The Radiative Decay of Green and Red Photoluminescent Phosphors: An Undergraduate Kinetics Experiment for Materials Chemistry

摘要

This article describes a laboratory experiment that allows the students to investigate the radiative properties of the green and red emitting phosphors that are employed in commercial fluorescent lamps. Making use of a spectrofluorometer, students first record the emission spectrum of a fluorescent lamp under normal operating conditions, and then they study the photoluminescent powder that coats the inner surface of commercial fluorescent tubes. The emissions of the green (Tb3+-activated) and red (Eu3+-activated) phosphors are optimized, and the respective decay curves are recorded and analyzed using the kinetic model for first-order, consecutive reactions. Students verify that the radiative decay of the green phosphor can be well reproduced using a mono-exponential function, whereas a bi-exponential function must be employed to fit properly the faster decay of the red phosphor, which exhibits a pronounced maximum ca. 130 μs after the end of the excitation pulse. This experiment has been developed for an upper-level undergraduate audience, and it is suitable for advanced physical-chemistry courses.