Novel selenium-doped carbon quantum dots derived from algae effectively enhanced the delivery and accumulation of selenium in tomato plants (Lycopersicum esculentum) via foliar application

Nano-selenium (Se) fertilizers and their foliar application are promising strategies for improving the efficiency of Se supplements in agricultural practices. Here, we synthesized novel Se-doped carbon quantum dots (Se-CQDs) from excessive algae biomass via two distinct Se-doping methods and examined their differences in Se delivery to tomatoes and contributions to the plant growth and development. The results indicated that Se-CQDs could be taken up directly by the plants and the samples synthesized via the co-cracking method (Se-CQDs1) were more effective in promoting plant biomass, mineral content, fruit quality, and Se accumulation in the plants, especially in the fruits, than those synthesized via the adsorption-reduction method (Se-CQDs2). The better performance of Se-CQDs1 could be explained by the much smaller hydrodynamic size (similar to 106.5 nm) and less negative zeta potential (-13.56 mV) relative to that of Se-CQDs2, which greatly contributed to the higher leaf penetration and transport in plant tissues. Moreover, Se was more difficult to release from Se-CQDs1 relative to Se-CQDs2 in a wide pH range as reflected by the Se release experiment, which enabled the slower release of Se from Se-CQDs1 during the foliar application and thus higher efficiency as a potential Se nano-carrier to plants. This study suggests that algae might be a promising raw material to synthesize Se-enriched nano-fertilizers and unveils the critical role of Se-doping patterns in increasing Se bioavailability to plants and consequently the quality of crops.

Automated summary

We synthesized novel Se-doped carbon quantum dots and compared two different Se-doping methods in their ability to deliver Se to tomatoes and promote plant growth and development. The samples synthesized via the co-cracking method showed better performance in increasing plant biomass, mineral content, fruit quality, and Se accumulation. This could be attributed to their smaller size and less negative charge, which facilitated better penetration and transport in plant tissues. The slower release of Se from these samples during foliar application also contributed to their higher efficiency as a potential Se nano-carrier.