Thermal-responsive phosphorescent nanotubes have been fabricated from the co-assembly of two neutral iridium complexes, which behave as the antenna chromophores and energy acceptors, respectively, in these highly ordered crystalline superstructures. By tuning the acceptor doping ratio in a range of 0 to 0.5 %, these tubes display color-tunable phosphorescence from green to red at room temperature, and it is attributed to the highly efficient light-harvesting and energy transfer within these materials. For the same reason, the acceptor emission in the nanotubes is amplified more than 800 times with respect to its pure non-emissive solid sample. The doped tubes show reversible thermal-responsiveness, in which the energy transfer was completely suppressed at 77 K and reactivated at room temperature. These processes were characterized by the in situ emission color (green, orange, and red) and spectral changes and lifetime measurements of isolated nanotubes. The temperature-controlled exciton dynamics are responsible for the luminescent thermochromism in these crystalline materials.
Keywords: energy transfer; exciton migration; iridium; luminescence; nanostructures.
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