Synthesis and characterization of Sr2Si5N8:Eu2+ agricultural films for enhanced plant photosynthesis

This research reports the synthesis of red-emitting Sr 2 Si 5 N 8 :Eu 2+ phosphor via direct silicon nitridation and its incorporation into biodegradable cellulose acetate (CA) films for agricultural light-conversion applications. The optimized Sr 2 Si 5 N 8 :Eu 2+ phosphor exhibits a strong emission band centered at 620 nm with CIE chromaticity coordinates of x = 0.649 and y = 0.346 and a luminous efficiency of 92 lm/W under near-UV excitation. Embedded at 2 wt% into CA, the composite films block approximately 95 % of ultraviolet radiation (250–400 nm) while maintaining around 75 % transparency in the photosynthetically active region. Mechanical testing shows that the Sr 2 Si 5 N 8 :Eu 2+ @CA films are 36 % stiffer and 41 % stronger than neat CA films, and retain 89.5 % of their initial photoluminescence intensity after 120 h of continuous 370 nm irradiation. Soil-burial experiments reveal a 39 % mass loss within 60 days, confirming that the composite films remain biodegradable despite the incorporation of the inorganic phosphor. Greenhouse trials with tomato plants demonstrate 20 % higher plant height, 39 % more leaves, 17 % larger leaf area and 25 % more fruits per plant compared with CA control films, accompanied by 29 % higher chlorophyll content in leaves and a 20 % increase in lycopene content in fruits. These results show that Sr 2 Si 5 N 8 :Eu 2+ @CA films can simultaneously modulate the incident light spectrum and enhance crop performance in an environmentally sustainable manner. To the best of our knowledge, this work presents the first demonstration of integrating an inorganic Sr 2 Si 5 N 8 :Eu 2+ nitride phosphor into a fully biodegradable cellulose acetate matrix and coupling detailed optical, mechanical, stability, biodegradation and greenhouse performance evaluations for light-conversion agricultural films.