Cerc Korošec Romana, Umek Polona, Gloter Alexandre, Padežnik Gomilšek Jana, Bukovec Peter
Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia.
Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana, Slovenia.
Beilstein J Nanotechnol. 2017 May 10;8:1032-1042. doi: 10.3762/bjnano.8.104. eCollection 2017.
α-MnO nanorods were synthesized via the hydrothermal decomposition of KMnO in an acidic environment in the presence of Co and Cr ions. Reactions were carried out at three different temperatures: 90, 130 and 170 °C. All prepared samples exhibit a tetragonal MnO crystalline phase. SEM-EDS analysis shows that cobalt cations are incorporated to a higher degree into the MnO framework than chromium ions, and that the content of the dopant ions decreases with increasing reaction temperature. The oxidation of Co to Co during the reaction was proved by an XANES study, while EXAFS results confirm that both dopant ions substitute Mn in the center of an octahedron. The K/Mn ratio in the doped samples synthesized at 170 °C is significantly lower than in the undoped samples. Analysis of an individual cobalt-doped α-MnO nanorod with HAADF-STEM reveals that the distribution of cobalt through the cross-section of the nanorod is uniform. The course of thermal decomposition of the doped nanorods is similar to that of the undoped ones. Dopant ions do not preserve the MnO phase at higher temperatures nor do they destabilize the cryptomelane structure.
通过在酸性环境中、在钴离子和铬离子存在的情况下对高锰酸钾进行水热分解来合成α-二氧化锰纳米棒。反应在三个不同温度下进行：90℃、130℃和170℃。所有制备的样品均呈现四方晶系的二氧化锰晶相。扫描电子显微镜-能谱分析表明，钴阳离子比铬离子更易掺入二氧化锰骨架中，且掺杂离子的含量随反应温度升高而降低。X射线吸收近边结构研究证明了反应过程中钴被氧化为钴离子，而扩展X射线吸收精细结构结果证实两种掺杂离子均在八面体中心取代锰。在170℃合成的掺杂样品中的钾/锰比明显低于未掺杂样品。用高角度环形暗场扫描透射电子显微镜对单个钴掺杂的α-二氧化锰纳米棒进行分析，结果表明钴在纳米棒横截面上的分布是均匀的。掺杂纳米棒的热分解过程与未掺杂纳米棒相似。掺杂离子在较高温度下既不能保持二氧化锰相，也不会破坏锰钾矿结构的稳定性。
