Photon energy up-conversion in colloidal TiO2 nanorods

Abazović, Nadica D.; Ruvarac-Bugarčić, Ivanka A.; Čomor, Mirjana I.; Bibić, N.; Ahrenkiel, S. P.; Nedeljković, Jovan M.

doi:10.1016/j.optmat.2007.05.038

Cited by 21 publications

(10 citation statements)

References 32 publications

(48 reference statements)

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“…The formation of well-defined TiO 2 nanorods most likely can be explained by the prolonged aging at elevated temperature. This is in agreement with literature data concerning hydrothermal synthesis of TiO 2 rods [ 21 , 29 , 30 ].…”

Section: Resultssupporting

confidence: 93%

“…One excitation energy is higher than the band gap energy of TiO 2 (4.1 eV) and the other is lower (2.07 eV). In the later case, the observed phenomenon is so called up-conversion (UC)—the observation of an emission at energies higher than the excitation energy [ 21 , 30 ]. It can be noticed that UC spectra have the same position of peaks/shoulders and similar intensities compared to the normal PL spectrum.…”

Section: Resultsmentioning

confidence: 99%

“…High energy peaks can be assigned to band edge luminescence of the TiO 2 particles, while lower energy peaks/shoulders are induced by the presence of the oxygen vacancies [ 21 , 30 ]. Among the other facts, it seems that radiative recombination of photogenerated charge carriers through oxygen vacancy–cascade can also be considered as the process which can decrease the photocatalytic activity of iron doped TiO 2 .…”

Section: Resultsmentioning

confidence: 99%

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Synthesis and Characterization of Rutile TiO2Nanopowders Doped with Iron Ions

et al. 2009

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Titanium dioxide nanopowders doped with different amounts of Fe ions were prepared by coprecipitation method. Obtained materials were characterized by structural (XRD), morphological (TEM and SEM), optical (UV/vis reflection and photoluminescence, and Raman), and analytical techniques (XPS and ICP-OES). XRD analysis revealed rutile crystalline phase for doped and undoped titanium dioxide obtained in the same manner. Diameter of the particles was 5–7 nm. The presence of iron ions was confirmed by XPS and ICP-OES. Doping process moved absorption threshold of TiO2into visible spectrum range. Photocatalytic activity was also checked. Doped nanopowders showed normal and up-converted photoluminescence.

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Synthesis and Characterization of Rutile TiO2Nanopowders Doped with Iron Ions

et al. 2009

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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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“…17 Abazovic ´et al observed the photon energy up-conversion in colloidal anatase TiO 2 nanorods at low excitation intensity. 18 The dye-sensitized solar cell made from TiO 2 nanorods having efficiency η of 1.8% under the xenon lamp intensity of 50 mW/cm 2 was investigated by Pan et al 19 Only the synthesis route of the TiO 2 @CdS core-shell nanostructures was described by Sun and Wang. 20 To the best of our knowledge, no one has reported detailed studies on the optical properties of the TiO 2 @CdS core-shell nanorods.…”

Section: Introductionmentioning

confidence: 99%

Optical Properties of the Type-II Core−Shell TiO₂@CdS Nanorods for Photovoltaic Applications

Das

2009

J. Phys. Chem. C

115

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The well-known surface-functionalized method has been employed to synthesize TiO 2 @CdS core-shell nanorods using citric acid as a surface-functionalized agent. By varying the concentration of the citric acid, core-shell nanorods of core diameter 36 nm with different shell thickness (19-34 nm) were formed. The UV-visible absorption spectra of the core-shell nanorods show a red shift of the band edge of uncoated TiO 2 , and the broadening of the absorption spectra is also observed with shell growth. Steady-state photoluminescence (PL) spectra of the core-shell nanorods give a new emission in the visible region and also red shift with the increasing shell thickness. Decay kinetics indicate that the average lifetime 〈τ〉 of the core-shell nanorods is larger than that of the uncoated TiO 2 , and it varies from nanoseconds to picoseconds. The current-voltage (I-V) curves of the core-shell nanorods give a photocurrent density that is 212 times greater than the dark current density.

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Photon energy up-conversion in colloidal TiO2 nanorods

Cited by 21 publications

References 32 publications

Synthesis and Characterization of Rutile TiO2Nanopowders Doped with Iron Ions

Synthesis and Characterization of Rutile TiO2Nanopowders Doped with Iron Ions

Clocking the Ultrafast Electron Cooling in Anatase Titanium Dioxide Nanoparticles

Optical Properties of the Type-II Core−Shell TiO₂@CdS Nanorods for Photovoltaic Applications

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Photon energy up-conversion in colloidal TiO2 nanorods

Cited by 21 publications

References 32 publications

Synthesis and Characterization of Rutile TiO2Nanopowders Doped with Iron Ions

Synthesis and Characterization of Rutile TiO2Nanopowders Doped with Iron Ions

Clocking the Ultrafast Electron Cooling in Anatase Titanium Dioxide Nanoparticles

Optical Properties of the Type-II Core−Shell TiO2@CdS Nanorods for Photovoltaic Applications

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Optical Properties of the Type-II Core−Shell TiO₂@CdS Nanorods for Photovoltaic Applications