Fluorescence patterning in films of a photoswitchable BODIPY-spiropyran dyad.

A BODIPY-spiropyran dyad was embedded within poly(methyl methacrylate) films spin-coated on glass slides. Visible illumination of the resulting materials excites selectively the BODIPY fragment, which then deactivates radiatively by emitting light in the form of fluorescence. Ultraviolet irradiation promotes the isomerization of the spiropyran component to the corresponding merocyanine. This photoinduced transformation activates electron and energy transfer pathways from the fluorescent to the photochromic fragment. Consistently, the BODIPY fluorescence is effectively suppressed within the photogenerated isomer. As a result, ultraviolet illumination with a laser, producing a doughnut-shaped spot on the sample, confines the fluorescent species within the doughnut hole. This behavior is an essential requisite for the implementation of super-resolution imaging schemes based on fluorescence photodeactivation. Thus, the operating principles governing the photochemical and photophysical response of this molecular switch can ultimately lead to the development of innovative probes for fluorescence nanoscopy.