[Near-infrared luminescence of Yb3+-chrome blue-black R complex].

In the present work, sensitized near-infrared fluorescence from Yb3+-chrome blue-black R (CBR) complex was studied. It was found that Yb3+ forms 1:2 complex with CBR in natural ethanol solution. The visible fluorescence from CBR was quenched when the complex forms, while the near-infrared fluorescence from Yb3+ was greatly enhanced. A mechanism in which CBR absorbs excitation light and transfers its energy to Yb3+ ions was suggested. Near-infrared fluorescence intensity of Yb3+ is proportional to its concentration under the experimental condition, and was not disturbed by the addition of a small amount of other lanthanide ions, which indicate that near-infrared fluorometric analysis should be promising in the determination of single langthanide ions.