Oscillation in Excited State Lifetimes with Size of Sub-nanometer Neutral (TiO2)nClusters Observed with Ultrafast Pump-Probe Spectroscopy

Jacob M. Garcia, Lauren F. Heald, Ryan E. Shaffer, Scott G. Sayres

Research output: Contribution to journalArticlepeer-review

Abstract

Neutral titanium oxide clusters of up to 1 nm in diameter (TiO2)n, with n < 10, are produced in a laser vaporization source and subsequently ionized by a sequence of femtosecond laser pulses. Using a 400 nm pump and 800 nm probe lasers, the excited state lifetimes of neutral (TiO2)n clusters are measured. All clusters exhibit a rapid relaxation lifetime of ∼35 fs, followed by a sub-picosecond lifetime that we attribute to carrier recombination. The excited state lifetimes oscillate with size, with even-numbered clusters possessing longer lifetimes. Density functional theory calculations show the excited state lifetimes are correlated with charge carrier localization or polaron-like formation in the excited states of neutral clusters. Thus, structural rigidity is suggested as a feature for extending excited state lifetimes in titania materials.

Original languageEnglish (US)
Pages (from-to)4098-4103
Number of pages6
JournalJournal of Physical Chemistry Letters
Volume12
Issue number16
DOIs
StatePublished - Apr 29 2021

ASJC Scopus subject areas

  • Materials Science(all)
  • Physical and Theoretical Chemistry

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