Aggregation morphology of planar engineered nanomaterials

S Drew Story; Stephen Boggs; Linda M Guiney; Mani Ramesh; Mark C Hersam; C Jeffrey Brinker; Sharon L Walker

doi:10.1016/j.jcis.2019.11.067

Aggregation morphology of planar engineered nanomaterials

J Colloid Interface Sci. 2020 Mar 1:561:849-853. doi: 10.1016/j.jcis.2019.11.067. Epub 2019 Nov 20.

Authors

S Drew Story¹, Stephen Boggs¹, Linda M Guiney², Mani Ramesh², Mark C Hersam², C Jeffrey Brinker³, Sharon L Walker⁴

Affiliations

¹ Department of Chemical and Environmental Engineering, University of California, Riverside, CA, USA.
² Departments of Materials Science and Engineering, Chemistry, and Medicine, Northwestern University, Evanston, IL, USA.
³ Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM, USA.
⁴ Department of Chemical and Environmental Engineering, University of California, Riverside, CA, USA; Department of Civil, Architectural, and Environmental Engineering, Drexel University, Philadelphia, PA, USA. Electronic address: slw385@drexel.edu.

PMID: 31771871
DOI: 10.1016/j.jcis.2019.11.067

Abstract

In this investigation, the utility of a static light scattering (SLS) technique to characterize aggregate morphology of two-dimensional engineered nanomaterials (2D ENMs) was systematically evaluated. The aggregation of graphene oxide (GO) and lithiated-molybdenum disulfide (Li-MoS₂) were measured and compared to that of a spherical reference colloid, carboxylate-modified latex (CML) nanoparticles. The critical coagulation concentration (CCC) for all dispersions was determined via analysis of aggregation kinetics using time-resolved dynamic light scattering. This technique allowed for the elucidation of the transition from the reaction-limited aggregation (RLA) regime to diffusion-limited aggregation (DLA). The findings of this study support the aggregation trends predicted by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and recent computer simulations of aggregation kinetics. For all nanomaterials, as ionic strength increased towards the respective the CCC, fractal dimension decreased; any increase in ionic strength beyond the CCC did not yield significant change in fractal dimension. Across comparable primary particle sizes and using both carbonaceous (GO) and inorganic (Li-MoS₂) 2D ENMs, this study further supports the use of SLS for the measurement of fractal dimension for 2D materials. To further support this claim, the aggregate morphology of GO in both RLA and DLA regimes was measured via cryogenic transmission electron microscopy.

Keywords: Aggregate morphology; Critical coagulation concentration; Fractal dimension; Static light scattering.