XPS analysis of oleylamine/oleic acid capped Fe3O4 nanoparticles as a function of temperature
XPS analysis of oleylamine/oleic acid capped Fe3O4 nanoparticles as a function of temperature
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DOI：
10.1016/j.apsusc.2014.02.006
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发表时间：
2014-06-01
影响因子：
6.7
通讯作者：
Langell, M. A.
中科院分区：
文献类型：
--
作者：
Wilson, D.;Langell, M. A.
以油胺和油酸为表面活性剂，采用溶剂热法合成了Fe3O4纳米粒子，并通过X射线光电子能谱（XPS）研究了其表面组成与温度的关系。合成的纳米颗粒的XPS是一致的表面组成的化学计量的Fe3O4封端的单齿羧酸盐和化学吸附胺的混合物，虽然表面富集在羧酸盐超过存在于合成反应浓度。合成和封端表面活性剂的方法有效地保护纳米颗粒表面免受可检测的羟基化。封端的纳米颗粒在373 K下稳定24 h，并且封端剂持续到523 K，此时油胺分解以解吸氮并从封端尾部存款脂肪族碳。羧酸盐在较宽的范围内分解，在883K下，一些羧酸盐保留在表面上。随着脂肪族封端尾部分解，氧化铁纳米颗粒经历显著还原。虽然引入的纳米颗粒基本上是Fe3O4，但随着纳米颗粒被加热到更高的温度，还原成FeO、Fe和Fe3C依次发生。(C)2014爱思唯尔有限公司版权所有。
Fe3O4 were synthesized solvothermally using oleylamine and oleic acid as surfactants, and the surface composition was determined by X-ray photoelectron spectroscopy (XPS) as a function of temperature, from the as-synthesized nanoparticles to those annealed under vacuum at 883K. XPS of the as-synthesized nanoparticles was consistent with a surface composition of stoichiometric Fe3O4 capped with a mixture of monodentate carboxylate and chemisorbed amine, although the surface was enriched in carboxylate over that present in the synthesis reaction concentration. The method of synthesis and capping surfactants effectively protect the nanoparticle surface from detectable hydroxylation. The capped nanoparticle is stable for 24 h at 373K, and the capping agents persist to 523K, at which point the oleylamine decomposes to desorb nitrogen and deposit aliphatic carbon from the capping tail. The carboxylate decomposes over a wider range and at 883K some carboxylate remains on the surface. The iron oxide nanoparticle undergoes substantial reduction as the aliphatic capping tail decomposes. While the as-introduced nanoparticle is essentially Fe3O4, reduction to FeO, Fe and Fe3C occurs sequentially as the nanoparticle is heated to higher temperatures. (C) 2014 Elsevier B.V. All rights reserved.