Materials

The ILs (BMIMCl, ≥99%, BMPYCl, >98%, BMPYRCl, 99%, and BMPIPCl, 99%, see Figure ​Figure11 for the structure of the cations) were purchased from Iolitec GmbH. Inorganic salts such as potassium chloride (KCl), sodium chloride (NaCl), and cesium chloride (CsCl) were bought from VWR. The raw HNT powder was purchased from Sigma-Aldrich. High purity water from a VWR Purity TU+ device was used for all the sample preparations. The measurements were carried out at 25 °C, and the HNT concentration was set to 10 mg/L. The water, salt, and IL solutions were filtered with a 0.1 μm syringe filter (Millex) prior to the sample preparation to avoid dust contamination.

Chemical structure of IL constituent cations used in the present study (BMIM⁺, 1-butyl-3-methylimidazolium; BMPY⁺, 1-butyl-2-methylpyridinium; BMPIP⁺, 1-butyl-1-methylpiperidinium; BMPYR⁺, 1-butyl-1-methylpyrrolidinium; chloride was used as the anion).