Synchrotron-Based Temperature-Dependent Terahertz and Far-Infrared Spectroscopy of Aerographite and Single-Walled Carbon Nanotube Aerogel

Synchrotron-based terahertz and far-infrared spectra of aerographite and single-walled carbon nanotube aerogel were acquired using the terahertz/far-infrared beamline at the Australian Synchrotron in the frequency range of 7–1000 cm−1 and temperature range of 6–300 K. We observe infrared absorption features at ~ 35, ~ 79, and ~ 889 cm−1 for aerographite and ~ 35, ~ 79, ~ 685, ~ 923, and ~ 950 cm−1 for single-walled carbon nanotube aerogel. Temperature dependences of the terahertz and far-infrared spectra reveal frequency shifts of the infrared absorption peaks with temperature. The “red-shift” behavior of peak positions (~ 35 and ~ 79 cm−1) can be attributed to the anharmonicity of vibrational potentials. The ~ 35 cm−1 mode is expected to be only Raman active. Its appearance in our infrared spectra suggests that structural disorder in our samples relaxed this selection rule.