Double local electromagnetic fields collaboratively enhanced triplet-triplet annihilation upconversion for efficient photocatalysis

Strong triplet-triplet annihilation upconversion (TTA-UC) of sub-bandgap photons is significant for the low-energy photon capture in photocatalytic technology. Herein, we report a strategy to enhance TTA-UC for achieving efficient photocatalysis, via the collaborative coupling of double local electromagnetic fields from the photonic band gap (PBG) and localized surface plasmon resonance (LSPR) effects. An upconversion-photocatalysis film was constructed by depositing CdS on a poly(vinylidenefluoride) inverse opal photonic crystal consisting of metal nanoparticles and platinum(ii)-octaethylporphyrin & 9,10-diphenylanthracene. As a result of the synergism of double local electromagnetic fields, the TTA-UC fluorescence intensity is increased by 10.74 times at most with the highest quantum yield of 11.05%, which far surpasses that improved by the single action of different PBG and LSPR effects. Based on the TTA-UC process enhanced by the synergism, the upconversion-photocatalysis film exhibits a 3.29-fold and 5.25-fold increase in the photocatalytic degradation rate of organic compounds under visible and green light, respectively. This work offers a distinctive way to fortify the TTA-UC fluorescence for efficient photocatalysis.