Size-dependent modifications of the Raman spectrum of rutile TiO2

Swamy, Varghese; Muddle, Barrington Charles; Dai, Qing

doi:10.1063/1.2364123

Cited by 282 publications

(219 citation statements)

References 28 publications

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“…Three additional bands at 255, 418, and 603 cm −1 can be seen in Fig. 10(a)-2, which corre- spond to the Raman-active modes of E g , A 1g , and B 2g , respectively, for rutile TiO 2 [26]. This result suggests that oxidation of genuine Ti 4 O 7 to rutile TiO 2 occurred on the surface, which was observable when the laser radiation was tuned to high excitation energy.…”

Section: Surface Characterization Using Raman Spectroscopy and Xpsmentioning

confidence: 56%

Magneli phase Ti4O7 electrode for oxygen reduction reaction and its implication for zinc-air rechargeable batteries

Li¹,

Zhu²,

Qu³

et al. 2010

Electrochimica Acta

164

133

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In this paper, Magneli phase Ti 4 O 7 was successfully synthesized using a TiO 2 reduction method, and characterized using X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The electrode coated with this Ti 4 O 7 material showed activities for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). For the ORR, several parameters, including overall electron transfer number, kinetic constants, electron transfer coefficient, and percentage H 2 O 2 production, were obtained using the rotating ring-disk electrode (RRDE) technique and the Koutecky-Levich theory. The overall electron transfer number was found to be between 2.3 and 2.9 in 1, 4, and 6 M KOH electrolytes, suggesting that the ORR process on the Ti 4 O 7 electrode was a mixed process of 2-and 4-electron transfer pathways. Electrochemical durability tests, carried out in highly concentrated KOH electrolyte, confirmed that this Ti 4 O 7 is a stable electrode material, suggesting that it should be a feasible candidate for the aircathodes of zinc-air batteries. To understand the stability of this material, Raman and XPS spectra were also collected for the Ti 4 O 7 samples before and after the stability tests. The results and analysis revealed that a thin layer of TiO 2 formed on the Ti 4 O 7 surface, which may have prevented further oxidation into the bulk of the Ti 4 O 7 electrode.Crown

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Section: Surface Characterization Using Raman Spectroscopy and Xpsmentioning

confidence: 56%

Magneli phase Ti4O7 electrode for oxygen reduction reaction and its implication for zinc-air rechargeable batteries

Li¹,

Zhu²,

Qu³

et al. 2010

Electrochimica Acta

164

133

View full text Add to dashboard Cite

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“…The A 1g (603 cm -1 ) and Eg (432 cm -1 ) modes as well as a second-order peak at about 240 cm -1 are the dominant peaks and characteristic of the rutile phase of TiO 2 . The Raman peak at about 105 cm -1 and a broad band at about 685 cm -1 are due to a size effect and indicate that the size of the particles is less than 10 nm [38]. SEM images show that uniform spheres with a diameter of 200-400 nm can be obtained on a large scale (see Fig.…”

Section: Synthesis Of Rutile Tio 2 Nanostructuresmentioning

confidence: 93%

Large scale photochemical synthesis of M@TiO2 nanocomposites (M = Ag, Pd, Au, Pt) and their optical properties, CO oxidation performance, and antibacterial effect

et al. 2010

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Well-dispersed M@TiO 2 (M = Ag, Pd, Au, Pt) nanocomposite particles with a diameter of 200-400 nm can be synthesized on a large scale by a clean photochemical route which does not require any additives using spherical rutile nanoparticles as a support. The sizes of Pt, Au, and Pd nanoparticles formed on the surface of TiO 2 particles are about 1 nm, 5 nm, and 5 nm, respectively, and the diameter of Ag nanoparticles is in the range 2-20 nm. Moreover, the noble metal nanoparticles have good dispersity on the particles of the TiO 2 support, resulting in excellent catalytic activities. Complete conversion in catalytic CO oxidation is reached at temperatures as low as 333 and 363 K, respectively, for Pt@TiO 2 and Pd@TiO 2 catalysts. In addition, the antibacterial effects of the as-synthesized TiO 2 nanoparticles, silver nanoparticles, and Au@TiO 2 and Ag@TiO 2 nanocomposites have been tested against Gram-negative Escherichia coli (E. coli) bacteria. The results demonstrate that the presence of the TiO 2 matrix enhances the antibacterial effect of silver nanoparticles, and the growth of E. coli can be completely inhibited even if the concentration of Ag in Ag@TiO 2 nanocomposite is very low (10 μg/mL).

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“…The integrated intensity of the line at 834 cm −1 is ∼ 5.5 times larger than that of the corresponding shoulder for a virgin TiO 2 . In virgin TiO 2 the B 2g mode represents an asymmetric (Ti-O) stretching vibration of the (TiO 6 )-octahedra (Ti ions are surrounded by six O ions) 21 . It is therefore sensitive to the short-range order and the bond strength in the crystal, i.e., the local environment of the Ti ions.…”

mentioning

confidence: 99%

Origin of magnetic moments in defectiveTiO2single crystals

et al. 2009

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In this paper we show that ferromagnetism can be induced in pure TiO2 single crystals by oxygen ion irradiation. By combining x-ray diffraction, Raman-scattering, and electron spin resonance spectroscopy, a defect complex, i.e. Ti 3+ ions on the substitutional sites accompanied by oxygen vacancies, has been identified in irradiated TiO2. This kind of defect complex results in a local (TiO6−x) stretching Raman mode. We elucidate that Ti 3+ ions with one unpaired 3d electron provide the local magnetic moments.Recently, ferromagnetism has been observed in nonmagnetically doped, but defective oxides, including TiO 2 1,2,3,4 . This kind of observation challenges the conventional understanding of ferromagnetism, which is rather due to spin-split states or bands. Thus, one fundamental question must be answered: where are the moments located? Intensive theoretical work has been performed to understand the ferromagnetism in defective oxides 5,6,7 . In these papers, the triplet states of p-like electrons, located at cation or oxygen vacancies, yield the local moments, leading to a kind of ferromagnetism without the involvement of 3d electrons. Experimentally the ferromagnetism in undoped TiO 2 has been found to relate with oxygen vacancies (O V ) 2,3 , however, its mechanism remains unclear. It is worth to note that Ti 3+ ions with one 3d electron are usually generated in slightly reduced TiO 2 . When O is removed, the excess electrons are unpaired 8 . They can occupy the nearby localized Ti 3d orbit and therefore convert Ti 4+ ions to Ti 3+ ions. In a reduced rutile TiO 2 (110) surface, such a defect complex, Ti 3+ -O V , has been well studied by first-principles calculations 9,10 and experimentally by resonant photoelectron diffraction 11 . Therefore, experimental work is needed to clarify whether the magnetic moments in defective TiO 2 is due to unpaired 3d electrons localized on Ti 3+ ions.Ion irradiation is a non-equilibrium and reproducible method of inducing defects. Energetic ions displace atoms from their equilibrium lattice sites, thus creating mainly vacancies and interstitials. The amount of defects can be controlled by the ion fluence and energy. In this paper, we irradiated rutile TiO 2 single crystals with 2-MeV O ions, resulting in a projected range of 1.52 µm and a longitudinal straggling of 0.16 µm as calculated by SRIM code (The Stopping and Range of Ions in Matter) 12 . As a result of this irradiation, the formation of Ti/O vacancies/interstitials is expected 12 . We selected high-energy oxygen ions as projectiles to avoid the introduction of foreign elements. Moreover, from a ballistic point of view, the creation of oxygen vacancies is more efficient, e.g., by a factor of 1.5 larger than the Ti-vacancy creation. From SRIM calculations it is also evident that, at the given energy, the maximum atomic concentration of the implanted oxygen ions is by a factor of 500 smaller than the concentration of oxygen recoils. For the region of maximum defect creation, i.e., at the end of the ion range, those project...

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Size-dependent modifications of the Raman spectrum of rutile TiO2

Cited by 282 publications

References 28 publications

Magneli phase Ti4O7 electrode for oxygen reduction reaction and its implication for zinc-air rechargeable batteries

Magneli phase Ti4O7 electrode for oxygen reduction reaction and its implication for zinc-air rechargeable batteries

Large scale photochemical synthesis of M@TiO2 nanocomposites (M = Ag, Pd, Au, Pt) and their optical properties, CO oxidation performance, and antibacterial effect

Origin of magnetic moments in defectiveTiO2single crystals

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