How can we determine the “components” to take in fluorescent lifetime analysis?

Answer 1

Dear Sandeap,
I have never done this experiment but try this:

For a pure substance we usually find just one exponential decay (1-exp(-kt)). There may be more if there is more than one forbidden transition in the substance. Plot your results on a graph of Intensity/time and find where the output has dropped to 1/e of its original value. (the graph is self similar so it does not matter where you start you will always get the same time constant T)

For a mixed compound, such as the powder from an fluorescent tube (!!!!! treat it as a heavy metal poison!!!!) you will have a number of the above graphs all superimposed on (added) each other.
The first thing to do is CHEAT. Try to find out how many dyes the manufacturer has used in his coatings - this is so you know roughly where you are going.
Plot the time graph again and see if you can identify an exponential decay at the beginning of your graph.
Now look at the very tail end and see if you have another decay there.
Redraw these two decays in their pure form and subtract there values away from your original graph. You may find that you have only 'noise' left and you are finished.
Otherwise keep repeating the process until any remaining exponential tendency disappears, and hope this corresponds with the information you have on the dyes present. (The manufacturer may not always tell you all of them).
See if somebody in a Chemistry Lab can do a Rare Earth and other(eg Zn, Cd) analysis for you, so you can guess at the number of dyes used.

See if you can do a more sophisticated Mathematical Analysis on your graph - I don't know of one based om exp(-kt) bu you may be lucky.

Hope this helps you.

CopyLeft:RC
ps send me an email on how you got on!