Fast lifetime and amplitude determination in luminescence exponential decays

In this work a novel algorithm for the fitting of an exponential decay luminescence curve is proposed. It is based on the integration of the luminescence intensity over two or three temporal windows in different states of the sample: steady state with and without optical excitation and during the whole luminescence intensity decay. These measurements allow to obtain the amplitude of the signal, the offset and the lifetime respectively, not only for single exponential decays, but also for multiple exponential behavior, if averaged values are considered. The proposed approach does not require a very fast instrumentation, since the width of the integration windows are fixed to values much higher than the expected lifetime of the sample, which represents a clear advantage over other window-based methods for the determination of luminescence lifetime. In addition, no previous knowledge of the expected lifetime is necessary. Specifically, this algorithm is applied for the fitting of the luminescence curve of an oxygen sensor based on PtOEP, and implemented on a very reduced and simple electronics, consisting basically on a digital color detector of 12-bits resolution that allow to define integration times high enough for measurements of the intensity using this approach. Good results are achieved, proving the benefits of the method.