Ionic liquid-modified dyes and their sensing performance toward acids in aqueous and non-aqueous solutions

Six ionic liquid (IL)-modified dyes were synthesized and characterized. Compared to the methyl red and methyl orange, these IL-modified [MR](-) - or [MO](-)-based dyes exhibit lower melting points and enhanced solubility, and can be used as sensitive indicators towards free proton in both aqueous and non-aqueous solutions. This work also supplies a new concept of developing novel modified materials with the ILs.