Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

Generations Yi Ma,† Xiuli Wang,† Yushuai Jia,† Xiaobo Chen,‡ Hongxian Han,*,† and Can Li*,† †State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Dalian National Laboratory for Clean Energy, 457 Zhongshan Road, Dalian 116023, China ‡Department of Chemistry, College of Arts and Sciences, University of Missouri-Kansas City, 5100 Rockhill Road, Kansas City, Missouri 64110, United States

Titanium dioxide-based nanomaterials for photocatalytic fuel generations.

Review of photoluminescence performance of nano-sized semiconductor materials and its relationships with photocatalytic activity

The increasing need for new materials capable of solar fuel generation is central in the development of a green energy economy. In this contribution, we demonstrate that black TiO2 nanoparticles obtained through a one-step reduction/crystallization process exhibit a bandgap of only 1.85 eV, which matches well with visible light absorption. The electronic structure of black TiO2 nanoparticles is determined by the unique crystalline and defective core/disordered shell morphology. We introduce new insights that will be useful for the design of nanostructured photocatalysts for energy applications.

Effect of nature and location of defects on bandgap narrowing in black TiO2 nanoparticles.

Pt/TiO2 nanosheets with exposed (001) facets were fabricated by a simple hydrothermal route in a Ti(OC4H9)4-HF-H2O mixed solution followed by a photochemical reduction deposition of Pt nanoparticles on TiO2 nanosheets under xenon lamp irradiation. The prepared samples were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption−desorption isotherms, UV−vis diffuse reflectance spectroscopy, and photoluminescence (PL) spectroscopy. Production of •OH radicals on the TiO2 surface was detected by the PL technique using coumarin as a probe molecule. The effects of Pt loading on the rates of photocatalytic hydrogen production of the as-prepared samples in ethanol aqueous solution were investigated and discussed. The results showed that the photocatalytic hydrogen production rates of TiO2 nanosheets from the ethanol aqueous solutions were significantly enhanced by loaded Pt on the TiO2 nanosheets, and the latter with a 2 wt % of deposited Pt exhi...

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Hydrogen Production by Photocatalytic Water Splitting over Pt/TiO2 Nanosheets with Exposed (001) Facets

Titanium dioxide (TiO2 ) nanocrystals are prepared by a hydrolysis process of tetrabutyl titanate. Nanocrystal samples with various sizes of 6.8-27.9 nm are obtained after annealing from 100 to 650 °C. The crystal structures and the average particle sizes are examined using x-ray diffraction. Raman scattering was employed to investigate the evolution of the anatase phase in the nanocrystals during annealing. Phonon confinement and non-stoichiometry effects are responsible for the blueshift and broadening of the lowest-frequency Eg Raman mode. The influence of interfacial vibrations on the Raman linewidth is also discussed.

https://iopscience.iop.org/article/10.1088/0022-3727/33/8/305/pdf

Raman scattering study on anatase TiO2 nanocrystals

Titanium dioxide (TiO2) nanocrystals were prepared by a hydrolysis process of tetrabutyl titanate. X-ray diffraction and Raman scattering showed that the as-prepared TiO2 nanocrystals have anatase structure of TiO2, and that the monophase anatase nanocrystals can be achieved through a series of annealing treatments below 650 °C. We measured photoluminescence (PL) spectra of the TiO2 nanocrystals. Under 2.41–2.71 eV laser irradiation, the TiO2 nanocrystals displayed strong visible light emission with maxima of 2.15–2.29 eV even at excitation power as low as 0.06 W/cm2. To identify the PL mechanism in the TiO2 nanocrystals, the dependences of the PL intensity on excitation power and irradiation time were investigated. The experimental results indicated that the radiative recombination is mediated by localized levels related to surface defects residing in TiO2 nanocrystallites.

Photoluminescence in anatase titanium dioxide nanocrystals

http://lib.fibopt.ru/Articles/PAPER/GPI/PhLetv340%20p220-227.pdf

Size and phonon-confinement effects on low-frequency Raman mode of anatase TiO2 nanocrystal

Titanium dioxide nanocrystal with a mixture of anatase and brookite was prepared by sol–gel method. The effects of the grain size and the phase content on the transition were studied for TiO2 nanocrystal annealed in air for 1 h at the temperature range 200–650 °C. The experimental results indicate that the phase transition sequence depends on relative grain size between anatase and brookite. Under the same grain sizes anatase, brookite, and rutile is the most stable at the size smaller than 4.9 nm, between 4.9 and 30 nm, and larger than 30 nm, respectively. Thermodynamic analysis gives an empirical expression on a critical grain size of brookite Dc, which dominates the transition sequence between anatase and brookite. As the size of brookite Db reaches Dc, brookite and anatase phases transform directly to rutile. When Db > Dc, anatase phase transforms to brookite and than brookite to rutile and/or directly to rutile; when Db

Size effect on phase transition sequence of TiO2 nanocrystal

Nanocrystalline SrTiO3 was prepared by a stearic acid sol-gel technique. X-ray measurements showed that the sample obtained is of good quality and the grain sizes range from 26 to 120 nm. One blue photoluminescence (PL) band at around 470 nm was observed at room temperature. Investigation of the dependence of the visible emission band on annealing temperatures and grain sizes showed that the effects of grain size and dielectric confinement play important roles, and that oxygen vacancies may act as the radiative centres responsible for the observed visible emission band. The mechanism for the luminescence is explained within the framework of self-trapped excitons.

https://iopscience.iop.org/article/10.1088/0953-8984/11/29/312/pdf

Zhen Yin

Papers

Raman scattering study on anatase TiO2 nanocrystals

Photoluminescence in anatase titanium dioxide nanocrystals

Size and phonon-confinement effects on low-frequency Raman mode of anatase TiO2 nanocrystal

Size effect on phase transition sequence of TiO2 nanocrystal

Roles of defects and grain sizes in photoluminescence of nanocrystalline SrTiO3