Photoluminescence of Anatase and Rutile TiO<sub>2</sub> Particles

Abazović, Nadica D.; Čomor, Mirjana I.; Dramićanin, Miroslav D.; Jovanović, Dragana J.; Ahrenkiel, S. P.; Nedeljković, Jovan M.

doi:10.1021/jp064454f

Cited by 437 publications

(270 citation statements)

References 62 publications

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“…Thus, we estimate a quantum yield of ∼ 1.3 × 10 −6 . This is consistent with the fact that the quantum yield of anatase TiO 2 NPs at room temperature and under steady-state conditions has been found ∼ 2.5 × 10 −3 [72,73]. Indeed, the latter represents an upper limit to the PL quantum yield that can be obtained in anatase TiO 2 NPs at room temperature and, as expected, it implies that the radiative decay channel is not efficient in this material.…”

Section: S7 Ultrafast Photoluminescencesupporting

confidence: 89%

Clocking the Ultrafast Electron Cooling in Anatase Titanium Dioxide Nanoparticles

et al. 2018

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The recent identification of strongly bound excitons in room temperature anatase TiO 2 single crystals and nanoparticles underscores the importance of bulk many-body effects in samples used for applications. Here, for the first time, we unravel the interplay between many-body interactions and correlations in highly-excited anatase TiO 2 nanoparticles using ultrafast two-dimensional deepultraviolet spectroscopy. With this approach, under non-resonant excitation, we disentangle the optical nonlinearities contributing to the bleach of the lowest direct exciton peak. This allows us to clock the ultrafast timescale of the hot electron thermalization in the conduction band with unprecedented temporal resolution, which we determine to be < 50 fs, due to the strong electronphonon coupling in the material. Our findings call for the design of alternative resonant excitation schemes in photonics and nanotechnology.1 arXiv:1703.07818v2 [cond-mat.mes-hall] 13 Jan 2018In the last decades, anatase TiO 2 has attracted huge interest as one of the most promising materials for a variety of challenging applications, ranging from photocatalysis [1,2] and photovoltaics [3] to sensors [4,5]. Since these technologies involve charge transport, thermalization and localization, they call for studies of the fast electron and hole dynamics, which provide a deep knowledge of the nature of the photogenerated/injected charge carriers and of the energy balance therein. These processes intimately depend on the details of the electronic structure and the presence of many body-effects in the material. Since anatase TiO 2 is a d 0 transition metal oxide, strong electron-electron correlations do not play a substantial role in the electronic structure [6]. Hence, this solid can be classified within the simple band insulator scheme, in which the forbidden energy gap arises as a result of band theory and is not a consequence of the strong on-site Coulomb interaction. However, different to conventional band insulators, anatase TiO 2 represents a peculiar example in which electron-phonon interaction and electron-hole correlation become relatively strong and influence the optical spectra. On the one hand, the presence of a moderately large electron-phonon coupling in anatase TiO 2 has often been invoked to interpret experimental results naturally pointing to the polaronic (self-trapped) picture [7][8][9][10][11][12][13]. Notable examples include the low temperature green photoluminescence (PL) due to self-trapped excitons [14][15][16][17][18][19][20] and the room temperature electron mobilities whose values are limited by strong scattering with phonons [10]. On the other hand, many-body correlations have been thought to be negligible in this material and, as such, they remained widely unexplored. Recently, by employing state-of-the-art experimental [21] and computational techniques [21][22][23][24][25], the substantial role of electron-hole Coulomb correlations was unravelled in the anatase polymorph of TiO 2 . Strongly bound direct excitons were...

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Section: S7 Ultrafast Photoluminescencesupporting

confidence: 89%

Clocking the Ultrafast Electron Cooling in Anatase Titanium Dioxide Nanoparticles

et al. 2018

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“…The UV emission is considered as the band edge emission of the host TiO 2, and the 431 nm peak can be ascribed to self-trapped excitations localized in TiO 6 octahedra (Wan et al 2010). The existences of green emission peak at 587 nm explain the presence of oxygen vacancies (Abazovic et al 2006). When compared with bare TiO 2 , the PL emission bands of doped product are blue shifted with intensity reduction in the UV band and enhancement in the visible bands (Kirit and Dimple 2012).…”

Section: Photoluminescence (Pl)mentioning

confidence: 98%

Synthesis and characterization of undoped and cobalt-doped TiO2 nanoparticles via sol–gel technique

et al. 2014

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TiO 2 nanoparticles doped with different concentrations of cobalt (4, 8, 12 and 16 %) were synthesized by sol-gel method at room temperature with appropriate reactants. In general, TiO 2 can exist in anatase, rutile, and brookite phases. In this present study, we used titanium tetra iso propoxide and 2-propanol as a common starting materials and the obtained products were calcined at 500°C and 800°C to get anatase and rutile phases, respectively. The crystalline sizes of the doped and undoped TiO 2 nanoparticles were observed with X-ray diffraction (XRD) analysis. The functional groups of the samples were identified by Fourier transform infrared spectroscopy (FTIR). From UV-VIS diffuse reflectance spectra (DRS), the band gap energy and excitation wavelength of doped and undoped TiO 2 nanoparticles were identified. The defect oriented emissions were seen from photoluminescence (PL) study. The spherical uniform size distribution of particles and elements present in the samples was determined using two different techniques viz., scanning electron microscopy (SEM) with energy-dispersive spectrometer (EDX) and transmission electron microscope (TEM) with selected area electron diffraction (SAED) pattern. The second harmonic generation (SHG) efficiency was also found and the obtained result was compared with potassium di hydrogen phosphate (KDP).

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“…24 The defect states originating from trapped electrons appear around 1.0 eV below the conduction band minimum (CBM), which induces band gap narrowing as optimal value for photocatalyst. 23,[25][26][27] Herein, we systemically investigate the properties of stoichiometric (TiO 2 ) 35 anatase NP and neutral single oxygen removed one. The bipyramidal (TiO 2 ) 35 NP, maintaining anatase structure after geometrical relaxation, seems to be a proper model to study the physical and electronic properties of oxygen vacancy in TiO 2 NP by comparing those of bulk and slab surface.…”

Section: Introductionmentioning

confidence: 99%

Single oxygen vacancies of (TiO₂)₃₅as a prototype reduced nanoparticle: implication for photocatalytic activity

Kim

Lee

et al. 2016

Phys. Chem. Chem. Phys.

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Titanium dioxide (TiO2), as a semiconductor metal oxide, has been one of the most popular materials studied in the field of photocatalysis. In the present study, the properties of single oxygen vacancies of (TiO2)35, a prototype of anatase nanoparticle, were investigated by DFT calculations. (TiO2)35 is the minimum sized model (~ 2 nm) as bipyramidal nanoparticle with anatase phase and eight {101} facets. All the available oxygen vacancies at various sites according to position, coordination number, and distance from the center atom were examined. The geometric, energetic and electronic properties of the reduced TiO2 clusters were analyzed by hybrid DFT functionals with different Hartree-Fock exchange ratio (0, 12.5 and 25 %). It was found that the structure of pristine (TiO2)35 is somewhat different from bulk lattice with relatively high surface to volume ratio. Moreover, the particular high (three)-coordinated oxygen atom is energetically most favorable for oxygen vacancy formation from nanoparticle mainly due to substantially high relaxation energy. TiO2 nanoparticle has low oxygen vacancy formation energy and narrow band gap by defect state, and can be utilized as an efficient photocatalyst material.

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Photoluminescence of Anatase and Rutile TiO₂ Particles

Cited by 437 publications

References 62 publications

Clocking the Ultrafast Electron Cooling in Anatase Titanium Dioxide Nanoparticles

Clocking the Ultrafast Electron Cooling in Anatase Titanium Dioxide Nanoparticles

Synthesis and characterization of undoped and cobalt-doped TiO2 nanoparticles via sol–gel technique

Single oxygen vacancies of (TiO₂)₃₅as a prototype reduced nanoparticle: implication for photocatalytic activity

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Photoluminescence of Anatase and Rutile TiO2 Particles

Cited by 437 publications

References 62 publications

Clocking the Ultrafast Electron Cooling in Anatase Titanium Dioxide Nanoparticles

Clocking the Ultrafast Electron Cooling in Anatase Titanium Dioxide Nanoparticles

Synthesis and characterization of undoped and cobalt-doped TiO2 nanoparticles via sol–gel technique

Single oxygen vacancies of (TiO2)35as a prototype reduced nanoparticle: implication for photocatalytic activity

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Product

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Photoluminescence of Anatase and Rutile TiO₂ Particles

Single oxygen vacancies of (TiO₂)₃₅as a prototype reduced nanoparticle: implication for photocatalytic activity