun Liu 《Journal of Solid State Electrochemistry》2010,14(4):571-578
Anatase TiO2 nanoribbons/nanotubes (TiO2-NRTs) have been synthesised successfully via a reflux method followed by drying in a vacuum oven, and then, silver-coated
TiO2 NRTs (Ag/TiO2-NRTs) were prepared by coating silver particles onto the TiO2-NRTs surface by the traditional silver mirror reaction. The physical properties of the synthesised products were examined
in detail using X-ray diffraction, field emission gun scanning electron microscopy, energy-dispersive X-ray spectroscopy,
and transmission electron microscopy, respectively. The results indicated that the Ag nanoparticles were uniformly deposited
on the surface of the TiO2 nanoribbons/nanotubes. The electrochemical properties were investigated by a variety of techniques. The rate capability and
cycle durability for the Ag/TiO2-NRTs were improved compared with TiO2-NRTs. It is speculated that the Ag-coated TiO2 nanoribbons/nanotubes are an effective anode candidate for lithium ion batteries. 相似文献
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14.
Agata Roguska Andrzej KudelskiMarcin Pisarek Magdalena OparaMaria Janik-Czachor 《Vibrational Spectroscopy》2011,55(1):38-43
Tubular arrays of TiO2 nanotubes (ranging in diameter from 40 to 110 nm) on a Ti substrate were used as a support for Ag deposits obtained by the sputter deposition technique where the amount of Ag varied from 0.01 to 0.2 mg Ag/cm2. Those composite supports were intended for surface-enhanced Raman scattering (SERS) investigations. Composite samples of Ag/TiO2 nanotube/Ti were studied with the aid of scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) to reveal their characteristic morphological and chemical features. Raman spectra of pyridine (as a probe molecule) were measured at different cathodic potentials ranging from −0.2 down to −1.2 V after the pyridine had been adsorbed on the Ag-covered TiO2 nanotube/Ti substrates. In addition, SERS spectra on a bulk standard activated Ag substrate were also measured.The SERS activity of the composite samples was strongly dependent on the amount of Ag deposit. At and above 0.06 mg Ag/cm2, the SERS signal was even higher than that for the Ag reference substrate. The high activity of the composites is mainly a result of their specific morphology. The high SERS sensitivity on the surface morphology made it possible to monitor very small temporal changes in the Ag clusters. This rearrangement was not detectable with microscopic (SEM) or microanalytical (AES) methods. 相似文献
15.
A series of Ag‐enhanced TiO2–x/C composites (Ag/TiO2–x/C composites) with metal‐organic frameworks (MOFs) as precursors were prepared, and their photocatalytic activities were evaluated by the UV‐light driven photodegradation behaviors of methyl blue (MB). The as‐obtained samples were characterized by several techniques such as SEM, XRD, N2‐adsorption, XPS, UV/Vis spectrophotometry and UV/Vis diffuse‐reflectance spectra. The best photocatalytic performance was achieved in Ag/TiO2–x/C composite pyrolyzed at 1000 °C (ATC‐P10) due to rapid capture of electrons caused by silver doping, higher density of TiO2–x lattice oxygen vacancies for better trapping of electrons, and high surface area due to reduction and evaporation of metallic Zn. No obvious deactivation was observed after 10 cycles of UV‐light degradation of MB under the same experimental conditions. This report reveals a new approach to prepare stable and highly efficient UV‐light‐driven photocatalysts for organic pollutants in water. 相似文献
16.
Ming-Yue Ding De-Shui Meng Yan-Hong Tang Cheng-Bin Liu Sheng-Lian Luo 《Chemical Papers》2015,69(11):1411-1420
One-dimensional (1D) Ag/AgBr/TiO2 nanofibres (NFs) have been successfully fabricated by the one-pot electrospinning method. In comparison with bare TiO2 NFs and Ag/AgBr/PVP (polyvinylpyrrolidone) NFs, the 1D Ag/AgBr/TiO2 NFs photocatalyst exhibits much higher photocatalytic activity in the degradation of a commonly used dye, methylene blue (MB), under visible light. The photocatalytic removal efficiency of MB over Ag/AgBr/TiO2 NFs achieves almost 100 % in 20 min. The photocatalytic reaction follows the first-order kinetics and the rate constant (k) for the degradation of MB by Ag/AgBr/TiO2 NFs is 5.2 times and 6.6 times that of Ag/AgBr/PVP NFs and TiO2 NFs, respectively. The enhanced photocatalytic activity is ascribed to the stronger visible light absorption, more effective separation of photogenerated electron-hole pairs, and faster charge transfer in the long nanofibrous structure. The Ag/AgBr/TiO2 NFs maintain a highly stable photocatalytic activity due to its good structural stability and the self-stability system of Ag/AgBr. The mechanisms for photocatalysis associated with Ag/AgBr/TiO2 NFs are proposed. The degradation of MB in the presence of scavengers reveals that h+ and ?O 2 ? significantly contribute to the degradation of MB. 相似文献
17.
L. Zhang C. H. Ma J. Wang S. G. Li Y. Li 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2014,88(12):2271-2279
In this study, Ag deposited TiO2 (Ag/TiO2) composites were prepared by three different methods (Ultraviolet Irradiation Deposition (UID), Vitamin C Reduction (VCR) and Sodium Borohydride Reduction (SBR)) for the visible-light photocatalytic degradation of organic dyes in magnetic field. And then the prepared Ag deposited TiO2 (Ag/TiO2) composites were characterized physically by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The visible-light photocatalytic activities of these three kinds of Ag deposited TiO2 (Ag/TiO2) composites were examined and compared through the degradation of several organic dyes under visible-light irradiation in magnetic field. In addition, some influence factors such as visible-light irradiation time, organic dye concentration, revolution speed, magnetic field intensity and organic dye kind on the visible-light photocatalytic activity of Ag deposited TiO2 (Ag/TiO2) composite were reviewed. The research results showed that the presence of magnetic field significantly enhanced the visible-light photocatalytic activity of Ag deposited TiO2 (Ag/TiO2) composites and then contributed to the degradation of organic dyes. 相似文献
18.
采用脉冲激光沉积术(PLD)同质外延生长了表面原子级平整的6%(原子比)Cr 掺杂的金红石相TiO2(110)单晶薄膜, 采用扫描隧道显微镜(STM)、扫描隧道谱(STS)、X 射线光电子能谱(XPS)和紫外光电子能谱(UPS)对其进行了表征. 结果表明: Cr 掺杂对TiO2(110)-(1×1)表面的形貌没有明显影响, 但是提高了掺杂薄膜在负偏压的导电性; Cr与晶格O键合而呈现+3价态, 由此在TiO2的价带顶上方~0.4 eV处引入杂质能级. 紫外-可见光吸收谱显示薄膜的光吸收能力被扩展到~650 nm, 处于可见光范围. 借助STM以单个甲醇分子的光解反应检测了薄膜的光催化活性. 仅观察到紫外光照射下甲醇分子的脱氢反应, 在可见光照射下(λ>430 nm)甲醇分子没有发生反应, 表明单独的Cr掺杂可能不足以提高TiO2在可见光下的催化活性. 相似文献
19.
《Surface and interface analysis : SIA》2018,50(2):171-179
TiO2 thin films with various Mo concentrations have been deposited on glass and n‐type silicon (100) substrates by this radio‐frequency (RF) reactive magnetron sputtering at 400°C substrate temperature. The crystal structure, surface morphology, composition, and elemental oxidation states of the films have been analyzed by using X‐ray diffraction, field emission scanning electron microscopy, atomic force microscopy, and X‐ray photoelectron spectroscopy, respectively. Ultraviolet‐visible spectroscopy has been used to investigate the degradation, transmittance, and absorption properties of doped and undoped TiO2 films. The photocatalytic degradation activity of the films was evaluated by using methylene blue under a light intensity of 100 mW cm−2. The X‐ray diffraction patterns show the presence of anatase phase of TiO2 in the developed films. X‐ray photoelectron spectroscopy studies have confirmed that Mo is present only as Mo6+ ions in all films. The Mo/TiO2 band gap decreases from ~3.3 to 3.1 eV with increasing Mo dopant concentrations. Dye degradation of ~60% is observed in Mo/TiO2 samples, which is much higher than that of pure TiO2. 相似文献
20.
In this paper, a novel TiO2 nanosheets assembled double‐wall hollow sphere (DHS)has been prepared successfully via hydrothermal treatment of SiO2@TiO2 with the assistant of CTAB.The prepared samples are characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron spin resonance (ESR), X‐ray diffraction (XRD) and X‐ray photoelectron spectra (XPS), etc.Results show that redeposited silica species play a key role in the formation of the double‐wall structure. The as‐synthesized DHS nanostructure exhibits a large surface area (417.6 m2 g‐1) and excellent mechanical strength. Furthermore, after decoration of Ag and calcination treatment, the double‐shelled TiO2/Ag heterostructures show an enhanced photocatalytic performance in the degradation of RhB under UV or visible light irradiations for the following reasons: the surface plasmon resonance effect of Ag, strong interaction between Ag and TiO2 nanosheets, large surface area, excellent adsorption capacityand unique double‐wall structure. On the basis of the experimental results, a possible mechanism for pollutantdegradation under visual light irradiation has been proposed. 相似文献