A fluorescent temperature probe based on the association between the excited states of 4-(N,N-dimethylamino)benzonitrile and beta-cyclodextrin.
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.
Figueroa
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Department of Chemistry, University of Puerto Rico, San Juan 00931-3346.
el Baraka
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Quiñones
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Rosario
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Deumié
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D003505:Cyclodextrins / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D009570:Nitriles / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D047392:beta-Cyclodextrins
C115085:4-(n,n-dimethylamino)benzonitrile; D003505:Cyclodextrins; D005456:Fluorescent Dyes; D009570:Nitriles; D047392:beta-Cyclodextrins; C031215:betadex