Liu Bei, Han Zixin, Pan Yu, Liu Xun, Zhang Meng, Wan Aling, Wang Zhongying
School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
Environ Sci Technol. 2023 Aug 15;57(32):11999-12009. doi: 10.1021/acs.est.3c03216. Epub 2023 Aug 3.
Cerium oxide (CeO) nanoparticles are one of the most important engineered nanomaterials with demonstrated applications in industry. Although numerous studies have reported the plant uptake of CeO, its fate and transformation pathways and mechanisms in plant-related conditions are still not well understood. This study investigated the stability of CeO in the presence of organic ligands (maleic and citric acid) and light irradiation. For the first time, we found that organic ligands and visible light had a synergistic effect on the reductive dissolution of CeO with up to 30% Ce releases after 3 days, which is the highest release reported so far under environmental conditions. Moreover, the photoinduced dissolution of CeO in the presence of citrate was much higher than that in maleate, which are adsorbed on the surface of CeO through inner-sphere and outer-sphere complexation, respectively. A novel ligand-dependent photodissolution mechanism was proposed and highlighted: upon electron-hole separation under light irradiation, the inner-sphere complexed citrate is more capable of consuming the hole, prolonging the life of electrons for the reduction of Ce(IV) to Ce(III). Finally, reoxidation of Ce(III) by oxygen was observed and discussed. This comprehensive work advances our knowledge of the fate and transformation of CeO in plant surroundings.
氧化铈（CeO）纳米颗粒是工业中已证明有应用的最重要的工程纳米材料之一。尽管众多研究报道了植物对CeO的吸收，但其在植物相关条件下的归宿、转化途径和机制仍未得到很好的理解。本研究调查了在有机配体（马来酸和柠檬酸）和光照存在下CeO的稳定性。首次发现有机配体和可见光对CeO的还原溶解有协同作用，3天后Ce释放量高达30%，这是迄今为止在环境条件下报道的最高释放量。此外，在柠檬酸盐存在下CeO的光致溶解远高于在马来酸盐存在下的情况，它们分别通过内球络合和外球络合吸附在CeO表面。提出并强调了一种新的依赖配体的光溶解机制：在光照下电子 - 空穴分离时，内球络合的柠檬酸盐更能消耗空穴，延长电子将Ce(IV)还原为Ce(III)的寿命。最后，观察并讨论了氧气对Ce(III)的再氧化作用。这项全面的工作推进了我们对CeO在植物环境中归宿和转化的认识。
