Kinetics process of room temperature phosphorescence and fluorescence of gadolinium porphyrin in aqueous solution

Abstract

The behavior of room temperature phosphorescence quenching and fluorescence enhancing of gadolinium labeled sinoporphyrin sodium (Gd-DVDMS) in the aqueous solution were studied. Gd-DVDMS was characterized by various techniques including mass spectra, Fourier transform infrared spectra and transmission electron microscopy. The optical behavior was monitored through UV–vis absorption spectra and photoluminescence spectra. The result shows that the phosphorescence intensity gradually quenches, almost disappears after dissolved 120 min, meanwhile the fluorescence intensity enhances 5 times. The above behavior is attributed to the decreased population of Gd-DVDMS as first excited triplet state (T1). Based on the time-invariant of both absorption spectra and phosphorescence decay curves at 710 nm of Gd-DVDMS in different dissolution time, the reason for the decreased population of Gd-DVDMS in T1 state is that the intersystem crossing from first excited state (S1) to T1 is prevented. In addition, the fluorescent decay curves of Gd-DVDMS initially dissolved in the aqueous solution and dissolved for 120 min were also measured for comparison. The big change in fluorescent lifetime further proves the conclusion that intersystem crossing is prevented, meanwhile, the increase in fluorescence intensity is demonstrated. In this work, the possibility of decomposition of Gd-DVDMS is excluded because the phosphorescence decay curve in Gd-DVDMS aqueous solution is sensible to DVDMS.