Researchers have uncovered a surprising new role for nano-biochar, showing that it can drive the natural formation and accumulation of silver nanoparticles in rice roots. The study, published in Biochar, reveals how this tiny carbon material interacts with plant roots to transform silver ions into metallic nanoparticles, potentially affecting both plant health and the movement of metals in the environment.
Silver is widely used in electronics, medicine, and antimicrobial products, which leads to the release of silver ions into soils and waterways. These ions are highly reactive and can pose risks to living organisms. In contrast, silver nanoparticles are more stable and less toxic. Yet how these particles form naturally in soils has remained unclear.
Led by Shiguo Gu and Fei Lian from Hebei University of Technology, the research team discovered that nano-biochar acts as an electron shuttle in the rhizosphere, the narrow zone of soil surrounding plant roots. When nano-biochar was added to the growth environment of rice plants, it transferred electrons to oxygen released from the roots. This process generated superoxide radicals that in turn reduced silver ions to form silver nanoparticles. The team used high-resolution microscopy and single-particle ICP-MS to confirm that the nanoparticles not only formed around the roots but also accumulated inside rice leaves and cells.
Interestingly, a moderate amount of nano-biochar promoted silver nanoparticle formation, while excessive amounts reduced oxygen secretion from roots and suppressed the process. The researchers also found that nano-biochar reduced the total uptake of silver by rice, suggesting that it can both protect plants from toxic metals and influence how metals move through the soil–plant system.
"Our findings highlight that nano-biochar is not just a passive soil amendment but an active participant in chemical transformations in the rhizosphere," said Lian. "It plays a catalytic role in regulating redox-active metals and could influence how these elements cycle through ecosystems."
The study raises new questions about the potential for naturally occurring nanoparticles to enter the food chain. At the same time, it opens opportunities to harness biochar's reactivity to improve soil health and enhance sustainable agricultural practices. The authors suggest that understanding and managing the dual effects of nano-biochar, its ability to detoxify metals while promoting nanoparticle formation, will be key to ensuring both environmental safety and food security.
===
Journal Reference: Gu, S., Sun, B., Wang, F. et al. Insight into the crucial role of nano-biochar in the natural formation and bioaccumulation of silver nanoparticles in the rhizosphere by single-particle ICP-MS. Biochar 7, 111 (2025). https://doi.org/10.1007/s42773-025-00492-w
===
About Biochar
Biochar is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.
