Molecular mechanisms for delicately tuning the morphology and properties of Fe3O4 nanoparticle clusters

Abstract

Herein, a polyol method has been explored for producing magnetic iron oxide nanoparticle clusters that are potentially useful as contrast agents for magnetic resonance imaging (MRI), as drug carriers in tumor therapy, and for bioseparation. The oriented attachment growth of primary particles is widely accepted as a major driving force for the formation of clusters; on the other hand, the commonly used high-boiling point alcohols are used as high-temperature reaction media and reductants in particular for the formation of primary magnetite nanoparticles. However, the role of alcohols remains far from being understood. Herein, systematic studies were carried out to further reveal the molecular role of the high-boiling point alcohols and that of the commonly used stabilizing agent poly(acrylic acid) (PAA). The impact of the structure of alcohols, e.g., monohydric and dihydric alcohols with different chain lengths, on the morphology of the resulting clusters was investigated in detail. The experimental results reveal that the crosslinking effect of the oxidized dihydric alcohols determines the formation of Fe₃O₄ particle clusters, whereas PAA helps in the formation of spherical clusters by reducing the surface tension. Based on a combination of magnetic measurements and drug loading tests, the impacts of the structures of dihydric alcohols on the magnetic properties, especially on the magnetic response to external fields and drug loading capacities, have been disclosed; in brief, the current study clearly discloses the role of the high-boiling point alcohols in the formation of magnetite particle clusters for the first time, which is beneficial for fine tuning the overall morphology and internal molecular structure of the resulting particle clusters to improve their magnetic response, drug loading efficiency, and MRI contrast enhancing performance.