Behaviour of iron oxide (Fe3O4) Janus particles in overlapping external AC electric and static magnetic fields
Behaviour of iron oxide (Fe3O4) Janus particles in overlapping external AC electric and static magnetic fields
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DOI：
10.1039/c3sm50839k
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发表时间：
2013-01-01
期刊：
影响因子：
3.4
通讯作者：
Kretzschmar, Ilona
中科院分区：
文献类型：
--
作者：
Ruditskiy, Aleksey;Ren, Bin;Kretzschmar, Ilona
研究了具有磁、电各向异性的Fe_3O_4包覆Janus粒子在交变电场和静磁场叠加作用下的组装行为。通常，Fe3O4 Janus粒子已被证明分别在外部静磁场和交流电场中形成双链和交错链。在这里，Fe3O4 Janus粒子的反应顺序施加的AC电场和静磁场中的平行和垂直场的几何形状进行了研究，以阐明在何种程度上的Janus粒子的不对称性可以独立地解决每个字段在组装过程中。一个平行的场的几何形状导致的Janus粒子链的收缩，而垂直场的几何形状导致首先旋转的Janus粒子链朝向更占主导地位的领域，然后由菱面体堆叠的链成二维的，两个粒子厚片作为结果的较弱的字段。测试的每个场几何形状中的Janus粒子聚集行为通过特征角θ和粒子间距离d进行参数化。所观察到的Fe3O4 Janus粒子的响应被示出由外部AC电场和静磁场分别在帽中产生的电偶极子和磁偶极子的相互作用以及聚苯乙烯粒子的极化驱动。组装行为的可逆性与以下事实强烈相关：电偶极子在AC电场关闭后立即消失，而磁偶极子即使在静态磁场被移除后也永久地保持在Fe3O4帽中。因此，Fe3O4 Janus粒子组装行为是响应于电场和磁场，它们的行为可以通过外部场的序列和相对取向来操纵。
The assembly behaviour of Fe3O4-capped Janus particles with magnetically and electrically anisotropic properties is investigated in overlapping external AC electric and static magnetic fields. Generally, Fe3O4 Janus particles have been shown to form double and staggered chains in external static magnetic and AC electric fields, respectively. Here, the reaction of Fe3O4 Janus particles to sequentially applied AC electric and static magnetic fields in parallel and perpendicular field geometry is studied in order to elucidate to what extend the asymmetric nature of the Janus particle can be addressed independently by each field during assembly. A parallel field geometry leads to contraction of the Janus particle chains, whereas a perpendicular field geometry leads first to the rotation of the Janus particle chains towards the more dominant field followed by rhombohedral stacking of the chains into two-dimensional, two-particle thick sheets as a result of the weaker field. The Janus particle assembly behaviour in each field geometry tested is parameterized by the characteristic angle, theta, and the inter-particle distance, d. The observed response of the Fe3O4 Janus particles is shown to be driven by the interaction of electric and magnetic dipoles generated in the caps by the external AC electric and static magnetic fields, respectively, as well as the polarization of the polystyrene particle. Reversibility of the assembly behaviour correlates strongly with the fact that the electric dipoles disappear immediately after the AC electric field is turned off, whereas the magnetic dipoles remain permanently in the Fe3O4 caps even after the static magnetic field is removed. As a result, the Fe3O4 Janus particle assembly behaviour is responsive to both the electric and the magnetic fields and their behaviour can be manipulated by the sequence and relative orientation of the external fields.