Femtosecond time-resolved X-ray absorption spectroscopy of anatase TiO2 nanoparticles using XFEL

Obara, Yuzo; Ito, Hironori; Ito, Tomoyoshi; Kurahashi, Naoya; Thürmer, Stephan; Tanaka, Hiroki; Katayama, Tetsuo; Togashi, Tadashi; Owada, Shigeki; Yamamoto, Yoichi; Karashima, Shutaro; Nishitani, Junichi; Yabashi, Makina; Suzuki, Toshinori; Misawa, Kazuhiko

doi:10.1063/1.4989862

Cited by 59 publications

(56 citation statements)

References 47 publications

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“…This work followed our previous study of plasmon-induced hot electron transfer in Au-TiO2 nanostructures [46]. In the context of X-ray spectroscopic investigations we note that electron transfer to defective Ti sites in undoped or dye-sensitized TiO2 NPs has been demonstrated by time resolved methods on the 100 ps time scale by Rittmann Frank et al [47] and more recently on the 100 fs time scale by Obara et al [48].…”

Section: Introductionmentioning

confidence: 55%

Charge carrier dynamics and visible light photocatalysis in vanadium-doped TiO2 nanoparticles

Rossi

Pasquini

Catone

et al. 2018

Applied Catalysis B: Environmental

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Vanadium-doped TiO2 nanoparticles (V-TiO2 NPs) with a V/Ti ratio of 3.0 at. % were prepared by gas-phase condensation and subsequent oxidation at elevated temperature. Both photocatalytic activity for -NO2 reduction and photoelectrochemical water splitting were induced by V-doping in the visible spectral range > 450 nm, where undoped TiO2 NPs are completely inactive. The photocatalytic properties were correlated with the ultrafast dynamics of the photoexcited charge carriers studied by femtosecond transient absorption (TA) spectroscopy with three different excitation wavelengths, i.e. e = 330, 400, and 530 nm. Only in V-doped NPs, the photoexcitation of electrons into the conduction band by sub-bandgap irradiation (e = 530 nm) was detected by TA spectroscopy. This observation was associated with electronic transitions from an intra-gap level localized on V 4+ cations. The photoexcited electrons subsequently relaxed, with characteristic times of 200-500 ps depending on e, into Ti-related surface traps that possessed suitable energy to promote -NO2 reduction. The photoexcited holes migrated to long-lived surface traps with sufficient overpotential for the oxidization of both 2-propanol and water. On the basis of TA spectroscopy and photocurrent measurements, the position of the dopant-induced intra-gap level was estimated as 2.2 eV below the conduction band minimum.

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Section: Introductionmentioning

confidence: 55%

Charge carrier dynamics and visible light photocatalysis in vanadium-doped TiO2 nanoparticles

Rossi

Pasquini

Catone

et al. 2018

Applied Catalysis B: Environmental

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“…This trapping time was later confirmed by ultrafast electron diffraction studies of the Zewail group 260 on photoexcited titanosilicate materials consisting exclusively of pentacoordinated Ti centres. Very recently, Obara et al 261 repeated the experiment described in Ref. 26, but this time with X-ray pulses from the free electron laser.…”

Section: Inter-site Charge Transfer In Sensitized Transition Metal Oxmentioning

confidence: 98%

Charge migration and charge transfer in molecular systems

Wörner

Arrell

Banerji

et al. 2017

Structural Dynamics

194

163

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The transfer of charge at the molecular level plays a fundamental role in many areas of chemistry, physics, biology and materials science. Today, more than 60 years after the seminal work of R. A. Marcus, charge transfer is still a very active field of research. An important recent impetus comes from the ability to resolve ever faster temporal events, down to the attosecond time scale. Such a high temporal resolution now offers the possibility to unravel the most elementary quantum dynamics of both electrons and nuclei that participate in the complex process of charge transfer. This review covers recent research that addresses the following questions. Can we reconstruct the migration of charge across a molecule on the atomic length and electronic time scales? Can we use strong laser fields to control charge migration? Can we temporally resolve and understand intramolecular charge transfer in dissociative ionization of small molecules, in transition-metal complexes and in conjugated polymers? Can we tailor molecular systems towards specific charge-transfer processes? What are the time scales of the elementary steps of charge transfer in liquids and nanoparticles? Important new insights into each of these topics, obtained from state-of-the-art ultrafast spectroscopy and/or theoretical methods, are summarized in this review.

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“…More recently, Collet and co-workers extended these studies to SCO molecular crystals 137 . At SACLA, studies were performed on an Fe-complex, [Fe III (C 2 O 4 ) 3 ] 3+ in solution, 138 delivering insight into the photoinduced electronic and structural changes in the system, while the photoinduced charge carrier dynamics was investigated in the case of WO 3 nanoparticles, 139 and of TiO 2 140 . The latter studies repeated those by Santomauro et al 125 using the slicing scheme, but this time with a greatly enhanced S/N, which allowed them to detect a factor of 3 between the electron trapping time (∼100 fs) and the ensuing structural relaxation of the trap (∼300 fs).…”

Section: Applications In Chemistrymentioning

confidence: 99%