Complete Exchange of the Hydrophobic Dispersant Shell on Monodisperse Superparamagnetic Iron Oxide Nanoparticles

Abstract

High-temperature synthesized monodisperse superparamagnetic iron oxide nanoparticles are obtained with a strongly bound ligand shell of oleic acid and its decomposition products. Most applications require a stable presentation of a defined surface chemistry; therefore, the native shell has to be completely exchanged for dispersants with irreversible affinity to the nanoparticle surface. We evaluate by attenuated total reflectance−Fourier transform infrared spectroscopy (ATR−FTIR) and thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) the limitations of commonly used approaches. A mechanism and multiple exchange scheme that attains the goal of complete and irreversible ligand replacement on monodisperse nanoparticles of various sizes is presented. The obtained hydrophobic nanoparticles are ideally suited for magnetically controlled drug delivery and membrane applications and for the investigation of fundamental interfacial properties of ultrasmall core–shell architectures.

Co nanocrystals engineering

“…The size and shape of the nanoparticles depend on the Co/acid ratio and concentration of free acid in the medium as confirmed by theoretical calculations [39]. It is well known from literature results that in such conditions, the nanoparticles are stabilized by a double layer coating of oleic acid [40] as depicted in figure 4.…”

Thermoresponsive Polypeptoid‐Coated Superparamagnetic Iron Oxide Nanoparticles by Surface‐Initiated Polymerization

“…The amount of initiator in the nitrodopamine‐coated core sample (Fe 3 O 4 ‐NH 2 ) determined by TGA corresponds to 8.9 molecules nm −2 (Table ). Taking into account that the maximal grafting density of nitrodopamine on SPION is ≈3 molecules nm −2 , it is expected that the Fe 3 O 4 ‐NH 2 sample contains free nitrodopamine, despite the numerous repeated washing steps during the purification (see Section ).…”

Environmental implications and applications of engineered nanoscale magnetite and its hybrid nanocomposites: A review of recent literature

“…Most applications require a stable presentation of a defined surface chemistry; therefore, the native shell has to be completely exchanged for dispersants with irreversible affinity to the NP surface. A multiple exchange scheme has been developed to completely and irreversibly replace ligand on monodisperse MNPs synthesized with a strongly bound ligand shell of oleic acid [32]. Ligand exchange employing either citric acid or meso-2,3-dimercaptosuccinic acid (DMSA) ligand has been used to change monodisperse hydrophobic MNPs to hydrophilic MNPs produced by thermal decomposition of Fe(acac)3 in benzyl ether [33].…”