Surface Induced Order in Room Temperature Ionic Liquids and Its Effect on Piezoelectric Response

We compare the direct piezoelectric response of the room temperature ionic liquid (RTIL) <i>N</i>-butylpyridinium bis-(trifluoromethyl-sulfonyl)-imide (C₄Py TFSI) under conditions where pressure is applied to the bulk RTIL in a vessel with a bare ITO interface and a vessel with an ITO interface modified with a monolayer of a pyridinium-containing amphiphile. We find that the presence of a single monolayer of the pyridinium amphiphile poises the RTIL structurally to produce a measurably larger piezoelectric response. The extent of order imposed by the presence of the monolayer is likely limited by the intrinsic surface roughness and structural irregularity of the ITO-coated glass support used.