Molecular dynamics simulations have been performed to explore the solvation structures and vibrational spectra of ethylammonium nitrate(EAN)ionic liquid around various single-walled carbon nanotubes(SWNTs).Our simulation results demonstrate that both cations and anions show a cylindrical double-shell solvationstructure around the SWNTs regardless of the nanotube diameter.In the first solvation shell,the CH3 groups of cations arefound to be closer to the SWNT surface than the NH3 + groups due to the solvophobic nature of CH3 groups,while the NO3- anions tend to lean on the nanotube surface with three O atoms face to the bulk EAN.On the other hand,the intensities of both C-H(the CH3 group of cation)and N-O(anion)asymmetric stretching bandsat the EAN/SWNT interface arefound to be slightly higher than the corresponding bulk values owing to the accumulation and orientation of cations and anions in the first solvation shell.More interestingly,the N-Ostretching band exhibits a red shift of around 10 cm-1 with respect to the bulk value,which is quite contrary to the blue shift of OH stretching band of water molecules at the hydrophobic interfaces.Such a red shift of the N-O stretching mode can be attributed to the enhanced hydrogen bonds(HBs)of the NO3- anions in the first solvation shell.Our simulation results provide a molecular-level understanding of the interfacial vibrational spectra of EAN ionic liquid on the SWNT surface and their connection with the relevant solvation structures and interfacial HBs.