Observation of frequency-domain fluorescence anomalous phase advance due to dark-state hysteresis

Evangelos Gatzogiannis, Xinxin Zhu, Ya-Ting Kao, Wei Min*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Frequency-domain fluorescence spectroscopy, commonly referred to as phase fluorometry, is a classic approach to study the lifetime dynamics of fluorescent systems. Here we report an interesting phenomenon: unlike conventional fluorescence lifetime phase fluorometry in which the fluorescence trace always lags behind the modulated excitation source, the detected signal from certain fluorophores can actually exhibit fluorescence anomalous phase advance (FAPA) as if the fluorescence is emitted "ahead"of the source. FAPA is pronounced only within a range of modulation frequencies that are outside quasi-static and quasi-equilibrium conditions. We attribute FAPA to photoinduced dark state hysteresis, supported by both simulations of photodynamic transitions and experiments with dark-state promoters and quenchers. Being a fast and straightforward frequency-domain reporter, FAPA offers a unique and specific contrast mechanism for dark state dynamics sensing and imaging.

Original languageEnglish
Pages (from-to)461-466
Number of pages6
JournalJournal of Physical Chemistry Letters
Issue number5
StatePublished - 3 Mar 2011

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