Colloidal Stability and Aggregation Mechanism in Aqueous Suspensions of TiO2 Nanoparticles Prepared by Sol-Gel Synthesis

Gertrude Kignelman; Samuel Eyley; Chen Zhou; Bensu Tunca; Maurice Gonon; Driss Lahem; Jin W Seo; Wim Thielemans

doi:10.1021/acs.langmuir.1c02533

Colloidal Stability and Aggregation Mechanism in Aqueous Suspensions of TiO₂ Nanoparticles Prepared by Sol-Gel Synthesis

Langmuir. 2021 Dec 28;37(51):14846-14855. doi: 10.1021/acs.langmuir.1c02533. Epub 2021 Dec 16.

Authors

Gertrude Kignelman¹, Samuel Eyley¹, Chen Zhou², Bensu Tunca³, Maurice Gonon⁴, Driss Lahem⁵, Jin W Seo³, Wim Thielemans¹

Affiliations

¹ Sustainable Materials Lab, Department of Chemical Engineering, KU Leuven Campus Kulak Kortrijk, Etienne Sabbelaan 53, Box 7659, Kortrijk 8500, Belgium.
² National Engineering Research Center of Chemical Fertilizer Catalyst, Fuzhou University, Fuzhou 350002, China.
³ Department of Materials Engineering, KU Leuven, Leuven 3001, Belgium.
⁴ University of Mons Materials Institute, Mons 7000, Belgium.
⁵ Materia Nova Materials Science Unit, Mons 7000, Belgium.

PMID: 34914876
DOI: 10.1021/acs.langmuir.1c02533

Abstract

Understanding the colloidal stability and aggregation behavior of TiO₂ nanoparticles in aqueous suspension is a prerequisite to tune supracolloidal structure formation. While the aggregation mechanism for dried TiO₂ nanopowders is well documented, there is still work to be done to understand TiO₂ nanoparticle aggregation in suspension. Therefore, this work focuses on the colloidal stability and aggregation mechanism of TiO₂ nanoparticle aqueous suspensions prepared using a straightforward one-step sol-gel-based approach over a concentration range of 0.5-5 wt %. Fully crystalline nanoparticles consisting primarily of anatase were obtained. After assessing the colloidal stability of the as-prepared suspensions, small-angle X-ray scattering coupled with fractal analysis was carried out. This analysis showed, for the first time, how the TiO₂ nanoparticle aggregation mechanism─predicted by the diffusion limited cluster-cluster aggregation (DLCA) and diffusion limited particle-cluster aggregation (DLA) theories─depends directly on the starting concentration in the aqueous suspensions. We found that concentrated suspensions favored DLA, while dilute suspensions tend to follow the DLCA mechanism. The effect of the aggregation mechanism on the aggregate shape is also discussed.