Spectroscopic measurements of temperature with uranyl compounds

A new class of fluorescent probes for measuring temperature is described. The intensities of the strong fluorescence bands of uranyl acetate, uranyl nitrate hexahydrate, and uranyl orthophosphate were recorded when the uranyl compound was illuminated with an argon-ion laser operating at 488 mn. The intensity ratio of two fluorescence bands of uranyl acetate at room temperature were determined for five freshly prepared samples and shown to be independent of the intensity of the laser excitation and optical alignment. The intensities of the fluorescence bands lying between 500 and 570 nm were measured at various temperatures ranging from 77 to 295 K. The ratio of the intensities or two fluorescence bands was calculated and shown to vary linearly with temperature. A linear fit provided the slope. The largest positive slope of all the intensity ratios associated with uranyl acetate was 6.02 X 10(-3) K-1, that associated with uranyl orthophosphate was 4.68 X 10(-3) K-1, and that associated with uranyl nitrate hexahydrate was 1.81 X 10(-3) K-1. The potential of uranyl compounds as a new group of temperature probes is discussed.