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O: Fachverband Oberflächenphysik

O 23: Poster Ultrafast Electron Dynamics

O 23.6: Poster

Montag, 17. März 2025, 18:00–20:00, P2

Transient IR pump-probe spectroscopy on AuNP-TiO₂ structures — •Lisa Mehner¹, Wouter Koopman¹, Felix Stete¹, Steven Berth¹, Alexander von Reppert¹, and Matias Bargheer^1,2 — ¹Insitute for Physics and Astronomy, University of Potsdam — ²Helmholtz-Zentrum Berlin

Photocatalysts can enhance redox reactions by supplying energetic electrons and holes. Combining gold nanoparticles (AuNP) and TiO₂ nanoparticles (NP) presents a promising route for realizing broad band photocatalysts as AuNP allow broad band absorption and TiO₂NP provide a long excited carrier lifetime. Electrons excited in the AuNP can transfer into the semiconductor if the energy is sufficient to overcome the interfacial Schottky barrier. Transferred electrons are expected to have a prolonged lifetime in the TiO₂ conduction band, since no vacancies are available for recombination in the valence band. Here, we present our initial findings on charge transfer of a TiO₂NP+AuNP sample measured by transient pump-probe spectroscopy with optical pump-pulses and IR probe-pulses. Our measurements confirm the transfer of charges to the conduction band . Comparing TiO₂NP+AuNP to pure TiO₂NP suggests that both electron transfer from Au to TiO₂ as well as direct excitation of TiO₂ trap states occurs. The decrease in carrier lifetime with increasing fluence moreover indicates back transfer of charges from TiO₂ to Au.

Keywords: Ultrafast spectroscopy; charge transfer; Schottky barrier; heterojunction metal semiconductor