Location of Hole and Electron Traps on Nanocrystalline Anatase TiO<sub>2</sub>

Mercado, Candy C.; Knorr, Fritz J.; McHale, Jeanne L.; Usmani, Shirin M.; Ichimura, Atsushi; Saraf, Laxmikant V.

doi:10.1021/jp301680d

Cited by 194 publications

(239 citation statements)

References 75 publications

(127 reference statements)

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“…Secondly, length of isopropanol is smaller than the n-propanol, which can affect the bond length/ orientation in Ti-O-Ti three Low Temperature Synthesis of Mixed Phase Titania Nanoparticles with High Yield, its Mechanism and Enhanced Photoactivity from TiO 2 to dye. Secondly, Mercado et al, 19 systematically showed that stoichiometric variation in rutile and anatase (or mixed) phase of TiO 2 affects the electron transfer ability and hence its photo-catalytic activity. The observed variations in n-TiO 2 and i-TiO 2 have been attributed to the variation in their redox behavior (ie.…”

Section: Resultsmentioning

confidence: 99%

Low Temperature Synthesis of Mixed Phase Titania Nanoparticles with High Yield, its Mechanism and Enhanced Photoactivity

Chaudhari

Mishra

2016

Mat. Res.

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Section: Resultsmentioning

confidence: 99%

Low Temperature Synthesis of Mixed Phase Titania Nanoparticles with High Yield, its Mechanism and Enhanced Photoactivity

Chaudhari

Mishra

2016

Mat. Res.

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“…In principle, indirect excitons would be allowed to form through the mediation of phonon modes. However, in the case of anatase TiO 2 nanosystems, their existence at room temperature has been disproven by extensive measurements [18,[47][48][49] and by the results we present in the following. As such, many-body processes such as exciton-exciton annihilation can be excluded.…”

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confidence: 77%

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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“…Nanocomposites dispersed in ethanol were thereafter deposited onto ITO-coated glass using the doctor blade method. 38 This photoanode electrode was then sintered at 300 °C for 30 min on a hot plate. Eosin B dye (150 µL) was added using a micropipette onto the anode electrode.…”

Section: Methodsmentioning

confidence: 99%

“…38 MWCNTs have been shown to reduce recombination rates by effectively capturing and transporting generated electrons from the titania and thus reducing recombination with generated holes. 33,54 From Fig.…”

Section: Photoluminescencementioning

confidence: 99%

Multiwalled carbon nanotube-titania nanocomposites: Understanding nano-structural parameters and functionality in dye-sensitized solar cells

Mombeshora¹,

Simoyi²,

Nyamori³

et al. 2015

S.Afr.j.chem

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Nanocomposites consisting of multiwalled carbon nanotubes and titania were synthesized by two methods, namely, sol-gel and chemical vapour deposition (CVD) methods. The work takes advantage of the bridging ability of nanotechnology between macromolecules and the solid state process in engineering alternative nanomaterials for various applications including solar cell fabrication. Physical and chemical characterization of the mesoporous nanocomposites from the two synthetic methods were investigated using Raman spectroscopy, thermogravimetric analysis, Fourier transformation infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, surface characterization and X-ray diffraction analysis. Physicochemical properties in the nanocomposites such as thermal stability, pore volume, crystallinity and surface area were observed to be a subject of MWCNT: titania ratios and synthetic methods. From the CVD synthetic method, observed attributes include more uniform and smoother coating; better crystallinity and larger pore width than sol-gel method. On the other hand, nanocomposites from sol-gel synthetic method had larger surface areas, were more defective and less thermally stable than those from CVD. Nanocomposites by the CVD method performed 39.2 % more efficient than those from sol-gel in light-harvesting experiments. The study shows that the nanocomposites synthesized were more effective than titania alone when the cheaper natural dye, Eosin B, was used. This highlights the great potential of typical nanomaterials in improving the performances of titania in DSSCs as well as lowering the cost of the ultimate devices.

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Location of Hole and Electron Traps on Nanocrystalline Anatase TiO₂

Cited by 194 publications

References 75 publications

Low Temperature Synthesis of Mixed Phase Titania Nanoparticles with High Yield, its Mechanism and Enhanced Photoactivity

Low Temperature Synthesis of Mixed Phase Titania Nanoparticles with High Yield, its Mechanism and Enhanced Photoactivity

Clocking the Ultrafast Electron Cooling in Anatase Titanium Dioxide Nanoparticles

Multiwalled carbon nanotube-titania nanocomposites: Understanding nano-structural parameters and functionality in dye-sensitized solar cells

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Location of Hole and Electron Traps on Nanocrystalline Anatase TiO2

Cited by 194 publications

References 75 publications

Low Temperature Synthesis of Mixed Phase Titania Nanoparticles with High Yield, its Mechanism and Enhanced Photoactivity

Low Temperature Synthesis of Mixed Phase Titania Nanoparticles with High Yield, its Mechanism and Enhanced Photoactivity

Clocking the Ultrafast Electron Cooling in Anatase Titanium Dioxide Nanoparticles

Multiwalled carbon nanotube-titania nanocomposites: Understanding nano-structural parameters and functionality in dye-sensitized solar cells

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Location of Hole and Electron Traps on Nanocrystalline Anatase TiO₂