The impact of ammonium hydroxide flow rate on iron oxide nanoparticle hydrodynamic size and colloidal stability

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Vol. 702; p. 135018
• Main Authors: Paige, Stephen, Sedighi, Omid, Stender, Ian, Doiron, Amber L.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.12.2024
• Subjects: Ammonium hydroxide; Co-precipitation; Colloidal stability; Flow rate; Hydrodynamic size; Particle size; Polydispersity; Precipitation agent; Hydrodynamic size; Precipitation agent; Particle size; Flow rate; Colloidal stability; Polydispersity; Co-precipitation; Ammonium hydroxide
• ISSN: 0927-7757
• DOI: 10.1016/j.colsurfa.2024.135018

Precise control over the synthesis of iron oxide nanoparticles is essential to achieving optimal particle characteristics such as size, hydrodynamic size, polydispersity index, and zeta potential, all of which significantly influence colloidal stability. The commonly used co-precipitation technique often leads to high polydispersity and variable particle sizes, resulting in poor colloidal stability. This study demonstrates that varying the ammonium hydroxide flow rate during co-precipitation significantly affects particle size, hydrodynamic size, aggregation, and colloidal stability. An optimal flow rate of 4.25 mmol/min produced smaller, more uniform, and colloidally stable nanoparticles. Nanoparticle tracking analysis showed that this flow rate resulted in the smallest and most consistent hydrodynamic size of 123.3 ± 0.7 nm, while both higher and lower flow rates yielded larger and more polydisperse particles, up to 155.8 ± 20 nm. Dynamic light scattering confirmed that the 4.25 mmol/min rate produced the lowest polydispersity index of 0.21 ± 0.04, indicating the highest uniformity. Additionally, UV-Vis measurements demonstrated that nanoparticles synthesized at this optimal flow rate exhibited minimal changes in absorbance over 24 h, indicating superior colloidal stability. This study highlights the importance of optimizing the flow rate during the co-precipitation synthesis of IONPs to control particle hydrodynamic size and polydispersity, which are crucial parameters for numerous biomedical, chemical, and environmental applications. [Display omitted] •Varying flow rates impact IONP hydrodynamic size and colloidal stability.•Optimal flow rate at 4.25 mmol/min for smallest, most uniform IONPs.•Lower polydispersity index (0.21 ± 0.04) achieved at optimal flow rate.•Nanoparticles show minimal absorbance changes over 24 h at optimal rate.•Precise flow rate control is crucial for biomedical, chemical, and environmental applications.