The local structures between nano-TiO2 and 1-ethyl-3-methylimidazolium trifluorornethanesulfonate (EMI+TFS- ) and 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMI+TES-) were investigated using high-pressure infrared spectroscopy. No significant changes in C-H spectral features of EMI+TFS- were observed in the presence of nano-TiO2 under ambient pressure. As the EMI+TES-/nano-TiO2 mixture was compressed to 0.3 GPa, the imidazolium C-H absorptions became two sharp bands at 3108 and 3168 cm(-1), respectively, and the alkyl C-H stretching absorption exhibits a new band at 3010 cm(-1) associated with a weaker band at 3028 cm(-1). It appears that pressure stabilizes the isolated conformations due to pressure-enhanced imidazolium C-H-nano-TiO2 interactions. Our results also reveal that alkyl C-H groups play non-negligible roles at the conditions of high pressures. The results of BMI+TFS-/nano-TiO2 are remarkably different from what is revealed for EMI+TFS-/nano-TiO2. The spectral features and band frequencies of BMI+TFS-/nano-TiO2 are almost identical to those of pure BMI+TES- under various pressures. This study demonstrates that changes to the alkyl chain length of the cation could be made to control the order and strength of ionic liquid/nano-TiO2 interactions.
- DOT-O INTERACTIONS; REACTION VOLUMES; HYDROGEN-BONDS; INFRARED-SPECTROSCOPY; SILICA NANOPARTICLES; TEMPERATURE; ACTIVATION; SURFACE; WATER; INTERFACE
Chang, H-C., Chang, S-C., Hung, T-C., Jiang, J. C., Kuo, J. L., & Lin, S. H. (2011). A High-Pressure Study of the Effects of TiO2 Nanoparticles on the Structural Organization of Ionic Liquids. Journal of Physical Chemistry C, 115(48), 23778-23783. https://doi.org/10.1021/jp208425m