Long‐Term Colloidally Stable Aqueous Dispersions of ≤5 nm Spinel Ferrite Nanoparticles. Issue 11 (27th November 2020)

• Record Type: Journal Article
• Authors: Eckardt, Mirco; Thomä, Sabrina L. J.; Dulle, Martin; Hörner, Gerald; Weber, Birgit; Förster, Stefan; Zobel, Mirijam
• Is Part Of: ChemistryOpen. Volume 9:Issue 11(2020)
• Page Start: 1214
• Page End: 1220
• Publication Date: 2020-11-27
• Subjects: colloidal stability -- nanoparticles -- spinel phase -- SAXS -- ferrites; Chemistry -- Periodicals; 540; 540.5
• DOI: 10.1002/open.202000313
• Languages: English
• ISSNs: 2191-1363

Abstract

Abstract: Applications in biomedicine and ferrofluids, for instance, require long‐term colloidally stable, concentrated aqueous dispersions of magnetic, biocompatible nanoparticles. Iron oxide and related spinel ferrite nanoparticles stabilized with organic molecules allow fine‐tuning of magnetic properties via cation substitution and water‐dispersibility. Here, we synthesize≤5 nm iron oxide and spinel ferrite nanoparticles, capped with citrate, betaine and phosphocholine, in a one‐pot strategy. We present a robust approach combining elemental (CHN) and thermal gravimetric analysis (TGA) to quantify the ratio of residual solvent molecules and organic stabilizers on the particle surface, being of particular accuracy for ligands with heteroatoms compared to the solvent. SAXS experiments demonstrate the long‐term colloidal stability of our aqueous iron oxide and spinel ferrite nanoparticle dispersions for at least 3 months. By the use of SAXS we approved directly the colloidal stability of the nanoparticle dispersions for high concentrations up to 100 g L −1 . Abstract : Long‐term colloidal stability of aqueous dispersions of 3 to 5 nm sized superparamagnetic spinel ferrite nanoparticles in 5 different compositions is showcased via SAXS for concentrations up to 100 g L −1 over at least 3 months. A robust TGA‐CHN analytics approach quantifies the surface composition of organic ligands, residual solvent and water.