The PL int will be higher in the case of Fl, but both are supposed to overlap. Then how do know if the system has delayed Fl emission?
Without measuring lifetime, how to distinguish between fluorescence and delayed fluorescence?
1. Must to measure time resolved (PL, FL) spectra
Without measuring lifetime, how to distinguish between fluorescence and delayed fluorescence?
Your spectrum will consists of 2 fluorescent components corresponding to 2 different lifetimes: 1 short and 1 longer. Normally, two fluorescent components will be assigned to two different luminescence centers even though their emission may be the same (Normally these emission are different). To distinguish these radiation components, it is best to perform time-resolved emission spectroscopy. The result is a series of emission spectra corresponding to different delay time values. Changes of the emission components in the each spectrum can be observed, which depend on the delay time value. In that spectrum you can observe which emission components appear corresponding to short delay time and which emission components correspond to long delay time.
In all ways, measuring life time is still the simplest and easiest to perform!
Presence of oxygen quenches the delayed fluorescence just like phosphorescence. Change of fluorescence intensity in the absence/presence of oxygen also indicate delayed fluorescence. You can simply purge your sample with argon/nitrogen during measurement.
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