Department of Experimental Physics and Department of Physical Chemistry, Regional Centre of Advanced Technologies and Materials, Faculty of Science, Palacky University in Olomouc, Slechtitelu 27, 783 71 Olomouc, Czech Republic.
Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague 6, Czech Republic.
Nat Commun. 2016 Sep 15;7:12879. doi: 10.1038/ncomms12879.
Superparamagnetism is a phenomenon caused by quantum effects in magnetic nanomaterials. Zero-valent metals with diameters below 5 nm have been suggested as superior alternatives to superparamagnetic metal oxides, having greater superspin magnitudes and lower levels of magnetic disorder. However, synthesis of such nanometals has been hindered by their chemical instability. Here we present a method for preparing air-stable superparamagnetic iron nanoparticles trapped between thermally reduced graphene oxide nanosheets and exhibiting ring-like or core-shell morphologies depending on iron concentration. Importantly, these hybrids show superparamagnetism at room temperature and retain it even at 5 K. The corrected saturation magnetization of 185 Am(2) kg(-1) is among the highest values reported for iron-based superparamagnets. The synthetic concept is generalized exploiting functional groups of graphene oxide to stabilize and entrap cobalt, nickel and gold nanoparticles, potentially opening doors for targeted delivery, magnetic separation and imaging applications.
超顺磁性是一种由磁性纳米材料中的量子效应引起的现象。直径小于 5nm 的零价金属被认为是超顺磁金属氧化物的优越替代品，因为它们具有更大的超自旋大小和更低的磁无序程度。然而，由于其化学不稳定性，此类纳米金属的合成受到了阻碍。在这里，我们提出了一种制备空气稳定的超顺磁性氧化铁纳米粒子的方法，这些纳米粒子被夹在热还原氧化石墨烯纳米片之间，并根据铁浓度呈现出环状或核壳状的形态。重要的是，这些混合物在室温下表现出超顺磁性，甚至在 5K 时也能保持。经修正的饱和磁化强度为 185Am2kg-1，是报道的基于铁的超顺磁体中最高值之一。该合成概念通过利用氧化石墨烯的官能团进行了推广，以稳定和捕获钴、镍和金纳米粒子，这可能为靶向输送、磁性分离和成像应用开辟了道路。
