LUMINESCENT PROPERTIES OF EUROPIUM AND TERBIUM COMPLEXES: THE INFLUENCE OF SOLVENTS AND pH
Rare earth metals are highly luminescent in the visible range of the spectrum and have long luminescence lifetimes. Such properties of lanthanides allow them to be used to create luminescent complexes that can be used, for instance, for biomedical purposes or in the creation of lasers and optical fibers. The effect of a mixture of various solvents (glycerin, methanol, water, heavy water) on the luminescent characteristics of europium(III) and terbium(III) complexes with various organic ligands based on 2,2’-bipyridyl and 1,10-phenanthroline was studied, and experiments were conducted to study the dependence of luminescent properties on pH. Solar PB2201 spectrophotometer was used to obtain absorption spectra. The emission and excitation luminescence spectra, luminescence kinetics were recorded using a Solar CM2203 spectrometer. The luminescence lifetime was calculated for various solutions. The results showed that the luminescence lifetime decreases when decreasing the methanol concentration in a glycerol/methanol solution. In addition, for water-soluble complexes, the dependence of the luminescence lifetime on the concentration of methanol was linear. It was also found that the luminescence lifetime decreases with a decrease in the concentration of methanol in a mixture of methanol and water and increases with a decrease in the concentration of methanol in a mixture of methanol and heavy water. When studying the dependence of the luminescence lifetime on pH, it was found that when the pH value decreases, the lifetime decreases, and the quantum yield increases in a more alkaline environment. The results have been obtained under the support of the RSF grant no. 16-13-10451 and RFBR project no. 18-02-01023.
Lomonosov Moscow State University, faculty of physics, Moscow, Russia
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