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.