Preparation and characterization of the TiO2 ultrafine particles by detonation method

Qu, Yandong; Li, Xiaojie; Rui-yong, LI; Yan, Honghao; Ouyang, Xinping; Wang, Xiaohong

doi:10.1016/j.materresbull.2007.02.038

Cited by 20 publications

(9 citation statements)

References 18 publications

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“…From our investigations, site disorder, as it is reported by Muñoz et al 29 and de la Calle et al, 27 seems to be very unlikely for our samples. Nevertheless, a 3% disorder of Mn/Fe atoms for the composition x = 1 cannot be excluded taking our esd into account.…”

Section: Discussionsupporting

confidence: 65%

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EXAFS, XANES, and DFT study of the mixed-valence compoundYMn2O5: Site-selective substitution of Fe for Mn

et al. 2010

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In YMn 2 O 5 , the Mn atoms occupy two nonequivalent Wyckoff sites within the unit cell exhibiting different oxygen coordinations, i.e., the system can be characterized as a mixed-valence compound. For the formation of the orthorhombic crystal structure, Jahn-Teller distortions are assumed to play an important role. In this study, we aimed at the investigation of the crystal structure changes upon the substitution of Mn by the non-JahnTeller cation Fe 3+ . Therefore, we synthesized a series of YMn 2−x Fe x O 5 powder samples with x = 0, 0.5, and 1 by a citrate technique. We utilized extended x-ray absorption fine structure ͑EXAFS͒ and x-ray absorption near-edge structure ͑XANES͒ analysis as well as density-functional theory ͑DFT͒ to investigate the two nonequivalent Wyckoff sites within the orthorhombic crystal structure ͑confirmed for all compositions͒ occupied by transition-metal atoms. For quantitative determination of structural short-range order, all plausible options of substitution of Fe for Mn are discussed. On the basis of these evaluations, the EXAFS and XANES behavior is analyzed and appropriate crystallographic weights are assigned to the subset of structural models in accordance with the experimental data. From EXAFS analysis, using multiple-scattering theory, we conclude only the 4h Wyckoff site to be occupied by Fe ͓occupancy refined is ͑100Ϯ 3͒% in case of x =1͔. Furthermore, taking the XANES spectra into account, we are able to verify the EXAFS results and additionally explain the differences in the Mn K XANES spectra in dependence on x to be caused by changes in the dipole transitions to 4p final states. From quantitative pre-edge analysis an oxidation number of +4 for the Mn atom for x =1 is determined whereas the Fe valence is shown to be unchanged. Since the substitution process only involves one Wyckoff site, the experimentally observed limit to a maximum amount of x = 1 is explained. Additionally, a possible disorder, discussed in the literature, is not proven for our samples. With DFT calculations, the experimental findings are verified on the basis of the total energy of the different possible electronic configurations. Crystal-field effects are identified to be responsible for the site-selective substitution of Fe for Mn.

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Section: Discussionsupporting

confidence: 65%

“…From neutron powder diffraction ͑NPD͒ data, these authors concluded that about 5% of octahedrally coordinated Fe exists. Also for the compound YMnGaO 5 de la Calle et al 27 reported a mixed occupancy of the TM sites ͑3% of Mn 4f positions were occupied by Ga and 26% of Ga 4h positions were occupied by Mn͒ using NPD analysis.…”

Section: Introductionmentioning

confidence: 99%

EXAFS, XANES, and DFT study of the mixed-valence compoundYMn2O5: Site-selective substitution of Fe for Mn

et al. 2010

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“…The characteristic reflection peaks of the rutile TiO 2 structure can be observed. Comparison with the standard pattern for TiO 2 [21,22] shows that the the peaks can be assigned to the 110, 101, 111, 211, 220, and 301 reflections. The XRD patterns of the unmodifi ed TiO 2 -NTs and FITC-TiO 2 -NTs are similar, showing that TiO 2 exists as a single rutile phase in both materials.…”

Section: Tem and Confocal Imagingmentioning

confidence: 94%

Direct imaging of titania nanotubes located in mouse neural stem cell nuclei

et al. 2009

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Titania nanotubes (TiO 2 -NTs) are a potential drug vehicle for use in nanomedicine. To this end, a preliminary study of the interaction of a model cell with TiO 2 -NTs has been carried out. TiO 2 -NTs were first conjugated with a fl uorescent label, fl uorescein isothiocyanate (FITC). FITC-conjugated titania nanotubes (FITC-TiO 2 -NTs) internalized in mouse neural stem cells (NSCs, line C17.2) can be directly imaged by confocal microscopy. The confocal imaging showed that FITC-TiO 2 -NTs readily entered into the cells. After co-incubation with cells for 24 h, FITC-TiO 2 -NTs localized around the cell nucleus without crossing the karyotheca. More interestingly, the nanotubes passed through the karyotheca entering the cell nucleus after co-incubation for 48 h. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were also employed in tracking the nanotubes in the cell. These results will be of benefi t in future studies of TiO 2 -NTs for use as a drug vehicle, particularly for DNA-targeting drugs.

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“…Detonation [21,22] refers to the dynamic preparation of nanomaterials; the method presents various characteristics, such as high synthesis efficiency, simple operation, and low equipment requirements. Li et al [23][24][25][26] synthesized TiO 2 from mixtures of high-energy explosive (RDX), ammonium nitrate, and Ti precursor, but the TiO 2 particles obtained were larger than 10 nm. During the detonation reaction of explosives, obtaining a small particle size is difficult because of the high temperature and pressure of the reaction system [27].…”

Section: Introductionmentioning

confidence: 99%