Dual-layered up-conversion films with tunable multi-peaks spectrum for efficient photocatalytic degradation

The incorporation of multiple up-conversion (UC) materials into dual-layered UC films presents a promising strategy for achieving multi-peaks spectrum. Here, we developed dual-layered UC films containing triplet-triplet annihilation up-conversion luminescence (TTA-UCL) chromophores and NaYF₄:Yb³⁺,Tm³⁺ nanoparticles to enable multi-peaks emissions at 340−360 and 390 nm in the transmission manner and 340, 360 and 400–440 nm in the reflection manner under irradiations of green and NIR light. The light absorption and emission behaviors from different film surfaces were studied clearly. Besides, TiO₂ and g-C₃N₄ with different absorption spectra were chosen to verify the availability of the dual-layered films to tune emission spectra. When both green and NIR light were used simultaneously, TiO₂ and g-C₃N₄ can degrade tetracycline (TC) by 2.14 and 1.77 times more than the cases where single light was used alone. The photocatalytic abilities of TiO₂ or g-C₃N₄ can be further improved by the selective increase in NIR or green light power density due to their different absorption spectra. The dual-layered films containing TTA-UCL chromophores and NaYF₄:Yb³⁺,Tm³⁺ nanoparticles provide a candidate framework for UC systems with tunable short-wavelength spectra to expand their applications in the fields of photocatalysis.