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A fluorescent temperature probe based on the association between the excited states of
I D Figueroa1, M el Baraka, E Quiñones
1Department of Chemistry, University of Puerto Rico, San Juan 00931-3346.
Abstract:
A temperature probe based on the fluorescence properties of the two excited states of 4-(N,N-dimethylamino)benzonitrile (DMABN) in equilibrium with beta-cyclodextrin (CD) in aqueous solution is presented. The fluorescence intensity of the Franck-Condon excited state (FB) as a function of temperature shows a straight line with a correlation better than 0.99 in the 283-308 K temperature interval. On the other hand, the fluorescence intensity of the twisted internal charge-transfer state (FA) remains constant in the same temperature interval because the binding of DMABN in the A* state to CD is isoenthalpic and entropy driven. It is found that the FA/FB ratio is independent of the excitation intensity at a specified temperature, shows a linear relationship with temperature, and allows temperature measurements with a resolution of +/- 2.5 K.
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