Self‐Assembly of CoPt Magnetic Nanoparticle Arrays and its Underlying Forces. Issue 34 (29th July 2018)

• Record Type: Journal Article
• Authors: Bian, Baoru; Chen, Guoxin; Zheng, Qiang; Du, Juan; Lu, Huanming; Liu, J. Ping; Hu, Yong; Zhang, Zhidong
• Is Part Of: Small. Volume 14:Issue 34(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-07-29
• Subjects: CoPt nanoparticle superlattice -- driving force -- in situ TEM -- self‐assembly; Nanotechnology -- Periodicals; Nanoparticles -- Periodicals; Microtechnology -- Periodicals; 620.5
• DOI: 10.1002/smll.201801184
• Languages: English
• ISSNs: 1613-6810

Abstract

Abstract: 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. Abstract : Clean CoPt nanoparticles synthesized without any surfactant are used to in situ observe the magnetic nanoparticle self‐assembly process and two types of superlattice arrays are achieved. Magnetic dipole interactions facilitate the NPs to self‐assemble into chains, and equidistant superlattice arrays are formed mainly due to van der Waals forces, while tight unequal distant superlattice arrays are formed mainly attributing to dipolar interactions.