Enhancing photosynthesis of microalgae via photoluminescent g-C3N4 accelerated photoelectrons transfer in photosystem

Using photoluminescent (PL) graphitic carbon nitride (g-C 3 N 4 ) to convert ultraviolet (UV) light into chloroplast absorbed blue or near infrared (NR) is an attractive methodology to facilitate sunlight energy storage and carbon sequestration by microalgae. However, most researches focus on inhibiting water bloom by g-C 3 N 4 , applying PL g-C 3 N 4 to promote growth of microalgae is rarely reported. Accordingly, PL g-C 3 N 4 is synthesized by a microwave heating method and co–cultured with Chlorella vulgaris ( C. vulgaris ) with concentration of 0, 50, and 250 mg/L, named as C. vulgaris -0, C. vulgaris -50, and C. vulgaris -250, respectively, to study effect of PL g-C 3 N 4 on growth of C. vulgaris . Results indicate that there is no significant effect of microwave synthesized g-C 3 N 4 on morphology of microalgae cells, while cell viability and growth rate of C. vulgaris -50 is obviously enhanced. Further analysis indicates that, on the one hand, PL fluorescence at 615 nm enlarges light absorption of microalgae; on the other hand, photogenerated electrons by g-C 3 N 4 accelerate electron transfer in photosystem, subsequently enhancing formation of NADPH and ATP, which is favorable to growth of microalgae. Metabolism analysis illustrates that glucose, fructose, and galactose, involved in glycolysis and photosynthesis, are all up-regulated in C. vulgaris -50 group. This work reveals low concentration of PL g-C 3 N 4 facilitates protein synthesis and energy metabolism through enhancing light absorption and electron transfers, providing a biochemical strategy to enhance carbon sequestration.