Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (07): 1725-1729.doi: 10.3866/PKU.WHXB20110731

• CATALYSIS AND SURFACE SCIENCE • Previous Articles     Next Articles

Melting Point and Structure of Ionic Liquid [EMIM][PF6] on the Surface of Nano-SiOx Particles

LIU Yu-Sheng1,2, FU Hai-Ying1, TANG Zhong-Feng1, HUANG Wei1, WU Guo-Zhong1   

  1. 1. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 210800, P. R. China;
    2. Xuzhou Institute of Technology, Xuzhou 221000, Jiangsu Province, P. R. China
  • Received:2011-03-14 Revised:2011-05-03 Published:2011-06-28
  • Contact: WU Guo-Zhong
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (11079007, 20973192).


The 1-ethyl-3-methyl imidazolium hexafluorophosphate ionic liquid ([EMIM][PF6]) was absorbed onto the surfaces of several kinds of nano-SiOx particles by mechanical grinding using an agate mortar. The samples were investigated by differential scanning calorimetry (DSC), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). We found that the melting point of the [EMIM][PF6] adsorbed on the surface of nano-SiOx was significantly less than that of the bulk ionic liquid. For the pure ionic liquid [EMIM][PF6], the melting point was 62 ℃. After absorption onto SiOx nanoparticles the melting point decreased to 52 ℃ and ΔT was -10 ℃. For the other two types of nano-SiOx particles the ΔT was -20 and -17 ℃, respectively. These results indicate that the melting point depression was dependent on the surface properties of the nano-SiOx particles. Furthermore, the characteristics of the surface-adsorbed ionic liquid were also found to be quite different from that of the bulk ionic liquid by Raman and XRD analyses. The difference in the density of the surface hydroxyl groups and the specific surface area of the nano-SiOx particles may induce different interfacial interactions between [EMIM][PF6] and the nano-SiOx particles. Our results suggest that the density of the surface hydroxyl groups and specific surface area are the major factors responsible for the behavior of the adsorbed ionic liquid [EMIM][PF6].

Key words: Nano-SiOx, Ionic liquid, Melting point, Phase transition


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