Fabrication of single-crystalline Co3O4 nanorods via a low-temperature solvothermal process

Co₃O₄ nanorods with average diameter and length of ∼ 50 nm and 1 μm were successfully prepared via a simple surfactant-assisted solvothermal method at 160 °C for 12 h. The formation of Co₃O₄ nanorods is attributed to alcoholysis of cobalt ions dispersed in ethanol in the presence of a capping agent—CTAB. The composition and purity of the sample were characterized by X-ray diffraction (XRD). Transmission and scanning electron microscopy images show that the particles are homogenous and have the shape of rods. The mechanism of forming Co₃O₄ nanorods is also discussed.     

Nonaqueous sol-gel synthesis and growth mechanism of single crystalline TiO2 nanorods with high photocatalytic activity

In this paper, we report on a nonaqueous synthesis of single crystalline anatase TiO₂ nanorods by reaction between TiCl₄ and benzyl alcohol at a low temperature of 80 °C. The resulting samples were characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, nitrogen adsorption, X-ray photoelectron spectrometry and UV-vis diffuse reflectance spectroscopy. We proposed that the TiO₂ nanorods were formed through an oriented attachment mechanism. More importantly, these single crystalline anatase TiO₂ nanorods exhibited significantly higher photocatalytic activities than commercial photocatalyst P25. This study provides an environmentally friendly and economic approach to produce highly active TiO₂ photocatalyst.     

Investigation on solar photocatalytic activity of TiO2 loaded composite: TiO2/Eggshell, TiO2/Clamshell and TiO2/CaCO3

The TiO₂/Eggshell, TiO₂/Clamshell and TiO₂/CaCO₃ loaded composites were prepared by sol-gel method and characterized by XRD and SEM. Their photocatalytic activities were measured through the degradation of Acid Red B under solar light irradiation. The influences of TiO₂ loaded content, heat-treated temperature and time on the photocatalytic activities were reviewed. The effects of irradiation time and dye initial concentration on the photocatalytic degradation were also investigated. The results showed that the photocatalytic activity can be greatly enhanced by appropriate TiO₂ loaded content.     

Impact of reaction temperature,stirring and cosolvent on the solvothermal synthesis of anatase TiO2 and TiO2/titanate hybrid nanostructures: Elucidating the growth mechanism

One-dimensional anatase TiO₂ and hybrid TiO₂/titanate nanostructures are synthesized by a simple low temperature solvothermal route followed by the Na⁺/H⁺ ion-exchange and final calcination process. We investigated the impact of reaction temperature, stirring conditions and cosolvent on the morphologies of the as-prepared nanostructures. Nanotubes and nanorods are formed in alkaline solution, while nanorods/nanowires and nanoporous nanoribbons are formed in alkaline water–ethanol and alkaline water–ethylene glycol mixed solvents, respectively. X-ray diffraction, Raman scattering and high-resolution transmission electron microscopy studies are employed to identify the structure and phase composition. The formation of different morphologies of the as-synthesized nanostructures is investigated by field emission scanning electron microscopy and transmission electron microscopy. The growth mechanism and reaction process of the as-prepared nanostructures are explained based on the experimental observations. The photoluminescence, optical absorption and the tuning of band gap of the prepared samples are also studied. This work will be valuable for understanding the growth mechanism of various nanostructured TiO₂ and to explore the commercial applications of nanoporous nanoribbons of TiO₂.     

A low-temperature process to synthesize rutile phase TiO2 and mixed phase TiO2 composites

This works employed K₂Ti₄O₉, a novel Ti source, to prepare TiO₂ powders. By a “low-temperature dissolution-reprecipitation process” (LTDRP), rutile phase TiO₂ was successfully synthesized after reacting at 50 °C for 48 h. The obtained sample showed a specific surface area about 45 m²/g, and excellent activity in photo-destruction of NO_x gas. The coupling of rutile phase TiO₂ with commercial anatase TiO₂ showed significant effect in further enhancing the photocatalytic activity.     

Structural engineering of thin films of vertically aligned TiO2 nanorods

Self-assembled and vertically aligned rutile titania nanorods and thin films with a preferred [002] axial orientation were grown on substrates of fluorine-doped tin dioxide, using a hydrothermal method. Each nanorod was made of a bundle of densely packed and ultra fine nano-fibers growing along the [002] direction. The results show that ethanol substitution of water as solvent is highly effective in promoting the one-dimensional growth of the rutile nanorods and increasing their packing density in the thin films, which offers a simple-but-effectual leverage to monitor the nanorod structures for varied applications.     

Fabrication of photocatalytic heat-mirror with TiO2/TiN/TiO2 stacked layers

The photocatalytic heat-mirror based on TiO₂/TiN/TiO₂ stacked layers is prepared by reactive magnetron sputtering on quartz substrates under substrate-heating condition. We find that the addition of a thin Ti interlayer between the TiN and the outer TiO₂ layers drastically improves the heat-insulating performance. This type of stacked layer also exhibits higher photocatalytic activity for decomposition of acetaldehyde gas, compared with a TiO₂ single layer. The optical property of the TiN in TiO₂/TiN/TiO₂ stacked layers is the key not only revealing excellent heat-insulating effect but also improving the photocatalytic performance of the outer TiO₂ layers in the stacked layers.     

Novel construction of CdS-encapsulated TiO2 nano test tubes corked with ZnO nanorods

A novel TiO₂ nanotube array/CdS nanoparticle/ZnO nanorod (TiO₂ NT/CdS/ZnO NR) photocatalyst was constructed by chemical assembling CdS into the TiO₂ NTs, and then laying ZnO NRs on the surface. The SEM results showed that the TiO₂ NTs looked like many “nano test tubes” and the ZnO NRs served as the corks to seal the nozzle. This photocatalyst exhibited a wide absorption range (200-535 nm) in both ultraviolet and visible regions (UV-vis region), and maintained very high photoelectrocatalytic (PEC) activities. The maximum photoelectric conversion efficiencies (η) of TiO₂ NT/CdS/ZnO NRs are 31.8 and 5.98% under UV light (365 nm) and visible light (420-800 nm), respectively.     

Several shape-controlled TiO2/TiB2 hybrid materials with a combined growth mechanism

Several kinds of TiO₂/TiB₂ hybrid materials with different morphologies, including hollow bipyramid structure with truncations, pineapple structure, urchin structure and nanowall structure, have been successfully synthesized by a facile solvothermal approach in the aqueous solution of ethylenediamine. The effect of ethylene ediamine on the shape change of the final products was investigated in detail. With the increase of ethylenediamine, anatase TiO₂ on the TiB₂ core is gradually evolved from nanoparticles, nanorods to nanosheets. Based on attachment theory, Oswald ripening phenomenon, chelating effect and Kirkendall effect, a possible formation mechanism for such TiO₂/TiB₂ hybrid materials was proposed to explain the morphology evolution.     

Fabrication of polycrystalline TiO2 nanopatterns by TiO2 sol base imprint lithography

This paper reports a process for fabricating TiO₂ nano-patterns using nanoimprint lithography and a sol–gel method. An ethanol-based TiO₂ sol was prepared using tetrabutylorthotitanate as a precursor and used as an imprint resin. A replicated polydimethylsiloxane (PDMS) mold was used as an imprint stamp. During the imprinting process at 5 atm and 200 °C for 1 h, the TiO₂ sol changed to a TiO₂ gel by absorbing the solvent into the PDMS mold. After imprinting, a TiO₂ gel pattern was formed on an oxidized Si wafer. After subsequent annealing, it confirmed that patterns of the master template were transferred to TiO₂ patterns by Scanning Electron Microscopy. Furthermore, Transmission Electron Microscopy and X-Ray Diffraction showed that the TiO₂ gel patterns had been converted to an inorganic polycrystalline TiO₂ pattern.     

TiO2-VOx纳米复合膜制备及耐腐蚀性研究

采用溶胶-凝胶法和浸渍提拉技术在316L不锈钢(316Lss)表面构筑纳米TiO2,TiO2/TiO2-VOx/TiO2复合膜,应用AFM和XRD表征膜的形貌及结构,并用光、电化学方法测试复合膜在0.5 mol/L NaCl溶液中暗态或紫外照射下的耐腐蚀性能,结果表明TiO2/TiO2-VOx/TiO2复合膜具有双重保护功能,即在紫外光照下可以起到光生阴极保护的作用,特别是当停止光照后,光生电位仍可维持在较低的电位长达6h以上;作为覆盖层纳米复合膜又可作为良好的阻挡层显著提高金属的耐腐蚀性.     

A simple L-cystine-assisted solvothermal approach to Cu3SbS3 nanorods

A simple L-cystine-assisted synthetic route has been successfully developed to prepare Cu₃SbS₃ nanorods under solvothermal conditions. In this synthetic system, we used CuCl₂ as the copper source, SbCl₃ as the antimony source, and L-cystine as both sulfur source and complexing reagent. The obtained Cu₃SbS₃ nanorods were characterized by XRD, XPS, FESEM and TEM (HRTEM). The results showed that the Cu₃SbS₃ nanorods were 100-150 nm in width and several micrometers in length. A possible formation mechanism for Cu₃SbS₃ nanorods was also discussed. The proposed solvothermal method using L-cystine as the sulfur source provides an alternative approach to prepare other ternary semiconductor nanomaterials.     

Single crystal TiO2 nanorods: Large-scale synthesis and field emission

A facile growth procedure of low-pressure chemical vapor deposition has been developed to synthesize single crystal TiO₂ nanorods on Ni-coated Ti substrate. The results indicate that the as-prepared nanorods are high purity single crystal with a [110] preferential orientation. Using directly the nanorods as emitters, their field emission (FE) properties have been investigated. The turn-on field of the nanorods decreases from 3.96 V/μm to 2.98, and 2.16 V/μm as the growth temperature increases from 700 °C to 750, and 800 °C, respectively. In addition, the nanorods show good FE stability during 480 min. Such behavior is mainly related to the morphology of nanorods, which depends on the growth temperature. Also, the growth mechanisms of the nanorods are analyzed in detail based on the experimental results.     

Formation of hydroxyapatite nanorods and anatase TiO2 on CaTiO3 powder using hydrothermal treatment

Hydroxyapatite (HAp) nanorods and anatase TiO₂ (ATO) were fabricated on the surface of CaTiO₃ (CTO) by hydrothermally treating a CTO powder with a β-glycerophosphoric acid disodium salt pentahydrate (β-GP)-containing solution. The aspects of HAp and ATO formation were examined by changing the pH of the hydrothermal solutions to 5, 7, 9, 11 and 13. There were no products formed on the CTO powder by hydrothermal treatment in strong alkaline environments of pH 13. HAp nanorods and ATO were observed on the CTO surface at pH 11-7. Their contents increased with decreasing pH of the hydrothermal solution. In an acidic solution (pH 5), the amount of CTO decreased drastically due to dissolution with the concomitant formation of tricalcium phosphate.     

Enhanced photoelectrocatalytic activity in TiO2 nanotube arrays modified with TiO2 nanoparticles

The use of TiO₂ nanotube arrays fabricated by anode oxidation of titanium sheets as a photoelectrocatalyst is limited by low surface activity owing to passive crystallization post-treatment. We report here on a vacuum assisted filling route for modifying TiO₂ nanotube arrays using high-activity anatase TiO₂ nanoparticles as a filling. Photoelectrocatalytic degradation experiments show that a nearly 4-fold activity enhancement in photoelectrocatalysis is achieved and good photoelectrocatalytic stability is kept after the nanotube arrays are filled with the high-activity TiO₂ nanoparticles. The remarkable enhancement in photoelectrocatalysis is ascribed to the key modification of the TiO₂ nanotube arrays using the high-activity TiO₂ nanoparticles. Our findings provide an insight into designing excellent photoelectrocatalysts by filling TNAs with available high-activity TiO₂ nanoparticles.     

Natural and persistent superhydrophilicity of SiO2/TiO2 and TiO2/SiO2 bi-layer films

Sol-gel SiO₂/TiO₂ and TiO₂/SiO₂ bi-layer films have been deposited from a polymeric SiO₂ solution and either a polymeric TiO₂ mother solution (MS) or a derived TiO₂ crystalline suspension (CS). The chemical and structural properties of MS and CS bi-layer films heat-treated at 500 °C have been investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscospy. Water contact angle measurements show that MS SiO₂/TiO₂ and CS TiO₂/SiO₂ bi-layer films exhibit a natural superhydrophilicity, but cannot maintain a zero contact angle for a long time over film aging. In contrast, CS SiO₂/TiO₂ bi-layer films exhibit a natural, persistent, and regenerable superhydrophilicity without the need of UV light. Superhydrophilic properties of bi-layer films are discussed with respect to the nature of the TiO₂ single-layer component and arrangement of the bi-layer structure, i.e. TiO₂ underlayer or overlayer.     

Synthesis of CdS nanorods by reacting CdCl2 nanorods with H2S at room temperature

We report the synthesis of CdS nanorods by reacting CdCl₂ nanorods with H₂S at room temperature. The preparation method was based on CdCl₂ nanorods employed as chemical template. The length and the diameter of the obtained CdS nanorods are about tens micron and 120−300 nm, respectively. The phase and the crystallographic structure of the products were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The composition of the products was investigated by X-ray photoelectron spectroscopy (XPS).     

Morphology controllable synthesis of TiO2 by a facile hydrothermal process

Titanium dioxide nanoparticles were prepared via a facile hydrothermal approach with titanium tetrabutoxide as a precursor under strongly acidic condition. The transmission electron microscopy results showed that novel flower-like, leaf-like, and rod-like TiO₂ nanoscale materials could be easily obtained by tailoring the concentration of the precursor and the reaction temperature. And the analysis from X-ray diffraction revealed that all the as-prepared products under different experimental conditions possessed a mixed crystal phase of anatase and rutile. The reasons for the phase formation were discussed. Larger proportion of rutile phase should be ascribed to the strongly acidic conditions. The growth mechanisms of TiO₂ nanostructures with various morphologies were also proposed.     

Hydrophilicity of anatase TiO2/Cr-doped TiO2 thin films with different band gaps

Based on the concept that the electron-hole separation effect caused by a different band-gap structure would improve its hydrophilicity, anatase-TiO₂/Cr-doped TiO₂ thin films were synthesized by DC magnetron sputtering. The optical band gaps of TiO₂ thin films decreased from 3.23 to 2.95 eV with increasing Cr-doping content. Multilayer TiO₂ thin films with different band gaps exhibited a superhydrophilicity under UV illumination. In particular, in anatase TiO₂ (3.23 eV)/4.8% Cr-doped TiO₂ (2.95 eV), the hydrophilicity, which indicated a contact angle of less than 20°, lasted for 48 h in the dark after UV illumination was discontinued. This outstanding result has rarely been reported for TiO₂ thin films, which confirmed that the prominent superhydrophilicity of anatase TiO₂/Cr-doped TiO₂/glass could be attributed to the retardation of electron-hole recombination caused by the band-gap difference.     

Hydrothermal growth of ferromagnetic Fe-doped TiO2 films

Polycrystalline Fe-doped TiO₂ anatase films were deposited on (001) oriented SrTiO₃ single crystal substrates at temperatures less than 200 °C from acidic aqueous solutions of titanyl sulfate and iron (III) nitrate. Epitaxial anatase TiO₂ films were obtained when the films were annealed in air at 900 °C. Room-temperature ferromagnetic Fe-doped TiO₂ thin films were obtained after repeated deposition and annealing steps. The observed saturation magnetization (>0.28μ_B/Fe) could not be attributed to the presence of secondary phase magnetic iron oxides or iron clusters.