Abstract
The measurement of fluorescence lifetimes in an undergraduate laboratory typically requires access to pulsed lasers. Commonly, a N2 laser is used to pump a dye or a frequency doubled Nd:YAG is used at 532 nm. While it is certainly valuable to introduce undergraduates to these lasers, it is also possible to perform fluorescence lifetime experiments using a pulsed-LED as an excitation source. The use of pulsed-LEDs does away with the safety concerns associated with lasers and laser dyes and simplifies the experimental procedure. In our experiment, the fluorescence lifetime of Ru(bpy)32+ is measured as a function of oxygen concentration. The concentration of oxygen is varied by addition of sodium sulfite to the aqueous solution and is monitored. Stern–Volmer plots are constructed, and the observed quenching rate constant is compared to the calculated bimolecular rate constant. Students also become acquainted with the simple circuit used to pulse the LED and with the use of the oscilloscope.
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