A Cocktail Approach Toward Tunable Organic Afterglow Systems

In this work, a cocktail approach toward tunable organic long-lived luminescence materials in solid, solution, and gel states is proposed. The tunable long-lived luminescence (τ > 0.7 s) is realized by controlling the energy transfer via manipulating the photo-induced isomerization of the energy acceptor (5). The afterglow can be regulated between blue and yellow emission upon irradiation of UV or visible light. And the “apparent lifetime” for the long-lived fluorescence is the same as the lifetime of the energy donor. The function is relying on the simple radiative energy transfer (reabsorption) between a long-lived phosphorescence and a highly efficient fluorescent isomer (5b), rather than the complicated communication between the excited state of the molecules such as Förster resonance energy transfer or Dexter energy transfer. The simple working principle endows this strategy with huge universality, flexibility, and operability. This work offers an extremely simple, feasible, and universal way to construct tunable afterglow materials in solid, solution, and gel states.