Nonlinear phosphorescence quenching mechanism of gadolinium labeled porphyrin by oxygen on filter paper

Nonlinear phosphorescence quenching mechanism of gadolinium labeled hematoporphyrin monomethyl ether (Gd-HMME) by oxygen on the filter paper was studied. The intensity Stern-Volmer plot was found to be approximately linear for oxygen concentration from 10% to 100%, but showing a negative curvature from 0% to 10%. The lifetime plot has similar changing trend. The intensity plot is slightly higher than the lifetime plot reflecting the existence of static quenching. The nonlinear responses were related to the nonlinear solubility of oxygen, which perfectly satisfy the nonlinear solubility model. Data analysis indicates that the static quenching rate constant is unchanged and the percentage of static quenching is about 35% 3% in the whole range of oxygen concentration. (C) 2015 Elsevier B.V. All rights reserved.