Emim bf4

Reagent grade chemicals were obtained from Sigma-Aldrich (St. Louis, MO, USA) and used without further purification. [EMIM][OTf] and [EMIM][BF₄] (Iolitec) were used as supplied, and deionized water was processed by Diwer Technologies water max w2 equipment (Weger Walter GmbH, Zona Artigianale, Italy).

Hen egg-white lysozyme (HEW lysozyme, E.C. number: 3.2.1.17, lyophilized powder, L 6876, 50,000 units mg⁻¹ protein) and other chemicals (Thioflavin T, HCl) were purchased from Sigma-Aldrich Chemicals Company (St Louis, MO, USA). The ionic liquids (ILs), 1-ethyl-3-methylimidazolium tetrafluoroborate (>98%) (EMIM-BF₄) and 1-ethyl-3-methylimidazolium acetate (95%) (EMIM-ac), were purchased from IoLiTec (Germany). For all measurements, lysozyme powder was dissolved in aqueous solution containing 0%, 0.5%, 1% and 5% (v/v) ILs to a final lysozyme concentration 2 mg/mL (140 μM). The pH was adjusted to 2.5 by a small amount of 1 M HCl before each experiment and carefully checked at every experimental step. The protein concentration was determined spectrophotometrically (UV/Vis JASCO V-630 spectrophotometer) using an extinction coefficient at 280 nm equal to 38,940 M⁻¹ cm⁻¹. Ultrapure deionized water (Milli-Q) was used for the experiments.

Some main materials used in this research are Nafion solution (DuPont, D2021 contained about 20 wt% polymer, 34 wt% water, and 46 wt% 1-propanol), 1-ethyl-3-methylimidazolium tetrafluoroborate (IOLITEC, EMImBF₄, 98%), 1-ethyl-3-methylimidazolium chloride (IOLITEC, EMImCl, 98%), N,N-dimethylacetamide (Sigma-Aldrich, DMAc, anhydrous, 99.8%), dimethylsulfoxide (Sigma-Aldrich, DMSO, anhydrous, 99.9%), ion-exchange resin (Sigma-Aldrich, Amberlite IRN78 OH hydroxide form), poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (Heraeus, PEDOT:PSS, CLEVIOS PH 1000), and milli-Q type 1 ultrapure water. 1-ethyl-3-methylimidazolium hydroxide (EMImOH) solution was prepared by passing EMImCl solution through a column filled with the ion-exchange resin (Supplementary Fig. 1).