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Self‐Assembly of CoPt Magnetic Nanoparticle Arrays and its Underlying Forces
Author(s) -
Bian Baoru,
Chen Guoxin,
Zheng Qiang,
Du Juan,
Lu Huanming,
Liu J. Ping,
Hu Yong,
Zhang Zhidong
Publication year - 2018
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201801184
Subject(s) - superlattice , materials science , van der waals force , nanoparticle , magnetic nanoparticles , self assembly , chemical physics , transmission electron microscopy , nanotechnology , particle (ecology) , particle size , rotation around a fixed axis , condensed matter physics , physics , molecule , chemistry , optoelectronics , classical mechanics , oceanography , quantum mechanics , geology
Nanoparticles covered with surfactants are often used to study particle motion patterns and self‐assembly processes in solutions. Surfactants have influence on the interparticle interactions and therefore on the particle motion tracks and final patterns. In this study, CoPt nanoparticles are synthesized in aqueous solution without any surfactant. In situ transmission electron microscopy observation is performed to monitor the self‐assemble process. Two types of magnetic nanoparticle superlattice arrays are formed: hexagonal equal distance superlattice arrays when particle size is 3 nm, and tight unequal distance superlattice arrays when particle size is 4.5 nm. It is interesting to observe that two small arrays merge into a large one through rotational and translational movements. A Monte Carlo simulation is carried out which successfully restores the whole process. It is identified that the underlying forces are van der Waals and magnetic dipolar interactions. The latter is responsible for orientation of each particle during the whole process. This investigation leads to a better understanding of the formation mechanism of magnetic nanoparticle superlattice arrays.