Root exudates as natural ligands that alter the properties of graphene oxide and environmental implications thereof†
Abstract
In the present work, we identified root exudates that were stimulated by pristine graphene oxide (PGO), including small-molecule acids, alcoholates, alkanes, amino acids and secondary metabolites. These exudates acted as ligands and became immobilized on the PGO to form ligand-GO complexes (LGO). Compared with PGO, LGO exhibited increased thickness, a higher C : O ratio, and reduced transparency and size. Nitrogen- and sulfur-containing groups were observed in LGO. LGO, with its decreased negative charges, was less stable than PGO. In addition, LGO exhibited more unpaired electrons and disordered structures and greater UV absorption compared with PGO. The above alterations in the properties of PGO that occurred after modification of the PGO by exudates induced significant malformations (abnormal tail flexure and pericardial edema) and the loss of mitochondrial membrane polarization in zebrafish as a model organism. This work revealed that root exudates act as natural ligands and significantly alter the properties of PGO.
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