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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)3 2+ 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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We determined calcium-to-fluorine (Ca/F) signal ratios at the surface and in the depth dimension in approximately 6000-year-old sheep and cattle bones using Ca I 671.8 and F I 685.6 emission lines. Because the bones had been previously analyzed for collagen preservation quality by measurement of C/N ratios at the Oxford Radiocarbon Accelerator Unit, we were able to examine the correlation between our ratios and quality of preservation. In the bones analyzed in this experiment, the Ca I 671.8/F I 685.6 ratio was generally lower and decreased with successive laser pulses into poorly preserved bones while the ratio was generally higher and increased with successive laser pulses into well-preserved bones. After 210 successive pulses, a discriminator value for this ratio (5.70) could be used to distinguish well-preserved and poorly preserved bones regardless of species.

Surface-enhanced Raman spectroscopy (SERS) substrates typically consist of gold or silver nanoparticles deposited on a non-conductive substrate. In Raman spectroscopy, the nanoparticles produce an enhancement of the electromagnetic field which, in turn, leads to greater electronic excitation of molecules in the local environment. Here, we show that these same surfaces can be used to enhance the signal-to-noise ratio obtained in laser-induced breakdown spectroscopy of aqueous solutions. In this case, the SERS substrates not only lower breakdown thresholds and lead to more efficient plasma initiation but also provide an appropriately wettable surface for the deposition of the liquid. We refer to this technique as surface-enhanced laser-induced breakdown spectroscopy.

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