Direct force measurements between silica particles in aqueous solutions of ionic liquids containing 1-butyl-3-methylimidazolium (BMIM).

Valentina Valmacco,Gregor Trefalt,Plinio Maroni,Michal Borkovec

doi:10.1039/c5cp02292d

Valentina Valmacco, Gregor Trefalt + Show 2 more

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https://doi.org/10.1039/c5cp02292d

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Abstract

Direct force measurements between silica particles were carried out using the colloidal probe technique, which is based on an atomic force microscope (AFM). The forces were investigated in aqueous solutions of ionic liquids (ILs) containing 1-butyl-3-methylimidazolium (BMIM) cations and chloride, dicyanamide, and thiocyanate as anions up to concentrations of about 1 M. The results were compared with the simple electrolyte KCl. ILs behave similar to the simple electrolyte at low concentrations, as the ILs dissociate fully into ions, and they lead to repulsive double layer forces. At higher concentrations, attractive van der Waals forces set in, but they are enhanced in the presence of ILs by additional attractive force, whose strength depends on the type of IL. This additional attraction probably originates from the interaction of adsorbed IL layers.

Highlights

IntroductionSuch suspensions are obtained during particle synthesis in ionic liquids (ILs),[1,2,3,4,5,6] and they are highly relevant in catalysis.[7,8,9,10,11] An important question concerns their stability over time or whether particle aggregates form
Particle suspensions in ionic liquids (ILs) currently attract substantial interest
Direct force measurements between silica particles were carried out using the colloidal probe technique, which is based on an atomic force microscope (AFM)

Summary

Introduction

Such suspensions are obtained during particle synthesis in ILs,[1,2,3,4,5,6] and they are highly relevant in catalysis.[7,8,9,10,11] An important question concerns their stability over time or whether particle aggregates form Such aggregates further influence the suspension rheology and control the formation of colloidal glasses or gels.[12,13,14] Recent investigations suggest that particles are often stable in pure ILs, but already a small amount of water can lead to destabilization. Silica, and latex particles were reported to be stable in dry ILs, while small amounts of water induced aggregation.[2,3,15,16]

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