Abstract Spectral and time-resolved fluorescence properties as well as relative fluorescence quantum yields of carbodiimide derivatives of 2, 5-diphenyloxazole (PPO)(prepared by H 2 S elimination from the corresponding thioureas), of some intermediates in the preparation, and of several other PPO derivatives were investigated in solution and in the solid state to test their suitability as solid scintillators. The carbodiimides reacted slowly with water ...