It really depends on what you mean by sensitive. Do you mean, can be used to sense something, for example oxygen where phosphorescence is obviously better. Or do you mean detecting the presence of a compound where the quantum yield of the emission is important.
As above, please give more information so that we can help you.
Fluorescence due to the following reasons:
(1) Phosphorescence is extensively quenched by oxygen under normal experimental conditions (i.e., oxygenated samples at room temperature)
(2) Phosphorescence is long-lived and therefore it produces a relatively small number of photons per second.
(3) Unlike fluorescence, phosphorescence requires a change in spin multiplicity and is, therefore, a forbidden transition. Consequently, phosphorescence rate constants are smaller than fluorescence rate constants.
(4) The first triplet excited state, from which phosphorescence arises, is closer to the ground state than the first singlet excited state, from which fluorescence arises. Therefore, the non-radiative deactivation of the first triplet excited state is more likely than the non-radiative deactivation of the corresponding first singlet excited state. See "Energy Gap Law".
There is often not a choice: compounds either show fluorescence OR phosphorescence. And it seems more systems have fluorescence than phosphorescence.
In principle, many, if not all, molecules show fluorescence as well as phosphorescence: from a singlet or a triplet state, respectively. Wether phosphorescence can be readily observed depends on the medium: best in frozen media, where quenching of the intrinsically long-lived (forbidden trioplet-singlet transiation) are sufficiently slowed down. Under such 'frozen conditions' , phosphoresccence can be more 'sensitive' (meaning?) than fluorescence, depending on the molecule/compound.
I agree with the above infos of the answerers and details about the T0--S0 transition for phosphorescence.
BUT YOUR QUESTION IS VERY,VERY VAGUE!!!
PLEASE NOTE that your question can be right and fast answered if you read p.e. the book of Theodor Förster about Fluorescence of Organic compounds (1982) e.g. Page 261 about phosphorescence.
Please give infos about your future proposal like :
- I want to investigate a kind of organic compound (Not your compound prior future publicaton) and I have this spectrometer ......... :
- I want to compare spectra of fluorescence or phosphorescence at room temperature condition with this solvent or at frozen condition with a mixture like diethylether, isopentane and ethanol (5 :5: 1) and so on...
Good luck and send more infos . Thank you in advance.
JRG
It really depends on what you mean by sensitive. Do you mean, can be used to sense something, for example oxygen where phosphorescence is obviously better. Or do you mean detecting the presence of a compound where the quantum yield of the emission is important.
As above, please give more information so that we can help you.
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