Photoinduced chesorluminescence from radical processes on ZrO2 surfaces

Photoexcitation of ZrO2 particles causes luminescence (τ∼15.0 s) which, after its termination, on addition of H2 causes emission of a light pulse that displays biphasic decay kinetics (τ1∼0.9 s and τ2∼15.5 s). The latter emission is referred to as a photoinduced chesorluminescence (PhICL). At 77 K, the longer-lived emission is thermally quenched. The shorter-lived emission is caused by electron trapping by the Va (anion vacancies) low energy traps; the longer-lived emission involves electron trapping by shallow traps, followed by detrapping and subsequent retrapping by the Va traps. Formation of highly energetic radical species is a necessary condition to observe PhICL emission.