离子液中介孔TiO2的制备及其形成机理研究

首次以不同咪唑基离子液为结构导向剂，通过水热合成制备出介孔TiO2分子筛。考察了合成条件对产物结构的影响，结果表明，离子液用量、离子液类型、晶化温度、晶化时间等因素对TiO2介孔分子筛的形成和孔道结构均有影响，其中晶化温度及离子液类型的影响最为明显，在较低晶化温度时（100℃）产物孔径分布范围宽，但仍为介孔结构，当温度升高到180℃时，孔径变大并开始失去介孔特征，机理为晶化温度会影响离子液与无机物的相互作用速度，高温时TiO2结晶度也会迅速提高导致失去介孔结构，最佳晶化温度为120℃；咪唑基离子液其碳链长度不同，使用短链离子液时产物无介孔结构，当使用长链离子液时产物孔道结构良好，作为结构导向剂其碳链长度会决定产物孔道生长趋势和长度，最佳离子液类型为[C16MIM]Br．X射线衍射谱（XRD）表明产物为锐钛矿型介孔TiO2；透射电镜（TEM）观察表明产物具有规整的孔道结构（3～4nm），与低温氮吸附法分析结果一致；激光粒度分析表明产物粒度较小（20～40nm）并且分布范围窄。     

The glass transition and thermodynamics of liquid and amorphous TiO(2) nanoparticles

The glass transition and thermodynamics of spherical liquid TiO(2) nanoparticles, with different sizes ranging from 2 to 5?nm, have been studied in a model under non-periodic boundary conditions. We use the pairwise interatomic potentials proposed by Matsui and Akaogi. Models have been obtained by cooling from the melt via molecular dynamics (MD) simulation. The structural properties of liquid nanoparticles at 3500?K have been analyzed in detail through the partial radial distribution functions (PRDFs), coordination number distributions, bond-angle distributions and interatomic distances. Moreover, we also show the radial density profile in nanoparticles. Calculations show that size effects on the structure of a model are significant and that liquid TiO(2) nanoparticles have a distorted pentahedral network structure with the mean coordination numbers Z(Ti-O)≈5.0 and Z(O-Ti)≈2.5, while amorphous TiO(2) nanoparticles have an octahedral network structure. The temperature dependence of the surface structure and surface energy of the nanoparticles has been obtained and is presented. In addition, the size dependence of the glass transition temperature and the temperature dependence of the diffusion constant of atomic species have been found and are discussed.     

Synthesis and characterization of anatase and rutile TiO2 nanorods by template-assisted method

Well-aligned anatase and rutile TiO₂ nanorods and nanotubes with a diameter of about 80–130 nm have successfully been fabricated via sol-gel template method. The prepared samples were characterized by using thermogravimetric (TG) and differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The XRD results indicated that the TiO₂ nanorods were crystallized in the anatase and rutile phases, after annealing at 400–800 °C for different periods of time from 0.2 to 10 h.     

Synthesis of mesoporous anatase TiO2 nanotubes by a hydrothermal treatment and their use in solid-state dye-sensitized solar cells

Mesoporous anatase TiO2 nanotubes (NTs) with the diameter of about 7 12 nm and the length of several hundred nanometers were synthesized by a hydrothermal method on commercial TiO2 particles in NaOH followed by HCI washing. The samples were characterized by X-ray diffraction (XRD), transmitting electron microscopy (TEM), and Brunauer-Emmet-Teller (BET) measurements. The hydrothermal treatment temperature at 130 degrees C was shown to affect not only the extent of particle-to-sheet conversion, and thus the resulting structures of the NTs, but also the anatase-to-rutile transformation. The surface area of the NTs was 200 m2g(-1). This value was much higher in comparison to TiO2 nanoparticles of 50 m2g(-1). It was also found that the NT photoelectrodes had a pronounced impact on the performance of solar cells as compared to nanoparticle ones. This was probably due to lead to a significantly higher specific dye loading and, for certain hydrothermal treatments, resulting in a doubling of the solar cell efficiency (in our case from 2.84% to 4.03% of AM 1.5 conditions).     

The controlled synthesis of stable gold nanoparticles in quaternary ammonium ionic liquids by simple heating

Stable gold nanoparticle (AuNP) colloids were synthesized in a class of quaternary ammonium-based room-temperature ionic liquids (QAILs), [Me(3)NC(2)H(4)OH](+)[Zn(n)Cl(2n + 1)](-) (n = 1 or 2), by heating in air at 135-145?°C. The QAIL was employed as a solvent, a reducing agent, and as a stabilizer. The size of the QAIL-AuNPs can be varied between 20 and 40 nm by changing the reaction temperature. A symproportionation reaction was employed to further decrease the size of the AuNPs by the addition of Au(3+) ions. The surface covering of QAIL on the AuNPs had a significant impact on their surface plasmon resonance (SPR), which was red-shifted. The AuNPs synthesized by this simple and environmentally friendly reaction can be realized in several minutes and also exhibit high stability and good reproducibility, providing a new facile approach to metal nanoparticle preparation.     

CO2-facilitated transport performance of poly(ionic liquids) in supported liquid membranes

Six types of PILs were designed and synthesized by radical polymerization reaction and ion exchange reaction and the ¹H NMR analysis and TG-MS analysis proved the successful procedure and their CO₂ permeation properties were evaluated. 1-butyl 3-methylimidazole double trifluoromethane sulfonate ([bmim][Tf₂N])-based facilitated transport membrane, with 10 wt% poly([ViEtIm] Tf₂N), showed an excellent CO₂ permeability of 920 Barrer, similar to that of the others investigated. PILs were distributed in the SILM using the “like dissolves like” theory to investigate the gas permeation separation performance before and after doping of the PILs in SILM. Owing to the reversible interaction between the CO₂ molecules and electropositive PIL chains, this supported ionic liquid membrane selectively transfer CO₂ more rapidly. The polymer chains play the role of mobile CO₂ carrier in the SLM, and introduce facilitated transport mechanism. This concept may provide a means for fabricating a highly permeable and selective membrane to break through Robeson’s upper bound.     

Self-organized TiO2 nanotube arrays: synthesis by anodization in an ionic liquid and assessment of photocatalytic properties

Self-organized TiO(2) nanotube (NT) arrays were produced by anodization in ethylene glycol (EG) electrolytes containing 1-n-butyl-3-methyl-imidazolium tetrafluoroborate (BMI.BF(4)) ionic liquid and water. The morphology of the as-formed NTs was considerably affected by changing the anodization time, voltage, and water and ionic liquid electrolyte concentrations. In general, a nanoporous layer was formed on the top surface of the TiO(2) NTs, except for anodization at 100 V with 1 vol % of BMI.BF(4), where the NT's mouth was revealed. The length and bottom diameter of the NTs as well as the pore diameter of the top layer showed a linear relationship with increased anodization voltage. These TiO(2) NTs were tested as photocatalysts for methyl orange photodegradation and hydrogen evolution from water/methanol solutions by UV light irradiation. The results show that the TiO(2) NTs obtained by anodization in EG/H(2)O/BMI.BF(4) electrolytes are active and efficient for both applications.     

Unveiling the controversial mechanism of reversible Na storage in TiO2 nanotube arrays: Amorphous versus anatase TiO2

Due to their inherent safety,low cost,and structural stability,TiO2 nanostructures represent a suitable choice as anode materials in sodium-ion batteries.In the recent years,various hypotheses have been proposed regarding the actual mechanism of the reversible insertion of sodium ions in the TiO2 structure,and previous reports are often controversial in this respect.Interestingly,when tested as binder-and conducting additive-free electrodes in laboratory-scale sodium cells,amorphous and crystalline (anatase) TiO2 nanotubular arrays obtained by simple anodic oxidation exhibit peculiar and intrinsically different electrochemical responses.In particular,after the initial electrochemical activation,anatase TiO2 shows excellent rate capability and very stable long-term cycling performance with larger specific capacities,and thus a clearly superior response compared with the amorphous counterpart.To obtain deeper insight,the present materials are thoroughly characterized by scanning electron microscopy and ex situ X-ray diffraction,and the insertion of sodium ions in the TiO2 bulk phases is systematically modeled by density functional theory calculations.The present results may contribute to the development of more systematic screening approaches to identify suitable active materials for highly efficient sodium-based energy storage systems.     

Synthesis and characterization of highly dispersed TiO2 nanocrystal colloids by microwave-assisted hydrothermal method

Anatase TiO₂ nanocrystal colloids with high dispersion and photocatalytic activity were rapidly synthesized from peroxo-titanium-acid precursor by microwave-assisted hydrothermal method within 30?min at low temperature (120–180?°C). The transmission electron microscopy results indicate that the as-prepared TiO₂ have a narrow particle size distribution (25–29?nm) and high dispersion. The crystal structure of all these products are pure anatase phase (XRD, Raman), and they show good crystallinity and large surface area (N₂ adsorption–desorption measurements BET). The results of the UV–Visible absorbance and Fourier transform infrared spectra indicate that the surface peroxo group Ti(O₂) still remains in TiO₂ nanoparticles prepared by microwave-assisted hydrothermal method at 120?°C, and this surface peroxo group can be decomposed effectively by drying at 140?°C. The photocatalytic activity of the as-prepared TiO₂ were evaluated by the degradation of reactive brilliant red X-3B, it is found that the as-prepared TiO₂ exhibited good photocatalytic performance. Moreover, the existence of surface peroxo group greatly suppressed the photocatalytic activity of the TiO₂ nanoparticles.     

Photocatalytic transformation of CO2 to CH4 and CO on acidic surface of TiO2 anatase

Recently, many studies have demonstrated that carbon dioxide can be converted to methane on TiO₂ surface by a photocatalytic process. We show that such a photo-reduction can be significantly affected by the presence of an acidic proton in powder samples of titania. Using in situ absorption gas-phase rovibrational spectroscopic detection of CH₄, CO and CO₂, we demonstrate that proton enhancement positively affects transformation of intermediate derivatives to methane during the photo-irradiation process via several reactions in which the electron transfer inside titania is coupled to oxygen transfer to the Ti³⁺ centers of TiO₂ structure. The yield of CH₄ or CO depends on the surface conditioning of titania: the formation of CH₄ is boosted by a presence of adsorbed HCl, while the formation of CO is boosted by adsorbed H₂SO₄.     

The electronic and optical properties of Eu/Si-codoped anatase TiO(2) photocatalyst

The electronic and optical properties of Eu/Si-codoped anatase TiO(2) are investigated using the density functional theory. The calculated results show that the synergistic effects of Eu/Si codoping can effectively extend the optical absorption edge, which can lead to higher visible-light photocatalytic activities than pure anatase TiO(2). To verify the reliability of our calculated results, nanocrystalline Eu/Si-codoped TiO(2) is prepared by a sol-gel-solvothermal method, and the experimental results also indicate that the codoping sample exhibits better absorption performance and higher photocatalytic activities than pure TiO(2).     

Unravelling the role of lithium and nickel doping on the defect structure and phase transition of anatase TiO2 nanoparticles

Journal of Materials Science - Anatase TiO2 nanoparticles doped either with Li or Ni have been synthesized via hydrolysis in variable concentrations. Microstructural analysis confirms the high...     

Synthesis of anatase TiO2 microspheres and their efficient performance in dye-sensitized solar cell

Nanomaterials play important role in performance of dye-sensitized solar cells. In this paper, highly phase pure anatase TiO₂ microspheres were synthesized using a low-cost hydrothermal route. Initially, X-ray diffraction studies and Raman spectroscopic analysis were carried out, and the formation of tetragonal structure of TiO₂ with the anatase phase was confirmed. The UV–Vis DRS studies showed the excellent reflectance and optical band-gap energy of 3.29 eV. The well-interconnected spherical nanoparticles with different sizes were examined by Field Emission Scanning Electron Microscopic analysis. The fabricated dye-sensitized solar cell (DSSC) composed of prepared TiO₂ microspheres as photoanode exhibited a higher power conversion efficiency (PCE) (η) of 5.4% as compared to commercial P25 with PCE of 3.6%. The higher J_sc (12.03 mA/cm²) in the fabricated DSSC due to efficient dye loading capacity and high light-scattering property was also observed.

     

Controllable synthesis and luminescence properties of TiO2:Eu3+ nanorods,nanoparticles and submicrospheres by hydrothermal method

Eu³⁺-doped TiO₂ nanocrystals with three kinds of morphologies (nanorods, nanoparticles, and submicrospheres) have been successfully fabricated in cetyltrimethylammonium bromide (CTAB)/water/cyclohexane/n-pentanol reverse micelle by hydrothermal method for the first time and their photoluminescence (PL) properties have also been studied. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), FT-IR, and PL spectra were used to characterize the samples. The acidic and alkaline conditions of the microemulsion play an important role in determining the geometric morphologies of the final products. TiO₂:Eu³⁺ with three different morphologies all exist only in anatase phase and show high luminescence intensity without further calcinations, which show its advantages of energy saving. The shape of emission spectra was independent of the morphologies of the products but the luminescence intensity of the TiO₂:Eu³⁺ materials is strongly dependent on their morphology. The results show that TiO₂:Eu³⁺ nanorods possess the strongest luminescence intensity among the three nanostructured samples.     

Synthesis and characterization of anatase TiO2 nanotubes and their use in dye-sensitized solar cells

Anatase TiO₂ nanotubes (NTs) with the diameter of about 12 nm and the length of several hundreds nanometers were synthesized by hydrothermal method. The samples were characterized by X-ray diffraction (XRD), transmitting electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmet–Teller (BET) measurements. The NTs are used to make composites photoanode with pristine TiO₂ nanoparticles in dye-sensitized solar cells (DSSCs). It was found that the NT/nanoparticle ratio had a pronounced impact on the performance of solar cells. The electrode composite has better photoelectric properties than the full nanoparticle and NTs solar cells. The optimum content NTs, was found to be 5%, at which content the incident photon to current efficiency was about 63.1%, an 13.8% increment compared to that using full P25 under the same condition.     

微乳液水热法低温制备TiO2纳米棒阵列及光电化学性能研究

利用微乳液水热法降低反应能,在透明导电玻璃衬底上低温合成出金红石相TiO2纳米棒阵列.利用X射线衍射、扫描电镜、紫外-可见光、阻抗谱等手段对样品进行结构形貌表征和光电化学性能测试.结果 表明:微乳液体系的加入可有效地降低体系表面能,诱发前驱物发生水解缩聚反应,促进TiO2晶粒在溶液-液相-固相三相界面成核和生长,实现低...