I can't access the primary article but it appears the authors are trying to oxidize a chromophore using in situ generated singlet oxygen from hydrogen peroxide.
The half-life of singlet oxygen is short, on the order of a few microseconds, but the diffusion time is also on the same timescale. Assuming singlet oxygen is still being generated when your oxidant solution is being added to the chromophore solution, I don't see why this procedure couldn't work. The singlet oxygen isn't stable of course but it would last long enough to cause some chemistry provided it was added while the generation reaction was still ongoing.