Giant two-photon absorption of anatase TiO2 in Au/TiO2 core-shell nanoparticles

Lijie Wang, Tsz Him Chow, Malte Oppermann, Jianfang Wang, Majed Chergui

Research output: Contribution to journalArticlepeer-review


We report on deep-to-near-UV transient absorption spectra of core-shell Au/SiO2Au/SiO2 and Au/TiO2Au/TiO2 nanoparticles (NPs) excited at the surface plasmon resonance of the Au core, and of UV-excited bare anatase TiO2TiO2 NPs. The bleaching of the first excitonic transition of anatase TiO2TiO2 at ∼3.8 eV∼3.8 eV is a signature of the presence of electrons/holes in the conduction band (CB)/valence band (VB) of the material. We find that while in bare anatase TiO2TiO2 NPs, two-photon excitation does not occur up to the highest used fluences (1.34 mJ/cm21.34 mJ/cm2), it takes place in the TiO2TiO2 shell at moderate fluences (0.18 mJ/cm20.18 mJ/cm2) in Au/TiO2Au/TiO2 core-shell NPs, as a result of an enhancement due to the plasmon resonance. We estimate the enhancement factor to be of the order of ∼108–109∼108–109. Remarkably, we observe that the bleach of the 3.8 eV band of TiO2TiO2 lives significantly longer than in bare TiO2TiO2, suggesting that the excess electrons/holes in the conduction/valence band are stored longer in this material.
Original languageEnglish (US)
Pages (from-to)1303-1313
Number of pages11
JournalPhotonics Research
Issue number7
StatePublished - Jun 28 2023

Bibliographical note

KAUST Repository Item: Exported on 2023-09-06
Acknowledgements: Horizon 2020 European Research Council Advanced Grant (DYNAMOX); Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (NCCR:MUST); China Scholarship Council. The authors thank Dr. L. Mewes, Dr. M. Puppin, and B. Bauer for helpful discussions. L.W. acknowledges support from the China Scholarship Council (CSC).

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics


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