Fluorescence lifetimes of the well characterized humic substance, armdale fulvic acid

Decay of luminescence from the well characterized humic substance, Armdale fulvic acid, has been measured with both nanosecond and picosecond flash excitation. In both aerated and deaerated solutions at pH between 2 and 7, three characteristic times are required to account for the decay envelope and these times vary over only a narrow range. The three are in the vicinity of 200 picosecond, 2 nanosecond, and 7 nanosecond respectively. Cu(II) complexation led to static quenching.