Control of nanostructures through pH-dependent self-assembly of nanoplatelets

Jing Chang; Huaizhi Shao; Bo Liu; Rogerio Manica; Zhen Li; Qingxia Liu; Zhenghe Xu

doi:10.1016/j.jcis.2020.07.093

Control of nanostructures through pH-dependent self-assembly of nanoplatelets

J Colloid Interface Sci. 2021 Jan 15;582(Pt A):439-445. doi: 10.1016/j.jcis.2020.07.093. Epub 2020 Jul 24.

Authors

Jing Chang¹, Huaizhi Shao², Bo Liu³, Rogerio Manica⁴, Zhen Li⁵, Qingxia Liu⁶, Zhenghe Xu⁷

Affiliations

¹ Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 1R1, Canada. Electronic address: jchang5@ualberta.ca.
² Key Laboratory of Coal Processing and Efficient Utilization (Ministry of Education), School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China. Electronic address: shaohuaizhicumt@outlook.com.
³ Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 1R1, Canada. Electronic address: liu3@ualberta.ca.
⁴ Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 1R1, Canada. Electronic address: manica@ualberta.ca.
⁵ College of Chemistry and Chemical Engineering, Xi'an University of Science and Technology, Xi'an, Shaanxi 710054, China. Electronic address: lizhenac@126.com.
⁶ Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 1R1, Canada. Electronic address: qingxia2@ualberta.ca.
⁷ Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 1R1, Canada; Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China. Electronic address: zhenghe.xu@ualberta.ca.

PMID: 32871296
DOI: 10.1016/j.jcis.2020.07.093

Abstract

Hypothesis: The self-assembly of platy clay particles is influenced by anisotropic surface charging properties of the particles. The Stern potentials of particle surfaces are controlled by solution pH. Consequently, the energy-favorable particle association varies with pH, leading to different self-assembly structures. Therefore, it should be possible to form desired nanostructure of final clay product through self-assembly of clay particles by controlling the surface charge through adjusting solution pH.

Experiments: Three different surfaces of kaolinite clay nanoparticles were selectively exposed for Stern potential determination using an atomic force microscope. Aggregation structures through particle self-assembly were predicted based on the analysis of interaction energies between various types of surfaces of kaolinite particles. The structures were visually confirmed using the freeze-dried scanning electron microscopy technique.

Findings: By reducing pH of a concentrated kaolinite suspension from 8 to 5 and 3, the dispersed kaolinite particles were self-assembled to a well-stacked configuration and card-house structure, respectively. Current study demonstrates that the pH-dependent surface properties of platy kaolinite nanoparticles can be successfully used to understand the macroscopic behavior (rheology) of kaolinite nanoparticle suspensions and design nanostructures of clay products (catalysts and sorbents). The pH-dependent self-assembly is also applicable to other platy particles of anisotropic surface (charging or wettability) properties.

Keywords: Atomic force microscope; Kaolinite; Nanostructure materials; Surface charge-controlled particle self-assembly; pH-dependent Stern potential.