Optical control of quantum dot luminescence via photoisomerization of a surface-coordinated, cationic dithienylethene

Photoisomerization of a coordinating, photochromic dithienylethene bearing a pyridine and a methylpyridinium group was investigated as a means to reversibly modulate the luminescence from CdSe-ZnS core-shell quantum dots. Resonance energy transfer and electron transfer are both plausible quenching mechanisms based on an increase in the spectral donor-acceptor overlap and an anodic shift in the reduction potential accompanying the isomerization reaction of the dithienylethene photoswitch. Photochemical degradation of both the quantum dot and photochromic quencher was observed after repeated cycling between the two isomers, suggesting irreversible electron transfer from the quantum dot to the dithienylethene as the dominant luminescence quenching mechanism.