Self-assembly of magnetic colloids with radially shifted dipoles
Self-assembly of magnetic colloids with radially shifted dipoles
复制标题
具有径向移动偶极子的磁性胶体的自组装
DOI：
10.1039/c9sm02020a
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发表时间：
2020
期刊：
影响因子：
3.4
通讯作者：
Córdova-Figueroa, Ubaldo M.
中科院分区：
文献类型：
--
作者：
Victoria-Camacho, Jonathan A.;DeLaCruz-Araujo, Ronal A.;Kretzschmar, Ilona;Córdova-Figueroa, Ubaldo M.
Janus胶体中的各向异性势提供了额外的自由度来控制颗粒聚集成不同尺寸和形态的结构。在这项工作中，我们进行布朗动力学模拟的磁性球形Janus胶体的稀悬浮液，其磁偶极矩径向移动到粒子的表面，以获得有价值的微观结构的见解。动态地检查属性，如平均集群大小，取向有序，成核和生长。根据偶极位移（s）-偶极位移与粒子半径之间的比率-和偶极耦合常数（λ）-磁偶极-偶极与布朗力之间的比率，观察到团簇结构和聚集过程的差异。使用这两个无量纲量，构造结构“相图”。每个相对应于独特的成核和生长行为和取向有序的偶极子内集群。在小λ时，粒子聚集和解聚，导致在小s时的短寿命团簇，而在高s时，粒子聚集成永久的三联体（长寿命团簇）。在高λ下，成核过程中形成的临界核是具有独特取向有序的三重态和四重态。然后这些小的簇作为构建块形成更大的结构，如单链，环状，岛状，蠕虫状和反平行双链簇。这项研究表明，胶体中的偶极位移可以作为一个控制参数的应用程序中，需要独特的大小，形态和聚集动力学的集群。
Anisotropic potentials in Janus colloids provide additional freedom to control particle aggregation into structures of different sizes and morphologies. In this work, we perform Brownian dynamics simulations of a dilute suspension of magnetic spherical Janus colloids with their magnetic dipole moments shifted radially towards the surface of the particle in order to gain valuable microstructural insight. Properties such as the mean cluster size, orientational ordering, and nucleation and growth are examined dynamically. Differences in the structure of clusters and in the aggregation process are observed depending on the dipolar shift (s)—the ratio between the displacement of the dipole and the particle radius—and the dipolar coupling constant (λ)—the ratio between the magnetic dipole–dipole and Brownian forces. Using these two dimensionless quantities, a structural “phase” diagram is constructed. Each phase corresponds to unique nucleation and growth behavior and orientational ordering of dipoles inside clusters. At small λ, the particles aggregate and disaggregate resulting in short-lived clusters at small s, while at high s the particles aggregate in permanent triplets (long-lived clusters). At high λ, the critical nuclei formed during the nucleation process are triplets and quadruplets with unique orientational ordering. These small clusters then serve as building blocks to form larger structures, such as single-chain, loop-like, island-like, worm-like, and antiparallel-double-chain clusters. This study shows that dipolar shifts in colloids can serve as a control parameter in applications where unique size, morphology, and aggregation kinetics of clusters are required.