Effects of surface modification on toxicity of CeO nanoparticles to lettuce.

Phytotoxicity of nanoceria (nCeO) has been reported, but there are few studies on how to reduce its phytotoxicity. In the present study, we modified nCeO with two organophosphates (nCeO@ATMP and nCeO@EDTMP) and compared their toxicity to lettuce with that of uncoated nCeO. The results showed that bare nCeO significantly inhibited the root growth of lettuce, leading to oxidative damages and root cell death. In contrast, after surface modification, the toxicity of nCeO@ATMP to lettuce was weakened, while nCeO@EDTMP was nontoxic to lettuce. It was found that the surface properties of the modified materials have been changed, resulting in sharp decreases in their bioavailability. Although nCeO with and without surface coatings were all transformed when interacting with plants, the absolute contents of Ce(III) in roots treated with modified nCeO decreased significantly, which may be the main reason for the reduction of toxicity. This study indicates that it is feasible to reduce the phytotoxicity of nanomaterials through surface coating.