Fine adjustment of emission wavelength, light-conversion quality, photostability of blue-violet light conversion agents based on FRET effect

Abstract

Single fluorescent chromophore is difficult to achieve efficient photoecological effect, meanwhile, the cost of light conversion agent should be more strictly controlled, thereby promoting the large-scale application of light conversion agricultural film. To solve the above problems, three carbazole derivatives CZ, TCZ and MCZ as donors of Förster resonance energy transfer, and the tris(carbazolyl) substituted triazine TPT as an acceptor of Förster resonance energy transfer, were designed and synthesized. Based on absorption and emission spectra, aggregation induced emission experiments, and light conversion quality tests, the best formulation of light conversion film are obtained. Among of them, TCZ@0.2TPT@EVAb and MCZ@0.2TPT@EVAb films (40% ethylene vinyl alcohol copolymer defined as EVAb film) show highest photosynthetic photon flux density at 400–500 nm, and matching fluorescence emission (458 nm and 461 nm). Under 20 h of intensified ultraviolet radiation (365 nm, 40 W), the emission intensity of TCZ@0.2TPT@EVAb and MCZ@0.2TPT@EVAb films can maintain over 94% of the initial value, showing excellent photostability. Compared with the blank EVAa/EVAb film, the transmittance of the doping films at 500–600 nm are up to 95.12%–99.64%, meaning excellent compatibility and dispersion of light conversion agent in doping films. It is worth mentioning that emission maxima of doping films can be continuously adjusted within the spectral range 430–480 nm, which is conducive to meet the photoecological needs of different crops. Finally, the doping films show low transmittance (1.78%–11.42%) at 200–350 nm, outlining excellent UV light conversion properties.