Nanotechnology. 2019 Feb 22;30(8):085703. doi: 10.1088/1361-6528/aae364. Epub 2018 Sep 21.
Cerium oxide nanomaterials (nanoceria, CNMs) are receiving increased attention from the research community due to their unique chemical properties, most prominent of which is their ability to alternate between the Ce and Ce oxidation states. While many analytical techniques and methods have been employed to characterize the amounts of Ce and Ce present (Ce/Ce ratio) within nanoceria materials, to-date no studies have used multiple complementary analytical tools (orthogonal analysis) with technique-independent oxidation state controls for quantitative determinations of the Ce/Ce ratio. Here, we describe the development of analytical methods measuring the oxidation states of nanoceria analytes using technique-independent Ce (CeAlO:Ge) and Ce (CeO) control materials, with a particular focus on x-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) approaches. The developed methods were demonstrated in characterizing a suite of commercial nanoceria products, where the two techniques (XPS and EELS) were found to be in good agreement with respect to Ce/Ce ratio. Potential sources of artifacts and discrepancies in the measurement results were also identified and discussed, alongside suggestions for interpreting oxidation state results using the different analytical techniques. The results should be applicable towards producing more consistent and reproducible oxidation state analyses of nanoceria materials.
氧化铈纳米材料（纳米氧化铈，CNMs）因其独特的化学性质而受到研究界的越来越多的关注，其中最突出的是其在 Ce 和 Ce 氧化态之间交替的能力。虽然已经使用了许多分析技术和方法来表征纳米氧化铈材料中存在的 Ce 和 Ce 的量（Ce/Ce 比），但迄今为止，还没有研究使用多种互补的分析工具（正交分析）和与技术无关的氧化态控制来对 Ce/Ce 比进行定量测定。在这里，我们描述了使用与技术无关的 Ce（CeAlO:Ge）和 Ce（CeO）控制材料来测量纳米氧化铈分析物的氧化态的分析方法的开发，特别关注 X 射线光电子能谱（XPS）和电子能量损失光谱（EELS）方法。所开发的方法在对一系列商业纳米氧化铈产品进行表征时得到了验证，这两种技术（XPS 和 EELS）在 Ce/Ce 比方面表现出很好的一致性。还确定并讨论了测量结果中可能存在的伪影和差异的潜在来源，并就使用不同分析技术解释氧化态结果提出了建议。该结果应该适用于对纳米氧化铈材料进行更一致和可重复的氧化态分析。
