Infrared and computational studies of the adsorption of methanol and ethanol on single-walled carbon nanotubes

The adsorption of methanol and ethanol on room-temperature single-walled carbon nanotubes (SWCNTs) has been investigated using Fourier transform infrared (FTIR) spectroscopy and two-level ONIOM calculations. Whereas methanol does not adsorb onto SWCNTs at room temperature, ethanol does adsorb molecularly under these conditions. The IR data show that the adsorbed ethanol is in an environment quite similar to that of liquid ethanol. Comparison to studies of clusters of ethanol indicates that adsorbed ethanol molecules likely form cyclic clusters of four or more molecules, and ONIOM calculations suggest that these clusters can form inside the largest-diameter nanotubes in the sample. The nature of ethanol adsorption has implications for previously reported measurements of changes in the electrical properties of SWCNTs upon ethanol adsorption.