Department of Geography, Earth and Environmental Sciences, University of Birmingham , Birmingham, U.K.
Center for Environmental Nanoscience and Risk, University of South Carolina , Columbia, South Carolina United States.
Environ Sci Technol. 2017 Jul 18;51(14):8010-8016. doi: 10.1021/acs.est.7b01130. Epub 2017 Jun 29.
Ceria nanoparticles (NPs) rapidly and easily cycle between Ce(III) and Ce(IV) oxidation states, making them prime candidates for commercial and other applications. Increased commercial use has resulted in increased discharge to the environment and increased associated risk. Once in complex media such as environmental waters or toxicology exposure media, the same redox transformations can occur, causing altered behavior and effects compared to the pristine NPs. This study used high resolution scanning transmission electron microscopy and electron energy loss spectroscopy to investigate changes in structure and oxidation state of small, polymer-coated ceria suspensions in complex media. NPs initially in either the III or IV oxidation states, but otherwise identical, were used. Ce(IV) NPs were changed to mixed (III, IV) NPs at high ionic strengths, while the presence of natural organic macromolecules (NOM) stabilized the oxidation state and increased crystallinity. The Ce(III) NPs remained as Ce(III) at high ionic strengths, but were modified by the presence of NOM, causing reduced crystallinity and degradation of the NPs. Subtle changes to NP properties upon addition to environmental or ecotoxicology media suggest that there may be small but important effects on fate and effects of NPs compared to their pristine form.
铈纳米粒子（NPs）在 Ce(III) 和 Ce(IV) 氧化态之间快速且容易地循环，这使它们成为商业和其他应用的首选候选物。商业用途的增加导致向环境中排放增加，相关风险也随之增加。一旦进入环境水或毒理学暴露介质等复杂介质中，同样的氧化还原转化就会发生，导致与原始 NPs 相比，行为和效果发生改变。本研究使用高分辨率扫描透射电子显微镜和电子能量损失光谱来研究复杂介质中小的聚合物包覆铈悬浮液的结构和氧化态变化。使用了初始处于 III 或 IV 氧化态但其他方面相同的 NPs。在高离子强度下，Ce(IV) NPs 转变为混合（III，IV）NPs，而天然有机大分子（NOM）的存在稳定了氧化态并增加了结晶度。在高离子强度下，Ce(III) NPs 保持为 Ce(III)，但 NOM 的存在使其结晶度降低并导致 NPs 降解。NP 加入环境或生态毒理学介质后性质的细微变化表明，与原始形式相比，NP 的命运和影响可能会有微小但重要的影响。
