Gas-phase generation of noble metal-tipped NiO nanorods by rapid thermal oxidation
Gas-phase generation of noble metal-tipped NiO nanorods by rapid thermal oxidation
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DOI：
10.1088/2053-1591/1/4/045021
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发表时间：
2014-12-01
影响因子：
2.3
通讯作者：
Hirasawa, Makoto
中科院分区：
文献类型：
--
作者：
Koga, Kenji;Hirasawa, Makoto
通过高分辨电子显微镜观察不同氧化条件下气相中氧化的镍和贵金属组成的合金纳米颗粒（NPs）的热氧化。当Ni0.8Au0.2纳米颗粒与氧气一起从室温加热时，氧化进行以形成Au-NiO核-壳结构，然而，Au核通过在高温下破坏NiO壳而溢出。相比之下，当合金NP经受快速热氧化时，这通过在高温（>= 500摄氏度）下加热NP然后突然暴露于氧气来实现，氧化各向异性地进行，使得NiO岛突出并堆积以形成NiO纳米棒。这导致Au尖端NiO纳米棒的形成，其中半球形Au尖端经由Au {111}/NiO{100}界面结合到NiO纳米棒。我们发现，通过改变合金纳米颗粒的Au摩尔分数（0.05-0.8），可以容易且广泛地控制Au-尖端NiO纳米棒中Au和NiO的相对尺寸。同样，Ni-Pt纳米颗粒的快速热氧化产生了Pt尖端的NiO纳米棒，其中球形Pt尖端半嵌入NiO纳米棒中。目前的气相方法具有很大的潜力，在清洁条件下制造功能的非对称杂化纳米结构。
The thermal oxidation of alloy nanoparticles (NPs) composed of nickel and a noble metal was investigated by high-resolution electron microscopic observations of the NPs oxidized in a gas phase under different oxidation conditions. When Ni0.8Au0.2 NPs were heated with oxygen from room temperature, oxidation progressed to form Au-NiO core-shell structures, however, the Au core spilled out by breaking the NiO shell at high temperatures. In contrast, when the alloy NPs were subjected to rapid thermal oxidation, which was enabled by heating the NPs at high temperatures (>= 500 degrees C) and then abruptly exposed to oxygen, oxidation advanced anisotropically such that a NiO island protruded and built up to form a NiO nanorod. This resulted in the formation of Au-tipped NiO nanorods in which a hemispherical Au tip bonded to a NiO nanorod via a Au {111}/NiO{100} interface. We found that the relative sizes of Au and NiO in Au-tipped NiO nanorods were easily and widely controlled by changing the Au mole fraction (0.05-0.8) of the alloy NPs. Similarly, rapid thermal oxidation of Ni-Pt NPs generated Pt-tipped NiO nanorods in which a spherical Pt tip was half-embedded in a NiO nanorod. The present gas-phase approach has great potential for fabricating functional asymmetric hybrid nanostructures in clean conditions.