CHED 1165 |
| Ruthenium is one of several transition metals capable of photoexcitation with a subsequent characteristic emission spectrum. The photophysics of Ru(II) complexes have been studied extensively for nearly forty years, but the use of these properties in sensing application has only recently been investigated. Prior work with ruthenium doped metal chelates suggest that energy transfer is a possible mechanism for excitation of Ru(bpy)3Cl2 (2,2-bipyridine) when introduced into a Zn(bpy)3Cl2 crystal lattice. In this mechanism Ru(bpy)3Cl2 is introduced to create an energy sink in the Zn(bpy)3Cl2 lattice, which has higher energy emitting states than Ru(bpy)3Cl2 in a native crystalline lattice. The host lattice should act as a satellite molecule to the Ru(bpy)3Cl2, absorbing additional radiation by its increased surface area. As a result of efficient excitation of the zinc lattice followed by energy transfer, the intensity of the Ru(bpy)3Cl2 emission is orders of magnitude greater than ruthenium alone. Observed increases in intensity, spanning the zinc and ruthenium absorption wavelengths, have been attributed to energy transfer. Despite the apparent observation of energy transfer, our results indicate that direct excitation of ruthenium is a more prominent contributor to the emission intensity. Detection limits were encountered at the nanogram and high picogram scale (Ru(bpy)3Cl2 mass). Lifetime measurements were used to measure the most likely mechanism of energy transfer for the doped crystal. A detectable rise-time was not observed discounting a triplet-triplet state energy transfer amongst the host and guest species. Inefficient energy transfer and a singlet-singlet energy transfer suggest the misinterpretation of prior studies. |
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Undergraduate Research Poster Session: Inorganic Chemistry
2:00 PM-4:00 PM, Monday, March 26, 2007 Hyatt Regency Chicago -- Riverside Center, Poster
Division of Chemical Education |