Determination of Fluorescence Lifetimes and Heterogeneity Analysis Using Time-Independent Phase-Resolved Intensity Measurements

Abstract

ABSTRACT The use of phase-resolved fluorescence spectroscopy (PRFS) for the determination of fluorescence lifetimes using both phase delay and demodulation relationships is compared with determinations using direct measurements of phase delay and demodulation. In the PRFS approach, values for the phase delay and demodulation were found from cosinusoidal curves constructed from the time-independent phase-resolved intensity data, using both cosine fits and polynomial fits. Results for the phase and modulation fluorescence lifetimes of PRODAN, 9,10 diphenylanthracene and 1,2,5,6 dibenzanthracene found using the direct and the PRFS approaches were in excellent agreement. Precisions for the direct approach determinations were better than those for the PRFS approach for the longer-lived emissions and slightly worse for the shorter-lived emission of PRODAN. Results for heterogeneity analysis of mixtures of POPOP and 9,10 diphenylanthracene and of PRODAN are also compared for the two approaches.