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Luminescence quenching

The following are from gated experiments in which a luminescence spectrum is collected at specified intervals after a laser pulse has excited the sample. The detectors are an intensified CCD array detector and an optical multichannel array detector, both by Roper Scientific. The software running both detectors is Roper's Winspec.

A paper describing these experiments is available from the American Chemical Society.

The 3D plots were all produced by simply importing the ascii output of the instrument as 2-d arrays, and then rendering the arrays in one step with the surface plotter.

Data was collected from silicate sol-gel thin films doped with europium, Eu, and rhodamine 700, R700. This is an energy transfer pair in which R700 quenches Eu's luminescence. This plot shows the Eu luminescence under no quenching by R700:

And this shows Eu under moderate quenching by R700:

The following is from a mesostructured film templated by the surfactant CTAB and containing the same amount of Eu and R700. Addition of surfactant alone improves energy transfer and R700 luminescence.

The following graph shows how the decay curves can be extracted from the pretty pictures trivially using Igor's programmability, and fit to exponentials functions of all sorts. These fits are then used to quantify energy transfer efficiency and to measure distances. Very similar results will be published in Journal of the American Chemical Society soon.

Finally, we have the transient absorption plot of a conducting polymer in solution. The polymer has a fluorescence lifetime of a few ns. The fluorescence appears as the negative "absorption" in the first few frames. The remaining frames show a triplet state centered near 600 nm with a lifetime of many microseconds.

Submitted by Payam Minoofar

Minoofar, P., B. Dunn, J. Zink, (2005). "Multiply Doped Nanostructured Silicate Sol-Gel Thin Films: Spatial Segregation of Dopants, Energy Transfer, and Distance Measurements." Journal of the American Chemical Society 127(8): 2656-2665 (download).