Europium-doped calcium pyrophosphates:: Allotropic forms and photo luminescent properties

in a search for new luminescent biological probes, we synthesized calcium pyrophosphates doped with europium up to an atomic Eu/(Eu + Ca) ratio of 2%. They were prepared by coprecipitating a mixture of calcium and europium salts with phosphate, After heating at 900 degrees C in air, two phases coexisted, identified its the beta calcium pyrophosphate form and EuPO4. Heating near 1250 degrees C ill air, during the beta - x transformation, europium ions substitute for Calcium ions ill the x. calcium pyrophosphate structure as, demonstrated by the spectroscopic study. Europium ions with both valence states (divalent and trivalent) were observed in the samples. Following the synthesis procedure, partial reduction of Eu3+ took place even in an oxidizing atmosphere, The 0.5%-doped compound could serve as a sensitive probe in biological applications. Depending oil the excitation wavelength. the luminescence occurs either in the red or in the blue regions, which discriminates it from parasitic signals arising from other dyes or organelles in live cells. (c) 2005 Elsevier Inc. All rights reserved.