DLVO Interaction energies for hollow particles: The filling matters

Authors: SHEN, CHONGYANG - China Agricultural University; Bradford, Scott; FLURY, MARKUS - Washington State University; HUANG, YUANFANG - China Agricultural University; WANG, ZHAN - China Agricultural University; LI, BAOGUO - China Agricultural University

Submitted to: Langmuir
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2018
Publication Date: 10/8/2018
Citation: Shen, C., Bradford, S.A., Flury, M., Huang, Y., Wang, Z., Li, B. 2018. DLVO Interaction energies for hollow particles: The filling matters. Langmuir. 34(43):12764-12775. https://doi.org/10.1021/acs.langmuir.8b02547.
DOI: https://doi.org/10.1021/acs.langmuir.8b02547

Interpretive Summary: Hollow colloids are increasingly being used in industrial and environmental applications. The interior filling of hollow colloids is an important design consideration for specific applications because it influences their interactions with surfaces. An approach was developed to determine the interaction of air or water filled hollow colloids with surfaces. Air filled colloids with thin shells were predicted to exhibit much less interaction with surfaces than water filled or especially solid colloids. However, air filled colloids are also more susceptible to aggregation. These results can explain experimental observations for carbon nanotubes and air bubbles, and will be of interest to scientists and engineers concerned with using colloids and nanoparticles to remediate subsurface hazardous waste sites.

Technical Abstract: A thorough knowledge of the interaction energy between a hollow particle (HP) and a surface or between two HPs is critical to the optimization of HP-based products and accurately assessing the environmental risks of HPs and HP-associated pollutants. The van der Waals (VDW) energy between a HP and a surface is often calculated by subtracting the VDW energies of the inner and outer HP geometries. In this study, we show that this subtraction method is only valid when the interior and exterior fluids are the same; e.g., for water filled HPs (WHPs). Expressions were developed to calculate VDW energies for HPs whose interiors were filled with air (AHPs). The VDW energies were then calculated between a planar surface and a spherical or cylindrical WHP and AHP, and between the WHPs or AHPs. The VDW attraction between a surface and a WHP was decreased at large separation distances compared to solid particles (SPs), and this reduced the depth of the secondary minimum. In contrast, the VDW attraction for AHPs and a surface was significantly reduced at all separation distances, and even became repulsive with thin shells, and this inhibited both primary and secondary minimum interactions. The VDW attraction between WHPs decreased with increasing shell thicknesses, and this reduced aggregation in both primary and secondary minima. In contrast, aggregation of AHPs was increased in both minima with decreasing shell thicknesses due to an increase in VDW attraction. Our theoretical calculations showed for the first time the evolution of VDW and total interaction energies for HPs with different interior fluids and shell thicknesses. These results help explain various experimental observations such as inhibited attachment and favorable aggregation for AHPs (e.g., carbon nanotubes) and favorable bubble coalescence.