Ionic liquids-mediated interactions between nanorods

Zhou Yu, Fei Zhang, Jingsong Huang, Bobby G. Sumpter, Rui Qiao

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Surface forces mediated by roomerature ionic liquids (RTILs) play an essential role in diverse applications including self-assembly, lubrication, and electrochemical energy storage. Therefore, their fundamental understanding is critical. Using molecular simulations, we study the interactions between two nanorods immersed in model RTILs at rod-rod separations where both structural and double layer forces are important. The interaction force between neutral rods oscillates as the two rods approach each other, similar to the classical structural forces. Such oscillatory force originates from the density oscillation of RTILs near each rod and is affected by the packing constraints imposed by the neighboring rods. The oscillation period and decay length of the oscillatory force are mainly dictated by the ion density distribution near isolated nanorods. When charges are introduced on the rods, the interaction force remains short-range and oscillatory, similar to the interactions between planar walls mediated by some protic RTILs reported earlier. Nevertheless, introducing net charges to the rods greatly changes the rod-rod interactions, e.g., by delaying the appearance of the first force trough and increasing the oscillation period and decay length of the interaction force. The oscillation period and decay length of the oscillatory force and free energy are commensurate with those of the space charge density near an isolated, charged rod. The free energy of rod-rod interactions reaches local minima (maxima) at rod-rod separations when the space charges near the two rods interfere constructively (destructively). The insight on the short-range interactions between nanorods in RTILs helps guide the design of novel materials, e.g., ionic composites based on rigid-rod polyanions and RTILs.

Original languageEnglish
Article number134704
JournalJournal of Chemical Physics
Volume147
Issue number13
DOIs
StatePublished - Oct 7 2017

Funding

We thank the ARC at Virginia Tech for generous allocations of computer time on the BlueRidge and NewRiver cluster. R.Q. gratefully acknowledges the support from NSF (CBET-1461842). R.Q. was partially supported by an appointment to the HERE program for faculty at the Oak Ridge National Laboratory (ORNL) administered by Oak Ridge Institute of Science and Education. J.H. and B.G.S. acknowledge work done at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. We thank Dr. Alpha Lee for insightful comments.

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