Phosphorescence lifetime measurements with sensor materials: Comparison of the four different detection platforms

Using several types of Pt-porphyrin based oxygen sensing materials and conditions, we evaluated comparatively four different detection platforms that perform phosphorescence lifetime (PLT) measurements in the microsecond time domain. The time-resolved fluorescence reader Victor 2, which utilises Rapid Lifetime Determination method and Xe-flash lamp excitation, produced stable but inaccurate readings at PLT values < 15 µs, affected by the flash-lamp afterglow and sensor heterogeneity in oxygenated conditions. The luminescence spectrometer Cary Eclipse, which utilises multi-point phosphorescence decay method, was able to partly correct these interfering factors and produce more accurate PLT values from mono- and bi-exponential fits, however short PLT values were still affected by Xe-flash lamp afterglow. The wide-field Tpx3Cam cam-era-based macroscope and the confocal laser-scanning FLIM/PLIM microscope, which use short-pulse excitation (ns LED or ps diode laser pulses, respectively) and TCSPC method, revealed the presence of short-lived components (1.5–6.0 µs) in sample decays, which have to be considered in PLT calculations. The imaging platforms produced more accurate and in-formative PLT data, but they operate with large volumes of raw and processed data. Overall, for each PLT platform a number of potential sources of error and measurement artefacts have been revealed, which can be minimised by careful optimisation of settings and validation with alternative platforms and sensor materials.